Micromachines

25 pages, 1891 KiB

Open AccessArticle

Research on Pneumatic Proportional Pressure Valve Based on Silicon Microfluidic Chip with V-Shaped Electrothermal Microactuator

by Jun Zhang, Chengjie Zhou and Yangfang Wu

Micromachines 2025, 16(5), 566; https://doi.org/10.3390/mi16050566 - 8 May 2025

Abstract

This study presents a pneumatic proportional pressure valve employing a silicon microfluidic chip (SMC) integrated with a V-shaped electrothermal microactuator, aiming to address the limitations of traditional solenoid-based valves in miniaturization and high-precision control. The SMC, fabricated via MEMS technology, leverages the thermal [...] Read more.

This study presents a pneumatic proportional pressure valve employing a silicon microfluidic chip (SMC) integrated with a V-shaped electrothermal microactuator, aiming to address the limitations of traditional solenoid-based valves in miniaturization and high-precision control. The SMC, fabricated via MEMS technology, leverages the thermal expansion of microactuator ribs to regulate pressure through adjustable orifices. A first-order transfer function between input voltage and displacement of the microactuator was derived through theoretical modeling and validated via COMSOL Multiphysics 5.2a simulations. Key geometric parameters of the actuator ribs—cross-section, number, inclination angle, width, span length and thickness—were analyzed for their influence on lever mechanism displacement, actuator displacement, static gain and time constant. AMESim 16.0-based simulations of single- and dual-chip valve structures revealed that increasing ζ shortens step-response rise time, while reducing τ improves hysteresis. Experimental validation confirmed the valve’s static and dynamic performance, achieving a step-response rise time of <40 ms, linearity within the 30–60% input voltage range, and effective tracking of sinusoidal control signals up to 8 Hz with a maximum pressure deviation of 0.015 MPa. The work underscores the potential of MEMS-based actuators in advancing compact pneumatic systems, offering a viable alternative to conventional solenoids. Key innovations include geometry-driven actuator optimization and dual-chip integration, providing insights into high-precision, low-cost pneumatic control solutions. Full article

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

17 pages, 10965 KiB

Open AccessArticle

Evaluation of Surface Integrity of Multi-Energy Field Coupling-Assisted Micro-Grinding Hastelloy Alloy

by Peng Bian, Zhenjing Duan, Yishuai Jia, Ziheng Wang, Shuaishuai Wang, Ji Tan, Yuyang Zhou, Jinlong Song and Xin Liu

Micromachines 2025, 16(5), 565; https://doi.org/10.3390/mi16050565 - 8 May 2025

Abstract

Hastelloy is widely used in the manufacturing of high-temperature components in the aerospace industry because of its high strength and corrosion-resistant physical properties, as well as its ability to maintain excellent mechanical properties at high temperatures. However, with developments in science and technology, [...] Read more.

Hastelloy is widely used in the manufacturing of high-temperature components in the aerospace industry because of its high strength and corrosion-resistant physical properties, as well as its ability to maintain excellent mechanical properties at high temperatures. However, with developments in science and technology, the amount of available components for use in high-temperature and corrosive environments is increasing, their structures are becoming more complex and varied, and requirements with regard to the surface quality of the components has also become more stringent. The integration of cold plasma (CP) and nano-lubricant minimum quantity lubrication (NMQL), within a multi-physics coupling-assisted micro-grinding process (CPNMQL), presents a promising strategy to overcome this bottleneck. In this paper, micro-grinding of Hastelloy C-276 was performed under dry, CP, NMQL, and CPNMQL conditions, respectively. Contact angle testing, X-ray photoelectron spectroscopy (XPS) analysis, and nano-scratch experiments were used to investigate the mechanism of CPNMQL and to compare the micro-milling performance under different cooling and lubrication conditions employing various characteristics such as grinding temperature, surface roughness, and 3D surface profile. The results showed that at different micro-grinding depths, the micro-grinding temperature and surface roughness were significantly reduced under CP, NMQL, and CPNMQL conditions compared to dry friction. Among them, CPNMQL showed the best performance, with 53.4% and 54.7% reductions in temperature and surface roughness, respectively, compared to the dry condition. Full article

(This article belongs to the Special Issue Recent Advances in Micro/Nanofabrication, 2nd Edition)

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21 pages, 595 KiB

Open AccessReview

Optical Detection Techniques for Biomedical Sensing: A Review of Printed Circuit Board (PCB)-Based Lab-on-Chip Systems

by Francisco Perdigones, Pablo Giménez-Gómez, Xavier Muñoz-Berbel and Carmen Aracil

Micromachines 2025, 16(5), 564; https://doi.org/10.3390/mi16050564 - 8 May 2025

Abstract

Lab on Printed Circuit Boards (Lab-on-PCB) technology has emerged as a promising platform, offering miniaturization, integration, and cost-effective fabrication for a wide range of sensing applications. This review explores the most common optical detection techniques implemented on printed circuit boards (PCBs), including absorbance, [...] Read more.

