Micromachines

18 pages, 5671 KB

Open AccessArticle

Investigation of Electron Transport Layer Influence on Asymmetric Bipolar Switching in Transparent BST-Based RRAM Devices

by Kai-Huang Chen, Ming-Cheng Kao, Hsin-Chin Chen, Yao-Chin Wang, Chien-Min Cheng and Wei-Min Xu

Micromachines 2025, 16(11), 1302; https://doi.org/10.3390/mi16111302 - 20 Nov 2025

Viewed by 324

Abstract

Ba_0.6Sr_0.4TiO₃ (BST) thin films were deposited on ITO substrates via rf magnetron sputtering, followed by structural and morphological characterization using XRD and FE-SEM. Metal–insulator–metal (MIM) RRAM devices were fabricated by depositing Al top electrodes, and their electrical properties [...] Read more.

Ba_0.6Sr_0.4TiO₃ (BST) thin films were deposited on ITO substrates via rf magnetron sputtering, followed by structural and morphological characterization using XRD and FE-SEM. Metal–insulator–metal (MIM) RRAM devices were fabricated by depositing Al top electrodes, and their electrical properties were examined through I–V measurements. The optimized BST films deposited at 40% oxygen concentration exhibited stable resistive switching, with an operating voltage of 3 V, an on/off ratio of 1, and a leakage current of 10⁻⁸ A. After rapid thermal annealing at 500 °C, the on/off ratio improved to 2 but leakage increased to 10⁻³ A. Incorporating an electron transport layer (ETL) effectively suppressed the leakage current to 10⁻⁵ A while maintaining the on/off ratio at 2. Moreover, a transition from bipolar to unipolar switching was observed at higher oxygen concentration (60%). These results highlight the role of ETLs in reducing leakage and stabilizing switching characteristics, providing guidance for the development of transparent, low-power, and high-reliability BST-based RRAM devices. This study aims to investigate the role of Ba_0.6Sr_0.4TiO₃ (BST) ferroelectric oxide as a functional switching layer in resistive random-access memory (RRAM) and to evaluate how interface engineering using an electron transport layer (ETL) can improve resistive switching stability, leakage suppression, and device reliability. Full article

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

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16 pages, 3257 KB

Open AccessArticle

A Two-Stage Unet Framework for Sub-Resolution Assist Feature Prediction

by Mu Lin, Le Ma, Lisong Dong and Xu Ma

Micromachines 2025, 16(11), 1301; https://doi.org/10.3390/mi16111301 - 20 Nov 2025

Viewed by 338

Abstract

Sub-resolution assist feature (SRAF) is a widely used resolution enhancement technology for improving image contrast and the common process window in advanced lithography processes. However, both model-based SRAF and rule-based SRAF methods suffer from challenges of adaptability or high computational cost. The primary [...] Read more.

Sub-resolution assist feature (SRAF) is a widely used resolution enhancement technology for improving image contrast and the common process window in advanced lithography processes. However, both model-based SRAF and rule-based SRAF methods suffer from challenges of adaptability or high computational cost. The primary learning-based SRAF method adopts an end-to-end mode, treating the entire mask pattern as a pixel map, and it is difficult to obtain precise geometric parameters for the commonly used Manhattan SRAFs. This paper proposes a two-stage Unet framework to effectively predict the centroid coordinates and dimensions of SRAF polygons. Furthermore, an adaptive hybrid attention mechanism is introduced to dynamically integrate global and local features, thus enhancing the prediction accuracy. Additionally, a warm-up cosine annealing learning rate strategy is adopted to improve the training stability and convergence speed. Simulation results demonstrate that the proposed method accurately and rapidly estimates the SRAF parameters. Compared to traditional neural networks, the proposed method can better predict SRAF patterns, with the mean pattern error and edge placement error values showing the most significant reductions. PE decreases from 25,776.44 to 15,203.33 and EPE from 5.8367 to 3.5283, respectively. This significantly improves the image fidelity of the lithography system. Full article

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

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26 pages, 1990 KB

Open AccessReview

Phenomenological Modeling of Shape Memory Alloys: A Review of Macroscopic Approaches

by Girolamo Costanza, Maria Elisa Tata and Saeed Danaee Barforooshi

Micromachines 2025, 16(11), 1300; https://doi.org/10.3390/mi16111300 - 20 Nov 2025

Viewed by 628

Abstract

Shape Memory Alloys (SMAs) have unique thermomechanical properties, including superelasticity and the shape memory effect, which has led them to be used in a wide range of applications, from biomedical devices to aerospace and civil engineering structures. These behaviors have been addressed by [...] Read more.

