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Development and Evaluation of Multi-Module Retinal Devices for Artificial Vision Applications
A Wrist Brace with Integrated Piezoelectric Sensors for Real-Time Biomechanical Monitoring in Weightlifting
Parametric Rule-Based Intelligent System (PRISM) for Design and Analysis of High-Strength Separable Microneedles
The Role of Pd-Pt Bimetallic Catalysts in Ethylene Detection by CMOS-MEMS Gas Sensor Dubbed GMOS

Journal Description

Micromachines

Micromachines is a peer-reviewed, open access journal on the science and technology of small structures, devices and systems, published monthly online by MDPI. The Chinese Society of Micro-Nano Technology (CSMNT) and AES Electrophoresis Society are affiliated with Micromachines and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), PubMed, PMC, Ei Compendex, dblp, and other databases.
Journal Rank: JCR - Q2 (Instruments and Instrumentation) / CiteScore - Q1 (Mechanical Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 17.2 days after submission; acceptance to publication is undertaken in 1.9 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Testimonials: See what our editors and authors say about Micromachines.
Companion journal: Micro.
Journal Cluster of Instruments and Instrumentation: Actuators, AI Sensors, Instruments, Micromachines and Sensors.

Impact Factor: 3.0 (2024); 5-Year Impact Factor: 3.1 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2072-666X

Latest Articles

27 pages, 10330 KB

Open AccessReview

SAW-Based Hydrogen Sensing: Mechanisms, Design Strategies, and Future Prospects

by Shengzhuo Chen, Jin Chai, Libo Gao, Rongjie Wang, Zhonggang Zhang, Ziming Ren, Hongyan Xu, Yihui Lan, Kezhen Ma and Meng Li

Micromachines 2025, 16(11), 1227; https://doi.org/10.3390/mi16111227 - 28 Oct 2025

Hydrogen is widely considered a clean and sustainable energy carrier due to its high energy density, abundant reserves, and zero carbon emissions during use. To ensure safety in hydrogen production, transportation, and utilization, the development of high-performance hydrogen sensors is of great importance. [...] Read more.

Hydrogen is widely considered a clean and sustainable energy carrier due to its high energy density, abundant reserves, and zero carbon emissions during use. To ensure safety in hydrogen production, transportation, and utilization, the development of high-performance hydrogen sensors is of great importance. Among various sensing technologies, surface acoustic wave (SAW) sensors have attracted considerable attention due to their unique advantages, including rapid response and high sensitivity, which originate from the excitation and reception of acoustic waves by interdigital transducers and the strong surface disturbance sensitivity of piezoelectric substrates. This paper systematically discusses the sensing mechanisms of SAW hydrogen sensors, analyzes the effects of piezoelectric substrates and hydrogen-sensitive materials on sensing performance, reviews recent progress in hydrogen-sensitive films, and explores optimization strategies in electrode structure design and signal processing. Finally, the main challenges are summarized, and future development directions are outlined, aiming to provide theoretical support for the design and application of high-performance SAW hydrogen sensors. Full article

(This article belongs to the Special Issue Piezoelectric Micro-/Nano Systems: Global Breakthroughs and Future Prospects)

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14 pages, 2151 KB

Open AccessArticle

ELID Polishing of Glass Substrates Using a Grainless Iron-Bonded Wheel with Free Abrasive Particles

by Huali Zhang, Xu Yan, Jicai Kuai and Dmitrii V. Ardashev

Micromachines 2025, 16(11), 1226; https://doi.org/10.3390/mi16111226 - 28 Oct 2025

Conventional polishing of glass substrates often results in surface scratches caused by passivated abrasive particles, leading to defects and reduced yield. To overcome this limitation, an iron-bonded wheel with free abrasive grains was proposed in ELID (Electrolytic In-process Dressing) grinding. The polishing mechanisms [...] Read more.

Conventional polishing of glass substrates often results in surface scratches caused by passivated abrasive particles, leading to defects and reduced yield. To overcome this limitation, an iron-bonded wheel with free abrasive grains was proposed in ELID (Electrolytic In-process Dressing) grinding. The polishing mechanisms were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and micro-indentation. Polishing efficiency was assessed via mass loss measurements, surface quality was characterized by atomic force microscopy (AFM), and optical transmittance was evaluated using a transmittance meter. Results indicate that the proposed wheel does not contain fixed abrasive particles but generates α-Fe₂O₃particles during polishing, effectively preventing surface scratches and achieving superior surface quality. The polishing efficiency ranged from 0.02 to 1.6 μm/min, with a resulting surface roughness of 2.1 nm. Furthermore, the glass substrates exhibited higher transmittance compared to those polished using conventional methods, contributing to improved display performance and brightness. This polishing technology demonstrates significant potential for applications in the display industry. Full article

(This article belongs to the Section D4: Glassy Materials and Micro/Nano Devices)

19 pages, 4778 KB

Open AccessArticle

Design of a Bandgap Reference Circuit for MEMS Integrated Accelerometers

by Wenbo Zhang, Shanshan Wang, Yihang Wang, Qiang Fu, Pengjun Wang and Xiangyu Li

Micromachines 2025, 16(11), 1225; https://doi.org/10.3390/mi16111225 - 28 Oct 2025

To meet the requirements of integrated accelerometers for a high-precision reference voltage under wide supply voltage range, high current drive capability, and low power consumption, this paper presents a bandgap reference operational amplifier (op-amp) circuit implemented in CMOS/BiCMOS technology. The proposed design employs [...] Read more.

