Micromachines

15 pages, 6002 KiB

Open AccessArticle

Effect of Flow Length on Pressure and Measurement of PEMFC Temperature by Using Thin-Film Thermocouples

by Huijin Guo, Zhihui Liu, Xingyu Li, Xingshu Wang, Maopeng Zhang, Shiqi Zhang, Zixi Wang and Wanyu Ding

Micromachines 2025, 16(5), 535; https://doi.org/10.3390/mi16050535 (registering DOI) - 29 Apr 2025

Abstract

Based on the COMSOL simulation software (v.6.1), this paper systematically investigates the influence law of runner length on the velocity and pressure distribution of cathode and anode gas runners in proton exchange membrane fuel cells (PEMFCs), and experimentally verifies the measurement effect of [...] Read more.

Based on the COMSOL simulation software (v.6.1), this paper systematically investigates the influence law of runner length on the velocity and pressure distribution of cathode and anode gas runners in proton exchange membrane fuel cells (PEMFCs), and experimentally verifies the measurement effect of thin-film thermocouples on the operating temperature of PEMFCs. The simulation results show that the maximum pressure of the cathode and anode increases nonlinearly with the increase in the runner length, while the velocity distribution remains stable; the shortening of the runners significantly reduces the friction loss along the flow path and optimizes the matching of the permeability of the porous medium. In addition, the NiCr/NiSi thin-film thermocouple prepared by magnetron sputtering exhibits high accuracy (Seebeck coefficient of 41.56 μV/°C) in static calibration and successfully captures the dynamic response characteristics of temperature in PEMFC operation. This study provides a theoretical basis and experimental support for the optimization of fuel cell flow channel design and temperature monitoring technology. Full article

(This article belongs to the Special Issue Micro/Nanostructures in Sensors and Actuators, 2nd Edition)

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24 pages, 7068 KiB

Open AccessArticle

Chip Formation Mechanisms When Cutting Amorphous Alloy with Cubic Boron Nitride Tools Based on Constitutive Equation Parameter Optimisation

by Jinguang Du, Dingkun Wang, Yaoxuan Guo, Wuyi Ming and Wenbin He

Micromachines 2025, 16(5), 534; https://doi.org/10.3390/mi16050534 (registering DOI) - 29 Apr 2025

Abstract

Owing to potential inaccuracies in the current stress–strain curve used for constructing the Johnson–Cook (JC) constitutive model of amorphous alloys, the parameters of the JC constitutive equation were derived using Oxley’s cutting theory, negative chamfer theoretical mechanics modelling, and the particle swarm optimisation [...] Read more.

Owing to potential inaccuracies in the current stress–strain curve used for constructing the Johnson–Cook (JC) constitutive model of amorphous alloys, the parameters of the JC constitutive equation were derived using Oxley’s cutting theory, negative chamfer theoretical mechanics modelling, and the particle swarm optimisation algorithm. A two-dimensional finite element cutting model was subsequently established using AdvantEdge software. The optimised constitutive model was used to simulate the main cutting force (Fz) and the backward force (Fy), which resulted in average errors of 12.461% and 9.161%, respectively. Based on the optimised constitutive model in which the JC constitutive equation parameters were derived using Oxley’s method, the variations in temperature, strain rate, and stress in the deformation zone during the cutting process were analysed. The chip microstructures revealed the transformation of lamellar chips into serrated chips resulting from a combination of plastic deformation, adiabatic shear, and shear slip. Full article

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

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25 pages, 20901 KiB

Open AccessArticle

Heat Transfer Enhancement of Diamond Rib Mounted in Periodic Merging Chambers of Micro Channel Heat Sink

by Xin Lu, Lu Wang, Liangbi Wang and Yao Hu

Micromachines 2025, 16(5), 533; https://doi.org/10.3390/mi16050533 (registering DOI) - 29 Apr 2025

Abstract

The heat transfer enhancement of diamond-shaped ribs mounted in the periodic merging chambers of microchannel (MC) heat sinks is investigated using a numerical method for Reynolds number in the region of 300–700. Compared to triangular, rectangular, and cylindrical ribs, diamond-shaped ribs achieve 3.59%, [...] Read more.

