Micromachines

20 pages, 5655 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Structure Design Optimization of a Differential Capacitive MEMS Accelerometer Based on a Multi-Objective Elitist Genetic Algorithm

by Dongda Yang, Yao Chu, Ruitao Liu, Xiwen Zhang, Saifei Yuan, Fan Zhang, Shengjie Xuan, Yunzhang Chi, Jiahui Liu, Zetong Lei and Rui You

Micromachines 2026, 17(1), 129; https://doi.org/10.3390/mi17010129 - 19 Jan 2026

Viewed by 344

Abstract

This article describes a global structure optimization methodology for microelectromechanical system devices based on a multi-objective elitist genetic algorithm. By integrating a parameterized model with a multi-objective evolutionary framework, the approach can efficiently explore design space and concurrently optimize multiple metrics. A differential [...] Read more.

This article describes a global structure optimization methodology for microelectromechanical system devices based on a multi-objective elitist genetic algorithm. By integrating a parameterized model with a multi-objective evolutionary framework, the approach can efficiently explore design space and concurrently optimize multiple metrics. A differential capacitive MEMS accelerometer is presented to demonstrate the method. Four key objectives, including resonant frequency, static capacitance, dynamic capacitance, and feedback force, are simultaneously optimized to enhance sensitivity, bandwidth, and closed-loop driving capability. After 25 generations, the algorithm converged to a uniformly distributed Pareto front. The experimental results indicate that, compared with the initial design, the sensitivity-oriented design achieves a 56.1% reduction in static capacitance and an 85.5% improvement in sensitivity. The global multi-objective optimization achieves a normalized hypervolume of 35.8%, notably higher than the local structure optimization, demonstrating its superior design space coverage and trade-off capability. Compared to single-objective optimization, the multi-objective approach offers a superior strategy by avoiding the limitation of overemphasizing resonant frequency at the expense of other metrics, thereby enabling a comprehensive exploration of the design space. Full article

(This article belongs to the Special Issue Artificial Intelligence for Micro Inertial Sensors)

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17 pages, 3126 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Multifunctional Peptide Linker Stably Anchors to Silica Spicules and Enables MMP-Responsive Release of Diverse Bioactive Cargos

by So-Hyung Lee, Suk-Hyun Kwon, Byung-Ho Song, In-Gyeong Yeo, Hyun-Seok Park, A-Ri Kim, Lee-Seul Kim, Ji-Min Noh, Hee-Jung Choi, Da-Jeoung Lim and Young-Wook Jo

Micromachines 2026, 17(1), 127; https://doi.org/10.3390/mi17010127 - 19 Jan 2026

Viewed by 186

Abstract

Silica spicules provide a natural transdermal conduit but require a linker that binds strongly under physiological conditions and releases payloads selectively in response to biological cues. Existing silane chemistries or polydopamine coatings lack enzyme responsiveness and show limited control over release. We created [...] Read more.

Silica spicules provide a natural transdermal conduit but require a linker that binds strongly under physiological conditions and releases payloads selectively in response to biological cues. Existing silane chemistries or polydopamine coatings lack enzyme responsiveness and show limited control over release. We created a 180-member peptide library with the motif L–X1–X2–[Y–F–Y]–A–L–G–P–H–C and screened for silica binding. Biophysical assays (circular dichroism, ζ-potential, quartz crystal microbalance, atomic force microscopy) and molecular dynamics identified high-affinity binders. The lead, P176, was tested for matrix metalloprotease (MMP)-responsive cleavage. Conjugation and release of Vitamin C and Stigmasterol were analyzed by HPLC and Franz diffusion cells. P176 showed high silica affinity (~55 µg mg⁻¹), robust biophysical signals (Δf −35 to −38 Hz; rupture force ~154 pN; ζ shift −22 to−11.5 mV), and favorable adsorption energy (−48.5 kcal mol⁻¹, contact 4.5 nm², 8.5 H-bonds). The MMP gate displayed efficient kinetics (Vmax 117.9 RFU·min⁻¹, Km 5.0 µM) with >90% cleavage at 60 min, reduced to 26% by inhibitor. Conjugation yields reached 87% (Vitamin C) and 77% (Stigmasterol). Franz diffusion showed MMP-dependent release (24 h: Vitamin C 90–96%, Stigmasterol 80–85%) with minimal basal leakage. Released Vitamin C enhanced collagen I to ~250% in fibroblasts, while Stigmasterol attenuated LPS-induced macrophage morphology; keratinocytes retained normal marker expression. This study demonstrates that a single amphipathic, sequence-programmed peptide can couple strong silica anchoring with protease-responsive release and broad payload compatibility, establishing a versatile platform for spicule-based transdermal and regenerative delivery. Full article

(This article belongs to the Section B5: Drug Delivery System)

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12 pages, 5511 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Low Temperature Effect of Resistance Strain Gauge Based on Double-Layer Composite Film

by Mengqiu Li, Zhiyuan Hu, Fengming Ye, Jiaxiang Wang and Zhuoqing Yang

Micromachines 2026, 17(1), 114; https://doi.org/10.3390/mi17010114 - 15 Jan 2026

Viewed by 203

Abstract

Strain gauges play a crucial role in numerous fields such as bridge and building structural health monitoring. However, traditional strain gauges generate spurious signals due to the temperature effect, which in turn affects their measurement accuracy. Herein, we propose a resistance strain gauge [...] Read more.

Strain gauges play a crucial role in numerous fields such as bridge and building structural health monitoring. However, traditional strain gauges generate spurious signals due to the temperature effect, which in turn affects their measurement accuracy. Herein, we propose a resistance strain gauge based on a double-layer composite film, which is characterized by an adjustable resistance temperature coefficient (TCR), an ultra-near-zero temperature effect, and good TCR repeatability. It is precisely through the combination of materials with positive and negative TCR, leveraging their opposing temperature resistance characteristics, that a low temperature effect has been achieved. Compared with the single-layer alloy-based strain gauge, the developed strain gauge based on double-layer composite film has greatly reduced sensitivity to temperature interference, and its TCR can be reduced to a ultra-near-zero value, approximately 0.8 ppm/°C, while the stability of TCR is excellent. In addition, the gauge factor of the strain gauge is 1.83, and it maintains excellent linearity. This work fully highlights the potential application value of the developed strain gauge in stress monitoring of bridges and building structures. Full article

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

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30 pages, 3247 KB

Open AccessFeature PaperEditor’s ChoiceArticle

The Clausius–Mossotti Factor in Dielectrophoresis: A Critical Appraisal of Its Proposed Role as an ‘Electrophysiology Rosetta Stone’

by Ronald Pethig

Micromachines 2026, 17(1), 96; https://doi.org/10.3390/mi17010096 - 11 Jan 2026

Viewed by 429

Abstract

The Clausius–Mossotti (CM) factor underpins the theoretical description of dielectrophoresis (DEP) and is widely used in micro- and nano-scale systems for frequency-dependent particle and cell manipulation. It has further been proposed as an “electrophysiology Rosetta Stone” capable of linking DEP spectra to intrinsic [...] Read more.

The Clausius–Mossotti (CM) factor underpins the theoretical description of dielectrophoresis (DEP) and is widely used in micro- and nano-scale systems for frequency-dependent particle and cell manipulation. It has further been proposed as an “electrophysiology Rosetta Stone” capable of linking DEP spectra to intrinsic cellular electrical properties. In this paper, the mathematical foundations and interpretive limits of this proposal are critically examined. By analyzing contrast factors derived from Laplace’s equation across multiple physical domains, it is shown that the CM functional form is a universal consequence of geometry, material contrast, and boundary conditions in linear Laplacian fields, rather than a feature unique to biological systems. Key modelling assumptions relevant to DEP are reassessed. Deviations from spherical symmetry lead naturally to tensorial contrast factors through geometry-dependent depolarisation coefficients. Complex, frequency-dependent CM factors and associated relaxation times are shown to inevitably arise from the coexistence of dissipative and storage mechanisms under time-varying forcing, independent of particle composition. Membrane surface charge influences DEP response through modified interfacial boundary conditions and effective transport parameters, rather than by introducing an independent driving mechanism. These results indicate that DEP spectra primarily reflect boundary-controlled field–particle coupling. From an inverse-problem perspective, this places fundamental constraints on parameter identifiability in DEP-based characterization. The CM factor remains a powerful and general modelling tool for micromachines and microfluidic systems, but its interpretive scope must be understood within the limits imposed by Laplacian field theory. Full article

(This article belongs to the Special Issue Advances in Electrokinetics for Cell Sorting and Analysis)

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16 pages, 24814 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Inverse Design of Thermal Imaging Metalens Achieving 100° Field of View on a 4 × 4 Microbolometer Array

by Munseong Bae, Eunbi Jang, Chanik Kang and Haejun Chung

Micromachines 2026, 17(1), 65; https://doi.org/10.3390/mi17010065 - 31 Dec 2025

Viewed by 700

Abstract

We present an inverse designed metalens for long-wave infrared (LWIR) imaging tailored to consumer and Internet of Things (IoT) platforms. Conventional LWIR optics either rely on costly specialty materials or suffer from low efficiency and narrow fields of view (FoV), limiting scalability. Our [...] Read more.