To meet the requirements of integrated accelerometers for a high-precision reference voltage under wide supply voltage range, high current drive capability, and low power consumption, this paper presents a bandgap reference operational amplifier (op-amp) circuit implemented in CMOS/BiCMOS technology. The proposed design employs a folded-cascode input stage, a push–pull Class-AB output stage, an adaptive output switching mechanism, and a composite frequency compensation scheme. In addition, overcurrent protection and low-frequency noise suppression techniques are incorporated to balance low static power consumption with high load-driving capability. Simulation results show that, under the typical process corner (TT), with VDD = 3 V and T = 25 °C, the op-amp achieves an output swing of 0.2 V~2.8 V, a low-frequency gain of 102~118 dB, a PSRR of 90 dB at 60 Hz, overcurrent protection of ±25 mA, and a phase margin exceeding 48.8° with a 10 μF capacitive load. Across the entire supply voltage range, the static current remains below 150 μA, while maintaining a line regulation better than 150 μV/V and a load regulation better than 150 μV/mA. These results verify the feasibility of achieving both high drive capability and high stability under stringent power constraints, making the proposed design well-suited as a bandgap reference buffer stage for integrated accelerometers, with strong engineering practicality and potential for broad application. Full article

(This article belongs to the Special Issue MEMS Inertial Device, 3rd Edition)

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46 pages, 13590 KB

Open AccessReview

A Review of Optical Metrology Techniques for Advanced Manufacturing Applications

by Fangyuan Zhao, Hanyao Tang, Xuerong Zou and Xinghui Li

Micromachines 2025, 16(11), 1224; https://doi.org/10.3390/mi16111224 - 28 Oct 2025

Advanced manufacturing places stringent demands on measurement technologies, requiring ultra-high precision, non-contact operation, high throughput, and real-time adaptability. Optical metrology, with its distinct advantages, has become a key enabler in this context. This paper reviews optical metrology techniques from the perspective of precision [...] Read more.

Advanced manufacturing places stringent demands on measurement technologies, requiring ultra-high precision, non-contact operation, high throughput, and real-time adaptability. Optical metrology, with its distinct advantages, has become a key enabler in this context. This paper reviews optical metrology techniques from the perspective of precision manufacturing applications, emphasizing precision positioning and surface topography measurement while noting the limitations of traditional contact-based methods. For positioning, interferometers, optical encoders, and time-of-flight methods enable accurate linear and angular measurements. For surface characterization, techniques such as interferometry, structured light profilometry, and confocal microscopy provide reliable evaluation across scales, from large structures to micro- and nano-scale features. By integrating these approaches, optical metrology is shown to play a central role in bridging macroscopic and nano-scale characterization, supporting both structural assessment and process optimization. This review highlights its essential contribution to advanced manufacturing, and offers a concise reference for future progress in high-precision and intelligent production. Full article

(This article belongs to the Section A：Physics)

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11 pages, 1602 KB

Open AccessArticle

DLL Design with Wide Input Duty Cycle Range and Low Output Clock Duty Cycle Error

by Binyu Qin, Haoyu Qin, Chenyu Fang, Leilei Zhao and Peter Poechmueller

Micromachines 2025, 16(11), 1223; https://doi.org/10.3390/mi16111223 - 27 Oct 2025

This paper presents the design of a Delay-Locked Loop (DLL) with a simple architecture and a wide input clock duty cycle range. The design is tailored to meet the increasing data rate and stringent clock requirements of modern semiconductor chips, with particular applicability [...] Read more.

This paper presents the design of a Delay-Locked Loop (DLL) with a simple architecture and a wide input clock duty cycle range. The design is tailored to meet the increasing data rate and stringent clock requirements of modern semiconductor chips, with particular applicability to dynamic random-access memory (DRAM) systems. The structure features two Bang-Bang Phase Detectors (BBPDs) to adjust the rising and falling edges of the divided clock. Implemented using a 65 nm CMOS process, the design was verified through simulation. At a working frequency of 3.2 GHz, the input clock duty cycle range spans from 18% to 72%, with a maximum output clock duty cycle error of just 0.6%, a peak-to-peak jitter of 15.73 ps, and a power consumption of 12.7 mW. Full article

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11 pages, 2245 KB

Open AccessArticle

A Three-Terminal Si-Ge Avalanche Photodiode with a Breakdown Voltage of 6.8 V and a Gain Bandwidth Product of 1377 GHz

by Chao Cheng, Jintao Xue, Xishan Yu, Jifang Mu and Binhao Wang

Micromachines 2025, 16(11), 1222; https://doi.org/10.3390/mi16111222 - 27 Oct 2025

Silicon–germanium (Si-Ge) avalanche photodiodes (APDs), fully compatible with complementary metal–oxide–semiconductor (CMOS) processes, are critical devices for high-speed optical communication. In this work, we propose a three-terminal Si-Ge APD on a silicon-on-insulator (SOI) substrate based on device simulation studies. The proposed APD employs a [...] Read more.

