Micromachines

17 pages, 4339 KB

Open AccessArticle

Research on Cantilever Beam Roller Tension Sensor Based on Surface Acoustic Wave

by Yang Feng, Bingkun Zhang, Yang Chen, Ben Wang, Hua Xia, Haoda Yu, Xulehan Yu and Pengfei Yang

Micromachines 2025, 16(9), 1044; https://doi.org/10.3390/mi16091044 - 11 Sep 2025

Abstract

This paper presents a design method for a continuous tension detection sensor based on a cantilever beam structure and compensates for the temperature drift of a SAW sensor based on a neural network algorithm. Firstly, a novel cantilever beam roller structure is proposed [...] Read more.

This paper presents a design method for a continuous tension detection sensor based on a cantilever beam structure and compensates for the temperature drift of a SAW sensor based on a neural network algorithm. Firstly, a novel cantilever beam roller structure is proposed to significantly enhance the sensitivity of the transmission of silk thread tension to a SAW tension sensor. Secondly, to improve the sensitivity of the SAW tension sensor, the COMSOL finite element method (FEM) is employed for simulation to determine the optimal IDT placement. An unbalanced split IDT design is utilized to suppress potential parasitic responses. Finally, the designed sensor is tested, and a GA-PSO-BP algorithm is employed to fit the test data for temperature compensation. The experimental results demonstrate that the temperature sensitivity coefficient of the data optimized by the GA-PSO-BP algorithm is reduced by an order of magnitude compared to the raw data, with reductions of

6.0409 \times 10^{- 3} {° C}^{- 1}

and

3.0312 \times 10^{- 3} {° C}^{- 1}

compared to the BP neural network and the PSO-BP algorithm, respectively. The average output error of the optimized data is reduced by 5.748% compared to the sensor measurement data, and it is also lower than both the BP neural network and the PSO-BP algorithm. It provides new design ideas for the development of tension sensors. Full article

(This article belongs to the Special Issue Surface and Bulk Acoustic Wave Devices, 2nd Edition)

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19 pages, 4438 KB

Open AccessArticle

Multi-Level Scale Attention Fusion Network for Adhesive Spots Segmentation in Microlens Packaging

by Yixiong Yan, Sijia Chen, Lian Duan, Dinghui Luo, Fan Zhang and Shunshun Zhong

Micromachines 2025, 16(9), 1043; https://doi.org/10.3390/mi16091043 - 11 Sep 2025

Abstract

The demand for high-quality beams from high-power lasers has led to the need for high-precision inspection of adhesion points for collimating lens packages. In this paper, we propose a Multi-Level Scale Attention Fusion Network (MLSAFNet) by fusing a Multi-Level Attention Module (MLAM) and [...] Read more.

The demand for high-quality beams from high-power lasers has led to the need for high-precision inspection of adhesion points for collimating lens packages. In this paper, we propose a Multi-Level Scale Attention Fusion Network (MLSAFNet) by fusing a Multi-Level Attention Module (MLAM) and a Multi-Scale Channel-Guided Module (MSCGM) to achieve highly accurate and robust adhesive spots detection. Additionally, we built a Laser Lens Adhesive Spots (LLAS) dataset using automated lens packaging equipment and performed pixel-by-pixel standardization for the first time. Extensive experimental results show that the mean intersection over union (mIoU) of MLSAFNet reaches 91.15%, and its maximum values of localization error and area measurement error are 21.83 μm and 0.003 mm², respectively, which are better than other target detection methods. Full article

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25 pages, 1808 KB

Open AccessReview

Nanomaterial-Powered Biosensors: A Cutting-Edge Review of Their Versatile Applications

by Payal Patial, Manish Deshwal, Shonak Bansal, Anjana Sharma, Kamaldeep Kaur and Krishna Prakash

Micromachines 2025, 16(9), 1042; https://doi.org/10.3390/mi16091042 - 11 Sep 2025

Abstract

Optimal sensing devices exhibit a combination of key performance attributes, including an extensive detection limit, exceptional selectivity, high sensitivity, consistent repeatability, precise measurement, and rapid response times with efficient analyte flow. In recent years, biosensing platforms incorporating nanoscale materials have garnered considerable attention [...] Read more.

Optimal sensing devices exhibit a combination of key performance attributes, including an extensive detection limit, exceptional selectivity, high sensitivity, consistent repeatability, precise measurement, and rapid response times with efficient analyte flow. In recent years, biosensing platforms incorporating nanoscale materials have garnered considerable attention due to their diverse applications across various scientific and technological domains. The integration of nanoparticles (NPs) in biosensor design primarily bridges the dimensional gap between the signal transduction element and the biological recognition component, both of which operate at nanometer scales. The synergistic combination of NPs with electrochemical techniques has facilitated the development of biosensors characterized by enhanced sensitivity and superior analyte discrimination capabilities. This comprehensive analysis examines the evolution and recent advancements in nanomaterial (NM)-based biosensors, encompassing an extensive array of nanostructures. These consists of one-dimensional nanostructures including carbon nanotubes (CNTs), nanowires (NWs), nanorods (NRs), and quantum dots (QDs), as well as noble metal and metal and metal oxide nanoparticles (NPs). The article examines how advancements in biosensing techniques across a range of applications have been fueled by the growth of nanotechnology. Researchers have significantly improved biosensor performance parameters by utilizing the distinct physiochemical properties of these NMs. The developments have increased the potential uses of nanobiosensors in a wide range of fields, from food safety and biodefense to medical diagnostics and environmental monitoring. The continuous developments in NM-based biosensors are the result of the integration of several scientific areas, such as analytical chemistry, materials science, and biotechnology. This interdisciplinary approach continues to drive innovations in sensor design, signal amplification strategies, and data analysis techniques, ultimately leading to more sophisticated and capable biosensing platforms. As the field progresses, challenges related to the scalability, reproducibility, and long-term stability of nanobiosensors are being addressed through innovative fabrication methods and surface modification techniques. These efforts aim to translate the promising results observed in laboratory settings into practical, commercially viable biosensing devices that can address real-world analytical challenges across various sectors. Full article

(This article belongs to the Special Issue New Advances in Wearable and Flexible Sensor Devices and Their Future Prospects)

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1 pages, 129 KB

Open AccessRetraction

RETRACTED: Yang et al. Design and Dynamic Simulation of a Novel Traveling Wave Linear Ultrasonic Motor. Micromachines 2022, 13, 557

by Lin Yang, Kaixi Yao, Weihao Ren, Liang Chen, Mojian Yang, Rongcheng Zhao and Siyu Tang

Micromachines 2025, 16(9), 1041; https://doi.org/10.3390/mi16091041 - 11 Sep 2025

Abstract

The journal retracts the article “Design and Dynamic Simulation of a Novel Traveling Wave Linear Ultrasonic Motor” [...] Full article

28 pages, 3409 KB

Open AccessArticle

Research on GNSS/MEMS IMU Array Fusion Localization Method Based on Improved Grey Prediction Model

by Yihao Chen, Jieyu Liu, Weiwei Qin and Can Li

Micromachines 2025, 16(9), 1040; https://doi.org/10.3390/mi16091040 - 11 Sep 2025

Abstract

To address the issue of decreased positioning accuracy caused by interference or blockage of GNSS signals in vehicle navigation systems, this paper proposes a GNSS/MEMS IMU array fusion localization method based on an improved grey prediction model. First, a multi-feature fusion GNSS confidence [...] Read more.