Shape Memory Alloys (SMAs) have unique thermomechanical properties, including superelasticity and the shape memory effect, which has led them to be used in a wide range of applications, from biomedical devices to aerospace and civil engineering structures. These behaviors have been addressed by phenomenological models, which represent them by simply establishing stress–strain and transformation characteristics without accounting for the microstructure. In this review article, the main phenomenological modeling examples are categorized and compared, including the main principles of operation, predictions, and limitations under operating thermomechanical loading conditions. In addition, the growing use of SMAs, especially in actuation, damping, vibration control, and energy harvesting, is explored, and the incorporation of modeling frameworks into optimization activities is discussed. The final part of the review deals with open challenges and future research directions, consisting of the development of models that more accurately predict SMAs under cyclic and/or non-proportional loading, a more robust association with commercial computational tools, and exploring the use of SMAs in new interdisciplinary areas. By bridging modeling approaches to application-based concepts, a platform is provided for the advancement of both the scientific development and practical use of shape memory alloys. Full article

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

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21 pages, 5478 KB

Open AccessArticle

Structural and Gas-Sensitive Characteristics of In₂O₃: Effect of Hydrothermal/Solvothermal Synthesis Conditions

by Mariya I. Ikim, Varvara A. Demina, Elena Y. Spiridonova, Olusegun J. Ilegbusi and Leonid I. Trakhtenberg

Micromachines 2025, 16(11), 1299; https://doi.org/10.3390/mi16111299 - 20 Nov 2025

Viewed by 375

Abstract

In₂O₃ nanoparticles were obtained by annealing precursors that had been hydrothermally/solvothermally synthesized at 200 °C using In(NO₃)₃·4.5H₂O as the starting material. Three solvents were used for the synthesis, namely water, alcohol and ethylene glycol. [...] Read more.

In₂O₃ nanoparticles were obtained by annealing precursors that had been hydrothermally/solvothermally synthesized at 200 °C using In(NO₃)₃·4.5H₂O as the starting material. Three solvents were used for the synthesis, namely water, alcohol and ethylene glycol. Urea or glycine additives were introduced into the reaction mixtures as stabilizing and structure-forming agents. The nanopowders obtained were characterized using X-ray diffraction, scanning and transmission electron microscopy, low-temperature nitrogen adsorption and X-ray photoelectron spectroscopy. The gas-sensing characteristics of the indium oxide-based sensors were investigated for the detection of hydrogen in air. It has been established that the nature of the solvent determines the phase composition and structure of indium oxide, while organic additives reduce the particle size and increase the specific surface area. It should be noted that the addition of glycine to an alcohol solution of indium nitrate during synthesis produces a phase transformation. The results show that the sensor based on In₂O₃ synthesized using this mixture has the best hydrogen sensing properties of all the materials considered in this study. Full article

(This article belongs to the Section C：Chemistry)

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12 pages, 5546 KB

Open AccessArticle

Design of a Multi-Beam Switching Antenna Loaded with a Square Metasurface

by Ningchuan Liu, Lin Huang and Lingxiao Huang

Micromachines 2025, 16(11), 1298; https://doi.org/10.3390/mi16111298 - 20 Nov 2025

Viewed by 365

Abstract

Multi-beam and beam-scanning antennas enable extensive communication coverage while mitigating multipath fading and enhancing spectrum utilization efficiency. This paper presents a transmissive metasurface antenna design, which utilizes a microstrip square-ring patch antenna with four feed ports as the excitation source. A 7 × [...] Read more.

