Micromachines

25 pages, 9640 KB

Open AccessReview

Advances in the Application of Electrostatics in Agriculture: A Review from Macroscale Spray Engineering to Microscale Plant Biostimulation

by Jie Cao, Zhelin Jin, Juan He, Guizhang Ju, Letian Mi, Yang Gao, Rui Lei and Guanggui Cheng

Micromachines 2025, 16(11), 1285; https://doi.org/10.3390/mi16111285 - 14 Nov 2025

Abstract

Electrostatic technology has emerged as a crucial tool for sustainable agricultural development due to its multifunctional characteristics. However, systematic and specialized investigations into its mechanism of action and application principles across diverse agricultural scenarios remain insufficient. Here, this review innovatively constructs a spatial [...] Read more.

Electrostatic technology has emerged as a crucial tool for sustainable agricultural development due to its multifunctional characteristics. However, systematic and specialized investigations into its mechanism of action and application principles across diverse agricultural scenarios remain insufficient. Here, this review innovatively constructs a spatial scale classification framework and categorizes it into macroscale spray engineering and microscale plant biostimulation. At the macroscale, electrostatic spraying leverages charged droplets’ properties (high surface charge density, strong electrostatic interaction, enhanced adsorption) to improve canopy deposition efficiency and reduce agrochemical drift losses. At the microscale, electrostatic fields induce electron/ion directional movement, providing non-contact stimulation to regulate plant physiological processes such as seed germination and nutrient uptake. We systematically summarize the latest research progress in electrostatic spraying and electrostatic biostimulation, and further compare them in terms of their fundamental mechanisms, targets, and stages of technological development. Finally, the current limitations and challenges for each technology are overviewed and the forward perspective for the efficient application of electrostatics in agriculture are outlined. This review provides theoretical references and technical guidelines for the application research of electrostatic spraying and electrostatic biostimulation, holding significant importance for promoting the standardized development of electrostatic technology in sustainable and precision agriculture. Full article

(This article belongs to the Special Issue Micro-Energy Harvesting Technologies and Self-Powered Sensing Systems)

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16 pages, 1568 KB

Open AccessArticle

Experimental Study on Temperature Compensation for Dual-Axis MEMS Accelerometers Using Adaptive Mode Decomposition and Hybrid Convolutional–Recurrent Temporal Network Modeling

by Yanchao Ren, Guodong Duan and Jingjing Jiao

Micromachines 2025, 16(11), 1284; https://doi.org/10.3390/mi16111284 - 14 Nov 2025

Abstract

This paper presents a novel temperature compensation approach for dual-axis Micro–Electro–Mechanical System (MEMS) accelerometers, integrating Adaptive Mode Decomposition (AMD) with Grey Wolf Optimization (GWO) and Hybrid Convolutional–Recurrent Temporal Network (HCR-TN). The proposed method aims to address temperature-induced bias drift, which significantly affects accelerometer [...] Read more.

This paper presents a novel temperature compensation approach for dual-axis Micro–Electro–Mechanical System (MEMS) accelerometers, integrating Adaptive Mode Decomposition (AMD) with Grey Wolf Optimization (GWO) and Hybrid Convolutional–Recurrent Temporal Network (HCR-TN). The proposed method aims to address temperature-induced bias drift, which significantly affects accelerometer performance. Experiments were conducted across a temperature range from −40 °C to +60 °C to evaluate the effectiveness of the compensation algorithm. The results show considerable improvements in bias stability, with the compensation method successfully reducing temperature-induced drift across both axes. Additionally, the algorithm was tested under realistic conditions, including noise and mechanical disturbances, demonstrating its robustness in practical applications. These findings highlight the potential of the proposed method for enhancing the reliability and accuracy of MEMS accelerometers in real-world sensing environments. Full article

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

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18 pages, 9527 KB

Open AccessArticle

Analysis of the Material Removal Process in Precision Milling of AZ91D Magnesium Alloy

by Jarosław Korpysa

Micromachines 2025, 16(11), 1283; https://doi.org/10.3390/mi16111283 - 13 Nov 2025

Abstract

The study investigated the material removal process during precision milling of AZ91D magnesium alloy. A high-speed camera enabling high-frequency image recording was used to observe the cutting zone. In effect, it was possible to observe the mechanism of the chip formation process at [...] Read more.