We present an inverse designed metalens for long-wave infrared (LWIR) imaging tailored to consumer and Internet of Things (IoT) platforms. Conventional LWIR optics either rely on costly specialty materials or suffer from low efficiency and narrow fields of view (FoV), limiting scalability. Our approach integrates adjoint-based inverse design with fabrication-aware constraints and a cone-shaped source model that efficiently captures oblique incidence during optimization. The resulting multi-level metalens achieves a wide FoV up to 100° while maintaining robust focusing efficiency and stable angle-to-position mapping on low-power

4 \times 4

microbolometer arrays representative of edge devices. We further demonstrate application-level imaging on

4 \times 4

microbolometer arrays, showing that the proposed metalens delivers a substantially wider FoV than a commercial narrow FoV lens while meeting low-resolution, low-cost, and low-power constraints for edge LWIR modules. By eliminating bulky multi-element stacks and reducing cost and form factor, the proposed design provides a practical pathway to compact, energy-efficient LWIR modules for consumer applications such as occupancy analytics, smart-building automation, mobile sensing, and outdoor fire surveillance. Full article

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

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30 pages, 16390 KB

Open AccessEditor’s ChoiceReview

Auger Electron Spectroscopy for Chemical Analysis of Passivated (Al,Ga)N-Based Systems

by Alina Domanowska and Bogusława Adamowicz

Micromachines 2026, 17(1), 47; https://doi.org/10.3390/mi17010047 - 30 Dec 2025

Viewed by 574

Abstract

This review summarizes the use of Auger Electron Spectroscopy (AES) for microchemical analysis of two different types of dielectric/(Al,Ga)N-based systems: (i) extrinsic dielectric PECVD SiO₂, ALD Al₂O₃, and ECR-CVD SiN_x films on Al_xGa_1−x [...] Read more.

This review summarizes the use of Auger Electron Spectroscopy (AES) for microchemical analysis of two different types of dielectric/(Al,Ga)N-based systems: (i) extrinsic dielectric PECVD SiO₂, ALD Al₂O₃, and ECR-CVD SiN_x films on Al_xGa_1−xN/GaN structures in the context of their application in microelectronic power devices and (ii) intrinsic Al₂O₃ films on AlN epitaxial layers grown by high-temperature oxidation for nanostructured technology of various gas/ion sensors. Particular attention is given to AES depth profiling across complete multilayer cross-sections, combining qualitative analysis of spectral line shape and intensity evolution as well as kinetic energy shifts with quantitative elemental depth distributions. This approach enables identification of chemical states and oxidation-related transformations at dielectric/semiconductor interfaces. Reported results demonstrate that AES provides micro- to nanometer-scale chemical information essential for distinguishing interfacial from the bulk properties. The capabilities and inherent limitations of AES depth profiling, including sputter-induced artifacts are also addressed, highlighting the role of optimized experimental conditions in reliable interface analysis. Full article

(This article belongs to the Special Issue GaN Power Devices: Recent Advances, Applications, and Perspectives)

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13 pages, 7642 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Mid-Wave Infrared Polarization Combiner Based on Reflective Metasurface

by Lulu Yang, Xin Wang, Xuhui Li and Liquan Dong

Micromachines 2026, 17(1), 36; https://doi.org/10.3390/mi17010036 - 28 Dec 2025

Viewed by 289

Abstract

Polarization beam combining (PBC) is an important technology for enhancing laser brightness. The conventional bulk polarization beam combiners are Brewster plates and birefringent polarization prisms. However, in the mid- and long-wave infrared range, the beam combining performance is limited by the transmission and [...] Read more.

Polarization beam combining (PBC) is an important technology for enhancing laser brightness. The conventional bulk polarization beam combiners are Brewster plates and birefringent polarization prisms. However, in the mid- and long-wave infrared range, the beam combining performance is limited by the transmission and birefringent coefficient of the available materials. In this paper, a polarization beam combiner based on a reflection metasurface was proposed. The phases of incident beams with orthogonal linear polarizations were individually manipulated by the side lengths of the rectangular silicon pillar. A metasurface polarization beam combiner operating band was designed and fabricated. When the two beams at 4.6 μm with orthogonal linear polarizations were incident on the metasurface at angles of −13.3° and 13.3°, respectively, they were reflected in the 0°-direction. The overall beam combining efficiency was 88.9%. When both of the quantum cascade lasers used in the experiments were in the fundamental transverse Gaussian mode, the measured beam quality factors M² of the combined beam were 1.21 and 1.14 along the fast and slow axes, respectively. Both simulation and experimental results demonstrated that the proposed metasurface was an efficient polarization beam combiner with negligible wavefront distortion. It is a promising alternative to traditional bulk optics for the mid- and long-wave infrared. Full article

(This article belongs to the Special Issue Advanced Optoelectronic Materials/Devices and Their Applications)

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26 pages, 88895 KB

Open AccessEditor’s ChoiceReview

Active Propelled Micro Robots in Drug Delivery for Urologic Diseases

by Chunlian Zhong, Menghuan Tang and Zhaoqing Cong

Micromachines 2026, 17(1), 24; https://doi.org/10.3390/mi17010024 - 25 Dec 2025

Viewed by 792

Abstract

Active propelled micro robots (MRs) represent a transformative shift in biomedical engineering, engineered to navigate physiological environments by converting chemical, acoustic, or magnetic energy into mechanical propulsion. Unlike passive delivery systems limited by diffusion and systemic clearance, MRs offer autonomous mobility, enabling precise [...] Read more.

Active propelled micro robots (MRs) represent a transformative shift in biomedical engineering, engineered to navigate physiological environments by converting chemical, acoustic, or magnetic energy into mechanical propulsion. Unlike passive delivery systems limited by diffusion and systemic clearance, MRs offer autonomous mobility, enabling precise penetration and retention in hard-to-reach tissues. This review provides comprehensive analysis of MR technologies within urology, a field uniquely suited for microrobotic intervention due to the urinary tract’s anatomical accessibility and fluid-filled nature. We explore how MRs address critical therapeutic limitations, including the high recurrence of kidney stones and the rapid washout of intravesical bladder cancer therapies. The review categorizes propulsion mechanisms optimized for the urinary environment, such as urea-fueled nanomotors and magnetic swarms. Furthermore, we detail emerging applications, including bioresorbable acoustic robots for tumor ablation and magnetic grippers for minimally invasive biopsies. Finally, we critically assess the path toward clinical translation, focusing on challenges in biocompatibility, real-time tracking (MRI, MPI, photoacoustic imaging), and the regulatory landscape for these advanced combination products. Full article

(This article belongs to the Special Issue Active Propelled Micro/Nano Technologies in Drug Delivery: Design, Fabrication and Applications)

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19 pages, 3290 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Magnetically Sculpted Microfluidics for Continuous-Flow Fractionation of Cell Populations by EpCAM Expression Level

by Zhenwei Liang, Xiaolei Guo, Xuanhe Zhang, Yiqing Chen, Chuan Du, Yuan Ma and Jiadao Wang

Micromachines 2026, 17(1), 9; https://doi.org/10.3390/mi17010009 - 22 Dec 2025

Viewed by 345

Abstract

Continuous-flow separation of magnetically labeled cells according to surface-marker expression levels is increasingly needed to study phenotypic heterogeneity and support downstream assays. Here, we present a microfluidic platform that uses spatially engineered soft magnetic strips (SMS) to sculpt lateral magnetic deflection fields for [...] Read more.

Continuous-flow separation of magnetically labeled cells according to surface-marker expression levels is increasingly needed to study phenotypic heterogeneity and support downstream assays. Here, we present a microfluidic platform that uses spatially engineered soft magnetic strips (SMS) to sculpt lateral magnetic deflection fields for quantitative, label-guided cell fractionation. Under a uniform bias field, the SMS generates controllable magnetic gradients within the microchannel, producing distinct lateral velocities among EpCAM-labeled tumor cells that carry different Dynabead loads, which indirectly report membrane protein expression. Multi-outlet collection converts these “race-based” trajectory differences into discrete expression-level-resolved fractions. A COMSOL–MATLAB framework and a force-equivalent metric |(H·∇)H| are used to optimize key structural parameters of the magnetic interface, including strip thickness, width, and vertical spacing from the flow channel. Three journey nodes at 1.5, 3, and 9 mm along the flow path define a three-stage cascade that partitions MDA-MB-231, Caco-2, and A549 cells into four EpCAM-related magnetic subgroups: high (H), medium (M), low (L), and near-negative (N). Experiments show that the sorted fractions follow the expected expression trends reported in the literature, while maintaining high cell recovery (>90%) and viability retention of 98.2 ± 1.3%, indicating compatibility with downstream whole-blood assays and culture. Rather than introducing a new biomarker, this work establishes a quantitative magnetic-field design strategy for continuous microfluidic sorting, in which the spatial configuration of soft magnetic elements is exploited to implement expression-level-dependent fractionation in next-generation magneto-fluidic separation systems. Full article

(This article belongs to the Special Issue Microfluidic Chips for Biomedical Applications)

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45 pages, 4439 KB

Open AccessEditor’s ChoiceReview

Gallium Nitride for Space Photovoltaics: Properties, Synthesis Methods, Device Architectures and Emerging Market Perspectives

by Anna Drabczyk, Paweł Uss, Katarzyna Bucka, Wojciech Bulowski, Patryk Kasza, Paula Mazur, Edyta Boguta, Marta Mazur, Grzegorz Putynkowski and Robert P. Socha

Micromachines 2025, 16(12), 1421; https://doi.org/10.3390/mi16121421 - 18 Dec 2025

Viewed by 1083

Abstract

Gallium nitride (GaN) has emerged as one of the most promising wide-bandgap semiconductors for next-generation space photovoltaics. In contrast to conventional III–V compounds such as GaAs and InP, which are highly efficient under terrestrial conditions but suffer from radiation-induced degradation and thermal instability, [...] Read more.

