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Micromachines
Volume 17
Issue 4
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Micromachines, Volume 17, Issue 4 (April 2026) – 114 articles

Cover Story (view full-size image): Dark current is a key limiting factor in photodiode performance, setting the noise floor and restricting sensitivity in low-light conditions. This review analyzes the main physical mechanisms responsible for dark current, including diffusion, Shockley–Read–Hall generation, trap-assisted tunneling, band-to-band tunneling, and surface leakage. Each mechanism is discussed in terms of its origin and distinguishing characteristics. Various reduction strategies are examined, such as thermal management, surface passivation (notably ALD Al2O3), guard ring designs, gettering and defect control, doping optimization, and bias management. Advanced device concepts like pinned photodiodes and black silicon are also considered. The review covers silicon, germanium, III–V, and emerging materials, with applications in near-infrared detection, CMOS imaging, SPADs, and Time-of-Flight systems. View this paper
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26 pages, 13734 KB  
Article
Light-Driven Self-Pulsating Hydrogel with a Sliding-Delay Mechanism for Micro-Actuation and Microfluidic Applications
by Xingui Zhou, Huailei Peng, Yunlong Qiu and Cong Li
Micromachines 2026, 17(4), 503; https://doi.org/10.3390/mi17040503 - 21 Apr 2026
Cited by 8 | Viewed by 512
Abstract
Light-responsive hydrogel-based oscillators typically exhibit small oscillation amplitudes because solvent diffusion is intrinsically slow, and their dependence on external periodic light modulation further results in limited amplitude, poor stability, and insufficient autonomy. Inspired by the trigger and sliding mechanism of the ancient crossbow, [...] Read more.
Light-responsive hydrogel-based oscillators typically exhibit small oscillation amplitudes because solvent diffusion is intrinsically slow, and their dependence on external periodic light modulation further results in limited amplitude, poor stability, and insufficient autonomy. Inspired by the trigger and sliding mechanism of the ancient crossbow, this study introduces an innovative system that integrates a sliding-block mechanism with time-delay feedback, breaking from conventional approaches that rely on hydrogel inertia or external modulation, within a purely theoretical and simulation-based framework. By establishing a nonlinear dynamic model coupling solvent diffusion, photoisomerization, and optical attenuation, this research shows through numerical simulations that the system can exhibit two distinct modes under constant illumination: a stable state and a self-sustained oscillatory state. The model predicts that the oscillation frequency can be flexibly tuned by varying key parameters, including the crosslinking density, Flory–Huggins interaction parameters of the spiropyran and hydrophilic polymer, ring-opening reaction rate, light intensity, fraction of light-sensitive molecules, and sliding displacement, whereas the initial absorption coefficient has only a minor influence. The slider displacement is also identified as an effective means to regulate the oscillation amplitude. Furthermore, the expansion force at the container bottom is predicted to oscillate synchronously with the hydrogel’s volume change. This theoretical framework represents a paradigm shift from “static small deformation” to “dynamic large-amplitude oscillation”, significantly enhancing the mechanical responsiveness of the material. This work provides a novel and controllable strategy for the conceptual design of autonomous light-driven micromechanical systems. Full article
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34 pages, 1888 KB  
Review
Heteroepitaxial 3C-SiC for MEMS Applications
by Angela Garofalo, Annamaria Muoio, Luca Belsito, Sergio Sapienza, Matteo Ferri, Alberto Roncaglia and Francesco La Via
Micromachines 2026, 17(4), 502; https://doi.org/10.3390/mi17040502 - 21 Apr 2026
Cited by 1 | Viewed by 1611
Abstract
Silicon carbide (SiC) has emerged as a highly attractive material for microelectromechanical systems (MEMS) operating in harsh environments, owing to its outstanding mechanical, thermal, and chemical properties. This review provides a comprehensive overview of the advantages and limitations of SiC-based MEMS, with particular [...] Read more.
Silicon carbide (SiC) has emerged as a highly attractive material for microelectromechanical systems (MEMS) operating in harsh environments, owing to its outstanding mechanical, thermal, and chemical properties. This review provides a comprehensive overview of the advantages and limitations of SiC-based MEMS, with particular emphasis on the strong interdependence between material structure, mechanical properties, and epitaxial growth processes. The role of defects, residual stress, and crystal quality is discussed in relation to device performance and reliability. Special attention is devoted to cubic SiC grown on silicon substrates, highlighting how growth-induced features influence the mechanical response of micromachined structures. Furthermore, a detailed analysis of the quality factor (Q-factor) is presented for 3C-SiC (111)/Si resonators, including the development of analytical models and their validation through numerical simulations performed using COMSOL Multiphysics (Version 6.1). The necessity of incorporating anisotropic loss factors in numerical modeling is demonstrated to be essential for accurately describing the experimentally observed behavior. This review aims to provide design guidelines and modeling strategies for the optimization of SiC MEMS, supporting their further development for high-performance and extreme-environment applications, including pressure sensors, mechanical resonators and high-stress-tolerant sensors. Full article
(This article belongs to the Special Issue MEMS and NEMS Sensors: Innovations, Applications, and Future Directions in Micro/Nano Technologies)
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24 pages, 2087 KB  
Article
The Influence of Polyethyleneimine’s Molecular Weight on the Physical, Chemical, and Biological Properties of Chitosan–Polyethyleneimine Carbon Dots and In Vitro Performances
by Sahin Demirci, Mehtap Sahiner, Selin S. Suner and Nurettin Sahiner
Micromachines 2026, 17(4), 501; https://doi.org/10.3390/mi17040501 - 20 Apr 2026
Viewed by 934
Abstract
This study reports the effect of polyethyleneimine’s molecular weight (PEI, Mn: 1200, 10,000, and 60,000 g/mol, denoted as PEI1.2, PEI10, and PEI60) on the physical, chemical, and biological characteristics of carbon dots (Cdots) derived from chitosan (Chi) [...] Read more.
This study reports the effect of polyethyleneimine’s molecular weight (PEI, Mn: 1200, 10,000, and 60,000 g/mol, denoted as PEI1.2, PEI10, and PEI60) on the physical, chemical, and biological characteristics of carbon dots (Cdots) derived from chitosan (Chi) and PEI (Chi-PEI Cdots). The size of Chi Cdots was 41.5 ± 6.1 nm, which increased to 50.9 ± 5.9, 71.4 ± 4.2, and 93.3 ± 7.4 nm with the preparation of Chi-PEI1.2, Chi-PEI10 and Chi-PEI60 Cdots. The fluorescence properties and quantum yield% values of the Cdots prepared from Chi, PEI1.2, PEI10, and PEI60 and their corresponding biopolymeric Chi-PEI Cdots were compared. A higher quantum yield of 26 ± 1.6% was observed for Chi-PEI1.2. This decreased with the increasing molecular weight of PEI and was calculated to be 15 ± 1.9% for Chi-PEI60. All the prepared bare Chi, bare PEI and corresponding bipolymeric Chi-PEI Cdots were observed to be nonhemolytic up to a 1 mg/mL concentration. Lower cytotoxic properties were observed for Chi-PEI Cdots on L929 fibroblast cells compared to their corresponding bare forms. Higher cell viability was observed for Chi-PEI1.2 Cdots with 95% viability in the presence of a 1000 µg/mL concentration. The antibacterial activity of the prepared Cdots against pathogens such as E. coli, K. pneumoniae, S. aureus, B. subtilis, and C. albicans was investigated and compared. Lower MIC and MBC values were determined for Chi-PEI10 against C. albicans with values of 12.5 and 50 mg/mL, respectively. Although the antibacterial properties of Chi-PEI Cdots were less strong than those of bare Cdots derived from individual Chi and PEI molecules, their light-induced antibacterial activities were found to be better. Full article
(This article belongs to the Special Issue Biosensors for Biomedical, Agricultural and Environmental Applications)
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20 pages, 11104 KB  
Article
Theoretical Analysis and Structural Optimization of Overload-Protected MEMS Hydrophones
by Yuhan Ren, Jinming Ti, Qingqing Fan, Yanfeng Huang and Junhong Li
Micromachines 2026, 17(4), 500; https://doi.org/10.3390/mi17040500 - 20 Apr 2026
Viewed by 1266
Abstract
MEMS hydrophones, as critical sensors for maritime security and underwater information acquisition, have sensitive membrane structures that exhibit insufficient ability to withstand hydrostatic pressure, necessitating an overload-protection design. Based on buckling stability theory, a collaborative optimization method for overload-protection column design was proposed, [...] Read more.