The heat transfer enhancement of diamond-shaped ribs mounted in the periodic merging chambers of microchannel (MC) heat sinks is investigated using a numerical method for Reynolds number in the region of 300–700. Compared to triangular, rectangular, and cylindrical ribs, diamond-shaped ribs achieve 3.59%, 13.24%, and 6.34% higher enhancement effects, respectively, under the same mass flow rate. Further analysis of geometric parameters (length, width, and height) and rib positioning reveals that a rib height of h/H_ch = 0.8 provides optimal heat dissipation performance. For Re < 500, the optimal configuration is a rib length of l/L_merg = 0.55 and a width of b/W_ch = 0.8, while for 500 < Re < 700, it shifts to l/L_merg = 0.36 and b/W_ch = 1.6. For s/L_merg, the smaller it is, the shorter the main flow separation time, thereby improving heat transfer efficiency. Full article

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

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13 pages, 6281 KiB

Open AccessArticle

Heavy Ions Induced Single-Event Transient in SiGe-on-SOI HBT by TCAD Simulation

by Yuedecai Long, Abuduwayiti Aierken, Xuefei Liu, Mingqiang Liu, Changsong Gao, Gang Wang, Degui Wang, Sandip Majumdar, Yundong Xuan, Mengxin Liu and Jinshun Bi

Micromachines 2025, 16(5), 532; https://doi.org/10.3390/mi16050532 (registering DOI) - 29 Apr 2025

Abstract

In this work, the effects of heavy ion strike position, incident angle, linear energy transfer (LET) value, ambient temperature, bias conditions, and the synergistic effects of total dose irradiation on the single-event transient (SET) in silicon-germanium heterojunction bipolar transistors on silicon-on-insulator (SiGe-on-SOI HBTs) [...] Read more.

In this work, the effects of heavy ion strike position, incident angle, linear energy transfer (LET) value, ambient temperature, bias conditions, and the synergistic effects of total dose irradiation on the single-event transient (SET) in silicon-germanium heterojunction bipolar transistors on silicon-on-insulator (SiGe-on-SOI HBTs) were investigated using TCAD simulations. It was demonstrated that, compared to the bulk SiGe HBT, the SiGe-on-SOI HBT exhibits lower transient current and less charge collection, indicating better resistance to SET. The SET response is more pronounced when heavy ions strike vertically from the emitter and base regions. Transient current and collected charge escalate with increasing incident angle, demonstrating a strong linear correlation with LET values. As the temperature decreases, the peak transient current increases, while the pulse duration decreases and the total collected charge diminishes. After total dose irradiation, the peak transient current in the SiGe-on-SOI HBT decreases, whereas the damage was more severe in the absence of irradiation. Under collector positive bias and positive bias, significant SET responses were observed, while cutoff bias and substrate bias exhibited better resistance to SET damage. These findings provide critical insights into radiation-hardened design strategies for the SiGe-on-SOI HBT. Full article

(This article belongs to the Special Issue Future Prospects of Thin-Film Transistors and Their Applications, 2nd Edition)

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25 pages, 2513 KiB

Open AccessReview

Protein Manipulation via Dielectrophoresis: Theoretical Principles and Emerging Microfluidic Platforms

by Zuriel Da En Shee, Ervina Efzan Mhd Noor and Mirza Farrukh Baig

Micromachines 2025, 16(5), 531; https://doi.org/10.3390/mi16050531 (registering DOI) - 29 Apr 2025

Abstract

Dielectrophoresis (DEP) has been widely employed in microfluidic platforms for particle or cell manipulation in biomedical science applications due to its accurate, fast, label-free, and low-cost diagnostic technique. However, the application of the DEP technique towards protein manipulation has yet to be extensively [...] Read more.

Dielectrophoresis (DEP) has been widely employed in microfluidic platforms for particle or cell manipulation in biomedical science applications due to its accurate, fast, label-free, and low-cost diagnostic technique. However, the application of the DEP technique towards protein manipulation has yet to be extensively explored due to the challenges of the complexity of protein itself, such as its complex morphologies, extremely minuscule particle size, inherent electrical properties, and temperature sensitivity, which make it relatively more challenging. Furthermore, given that protein DEP investigation requires entering the micro- to nano-scale level of DEP configuration, various challenging factors such as electrohydrodynamic effects, electrolysis, joule heating, and electrothermal force that emerge will make it more difficult in realizing protein DEP investigation. This review study has discussed the fundamental theory of DEP and considerations toward protein DEP manipulation. In particular, it focused on the DEP theoretical principle towards protein, protein DEP application challenges, microfluidic platform considerations, medium considerations, and a critically reviewed list of protein bioparticles that have been investigated were all highlighted. Full article