Silicon–germanium (Si-Ge) avalanche photodiodes (APDs), fully compatible with complementary metal–oxide–semiconductor (CMOS) processes, are critical devices for high-speed optical communication. In this work, we propose a three-terminal Si-Ge APD on a silicon-on-insulator (SOI) substrate based on device simulation studies. The proposed APD employs a separate absorption and multiplication structure, achieving an ultra-low breakdown voltage of 6.8 V. The device operates in the O-band, with optical signals laterally coupled into the Ge absorption layer via a silicon nitride (Si₃N₄) waveguide. At a bias of 2 V, the APD exhibits a responsivity of 0.85 A/W; under a bias of 6.6 V, it achieves a 3-dB optoelectronic (OE) bandwidth of 51 GHz, a direct current gain of 27, and a maximum gain–bandwidth product (GBP) of 1377 GHz. High-speed performance is further confirmed through eye-diagram simulations at 100 Gbps non-return-to-zero (NRZ) and 200 Gbps four-level pulse amplitude modulation (PAM4). These results clearly show the strong potential of the proposed APD for optical communication and interconnect applications under stringent power and supply voltage constraints. Full article

(This article belongs to the Special Issue Photonic and Optoelectronic Devices and Systems, Third Edition)

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12 pages, 2344 KB

Open AccessArticle

Effect of Geometric Design on the Mechanical Performance of Digital Light Processing (DLP)-Printed Microneedles

by Tuba Bedir, Siba Sundar Sahoo, Sachin Kadian, Oguzhan Gunduz and Roger Narayan

Micromachines 2025, 16(11), 1221; https://doi.org/10.3390/mi16111221 - 27 Oct 2025

This study describes the processing of microneedle (MN) arrays with three different heights of arrowhead (600 µm (A1), 800 µm (A2), and 1000 µm (A3)), pyramid (600 µm (P1), 800 µm (P2), and 1000 µm (P3)), and turret (600 µm (T1), 800 µm [...] Read more.

This study describes the processing of microneedle (MN) arrays with three different heights of arrowhead (600 µm (A1), 800 µm (A2), and 1000 µm (A3)), pyramid (600 µm (P1), 800 µm (P2), and 1000 µm (P3)), and turret (600 µm (T1), 800 µm (T2), and 1000 µm (T3)) designs using a digital light processing (DLP)-based 3D printing method. The 3D-printed MNs were examined for their morphological characteristics and mechanical performance. Scanning electron microscopy (SEM) imaging confirmed that all of the MNs were fabricated without fracture or bending. Each design exhibited distinct structural characteristics: arrowhead MNs displayed a well-defined morphology with sharp tips, pyramid MNs showed slight layering, and turret MNs, characterized by a wider base and sharp tips, had a smoother surface compared to the other designs. Mechanical tests revealed that the arrowhead MNs carried less load and were more prone to bending, while the pyramid and turret designs provided higher mechanical stability and penetration capacity. The pyramid design (P3) showed the highest mechanical strength, while turret MNs offered a more stable performance despite lower penetration capacity. These findings highlight the critical role of geometric design in optimizing MN performance for effective transdermal drug delivery. Full article

(This article belongs to the Special Issue Current Trends in Microneedles: Design, Fabrication and Applications)

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2 pages, 135 KB

Open AccessRetraction

RETRACTED: Durairaju et al. Synthesis and Characterization of Pyridine-Grafted Copolymers of Acrylic Acid–Styrene Derivatives for Antimicrobial and Fluorescence Applications. Micromachines 2021, 12, 672

by Periyan Durairaju, Chinnasamy Umarani, Jothi Ramalingam Rajabather, Amer M. Alanazi, Govindasami Periyasami and Lee D. Wilson

Micromachines 2025, 16(11), 1220; https://doi.org/10.3390/mi16111220 - 27 Oct 2025

The journal retracts the article “Synthesis and Characterization of Pyridine-Grafted Copolymers of Acrylic Acid–Styrene Derivatives for Antimicrobial and Fluorescence Applications” [...] Full article

16 pages, 3325 KB

Open AccessArticle

Comparison of Environmentally Friendly Cleaning Agents and Organic Solvent Cleaning Processes in the Fabrication of Flexible Nine-in-One Microsensors and Their Application in Hydrogen/Vanadium Redox Flow Batteries

by Chi-Yuan Lee, Guo-Bin Jung, Huan-Chu Chen, Mau-Hsiung Chen, Chia-Hung Chen, Kuan-Ting Lai, Cheng-Kai Liao, Yung-Lin Chang and Hao-Peng Chang

Micromachines 2025, 16(11), 1219; https://doi.org/10.3390/mi16111219 - 26 Oct 2025

This study focuses on the pre-treatment cleaning technology for the polyimide (PI) substrate of flexible nine-in-one microsensors. The environmentally friendly cleaning agent B, developed by Sea Energe, was innovatively used to replace traditional organic solutions (acetone, methanol, and isopropyl alcohol) to verify its [...] Read more.