Gallium nitride (GaN) has emerged as one of the most promising wide-bandgap semiconductors for next-generation space photovoltaics. In contrast to conventional III–V compounds such as GaAs and InP, which are highly efficient under terrestrial conditions but suffer from radiation-induced degradation and thermal instability, GaN offers an exceptional combination of intrinsic material properties ideally suited for harsh orbital environments. Its wide bandgap, high thermal conductivity, and strong chemical stability contribute to superior resistance against high-energy protons, electrons, and atomic oxygen, while minimizing thermal fatigue under repeated cycling between extreme temperatures. Recent progress in epitaxial growth—spanning metal–organic chemical vapor deposition, molecular beam epitaxy, hydride vapor phase epitaxy, and atomic layer deposition—has enabled unprecedented control over film quality, defect densities, and heterointerface sharpness. At the device level, InGaN/GaN heterostructures, multiple quantum wells, and tandem architectures demonstrate outstanding potential for spectrum-tailored solar energy conversion, with modeling studies predicting efficiencies exceeding 40% under AM0 illumination. In this review article, the current state of knowledge on GaN materials and device architectures for space photovoltaics has been summarized, with emphasis placed on recent progress and persisting challenges. Particular focus has been given to defect management, doping strategies, and bandgap engineering approaches, which define the roadmap toward scalable and radiation-hardened GaN-based solar cells. With sustained interdisciplinary advances, GaN is anticipated to complement or even supersede traditional III–V photovoltaics in space, enabling lighter, more durable, and radiation-hard power systems for long-duration missions beyond Earth’s magnetosphere. Full article

(This article belongs to the Special Issue Thin Film Microelectronic Devices and Circuits, 2nd Edition)

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13 pages, 3501 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Channel-Free Micro-Well–Template-Assisted Magnetic Particle Trapping for Efficient Single-Particle Isolation

by Jin-Yeong Park, Kyeong-Taek Nam, Young-Ho Nam, Yong-Kweon Kim, Seung-Ki Lee and Jae-Hyoung Park

Micromachines 2025, 16(12), 1397; https://doi.org/10.3390/mi16121397 - 11 Dec 2025

Viewed by 559

Abstract

This study presents a channel-free, micro-well–template-assisted magnetic particle trapping method for efficient single-particle isolation without the need for microfluidic channels. Dual-surface silicon micro-well arrays were fabricated using photolithography, PE-CVD, and DRIE processes, featuring hydrophilic well interiors and hydrophobic outer surfaces to enhance trapping [...] Read more.

This study presents a channel-free, micro-well–template-assisted magnetic particle trapping method for efficient single-particle isolation without the need for microfluidic channels. Dual-surface silicon micro-well arrays were fabricated using photolithography, PE-CVD, and DRIE processes, featuring hydrophilic well interiors and hydrophobic outer surfaces to enhance trapping performance. The proposed method combines magnet-assisted sedimentation with rotational sweeping of a glass slide placed above the micro-well array, enabling rapid and uniform particle confinement within a 250 × 250 well array. Experimental results showed that the trapping efficiency increased with the well width and depth, achieving over 93.8% within three trapping cycles for optimized structures. High single-particle occupancy was obtained for wells of comparable size to the particle diameter, while deeper wells enabled stable trapping with minimal loss. The entire trapping process was completed within five minutes per cycle, demonstrating a rapid, simple, and scalable approach applicable to digital immunoassay systems for ultrasensitive biomolecule detection. Full article

(This article belongs to the Special Issue Microfluidics in Biomedical Research)

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24 pages, 3720 KB

Open AccessEditor’s ChoiceReview

Metallic Particles in Sodium Battery Anodes: A Review

by Rafaela Ruiz, Carlos Pérez-Vicente and Ricardo Alcántara

Micromachines 2025, 16(12), 1391; https://doi.org/10.3390/mi16121391 - 8 Dec 2025

Viewed by 716

Abstract

Sodium-ion batteries have emerged as a promising alternative to lithium-ion systems, due to the abundance and low cost of sodium resources. However, the demand for higher performance is always increasing, and developing new electrode materials and optimizing their behavior in full cells is [...] Read more.

Sodium-ion batteries have emerged as a promising alternative to lithium-ion systems, due to the abundance and low cost of sodium resources. However, the demand for higher performance is always increasing, and developing new electrode materials and optimizing their behavior in full cells is necessary. Their electrochemical performance remains limited by challenges related to the anode materials. A fundamental understanding of electrode materials is essential to advance their practical application, for example, by designing strategies to minimize irreversible processes and enhance the reversible capacity. Thus, the properties of metals, including nanoparticles and clusters, are critical for various types of sodium batteries, such as sodium-ion microbatteries. Additionally, metallic nanoparticles exhibiting special properties are generated in situ at the negative electrode during the electrochemical cycling of certain batteries. This review focuses on their formation mechanisms, structural and electrochemical effects, and strategies to control their distribution and size. Particular attention is given to the interaction between metallic particles and carbon matrices, as well as their influence on capacity. Finally, current limitations and future perspectives for optimizing the properties of the metallic particles in advanced sodium battery anodes are highlighted. Full article

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

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11 pages, 2440 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Internal Temperature Measurement of Optically Levitated Particles in Vacuum by Raman Thermometry

by Kou Li, Jiaming Liu, Xincai Xu, Zhuangzhuang Wang, Nan Li, Han Cai, Wenqiang Li and Huizhu Hu

Micromachines 2025, 16(12), 1388; https://doi.org/10.3390/mi16121388 - 7 Dec 2025

Viewed by 478

Abstract

An optical levitation system in a vacuum is an efficient system to investigate the dynamics of isolated micro- and nanoparticles. However, the motion and stability of the trapped particles in this system can be affected by the internal temperature, which remains a challenge [...] Read more.

An optical levitation system in a vacuum is an efficient system to investigate the dynamics of isolated micro- and nanoparticles. However, the motion and stability of the trapped particles in this system can be affected by the internal temperature, which remains a challenge to measure. Conventional methods are constrained by material specificity or lack the capability for direct temperature measurement. Here, we demonstrate the application of Raman thermometry for non-contact temperature detection of an optically levitated fused silica sphere in vacuum. In addition, the experimental results reveal a linear increase in particle temperature with laser power, consistent with photothermal theory. The integration of Raman thermometry with the optical levitation system enables high-precision thermal sensing at the microscale, offering significant potential for applications in precision metrology and fundamental physics. Full article

(This article belongs to the Special Issue Optical Tweezers and Their Applications)

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16 pages, 2897 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Self-Powered Microfluidic System Based on Double-Layer Rotational Triboelectric Nanogenerator

by Yiming Zhong, Haofeng Li and Dongping Wu

Micromachines 2025, 16(12), 1386; https://doi.org/10.3390/mi16121386 - 6 Dec 2025

Viewed by 585

Abstract

Self-powered microfluidic systems represent a promising direction toward autonomous and portable lab-on-chip technologies, yet conventional electrowetting platforms remain constrained by bulky high-voltage supplies and intricate control circuitry. In this work, we design a triboelectric nanogenerator (TENG)-based microfluidic system that harvests mechanical energy for [...] Read more.

Self-powered microfluidic systems represent a promising direction toward autonomous and portable lab-on-chip technologies, yet conventional electrowetting platforms remain constrained by bulky high-voltage supplies and intricate control circuitry. In this work, we design a triboelectric nanogenerator (TENG)-based microfluidic system that harvests mechanical energy for droplet manipulation without any external electronics. The TENG integrates two triboelectric units with a 25° phase offset, enabling periodic high-voltage generation. Finite element simulations elucidate the electric field distributions of the TENG and microfluidic chip, validating the operating principle of the integrated microfluidic system. Experimental studies further quantify the effects of electrode geometry and rotational speed on the critical drivable droplet volume, demonstrating stable transport over linear, S-shaped, and circular trajectories. Remarkably, the droplet motion direction can be instantaneously reversed by reversing the TENG rotation direction, achieving bidirectional control without auxiliary circuitry. This work establishes a voltage-optimized, structurally tunable, and fully self-powered platform, offering a new paradigm for portable digital microfluidics. Full article

(This article belongs to the Special Issue Celebration of 60th Anniversary of Moore's Law: The Significant Milestone in Micromachines)

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19 pages, 4754 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Small Object Localization with 90% Annotation Reduction by Positive-Unlabeled Learning

by Xiao Zhou, Shihong Wang, Weiguo Hu, Zhaohao Xie, Zheng Pang, Zhuo Jiang and Zhen Cheng

Micromachines 2025, 16(12), 1379; https://doi.org/10.3390/mi16121379 - 3 Dec 2025

Viewed by 458

Abstract

Small object localization is one of the most challenging tasks owing to the poor visual appearance and noisy representation caused by the intrinsic structure of small targets. Recent advances in localizing small objects are mainly dependent on regression-based counting approaches, which require considerable [...] Read more.

Small object localization is one of the most challenging tasks owing to the poor visual appearance and noisy representation caused by the intrinsic structure of small targets. Recent advances in localizing small objects are mainly dependent on regression-based counting approaches, which require considerable annotations for training. As a contrast, human learners can quickly master labeling skills from only a few annotation examples. In this paper, we attempt to simulate this training mechanism and propose a novel positive-unlabeled (PU) learning based approach that can localize small objects by learning from partial point annotations. We evaluate our approach on five typical datasets of small objects involving a single cell, an animal/insect, and human crowds. Quantitative experimental results show that our approach has achieved inspiring localization performance (F1 score > 0.75) even under the supervision of less than 10% of the overall point annotations. This approach paves the way for low-annotation-cost single-cell analysis within microfluidic droplets. Full article

(This article belongs to the Special Issue Microfluidics for Single Cell Detection and Cell Sorting)

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13 pages, 2824 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Development of Metal-Enhanced Fluorescence Nanorods on Micro Post Arrays for Portable Detection of Human Semen Biomarkers

by Seongmin Lee, Won Il Heo, Kui Young Park, Seong Jun Seo, Xun Lu and Seok-min Kim

Micromachines 2025, 16(12), 1378; https://doi.org/10.3390/mi16121378 - 2 Dec 2025

Viewed by 446

Abstract

Rapid and reliable on-site identification of body fluids is essential in forensic and field diagnostic applications. Commercial kits provide only single results and often suffer from cross-reactivity, while conventional microarrays offer multiplex capability but lack sufficient fluorescence intensity for field-deployable systems. In this [...] Read more.

