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Micromachines
Volume 16
Issue 2
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Micromachines, Volume 16, Issue 2 (February 2025) – 129 articles

Cover Story (view full-size image): Intracortical microelectrode arrays (MEAs) are essential for recording neural signals, with them offering insights into both healthy and diseased states. However, their reliability for long-term recording is limited by the foreign body response (FBR), including gliosis and neuronal loss near implant sites. Using amorphous silicon carbide (a-SiC) MEAs with reduced cross-sectional areas, which enhances flexibility while maintaining implantation stiffness, we compared the performance of a-SiC MEAs to conventional silicon-based probes over a period of 16 weeks in the rat motor cortex. Our results demonstrate that a-SiC MEAs exhibit superior chronic recording performance, mitigate the FBR, and achieve higher active electrode yields. Our findings highlight the potential of a-SiC technology for stable, long-term neural interfaces, advancing applications in neuroprosthetics and neuromodulation. View this paper
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21 pages, 8496 KiB  
Article
Study on Spatiotemporal Variation in Internal Temperature Field in Quartz Flexible Accelerometer
by Zhigang Zhang, Fangxiang Tang, Ziwei Zhao, Zhao Zhang and Lijun Tang
Micromachines 2025, 16(2), 241; https://doi.org/10.3390/mi16020241 - 19 Feb 2025
Viewed by 613
Abstract
Quartz flexible accelerometers (QFAs) are a type of temperature-sensitive sensor, whereby a change in temperature will cause the key parameters of the accelerometer to drift and cause stability errors. Due to the absence of effective methods for sensing the temperature of internal accelerometer [...] Read more.
Quartz flexible accelerometers (QFAs) are a type of temperature-sensitive sensor, whereby a change in temperature will cause the key parameters of the accelerometer to drift and cause stability errors. Due to the absence of effective methods for sensing the temperature of internal accelerometer components, existing temperature error correction approaches primarily rely on shell temperature measurements to establish correction models. Consequently, most correction methods achieve higher accuracy during the steady-state heat conduction phase of the accelerometer, whereas the correction error markedly increases during the transient heat conduction phase. To elucidate the temperature discrepancy between the QFA shell and its internal components and to support the development of a temperature error correction method for QFAs based on the internal temperature as a reference, this paper investigated the heat exchange dynamics between the interior and exterior of a QFA. A thermal conduction simulation model of the QFA was established, from which the spatiotemporal distribution patterns of the internal temperature field were derived. The results indicate that the temperature of the QFA shell changes significantly faster than that of the internal meter head in the early stage of the temperature change. The temperature gradient between the shell and the meter head first increases and then decreases, and the rate of temperature change in the upper part of the accelerometer is faster than that in the lower part. Before thermal equilibrium is reached, the temperature distribution inside the accelerometer is uneven in terms of time and space. Inside the accelerometer, the yoke iron, swing plate assembly, servo circuit, and magnetic steel assembly are the main components that exhibit differences in the internal temperature change in the QFA. When developing the temperature error correction method, it was crucial to address and mitigate the impact of temperature variations among these components. The average RMSE between the predicted temperature from the heat transfer model established in this paper and the experimental results was 0.4 °C. This indicates that the model can accurately predict the temperature variation within the QFA, thereby providing robust support for investigating the temperature behavior inside the QFA and offering essential technical foundations for enhancing the accuracy of the temperature error correction method. Full article
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20 pages, 7158 KiB  
Article
Coded Ultrasonic Ranging for the Distance Measurement of Coaxial Rotor Blades
by Yaohuan Lu, Zhen Qiu, Shan Zhang, Wenchuan Hu, Yongqiang Qiu and Zurong Qiu
Micromachines 2025, 16(2), 240; https://doi.org/10.3390/mi16020240 - 19 Feb 2025
Cited by 1 | Viewed by 485
Abstract
Coaxial rotor helicopters have a wide range of civilian and military applications; however, the collision risk of the upper and lower blades that comes with the coaxial rotor system remains. This paper introduces a blade-tip distance measurement method based on coded ultrasonic ranging [...] Read more.
Coaxial rotor helicopters have a wide range of civilian and military applications; however, the collision risk of the upper and lower blades that comes with the coaxial rotor system remains. This paper introduces a blade-tip distance measurement method based on coded ultrasonic ranging to tackle this challenge. Coded ultrasonic ranging with phase modulation was adopted to improve the measurement rate. In this paper, seven-bit M-sequences and Gold codes are chosen with four periods of 200 kHz sine wave carriers as the excitation signals, and the received signals are filtered by a bandpass filter and decoded by a matching filter. The coding performance is evaluated by the distinguishability and energy level of the received signals. The experimental results show that the measurement rate can reach 3060 Hz for a distance of one meter. They also give the potential solution for other high-speed measurement problems. Full article
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14 pages, 4447 KiB  
Article
Mode Optimization of Microelectromechanical-System Traveling-Wave Ultrasonic Motor Based on Kirigami
by Rong Li, Longqi Ran, Cong Wang, Jiangbo He and Wu Zhou
Micromachines 2025, 16(2), 239; https://doi.org/10.3390/mi16020239 - 19 Feb 2025
Viewed by 2057
Abstract
High-quality traveling waves in stators are critical for traveling-wave ultrasonic motors (TUSMs) to achieve good stability and efficiency. However, the modal splitting and shape distortion that is induced by the anisotropic elasticity induce severe traveling wave distortion. In this study, mode optimization based [...] Read more.
High-quality traveling waves in stators are critical for traveling-wave ultrasonic motors (TUSMs) to achieve good stability and efficiency. However, the modal splitting and shape distortion that is induced by the anisotropic elasticity induce severe traveling wave distortion. In this study, mode optimization based on kirigami is proposed to suppress modal splitting and shape distortion. Initially, the kirigami pattern on the inner boundary of the stator was built by linear interpolation. Subsequently, the optimization model for the orthogonal modes with even and odd nodal diameters was established. An extended Nelder–Mead Simplex Algorithm with the advantages of derivative-free and bound constraints was employed to search the solution. After optimization, the mode shape of the orthogonal modes with odd nodal diameters was much closer to the sine-style. For instance, the distortion of the B13 mode was significantly reduced to 0.003. Meanwhile, the intrinsic frequency matching was still retained after the optimization. In contrast, the optimization suppressed both the frequency splitting and shape distortion of the orthogonal modes, with even nodal diameters. For instance, the frequency splitting relating to the B14 mode was significantly reduced from 380 Hz to 1 Hz, and the shape distortion was as low as 0.004. Full article
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24 pages, 11146 KiB  
Article
Programmable Photonic Logic Array Based on Micro-Ring Resonators and All-Optical Modulation
by Jia Liu, Shenghang Zhou and Xiubao Sui
Micromachines 2025, 16(2), 238; https://doi.org/10.3390/mi16020238 - 19 Feb 2025
Viewed by 676
Abstract
All-optical computing is an emerging information processing technology. As a cutting-edge technology in the field of photonics, it effectively leverages the unique advantages of photons to achieve rapid computation. However, the lack of a fully functional and programmable design has slowed the progress [...] Read more.