This study focuses on the pre-treatment cleaning technology for the polyimide (PI) substrate of flexible nine-in-one microsensors. The environmentally friendly cleaning agent B, developed by Sea Energe, was innovatively used to replace traditional organic solutions (acetone, methanol, and isopropyl alcohol) to verify its feasibility and application potential in Micro-Electro-Mechanical Systems (MEMS) processes. Cleaning agent B, developed by Sea Energe, was used for the first time to clean the PI substrate of flexible nine-in-one microsensors, and the flexible nine-in-one microsensor was used as a verification platform to compare the cleaning performance with traditional organic solutions (acetone, methanol, and isopropyl alcohol). The experimental results proved that cleaning agent B developed by Sea Energe effectively removed contamination from the PI substrate surface while avoiding the environmental impact and process compatibility issues associated with traditional organic solvents. To verify its reliability, the developed flexible nine-in-one microsensor was embedded in the hydrogen end flow channel of a hydrogen/vanadium redox flow battery (HVRFB) to perform real-time monitoring of multiple parameters, including hydrogen concentration, voltage, current, conductivity, temperature, humidity, flow, pressure, and pH. The experimental results proved that using cleaning agent B, developed by Sea Energe, to clean the PI substrate and the subsequent flexible nine-in-one microsensor resulted in comparable operational stability and measurement accuracy to traditional organic solution (acetone, methanol, and isopropyl alcohol) cleaning processes. This experimental result verifies that cleaning agent B, developed by Sea Energe, not only has an excellent cleaning effect, but also meets the requirements for highly reliable microsensor development, potentially offering an alternative solution for the future introduction of green processes into semiconductors, MEMSs, and various application fields. Full article

(This article belongs to the Special Issue Novel Devices, Emerging Applications and Advances in MEMS Fabrication Processes, 2nd Edition)

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16 pages, 6905 KB

Open AccessArticle

A Hybrid Fuzzy-PSO Framework for Multi-Objective Optimization of Stereolithography Process Parameters

by Mohanned M. H. AL-Khafaji, Abdulkader Ali Abdulkader Kadauw, Mustafa Mohammed Abdulrazaq, Hussein M. H. Al-Khafaji and Henning Zeidler

Micromachines 2025, 16(11), 1218; https://doi.org/10.3390/mi16111218 - 26 Oct 2025

Additive manufacturing is driving a significant change in industry, extending beyond prototyping to the inclusion of printed parts in final designs. Stereolithography (SLA) is a polymerization technique valued for producing highly detailed parts with smooth surface finishes. This study presents a hybrid intelligent [...] Read more.

Additive manufacturing is driving a significant change in industry, extending beyond prototyping to the inclusion of printed parts in final designs. Stereolithography (SLA) is a polymerization technique valued for producing highly detailed parts with smooth surface finishes. This study presents a hybrid intelligent framework for modeling and optimizing the SLA 3D printer process’s parameters for Acrylonitrile Butadiene Styrene (ABS) photopolymer parts. The nonlinear relationships between the process’s parameters (Orientation, Lifting Speed, Lifting Distance, Exposure Time) and multiple performance characteristics (ultimate tensile strength, yield strength, modulus of elasticity, Shore D hardness, and surface roughness), which represent complex relationships, were investigated. A Taguchi design of the experiment with an L18 orthogonal array was employed as an efficient experimental design. A novel hybrid fuzzy logic–Particle Swarm Optimization (PSO) algorithm, ARGOS (Adaptive Rule Generation with Optimized Structure), was developed to automatically generate high-accuracy Mamdani-type fuzzy inference systems (FISs) from experimental data. The algorithm starts by customizing Modified Learn From Example (MLFE) to create an initial FIS. Subsequently, the generated FIS is tuned using PSO to develop and enhance predictive accuracy. The ARGOS models provided excellent performances, achieving correlation coefficients (R²) exceeding 0.9999 for all five output responses. Once the FISs were tuned, a multi-objective optimization was carried out based on the weighted sum method. This step helped to identify a well-balanced set of parameters that optimizes the key qualities of the printed parts, ensuring that the results are not just mathematically ideal, but also genuinely helpful for real-world manufacturing. The results showed that the proposed hybrid approach is a robust and highly accurate method for the modeling and multi-objective optimization of the SLA 3D process. Full article

(This article belongs to the Special Issue Emerging Micro Manufacturing Technologies and Applications, 3rd Edition)