Rapid and reliable on-site identification of body fluids is essential in forensic and field diagnostic applications. Commercial kits provide only single results and often suffer from cross-reactivity, while conventional microarrays offer multiplex capability but lack sufficient fluorescence intensity for field-deployable systems. In this study, we present a highly sensitive nanorods on micro post array (NMPA) substrate and a smartphone-based portable detection system. The NMPA substrate integrates metal nanorods with UV-imprinted micro post structures to produce metal-enhanced fluorescence and improved signal localization. When evaluated using a microarray scanner, the substrate achieved high sensitivity, detecting semen diluted up to 1/100,000. The portable smartphone system further demonstrated simultaneous detection of three semen biomarkers (PSA, ACPP, and Semenogelin-1) at a 1/1000 dilution, matching the detection limit of commercial kits. Specificity tests using blood, saliva, urine, vaginal fluid, and environmental contaminants showed no false-positive responses. These results highlight the potential of the NMPA system as a portable diagnostic technology capable of rapid (<15 min), multiplex, and highly sensitive detection in field environments. Future work will focus on quantitative calibration, substrate stability assessment, and expansion toward multi biomarker panels for broader forensic and clinical applications. Full article

(This article belongs to the Section B4: Point-of-Care Devices)

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9 pages, 1807 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Enhanced Efficiency and Reliability of AlGaN UVC-LED with Tapered Hole Injection Layer

by Linlin Xu, Yang Peng, Feng Wu, Wei Guo, Jiangnan Dai and Changqing Chen

Micromachines 2025, 16(12), 1376; https://doi.org/10.3390/mi16121376 - 2 Dec 2025

Viewed by 487

Abstract

In this work, the electrical and optical performance of AlGaN-based ultraviolet-C light-emitting diodes (UVC-LEDs) with a tapered Al-content hole injection layer was investigated both theoretically and experimentally. A total of 1000 h of real-time electrical stress was conducted to study the degradation process [...] Read more.

In this work, the electrical and optical performance of AlGaN-based ultraviolet-C light-emitting diodes (UVC-LEDs) with a tapered Al-content hole injection layer was investigated both theoretically and experimentally. A total of 1000 h of real-time electrical stress was conducted to study the degradation process of such devices. UVC-LED incorporating a hole injection layer with a larger gradient was found to significantly suppress the degradation process compared to a sample with a smaller tapering gradient. Marginal efficiency droop of only 4.55% as well as 66% improved light output power, were identified for the proposed design under a current density of approximately 100 A/cm². It was unambiguously demonstrated that UVC-LED with a greatly tapered hole injection layer facilitates both electron blocking and hole injection, providing a promising pathway towards the development of high-efficiency UV emitters. Full article

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

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15 pages, 8068 KB

Open AccessFeature PaperEditor’s ChoiceArticle

High-Quality and High-Efficiency Fabrication of Microlens Array by Rotary Profile Cutting Method

by Liheng Gao, Xiuwen Sun, Qian Yu, Yinhui Wang, Md Nasir Uddin, Ruijue Duan, Gang Wang, Zhikang Zhou, Qiuchen Xie, Tao Sun and Tianfeng Zhou

Micromachines 2025, 16(12), 1374; https://doi.org/10.3390/mi16121374 - 1 Dec 2025

Viewed by 457

Abstract

To enhance the fabrication consistency and surface quality of microlens array (MLA) molds, this study presents a high-quality and high-efficiency rotary profile-cutting (RPC) method conducted on a four-axis ultraprecision machining platform. A geometric model is established to define the relationship between tool parameters [...] Read more.

To enhance the fabrication consistency and surface quality of microlens array (MLA) molds, this study presents a high-quality and high-efficiency rotary profile-cutting (RPC) method conducted on a four-axis ultraprecision machining platform. A geometric model is established to define the relationship between tool parameters and microlens structural features, and the toolpath is optimized by refining control points to enhance machining accuracy. In addition, a novel tool-setting error characterization approach is developed, enabling submicron-level positioning of the diamond tool, with errors in the X and Y directions controlled within 1 μm. Experimental validation demonstrates the successful fabrication of a 6 × 6 square-array MLA mold with a curvature radius of 507 μm using the proposed RPC method. Subsequent replication of MLA through precision glass molding (PGM) yielded structures with a peak-to-valley (PV) value below 354 nm and surface roughness (Ra) below 11 nm. Optical performance tests confirm the high consistency and accuracy of the fabricated MLA, highlighting the potential of the proposed RPC technique for advanced optical component manufacturing. Full article

(This article belongs to the Special Issue Ultra-Precision Micro Cutting and Micro Polishing)

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22 pages, 3241 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploring Pump–Probe Response in Exciton–Biexciton Quantum Dot–Metal Nanospheroid Hybrids

by Spyridon G. Kosionis, Dimitrios P. Alevizos and Emmanuel Paspalakis

Micromachines 2025, 16(12), 1319; https://doi.org/10.3390/mi16121319 - 25 Nov 2025

Viewed by 537

Abstract

We study the optical susceptibility of a CdSe-based semiconductor quantum dot with a cascade exciton–biexciton configuration, which is coupled via the Coulomb interaction to a gold spheroidal nanoparticle, in the presence of a nearly resonant strong pump field and a weak probe field. [...] Read more.

We study the optical susceptibility of a CdSe-based semiconductor quantum dot with a cascade exciton–biexciton configuration, which is coupled via the Coulomb interaction to a gold spheroidal nanoparticle, in the presence of a nearly resonant strong pump field and a weak probe field. We take both fields’ polarization vectors to be parallel to the interparticle axis, derive the equations of motion for the density matrix, and proceed with a perturbative expansion approach to calculate the components of the density matrix associated with the effective optical susceptibility, which describes processes to first order in the probe field and to all orders in the pump field. We present spectra of the effective susceptibility and examine their dependence on the metal nanoparticle’s geometric characteristics for various interparticle distances and pump field detunings, under both one- and two-photon resonance conditions. The role of the biexciton energy shift is also studied. Lastly, we introduce a dressed-state picture to elucidate the origin of the observed spectral features. Our calculations reveal that reducing the interparticle distance and increasing the metal nanoparticle aspect ratio enhance the exciton–plasmon coupling, leading to pronounced resonance splitting, spectral shifts, and broadened gain regions. Prolate nanoparticles aligned with the field polarization exhibit the strongest coupling and the widest gain bandwidth, whereas oblate geometries produce nearly overlapping resonances. Under exact resonance, the probe displays zero absorption with a negative dispersion slope, indicating slow-light behavior. These results demonstrate the tunability of hybrid CdSe-Au nanostructures for designing nanoscale optimal amplifiers, modulators, and sensors. Full article

(This article belongs to the Special Issue Emerging Trends in Optoelectronic Device Engineering)

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16 pages, 4549 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Miniature Electromagnetic and Mechanical Resonators for Measurements of Acceleration with the Help of Nitrogen-Vacancy Color Centers

by Marina Rezinkina, Oleg Rezinkin, Fedor Jelezko and Claus Braxmaier

Micromachines 2025, 16(12), 1311; https://doi.org/10.3390/mi16121311 - 23 Nov 2025

Viewed by 2307

Abstract

Using mathematical and physical modeling, we investigate the influence of the configuration and parameters of miniature electromagnetic and mechanical resonators on their output characteristics. Such electromagnetic resonators are required for the microwave excitation of nitrogen-vacancy color centers, which are used as sensors for [...] Read more.

Using mathematical and physical modeling, we investigate the influence of the configuration and parameters of miniature electromagnetic and mechanical resonators on their output characteristics. Such electromagnetic resonators are required for the microwave excitation of nitrogen-vacancy color centers, which are used as sensors for various physical quantities, including acceleration, force, and magnetic field induction. The mechanical resonators under consideration are designed for measuring acceleration using nitrogen–vacancy color centers. As a result of these studies, we selected the types of miniature electromagnetic and mechanical resonators that ensure the efficient operation of nitrogen–vacancy color center sensors. Full article

(This article belongs to the Special Issue Advancing MEMS/MOEMS Sensors: AI-Driven Optimization and Emerging Applications)

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18 pages, 3600 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Active–Passive Vibration Control of Cantilever Beam Based on Magnetic Spring with Negative Stiffness and Piezoelectric Actuator

by Min Wang, Zhiwei Jiang, Wei Jiang, Xianghui Feng, Jiheng Ding, Yi Sun, Huayan Pu and Songquan Liao

Micromachines 2025, 16(12), 1307; https://doi.org/10.3390/mi16121307 - 21 Nov 2025

Viewed by 852

Abstract

To enhance the low-frequency vibration suppression capability of cantilever beams, a magnetically tunable piezoelectric cantilever beam structure (MTPCBS) is proposed in this paper. A magnetic spring with negative stiffness (NSMS) is fixed at the free end of a cantilever beam, forming a quasi-zero-stiffness [...] Read more.

To enhance the low-frequency vibration suppression capability of cantilever beams, a magnetically tunable piezoelectric cantilever beam structure (MTPCBS) is proposed in this paper. A magnetic spring with negative stiffness (NSMS) is fixed at the free end of a cantilever beam, forming a quasi-zero-stiffness structure. Meanwhile, a macro-fiber composite (MFC) patch is bonded near the root of the beam to implement active skyhook damping control for active vibration control. A theoretical model of the cantilever beam, NSMS, and MFC is established, and the displacement transmissibility of the MTPCBS is derived. The influences of the magnet distance of the NSMS and the control gain of the controller are investigated via simulation. Experimental results indicate that compared to the single beam, the effective vibration isolation frequency of the proposed MTPCBS shifts from 15.3 Hz to 4.6 Hz. When subjected to random vibration excitation ranging from 1 to 80 Hz, the root mean square (RMS) value of vibration decreases from 0.03 g to 1.77 × 10⁻³ g, with the vibration attenuation rate improving from −50% to 91%. The proposed MTPCBS and active–passive vibration control method for cantilever beams significantly enhances low-frequency vibration suppression capabilities, providing a feasible strategy for achieving broadband vibration suppression. Full article

(This article belongs to the Special Issue Exploration and Application of Piezoelectric Smart Structures)

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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 710

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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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 557

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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15 pages, 2988 KB

Open AccessFeature PaperEditor’s ChoiceArticle

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

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

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

Cited by 1 | Viewed by 796

Abstract

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

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

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

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12 pages, 2307 KB

Open AccessFeature PaperEditor’s ChoiceArticle

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

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

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

Viewed by 642

Abstract

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

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

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

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11 pages, 1931 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Novel Nano-Scale Biosensor for Measuring Hemoglobin Oxygen Saturation Using Carbon Quantum Dots

by Jeehyun Lee, Xuan Ru Liew, Justin Kok Soon Tan and Sangho Kim

Micromachines 2025, 16(11), 1261; https://doi.org/10.3390/mi16111261 - 6 Nov 2025

Viewed by 3430

Abstract

Hemoglobin oxygen (HbO₂) saturation is a critical biomarker in patient care, yet conventional measurement approaches are often costly and require extensive calibration. To address these limitations, the present study proposes a novel biosensor derived from paper-based carbon quantum dots (CQDs) fabricated [...] Read more.