The study investigated the material removal process during precision milling of AZ91D magnesium alloy. A high-speed camera enabling high-frequency image recording was used to observe the cutting zone. In effect, it was possible to observe the mechanism of the chip formation process at different stages of the cutting flutes performance. Experiments were conducted with different feeds per tooth in order to detect the occurrence of ploughing. Results showed that the both cutting flutes of the end mill did not perform in a uniform manner. Material was predominantly removed by first flute, as a result of which chips formed by this flute were much larger than those generated by the other flute. Nevertheless, the shearing process proceeded effectively even at low feed values. Results also showed that large burrs were formed when machining was conducted with low feed per tooth, which confirmed a significant contribution of plastic deformation to burrs formation. An increase in feed per tooth, however, made it possible to minimize the phenomenon of burrs formation. Full article

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

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13 pages, 3687 KB

Open AccessArticle

Stretchable Porous Membranes for Barrier Tissue Models with Real-Time Measurement and Biomimetic Cyclic Strain

by Alexander P. M. Guttenplan, Joseph W. F. Robertson and Darwin R. Reyes

Micromachines 2025, 16(11), 1282; https://doi.org/10.3390/mi16111282 - 13 Nov 2025

Abstract

In recent years, the development of stretchable electronic devices with mechanical properties similar to those of human tissues has attracted increasing research interest in biomedical engineering, wearables, and other fields. These devices have demonstrated, and some other researchers have already shown, promising advancements [...] Read more.

In recent years, the development of stretchable electronic devices with mechanical properties similar to those of human tissues has attracted increasing research interest in biomedical engineering, wearables, and other fields. These devices have demonstrated, and some other researchers have already shown, promising advancements towards applications that span from measurements of the disruption of model barrier tissues to wearable or implantable devices, soft robotics, and the development of flexible and stretchable batteries. For example, models of barrier tissues, consisting of two compartments separated by a porous membrane, have been used to measure their integrity as well as to investigate the passage of drugs, toxins, and cancer cells through these tissues. Some of these models include an elastomeric membrane which can be stretched to model processes such as breathing and gut peristalsis, while others include electrodes for real-time measurement of barrier tissue integrity. However, to date, microelectrodes have not been fabricated directly on a porous elastomeric membrane. Here, we present lithographically patterned gold electrodes on porous PDMS membranes that enable electronic sensing capabilities in addition to mechanical manipulation. These membranes are incorporated into vacuum-actuated devices which impart cyclic mechanical strain, and their suitability for electrical impedance measurements, even after 1000 stretching cycles under fluids similar to cell culture media, is demonstrated. In the future, we expect to use these electrodes to measure the disruption in model cell barriers as well as to dielectrophoretically trap cells in a region of interest for more rapid assembly of a model tissue. Other areas like wearables, robotics, and power sources will greatly benefit from the further development of this technology. Full article

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

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19 pages, 2395 KB

Open AccessArticle

Response Surface Methodology for Optimizing the Design Parameters of Ultrasonic Liquid-Level Measurement System

by Wanjia Gao, Wendong Zhang and Yue Tian

Micromachines 2025, 16(11), 1281; https://doi.org/10.3390/mi16111281 - 13 Nov 2025

Abstract

This study addresses the high-precision requirements for liquid-level detection of propellants in aerospace rockets and optimizes the design parameters of an ultrasonic liquid-level measurement system based on the response surface method (RSM). Meanwhile, a quantitative correlation model between multiple physical parameters and output [...] Read more.

This study addresses the high-precision requirements for liquid-level detection of propellants in aerospace rockets and optimizes the design parameters of an ultrasonic liquid-level measurement system based on the response surface method (RSM). Meanwhile, a quantitative correlation model between multiple physical parameters and output voltage is established through theoretical derivation. Firstly, the effects of piezoelectric ceramic sheet diameter, ultrasonic frequency, excitation voltage and liquid temperature on the output voltage are investigated. The optimum conditions were obtained by one-way tests, where the output voltage reached its maximum when the diameter of the piezoelectric ceramic sheet was 15 mm and the frequency was 1 MHz. The excitation voltage was positively correlated with the output voltage. Elevated liquid temperature enhanced the echo amplitude. The influence of law remained consistent across different liquid levels. Subsequently, under the liquid level of 12 cm (half-full operating condition), a three-factor, three-level response surface methodology (RSM) analysis experiment was conducted, focusing on three factors that significantly affect energy transfer efficiency: piezoelectric ceramic sheet diameter (D), ultrasonic frequency (f), and liquid temperature (T). The best parameter combination was obtained through model optimization: D = 14.773 mm, f = 0.878 MHz, T = 33.661 °C. The predicted U-value was 8.976 V. The validation experiments demonstrated that the error rates between the measured average voltage values and the predicted values under different liquid levels were all <1%, and the coefficient of variation (CV) of the output signal was reduced to 0.9%. This not only meets the error requirements for aerospace liquid-level measurement but also verifies the reliability of the optimized model. This study significantly enhances the output signal stability and measurement accuracy, providing support for the liquid-level detection of aerospace propellants and high-precision liquid-level measurement in industrial applications. Full article

(This article belongs to the Special Issue Acoustic Transducers and Their Applications, 3rd Edition)