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10 pages, 1724 KB

Open AccessArticle

Fabrication Process Research for Silicon-Waveguide-Integrated Cavity Optomechanical Devices Using Magnesium Fluoride Protection

by Chengwei Xian, Pengju Kuang, Ning Fu, Zhe Li, Changsong Wang, Yi Zhang, Rudi Zhou, Guangjun Wen, Boyu Fan and Yongjun Huang

Micromachines 2025, 16(11), 1217; https://doi.org/10.3390/mi16111217 - 26 Oct 2025

As an emerging platform for high-precision sensing, integrated silicon-waveguide-based cavity optomechanical devices face a critical fabrication challenge in the co-fabrication of silicon-on-insulator (SOI) micromechanical structures and optical waveguides: the silicon oxide (SiO₂) layer beneath the waveguides is susceptible to etching during [...] Read more.

As an emerging platform for high-precision sensing, integrated silicon-waveguide-based cavity optomechanical devices face a critical fabrication challenge in the co-fabrication of silicon-on-insulator (SOI) micromechanical structures and optical waveguides: the silicon oxide (SiO₂) layer beneath the waveguides is susceptible to etching during hydrofluoric acid (HF) release of the microstructures, leading to waveguide collapse and significantly reducing production yields. This study proposes a novel selective protection process based on a magnesium fluoride (MgF₂) thin film to address the critical challenge of long-range waveguide collapse during hydrofluoric acid (HF) etching. By depositing a MgF₂ protective layer over the waveguide regions via optical coating technology, localized protection of specific SiO₂ areas during HF etching is achieved. The experimental results demonstrate the successful release of silicon waveguides with lengths of up to 5000 μm and a significant improvement in production yield. This work provides a compatible and efficient strategy for the fabrication of robust photonic–microelectromechanical integrated devices. Full article

(This article belongs to the Collection Optical MEMS: Design, Fabrication, Control, Modeling and Developments)

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16 pages, 3651 KB

Open AccessArticle

Investigation on High-Temperature and High-Field Reliability of NMOS Devices Fabricated Using 28 nm Technology After Heavy-Ion Irradiation

by Yanrong Cao, Zhixian Zhang, Longtao Zhang, Miaofen Li, Shuo Su, Weiwei Zhang, Youli Xu, Dingqi Huang, Le Liu, Ling Lv and Xiaohua Ma

Micromachines 2025, 16(11), 1216; https://doi.org/10.3390/mi16111216 - 25 Oct 2025

This paper investigates the degradation of 28 nm technology NMOS devices under high-temperature and high-field conditions following heavy-ion irradiation. The effects of stress time, stress magnitude, temperature, device structural dimensions, and heavy-ion radiation fluence on device degradation were analyzed. The results indicate that [...] Read more.

This paper investigates the degradation of 28 nm technology NMOS devices under high-temperature and high-field conditions following heavy-ion irradiation. The effects of stress time, stress magnitude, temperature, device structural dimensions, and heavy-ion radiation fluence on device degradation were analyzed. The results indicate that under positive gate bias stress, the threshold voltage of NMOS devices exhibits a continuous positive shift. Increased stress time, higher stress magnitude, elevated temperature, and reduced device structural dimensions all aggravate device degradation. The combined effects of electrical stress and radiation lead to a degradation that initially decreases and then increases. This is because the trap charges generated in the gate oxide layer by radiation are positive charges at low fluence, compensating for the negative charges generated under electrical stress, thereby reducing degradation. However, at high fluence, the negative interface trap charges increase, while radiation also generates positive charges in the shallow trench isolation (STI) region. These two factors collectively contribute to increased device degradation. Full article

(This article belongs to the Special Issue Advanced Nano-Semiconductor Devices: Design, Modeling and Next-Generation AI Applications)

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23 pages, 3153 KB

Open AccessArticle

Domain-Specific Acceleration of Gravity Forward Modeling via Hardware–Software Co-Design

by Yong Yang, Daying Sun, Zhiyuan Ma and Wenhua Gu

Micromachines 2025, 16(11), 1215; https://doi.org/10.3390/mi16111215 - 25 Oct 2025

The gravity forward modeling algorithm is a compute-intensive method and is widely used in scientific computing, particularly in geophysics, to predict the impact of subsurface structures on surface gravity fields. Traditional implementations rely on CPUs, where performance gains are mainly achieved through algorithmic [...] Read more.