Lab on Printed Circuit Boards (Lab-on-PCB) technology has emerged as a promising platform, offering miniaturization, integration, and cost-effective fabrication for a wide range of sensing applications. This review explores the most common optical detection techniques implemented on printed circuit boards (PCBs), including absorbance, fluorescence, and chemiluminescence, discussing their working principles, advantages, and limitations in the context of PCB-based sensing. Additionally, evanescent wave generation is considered as an alternative optical approach with benefits for specific applications. Elements such as excitation sources, photodetectors, and the distinguishing characteristics of each method are analyzed to provide a comprehensive, but concise, overview of the field. Emphasis is placed on how the PCB platform influences the performance, sensitivity, and feasibility of these detection methods, highlighting relevant design considerations. This work aims to provide a solid foundation for researchers interested in optical sensing within this technology, serving as a reference for future developments and applications in PCB-based optical detection. Full article

(This article belongs to the Special Issue Lab on Chips and Optical Detection Methods)

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Graphical abstract

22 pages, 10376 KiB

Open AccessArticle

Thermal Error Prediction in High-Power Grinding Motorized Spindles for Computer Numerical Control Machining Based on Data-Driven Methods

by Quanhui Wu, Yafeng Li, Zhengfu Lin, Baisong Pan, Dawei Gu and Hailin Luo

Micromachines 2025, 16(5), 563; https://doi.org/10.3390/mi16050563 - 7 May 2025

Abstract

The thermal error of the high-power grinding motorized spindle, caused by heating, seriously affects machining accuracy. In this paper, an ensemble learning algorithm is used to predict the thermal error of a high-precision motorized spindle. The subsequent problem of thermal error compensation can [...] Read more.

The thermal error of the high-power grinding motorized spindle, caused by heating, seriously affects machining accuracy. In this paper, an ensemble learning algorithm is used to predict the thermal error of a high-precision motorized spindle. The subsequent problem of thermal error compensation can be effectively solved by a suitable thermal error model, which is crucial for improving the machining accuracy of the actual machining process. Firstly, the steady-state temperature field of the grinding motorized spindle is analyzed and used to determine the position of the sensors. Then, a signal acquisition instrument is used to monitor real-time temperature data. After that, experimental results are obtained, followed by verification. Finally, based on experimental data and the optimization results of temperature measurement points, temperature data are used as the input variable, and thermal deformation data are used as the output variable. The ensemble learning model is composed of different weak learners, which include multiple linear regression, back-propagation, and radial basis function neural networks. Different weak learners are trained using datasets separately, and the output of the weak learners is used as input to the model. Through integrating strategies, an ensemble learning model is established and compared with a weak learner. The error residual set of the ensemble learning model remains within [−0.2, 0.2], and the prediction performance shows that the ensemble learning model has a better predictive effect and strong robustness. Full article

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

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13 pages, 2011 KiB

Open AccessArticle

High-Efficiency Drug Loading in Lipid Vesicles by MEMS-Driven Gigahertz Acoustic Streaming

by Bingxuan Li, Haopu Wang, Zhen Wang, Huikai Xie and Yao Lu

Micromachines 2025, 16(5), 562; https://doi.org/10.3390/mi16050562 - 7 May 2025

Abstract

Drug carriers hold significant promise for precision medicine but face persistent challenges in balancing high encapsulation efficiency with structural preservation during active loading. In this study, we present a microelectromechanical system (MEMS)-driven platform that can generate gigahertz (GHz)-frequency acoustic streaming (1.55 GHz) to [...] Read more.