To address the issue of decreased positioning accuracy caused by interference or blockage of GNSS signals in vehicle navigation systems, this paper proposes a GNSS/MEMS IMU array fusion localization method based on an improved grey prediction model. First, a multi-feature fusion GNSS confidence evaluation algorithm is designed to assess the reliability of GNSS data in real time using indicators such as signal strength, satellite visibility, and solution consistency; second, to overcome the limitations of traditional grey prediction models in processing vehicle complex motion data, two key improvements are proposed: (1) a dynamic background value optimization method based on vehicle motion characteristics, which dynamically adjusts the weight coefficients in the background value construction according to vehicle speed, acceleration, and road curvature, enhancing the model’s sensitivity to changes in vehicle motion state; (2) a residual sequence compensation mechanism, which analyzes the variation patterns of historical residual sequences to accurately correct the prediction results, significantly improving the model’s prediction accuracy in nonlinear motion scenarios; finally, an adaptive fusion framework under normal and denied GNSS conditions is constructed, which directly fuses data when GNSS is reliable, and uses the improved grey model prediction results as virtual measurements for fusion during signal denial. Simulation and vehicle experiments verify that: compared to the traditional GM(1,1) model, the proposed method improves prediction accuracy by 31%, 52%, and 45% in straight, turning, and acceleration scenarios, respectively; in a 30-s GNSS denial scenario, the accuracy is improved by over 79% compared to pure INS methods. Full article

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16 pages, 4723 KB

Open AccessArticle

A Novel Motion Platform Based on Dual Driving Feet Linear Ultrasonic Motor

by Yue Jian, Zhen Liu, Ping Yao, Wenjie Zhou, Junfeng He and Huazhuo Liang

Micromachines 2025, 16(9), 1039; https://doi.org/10.3390/mi16091039 - 10 Sep 2025

Abstract

This paper presents a novel motion platform based on a π-shaped linear ultrasonic motor. Initially, a new preload device was designed in accordance with established criteria for high-power linear ultrasonic motors. Mounted on the base structure, this mechanism neither interferes with the stator’s [...] Read more.

This paper presents a novel motion platform based on a π-shaped linear ultrasonic motor. Initially, a new preload device was designed in accordance with established criteria for high-power linear ultrasonic motors. Mounted on the base structure, this mechanism neither interferes with the stator’s high-frequency vibrations nor couples with the mover’s motion. Structural parameters were determined through theoretical modeling, while experimental validation confirmed the mechanism’s capability to deliver stable and appropriate preload throughout the motor’s complete operating cycle, thereby enhancing the platform’s operational stability and positioning accuracy. Subsequently, a novel mover was developed by replacing linear guides with a ceramic–ceramic mechanism. This mover features a compact structure and flexible design, facilitating both miniaturization and effective stroke amplification. The resulting platform achieves a 40% reduction in volume compared to conventional designs while extending the stroke to 150% of the original capacity. Finally, a prototype was fabricated and experimentally evaluated. Test results demonstrate output velocities exceeding 200 mm/s in both directions, with positioning accuracy reaching 1.1 μm. Full article

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

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23 pages, 3537 KB

Open AccessArticle

Optimized Design of Sparse Antenna Array for 2D Subarrays Based on GA-PSO Algorithm and Ambiguity Function

by Jian Yang, Jian Lu, Tong Zhu, Chuanxiang Li and Yinghui Quan

Micromachines 2025, 16(9), 1038; https://doi.org/10.3390/mi16091038 - 10 Sep 2025

Abstract

A sparse antenna array of subarrays can effectively reduce the digital channels of array antennas, system complexities, and hardware cost while simultaneously increasing the antenna aperture. In this study, a new optimal design is proposed for a sparse antenna array of subarrays in [...] Read more.

A sparse antenna array of subarrays can effectively reduce the digital channels of array antennas, system complexities, and hardware cost while simultaneously increasing the antenna aperture. In this study, a new optimal design is proposed for a sparse antenna array of subarrays in the full-phased multiple input multiple output (FPMIMO) operation mode based on genetic algorithm–particle swarm optimization (GA–PSO) and ambiguity functions. The proposed algorithm can adaptively adjust the number of optimization iterations for yielding the optimization results of the PSO algorithm and GA to ensure the global optimization performance of algorithms and combine ambiguity functions to determine the final optimized sparse antenna array of subarrays. The effectiveness of the proposed algorithm is verified via simulation tests. Full article

(This article belongs to the Special Issue RF Devices: Technology and Progress)

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52 pages, 2691 KB

Open AccessReview

Heterogeneous Integration Technology Drives the Evolution of Co-Packaged Optics

by Han Gao, Wanyi Yan, Dan Zhang and Daquan Yu

Micromachines 2025, 16(9), 1037; https://doi.org/10.3390/mi16091037 - 10 Sep 2025

Abstract

The rapid growth of artificial intelligence (AI), data centers, and high-performance computing (HPC) has increased the demand for large bandwidth, high energy efficiency, and high-density optical interconnects. Co-packaged optics (CPO) technology offers a promising solution by integrating photonic integrated circuits (PICs) directly within [...] Read more.

