Micromachines

10 pages, 4230 KB

Open AccessArticle

Enhanced UVC Responsivity of Heteroepitaxial α-Ga₂O₃ Photodetector with Ultra-Thin HfO₂ Interlayer

by SiSung Yoon, SeungYoon Oh, GyuHyung Lee, YongKi Kim, SunJae Kim, Ji-Hyeon Park, MyungHun Shin, Dae-Woo Jeon and GeonWook Yoo

Micromachines 2025, 16(7), 836; https://doi.org/10.3390/mi16070836 - 21 Jul 2025

Viewed by 928

Abstract

In this study, the influence of HfO₂ interlayer thickness on the performance of heteroepitaxial α-Ga₂O₃ layer-based metal–insulator–semiconductor–insulator–metal (MISIM) ultraviolet photodetectors is examined. A thin HfO₂ interlayer enhances the interface quality and reduces the density of interface traps, thereby [...] Read more.

In this study, the influence of HfO₂ interlayer thickness on the performance of heteroepitaxial α-Ga₂O₃ layer-based metal–insulator–semiconductor–insulator–metal (MISIM) ultraviolet photodetectors is examined. A thin HfO₂ interlayer enhances the interface quality and reduces the density of interface traps, thereby improving the performance of UVC photodetectors. The fabricated device with a 1 nm HfO₂ interlayer exhibited a significantly reduced dark current and higher photocurrent than a conventional metal–semiconductor–metal (MSM). Specifically, the 1 nm HfO₂ MISIM device demonstrated a photocurrent of 2.3 μA and a dark current of 6.61 pA at 20 V, whereas the MSM device exhibited a photocurrent of 1.1 μA and a dark current of 73.3 pA. Furthermore, the photodetector performance was comprehensively evaluated in terms of responsivity, response speed, and high-temperature operation. These results suggest that the proposed ultra-thin HfO₂ interlayer is an effective strategy for enhancing the performance of α-Ga₂O₃-based UVC photodetectors by simultaneously suppressing dark currents and increasing photocurrents and ultimately demonstrate its potential for stable operation under extreme environmental conditions. Full article

(This article belongs to the Special Issue Photodetectors and Their Applications)

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29 pages, 4438 KB

Open AccessReview

Microfluidic Sensors Integrated with Smartphones for Applications in Forensics, Agriculture, and Environmental Monitoring

by Tadsakamon Loima, Jeong-Yeol Yoon and Kattika Kaarj

Micromachines 2025, 16(7), 835; https://doi.org/10.3390/mi16070835 - 21 Jul 2025

Cited by 2 | Viewed by 2560

Abstract

The demand for rapid, portable, and cost-effective analytical tools has driven advances in smartphone-based microfluidic sensors. By combining microfluidic precision with the accessibility and processing power of smartphones, these devices offer real-time and on-site diagnostic capabilities. This review explores recent developments in smartphone-integrated [...] Read more.

The demand for rapid, portable, and cost-effective analytical tools has driven advances in smartphone-based microfluidic sensors. By combining microfluidic precision with the accessibility and processing power of smartphones, these devices offer real-time and on-site diagnostic capabilities. This review explores recent developments in smartphone-integrated microfluidic sensors, focusing on their design, fabrication, smartphone integration, and analytical functions with the applications in forensic science, agriculture, and environmental monitoring. In forensic science, these sensors provide fast, field-based alternatives to traditional lab methods for detecting substances like DNA, drugs, and explosives, improving investigation efficiency. In agriculture, they support precision farming by enabling on-demand analysis of soil nutrients, water quality, and plant health, enhancing crop management. In environmental monitoring, these sensors allow the timely detection of pollutants in air, water, and soil, enabling quicker responses to hazards. Their portability and user-friendliness make them particularly valuable in resource-limited settings. Overall, this review highlights the transformative potential of smartphone-based microfluidic sensors in enabling accessible, real-time diagnostics across multiple disciplines. Full article

(This article belongs to the Special Issue Microfluidic-Based Sensing)

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17 pages, 1494 KB

Open AccessArticle

All-Optical Encryption and Decryption at 120 Gb/s Using Carrier Reservoir Semiconductor Optical Amplifier-Based Mach–Zehnder Interferometers

by Amer Kotb, Kyriakos E. Zoiros and Wei Chen

Micromachines 2025, 16(7), 834; https://doi.org/10.3390/mi16070834 - 21 Jul 2025

Viewed by 835

Abstract

Encryption and decryption are essential components in signal processing and optical communication systems, providing data confidentiality, integrity, and secure high-speed transmission. We present a novel design and simulation of an all-optical encryption and decryption system operating at 120 Gb/s using carrier reservoir semiconductor [...] Read more.

Encryption and decryption are essential components in signal processing and optical communication systems, providing data confidentiality, integrity, and secure high-speed transmission. We present a novel design and simulation of an all-optical encryption and decryption system operating at 120 Gb/s using carrier reservoir semiconductor optical amplifiers (CR-SOAs) embedded in Mach–Zehnder interferometers (MZIs). The architecture relies on two consecutive exclusive-OR (XOR) logic gates, implemented through phase-sensitive interference in the CR-SOA-MZI structure. The first XOR gate performs encryption by combining the input data signal with a secure optical key, while the second gate decrypts the encoded signal using the same key. The fast gain recovery and efficient carrier dynamics of CR-SOAs enable a high-speed, low-latency operation suitable for modern photonic networks. The system is modeled and simulated using Mathematica Wolfram, and the output quality factors of the encrypted and decrypted signals are found to be 28.57 and 14.48, respectively, confirming excellent signal integrity and logic performance. The influence of key operating parameters, including the impact of amplified spontaneous emission noise, on system behavior is also examined. This work highlights the potential of CR-SOA-MZI-based designs for scalable, ultrafast, and energy-efficient all-optical security applications. Full article

(This article belongs to the Special Issue Integrated Photonics and Optoelectronics, 2nd Edition)

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10 pages, 895 KB

Open AccessArticle

Investigation on the Carrier Dynamics in P-I-N Type Photovoltaic Devices with Different Step-Gradient Distribution of Indium Content in the Intrinsic Region

by Yifan Song, Wei Liu, Junjie Gao, Di Wang, Chengrui Yan, Bohan Shi, Linyuan Zhang, Xinnan Zhao and Zeyu Liu

Micromachines 2025, 16(7), 833; https://doi.org/10.3390/mi16070833 - 21 Jul 2025

Viewed by 352

Abstract

InGaN-based photovoltaic devices have attracted great attention due to their remarkable theoretical potential for high efficiency. In this paper, the influence of different distributions of step-gradient indium content within the intrinsic region on the photovoltaic performance of P-I-N type InGaN/GaN solar cells is [...] Read more.