Multi-beam and beam-scanning antennas enable extensive communication coverage while mitigating multipath fading and enhancing spectrum utilization efficiency. This paper presents a transmissive metasurface antenna design, which utilizes a microstrip square-ring patch antenna with four feed ports as the excitation source. A 7 × 7 square patch metasurface is positioned above the feed source, facilitating the generation of four independently steerable beams by switching activation among the four feed ports. Operating at 12.6 GHz, the antenna achieves a gain of 10.4 dB. The 3 dB beamwidth of the beams from all four ports exceeds 23°. The proposed design offers advantages of structural simplicity, low profile, and cost-effectiveness. By leveraging transmissive metasurfaces, this approach combines the benefits of low profile and low cost with flexible manipulation of electromagnetic wave radiation, thereby providing a novel methodology for designing multi-beam communication antennas. Full article

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

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28 pages, 1299 KB

Open AccessReview

Integrated THz/FSO Communications: A Review of Practical Constraints, Applications and Challenges

by Jingtian Liu, Xiongwei Yang, Yi Wei and Feng Zhao

Micromachines 2025, 16(11), 1297; https://doi.org/10.3390/mi16111297 - 19 Nov 2025

Viewed by 769

Abstract

This paper presents a comprehensive review of integrated terahertz (THz) and free-space optical (FSO) communication systems, focusing on their potential to address the escalating demands for high-capacity, long-distance, and ultra-reliable transmission in future six-generation (6G) and space–air–ground integrated networks (SAGIN). The study systematically [...] Read more.

This paper presents a comprehensive review of integrated terahertz (THz) and free-space optical (FSO) communication systems, focusing on their potential to address the escalating demands for high-capacity, long-distance, and ultra-reliable transmission in future six-generation (6G) and space–air–ground integrated networks (SAGIN). The study systematically examines recent advancements in three critical areas: channel modeling, transmission performance, and integrated system architectures. Specifically, it analyzes THz and FSO channel characteristics, including attenuation mechanisms, turbulence effects, pointing errors, and noise sources, and compares their complementary strengths under diverse atmospheric conditions. Key findings reveal that THz communication achieves transmission rates up to several Tbps over distances of several kilometers but is constrained by molecular absorption and weather-induced attenuation, while FSO offers superior bandwidth-distance products yet suffers from turbulence-induced fading, posing significant reliability challenges. The integration of THz and FSO through adaptive switching strategies (e.g., hard and soft switching) demonstrates enhanced reliability and spectral efficiency, with experimental results showing seamless data rates exceeding Tbps in hybrid systems. However, challenges persist in transceiver hardware integration, algorithmic optimization, and dynamic resource allocation. The review concludes by identifying future research directions, including the development of unified channel models, shared architectures, and intelligent switching algorithms to achieve robust integrated communication infrastructures. Full article

(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies, 2nd Edition)

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17 pages, 4660 KB

Open AccessArticle

Structural Optimization and Simulation of Dual-Frequency Piezoelectric Micromachined Ultrasonic Transducers

by Fengwen Wang, Longlong Cao and Mingliang Jin

Micromachines 2025, 16(11), 1296; https://doi.org/10.3390/mi16111296 - 19 Nov 2025

Viewed by 476

Abstract

Ultrasound transducers are fundamental components in medical imaging systems, impacting resolution, sensitivity, and penetration depth. A key challenge in designing high-performance ultrasound transducers is balancing bandwidth and sensitivity. This study focuses on optimizing the backing layer of a dual-frequency piezoelectric micromachined ultrasound transducer [...] Read more.

Ultrasound transducers are fundamental components in medical imaging systems, impacting resolution, sensitivity, and penetration depth. A key challenge in designing high-performance ultrasound transducers is balancing bandwidth and sensitivity. This study focuses on optimizing the backing layer of a dual-frequency piezoelectric micromachined ultrasound transducer (PMUT) using polydimethylsiloxane (PDMS). COMSOL multi-physics version 6.2 finite element simulations and equivalent circuit modeling were employed to investigate the effects of PDMS backing layer thickness and geometry on frequency response characteristics, impedance matching, and acoustic sensitivity. The optimized PMUT structure demonstrated a significant enhancement in bandwidth, with the −6 dB bandwidth increasing to 92% at both 2.3 MHz and 6.8 MHz frequencies. The PDMS backing layer improved the matching of low- and high-frequency signals, enabling high sensitivity and reduced interface reflection losses. The incorporation of PDMS as the backing layer successfully expands the operational bandwidth of dual-frequency PMUTs while maintaining high sensitivity, offering promising potential for high-performance ultrasound imaging, particularly in medical applications requiring both deep penetration and high-resolution imaging. Full article