All-optical computing is an emerging information processing technology. As a cutting-edge technology in the field of photonics, it effectively leverages the unique advantages of photons to achieve rapid computation. However, the lack of a fully functional and programmable design has slowed the progress of this type of optical computing system, especially in optical logic computing. In this paper, we design and propose a programmable photonic logic array based on all-optical computing methods. By efficiently combining on-chip photonic devices such as micro-ring resonators, we have realized a complete set of reconfigurable all-optical logic computation functions, including basic logic such as IS&NOT, AND, and OR, as well as combined logic, such as XOR and XNOR. To the best of our knowledge, the proposed architecture not only introduces three structurally similar standard logic units but also allows for their multiple-level cascading to form a large-scale photonic logic array, enabling multifunctional logic computation. Furthermore, using two independent wavelengths to represent the high and low levels of logic can effectively reduce cross-talk and overlap between signals, decreasing the dependence on the strength of the optical signal and the decision threshold. Simulation results by Photonic Integrated Circuit Simulator (INTERCONNECT) demonstrate the effectiveness and feasibility of the proposed programmable photonic logic array. Full article
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19 pages, 5684 KiB  
Article
A Versatile and Modular Microfluidic System for Dynamic Cell Culture and Cellular Interactions
by Qasem Ramadan, Rana Hazaymeh and Mohammed Zourob
Micromachines 2025, 16(2), 237; https://doi.org/10.3390/mi16020237 - 19 Feb 2025
Viewed by 615
Abstract
A versatile and modular microfluidic system for cell co-culture has been developed. Microfluidic chips, each featuring dual compartments separated by a porous membrane, have been fabricated and assembled within the system to facilitate fluidic interconnection and cell–cell communication through the chip assembly. A [...] Read more.
A versatile and modular microfluidic system for cell co-culture has been developed. Microfluidic chips, each featuring dual compartments separated by a porous membrane, have been fabricated and assembled within the system to facilitate fluidic interconnection and cell–cell communication through the chip assembly. A set of fluidic valves has been successfully integrated to regulate the flow through the chip assembly. The system allows for chip assembly in various arrangements, including in parallel, in series, and complex connections. Individual chips can be interconnected or disconnected within the system at any time. Moreover, the spatial order and orientation of the chips can be adjusted as needed, enabling the study of different cell–cell arrangements and the impact of the presence or absence of specific cell types. The utility of the system has been evaluated by culturing and interconnecting multi-monolayers of intestinal epithelial cells as a model of the complex cellular system. Epithelial monolayers were grown in multiple chips and interconnected in various configurations. The transepithelial electrical resistance and permeability profiles were investigated in detail for these configurations upon treatment of the cells with dextran sulfate sodium. Immune cells were stimulated through the epithelial layers and the expression of inflammatory cytokines was detected. This miniaturized platform offers controlled conditions for co-culturing key cellular components and assessing potential therapeutic agents in a physiologically relevant setting. Full article
(This article belongs to the Special Issue Current Trends in Microfabrication Techniques for Lab-on-a-Chip and Biomedical Microdevices)
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17 pages, 6420 KiB  
Article
Dielectrophoretic Microfluidic Designs for Precision Cell Enrichments and Highly Viable Label-Free Bacteria Recovery from Blood
by Dean E. Thomas, Kyle S. Kinskie, Kyle M. Brown, Lisa A. Flanagan, Rafael V. Davalos and Alexandra R. Hyler
Micromachines 2025, 16(2), 236; https://doi.org/10.3390/mi16020236 - 19 Feb 2025
Cited by 1 | Viewed by 706
Abstract
Conducting detailed cellular analysis of complex biological samples poses challenges in cell sorting and recovery for downstream analysis. Label-free microfluidics provide a promising solution for these complex applications. In this work, we investigate particle manipulation on two label-free microdevice designs using cDEP to [...] Read more.
Conducting detailed cellular analysis of complex biological samples poses challenges in cell sorting and recovery for downstream analysis. Label-free microfluidics provide a promising solution for these complex applications. In this work, we investigate particle manipulation on two label-free microdevice designs using cDEP to enrich E. coli from whole human blood to mimic infection workflows. E. coli is still a growing source of bacteremia, sepsis, and other infections in modern countries, affecting millions of patients globally. The two microfluidic designs were evaluated for throughput, scaling, precision targeting, and high-viability recovery. While CytoChip D had the potential for higher throughput, given its continuous method of DEP-based sorting to accommodate larger clinical samples like a 10 mL blood draw, it could not effectively recover the bacteria. CytoChip B achieved a high-purity recovery of over 98% of bacteria from whole human blood, even in concentrations on the order of <100 CFU/mL, demonstrating the feasibility of processing and recovering ultra-low concentrations of bacteria for downstream analysis, culture, and drug testing. Future work will aim to scale CytoChip B for larger volume throughput while still achieving high bacteria recovery. Full article
(This article belongs to the Special Issue Micro/Nanotechnology for Cell Manipulation, Detection and Analysis)
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13 pages, 4545 KiB  
Article
An Optimized PZT-FBG Voltage/Temperature Sensor
by Shangpeng Sun, Feiyue Ma, Yanxiao He, Bo Niu, Cheng Wang, Longcheng Dai and Zhongyang Zhao
Micromachines 2025, 16(2), 235; https://doi.org/10.3390/mi16020235 - 19 Feb 2025
Viewed by 436
Abstract
The piezoelectric grating voltage sensor has garnered significant attention in the realm of intelligent sensing, attributed to its compact size, cost-effectiveness, robust electromagnetic interference (EMI) immunity, and high network integration capabilities. In this paper, we propose a PZT-FBG (piezoelectric ceramic–fiber Bragg grating) voltage–temperature [...] Read more.
