Micromachines doi: 10.3390/mi17080934

Authors: Ioan Doroftei Cristina-Magda Cazacu

Microgears enable mechanical power transmission, speed reduction, motion conversion, and synchronization in compact devices ranging from microelectromechanical systems to miniature robots and optically driven micromachines. Their behavior cannot, however, be inferred by geometrically scaling conventional gears alone. As size decreases, relative manufacturing errors, surface forces, friction, adhesion, environmental sensitivity, and metrological uncertainty become increasingly important, while torque capacity and stored kinetic energy decrease rapidly. This critical review integrates the design, manufacture, tribology, and system-level performance of microgears and microgear trains. It first clarifies dimensional terminology and derives the principal scaling relationships. It then compares external, internal, planetary, worm, bevel, compliant, and reconfigurable transmission architectures; evaluates silicon micromachining, electroforming, micro powder injection molding, microforming, micro-electrical discharge machining, ultrashort-pulse laser ablation, and additive microfabrication; and examines adhesion, friction, wear, lubrication, and environmental effects. Particular attention is paid to transmission efficiency, starting torque, backlash, transmission error, lifetime, and the influence of the measuring instrument on the observed response. The literature remains strongly weighted toward manufacturability and isolated components, whereas reproducible, loaded, system-level tests are comparatively scarce. On this basis, the review proposes a unified hierarchy of validation, a minimum functional test matrix, and scale-aware design indicators. The central conclusion is that successful microgear transmissions require concurrent design of geometry, process, surface condition, environment, load path, and measurement strategy.

Micromachines doi: 10.3390/mi17080933

Authors: Zhuohao Shi Han Wang Yibin Chen Shuai Chen Daohua Zhan Weicheng Ou

Vibration monitoring of glass substrate transfer systems is crucial for ensuring the stable operation of Flat Panel Display (FPD) manufacturing equipment. Fabrication defects in the functional nanofiber membrane of flexible vibration sensors can significantly degrade sensing performance and lead to inaccurate monitoring results. To address the challenge of achieving an effective balance between detection accuracy and inference efficiency in such defect-dense scenarios characterized by large variations in defect scale, this paper proposes a novel defect detection model, termed MA-YOLO. The proposed model incorporates four key architectural enhancements: the Multi-level Bidirectional Feature Aggregation Network (MLBAN), the Multi-Receptive Field Adaptive Fusion Module (MRAF), the Morphology-Adaptive Feature Extraction Module (MA-C2f), and the Interactive Dynamic Decoupling Head (IDDH). These components collaboratively improve defect feature extraction, multi-scale feature fusion, and localization performance while maintaining a lightweight architecture and high inference speed. Experimental results on a self-constructed defect dataset demonstrate that MA-YOLO achieves a mean Average Precision (mAP@0.5) of 91.9%, which is a 3.1 percentage point improvement over the baseline model. Moreover, with only 9.15 million parameters and an inference speed of 119.05 FPS, the proposed model exhibits superior overall performance compared with several mainstream and state-of-the-art object detection methods.

Micromachines doi: 10.3390/mi17080932

Authors: Fenglin Han Jing Wang Jinlong Wu Jing Yang Hu He Zhi Chen

The microstructure of ternary precursors significantly influences the electrochemical performance of ternary cathode materials and, consequently, the overall performance of lithium-ion batteries. In industrial production utilizing traditional co-precipitation methods, Scanning Electron Microscopy (SEM) is typically employed for particle detection. However, this approach is limited by offline sampling lag, poor representativeness, cumbersome sample preparation, and low efficiency, failing to achieve real-time quality feedback on production lines. To enable high-throughput particle detection, this study proposes a multi-layer PDMS chip designed for three-dimensional (3D) hydrodynamic focusing. The sheath fluid compressed the sample flow in horizontal and vertical directions, respectively, to form a flat ribbon flow passing through the detection area. High-fidelity raw images are captured for automated particle microstructure analysis. Firstly, a chemical pretreatment protocol was optimized to ensure stable precursor solution transport. Secondly, a three-layer composite microchannel featuring a sequential horizontal and vertical sheath-flow compression mechanism was designed, with its geometry optimized via Computational Fluid Dynamics (CFD) simulations. Subsequently, experimental optimizations of flow rate ratios were performed using sodium fluorescein, followed by validation with ternary precursor solutions. The results indicate that the microchannel achieves flattened monolayer focusing of randomly distributed precursor particles, compressing the sample stream height to approximately 15.44 μm, thereby maintaining the particle stream within the microscope’s depth of field and analyzing particle microstructure efficiently based on a microscopic image. Moreover, it is confirmed that the focused stream dimensions are primarily governed by the flow rate ratio, allowing for a flexible increase in detection throughput by adjusting the total flow rate. Different from static offline particle analyzers, this platform captures dynamic particle morphology under continuous flow, providing real-time data to guide co-precipitation reaction adjustment.

Micromachines doi: 10.3390/mi17080931

Authors: Chengyu He Wei Li Jianjun Li Qiquan Li Zhiang Xie Tao Du

Data movement has become a dominant bottleneck in modern artificial intelligence hardware, making in-memory computing a critical direction for energy-efficient and memory-centric architectures. Ferroelectric hafnium oxide provides a distinctive materials platform for this transition because field-driven polarization switching, non-volatility, CMOS compatibility, and nanoscale thickness scalability can be combined within a process-relevant oxide system. This review establishes a device-to-system perspective on HfO2-based and Hf0.5Zr0.5O2-based ferroelectric memories for in-memory computing. Instead of treating ferroelectric materials, memory devices, circuit primitives, and computing architectures as separate research topics, we examine how their mutual constraints define the achievable efficiency, precision, reliability, and scalability of hafnia-based computing systems. The discussion connects polarization engineering and defect control with charge-domain computation, threshold-state logic, associative search, analog weight representation, neuromorphic plasticity, and sensor-side processing. Particular emphasis is placed on the translation of ferroelectric functionality from individual devices to arrays, macros, and system-level accelerators. We identify variability, fatigue, charge trapping, multilevel-state uncertainty, peripheral overhead, and benchmarking inconsistency as the central barriers that prevent device-level advantages from directly becoming system-level gains. Finally, we outline a cross-layer roadmap in which ferroelectric stack engineering, variability-tolerant arrays, precision-scalable architectures, and SoC-level integration are co-optimized to enable reliable HZO-based memory-centric computing.

Micromachines doi: 10.3390/mi17080930

Authors: Kun Li

In recent years, high-energy-beam technologies and nano- and micro-scale advanced manufacturing have developed rapidly, injecting new vitality into modern engineering and expanding the possibilities for practical application [...]

Micromachines doi: 10.3390/mi17080929

Authors: Eman Elnabawy Nagham M. Elberishy Ahmed Backar Ali Toptas Ali Kilic Islam Shyha Mohamed A. Daha

Poly Butylene Succinate (PBS) and Poly Butylene Succinate-co-Adipate (PBSA) are biodegradable polyesters that have attracted considerable attention for nanofibre fabrication due to their environmentally friendly characteristics and favourable material properties. PBS nanofibres are known by relatively high rigidity, thermal stability and crystallinity, making them suitable for applications that require structural strength. However, the stiffness of PBS may reduce its flexibility and limit its processing performance in some applications. In contrast, PBSA nanofibres incorporate adipic acid into the polymer chain, which results in lower crystallinity, greater flexibility and reduced melting temperature. These characteristics enhance the elasticity and processability of PBSA-based materials. The differences in mechanical and thermal behaviour between PBS and PBSA arise from the modification of the polymer backbone in PBSA, making it more appropriate for applications that demand adaptable and flexible materials, such as tissue engineering and air filtration. Both nanofibre systems show significant potential for sustainable technologies. In this study, a comparative evaluation of PBS and PBSA nanofibres was conducted to investigate their morphology, crystallinity, mechanical behaviour and filtration performance. The results show that PBS nanofibres exhibit a higher crystallinity of approximately 45%. In contrast, PBSA nanofibres demonstrate a significantly higher strain, reaching nearly twice that of PBS nanofibres. Regarding filtration performance, both materials achieved filtration efficiencies of up to 93%, while maintaining relatively low pressure drops of 210 Pa for PBS and 200 Pa for PBSA. Furthermore, corona discharge treatment was applied to enhance electrostatic capture and maintain filtration efficiency during extended operation for up to seven days.

Micromachines doi: 10.3390/mi17080928

Authors: Guangan Yang Xu Guo Tianzhen Li Zheng Guo Geng Huang Yan Jiang Huabin Sun Hong Zhu

Enhancement behavior on saturation current of output characteristics in amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors under positive bias stress (PBS) is investigated. The threshold voltage (Vth) of the a-IGZO TFT demonstrates a typical positive shift during PBS. Notably, the output current at an identical overdrive voltage (Vov) initially rises with increasing bias stress duration. The observed phenomena are elucidated by the detrapping of positively charged defects situated at the interface between the dielectric and active layer due to electrons induced by bias stress during PBS, which diminishes carrier scattering at the channel interface. Following the full release of positive interface charge, additional electron trapping states emerge. The presence of trapped electrons intensifies carrier scattering at the channel interface, leading to a degradation in drive current. Low-frequency noise (LFN) measurements are conducted to verify the suggested mechanism of PBS instability in a-IGZO TFTs. Moreover, the energy distribution of PBS-induced traps is shown by C-V characterization to be exponential, dominated by shallow traps. Passivation greatly enhanced the PBS stability, which is attributed to hydrogen doping-induced defect passivation and the shielding of the back-channel interface from the air atmosphere.

Micromachines doi: 10.3390/mi17080927

Authors: Rufei Cui Boqi Ding Xiaoyu Zhao Jiangxing Chen Yongjun Zhang Xinyu Wang Yaxin Wang Renxian Gao Kun Zhang Fengyi Zhang Zhe Kong

Magnetically actuated soft robots enable untethered operation in confined and complex environments; however, achieving controllable directional locomotion in structurally symmetric systems remains a fundamental challenge due to intrinsic force cancellation under uniform fields. Here, we present a modular strategy that integrates assembled programmable magnetization with energy-biased symmetry-breaking joints to overcome this limitation. By embedding hard-magnetic NdFeB microparticles into an Ecoflex matrix, discrete magnetic units with programmable magnetization are fabricated and assembled into higher-order architectures. We show that asymmetric film constraints prescribe joint polarity and bias strain-energy distribution during actuation, producing distinct deformation modes (folding versus bending) under identical magnetic inputs. This energy asymmetry breaks the balanced response of symmetric structures, enabling net directional motion under spatially uniform magnetic fields. Based on this principle, a segmented crawler achieves a maximum speed of 5.42 mm s−1 under a half-wave magnetic field, while a quadruped robot realizes programmable multi-directional locomotion (±X, ±Y) via dual-field coupling, reaching a maximum speed of 3.125 mm s−1. These results demonstrate that modular magnetization and joint-mediated energy bias can cooperatively generate controllable directional locomotion through mechanically encoded symmetry breaking. This work provides a scalable design framework for programmable magnetic soft robots under spatially uniform magnetic fields.

Micromachines doi: 10.3390/mi17080926

Authors: Doha Abdelrahman Alain Savary Bernard Feuillard Marc Heuschkel Dario Principi Adrien Roux Christophe Besson

Achieving precise, untethered manipulation at the millimeter scale remains a fundamental challenge in minimally invasive medicine. Magnetic milligrippers have emerged as promising untethered tools for grasping, transporting, and releasing objects in confined anatomical environments, yet most existing rigid designs rely on multi-component assemblies with dedicated hinges or joints that require complex fabrication processes. Here, we present a simple, cost-effective rigid magnetic milligripper based on a folded titanium structure with two inclined permanent magnets. Actuated by a three-axis Helmholtz–Maxwell coil system, it enables orientation and translation control, as well as reversible opening. The actuation platform is coupled to a joystick-based control interface, allowing intuitive, real-time steering and opening of the milligripper by a single operator. The design is established with an analytical magnetic dipole model and validated through both finite-element simulations and experimental characterization, which together confirm reproducible, fully elastic operation across the investigated actuation range. The strong agreement between analytical, numerical, and experimental results establishes this architecture as a mechanically robust and scalable proof-of-concept platform for magnetic micromanipulation, with direct relevance to future minimally invasive biomedical applications.

Micromachines doi: 10.3390/mi17080925

Authors: Jin Zhang Dawu Lv Ye Yang Weijie Song Ruijin Yu Wenfeng Shen

High-performance ammonia (NH3) sensors play a critical role in environmental protection and noninvasive medical diagnosis. This work reports a new NH3 sensor based on Au-microsphere-decorated polyaniline (PANI) manufactured by a precise in situ inkjet printing method on a MEMS micro-hotplate. The in situ oxidative polymerization of aniline was performed directly on the MEMS platform using AuCl3 as a bifunctional oxidant and precursor, with a hierarchical morphology of microspheres (~750 nm) and nanorods (~250 nm). Reduced from Au3+ in the polymerization reaction, Au microparticles achieve substantial catalytic promotion by virtue of chemical sensitization and spillover effect. The optimized Au–PANI MEMS sensor exhibits a superlative response of 201% toward 1 ppm NH3 at room temperature, with an ultra-low theoretical limit of detection (LOD) of 0.42 ppb. Furthermore, the device demonstrates rapid response/recovery kinetics (76 s/72 s), exceptional selectivity against common interfering gases (SO2, CO, H2, etc.), and robust long-term stability with high response retention over two months. This research provides a scalable, cost-effective strategy for the mass production of miniaturized, high-sensitivity gas sensors for industrial and healthcare applications.

Micromachines doi: 10.3390/mi17080924

Authors: Haoze Lan Yingjie Xu

Microelectromechanical systems (MEMS) gyroscopes are now standard rate sensors in inertial navigation, automotive electronics, industrial automation, and medical instrumentation because they are inexpensive, compact, and readily integrated. Their accuracy, however, degrades with temperature: damping and quadrature coupling change, and readout-electronics behavior shifts, producing temperature-dependent zero-rate-output drift, elevated random noise, and poorer long-term stability. Hardware- and structure-based temperature compensation address part of the problem but carry cost and generality penalties, which has moved recent work toward data-driven software-based temperature-drift compensation. This review focuses on the fusion algorithms that have come to dominate that literature, organized as a four-stage pipeline: signal decomposition, learning-based drift modeling, adaptive filtering, and signal reconstruction. We examine how optimizer-tuned variational mode decomposition and improved empirical-mode-decomposition variants separate temperature-related components from noise; how deep temporal networks and optimizer-coupled learners model the nonlinear, time-lagged drift; and how adaptive Kalman variants and time-frequency filtering reconstruct a stable output. We close by identifying four open problems that recur across the recent gyroscope-specific work—cross-device generalization, temperature hysteresis, embedded real-time deployment, and physics-informed lightweight modeling.

Micromachines doi: 10.3390/mi17080923

Authors: Ling Li Shiyu Ji Xiaoguang Wei Yaohua Wang Qianqian Jiao Liang Wang Rui Liu Xinling Tang Ningfei Sun Ningyi Wang Xinyu Huo Yaqi Gao Jianye Ma Ruifeng Yue

A reverse-blocking integrated gate-commutated thyristor (RB-IGCT) incorporating a backside PN junction, referred to as PN-RBIGCT, is proposed and investigated using Sentaurus TCAD. The introduction of the PN junction establishes a reverse electric field in the anode region during turn-off, which accelerates carrier extraction and reduces switching losses. At a conduction current of 5 kA, a 40.4% reduction in turn-off energy loss (from 335.6 J to 200.0 J) is achieved, with only a moderate increase in the on-state voltage drop of the PN-RBIGCT from 1.44 V to 1.62 V.

Micromachines doi: 10.3390/mi17080922

Authors: Xin-Yu Duan Wei-Zong Li Yi-Xuan Zhang Ye Hui

Sparse antenna arrays are attractive for compact microwave and millimeter-wave front ends because they can achieve prescribed radiation performance with fewer radiating elements, thereby reducing the number of feeding channels, hardware cost, weight, and power consumption. However, the joint optimization of element positions and complex excitations remains challenging, since the element positions enter the array factor nonlinearly and the element-count objective is inherently combinatorial. This paper presents an iterative reweighted ℓ1 synthesis framework for sparse antenna arrays with continuous element positions. At each iteration, position perturbations are introduced and the array factor is linearized using a first-order Taylor expansion within a trust region. The resulting non-convex sparse synthesis problem is then approximated by convex programing through an iteratively reweighted ℓ1 relaxation, allowing the excitation amplitudes, phases, and element positions to be updated simultaneously. Additional aperture, minimum-spacing, and minimum-directivity requirements are formulated as convex constraints and incorporated when required, enabling joint control of sparsity, sidelobe level, physical layout, and radiation performance. The proposed method is validated through four representative examples, including a shaped-beam linear array, a tri-pattern reconfigurable linear array, a planar pencil-beam array, and a directivity-constrained planar array. Compared with fixed-grid reweighted ℓ1 methods under the same specifications, the proposed approach produces sparser layouts while avoiding the grid-resolution limitation. In the directivity-constrained benchmark, it also achieves competitive element reduction while enforcing a prescribed minimum element spacing. These results indicate that the proposed framework provides a flexible and practical synthesis tool for compact and integrated sparse antenna-array design.