(This article belongs to the Section A：Physics)

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18 pages, 5704 KB

Open AccessArticle

Multiphysics Measurement Method for Supercapacitors State of Health Determination

by Thomas Doucet, Jean-François Mogniotte, Raphaël Amiot, Alaa Hijazi, Pascal Venet, Minh-Quyen Le and Pierre-Jean Cottinet

Micromachines 2025, 16(11), 1295; https://doi.org/10.3390/mi16111295 - 19 Nov 2025

Viewed by 406

Abstract

This work presents a comparative study on the ageing of supercapacitors and a method for monitoring their state of health (SoH) through mechanical deformation. This study aims to evaluate the accelerated ageing behaviours of these systems under specific cycling conditions and temperatures, allowing [...] Read more.

This work presents a comparative study on the ageing of supercapacitors and a method for monitoring their state of health (SoH) through mechanical deformation. This study aims to evaluate the accelerated ageing behaviours of these systems under specific cycling conditions and temperatures, allowing the establishment of a correlation between SoH and casing deformation in supercapacitors. Experimental ageing tests revealed supercapacitors displayed an initial “burning” phase followed by a linear ageing trend. Strain gauges were employed to measure the mechanical deformation of supercapacitor casings, providing real-time insights into their SoH. Capacitance fading in supercapacitors was modelled using Brunauer–Emmett–Teller (BET) theory, hypothesizing that gas adsorption during ageing significantly contributes to performance decline. Model predictions were validated against experimental data, demonstrating a clear correlation between capacitance fading, internal resistance, remaining energy, and casing deformation. This work highlights the potential of mechanical deformation monitoring as a practical and non-invasive approach for assessing the SoH of supercapacitors. Full article

(This article belongs to the Special Issue Energy Conversion Materials/Devices and Their Applications, 2nd Edition)

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10 pages, 1539 KB

Open AccessArticle

A Compact L-Band Reconfigurable Dual-Mode Patch Filter

by Abdel Fattah Sheta, Majeed A. S. Alkanhal and Ibrahim Elshafiey

Micromachines 2025, 16(11), 1294; https://doi.org/10.3390/mi16111294 - 19 Nov 2025

Viewed by 348

Abstract

This research presents a novel dual-mode filter design that offers significant advantages in terms of frequency agility and miniaturization compared to conventional fixed multi-resonator filters. The design and implementation of a compact tunable bandpass filter are presented. The basic design structure is based [...] Read more.

This research presents a novel dual-mode filter design that offers significant advantages in terms of frequency agility and miniaturization compared to conventional fixed multi-resonator filters. The design and implementation of a compact tunable bandpass filter are presented. The basic design structure is based on a slotted non-degenerate dual-mode microstrip square patch. The slots are etched symmetrically, which makes the slotted dual-mode square patch equivalent to a two-coupled-resonator filter. The asymmetrical feed lines enable the excitation of dual resonant modes. The patch length, slot size, and dielectric material properties primarily determine the filter’s center frequency and bandwidth. Tunability is achieved by loading the slotted square patch with reversed bias varactor diodes located at the square patch corners, allowing electronic control of the filter center frequency. The design utilizes RT/Duroid 6010.2 laminates with a dielectric constant of 10.2 and a thickness of 0.635 mm. A bias tee at one of the filter ports is used to provide reverse bias to varactor diodes. Simulations and experimental results demonstrate tunable characteristics. Among the attractive features of the proposed design, good levels of insertion loss and impedance matching are noticed in the entire tunable band. The advantages of the proposed design make it well-suited for modern wireless technology applications in communication, radar, and satellite systems. Full article

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

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21 pages, 4835 KB

Open AccessReview

Review on Research Progress of Photoelectrochemical Biosensors

by Yu Zeng, Yuheng Wang and Yaqing Zhang

Micromachines 2025, 16(11), 1293; https://doi.org/10.3390/mi16111293 - 19 Nov 2025

Viewed by 610

Abstract

Photoelectrochemical (PEC) biosensors have emerged as a significant research focus in the fields of bioanalysis and medical diagnostics in recent years due to their high sensitivity, low background noise, and ease of miniaturization. This review summarizes the fundamental principles of PEC biosensors, recent [...] Read more.