The rapid growth of artificial intelligence (AI), data centers, and high-performance computing (HPC) has increased the demand for large bandwidth, high energy efficiency, and high-density optical interconnects. Co-packaged optics (CPO) technology offers a promising solution by integrating photonic integrated circuits (PICs) directly within or close to electronic integrated circuit (EIC) packages. This paper explores the evolution of CPO performance from various perspectives, including fan-out wafer level packaging (FOWLP), through-silicon via (TSV)-based packaging, through-glass via (TGV)-based packaging, femtosecond laser direct writing waveguides, ion-exchange glass waveguides, and optical coupling. Micro ring resonators (MRRs) are a high-density integration solution due to their compact size, excellent energy efficiency, and compatibility with CMOS processes. However, traditional thermal tuning methods face limitations such as high static power consumption and severe thermal crosstalk. To address these issues, non-volatile neuromorphic photonics has made breakthroughs using phase-change materials (PCMs). By combining the integrated storage and computing capabilities of photonic memory with the efficient optoelectronic interconnects of CPO, this deep integration is expected to work synergistically to overcome material, integration, and architectural challenges, driving the development of a new generation of computing hardware with high energy efficiency, low latency, and large bandwidth. Full article

(This article belongs to the Special Issue Emerging Packaging and Interconnection Technology, Second Edition)

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20 pages, 2420 KB

Open AccessArticle

Variational Bayesian Innovation Saturation Kalman Filter for Micro-Electro-Mechanical System–Inertial Navigation System/Polarization Compass Integrated Navigation

by Yu Sun, Xiaojie Liu, Xiaochen Liu, Huijun Zhao, Chenguang Wang, Huiliang Cao and Chong Shen

Micromachines 2025, 16(9), 1036; https://doi.org/10.3390/mi16091036 - 10 Sep 2025

Abstract

Aiming at the issue of time-varying measurement noise with heavy-tailed characteristics and outliers generated by the polarization compass (PC) in the micro-electro-mechanical system–inertial navigation system (MEMS-INS) and PC-integrated navigation system when it is subject to internal and external disturbances, an improved Variational Bayesian [...] Read more.

Aiming at the issue of time-varying measurement noise with heavy-tailed characteristics and outliers generated by the polarization compass (PC) in the micro-electro-mechanical system–inertial navigation system (MEMS-INS) and PC-integrated navigation system when it is subject to internal and external disturbances, an improved Variational Bayesian Innovation Saturation Robust Adaptive Kalman filter (VISKF) algorithm is proposed. This algorithm utilizes the variational Bayesian (VB) method based on Student’s t-distribution (STD) to approximately calculate the statistical characteristics of the time-varying measurement noise of the PC, thereby obtaining more accurate measurement noise statistical parameters. Additionally, the algorithm introduces an innovation saturation function and proposes an adaptive update strategy for the saturation boundary. It mitigates the problem of innovation value divergence in PC caused by outliers through a two-layer structure that can track the changes in the innovation value to adaptively adjust the saturation boundary. To verify the effectiveness of the algorithm, static and dynamic experiments were conducted on an unmanned vehicle. The experimental results show that compared with adaptive Kalman filter (AKF), variational Bayesian robust adaptive Kalman filter (VBRAKF), and innovation saturate robust adaptive Kalman filter (ISRAKF), the proposed algorithm improves the dynamic orientation accuracy by 76.89%, 67.23%, and 84.45%, respectively. Moreover, compared with other similar target algorithms, the proposed algorithm also has obvious advantages. Therefore, this method can significantly improve the navigation accuracy and robustness of the INS/PC integrated navigation system in complex environments. Full article

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

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12 pages, 4882 KB

Open AccessArticle

Mg-Doped P-Type AlN Thin Film Prepared by Magnetron Sputtering Using Mg-Al Alloy Targets

by Yulin Ma, Xu Wang and Kui Ma

Micromachines 2025, 16(9), 1035; https://doi.org/10.3390/mi16091035 - 10 Sep 2025

Abstract

Aluminum nitride (AlN), a III-V wide-bandgap semiconductor, has attracted significant attention for high-temperature and high-power applications. However, achieving p-type doping in AlN remains challenging. In this study, p-type AlN thin films were fabricated via magnetron sputtering using Mg-Al alloy targets with varying Mg [...] Read more.

Aluminum nitride (AlN), a III-V wide-bandgap semiconductor, has attracted significant attention for high-temperature and high-power applications. However, achieving p-type doping in AlN remains challenging. In this study, p-type AlN thin films were fabricated via magnetron sputtering using Mg-Al alloy targets with varying Mg concentrations (0.01 at.%, 0.02 at.%, and 0.5 at.%), followed by ex situ high-temperature annealing to facilitate Mg diffusion and electrical activation. The structural, morphological, and electrical properties of the films were systematically characterized using X-ray diffraction (XRD), white light interferometry (WLI), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Hall effect measurements. The results demonstrate that at a Mg doping concentration of 0.02 at.%, the films exhibit optimal crystallinity, uniform Mg distribution, and a favorable balance between carrier concentration and mobility, resulting in effective p-type conductivity. Increasing Mg doping leads to higher surface roughness and the formation of columnar and conical grain structures. While high Mg doping (0.5 at.%) significantly increases carrier concentration and decreases resistivity, it also reduces mobility due to enhanced impurity and carrier–carrier scattering, negatively impacting hole transport. XPS and EDS analyses confirm Mg incorporation and the formation of Mg-N and Al-Mg bonds. Overall, this study indicates that controlled Mg doping combined with high-temperature annealing can achieve p-type AlN films to a certain extent, though mobility and carrier activation remain limited, providing guidance for the development of high-performance AlN-based bipolar devices. Full article

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12 pages, 10348 KB

Open AccessArticle

The Effect of Dual-Layer Carbon/Iron-Doped Buffers in an AlGaN/GaN High-Electron-Mobility Transistor

by Po-Hsuan Chang, Chong-Rong Huang, Chia-Hao Liu, Kuan-Wei Lee and Hsien-Chin Chiu

Micromachines 2025, 16(9), 1034; https://doi.org/10.3390/mi16091034 - 10 Sep 2025

Abstract

This study compared the effectiveness of gallium nitride (GaN) with a single carbon-doped (C-doped) buffer layer and a composite carbon/iron-doped (C/Fe-doped) buffer layer within an AlGaN/GaN high-electron-mobility transistor (HEMT). In traditional power devices, Fe-doping has a large memory effect, causing Fe ions to [...] Read more.

This study compared the effectiveness of gallium nitride (GaN) with a single carbon-doped (C-doped) buffer layer and a composite carbon/iron-doped (C/Fe-doped) buffer layer within an AlGaN/GaN high-electron-mobility transistor (HEMT). In traditional power devices, Fe-doping has a large memory effect, causing Fe ions to diffuse outwards, which is undesirable in high-power-device applications. In the present study, a C-doped GaN layer was added above the Fe-doped GaN layer to form a composite buffer against Fe ion diffusion. Direct current (DC) characteristics, pulse measurement, low-frequency noise, and variable temperature analysis were performed on both devices. The single C-doped buffer layer in the AlGaN/GaN HEMT had fewer defects in capturing and releasing carriers, and better dynamic characteristics, whereas the composite C/Fe-doped buffers, by suppressing Fe migration toward the channel, showed higher vertical breakdown voltage and lower sheet resistance, and still demonstrated potential for further performance tuning to achieve enhanced semi-insulating behavior. With optimized doping concentrations and layer thicknesses, the dual-layer configuration offers a promising path toward improved trade-offs between leakage suppression, trap control, and dynamic performance for next-generation GaN-based power devices. Full article

(This article belongs to the Special Issue III–V Compound Semiconductors and Devices, 2nd Edition)

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9 pages, 5512 KB

Open AccessArticle

Design of N-Way Power Divider Based on TE₁₀ Mode Splitting Strategy

by Jianfeng Chen, Haidi Tang, Shengqi Zhang and Leijun Xu

Micromachines 2025, 16(9), 1033; https://doi.org/10.3390/mi16091033 - 10 Sep 2025

Abstract

This paper presents a novel 1-to-N power division architecture combining overmoded

{TE}_{10}

mode waveguides and modular N-way waveguide-to-microstrip mode converters. By decomposing the

{TE}_{10}

mode field distribution along the narrow wall of a rectangular waveguide, the proposed design enables [...] Read more.