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12 pages, 2818 KiB

Open AccessArticle

Influence of Inner Lining Atoms of Multilayered Hexagonal Boron Nitride Porous Membrane on Desalination

by Chulwoo Park and Daejoong Kim

Micromachines 2025, 16(5), 530; https://doi.org/10.3390/mi16050530 (registering DOI) - 29 Apr 2025

Abstract

Recent findings have demonstrated that the desalination and purification of contaminated water and the separation of ions and gases, besides solutions to other related issues, may all be achieved with the use of membranes based on artificial nanoporous materials. Before the expensive stages [...] Read more.

Recent findings have demonstrated that the desalination and purification of contaminated water and the separation of ions and gases, besides solutions to other related issues, may all be achieved with the use of membranes based on artificial nanoporous materials. Before the expensive stages of production and experimental testing, the optimum size and form of membrane nanopores could be determined using computer-aided modeling. The notion that rectangular nanopores created in a multilayered hexagonal boron nitride (h-BN) membrane in a way that results in different inner lining atoms would exhibit unique properties in terms of the water penetration rate is put forth and examined in the current study. Nanopores in boron nitride sheets can be generated with the inner lining of boron atoms (B-edged), nitrogen atoms (N-edged), or both boron and nitrogen atoms (BN-edged). In this study, we compared the three different inner-lined nanopores of boron nitride nanosheets to a comparable-sized graphene nanopore and evaluated the water conduction. Full article

(This article belongs to the Special Issue Nanomaterials for Micro/Nano Devices, 2nd Edition)

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13 pages, 4832 KiB

Open AccessArticle

Enhancement of Quality Factors in a 6.5 GHz Resonator Using Mo/SiC Composite Microstructures

by Binghui Lin, Yupeng Zheng, Haiyang Li, Yuqi Ren, Tingting Yang, Zekai Wang, Yao Cai, Qinwen Xu and Chengliang Sun

Micromachines 2025, 16(5), 529; https://doi.org/10.3390/mi16050529 (registering DOI) - 29 Apr 2025

Abstract

This study addresses the critical challenge of lateral acoustic wave energy leakage in high-frequency film bulk acoustic resonators (FBARs) and elucidates the reflection mechanism of acoustic waves at acoustic reflection boundaries. Based on the theory of acoustic impedance mismatch, a novel Mo/SiC composite [...] Read more.

This study addresses the critical challenge of lateral acoustic wave energy leakage in high-frequency film bulk acoustic resonators (FBARs) and elucidates the reflection mechanism of acoustic waves at acoustic reflection boundaries. Based on the theory of acoustic impedance mismatch, a novel Mo/SiC composite microstructure is designed to strategically establish multiple acoustic reflection boundaries along the lateral acoustic wave leakage paths. Finite element simulations reveal that SiC microstructures effectively suppress vibration amplitudes in non-resonant regions, thereby preventing acoustic wave leakage. By integrating Mo and SiC microstructures, the proposed composite structure significantly enhances the resonator’s acoustic confinement and energy retention capabilities. A resonator incorporating this Mo/SiC composite microstructure is fabricated, achieving a series resonance frequency of 6.488 GHz and a remarkable quality factor (Q) of 310. This represents a substantial 51.2% improvement in Q compared to the basic FBAR, confirming the effectiveness of the proposed design in mitigating lateral acoustic wave leakage and enhancing resonator performance for high-frequency, low-loss applications. This work offers valuable insights into the design of next-generation RF resonators for advanced wireless communication systems. Full article

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

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10 pages, 2779 KiB

Open AccessArticle

A High-Isolation Optically Transparent 2 × 2 Antenna Array Using Metal Mesh Material

by Yufeng Yu, Yuanjia Dong, Yangyang He and Yi-Feng Cheng

Micromachines 2025, 16(5), 528; https://doi.org/10.3390/mi16050528 (registering DOI) - 29 Apr 2025

Abstract

This paper presents the design and implementation of a compact, high-isolation, optically transparent 2 × 2 MIMO antenna array. Optical transparency is achieved using a copper-based metal mesh material, which serves as both the radiating element and the ground plane, ensuring high radiation [...] Read more.