Drug carriers hold significant promise for precision medicine but face persistent challenges in balancing high encapsulation efficiency with structural preservation during active loading. In this study, we present a microelectromechanical system (MEMS)-driven platform that can generate gigahertz (GHz)-frequency acoustic streaming (1.55 GHz) to enable nondestructive, power-tunable drug encapsulation in lipid vesicles. Utilizing DSPE-PEG-modified bilayers with hydrodynamic shear forces, our method achieves transient membrane permeability that preserves membrane integrity while permitting controlled doxorubicin (DOX) influx. We developed the GHz acoustic MEMS platform and applied it to systematically investigate two drug loading strategies: (1) loading DOX into giant unilamellar vesicles (GUVs, >10 μm in diameter) prior to extrusion into small unilamellar vesicles (SUVs, 100 nm) versus (2) direct acoustic loading into pre-formed SUVs. The GUV-first approach demonstrated better performance, achieving 60.04% ± 1.55% encapsulation efficiency (EE%) at 250 mW acoustic power—a 5.93% enhancement over direct SUV loading (54.11% ± 0.72%). Structural analysis via TEM confirmed intact SUV morphology post-loading, while power-dependent EE% analysis showed a linear trend. This work bridges gaps in nanocarrier engineering by optimizing drug loading strategies, aiming to offer a potential drug carrier platform for drug delivery in biomedical treatment in future. Full article

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

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27 pages, 27489 KiB

Open AccessReview

Advances in Magnetically Controlled Medical Robotics: A Review of Actuation Systems, Continuum Designs, and Clinical Prospects for Minimally Invasive Therapies

by Tiantian Kong, Qitong Zheng, Jiarong Sun, Chunxiao Wang, Huibin Liu, Zhizheng Gao, Zezheng Qiao and Wenguang Yang

Micromachines 2025, 16(5), 561; https://doi.org/10.3390/mi16050561 - 6 May 2025

Abstract

Magnetically controlled micro-robots hold immense potential for revolutionizing advanced medical applications, garnering significant research interest. This potential is underscored by the dual focus on magnetic control systems—both as driving forces and manipulation field sources—and magnetic continuums that have demonstrated clinical therapeutic efficacy. This [...] Read more.

Magnetically controlled micro-robots hold immense potential for revolutionizing advanced medical applications, garnering significant research interest. This potential is underscored by the dual focus on magnetic control systems—both as driving forces and manipulation field sources—and magnetic continuums that have demonstrated clinical therapeutic efficacy. This comprehensive review delves into the actuation characteristics of permanent magnet systems, electromagnetic systems, and commercially available magnetic control systems. It also explores innovative designs of magnetic wires and tubes serving as continuum structures and investigates the variable stiffness properties of magnetic continua, informed by material and structural attributes. Furthermore, the discussion extends to their prospective roles and future applications within the medical realm. The objective is to elucidate emerging trends in the study of magnetic control systems and magnetic continua, marked by an expanding operational scope and enhanced precision in manipulation. By aligning these trends with clinical challenges and requirements, this review seeks to refine research trajectories, expedite practical implementations, and ultimately advocate for minimally invasive therapies. These therapies, leveraging magnetic control systems and magnetic continuums as cutting-edge treatment modalities, promise transformative impacts on the future of healthcare. Full article

(This article belongs to the Special Issue Functional Materials and Microdevices, 2nd Edition)

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22 pages, 2007 KiB

Open AccessArticle

Design and Contact Performance Analysis of 3D-Printed Alloy Metal Inertial Micro Switch

by Jinghao Li, Zhipeng Li and Hejuan Chen

Micromachines 2025, 16(5), 560; https://doi.org/10.3390/mi16050560 - 5 May 2025

Abstract

In order to reduce space occupation and improve reliability, the modularization and integration of micro switches and their components are a necessary path for development. In this paper, a scheme for an alloy metal inertial micro switch using 3D printing technology is proposed [...] Read more.

In order to reduce space occupation and improve reliability, the modularization and integration of micro switches and their components are a necessary path for development. In this paper, a scheme for an alloy metal inertial micro switch using 3D printing technology is proposed for an integrated design. The switch realizes the turn-on function by causing the deformable electrodes to undergo plastic deformation and make close contact with the outer sleeve under the columnar block extrusion. The influence of electrode structure parameters on electrode contact performance was studied by the orthogonal experimental method. And the best parameter combination scheme for the electrode was determined. The aluminum alloy switch and titanium alloy switch were processed by SLM (selective laser melting) technology. The plastic deformation of the 3D-printed titanium alloy electrode occurred later than that of the 3D-printed aluminum alloy electrode under the same impact. The aluminum alloy electrode underwent plastic deformation and realized stable contact with a response time of 5 µs when the impact load was applied with an amplitude of 627 N and a pulse width of 2.7 ms (simulating high acceleration), which meets the application requirement of the response time being no more than 20 µs. The feasibility of 3D printing technology in high-precision and complex-structure micro switch manufacturing was verified. The research in this paper will provide guidance and reference for engineering applications. Full article

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

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18 pages, 5700 KiB

Open AccessArticle

A Highly Sensitive Giant Magnetoresistive (GMR) Biosensor Based on the Magnetic Flux Concentrator Effect

by Hao Sun, Jiao Li, Changhui Zhao, Chunming Ren, Tian Tian, Chong Lei and Xuecheng Sun

Micromachines 2025, 16(5), 559; https://doi.org/10.3390/mi16050559 - 3 May 2025

Abstract

Magnetic biosensors have wide applications in biological target detection due to their advantages such as low background noise, convenient detection, and low requirements for sample pretreatment. However, existing magnetic biosensors still have the drawback of low sensitivity compared to optical and electrochemical biosensors. [...] Read more.