Photoelectrochemical (PEC) biosensors have emerged as a significant research focus in the fields of bioanalysis and medical diagnostics in recent years due to their high sensitivity, low background noise, and ease of miniaturization. This review summarizes the fundamental principles of PEC biosensors, recent advances in photoactive materials, signal amplification strategies, and typical applications. Photoactive materials serve as the source of the sensor signal and can achieve signal enhancement through strategies such as heterostructure construction, localized surface plasmon resonance (LSPR) effects, and defect engineering. PEC sensors have been widely applied in areas such as cancer liquid biopsy and pathogen detection; however, challenges remain, including material biocompatibility, anti-interference capability in complex samples, and lack of standardized platforms. Future development trends include the design of green and low-toxicity photosensitive materials, integration with microfluidic and wearable devices, and artificial intelligence-assisted signal analysis, which will promote the translation of PEC biosensors toward clinical applications and real-time detection. Full article

(This article belongs to the Special Issue Emerging Devices and Technologies in BioMEMS for Biomarker Detection)

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29 pages, 10688 KB

Open AccessArticle

Multiscale Modeling of Thermo–Electro–Mechanical Coupling of BGA Solder Joints in Microelectronic Systems of Ruggedized Computers for Signal Integrity Analysis

by Pan Li, Jin Huang, Jie Zhang, Hongxiao Gong, Jianjun Wang, Daijiang Zuo, Mengyang Su and Jiwei Shi

Micromachines 2025, 16(11), 1292; https://doi.org/10.3390/mi16111292 - 18 Nov 2025

Viewed by 648

Abstract

Ruggedized computers are the core of modern communication, guidance, control, and data-processing systems, and typically operate under extreme environmental conditions. However, under extreme service conditions such as temperature cycling, vibration, and mechanical shock, thermo–electro–mechanical (TME) multi-physics coupling in ball grid array (BGA) solder [...] Read more.

Ruggedized computers are the core of modern communication, guidance, control, and data-processing systems, and typically operate under extreme environmental conditions. However, under extreme service conditions such as temperature cycling, vibration, and mechanical shock, thermo–electro–mechanical (TME) multi-physics coupling in ball grid array (BGA) solder joints is particularly significant, severely affecting system reliability and signal integrity. To comprehensively elucidate the effects of thermal, electrical, and mechanical fields on solder joints and signal transmission, this study proposes a multiscale multi-physics modeling and analysis framework for BGA solder joints in microelectronic systems of ruggedized computers, covering the computer system level, motherboard level, solder joint level, and solder interconnect level. A model correlation study under ten thermal cycling conditions demonstrated an accuracy of 88.89%, confirming the validity and applicability of the proposed model. Based on this validated framework and model, the temperature distribution, stress–strain response, and signal integrity characteristics were further analyzed under combined conditions of thermal cycling, random vibration, and mechanical shock. The results indicate that a rise in temperature in solder joints induces thermal stresses and deformations, while variations in electrical conductivity under thermal loading trigger electromigration and concentration evolution, which further couple with stress gradients to form TME multi-physics interactions. Under such coupling, critical solder balls exhibit stress concentration at the metallurgical interfaces, with a maximum von Mises stress of 191.51 MPa accompanied by plastic strain accumulation. In addition, the PCIe high-speed interconnect experienced a maximum deformation of 16.104 μm and a voltage amplitude reduction of approximately 18.51% after 928 thermal cycles, exceeding the normal operating range. This research provides a theoretical basis and engineering reference for reliability assessment and optimization design of microelectronic systems in ruggedized computers in complex service environments. Full article

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

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14 pages, 3541 KB

Open AccessArticle

A Solar Cell Compatible Super-Wideband Flexible Transparent Antenna with Enhanced Axial Ratio

by Nouman Rasool, Shuqi Yang, Chen Chen, Zhengming Tang, Kama Huang and Jinwei Gao

Micromachines 2025, 16(11), 1291; https://doi.org/10.3390/mi16111291 - 18 Nov 2025

Viewed by 327

Abstract

A super-wideband transparent antenna (SWTA) with wide axial ratio bandwidth (ARBW) featuring an enhanced ground plane and microstrip feeding is proposed. The antenna has planar dimensions of 0.20

λ_{0}

× 0.20

λ_{0}

× 0.003

λ_{0}

at its lowest frequency of [...] Read more.