InGaN-based photovoltaic devices have attracted great attention due to their remarkable theoretical potential for high efficiency. In this paper, the influence of different distributions of step-gradient indium content within the intrinsic region on the photovoltaic performance of P-I-N type InGaN/GaN solar cells is numerically investigated. Through the comprehensive analysis of carrier dynamics, it is found that for the device with the indium content decreasing stepwise from 50% at the top to 10% at the bottom in intrinsic region, the photovoltaic conversion efficiency is increased to 10.29%, which can be attributed to joint influence of enhanced photon absorption, reduced recombination rate, and optimized carrier transport process. Full article

(This article belongs to the Special Issue GaN-Based Materials and Devices: Research and Applications, 2nd Edition)

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4 pages, 894 KB

Open AccessEditorial

Photonics Gets a Makeover: The New Era of Perovskite Devices

by Muhammad Danang Birowosuto

Micromachines 2025, 16(7), 832; https://doi.org/10.3390/mi16070832 - 21 Jul 2025

Cited by 1 | Viewed by 1143

Abstract

The story of perovskite materials dates back over a century to the discovery of calcium titanate, known for its nearly cubic crystal structure [...] Full article

(This article belongs to the Section D1: Semiconductor Devices)

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4 pages, 163 KB

Open AccessEditorial

Editorial for the Topic on Magnetic Materials and Devices

by Viktor Sverdlov

Micromachines 2025, 16(7), 831; https://doi.org/10.3390/mi16070831 - 21 Jul 2025

Viewed by 353

Abstract

Magnets are materials that are characterized by their own persistent magnetic moments [...] Full article

(This article belongs to the Section E：Engineering and Technology)

22 pages, 5547 KB

Open AccessReview

Microfluidics-Engineered Microcapsules: Advances in Thermal Energy Storage and Regulation

by Yuhan Li, Jian Zhang, Lin Zhuo, Xianjing Wang, Jingyao Sun, Ping Xue and Ke Chen

Micromachines 2025, 16(7), 830; https://doi.org/10.3390/mi16070830 - 20 Jul 2025

Viewed by 940

Abstract

Phase-change microcapsules offer significant advantages for thermal energy storage and regulation. However, conventional mechanical agitation fabrication methods encounter difficulties in achieving monodispersity, precise size control, and structural uniformity. Droplet microfluidics emerges as a promising alternative, enabling controllable production of microcapsules with tunable sizes [...] Read more.

Phase-change microcapsules offer significant advantages for thermal energy storage and regulation. However, conventional mechanical agitation fabrication methods encounter difficulties in achieving monodispersity, precise size control, and structural uniformity. Droplet microfluidics emerges as a promising alternative, enabling controllable production of microcapsules with tunable sizes (1–1000 μm), programmable core–shell configurations, and high encapsulation efficiency. This review comprehensively summarizes recent advances in microfluidic strategies for phase-change microcapsules fabricating, including single encapsulation, multi-core encapsulation, and high-throughput parallelization and their applications in solar energy storage, building thermal regulation, electronics cooling, and smart textiles. The review highlights key challenges for future advancement which will unlock the full potential of microfluidics-engineered phase-change microcapsules in next-generation thermal energy technologies. Full article

(This article belongs to the Special Issue Advances in Microfluidic Chips for Chemical and Biomedical Applications)

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28 pages, 25758 KB

Open AccessArticle

Cam Design and Pin Defect Detection of Cam Pin Insertion Machine in IGBT Packaging

by Wenchao Tian, Pengchao Zhang, Mingfang Tian, Si Chen, Haoyue Ji and Bingxu Ma

Micromachines 2025, 16(7), 829; https://doi.org/10.3390/mi16070829 - 20 Jul 2025

Viewed by 506

Abstract

Packaging equipment plays a crucial role in the semiconductor industry by enhancing product quality and reducing labor costs through automation. Research was conducted on IGBT module packaging equipment (an automatic pin insertion machine) during the pin assembly process of insulated gate bipolar transistor [...] Read more.

Packaging equipment plays a crucial role in the semiconductor industry by enhancing product quality and reducing labor costs through automation. Research was conducted on IGBT module packaging equipment (an automatic pin insertion machine) during the pin assembly process of insulated gate bipolar transistor (IGBT) modules to improve productivity and product quality. First, the manual pin assembly process was divided into four stages: feeding, stabilizing, clamping, and inserting. Each stage was completed by separate cams, and corresponding step timing diagrams are drawn. The profiles of the four cams were designed and verified through theoretical calculations and kinematic simulations using a seventh-degree polynomial curve fitting method. Then, image algorithms were developed to detect pin tilt defects, pin tip defects, and to provide visual guidance for pin insertion. Finally, a pin insertion machine and its human–machine interaction interface were constructed. On-machine results show that the pin cutting pass rate reached 97%, the average insertion time for one pin was 2.84 s, the pass rate for pin insertion reached 99.75%, and the pin image guidance accuracy was 0.02 mm. Therefore, the designed pin assembly machine can reliably and consistently perform the pin insertion task, providing theoretical and experimental insights for the automated production of IGBT modules. Full article

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24 pages, 4549 KB

Open AccessReview

Research on Tbps and Kilometer-Range Transmission of Terahertz Signals

by Jianjun Yu and Jiali Chen

Micromachines 2025, 16(7), 828; https://doi.org/10.3390/mi16070828 - 20 Jul 2025

Viewed by 979

Abstract

THz communication stands as a pivotal technology for 6G networks, designed to address the critical challenge of data demands surpassing current microwave and millimeter-wave (mmWave) capabilities. However, realizing Tbps and kilometer-range transmission confronts the “dual attenuation dilemma” comprising severe free-space path loss (FSPL) [...] Read more.