This paper presents the design and implementation of a compact, high-isolation, optically transparent 2 × 2 MIMO antenna array. Optical transparency is achieved using a copper-based metal mesh material, which serves as both the radiating element and the ground plane, ensuring high radiation efficiency and minimal visual impact. The array consists of four monopole antennas, and mutual coupling is effectively suppressed through the integration of shorting decoupling branches and a common-ground structure. These techniques address both adjacent and diagonal (non-adjacent) coupling. A prototype was fabricated and experimentally validated. The experimental results demonstrate that the proposed antenna array achieves 20 dB isolation, 3.56 dB antenna gain, and 76% efficiency. Full article

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

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14 pages, 5337 KiB

Open AccessArticle

Research on Valveless Piezoelectric Pump Based on Coriolis Effect

by Qiufeng Yan, Zhiling Liu, Wanting Sun and Mengyao Jiang

Micromachines 2025, 16(5), 527; https://doi.org/10.3390/mi16050527 (registering DOI) - 29 Apr 2025

Abstract

In previous studies, a valveless piezoelectric pump with arc-shaped tubes (VPPAST) based on the Coriolis Effect was proposed. To promote the application of VPPAST in the field of navigation and guidance, it is vital to further explore the influences of the layout and [...] Read more.

In previous studies, a valveless piezoelectric pump with arc-shaped tubes (VPPAST) based on the Coriolis Effect was proposed. To promote the application of VPPAST in the field of navigation and guidance, it is vital to further explore the influences of the layout and structural parameters of arc-shaped tubes on the flow rate. Accordingly, in this study, the analysis of flow characteristics of fluid in arc-shaped tubes was conducted, and the velocity difference between the clockwise and counterclockwise flow of the liquid was reduced. Eventually, the flow equations of three layout modes of arc-shaped tubes were established. VPPAST with anomalous-direction arc-shaped tubes, single-arc-shaped tube, and same-direction arc-shaped tubes were produced using 3D printing technology. In addition, the valveless piezoelectric pump with the anomalous-direction arc-shaped tubes (VLPPADA) with different parameter flow tubes were also fabricated. Based on the resultant flow rates of each piezoelectric pump, it was demonstrated that the flow rate of the VLPPADA was the highest under the same driving conditions, and the flow rate can be determined as 1.72 mL/min when the driving voltage was set as 160 V at 14 Hz. It indicated that the pump flow rate of VLPPADA was directly proportional to the base radius and width of the arc-shaped tube. Full article

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

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14 pages, 1152 KiB

Open AccessArticle

Detection of Positive and Negative Pressure in a Double-Chamber Underwater Thruster

by Chong Cao, Chengchun Zhang, Chun Shen, Yasong Zhang, Wen Cheng, Zhengyang Wu and Luquan Ren

Micromachines 2025, 16(5), 526; https://doi.org/10.3390/mi16050526 (registering DOI) - 29 Apr 2025

Abstract

The aim of this paper is to develop a compact, rapid-response pressure sensor for underwater propulsion. Flexible pressure sensors are widely utilized in human–computer interactions and wearable electronic devices; however, manufacturing capacitive sensors that offer a broad pressure range and high sensitivity presents [...] Read more.

The aim of this paper is to develop a compact, rapid-response pressure sensor for underwater propulsion. Flexible pressure sensors are widely utilized in human–computer interactions and wearable electronic devices; however, manufacturing capacitive sensors that offer a broad pressure range and high sensitivity presents significant challenges. Inspired by the dermal papillary microstructure, a capacitive pressure sensor was prepared by infusing polydimethylsiloxane (PDMS) inside an anodic aluminum oxide (AAO) template and then demolding it. The resulting pressure sensor exhibits several key characteristics: high linearity in the range of −5.2 to 6.3 kPa, a comprehensive range for both positive and negative pressure sensing in air or water environments, a quick response time of 52 ms, a recovery time of 40 ms, and excellent stability. The sensor presented in this work is innovatively applied to detect underwater negative pressure, and it is employed for the swift detection of positive and negative pressure changes in underwater thrusters. This work highlights the promising potential of biomimetic flexible capacitive pressure sensors across various applications. Full article

(This article belongs to the Special Issue Advanced Applications in Microrobots)

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16 pages, 6070 KiB

Open AccessArticle

PDMS SlipChip: Optimizing Sealing, Slipping, and Biocompatibility Using Low-Viscosity Silicone Oils

by Rafia Inaam, Marcela F. Bolontrade, Shunya Okamoto, Takayuki Shibata, Tuhin Subhra Santra and Moeto Nagai