MEMS hydrophones, as critical sensors for maritime security and underwater information acquisition, have sensitive membrane structures that exhibit insufficient ability to withstand hydrostatic pressure, necessitating an overload-protection design. Based on buckling stability theory, a collaborative optimization method for overload-protection column design was proposed, integrating theoretical analysis, finite-element simulation, and process feasibility. An optimized design scheme for hydrophone overload-protection columns was established by comprehensively considering geometric buckling-resistant design, micro-gap anti-adhesion requirements, minimal impact on sensitivity, and micro/nano-fabrication constraints. The results indicate that intermediate slenderness columns with radii between 5.5 μm and 7.5 μm sufficiently meet both fabrication and operational requirements, effectively providing overload protection. Furthermore, at water depths not exceeding 382 m, the MEMS hydrophone can maintain the integrity of its membrane structure without column buckling. Full article
(This article belongs to the Special Issue Advances in Acoustic and Vibration MEMS)
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15 pages, 8446 KB  
Article
Solvent-Free Synthesis of Covalent Organic Frameworks for High-Performance Room Temperature Ammonia Sensing
by Jiayi Wu, Xinru Zhang, Hongwei Xue, Xiaorui Liang, Lei Zhang and Qiulin Tan
Micromachines 2026, 17(4), 499; https://doi.org/10.3390/mi17040499 - 20 Apr 2026
Viewed by 1101
Abstract
High-sensitivity rapid detection of ammonia (NH3) in environmental monitoring, industrial safety, early diagnosis, and other fields is of great significance. Covalent organic frameworks (COFs) have shown great potential in the field of gas sensing due to their designable porous structure and [...] Read more.
High-sensitivity rapid detection of ammonia (NH3) in environmental monitoring, industrial safety, early diagnosis, and other fields is of great significance. Covalent organic frameworks (COFs) have shown great potential in the field of gas sensing due to their designable porous structure and active sites. However, the traditional solvothermal synthesis method of COFs has problems such as cumbersome steps, high energy consumption and serious environmental pollution. Therefore, it is of great significance to invent a new method for COF synthesis that is green and efficient and makes it easy to conduct flexible ammonia gas sensing. This study first reported a solvent-free synthesis of imine connection 1,3,5-Triformylbenzene (TFB) and p-Phenylenediamine (PDA)—a new strategy for COF. This method innovatively employs zinc trifluoromethyl sulfonate (Zn(OTf)2) as a bifunctional catalyst. This catalyst not only efficiently catalyzes para-phenylenediamine, but its zinc ions also play a unique structural guiding role, guiding the reactants to be arranged in a directional manner, thereby constructing a highly ordered porous crystal structure. A series of characterizations confirmed that the obtained TFB-PDA-COF had good crystallinity and a high proportion of imine bonds (C=N). The powder material was coated onto a flexible polyimide (PI) substrate, successfully constructing a resistive ammonia gas sensor that operates at room temperature. The test results show that this sensor has a high response value, rapid response/recovery capability, and good selectivity for ammonia gas. More importantly, based on a flexible PI substrate, the device can maintain stable sensing performance even under repeated bending conditions, demonstrating its great potential in practical flexible electronic applications. This work not only provides a brand-new “zinc ion-guided” paradigm for the green and controllable synthesis of COF but also lays a material foundation for their application in the next-generation flexible sensing field. Full article
(This article belongs to the Special Issue Micro/Nanostructures in Sensors and Actuators, 2nd Edition)
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29 pages, 1821 KB  
Review
Thermal Effects in Microfluidic Electrokinetic Flows: From Limitation to Design Opportunity
by Tamal Roy
Micromachines 2026, 17(4), 498; https://doi.org/10.3390/mi17040498 - 20 Apr 2026
Cited by 1 | Viewed by 1484
Abstract
Microfluidic electrokinetic flows play a central role in applications such as lab-on-a-chip diagnostics, microelectronics cooling, and biomedical sample manipulation. These systems involve intricate heat transfer processes, including Joule heating from ionic currents, temperature-driven flow instabilities, and coupled thermal–fluid interactions, that crucially affect device [...] Read more.
Microfluidic electrokinetic flows play a central role in applications such as lab-on-a-chip diagnostics, microelectronics cooling, and biomedical sample manipulation. These systems involve intricate heat transfer processes, including Joule heating from ionic currents, temperature-driven flow instabilities, and coupled thermal–fluid interactions, that crucially affect device performance, reliability, and scalability. Current challenges include non-equilibrium charge dynamics, incomplete thermophysical property data for complex fluids, and thermal crosstalk in integrated platforms. This review summarizes the literature published over the past 20 years, with occasional reference to earlier work, covering the fundamental mechanisms of heat generation and dissipation in electrokinetic microflows; analytical, numerical, and experimental approaches for characterizing thermal effects; and discussion on the limitations and application-driven opportunities. It also highlights open questions and future research directions and offers a comprehensive view of design principles and guidelines for developing robust, thermally optimized electrokinetic microfluidic technologies. Full article
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33 pages, 5264 KB  
Article
Numerical Investigations on Heat Transfer Characteristics of Mono and Hybrid Nanofluids Using Microchannel Cooling for 21700 Batteries in Electric Vehicles
by Tai Duc Le and Moo-Yeon Lee
Micromachines 2026, 17(4), 497; https://doi.org/10.3390/mi17040497 - 18 Apr 2026
Cited by 1 | Viewed by 1173
Abstract
Efficient thermal management is critical for maintaining the safety, durability, and performance of lithium-ion batteries used in electric vehicles (EVs). In this study, a comprehensive numerical investigation is conducted to evaluate the heat transfer characteristics of mono- and hybrid-nanofluids in a microchannel-cooled lithium-ion [...] Read more.