A super-wideband transparent antenna (SWTA) with wide axial ratio bandwidth (ARBW) featuring an enhanced ground plane and microstrip feeding is proposed. The antenna has planar dimensions of 0.20

λ_{0}

× 0.20

λ_{0}

× 0.003

λ_{0}

at its lowest frequency of 1.33 GHz. The antenna is fabricated from a combination of PET and metal oxide thin films, which together enable its flexibility and transparency. The L-shaped strips attached to the ground perturb the electric field in the slot, exciting a pair of orthogonal modes and resulting in circular polarization. The proposed antenna demonstrate high performance with an impedance bandwidth of 182% (1.33–28.52 GHz), an axial ratio bandwidth of 66% (3.88–7.73 GHz), and attain a peak gain of 11.5 dBi. Moreover, with an optical transparency exceeding 90%, this design is a flexible, transparent, super-wideband (SWB) antenna capable of high data rates, easy integration, and beyond-visual-line-of-sight (BVLOS) operations. Full article

(This article belongs to the Special Issue Recent Advances in Electromagnetic Devices, 2nd Edition)

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15 pages, 4568 KB

Open AccessArticle

Development of Vacuum-Chamber-Type Capacitive Micro-Pressure Sensors

by Lung-Jieh Yang, De-Yu Jiang, Wei-Chen Wang, Chandrashekhar Tasupalli, Horng-Yuan Shih and Yi-Jen Wang

Micromachines 2025, 16(11), 1290; https://doi.org/10.3390/mi16111290 - 18 Nov 2025

Viewed by 422

Abstract

This study presents the development of a capacitive pressure sensor tailored for measuring the dynamic pressure of flow fields. The sensor is fabricated using the UMC 0.18 μm CMOS-MEMS process, incorporated with additional post-processing steps such as metal wet etching, supercritical CO₂ [...] Read more.

This study presents the development of a capacitive pressure sensor tailored for measuring the dynamic pressure of flow fields. The sensor is fabricated using the UMC 0.18 μm CMOS-MEMS process, incorporated with additional post-processing steps such as metal wet etching, supercritical CO₂ drying, and parylene encapsulation. The sensing architecture employs AD7746 as a capacitance-to-voltage converter (CVC), enabling the conversion of capacitance signals into voltage outputs for enhanced measurement fidelity. Structurally, the capacitive pressure sensor features a vacuum-sealed diaphragm capsule design with dual movable circular membranes functioning as sensing electrodes. A contact-mode capacitive configuration with a trapezoidal or Gong-like vacuum-chamber diaphragm is adopted to improve linearity and sensitivity. The output sensitivity was determined to be feasible for measuring dynamic pressure at 1–2 Pa resolution. Full article

(This article belongs to the Special Issue CMOS-MEMS Fabrication Technologies and Devices, 2nd Edition)

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32 pages, 10076 KB

Open AccessReview

Phase Engineering of Nanomaterials: Tailoring Crystal Phases for High-Performance Batteries and Supercapacitors

by Ramanadha Mangiri, Nandarapu Purushotham Reddy and Joonho Bae

Micromachines 2025, 16(11), 1289; https://doi.org/10.3390/mi16111289 - 16 Nov 2025

Viewed by 906

Abstract

Phase engineering has emerged as a powerful method for manipulating the structural and electrical characteristics of nanomaterials, resulting in significant enhancements in their electrochemical performance. This paper examines the correlation among morphology, crystal phase, and electrochemical performance of nanomaterials engineered for high-performance batteries [...] Read more.