Micromachines 2025, 16(5), 525; https://doi.org/10.3390/mi16050525 (registering DOI) - 29 Apr 2025

Abstract

The Polydimethylsiloxane (PDMS) SlipChip is a microfluidic platform enabling fluid manipulation without pumps or valves, simplifying operation and reducing reagent use. High-viscosity silicone oils (e.g., 5000–10,000 cSt) improve sealing but frequently block microfluidic channels, reducing usability. In contrast, low-viscosity oils (50–100 cSt) reduce [...] Read more.

The Polydimethylsiloxane (PDMS) SlipChip is a microfluidic platform enabling fluid manipulation without pumps or valves, simplifying operation and reducing reagent use. High-viscosity silicone oils (e.g., 5000–10,000 cSt) improve sealing but frequently block microfluidic channels, reducing usability. In contrast, low-viscosity oils (50–100 cSt) reduce blockages but may compromise sealing. This study addresses these challenges by optimizing the viscosity of silicone oil and the curing conditions of PDMS. Low-viscosity silicone oil (50 cSt) was identified as optimal, ensuring smooth slipping and reliable sealing without blockages. Curing conditions were also adjusted to balance adhesion and stiffness as follows: lower temperatures (50–60 °C) enhanced van der Waals adhesion, while higher temperatures (80 °C) increased stiffness. A mixed curing approach (80 °C for the top layer and 60 °C for the bottom layer) further improved performance. Biocompatibility testing using human osteosarcoma cells demonstrated minimal cytotoxicity with 50 cSt oil, supporting cell viability (95%) comparable to traditional multiwell plates. These findings provide practical guidelines for fabricating reliable and biocompatible SlipChips. Full article

(This article belongs to the Section B：Biology and Biomedicine)

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20 pages, 5605 KiB

Open AccessArticle

Startup Drift Compensation of MEMS INS Based on PSO–GRNN Network

by Songlai Han, Jingyi Xie and Jing Dong

Micromachines 2025, 16(5), 524; https://doi.org/10.3390/mi16050524 (registering DOI) - 29 Apr 2025

Abstract

The startup drift phenomenon that exists in MEMS INSs increases the navigation error, prolonging the start-up time. Aiming to resolve this problem, a startup drift compensation method based on a PSO-GRNN model is proposed in this paper. We adopted a correlation analysis to [...] Read more.

The startup drift phenomenon that exists in MEMS INSs increases the navigation error, prolonging the start-up time. Aiming to resolve this problem, a startup drift compensation method based on a PSO-GRNN model is proposed in this paper. We adopted a correlation analysis to determine the input parameters of the PSO-GRNN model that mainly affect startup drift. In the process of training this model, we used the PSO algorithm to optimize the spread parameter of the PSO-GRNN model. The information transmission function between particle swarms was used to find the best spread parameter by iterative optimization, the particle’s position was mapped to the GRNN model, and the GRNN model was constructed with the optimal position of the swarm as the spread parameter. This method can effectively compensate for startup drift and improve navigation accuracy. Startup drift compensation experiments were carried out at different ambient temperatures. Compared with the MEMS INS data without compensation, the standard deviation of the MEMS INS data with the proposed method decreased by more than 80.6%, and the peak-to-peak value of the MEMS INS data decreased by over 72.7%. Compared with the traditional method, the standard deviation of the MEMS INS data compensated via this method decreased by 54.5% on average, and the peak-to-peak value decreased by 42.8% on average. Meanwhile, the performance of this method was verified by navigation experiments. With the proposed method, the speed error improved by over 36.4%, and the position error improved by over 41.1%. The above experiments verified that the method of this paper significantly improved navigation performance. Full article

(This article belongs to the Special Issue MEMS Inertial Device, 2nd Edition)

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13 pages, 6668 KiB

Open AccessArticle

Current-Carrying Wear Behavior of the Laser-Alloyed Al/W Composite Layer Under Different Currents

by Heng Zhang, Bai Li, Yulong Zhu, Congwen Tang, Pengfei Sun, Tao Lai and Dengzhi Wang

Micromachines 2025, 16(5), 523; https://doi.org/10.3390/mi16050523 (registering DOI) - 29 Apr 2025

Abstract

The Al/W composite layer was fabricated on the surface of the aluminum alloy using laser alloying technology to enhance the current-carrying wear resistance. Additionally, the current-carrying wear behaviors of the Al/W composite layer and the aluminum alloy substrate were investigated under different currents. [...] Read more.