The piezoelectric grating voltage sensor has garnered significant attention in the realm of intelligent sensing, attributed to its compact size, cost-effectiveness, robust electromagnetic interference (EMI) immunity, and high network integration capabilities. In this paper, we propose a PZT-FBG (piezoelectric ceramic–fiber Bragg grating) voltage–temperature demodulation optical path architecture. This scheme effectively utilizes the originally unused temperature compensation reference grating, repurposing it as a temperature measurement grating. By employing FBGs with identical or similar parameters, we experimentally validate two distinct optical path connection schemes, before and after optimization. The experimental results reveal that, when the input voltage ranges from 250 V to 1800 V at a frequency of 50 Hz, the goodness of fit for the three fundamental waveforms is 0.996, 0.999, and 0.992, respectively. Furthermore, the sensor’s frequency response was tested across a frequency range of 50 Hz to 20 kHz, demonstrating that the measurement system can effectively respond within the sensor’s operational frequency range. Additionally, temperature measurement experiments showed a goodness of fit of 0.997 for the central wavelength of the FBG as the temperature increased. This research indicates that the improved optical path connection method not only accomplishes a synchronous demodulation of both temperature and voltage parameters but also markedly enhances the linearity and resolution of the voltage sensor. This discovery offers novel insights for further refining sensor performance and broadening the applications of optical voltage sensors. Full article
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11 pages, 936 KiB  
Article
FLIM-Phasor Analysis (FLIM-ϕ) of Aβ-Induced Membrane Order Alterations: Towards a Cell-Based Biosensor for Early Alzheimer’s Disease Diagnosis
by Antonella Battisti, Maria Grazia Ortore, Silvia Vilasi and Antonella Sgarbossa
Micromachines 2025, 16(2), 234; https://doi.org/10.3390/mi16020234 - 19 Feb 2025
Viewed by 753
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, and its early detection can be critical for a prompt intervention that can potentially slow down the disease progression and improve the patient’s quality of life. However, a diagnosis based solely on clinical symptoms can [...] Read more.
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, and its early detection can be critical for a prompt intervention that can potentially slow down the disease progression and improve the patient’s quality of life. However, a diagnosis based solely on clinical symptoms can be challenging, especially in the early stages, while the detection of specific biomarkers such as amyloid-β peptide (Aβ) and tau proteins can provide objective evidence for diagnosis. In this work, we explored the effects of Aβ peptide on cell membrane properties thanks to fluorescence lifetime imaging (FLIM) combined with the phasor analysis (FLIM-ϕ). The results showed that the membrane viscosity is altered by the presence of Aβ peptide and that cells experience this effect even at nanomolar concentrations of peptide. This considerable sensitivity opens up the possibility of envisioning a cell-based biosensor able to detect very low concentrations of Aβ in a biological fluid, thus enabling timely diagnosis and intervention. Full article
(This article belongs to the Special Issue Biosensors for Biomedical and Environmental Applications, Third Edition)
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5 pages, 163 KiB  
Editorial
Progress in RF-MEMS
by R. Niall Tait
Micromachines 2025, 16(2), 233; https://doi.org/10.3390/mi16020233 - 19 Feb 2025
Viewed by 2109
Abstract
As micro-electro-mechanical systems (MEMS) have evolved and matured over the last few decades, they have impacted a broad range of technologies and application areas [...] Full article
23 pages, 3852 KiB  
Article
Nanoparticle-Based DNA Biosensor: Synthesis of Novel Manganese Nanoparticles Applied in the Development of a Sensitive Electrochemical Double-Stranded/Single-Stranded DNA Biosensor
by Dilsat Ozkan-Ariksoysal, Elpida Pantelidou, Catherine Dendrinou-Samara and Stella Girousi
Micromachines 2025, 16(2), 232; https://doi.org/10.3390/mi16020232 - 18 Feb 2025
Viewed by 515
Abstract
The development of electrochemical DNA biosensors occurred by applying different organically coated Mn-NPs such as MnCO3@OAm, MnCO3@TEG and MnO2/Mn2O3@TEG, as well as naked MnCO3 NPs (where OAm = oleylamine and TEG = [...] Read more.
The development of electrochemical DNA biosensors occurred by applying different organically coated Mn-NPs such as MnCO3@OAm, MnCO3@TEG and MnO2/Mn2O3@TEG, as well as naked MnCO3 NPs (where OAm = oleylamine and TEG = tetraethylene glycol). The detection performances of PGEs were modified with different types of Mn-NPs, according to the guanine signal magnitudes obtained after double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) immobilization at these surfaces. DNA interaction studies were realized using UV-vis, circular dichroism (CD), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) techniques. In addition, a 3- to 5.4-fold increase in guanine response in the presence of dsDNA and a 2.3-fold increase in the presence of ssDNA were obtained with the developed biosensor. The increased signals in DNA immobilization at the electrode surfaces modified with Mn-NPs compared to bare PGE clearly show that the modification of Mn-NPs increases the electroactive surface area of the electrode. The detection limit (LOD) of dsDNA was calculated as 7.86 μg·L−1 using the MnO2/Mn2O3@TEG type of the Mn-NP-modified biosensor, while the detection limit of ssDNA was calculated as 3.49 μg·L−1 with the MnCO3@OAm type Mn-NP-modified biosensor. The proposed sensor was applied to a human DNA sample where the amount of dsDNA extract was found to be 0.62 ± 0.03 mg·L−1 after applying the MnO2/Mn2O3@TEG type of Mn-NP-modified biosensor. Full article
(This article belongs to the Section B1: Biosensors)
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13 pages, 1955 KiB  
Article
Enhancing the Sensitivity of a Thermal Microflow Sensor: A Comprehensive Modeling and Simulation Study
by Junhua Gao, Liangliang Tian and Zhengfu Cheng
Micromachines 2025, 16(2), 231; https://doi.org/10.3390/mi16020231 - 18 Feb 2025
Viewed by 2164
Abstract
The advancement of microfluidic technology has introduced new requirements for the sensitivity of microflow sensors. To address this, this paper presents a novel high-sensitivity thermal microflow sensor incorporating a heat-insulating cavity structure. The sensor utilizes porous silicon as the substrate and employs vanadium [...] Read more.
The advancement of microfluidic technology has introduced new requirements for the sensitivity of microflow sensors. To address this, this paper presents a novel high-sensitivity thermal microflow sensor incorporating a heat-insulating cavity structure. The sensor utilizes porous silicon as the substrate and employs vanadium dioxide as the thermistor element. This study employed COMSOL Multiphysics finite element software 5.6 to investigate the impact of materials and structural factors on the sensor’s sensitivity, as well as considering the dynamic laws governing their influence. Additionally, the effects of thermal expansion and thermal stress on the microstructure of the sensor are thoroughly examined. The research results show that the sensitivity of the sensor was influenced by key factors such as the distance between the heater and the thermistors, the diameter of the flow channel, the power of the heater, and the presence of an insulation cavity. The utilization of B-phase vanadium dioxide, known for its high temperature coefficient of resistance and suitable resistivity, led to a significant reduction in sensor size and a remarkable improvement in sensitivity. The implementation of four thermistors forming a Wheatstone full bridge further enhanced the sensor’s sensitivity. The sensor’s sensitivity was substantially higher when employing a porous silicon substrate compared with a silicon substrate. Moreover, the integration of a micro-bridge and four micro-beams composed of silicon nitride into the sensor’s structure further improved its sensitivity. The proposed design holds promise for enhancing the sensitivity of thermal microflow sensors and offers valuable insights for future advancements in MEMS technology. Full article
(This article belongs to the Special Issue Selected Papers From the 25th Annual Conference and 14th International Conference of Chinese Society of Micro-Nano Technology (CSMNT 2023))
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13 pages, 6068 KiB  
Article
Fabrication and Characterization of a Flexible Polyurethane-Based Triboelectric Nanogenerator for a Harvesting Energy System
by Saba Ejaz, Imran Shah, Shahid Aziz, Gul Hassan, Ahmed Shuja, Muhammad Asif Khan and Dong-Won Jung
Micromachines 2025, 16(2), 230; https://doi.org/10.3390/mi16020230 - 17 Feb 2025
Viewed by 742
Abstract
Powering wearable and portable devices, triboelectric nanogenerators (TENGs) are a considerably promising technology. Low-cost production, ease of fabrication, optimal efficiency, and high output performance are always key concerns in developing energy harvesting technologies. Optimum efficiency and high output are always key concerns. This [...] Read more.
