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Micromachines
Volume 16
Issue 1
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Micromachines, Volume 16, Issue 1 (January 2025) – 112 articles

Cover Story (view full-size image): Magnetic field-assisted control of magnetite location in a polymer composite is a promising strategy for flexible, conductive sensors. This study investigates the effect of static magnetic fields on thermoplastic elastomer (TPE) composites with magnetite and multi-walled carbon nanotubes (MWCNT). Composites with varying concentrations of magnetite and MWCNT were prepared by twin screw extrusion, and then compression moulded under a magnetic field. Applying a magnetic field to the melt at 190 °C enhanced magnetite/MWCNT interactions, substantially reducing electrical resistivity while maintaining thermal stability. Magnetite facilitated precise sensor positioning, demonstrating a scalable approach for enhancing sensor performance and positioning, with potential applications in flexible electronics. View this paper
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17 pages, 7273 KiB  
Article
Measurement and Analysis of Interconnects’ Resonance and Signal/Power Integrity Degradation in Glass Packages
by Youngwoo Kim
Micromachines 2025, 16(1), 112; https://doi.org/10.3390/mi16010112 - 20 Jan 2025
Viewed by 462
Abstract
In this article, resonance phenomena of high-speed interconnects and power delivery networks in glass packages are measured and analyzed. The resonances are generated in the interconnection by the physical dimension, cancelation of reactance components, and modes. When the resonances are generated in the [...] Read more.
In this article, resonance phenomena of high-speed interconnects and power delivery networks in glass packages are measured and analyzed. The resonances are generated in the interconnection by the physical dimension, cancelation of reactance components, and modes. When the resonances are generated in the operation frequency band, the signal/power integrity of the interconnect can be affected. As such, resonances generated in high-speed interconnects increase insertion loss, which degrades signal integrity. Also, resonances of the power delivery network (PDN) associated with boundary conditions increase PDN impedance, which degrades power integrity by generating power/ground noise and return current discontinuity of through vias. Recently, glass packaging has been gaining more attention due to its advantages associated with low substrate loss and large dimensions compared to silicon wafers. However, the low loss of the substrate and process variation may affect the resonance properties of interconnects. The resonance impacts on signal/power integrity must be analyzed, and mitigation plans should be proposed to maximize the advantages of the glass packaging technology. To analyze the resonance impacts on signal/power integrity, various glass package test vehicles are designed and fabricated. The fabricated test vehicles include transmission lines, PDNs, and patterns to measure an interaction between the through via and PDN. First, transmission line patterns that have 50-ohm characteristic impedance are measured. Due to the process variations, quarter-wave resonances are monitored, and at those frequencies, a sharp increase in insertion loss is observed, which deteriorates the signal integrity of the interconnect. Various PDN patterns are measured in the frequency domain, and regardless of the PDN shape, PDN impedance peaks are observed at the mode resonance frequencies. Due to a low-loss characteristic of the glass substrate, sharp PDN impedance peaks are generated at these frequencies. Also, at these frequencies, both signal and power integrity degradations are measured and analyzed. To fully benefit from the advantages of glass packaging technology, a thorough electrical performance analysis should be conducted to avoid resonances in the target frequency range. Full article
(This article belongs to the Special Issue Microelectronics Assembly and Packaging: Materials and Technologies, 2nd Edition)
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13 pages, 3590 KiB  
Article
A Precessing-Coin-like Rotary Actuator for Distal Endoscope Scanners: Proof-of-Concept Study
by Nirvana Gharib, Mohammad Reza Yousefi Darestani and Kenichi Takahata
Micromachines 2025, 16(1), 111; https://doi.org/10.3390/mi16010111 - 20 Jan 2025
Viewed by 632
Abstract
This paper presents, for the first time, a rotary actuator functionalized by an inclined disc rotor that serves as a distal optical scanner for endoscopic probes, enabling side-viewing endoscopy in luminal organs using different imaging/analytic modalities such as optical coherence tomography and Raman [...] Read more.