THz communication stands as a pivotal technology for 6G networks, designed to address the critical challenge of data demands surpassing current microwave and millimeter-wave (mmWave) capabilities. However, realizing Tbps and kilometer-range transmission confronts the “dual attenuation dilemma” comprising severe free-space path loss (FSPL) (>120 dB/km) and atmospheric absorption. This review comprehensively summarizes our group′s advancements in overcoming fundamental challenges of long-distance THz communication. Through systematic photonic–electronic co-optimization, we report key enabling technologies including photonically assisted THz signal generation, polarization-multiplexed multiple-input multiple-output (MIMO) systems with maximal ratio combining (MRC), high-gain antenna–lens configurations, and InP amplifier systems for complex weather resilience. Critical experimental milestones encompass record-breaking 1.0488 Tbps throughput using probabilistically shaped 64QAM (PS-64QAM) in the 330–500 GHz band; 30.2 km D-band transmission (18 Gbps with 543.6 Gbps·km capacity–distance product); a 3 km fog-penetrating link at 312 GHz; and high-sensitivity SIMO-validated 100 Gbps satellite-terrestrial communication beyond 36,000 km. These findings demonstrate THz communication′s viability for 6G networks requiring extreme-capacity backhaul and ultra-long-haul connectivity. Full article

(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies, 2nd Edition)

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19 pages, 9988 KB

Open AccessArticle

Research on Modification Technology of Laser Cladding Stellite6/Cu Composite Coating on the Surface of 316L Stainless Steel Plow Teeth

by Wenhua Wang, Qilang He, Wenqing Shi and Weina Wu

Micromachines 2025, 16(7), 827; https://doi.org/10.3390/mi16070827 - 20 Jul 2025

Cited by 1 | Viewed by 507

Abstract

Plow loosening machines are essential agricultural machinery in the agricultural production process. Improving the surface strengthening process and extending the working life of the plow teeth of the plow loosening machine are of great significance. In this paper, the preparation of Stellite6/Cu composite [...] Read more.

Plow loosening machines are essential agricultural machinery in the agricultural production process. Improving the surface strengthening process and extending the working life of the plow teeth of the plow loosening machine are of great significance. In this paper, the preparation of Stellite6/Cu composite coating on the surface of 316L steel substrate intended for strengthening the plow teeth of a plow loosening machine using laser cladding technology was studied. The influence of different laser process parameters on the microstructure and properties of Stellite6/Cu composite coating was investigated. The composite coating powder was composed of Stellite6 powder with a different weight percent of copper. Microstructural analysis, phase composition, elemental distribution, microhardness, wear resistance, and corrosion resistance of the composite coatings on the plow teeth were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), microhardness testing, energy dispersive spectroscopy (EDS), friction and wear testing, and electrochemical workstation measurements. The results showed that (1) When the laser power was 1000 W, the average hardness of the prepared Stellite6/Cu composite layer achieved the highest hardness, approximately 1.36 times higher than the average hardness of the substrate, and the composite coating prepared exhibited the best wear resistance; (2) When the scanning speed was 800 mm/min, the composite coating exhibited the lowest average friction coefficient and the optimal corrosion resistance in a 3.5% wt.% NaCl solution with a self-corrosion current density of −7.55 µA/cm²; (3) When the copper content was 1 wt.%, the composite coating achieved the highest average hardness with 515.2 HV, the lowest average friction coefficient with 0.424, and the best corrosion resistance with a current density of −8.878 µA/cm². Full article

(This article belongs to the Special Issue Laser Additive Manufacturing: Design, Materials, Processes and Applications, 3rd Edition)

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13 pages, 3688 KB

Open AccessArticle

Layer-by-Layer Engineered Zinc–Tin Oxide/Single-Walled Carbon Nanotube (ZTO/SWNT) Hybrid Films for Thin-Film Transistor Applications

by Yong-Jae Kim, Young-Jik Lee, Yeon-Hee Kim, Byung Seong Bae and Woon-Seop Choi

Micromachines 2025, 16(7), 825; https://doi.org/10.3390/mi16070825 - 20 Jul 2025

Viewed by 783

Abstract

Indium-based oxide semiconductors have been commercialized because of their excellent electrical properties, but the high cost, limited availability, and environmental toxicity of indium necessitate the development of alternative materials. Among the most promising candidates, zinc–tin oxide (ZTO) is an indium-free oxide semiconductor with [...] Read more.

Indium-based oxide semiconductors have been commercialized because of their excellent electrical properties, but the high cost, limited availability, and environmental toxicity of indium necessitate the development of alternative materials. Among the most promising candidates, zinc–tin oxide (ZTO) is an indium-free oxide semiconductor with considerable potential, but its relatively low carrier mobility and inherent limitations in thin-film quality demand further performance enhancements. This paper proposes a new approach to overcome these challenges by incorporating single-walled carbon nanotubes (SWNTs) as conductive fillers into the ZTO matrix and using a layer-by-layer multiple coating process to construct nanocomposite thin films. As a result, ZTO/SWNTs (0.07 wt.%) thin-film transistors (TFTs) fabricated with three coating cycles exhibited a high saturation mobility of 18.72 cm²/V·s, a threshold voltage of 0.84 V, and a subthreshold swing of 0.51 V/dec. These values represent an approximately four-fold improvement in mobility compared to ZTO TFT, showing that the multiple-coating-based nanocomposite strategy can effectively overcome the fundamental limitations. This study confirms the feasibility of achieving high-performance oxide semiconductor transistors without indium, providing a sustainable pathway for next-generation flexible electronics and display technologies. Full article

(This article belongs to the Special Issue Thin Film Deposition and Characterization in Micro- and Nano-Technology)

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16 pages, 2403 KB

Open AccessArticle

Optimization Design of the Two-Stage Reduction Micro-Drive Mechanism Based on Particle Swarm Algorithm

by Na Zhang, Dongmei Wang, Kai Li, Kaiyang Wei, Hongyu Ge and Manzhi Yang

Micromachines 2025, 16(7), 826; https://doi.org/10.3390/mi16070826 - 19 Jul 2025

Viewed by 338

Abstract

Achieving high-precision positioning operations in a small space was of great significance in aerospace, biomedical, and other fields. In order to obtain smaller displacements with higher accuracy, this paper focused on the design, optimization, and performance analysis of a two-stage reduction micro-drive mechanism. [...] Read more.

Achieving high-precision positioning operations in a small space was of great significance in aerospace, biomedical, and other fields. In order to obtain smaller displacements with higher accuracy, this paper focused on the design, optimization, and performance analysis of a two-stage reduction micro-drive mechanism. Using the principle of lever and the principle of balanced additional force, a two-stage reduction micro-motion mechanism without parasitic motion and non-motion directional force was designed, and the structure optimization of the mechanism was completed by employing the particle swarm algorithm. A finite element analysis was conducted to assess the strength, dynamics, and kinematic properties of the mechanism. Experimental methods were also employed to analyze its dynamic and kinematic properties. The analysis results demonstrated that the mechanism met the design requirements in terms of strength and dynamic properties, with a maximum error of 9.02% and a maximum kinematic error of 0.0267 μm. The achieved reduction ratio was 24.73:1. These results indicated that the mechanism possesses excellent strength and dynamic performance, a large reduction ratio, high motion accuracy, and good linearity. This paper contributes significantly to the advancement of research in precision mechanical motion and micro-drive mechanisms. Full article

(This article belongs to the Special Issue Advanced Manufacturing Technology and Systems, 3rd Edition)

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23 pages, 6645 KB

Open AccessArticle

Encapsulation Process and Dynamic Characterization of SiC Half-Bridge Power Module: Electro-Thermal Co-Design and Experimental Validation

by Kaida Cai, Jing Xiao, Xingwei Su, Qiuhui Tang and Huayuan Deng

Micromachines 2025, 16(7), 824; https://doi.org/10.3390/mi16070824 - 19 Jul 2025

Viewed by 2690

Abstract

Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. [...] Read more.

Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. This approach integrates in-depth electro-thermal simulation (LTspice XVII/COMSOL Multiphysics 6.3) with micro/nano-packaging processes (sintering/bonding). Firstly, a multifunctional double-pulse test board was designed for the dynamic characterization of SiC devices. LTspice simulations revealed the switching characteristics under an 800 V operating condition. Subsequently, a thermal simulation model was constructed in COMSOL to quantify the module junction temperature gradient (25 °C → 80 °C). Key process parameters affecting reliability were then quantified, including conductive adhesive sintering (S820-F680, 39.3 W/m·K), high-temperature baking at 175 °C, and aluminum wire bonding (15 mil wire diameter and 500 mW ultrasonic power/500 g bonding force). Finally, a double-pulse dynamic test platform was established to capture switching transient characteristics. Experimental results demonstrated the following: (1) The packaged module successfully passed the 800 V high-voltage validation. Measured drain current (4.62 A) exhibited an error of <0.65% compared to the simulated value (4.65 A). (2) The simulated junction temperature (80 °C) was significantly below the safety threshold (175 °C). (3) Microscopic examination using a Leica IVesta 3 microscope (55× magnification) confirmed the absence of voids at the sintering and bonding interfaces. (4) Frequency-dependent dynamic characterization revealed a 6 nH parasitic inductance via Ansys Q3D 2025 R1 simulation, with experimental validation at 8.3 nH through double-pulse testing. Thermal evaluations up to 200 kHz indicated 109 °C peak temperature (below 175 °C datasheet limit) and low switching losses. This work provides a critical process benchmark for the micro/nano-manufacturing of high-density SiC modules. Full article

(This article belongs to the Special Issue Recent Advances in Micro/Nanofabrication, 2nd Edition)

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27 pages, 4412 KB

Open AccessReview

Coupling Agents in Acoustofluidics: Mechanisms, Materials, and Applications

by Shenhao Deng, Yiting Yang, Menghui Huang, Cheyu Wang, Enze Guo, Jingui Qian and Joshua E.-Y. Lee

Micromachines 2025, 16(7), 823; https://doi.org/10.3390/mi16070823 - 19 Jul 2025

Viewed by 2767

Abstract

Acoustic coupling agents serve as critical interfacial materials connecting piezoelectric transducers with microfluidic chips in acoustofluidic systems. Their performance directly impacts acoustic wave transmission efficiency, device reusability, and reliability in biomedical applications. Considering the rapidly growing body of research in the field of [...] Read more.

Acoustic coupling agents serve as critical interfacial materials connecting piezoelectric transducers with microfluidic chips in acoustofluidic systems. Their performance directly impacts acoustic wave transmission efficiency, device reusability, and reliability in biomedical applications. Considering the rapidly growing body of research in the field of acoustic microfluidics, this review aims to serve as an all-in-one reference on the role of acoustic coupling agents and relevant considerations pertinent to acoustofluidic devices for anyone working in or seeking to enter the field of disposable acoustofluidic devices. To this end, this review seeks to summarize and categorize key aspects of acoustic couplants in the implementation of acoustofluidic devices by examining their underlying physical mechanisms, material classifications, and core applications of coupling agents in acoustofluidics. Gel-based coupling agents are particularly favored for their long-term stability, high coupling efficiency, and ease of preparation, making them integral to acoustic flow control applications. In practice, coupling agents facilitate microparticle trapping, droplet manipulation, and biosample sorting through acoustic impedance matching and wave mode conversion (e.g., Rayleigh-to-Lamb waves). Their thickness and acoustic properties (sound velocity, attenuation coefficient) further modulate sound field distribution to optimize acoustic radiation forces and thermal effects. However, challenges remain regarding stability (evaporation, thermal degradation) and chip compatibility. Further aspects of research into gel-based agents requiring attention include multilayer coupled designs, dynamic thickness control, and enhancing biocompatibility to advance acoustofluidic technologies in point-of-care diagnostics and high-throughput analysis. Full article

(This article belongs to the Special Issue Recent Development of Micro/Nanofluidic Devices, 2nd Edition)

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21 pages, 6795 KB

Open AccessArticle

Enhanced Metal Surface Processing Through the No-Stray-Corrosion Controllable Electrolyte DistributionElectrochemical Machining Method Utilizing a Water-Absorbent Porous Ball

by Jiankang Wang, Qiyuan Cao, Ye Chen, Wataru Natsu and Jianshu Cao

Micromachines 2025, 16(7), 822; https://doi.org/10.3390/mi16070822 - 18 Jul 2025

Viewed by 464

Abstract

The Electrochemical Machining (ECM) method is one of the most widely used processing methods in metal surface processing, due to its unique advantages. However, the electrolyte in ECM causes stray corrosion on the workpiece. To overcome these shortcomings, we have developed a no-stray-corrosion [...] Read more.

The Electrochemical Machining (ECM) method is one of the most widely used processing methods in metal surface processing, due to its unique advantages. However, the electrolyte in ECM causes stray corrosion on the workpiece. To overcome these shortcomings, we have developed a no-stray-corrosion ECM method called the controllable electrolyte distribution ECM (CED-ECM) method. However, its practical application in metal surface processing remains largely unexplored. In this study, to improve the CED-ECM method, we delved deeper into the aforementioned aspects by simulating the actual ECM process using COMSOL Multiphysics and rigorously validating the simulation results through practical experimental observations. Then, our efforts led to the application of the CED-ECM method to metal surface processing for the SUS304 workpiece, producing noteworthy results that manifest in diverse cross-sectional profiles on the processed surfaces. This research demonstrates a validated simulation framework for the CED-ECM process and establishes a method for creating user-defined surface profiles by controlling pass intervals, enabling new applications in surface texturing. Full article

(This article belongs to the Section E：Engineering and Technology)

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17 pages, 4312 KB

Open AccessArticle

Study on Electrical Characteristics and ECG Signal Acquisition Performance of Fabric Electrodes Based on Organizational Structure and Wearing Pressure

by Ming Wang, Jinli Zhou and Ge Zhang

Micromachines 2025, 16(7), 821; https://doi.org/10.3390/mi16070821 - 17 Jul 2025

Viewed by 519

Abstract

Obtaining stable ECG signals under both static and dynamic conditions, while ensuring comfortable wear, is a prerequisite for fabric-electrode applications. It is necessary to study the wearing pressure of fabric electrodes as well as their organizational structure. In this study, fabric electrodes with [...] Read more.