This paper presents a novel 1-to-N power division architecture combining overmoded

{TE}_{10}

mode waveguides and modular N-way waveguide-to-microstrip mode converters. By decomposing the

{TE}_{10}

mode field distribution along the narrow wall of a rectangular waveguide, the proposed design enables flexible power splitting into arbitrary output ports (even or odd numbers) through uniform sub-

{TE}_{10}

-mode waveguide pathways. To achieve the above function using microwave transmission lines, a tapered transition structure ensures wideband excitation of the overmoded waveguide, while linearly tapered slot antennas (LTSAs) serve as N-way mode converters. Prototypes with two-, three-, and four-channel outputs demonstrate excellent amplitude-phase uniformity (≤0.5 dB amplitude imbalance and ≤

5^{\circ}

phase deviation) across 6.5–12 GHz, with return loss <−10 dB. The modular 1-to-N power divider enables the rapid reconfiguration of output channels by simply replacing the mode converter module. Full article

(This article belongs to the Special Issue Electromagnetic Metamaterials and Metasurfaces: From Design to Applications)

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12 pages, 2523 KB

Open AccessArticle

Lightweight Design Method for Micromanufacturing Systems Based on Multi-Objective Optimization

by Shan Li and Seyed Hamed Hashemi Sohi

Micromachines 2025, 16(9), 1032; https://doi.org/10.3390/mi16091032 - 9 Sep 2025

Abstract

This study proposes a multi-stage collaborative design framework integrating sensitivity analysis, response surface methodology (RSM), and topology optimization for synergistic lightweighting and performance enhancement of micromanufacturing systems using ultra-precision computer numerical control (CNC) machine tools. Overall sensitivity analysis identified the base and column [...] Read more.

This study proposes a multi-stage collaborative design framework integrating sensitivity analysis, response surface methodology (RSM), and topology optimization for synergistic lightweighting and performance enhancement of micromanufacturing systems using ultra-precision computer numerical control (CNC) machine tools. Overall sensitivity analysis identified the base and column as stiffness-critical components, while the spindle box exhibited significant weight-reduction potential. Using spindle box wall and bottom thickness as variables, RSM models for mass and stress were constructed. Multi-objective optimization via a genetic clustering algorithm achieved a 57.2% (590 kg) weight reduction under stress constraints (<45 MPa). Subsequent variable-density topology optimization (SIMP model) reconfigured the rib layouts of the base and column under volume constraints, reducing their weights by 38.5% (2844 kg) and 41.5% (1292 kg), respectively. Whole-machine validation showed that maximum static deformation decreased from 0.17 mm to 0.09 mm, maximum stress reduced from 58 MPa to 35 MPa, and first-order natural frequency increased from 50.68 Hz to 84.08 Hz, significantly enhancing dynamic stiffness. Cumulative weight reduction exceeded 3000 kg, achieving a balance between lightweighting and static/dynamic performance improvement. This work provides an effective engineering pathway for a structural design of high-end micromanufacturing systems. Full article

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

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13 pages, 3362 KB

Open AccessArticle

Gate-Induced Static and Dynamic Nonlinearity Characteristics of Bilayer Graphene Field-Effect Transistors (Bi-GFETs)

by Varun Kumar Kakar, Munindra and Pankaj Kumar Pal

Micromachines 2025, 16(9), 1031; https://doi.org/10.3390/mi16091031 - 9 Sep 2025

Abstract

In this study, the nonlinearity characteristics of bilayer graphene field-effect transistors (Bi-GFETs) are analyzed by using a small-signal equivalent circuit. The static nonlinearity is determined by applying mathematical operation on the drain current equation of Bi-GFETs. Furthermore, the closed expressions for the second- [...] Read more.

In this study, the nonlinearity characteristics of bilayer graphene field-effect transistors (Bi-GFETs) are analyzed by using a small-signal equivalent circuit. The static nonlinearity is determined by applying mathematical operation on the drain current equation of Bi-GFETs. Furthermore, the closed expressions for the second- and third-order harmonic distortion (HD) and the intermodulation (IM) distortion of the second- and third-order for Bi-GFETs are analyzed graphically. Dynamic nonlinearity is studied and illustrated in the results by examining the input and output characteristics; i.e., the drain current versus the negative drain to the source voltage and the transfer characteristic curve at various gate voltages controlled by both the top gate as well as the back gate. The characteristic behavior of the gate voltage in Bi-GFETs at short channel lengths is observed and compared; that is, the characteristic curves exhibits strong nonlinearity, with a low power point with some kinks at high gate biasing and a constant linear region at low gate biasing. The quantitative values of the second-order harmonic distortion (HD) and intermodulation distortion (IM) of the proposed analytical model are −40 dB and −45 dB. Quantitative and qualitative outcomes of the characteristics of Bi-GFETs are compared with existing experimental data, which is available in the literature. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductor Devices: Materials, Fabrication, and Applications, 2nd Edition)

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13 pages, 7927 KB

Open AccessArticle

Dual-Mode Reconfigurable Frequency-Selective Surface for Switching Between Narrowband and Wideband Applications

by Batuhan Uslu, Sena Esen Bayer Keskin and Nurhan Türker Tokan

Micromachines 2025, 16(9), 1030; https://doi.org/10.3390/mi16091030 - 8 Sep 2025

Abstract

This study presents a reconfigurable frequency-selective surface (R-FSS) designed to dynamically switch between WLAN, WiMAX, and sub-6 GHz band frequencies. The electronic switching mechanism of this R-FSS is controlled in real-time using PIN-diodes. Depending on the activation state of these diodes, the structure [...] Read more.