This paper presents, for the first time, a rotary actuator functionalized by an inclined disc rotor that serves as a distal optical scanner for endoscopic probes, enabling side-viewing endoscopy in luminal organs using different imaging/analytic modalities such as optical coherence tomography and Raman spectroscopy. This scanner uses a magnetic rotor designed to have a mirror surface on its backside, being electromagnetically driven to roll around the cone-shaped hollow base to create a motion just like a precessing coin. An optical probing beam directed from the probe’s optic fiber is passed through the hollow cone to be incident and bent on the back mirror of the rotating inclined rotor, circulating the probing beam around the scanner for full 360° sideway imaging. This new scanner architecture removes the need for a separate prism mirror and holding mechanics to drastically simplify the scanner design and thus, potentially enhancing device miniaturization and reliability. The first proof-of-concept is developed using 3D printing and experimentally analyzed to reveal the ability of both angular stepping at 45° and high-speed rotation up to 1500 rpm within the biologically safe temperature range, a key function for multimodal imaging. Preliminary optical testing demonstrates continuous circumferential scanning of the laser beam with no blind spot caused by power leads to the actuator. The results indicate the fundamental feasibility of the developed actuator as an endoscopic distal scanner, a significant step to further development toward advancing optical endoscope technology. Full article
(This article belongs to the Special Issue MEMS Actuators and Their Applications)
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20 pages, 24743 KiB  
Article
Investigation of Chip Morphology in Elliptical Vibration Micro-Turning of Silk Fibroin
by Zhengjian Wang, Xichun Luo, Jining Sun, Wenkun Xie, Yinchuan Piao, Yonghang Jiang and Xiuyuan Chen
Micromachines 2025, 16(1), 110; https://doi.org/10.3390/mi16010110 - 19 Jan 2025
Viewed by 727
Abstract
Silk fibroin, known for its biocompatibility and biodegradability, holds significant promise for biomedical applications, particularly in drug delivery systems. The precise fabrication of silk fibroin particles, specifically those ranging from tens of nanometres to hundreds of microns, is critical for these uses. This [...] Read more.
Silk fibroin, known for its biocompatibility and biodegradability, holds significant promise for biomedical applications, particularly in drug delivery systems. The precise fabrication of silk fibroin particles, specifically those ranging from tens of nanometres to hundreds of microns, is critical for these uses. This study introduces elliptical vibration micro-turning as a method for producing silk fibroin particles in the form of cutting chips to serve as carriers for drug delivery systems. A hybrid finite element and smoothed particle hydrodynamics (FE-SPH) model was used to investigate how vibration parameters, such as frequency and amplitude, influence chip formation and morphology. This research is essential for determining the size and shape of silk fibroin particles, which are crucial for their effectiveness in drug delivery systems. The results demonstrate the superior capability of elliptical vibration micro-turning for producing shorter, spiral-shaped chips in the size range of tens of microns, in contrast to the long, continuous chips with zig-zag folds and segmented edges generated by conventional micro-turning. The unique zig-zag shapes result from the interplay between the high flexibility and hierarchical structure of silk fibroin and the controlled cutting environment provided by the diamond tool. Additionally, higher vibration frequencies and lower vertical amplitudes promote chip curling, facilitate breakage, and improve chip control, while reducing cutting forces. Experimental trials further validate the accuracy of the hybrid model. This study represents a significant advancement in the processing of silk fibroin film, offering a complementary approach to fabricating short, spiral-shaped silk fibroin particles with a high surface-area-to-volume ratio compared to traditional spheroids, which holds great potential for enhancing drug-loading efficiency in high-precision drug delivery systems. Full article
(This article belongs to the Special Issue Advances in Digital Manufacturing and Nano Fabrication)
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12 pages, 4448 KiB  
Article
Research on Envelope Profile of Lithium Niobate on Insulator Stepped-Mode Spot Size Converter
by Jianfeng Bao, Dengcai Yang, Zhiyu Chen, Jingyuan Zhang and Feng Yang
Micromachines 2025, 16(1), 109; https://doi.org/10.3390/mi16010109 - 19 Jan 2025
Viewed by 711
Abstract
To enhance the end-face coupling efficiency of lithium niobate on insulator (LNOI) chips, in conjunction with current device fabrication processes, a stepped spot size converter (SSC) based on a special outer envelope profile has been proposed and investigated. This stepped SSC can reduce [...] Read more.