Hemoglobin oxygen (HbO₂) saturation is a critical biomarker in patient care, yet conventional measurement approaches are often costly and require extensive calibration. To address these limitations, the present study proposes a novel biosensor derived from paper-based carbon quantum dots (CQDs) fabricated through a one-step thermal treatment. CQDs are carbon-based nanoparticles renowned for their excellent biocompatibility, low toxicity, thermal stability, and remarkable optical properties. To quantify HbO₂ saturation, we exploit their photoluminescence, which enables photoinduced electron transfer and fluorescence quenching with hemoglobin. Our results demonstrated that the peak fluorescence intensity of CQDs shows a strong linear correlation with HbO₂ saturation. Variations in HbO₂ saturation levels were achieved with sodium dithionite and determined using Winterbourn’s equations. Our CQD-based HbO₂ saturation measurements closely agreed with those obtained from conventional spectrophotometric analysis. Thus, this investigation highlights the potential of CQDs as a biosensor for effective HbO₂ saturation measuring without extensive calibration. 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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26 pages, 23199 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Development and Validation of a Multimodal Wearable Belt for Abdominal Biosignal Monitoring with Application to Irritable Bowel Syndrome

by Amir Mohammad Karimi Forood, Sibi M. Pandian, Riley Q. McNaboe, Thuany De Carvalho Lachos, Daniel Octavio Lantigua and Hugo F. Posada-Quintero

Micromachines 2025, 16(11), 1255; https://doi.org/10.3390/mi16111255 - 1 Nov 2025

Viewed by 997

Abstract

Visceral pain in Irritable Bowel Syndrome (IBS) is difficult to evaluate objectively due to its complex physiological nature and lack of reliable biomarkers. Given the complexity of IBS, a multimodal physiological monitoring approach, combining electrodermal activity (EDA), electrocardiogram (ECG), and surface electromyography (sEMG), [...] Read more.

Visceral pain in Irritable Bowel Syndrome (IBS) is difficult to evaluate objectively due to its complex physiological nature and lack of reliable biomarkers. Given the complexity of IBS, a multimodal physiological monitoring approach, combining electrodermal activity (EDA), electrocardiogram (ECG), and surface electromyography (sEMG), offers a promising approach to capture the autonomic and muscular responses linked to visceral pain. However, no existing wearable device supports simultaneous EDA, ECG, and sEMG acquisition from the abdomen in a format suitable for long-term, real-world use. This study presents the development and validation of a novel wearable belt for concurrent ECG, sEMG, and EDA monitoring, with EDA measured at both the torso and wrist. The system was built using modified BITalino platforms with custom-fabricated reusable electrodes and Bluetooth connectivity for real-time smartphone display. Signal quality was validated against laboratory-grade systems in 20 healthy participants during a four-stage protocol involving cognitive, orthostatic, muscular, and combined stress tasks. Time and frequency-domain analyses showed high correlations and comparable spectral features across all modalities. The belt maintained stable skin contact even during movement-intensive tasks. By enabling anatomically targeted, multimodal data acquisition, this wearable system supports real-world visceral pain assessment in IBS and is ready for deployment in ambulatory and home-based monitoring scenarios. Full article

(This article belongs to the Special Issue Next-Generation Wearable Technologies: Integrating Smart Sensing, Biomedical Innovation, and Sustainable Energy Solutions)

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29 pages, 2301 KB

Open AccessEditor’s ChoiceReview

Advances in Impedimetric Biosensors: Current Applications and Future Directions

by Ashmit Verma, Mohammad Arqam and Arwa Fraiwan

Micromachines 2025, 16(11), 1244; https://doi.org/10.3390/mi16111244 - 31 Oct 2025

Cited by 1 | Viewed by 1662

Abstract

Impedimetric biosensors have emerged as a versatile class of electrochemical devices, enabling highly sensitive and real-time detection of diverse analytes. Their applications extend across healthcare diagnostics, environmental monitoring, food safety, and agriculture. By virtue of their compact size, high sensitivity, selectivity, portability, and [...] Read more.

Impedimetric biosensors have emerged as a versatile class of electrochemical devices, enabling highly sensitive and real-time detection of diverse analytes. Their applications extend across healthcare diagnostics, environmental monitoring, food safety, and agriculture. By virtue of their compact size, high sensitivity, selectivity, portability, and ease of operation, these sensors have advanced rapidly in both research and practical applications. This review consolidates the wide spectrum of current applications and technological advances reported in the literature. Additionally, it examines the prospects of integrating impedimetric biosensors with emerging technology fields, including artificial intelligence, machine learning, and flexible and wearable devices. By providing an overview of the different categories of impedimetric biosensors, their detection strategies, sensing modalities, and applications, this review presents a comprehensive perspective on the current progress and future opportunities in impedimetric biosensing. Full article

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

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14 pages, 16744 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Robotic Drop-Coating Graphite–Copper PDMS Soft Pressure Sensor with Fabric-Integrated Electrodes for Wearable Devices

by Zeping Yu, Yunhao Zhang, Lingpu Ge, Daisuke Miyata, Zhongnan Pu, Chenghong Lu and Lei Jing

Micromachines 2025, 16(11), 1247; https://doi.org/10.3390/mi16111247 - 31 Oct 2025

Viewed by 1026

Abstract

Flexible pressure sensors are essential for wearable electronics, human–machine interfaces, and soft robotics. However, conventional Polydimethylsiloxane (PDMS)-based sensors often suffer from limited conductivity, poor filler dispersion, and low structural integration with textile substrates. In this work, we present a robotic drop-coating approach for [...] Read more.

Flexible pressure sensors are essential for wearable electronics, human–machine interfaces, and soft robotics. However, conventional Polydimethylsiloxane (PDMS)-based sensors often suffer from limited conductivity, poor filler dispersion, and low structural integration with textile substrates. In this work, we present a robotic drop-coating approach for fabricating graphite–copper nanoparticle (G-CuNP)/PDMS composite pressure sensors with textile-integrated electrodes. By precisely controlling droplet deposition, a three-layer sandwiched structure was realized that ensures uniformity and scalability while avoiding the drawbacks of conventional full-line coating. The effects of filler loading and graphite nanoparticle (GNP) and copper nanoparticle (CuNP) ratios were systematically investigated, and the optimized sensor was obtained at 40 wt% total fillers with a graphite content of 55 wt%. The fabricated device exhibited high sensitivity in the low-pressure region, stable performance in the medium- and high-pressure ranges, and an exponential saturation fitting with R² = 0.998. The average hysteresis was 7.42%, with excellent cyclic stability over 1000 loading cycles. Furthermore, a hand-shaped sensor matrix composed of five distributed sensing units successfully distinguished grasping behaviors of lightweight and heavyweight objects, demonstrating multipoint force mapping capability. This study highlights the advantages of robotic drop-coating for scalable fabrication and provides a promising pathway toward low-cost, reliable, and wearable soft pressure sensors. Full article

(This article belongs to the Section A：Physics)

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46 pages, 13590 KB

Open AccessEditor’s ChoiceReview

A Review of Optical Metrology Techniques for Advanced Manufacturing Applications

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

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

Cited by 2 | Viewed by 5462

Abstract

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

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

(This article belongs to the Section A：Physics)

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33 pages, 3868 KB

Open AccessEditor’s ChoiceReview

Application of Polymer Lubricants in Triboelectric Energy Harvesting: A Review

by Ali Nawaz and Hong-Joon Yoon

Micromachines 2025, 16(11), 1195; https://doi.org/10.3390/mi16111195 - 22 Oct 2025

Viewed by 932

Abstract

The range of lubricant applications has broadened to include multiple sectors, aiming to optimize the operational efficiency of mechanical systems. Given their adaptable friction-reducing properties, lubricants have recently been incorporated into energy harvesting technologies such as triboelectric nanogenerators (TENGs). In such devices, lubricants [...] Read more.

The range of lubricant applications has broadened to include multiple sectors, aiming to optimize the operational efficiency of mechanical systems. Given their adaptable friction-reducing properties, lubricants have recently been incorporated into energy harvesting technologies such as triboelectric nanogenerators (TENGs). In such devices, lubricants are essential for mitigating wear, facilitating heat dissipation, eliminating contaminants, and prolonging the service life of mechanically actuated energy harvesters. Notably, emerging developments in sliding and rotational-mode TENGs leverage lubricants to improve electrical output while reducing interface degradation. However, despite significant potential, TENGs still face inherent challenges, including interface friction and energy losses from air breakdown. Recent research indicates that these drawbacks can be effectively addressed by the intentional use of polymer-based lubricants, which contribute to maintaining micro/nanostructured surfaces and minimizing air breakdown, thereby enhancing charge storage capability and increasing device robustness. This review systematically examines the categories, physicochemical attributes, and operational roles of polymeric lubricants used in TENG technology. It underscores their combined function is both primary and support materials to augment triboelectric efficiency. In addition, the article assesses how different lubricants impact device performance and durability, providing a critical analysis of their suitability based on the operational benchmarks of lubricant-embedded TENG configurations. Full article

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

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30 pages, 7417 KB

Open AccessEditor’s ChoiceReview

Towards Advanced Materials: Functional Perspectives of Co-Doped ZnO Thin Films

by Mariuca Gartner, Mariana Chelu, Anna Szekeres and Peter Petrik

Micromachines 2025, 16(10), 1179; https://doi.org/10.3390/mi16101179 - 18 Oct 2025

Cited by 3 | Viewed by 1686

Abstract

Zinc oxide (ZnO) thin films have attracted increasing attention as promising materials for sensing applications due to their wide band gap, high exciton binding energy, and remarkable chemical stability. However, the inherent limitations of pure ZnO, such as moderate sensitivity, selectivity, and relatively [...] Read more.