Micromachines doi: 10.3390/mi17080921

Authors: Fahad Sulaiman Obaid Muhammed Anaz Khan

Electrohydrodynamic emission from a sessile droplet depends on a coupled balance among electric traction, capillarity, gravity, charge transport and liquid motion. The present work addresses only the electrostatic-loading part of that problem. Verification-backed axisymmetric and three-dimensional Laplace solvers are used to map how parallel-plate, on-axis-pin, off-axis-pin and bipolar double-pin electrodes redistribute the normal electric field over a prescribed conducting water-droplet interface. The primary response is the dimensionless electric capillary number, CaE = ε0En2Rv/γ. To compare geometries on a common voltage scale, V1 is defined as the applied voltage at which the peak prescribed-interface loading reaches CaE = 1. V1 is a normalisation voltage and not a jetting or stability threshold. The axisymmetric solver reproduces the exact conducting-hemisphere solution to within 0.07% at the finest grid. The three-dimensional finite-difference results are mesh-assessed, and their normalised surface-field topology is cross-checked against an independently implemented Galerkin finite-element model. At 4 kV, the finite parallel-plate cell produces an apex enhancement of 3.24 relative to V/H. Replacing the plate with an on-axis 1 mm pin reduces the apex field by 39.5%, which corresponds to a 63% reduction in CaE, and increases V1 from approximately 5.0 to 8.2 kV. Lateral pin displacement moves the surface-field maximum away from the apex and produces a broad nominal plateau near d = 5–7 mm, although the sub-grid steering distance remains sensitive to mesh and extraction settings. The bipolar double-pin configuration produces two symmetric surface-field maxima together with a near-null at the apex. This topology, but not its absolute magnitude, is reproduced by the finite-element cross-check. A Gaussian-process model interpolates the one-dimensional offset family accurately under leave-one-offset-out validation (R2 = 0.999). Four Bayesian-optimisation trials locate the broad steering plateau but show no visible evaluation-count advantage over random sampling in this one-dimensional test. A three-mesh study gives a reported field-magnitude mesh-sensitivity estimate of approximately 6.2% at the finest grid (rising to about 9.5% at the h = 0.20 mm production mesh) for the representative three-dimensional case, and an indicative combined-uncertainty band of approximately 10% is shown for V1 in the exploratory trade-off plot. Illustrative Young–Laplace profiles at contact angles of 70° to 110° preserve the comparative pin-versus-plate field reduction, whereas V1 varies by up to approximately 50%. A simplified Peek-law screening estimate places corona inception (the pin being cathodic) in the approximate range of 4.8–10 kV, which is comparable to the on-axis-pin V1, so gas discharge may intervene before large electrocapillary loading is reached in ambient air. The results establish electrode geometry as a controllable electrostatic-loading parameter while explicitly deferring coupled stability analysis and experimental validation. By resolving this loading on a single exact-solution-verified basis, the study quantifies electrode geometry as a control parameter that idealised enhancement factors and the nominal gap field cannot capture and provides a verified fixed-interface reference state for subsequent coupled electrohydrodynamic modelling.

Micromachines doi: 10.3390/mi17080920

Authors: Hiroaki Nishiza Masahito Horie Masakazu Ito Hisao Enomoto

Through-glass via (TGV) substrates have attracted increasing attention as interposers and core substrates for advanced packaging. However, contaminants adhere to glass surfaces; in particular, airborne organic substances increase the contact angle, hindering the penetration of cleaning solutions into TGVs and thereby reducing the cleaning effect. Reducing the cleaning-solution surface tension by adding a surfactant may promote penetration into TGVs with high contact angles. This study investigated the effect of cleaning-solution surface tension on cleanability inside TGVs. Under the tested conditions, the contact angle outside the TGV after cleaning was 3–4° for all cleaning solutions, regardless of their surface tension. In contrast, the contact angle inside the TGV after cleaning decreased with decreasing surface tension. At 27.5 and 41.8 mN/m, the contact angle inside the TGV after cleaning decreased to 3–4° under both conditions. These results indicate that the surface tension of the cleaning solution affects the cleanability inside the TGV. For a TGV with an opening diameter of 20 μm and an aspect ratio of 10, cleaning with a 27.5 mN/m solution prior to electroless Cu plating was associated with reduced void formation and film thickness variation in the Cu film inside the TGV under the tested conditions.

Micromachines doi: 10.3390/mi17080919

Authors: Rangaraajan Muralidaran Paritosh Dubey Kuldeep Singh Gour Shuvam Pawar Vinod Belwanshi Jacopo Iannacci

This article reviews the reactive magnetron sputtering of piezoelectric Aluminium Nitride (AlN) thin films, with a focus on process parameter optimisation and system-level deposition challenges. AlN is a leading material for MEMS and RF applications owing to its c-axis (002) orientation, high acoustic velocity, wide bandgap (∼6.2 eV), and CMOS compatibility. We review the influence of sputtering power, nitrogen flow ratio, substrate temperature, and target-to-substrate distance on crystallographic quality and document practical hardware challenges, including vacuum leakage, grounding faults, target erosion, and mass flow controller drift, that critically affect reproducibility but are systematically underreported in the literature. A perspective is provided on emerging application domains where optimised AlN films address current performance gaps, including next-generation RF/telecom systems towards 6G and Future Networks, harsh environment sensing and actuation, biomedical ultrasound, and IoT energy harvesting. The complementarity between AlN and Silicon Carbide (SiC) is discussed for high-temperature, high-power, and radiation-hard MEMS, where AlN/SiC heterostructures combine the piezoelectric activity of AlN with the mechanical and chemical robustness of SiC. It also incorporates a discussion of dopant- and heteroepitaxy-based AlN engineering, AlN deposition on a wider range of substrates, the role of seed and electrode underlayers, and pulsed-DC sputtering as a third power supply mode alongside RF and conventional DC.

Micromachines doi: 10.3390/mi17080918

Authors: Zhihang Li Weili Tang Qingshan Duan Xinxin Li Mingchun Wang

The Triboelectric Nanogenerator (TENG), as an emerging self-powered sensor, is widely used in the field of rotating machinery bearing fault diagnosis. Due to its working principle based on frictional electrification and electrostatic induction effects, the surface morphology and charge transfer efficiency of the friction layer have a significant impact on the output performance of TENGs. Under long-term mechanical motion, the friction layer may experience wear, and continuous wear can lead to surface morphology damage and even damage to the friction layer structure, gradually destroying the TENG’s signal acquisition and output capabilities, causing signal degradation and bearing fault feature deviation, which results in a decrease in bearing fault diagnosis accuracy. Traditional solutions focus on material properties and structure. This article derives the mechanism of the influence of friction layer thickness on the output signal through the TENG output voltage formula and simulates different degrees of wear with friction layers of different thicknesses to conduct deep learning-based bearing fault diagnosis experiments. The experimental results show that although the CNN model can recognize TENG signals well for bearing fault classification, the bearing fault features of the worn signals shift, and the accuracy of CNN diagnosis decreases. The introduction of a one-dimensional self-attention-enhanced convolutional neural network model and an incremental learning method improved the accuracy of bearing fault diagnosis after wear and tear. This study provides theoretical support and practical solutions for long-term, stable bearing fault diagnosis in TENG under wear conditions.

Micromachines doi: 10.3390/mi17080917

Authors: Yuansheng Chen Hao Lou Jian Wang Shaona Liu

Piezoelectric flexure micro-positioning stages are essential micromotion actuators for micro-assembly, atomic force microscopy and nano-manufacturing, but intrinsic hysteresis nonlinearity of piezoelectric stacks distorts the linear voltage-to-displacement mapping and induces significant micro-positioning errors. Conventional hysteresis compensation based on offline-calibrated Krasnosel’skii-Pokrovskii (KP) models cannot adapt to time-varying excitation, whereas state-of-the-art adaptive KP control requires auxiliary dynamic equations and imposes high computational overhead on miniature real-time controllers. To address these limitations, this paper develops a single-degree-of-freedom micromotion positioning device equipped with symmetric two-stage displacement amplification mechanisms and straight circular flexure hinges. ANSYS finite element simulations validate the mechanical stiffness, structural safety and linear amplification characteristic of the micro-positioning stage, achieving a maximum output stroke of 95.95 μm. A discretized KP hysteresis model is constructed to accurately capture the asymmetric rate-dependent hysteresis of piezoelectric stacks. On this basis, a lightweight adaptive inverse control framework is proposed, which realizes online tuning of KP weights through gradient descent iteration only relying on real-time position feedback, eliminating static pre-calibration and extra dynamic correction links. Tracking experiments under 0.1–2 Hz sinusoidal waveforms and 3–7 V variable-amplitude sinusoidal waveforms are implemented. Experimental results show that the proposed approach reduces the root-mean-square error (RMSE) by 7.41–85.65% and the mean absolute percentage error (MAPE) by 7.56–87.81% compared with uncompensated open-loop micromotion control. The combined micro-flexure mechanical design and adaptive hysteresis compensation strategy greatly improves positioning accuracy and anti-interference capacity, offering a low-computation technical route for high-performance micro-positioning systems.

Micromachines doi: 10.3390/mi17080916

Authors: Kai Xing Yugang Zhao Qilong Fan Li Guo Zhi Qi Kaihao Ma Guangzheng Chen

To achieve accurate prediction of surface roughness (Ra) in magnetic abrasive finishing (MAF) of the inner wall of Co–Cr alloy vascular stent tubing, and to obtain the optimal process parameter combination for improving the inner surface quality, iron-based diamond magnetic abrasive powders (MAPs) were prepared via plasma melting, centrifugal spraying and rapid solidification. MAF experiments were conducted on Co–Cr alloy vascular stent tubing with an inner diameter of 1.6 mm and an outer diameter of 1.8 mm, and the effects of tube rotational speed, magnetic pole feed rate, abrasive particle size and working gap on surface roughness were investigated. An orthogonal experiment was designed, and a surface roughness prediction model based on particle swarm optimization (PSO) and support vector machine (SVM) was established. Simulation results indicate that the proposed PSO-SVM surface roughness prediction model achieved a coefficient of determination (R2) of 0.96771, a root-mean-square error (RMSE) of 0.0012756 μm, and a mean absolute percentage error (MAPE) of 1.061%. The optimal parameter combination obtained by PSO-SVM optimization was a tube rotational speed of 832.6384 r·min−1, a magnetic pole feed rate of 129.6784 mm·min−1, a working gap of 0.5324 mm, and an abrasive particle size of 132.4185 µm. Under these conditions, the experimentally obtained surface roughness was 0.0949 μm, with a relative error of 0.58% compared to the model-predicted value. The results demonstrate that the established PSO-SVM surface roughness prediction model possesses favorable predictive capability, and its combination with MAF technology enables superior surface quality.

Micromachines doi: 10.3390/mi17080915

Authors: Zhihao Zhang Yazhou Zhang Chunlei He

In this study, the surface pit formation mechanism during single-point diamond face turning of a particle-reinforced polymer matrix composite (PRPMC) was investigated using finite element simulations. Based on the identified pit formation mechanisms, a surface roughness prediction model was developed and validated through face turning experiments. The results show that particle fracture and interfacial debonding are the primary origins of surface pits. Increasing cutting depth promotes the transition from particle fracture to interfacial debonding, leading to larger pits and higher surface roughness. A rake angle of −15° and a larger tool nose radius improve surface quality by suppressing pit formation and plastic side flow. The proposed model accurately predicts the effects of cutting depth, rake angle, and tool nose radius on surface roughness, with a maximum prediction error of 9.20% and an average error of 4.66%. This study provides a theoretical basis for surface roughness prediction and process parameter optimization in single-point diamond face turning of PRPMCs.

Micromachines doi: 10.3390/mi17080914

Authors: Mingyang Liu Guang Lu Bing Wang Hao Zhang

To overcome the large size of conventional high-gain antennas and the structural complexity of typical photonic crystal antennas, this paper proposes a cavity-free photonic crystal (PC) antenna driven by microwave-band Tamm plasmon polaritons (TPPs), which eliminates the conventional half-wavelength resonant cavity while maintaining a moderate total height (38.4 mm, ~2.1λ0). The core innovation of this work lies in shifting the gain-enhancement paradigm from traditional bulky, volume-based spatial resonances to a direct 2-D interface feeding strategy. By rigorously satisfying the phase-matching condition between a one-dimensional PC and a highly reflective substrate, a strong TPP mode is excited. Distinct from conventional designs, we embed a simple microstrip patch exactly at this phase-matched boundary to directly exploit the extreme electric field localization of TPPs. This novel mechanism enables a cavity-free architecture that achieves highly directional emission without complex feeding networks or metallic cavities. Simulations and measurements exhibit excellent agreement. At 16.43 GHz, the measured peak gain reaches 16.4 dBi, with 3-dB beamwidths of 13.5° and 18.5°. Ultimately, this TPP-driven paradigm offers a practical solution tailored for advanced wireless communications and radio astronomy.

Micromachines doi: 10.3390/mi17080910

Authors: Chunmei Wang Congyi Zhu Qi Zhang Shuangsheng Zhang Ling Zhang Jiang Wu Guoliang Zhang

Titanium and titanium alloys have been widely used in clinical implants such as dental implants due to their high strength and corrosion resistance. However, their inherent biological inertness and mismatch with the elastic modulus of human bone tissue restrict bone healing and reconstruction. In this study, pure titanium was first modified by micro-arc oxidation (MAO), and then a biodegradable soybean protein isolate (SPI)/polylactic acid (PLA)–polycaprolactone (PCL) composite coating was prepared by using the spin-coating method. The coating was systematically characterized by scanning electron microscopy (SEM), an energy spectrometer (EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and atomic force microscopy (AFM), confirming that the composite coating was successfully prepared. An evaluation of the physical and chemical properties showed that the introduction of SPI significantly improved the hydrophilicity, surface roughness and adhesion to the substrate of the coating, regulated the degradation rate, and reduced the elastic modulus to the range of 10–30 GPa, which matches human bone tissue. At the same time, it enhanced corrosion resistance. In vitro MC3T3-E1 osteoblast experiments showed that the coating containing 50% SPI showed better cell compatibility, adhesion ability and osteogenic inducibility, and all groups had good blood compatibility. The SPI/PLA–PCL composite coating effectively improves the biological activity of the pure titanium surface and provides a feasible strategy for the surface modification of titanium implants and bone defect repair.

Micromachines doi: 10.3390/mi17080913

Authors: Yuheng Liu Tao Zhang Huake Su Jiahao Chen Xiangdong Li Shengrui Xu Zeyang Ren Weidong Zhu Yu Du Yue Hao Jincheng Zhang

In this work, a novel Schottky-gated p-channel GaN field-effect transistor (PFET) with a tunable n-GaN sub-gate layer is investigated. Terminal-current analysis under the actual drain-bias condition shows that the gate-current contribution remains limited within the defined effective operating range of VGS ≥ −3.2 V, whereas gate-related current becomes significant at more negative gate biases. Carrier-resolved and spatial current analyses further confirm that, within this operating range, the drain current is predominantly carried by holes through an interfacial hole channel near the p-GaN/AlGaN heterointerface. Benefiting from the intentionally introduced p–n junction beneath the groove gate, the built-in electric field effectively depletes the p-GaN channel, enabling a robust transition from depletion-mode to enhancement-mode (E-mode) operation. By precisely scaling the n-GaN layer thickness (0–5 nm) and donor concentration (3.0 × 1017 cm−3 to 3.0 × 1019 cm−3), the buried p-n junction modulates the depletion condition and hole distribution beneath the gate. The optimized device exhibits a significantly improved subthreshold swing (SS) of 348 mV/dec, while maintaining a stable ION/IOFF ratio on the order of 102. This tunable sub-gate architecture provides a highly flexible platform for optimizing E-mode GaN PFETs, showing great promise for high-performance complementary logic applications.

Micromachines doi: 10.3390/mi17080912

Authors: Md Imran Hossain Sitansu Sekhar Nanda Dong Kee Yi

The repair and functional restoration of skeletal muscle tissue following trauma, degenerative disease, or volumetric muscle loss remains a significant unmet clinical challenge in tissue engineering, where the need to recapitulate the anisotropic architecture, mechanical compliance, and high metabolic demands of native muscle imposes stringent requirements on biomaterial design. Traditional cell culturing and scaffold fabrication strategies have proven insufficient to address these demands in isolation, particularly in integrating mechanical integrity, biochemical functionality, and biological activity within a single biomaterial system. Recent advances in material science have accelerated the evolution of skeletal muscle tissue engineering toward a more precise and technologically sophisticated discipline. In this context, surface-engineered magnetic nanoparticle (MNP) hybrids have emerged as a promising multifunctional platform, owing to their intrinsic biocompatibility, tunable physicochemical properties, and rapid, non-invasive responsiveness to external magnetic fields. These unique characteristics have enabled the development of magnetic force-based tissue engineering strategies, facilitating controlled myogenic cell organization, magnetically guided delivery of therapeutic agents and stem cells, enhanced muscle construct formation within responsive scaffolds, and real-time non-invasive monitoring of engineered systems via MRI. This review systematically synthesizes the recent advances in surface-engineered MNP platforms for skeletal muscle tissue engineering, covering organic and inorganic coating strategies, magnetically responsive scaffold integration, guided cell and drug delivery, and construct monitoring, whilst critically appraising the biocompatibility, biodistribution, and regulatory challenges that currently define the translational pathway for MNP-augmented skeletal muscle constructs.

Micromachines doi: 10.3390/mi17080911

Authors: Wei Xu Changxu Qu Jian Hao Tingting Hao Yabin Wang Zheng Zhao Yongnan Tan Jing Wang

A charge-balanced aqueous hybrid supercapacitor was constructed by coupling Co-modified MnWO4 nanorods with H2O2-treated carbon nanotubes (OH-CNTs) in 1 M KOH. The samples were designated by the nominal Co/(Mn + Co) precursor molar fraction; ICP-OES measured bulk Co fractions of 0.09 ± 0.01, 0.47 ± 0.03, and 0.75 ± 0.04 mol% for the nominal 0.1, 0.5, and 0.8 mol% samples, respectively. Rietveld refinement confirmed retention of the monoclinic P2/c MnWO4 phase with only small composition-dependent lattice changes. At an active-material loading of 2.00 ± 0.05 mg cm−2, the optimized nominal 0.5 mol% sample delivered 429.5 ± 11.0 C g−1 (119.3 ± 3.1 mAh g−1) at 1 A g−1 and retained 280.5 ± 8.5 C g−1 (77.9 ± 2.4 mAh g−1) at 15 A g−1. Because the positive electrode exhibits battery-type behavior, specific charge and specific capacity are used as the primary performance descriptors. Over −0.9–0 V vs. SCE, pristine CNT and OH-CNT electrodes delivered of 189.0 ± 7.2 and 246.6 ± 8.1 C g−1, corresponding to electrode-level apparent specific capacitances of 215 ± 8 and 280 ± 9 F g−1 at 1 A g−1 after correction for the measured IR drop. These values apply to the stated 90:5:5 CNT (or OH-CNT)/acetylene-black/PVDF formulation and CNT-active-mass normalization and should not be interpreted as intrinsic capacitances of isolated commercial MWCNT powders. Charge matching based on the measured gave m+/m− = 0.574; integration at the actual device loadings yielded q+ = 0.861 ± 0.015 C and q− = 0.854 ± 0.015 C (q+/q− = 1.008). The device operated over 0–1.6 V and delivered 97.9 ± 3.1 F g−1 at 0.51 A g−1, corresponding to 34.8 Wh kg−1 at 408 W kg−1 when normalized to the combined active mass of both electrodes. Three independently assembled devices retained 96.0 ± 0.7% of the initial capacitance and showed a coulombic efficiency of 98.8 ± 0.1% at the 10,000th cycle at 5.13 A g−1. Device metrics are normalized to the combined active mass of both electrodes and exclude current collectors, separator, electrolyte, and packaging.