Obtaining stable ECG signals under both static and dynamic conditions, while ensuring comfortable wear, is a prerequisite for fabric-electrode applications. It is necessary to study the wearing pressure of fabric electrodes as well as their organizational structure. In this study, fabric electrodes with different organizational structures (plain weave, twill weave, and satin weave) were prepared using silver-plated nylon conductive yarns as weft yarns and polyester yarns as warp yarns. The electrical characteristics of these structures of fabric electrodes were analyzed under different wearing pressures (2 kPa, 3 kPa, 4 kPa, and 5 kPa), and their effects on the quality of static and dynamic ECG signals acquired from human body were examined. The results showed that the contact impedance of the twill and satin weave structured electrodes with the skin was smaller and more stable than that of the plain weave structured electrodes. Furthermore, when a wearing pressure of 3–4 kPa was applied to the satin-structured electrodes, they not only provided satisfactory comfort but also collected stable static and dynamic ECG signals during daily exercise. These results can provide a reference for the application of fabric electrodes in ECG monitoring devices and an important basis for the design of intelligent ECG clothing. Full article

(This article belongs to the Special Issue Advances in Flexible and Wearable Electronics: Devices and Systems)

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26 pages, 5856 KB

Open AccessReview

MXene-Based Gas Sensors for NH₃ Detection: Recent Developments and Applications

by Yiyang Xu, Yinglin Wang, Zhaohui Lei, Chen Wang, Xiangli Meng and Pengfei Cheng

Micromachines 2025, 16(7), 820; https://doi.org/10.3390/mi16070820 - 17 Jul 2025

Viewed by 710

Abstract

Ammonia, as a toxic and corrosive gas, is widely present in industrial emissions, agricultural activities, and disease biomarkers. Detecting ammonia is of vital importance to environmental safety and human health. Sensors based on MXene have become an effective means for detecting ammonia gas [...] Read more.

Ammonia, as a toxic and corrosive gas, is widely present in industrial emissions, agricultural activities, and disease biomarkers. Detecting ammonia is of vital importance to environmental safety and human health. Sensors based on MXene have become an effective means for detecting ammonia gas due to their unique hierarchical structure, adjustable surface chemical properties, and excellent electrical conductivity. This study reviews the latest progress in the use of MXene and its composites for the low-temperature detection of ammonia gas. The strategies for designing MXene composites, including heterojunction engineering, surface functionalization, and active sites, are introduced, and their roles in improving sensing performance are clarified. These methods have significantly improved the ability to detect ammonia, offering high selectivity, rapid responses, and ultra-low detection limits within the low-temperature range. Successful applications in fields such as industrial safety, food quality monitoring, medical diagnosis, and agricultural management have demonstrated the multi-functionality of this technology in complex scenarios. The challenges related to the material’s oxidation resistance, humidity interference, and cross-sensitivity are also discussed. This study aims to briefly describe the reasonable design based on MXene sensors, aiming to achieve real-time and energy-saving environmental and health monitoring networks in the future. Full article

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14 pages, 4871 KB

Open AccessArticle

Study on Laser Surface Texturing and Wettability Control of Silicon Nitride Ceramic

by Hong-Jian Wang, Jing-De Huang, Bo Wang, Yang Zhang and Jin Wang

Micromachines 2025, 16(7), 819; https://doi.org/10.3390/mi16070819 - 17 Jul 2025

Viewed by 468

Abstract

Silicon nitride (Si₃N₄) ceramic is widely used in the production of structural components. The surface wettability is closely related to the service life of materials. Laser surface texturing is considered an effective method for controlling surface wettability by processing [...] Read more.

Silicon nitride (Si₃N₄) ceramic is widely used in the production of structural components. The surface wettability is closely related to the service life of materials. Laser surface texturing is considered an effective method for controlling surface wettability by processing specific patterns. This research focused on the laser surface texturing of a Si₃N₄ ceramic, employing rectangular patterns instead of the typical dimple designs, as these had promising applications in heat transfer and hydrodynamic lubrication. The effects of scanning speed and number of scans on the change of the morphologies and dimensions of the grooves were investigated. The results indicated that the higher scanning speed and fewer number of scans resulted in less damage to the textured surface. As the scanning speed increased, the width and depth of the grooves decreased significantly first, and then fluctuated. Conversely, increasing the number of scans led to an increase in the width and depth of the grooves, eventually stabilizing. The analysis of the elemental composition of different areas on the textured surface presented a notable increase in oxygen content at the grooves, while Si and N levels decreased. It was mainly caused by the chemical reaction between Si₃N₄ ceramic and oxygen during laser surface texturing in an air environment. This study also assessed the wettability of the textured surface, finding that the contact angle of the water droplet was significantly affected by the groove dimensions. After laser surface texturing, the contact angle increased from 35.51 ± 0.33° to 57.52 ± 1.83°. Improved wettability was associated with smaller groove volume, indicating better hydrophilicity at lower scanning speed and enhanced hydrophobicity with a fewer number of scans. Full article

(This article belongs to the Special Issue Advances in Digital Manufacturing and Nano Fabrication)

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41 pages, 2729 KB

Open AccessReview

Memristor Emulator Circuits: Recent Advances in Design Methodologies, Healthcare Applications, and Future Prospects

by Amel Neifar, Imen Barraj, Hassen Mestiri and Mohamed Masmoudi

Micromachines 2025, 16(7), 818; https://doi.org/10.3390/mi16070818 - 17 Jul 2025

Viewed by 1281

Abstract

Memristors, as the fourth fundamental circuit element, have attracted significant interest for their potential in analog signal processing, computing, and memory storage technologies. However, physical memristor implementations still face challenges in reproducibility, scalability, and integration with standard CMOS processes. Memristor emulator circuits, implemented [...] Read more.