Magnetic biosensors have wide applications in biological target detection due to their advantages such as low background noise, convenient detection, and low requirements for sample pretreatment. However, existing magnetic biosensors still have the drawback of low sensitivity compared to optical and electrochemical biosensors. This paper presents the novel design of a high-sensitivity magnetic biosensor by utilizing the magnetic field line convergence effect, which was applied to bacterial detection. The results indicate that it can achieve a detection limitation of 10 CFU/mL, demonstrating that it can be implemented in high-sensitivity biological target detection. Full article

(This article belongs to the Section B1: Biosensors)

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13 pages, 3748 KiB

Open AccessArticle

Compact, Broadband, and High-Gain Four-Port MIMO Antenna for Future Millimeter Wave Applications

by Esraa Mousa Ali, Shine Let Gunamony, Mohamad A. Alawad and Turki Essa Alharbi

Micromachines 2025, 16(5), 558; https://doi.org/10.3390/mi16050558 - 3 May 2025

Abstract

A wideband antenna with a relatively compact size along with a multiple input and multiple output (MIMO) configuration for millimeter wave applications is proposed in this work. The antenna offers a low profile and simple structure. First of all, an antenna is designed [...] Read more.

A wideband antenna with a relatively compact size along with a multiple input and multiple output (MIMO) configuration for millimeter wave applications is proposed in this work. The antenna offers a low profile and simple structure. First of all, an antenna is designed using Rogers RT/duroid 6002 (Rogers Corporation, Chandler, AZ, USA) with a thickness of 0.79 mm, offering wideband ranges from 21 to 35 GHz. Subsequently, the unit element is converted into a four-port MIMO antenna to improve the capacity of the system, resulting in a high data rate, which is critical for 5G as well as for devices operating in the mm wave spectrum. The proposed work exhibits total dimensions of 24 × 24 mm² and offers a peak gain of 8.5 dBi, with an efficiency of more than 80%. The MIMO performance parameters are also studied, and the antenna offers exceptional performance in terms of mutual coupling (S_ij) without inserting a decoupling structure, envelop correlation coefficient (ECC), and diversity parameters. The proposed MIMO antenna offers a minimum isolation of −25 dBi and an ECC of less than 0.018. All the other MIMO parameter values lie below the acceptable range. The High Frequency Structure Simulator (HFSS) EM software (v.19) tool is used to analyze the antenna and study its performance. The simulated outcomes are verified by fabricating a prototype, where the result offers a good comparison among both results. Moreover, the contrast in terms of different performance parameters is carried out amongst recent research articles, highlighting the key contribution of the presented design. A compact size antenna with a wideband, simplified structure, and stable performance throughout the working band is achieved; thus, it is a solid contender for mm wave applications and 5G devices. Full article

(This article belongs to the Special Issue Microwave Passive Components, 2nd Edition)

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8 pages, 2864 KiB

Open AccessPerspective

Wireless Optogenetic Microsystems Accelerate Artificial Intelligence–Neuroscience Coevolution Through Embedded Closed-Loop System

by Sungcheol Hong

Micromachines 2025, 16(5), 557; https://doi.org/10.3390/mi16050557 - 3 May 2025

Abstract

Brain-inspired models in artificial intelligence (AI) originated from foundational insights in neuroscience. In recent years, this relationship has been moving toward a mutually reinforcing feedback loop. Currently, AI is significantly contributing to advancing our understanding of neuroscience. In particular, when combined with wireless [...] Read more.