Zinc oxide (ZnO) thin films have attracted increasing attention as promising materials for sensing applications due to their wide band gap, high exciton binding energy, and remarkable chemical stability. However, the inherent limitations of pure ZnO, such as moderate sensitivity, selectivity, and relatively high operating temperatures, limit its widespread use in advanced sensing technologies. Co-doping, or dual doping with two distinct elements, has emerged as an effective strategy to overcome these challenges by synergistically tailoring the structural, electronic, and surface properties of ZnO thin films. This review provides a comprehensive overview of recent advances in the development of co-doped ZnO thin films for sensing applications. The focus is on the role of different combinations of dopants, including transition metals, rare earth elements, and non-metals, in modulating the charge carrier concentration, oxygen vacancy density, and adsorption dynamics. These effects collectively enhance the sensing properties and long-term stability and reduce detection limits. The analysis highlights the correlations between synthesis methods, dopant incorporation mechanisms, and resulting sensor performance. Key challenges such as dopant clustering, reproducibility, and scalability are discussed, along with emerging opportunities in flexible room-temperature sensor platforms. Overall, it has been demonstrated that co-doped ZnO thin films represent a versatile and tunable class of sensing materials with strong potential for next-generation environmental and biomedical monitoring. Full article

(This article belongs to the Special Issue Functional Thin Films in Semiconductor Devices and Various Sensing Technologies)

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23 pages, 18716 KB

Open AccessEditor’s ChoiceReview

Electromagnetic Tracking System for Medical Micro Devices: A Review

by Mingshan He, Aoji Zhu and Lidong Yang

Micromachines 2025, 16(10), 1175; https://doi.org/10.3390/mi16101175 - 16 Oct 2025

Viewed by 2691

Abstract

Minimally invasive surgery (MIS) has become increasingly favored by both patients and surgeons owing to its advantages such as shortened recovery times and reduced surgical trauma. To enhance intraoperative feedback from surgical instruments while minimizing harmful radiation exposure, a wide range of electromagnetic [...] Read more.

Minimally invasive surgery (MIS) has become increasingly favored by both patients and surgeons owing to its advantages such as shortened recovery times and reduced surgical trauma. To enhance intraoperative feedback from surgical instruments while minimizing harmful radiation exposure, a wide range of electromagnetic tracking systems (EMTS) has been developed at micro scales for medical applications. This review provides a comprehensive summary of advances in the field over the past five years, with an emphasis on the working principles of EMTS, system architecture, current research progress, and clinical applications. In comparison to other review papers, this article focuses specifically on EMTS for medical micro-devices, such as robotic catheters, endoscopes, and capsule robots. Moreover, Representative research studies and commercial systems are presented along with their clinical implementations, placing greater emphasis on the translation of EMTS into medical applications. Finally, this review outlines and discusses future research directions, highlighting major challenges and potential opportunities for advancing the integration of EMTS into routine clinical workflows. Full article

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

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13 pages, 3442 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Patterning Fidelity Enhancement and Aberration Mitigation in EUV Lithography Through Source–Mask Optimization

by Qi Wang, Qiang Wu, Ying Li, Xianhe Liu and Yanli Li

Micromachines 2025, 16(10), 1166; https://doi.org/10.3390/mi16101166 - 14 Oct 2025

Cited by 1 | Viewed by 1523

Abstract

Extreme ultraviolet (EUV) lithography faces critical challenges in aberration control and patterning fidelity as technology nodes shrink below 3 nm. This work demonstrates how Source–Mask Optimization (SMO) simultaneously addresses both illumination and mask design to enhance pattern transfer accuracy and mitigate aberrations. Through [...] Read more.

Extreme ultraviolet (EUV) lithography faces critical challenges in aberration control and patterning fidelity as technology nodes shrink below 3 nm. This work demonstrates how Source–Mask Optimization (SMO) simultaneously addresses both illumination and mask design to enhance pattern transfer accuracy and mitigate aberrations. Through a comprehensive optimization framework incorporating key process metrics, including critical dimension (CD), exposure latitude (EL), and mask error factor (MEF), we achieve significant improvements in imaging quality and process window for 40 nm minimum pitch patterns, representative of 2 nm node back-end-of-line (BEOL) requirements. Our analysis reveals that intelligent SMO implementation not only enables robust patterning solutions but also compensates for inherent EUV aberrations by balancing source characteristics with mask modifications. On average, our results show a 4.02% reduction in CD uniformity variation, concurrent with a 1.48% improvement in exposure latitude and a 5.45% reduction in MEF. The proposed methodology provides actionable insights for aberration-aware SMO strategies, offering a pathway to maintain lithographic performance as feature sizes continue to scale. These results underscore SMO’s indispensable role in advancing EUV lithography capabilities for next-generation semiconductor manufacturing. Full article

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

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14 pages, 4357 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Thermal Gas Flow Sensor Using SiGe HBT Oscillators Based on GaN/Si SAW Resonators

by Wenpu Cui, Jie Cui, Wenchao Zhang, Guofang Yu, Di Zhao, Jingqing Du, Zhen Li, Jun Fu and Tianling Ren

Micromachines 2025, 16(10), 1151; https://doi.org/10.3390/mi16101151 - 10 Oct 2025

Viewed by 677

Abstract

This paper presents a thermal gas flow sensing system, from surface acoustic wave (SAW) temperature sensor to oscillation circuit and multi-module miniaturization integration. A single-port GaN/Si SAW resonator with single resonant mode and excellent characteristics was fabricated. Combined with an in-house-developed SiGe HBT, [...] Read more.

This paper presents a thermal gas flow sensing system, from surface acoustic wave (SAW) temperature sensor to oscillation circuit and multi-module miniaturization integration. A single-port GaN/Si SAW resonator with single resonant mode and excellent characteristics was fabricated. Combined with an in-house-developed SiGe HBT, a temperature-sensitive high-frequency oscillator was constructed. Under constant temperature control, system-level flow measurement was achieved through dual-oscillation configuration and modular integration. The fabricated SAW device shows a temperature coefficient of frequency (TCF) −28.29 ppm/K and temperature linearity 0.998. The oscillator operates at 1.91 GHz with phase noise of −97.72/−118.62 dBc/Hz at 10/100 kHz offsets. The system demonstrates excellent dynamic response and repeatability, directly measuring 0–50 sccm flows. For higher flows (>50 sccm), a shunt technique extends the test range based on the 0–10 sccm linear region, where response time is <1 s with error <0.9%. Non-contact operation ensures high stability and long lifespan. The sensor shows outstanding performance and broad application prospects in flow measurement. Full article

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32 pages, 4265 KB

Open AccessEditor’s ChoiceReview

A Review on Biomedical, Biomolecular, and Environmental Monitoring Applications of Cysteamine Functionalized Nanomaterials

by Muthaiah Shellaiah

Micromachines 2025, 16(10), 1144; https://doi.org/10.3390/mi16101144 - 8 Oct 2025

Cited by 2 | Viewed by 1299

Abstract

Functionalizing agents enhance the photophysical properties of nanomaterials, thereby broadening their applications. Among these agents, cysteamine (SH-(CH₂)₂-NH₂) is unique because of its free thiol (-SH) and amino (-NH₂) groups. The presence of free -SH or [...] Read more.

Functionalizing agents enhance the photophysical properties of nanomaterials, thereby broadening their applications. Among these agents, cysteamine (SH-(CH₂)₂-NH₂) is unique because of its free thiol (-SH) and amino (-NH₂) groups. The presence of free -SH or -NH₂ groups significantly enhances the functionalization of highly stable nanomaterials. These stable nanomaterials, which contain free -SH or -NH₂ groups, can effectively bind with biomedical, biomolecular, and environmental analytes, improving sensor performance and making them valuable materials. In this context, cysteamine-functionalized nanoparticles (NPs), quantum dots (QDs), nanoclusters (NCs), nanocomposites, and other nanostructures have been demonstrated to be useful for quantifying biomedical, biomolecular, and environmental analytes. To date, no review has outlined the functionalizing ability of cysteamine or the application of cysteamine-functionalized nanomaterials in biomedical, biomolecular, and environmental analyte monitoring. This review emphasizes the role of cysteamine in producing stable nanomaterials and detecting specific biomedical, biomolecular, and ecological analytes. It also covers general protocols for functionalizing with cysteamine, the mechanistic basis of analyte detection, and their advantages, limitations, and prospects. Full article

(This article belongs to the Special Issue Nanoparticle-Based (Bio)Sensors for Biomedical and Environmental Monitoring)

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20 pages, 4013 KB

Open AccessEditor’s ChoiceReview

Bioengineering 3D Pancreatic Cancer Models with Fibrotic Stroma for In Vitro Cancer Modeling

by Xingrun Lan, Keke Chen and Xiaoyun Wei

Micromachines 2025, 16(10), 1140; https://doi.org/10.3390/mi16101140 - 2 Oct 2025

Viewed by 1968

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains highly lethal due to late diagnosis, high malignancy, and profound resistance to therapy. Traditional two-dimensional (2D) cell cultures fail to recapitulate the complex tumor microenvironment (TME), especially the fibrotic stroma, which is crucial for the progression of PDAC [...] Read more.