Memristors, as the fourth fundamental circuit element, have attracted significant interest for their potential in analog signal processing, computing, and memory storage technologies. However, physical memristor implementations still face challenges in reproducibility, scalability, and integration with standard CMOS processes. Memristor emulator circuits, implemented using analog, digital, and mixed components, have emerged as practical alternatives, offering tunability, cost effectiveness, and compatibility with existing fabrication technologies for research and prototyping. This review paper provides a comprehensive analysis of recent advancements in memristor emulator design methodologies, including active and passive analog circuits, digital implementations, and hybrid approaches. A critical evaluation of these emulation techniques is conducted based on several performance metrics, including maximum operational frequency range, power consumption, and circuit topology. Additional parameters are also taken into account to ensure a comprehensive assessment. Furthermore, the paper examines promising healthcare applications of memristor and memristor emulators, focusing on their integration into biomedical systems. Finally, key challenges and promising directions for future research in memristor emulator development are outlined. Overall, the research presented highlights the promising future of memristor emulator technology in bridging the gap between theoretical memristor models and practical circuit implementations. Full article

(This article belongs to the Section E：Engineering and Technology)

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10 pages, 2486 KB

Open AccessArticle

Performance of Miniature Carbon Nanotube Field Emission Pressure Sensor for X-Ray Source Applications

by Huizi Zhou, Wenguang Peng, Weijun Huang, Nini Ye and Changkun Dong

Micromachines 2025, 16(7), 817; https://doi.org/10.3390/mi16070817 - 17 Jul 2025

Viewed by 2674

Abstract

There is a lack of an effective approach to measure vacuum conditions inside sealed vacuum electronic devices (VEDs) and other small-space vacuum instruments. In this study, the application performance of an innovative low-pressure gas sensor based on the emission enhancements of multi-walled carbon [...] Read more.

There is a lack of an effective approach to measure vacuum conditions inside sealed vacuum electronic devices (VEDs) and other small-space vacuum instruments. In this study, the application performance of an innovative low-pressure gas sensor based on the emission enhancements of multi-walled carbon nanotube (MWCNT) field emitters was investigated, and the in situ vacuum performance of X-ray tubes was studied for the advantages of miniature dimension and having low power consumption, extremely low outgassing, and low thermal disturbance compared to conventional ionization gauges. The MWCNT emitters with high crystallinity presented good pressure sensing performance for nitrogen, hydrogen, and an air mixture in the range of 10⁻⁷ to 10⁻³ Pa. The miniature MWCNT sensor is able to work and remain stable with high-temperature baking, important for VED applications. The sensor monitored the in situ pressures of the sealed X-ray tubes successfully with high-power operations and a long-term storage of over two years. The investigation showed that the vacuum of the sealed X-ray tube is typical at a low 10⁻⁴ Pa level, and pre-sealing degassing treatments are able to make the X-ray tube work under high vacuum levels with less outgassing and keep a stable high vacuum for a long period of time. Full article

(This article belongs to the Section D：Materials and Processing)

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14 pages, 7197 KB

Open AccessArticle

Study on Self-Sharpening Mechanism and Polishing Performance of Triethylamine Alcohol on Gel Polishing Discs

by Yang Lei, Lanxing Xu and Kaiping Feng

Micromachines 2025, 16(7), 816; https://doi.org/10.3390/mi16070816 - 16 Jul 2025

Viewed by 343

Abstract

To address the issue of surface glazing that occurs during prolonged polishing with gel tools, this study employs a triethanolamine (TEA)-based polishing fluid system to enhance the self-sharpening capability of the gel polishing disc. The inhibitory mechanism of TEA concentration on disc glazing [...] Read more.

To address the issue of surface glazing that occurs during prolonged polishing with gel tools, this study employs a triethanolamine (TEA)-based polishing fluid system to enhance the self-sharpening capability of the gel polishing disc. The inhibitory mechanism of TEA concentration on disc glazing is systematically analyzed, along with its impact on the gel disc’s frictional wear behaviour. Furthermore, the synergistic effects of process parameters on both surface quality and material removal rate (MRR) of SiC are examined. The results demonstrate that TEA concentration is a critical factor in regulating polishing performance. At an optimal concentration of 4 wt%, an ideal balance between chemical chelation and mechanical wear is achieved, effectively preventing glazing while avoiding excessive tool wear, thereby ensuring sustained self-sharpening capability and process stability. Through orthogonal experiment optimization, the best parameter combination for SiC polishing is determined: 4 wt% TEA concentration, 98 N polishing pressure, and 90 rpm rotational speed. This configuration delivers both superior surface quality and desirable MRR. Experimental data confirm that TEA significantly enhances the self-sharpening performance of gel discs through its unique complex reaction. During the rough polishing stage, the MRR increases by 34.9% to 0.85 μm/h, while the surface roughness S_a is reduced by 51.3% to 6.29 nm. After subsequent CMP fine polishing, an ultra-smooth surface with a final roughness of 2.33 nm is achieved. Full article

(This article belongs to the Special Issue Ultra-Precision Surface Abrasive Micro-Machining: Advances and Applications)

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16 pages, 11669 KB

Open AccessArticle

Design and Electromagnetic Performance Optimization of a MEMS Miniature Outer-Rotor Permanent Magnet Motor

by Kaibo Lei, Haiwang Li, Shijia Li and Tiantong Xu

Micromachines 2025, 16(7), 815; https://doi.org/10.3390/mi16070815 - 16 Jul 2025

Viewed by 2650

Abstract

In this study, we present the design and electromagnetic performance optimization of a micro-electromechanical system (MEMS) miniature outer-rotor permanent magnet motor. With increased attention towards higher torque density and lower torque pulsations in MEMS micromotor designs, an adaptation of an external rotor can [...] Read more.

In this study, we present the design and electromagnetic performance optimization of a micro-electromechanical system (MEMS) miniature outer-rotor permanent magnet motor. With increased attention towards higher torque density and lower torque pulsations in MEMS micromotor designs, an adaptation of an external rotor can be highly attractive. However, with the design complexity involved in such high-performance MEMS outer-rotor motor designs, the ultra-miniature 3D coil structures and the thin-film topology surrounding the air gap have been one of the main challenges. In this study, an ultra-thin outer-rotor motor with 3D MEMS silicon-based coils and a MEMS-compatible manufacturing method for the 3D coils is presented. Additionally, finite element simulations are conducted for the thin-film topology around the air gap to optimize performance characteristics such as torque developed, torque pulsations, and back electromotive force amplitude. Ultimately, the average magnetic flux density increased by 37.1%, from 0.361 T to 0.495 T. The root mean square (RMS) value of the back EMF per phase rises by 14.4%. Notably, the average torque is improved by 11.3%, while the torque ripple is significantly reduced from 1.281 mNm to 0.74 mNm, corresponding to a reduction of 49.9% in torque ripple percentage. Full article

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19 pages, 4958 KB

Open AccessArticle

Understanding the Nanoindentation Edge Effect of Single-Crystal Silicon Using Molecular Dynamics Simulations

by Chao Long, Ruihan Li, Pengyue Zhao, Ziteng Li, Shuhao Kang, Duo Li and Huan Liu

Micromachines 2025, 16(7), 814; https://doi.org/10.3390/mi16070814 - 16 Jul 2025

Viewed by 497

Abstract

The edge effect refers to what occurs when an object undergoes elastic contact with the edge of a material. This is common in practical applications, but the understanding of this phenomenon is not yet mature enough, and understanding the microscopic characteristics of the [...] Read more.