Brain-inspired models in artificial intelligence (AI) originated from foundational insights in neuroscience. In recent years, this relationship has been moving toward a mutually reinforcing feedback loop. Currently, AI is significantly contributing to advancing our understanding of neuroscience. In particular, when combined with wireless optogenetics, AI enables experiments without physical constraints. Furthermore, AI-driven real-time analysis facilitates closed-loop control, allowing experimental setups across a diverse range of scenarios. And a deeper understanding of these neural networks may, in turn, contribute to future advances in AI. This work demonstrates the synergy between AI and miniaturized neural technology, particularly through wireless optogenetic systems designed for closed-loop neural control. We highlight how AI is now revolutionizing neuroscience experiments from decoding complex neural signals and quantifying behavior, to enabling closed-loop interventions and high-throughput phenotyping in freely moving subjects. Notably, AI-integrated wireless implants can monitor and modulate biological processes with unprecedented precision. We then recount how neuroscience insights derived from AI-integrated neuroscience experiments can potentially inspire the next generation of machine intelligence. Insights gained from these technologies loop back to inspire more efficient and robust AI systems. We discuss future directions in this positive feedback loop between AI and neuroscience, arguing that the coevolution of the two fields, grounded in technologies like wireless optogenetics and guided by reciprocal insight, will accelerate progress in both, while raising new challenges and opportunities for interdisciplinary collaboration. Full article

(This article belongs to the Section B：Biology and Biomedicine)

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12 pages, 5077 KiB

Open AccessArticle

Optimization of Low-Voltage p-GaN Gate HEMTs for High-Efficiency Secondary Power Conversion

by Lili Zhai, Xiangdong Li, Jian Ji, Lu Yu, Liang Chen, Yaoming Chen, Haonan Xia, Zhanfei Han, Junbo Wang, Xi Jiang, Song Yuan, Tao Zhang, Yue Hao and Jincheng Zhang

Micromachines 2025, 16(5), 556; https://doi.org/10.3390/mi16050556 - 2 May 2025

Abstract

The explosive demand for high-performance secondary power sources in artificial intelligence (AI) has brought significant opportunities for low-voltage GaN devices. This paper focuses on research on high-efficiency and high-reliability low-voltage p-GaN gate HEMTs with a gate–drain distance, L_GD, of 1 to [...] Read more.

The explosive demand for high-performance secondary power sources in artificial intelligence (AI) has brought significant opportunities for low-voltage GaN devices. This paper focuses on research on high-efficiency and high-reliability low-voltage p-GaN gate HEMTs with a gate–drain distance, L_GD, of 1 to 3 μm in our pilot line, manufactured on 6-inch Si using a CMOS-compatible process, with extraordinary wafer-level uniformity. Specifically, these fabricated p-GaN gate HEMTs with an L_GD of 1.5 μm demonstrate a blocking voltage of over 180 V and a high V_TH of 1.6 V and exhibit a low R_ON of 2.8 Ω·mm. It is found that device structure optimization can significantly enhance device reliability. That is, through the dedicated optimization of source field plate structure and interlayer dielectric (ILD) thickness, the dynamic ON-resistance, R_ON, degradation of devices with an L_GD of 1.5 µm was successfully suppressed from 60% to 20%, and the V_TH shift was significantly reduced from 1.1 to 0.5 V. Further, the devices also passed preliminary gate bias stress and high-voltage OFF-state stress tests, providing guidance for preparing high-performance, low-voltage p-GaN gate HEMTs in the future. Full article

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

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20 pages, 2666 KiB

Open AccessReview

Development of Energy-Selective Surface for Electromagnetic Protection

by Jinghao Lv, Caofei Luo, Jiwei Zhao, Haoran Han, Huan Lu and Bin Zheng

Micromachines 2025, 16(5), 555; https://doi.org/10.3390/mi16050555 - 1 May 2025

Abstract

Energy-selective surfaces (ESSs) have gained attention as an advanced electromagnetic protection technology. This review discusses the evolution of ESSs, focusing on four key areas: frequency bandwidth expansion, material innovations, functional enhancements, and application diversification. ESSs have evolved from narrowband designs to providing ultra-wideband [...] Read more.

Energy-selective surfaces (ESSs) have gained attention as an advanced electromagnetic protection technology. This review discusses the evolution of ESSs, focusing on four key areas: frequency bandwidth expansion, material innovations, functional enhancements, and application diversification. ESSs have evolved from narrowband designs to providing ultra-wideband protection, covering L-band to K-band frequencies. New designs, including non-reciprocal mechanisms and cascaded filters, enhance the shielding efficiency. Material advancements like the use of vanadium dioxide (VO₂) and micro–nano fabrication techniques have reduced costs and improved performance, enabling higher-frequency applications. Future developments aim to overcome the current limitations, offering a broader bandwidth, higher power tolerance, and faster response times. ESSs play a key role in integrated electromagnetic protection systems. Full article

(This article belongs to the Special Issue Novel Electromagnetic and Acoustic Devices)

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46 pages, 6940 KiB

Open AccessReview

High-Performance Carbon Nanotube Electronic Devices: Progress and Challenges

by Zirui Zhang, Nie Zhang and Zhiyong Zhang

Micromachines 2025, 16(5), 554; https://doi.org/10.3390/mi16050554 - 1 May 2025

Abstract

As silicon-based complementary metal-oxide-semiconductor (CMOS) technology approaches its physical and scaling limits at sub-3-nanometer nodes, critical challenges including the short-channel effect (SCE), surging power consumption, and aggravated parasitic effects have severely constrained further improvements in device performance, integration density, and energy efficiency. Carbon [...] Read more.