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15 pages, 4653 KB

Open AccessArticle

Design, Fabrication, and Characterization of a Piezoelectric Micromachined Ultrasonic Transducer with a Suspended Cantilever Beam-like Structure with Enhanced SPL for Air Detection Applications

by Yanyuan Ba, Yiming Li and Yuanhang Zhou

Micromachines 2025, 16(11), 1280; https://doi.org/10.3390/mi16111280 - 13 Nov 2025

Abstract

Air-coupled ultrasonic detection demands high transmission performance from piezoelectric micromachined ultrasonic transducers (PMUTs). However, existing microelectromechanical system (MEMS)-based PMUTs deliver limited output, which compromises measurement accuracy and constrains further development. This work proposes a novel PMUT design with a cantilevered, boundary-suspended diaphragm that [...] Read more.

Air-coupled ultrasonic detection demands high transmission performance from piezoelectric micromachined ultrasonic transducers (PMUTs). However, existing microelectromechanical system (MEMS)-based PMUTs deliver limited output, which compromises measurement accuracy and constrains further development. This work proposes a novel PMUT design with a cantilevered, boundary-suspended diaphragm that relieves residual stress, relaxes edge constraints, increases the mechanical degrees of freedom, and enables larger vibration amplitudes. Additionally, this work develops an accurate air-coupling model to predict device performance and a streamlined micro-nanofabrication process for device realization. Experimental results show that under a 1 Vpp (−5 Voffset) drive, the device achieves a peak acoustic pressure of 4.004 Pa at 69.3 kHz, measured at 10 cm distance in air, corresponding to a maximum sound pressure level of 106.02 dB (re 2 × 10⁻⁵ Pa). Compared to a traditional PMUT at 98.45 dB, this represents a 7.57 dB improvement and, to our knowledge, the highest reported sound pressure level at 10 cm for a single PMUT operating near 70 kHz under a 1 Vpp excitation. These results validate the significant enhancement in transmission performance achieved by the proposed topological structure, offering a solution to overcome the common bottleneck of insufficient output in PMUTs, and indicate strong potential for broader air-coupled sensing applications. Full article

(This article belongs to the Special Issue Piezoelectric MEMS/NEMS—Materials, Devices, and Applications, Third Edition)

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11 pages, 3075 KB

Open AccessCommunication

Highly Sensitive Si-Based Electrolyte-Gated Transistor Array for Multiplexed Detection of Arboviruses

by Seonghwan Shin, Jeonghyeon Do, Jongmin Son and Jeong-Soo Lee

Micromachines 2025, 16(11), 1279; https://doi.org/10.3390/mi16111279 - 13 Nov 2025

Abstract

Multiplexed detection of arboviruses using a 4 × 4 Si-based electrolyte-gated transistor (EGT) array functionalized with specific aptamers has been investigated. The Si-based EGTs were fabricated using conventional Si microfabrication processes. The EGTs showed excellent intrinsic electrical characteristics, including a low threshold voltage [...] Read more.

Multiplexed detection of arboviruses using a 4 × 4 Si-based electrolyte-gated transistor (EGT) array functionalized with specific aptamers has been investigated. The Si-based EGTs were fabricated using conventional Si microfabrication processes. The EGTs showed excellent intrinsic electrical characteristics, including a low threshold voltage of 0.8 V, a sub-threshold swing of 75 mV/dec, and a gate leakage of <10 pA, ensuring uniform device performance with low device-to-device variation. Aptamers specific to the yellow fever virus nonstructural protein 1 (YF), dengue virus nonstructural protein 1 (DN), and chikungunya virus envelope protein 2 (CHK) were functionalized on EGT arrays to evaluate individual and multiplexed detection. In individual-target detections, concentration-dependent negative shifts in threshold voltage were observed, and relevant limits of detection (LOD) as low as 38.6 pg/mL, 95.2 pg/mL, and 1.6 ng/mL were extracted for YF, DN, and CHK, respectively. In multiplexed detections, sensitivities decreased and variations increased relative to the individual responses, resulting in higher LODs. The extracted LODs were 0.2 ng/mL, 0.6 ng/mL, and 2.8 ng/mL for YF, DN, and CHK, respectively, which are lower than those reported for other methods. These results suggest that Si-based EGT arrays are promising as a scalable, low-cost, and highly sensitive biosensing platform for multiplexed arbovirus detection and point-of-care diagnostics. Full article

(This article belongs to the Special Issue Microsystems for Point-of-Care Testing and Diagnostics)

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20 pages, 4117 KB

Open AccessReview

An Overview on Formation of Radiation-Induced Interface Traps in Silicon-Based Devices

by Xuehui Dai, Min Zhu, Fei Wu, Yanru Ren and Minghui Liu

Micromachines 2025, 16(11), 1278; https://doi.org/10.3390/mi16111278 - 13 Nov 2025

Abstract

In an ionizing radiation environment, the formation of interface traps affects transistor performance, which may lead to device failure. This article reviews interface trap formation mechanisms in silicon-based devices. It explores interface trap types, electrical properties, and their impacts on devices’ performance. Finally, [...] Read more.