This study presents a reconfigurable frequency-selective surface (R-FSS) designed to dynamically switch between WLAN, WiMAX, and sub-6 GHz band frequencies. The electronic switching mechanism of this R-FSS is controlled in real-time using PIN-diodes. Depending on the activation state of these diodes, the structure operates in three distinct modes. Among the three modes, one exhibits polarization-stable wideband suppression, whereas the other two demonstrate polarization selectivity by interchanging between the dual-narrow and single-wide stopband regimes under orthogonal polarizations. The design is described with an equivalent-circuit model, corroborated by full-wave electromagnetic simulations, and validated through measurements of a fabricated prototype. This reconfigurability allows the proposed structure to operate across WLAN, sub-6 GHz, and WiMAX frequency ranges either with two narrow stopbands or with a single-wide stopband, while providing polarization selectivity for frequency-selective applications. Full article

(This article belongs to the Special Issue RF MEMS and Microsystems)

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24 pages, 11527 KB

Open AccessArticle

Study on the Preparation of Diamond Film Substrates on AlN Ceramic and Their Performance in LED Packaging

by Shasha Wei, Yusheng Sui, Yunlong Shi, Junrong Chen, Tianlei Dong, Rongchuan Lin and Zheqiao Lin

Micromachines 2025, 16(9), 1029; https://doi.org/10.3390/mi16091029 - 8 Sep 2025

Abstract

Aluminum nitride (AlN) ceramic materials have relatively low thermal conductivity and poor heat dissipation performance, and are increasingly unsuitable for high-power LED packaging. In this study, diamond films were deposited on AlN ceramic substrates by microwave plasma chemical vapor deposition (MPCVD). The effects [...] Read more.

Aluminum nitride (AlN) ceramic materials have relatively low thermal conductivity and poor heat dissipation performance, and are increasingly unsuitable for high-power LED packaging. In this study, diamond films were deposited on AlN ceramic substrates by microwave plasma chemical vapor deposition (MPCVD). The effects of different process parameters on the crystal quality, surface morphology and crystal orientation of diamond films were studied, and the high thermal conductivity of diamond was used to enhance the heat dissipation ability of AlN ceramic substrates. Finally, the junction temperature and thermal resistance of LED devices packaged on AlN ceramic–diamond composite substrate, AlN ceramic substrate and aluminum substrate were tested. The experimental results show that compared with the traditional aluminum and AlN ceramic substrates, AlN ceramic–diamond composite substrates show excellent heat dissipation performance, especially under high-power conditions. Full article

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

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38 pages, 7252 KB

Open AccessReview

Advancements in Wearable Antenna Design: A Comprehensive Review of Materials, Fabrication Techniques, and Future Trends in Wireless Communication

by Zhikai Cao and Mai Lu

Micromachines 2025, 16(9), 1028; https://doi.org/10.3390/mi16091028 - 8 Sep 2025

Viewed by 18

Abstract

With the continuous development of wireless communication technology, the demand for wearable communication devices has rapidly increased. The antenna is one of the key components in communication devices, directly affecting the performance of wearable communication devices. As a result, wearable antenna design has [...] Read more.

With the continuous development of wireless communication technology, the demand for wearable communication devices has rapidly increased. The antenna is one of the key components in communication devices, directly affecting the performance of wearable communication devices. As a result, wearable antenna design has become a research hotspot in recent years. Wearable antennas are widely used in various fields of daily life, including healthcare, sports and entertainment, the internet of things (IoT), and military positioning. In the last decade, related researchers have studied wearable antennas from various perspectives, and this paper summarizes the design and fabrication of wearable antennas more comprehensively and systematically. This review covers material selection, manufacturing techniques, miniaturization technologies, and performance metrics, while addressing key design considerations. It also highlights recent research, applications in critical fields, and future development trends, offering valuable insights for the design and study of wearable antennas. Full article

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

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11 pages, 3178 KB

Open AccessArticle

Effect of Bias Voltage on the Crystal Growth of AlN(002) Thin Films Fabricated by Reactive Magnetron Sputtering

by Yong Du, Haowen Zou, Tiejun Li and Guifang Shao

Micromachines 2025, 16(9), 1027; https://doi.org/10.3390/mi16091027 - 8 Sep 2025

Viewed by 258

Abstract

The study investigates the influence of bias voltage on the structural and morphological properties of aluminum nitride AlN (002) thin films deposited on sapphire substrates via reactive magnetron sputtering for high-frequency surface acoustic wave (SAW) devices. The results indicate that applying a positive [...] Read more.

The study investigates the influence of bias voltage on the structural and morphological properties of aluminum nitride AlN (002) thin films deposited on sapphire substrates via reactive magnetron sputtering for high-frequency surface acoustic wave (SAW) devices. The results indicate that applying a positive bias voltage (>0 V) yields AlN films with compact and uniform surfaces. As bias increases, the deposition rate initially rises before declining, while root–mean–square (RMS) roughness progressively decreases, reaching a minimum at 100 V, significantly enhancing surface quality. X-ray diffraction (XRD) analysis reveals enhanced (002) preferential orientation with increasing bias, indicating improved crystallinity. These findings demonstrate that optimized bias voltage not only refines surface morphology but also strengthens crystal alignment, particularly along the (002) plane, making AlN films highly suitable for high-frequency SAW applications, and provides data for the preparation of higher-quality AlN films. Full article

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22 pages, 4991 KB

Open AccessReview

Meta-Optics for Optical Engineering of Next-Generation AR/VR Near-Eye Displays

by Junoh Lee and Sun-Je Kim

Micromachines 2025, 16(9), 1026; https://doi.org/10.3390/mi16091026 - 7 Sep 2025

Viewed by 260

Abstract

Meta-optics, enabled by metasurfaces consisting of two-dimensional arrays of meta-atoms, offers ultrathin and multi-functional control over the vectorial wavefront of light at subwavelength scales. The unprecedented optical element technology is a promising candidate to overcome key limitations in augmented reality (AR) and virtual [...] Read more.