Pancreatic ductal adenocarcinoma (PDAC) remains highly lethal due to late diagnosis, high malignancy, and profound resistance to therapy. Traditional two-dimensional (2D) cell cultures fail to recapitulate the complex tumor microenvironment (TME), especially the fibrotic stroma, which is crucial for the progression of PDAC and drug response. In vitro three-dimensional (3D) models, which provide more physiologically relevant features such as tight cell–cell and cell-extracellular matrix (ECM) interactions, as well as 3D architecture, have been regarded as highly promising models in PDAC research. This review summarizes some representative in vitro PDAC models, including 3D spheroids, tumor-on-a-chip, bioprinted constructs, and patient-derived organoids (PDOs), particularly focused on the advances in bioengineering strategies for the integration of the key stomal components for microenvironment recapitulation and their applications. Additionally, we discuss the current challenges facing 3D models and propose potential strategies for constructing in vitro models that more accurately simulate the pathophysiology of the fibrotic stroma, aiming for their application in clinical settings. Full article

(This article belongs to the Special Issue 3D Tissue Engineering Techniques and Their Applications)

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28 pages, 3829 KB

Open AccessEditor’s ChoiceReview

Automated Platforms in C. elegans Research: Integration of Microfluidics, Robotics, and Artificial Intelligence

by Tasnuva Binte Mahbub, Parsa Safaeian and Salman Sohrabi

Micromachines 2025, 16(10), 1138; https://doi.org/10.3390/mi16101138 - 1 Oct 2025

Viewed by 4182

Abstract

Caenorhabditis elegans is one of the most extensively studied model organisms in biology. Its advantageous features, including genetic homology with humans, conservation of disease pathways, transparency, short lifespan, small size and ease of maintenance have established it as a powerful system for research [...] Read more.

Caenorhabditis elegans is one of the most extensively studied model organisms in biology. Its advantageous features, including genetic homology with humans, conservation of disease pathways, transparency, short lifespan, small size and ease of maintenance have established it as a powerful system for research in aging, genetics, molecular biology, disease modeling and drug discovery. However, traditional methods for worm handling, culturing, scoring and imaging are labor-intensive, low throughput, time consuming, susceptible to operator variability and environmental influences. Addressing these challenges, recent years have seen rapid innovation spanning microfluidics, robotics, imaging platforms and AI-driven analysis in C. elegans-based research. Advances include micromanipulation devices, robotic microinjection systems, automated worm assays and high-throughput screening platforms. In this review, we first summarize foundational developments prior to 2020 that shaped the field, then highlight breakthroughs from the past five years that address key limitations in throughput, reproducibility and scalability. Finally, we discuss ongoing challenges and future directions for integrating these technologies into next-generation automated C. elegans research. Full article

(This article belongs to the Special Issue Advances in Microfluidic Chips for Chemical and Biomedical Applications)

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28 pages, 5109 KB

Open AccessEditor’s ChoiceReview

Advances in Silicon-Based UV Light Detection

by Arif Kamal, Seongin Hong and Heongkyu Ju

Micromachines 2025, 16(10), 1130; https://doi.org/10.3390/mi16101130 - 30 Sep 2025

Viewed by 1842

Abstract

Silicon (Si), the cornerstone semiconductor in the micro-electronics industry, can provide a cost-efficient platform with mature technologies for photodetection in visible and near-infrared regions. However, its intrinsic properties, such as a narrow bandgap and the shallow penetration depth of ultraviolet (UV) light into [...] Read more.

Silicon (Si), the cornerstone semiconductor in the micro-electronics industry, can provide a cost-efficient platform with mature technologies for photodetection in visible and near-infrared regions. However, its intrinsic properties, such as a narrow bandgap and the shallow penetration depth of ultraviolet (UV) light into its surface with surface trap states, remain challenges, rendering it unsuitable for effective UV light detection. Various techniques have been reported to circumvent these surface defect-induced difficulties. In addition, wide-bandgap semiconductors that favor UV light absorption in a solar-blind way have been combined with Si for UV light detection in order to retain the device’s compatibility with Si-CMOS processes, though it still faces challenges that need to be overcome. This review starts with concepts of basic parameters of photodetectors and categorizes UV photodetectors according to their detection mechanisms. We also present a review of wide-bandgap semiconductor-based UV light detectors and those based on Si, with a discussion of surface defect minimization. In addition, we review the hybrid structure of the two kinds, i.e., wide-bandgap semiconductors and Si, and discuss their properties that produce synergistic effects. Lastly, we provide conclusions and outlooks for the possible development of next-generation UV light detectors based on Si. Full article

(This article belongs to the Special Issue Photodetectors and Their Applications)

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25 pages, 9895 KB

Open AccessEditor’s ChoiceReview

Harnessing Microfluidics for the Effective and Precise Synthesis of Advanced Materials

by Xinlei Qi and Guoqing Hu

Micromachines 2025, 16(10), 1106; https://doi.org/10.3390/mi16101106 - 28 Sep 2025

Viewed by 2360

Abstract

Microfluidic methods are powerful platforms for synthesizing advanced functional materials because they allow for precise control of microscale reaction environments. Microfluidics manipulates reactants in lab-on-a-chip systems to enable the fabrication of highly uniform materials with tunable properties, which are crucial for drug delivery, [...] Read more.

Microfluidic methods are powerful platforms for synthesizing advanced functional materials because they allow for precise control of microscale reaction environments. Microfluidics manipulates reactants in lab-on-a-chip systems to enable the fabrication of highly uniform materials with tunable properties, which are crucial for drug delivery, diagnostics, catalysis, and nanomaterial design. This review emphasizes recent progress in microfluidic technologies for synthesizing functional materials, with a focus on polymeric, hydrogel, lipid-based, and inorganic particles. Microfluidics provides exceptional control over the size, morphology, composition, and surface chemistry of materials, thereby enhancing their performance through uniformity, tunability, hierarchical structuring, and on-chip functionalization. Our review provides novel insights by linking material design strategies with fabrication methods tailored to biomedical applications. We also discuss emerging trends, such as AI-driven optimization, automation, and sustainable microfluidic practices, offering a practical and forward-looking perspective. As the field advances toward robust, standardized, and user-friendly platforms, microfluidics has the potential to increase industrial adoption and enable on-demand solutions in nanotechnology and personalized medicine. Full article

(This article belongs to the Special Issue Advances in Microfluidic Chips for Chemical and Biomedical Applications)

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19 pages, 7670 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A CMOS Hybrid System for Non-Invasive Hemoglobin and Oxygen Saturation Monitoring with Super Wavelength Infrared Light Emitting Diodes

by Hyunjin Park, Seoyeon Kang, Jiwon Kim, Jeena Lee, Somi Park and Sung-Min Park

Micromachines 2025, 16(10), 1086; https://doi.org/10.3390/mi16101086 - 25 Sep 2025

Viewed by 942

Abstract

This paper presents a CMOS-based hybrid system capable of noninvasively quantifying the total hemoglobin (tHb), the oxygen saturation (SpO₂), and the heart rate (HR) by utilizing five-wavelength (670, 770, 810, 850, and 950 nm) photoplethysmography. Conventional pulse oximeters are limited to [...] Read more.

This paper presents a CMOS-based hybrid system capable of noninvasively quantifying the total hemoglobin (tHb), the oxygen saturation (SpO₂), and the heart rate (HR) by utilizing five-wavelength (670, 770, 810, 850, and 950 nm) photoplethysmography. Conventional pulse oximeters are limited to the measurements of SpO₂ and heart rate, therefore hindering the real-time estimation of tHb that is clinically essential for monitoring anemia, chronic diseases, and postoperative recovery. Therefore, the proposed hybrid system enables us to distinguish between the concentrations of oxygenated (HbO₂) and deoxygenated hemoglobin (Hb) by using the absorption characteristics of five wavelengths from the visible to near-infrared range. This CMOS hybrid mixed-signal architecture includes a light emitting diode (LED) driver as a transmitter and an optoelectronic receiver with on-chip avalanche photodiodes, followed by a field-programmable gate array (FPGA) for a real-time signal processing pipeline. The proposed hybrid system, validated through post-layout simulations and algorithmic verification, achieves high precision with ±0.3 g/dL accuracy for tHb and ±1.5% for SpO₂, while the heart rate is extracted via 1024-point Fast Fourier Transform (FFT) with an error below ±0.2%. These results demonstrate the potential of a CMOS-based hybrid system as a feasible solution to achieve real-time, low-power, and high-accuracy analysis of bio-signals for clinical and home-use applications. Full article

(This article belongs to the Special Issue Celebration of 60th Anniversary of Moore's Law: The Significant Milestone in Micromachines)

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23 pages, 4516 KB

Open AccessEditor’s ChoiceReview

Photoelectrochemical Oxidation and Etching Methods Used in Fabrication of GaN-Based Metal-Oxide-Semiconductor High-Electron Mobility Transistors and Integrated Circuits: A Review

by Ching-Ting Lee and Hsin-Ying Lee

Micromachines 2025, 16(10), 1077; https://doi.org/10.3390/mi16101077 - 23 Sep 2025

Viewed by 862

Abstract

The photoelectrochemical oxidation method was utilized to directly grow a gate oxide layer and simultaneously create gate-recessed regions for fabricating GaN-based depletion-mode metal-oxide-semiconductor high-electron mobility transistors (D-mode MOSHEMTs). The LiNbO₃ gate ferroelectric layer and stacked gate oxide layers of LiNbO₃/HfO [...] Read more.

The photoelectrochemical oxidation method was utilized to directly grow a gate oxide layer and simultaneously create gate-recessed regions for fabricating GaN-based depletion-mode metal-oxide-semiconductor high-electron mobility transistors (D-mode MOSHEMTs). The LiNbO₃ gate ferroelectric layer and stacked gate oxide layers of LiNbO₃/HfO₂/Al₂O₃ were respectively deposited on the created gate-recessed regions using the photoelectrochemical etching method to fabricate the GaN-based enhancement mode MOSHEMTs (E-mode MOSHEMTs). GaN-based complementary integrated circuits were realized by monolithically integrating the D-mode MOSHEMTs and the E-mode MOSHEMTs. The performances of the inverter circuit manufactured using the integrated GaN-based complementary MOSHEMTs were measured and analyzed. Full article

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

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14 pages, 3445 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Hybrid Actuation MEMS Micromirror with Decoupled Piezoelectric Fast Axis and Electromagnetic Slow Axis for Crosstalk Suppression

by Haoxiang Li, Jiapeng Hou, Zheng Gong, Huijun Yu, Yue Liu and Wenjiang Shen

Micromachines 2025, 16(9), 1072; https://doi.org/10.3390/mi16091072 - 22 Sep 2025

Cited by 2 | Viewed by 3535

Abstract

Electromagnetic micro-electro-mechanical system (MEMS) micromirrors are widely used in optical scanning systems but often encounter mechanical crosstalk due to the use of shared drive coils. This phenomenon leads to parasitic motion along the slow axis during fast-axis operation, resulting in undesirable elliptical scanning [...] Read more.