Efficient thermal management is critical for maintaining the safety, durability, and performance of lithium-ion batteries used in electric vehicles (EVs). In this study, a comprehensive numerical investigation is conducted to evaluate the heat transfer characteristics of mono- and hybrid-nanofluids in a microchannel-cooled lithium-ion battery module. A three-dimensional computational model of a 5S7P battery module composed of cylindrical 21700 cells is developed. Battery heat generation during 3C high discharge rate operation is predicted using the Newman-Tiedemann-Gu-Kim (NTGK) electrochemical model, while coolant flow and heat transfer are simulated using the governing conservation equations for mass, momentum, and energy. The cooling system consists of six liquid-cooling plates with circular microchannels. The performance of water-glycol (50/50) coolant is compared with several mono nanofluids of Al2O3 and Cu, and hybrid nanofluids of Al2O3-Cu, Al2O3-MWCNT, Al2O3-Graphene, Cu-MWCNT, and Cu-Graphene across multiple coolant flow rates from 1–5 LPM. The results demonstrate that nanofluids significantly enhance convective heat transfer and reduce battery temperature compared with the conventional water-glycol coolant. Among the investigated coolants, the Al2O3-Cu hybrid nanofluid (0.45–0.45%) operating at 1 LPM achieves the best overall thermo-hydraulic performance with a performance evaluation criterion (PEC) of 1.065. Further analysis of nanoparticle composition ratios shows that a Cu-dominant hybrid mixture (Al2O3-Cu: 0.27–0.63%) slightly improves the PEC to 1.0657, indicating marginally superior cooling performance. The findings highlight the potential of hybrid nanofluids as advanced coolants for microchannel-based battery thermal management systems in EVs, particularly under moderate coolant flow conditions. Full article
(This article belongs to the Special Issue Microfluidic Systems for Sustainable Energy)
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25 pages, 6217 KB  
Article
Deep Learning-Based Prediction and Compensation of Performance Degradation in Flexible Sensors
by Zhiyuan Wang, Tong Zhang, Luyang Zhang, Xiao Wang, Youli Yao, Qiang Liu, Yijian Liu and Da Chen
Micromachines 2026, 17(4), 496; https://doi.org/10.3390/mi17040496 - 18 Apr 2026
Cited by 1 | Viewed by 1066
Abstract
Flexible deformation sensors inevitably suffer from sensitivity degradation and severe measurement errors during long-term cyclic stretching due to structural fatigue. Traditional material-level optimizations are costly and lack dynamic adaptability. Herein, we propose an artificial intelligence (AI)-driven predict-and-compensate framework for the online calibration of [...] Read more.
Flexible deformation sensors inevitably suffer from sensitivity degradation and severe measurement errors during long-term cyclic stretching due to structural fatigue. Traditional material-level optimizations are costly and lack dynamic adaptability. Herein, we propose an artificial intelligence (AI)-driven predict-and-compensate framework for the online calibration of flexible sensors. To overcome training sample scarcity, a generative adversarial network (GAN) performs temporal data augmentation. Subsequently, a hybrid deep learning framework integrating long short-term memory (LSTM) networks and a Sequence Attention mechanism is employed. This architecture accurately captures both local signal fluctuations and multiscale long-term decay trends, enabling precise multi-step prediction and output compensation. Experimental evaluations validate that this strategy significantly suppresses sensor response drift. Under cyclic loading, an initially substantial relative measurement error of 48.63% plummets to 7.16% post-calibration, with typical errors consistently reduced to the ~1% level. Furthermore, when deployed in a smart glove gesture recognition system, this method successfully restores the recognition accuracy from a fatigue-induced low of 75.73% (after 200 stretch cycles) back to 97.70%. This generative and attention-based deep learning paradigm offers robust, real-time error calibration, providing a highly viable solution for extending the long-term reliability and stability of flexible sensor systems. Full article
(This article belongs to the Special Issue Micro- and Nanosensors: Fabrication, Applications and Performance Enhancements, 4th Edition)
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26 pages, 11408 KB  
Article
A 2-GS/s 35.9-fJ/conv.-step Voltage–Time Hybrid Pipelined ADC with Digital Background Calibration in 28-nm CMOS
by Yuan Chang, Chenghao Zhang, Yihang Yang, Chaoyang Zhang, Maliang Liu, Dongdong Chen and Yintang Yang
Micromachines 2026, 17(4), 495; https://doi.org/10.3390/mi17040495 - 17 Apr 2026
Viewed by 641
Abstract
This paper presents a 2-GS/s voltage–time hybrid pipelined analog-to-digital converter (ADC) with a 14-bit digital output, implemented in a 28-nm CMOS process. To alleviate the gain–bandwidth–power trade-off in deeply scaled technologies, the proposed architecture employs a SHA-less front-end and a low-gain inverter-based push–pull [...] Read more.
This paper presents a 2-GS/s voltage–time hybrid pipelined analog-to-digital converter (ADC) with a 14-bit digital output, implemented in a 28-nm CMOS process. To alleviate the gain–bandwidth–power trade-off in deeply scaled technologies, the proposed architecture employs a SHA-less front-end and a low-gain inverter-based push–pull RA for energy-efficient coarse quantization. The residue is then transferred to the time domain via a highly linear constant-current voltage-to-time converter (CC-VTC) and digitized by a four-channel time-interleaved gated-ring-oscillator (GRO) TDC. To recover dynamic linearity degraded by low-gain amplification and interleaving mismatches, a multiplier-less digital background calibration engine is implemented. Leveraging mean absolute value (MAV) statistics and dither-injected least-mean-squares (LMS) algorithms, it effectively compensates for inter-channel and interstage errors with minimal hardware overhead. The prototype occupies an active area of 0.16 mm2. At 2 GS/s, the ADC achieves a Nyquist SNDR of 63.42 dB and an SFDR of 73.71 dB, corresponding to an ENOB of 10.24 bits. Consuming 86.9 mW from a 1-V supply, it achieves a Walden FoM of 35.9 fJ/conv.-step. Measurement results from multiple chips under a wide range of operating conditions verify the robustness of the proposed ADC. Full article
(This article belongs to the Section D1: Semiconductor Devices)
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36 pages, 38341 KB  
Review
Surface Acoustic Wave Devices: New Mechanisms, Enabling Techniques, and Application Frontiers
by Hongsheng Xu, Xiangyu Liu, Weihao Ye, Xiangyu Zeng, Akeel Qadir and Jinkai Chen
Micromachines 2026, 17(4), 494; https://doi.org/10.3390/mi17040494 - 17 Apr 2026
Viewed by 1389
Abstract
Surface Acoustic Wave (SAW) technology, long central to analog signal processing and RF filtering, is undergoing a major renewal. Driven by advances that decouple SAWs from traditional piezoelectric materials and fixed-function devices, the field is gaining unprecedented control over acoustic, optical, and electronic [...] Read more.
Surface Acoustic Wave (SAW) technology, long central to analog signal processing and RF filtering, is undergoing a major renewal. Driven by advances that decouple SAWs from traditional piezoelectric materials and fixed-function devices, the field is gaining unprecedented control over acoustic, optical, and electronic interactions at the micro and nanoscale. This review synthesizes these developments across four fronts: new physical mechanisms for SAW manipulation, emerging material platforms, ranging from thin films to 2D systems, along with reconfigurable device architectures and circuits, and the expanding landscape of applications they enable. Optical methods are reshaping how SAWs are generated and controlled, bypassing the limits of conventional electromechanical coupling. Coherent optical excitation of high-Q SAW cavities via Brillouin-like optomechanical interactions now grants access to modes in non-piezoelectric substrates such as diamond and silicon, while on-chip SAW excitation in photonic waveguides through backward stimulated Brillouin scattering opens new integrated sensing routes. In parallel, magneto-acoustic experiments have revealed nonreciprocal SAW diffraction from resonant scattering in magnetoelastic gratings. On the device side, ZnO thin-film transistors integrated on LiNbO3 exploit acoustoelectric coupling to realize voltage-tunable phase shifters; UHF Z-shaped delay lines achieve high sensitivity in a compact footprint; and parametric synthesis of wideband, multi-stage lattice filters targets 5G-class performance. Atomistic simulations show that SAW propagation in 2D MXene films can be engineered via surface terminations, while aerosol jet printing and SAW-assisted particle patterning provide agile, cleanroom-light fabrication of microfluidic and magnetic components. These advances enable applications ranging from hybrid quantum systems and quantum links to lab-on-a-chip particle control, SBS-based and UHF sensing, reconfigurable RF front-ends, and soft robotic actuators based on patterned magnetic composites. At the same time, optical techniques offer non-contact probes of dissipation, and MXenes and other emerging materials open new regimes of acoustic control. Conclusively, they are transforming SAW technology into a versatile, programmable platform for mediating complex interactions in next-generation electronic, photonic, and quantum systems. Full article
(This article belongs to the Special Issue Surface and Bulk Acoustic Wave Devices, 2nd Edition)
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18 pages, 1555 KB  
Article
Intrinsic Relations Between Transmission and Reflection in Metamaterials
by Boli Xu and Renbin Zhong
Micromachines 2026, 17(4), 493; https://doi.org/10.3390/mi17040493 - 17 Apr 2026
Viewed by 464
Abstract
Metamaterials possess high freedom on structural design, yet their ability to modulate electromagnetic waves is subject to intrinsic constraints that are independent of specific meta-atom geometries. The constraints are revealed by analyzing the statistical amplitudes and phases of transmission and reflection wave in [...] Read more.