Meta-optics, enabled by metasurfaces consisting of two-dimensional arrays of meta-atoms, offers ultrathin and multi-functional control over the vectorial wavefront of light at subwavelength scales. The unprecedented optical element technology is a promising candidate to overcome key limitations in augmented reality (AR) and virtual reality (VR) near-eye displays particularly in achieving compact, eyeglass-type form factors with a wide field-of-view, a large eyebox, high resolution, high brightness, and reduced optical aberrations, at the same time. This review highlights key performance bottlenecks of AR/VR displays in the perspective of optical design, with an emphasis on their practical significance for advancing current technologies. We then examine how meta-optical elements are applied to VR and AR systems by introducing and analyzing the major milestone studies. In case of AR systems, particularly, two different categories, free-space and waveguide-based architectures, are introduced. For each category, we summarize studies using metasurfaces as lenses, combiners, or waveguide couplers. While meta-optics enables unprecedented miniaturization and functionality, it also faces several remaining challenges. The authors suggest potential technological directions to address such issues. By surveying recent progress and design strategies, this review provides a comprehensive perspective on the role of meta-optics in advancing the optical engineering of next-generation AR/VR near-eye displays. Full article

(This article belongs to the Special Issue Advances in Nanophotonics: Physics, Materials, and Applications)

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14 pages, 2389 KB

Open AccessArticle

Neural Synaptic Simulation Based on ZnAlSnO Thin-Film Transistors

by Yang Zhao, Chao Wang, Laizhe Ku, Liang Guo, Xuefeng Chu, Fan Yang, Jieyang Wang, Chunlei Zhao, Yaodan Chi and Xiaotian Yang

Micromachines 2025, 16(9), 1025; https://doi.org/10.3390/mi16091025 - 7 Sep 2025

Viewed by 220

Abstract

In the era of artificial intelligence, neuromorphic devices that simulate brain functions have received increasingly widespread attention. In this paper, an artificial neural synapse device based on ZnAlSnO thin-film transistors was fabricated, and its electrical properties were tested: the current-switching ratio was 1.18 [...] Read more.

In the era of artificial intelligence, neuromorphic devices that simulate brain functions have received increasingly widespread attention. In this paper, an artificial neural synapse device based on ZnAlSnO thin-film transistors was fabricated, and its electrical properties were tested: the current-switching ratio was 1.18 × 10⁷, the subthreshold oscillation was 1.48 V/decade, the mobility was 2.51 cm²V⁻¹s⁻¹, and the threshold voltage was −9.40 V. Stimulating artificial synaptic devices with optical signals has the advantages of fast response speed and good anti-interference ability. The basic biological synaptic characteristics of the devices were tested under 365 nm light stimulation, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), short-term plasticity (STP), and long-term plasticity (LTP). This device shows good synaptic plasticity. In addition, by changing the gate voltage, the excitatory postsynaptic current of the device at different gate voltages was tested, two different logical operations of “AND” and “OR” were achieved, and the influence of different synaptic states on memory was simulated. This work verifies the application potential of the device in the integrated memory and computing architecture, which is of great significance for promoting the high-quality development of neuromorphic computing hardware. Full article

(This article belongs to the Special Issue Advanced Wide Bandgap Semiconductor Materials and Devices)

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16 pages, 1823 KB

Open AccessArticle

Coupling and Preload Analysis of Piezoelectric Actuator and Nonlinear Stiffness Mechanism

by Wei Wang, Jinchuan Zheng, Zhe Sun and Xiaoqi Chen

Micromachines 2025, 16(9), 1024; https://doi.org/10.3390/mi16091024 - 6 Sep 2025

Viewed by 266

Abstract

This article presents a comprehensive investigation of the dynamic coupling between a piezoelectric actuator (PZT) and its driving nonlinear stiffness mechanism (NSM) stage for precise positioning control. Particular emphasis is placed on the preload-induced effects on the force transmission and structural separation between [...] Read more.

This article presents a comprehensive investigation of the dynamic coupling between a piezoelectric actuator (PZT) and its driving nonlinear stiffness mechanism (NSM) stage for precise positioning control. Particular emphasis is placed on the preload-induced effects on the force transmission and structural separation between the PZT and NSM. To ensure continuous mechanical contact between them, we propose a no-separation criterion based on acceleration matching, from which the minimum preload requirement is analytically derived. Additionally, static and dynamic simulations reveal that increasing the preload force from 0 N to 10 N can push the first natural frequency of the holistic system from

214.21

Hz to

258.17

Hz, respectively. This beneficially enhances the displacement consistency across different geometric configurations. Moreover, an appropriate preload force can prevent separation and increase system stiffness while reducing nonlinear deformation. Experimental results verifies that a preload of 10 N can prevent the separation between the PZT and NSM stage and maintain achievable output displacement of the stage within the range from

54.35 μ

m to

129.42 μ

m. This article offers the analytical results of preload setting to guarantee reliable actuation for nonlinear precision positioning stages. Full article

(This article belongs to the Special Issue Design and Real Time Implementation of Intelligent Control Schemes for Actuators)

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13 pages, 2332 KB

Open AccessArticle

Structure and Temperature Dependence of Solder Layer and Electric Parameters in IGBT Modules

by Jibing Chen, Yanfeng Liu, Bowen Liu and Yiping Wu

Micromachines 2025, 16(9), 1023; https://doi.org/10.3390/mi16091023 - 5 Sep 2025

Viewed by 214

Abstract

IGBT high-power devices are subjected to various extreme working conditions for long periods and are affected by multiple loading conditions, inevitably leading to various aging and failure issues. Among them, the solder layer, as one of the weakest parts in the packaging structure [...] Read more.

IGBT high-power devices are subjected to various extreme working conditions for long periods and are affected by multiple loading conditions, inevitably leading to various aging and failure issues. Among them, the solder layer, as one of the weakest parts in the packaging structure of IGBT modules, has rarely been studied regarding its thermal fatigue characteristics and interface structure evolution behavior. In this work, a rapid temperature test chamber was used to conduct a thermal fatigue temperature cycling experiment on IGBT modules from −40 to 150 °C. The microscopic structural evolution behavior and the growth pattern of intermetallic compounds (IMC) during the solder layer’s thermal fatigue process of the IGBT modules were studied. At the same time, the changes in relevant static parameters of the IGBT after thermal cycling fatigue were tested using an oscilloscope and a power device analyzer, thereby clarifying the failure mechanism of the IGBT module. This provides a theoretical basis and data support for the thermal design and reliability assessment of IGBT modules. Full article

(This article belongs to the Special Issue Insulated Gate Bipolar Transistor (IGBT) Modules, 2nd Edition)

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7 pages, 206 KB

Open AccessEditorial

Editorial for the Special Issue on the Application of Microfluidic Technology in Bioengineering

by Shuli Wang and Yigang Shen

Micromachines 2025, 16(9), 1022; https://doi.org/10.3390/mi16091022 - 5 Sep 2025

Viewed by 318

Abstract

Microfluidics, also called lab-on-a-chip, is a cutting-edge technology in contemporary interdisciplinary science [...] Full article

(This article belongs to the Special Issue Application of Microfluidic Technology in Bioengineering)

14 pages, 2637 KB

Open AccessArticle

Integration of High-Brightness QLED-Excited Diamond Magnetic Sensor

by Pengfei Zhao, Junjun Du, Jinyu Tai, Zhaoqi Shang, Xia Yuan and Yuanyuan Shi

Micromachines 2025, 16(9), 1021; https://doi.org/10.3390/mi16091021 - 4 Sep 2025

Viewed by 389

Abstract

The nitrogen-vacancy (NV) center magnetic sensor, leveraging nitrogen-vacancy quantum effects, enables high-sensitivity magnetic field detection via optically detected magnetic resonance (ODMR). However, conventional single-point integrated devices suffer from limitations such as inefficient regional magnetic field detection and challenges in discerning the directional variations [...] Read more.