Micromachines doi: 10.3390/mi17080907

Authors: Li Yang Simin Zhao Hailong Duan Xinrui Kan Jing Yang Jia Xing

Defect detection in electroluminescence (EL) images of solar cells remains challenging because defects are often small, exhibit subtle grayscale variations, and are obscured by complex cell-texture backgrounds. These conditions can attenuate defect features as they propagate through deep layers and make them difficult to distinguish from background patterns, thereby limiting the ability of detection models to accurately localize and classify defects. To address these issues, this study proposes a Wavelet-Aware Selective Reconstruction Network (WASR) for solar cell defect detection. A frequency-aware encoding strategy built around the Wavelet-Aware Downsampling Encoder (WADE) module preserves fine-grained defect cues by jointly modeling spatial and frequency-domain characteristics. In addition, a Cross-Scale Context Fusion Module (CCFM) improves multilevel feature transmission and fusion, whereas a Selective Reconstruction Detection Head (SRD-Head) performs selective feature reconstruction with residual enhancement. Together, these modules enhances defect perception capability under low-contrast conditions and complex backgrounds. Compared with the YOLO11 baseline, WASR increases mAP@0.5 by 2.4 percentage points, reduces the parameter count by 0.62 M, and improves inference speed by 23 FPS. The results show that WASR provides a favorable balance between detection accuracy and computational efficiency. Ablation experiments and visualization results further confirm the contribution of the proposed components under challenging conditions.

Micromachines doi: 10.3390/mi17080909

Authors: Tayebeh Azadmousavi Saghi Forouhi Ebrahim Ghafar-Zadeh

Capacitive sensors implemented in complementary metal-oxide-semiconductor (CMOS) technology are widely used in lab-on-chip (LoC), biomedical, and microfluidic systems. While most capacitive sensor interfaces are designed for high-resolution capacitance quantification, many practical applications require only binary decisions, event detection, or state discrimination. In such scenarios, conventional readout architectures introduce unnecessary circuit complexity, power consumption, latency, and data-processing overhead. This paper presents a CMOS cross-coupled-based capacitance detector (CBCD) that directly converts the imbalance between a sensing capacitance and a reference capacitance into a digital output. By exploiting regenerative positive feedback in a dynamic latch architecture, the proposed detector integrates sensing, comparison, and digitization within a single stage, eliminating the need for analog amplification, analog-to-digital conversion, frequency-based readout, and external thresholding circuitry. Circuit-level simulations show the ability to detect extremely small capacitance differences, demonstrate robust operation across a wide range of input capacitances, and achieve negligible power consumption. Process-corner, noise, and Monte Carlo analyses further verify reliable operation in the presence of device mismatch and process variations. Owing to its compact structure, digital-native output, and energy-efficient operation, the proposed CBCD is well suited for decision-driven sensing applications, including droplet presence detection, bubble monitoring, threshold-based diagnostics, event detection, and time-of-evaporation (ToE) measurements. The proposed architecture provides a scalable and low-complexity front-end solution for next-generation CMOS-integrated sensing platforms.

Micromachines doi: 10.3390/mi17080908

Authors: Afef Dhaffouli Paul E. D. Soto-Rodríguez Soledad Carinelli Houcine Barhoumi José Luis González-Mora Pedro A. Salazar-Carballo

An electrochemical sensor based on a novel composite of electrochemically reduced graphene oxide, polypyrrole-coated magnetic nanoparticles (MNPs@PPy), and Nafion was developed for dopamine (DA) detection. The structural, thermal, and electrochemical properties of the composite were validated through a combination of advanced spectroscopic techniques, thermal profiling, electron microscopy, and impedance analyses. Under optimized conditions, differential pulse voltammetry (DPV) revealed a high sensitivity (1.573 A·M−1·cm−2, R2 = 0.9874) and a limit of detection (LOD) of 5.4 × 10−9 M for DA. The sensor displayed excellent selectivity, showing minimal interference from ascorbic acid, uric acid, and acetaminophen. Repeatability and reproducibility were confirmed (coefficient of variation ~8%). Real-sample analysis of urine and blood demonstrated recovery rates between 75 and 116%.

Micromachines doi: 10.3390/mi17080906

Authors: Dohyeon Mun Jae-Young Bae

As the power and voltage of electric vehicles increase, the thermal stability of battery components, such as busbars, becomes critical. This study proposes a method for inorganic thermal insulation and insulating coating using alumina–silica hybrid particles deposited via electrophoretic deposition (EPD). We investigated the effects of copper substrate pre-treatment and the weight ratio of tetraethylorthosilicate (TEOS) to methyltrimethoxysilane (MTMS) on the quality of the coating. AFM analysis confirmed that a 1-min pre-treatment optimized surface roughness, which helped prevent cracks during the drying process. Among the various compositions tested, the sample with 30% TEOS demonstrated the highest thermal stability (670 °C) and dispersion stability (zeta potential of −15.5 mV), attributed to the increased density of the siloxane network. All samples maintained insulation performance up to 6.3 kV. These findings present an effective strategy for enhancing the fire safety of EV electrode materials.

Micromachines doi: 10.3390/mi17080905

Authors: Yuanyu Yu Xin Liu Jiujiang Wang Shuang Zhang Sio Hang Pun

Capacitive micromachined ultrasonic transducers (CMUTs) have been extensively investigated for applications in medical imaging and industrial non-destructive testing. However, their relatively low acoustic pressure output remains a major limitation to broader adoption. This paper proposes a CMUT structure that combines collapse-mode operation with a trenched membrane to enhance output performance. An analytical model based on von Kármán large-deflection plate theory is developed to estimate the optimal radial position of the trench, thereby defining the search space for subsequent Bayesian optimization. Single-parameter sequential Bayesian optimizations are first performed to identify the individual effects and optimal ranges of the trench’s radial position, depth, and width. Subsequently, a three-parameter global Bayesian optimization framework is employed for global parameter refinement. The three-parameter joint optimization reveals strong synergistic interactions among the design variables, achieving a higher output pressure of 72.34 kPa compared to 70.02 kPa from sequential approaches. Under identical operating conditions, the optimized trenched membrane CMUT exhibits a 100.15% increase in output acoustic pressure and a 28.77% improvement in the pressure-bandwidth product compared to a uniform membrane. Statistical analysis across multiple independent runs yielded a coefficient of variation (CV) of only 0.052% for the output pressure in the three-parameter global optimization results. This confirms that the proposed framework robustly optimizes CMUT designs for high output pressure, offering a promising technical approach to enhancing device performance.

Micromachines doi: 10.3390/mi17080904

Authors: Parnapalle Ravi Jin-Seo Noh

The development of efficient visible-light-driven semiconductor photocatalysts is essential for scalable and sustainable green hydrogen production. Among ternary metal oxides, MV2O6 (M = Zn, Ni, Cu, Mn, Co, etc.) metavanadates have attracted considerable interest because of their narrow band gaps (~1.8–2.5 eV), strong visible-light absorption, and unique edge-sharing VO6 octahedral framework that promotes charge separation. This review summarizes recent advances in the design, synthesis, and electronic engineering of MV2O6-based photocatalysts for solar water splitting. Since direct particulate overall water splitting has only been demonstrated for MnV2O6, whereas ZnV2O6, NiV2O6, and CuV2O6 have mainly been investigated as photoelectrodes, both particulate photocatalytic and photoelectrochemical (PEC) systems are critically examined. The review clearly distinguishes these two configurations, highlighting how PEC studies provide valuable insights into charge transport, interfacial processes, and reaction kinetics while recognizing the additional challenges associated with suspension-based photocatalysis. Fundamental crystal structures, electronic band alignments, and charge-transfer characteristics of MV2O6 compounds are discussed, followed by recent advances in synthesis strategies, including hydrothermal, sol–gel, and deep eutectic solvent (DES)-assisted methods, together with morphology and defect engineering. Particular attention is given to oxygen-vacancy formation and its influence on visible-light absorption and charge separation. Modification strategies, including elemental doping, cocatalyst loading, and the construction of Z-scheme and step-scheme (S-scheme) heterojunctions, are critically evaluated for improving photocatalytic efficiency. Finally, the review discusses the key challenges that limit practical applications, including unfavorable band-edge positions, rapid carrier recombination, sluggish surface reaction kinetics, photostability, and the need to establish composition–structure–activity relationships. Future perspectives emphasize rational materials design through advanced characterization, theoretical calculations, and scalable synthesis approaches to accelerate the development of efficient MV2O6 photocatalysts for solar-driven hydrogen production.

Micromachines doi: 10.3390/mi17080903

Authors: Joseph B. Bernstein

Bias Temperature Instability (BTI) remains one of the principal reliability challenges limiting advanced CMOS technologies. Although degradation is commonly described by an empirical power–law relationship, the power–law exponent is generally regarded only as a fitting parameter used for lifetime extrapolation. This Perspective reexamines a previously published Multiple-Temperature Operational Life (MTOL) dataset to investigate whether the measured exponent contains previously overlooked physical information. Individual ring oscillators stressed under identical voltage and temperature conditions exhibit substantially different, yet reproducible, power–law exponents. When these measurements are analyzed over a broader temperature range, the apparent statistical scatter reveals a systematic kinetic dependence that produces a remarkably consistent lifetime relationship after incorporating the experimentally measured exponent into the Arrhenius analysis. The resulting intrinsic activation energy is significantly smaller than values obtained using conventional extrapolation methods, suggesting that part of the apparent activation energy arises from neglecting the temperature dependence of the degradation exponent. A recently proposed thermodynamic formulation based on Gibbs free energy and correlation entropy is presented as one possible physical interpretation of these observations, in which the power–law exponent reflects the correlation between successive degradation events rather than merely an empirical fitting constant. More generally, this Perspective suggests that the power–law exponent should be regarded as a measurable kinetic quantity whose systematic variation may provide additional insight into degradation mechanisms in BTI and other reliability phenomena.

Micromachines doi: 10.3390/mi17080902

Authors: Mary Krystelle Catacutan Sungmun Lee Michael Pycraft Hughes

To survive, cells are able to adapt to a wide range of adverse conditions, such as varying pH from optimal (~7.4). They do this through mechanisms including acid-sensing ion channels, which alter cytosolic ion content and thus the cell’s electrophysiological profile. However, the impact of this adaptation on cellular electrophysiology remains unexplored. We investigated the effects of culture at a range of extracellular pH on the electrophysiological features of breast cancer cell lines MDA-MB-231 and MCF-7. Cells were subject to an acid–neutral–base pH from 3.0 to 9.2, after which their membrane potential (Vm), cytoplasm conductivity σcyto, effective membrane conductance Geff, and ζ-potential were measured. Cells were also analyzed after permeabilization, to examine whether observed changes were due to cell surface chemistry, or to Vm. Both cell lines exhibited different electrophysiological phenotypes in acidic environments (pH < 6.7); MDA-MB-231 exhibited statistically significant differences in ζ-potential, Vm, Geff and σcyto; MCF-7 only exhibited significant differences in σcyto. These findings suggest cells adapt to acidic microenvironments by altering Vm and potentially ζ-potential, reducing the extracellular potential, and hence potentially lowering proton concentration at the extracellular membrane surface. This offers new insights into potential therapeutic avenues to target the pH-dependent adaptations of cancer cells.

Micromachines doi: 10.3390/mi17080900

Authors: Xiaoqin Li Wanting Rong Diqun Yan Xiali Han Shanshan Wang Wenbo Zhang Hao Ye Xiangyu Li

To address the challenge that microelectromechanical system (MEMS) gyroscope electrostatic force-modulated closed-loop self-excited driving circuits experience significant dynamic variations in capacitive load and driving demand under different operating conditions, such as start-up, steady-state resonance maintenance, and environmental perturbations, making it difficult to simultaneously achieve strong driving capability, stable oscillation, and low power consumption, this paper proposes a high-energy-efficiency adaptive output operational amplifier architecture. Based on a dynamic load-sensing mechanism, the design introduces a three-threshold decision scheme combining a high threshold, a low threshold, and a mid-supply reference voltage. By coordinating a continuous-time voltage detection circuit with a bidirectional shift register, the proposed approach enables accurate identification of the output state and the load level. A time-division-multiplexed two-stage control strategy is adopted to rapidly compensate for the drive capability under abrupt load changes, while proactively disabling redundant output units under steady-state conditions, thereby achieving power delivery on demand. The output stage employs a Class-AB push–pull structure integrating an improved low-leakage single-pole double-throw (SPDT) switch, which hard shuts off the power transistors in the non-operating state to effectively eliminate the subthreshold leakage current. Circuit simulations in a 0.18 μm CMOS process demonstrate that the proposed operational amplifier can adaptively regulate its output current in real time according to variations in the gyroscope driving demand, ensuring sufficient an electrostatic driving force and oscillation stability during transient conditions while significantly reducing static power consumption during the resonance steady state. The proposed design provides an effective solution for high-performance and high-energy-efficiency interface circuit design in MEMS gyroscope electrostatic force-modulated closed-loop self-excited driving systems.

Micromachines doi: 10.3390/mi17080901

Authors: Youssef O. Al-Ghamdi Amani Chrouda Nicole Jaffrezic-Renault Hamdi Ben Halima

Glyphosate is among the most widely used herbicides worldwide, and its extensive application has led to increasing concerns regarding environmental contamination and potential risks to human health. The persistence of this compound in soil and aquatic environments has created an urgent demand for analytical methods that are rapid, reliable, and economically feasible. In the present study, a microconductometric sensing platform was developed for glyphosate determination using a PVC liquid membrane incorporating an [o-COSAN]⁻/glyphosate ion-pair complex deposited onto interdigitated electrodes. The proposed sensor provided a linear analytical response over the concentration range of 1.0 × 10⁻5 to 2.5 × 10⁻3 M, with a detection limit of 4 μM. The device also exhibited excellent analytical performance, with reproducibility and repeatability values of 3% and 8% (RSD), respectively. Furthermore, the sensor maintained stable performance for more than three months and showed a high degree of selectivity toward glyphosate when evaluated against potential interfering compounds, including AMPA and carbofuran. These results demonstrate the potential of the proposed sensing platform as a simple, sensitive, and cost-effective tool for glyphosate monitoring in environmental samples.

Micromachines doi: 10.3390/mi17080899

Authors: Shengsheng Wei Yina He Yipeng Wang Junqiang Wang Mengwei Li

High-g accelerometers are in high demand across sectors such as aerospace, defense, and industrial inspection. This paper presents a MEMS accelerometer based on graphene piezoresistors, designed for precise acceleration measurement under sudden impacts, intense vibrations, and extreme conditions, such as engine fault diagnosis and weapon impact testing. A step-by-step structural optimization and simulation analysis were conducted using finite-element simulation. Taking the peak strain at the beam root, the first-order natural frequency, and the maximum equivalent stress as optimization objectives, progressive parametric optimization was sequentially performed on four progressive architectures: a simple beam, a beam mass, a beam mass with stress concentration grooves, and a beam mass with stress concentration grooves and symmetric masses. The results indicate that the introduction of a central mass enhances the peak strain by more than 15 times compared to the simple beam. The addition of stress concentration grooves further increases the strain by approximately 30%. Finally, the incorporation of symmetric masses yields a further 9% strain enhancement while reducing cross-axis sensitivity by 5.6%, effectively suppressing off-axis interference. The final structure achieves maximized strain while maintaining a first-order natural frequency above 200 kHz, with the maximum equivalent stress staying within the allowable limit. This optimal comprehensive performance provides essential technical support for high-performance graphene-based accelerometers. In addition to the mechanical structural optimization, the graphene piezoresistors were treated as surface sensing regions at the beam-root locations, and the area-averaged longitudinal strain was extracted as the input of a piezoresistive transduction model. The simulated strain was converted to resistance variation and bridge output voltage using a graphene gauge-factor-based readout model incorporating contact-resistance effects, thereby providing a sensor-level electromechanical performance estimation for the proposed high-g accelerometer.

Micromachines doi: 10.3390/mi17080898

Authors: Jianxiang Wang Hongbin Chen Yu Zhang Jingmei Li Zhengyun Zhong Yue Li Yanzhang Yang Man Zhang Meng Zhang Wu Zhang Lip Ket Chin

Flexible capacitive sensors for electronic skins and soft robotic systems are expected to provide not only high-pressure sensitivity but also multifunctional sensing capabilities. However, conventional dielectric layer designs often suffer from a trade-off among multiple functionalities. To address this challenge, we developed a flexible sensor featuring a hybrid microstructured functional layer for pressure sensing, distance monitoring, and material identification. The functional layer was a polydimethylsiloxane (PDMS) film embedded with micro-sized sugar particles and patterned with microstructures on its surface. The pressure-sensing performance, such as pressing sensitivity, response time, and hysteresis, was first evaluated. The pressure sensitivity reached 3.55 × 10−2 kPa−1 at an applied force of 1 N, which is significantly greater than that of the sensor using either a flat PDMS layer or a PDMS film embedded solely with sugar particles. The hybrid microstructured sensor also exhibited superior performance in terms of hysteresis and repeatability. Moreover, the sensor was shown to measure the distance to an object with a sensitivity of 0.023 mm−1. Furthermore, the robust identification of materials with different permittivities was demonstrated using the flexible sensor. Given its multifunctional, non-contact, and high-sensitivity capabilities, this flexible sensor holds significant potential for integration into advanced electronic skins, intelligent soft robotics for tactile object sorting, and human–-machine interfaces.