In an ionizing radiation environment, the formation of interface traps affects transistor performance, which may lead to device failure. This article reviews interface trap formation mechanisms in silicon-based devices. It explores interface trap types, electrical properties, and their impacts on devices’ performance. Finally, the main factors affecting the formation of interface traps are summarized. By reviewing these issues and exploring future research directions, guidance will be provided for the design of radiation-resistant devices to enhance their reliability in irradiated environments. Full article

(This article belongs to the Special Issue Silicon-Based Photonic Technology and Devices)

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14 pages, 1999 KB

Open AccessArticle

Analytical Modelling of Orthotropic Transient Heat Conduction in the Thermal Therapy Mask Within the Symplectic Framework

by Jinbao Li, Dian Xu, Chengjie Guo, Zhishan Chen, Linchi Jiang and Rui Li

Micromachines 2025, 16(11), 1277; https://doi.org/10.3390/mi16111277 - 13 Nov 2025

Abstract

The thermal therapy mask, as a wearable device, requires precise thermal management to ensure therapeutic efficacy and safety, which necessitates a detailed investigation of its heat conduction behavior under complex conditions. However, the heat convective behavior of an orthotropic thermal therapy mask with [...] Read more.

The thermal therapy mask, as a wearable device, requires precise thermal management to ensure therapeutic efficacy and safety, which necessitates a detailed investigation of its heat conduction behavior under complex conditions. However, the heat convective behavior of an orthotropic thermal therapy mask with an embedded line heat source under practical operational conditions has not yet been rigorously investigated. Therefore, this study addresses this specific problem by abstracting it into a 2D orthotropic transient heat conduction problem with a line heat source under Robin BCs, and derives its analytical solution using the SSM without any assumption of solution form. The SSM first transforms the governing equation into the frequency domain via the Laplace transform technique and reformulates it within the Hamiltonian framework. The original problem is then decomposed into two subproblems, which are solved by the method of separation of variables and the symplectic eigen expansion. The final analytical solution is obtained through superposing the solutions of the subproblems, and its accuracy is validated through comparison with the finite element method. The influence of the heat convection coefficient on the thermal behavior is systematically analyzed, revealing that increasing the heat convection coefficient accelerates the procedure from transient to steady state and results in reduced steady-state temperature. Furthermore, the analysis of orthotropic thermal conductivity reveals a “short-plank effect”, where the temperature evolution is limited by the smaller thermal conductivity. This study provides benchmark results for accurate and efficient thermal prediction and may enable an extension to broader applications in flexible electronics such as wearable sensors and displays. Full article

(This article belongs to the Special Issue Structural Analyses and Designs for Flexible/Stretchable Electronics, 3rd Edition)

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15 pages, 9878 KB

Open AccessArticle

W-Band Through-Wall Radar Using a High-Gain Frequency-Scanning SSPP Antenna

by Zhenfeng Tian, Jinling Zhang, Wang Yan, Yingzhe Wang, Xiongzhi Zhu, Xiaoqing Zhang and Pan Pan

Micromachines 2025, 16(11), 1276; https://doi.org/10.3390/mi16111276 - 13 Nov 2025

Abstract

This letter presents a high-gain frequency-controlled beam-scanning antenna specifically designed for through-wall radar (TWR) applications in the W band. The antenna leverages the leaky-wave radiation generated by spoof surface plasmon polaritons (SSPPs) propagating on sinusoidally modulated reactance surfaces (SMRS). Periodically arranged quasi-H-shaped metallic [...] Read more.

This letter presents a high-gain frequency-controlled beam-scanning antenna specifically designed for through-wall radar (TWR) applications in the W band. The antenna leverages the leaky-wave radiation generated by spoof surface plasmon polaritons (SSPPs) propagating on sinusoidally modulated reactance surfaces (SMRS). Periodically arranged quasi-H-shaped metallic cells are employed to achieve beam scanning. The integration of a flared structure at the apex of the designed SSPP antenna results in a significant gain enhancement, yielding an approximate increase of 10 dB. From 92.8 to 97.6 GHz, the antenna exhibits a reflection coefficient of |S11| < −10 dB, provides a high scanning rate of 4.05°/%, and achieves a realized gain of 20.9 dBi. This design eliminates the necessity for mechanical rotators and phase shifters that are typical in traditional TWR systems, significantly reducing system complexity and cost. A vehicle-mounted W-band TWR system was developed, integrating the designed SSPP antenna and employing linear frequency modulation technology to emit millimeter-wave signals for electronic scanning detection. With an economical and efficient design approach, testing has demonstrated that the system can perform through-wall imaging at a distance of 10 m, both in stationary and in motion conditions. Full article