As silicon-based complementary metal-oxide-semiconductor (CMOS) technology approaches its physical and scaling limits at sub-3-nanometer nodes, critical challenges including the short-channel effect (SCE), surging power consumption, and aggravated parasitic effects have severely constrained further improvements in device performance, integration density, and energy efficiency. Carbon nanotubes (CNTs), with their superior electrical properties, exceptional gate controllability enabled by one-dimensional nanostructure, and compatibility with existing semiconductor processes, have emerged as an ideal candidate material for post-silicon high-performance electronics. Since their discovery, CNT electronics have evolved from fundamental research to a comprehensive technological framework. This review first systematically elaborates the physical characteristics of CNTs and operation mechanisms of electronic devices. Subsequently, we comprehensively summarize recent research progress in high-performance CNT electronic devices with particular emphasis on their breakthrough achievements. Through critical analysis of current developments, we thoroughly discuss fundamental challenges in material synthesis, device fabrication, and circuit integration, while evaluating potential solutions. Finally, we concentrate on future development directions for high-performance CNT devices, aiming to call for collaborative efforts from both academia and industry to accelerate the transition of CNT electronics from laboratory research to industrial implementation. Full article

(This article belongs to the Special Issue Multifunctional Transistors: Outlooks and Challenges)

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16 pages, 6714 KiB

Open AccessArticle

Numerical Simulation of Gravitactic Bioconvection with Nanoparticles: An Application of Solids Removal in Wastewater Using a Thermal Source

by Alejandra M. Mil-Martínez, René O. Vargas, Aldo Gómez-López, Alejandro Zacarías, Juan P. Escandón, Enrique García-Leal and Rubén Mil-Martínez

Micromachines 2025, 16(5), 553; https://doi.org/10.3390/mi16050553 - 30 Apr 2025

Abstract

The results of numerical simulations of gravitactic bioconvection influenced by nanoparticles suspended in water are analyzed. In this work, two cases are established which consider the removal of nanometric particles suspended in wastewater. The competence among the bioconvection of Paramecium caudatum, natural [...] Read more.

The results of numerical simulations of gravitactic bioconvection influenced by nanoparticles suspended in water are analyzed. In this work, two cases are established which consider the removal of nanometric particles suspended in wastewater. The competence among the bioconvection of Paramecium caudatum, natural convection and buoyancy of nanoparticles phenomena in an aqueous suspension is presented. The position of a thermal source to control the orientation of microorganisms when swimming is analyzed. Numerical simulations are carried out using the finite difference method in an ADI scheme, employing stream-vorticity formulations and equations for microorganisms, nanoparticle concentration, and energy. The percentage of nanoparticles is considered using the Rayleigh number, which includes the effect of Brownian and thermophoretic parameters. At low values of the Brownian parameter

δ_{B m} = 0.1

, thermophoretic parameter

δ_{T m} = 0.1

, and the nanoparticles Rayleigh number

0.005 < R a_{n} < 0.015

, the swimming of microorganisms contributed to streamlines across which nanoparticles traveled in response to a thermal control source. Thus, the results obtained suggest an alternative approach to the removal of solids such as heavy metals in polluting waters. The development of this type of technology will help in the bioremediation of wastewater. Full article

(This article belongs to the Special Issue Exploring the Potential Applications of Microfluidics)

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20 pages, 5238 KiB

Open AccessArticle

Low-Temperature Electrospinning-Fabricated Three-Dimensional Nanofiber Scaffolds for Skin Substitutes

by Qiqi Dai, Huazhen Liu, Wenbin Sun, Yi Zhang, Weihuang Cai, Chunxiang Lu, Kaidi Luo, Yuanyuan Liu and Yeping Wang

Micromachines 2025, 16(5), 552; https://doi.org/10.3390/mi16050552 - 30 Apr 2025

Abstract

Severe skin damage poses a significant clinical challenge, as limited availability of skin donors, postoperative skin defects, and scarring often impair skin function. Traditional two-dimensional (2D) nanofibers exhibit small pore sizes that hinder cellular infiltration, unable to simulate the three-dimensional (3D) structure of [...] Read more.