The gravity forward modeling algorithm is a compute-intensive method and is widely used in scientific computing, particularly in geophysics, to predict the impact of subsurface structures on surface gravity fields. Traditional implementations rely on CPUs, where performance gains are mainly achieved through algorithmic optimization. With the rise of domain-specific architectures, FPGA offers a promising platform for acceleration, but faces challenges such as limited programmability and the high cost of nonlinear function implementation. This work proposes an FPGA-based co-processor to accelerate gravity forward modeling. A RISC-V core is integrated with a custom instruction set targeting key computation steps. Tasks are dynamically scheduled and executed on eight fully pipeline processing units, achieving high parallelism while retaining programmability. To address nonlinear operations, we introduce a piecewise linear approximation method optimized via stochastic gradient descent (SGD), significantly reducing resource usage and latency. The design is implemented on the AMD UltraScale+ ZCU102 FPGA (Advanced Micro Devices, Inc. (AMD), Santa Clara, CA, USA) and evaluated across several forward modeling scenarios. At 250 MHz, the system achieves up to 179× speedup over an Intel Xeon 5218R CPU (Intel Corporation, Santa Clara, CA, USA) and improves energy efficiency by 2040×. To the best of our knowledge, this is the first FPGA-based gravity forward modeling accelerate design. Full article

(This article belongs to the Special Issue Recent Advances in Field-Programmable Gate Array (FPGA))

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8 pages, 1493 KB

Open AccessArticle

Single-Crystalline Si Stacked AlGaN/GaN High-Electron-Mobility Transistors with Enhanced Two-Dimensional Electron Gas Density

by Goeun Ham, Eungyeol Shin, Sangwon Yoon, Jihoon Yang, Youngjin Choi, Gunwoo Lim and Kwangeun Kim

Micromachines 2025, 16(11), 1214; https://doi.org/10.3390/mi16111214 - 25 Oct 2025

High-electron-mobility transistors (HEMTs) are characterized by the formation of a two-dimensional electron gas (2DEG) induced by the polarization effects. Considerable studies have been conducted to improve the electrical properties of HEMTs by regulating the 2DEG density. In this study, a Si/GaN heterojunction was [...] Read more.

High-electron-mobility transistors (HEMTs) are characterized by the formation of a two-dimensional electron gas (2DEG) induced by the polarization effects. Considerable studies have been conducted to improve the electrical properties of HEMTs by regulating the 2DEG density. In this study, a Si/GaN heterojunction was fabricated through the transfer of a heavily boron-doped Si nanomembrane. The holes in the p-Si layer integrated on top of the HEMT not only increased the surface positive charge, which eventually increased the density of electrons at the AlGaN/GaN interface, but also acted as a passivation layer to improve the performance of AlGaN/GaN HEMTs. Electrical characterization revealed that the maximum drain current increased from 668 mA/mm to 740 mA/mm, and the maximum transconductance improved from 200.2 mS/mm to 220.4 mS/mm. These results were due to the surface positive charge induced by the p-Si layer, which lowered the energy band diagram and increased the electron concentration at the AlGaN/GaN interface by a factor of 1.4 from 1.52 × 10²⁰ cm⁻³ to 2.11 × 10²⁰ cm⁻³. Full article

(This article belongs to the Special Issue III-V Optoelectronics and Semiconductor Process Technology, Second Edition)

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32 pages, 14254 KB

Open AccessArticle

Experimental and Numerical Study on Various Liquid-Cooled Heat Sinks Including Topology Optimization

by Ge Shi, Yanwei Dai, Zhongjun Yu, Xingyao Zeng, Cheng Tan, Haibo Zhang, Guang Yang and Fei Qin

Micromachines 2025, 16(11), 1213; https://doi.org/10.3390/mi16111213 - 25 Oct 2025

With the rapid advancement in millimeter-wave antennas, heat dissipation of array heat sources faces significant challenges due to increasing requirements on power density and miniaturization. Efficient thermal management is essential to ensure reliability and performance, particularly in high-power applications such as millimeter-wave antennas. [...] Read more.

With the rapid advancement in millimeter-wave antennas, heat dissipation of array heat sources faces significant challenges due to increasing requirements on power density and miniaturization. Efficient thermal management is essential to ensure reliability and performance, particularly in high-power applications such as millimeter-wave antennas. This study investigates liquid-cooled heat sinks featuring an inlet and outlet on the same side. A topology optimization method is employed to design an efficient heat sink, minimizing both average temperature and fluid dissipation. The optimized design is compared with common liquid-cooled heat sinks, including series, parallel, pin rib, and tree channels, through experimental and numerical simulations. A dedicated liquid-cooled experimental platform is developed to evaluate thermal and fluid characteristics under different flow rates. The results demonstrate that the topology optimization channels achieve superior thermal uniformity and lower pressure drop compared to traditional designs. The average temperatures of the heat sources in topology optimization I and II channels are 6% and 4% lower than those in the other flow channels, respectively, and the topology optimization I channel exhibits the most favorable fluid characteristics, with a pressure drop 9% lower than that of the parallel flow channel. Specifically, the topology optimization I and II channels exhibit balanced heat dissipation and flow resistance, while the series channel suffers from excessive pressure losses. The findings provide valuable insights for optimization, offering a practical method for enhancing thermal management in millimeter-wave antenna applications. Full article

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14 pages, 4151 KB

Open AccessArticle

Soft-Error-Resilient Static Random Access Memory with Enhanced Write Ability for Radiation Environments

by Se-Yeon Park, Eun Gyo Jeong and Sung-Hun Jo

Micromachines 2025, 16(11), 1212; https://doi.org/10.3390/mi16111212 - 24 Oct 2025

As semiconductor technologies advance, SRAM cells deployed in space systems face heightened sensitivity to radiation-induced soft errors. In conventional 6T SRAM, when high-energy particles strike sensitive nodes, single-event upsets (SEUs) may occur, flipping stored bits. Furthermore, with aggressive scaling, charge sharing among adjacent [...] Read more.