The Al/W composite layer was fabricated on the surface of the aluminum alloy using laser alloying technology to enhance the current-carrying wear resistance. Additionally, the current-carrying wear behaviors of the Al/W composite layer and the aluminum alloy substrate were investigated under different currents. The results indicate that the presence of hard phases such as W and Al₄W in the composite layer significantly enhanced the wear resistance of the material. Specifically, the average friction coefficient of the Al/W composite layer under different currents was reduced by approximately 9.3–35.8% compared to the aluminum alloy substrate, and the wear rate under current-carrying conditions decreased by about 1.9–6.0 times. For the aluminum alloy substrate, adhesive wear is the dominant mechanism under currents ranging from 0 to 60 A. However, as the current increased to 80 A, the severity of arc erosion intensified, and the wear mechanism transitioned to a combination of arc erosion and adhesive wear. In contrast, for the Al/W composite layer, abrasive wear was the dominant wear mechanism in the absence of electrical current. Upon the introduction of the current, the wear mechanism changed to a coupling effect of arc erosion and adhesive wear. Full article

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

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79 pages, 3684 KiB

Open AccessReview

Advancements in Wearable and Implantable BioMEMS Devices: Transforming Healthcare Through Technology

by Vishnuram Abhinav, Prithvi Basu, Shikha Supriya Verma, Jyoti Verma, Atanu Das, Savita Kumari, Prateek Ranjan Yadav and Vibhor Kumar

Micromachines 2025, 16(5), 522; https://doi.org/10.3390/mi16050522 (registering DOI) - 28 Apr 2025

Abstract

Wearable and implantable BioMEMSs (biomedical microelectromechanical systems) have transformed modern healthcare by enabling continuous, personalized, and minimally invasive monitoring, diagnostics, and therapy. Wearable BioMEMSs have advanced rapidly, encompassing a diverse range of biosensors, bioelectronic systems, drug delivery platforms, and motion tracking technologies. These [...] Read more.

Wearable and implantable BioMEMSs (biomedical microelectromechanical systems) have transformed modern healthcare by enabling continuous, personalized, and minimally invasive monitoring, diagnostics, and therapy. Wearable BioMEMSs have advanced rapidly, encompassing a diverse range of biosensors, bioelectronic systems, drug delivery platforms, and motion tracking technologies. These devices enable non-invasive, real-time monitoring of biochemical, electrophysiological, and biomechanical signals, offering personalized and proactive healthcare solutions. In parallel, implantable BioMEMS have significantly enhanced long-term diagnostics, targeted drug delivery, and neurostimulation. From continuous glucose and intraocular pressure monitoring to programmable drug delivery and bioelectric implants for neuromodulation, these devices are improving precision treatment by continuous monitoring and localized therapy. This review explores the materials and technologies driving advancements in wearable and implantable BioMEMSs, focusing on their impact on chronic disease management, cardiology, respiratory care, and glaucoma treatment. We also highlight their integration with artificial intelligence (AI) and the Internet of Things (IoT), paving the way for smarter, data-driven healthcare solutions. Despite their potential, BioMEMSs face challenges such as regulatory complexities, global standardization, and societal determinants. Looking ahead, we explore emerging directions like multifunctional systems, biodegradable power sources, and next-generation point-of-care diagnostics. Collectively, these advancements position BioMEMS as pivotal enablers of future patient-centric healthcare systems. Full article

(This article belongs to the Special Issue Wearable and Implantable Bio-MEMS Devices and Applications, 2nd Edition)

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16 pages, 7093 KiB

Open AccessArticle

Design and Implementation of a High-Throughput Digital Microfluidic System Based on Optimized YOLOv8 Object Detection

by Ming Cao, Wufeng Duan, Zuwei Huang, Huihong Liang, Fanrong Ai and Xianming Liu

Micromachines 2025, 16(5), 521; https://doi.org/10.3390/mi16050521 (registering DOI) - 28 Apr 2025

Abstract

To address the challenges of excessive control pins and inefficient high-throughput droplet manipulation in conventional digital microfluidic chips, this study developed a parallel-motion digital microfluidic system integrated with an image acquisition device. The system employs an enhanced YOLOv8 object detection model for droplet [...] Read more.