Powering wearable and portable devices, triboelectric nanogenerators (TENGs) are a considerably promising technology. Low-cost production, ease of fabrication, optimal efficiency, and high output performance are always key concerns in developing energy harvesting technologies. Optimum efficiency and high output are always key concerns. This research addresses the ongoing challenge of raising efficient, flexible, and lightweight energy harvesting systems for recent wearable technologies. In this research, a triboelectric nanogenerator is proposed for harvesting the triboelectric effect. Using polyurethane (PU), a bendable TENG that is in the vertical contact separation mode was developed. UV-curable PU forms the basis of TENGs. A sponge, repurposed from landfill waste, acts by means of a spacer to maintain a consistent air gap between the tribo-layers for enhanced triboelectrification. The triboelectric nanogenerators formed a Voc approaching 500 V and a current of ~2 µA and also showed high performance with a power density of 8.53 W/m2. In addition, the triboelectric nanogenerator can light LEDs and charge capacitors, making it a self-powered energy source for portable devices, Wi-Fi, and monitoring systems. The proposed TENG provides a capable solution for sustainable, self-powered wearable electronics and has the potential for further development in energy-efficient and eco-friendly applications. Full article
(This article belongs to the Special Issue Piezoelectric Devices and System in Micromachines)
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14 pages, 3597 KiB  
Article
TCAD Simulation Study of Electrical Performance of a Novel High-Purity Germanium Drift Detector
by Mingyang Wang, Zheng Li, Bo Xiong and Yongguang Xiao
Micromachines 2025, 16(2), 229; https://doi.org/10.3390/mi16020229 - 17 Feb 2025
Viewed by 511
Abstract
High-purity germanium (HPGe) detectors occupy a prominent position in fields such as radiation detection and aerospace because of their excellent energy resolution and wide detection range. To achieve a broader detection range, conventional HPGe detectors often need to be expanded to cubic-centimeter-scale volumes. [...] Read more.
High-purity germanium (HPGe) detectors occupy a prominent position in fields such as radiation detection and aerospace because of their excellent energy resolution and wide detection range. To achieve a broader detection range, conventional HPGe detectors often need to be expanded to cubic-centimeter-scale volumes. However, this increase in volume leads to a large detector area, which in turn increases the detector capacitance, affecting the detector’s noise level and performance. To address this issue, this study proposes a novel high-purity germanium drift detector (HPGeDD). The design features a small-area central collecting cathode surrounded by concentric anode rings, with a resistive chain interposed between the anode rings to achieve self-dividing voltage. This design ensures that the detector’s capacitance is only related to the area of the central collecting cathode, independent of the overall active area, thus achieving a balance between a small capacitance and large active area. Electrical performance simulations of the novel detector were conducted using the semiconductor simulation software Sentaurus TCAD (P-2019.03). The results show a smooth electric potential distribution within the detector, forming a lateral electric field, as well as a lateral hole drift channel precisely directed toward the collecting cathode. Furthermore, simulations of heavy ion incidence were performed to investigate the detector’s carrier collection characteristics. The simulation results demonstrate that the HPGeDD exhibits advantages such as fast signal response and short collection time. The design proposal presented in this study offers a new solution to the problem of excessive capacitance in conventional HPGe detectors, expands their application scope, and provides theoretical guidance for subsequent improvements, optimizations, and practical manufacturing. Full article
(This article belongs to the Special Issue Photonic and Optoelectronic Devices and Systems, Third Edition)
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15 pages, 5329 KiB  
Article
Dynamics Research of the Hopfield Neural Network Based on Hyperbolic Tangent Memristor with Absolute Value
by Huiyan Gao and Hongmei Xu
Micromachines 2025, 16(2), 228; https://doi.org/10.3390/mi16020228 - 17 Feb 2025
Viewed by 535
Abstract
Neurons in the brain are interconnected through synapses. Local active memristors can both simulate the synaptic behavior of neurons and the action potentials of neurons. Currently, the hyperbolic tangent function-type memristors used for coupling neural networks do not belong to local active memristors. [...] Read more.
Neurons in the brain are interconnected through synapses. Local active memristors can both simulate the synaptic behavior of neurons and the action potentials of neurons. Currently, the hyperbolic tangent function-type memristors used for coupling neural networks do not belong to local active memristors. To take advantage of local active memristors and consider the multi-equilibrium point problem, a cosine function is introduced into the state equation, resulting in the design of an absolute value hyperbolic tangent-type double local active memristor, and it is used as a coupling synapse to replace a synaptic weight in a 3-neuron HNN. Then, basic dynamical analysis methods are used to study the effects of different memristor synapse coupling strengths and different initial conditions on the dynamics of the neural network. The research results indicate that dynamical behavior of memristor Hopfield neural network is closely related to the synaptic coupling strengths and the initial conditions, and this neural network exhibits rich dynamical behaviors, including the coexistence of chaotic and periodic attractors, super-multistability phenomena, etc. Finally, the neural network was implemented using an FPGA development board, verifying the hardware feasibility of this system. Full article
(This article belongs to the Special Issue Novel Computing Architectures and Digital Circuit Designs Using Memristors and Memristive Systems, 2nd Edition)
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30 pages, 23922 KiB  
Article
The Influence of Contour Form Geometric Features and the Number of Cutting Passes on the Surface Quality Characteristics and Critical Points of Cutting Tools Fabricated by Wire Electrical Discharge Machining (WEDM)
by Amir Alinaghizadeh, Bahman Azarhoushang and Mohammadjafar Hadad
Micromachines 2025, 16(2), 227; https://doi.org/10.3390/mi16020227 - 17 Feb 2025
Viewed by 395
Abstract
Since one of the effective methods for producing the form-cutting tools used in the form-turning process involves utilizing a wire cut machine, the effect of the geometric characteristics of the form contour on reducing the negative effects of the recast layer was investigated [...] Read more.