Phase engineering has emerged as a powerful method for manipulating the structural and electrical characteristics of nanomaterials, resulting in significant enhancements in their electrochemical performance. This paper examines the correlation among morphology, crystal phase, and electrochemical performance of nanomaterials engineered for high-performance batteries and supercapacitors. The discourse starts with phase engineering methodologies in metal-based nanomaterials, including the direct synthesis of atypical phases and phase transformation mechanisms that provide metastable or mixed-phase structures. Special emphasis is placed on the impact of these synthetic processes on morphology and surface properties, which subsequently regulate charge transport and ion diffusion during electrochemical reactions. Additionally, the investigation of phase engineering in transition metal dichalcogenide (TMD) nanomaterials highlights how regulated phase transitions and heterophase structures improve active sites and conductivity. The optimized phase-engineered ZnCo₂O₄@Ti₃C₂ composite exhibited a high specific capacitance of 1013.5 F g⁻¹, a reversible capacity of 732.5 mAh g⁻¹, and excellent cycling stability, with over 85% retention after 10,000 cycles. These results confirm that phase and morphological control can substantially enhance charge transport and electrochemical durability, offering promising strategies for next-generation batteries and supercapacitors. The paper concludes by summarizing current advancements in phase-engineered nanomaterials for lithium-ion, sodium-ion, and lithium-sulfur batteries, along with supercapacitors, emphasizing the significant relationship between phase state, morphology, and energy storage efficacy. This study offers a comprehensive understanding of the optimal integration of phase and morphological control in designing enhanced electrode materials for next-generation electrochemical energy storage systems. Full article

(This article belongs to the Special Issue Low-Dimensional Nano-Scaled Materials: From Principles to Device Application)

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14 pages, 5574 KB

Open AccessArticle

Microfluidic Concentration Manipulation via Controllable AC Electroosmotic Flow

by Jingliang Lv, Yulong Pei and Jianqi Sun

Micromachines 2025, 16(11), 1288; https://doi.org/10.3390/mi16111288 - 15 Nov 2025

Viewed by 398

Abstract

The ability to precisely prepare microfluids with targeted concentrations is critical for numerous applications, including protein crystallization and drug efficacy evaluation. This study presents an efficient microfluidic method for the continuous preparation of fluids at desired concentrations utilizing AC electroosmosis (ACEO). Two miscible [...] Read more.

The ability to precisely prepare microfluids with targeted concentrations is critical for numerous applications, including protein crystallization and drug efficacy evaluation. This study presents an efficient microfluidic method for the continuous preparation of fluids at desired concentrations utilizing AC electroosmosis (ACEO). Two miscible fluids of different initial concentrations are introduced through separate inlets. Target concentrations are achieved through ACEO-driven mixing, where fluid manipulation via electric signal and flow velocity control enables precise concentration adjustment at the outlet. To elucidate the concentration control mechanism via ACEO, we develop a three-dimensional numerical model coupling electric, flow, and concentration fields. Our results demonstrate that concentration modulation is significantly influenced by intrinsic fluid properties and external control parameters, including fluid viscosity, conductivity, axial fluid velocity, driving voltage, and signal frequency. Specifically, higher fluid viscosity and conductivity dampen electroosmotic flow, necessitating increased voltage to achieve target concentration. Axial fluid velocity determines the residence time in the mixing zone, directly affecting mixing efficiency and concentration control effect. The intensity of ACEO flow increases with applied voltage, enabling tunable mixing performance and outlet concentration. Overall, the simplicity of device design combined with precise concentration manipulation makes this method particularly attractive for applications requiring accurate fluid preparation. Full article

(This article belongs to the Special Issue Recent Development of Micro/Nanofluidic Devices, 2nd Edition)

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14 pages, 5673 KB

Open AccessArticle

Effect of Graphene Oxide Particle Size on the Enzymatic Synthesis of Polyaniline Films

by Cynthia Guerrero-Bermea, Selene Sepulveda-Guzman and Rodolfo Cruz-Silva

Micromachines 2025, 16(11), 1287; https://doi.org/10.3390/mi16111287 - 15 Nov 2025

Viewed by 437

Abstract

In this work, the effect of aqueous dispersions of graphene oxide (GO) and nanosized graphene oxide (nGO) on the enzymatic polymerization of polyaniline (PANI) was studied. The enzymatic polymerization of PANI was carried out in aqueous medium using toluenesulfonic acid (TSA) as the [...] Read more.