Severe skin damage poses a significant clinical challenge, as limited availability of skin donors, postoperative skin defects, and scarring often impair skin function. Traditional two-dimensional (2D) nanofibers exhibit small pore sizes that hinder cellular infiltration, unable to simulate the three-dimensional (3D) structure of the skin. To address these issues, we developed 3D porous nanofiber scaffolds composed of polycaprolactone–polylactic acid–mussel adhesive protein (PLGA-PCL-MAP) using low-temperature electrospinning combined with nano-spray technology. Meanwhile, this 3D scaffold features high porosity, enhanced water absorption, and improved air permeability. The incorporation of mussel adhesive protein (MAP) further increased the scaffold’s adhesive properties and biocompatibility. In vitro experiments demonstrated that the 3D nanofiber scaffolds significantly promoted the adhesion, proliferation, and migration of epidermal keratinocytes (HaCaTs) and human fibroblasts (HFBs), while providing ample space for inward cellular growth. Successful co-culture of HaCaT and HFBs within the scaffold revealed key functional outcomes: HaCaTs expressed keratinocyte differentiation markers CK10 and CK14, while HFBs actively secreted extracellular matrix components critical for wound healing, including collagen I, collagen III, and fibronectin. This skin substitute with a composite structure of epidermis and dermis based on three-dimensional nanofiber scaffolds can be used as an ideal skin replacement and is expected to be applied in wound repair in the future. Full article

(This article belongs to the Section B2: Biofabrication and Tissue Engineering)

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19 pages, 8898 KiB

Open AccessArticle

Modeling and Optimization of Structural Parameters for High-Efficiency Multi-Jet Polishing of Optical Glass

by Zhongchen Cao, Yiwei Miao, Ming Wang and Zhenfeng Zhu

Micromachines 2025, 16(5), 551; https://doi.org/10.3390/mi16050551 - 30 Apr 2025

Abstract

Multi-jet polishing (MJP) is a promising method for enhanced polishing efficiency by integrating multiple nozzles, allowing for the high-efficiency polishing of large-scale surfaces. However, the optimization of the structural parameters, such as the distribution form of the nozzles and outlet diameter, remains a [...] Read more.

Multi-jet polishing (MJP) is a promising method for enhanced polishing efficiency by integrating multiple nozzles, allowing for the high-efficiency polishing of large-scale surfaces. However, the optimization of the structural parameters, such as the distribution form of the nozzles and outlet diameter, remains a critical challenge for achieving uniform and stable polishing performance. This paper presents a dynamic model of MJP based on the theory of fluid dynamic pressure and particle erosion. The flow field and particle motion characteristics in multi-nozzle jet polishing were studied using simulation experiments. The influence of the nozzle spacing and form and outlet diameter on the flow field characteristics and material removal profile was explored, and the structural parameters of the multi-nozzle polishing tool were optimized. According to the simulation results, two kinds of multi-nozzle polishing tools with a linear arrangement and cross arrangement were processed, and a series of single-point and surface polishing experiments was carried out. The optimized multi-nozzle jet polishing tool has no interference in the removal contour of each point, exhibits high consistency and stability, and is consistent with the theoretical model prediction results, which effectively improve the surface polishing efficiency. The results can provide a theoretical and experimental reference for MJP in the ultra-precision and high-efficiency polishing of large-sized components. Full article

(This article belongs to the Special Issue Precision Optical Manufacturing and Processing)

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20 pages, 6941 KiB

Open AccessReview

Random Lasers Based on Tellurite and Germanate Glasses and Glass-Ceramics Doped with Rare-Earth Ions

by Davinson M. da Silva, Josivanir G. Câmara, Niklaus U. Wetter, Jessica Dipold, Luciana R. P. Kassab and Cid B. de Araújo

Micromachines 2025, 16(5), 550; https://doi.org/10.3390/mi16050550 - 30 Apr 2025

Abstract

Random lasers (RLs) based on glasses and glass-ceramics doped with rare-earth ions (REI) deserve great attention because of their specific physical properties such as large thermal stability, possibility to operate at high intensities, optical wavelength tunability, and prospects to operate Fiber-RLs, among other [...] Read more.