Since one of the effective methods for producing the form-cutting tools used in the form-turning process involves utilizing a wire cut machine, the effect of the geometric characteristics of the form contour on reducing the negative effects of the recast layer was investigated in this research. The basic assumption of the components for each type of profile form is based on a combination of four modes, i.e., concave arc, convex arc, flat surface, and oblique surface. Based on this, samples were fabricated as cutting tools with three different radii: a convex arc, a concave arc, and a flat surface. During the wire electrical discharge machining (WEDM) operation, one-pass mode was used to create a rough surface, two passes resulted in a semi-finished surface, and three passes resulted in a finished surface. Furthermore, the difference between the surface quality of the recast layer in the two areas above the workpiece or the wire entry point and the bottom area of the workpiece or the wire exit point was studied. Finally, the effect of the direction, size of the curvature and the number of passes in the electric discharge process of the wire on the recast layer was shown, and it was observed that with the increase in the number of passes in WEDM, the thickness of the recast layer was reduced, along with the uniformity of the cutting contour section in the areas close to the cutting region. The entry of the wire was greater than that in the areas near the exit of the wire. Full article
(This article belongs to the Special Issue Recent Advances in Micro/Nanofabrication, 2nd Edition)
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21 pages, 3114 KiB  
Review
Redesigning FDM Platforms for Bio-Printing Applications
by Burak Turker
Micromachines 2025, 16(2), 226; https://doi.org/10.3390/mi16020226 - 16 Feb 2025
Viewed by 601
Abstract
Fused Deposition Modeling (FDM) is a prominent additive manufacturing technique known for its ability to provide cost-effective and fast printing solutions. FDM enables the production of computer-aided 3D designs as solid objects at macro scales with high-precision alignment while sacrificing excellent surface smoothness [...] Read more.
Fused Deposition Modeling (FDM) is a prominent additive manufacturing technique known for its ability to provide cost-effective and fast printing solutions. FDM enables the production of computer-aided 3D designs as solid objects at macro scales with high-precision alignment while sacrificing excellent surface smoothness compared to other 3D printing techniques such as SLA (Stereolithography) and SLS (Selective Laser Sintering). Electro-Spinning (ES) is another technique for producing soft-structured nonwoven micro-scale materials, such as nanofibers. However, compared to the FDM technique, it has limited accuracy and sensitivity regarding high-precision alignment. The need for high-precision alignment of micro-scaled soft structures during the printing process raises the question of whether FDM and ES techniques can be combined. Today, the printing technique with such capability is called Melt Electro Writing (MEW), and in practice, it refers to the basic working principle on which bio-printers are based. This paper aims to examine how these two techniques can be combined affordably. Comparatively, it presents output production processes, design components, parameters, and materials used in output production. It discusses the limitations and advantages of such a hybrid platform, specifically from the perspective of engineering design and its biomedical applications. Full article
(This article belongs to the Section D3: 3D Printing and Additive Manufacturing)
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22 pages, 15716 KiB  
Article
Development of a Next-Generation Cooling Channel Technology with High Cooling Efficiency by Roughing Cooling Channels Using a Combination of Laser Machining and Embossing Techniques
by Chil-Chyuan Kuo, Geng-Feng Lin, Armaan Farooqui, Song-Hua Huang and Shih-Feng Tseng
Micromachines 2025, 16(2), 225; https://doi.org/10.3390/mi16020225 - 16 Feb 2025
Viewed by 550
Abstract
This study investigates the development of a rapid wax injection tooling with enhanced heat dissipation performance using aluminum-filled epoxy resin molds and cooling channel roughening technology. Experimental evaluations were conducted on cooling channels with eleven surface roughness variations, revealing that a maximum roughness [...] Read more.
This study investigates the development of a rapid wax injection tooling with enhanced heat dissipation performance using aluminum-filled epoxy resin molds and cooling channel roughening technology. Experimental evaluations were conducted on cooling channels with eleven surface roughness variations, revealing that a maximum roughness of 71.9 µm achieved an 81.48% improvement in cooling efficiency compared to smooth channels. The optimal coolant discharge rate was determined to be 2 L/min. The heat dissipation time for wax patterns was significantly reduced, enabling a cooling time reduction of approximately 12 s per product. For a production scale of 100,000 units, this equates to a time savings of about 13 days. Empirical equations were established for estimating heat dissipation time and pressure drop, with a high coefficient of determination. This research provides a valuable contribution to the mold and dies manufacturing industry, offering practical solutions for sustainable and efficient production processes. Full article
(This article belongs to the Special Issue Laser Micro/Nano-Fabrication)
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12 pages, 1905 KiB  
Article
Analysis and Prediction of Melt Pool Geometry in Rectangular Spot Laser Cladding Based on Ant Colony Optimization–Support Vector Regression
by Junhua Wang, Jiameng Wang, Xiaoqin Zha, Yan Lu, Kun Li, Junfei Xu and Tancheng Xie
Micromachines 2025, 16(2), 224; https://doi.org/10.3390/mi16020224 - 16 Feb 2025
Viewed by 2357
Abstract
The rectangular spot laser cladding system, due to its large spot size and high efficiency, has been widely applied in laser cladding equipment, significantly improving cladding’s efficiency. However, while enhancing cladding efficiency, the rectangular spot laser cladding system may also affect the stability [...] Read more.
The rectangular spot laser cladding system, due to its large spot size and high efficiency, has been widely applied in laser cladding equipment, significantly improving cladding’s efficiency. However, while enhancing cladding efficiency, the rectangular spot laser cladding system may also affect the stability of the melt pool, thereby impacting the cladding’s quality. To accurately predict the melt pool morphology and size during wide beam laser cladding, this study developed a melt pool monitoring system. Through real-time monitoring of the melt pool morphology, image processing techniques were employed to extract features such as the melt pool width and area. The study used laser power, scanning speed, and the powder feed rate as input variables, and established a prediction model for the melt pool width and area based on Support Vector Regression (SVR). Additionally, an Ant Colony Optimization (ACO) algorithm was applied to optimize the SVR model, resulting in an ACO-SVR-based prediction model for the melt pool. The results show that the relative error in predicting the melt pool width using the ACO-SVR model is less than 2.2%, and the relative error in predicting the melt pool area is less than 9.13%, achieving accurate predictions of the melt pool width and area during rectangular spot laser cladding. Full article
(This article belongs to the Special Issue Integrated Photonics and Optoelectronics, 2nd Edition)
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21 pages, 4175 KiB  
Article
Dynamic Performance Evaluation of Bidirectional Bridgeless Interleaved Totem-Pole Power Factor Correction Boost Converter
by Hsien-Chie Cheng, Wen-You Jhu, Yu-Cheng Liu, Da-Wei Zheng, Yan-Cheng Liu and Tao-Chih Chang
Micromachines 2025, 16(2), 223; https://doi.org/10.3390/mi16020223 - 16 Feb 2025
Viewed by 683
Abstract
This study aims to conduct an assessment of the dynamic characteristics of a proposed 6.6 kW bidirectional bridgeless three-leg interleaved totem-pole power factor correction (PFC) boost converter developed for the front-end stage of electric vehicle onboard charger applications during load cycles. This proposed [...] Read more.