Micromachines doi: 10.3390/mi17080897

Authors: Qiang Lai Junpeng Yao Yuyu Wu Bin Zhao Xiuying Sui Bing Xie Chunlei Liu Feng Wu

Deep complex carbonate reservoirs contain different types of pore space, including vugs and fractures. Their gas–water distributions and flow characteristics are complex. The effect of pore structure and gas–water flow on resistivity in deep complex carbonate reservoirs remains unclear. This uncertainty creates challenges for natural gas exploration and development. A gas–water displacement and impedance synchronous measurement platform was established. Three types of glass-etched micromodels were fabricated from CT images of real carbonate cores. These models included a fracture–vuggy type with large aperture, a fracture–vuggy type with small aperture, and a vuggy type. After the micromodels were saturated with dyed formation water, gas–water displacement and water–gas displacement were conducted sequentially. Microscopic images of gas–water distribution, water saturation, resistivity, and resistivity index were obtained. The results showed that gas preferentially entered connected fractures and large pore throats, forming preferential channels. Residual water was mainly retained in vug corners, narrow throats, and weakly connected zones. During gas–water displacement, resistivity increased as water saturation decreased. The resistivity response showed a three-stage pattern of slow increase, rapid increase, and subsequent slow increase. During water–gas displacement, resistivity decreased as water saturation increased. The resistivity response showed a three-stage pattern of slow decrease, rapid decrease, and subsequent slow decrease. All three models exhibited non-Archie behavior. The stage-specific saturation exponent n ranged from 2.62 to 13.10, 4.36 to 7.24, and 5.37 to 9.84 for the fracture–vuggy type with large aperture, fracture–vuggy type with small aperture, and vuggy type, respectively. Their overall n values were 7.26, 6.36, and 5.39, showing that the fracture–vuggy type with large aperture had the most abrupt electrical response. This study clarified the relationship between gas–water flow characteristics and conductive response in carbonate rocks with different pore structures. The results provide pore-scale experimental evidence for water-invasion identification, remaining gas evaluation, and calibration of rock electrical parameters in complex carbonate reservoirs.

Micromachines doi: 10.3390/mi17080896

Authors: Yikun Yang Chenyao Huang Jie Chen Yixian Xie Yuying Feng Xi Cao Zhengjie Guo Fuyueyang Tan Chuanjie Xin Zaijin Li Yi Qu Lin Li

High-power semiconductor laser diode arrays (LDAs) are pivotal for applications such as optical pumping, industrial manufacturing, and precision measurement, yet they face inherent bottlenecks in balancing high output power, superior beam quality, and stable phase synchronization. The Talbot cavity, leveraging the Talbot self-imaging effect, has emerged as a core external cavity technology to address these challenges, enabling global coupling and passive phase locking of LDAs. This paper systematically reviews the research progress of Talbot cavities in phase-locked LDAs under global coupling. It elaborates on the fundamental principle of Talbot-effect-based phase locking, along with the structural characteristics and working mechanisms of three typical Talbot cavity configurations: conventional Talbot cavities, V-shaped Littrow–Talbot cavities, and monolithic integrated Talbot cavities. Furthermore, it summarizes key experimental advancements of LDAs, covering diverse laser media (e.g., near-infrared, blue, terahertz, and mid-infrared antimonide lasers) and array scales ranging from a few to thousands of emitters, with representative performance metrics including far-field visibility up to 99%, narrowed spectral linewidths achieving 20–50 pm for blue LDA, and output power exceeding 200 W. Numerical simulation progress on supermodel stability and parameter optimization is also discussed. Finally, the current challenges, such as thermal crosstalk and integration complexity, are analyzed, and future prospects involving intelligent control and novel physical mechanisms are outlined. This review aims to provide a comprehensive reference for the further development and practical application of high-brightness phase-locked laser sources.

Micromachines doi: 10.3390/mi17080895

Authors: Yicun Zhu Bingsan Chen Yongchao Xu Hongping Liao Chunyu Li Shusheng Chen

Polycrystalline diamond (PCD) has broad application prospects in semiconductors, optical windows and other advanced fields. Nevertheless, its ultrahigh hardness and chemical inertness pose significant challenges for achieving high-quality surface planarization. Although conventional mechanical lapping is widely adopted, it still suffers from poor surface quality and a lack of theoretical guidance for process parameter selection. This study presents a systematic experimental and simulation investigation on both rough and fine lapping of PCD, focusing on tool selection and process optimization. In the rough lapping stage, three types of fixed diamond abrasive discs with resin, bronze, and vitrified bonds were compared. The soft and tough resin-bonded disc yields the best performance, reducing surface roughness Ra from 420 nm to 106 nm. In the fine lapping stage, three metallic discs—Cu, Fe, and WC-Co—were evaluated. The high-stiffness WC-Co disc achieves the best results, with an Ra of 11.2 nm under conditions of 0.45 MPa and 600 r/min. Molecular dynamics (MD) simulations further reveal that increasing lapping pressure significantly enhances the material removal rate but concurrently aggravates subsurface damage (SSD), while the effect of speed is considerably smaller. Therefore, pressure emerges as the key parameter that requires balanced optimization in the fine lapping process.

Micromachines doi: 10.3390/mi17080894

Authors: Chenguang Zhang Hong Yin Liang Shi Xuan Wen Zheng Ma Hanwu Jia

Single-event burnout (SEB) remains a persistent threat to SiC power MOSFETs in space, yet rapid evaluation of SEB susceptibility without costly heavy-ion campaigns is challenging. This work demonstrates that femtosecond laser two-photon absorption (TPA) can fill that role for a commercial 1200 V SiC MOSFET—provided the laser energy is correctly mapped to heavy-ion linear energy transfer (LET). We derive an equivalent LET model that incorporates the thermal spike effect, giving LET_eq = Γ1E02 + Γ2E04, which corrects the classical square law at high excitation intensities where it fails. Three ionization-driven failure signatures emerge: drain-to-gate and drain-to-source single-event leakage current (SELC), and SEB. The SEB threshold saturates near 500 V once LET exceeds 25 MeV·cm2/mg—roughly 42% of the device’s 1200 V rating. From these thresholds, we define a safe operating area: below 200 V is safe, 200–600 V risks SELC degradation, and above 600 V carries high SEB risk. Benchmarking against published heavy-ion data shows SEB threshold agreement within 15%, and within 5% at high LET. We stress that the TPA method captures ionization-driven effects only; it does not replicate displacement damage. These results support rapid, laser-based screening of SiC power devices for radiation hardness.

Micromachines doi: 10.3390/mi17080893

Authors: Xianli Tang Yonghao Jia Yuandong Gu

Surface acoustic wave (SAW) resonators are widely employed to design radio-frequency (RF) filters in wireless communication. To adapt to various application scenarios, the article proposes an equivalent circuit model based on the Butterworth–Van Dyke (BVD) model for SAW devices operating with spurious modes and at extreme ambient temperatures. In cases where the resonance frequencies of the spurious modes are close to those of the main mode, isolation capacitances (IC) are proposed in the modeling process. With the IC, the different resonance frequencies produced by the proposed equivalent circuit model can be flexibly adjusted. The extreme temperature influence on the SAW resonators is investigated using the proposed model. In the temperature-dependent test environment, the performance of the SAW devices changes, and these changes are captured by the proposed model. Especially for the resonators’ spurious-mode frequencies, which are less influenced by temperature near room temperature unless extreme temperatures are applied. The parameters motional resistance Rm and motional inductance Lm are considered temperature-dependent and are used to describe the influence of the ambient temperature. The RF characteristics of the SAW devices are modeled with the proposed model and verified with measurement data. The consistent results between the measured data and simulated data indicate that the proposed model is accurate and the modeling work is effective.

Micromachines doi: 10.3390/mi17080892

Authors: Mohamed Hamdaoui

Foot-worn electromagnetic harvesters are driven by irregular rigid-body motion, while their response is limited by mechanical stroke, coil geometry, mounting direction, and the electrical interface. This paper presents a reproducible numerical design study of a finite-stroke magnetic quasi-zero-stiffness (QZS) moving-magnet harvester. Two public three-axis foot-IMU records are processed with stated gyroscope-bias estimation, six-axis attitude estimation, gravity removal, residual-offset correction, filtering, and angular-acceleration calculation. Three explicit axes are used in the design screen, and the selected candidate is then evaluated over a 62-direction spherical grid. Rigid-body angular-acceleration and centripetal terms are included for specified sensor-to-harvester offsets. Two normalized magnetic force laws are compared. The electrical model uses position-dependent flux linkage, explicit series connection and polarity of coil sections, winding-derived resistance, and a position-dependent electromagnetic reaction force. A fixed-seed random screen evaluates 720 geometry-constrained candidates. The highest-ranked nominal candidate is a 150 mm external foot-worn module with a 40.6 g moving mass, a 30 mm hard half-stroke, 1649 turns in two series sections, and a 25.27 mm coil outer diameter. Across 72 design-screen cases formed from 12 five-second windows, three mounting axes, and two magnetic laws, this candidate remained hard-stroke- and design-stroke-safe. Its conditional ideal load-side power had a 10th percentile of 1.38 mW and a median of 2.03 mW. In the 62-direction check, all 1488 cases remained hard-stroke-safe; two opposite directions each produced one design-stroke exceedance, with a maximum displacement of 24.15 mm. Re-ranking all 30 Stage-2 candidates under coupling and magnetic-stiffness changes retained the long geometry family, although a 30% coupling reduction changed the highest-ranked candidate from 600 to 632. Soft-stop sensitivity, equation-level consistency, and multi-case Runge–Kutta convergence are also reported. The results support finite-stroke design screening, but they do not constitute prototype, finite-element, or delivered-power validation.

Micromachines doi: 10.3390/mi17080891

Authors: Cheol Woong Kim Geonwoo Park Hae June Lee

Low-damage plasma processing of atomically thin MoS2 requires simultaneous control of ion species, energy, and incident angle, yet the discharge mechanisms governing Ar/O2 plasma and their connection to surface damage remain insufficiently understood. Here, we investigate the effect of the Ar/O2 mixing ratio on the spatial distributions of charged particles, the plasma potential, and the substrate-incident ion energy and angular distributions in a low-voltage, single-frequency capacitively coupled plasma using a two-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) simulation. At a fixed pressure of 50 mTorr with the Ar/O2 ratio varied from 9:1 to 2:8, the ion energy and angular distributions were collected at the center and edge of the powered electrode. Increasing the oxygen fraction reduced the electron density while enhancing the O− density and electronegativity, driving an electropositive-to-electronegative transition near 8:2, and shifted the dominant positive ion from Ar+ to O2+, with O+ remaining minor owing to charge-exchange loss. The plasma potential and ion-energy peaks generally increased with the oxygen fraction but showed nonmonotonic dependence, while radial edge fields tilted and broadened the angular distributions. To link the ion and oxygen-radical fluxes to MoS2 processing without assuming uncertain surface-response coefficients, we interpreted the ion and oxygen-radical fluxes through a phenomenological two-channel surface-reaction scheme, introducing a damaging ion fraction and a radical-to-ion flux ratio. Their opposing trends reveal an intrinsic trade-off, indicating that an intermediate O2 fraction offers a more favorable low-damage window than either Ar-rich or strongly oxygen-rich conditions.

Micromachines doi: 10.3390/mi17080890

Authors: Yuanyuan Xie Lei Li

Ti-6Al-4V alloy possesses excellent specific strength, corrosion resistance, and biocompatibility, rendering it widely applicable in aerospace, marine engineering and biomedical fields. Selective laser melting (SLM) serves as an effective technique for manufacturing complex Ti-6Al-4V components. However, SLM-formed specimens generally suffer from surface defects such as high surface roughness, adhered powders, spheroidized particles, and localized spatter, which degrade their service performance and limit further practical applications. Therefore, effective surface modification is urgently required. This work systematically explores the synergistic effects of sandblasting at various angles followed by acid pickling on the surface characteristics of SLM-formed Ti-6Al-4V alloy. The SLM Ti-6Al-4V samples were first treated by sandblasting at different impact angles and then subjected to acid pickling. Material mass loss, micro-morphology, surface roughness, contact angle, surface microhardness, abrasive-particle embedment and surface residual stress were measured and analyzed. The results show that sandblasting angle exerts a remarkable influence on material removal behavior, abrasive-particle embedment and near-surface mechanical response. Scanning electron microscopy (SEM) observations indicate that sandblasting at different angles can not only effectively eliminate surface-adhered powders, but also generate impact pits, cutting grooves, and ploughing marks whose morphologies vary with sandblasting angles. The subsequent acid pickling process further removes loose particles and sharp protrusions, and promotes the formation of microscale surface structures. Benefiting from the combined effects of mechanical sandblasting and chemical acid pickling, the alloy samples exhibit substantially reduced surface roughness and enhanced surface wettability. Meanwhile, sandblasting induces work hardening and thus increases surface microhardness and surface residual stress, while acid pickling regulates surface morphology and the state of the work-hardened layer to a certain degree. Overall, this study provides an economical, efficient, and industrially feasible composite surface modification approach to reduce surface roughness, enhance hydrophilicity, and tailor surface hardness of SLM Ti-6Al-4V alloy.

Micromachines doi: 10.3390/mi17080888

Authors: Xinqing Li Tao Long Jun Zhao Shunmao Lu Yongguang Xiao Zheng Li

This study proposes and validates a unified geometry-based capacitance model for four representative silicon detector architectures: planar, 3D trench electrode, 3D spherical electrode, and silicon drift detector (SDD). Closed-form analytical expressions explicitly relate capacitance to key geometric parameters—anode radius, depletion thickness, electrode depth, and electrode spacing—and the resulting geometric scaling laws are rigorously verified by combining physical modeling, TCAD simulation, and experimental measurement. A central finding is that for highly symmetric structures, capacitance is governed almost exclusively by the radius of the collecting anode and is essentially independent of the overall detector volume, thereby defining an ideal low-capacitance limit. For the SDD, a hemispherical capacitor approximation accurately captures this anode-dominated behavior, and measurements on prototypes together with independent literature data confirm that the total capacitance can be decomposed into an intrinsic geometric component and a parasitic contribution. This work provides a unified framework and direct cross-structure design guidelines for minimizing capacitance toward ultra-low-noise, high-performance silicon detectors.

Micromachines doi: 10.3390/mi17080889

Authors: Xiangxin Cao Pengfei Wang Minhan Mi Xinyu Liu Dongxu Xiao Xiang Du Maoteng Lu Feiyang Chen Zhentong Huang Jingyun Yao Yinyin Liang Kehui Cui Xiaohua Ma Yue Hao

This paper proposed a high-efficiency thin-barrier gallium nitride (GaN) high electron mobility transistor (HEMT) with scaled gate-length (Lg) for millimeter-wave (mmW) frequency applications. A two-step etching process is adopted in this work, where an Ar-free etching was used for the secondary etching (SE) step. After partial etching of the Silicon nitride (SiN) passivation layer in the gate foot region, the Lg can be stably controlled at <100 nm, the root mean square (RMS) roughness of the AlGaN barrier layer is 0.248 nm, and the mobility degradation has been effectively suppressed. The fabricated device achieved a maximum drain current density (IDS.max) of 1644.2 mA/mm, a peak transconductance (gm.max) of 764.1 mS/mm, and a current collapse ratio of 4.7%. In addition, the current gain cutoff frequency (fT) of 105.4 GHz and maximum oscillation frequency (fMAX) of 154.4 GHz were obtained at drain source voltage (Vds) of 8 V. Furthermore, at 30 GHz, the fabricated device achieved a saturated output power density (Psat) of 4.4 W/mm and a maximum power-added efficiency (PAEmax) of 66.0%, with a significant improvement of 15.7% and 5.3% compared with the device fabricated by Ar-containing etching, demonstrating the superiority of the Ar-free etching approach.

Micromachines doi: 10.3390/mi17080887

Authors: András Szenes László Pothorcki Balázs Bánhelyi Mária Csete

Superconducting nanowire single-photon detectors (SNSPDs) were numerically designed by integrating periodic plasmonic structures onto hBN-protected superconducting BSCCO patterns to enhance absorptance. The numerical investigation of optimized nanocavity array (NCAI) and nanocavity trench array (NCTAI) SNSPDs has revealed that more than one-order-of-magnitude higher absorptance can be achieved at perpendicular incidence, compared to the corresponding meandered BSCCO pattern in a simple resonant optical cavity. The presented SNSPD designs are considerably improved via first and third quarter wavelength nanocavity resonances, as evidenced by the near-field maps and validated by the standard retrieval method. Although the NCAI-SNSPD exhibits a slightly larger absorptance, the NCTAI-SNSPD remains potentially competitive due to its smaller filling factor, which may be beneficial for reduced charge-crowding effect.

Micromachines doi: 10.3390/mi17080886

Authors: Shufan Li Yusuo Tian Yang Zhang Huatan Chen Wenwang Li Gaofeng Zheng Xiang Wang

Flexible electromagnetic actuators have attracted considerable attention for applications in soft robotics, adaptive manipulation, and human–machine interaction due to their fast response, large deformation capability, and inherent compliance. However, the concurrent application of high actuation performance and long-term cyclic durability remains a major challenge, particularly for liquid metal (LM)-based soft systems, where interfacial instability between LM conductors and polymer substrates often leads to performance degradation. In this work, we report a fabrication strategy in which patterned eutectic gallium–indium (EGaIn) liquid metal circuits are directly written onto electrospun graphene oxide/thermoplastic polyurethane (GO/TPU) nanofiber membranes. The incorporation of graphene oxide significantly enhances interfacial adhesion through hydrogen bonding interactions between oxygen-containing functional groups in GO and the native Ga2O3 layer on the LM surface, while the electrospun fibrous architecture further improves mechanical interlocking and structural stability. As a result, the fabricated actuator exhibits robust electromechanical performance, achieving a maximum bending deformation of 90° under a driving current of 0.8 A and maintaining stable operation over 2000 actuation cycles with negligible performance degradation. To further demonstrate its practical functionality, a soft robotic gripper was constructed based on the optimized actuator configuration. The gripper enables the stable grasping and lifting of objects with a weight up to seven times its own mass, while maintaining safe and compliant interaction with fragile objects. This work provides a simple yet effective strategy to simultaneously enhance actuation efficiency, interfacial stability, and mechanical reliability in LM-based GO/TPU flexible electromagnetic actuator systems, offering promising potential for next-generation soft robotic applications.