The edge effect refers to what occurs when an object undergoes elastic contact with the edge of a material. This is common in practical applications, but the understanding of this phenomenon is not yet mature enough, and understanding the microscopic characteristics of the material regarding this phenomenon is necessary. This article investigates the edge effects of single-crystal silicon at different indentation positions through molecular dynamics simulations. The results indicate that the edge effect of the indentation is influenced by the indentation position and depth. The closer the indentation head is to the edge of the workpiece, the more particles are extruded from the side of the workpiece and the wider the collapse range of the indentation surface. At the same time, the indentation position also affects the distribution of the von Mises stress and phase transition area. When the edge effect occurs, the von Mises stress and phase transition region tend to be concentrated near the workpiece edge. This study demonstrates the atomic-scale deformation mechanism of single-crystal silicon under varying indentation positions. Full article

(This article belongs to the Special Issue Recent Advances in Nanoindentation Techniques)

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38 pages, 5046 KB

Open AccessReview

Photonics on a Budget: Low-Cost Polymer Sensors for a Smarter World

by Muhammad A. Butt

Micromachines 2025, 16(7), 813; https://doi.org/10.3390/mi16070813 - 15 Jul 2025

Viewed by 1407

Abstract

Polymer-based photonic sensors are emerging as cost-effective, scalable alternatives to conventional silicon and glass photonic platforms, offering unique advantages in flexibility, functionality, and manufacturability. This review provides a comprehensive assessment of recent advances in polymer photonic sensing technologies, focusing on material systems, fabrication [...] Read more.

Polymer-based photonic sensors are emerging as cost-effective, scalable alternatives to conventional silicon and glass photonic platforms, offering unique advantages in flexibility, functionality, and manufacturability. This review provides a comprehensive assessment of recent advances in polymer photonic sensing technologies, focusing on material systems, fabrication techniques, device architectures, and application domains. Key polymer materials, including PMMA, SU-8, polyimides, COC, and PDMS, are evaluated for their optical properties, processability, and suitability for integration into sensing platforms. High-throughput fabrication methods such as nanoimprint lithography, soft lithography, roll-to-roll processing, and additive manufacturing are examined for their role in enabling large-area, low-cost device production. Various photonic structures, including planar waveguides, Bragg gratings, photonic crystal slabs, microresonators, and interferometric configurations, are discussed concerning their sensing mechanisms and performance metrics. Practical applications are highlighted in environmental monitoring, biomedical diagnostics, and structural health monitoring. Challenges such as environmental stability, integration with electronic systems, and reproducibility in mass production are critically analyzed. This review also explores future opportunities in hybrid material systems, printable photonics, and wearable sensor arrays. Collectively, these developments position polymer photonic sensors as promising platforms for widespread deployment in smart, connected sensing environments. Full article

(This article belongs to the Section A：Physics)

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9 pages, 2576 KB

Open AccessArticle

Novel Debris Material Identification Method Based on Impedance Microsensor

by Haotian Shi, Yucai Xie and Hongpeng Zhang

Micromachines 2025, 16(7), 812; https://doi.org/10.3390/mi16070812 - 14 Jul 2025

Viewed by 386

Abstract

Oil condition monitoring can ensure the safe operation of mechanical equipment. Metal debris is full of friction information, and the identification of debris material helps to locate wear of parts. A method based on impedance analysis is proposed to identify debris material in [...] Read more.

Oil condition monitoring can ensure the safe operation of mechanical equipment. Metal debris is full of friction information, and the identification of debris material helps to locate wear of parts. A method based on impedance analysis is proposed to identify debris material in this article. The differences in permeability and conductivity result in the nonlinear variation trend of inductance–resistance amplitude with debris volume. By establishing a database of amplitude–size curves, debris information (material and size) can be obtained through impedance analysis. Based on experimental and simulation results, iron, stainless steel, aluminum, copper, and brass particles are effectively distinguished. This method is not affected by oil’s light transmittance, other impurities, and debris surface dirt and can be used to distinguish metals with similar colors. This work provides a novel solution for debris material identification, which is expected to promote the development of fault diagnosis. Full article

(This article belongs to the Special Issue MEMS/NEMS Devices and Applications, 3rd Edition)

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25 pages, 10123 KB

Open AccessArticle

Fabrication of Micro-Holes with High Aspect Ratios in C_f/SiC Composites Using Coaxial Waterjet-Assisted Nanosecond Laser Drilling

by Chenhu Yuan, Zenggan Bian, Yue Cao, Yinan Xiao, Bin Wang, Jianting Guo and Liyuan Sheng

Micromachines 2025, 16(7), 811; https://doi.org/10.3390/mi16070811 - 14 Jul 2025

Cited by 1 | Viewed by 477

Abstract

In the present study, the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in C_f/SiC composites, coupled with nanosecond laser drilling in air for fabricating micro-holes with high aspect ratios, were investigated. The surface morphology, reaction products, and micro-hole shapes were thoroughly [...] Read more.

In the present study, the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in C_f/SiC composites, coupled with nanosecond laser drilling in air for fabricating micro-holes with high aspect ratios, were investigated. The surface morphology, reaction products, and micro-hole shapes were thoroughly examined. The results reveal that, for the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in the C_f/SiC composite, the increasing of waterjet velocity enhances the material removal rate and micro-hole depth, but reduces the micro-hole diameter and taper angle. The coaxial waterjet isolates the laser-ablated region and cools down the corresponding region rapidly, leading to the formation of a mixture of SiC, SiO₂, and Si on the surface. As the coaxial waterjet velocity increases, the morphology of residual surface products changes from a net-like structure to individual spheres. Coaxial waterjet-assisted nanosecond laser drilling, with a waterjet velocity of 9.61 m/s, achieves micro-holes with a good balance between efficiency and quality. For the fabrication of micro-holes with a high aspect ratio in C_f/SiC composites, micro-holes fabricated by nanosecond laser drilling in air exhibit obvious taper features, which should be ascribed to the combined effects of spattering slag, plasma, and energy dissipation. The application of coaxial waterjet-assisted nanosecond laser drilling on micro-holes fabricated by laser drilling in air effectively expands the hole diameter. The fabricated micro-holes have very small taper angles, with clean wall surfaces and almost no reaction products. This approach, combining nanosecond laser drilling in air followed by coaxial waterjet-assisted nanosecond laser drilling, offers a promising technique for fabricating high-quality micro-holes with high aspect ratios in C_f/SiC composites. Full article

(This article belongs to the Special Issue Optical and Laser Material Processing, 2nd Edition)

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11 pages, 2799 KB

Open AccessArticle

Development of LPFG-Based Seawater Concentration Monitoring Sensors Packaged by BFRP

by Zhe Zhang, Tongchun Qin, Yuping Bao and Jianping He

Micromachines 2025, 16(7), 810; https://doi.org/10.3390/mi16070810 - 14 Jul 2025

Viewed by 414

Abstract

Leveraging the sensitivity of long-period fiber grating (LPFG) to changes in the environmental refractive index, an LPFG-based seawater concentration monitoring sensor is proposed. Considering the highly saltine and alkali characteristics of the sensor’s operating environment, the proposed sensor is packaged by basalt fiber-reinforced [...] Read more.