(This article belongs to the Special Issue RF and Power Electronic Devices and Applications)

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21 pages, 3185 KB

Open AccessArticle

BPEI-Based N-Doped Carbon Dots with Sensitive and Selective Cu²⁺ Ion-Sensing Ability

by Sahin Demirci, Jorge H. Torres and Nurettin Sahiner

Micromachines 2025, 16(11), 1275; https://doi.org/10.3390/mi16111275 - 13 Nov 2025

Abstract

In this research, we examined the potential sensor characteristics of branched polyethyleneimine (BPEI)-derived carbon dots (CDs) synthesized using BPEI as a nitrogen source and citric acid (CA) as a carbon source, specifically for the recognition of various metal ions. Among the BPEI CDs [...] Read more.

In this research, we examined the potential sensor characteristics of branched polyethyleneimine (BPEI)-derived carbon dots (CDs) synthesized using BPEI as a nitrogen source and citric acid (CA) as a carbon source, specifically for the recognition of various metal ions. Among the BPEI CDs produced with different amounts of BPEI to CA BPEI:CA ratios of 0.5:1, 1:1, and 2:1 w/w, named as BPEI^0.5 CD, BPEI¹ CD, and BPEI² CD, respectively. The BPEI^0.5 CD, which contains the least BPEI, exhibited the highest fluorescence intensity: 50,300 a.u. in a 0.6 mg/mL solution were recorded as λ_em: 420 nm at λ_ex: 360 nm and 600 V PMT voltage with 5 nm of slit width for both excitation and emission. We investigated the fluorescence variations in BPEI CD-based CDs in 2 mL solutions containing Cd²⁺, Co²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ metal ions at various concentrations. Amongst these metal ions, the most pronounced sensitivity was noted for Cu²⁺ ions with a limit of detection (LOD) value of 0.39 ppm. For BPEI CDs created with BPEI:CA ratios of 0.5:1, 1:1, and 2:1 w/w, the sensitivity to Cu²⁺ ions increased with a higher BPEI ratio, with a LOD value of 0.30 ppm recorded for BPEI² CDs. Moreover, Cu²⁺ ion solutions were prepared from various salts, including chloride, acetate, nitrate, and sulfate; aside from some fluorescence variation observed for BPEI^0.5 CDs, no significant difference in BPEI CD fluorescence change was observed with the use of the various salt solutions of Cu²⁺ ion. In quenching experiments conducted on mixtures of Cd²⁺, Co²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ metal ions with Cu²⁺, it was noted that BPEI CDs displayed selectivity for Cu²⁺ ions. Furthermore, the structures of BPEI CDs have been effectively utilized in real water samples, such as tap water and seawater, demonstrating a quenching capability of over 65% in the presence of 50 ppm Cu²⁺ ions. Full article

(This article belongs to the Special Issue Micro/Nano Optical Devices and Sensing Technology)

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22 pages, 4342 KB

Open AccessArticle

Differential Single-Crystal Waveguide Ultrasonic Temperature Measurements Based on Magnetostriction

by Yanlong Wei, Gang Yang, Gao Wang, Haijian Liang, Hui Qi, Xiaofang Mu, Zhen Tian, Fujiang Yuan and Qianxiang Zhang

Micromachines 2025, 16(11), 1274; https://doi.org/10.3390/mi16111274 - 13 Nov 2025

Abstract

In extremely harsh high-temperature environments in aerospace, industrial manufacturing and other fields, traditional ultrasonic temperature measurement technology has certain limitations. This paper proposes a differential single crystal sapphire ultrasonic temperature measurement method based on the magnetostrictive effect. This method abandons the traditional sensitive [...] Read more.

In extremely harsh high-temperature environments in aerospace, industrial manufacturing and other fields, traditional ultrasonic temperature measurement technology has certain limitations. This paper proposes a differential single crystal sapphire ultrasonic temperature measurement method based on the magnetostrictive effect. This method abandons the traditional sensitive flexural structure and uses two single-crystal sapphire waveguides of the same material, same diameter, and slightly different lengths as sensing elements. By measuring the time delay difference between their end-face echoes, the sound velocity is inverted and the temperature is measured. COMSOL multi-physics v6.1 simulation was used to optimize the bias magnetic field design of the magnetostrictive transducer, which improved the system’s energy conversion efficiency and high-temperature stability. Experimental results show that in the range of 300–1200 °C, the sensor delay increases monotonically with increasing temperature, the sound speed shows a downward trend, and the repeatability error is less than 5%; the differential processing method effectively suppresses common mode noise in the range of 300–700 °C, and still shows high sensitivity above 800 °C. This research offers a technical solution with high reliability and accuracy for temperature monitoring in extreme environments such as those characterized by high temperatures and high pressures. Full article