To enhance the end-face coupling efficiency of lithium niobate on insulator (LNOI) chips, in conjunction with current device fabrication processes, a stepped spot size converter (SSC) based on a special outer envelope profile has been proposed and investigated. This stepped SSC can reduce the coupling loss between the LNOI waveguide and a normal single-mode optical fiber. First, the output waveguide of a mode converter was proposed and simulated, in which the mode field had the biggest overlapping integral factor with a single-mode fiber (MDF ≈ 9.8 μm). Then, a stepped LNOI waveguide, the basic structure of the mode converter, with three kinds of outer envelope profile, was proposed and analyzed. Through analysis of the impacts of different envelope profiles on mode spot conversion efficiency, the relationship between envelope profile and propagation efficiency was obtained. Additionally, the rule of LNOI stair height variation tendency and the pattern of mode spot conversion efficiency for the multi-step mode spot converter in LNOI were obtained. Ultimately, a stepped SSC with a COS-shaped envelope curve was adopted. When this stepped SSC is coupled to single-mode fiber with a mode-field diameter of 9.8 μm, the coupling efficiency of the TE mode was 95.35% at the wavelength of 1550 nm. Full article
(This article belongs to the Special Issue Optoelectronic Fusion Technology)
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13 pages, 2458 KiB  
Article
Temperature-Responsive Hybrid Composite with Zero Temperature Coefficient of Resistance for Wearable Thermotherapy Pads
by Ji-Yoon Ahn, Dong-Kwan Lee, Min-Gi Kim, Won-Jin Kim and Sung-Hoon Park
Micromachines 2025, 16(1), 108; https://doi.org/10.3390/mi16010108 - 19 Jan 2025
Viewed by 514
Abstract
Carbon-based polymer composites are widely used in wearable devices due to their exceptional electrical conductivity and flexibility. However, their temperature-dependent resistance variations pose significant challenges to device safety and performance. A negative temperature coefficient (NTC) can lead to overcurrent risks, while a positive [...] Read more.
Carbon-based polymer composites are widely used in wearable devices due to their exceptional electrical conductivity and flexibility. However, their temperature-dependent resistance variations pose significant challenges to device safety and performance. A negative temperature coefficient (NTC) can lead to overcurrent risks, while a positive temperature coefficient (PTC) compromises accuracy. In this study, we present a novel hybrid composite combining carbon nanotubes (CNTs) with NTC properties and carbon black (CB) with PTC properties to achieve a near-zero temperature coefficient of resistance (TCR) at an optimal ratio. This innovation enhances the safety and reliability of carbon-based polymer composites for wearable heating applications. Furthermore, a thermochromic pigment layer is integrated into the hybrid composite, enabling visual temperature indication across three distinct zones. This bilayer structure not only addresses the TCR challenge but also provides real-time, user-friendly temperature monitoring. The resulting composite demonstrates consistent performance and high precision under diverse heating conditions, making it ideal for wearable thermotherapy pads. This study highlights a significant advancement in developing multifunctional, temperature-responsive materials, offering a promising solution for safer and more controllable wearable devices. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in 'Materials and Processing' 2024)
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17 pages, 12970 KiB  
Article
Design of Dielectric Elastomer Actuator and Its Application in Flexible Gripper
by Xiaoyu Meng, Jiaqing Xie, Haoran Pang, Wenchao Wei, Jiping Niu, Mingqiang Zhu, Fang Gu, Xiaohuan Fan and Haiyan Fan
Micromachines 2025, 16(1), 107; https://doi.org/10.3390/mi16010107 - 19 Jan 2025
Viewed by 553
Abstract
Dielectric elastomer actuators (DEAs) are difficult to apply to flexible grippers due to their small deformation range and low output force. Hence, a DEA with a large bending deformation range and output force was designed, and a corresponding flexible gripper was developed to [...] Read more.
Dielectric elastomer actuators (DEAs) are difficult to apply to flexible grippers due to their small deformation range and low output force. Hence, a DEA with a large bending deformation range and output force was designed, and a corresponding flexible gripper was developed to realize the function of grasping objects of different shapes. The relationship between the pre-stretch ratio and DEA deformation degree was tested by experiments. Based on the performance test results of the dielectric elastomer (DE), the bending deformation process of DEAs with different shapes was simulated by Finite Element Method (FEM) simulation. DEAs with different shapes were prepared through laser cutting and the relationship between the voltage and the bending angle, and the output force of the DEAs was measured. The result shows that under uniaxial stretching, the deformation of the DEA in the stretching direction gradually increases and decreases in the unstretched direction with the increase in the pre-stretch ratio. Under biaxial stretching, DEA deformation increases with the increase in the pre-stretch ratio. The shape of the DEA has a certain influence on the bending deformation range under the same conditions, and the elliptical DEA has a larger bending deformation range and higher output force compared with the rectangular DEA and the trapezium DEA. The elliptical DEA can produce a bending deformation of 40° and an output force of 37.2 mN at a voltage of 24 kV. The three-finger flexible gripper composed of an elliptical DEA can realize the grasping of a paper cup. Full article
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11 pages, 1773 KiB  
Article
Design and Study of a Novel P-Type Junctionless FET for High Performance of CMOS Inverter
by Bin Wang, Ziyuan Tang, Yuxiang Song, Lu Liu, Weitao Yang and Longsheng Wu
Micromachines 2025, 16(1), 106; https://doi.org/10.3390/mi16010106 - 17 Jan 2025
Viewed by 472
Abstract
In this paper, a novel p-type junctionless field effect transistor (PJLFET) based on a partially depleted silicon-on-insulator (PD-SOI) is proposed and investigated. The novel PJLFET integrates a buried N+-doped layer under the channel to enable the device to be turned off, leading to [...] Read more.