Metamaterials possess high freedom on structural design, yet their ability to modulate electromagnetic waves is subject to intrinsic constraints that are independent of specific meta-atom geometries. The constraints are revealed by analyzing the statistical amplitudes and phases of transmission and reflection wave in some representative metamaterials. Based on scattering theory, a reconstructed and more general description of the electromagnetic modulation process in metamaterials is established. Two explicit and geometry-independent corollaries concerning the coupling between transmission and reflection waves are further obtained and verified. The results provide a new perspective on the fundamental modulation mechanism of metamaterials on electromagnetic waves. Full article
(This article belongs to the Special Issue Broadband Terahertz Devices and Communication Technologies, 2nd Edition)
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12 pages, 1671 KB  
Article
On-Chip AC Electrothermal Pump for Pulsatile Perfusion
by Itaru Kawata, Sosuke Kobayashi, Yoshiyasu Ichikawa and Masahiro Motosuke
Micromachines 2026, 17(4), 492; https://doi.org/10.3390/mi17040492 - 17 Apr 2026
Viewed by 833
Abstract
Microphysiological systems (MPSs) have emerged as promising platforms for drug discovery and in vitro pharmacological testing. MPSs aid to reproduce physiologically relevant microenvironments, in which controlled perfusion can play important role. In this study, an on-chip AC electrothermal (ACET) pump was developed for [...] Read more.
Microphysiological systems (MPSs) have emerged as promising platforms for drug discovery and in vitro pharmacological testing. MPSs aid to reproduce physiologically relevant microenvironments, in which controlled perfusion can play important role. In this study, an on-chip AC electrothermal (ACET) pump was developed for pulsatile perfusion in microfluidic cell culture systems. The proposed pump generates fluid motion through the interaction between an applied electric field and temperature-dependent gradients in the electrical properties of the fluid. Pulsatile perfusion was produced by periodic application of an AC voltage to the electrode array, and the pulsation cycle could be controlled electrically. The maximum flow velocity increased with the applied AC voltage, demonstrating tunable flow generation by the ACET pump. To evaluate the applicability of the developed system to cell culture, human mesenchymal stem cells (hMSCs) were cultured under pulsatile perfusion conditions for five days. The results showed that osteogenic differentiation under pulsatile perfusion was higher than that under static culture conditions. These findings demonstrate the potential of the proposed on-chip ACET pump as a simple and effective platform for generating physiologically relevant pulsatile perfusion in microphysiological systems. Full article
(This article belongs to the Collection Micro/Nanoscale Electrokinetics)
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24 pages, 395 KB  
Article
Modelling Key Performance Indicators (KPIs) in the Optimisation of Nanoimprint Lithography (NIL) Processes
by Andrzej Pacana and Karolina Czerwińska
Micromachines 2026, 17(4), 491; https://doi.org/10.3390/mi17040491 - 17 Apr 2026
Viewed by 963
Abstract
Nanoimprint lithography (NIL) plays an increasingly important role in modern nanomanufacturing processes, but its effective application in production conditions requires precise tools for evaluating and optimising technological processes. The aim of the study was to develop and model key performance indicators (KPIs) supporting [...] Read more.
Nanoimprint lithography (NIL) plays an increasingly important role in modern nanomanufacturing processes, but its effective application in production conditions requires precise tools for evaluating and optimising technological processes. The aim of the study was to develop and model key performance indicators (KPIs) supporting the optimisation of the quality, stability and efficiency of nanoimprint lithography processes. As part of the selection of indicators, a literature review, surveys and in-depth interviews with industry experts were conducted, which enabled the identification of indicators relevant from a technological practice perspective. The proposed KPI classification was directly linked to the stages of the NIL process, creating a basis for operational performance control and process capability analysis. A novel aspect is the proposal of an integrated KPI model that combines the classification of indicators based on the stages of the NIL process with their direct link to technological parameters and measurable quality effects. These indicators have been linked to critical process parameters for different NIL variants, including Thermal NIL, UV-NIL, Roll-to-Roll NIL and Step-and-Repeat NIL, using a process analysis and multi-criteria optimisation approach. Research indicates that the use of an integrated KPI model improves the accuracy of nanostructure mapping, reduced defect density, and increased process efficiency without compromising technological stability. The proposed approach is a universal tool supporting NIL process control, its scaling to industrial applications, and integration with statistical process control and data-driven optimisation methods. Full article
(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies, 3rd Edition)
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15 pages, 2500 KB  
Article
Electromechanical Coupling Analysis of a Piezoelectric–Flexoelectric–Semiconductor Cantilever Beam
by Yaxuan Su, Xuezhi Wu and Zhidong Zhou
Micromachines 2026, 17(4), 490; https://doi.org/10.3390/mi17040490 - 17 Apr 2026
Viewed by 1450
Abstract
This paper presents a theoretical study on the electromechanical coupling response of piezoelectric–flexoelectric–semiconductor (PFS) nanocantilevers by adopting flexoelectric elasticity and semiconductor theory. A unified mechanical–electrical model is established to incorporate a strain gradient, the piezoelectric effect, semiconducting characteristics, and flexoelectricity at micro-/nanoscales. Analytical [...] Read more.
This paper presents a theoretical study on the electromechanical coupling response of piezoelectric–flexoelectric–semiconductor (PFS) nanocantilevers by adopting flexoelectric elasticity and semiconductor theory. A unified mechanical–electrical model is established to incorporate a strain gradient, the piezoelectric effect, semiconducting characteristics, and flexoelectricity at micro-/nanoscales. Analytical solutions for deflection, electric potential, and electron concentration are obtained under three types of electrical boundary conditions. Numerical results show that flexoelectricity significantly enhances the effective bending stiffness of the beam under open-circuit conditions with or without surface electrodes, especially in thinner structures. With a fixed external electric potential condition, the applied potential can effectively modulate the deflection by adjusting the polarization field. The induced electric potential, under the open-circuit condition with surface electrodes, exhibits a peak value at a critical thickness and flexoelectric coefficient due to the synergistic effect of the strain gradient and flexoelectricity. The electron screening effect induced by the high doping concentration is found to suppress the induced potential considerably. The present work provides a fundamental understanding of PFS coupling and provides guidance for the design of high-sensitivity micro–nano-electromechanical systems/devices. Full article
(This article belongs to the Special Issue MEMS Sensors and Actuators: Design, Fabrication and Applications, 2nd Edition)
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15 pages, 1615 KB  
Article
First-Principles Investigation of Glucose Adsorption and Sensing-Related Electronic Modulation on Ti3C2O2 MXene
by Muheeb Rafiq, Baoyang Lu, Paolo Matteini, Yanfang Wu, Byungil Hwang and Sooman Lim
Micromachines 2026, 17(4), 489; https://doi.org/10.3390/mi17040489 - 17 Apr 2026
Viewed by 1042
Abstract
Two-dimensional Ti3C2O2 MXene has emerged as a promising electrode material for non-enzymatic glucose sensing due to its metallic conductivity and biocompatibility. However, the atomic-scale sensing mechanism remains unclear. This DFT study uses the PBE functional with the D3(BJ) [...] Read more.