(This article belongs to the Section A：Physics)

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14 pages, 6087 KB

Open AccessArticle

Secure Angle-Based Geometric Elimination (SAGE) for Microrobot Path Planning

by Youngji Ko, Seung-hyun Im, Hana Choi, Byungjeon Kang, Jayoung Kim, Taeksu Lee, Jong-Oh Park and Doyeon Bang

Micromachines 2025, 16(11), 1273; https://doi.org/10.3390/mi16111273 - 12 Nov 2025

Abstract

Microrobot navigation in constrained environments requires path planning methods that ensure both efficiency and collision avoidance. Conventional approaches, which typically combine graph-based path finding with geometric path simplification, effectively reduce path complexity but often generate collision-prone paths because wall boundaries are not considered [...] Read more.

Microrobot navigation in constrained environments requires path planning methods that ensure both efficiency and collision avoidance. Conventional approaches, which typically combine graph-based path finding with geometric path simplification, effectively reduce path complexity but often generate collision-prone paths because wall boundaries are not considered during simplification. Therefore, to overcome this limitation, we present Secure Angle-based Geometric Elimination (SAGE), a single-pass path-simplification algorithm that converts pixel-level shortest paths into low-complexity trajectories suitable for real-time collision-free navigation of microrobots. SAGE inspects consecutive triplets (p_i, p_i+₁, p_i+₂) and removes the middle point when the turning angle is smaller than threshold (∠p_ip_i+₁p_i+₂ ≤ θ_th) or the direct segment (p_i → p_i+₂) is collision-free. Quantitative analysis shows that SAGE achieves approximately 5% shorter path length, 20% lower turning cost and 0% collision rate, while maintaining computation comparable to the Ramer–Douglas–Peucker algorithm. Integration with Dijkstra and RRT planners confirms scalability across complex maze and vascular environments. Experimental microrobot demonstrations show navigation with complete collision avoidance, establishing SAGE as an efficient and reliable framework for high-speed microrobot navigation and automation in lab-on-a-chip, chemical-reaction and molecular-diagnostic systems. Full article

(This article belongs to the Special Issue Advanced Intelligent Robotic Systems: From Microrobots to Wearable Robots, 2nd Edition)

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15 pages, 2988 KB

Open AccessArticle

Microhand Platform Equipped with Plate-Shaped End-Effectors Enables Precise Probing of Intracellular Structure Contribution to Whole-Cell Mechanical Properties

by Masahiro Kawakami, Masaru Kojima, Toshihiko Ogura, Atsushi Kubo, Tatsuo Arai and Shinji Sakai

Micromachines 2025, 16(11), 1272; https://doi.org/10.3390/mi16111272 - 12 Nov 2025

Abstract

Cellular mechanical properties are critical indicators of cellular state and promising disease biomarkers. This study introduces a novel microhand system, featuring chopstick-like plate-shaped end-effectors, designed for stable and high-precision single-cell mechanical characterization. First, we automated the force sensor calibration to overcome the inefficiency [...] Read more.

Cellular mechanical properties are critical indicators of cellular state and promising disease biomarkers. This study introduces a novel microhand system, featuring chopstick-like plate-shaped end-effectors, designed for stable and high-precision single-cell mechanical characterization. First, we automated the force sensor calibration to overcome the inefficiency and unreliability of conventional manual methods. To validate the system’s sensitivity, we precisely quantified the mechanical contributions of subcellular components, such as the actin cytoskeleton and chromatin, by measuring stiffness reductions after treatment with Cytochalasin D and Trichostatin A, respectively. Notably, when applied to a cellular model of Hutchinson–Gilford progeria syndrome, we successfully captured disease-induced mechanical alterations. A distinct population of high-stiffness cells was detected in progerin-overexpressing cells, a feature not observed in the control groups. Furthermore, by controlling the indentation speed and depth, the mechanical properties of the cytoplasm and nucleus could be distinctly evaluated. These results demonstrate that our microhand system is a highly sensitive and robust platform, capable of detecting subtle, disease-related changes and elucidating the contributions of specific subcellular structures to cell mechanics. Full article

(This article belongs to the Special Issue Next-Generation Biomedical Devices)

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12 pages, 1608 KB

Open AccessArticle

Numerical Investigation of Microporous Insulation for Power Reduction in Zero-Heat-Flux Thermometry

by Dong-Jin Lee and Dae Yu Kim

Micromachines 2025, 16(11), 1271; https://doi.org/10.3390/mi16111271 - 12 Nov 2025

Abstract

Zero-heat-flux (ZHF) thermometry is a clinically validated method for non-invasive core body temperature monitoring, yet its broad adoption in wearable applications is constrained by the high power consumption of the heater element. In this study, we numerically investigate the role of microporous insulation [...] Read more.