As semiconductor technologies advance, SRAM cells deployed in space systems face heightened sensitivity to radiation-induced soft errors. In conventional 6T SRAM, when high-energy particles strike sensitive nodes, single-event upsets (SEUs) may occur, flipping stored bits. Furthermore, with aggressive scaling, charge sharing among adjacent devices can trigger single-event multi-node upsets (SEMNU). To address these reliability concerns, this study presents a radiation-hardened SRAM design, SHWA18T, tailored for space applications. The proposed architecture is evaluated against IASE16T, PRO14T, PRO16T, QCCS, SIRI, and SEA14T. Simulation analysis demonstrates that SHWA18T achieves improved performance, particularly in terms of critical charge and write capability. The design was implemented in 90 nm CMOS technology at a 1 V supply. With enhanced robustness, the cell withstands both SEUs and SEMNUs, thereby guaranteeing stable data retention in space environments. Full article

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

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14 pages, 7812 KB

Open AccessArticle

Study on Microstructures and Properties of FeCoNiCuAlSi_x High-Entropy Alloy Composite Coatings by Laser Cladding

by Xinyu Zhang, Chun Guo, Guangcan Huang, Zheng Peng, Ruizhang Hu, Qingcheng Lin and Tianyuan Lu

Micromachines 2025, 16(11), 1211; https://doi.org/10.3390/mi16111211 - 24 Oct 2025

FeCoNiCuAl high-entropy alloys exhibit remarkable mechanical properties; nevertheless, these materials struggle to withstand harsh environments because of their insufficient resistance to wear and corrosion. The addition of Si can significantly enhance the alloy’s high-temperature performance, hardness, and wear resistance, thereby making it more [...] Read more.

FeCoNiCuAl high-entropy alloys exhibit remarkable mechanical properties; nevertheless, these materials struggle to withstand harsh environments because of their insufficient resistance to wear and corrosion. The addition of Si can significantly enhance the alloy’s high-temperature performance, hardness, and wear resistance, thereby making it more suitable for applications in high-temperature or corrosive environments. To overcome these drawbacks, this research investigates how varying Si content affects the microstructure and properties of FeCoNiCuAl coatings. Composite coatings of FeCoNiCuAlSi_x (x = 0, 0.5, 1.0, 1.5, 2.0) were fabricated on 65 Mn substrates using laser cladding. Various testing methods, including metallographic microscopy, Vickers hardness testing, friction and wear testing, and electrochemical analysis, were employed to examine the phase structure, microstructure, and hardness of the coating. It is observed that the FeCoNiCuAl coating begins with a uniform FCC phase structure. However, as the Si content increases, a phase transformation to the BCC structure occurs. The microstructure is primarily composed of isometric crystals and dendrites that become finer and more compact with higher Si content. For the FeCoNiCuAlSi_2.0 coating, the microhardness reaches 581.05 HV_0.2. Additionally, wear resistance shows a positive correlation with Si content. Electrochemical testing in NS4 solution shows that the corrosion potential of the coating increases from −0.471 V for FeCoNiCuAl to −0.344 V for FeCoNiCuAlSi_2.0, while the corrosion current density decreases from 1.566 × 10⁻⁶ A/cm² to 4.073 × 10⁻⁶ A/cm². These results indicate that Si addition plays a crucial role in enhancing the mechanical properties and corrosion resistance of FeCoNiCuAl coatings, making them more suitable for high-performance applications in extreme environments. Full article

(This article belongs to the Special Issue Future Prospects of Additive Manufacturing, 2nd Edition)

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14 pages, 5284 KB

Open AccessArticle

Impact of Phase Defects on the Aerial Image in High NA Extreme Ultraviolet Lithography

by Kun He and Zhinan Zeng

Micromachines 2025, 16(11), 1210; https://doi.org/10.3390/mi16111210 - 24 Oct 2025

With the development of extreme ultraviolet (EUV) lithography technology to higher numerical aperture (NA), it provides higher resolution imaging quality, which may be more sensitive to the phase defect in EUV mask. Therefore, it is necessary to comprehensively understand the effect of phase [...] Read more.