To address the challenges of excessive control pins and inefficient high-throughput droplet manipulation in conventional digital microfluidic chips, this study developed a parallel-motion digital microfluidic system integrated with an image acquisition device. The system employs an enhanced YOLOv8 object detection model for droplet recognition. By enabling parallel droplet transportation and processing, it significantly improves operational efficiency and detection accuracy. For droplet recognition, the YOLOv8 model was optimized through the integration of GAM_Attention and EMA mechanisms, which strengthen feature extraction capabilities and detection performance. Experimental results demonstrated that the optimized model achieves remarkable accuracy and robustness in droplet detection tasks, with mAP50 increasing from 96.5% to 98.7% and mAP50–90 improving from 65.8% to 68.5%. The system exhibits enhanced detection precision and real-time responsiveness, maintaining an error rate below 0.53%. Furthermore, a host computer interface was implemented for multi-droplet path planning and feedback, establishing a closed-loop control system. This work provides an efficient and reliable solution for high-throughput operations in microfluidic chip applications. Full article

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22 pages, 5142 KiB

Open AccessArticle

ZnFe₂O₄/GQDs Nanoparticles as Peroxidase Mimics for Sensitive and Selective Colorimetric Detection of Glucose in Real Samples

by Claudia Cirillo, Mariagrazia Iuliano and Maria Sarno

Micromachines 2025, 16(5), 520; https://doi.org/10.3390/mi16050520 (registering DOI) - 28 Apr 2025

Abstract

Glucose detection is critical in addressing health and medical issues related to irregular blood levels. Colorimetry, a simple, cost-effective, and visually straightforward method, is often employed. Traditional enzymatic detection methods face drawbacks such as high costs, limited stability, and operational challenges. To overcome [...] Read more.

Glucose detection is critical in addressing health and medical issues related to irregular blood levels. Colorimetry, a simple, cost-effective, and visually straightforward method, is often employed. Traditional enzymatic detection methods face drawbacks such as high costs, limited stability, and operational challenges. To overcome these, enzyme mimics or artificial nano-enzymes based on inorganic nanomaterials have garnered attention, but their cost and susceptibility to inactivation limit applications. This study presents a ZnFe₂O₄/GQDs nanocomposite as an innovative enzyme mimic, addressing key requirements like low cost, high stability, biocompatibility, and wide operational range. Synthesized using a simple and inexpensive method, the composite benefits from the synergistic interaction between ZnFe₂O₄ nanoparticles and graphene quantum dots (GQDs), resulting in excellent magnetic properties, high surface area, and functional versatility. The material demonstrated remarkable sensitivity with a detection limit of 7.0 μM across a range of 5–500 μM and achieved efficient peroxidase-like activity with Km values of 0.072 and 0.068 mM and Vmax of 4.58 × 10⁻⁸ and 8.29 × 10⁻⁸ M/s for TMB and H₂O₂, respectively. The nanocomposite also exhibited robust recyclability, retaining performance over six reuse cycles. Full article

(This article belongs to the Section C：Chemistry)

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12 pages, 2838 KiB

Open AccessArticle

Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer

by Chenchen Zhang and Srinivas Tadigadapa

Micromachines 2025, 16(5), 519; https://doi.org/10.3390/mi16050519 (registering DOI) - 28 Apr 2025

Abstract

In this paper, we explore the use of chip-scale blown glass microbubble structures for MEMS packaging applications. Specifically, we demonstrate the efficacy of this method of packaging for the improvement of the lifetime of a ferrofluid-based magnetoviscous magnetometer. We have previously reported on [...] Read more.