The nitrogen-vacancy (NV) center magnetic sensor, leveraging nitrogen-vacancy quantum effects, enables high-sensitivity magnetic field detection via optically detected magnetic resonance (ODMR). However, conventional single-point integrated devices suffer from limitations such as inefficient regional magnetic field detection and challenges in discerning the directional variations of dynamic magnetic fields. To address these issues, this study proposes an array- based architecture that innovatively substitutes the conventional 532 nm laser with quantum-dot light-emitting diodes (QLEDs). Capitalizing on the advantages of QLEDs—including compatibility with micro/nano-fabrication processes, wavelength tunability, and high luminance—a 2 × 2 monolithically integrated magnetometer array was developed. Each sensor unit achieves a magnetic sensitivity of below 26 nT·Hz^−1/2 and a measurable range of ±120 μT within the 1–10 Hz effective bandwidth. Experimental validation confirms the array’s ability to simultaneously resolve multi-regional magnetic fields and track dynamic field orientations while maintaining exceptional device uniformity. This advancement establishes a scalable framework for the design of large-scale magnetic sensing arrays, demonstrating significant potential for applications requiring spatially resolved and directionally sensitive magnetometry. Full article

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16 pages, 7343 KB

Open AccessArticle

Accelerated Super-Resolution Reconstruction for Structured Illumination Microscopy Integrated with Low-Light Optimization

by Caihong Huang, Dingrong Yi and Lichun Zhou

Micromachines 2025, 16(9), 1020; https://doi.org/10.3390/mi16091020 - 3 Sep 2025

Viewed by 327

Abstract

Structured illumination microscopy (SIM) with π/2 phase-shift modulation traditionally relies on frequency-domain computation, which greatly limits processing efficiency. In addition, the illumination regime inherent in structured illumination techniques often results in poor visual quality of reconstructed images. To address these dual challenges, this [...] Read more.

Structured illumination microscopy (SIM) with π/2 phase-shift modulation traditionally relies on frequency-domain computation, which greatly limits processing efficiency. In addition, the illumination regime inherent in structured illumination techniques often results in poor visual quality of reconstructed images. To address these dual challenges, this study introduces DM-SIM-LLIE (Differential Low-Light Image Enhancement SIM), a novel framework that integrates two synergistic innovations. First, the study pioneers a spatial-domain computational paradigm for π/2 phase-shift SIM reconstruction. Through system differentiation, mathematical derivation, and algorithm simplification, an optimized spatial-domain model is established. Second, an adaptive local overexposure correction strategy is developed, combined with a zero-shot learning deep learning algorithm, RUAS, to enhance the image quality of structured light reconstructed images. Experimental validation using specimens such as fluorescent microspheres and bovine pulmonary artery endothelial cells demonstrates the advantages of this approach: compared with traditional frequency-domain methods, the reconstruction speed is accelerated by five times while maintaining equivalent lateral resolution and excellent axial resolution. The image quality of the low-light enhancement algorithm after local overexposure correction is superior to existing methods. These advances significantly increase the application potential of SIM technology in time-sensitive biomedical imaging scenarios that require high spatiotemporal resolution. Full article

(This article belongs to the Special Issue Advanced Biomaterials, Biodevices, and Their Application)

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9 pages, 2005 KB

Open AccessArticle

Curling of Gel Scaffold Layer for Cell Culture by a Deformable Microactuator Mat Toward Biological Canal Formation

by Satoshi Konishi, Shiho Shimizu and Katsunori Sakai

Micromachines 2025, 16(9), 1019; https://doi.org/10.3390/mi16091019 - 3 Sep 2025

Viewed by 353

Abstract

A gel scaffold for a biological canal is formed using a deformable soft microactuator mat. Three-dimensional cellular tissue structures are important for organ-on-a-chip in in-vitro biomimetic models. However, most traditional cellular tissues have been cultured in a dish or transwell. Furthermore, cellular culture [...] Read more.

A gel scaffold for a biological canal is formed using a deformable soft microactuator mat. Three-dimensional cellular tissue structures are important for organ-on-a-chip in in-vitro biomimetic models. However, most traditional cellular tissues have been cultured in a dish or transwell. Furthermore, cellular culture on the inner wall of pre-manufactured channels has been recently reported. In this study, we propose a deformable actuator mat that can transform a flat structure into a tubular structure. The active mat, which is composed of pneumatic balloon actuator arrays, assembles a biological canal from a flat sheet of a gel scaffold for cell culture. The mat can return to its initial flat state so that the gel-based canal structure with cells can self-stand. A self-standing tubular gel structure is demonstrated as a biomimetic canal toward a biological canal with cells. A self-standing tubular gel structure has permeability, which is important for evaluation of pharmacokinetics. The actuator mat under the gel layers was curled into a tubular shape (approximately 1 mm diameter) and returned after the assembly. Culturing cellular tissues on a demonstrated gel structure will reproduce the biological permeability of organs such as an intestinal tract. This study confirms the gel-based canal formation process without cells as a feasibility study. The proposed technique has potential for the flexible design of biological three-dimensional structures, thereby contributing to pharmacokinetics research. Full article

(This article belongs to the Special Issue Micro/Nano Systems and Devices for Biomedical Applications: Design, Fabrication and Applications)

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11 pages, 1944 KB

Open AccessArticle

Dual-Mode Flexible Pressure Sensor Based on Ionic Electronic and Piezoelectric Coupling Mechanism Enables Dynamic and Static Full-Domain Stress Response

by Yue Ouyang, Shunqiang Huang, Zekai Huang, Shengyu Wu, Xin Wang, Sheng Chen, Haiyan Zhang, Zhuoqing Yang, Mengran Liu and Libo Gao

Micromachines 2025, 16(9), 1018; https://doi.org/10.3390/mi16091018 - 3 Sep 2025

Viewed by 415

Abstract

Flexible pressure sensors have shown promise applications in scenarios such as robotic tactile sensing due to their excellent sensitivity and linearity. However, the realization of flexible pressure sensors with both static and dynamic response capabilities still face significant challenges due to the properties [...] Read more.