Two-dimensional Ti3C2O2 MXene has emerged as a promising electrode material for non-enzymatic glucose sensing due to its metallic conductivity and biocompatibility. However, the atomic-scale sensing mechanism remains unclear. This DFT study uses the PBE functional with the D3(BJ) dispersion correction to elucidate glucose–MXene interactions under idealized vacuum conditions. Pristine Ti3C2O2 shows metallic behavior with a density of states of about 8.2 states per electron volt at the Fermi level, dominated by Ti 3d states. β-d-glucose adsorbs onto the surface through hydrogen bonding, with an adsorption energy of −0.82 eV at a separation distance of 2.8 angstroms. Bader analysis indicates a transfer of about 0.15 electrons from MXene to glucose, resulting in a Fermi level shift of about −0.15 eV and an 18% reduction in the density of states at the Fermi level. These changes correspond to an estimated sensitivity of approximately 0.6 μA mM−1 cm−2 and a detection limit of about 17 µM, consistent with reported experimental performance of MXene-based sensors. Comparative adsorption calculations for common sweat interferents yield −0.45 eV for lactate and −0.25 eV for urea, indicating weaker interfacial affinity than glucose; these values reflect thermodynamic binding strength and possible surface occupation rather than definitive electrochemical selectivity, which additionally depends on redox potential, electron-transfer kinetics, and operating bias. We acknowledge three main limitations: first, the model considers only pure oxygen termination rather than mixed oxygen, hydroxyl, and fluorine terminations; second, the calculations are performed under vacuum rather than in aqueous conditions; third, the study is based on static zero kelvin structures rather than finite temperature dynamics. Despite these idealizations, the results provide baseline mechanistic insights to support rational design of MXene-based glucose sensors. Full article
(This article belongs to the Topic Wearable Biosensors: Materials, Devices, and Data Processing Using AI)
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12 pages, 2471 KB  
Article
Design and Implementation of Miniaturized Low-Frequency Flexibility-Enhanced Rotating Cantilever Beam Piezoelectric MEMS Microphone
by Bingchen Wu, Gong Chen, Changzhi Zhong and Tao Wang
Micromachines 2026, 17(4), 488; https://doi.org/10.3390/mi17040488 - 17 Apr 2026
Viewed by 1576
Abstract
In response to the pressing need for miniaturized MEMS microphones in wearable technology and mobile devices, and to surmount the technical limitations inherent in conventional piezoelectric microphones, which typically depend on enlarging chip dimensions or decreasing stiffness to attain low resonance frequencies, this [...] Read more.
In response to the pressing need for miniaturized MEMS microphones in wearable technology and mobile devices, and to surmount the technical limitations inherent in conventional piezoelectric microphones, which typically depend on enlarging chip dimensions or decreasing stiffness to attain low resonance frequencies, this study introduces a novel piezoelectric MEMS microphone (PMM) design predicated on a flexibility-enhanced rotating structure. The proposed design utilizes an aluminum scandium nitride (Al0.8Sc0.2N) piezoelectric thin film with 20% scandium doping and incorporates four equivalent sensing units formed by four curved cutting lines centrally located on the chip. This configuration employs a nested arrangement of four cantilever beams to substantially increase vibration compliance, thereby effectively lowering the natural frequency without altering the chip’s external size. Three-dimensional finite element simulations reveal that, relative to traditional triangular cantilever beam architectures, the flexibility-enhanced rotating structure reduces the natural frequency from 15.6 kHz to 13.49 kHz while enhancing sensitivity from −44.6 dB to −40 dB. The device was fabricated via a comprehensive microfabrication process and subsequently characterized within a standardized acoustic testing environment. Experimental results indicate that the microphone attains a sensitivity of −43.84 dB at 1 kHz and exhibits a first resonance frequency of 13.5 kHz, closely aligning with simulation predictions. Furthermore, the signal-to-noise ratio (SNR) reaches 58.3 dB across the full range of human-audible frequencies. By leveraging the flexibility-enhanced rotating structure, this work achieves an optimal compromise between elevated sensitivity and reduced resonance frequency within a compact form factor, thereby offering a viable technical solution for the advancement of high-performance miniature acoustic sensors. Full article
(This article belongs to the Special Issue Acoustic Transducers and Their Applications, 3rd Edition)
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10 pages, 1423 KB  
Article
Synthesis, Electron Transport Behavior, and Enhanced Blue Light Stability of Polyfluorene-Poly(Methyl Methacrylate) Diblock Copolymers
by Ruoyu Jiang, Changchun Liu, Jin Cheng and Kenji Ogino
Micromachines 2026, 17(4), 487; https://doi.org/10.3390/mi17040487 - 16 Apr 2026
Cited by 1 | Viewed by 460
Abstract
Poly(9,9-di-n-octylfluorene) (PFO) suffers from interchain aggregation, which degrades its blue spectral stability and charge transport. To address this, a series of rod-coil diblock copolymers (PFO-b-PMMAs) with varying poly(methyl methacrylate) (PMMA) chain lengths were synthesized via Steglich coupling. The non-conjugated [...] Read more.
Poly(9,9-di-n-octylfluorene) (PFO) suffers from interchain aggregation, which degrades its blue spectral stability and charge transport. To address this, a series of rod-coil diblock copolymers (PFO-b-PMMAs) with varying poly(methyl methacrylate) (PMMA) chain lengths were synthesized via Steglich coupling. The non-conjugated PMMA blocks act as bulky steric spacers in the solid state, effectively suppressing detrimental PFO aggregation and enhancing pure blue emission stability. Furthermore, moderate PMMA blocks (PFO-b-PMMA1 and PFO-b-PMMA2) promote favorable β-phase formation and ordered crystalline packing. This microstructural optimization yields a maximum electron mobility of 1.98 × 10−6 cm2/(V·s) for PFO-b-PMMA2, markedly higher than the PFO-2 homopolymer (4.13 × 10−7 cm2/(V·s)). However, an overlong PMMA block (PFO-b-PMMA3) introduces excessive steric hindrance (Tg = 66 °C) that disrupts crystallization, acting as an insulating barrier that reduces mobility. Thus, precisely tuning the non-conjugated block length effectively maximizes both the blue spectral stability and electron transport capabilities of PFO-based materials. Full article
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45 pages, 5981 KB  
Review
Advances and Challenges of Capacitive Micromachined Ultrasonic Transducers in Medical Imaging
by Yuanyu Yu, Xin Liu, Jiujiang Wang and Shuang Zhang
Micromachines 2026, 17(4), 486; https://doi.org/10.3390/mi17040486 - 16 Apr 2026
Cited by 2 | Viewed by 1306
Abstract
Capacitive micromachined ultrasonic transducers (CMUTs) have been developed over the past 30 years and achieved practical applications in both medical imaging and industrial non-destructive testing. This article presents the fundamental principles of CMUTs and surveys fabrication technologies, offering a comprehensive review of major [...] Read more.