This study aims to conduct an assessment of the dynamic characteristics of a proposed 6.6 kW bidirectional bridgeless three-leg interleaved totem-pole power factor correction (PFC) boost converter developed for the front-end stage of electric vehicle onboard charger applications during load cycles. This proposed PFC boost converter integrates the self-developed silicon carbide (SiC) power MOSFET modules for achieving high efficiency and high power density. To assess the switching transient behavior, power loss, and efficiency of the SiC MOSFET power modules, a fully integrated electromagnetic-circuit coupled simulation (ECCS) model that incorporates an electromagnetic model, an equivalent circuit model, and an SiC MOSFET characterization model are used. In this simulation model, the impact of parasitic effects on the system’s performance is considered. The accuracy of the ECCS model is confirmed through comparing the calculated results with the experimental data obtained through the double pulse test and the closed-loop converter operation. Furthermore, a comparative study between the interleaved and non-interleaved topologies is also performed in terms of power loss and efficiency. Additionally, the performance of the SiC MOSFET-based PFC boost converter is further compared with that of the silicon (Si) insulated gate bipolar transistor (IGBT)-based one. Finally, a parametric analysis is carried out to explore the impact of several operating conditions on the power loss of the proposed totem-pole PFC boost converter. Full article
(This article belongs to the Section D1: Semiconductor Devices)
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12 pages, 3094 KiB  
Article
High-Pulse-Repetition-Rate Eye-Safe Raman Laser with Acousto-Optic Q-Switched Device
by Yu-Hsin Hsu, Song-Qing Lin, Dai-Jun Liu, Hsing-Chih Liang and Yung-Fu Chen
Micromachines 2025, 16(2), 222; https://doi.org/10.3390/mi16020222 - 16 Feb 2025
Viewed by 537
Abstract
The acousto-optic Q-switch is exploited to develop a high-repetition-rate eye-safe Raman laser at 1526 nm. The Nd:YVO4 and KGW crystals are employed as the fundamental laser and Stokes Raman gain materials, respectively. The influence of the gate-open time on the performance is [...] Read more.
The acousto-optic Q-switch is exploited to develop a high-repetition-rate eye-safe Raman laser at 1526 nm. The Nd:YVO4 and KGW crystals are employed as the fundamental laser and Stokes Raman gain materials, respectively. The influence of the gate-open time on the performance is systematically explored for the repetition rate between 80 and 150 kHz. The separate configuration is used to construct the resonant cavities for the fundamental and Stokes waves to achieve a pulse width that is as short as possible. Under the optimal alignment, the average output power can exceed 5.0 W at a pump power of 30 W for a repetition rate within 100–150 kHz with a gate-open time of 0.5 μs. In addition, the output peak power can be greater than 10 kW for a pulse repetition rate between 80 and 120 kHz. The optical-to-optical conversion efficiency is up to 16.7%, which is better than that obtained by the Nd:YVO4/YVO4 system. Full article
(This article belongs to the Special Issue Surface and Bulk Acoustic Wave Devices)
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14 pages, 8059 KiB  
Article
The Effect of Through-Silicon-Via Thermal Stress on Metal-Oxide-Semiconductor Field-Effect Transistor Properties Under Cooling to Ultra-Low Temperatures
by Wenting Xie, Xiaoting Chen, Liting Zhang, Xiangjun Lu, Bing Ding and An Xie
Micromachines 2025, 16(2), 221; https://doi.org/10.3390/mi16020221 - 15 Feb 2025
Viewed by 572
Abstract
The thermal through-silicon-via (TTSV) has a serious thermal stress problem due to the mismatch of the coefficient of thermal expansion between the Si substrate and filler metal. At present, the thermal stress characteristics and strain mechanism of TTSV are mainly concerned with increases [...] Read more.
The thermal through-silicon-via (TTSV) has a serious thermal stress problem due to the mismatch of the coefficient of thermal expansion between the Si substrate and filler metal. At present, the thermal stress characteristics and strain mechanism of TTSV are mainly concerned with increases in temperature, and its temperature range is concentrated between 173 and 573 K. By employing finite element analysis and a device simulation method based on temperature-dependent material properties, the impact of TTSV thermal stress on metal-oxide-semiconductor field-effect transistor (MOSFET) properties is investigated under cooling down from room temperature to the ultra-low temperature (20 mK), where the magnitude of thermal stress in TTSV is closely associated with the TTSV diameter and results in significant tension near the Cu-Si interface and consequently increasing the likelihood of delamination and cracking. Considering the piezoresistive effect of the Si substrate, both the TTSV diameter and the distance between TTSV and MOSFET are found to have more pronounced effects on electron mobility along [100] crystal orientation and hole mobility along [110] crystal orientation. Applying a gate voltage of 3 V, the saturation current for the 45 nm-NMOS transistor oriented along channel [100] experiences a variation as high as 34.3%. Moreover, the TTSV with a diameter of 25 μm generates a change in MOSFET threshold voltage up to −56.65 mV at a distance as short as 20 μm. The influences exerted by the diameter and distance are consistent across carrier mobility, saturation current, and threshold voltage parameters. Full article
(This article belongs to the Special Issue Applications of Data Sciences in Semiconductor Industry: Design, Manufacturing, Packaging and Testing)
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9 pages, 3876 KiB  
Article
A 3.2–3.6 GHz GaN Doherty Power Amplifier Module Based on a Compact Low-Loss Combiner
by Xiyu Wang, Dehan Wang, Wenming Li, Xiaolin Lv, Kai Cui, Haijun Liu and Kai Kang
Micromachines 2025, 16(2), 220; https://doi.org/10.3390/mi16020220 - 15 Feb 2025
Viewed by 667
Abstract
In this paper, a 3.2–3.6 GHz two-stage Doherty power amplifier (PA) module is proposed for fifth-generation (5G) massive multiple-input multiple-output (MIMO) base stations. A detailed design method and procedure for a compact and low-loss combiner suitable for the Doherty PA module are introduced. [...] Read more.