Zero-heat-flux (ZHF) thermometry is a clinically validated method for non-invasive core body temperature monitoring, yet its broad adoption in wearable applications is constrained by the high power consumption of the heater element. In this study, we numerically investigate the role of microporous insulation in minimizing energy demand while preserving measurement accuracy. A three-dimensional finite element model of a ZHF probe was implemented in COMSOL Multiphysics 5.4, consisting of a resistive heater, a microporous insulation shell, and a skin-equivalent substrate regulated by proportional–integral–derivative (PID) control. A Taguchi L9 orthogonal array was utilized to systematically investigate the effects of porosity (0–90%), insulation thickness (2–4 mm), and the convective heat transfer coefficient (5–15 W/m²·K) on the thermal performance of the ZHF thermometry system. Two performance metrics—heater energy consumption and settling time—were analyzed using analysis of variance (ANOVA). The results indicated that porosity accounted for more than 95% of the variance in heater power and over 80% of the variance in settling time. The configuration with φ = 90% and t = 3 mm demonstrated a balanced trade-off between energy efficiency and transient response for low-power ZHF thermometry. These findings provide design insights for energy-efficient wearable temperature sensors. Full article

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

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12 pages, 2307 KB

Open AccessArticle

Application of Droplet-Array Sandwiching Technology to Click Reactions for High-Throughput Screening

by Yoshinori Miyata, Shoma Nishimura, Sora Kawakami, Yuriko Higuchi and Satoshi Konishi

Micromachines 2025, 16(11), 1270; https://doi.org/10.3390/mi16111270 - 12 Nov 2025

Abstract

High-throughput screening (HTS) is an essential process in drug discovery, requiring platforms that ensure reagent economy, high efficiency, and resistance to cross-contamination. Click chemistry is well suited for HTS because of its biocompatibility, high selectivity, and quantitative fluorescent readout. We focus on droplet-array [...] Read more.

High-throughput screening (HTS) is an essential process in drug discovery, requiring platforms that ensure reagent economy, high efficiency, and resistance to cross-contamination. Click chemistry is well suited for HTS because of its biocompatibility, high selectivity, and quantitative fluorescent readout. We focus on droplet-array sandwiching technology (DAST), in which two droplet microarrays (DMAs) are vertically opposed to achieve solute transport and reagent mixing by controlled contact and separation. Herein, we integrate click chemistry with DAST and evaluate its feasibility as a HTS platform. In DAST, DMAs are formed on wettability-patterned (WP; hydrophilic/hydrophobic) substrates, preserving resistance to cross-contamination. First, we immobilized dibenzocyclooctyne (DBCO) on a WP substrate and verified the occurrence of DBCO–azide reaction using an azide-functional fluorescent dye. The fluorescence intensity increased with concentration and reached a plateau at higher concentrations, indicating saturation behavior in the DBCO–azide click reaction. Second, acoustic mixing with repeated droplet contact–separation was applied to generate concentration gradients on a single substrate while maintaining droplet independence. Third, we qualitatively reproduced the expected concentration dependence of manual handling by combining DAST-based gradient formation with click reaction fluorescence readout. These results reveal that DAST enables a reagent-efficient, cross-contamination-resistant, and low-instrument-dependent HTS foundation for click-chemistry-based assays. Full article

(This article belongs to the Special Issue Advanced Developments in Droplet Microfluidics)

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24 pages, 3955 KB

Open AccessReview

The ESD Robustness and Protection Technology of P-GaN HEMT

by Yijun Shi, Yantao Chen, Liang He, Xinghuan Chen, Yuan Chen and Guoguang Lu

Micromachines 2025, 16(11), 1269; https://doi.org/10.3390/mi16111269 - 11 Nov 2025

Abstract

This work first analyzes the failure behaviors of P-GaN HEMTs with different gate structures (Schottky gate vs. Ohmic gate) under both forward and reverse ESD stresses. It reveals that the Schottky gate structure lacks effective electrostatic charge discharge paths, which leads to the [...] Read more.

This work first analyzes the failure behaviors of P-GaN HEMTs with different gate structures (Schottky gate vs. Ohmic gate) under both forward and reverse ESD stresses. It reveals that the Schottky gate structure lacks effective electrostatic charge discharge paths, which leads to the accumulation of transient charges generated by ESD stress in the gate terminal, resulting in significant transient overvoltage and ultimately causing breakdown failure. Subsequently, the paper systematically reviews three existing unidirectional ESD protection technologies based on the P-GaN HEMT platform. While these technologies can discharge transient electrostatic charges generated by both forward and reverse ESD stresses, they operate in diode mode during reverse ESD events, exhibiting excessively low reverse triggering voltage. Furthermore, unidirectional ESD protection structures based on resistive voltage division and diode voltage division introduce substantial forward and reverse leakage currents. Finally, the article evaluates four bidirectional GaN ESD protection technologies. These bidirectional structures can likewise discharge transient charges from both forward and reverse ESD stresses. Compared to unidirectional approaches, the key advantage of bidirectional ESD protection lies in its ability to provide an appropriate reverse triggering voltage during reverse ESD events, thereby effectively clamping the reverse potential to the desired level. However, likewise, bidirectional ESD protection schemes based on resistive or diode voltage division also inevitably introduce relatively large forward and reverse leakage currents. Full article