In this paper, we explore the use of chip-scale blown glass microbubble structures for MEMS packaging applications. Specifically, we demonstrate the efficacy of this method of packaging for the improvement of the lifetime of a ferrofluid-based magnetoviscous magnetometer. We have previously reported on the novel concept of a ferrofluid based magnetometer in which the viscoelastic response of a ferrofluid interfacial layer on a high frequency shear wave quartz resonator is sensitively monitored as a function of applied magnetic field. The quantification of the magnetic field is accomplished by monitoring the at-resonance admittance characteristics of the ferrofluid-loaded resonator. While the proof-of-concept measurements of the device have been successfully made, under open conditions, the evaporation of the carrier fluid of the ferrofluid continuously changes its viscoelastic properties and compromises the longevity of the magnetometer. To prevent the evaporation of the ferrofluid, here, we seal the ferrofluid on top of the micromachined quartz resonator within a blown glass hemispherical microbubble attached to it using epoxy. The magnetometer design used a bowtie-shaped thin film Metglas (Fe₈₅B₅Si₁₀) magnetic flux concentrator on the resonator chip. A four-times smaller noise equivalent, a magnetic field of 600 nT/√Hz at 0.5 Hz was obtained for the magnetometer using the Metglas flux concentrator. The ferrofluid-based magnetometer is capable of sensing magnetic fields up to a modulation frequency of 40 Hz. Compared with the unsealed ferrofluid device, the lifetime of the glass microbubble integrated chip packaged device improved significantly from only a few hours to over 50 days and continued. Full article

(This article belongs to the Special Issue Microelectronics Assembly and Packaging: Materials and Technologies, 2nd Edition)

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17 pages, 10237 KiB

Open AccessReview

Research Progress on Micromachining Technologies Used to Fabricate Terahertz Micro-Metallic Rectangular Cavity Structures

by Xiaolei Bi, Xuemin Li, Bin Li and Xueli Cheng

Micromachines 2025, 16(5), 518; https://doi.org/10.3390/mi16050518 (registering DOI) - 28 Apr 2025

Abstract

Terahertz metal rectangular cavity structures are widely used in terahertz devices due to their performance advantages, and various microfabrication techniques have been applied to the manufacturing of their high performance. In this paper, several typical application fields of terahertz technology and the reasons [...] Read more.

Terahertz metal rectangular cavity structures are widely used in terahertz devices due to their performance advantages, and various microfabrication techniques have been applied to the manufacturing of their high performance. In this paper, several typical application fields of terahertz technology and the reasons for its application in these fields are elaborated in detail. Several typical terahertz devices with terahertz metal rectangular cavity structures are introduced in detail. The research progress of various micromachining techniques for manufacturing terahertz rectangular cavity structures, such as DRIE, UV-LIGA, micro-milling, LTCC, 3D printing, and electrochemical micromachining, is discussed in detail. Finally, the advantages and disadvantages of various micromachining techniques for manufacturing terahertz micro-rectangular cavity structures are discussed, and the results show that electrochemical micromachining technology and micro-nano 3D printing technology are relatively promising methods for the manufacturing of high-frequency terahertz rectangular cavity structures. Full article

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

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10 pages, 4044 KiB

Open AccessArticle

Photonic–Electronic Modulated a-IGZO Synaptic Transistor with High Linearity Conductance Modulation and Energy-Efficient Multimodal Learning

by Zhidong Hou, Jinrong Shen, Yiming Zhong and Dongping Wu

Micromachines 2025, 16(5), 517; https://doi.org/10.3390/mi16050517 - 28 Apr 2025

Abstract

Brain-inspired neuromorphic computing is expected to overcome the von Neumann bottleneck by eliminating the memory wall between processing and memory units. Nevertheless, critical challenges persist in synaptic device implementation, particularly regarding nonlinear/asymmetric conductance modulation and multilevel conductance states, which substantially impede the realization [...] Read more.

Brain-inspired neuromorphic computing is expected to overcome the von Neumann bottleneck by eliminating the memory wall between processing and memory units. Nevertheless, critical challenges persist in synaptic device implementation, particularly regarding nonlinear/asymmetric conductance modulation and multilevel conductance states, which substantially impede the realization of high-performance neuromorphic hardware. This study demonstrates a novel advancement in photonic–electronic modulated synaptic devices through the development of an amorphous indium–gallium–zinc oxide (a-IGZO) synaptic transistor. The device demonstrates biological synaptic functionalities, including excitatory/inhibitory post-synaptic currents (EPSCs/IPSCs) and spike-timing-dependent plasticity, while achieving excellent conductance modulation characteristics (nonlinearity of 0.0095/−0.0115 and asymmetric ratio of 0.247) and successfully implementing Pavlovian associative learning paradigms. Notably, systematic neural network simulations employing the experimental parameters reveal a 93.8% recognition accuracy on the MNIST handwritten digit dataset. The a-IGZO synaptic transistor with photonic–electronic co-modulation serves as a potential critical building block for constructing neuromorphic architectures with human-brain efficiency. Full article

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

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