In this paper, a novel p-type junctionless field effect transistor (PJLFET) based on a partially depleted silicon-on-insulator (PD-SOI) is proposed and investigated. The novel PJLFET integrates a buried N+-doped layer under the channel to enable the device to be turned off, leading to a special work mechanism and optimized performance. Simulation results show that the proposed PJLFET demonstrates an Ion/Ioff ratio of more than seven orders of magnitude, with Ion reaching up to 2.56 × 10−4 A/μm, Ioff as low as 3.99 × 10−12 A/μm, and a threshold voltage reduced to −0.43 V, exhibiting excellent electrical characteristics. Furthermore, a new CMOS inverter comprising a proposed PJLFET and a conventional NMOSFET is designed. With the identical geometric dimensions and gate electrode, the pull-up and pull-down driving capabilities of the proposed CMOS are equivalent, showing the potential for application in high-performance chips in the future. Full article
(This article belongs to the Special Issue Recent Advances and Challenges in Nanoscale and Microscale Semiconductor Devices)
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11 pages, 6457 KiB  
Article
Simulation of Normally-Off Vertical GaN MOSFET with a Novel Enhanced Sidewall Channel by Selective Area Growth
by Jiyao Du, Taofei Pu, Xiaobo Li, Liuan Li, Jinping Ao and Hongwei Gao
Micromachines 2025, 16(1), 105; https://doi.org/10.3390/mi16010105 - 17 Jan 2025
Viewed by 472
Abstract
In the present study, a novel normally-off vertical GaN MOSFET with an enhanced AlGaN/GaN channel on the sidewall has been proposed using the technology computer-aided design (TCAD) simulation. By using the selective area growth process, the trench structure and the enhanced sidewall channel [...] Read more.
In the present study, a novel normally-off vertical GaN MOSFET with an enhanced AlGaN/GaN channel on the sidewall has been proposed using the technology computer-aided design (TCAD) simulation. By using the selective area growth process, the trench structure and the enhanced sidewall channel are formed simultaneously, which is beneficial to enhance the conduction capability compared with the conventional trenched MOSFET. It demonstrates that a proper hole concentration and thickness of the p-GaN layer are key parameters to balance the threshold voltage, on-state resistance, and off-state breakdown voltage, resulting in the highest Baliga’s figure of merit value. Furthermore, a p-GaN shield layer is also adopted as a junction termination extension to modulate the electric field around the trench bottom. By optimizing the device parameters, a normally-off GaN MOSFET with good performance is designed. Full article
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15 pages, 5253 KiB  
Article
Interface Acoustic Waves in 128° YX-LiNbO3/SU-8/Overcoat Structures
by Cinzia Caliendo, Massimiliano Benetti, Domenico Cannatà, Farouk Laidoudi and Gaetana Petrone
Micromachines 2025, 16(1), 99; https://doi.org/10.3390/mi16010099 - 16 Jan 2025
Viewed by 527
Abstract
The propagation of interface acoustic waves (IAWs) in 128° YX-LiNbO3/SU-8/overcoat structures was theoretically studied and experimentally investigated for different types of overcoat materials and thicknesses of the SU-8 adhesive layer. Three-dimensional finite element method analysis was performed using Comsol Multiphysics software [...] Read more.