Random lasers (RLs) based on glasses and glass-ceramics doped with rare-earth ions (REI) deserve great attention because of their specific physical properties such as large thermal stability, possibility to operate at high intensities, optical wavelength tunability, and prospects to operate Fiber-RLs, among other characteristics of interest for photonic applications. In this article, we present a brief review of experiments with RLs based on tellurite and germanate glasses and glass-ceramics doped with neodymium (Nd³⁺), erbium (Er³⁺), and ytterbium (Yb³⁺) ions. The glass samples were fabricated using the melt-quenching technique followed by controlled crystallization to achieve the glass-ceramics. Afterwards, the samples were crushed to obtain the powder samples for the RLs experiments. The experiments demonstrated RLs emissions at various wavelengths, with feedback mechanisms due to light scattering at grain/air and crystalline/glass interfaces. The phenomenon of replica symmetry breaking was verified through statistical analysis of the RLs intensity fluctuations, indicating a photonic phase-transition (corresponding to the RL threshold) analogous to the paramagnetic-to-spin glass transition in magnetic materials. The various results reported here highlight the potential of glasses and glass-ceramics for the development of RLs with improved performance in terms of reduction of laser threshold and large lifetime of the active media in comparison with organic materials. Full article

(This article belongs to the Collection Microdevices and Applications Based on Advanced Glassy Materials)

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22 pages, 2175 KiB

Open AccessArticle

HE-BiDet: A Hardware Efficient Binary Neural Network Accelerator for Object Detection in SAR Images

by Dezheng Zhang, Zehan Liang, Rui Cen, Zhihong Yan, Rui Wan and Dong Wang

Micromachines 2025, 16(5), 549; https://doi.org/10.3390/mi16050549 - 30 Apr 2025

Abstract

Convolutional Neural Network (CNN)-based Synthetic Aperture Radar (SAR) target detection eliminates manual feature engineering and improves robustness but suffers from high computational costs, hindering on-satellite deployment. To address this, we propose HE-BiDet, an ultra-lightweight Binary Neural Network (BNN) framework co-designed with hardware acceleration. [...] Read more.

Convolutional Neural Network (CNN)-based Synthetic Aperture Radar (SAR) target detection eliminates manual feature engineering and improves robustness but suffers from high computational costs, hindering on-satellite deployment. To address this, we propose HE-BiDet, an ultra-lightweight Binary Neural Network (BNN) framework co-designed with hardware acceleration. First, we develop an ultra-lightweight SAR ship detection model. Second, we design a BNN accelerator leveraging four-directions of parallelism and an on-chip data buffer with optimized addressing to feed the computing array efficiently. To accelerate post-processing, we introduce a hardware-based threshold filter to eliminate redundant anchor boxes early and a dedicated Non-Maximum Suppression (NMS) unit. Evaluated on SAR-Ship, AirSAR-Ship 2.0, and SSDD, our model achieves 91.3%, 71.0%, and 92.7% accuracy, respectively. Implemented on a Xilinx Virtex-XC7VX690T FPGA, the system achieves

189.3

FPS, demonstrating real-time capability for spaceborne deployment. Full article

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

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28 pages, 15377 KiB

Open AccessArticle

Development of a Piezoelectric-Driven XYθ_z Nano-Positioning Stage with High Load-Bearing Capacity Enabled by Over-Constrained Guiding Configuration

by Bin Liu, Lingchen Meng, Shuaishuai Lu, Fei Wang, Pengbo Liu and Peng Yan

Micromachines 2025, 16(5), 548; https://doi.org/10.3390/mi16050548 - 30 Apr 2025

Abstract

A novel over-constrained XYθ_z nano-positioning stage with a high load-bearing capacity is proposed. This serially connected displacement stage adopts an embedded structural design that integrates a translation stage with a rotation stage in series. The Z-axis amplification mechanism employs out-of-plane actuation, realising [...] Read more.

A novel over-constrained XYθ_z nano-positioning stage with a high load-bearing capacity is proposed. This serially connected displacement stage adopts an embedded structural design that integrates a translation stage with a rotation stage in series. The Z-axis amplification mechanism employs out-of-plane actuation, realising a compact solution for three-axis independent motion. The hybrid amplification mechanism designed in the translation stage ensures enhanced output displacement and structural stiffness. The hybrid-parallel amplification mechanism comprises a lever-type displacement amplifier and a Scott–Russell displacement amplifier connected in series, which is then connected in parallel with a bridge-type displacement amplifier. An over-constrained mechanism is introduced to impose redundant constraints along the Z-axis, effectively suppressing parasitic displacement in the Z-direction while enhancing resistance to out-of-plane deformation. A quasi-static model of the XYθ_z motion stage was established to comprehensively characterise the deformation behaviour of the stage, which was verified by finite element simulations and experiments on the prototype. The experimental results indicate that the XYθ_z stage achieves a large motion range (up to 152.22 μm × 151.3 μm × 2.885 mrad) while maintaining excellent anti-deformation capability 200 nm at 4 kg loading. Full article

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