Capacitive micromachined ultrasonic transducers (CMUTs) have been developed over the past 30 years and achieved practical applications in both medical imaging and industrial non-destructive testing. This article presents the fundamental principles of CMUTs and surveys fabrication technologies, offering a comprehensive review of major advances and challenges in medical ultrasound and photoacoustic imaging applications. The article further reviews and analyzes three primary challenges currently confronting CMUTs in medical imaging applications: lower output acoustic pressure, dielectric charging effects, and the need for high bias voltage. It also presents and discusses a potential combined approach to comprehensively address these challenges, with the aim of enhancing CMUT performance and broadening clinical adoption. Full article
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15 pages, 6186 KB  
Article
A 2–6 GHz Ultra-Wideband Shared-Aperture Antenna Array for 5G Multi-Band Base Station
by Lingang Yang, Junkai He, Yuqing Gao, Yue Wang and Jun Wang
Micromachines 2026, 17(4), 485; https://doi.org/10.3390/mi17040485 - 16 Apr 2026
Viewed by 1345
Abstract
This paper proposes a non-overlapping planar cross-arranged ultra-wideband shared-aperture base station antenna array targeting the 2 to 6 GHz application bandwidth. The low-frequency module (double-layer parasitic coupling) and the high-frequency module (chamfered slotted patch) are independently designed, and metal baffles are introduced around [...] Read more.
This paper proposes a non-overlapping planar cross-arranged ultra-wideband shared-aperture base station antenna array targeting the 2 to 6 GHz application bandwidth. The low-frequency module (double-layer parasitic coupling) and the high-frequency module (chamfered slotted patch) are independently designed, and metal baffles are introduced around the antenna elements to reshape the boundary conditions and physically block the electromagnetic coupling paths. Both simulation and experimental results demonstrate that the fabricated prototype successfully exceeds the targeted 2–6 GHz spectrum, achieving an actual continuous coverage from 1.84 to 6.3 GHz. Specifically, the antenna achieves a gain higher than 5.9 dBi in the measured low-frequency band (1.84–3.72 GHz) and higher than 6.1 dBi in the high-frequency band (3.63–6.3 GHz), with a voltage standing wave ratio (VSWR) below 2 across the entire band. The metal baffles successfully correct the high-frequency radiation pattern distortion and ensure stable directional radiation over the full operating bandwidth. This design provides an efficient, robust, and manufacturable solution for 5G offshore wind power multi-band base station antennas. Full article
(This article belongs to the Special Issue Electromagnetic Metamaterials and Metasurfaces: From Design to Applications)
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13 pages, 2585 KB  
Article
Design and Research of 2-DOF Piezoelectric Nanopositioning Stage with Multiple Displacement Amplifiers and Decoupling Beams
by Jing Yin, Chen Zhou, Xiaoting Chen and Dongcai Liu
Micromachines 2026, 17(4), 484; https://doi.org/10.3390/mi17040484 - 16 Apr 2026
Viewed by 628
Abstract
A piezoelectric (PZT) nanopositioning stage with large stroke and low crosstalk is relatively appealing for microdisplacement operation. Rhombus and lever amplifiers are used to increase the overall displacement amplification ratio (DAR), and the symmetry of the amplification structure reduces the coupling error. At [...] Read more.
A piezoelectric (PZT) nanopositioning stage with large stroke and low crosstalk is relatively appealing for microdisplacement operation. Rhombus and lever amplifiers are used to increase the overall displacement amplification ratio (DAR), and the symmetry of the amplification structure reduces the coupling error. At the same time, decoupling beams are used to balance the stiffness in the x- and y-directions, thereby reducing the crosstalk of the stage. Theoretical analysis, kinematics modeling, and finite element simulation were carried out to verify the feasibility of the PZT nanopositioning stage, and an experimental prototype was manufactured. The prototype test results indicate that the workspace of the stage is 312 μm × 312 μm, the DAR is approximately 9.3, and the first natural frequency is approximately 76 Hz. Moreover, the area efficiency is 6.03, which indicates that the stage is compact. The results prove that the developed stage possesses a good property for microdisplacement operation. Full article
(This article belongs to the Special Issue Piezoelectric Actuators and Motors: From Theory to Applications)
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16 pages, 7238 KB  
Article
Design and Fabrication of High-Frequency Resonant Micro-Accelerometer Based on Piezoelectric Stiffening Effect
by Ankesh Todi, Hakhamanesh Mansoorzare and Reza Abdolvand
Micromachines 2026, 17(4), 483; https://doi.org/10.3390/mi17040483 - 16 Apr 2026
Cited by 1 | Viewed by 1465
Abstract
In this work, a novel approach for implementing a resonant micro-accelerometer is demonstrated that may extend the operating frequency of such devices to several tens of MHz, which may enable direct wireless signal transfer. The proposed resonant accelerometer consists of a hybrid structure: [...] Read more.
In this work, a novel approach for implementing a resonant micro-accelerometer is demonstrated that may extend the operating frequency of such devices to several tens of MHz, which may enable direct wireless signal transfer. The proposed resonant accelerometer consists of a hybrid structure: a piezoelectric micro-resonator and a capacitive mass-spring (CMS) system (that are mechanically separated but electrically interconnected). The sensor utilizes the piezoelectric stiffening mechanism, which translates the acceleration-induced displacement of the capacitive mass-spring (CMS) structure into a shift in the resonance frequency of the interconnected resonator. The operating principle is elaborated upon in detail, supported by simulation and experimental results. Additionally, a novel fabrication technique is presented to realize a suspended fixed bi-layer electrode for the CMS in which a hardened layer of photoresist is utilized as a sacrificial layer. The experimental sensitivity of a fully functional device is reported to be ~6 Hz/g at 25 MHz (~0.23 ppm/g), which closely matches the simulated sensitivity of ~7 Hz/g (~0.278 ppm/g) for the fabricated capacitive gap of ~7 µm. Full article
(This article belongs to the Special Issue Solid-State Sensors, Actuators and Microsystems—Transducers 2025)
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8 pages, 3120 KB  
Article
Improved Threshold Voltage Stability of p-GaN Gate HEMTs Under Off-State Drain Stress Using p-NiO RESURF Terminal
by Jun Pan, Xiangru Ye, Ruixi Jiang, Ailin Miao, Fuxiang Miao, Zhiyi Mao, Yanghu Peng, Hui Guo and Jianming Lei
Micromachines 2026, 17(4), 482; https://doi.org/10.3390/mi17040482 - 16 Apr 2026
Cited by 1 | Viewed by 801
Abstract
A comparative study was undertaken to examine the VTH stability of p-GaN gate high electron mobility transistors (HEMTs) without the p-NiO reduced surface field (RESURF) terminal and with the RESURF terminal under off-state drain voltage stress and negative gate stress, involving in-depth [...] Read more.
A comparative study was undertaken to examine the VTH stability of p-GaN gate high electron mobility transistors (HEMTs) without the p-NiO reduced surface field (RESURF) terminal and with the RESURF terminal under off-state drain voltage stress and negative gate stress, involving in-depth analyses of the net negative charge accumulation processes in the gate region and buffer layer, thereby revealing the degradation mechanisms of the devices. The findings indicate that the p-NiO RESURF terminal effectively enhances the stability of VTH under off-state drain voltage stress by injecting holes into the buffer layer and hence initiating a light-pumping effect, and simultaneously also by flattening the electric field peak on the drain side beneath the gate and thus significantly mitigating hole loss in the gate region and electron capture in the buffer layer. This study provides a theoretical basis for the application of the p-NiO RESURF terminal in p-GaN HEMTs. Full article
(This article belongs to the Section D1: Semiconductor Devices)
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19 pages, 4431 KB  
Article
A Parameter-Agnostic Adaptive Compensation in Memristor-Based Neuromorphic Systems for Parasitic Resistance
by Texu Liu, Hanbo Ren, Peiwen Tong, Wei Wang, Qingjiang Li, Meng Xia, Yi Sun, Rongrong Cao, Bing Song, Zhiwei Li and Haijun Liu
Micromachines 2026, 17(4), 481; https://doi.org/10.3390/mi17040481 - 16 Apr 2026
Viewed by 770
Abstract
Memristor-based neuromorphic computing offers a promising pathway for efficient in-memory processing. However, the scalability and reliability of such systems are severely compromised by parasitic resistances (including line and input resistances) in crossbar arrays, which cause significant IR-drop during vector–matrix multiplication (VMM). Existing research [...] Read more.