With the development of extreme ultraviolet (EUV) lithography technology to higher numerical aperture (NA), it provides higher resolution imaging quality, which may be more sensitive to the phase defect in EUV mask. Therefore, it is necessary to comprehensively understand the effect of phase defect on the imaging quality depending on the NA. We simulated aerial images of patterned EUV masks for the EUV lithography exposure tool of NA = 0.55 and NA = 0.33 using the rigorous coupled-wave analysis (RCWA) method. The results shows that higher NA enhances the contrast of aerial images, which, in turn, provides greater tolerance for phase defect. This indicates that high NA can mitigate the negative impact of phase defect on imaging quality to some extent. Furthermore, it is found that both the defect signal and the intensity loss ratio of the aerial image first increase and then decrease as the width of the phase defect increases, due to the height/width ratio of the phase defect. Meanwhile, the defect width corresponding to the maximum phase defect signal tends to become smaller as the NA becomes larger. It is also worth noting that when NA = 0.33, variations in the position of the phase defect led to fluctuations in the CD error due to the shadow effect of the absorber, while it diminishes at NA = 0.55. This is because a higher NA of 0.55 provides a stronger background field, which suppresses the shadow effect of the absorber more effectively than it does at NA = 0.33. Full article

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

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16 pages, 7998 KB

Open AccessArticle

A Wideband Multi-Polarized Microstrip Antenna with High Polarization Isolation Based on Dual-Circular Polarization

by Xuenan Wang, Hongcheng Zhou, Xinhui Wang, Xia Lei, Boyang Hao, Mian Zhong and Chao Zhou

Micromachines 2025, 16(11), 1209; https://doi.org/10.3390/mi16111209 - 24 Oct 2025

To address the limited overlapping bandwidth across polarization modes in conventional multi-polarized antennas, this paper proposes a wideband multi-polarized microstrip antenna with high polarization isolation. Based on the theory of orthogonal dual-circular polarization synthesis, the proposed antenna achieves left-hand circular polarization (LHCP) and [...] Read more.

To address the limited overlapping bandwidth across polarization modes in conventional multi-polarized antennas, this paper proposes a wideband multi-polarized microstrip antenna with high polarization isolation. Based on the theory of orthogonal dual-circular polarization synthesis, the proposed antenna achieves left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) under a single-port excitation mode, and can generate arbitrary linear polarization (LP) by simply adjusting the phase when dual-fed. For verification, a prototype operating at the C-band is designed, fabricated, and measured. The measured results agree well with the simulations. For linear polarization, the measured 10 dB bandwidth ranges from 4 GHz to 8 GHz (relative bandwidth of 66.7%), with polarization isolation exceeding 26 dB. For circular polarization, the measured bandwidth (for 10 dB return loss and 3 dB axial ratio) spans 4.1–8 GHz (relative bandwidth of 64.5%), with polarization isolation greater than 15 dB. The linear polarization gain is slightly higher than the circular polarization gain, with a maximum gain of 4.3 dB. The proposed antenna simultaneously features multi-polarization, a wide bandwidth, a low profile (0.03 λ₀), and high polarization isolation, which can meet the urgent demand for multi-polarized antennas in modern multi-functional integrated wireless systems, such as communication systems, radar, and unmanned aerial vehicles (UAVs). Full article

(This article belongs to the Special Issue Integration of MEMS, 3D Printing, and Nano-Enabled Technologies in Wireless Communication and Sensing Systems)

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14 pages, 3279 KB

Open AccessArticle

An Integrated Microfluidic System for One-Stop Multiplexed Exosomal PD-L1 and MMP9 Automated Analysis with Deep Learning Model YOLO

by Yunxing Lu, Wenjing Zhang, Qiang Shi, Jianan Hui, Jieyu Wang, Yiman Song and Xiaoyue Yang

Micromachines 2025, 16(11), 1208; https://doi.org/10.3390/mi16111208 - 24 Oct 2025

While immune escape and physical invasion are two key pathways in tumor development, traditional methods for analyzing their exosomal markers are often complex and face identification bias. Microfluidic technology offers significant advantages for non-invasive liquid biopsy, particularly in the analysis of tumor progression [...] Read more.

While immune escape and physical invasion are two key pathways in tumor development, traditional methods for analyzing their exosomal markers are often complex and face identification bias. Microfluidic technology offers significant advantages for non-invasive liquid biopsy, particularly in the analysis of tumor progression markers carried by exosomes. Here, we developed an integrated microfluidic system for the sensitive, accurate, totally on-chip exosome isolation and automatic quantification of tumor progression markers PD-L1 and MMP9. This platform leverages microfluidic design principles for efficient sample mixing and monodisperses microbeads for precise analysis, allowing for complete processing within 40 min. The system’s high efficiency and precision are further enhanced by a lightweight YOLOv5-based positional migration strategy that automates fluorescence quantification. Validation using four different cell lines demonstrated distinct exosomal protein signatures with a low detection limit of 12.58 particles/μL. This innovative microfluidic chip provides a sensitive and easy-to-handle tool for exosomal marker analysis, holding great potential for cancer identification and personalized therapy guidance in the era of point-of-care testing (POCT). Full article

(This article belongs to the Special Issue Microfluidic Systems for Biomedical Analysis, Detection and Diagnosis—Second Edition)

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