Flexible pressure sensors have shown promise applications in scenarios such as robotic tactile sensing due to their excellent sensitivity and linearity. However, the realization of flexible pressure sensors with both static and dynamic response capabilities still face significant challenges due to the properties of the sensing materials themselves. In this study, we propose a flexible pressure sensor that integrates piezoelectric and ionic capacitance mechanisms for full-domain response detection of dynamic and static forces: a “sandwich” sensing structure is constructed by printing a mixture of multi-walled carbon nanotubes (MWCNTs) onto the surface of the upper and lower electrodes, and sandwiching a polyvinylidene fluoride (PVDF) thin film between the electrodes. The device exhibits a sensitivity of 0.13 kPa⁻¹ in the pressure range of 0–150 kPa. The sensor has a rapid dynamic response (response time 19 ms/12 ms) with a sensitivity of 0.49 mV kPa⁻¹ based on the piezoelectric mechanism and a linearity of 0.9981 based on the ionic capacitance mechanism. The device maintains good response stability under the ball impact test, further validating its potential application in static/dynamic composite force monitoring scenarios. Full article

(This article belongs to the Special Issue Flexible and Wearable Sensors, 4th Edition)

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19 pages, 10042 KB

Open AccessReview

Recent Progress of Powering IoT Based on Thermoelectric Technology

by Jinhong Dai, Haitao Deng, Jingwen Huang and Xiaosheng Zhang

Micromachines 2025, 16(9), 1017; https://doi.org/10.3390/mi16091017 - 31 Aug 2025

Viewed by 645

Abstract

With the rapid advancement of electronic devices, Internet of Things (IoT) technology has become increasingly integrated into everyday life. However, its broader development has been restricted by challenges related to long-term maintenance and the frequent need for power source replacements. Among the available [...] Read more.

With the rapid advancement of electronic devices, Internet of Things (IoT) technology has become increasingly integrated into everyday life. However, its broader development has been restricted by challenges related to long-term maintenance and the frequent need for power source replacements. Among the available power supply solutions, thermoelectric power generation has garnered significant interest due to its high reliability. Nevertheless, the widespread application of thermoelectric generators (TEGs) in IoT remains limited due to their relatively low conversion efficiency and structural fragility. This review systematically summarizes recent strategies aimed at enhancing the output performance and durability of TEGs through improvements in manufacturing processes and performance optimization techniques. It highlights several fabrication methods capable of endowing devices with superior flexibility and reliability, including screen printing, chemical vapor deposition (CVD), and electrospray deposition. Additionally, we discuss two key approaches for improving power generation performance: advanced material selection and multi-mechanism hybridization. Finally, the article explores the applications of TEGs in thermal energy harvesting from wearable devices, ambient environments, and aerospace fields, demonstrating their substantial potential to provide sustainable energy for IoT devices. Full article

(This article belongs to the Special Issue Research Progress in Energy Harvesters and Self-Powered Sensors)

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20 pages, 13471 KB

Open AccessArticle

Numerical Investigation of Vortex-Induced Enhancement in the Mixing Characteristics of Double-Spiral and Serpentine Microchannels

by Litao Qin, Zhen Jiang, Dongjian Zhou, Jincai Yue and Huanong Cheng

Micromachines 2025, 16(9), 1016; https://doi.org/10.3390/mi16091016 - 31 Aug 2025

Viewed by 421

Abstract

To enhance passive mixing in microchannels, T-shaped double-spiral and serpentine microchannels with identical curvature radii were designed and numerically analyzed across a Reynolds number (Re) range of 1 to 300. The double-spiral microchannel exhibited superior mixing performance at Re ≤ 200, [...] Read more.

To enhance passive mixing in microchannels, T-shaped double-spiral and serpentine microchannels with identical curvature radii were designed and numerically analyzed across a Reynolds number (Re) range of 1 to 300. The double-spiral microchannel exhibited superior mixing performance at Re ≤ 200, which is primarily attributed to the efficient utilization of Dean vortices. In contrast, the serpentine microchannel showed better performance at Re ≥ 250, benefiting from the early formation of four-vortex structures induced by periodic curvature reversals. To further enhance the performance of the serpentine microchannel at low Re, groove structures with varying orientation angles were incorporated. The introduction of the groove structures generated lateral secondary flows that not only increased flow disturbances but also disrupted the symmetry of the Dean vortices. Among these configurations, Structure 2, with a 45° angle between the groove direction and centrifugal force, exhibited the most pronounced enhancement in vortex intensity, as the secondary flows induced by the grooves synergistically interacted with the Dean vortices. This configuration resulted in the highest mixing enhancement (>50%). This study provides valuable insights into geometry-driven mixing mechanisms and offers design guidelines for high-efficiency micromixers across a wide range of Re. Full article

(This article belongs to the Collection Micromixers: Analysis, Design and Fabrication)

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19 pages, 5988 KB

Open AccessArticle

Design of Hydrogel Microneedle Arrays for Physiology Monitoring of Farm Animals

by Laurabelle Gautier, Sandra Wiart-Letort, Alexandra Massé, Caroline Xavier, Lorraine Novais-Gameiro, Antoine Hoang, Marie Escudé, Ilaria Sorrentino, Muriel Bonnet, Florence Gondret, Claire Verplanck and Isabelle Texier

Micromachines 2025, 16(9), 1015; https://doi.org/10.3390/mi16091015 - 31 Aug 2025

Viewed by 462

Abstract

For monitoring animal adaptation when facing environmental challenges, and more specifically when addressing the impacts of global warming—particularly responses to heat stress and short-term fluctuations in osmotic regulations in the different organs influencing animal physiology—there is an increasing demand for digital tools to [...] Read more.

For monitoring animal adaptation when facing environmental challenges, and more specifically when addressing the impacts of global warming—particularly responses to heat stress and short-term fluctuations in osmotic regulations in the different organs influencing animal physiology—there is an increasing demand for digital tools to understand and monitor a range of biomarkers. Microneedle arrays (MNAs) have recently emerged as promising devices minimally invasively penetrating human skin to access dermal interstitial fluid (ISF) to monitor deviations in physiology and consequences on health. The ISF is a blood filtrate where the concentrations of ions, low molecular weight metabolites (<70 kDa), hormones, and drugs, often closely correlate with those in blood. However, anatomical skin differences between human and farm animals, especially large animals, as well as divergent tolerances of such devices among species with behavior specificities, motivate new MNA designs. We addressed technological challenges to design higher microneedles for farm animal (pigs and cattle) measurements. We designed microneedle arrays composed of 37 microneedles, each 2.8 mm in height, using dextran-methacrylate, a photo-crosslinked biocompatible biopolymer-based hydrogel. The arrays were characterized geometrically and mechanically. Their abilities to perforate pig and cow skin were demonstrated through histological analysis. The MNAs successfully absorbed approximately 10 µL of fluid within 3 h of application. Full article

(This article belongs to the Special Issue Biosensors for Biomedical, Agricultural and Environmental Applications)

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Micromachines, Volume 16, Issue 9 (September 2025) – 79 articles

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