Micromachines doi: 10.3390/mi17080885

Authors: Agnieszka Urbańska Magdalena Pajączkowska Joanna Nowicka Julia Kensy Jan Kiryk Łucja Janek Rafał Wiench Dariusz Skaba Maciej Dobrzyński Jacek Matys

Bacterial fluorescence generated by endogenous fluorophores may provide an optical approach for monitoring microbial fluorescence responses. The aim of this study was to analyse temporal changes in the Hue parameter, defined as an image-derived component of the HSB colour space representing the dominant colour tone, and to characterize strain-associated fluorescence response profiles under 405 nm violet-light excitation. A total of 28 reference bacterial strains were examined. Each strain was inoculated at eight distinct locations on a separate BHI agar plate, yielding eight colonies per strain. At 24, 48, 72, 96, and 168 h of incubation, the same colonies were repeatedly exposed for 45 s to a 405 nm continuous-wave diode laser operating at 200 mW and imaged in a completely darkened room using an iPhone 14, a yellow emission filter, and fixed acquisition geometry. The JPEG images were converted to the HSB colour space in ImageJ software (version 1.54), and background-corrected Hue values were calculated for each colony as ΔHue = Hmean − Hmean_BG using the corresponding colony and agar-background regions of interest. A complementary qualitative visual assessment was performed, and aligned rank transform ANOVA was used to evaluate the effects of bacterial strain, incubation time, and their interaction. ΔHue values differed significantly between strains and across incubation time points, with significant strain × time interactions observed in both rod-shaped and coccal bacteria (all p < 0.001). Exploratory planned contrasts also showed differences between the predefined Gram-staining groups (p = 0.0002) and between rod-shaped and coccal bacteria (p < 0.0001); however, these comparisons do not establish independent effects of Gram status or cellular morphology. The recorded fluorescence signal was generally weak, although visible temporal changes occurred in selected strains, including Staphylococcus aureus ATCC 6538P and Proteus mirabilis PCM 543. Overlap between ΔHue distributions limited separation of some strains. Background-corrected Hue analysis enabled exploratory within-dataset monitoring of temporal fluorescence colour changes under the applied in vitro imaging protocol. However, the overlap between ΔHue distributions and the technical limitations of the imaging system preclude the use of ΔHue as a standalone bacterial identification or diagnostic parameter.

Micromachines doi: 10.3390/mi17080884

Authors: Jigarkumar Modi Ruizhi Jin Kejun Dong Gu Fang

The dynamics of active particles are increasingly being leveraged to design and control micro-robotic swarms. Local interactions play a crucial role in the phase transitions of active particles; how the combined effects of alignment, short-range repulsion, and boundary interactions regulate their packing structure and collective order with different confinement scales remains less systematically explored. In this study, we investigate the packing of active particles within a confined region, focusing on the role of local interaction rules in shaping both the packing structure and the polar order parameter. The effects of key controlling variables related to local interaction rules, including interaction radius, repulsion radius, confined boundary radius, and noise strength, are numerically studied. Specifically, by comparing systems with and without velocity–alignment interactions, we reveal the role of alignment in dictating both structural and dynamical properties of the ensemble. To quantify the packing structure, we employ Voronoi tessellation to evaluate both local and global packing densities. The results show that strong confinement induces a jammed state in which alignment effects are suppressed, resulting in high global packing density and low polar order, regardless of the noise amplitude. Upon increasing the boundary radius beyond a critical threshold, the system unjams, enabling alignment interactions to significantly enhance both the polar order parameter and packing density. Interestingly, the relationship between global packing density and micro-structural parameters, such as coordination number and Voronoi tessellation metrics, is similar in the systems with and without alignment. Our results demonstrate that collective packing and phase behaviour of active matter are governed by the nontrivial interplay between alignment, confinement, and noise, with alignment interactions driving the transition from disordered to ordered states as geometric constraints are relaxed, offering critical insights for the design of targeted micro-robotic swarms and active microfluidic sorting systems.

Micromachines doi: 10.3390/mi17080883

Authors: Feng Zhao Wentao Huang Jianguo Liao Xiaodong Chen Fengchen Zhai Xueyan Chen

Displacement magnification (DM) is one of the key indicators to measure the performance of a micromanipulator. Based on the principle of triangle amplification, a series of three-stage displacement amplification (DA) micromanipulators is designed in this paper, which is driven by a piezoelectric actuator. The mechanism is composed of a compound rhombus mechanism, a bridge mechanism and two parallelogram mechanisms. The compound rhombus mechanism is located at the front end and has high stiffness characteristics. The bridge mechanism is located at the back end and is connected to the parallelogram mechanism to realize the parallel output of the clamping end. The DM model of the mechanism is established. On this basis, the structural size optimization design is carried out. With the goal of maximizing the DM, the key geometric parameters such as the thickness and length of the hinge and the section size of the key rod are selected as the design variables. Considering the constraints of material strength and input stiffness, the parameters of the micromanipulator are optimized. The correctness of the optimization method is verified by finite element simulation and experimental test. The results show that the DM of the optimized micromanipulator is significantly improved under the premise of maintaining sufficient stiffness, which can effectively guide the performance improvement and structural design of the micromanipulator.

Micromachines doi: 10.3390/mi17080882

Authors: Changde He Shuo Liu Hanchi Chai Dandan Li Chengrui Liu Wanjia Gao Yuhua Yang Licheng Jia Guojun Zhang Renxin Wang Jiangong Cui Wendong Zhang

To address the need for bubble detection in industrial silicone sealing rings, this paper presents a compact non-invasive ultrasonic monitoring system based on a capacitive micromachined ultrasonic transducer (CMUT) array, aiming to overcome the limitations of conventional X-ray inspection in terms of safety, portability, and real-time in situ monitoring. The system comprises two 8.8 mm × 8.8 mm CMUT arrays with associated transmitting and receiving circuitry. The silicone thickness is determined using the time-of-flight (TOF) method, while bubble size is quantitatively estimated by combining received signal amplitude analysis, which characterizes bubble-induced attenuation, with correlation function evaluation. Experimental measurements on industrial-grade silicone samples and finite element simulations demonstrate that the system achieves a spatial resolution of 0.5 mm and effectively captures attenuation variations caused by bubbles. The integrated strategy of TOF, amplitude analysis, and correlation assessment ensures reliable non-destructive evaluation. Compared with X-ray inspection, the proposed system is safer, more portable, and suitable for real-time on-site monitoring, thereby significantly improving quality control efficiency in silicone manufacturing. This study provides a novel CMUT-array-based solution for quantitative bubble detection in silicone media, offering both high resolution and practical application potential.

Micromachines doi: 10.3390/mi17080881

Authors: Jiawei Mei Jin Tian Huanzong Ke Yikang Liang

Owing to its infinite shelf-life under ambient conditions, satisfactory recyclability, and great reparability, carbon fiber-reinforced polyphenylene sulfide (CF/PPS) has been increasingly applied in the near-net-shape manufacture of high-value components. Longitudinal torsional ultrasonic vibration-assisted milling (LTUVAM) shows strong potential as an advanced processing technology for the efficient precision machining of composites. However, studies and models on the explanation of LTUVAM of CF/PPS composites seem to be missing in the literature. This paper proposes a finite element analysis method for LTUVAM of UD-CF/PPS processes. The kinematic analysis of the LTUVAM is proposed first, then the mechanism of surface formation during UD-CF/PPS milling process is provided. A simulation method which could simultaneously achieve both longitudinal and torsional vibration motions is introduced in the finite element model, enabling the simulation of LTUVAM of UD-CF/PPS composites. The experimental validations were conducted under both CM and LTUVAM conditions with three different cutters, demonstrating that cutting force simulations have significant agreement with experimental data, and both simulation and experiment indicate that LTUVAM produces superior surface quality compared to CM; the fiber debonding at the microscopic level could be eliminated and the height of machined surfaces could be significantly reduced when LTUVAM is utilized. These findings could also open avenues for clarification of other scientific queries such as cutting parameters optimization, cutting tool selection, and modeling of the UD-CF/PPS drilling process.

Micromachines doi: 10.3390/mi17080880

Authors: Seungmin Song JunHyeong Park JungBeen Cho Seyeon Tak Taehun Kim Kyungtaek Min Sung-Nam Lee

Silk fibroin (SF) is a promising bio-compatible material for transient and bio-integrated memory devices; however, its relatively high leakage current and limited resistance state stability remain critical issues. In this study, Ag/SF–TiO2/Pt bio-memristors were fabricated using SF–TiO2 composite films with TiO2 nanoparticle concentrations of 0, 0.25, 0.5, and 1.0 wt%. SEM analysis showed that TiO2 incorporation increased particle aggregation while maintaining continuous film morphology. Optical analyses revealed that TiO2 nanoparticles reduced the apparent optical gap, enhanced sub-bandgap absorption, and suppressed photoluminescence intensity, indicating the formation of defect- and trap-related states. Electrical measurements demonstrated that TiO2 incorporation effectively reduced leakage current and stabilized the high-resistance state. The devices exhibited stable bipolar resistive switching within ±1 V, with enhanced Ion/Ioff ratios of approximately 104–105 after TiO2 addition. Endurance and retention measurements confirmed reliable switching over 100 cycles and stable resistance states up to 104 s. Capacitance analysis further revealed resistance state-dependent charge storage behavior, with higher capacitance in the low-resistance state due to conductive filament formation and TiO2-assisted interfacial polarization. These results indicate that TiO2 nanoparticles effectively modulate charge trapping, leakage suppression, and memory stability in SF-based bio-memristors.

Micromachines doi: 10.3390/mi17080879

Authors: Zhao Liu Hu Yang Haotong Ma

Acoustically levitated thin reflective plates provide a promising approach for contactless optical beam steering by eliminating mechanical hinges, sliding interfaces, and the associated wear and friction losses. However, unlike conventional spherical particles or droplets, thin planar reflectors exhibit highly geometry-dependent acoustic force distributions and are highly susceptible to lateral drift and angular destabilization when the acoustic field is dynamically reconfigured for beam steering. Here, we present a theoretical and simulation-based stability analysis of an acoustically levitated thin reflective plate driven by a phase-controlled dual-array acoustic field. A reduced-order model based on the Gor’kov potential is developed to characterize the acoustic potential landscape, escape-barrier depth, and local restoring stiffness during phase-gradient-induced mirror tilting. The simulations reveal that increasing the phase gradient progressively distorts the trapping potential and reduces the available trapping stability margin. Among the translational degrees of freedom, the lateral restoring stiffness deteriorates much more rapidly than the axial stiffness, indicating that lateral slippage is the primary instability pathway during continuous steering. Parametric analysis further shows that thinner mirrors with larger radii can improve trapping stability by increasing the effective acoustic interaction area while reducing gravitational and inertial penalties. The influence of non-ideal acoustic driving conditions is also evaluated to determine practical operating limits for stable operation. These results clarify the stability mechanisms governing acoustically suspended planar reflectors and provide theoretical design guidelines for robust contactless optical beam-steering systems.

Micromachines doi: 10.3390/mi17080878

Authors: Xinyi Qiu Xiaxia Cui Yiqing Liu Hui Liu Biao Cheng Jiahan Zhang Qiang Tang

Open-surface coalescence of microdroplets is essential for droplet-based microreactors, emulsion processing, and multiphase microfluidics, yet existing methods often require closed channels or patterned electrodes. Here, we report a corona-driven open-oil-film platform that achieves voltage-regulated coalescence of aqueous microdroplets in a simple needle–plate electrode configuration. Positive corona discharge induces coupled electrohydrodynamic effects—including ion transport, interfacial charge redistribution, and Maxwell stresses—that drive oil-film contraction and charge-regulated droplet bouncing, thereby reducing inter-droplet spacing and promoting successive merging. The coalescence rate and final droplet size are tunable via the applied voltage and oil volume: complete coalescence into a single droplet is achieved at 12 kV, and an optimal oil volume of 60 μL maximizes confinement efficiency. To enable quantitative, frame-by-frame analysis, we develop an improved YOLOv5–OC-SORT framework that yields an overall mAP@0.5 of 0.905 for automatic droplet detection and tracking. As a proof-of-concept, the platform achieves electro-demulsification of a surfactant-stabilized water-in-oil emulsion, increasing the average droplet diameter from ~0.005 mm to ~0.2 mm and enabling effective oil–water separation. This work provides a simple, electrode-pattern-free strategy for controllable droplet coalescence and open-surface emulsion breaking.

Micromachines doi: 10.3390/mi17080877

Authors: Meryem Altay Hakan Aydın Adem Karşı

This study investigates the effects of powder type and layer-dependent energy input on the structural and mechanical performance of multi-layer laser cladding applied on FGS600-3A ductile cast iron. Three cladding powders (Ferro 55, Castolin 16604, and Metco 41C) were deposited under constant and variable energy input to examine the effects on macrostructure, porosity, microhardness, residual stresses, and thermal history. The results demonstrate that powder composition plays a decisive role in deposition quality. Ferro 55 exhibited the lowest porosity and the most favorable hardness distribution, whereas Metco 41C had high porosity, low hardness, and severe transverse cracking. Castolin 16604 displayed intermediate performance with deeper high-hardness penetration. Layer-dependent energy strategies improved porosity and hardness behavior for Ferro 55 and Castolin 16604; however, excessively low energy input limited hardness depth. Residual stress measurements revealed low stress levels for Ferro 55, compressive stress for Castolin 16604, and high tensile stress for Metco 41C, correlating strongly with cracking tendency. Overall, Ferro 55 and Castolin 16604 were identified as suitable candidates for multi-layer repair and surface modification of cast iron molds, while Metco 41C demonstrated limited applicability due to its porosity, hardness, and stress characteristics. This study emphasizes the importance of layer-specific parameter optimization to achieve defect-free and mechanically strong laser cladding.

Micromachines doi: 10.3390/mi17080876

Authors: Xiaocheng Zhu Oleksii Cherkun Jie Xu Zhan Hu Bin Wang Haiying Hu Zhiming Cai Bin Guo

Micro-Newton cold-gas thrusters are promising actuators for precision space missions, but their performance is strongly influenced by the integrated head architecture. This study presents the design, fabrication, and experimental validation of a piezoelectrically controlled cold-gas microthruster head for space-based gravitational-wave detection missions. The proposed head integrates a cone-needle throttle, a micro-orifice interface, and a downstream micro-nozzle, thereby converting actuator displacement into a regulated mass flow and ultimately into thrust. One-dimensional theory was first used for preliminary sizing, and Direct Simulation Monte Carlo (DSMC) analysis of the complete throttle-nozzle geometry was then applied to determine the final design parameters under rarefied-flow conditions. The selected design uses a throat radius of 29 μm and a needle half-angle of 10 degrees. Following fabrication and structural characterization, the integrated device was validated through mass-flow calibration and vacuum thrust testing. The experimental results show that the pressure-decay-based calibration provides a consistent mapping between actuation command, calibrated flow rate, and thrust output. The measured flow–thrust relation preserves the high linearity predicted by simulation, while the experimentally evaluated specific impulse meets the specified design target over the tested range. In addition, thrust-resolution testing at a baseline thrust of approximately 98.4 micro-Newton demonstrates a minimum resolvable step of 50 nano-Newton, and the measured thrust-noise amplitude spectral density remains below 0.07 micro-Newton/sqrt(Hz) over the 10 mHz–1 Hz band for the tested thrust levels. These results support the feasibility of the proposed integrated cold-gas microthruster head and its device-level validation approach for future space-based gravitational-wave detection applications.

Micromachines doi: 10.3390/mi17080875

Authors: Jing Zhao Wanting Wei Haotian Zheng Qiyuan Cao Limei Ma Jiankang Wang

Controllable Electrolyte Distribution Electrochemical Machining (abbreviated as CED-ECM) is a novel ECM method for shallow groove (with a depth of about several μm to tens μm) fabrication on precision metal surfaces. Rapid and accurate detection of CED-ECM-processed grooves is essential for quality control and automated production cycles. However, these grooves exhibit minute scale, irregular morphology, and low contrast against the metallic background, while grayscale microscopic imaging provides only single-channel information. To address these challenges, this research proposes a lightweight instance segmentation network based on pseudo-multimodal wavelet network (abbreviated as PMW-YOLO). First, a pseudo-multimodal channel fusion strategy expands single grayscale images into three complementary channels: original grayscale, CLAHE-enhanced grayscale, and multiscale Sobel gradients. This design explicitly injects illumination robustness and edge priors without additional acquisition cost. Second, a Discrete Wavelet Transform-based downsampling module, termed DWTDown, is integrated into the backbone to preserve high-frequency edge details while reducing model parameters and GFLOPs. Ablation studies further investigate the contributions of an Efficient Multiscale Attention module, a boundary-aware mask loss, and data-centric augmentation strategies. Experiments on an in-house CED-ECM dataset validate the effectiveness of PMW-YOLO for automated groove inspection.

Micromachines doi: 10.3390/mi17080874

Authors: Mohammad Abdul Alim Christophe Gaquiere

We examine the bias- and temperature-dependent direct current, radio frequency, and equivalent-circuit characteristics of a 150 nm AlGaN/GaN/SiC high-electron-mobility transistor (HEMT) for high-frequency applications. DC and S-parameter measurements on the wafer were conducted under various gate-bias settings within a varying thermal condition (−40 °C to 150 °C). The findings suggest a distinct decrease in drain current and transconductance with rising temperature, mostly attributed to heightened carrier dispersion and self-heating effects. At Vds = 15 V, the Ids decreases from 247.63 mA at −40 °C to 142.94 mA at 150 °C. The maximum transconductance decreases from approximately 56.5 mS to 31.5 mS. The assessed thermal resistance varies from 6.3 °C·mm/W to 11 °C·mm/W, signifying an increasing thermal limitation at elevated temperatures. The device has a point at which the temperature coefficient is zero at Vgs = −7.0 V, where the threshold-voltage shift and mobility degradation counterbalance one another. Small signal investigation indicates that ft decreases from approximately 53 GHz to 39 GHz, whereas fmax declines from 107 GHz to 74 GHz within this temperature range. The derived equivalent-circuit characteristics demonstrate the temperature sensitivity of intrinsic capacitances, resistances, transconductance, and delay components, but extrinsic capacitances and inductances exhibit comparatively lower temperature sensitivity. The measured and modeled S-parameters are in strong agreement, hence validating the extraction methodology. The findings may serve as valuable guidance for bias optimization and thermally conscious RF circuit design with GaN HEMT technology.