In this paper, a 3.2–3.6 GHz two-stage Doherty power amplifier (PA) module is proposed for fifth-generation (5G) massive multiple-input multiple-output (MIMO) base stations. A detailed design method and procedure for a compact and low-loss combiner suitable for the Doherty PA module are introduced. Based on the proposed combiner, a Doherty PA module is implemented using gallium nitride (GaN) transistors and surface-mounted devices (SMDs) with a packaged size of 8 × 8 mm2. The proposed two-stage Doherty PA module achieves a 3 dB small-signal bandwidth of 3.1–3.9 GHz and a peak gain of 31.7 dB. From 3.2 to 3.6 GHz, the saturated output power is 40.4–41.1 dBm. Moreover, the measured saturated drain efficiency (DE) and 8 dB power back-off (PBO) DE reach 51–56.6% and 45.5–48.6%, respectively. Full article
(This article belongs to the Special Issue Advanced Wide Bandgap Semiconductor Materials and Devices)
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11 pages, 5969 KiB  
Article
W-Band Low-Noise Amplifier with Improved Stability Using Dual RC Traps in Bias Networks on a 0.1 μm GaAs pHEMT Process
by Seong-Hee Han and Dong-Wook Kim
Micromachines 2025, 16(2), 219; https://doi.org/10.3390/mi16020219 - 15 Feb 2025
Viewed by 521
Abstract
This paper demonstrates that potential oscillations in various frequency bands of monolithic microwave integrated circuits (MMICs) can be effectively suppressed using well-designed dual RC traps in the bias networks. The proposed approach is applied to the design and development of a highly stable [...] Read more.
This paper demonstrates that potential oscillations in various frequency bands of monolithic microwave integrated circuits (MMICs) can be effectively suppressed using well-designed dual RC traps in the bias networks. The proposed approach is applied to the design and development of a highly stable W-band low-noise amplifier (LNA) MMIC for high-precision millimeter-wave applications. The amplifier is fabricated using the 0.1 µm GaAs pHEMT process from Win Semiconductors. The cascaded four-stage design consists of two low-noise-optimized stages, followed by two high-gain-tuned stages. Stability is enhanced through the integration of dual RC traps in the bias networks, which is rigorously evaluated using stability factors (K and μ) and network determinant function (NDF) encirclement analysis. In low-noise mode, the developed low-noise amplifier MMIC achieves a noise figure of 5.6−6.2 dB and a linear gain of 17.8−19.8 dB over the 90−98 GHz frequency range, while only consuming a DC power of 96 mW. In high-gain mode, it has a noise figure of 6.2−6.9 dB and a linear gain of 19.8−21.7 dB. Full article
(This article belongs to the Special Issue RF Devices: Technology and Progress)
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11 pages, 2717 KiB  
Article
Vapor-Assisted Method to Deposit Compact (CH3NH3)3Bi2I9 Thin Films for Bismuth-Based Planar Perovskite Solar Cells
by Zihao Gao, Xinjie Wang, Zhen Sun, Ping Song, Xiyuan Feng and Zhixin Jin
Micromachines 2025, 16(2), 218; https://doi.org/10.3390/mi16020218 - 14 Feb 2025
Viewed by 562
Abstract
Bismuth-based perovskite derivatives, (CH3NH3)3Bi2I9 (MBI), are promising non-toxic light-absorbing materials widely used in various photoelectric devices because of their excellent stability. However, MBI-based perovskite solar cells (PSCs) are limited by poor film quality, and [...] Read more.
Bismuth-based perovskite derivatives, (CH3NH3)3Bi2I9 (MBI), are promising non-toxic light-absorbing materials widely used in various photoelectric devices because of their excellent stability. However, MBI-based perovskite solar cells (PSCs) are limited by poor film quality, and the performance of such a device is far behind that of lead-based PSCs. In this work, the crystal structure and morphological properties of MBI films were compared across different preparation methods. The two-step vapor-assisted method can prepare continuous dense MBI films because MBI crystal nucleation is induced by the BiI3 seed layer. The MBI film grown by this method is better for the production of excellent PSCs compared to the film prepared by the solution method. The best photovoltaic device based on the MBI film could obtain a power conversion efficiency of 1.13%. An MBI device is stored in the glove box for 60 days, and the device’s performance is maintained at 99%. These results indicate that the vapor-assisted deposition of MBI films can be an effective method to improve the performance of bismuth-based planar PSCs. Full article
(This article belongs to the Special Issue Energy Conversion Materials/Devices and Their Applications)
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16 pages, 10336 KiB  
Article
A Design of a Small-Aperture Low-Profile Omnidirectional Conformal Antenna
by Jieying Bai, Xi Li, Ziyu Zhang, Junjun Wu and Lin Yang
Micromachines 2025, 16(2), 217; https://doi.org/10.3390/mi16020217 - 14 Feb 2025
Viewed by 524
Abstract
In this article, a small-aperture, low-profile, and omnidirectional conformal antenna is proposed which can be utilized on space-limited equipment platforms such as airplanes, ships, and vehicles. The antenna consists of an open metal cavity, a discone antenna, a parasitic structure, and a radome. [...] Read more.
In this article, a small-aperture, low-profile, and omnidirectional conformal antenna is proposed which can be utilized on space-limited equipment platforms such as airplanes, ships, and vehicles. The antenna consists of an open metal cavity, a discone antenna, a parasitic structure, and a radome. The small aperture and low-profile design of the metal cavity result in a rapid narrowing of the bandwidth of the discone antenna. Therefore, we introduce a parasitic structure that not only enlarges the impedance bandwidth by adding a resonant point, but can also be used to adjust the unroundness of the horizontal pattern. Meanwhile, the conformal design of the antenna with four surfaces of different curvatures is presented. The simulation and testing results demonstrate that the antenna can achieve a VSWR of less than 2 within a bandwidth of 1.95–2.62 GHz (29.3%), with a minimum aperture of 0.43 omnidirectional radiation pattern, with a gain exceeding −2.2 dBi in the azimuthal plane. This antenna offers the advantages of a small aperture, low profile, and conformal capability. Furthermore, the resonances of high and low frequencies can be adjusted through two different structures, enhancing the flexibility of antenna design. Full article
(This article belongs to the Section E：Engineering and Technology)
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15 pages, 3565 KiB  
Article
pH Measurements Using Leaky Waveguides with Synthetic Hydrogel Films
by Victoria Wensley, Nicholas J. Goddard and Ruchi Gupta
Micromachines 2025, 16(2), 216; https://doi.org/10.3390/mi16020216 - 14 Feb 2025
Viewed by 553
Abstract
Leaky waveguides (LWs) are low-refractive-index films deposited on glass substrates. In these, light can travel in the film while leaking out at the film–substrate interface. The angle at which light can travel in the film is dependent on its refractive index and thickness, [...] Read more.