Leveraging the sensitivity of long-period fiber grating (LPFG) to changes in the environmental refractive index, an LPFG-based seawater concentration monitoring sensor is proposed. Considering the highly saltine and alkali characteristics of the sensor’s operating environment, the proposed sensor is packaged by basalt fiber-reinforced polymer (BFRP), and the sensor’s sensitivities were studied by sodium chloride and calcium chloride solution concentration experiments and one real-time sodium chloride solution concentration monitoring experiment. The test results show the wavelength of LPFG, a 3 dB bandwidth and a peak loss of LPFG’s spectrogram change with changes in the concentration of sodium chloride or calcium chloride solutions, but only the wavelength has a good linear relationship with the change in solution concentration, and the sensing coefficient is −0.160 nm/% in the sodium chloride solution and −0.225 nm/% in the calcium chloride solution. The real-time monitoring test further verified the sensor’s sensing performance, with an absolute measurement error of less than 1.8%. The BFRP packaged sensor has good corrosion resistance and a simple structure, and it has a certain application value in the monitoring of salinity in the marine environment and coastal soil. Full article

(This article belongs to the Special Issue MEMS Sensors and Actuators: Design, Fabrication and Applications, 2nd Edition)

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20 pages, 23222 KB

Open AccessArticle

A Multi-View Three-Dimensional Scanning Method for a Dual-Arm Hand–Eye System with Global Calibration of Coded Marker Points

by Tenglong Zheng, Xiaoying Feng, Siyuan Wang, Haozhen Huang and Shoupeng Li

Micromachines 2025, 16(7), 809; https://doi.org/10.3390/mi16070809 - 13 Jul 2025

Viewed by 806

Abstract

To achieve robust and accurate collaborative 3D measurement under complex noise conditions, a global calibration method for dual-arm hand–eye systems and multi-view 3D imaging is proposed. A multi-view 3D scanning approach based on ICP (M3DHE-ICP) integrates a multi-frequency heterodyne coding phase solution with [...] Read more.

To achieve robust and accurate collaborative 3D measurement under complex noise conditions, a global calibration method for dual-arm hand–eye systems and multi-view 3D imaging is proposed. A multi-view 3D scanning approach based on ICP (M3DHE-ICP) integrates a multi-frequency heterodyne coding phase solution with ICP optimization, effectively correcting stitching errors caused by robotic arm attitude drift. After correction, the average 3D imaging error is 0.082 mm, reduced by 0.330 mm. A global calibration method based on encoded marker points (GCM-DHE) is also introduced. By leveraging spatial geometry constraints and a dynamic tracking model of marker points, the transformation between multi-coordinate systems of the dual arms is robustly solved. This reduces the average imaging error to 0.100 mm, 0.456 mm lower than that of traditional circular calibration plate methods. In actual engineering measurements, the average error for scanning a vehicle’s front mudguard is 0.085 mm, with a standard deviation of 0.018 mm. These methods demonstrate significant value for intelligent manufacturing and multi-robot collaborative measurement. Full article

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19 pages, 5491 KB

Open AccessArticle

Design of an Angled Single-Excitation Elliptical Vibration System

by Qiang Liu, Xiping He, Weiguo Wang and Yanning Yang

Micromachines 2025, 16(7), 808; https://doi.org/10.3390/mi16070808 - 13 Jul 2025

Viewed by 349

Abstract

An angled single-excitation elliptical vibration system for ultrasonic-assisted machining was developed in this paper, which was composed of a giant magnetostrictive transducer and an angled horn. Based on the continuous boundary conditions between the components, the frequency equation of the angled vibration system [...] Read more.

An angled single-excitation elliptical vibration system for ultrasonic-assisted machining was developed in this paper, which was composed of a giant magnetostrictive transducer and an angled horn. Based on the continuous boundary conditions between the components, the frequency equation of the angled vibration system was derived, and the resonant frequencies of vibration systems with different angles were theoretically calculated. The finite element method was employed to investigate the impact of varying angles on the resonant frequency, elliptical trajectory, phase difference, and output amplitude of the vibration systems. The electrical impedance of the vibration system and the longitudinal and transverse vibration amplitudes at the end face of the horn were tested experimentally. The results show that the resonant frequency and phase difference in the vibration system decreased, the transverse amplitude of the output elliptical trajectory increased, and the longitudinal amplitude decreased with the increase in the included angle. The elliptical trajectories obtained from the test were generally consistent with the calculated results, and the calculated values of the resonant frequencies of the three angled vibration systems were in good agreement with the experimental test values. Full article

(This article belongs to the Special Issue Acoustic Transducers and Their Applications, 2nd Edition)

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18 pages, 3047 KB

Open AccessArticle

A Rotary Piezoelectric Electromagnetic Hybrid Energy Harvester

by Zhiyang Yao and Chong Li

Micromachines 2025, 16(7), 807; https://doi.org/10.3390/mi16070807 - 11 Jul 2025

Viewed by 505

Abstract

To collect the energy generated by rotational motion in the natural environment, a piezoelectric electromagnetic hybrid energy harvester (HEH) based on a planetary gear system is proposed. The harvester combines piezoelectric and electromagnetic effects and is mainly used for collecting low-frequency rotational energy. [...] Read more.

To collect the energy generated by rotational motion in the natural environment, a piezoelectric electromagnetic hybrid energy harvester (HEH) based on a planetary gear system is proposed. The harvester combines piezoelectric and electromagnetic effects and is mainly used for collecting low-frequency rotational energy. The HEH has a compact structure and contains four sets of piezoelectric energy harvesters (PEHs) and electromagnetic energy harvesters (EMHs) inside. The working principle of the energy harvester is analyzed, its theoretical model is established, and a simulation analysis is conducted. To verify the effectiveness of the design, an experimental device is constructed. The results indicate that the HEH can generate an average output power of 250 mW under eight magnets and an external excitation frequency of 7 Hz. In actual power supply testing, the HEH can light up 60 LEDs and provide stable power supply for the temperature–humidity meter. Full article

(This article belongs to the Special Issue MEMS/NEMS Devices and Applications, 3rd Edition)

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