Micromachines doi: 10.3390/mi17070873

Authors: Siyao Luan Guoqing Ren Jinghao Liu Jiru Xian Xin Ma Xiaoyi Li

Accurate ocean wave sensing in polar and other low-temperature marine environments is of great significance for marine environmental observation, climate research, and navigation safety. However, conventional wave sensors rely on external power supplies and suffer from poor stability under low-temperature and high-salinity conditions, making long-term self-powered waves sensing a significant challenge. Herein, a highly stable composite eutectogel electrode is developed by integrating sodium lignosulfonate, Fe3+ crosslinking, Zn2+-carboxylate coordination interactions, and a choline chloride/urea deep eutectic solvent (DES). The DES effectively suppresses solvent crystallization and endows the gel with excellent low-temperature tolerance, while the synergistic effect of metal coordination and multiple non-covalent interactions constructs a robust ion-conducting network with enhanced structural stability. Furthermore, eutectogel-based composite electrode architecture is designed to improve electrical conductivity and charge collection efficiency, thereby enabling stable electrical output under harsh marine conditions. Based on the as-prepared eutectogel electrode, a self-powered solid–liquid triboelectric nanogenerator is fabricated for ocean wave-motion sensing. The device can detect the wave amplitude, with an accuracy of 0.2 cm, and sense the frequency of waves ranging from 0.2 Hz to 1.6 Hz. More importantly, the SL-TENG exhibits excellent environmental adaptability, operating reliably in 3.5 wt% simulated seawater and at 0 °C. The current retention ratio reaches approximately 91% at 0 °C, which is significantly higher than that of the hydrogel-based device (≈6%). The remarkably low-temperature and salt-tolerant performance originates from the stable ion-transport network and anti-freezing characteristics of the eutectogel electrode. This work provides an effective strategy for constructing environmentally resilient eutectogel-based triboelectric devices and offers a promising route toward self-powered wave sensing systems for long-term deployment in harsh marine environments.

Micromachines doi: 10.3390/mi17070872

Authors: Bo Huang Pengyue Zhao Liang Qiao Ruihan Li Meng Li Shuhan Peng Huan Liu

This study investigates the material removal mechanism and the evolution of subsurface damage (SSD) in single-crystal silicon during ultra-precision machining using molecular dynamics (MD) simulations. A three-dimensional MD model was established by employing Tersoff and Morse interaction potentials to evaluate the effects of different cutting strategies on cutting response, stress distribution, surface morphology, and defect evolution. The results show that the multi-pass cutting strategy effectively reduces the mean cutting force and suppresses severe stress concentration regions exceeding 7 GPa. This improvement is mainly attributed to the progressive release of residual stress and the more gradual removal of material during successive cutting passes. The formation of SSD is dominated by lattice distortion and amorphous phase transformation, both of which are closely associated with localized high von Mises stress beneath the machined surface. Further analyses of surface morphology and defect density indicate that a multi-pass strategy with a single-pass cutting depth below 1 nm provides a favorable balance between machining efficiency and surface integrity. These findings provide atomistic insights into damage suppression and process optimization for the ultra-precision machining of brittle semiconductor materials.

Micromachines doi: 10.3390/mi17070871

Authors: Chong-Zhi Han Zhanhong Qiu Jun Xiao Pengyu Zhang Wei He Ziji Zhang Lu Liu

In this paper, a tri-band omnidirectional shark-fin antenna for vehicular communications is proposed, which can cover three operating bands: Ultra High Frequency (UHF, 400–470 MHz), LTE Band 5 (824.2–879.2 MHz), and LTE-1800 (1765–1880 MHz). The antenna integrates a central UHF monopole and a pair of symmetric printed radiating elements within a compact shark-fin radome. The printed elements excite independent resonant modes in each band by using T-shaped and I-shaped radiating branches; broadband matching and balanced excitation are realized through a tapered impedance transformation network; and a dual-band array configuration is adopted to improve gain and stabilize radiation patterns. The monopole and printed elements form a collaborative array in a limited space, achieving structural miniaturization while obtaining good isolation and omnidirectional radiation characteristics. Results show that the peak gain of the antenna is 2.3 dBi in the UHF band and 7.2 dBi in the LTE-1800 band, and the isolation is better than 10 dB. The measured results are consistent with simulations, verifying the feasibility of the proposed design for application in high-performance vehicular communication systems.

Micromachines doi: 10.3390/mi17070870

Authors: Wei Xu Changxu Qu Mingzhao Xing Tingting Hao Jian Hao Zheng Zhao Jing Wang

Ce-modified MnCo2O4 flower-like nanosheet electrodes were prepared on nickel foam by a hydrothermal-calcination route and sequentially optimized with respect to reaction time, nominal Ce content, and PVP addition. Comparative SEM, XRD, XPS, and N2-sorption analyses identify MnCo2O4-9 h-3%Ce-PVP as the optimized electrode, with an open hierarchical nanosheet network and a BET surface area of 210.0 m2 g−1. The direct XRD/XPS control comparison distinguishes Ce-associated lattice and surface-state changes from PVP-associated synthesis effects without treating either trend as proof of substitutional Ce occupancy or quantitatively established oxygen vacancies. Likewise, PVP is treated as a morphology-directing additive whose transient adsorption or bridging role remains a synthesis hypothesis rather than a directly verified molecular mechanism. The optimized positive electrode delivers 2008 F g−1 at 1 A g−1, retains 1227 F g−1 at 20 A g−1, and shows 99.0% capacitance retention after 10,000 cycles at 5 A g−1. A carbon-supported iron oxide negative electrode, designated C/Fe2O3 only as a sample label because its exact oxide phase was not independently resolved by XRD or Raman spectroscopy, provides 443 F g−1 at 1 A g−1. The resulting charge-balanced asymmetric device operates over 0–1.6 V and delivers 34.6 F g−1 at 1 A g−1, corresponding to 12.30 Wh kg−1 at 0.8 kW kg−1. At 10 A g−1, it retains 29.8 F g−1 and delivers 10.60 Wh kg−1 at 8.0 kW kg−1, equivalent to 86.1% capacitance retention over a tenfold increase in current density. All device-level gravimetric values are calculated using the total active mass of both electrodes.

Micromachines doi: 10.3390/mi17070869

Authors: Lin Fa Jinyue Li Huiting Yang Yulin Xu Hongyi Zhu Xiangrong Fang Xiao Zou Ning Shen Meishan Zhao

Accurate measurement of attenuation during acoustic wave propagation in viscoelastic solid media is of theoretical and practical significance. Conventional studies primarily rely on analogies to models of electromagnetic wave attenuation in non-ideal media. Many modern models of acoustic attenuation rely on continuum mechanics and complex material properties. Although there are similarities between acoustic and electromagnetic waves, conventional models overlook their fundamental physical differences and neglect the influence of particle-vibration damping in viscoelastic media. Additionally, in applications with a single-transmitter and dual-receiver configuration, the effects of specific characteristics on the measurement of the acoustic attenuation coefficient are eliminated in both the electric–acoustic conversion of the transmitting transducer and the acoustic–electric conversion of the receiving transducer. The discrepancies in geometric parameters (size and shape) between the two measurement modules lead to inconsistent frequency responses, thereby introducing measurement errors in acoustic attenuation. To address these issues, we investigate the coupling mechanism between particle vibration damping and wave propagation attenuation, derive an analytical expression for the acoustic attenuation coefficient that accounts for this coupling, and propose a new method for accurately measuring acoustic attenuation in viscoelastic solid media. The experimental results validate the theoretical predictions of acoustic attenuation.

Micromachines doi: 10.3390/mi17070868

Authors: Yves Janssens Erwin Berenschot Minh Nguyen Niels Tas

Barium-doped Lead Zirconate Titanate Pb0.9Ba0.1(Zr0.53Ti0.47)O3 films with a (001)-dominant orientation were deposited on bulk silicon (Si) substrates using pulsed laser deposition (PLD). Due to the large electromechanical coupling coefficient (K2) of the P(B)ZT layer and the larger shear modulus of the Si substrate compared to the P(B)ZT film, it is possible to obtain higher-order acoustic-resonant modes (Sezawa mode) with SAW wavelength (λ)–piezoelectric film thickness (h) ratios below h/λ < 0.2. Due to the ferroelectric properties of the P(B)ZT film, the resonator’s performance can be improved by increasing the electric polarization. Consequently, the measured quality (Q) factors can be improved from 50 to 200 and the K2 values can be improved from 2 to 5% with the resonance frequency ranging from 275 to 500 MHz.

Micromachines doi: 10.3390/mi17070867

Authors: Faroug Ismael Pengfei Sun Yihe Liu Honghao Li Yufei Gao

Sapphire crystal, owing to its high hardness, chemical inertness, thermal stability, optical transparency, and superior dielectric strength, as well as resistance to scratching, abrasion, friction, and wear, is widely utilized in a broad range of engineering applications. Slicing is the most critical step in sapphire industry processing, as it largely dictates the final surface quality and morphology. Conventional wire sawing methods often lead to undesirable surface defects, while ultrasonic-assisted diamond wire sawing (UADWS) offers potential advantages through enhanced abrasive self-sharpening, micro-hammering, and improved lubricant penetration. However, its influence on sapphire slicing remains insufficiently studied. This study investigates the effects of UADWS parameters—ultrasonic amplitude, horn application position, feed speed, and wire speed—on the surface quality of sapphire crystals. Both single-factor and orthogonal five-level experiments were designed, taking wire and feed speed within industrial parameter ranges. Surface roughness (Ra) and waviness peak–valley (PV) difference were used as evaluation indices, and range and variance analyses were performed. In addition, power regression models were developed to predict Ra and PV under varying conditions. The surface morphology results from single-factor experiments reveal that increasing feed speed and wire speed reduces the effectiveness of ultrasonic assistance, while application horn position exerts only a minor influence. Overall, orthogonal analysis confirmed that the relative influence of process parameters on surface quality follows the order: feed speed > wire speed > amplitude > application horn position. These findings establish a foundation for optimizing the sawing and ultrasonic parameters of UADWS to enhance sapphire surface quality, reduce downstream processing requirements, and clarify the importance of controlling feed speed and wire speed.

Micromachines doi: 10.3390/mi17070866

Authors: Zengyan Zhu Dayang Wang Yan Li

The accurate measurement of solid concentration in horizontal gas–solid flows is very important to guarantee production efficiency and process control. However, gravity causes uneven particle distribution, which creates a strong nonlinear relationship between sensor signals and solid concentration. When particle distribution changes, a single linear measurement model cannot provide enough detection accuracy. This paper proposes an adaptive model matching strategy for solid concentration measurement in horizontal gas–solid flows by using array capacitive sensor. The array capacitive sensor works with two excitation modes. The concave-ring excitation mode collects particle distribution information, and the multi-electrode excitation mode obtains solid concentration. These two types of signals build a dynamic matching relationship between particle distribution features and measurement models. In detail, signals from concave-ring excitation are input into the BP-Adaboost algorithm to classify particle distribution states. Multiple linear measurement models between multi-electrode signals and solid concentration are built through K-means clustering. After recognizing the particle distribution type, the Euclidean distance is used to automatically select the corresponding measurement model. A 3D simulation model combining gas–solid two-phase flow and electrostatic field is set up to test the feasibility of the proposed measurement method. Laboratory experiments are also conducted to prove its reliability. The test results show that the method can adapt well to various particle distribution states. Within the solid concentration range of 0.34–14.08%, the average relative measurement error is 4.41%. This method effectively improves the measurement accuracy of solid concentration in horizontal gas–solid two-phase flow.

Micromachines doi: 10.3390/mi17070865

Authors: Ping Li Chen Yan Liangchen Lu Haoyu Wang Wenxuan Shi Yiping Han

Based on generalized Lorenz–Mie theory (GLMT) and the Maxwell stress tensor (MST) method, this study investigates the modulation mechanism of the axial optical torque Nz exerted on Cs2AgBiBr6 (CABB) perovskite-coated gold nanospheres under vector Bessel-beam illumination. The results show that the CABB shell reconstructs the torque-resonance channels of the coated particle by modifying both the dispersive dielectric environment around the gold core and the core–shell interfacial response. As the shell thickness increases, the dominant response undergoes a continuous redshift. The polarization state, half-cone angle α0, and order l of the incident vector Bessel beam serve as external optical-field degrees of freedom that regulate the incident angular-momentum channels, thereby enabling coordinated control over the torque peak magnitude, spectral line shape, and torque direction. Analyses of the near-field distributions, Poynting-vector distributions, and Mie-order decomposition reveal that the strong torque response arises from selective coupling between the intrinsic Mie channels of the core–shell particle and the vectorial structure of the incident light, rather than simply from local field-intensity enhancement. This study provides a theoretical basis for tunable Nz responses in perovskite–plasmonic hybrid nanostructures and for structured-light-driven rotational manipulation at the nanoscale.

Micromachines doi: 10.3390/mi17070864

Authors: Junlin Wu Yanqing Luo Junzhe Hu Shirong Li Sen Cai Tiedong Cheng Ping Zhang Pei Li Shengkun Jiang Ziqiang Liu Guitai Wu Sergey Mikhailovich Kopytov Jin Yang

With the advancement of High-NA EUV lithography and the continued evolution of transistor architectures toward GAA and CFET, semiconductor manufacturing has entered the sub-3 nm technology node era. At advanced nodes, photon shot noise becomes increasingly significant, while the process tolerance window narrows substantially. Photoresist film-formation-related defects may originate from multiple stages of the fabrication process, including coating, exposure, post-exposure bake, development, and etching/stripping, and are strongly influenced by microscopic stochastic effects. However, the isolated optimization of materials, processes, or intelligent control strategies still suffers from significant limitations. Therefore, this review systematically examines the formation mechanisms and cross-process evolution of photoresist film-formation-related defects within the development trajectory of advanced lithography. An integrated materials–process–intelligence co-optimization framework is proposed to elucidate the coupling mechanisms among these three dimensions and the construction of a full-chain closed-loop control strategy. The current challenges and future development directions are summarized, providing optimization insights for both academic research and industrial implementation. This review aims to establish a defect-control framework integrating fundamental understanding with engineering considerations, thereby supporting low defectivity, high robustness, and improved manufacturability for sub-3 nm node patterning.

Micromachines doi: 10.3390/mi17070863

Authors: Hsuan-Yu Chen Chiachung Chen

Portable sensing systems are increasingly important in biological and chemical analyses because they can provide analytical information at the point of decision-making. While traditional laboratory methods remain crucial for reference measurements, regulatory validation, and high-precision quantification, portable systems emphasize rapid response, convenience, cost-effectiveness, robustness, and relevance to decision-making. This paper views portable sensing systems as integrated analytical platforms rather than isolated sensing elements. The paper discusses recognition elements, including enzymes, antibodies, nucleic acid probes, aptamers, molecularly imprinted polymers, nanomaterials, and hybrid recognition interfaces, as well as electrochemical, optical, mass-sensitive, thermal, field-effect, and hybrid sensing technologies. Furthermore, this paper reviews platform designs, including paper-based analytical devices, chip lab systems, smartphone-assisted sensors, wearable and flexible sensors, handheld instruments, and wireless sensor networks. It explores their applications in sample handling, calibration, data processing, and field deployment. Applications of this technology include point-of-care diagnostics, pathogen detection, wearable health monitoring, agriculture, veterinary medicine, environmental monitoring, food safety, industrial process control, forensic analysis, public safety, and occupational exposure assessment. The report focuses on sample acquisition, miniaturized preparation, reagent storage, matrix interference, calibration transfer, signal conditioning, machine learning, cloud platforms, analytical validation, and decision support. Furthermore, it identifies key obstacles to translating academic prototypes into industrial products, including reproducibility, stability, manufacturability, ease of use, cybersecurity, regulatory approval, and market acceptance. Future development requires fully integrated sample-to-result systems, multimodal sensing, artificial intelligence, sustainable single-use materials, self-powered devices, and system-level validation under real-world operating conditions.

Micromachines doi: 10.3390/mi17070862

Authors: Serguei P. Murzin

This review presents a comprehensive analysis of the physicochemical mechanisms underlying surface engineering of Cu–Zn alloys through femtosecond laser processing. It focuses on the coupled evolution of laser-induced plasma formation, selective ablation, nonequilibrium Zn redistribution, and plasma-assisted oxidation. Experimental and theoretical evidence indicates that ZnO formation cannot be explained by gas-phase reactions or surface oxidation alone, but results from the interplay of plasma processes, diffusion-controlled Zn redistribution, and heterogeneous oxidation under nonequilibrium conditions. A plasma–surface–diffusion framework is employed to interpret these coupled processes, linking selective Zn redistribution, plasma-assisted oxidation, and ZnO formation within the laser-modified surface layer. The review discusses ZnO evolution, including the influence of supersaturation, defects, and relaxation times, and highlights the effects of laser-induced structuring on reaction kinetics, energy redistribution, and mass transport. Comparison with plasma-assisted and gas-phase ZnO synthesis demonstrates common kinetic stages while emphasizing the localized and transient nature of femtosecond laser processing. This integrated interpretation provides a mechanistic basis for controlled ZnO formation. Overall, ZnO formation on Cu–Zn alloys is interpreted through a multiscale physicochemical approach integrating nonequilibrium electron excitation, plasma evolution, Zn redistribution, heterogeneous oxidation, and surface morphology, providing a framework for the rational optimization of laser-functionalized brass surfaces.

Micromachines doi: 10.3390/mi17070861

Authors: Youqiang Xing Guochao Li Zhaoju Zhu

Advanced manufacturing technology and systems (AMTS) combine principles of mechanical engineering with design innovation to produce high-quality products with enhanced efficiency, flexibility, and precision [...]

Micromachines doi: 10.3390/mi17070860

Authors: Youshu Yue Qiang Zhu Huan Li

To address the challenges of low image quality and difficult feature extraction of weld beads caused by the complex dynamics of the molten pool, intense arc light, and spatter interference during wire arc additive manufacturing (WAAM) of 316L stainless steel, this paper develops a binocular vision-based dynamic molten pool tracking system and conducts image processing and feature analysis. Two high-speed CMOS cameras are employed to capture images of the molten pool and weld bead. Camera calibration is performed to convert pixel coordinates to world coordinates. The denoising performance of five filtering methods, namely mean, Gaussian, median, maximum, and minimum filters, is systematically compared, and the minimum filter is selected for noise reduction. Adaptive threshold binarization, adapthisteq image enhancement, and morphological threshold segmentation are integrated to effectively separate the weld bead from the background. Four edge detection algorithms—Sobel, Robert, Laplacian, and Canny—are compared, and the Canny algorithm combined with Hough transform line fitting is determined to achieve complete and continuous extraction of the weld bead contour. The Intersection over Union (IoU) metric is introduced for image quality screening. When IoU is set to 0.3, the detection accuracy exceeds 90%, effectively eliminating defective images caused by spatter, explosion, trailing, and other disturbances. The proposed method facilitates stable extraction of geometric parameters (e.g., pixel area of the weld bead and height/width of the molten pool), thereby offering a feasible image-processing solution for dynamic molten-pool monitoring and online quality assessment of 316L stainless steel components fabricated by wire arc additive manufacturing.