Leaky waveguides (LWs) are low-refractive-index films deposited on glass substrates. In these, light can travel in the film while leaking out at the film–substrate interface. The angle at which light can travel in the film is dependent on its refractive index and thickness, which can change with pH when the film is made of pH-responsive materials. Herein, we report an LW comprising a waveguide film made of a synthetic hydrogel containing the monomers acrylamide and N-[3-(dimethylamino)propyl]methacrylamide (DMA) and a bisacrylamide crosslinker for pH measurements between 4 and 8. The response of the LW pH sensor was reversible and the response times were 0.90 ± 0.14 and 2.38 ± 0.22 min when pH was changed from low to high and high to low, respectively. The reported LW pH sensor was largely insensitive to typical concentrations of common interferents, including sodium chloride, urea, aluminum sulfate, calcium chloride, and humic acid. Compared to a glass pH electrode, the measurement range is smaller but is close to the range required for monitoring the pH of drinking water. The pH resolution of the hydrogel sensor was ~0.004, compared to ~0.01 for the glass electrode. Full article
(This article belongs to the Special Issue Manufacturing and Application of Advanced Thin-Film-Based Device)
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11 pages, 9499 KiB  
Communication
A Complementary Metal-Oxide Semiconductor (CMOS) Analog Optoelectronic Receiver with Digital Slicers for Short-Range Light Detection and Ranging (LiDAR) Systems
by Yunji Song and Sung-Min Park
Micromachines 2025, 16(2), 215; https://doi.org/10.3390/mi16020215 - 13 Feb 2025
Viewed by 618
Abstract
This paper introduces an analog differential optoelectronic receiver (ADOR) integrated with digital slicers for short-range LiDAR systems, consisting of a spatially modulated P+/N-well on-chip avalanche photodiode (APD), a cross-coupled differential transimpedance amplifier (CCD-TIA) with cross-coupled active loads, a continuous-time linear equalizer [...] Read more.
This paper introduces an analog differential optoelectronic receiver (ADOR) integrated with digital slicers for short-range LiDAR systems, consisting of a spatially modulated P+/N-well on-chip avalanche photodiode (APD), a cross-coupled differential transimpedance amplifier (CCD-TIA) with cross-coupled active loads, a continuous-time linear equalizer (CTLE), a limiting amplifier (LA), and dual digital slicers. A key feature is the integration of an additional on-chip dummy APD at the differential input node, which enables the proposed ADOR to outperform a traditional single-ended TIA in terms of common-mode noise rejection ratio. Also, the CCD-TIA utilizes cross-coupled PMOS-NMOS active loads not only to generate the symmetric output waveforms with maximized voltage swings, but also to provide wide bandwidth characteristics. The following CTLE extends the receiver bandwidth further, allowing the dual digital slicers to operate efficiently even at high sampling rates. The LA boosts the output amplitudes to suitable levels for the following slicers. Then, the inverter-based slicers with low power consumption and a small chip area produce digital outputs. The fabricated ADOR chip using a 180 nm CMOS process demonstrates a 20 dB dynamic range from 100 μApp to 1 mApp, 2 Gb/s data rate with a 490 fF APD capacitance, and 22.7 mW power consumption from a 1.8 V supply. Full article
(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications, 2nd Edition)
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15 pages, 7450 KiB  
Article
A Wafer-Level Fabricated Heating–Vacuum Micro-Platform with Resonant MEMS Monolithically Integrated
by Kaixuan He, Rui Feng, Yu Zheng, Lijian Guo, Qichao Liao, Dongfang Song, Yuan Xiang and Xinxin Li
Micromachines 2025, 16(2), 214; https://doi.org/10.3390/mi16020214 - 13 Feb 2025
Viewed by 644
Abstract
This paper presents a silicon-based wafer-level vacuum packaging platform with a monolithically integrated micro-oven. This system provides vacuum and constant temperature operating conditions to improve the performance of resonant micro-electro-mechanical systems (MEMS) devices. Based on a three-layer wafer-level vacuum packaging process, the platform [...] Read more.
This paper presents a silicon-based wafer-level vacuum packaging platform with a monolithically integrated micro-oven. This system provides vacuum and constant temperature operating conditions to improve the performance of resonant micro-electro-mechanical systems (MEMS) devices. Based on a three-layer wafer-level vacuum packaging process, the platform integrates a silicon thermistor, a thermal isolation structure, and a heater with the addition of a mask and an additional silicon wafer. This wafer-level vacuum-packaging platform achieved a vacuum level of approximately 6 mTorr. Due to the micro-oven, the temperature coefficient of the resonant frequency for the MEMS resonator was reduced by 48 times, and the temperature coefficient of the quality factor was reduced 19 times within the temperature range of −40 °C to 80 °C. The heater of the micro-oven consumed about 364 mW of power when the ambient temperature was −40 °C and the temperature controlled by the micro-oven was 100 °C. This method enables the wafer-level integration of the thermistor, thermal isolation structure, heater, and vacuum-packaged resonator, offering advantages such as low cost, efficient batch production, and high performance. Full article
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5 pages, 193 KiB  
Editorial
Etching: The Art of Semiconductor Micromachining
by Lucia Romano
Micromachines 2025, 16(2), 213; https://doi.org/10.3390/mi16020213 - 13 Feb 2025
Viewed by 907
Abstract
Etching makes a pattern design a real 3D object [...] Full article
20 pages, 12699 KiB  
Article
Reliability Analysis of Complex PCB Assemblies Under Temperature Cycling and Random Vibration
by Wenchao Tian, Feiyang Li, Mang He, Haoyue Ji and Si Chen
Micromachines 2025, 16(2), 212; https://doi.org/10.3390/mi16020212 - 13 Feb 2025
Viewed by 692
Abstract
This paper examined the reliability of complex PCB assemblies under random vibration and temperature cycling, which are two primary causes of assembly failure. A combination of finite element simulation and environmental testing was employed to investigate the effects of different reinforcement methods and [...] Read more.
This paper examined the reliability of complex PCB assemblies under random vibration and temperature cycling, which are two primary causes of assembly failure. A combination of finite element simulation and environmental testing was employed to investigate the effects of different reinforcement methods and solder joint morphology on assembly reliability. The linear accumulation of damage was utilized to predict assembly failure, and the predicted failure damage was compared with the damage extracted post-testing to validate the simulation analysis. The results indicate that SAC305 solder exhibits greater strength than Sn63Pb37 solder in withstanding temperature cycling fatigue, yet is weaker than Sn63Pb37 solder in withstanding random vibration fatigue. When the solder is Sn63Pb37, the temperature cycling life of the assembly with the bottom filled and the corners fixed is reduced by 92.3% and 99.3%, respectively, compared to the unreinforced method, while the random vibration life is enhanced by 84 times and 3.9 times, respectively. An increase in pad diameter is advantageous for improving the random vibration life of the assembly, but results in a decrease in the temperature cycling life. When the lower pad diameter ranges from 0.35 mm to 0.55 mm, the assembly temperature cycling life decreases by 28.83%, 82.03%, 90.66%, and 91.22% with the increase of the lower pad diameter, and the random vibration life improves by 4.8 times, 9.5 times, 20.4 times, and 33.6 times, respectively. The predicted locations of vulnerable solder joints for the assembly are consistent with the experimental results, and the failure prediction accuracy of the assembly is 88.89%. Full article
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