Electromagnetic micro-electro-mechanical system (MEMS) micromirrors are widely used in optical scanning systems but often encounter mechanical crosstalk due to the use of shared drive coils. This phenomenon leads to parasitic motion along the slow axis during fast-axis operation, resulting in undesirable elliptical scanning patterns that degrade image quality. To tackle this issue, a hybrid actuation scheme is proposed in which a piezoelectric actuator drives the fast axis through an S-shaped spring structure, achieving a resonance frequency of 792 Hz, while the slow axis is independently driven by an electromagnetic actuator operating in quasi-static mode. Finite element simulations and experimental measurements validate that the proposed decoupled design significantly suppresses mechanical crosstalk. When the fast axis is driven to a 40° optical scan angle, the hybrid system reduces the parasitic slow-axis deflection (typically around 1.43°) to a negligible level, thereby producing a clean single-line scan. The piezoelectric fast axis exhibits a quality factor of Q = 110, while the electromagnetic slow axis achieves a linear 20° deflection at 20 Hz. This hybrid design facilitates a distortion-free field of view measuring 40° × 20° with uniform line spacing, presenting a straightforward and effective solution for high-precision scanning applications such as LiDAR (Light Detection and Ranging) and structured light projection. Full article

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

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23 pages, 8269 KB

Open AccessFeature PaperEditor’s ChoiceArticle

A Novel Double-Diamond Microreactor Design for Enhanced Mixing and Nanomaterial Synthesis

by Qian Peng, Guangzu Wang, Chao Sheng, Haonan Wang, Yao Fu and Shenghong Huang

Micromachines 2025, 16(9), 1058; https://doi.org/10.3390/mi16091058 - 18 Sep 2025

Cited by 1 | Viewed by 1049

Abstract

This study introduces the Double-Diamond Reactor (DDR), a novel planar passive microreactor designed to overcome the following conventional limitations: inefficient mass transfer, high flow resistance, and clogging. The DDR integrates splitting–turning–impinging (STI) hydrodynamic principles via CFD-guided optimization, generating chaotic advection to enhance mixing. [...] Read more.

This study introduces the Double-Diamond Reactor (DDR), a novel planar passive microreactor designed to overcome the following conventional limitations: inefficient mass transfer, high flow resistance, and clogging. The DDR integrates splitting–turning–impinging (STI) hydrodynamic principles via CFD-guided optimization, generating chaotic advection to enhance mixing. Experimental evaluations using Villermaux–Dushman tests showed a segregation index (

X_{s}

) as low as 0.027 at 100 mL·min⁻¹, indicating near-perfect mixing. In BaSO₄ nanoparticle synthesis, the DDR achieved a 46% smaller average particle size (95 nm) and narrower distribution (

σ_{g} = 1.27

) compared to reference designs (AFR-1), while maintaining low pressure drops (<20 kPa at 60 mL·min⁻¹). The DDR’s superior performance stems from its hierarchical flow division and concave-induced vortices, which eliminate stagnant zones. This work demonstrates the DDR’s potential for high-throughput nanomaterial synthesis with precise control over particle characteristics, offering a scalable and energy-efficient solution for advanced chemical processes. Full article

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

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16 pages, 1847 KB

Open AccessFeature PaperEditor’s ChoiceArticle

The Fluidic Shear Stress Loading Method Enables Mechanobiological Stimulation in an On-Chip Pump-Integrated Microphysiological System

by Jin Hong Yap, Satoshi Ishizaki, Hiroko Nakamura, Kenta Shinha and Hiroshi Kimura

Micromachines 2025, 16(9), 1051; https://doi.org/10.3390/mi16091051 - 15 Sep 2025

Viewed by 1393

Abstract

Microphysiological systems (MPSs), such as organ-on-a-chip platforms, are promising alternatives to animal testing for drug development and physiological research. The BioStellar™ Plate is a commercial MPS platform featuring an open-top culture chamber design with on-chip stirrer pumps that circulate culture medium through six [...] Read more.

Microphysiological systems (MPSs), such as organ-on-a-chip platforms, are promising alternatives to animal testing for drug development and physiological research. The BioStellar™ Plate is a commercial MPS platform featuring an open-top culture chamber design with on-chip stirrer pumps that circulate culture medium through six independent, dual microchannel-connected chamber multiorgan units. Although this design enables a circular flow, the open-top culture chamber format prevents the application of fluidic shear stress, a force that cells experience in vivo, which affects their behavior and function. To address this, we developed two fluidic shear stress attachments for the BioStellar™ Plate. These attachment channel fluids provide controlled mechanical stimulation to cultured cells. The flow dynamics were simulated using COMSOL Multiphysics to estimate shear stress levels. The attachments were fabricated and validated through fluorescent bead tracking and biological assays. The FSSA-D is designed for flat-bottom standard cell cultures, while the FSSA-I is designed for epithelial monolayers, enabling the application of fluidic shear stress across the basal membrane. Experiments with intestinal epithelial cells (Caco-2) demonstrated that both attachments enhanced cell barrier function under a fluidic environment, as indicated by higher transepithelial electrical resistance (TEER). These findings demonstrate that the attachments are practical tools for mechanobiology research with MPS platforms. Full article

(This article belongs to the Special Issue Micro-/Nanofluidic and Lab-on-a-Chip Devices for Biomedical Applications, 3rd Edition)

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53 pages, 2691 KB

Open AccessFeature PaperEditor’s ChoiceReview

Heterogeneous Integration Technology Drives the Evolution of Co-Packaged Optics

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

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

Cited by 1 | Viewed by 6826

Abstract

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

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

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

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22 pages, 4991 KB

Open AccessFeature PaperEditor’s ChoiceReview

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

by Junoh Lee and Sun-Je Kim

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

Cited by 4 | Viewed by 4063

Abstract

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

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

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

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19 pages, 5988 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Design of Hydrogel Microneedle Arrays for Physiology Monitoring of Farm Animals

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

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

Viewed by 1459

Abstract

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

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

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

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46 pages, 3495 KB

Open AccessFeature PaperEditor’s ChoiceReview

Assembly and Interconnection Technologies for 3D Plastic Circuit Carriers: An Overview of Technologies, Materials, and Applications

by Kai Werum, Wolfgang Eberhardt, Dieter Reenaers, Thomas Mager, Mika Endl, André Zimmermann and Wim Deferme

Micromachines 2025, 16(9), 980; https://doi.org/10.3390/mi16090980 - 26 Aug 2025

Viewed by 2913

Abstract

This paper aims to present an overview of the state-of-the-art materials and technologies that can be used to create electronic circuits on 3D plastic carriers also known as 3D electronics. Strategies for print-based and laser-based 3D electronics will be discussed as well as [...] Read more.

This paper aims to present an overview of the state-of-the-art materials and technologies that can be used to create electronic circuits on 3D plastic carriers also known as 3D electronics. Strategies for print-based and laser-based 3D electronics will be discussed as well as the techniques to apply the circuit carrier and the way interconnection technology can be used to combine electronic components on top of the circuit carrier. A basic explanation of the functional principles, materials, and applications is given for different substrate and interconnection technologies. The aim is to make it easier to compare different technologies and its required materials to make the right decisions on what technology is best suited for the job. For this purpose, comparison tables for 3D plastic circuit carrier technologies and substrate materials considering their temperature stability were created. It can be concluded that there are a lot of influencing factors that determine which technologies are best suited for application. The most important factors are the 3D complexity and the field of application, the required structure size of the circuit, and the required production quantity. Full article

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

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23 pages, 3673 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Backpropagation Neural Network-Based Prediction Model of Marble Surface Quality Cut by Diamond Wire Saw

by Hui Dong, Fan Cui, Zhipu Huo and Yufei Gao

Micromachines 2025, 16(9), 971; https://doi.org/10.3390/mi16090971 - 23 Aug 2025

Viewed by 1007

Abstract

Marble is widely used in the field of construction and home decoration because of its high strength, high hardness and good wear resistance. Diamond wire sawing has been applied in marble cutting in industry due to its features such as low material loss, [...] Read more.

Marble is widely used in the field of construction and home decoration because of its high strength, high hardness and good wear resistance. Diamond wire sawing has been applied in marble cutting in industry due to its features such as low material loss, high cutting accuracy and low noise. The sawing surface quality directly affects the subsequent processing efficiency and economic benefit of marble products. The surface quality is affected by multiple parameters such as process parameters and workpiece sizes, making it difficult to accurately predict through traditional empirical equations or linear models. To improve prediction accuracy, this paper proposes a prediction model based on backpropagation (BP) neural network. Firstly, through the experiments of sawing marbles with the diamond wire saw, the datasets of surface roughness and waviness under different process parameters were obtained. Secondly, a BP neural network model was established, and the mixed-strategy-improved whale optimization algorithm (IWOA) was used to optimize the initial weight and threshold of the network, and established the IWOA-BP neural network model. Finally, the performance of the model was verified by comparison with the traditional models. The results showed that the IWOA-BP neural network model demonstrated the optimal prediction performance in both the surface roughness Ra and waviness Wa. The minimum predicted values of the root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) were 0.0342%, 0.0284% and 1.5614%, respectively, which proved that the model had higher prediction accuracy. This study provides experimental basis and technical support for the prediction of the surface quality of marble material cut by diamond wire saw. Full article

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

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