Micromachines doi: 10.3390/mi17070859

Authors: Elif Aktepe Uçman Ergün

In Fusion Deposition Modeling-based manufacturing, process parameters affect the mechanical and physical properties of the print. Considering these properties, accurately predicting print quality is essential. This is where machine learning (ML) models for three-dimensional (3D) print quality prediction come to the forefront. In this study, a dataset was prepared under strict operational measurement standards—utilizing the Interquartile Range (IQR) method for data sanitization—encompassing 10 material types, 2 printer types, and 4 printing parameters. Five hundred different sample combinations were prepared and printed in sets of three according to ISO 527-2 Type 4 standard dimensions. Tensile, hardness, and surface roughness tests were applied to the prepared samples. Using this validated dataset, a Hybrid Multi-Material Quality–Ensemble System–Stacking–Gradient Boosting Regressor (HMQ-ES-Stack-GBR) architecture is proposed as a diagnostic framework for multi-output quality prediction. Particularly in terms of quality outputs such as tensile strength, hardness, and surface roughness, while also providing a quantitative analysis of the effect of material type on print quality. Furthermore, a multi-objective optimization pipeline integrating three distinct meta-heuristic algorithms—Non-dominated Sorting Genetic Algorithm II (NSGA-II), Particle Swarm Optimization (PSO), and Grey Wolf Optimizer (GWO)—was coupled with the framework to systematically derive material-specific optimal processing parameter configurations. Furthermore, the study shows that open-system printers exhibit higher prediction errors than closed-system printers. Reflecting system-induced variability rather than full hardware independence. Although the study is limited to internal validation within the current experimental design and includes material imbalance across filament groups, the findings suggest that the proposed framework provides a promising diagnostic decision-support tool for pre-print quality estimation within the studied dataset. By accurately reflecting rather than physically overcoming manufacturing variability, it supports decision-making processes through pre-print quality estimation, thereby enabling proactive interventions that reduce raw material, time, and energy losses.

Micromachines doi: 10.3390/mi17070858

Authors: Xiyuan Feng Dian Lin Yuxiang Zhao Jie Xiong Wei Liu Yunlei Zhong Chenhao Zhuo Yue Yin

Reconfigurable radio-frequency (RF) front ends employ N-path filters to achieve digitally tunable frequency selectivity, high linearity, and low static power. However, their linear periodically time-varying (LPTV) operation complicates analysis because an input tone is translated to multiple output harmonics. This tutorial review synthesizes the principal methods for analyzing N-path filters, comparing continuous-time window function analysis, discrete-time ordinary differential equation (ODE) modeling, and adjoint network methods. We evaluate and compare their underlying assumptions, outputs, and computational burdens. Additionally, we present an educational time-domain interpretation based on orthogonal sine/cosine excitation. This viewpoint connects capacitor averaging and path-to-path phase cancellation with harmonic transfer functions (HTFs). Rather than replacing rigorous HTF formulations, this interpretation provides a physically intuitive explanation for the fundamental coefficient H0(f) and the gain-null condition at fin=kNfs. The numerical integration of the switched-RC equations serves as a consistency check. For a four-path example with Γ=τ/(RC)=0.02, the numerical values of |H0(fs)| and |H0(2fs)| differ from the intuitive limits by less than 0.001 dB. The residual responses at 4fs and 8fs are −49.95 dB and −55.97 dB, respectively. Finally, we extend the orthogonal-excitation relationship to extract higher-order HTFs. This tutorial synthesis clarifies how these established analytical methods relate and guides selection for specific applications.

Micromachines doi: 10.3390/mi17070857

Authors: Yang Jiang Xinyuan Yang Zihao Zuo Yunkai Chen Shizhuo Zhang Hong Jiang Shaojie Gu Yanhong Peng

Tensegrity structures have lightweight, compliant, impact-resistant, and large-deformation characteristics, providing a deformable structural solution for mobile robots in complex environments. Inspired by earthworm peristaltic locomotion, this study proposes BAM-STR, a soft tensegrity robot driven by McKibben pneumatic artificial muscles. The robot adopts a three-layer, three-strut tensegrity structure, and the McKibben pneumatic artificial muscles are arranged at the diagonal and additional tendon positions to generate axial–radial coupled deformation under low-pressure actuation. A bio-inspired segmented peristaltic waveform control strategy is further designed. By sequentially activating and releasing the artificial muscles in the three tensegrity units, the robot generates an axially propagating deformation wave and achieves continuous forward crawling. Experimental results show that BAM-STR can achieve approximately 31% axial contraction and 21% radial expansion at an input pressure of 100kPa. When the control time interval is ΔT=1.0–1.25s, the robot reaches its maximum average crawling speed of approximately 6.5mm/s. Multi-scenario experiments further show that BAM-STR can adapt to channel widths ranging from 190 to 235mm, complete continuous crawling while carrying an additional payload of 200g, and maintain forward locomotion on a rough artificial grass surface. These results indicate that BAM-STR has path-width adaptability, load-carrying crawling capability, and rough-ground adaptability.

Micromachines doi: 10.3390/mi17070856

Authors: Yali Li Shuming Chen Jintao Wang

Developing white organic light-emitting diodes (WOLEDs) with high exciton utilization, balanced charge transport, and stable complementary emission remains a challenge for solid-state lighting and display applications. Herein, a triplet reverse intersystem crossing (RISC)-assisted strategy is proposed to enhance triplet exciton harvesting to construct efficient hybrid WOLEDs. The increased RISC channels promote the up-conversion of triplet excitons into radiative singlet excitons, thereby improving the overall exciton utilization efficiency. By further introducing an ultrathin PO-01 layer as an orange orange-emitting component, a hybrid WOLED with a current efficiency of 49.1 cd/A and 34.8 lm/W is realized. Moreover, suppressed efficiency roll-offs and stable spectra are achieved due to balanced charge transport. This work provides a practical route toward high-performance WOLEDs.

Micromachines doi: 10.3390/mi17070854

Authors: Hsin-Yi Tsai Yu-Hsuan Lin Kuo-Cheng Huang J. Andrew Yeh Chen-Ju Lee

Silicon carbide (SiC) has high thermal conductivity and thermal stability; however, its high hardness and brittleness make the fabrication of three-dimensional (3D) SiC microstructures—particularly those intended for thermal management of power devices—highly challenging. Because SiC exhibits strong absorption in the ultraviolet (UV) spectral range, this study conducted UV nanosecond laser irradiation to perform dry, direct-write processing on SiC, with material removal achieved through vaporization. It established an optimization workflow covering processes from the selection of planar processing parameters to the fabrication of 3D micropillar arrays with high surface quality and geometric fidelity. The key process variables were the pulse repetition frequency, nominal laser power, number of repeated scans per layer, and number of Z-direction focal shifts between layers. The micropillar arrays fabricated using the proposed approach were characterized in terms of their total material removal depth, sidewall verticality, and top-surface roughness. The results indicated that processing with a high repetition frequency resulted in favorable sidewall verticality; however, the pillar top surfaces were susceptible to high roughness resulting from spatter and melt backfilling. To address this problem, a strategy involving the fabrication of fewer shifting layers and the use of more scan repetitions per layer was employed. This strategy mitigated cumulative defocus errors, increased the total material removal depth, and achieved a suitable balance among removal depth, sidewall verticality, and top-surface roughness. Overall, this study provides practical guidelines for the direct-write 3D microstructuring of hard materials such as SiC. These guidelines have potential applications in the rapid fabrication of chip-level heat dissipation microstructures. They can reduce process complexity and manufacturing cost while improving design flexibility for 3D thermal architectures.

Micromachines doi: 10.3390/mi17070855

Authors: Zhijie Huang Shixiong Wu Zhichao Yuan Zeyu Wang Cuimin Sun Hui You

In micro-extrusion and direct ink writing, the nozzle outlet diameter is often used to estimate the deposited line width or free-filament diameter. However, highly loaded conductive silver pastes may exhibit pronounced extrusion swell after leaving the nozzle, resulting in a filament diameter larger than the nozzle inner diameter. To quantify this deviation, this study proposes a single-parameter semi-theoretical correction model based on radial force balance at the nozzle exit, integrating Herschel–Bulkley yield stress–shear-thinning rheology with a finite-deformation description. The exit radial stress is derived from pressure-driven circular tube flow, while the post-exit radial expansion is balanced against atmospheric constraint. A comprehensive correction force constant, C, is introduced to account for wall-induced energy dissipation, particle-structure rearrangement, residual elastic recovery, and model simplifications. After calibration using a transition-swelling nozzle, C was determined as 1.03 × 10−2 N. The model was applied to six nozzle diameters and four nozzle length–pressure conditions. For Nozzles 1–4 with significant swelling, the mean absolute percentage error was 5.31%, while the overall error for all six nozzles was 11.84%, mainly due to overestimation for the nearly non-swelling Nozzle 6. For varying nozzle lengths, the error was 5.20%, and both experimental and predicted swell ratios decreased with increasing effective nozzle length. The model provides a semi-theoretical tool for estimating free-filament dimensions and analyzing nozzle-length effects, primarily under pronounced-swell conditions. Its predictive capability becomes limited as the swell ratio approaches unity, where additional corrections for wall slip, relaxation, and the zero-swell boundary are required.

Micromachines doi: 10.3390/mi17070853

Authors: Pengying Xu Shaoyi Liu Lu Hao Jitang Zhang Yan Wang Qiulin Tan Congsi Wang

To achieve high interconnect density in 2.5D packages, various microscale structures such as through-silicon vias (TSVs), microbumps, and redistribution layers (RDLs) are employed. These features typically exist at the micron scale, whereas other package components span millimeter to centimeter scales, resulting in a wide range of physical dimensions within the package. Although finite element analysis (FEA) has proven effective for evaluating the mechanical and thermal characteristics of 2.5D packages, the inherent multi-scale nature poses significant computational challenges and numerical convergence issues, severely hindering the design and analysis of increasingly dense packages. To address this problem, this paper proposes an efficient numerical homogenization method for the mechanical and thermal analysis of 2.5D packages. The method employs periodic boundary conditions (PBCs) based on the concept of referential statistical volume elements (rSVEs). In this approach, typical microstructures—including TSVs, microbumps, and RDL traces together with the surrounding matrix material—are treated as a homogeneous medium, and the equivalent material properties of the multi-scale structures are evaluated. These properties include the stiffness matrices (from which the equivalent Young’s modulus, shear modulus, and Poisson’s ratio can be derived), coefficients of thermal expansion, and thermal conductivity. Validation results demonstrate that the proposed method ensures continuity of displacement, stress, strain, and heat flux across opposite surface pairs of the rSVEs. Compared with experimental measurements and other existing homogenization techniques, the method accurately determines the equivalent material properties of complex multi-scale structures without being restricted to specific geometries, while significantly improving computational efficiency. Finally, the proposed numerical homogenization method is successfully applied to wafer warpage analysis during the manufacturing process and to thermal analysis under operating conditions. The results indicate that the method achieves high computational efficiency while maintaining accuracy in both mechanical and thermal analyses of 2.5D packages, thereby laying a solid foundation for the development of next-generation 2.5D package structures.

Micromachines doi: 10.3390/mi17070852

Authors: Xianjin Lan Jiangyifan Wang Ligang Liu Yuanlin Xu Chaojie Yang Min Zhang

This study systematically investigates the effects of varying Ni doping levels (1.0–7.0 wt.%) on the microstructure, static magnetic properties, and high-frequency dynamic magnetic performance of Fe-5.5 wt.% Si soft magnetic composites (SMCs). Toroidal core samples were fabricated using powder metallurgy combined with silicone resin coating and high-temperature annealing. The influence of Ni doping on phase composition, morphology, saturation magnetization, coercivity, effective permeability, quality factor, total core loss and its components, and DC bias characteristics was comprehensively evaluated by XRD, SEM, EDS, hysteresis loop testing, and DC bias measurements. The results indicate that an appropriate Ni content (3.0–5.0 wt.%) promotes the formation of α-Fe(Si,Ni) solid solution and (Fe,Ni)3Si ordered phases, optimizes grain size and structural ordering, enhances saturation magnetization, and reduces coercivity. In contrast, excessive Ni doping (7.0 wt.%) leads to Ni segregation at grain boundaries, forming strong pinning centers that significantly increase coercivity and hysteresis loss. Within the wide frequency range of 1–100 kHz, Ni doping improves the permeability retention under DC bias but reduces the initial effective permeability. Notably, the sample with 5.0 wt.% Ni exhibits the highest quality factor (Q value) across the entire frequency range, demonstrating the best overall performance. This study provides experimental evidence and theoretical guidance for developing high-saturation-resistance, low-loss soft magnetic composites for medium-to-high-frequency applications.

Micromachines doi: 10.3390/mi17070851

Authors: Mohammad Aslam Danishuddin Mathivanan Durai Praveen Kumar Elangovan Erusappan Surinder Kaur Brar Rohit Kumar Singh Gautam Mohd Quasim Khan

The increasing need for electrochemical energy storage systems with high power density and long-term stability has driven intensive efforts to develop next-generation electrode materials that surpass the limitations of conventional carbonaceous and transition metal-based architectures. In this context, bismuth ferrite (BiFeO3; BFO), which is also known as perovskite oxide, has been employed as a promising electrode material for energy storage applications. In the past few years, BFO and its hybrid materials have emerged as promising candidates for the fabrication of supercapacitors. However, their practical development is constrained by limited intrinsic electrical conductivity, sluggish charge-transfer kinetics, and structural instability under repeated cycling. This review critically examines recent progress in BFO-based electrode materials for supercapacitor applications. The synthesis methods for BFO-based materials have been discussed, and their advantages and limitations have been compared. Furthermore, the electrochemical performance of BFO-based hybrid materials for supercapacitor application has been critically examined. The energy storage mechanism and limitations of BFO-based supercapacitors have been discussed. Future perspectives for BFO-based materials for energy storage applications have been discussed.

Micromachines doi: 10.3390/mi17070850

Authors: Annamaria Muoio Angela Garofalo Francesco La Via

Silicon carbide (SiC) is a key material for next-generation miniaturized devices and MEMS operating in harsh environments. This paper presents a comprehensive investigation of anisotropic damping mechanisms in heteroepitaxial 3C-SiC double-clamped beam resonators for MEMS applications. Unlike conventional isotropic loss-factor models, which assign a single scalar damping coefficient to all deformation directions, the proposed framework employs a full 6 × 6 loss-factor tensor expressed in Voigt notation, implemented within the COMSOL Multiphysics finite element environment. The tensor formulation enables the direction-dependent description of energy dissipation, capturing the coupling between shear and normal strain modes that arises from the (111) crystallographic orientation and from the heteroepitaxial defect structure of 3C-SiC grown on silicon substrates. The effects of film thickness, effective Young’s modulus, and residual stress on elastic modulus, resonance frequency, and Q-factor are systematically analyzed across five wafers (w1–w5, thickness range 293–890 nm). Experimentally calibrated anisotropic loss-factor matrices are extracted via least-squares fitting to measured Q-factors, and their Frobenius norms are found to correlate negatively with resonance frequency. The anisotropic model reduces Q-factor prediction errors to below 1% for all wafers, significantly outperforming the isotropic approach, particularly for films thicker than 600 nm. These results demonstrate that an accurate treatment of directional dissipation is essential for the design of high-Q resonators and high-sensitivity strain sensors targeted at geophysical monitoring applications.

Micromachines doi: 10.3390/mi17070849

Authors: Nico E. Galarza Nathan Jackson

Piezoelectric energy harvesters (PEHs) have emerged as a promising solution for self-powered small-scale electronic systems; however, their narrow operational bandwidth limits performance under varying excitation conditions commonly found in ambient environments. To address this limitation, this study proposes a passive multi-chamber proof-mass design containing internal free-moving masses to enhance the frequency bandwidth of a PEH through nonlinear dynamics. Multiple proof-mass models were designed and experimentally evaluated using tungsten and Teflon spherical movable masses under 0.5 g and 1 g excitation levels. Design alterations include varying the number of chambers, which in essence reduces the maximum lateral displacement of the movable mass. Baseline characterization was first conducted using empty proof-mass configurations, followed by fixed-mass and free-mass testing to isolate the effects of dynamic mass repositioning. The results demonstrate that baseline and fixed-mass configurations remained limited to bandwidths in the 5–8 Hz range. In contrast, free-mass configurations produced significant bandwidth enhancement across all models. The largest bandwidth increase consisted of a multiple-chamber proof-mass design, which resulted in a bandwidth of 72 Hz using tungsten rolling spheres at 1 g excitation, corresponding to a 1400% increase relative to the baseline conditions.

Micromachines doi: 10.3390/mi17070848

Authors: Paulius Skėrys Rimvydas Gaidys

Piezoelectric cantilever beams are among the most popular vibration energy harvesting devices. Maximization of the spatial distribution of axial strain along this beam (objective function) increases harvesting efficiency. In vibro-impact systems, mechanical contact can excite higher-order vibration modes, making the second eigenfrequency particularly relevant for energy harvesting under such nonlinear operating conditions. Therefore, the harvester geometry should be designed to maximize the harvested energy associated with this mode. In many practical applications, cantilever-based harvesters are subjected to complex and broadband excitation conditions, where multiple vibration modes, including the second eigenfrequency, contribute to the overall response. Therefore, optimization at the second eigenfrequency is essential for improving energy harvesting performance under realistic operating conditions. In this study, to maximize axial strain, a thickness shape optimal design is proposed, and a finite element-based optimization scheme is constructed to maximize harvesting efficiency. Optimization is performed subject to a fixed second eigenfrequency of the cantilever beam, using the eigenmode equation as the state equation in the optimization procedure. The optimized shape for maximal strain integral at the second bending resonance is determined. Experimental results validate the findings of the optimization, showing an increase in strain for the optimized-shaped beam compared to a uniform-thickness beam with the same eigenfrequency. It should be noted that experimental validation is subject to certain limitations, including manufacturing precision and environmental influences. The manufacturing of specimens can only be achieved within a limited precision, resulting in deviations from the ideal optimized geometry. Additionally, the experimental environment may influence the measured response, and simplified boundary conditions can introduce discrepancies between numerical and experimental results.