Memristor-based neuromorphic computing offers a promising pathway for efficient in-memory processing. However, the scalability and reliability of such systems are severely compromised by parasitic resistances (including line and input resistances) in crossbar arrays, which cause significant IR-drop during vector–matrix multiplication (VMM). Existing research often suffers from high computational latency or relies on the precise extraction of parasitic parameters, which is impractical and computationally expensive for large-scale integration. To overcome these limitations, we propose a Parameter-Agnostic Adaptive Compensation (PAAC) method based on a distributed linear approximation model. By analyzing the circuit characteristics, we conquered the challenge of coupling between parasitic effects and output current, deriving a simplified linear relationship that requires no prior knowledge of specific resistance values. The PAAC method involves only a single-step pre-calibration experiment to determine a global compensation factor, achieving an ultra-low computational complexity during inference. We validated the method using a comprehensive two-stage strategy: board-level hardware experiments confirmed its feasibility by reducing current distortion from 71% to 2%, while extensive large-scale HSPICE simulations verified its scalability, restoring classification accuracy from 89% to 95%. This work provides a robust, low-overhead solution that eliminates the dependency on precise parameter modeling, facilitating the realization of large-scale, high-precision neuromorphic hardware. Full article
(This article belongs to the Special Issue Neuromorphic Memory and Computing-in-Memory Architectures: From Devices to Systems)
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15 pages, 2135 KB  
Article
An Electrohydrodynamic Phase-Field Model for Contact Angle Hysteresis in Electrowetting Pixels: Decoupling Physical Pinning and Charge Trapping
by Qingsong Lu, Li Wang, Feng Li, Yanjun Yang, Qifu Liu, Xinying Wang, Feng Chi, Liming Liu and Zichuan Yi
Micromachines 2026, 17(4), 480; https://doi.org/10.3390/mi17040480 - 15 Apr 2026
Viewed by 800
Abstract
Precise manipulation of two-phase flow in micro-confined electrowetting pixels is limited by contact angle hysteresis (CAH). To elucidate this non-equilibrium process, we establish a high-fidelity electrohydrodynamic (EHD) phase-field simulation framework. The model rigorously couples Navier–Stokes equations with molecular kinetic theory (MKT) to characterize [...] Read more.
Precise manipulation of two-phase flow in micro-confined electrowetting pixels is limited by contact angle hysteresis (CAH). To elucidate this non-equilibrium process, we establish a high-fidelity electrohydrodynamic (EHD) phase-field simulation framework. The model rigorously couples Navier–Stokes equations with molecular kinetic theory (MKT) to characterize energy dissipation at the three-phase contact line (TCL) and further integrates charge transport kinetics. Numerical results reveal CAH is driven by physical pinning and interfacial charge trapping, with the latter dominating interfacial retreat and causing significant residual displacement. Furthermore, analysis shows alternating current (AC) waveforms mitigate charge accumulation and promote depinning via micro-oscillations, minimizing the hysteresis loop compared to direct current (DC) waveforms. Additionally, an overdrive strategy utilizing a suprathreshold Maxwell stress pulse rapidly overcomes static friction. This strategy significantly improves transient dynamics, substantially reducing the time to reach 90% of the steady-state target from 19.6 ms (under standard DC waveform driving) to 7.4 ms. This work provides a comprehensive theoretical basis and design criteria for optimizing active driving strategies in optofluidic and digital microfluidic systems. Full article
(This article belongs to the Special Issue Advances in Optoelectronic Devices, 3rd Edition)
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13 pages, 10825 KB  
Article
Genetic Algorithm-Optimized Volume Holographic Gratings in Ultra-Thin MiniLED Modules
by Zechao Shen, Yue Zhang, Guoqiang Lv, Zi Wang and Qibin Feng
Micromachines 2026, 17(4), 479; https://doi.org/10.3390/mi17040479 - 15 Apr 2026
Viewed by 581
Abstract
The design of volume holographic gratings (VHGs) is traditionally based on monochromatic plane waves. However, practical applications often involve light sources with broad wavelength bandwidths and certain emission areas, such as LEDs and MiniLEDs, which cause significant Bragg mismatch and degrade diffraction efficiency. [...] Read more.
The design of volume holographic gratings (VHGs) is traditionally based on monochromatic plane waves. However, practical applications often involve light sources with broad wavelength bandwidths and certain emission areas, such as LEDs and MiniLEDs, which cause significant Bragg mismatch and degrade diffraction efficiency. To address this fundamental challenge, this paper proposes a novel, to the best of our knowledge, genetic algorithm (GA)-based optimization method for VHG design. A ray-tracing analysis model that fully incorporates the spectral and spatial characteristics of extended broadband sources is established. The GA optimizes the grating fabrication angles by minimizing a fitness function defined as the residual energy after diffraction, thereby achieving optimal performance under non-ideal illumination conditions. The effectiveness of the proposed method is demonstrated through a case study: suppressing the high-intensity central beam in an ultra-thin MiniLED backlight module (BLM). Simulation and experimental results show that the GA-optimized VHG significantly reduces the peak irradiance from 5.01 W/cm2 to 4.14 W/cm2 at an optical distance (OD) of 0.5 mm. This work provides a robust and source-adaptive design methodology for VHGs, with potential applications extending beyond backlighting to areas such as augmented reality, holographic displays, and optical communications. Full article
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22 pages, 18366 KB  
Article
Hybrid Carbonyl Iron/Iron Oxide Microfiber Textile Membranes with Magnetically Tunable Capacitance Under Compressive Loading
by Ioan Bica, Eugen Mircea Anitas, Octavian Madalin Bunoiu, Liviu Chirigiu and Gabriel Pascu
Micromachines 2026, 17(4), 478; https://doi.org/10.3390/mi17040478 - 15 Apr 2026
Viewed by 508
Abstract
Flexible textile membranes were prepared by impregnating woven cotton fabrics with silicone oil (SO)-based suspensions containing carbonyl iron (CI) microparticles and iron oxide microfibers (μFe). The microfibers were obtained by a microwave-assisted microplasma process and then co-dispersed with CI in SO. [...] Read more.
Flexible textile membranes were prepared by impregnating woven cotton fabrics with silicone oil (SO)-based suspensions containing carbonyl iron (CI) microparticles and iron oxide microfibers (μFe). The microfibers were obtained by a microwave-assisted microplasma process and then co-dispersed with CI in SO. In the final membranes, the CI content was kept constant at ΦCI=10 vol.%, whereas the microfiber fraction was 0, 10 and 20 vol.%. The resulting membranes were used as dielectric layers in planar capacitors and examined at 1 kHz under a static magnetic field of up to 150 mT and compressive pressure up to 10 kPa. In every composition, the capacitance rose with increasing magnetic flux density, but both the zero-field capacitance and the field-induced capacitance change became smaller as the microfiber content increased. A monotonic, nearly linear increase in capacitance was also observed under compression over the tested pressure range. Within a simplified parallel-plate and magnetic-stress analysis, the capacitance data were further used to estimate the apparent relative permittivity, together with capacitance-derived indicators of deformation and stiffness. These estimates suggest field-induced stiffening of the membranes and a higher apparent low-field stiffness at higher microfiber loading. The obtained hybrid CI/μFe-based textile membranes can serve as composition-tunable dielectric layers whose electrical response is influenced by both magnetic field and compressive loading, making them relevant for flexible capacitor-based elements. Full article
(This article belongs to the Special Issue MEMS and NEMS Sensors: Innovations, Applications, and Future Directions in Micro/Nano Technologies)
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16 pages, 1854 KB  
Article
Multiscale Analysis of Size-Dependent Vibration of Graphene Nanoelectromechanical Resonators
by Wenhua Li and Wenchao Tian
Micromachines 2026, 17(4), 477; https://doi.org/10.3390/mi17040477 - 15 Apr 2026
Cited by 1 | Viewed by 1306
Abstract
The size-dependent out-of-plane vibrational behavior of graphene-based nanoelectromechanical (NEMS) resonators is investigated using a molecular mechanics (MM) finite element approach. Each carbon–carbon (C–C) bond is modeled as an Euler–Bernoulli beam element, with the bending stiffness derived from the bond-angle potential, yielding an equivalent [...] Read more.