(This article belongs to the Topic Wide Bandgap Semiconductor Electronics and Devices)

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36 pages, 7768 KB

Open AccessArticle

Microfluidic Nanosensor for Label-Free Multiplexed Detection of Breast Cancer Biomarkers via Surface-Enhanced Reflective FTIR Spectroscopy Using Thin Gold Films and Antibody-Oriented Gold Nanourchin: Feasibility Study

by Mohammad E. Khosroshahi, Gayathri Senthilchelvan and Victor Oyebolu

Micromachines 2025, 16(11), 1268; https://doi.org/10.3390/mi16111268 - 11 Nov 2025

Abstract

The simultaneous detection of multiple cancer biomarkers using microfluidic multiplexed immunosensors is gaining significant interest in the field of Point-of-Care diagnostics. This study highlights integrating surface-enhanced infrared Fourier transform (SE-FTIR) with a plasmonic-active nanostructure thin film (PANTF) on a printed circuit board (PCB), [...] Read more.

The simultaneous detection of multiple cancer biomarkers using microfluidic multiplexed immunosensors is gaining significant interest in the field of Point-of-Care diagnostics. This study highlights integrating surface-enhanced infrared Fourier transform (SE-FTIR) with a plasmonic-active nanostructure thin film (PANTF) on a printed circuit board (PCB), housed within a microfluidic device for rapid, non-destructive detection of breast cancer (BC). Detection uses monoclonal antibody (mAb)-functionalized gold nanourchins (GNUs) on dual sensing regions. A total of 12 serum samples (24 data points) were tested for HER-II and CA 15-3. The system demonstrated a SE-FTIR enhancement factor (EF) of ~0.18 × 10⁵ using Rhodamine 6G (R6G). Calibration with HER-II (1–100 ng/mL) and CA 15-3 (10–100 U/mL) showed linear responses (R² = 0.8 and 0.76, respectively). Measurements of unknowns were performed at 1 µL/min over 68 min, with 43 min for biomarker interaction. SE-FTIR spectra were recorded at active zones and analyzed using SpectraView (SV), a custom Python 3.12-based tool. Data preprocessing included filtering (SciPy’s filtfilt) and baseline correction using the Improved Asymmetric Least Squares (IASLS) algorithm (pybaselines.Whittaker). Fourier cross-correlation (FCC) showed stronger signal consistency for HER-II. Partial Least Squares (PLS) regression, a dimensionality reduction technique, enabled clear discrimination between the samples and types, with classification accuracy reaching 1.0. Cancer staging based on these biomarkers yielded an overall accuracy of 0.54, indicating that classification regardless of biomarker type. Further studies involving larger and more diverse sample sets are critical before any definitive conclusions can be drawn. Full article

(This article belongs to the Special Issue Biosensors and Their Applications in Disease Characterization and Diagnosis)

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32 pages, 4796 KB

Open AccessArticle

Temporal Extrapolation Generalization of Proper Orthogonal Decomposition (POD) and Radial Basis Function (RBF) Surrogates for Transient Thermal Fields in Multi-Heat-Source Electronic Devices

by Wenjun Zhao and Bo Zhang

Micromachines 2025, 16(11), 1267; https://doi.org/10.3390/mi16111267 - 10 Nov 2025

Abstract

Efficient and accurate prediction of transient temperature fields is critical for thermal management of electronic devices with multiple heat sources. In this study, a reduced-order surrogate modeling approach is developed based on proper orthogonal decomposition (POD) and radial basis function (RBF) neural networks. [...] Read more.

Efficient and accurate prediction of transient temperature fields is critical for thermal management of electronic devices with multiple heat sources. In this study, a reduced-order surrogate modeling approach is developed based on proper orthogonal decomposition (POD) and radial basis function (RBF) neural networks. The method maps time-conditioned modal coefficients in a parameter–time space, enabling robust temporal extrapolation beyond the training horizon. A multi-heat-source conduction model typical of electronic packages is used as the application scenario. Numerical experiments demonstrate that the proposed POD–RBF surrogate achieves high predictive accuracy (global MRE < 3%) with significantly reduced computational cost, offering strong potential for real-time thermal monitoring and management in electronic systems. Full article

(This article belongs to the Special Issue Thermal Transport and Management of Electronic Devices)

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