Micromachines doi: 10.3390/mi17070847

Authors: Jieguang Huang Haoyu Zhong Zhijun Wang Tingting Xu Lifei Wang

Abrasive flow machining (AFM) is an effective finishing process for complex internal surfaces, particularly cavities, intersecting holes, and micro-channels that are difficult to access using conventional tools. However, when low-viscosity abrasive media is used (here defined, relative to conventional putty-like viscoelastic AFM carriers (with apparent viscosities of 103–105 mPa·s), as a water-based slurry with an apparent viscosity below 300 mPa·s over the operating shear-rate range), unfavorable flow conditions during the initial polishing stage can induce local over-polishing, erosion depressions, stepped patterns, and cavitation pits, resulting in non-uniform surface quality. The relationship between these flow behaviors and polishing defects remains insufficiently understood. To address this issue, this study investigates the AFM process applied to turbine blade film cooling holes through combined experimental and numerical approaches. The observed defects include erosion depressions, stepped surface patterns, and cavitation pits. The effects of abrasive injection pressure, flow velocity, hole geometry, abrasive viscosity, and particle size on defect formation are systematically examined. The results show that the initial abrasive filling level strongly affects defect distribution by altering the evolution of shear fields and void regions within the hole. Experimentally, at high Reynolds numbers (Re > 2 × 104), intensified local shear and cavitation promote defect formation, while a moderate inclination angle (45–60°) and a higher aspect ratio (>8) are favorable for polishing uniformity. Complementary numerical simulations further indicate that smaller abrasive particles (<5 μm) and a moderate abrasive viscosity (~60 mPa·s) are predicted to improve polishing uniformity. This study clarifies the fluid-dynamic origin of polishing defects in film cooling holes and provides process guidance for suppressing local over-polishing, cavitation, and uneven material removal.

Micromachines doi: 10.3390/mi17070846

Authors: Sanjay Yadav Efe Precious Onakpojeruo Cedric Lansangan Rameshwar Patil

Boron neutron capture therapy (BNCT) is a radiotherapeutic modality that enables tumor-targeted cell killing. The nuclear capture reaction between boron-10 (10B) and low-energy thermal neutrons produces high linear energy transfer (LET) particles (α-particles and recoiling lithium nuclei), each of which have short path lengths within the diameter of a single mammalian cell. The deposited energy creates clustered DNA double-strand breaks that are cytotoxic in these tumor cells while sparing the surrounding healthy tissues. This advantage makes BNCT a highly attractive treatment modality compared to conventional radiotherapy. Nevertheless, despite its theoretical precision, the clinical translation of BNCT remains constrained by suboptimal tumor-selective boron delivery; insufficient intracellular accumulation; and heterogeneous biodistribution profiles associated with conventional small-molecule-based boron agents, such as boronophenylalanine (BPA) and sodium borocaptate (BSH). While the development of new accelerator-based neutron sources (ABNSs) has renewed interest in BNCT, effective 10B delivery remains a major challenge. To address this, nanomedicine has been steadily on the rise in cancer research. In recent years, nanocarrier-based delivery systems have emerged as a transformative alternative delivery strategy. Nanodrugs offer several advantages over conventional small-molecule drugs, such as improved solubility, increased plasma half-life, enhanced permeability and retention in tumors, and active targeting, as well as decreased systemic toxicity and drug resistance. In recent years, nanocarrier-based delivery systems have emerged as a transformative strategy for 10B delivery. In this focused review, we will discuss various types of nanocarriers used for boron drug delivery that enhance boron loading efficiency and evaluate what enables their selective delivery to and accumulation within tumor cells.

Micromachines doi: 10.3390/mi17070845

Authors: Alexandru Paolo Mardare Mamoun Morh Aldo Ghisi

To exploit ultra-low power logic and architectural design techniques for bio-sensors in the human body, wireless ultrasonic techniques have emerged as a strong candidate for intra-body power transmission, thanks to lower medium attenuation and higher permitted safe intensity levels. When sub-100 μm dimensions are considered for the bio-sensor, most devices struggle to guarantee a suitable voltage and power for digital electronics due to additional scaling requirements. This study investigates three alternative piezoelectric micromachined ultrasonic transducers in aluminum nitride doped with scandium, as reported in the literature, operating in the range 1–10 MHz. Their respective advantages and limitations with regard to energy harvesting and signal transmission performance are analyzed. It is shown that devices with footprints of less than 100 × 100 μm2 can achieve voltage outputs of over 150 mV and average power greater than 100 nW.

Micromachines doi: 10.3390/mi17070844

Authors: Paolo Salvemme Diego Vennarini Riccardo Frisenda

We report a tabletop, versatile and lithography-free electrical contacting method for two-dimensional (2D) materials and van der Waals (vdW) heterostructures based on silver paint micromanipulation (SPMM). Operated under an ambient optical microscope, this additive, room-temperature approach circumvents the chemical solvents and high temperatures associated with conventional cleanroom processing used in electrode fabrication. We validate the efficacy of this strategy by fabricating devices based on high-quality mechanically exfoliated thin flakes on both rigid SiO2/Si and flexible polycarbonate substrates. On rigid supports, SPMM-contact multilayer graphene devices exhibit linear Ohmic behavior with excellent environmental stability over multiple days and an ambipolar field effect. Gate-tunable multilayer graphene/few-layer MoS2/multilayer graphene field-effect transistors demonstrate n-type gating with a two-terminal carrier mobility of 60 cm2Vs and time-resolved photoresponse under 660 nm and 415 nm illumination, with responsivities as high as 10 A/W at the lowest incident powers. The SPMM method can also be carried out on flexible polymeric substrates such as polycarbonate, which is notoriously difficult to work with in microfabrication. We demonstrate a flexible multilayer graphene device that functions as highly responsive piezoresistive strain sensors at low deformations with a gauge factor of 50. Finally, a fully integrated flexible vdW photodetector is tested up to 1.2% uniaxial tensile strain. Despite experiencing local micro-fracturing of the MoS2 channel, the localized vdW junctions maintain robust charge collection, yielding photodetecting capabilities under tensile strain. This simple and cost-effective electrical contacting technique establishes a highly accessible platform for the rapid prototyping and mechanical testing of next-generation optoelectronics and flexible electronics based on 2D materials and vdW heterostructures.

Micromachines doi: 10.3390/mi17070843

Authors: Yan Liu Yongxin Deng Quanwei Zhang Huafeng Li Jue Wang Yuan Wang Fabin Cheng Haijun Han Peng Zhang

Silicon carbide (SiC), a third-generation wide-bandgap semiconductor, demonstrates prominent application advantages for extreme-environment sensing scenarios including deep-space exploration, nuclear reactor monitoring, and fusion device diagnosis, which benefit from its excellent radiation resistance, high-temperature stability, and chemical inertness. This review systematically investigates the action mechanisms of different radiation environments on the electrical and mechanical properties of SiC-based sensors, with emphasis on the regulatory effects of radiation-induced defects on key sensing parameters, including piezoresistive properties, charge-collection efficiency, leakage current, and sensitivity. In addition, this paper discusses the response behavior and research progress of SiC sensors applied in mixed radiation fields. Existing research confirms that although high-fluence radiation can induce lattice defects and further result in the degradation of SiC sensor sensing performance, SiC still retains remarkable advantages in intrinsic radiation resistance. The sensing reliability of SiC in extreme environments can be further improved via device-structure optimization and material-modification strategies. This review is expected to provide a theoretical reference for the development and design of SiC sensors applied in advanced nuclear energy, aerospace, and nuclear medicine fields.

Micromachines doi: 10.3390/mi17070842

Authors: Lingzhi Ding Guangchao Song Guili Gao Dequan Shi

Magnetorheological Finishing (MRF) technology, as a deterministic machining method featuring flexibility, controllability, and extremely low subsurface damage, has become one of the most promising technologies in the field of ultra-precision polishing. This review systematically summarizes the research progress of MRF technology in aspects such as polishing fluid preparation and rheological properties, material removal mechanisms and theoretical models, classification and optimization of equipment and processes, multi-energy field hybrid technologies, and intelligent development. First, starting from the composition, nonlinear rheological models, and stability optimization of the magnetorheological polishing fluid, the decisive influence of fluid properties on finishing performance is elucidated. Second, the macroscopic mechanical removal mechanism and the atomic-scale material removal mechanism are analyzed, and the establishment and development of material removal function and polishing force models are reviewed. Third, MRF equipment is systematically classified according to tool morphology, and advanced hybrid polishing technologies such as ultrasonic-assisted, electrochemical-assisted, and laser-assisted methods are discussed. Furthermore, the effects of key process parameters, magnetic field configuration optimization, and dwell time algorithms on machining accuracy and efficiency are analyzed in depth. Finally, typical applications of MRF technology in aerospace, biomedical, optoelectronic information and other fields are summarized, the current technical bottlenecks are pointed out, and future development trends toward intelligence, greenization, and standardization are prospected. This review aims to provide comprehensive theoretical references and technical guidance for researchers in the MRF field, and to promote further application and development of this technology in precision manufacturing.

Micromachines doi: 10.3390/mi17070841

Authors: Changqing Xu Yi Liu Yiqiang Chen

Semiconductor devices and integrated circuits are increasingly deployed in automobiles, avionics, aerospace platforms, radiation-monitoring systems, high-power optoelectronics, and other safety- or mission-critical applications [...]

Micromachines doi: 10.3390/mi17070840

Authors: Luca Manini Elisabetta Poeta Estefanía Núñez-Carmona Veronica Sberveglieri

Beer quality assessment increasingly requires rapid and scalable analytical tools for product discrimination and authenticity control. In this study, a data-driven metal oxide semiconductor (MOX) chemosensing approach was investigated for the discrimination of commercial lager beers with different alcohol contents and brands. Alcoholic and alcohol-free beer samples from four commercial brands were analyzed using a six-element SnO2-based MOX sensor array, and the resulting response patterns were classified using supervised machine-learning algorithms. Headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS) was employed as a reference technique to characterize volatile organic compound profiles and support the interpretation of sensor-based fingerprints. GC–MS analysis highlighted a shared volatile backbone dominated by fermentation-related compounds, while also revealing brand- and category-dependent differences in VOC distribution. The MOX sensor array captured these differences as multidimensional volatile fingerprints. Machine-learning models achieved high classification performance in brand-matched alcoholic versus alcohol-free comparisons, with balanced accuracy ranging from 0.937 to 1.000, while brand discrimination within the same category reached balanced accuracy values of 0.875 (alcoholic) and 0.933 (alcohol-free). These results highlight MOX-based chemosensing combined with data-driven analysis as a rapid, portable platform for beer discrimination, with applications in food quality screening, authenticity assessment, and at-line monitoring.

Micromachines doi: 10.3390/mi17070839

Authors: Hao Liang Liang Chen Haifeng Zhang Xiaowei Liu

Droplet splitting technology on open digital microfluidic platforms still faces significant challenges in terms of process complexity, the degree of automation, and operating conditions, which hinder its further development. This study proposes a fully automated method for precise droplet splitting based on printed circuit boards with open-coplanar asymmetric electrodes and a slippery liquid-infused porous surface. This method uses simple square electrodes arranged in a 3 × 5 array, combined with low-adhesion blade-assisted cutting and electrowetting-on-dielectric to drive droplet splitting, enabling accurate, stable, and repeatable automated droplet splitting on an open digital microfluidic platform. It has the advantages of a simple method, easy maintenance and integration, and high automation. This study systematically investigated the effects of droplet volume, applied voltage, blade thickness, cutting speed, and electrode shape on droplet splitting performance. We developed an active droplet position calibration method based on a simple 3 × 3 square electrode array combined with an enveloping voltage configuration strategy. For droplets with a volume of 10 μL, the positioning error can be controlled to within 0.06 mm, representing a reduction of more than 95% compared to the conventional EWOD free drive method. The experimental results show that to achieve stable and approximately equal-volume droplet splitting, the cutting speed needs to exceed the critical value related to the blade thickness. Among the square, zigzag, and hexagonal electrode shapes tested, the square electrode required the lowest splitting voltage. When the blade thickness is 0.3 mm, the droplets can be successfully split at a minimum voltage of 165 V. After increasing the splitting voltage to 400 V, the droplet splitting time was reduced from 5.57 s to 0.27 s, with a reduction of 95.2%, which significantly improves droplet splitting efficiency. This method provides a practical, stable, automated, and precise droplet splitting method for sample preparation, biochemical reactions, and portable droplet analysis systems.

Micromachines doi: 10.3390/mi17070838

Authors: Zhilin Yan Wenqiang Fan Longjie Zhang Wanxiao Gao Cunwei Zhang Jiaming Zhang Tie Li Yancheng Guo Yulei Wang Zhiwei Lu Qiunan Yang Zhenxu Bai

Laser frequency stabilization underpins precision metrology, optical atomic clocks, quantum optics, and laser spectroscopy. In recent years, field-programmable gate arrays (FPGAs) have become attractive for this task because signal generation, phase-sensitive detection, digital filtering, feedback control, lock monitoring, and automatic re-locking can be integrated on compact and reconfigurable platforms. This review examines recent progress in FPGA-based laser frequency stabilization from four linked perspectives: stabilization principles, digital implementation, system architecture, and intelligent control. We first summarize representative error-signal generation methods, including Pound–Drever–Hall locking, saturation absorption spectroscopy, frequency modulation spectroscopy, and modulation transfer spectroscopy. We then discuss the FPGA functions that determine practical performance, such as data acquisition, direct digital synthesis, digital demodulation, proportional-integral-derivative (PID)/infinite impulse response (IIR) filtering, latency management, and lock-state monitoring. Mixed-signal, all-digital, distributed, and machine-learning-assisted systems are compared to show how bandwidth, latency, stability, integration, cost, and automation are balanced in different designs. This review closes by identifying remaining challenges in analog-to-digital converter/digital-to-analog converter (ADC/DAC) resolution, converter noise, loop latency, actuator bandwidth, long-term robustness, and algorithm portability, and by outlining future directions toward low-latency, software-defined, and intelligent stabilization platforms.

Micromachines doi: 10.3390/mi17070837

Authors: Hyunbin Kang Eunyeop Ji Vassilia Zorba Dongkyoung Lee Minok Park

The slitting of aluminum (Al) foil is a critical process in secondary battery manufacturing, where cut quality directly affects electrode uniformity and production yield. Although femtosecond (fs) laser processing has emerged as a promising approach for high-precision foil cutting, residual debris generated during material removal can degrade product quality and requires accurate process evaluation. In this study, a hybrid framework combining adaptive computer vision and eXtreme Gradient Boosting (XGBoost) was developed for automated debris quantification, quality classification, and process optimization of fs laser-processed Al foils. The image processing algorithm automatically detects debris boundaries from scanning electron microscopy images and extracts key geometrical descriptors, which are subsequently used as input features for XGBoost models. The developed framework successfully distinguished acceptable and defective processing conditions and accurately predicted residual debris sizes. Experimental validation under previously unseen processing conditions confirmed excellent agreement between predicted and measured debris sizes. By enabling automated and interpretable quality assessment, the proposed framework provides a scalable foundation for defect quantification and machine-learning-assisted process optimization in advanced laser manufacturing.

Micromachines doi: 10.3390/mi17070836

Authors: Tailong Shi Wending Yang Qi Li Jingxuan Yang Zhonghao Li Hua Hong Zhong Zhang Guodong Zhang Andrew C. Chang

Due to its excellent electrical and thermal performance, glass packaging demonstrates significant potential in heterogeneous integration of chiplets advanced packaging system, but limited by its poor interfacial adhesion strength between glass and metals. This article studies the mechanisms of glass–metal bonding interface at the microscale level, and the adhesion strength at the macroscale level. In detail, the changes of the adhesion strength after glass surface activation, annealing and micro-etching processes were characterized, and the correlation between the microscale mechanisms and the macroscale adhesion variations of each process was studied. X-ray photoelectron spectroscopy (XPS) results indicate that the increase in Si-OH bond is the key to glass surface activation. Fourier transform infrared spectroscopy (FTIR) was applied to quantitatively correlate the dynamic evolution of surface polar hydroxyl groups on glass substrates with the subsequent glass–metal interfacial bonding strength, and verified the conclusion above. The adhesion strength increased by 2.3 times after surface activation, and by 4.1 times after annealing, while it decreased slightly after etching. Furthermore, the glass–Ti seed layer interface was studied at the atomic level to better analyze the changes in macroscopic adhesion. XPS depth profiling confirmed the formation of Si-O-Ti bonds at the glass–Ti interface, which may contribute to the enhanced adhesion. After annealing, X-ray diffractometer (XRD) characterization revealed the great change in grain structure caused a reduction in residual stress within the plated layer.

Micromachines doi: 10.3390/mi17070835

Authors: Hajime Miyashita Kenta Shinha Hiroko Nakamura Moeno Kadoguchi Hiroshi Arakawa Hiroshi Kimura

Conventional in vitro assays and many microphysiological systems struggle to generate time-dependent drug exposure profiles because medium replacement simultaneously removes or re-adds drugs in the culture compartment. Here, we developed an Open-access Dialysis Membrane-integrated Microfluidic Device (O-DMiMD) that uses molecular weight-dependent transport across a dialysis membrane to decouple nutrient supply from drug exposure control. The device comprises a cell culture compartment (CCC) and a donor compartment (DC) separated by a dialysis membrane. Transport functions were evaluated using Lucifer Yellow, FITC-dextran, and glucose, followed by drug-response studies using SN-38 and T-DM1 under different medium change conditions. Lucifer Yellow and glucose permeated through the dialysis membrane, whereas FITC-dextran was retained. DC medium change supplied glucose to the CCC and maintained A549/HepG2 co-culture proliferation comparably to direct CCC medium replacement. For SN-38, partial transport to the DC and retention in the CCC generated time-dependent exposure profiles; in A549/HepaRG co-culture, medium change conditions altered A549 viability. For T-DM1, conditions with or without re-addition to the CCC produced different SK-BR-3 responses, suggesting exposure-dependent effects for high-molecular-weight drugs. The O-DMiMD provides an open-access in vitro platform for evaluating drug responses under exposure profiles governed by molecular weights, protein binding, medium changes, and metabolic cell contexts.