The size-dependent out-of-plane vibrational behavior of graphene-based nanoelectromechanical (NEMS) resonators is investigated using a molecular mechanics (MM) finite element approach. Each carbon–carbon (C–C) bond is modeled as an Euler–Bernoulli beam element, with the bending stiffness derived from the bond-angle potential, yielding an equivalent plate flexural rigidity D = (√3/6) kθ. The natural frequencies of the first four vibration modes are computed for square graphene sheets of increasing size with both zigzag (ZZ) and armchair (AC) chirality configurations under simply supported boundary conditions on all four edges. A chirality-induced frequency deviation δ(L) is defined to quantify the difference between ZZ and AC results, and a threshold size L* is identified as the sheet size at which δ falls below 1%. For mode 1, the threshold is L* = 18.5 nm; the values increase monotonically to 24.5 nm, 28.0 nm, and 31.5 nm for modes 2 through 4, indicating that higher modes require larger sheet dimensions before continuum plate theory becomes reliable. A dimensionless frequency parameter Ω = fMM/fCT is introduced to directly compare MM predictions with the Kirchhoff plate theory analytical solution, and the AC frequency ratio Ω = fMM/fCT is shown to converge toward unity with increasing sheet size. The present results provide quantitative design guidelines for graphene NEMS resonators and establish the minimum device dimensions for which isotropic continuum models yield accurate dynamic predictions. Full article
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18 pages, 3976 KB  
Article
Gradient-Field-Based Force-Driven Control of a Mudskipper-Inspired Magnetic Microrobot for Intestinal Applications
by Yijie Du, Huiting Xie, Wenqi Zhang, Yuting Mao and Gongxin Li
Micromachines 2026, 17(4), 476; https://doi.org/10.3390/mi17040476 - 15 Apr 2026
Cited by 1 | Viewed by 573
Abstract
Magnetically driven microrobots operating in intestinal environments face two major challenges: difficulty in traversing low-height confined spaces and limited local visibility caused by mucosal obstruction. To address these issues, this study proposes a gradient-field-based force-driven control method for a mudskipper-inspired magnetic microrobot. By [...] Read more.
Magnetically driven microrobots operating in intestinal environments face two major challenges: difficulty in traversing low-height confined spaces and limited local visibility caused by mucosal obstruction. To address these issues, this study proposes a gradient-field-based force-driven control method for a mudskipper-inspired magnetic microrobot. By establishing the mapping among coil current, magnetic field, and magnetic force at the robot working point, and by solving the control input through singular value decomposition and linear programming, effective magnetic-force output along a desired direction was achieved. On this basis, two representative force-driven motions were designed. The first was a translational mode based on pulsed magnetic-force actuation for stable navigation in low-height confined spaces. The second was a lifting mode based on continuous loading and gradual adjustment of the magnetic-force upper bound to locally lift a flexible “mucosa-like” membrane, thereby simulating intestinal mucosal elevation and local visual field expansion. Experimental results showed that the robot could stably pass through narrow tunnels and effectively lift an overlying flexible membrane under vertical magnetic-force actuation. The proposed method extends both the locomotion capability and the local interaction capability of the mudskipper-inspired magnetic microrobot, and demonstrates a feasible proof-of-concept approach for confined-space navigation and localized manipulation in intestinal applications. Full article
(This article belongs to the Special Issue Functional Materials and Microdevices, 2nd Edition)
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25 pages, 10269 KB  
Article
Study on the Material Removal Mechanism of FGH99 by Laser-Induced Microjet Assisted Ablation at Different Incidence Angles
by Yixin Duan, Zhen Zhang, Zefei Zhu and Jing Ni
Micromachines 2026, 17(4), 475; https://doi.org/10.3390/mi17040475 - 15 Apr 2026
Viewed by 579
Abstract
Laser-induced microjet-assisted ablation is an emerging technology in the field of laser processing. However, the influence of solid boundaries on jet behavior and the associated material removal mechanism remains unclear after observing and analyzing the ablation process. To address this, the present study [...] Read more.
Laser-induced microjet-assisted ablation is an emerging technology in the field of laser processing. However, the influence of solid boundaries on jet behavior and the associated material removal mechanism remains unclear after observing and analyzing the ablation process. To address this, the present study systematically investigates the effect of the incidence angle on the processing efficiency and material removal mechanism in laser-induced microjet ablation. By controlling the laser power and liquid layer thickness, the dynamic behavior of the microjet, material removal performance, and surface morphology evolution under different inclination angles were explored. Based on video analysis and OpenCV processing, the regulation of jet morphology and impact mode by the incidence angle was revealed. Combined with white light interferometry and ultra-depth-of-field three-dimensional microscopy, the ablation depth and material removal rate were quantitatively characterized. The results showed that under normal incidence, the maximum material removal rate of 0.092 mm3/s was achieved at 9 W, while further increases in power led to a decrease in removal rate due to bubble aggregation. When the sample was tilted to 15°, the material removal rate reached 0.163 mm3/s, representing a 106.30% improvement compared to that at 0°, and the ablation depth also peaked with an average maximum depth of 12.32 ± 0.58 μm and a single-point maximum of 54.36 μm. Furthermore, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to elucidate the microstructural features and elemental distribution under different process parameters. Through multi-parameter experiments, this study achieved process parameter optimization and clarified the material removal mechanism influenced by different incidence angles, providing both a process reference and theoretical basis for efficient micro-machining of aerospace materials. Full article
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38 pages, 4734 KB  
Review
Quantum Dot Solar Cells: Background, Progress, and Perspective
by Kumar Neupane, Jeff Kabel, Join Uddin, Raksha Dubey, Rojina Ojha, Dongyan Zhang and Yoke Khin Yap
Micromachines 2026, 17(4), 474; https://doi.org/10.3390/mi17040474 - 15 Apr 2026
Cited by 2 | Viewed by 3633
Abstract
The discovery of quantum dots (QDs) earned a Nobel Prize and has led to widespread applications in research and technology. In this review, we focus on the use of QDs in solid-state solar cells (QDSCs). We begin with an overview of the basic [...] Read more.
The discovery of quantum dots (QDs) earned a Nobel Prize and has led to widespread applications in research and technology. In this review, we focus on the use of QDs in solid-state solar cells (QDSCs). We begin with an overview of the basic principles of SCs. Then, we discuss how device architecture has developed over recent decades, setting the stage for the final section on fourth-generation solar cells (Perspective section). We also highlight progress in material development, starting with lead- and cadmium-based QDs and progressing to more recent carbon- and perovskite-based QDs. Additionally, we review materials used for electron-transport layers (ETLs) and hole-transport layers (HTLs). The articles also present recent advances in QDSCs across various QD types. In the final section, we recommend that future research focus on three main areas: QD active-layer materials, material interfaces, and device architecture. These efforts could lead to sustainable QDSCs that potentially surpass the Shockley–Queisser (SQ) limit. Full article
(This article belongs to the Special Issue Low-Dimensional Nano-Scaled Materials: From Principles to Device Application)
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