In this work, the effect of aqueous dispersions of graphene oxide (GO) and nanosized graphene oxide (nGO) on the enzymatic polymerization of polyaniline (PANI) was studied. The enzymatic polymerization of PANI was carried out in aqueous medium using toluenesulfonic acid (TSA) as the dopant, horseradish peroxidase (HRP) as the catalyst, and hydrogen peroxide (H₂O₂) as the oxidant, using 1.0, 2.5, and 5.0 wt% of GO and nGO. The morphology of PANI-GO/nGO composites was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further characterization was performed by thermogravimetric analysis (TGA) and spectroscopic techniques such as ultraviolet–visible (UV–Vis), Fourier-transform infrared (FTIR), Raman and X-ray photoelectronics (XPS). SEM images showed that during enzymatic polymerization, PANI completely covers the GO/nGO sheets. Furthermore, physicochemical results confirmed the production of a hybrid PANI-GO/nGO material with Van der Waals-type interactions between the oxygen-based functional groups of GO and the secondary amino bond (-NH-) of PANI. Also, cyclic voltammetry experiments were carried out in situ during the polymerization of PANI-GO/nGO films. The electrochemical response of PANI-GO/nGO composites reflects two broad oxidation peaks around 300 mV and 500 mV during anodic scanning, with reversible oxidation during cathodic scanning. Classical molecular dynamics simulations were used to understand the mechanism of the composite film’s growth. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials: Synthesis, Characterization and Device Application, 2nd Edition)

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16 pages, 1997 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A 3D-Printed PMMA Microneedle-Based TSA-ELISA Platform for Noninvasive Inflammatory Biomarker Detection

by Minghui Xu, Qingyu Ruan and Yukun Ren

Micromachines 2025, 16(11), 1286; https://doi.org/10.3390/mi16111286 - 14 Nov 2025

Viewed by 466

Abstract

Inflammatory cytokines and proteins are essential indicators of immune status and disease progression; however, conventional assays rely on invasive sampling and complex processing, restricting their use in real-time monitoring. Here, we present a 3D-printed poly(methyl methacrylate) (PMMA) microneedle-based biosensing platform integrated with a [...] Read more.

Inflammatory cytokines and proteins are essential indicators of immune status and disease progression; however, conventional assays rely on invasive sampling and complex processing, restricting their use in real-time monitoring. Here, we present a 3D-printed poly(methyl methacrylate) (PMMA) microneedle-based biosensing platform integrated with a tyramide signal amplification–enhanced enzyme-linked immunosorbent assay (TSA–ELISA) for noninvasive and highly sensitive detection of inflammatory biomarkers in interstitial fluid. The microneedles exhibit precise geometry, adequate mechanical strength, and excellent biocompatibility, facilitating efficient skin penetration and biomarker capture. Stepwise chemical functionalization ensured stable antibody immobilization, while TSA significantly amplified detection signals. The platform achieved reliable, reproducible, and multiplex detection of cytokines and albumin in both healthy individuals and patients with inflammatory skin conditions. Notably, the measured cytokine level in lesional skin of eczema patients was 97.7 pg/mL, showing a significant difference from the 62.8 pg/mL observed in healthy subjects. This MN-based TSA–ELISA system offers a robust and minimally invasive strategy for monitoring inflammation-related biomarkers, holding great potential for clinical diagnostics and personalized healthcare applications. Full article

(This article belongs to the Section B1: Biosensors)

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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

Viewed by 704

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

Viewed by 891

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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17 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

Viewed by 319

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

Viewed by 674

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

Viewed by 382

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

Cited by 1 | Viewed by 661

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 AccessEditor’s ChoiceCommunication

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

Viewed by 415

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

Viewed by 533

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

Viewed by 378

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

Viewed by 419

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

Viewed by 465

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

Viewed by 385

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

Viewed by 433

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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Micromachines, Volume 16, Issue 11 (November 2025) – 112 articles

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