The propagation of interface acoustic waves (IAWs) in 128° YX-LiNbO3/SU-8/overcoat structures was theoretically studied and experimentally investigated for different types of overcoat materials and thicknesses of the SU-8 adhesive layer. Three-dimensional finite element method analysis was performed using Comsol Multiphysics software to design an optimized multilayer configuration able to achieve an efficient guiding effect of the IAW at the LiNbO3/overcoat interface. Numerical analysis results showed the following: (i) an overcoat faster than the piezoelectric half-space ensures that the wave propagation is confined mainly close to the surface of the LiNbO3, although with minimal scattering in the overcoat; (ii) the presence of the SU-8, in addition to performing the essential function of an adhesive layer, can also promote the trapping of the acoustic energy toward the surface of the piezoelectric substrate; and (iii) the electromechanical coupling efficiency of the IAW is very close to that of the surface acoustic wave (SAW) along the bare LiNbO3 half-space. The numerical predictions were experimentally assessed for some SU-8 layer thicknesses and overcoat material types. The propagation of the IAWs was experimentally measured in LiNbO3/SU-8/fused silica, LiNbO3/SU-8/(001)Si, and LiNbO3/SU-8/c-Al2O3 structures for an SU-8 layer about 15 µm thick; the velocities of the IAWs were found in good agreement with the theoretically calculated values. Although the interest in IAWs was born many years ago for packageless applications, it can currently be renewed if thought for applications in microfluidics. Indeed, the IAWs may represent a valid alternative to standing SAWs, which are strongly attenuated when travelling beneath the walls of polydimethylsiloxane (PDMS) microfluidic channels for continuous flow particle manipulation, provided that the channel is excavated into the overcoating. Full article
(This article belongs to the Section A：Physics)
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5 pages, 155 KiB  
Editorial
Recent Advances in Electromagnetic Devices: Design and Optimization
by Chanik Kang and Haejun Chung
Micromachines 2025, 16(1), 98; https://doi.org/10.3390/mi16010098 - 16 Jan 2025
Viewed by 587
Abstract
Electromagnetic devices are a continuous driving force in cutting-edge research and technology, finding applications in diverse fields such as optics [...] Full article
(This article belongs to the Special Issue Recent Advances in Electromagnetic Devices)
17 pages, 5715 KiB  
Article
Nano-Perforated Silicon Membrane with Monolithically Integrated Buried Cavity
by Sanjeev Vishal Kota, Anil Thilsted, Daniel Trimarco, Jesper Yue Pan, Ole Hansen, Jörg Hübner, Rafael Taboryski and Henri Jansen
Micromachines 2025, 16(1), 104; https://doi.org/10.3390/mi16010104 - 16 Jan 2025
Viewed by 586
Abstract
A wafer-scale process for fabricating monolithically suspended nano-perforated membranes (NPMs) with integrated support structures into silicon is developed. Existing fabrication methods are suitable for many desired geometries, but face challenges related to mechanical robustness and fabrication complexity. We demonstrate a process that utilizes [...] Read more.
A wafer-scale process for fabricating monolithically suspended nano-perforated membranes (NPMs) with integrated support structures into silicon is developed. Existing fabrication methods are suitable for many desired geometries, but face challenges related to mechanical robustness and fabrication complexity. We demonstrate a process that utilizes the cyclic deposit, remove, etch, and multi-step (DREM) process for directional etching of high-aspect-ratio (HAR) 300 nm in diameter nano-pores of 700 nm pitch. Subsequently, a buried cavity beneath the nano-pores is formed by switching to an isotropic etch, which effectively yields a thick NPM. Due to this architecture’s flexibility and process robustness, structural parameters such as membrane thickness, diameter, integrated support structures, and cavity height can be adjusted, allowing a wide range of NPM geometries. This work presents NPMs with final thicknesses of 4.5 µm, 6.5 µm, and 12 µm. Detailed steps of this new approach are discussed, including the etching of a through-silicon-via to establish the connection of the NPM to the macro-world. Our approach to fabricating NPMs within single-crystal silicon overcomes some of the limitations of previous methods. Owing to its monolithic design, this NPM architecture permits further enhancements through material deposition, pore size reduction, and surface functionalization, broadening its application potential for corrosive environments, purification and separation processes, and numerous other advanced applications. Full article
(This article belongs to the Special Issue Micro and Nano Machining Processes, 3rd Edition)
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29 pages, 7662 KiB  
Review
Advancements in MEMS Micromirror and Microshutter Arrays for Light Transmission Through a Substrate
by Shilby Baby, Mustaqim Siddi Que Iskhandar, Md Kamrul Hasan, Steffen Liebermann, Jiahao Chen, Hasnain Qasim, Shujie Liu, Eslam Farrag, Dennis Löber, Naureen Ahmed, Guilin Xu and Hartmut Hillmer
Micromachines 2025, 16(1), 103; https://doi.org/10.3390/mi16010103 - 16 Jan 2025
Viewed by 514
Abstract
This paper reviews and compares electrostatically actuated MEMS (micro-electro-mechanical system) arrays for light modulation and light steering in which transmission through the substrate is required. A comprehensive comparison of the technical achievements of micromirror arrays and microshutter arrays is provided. The main focus [...] Read more.
This paper reviews and compares electrostatically actuated MEMS (micro-electro-mechanical system) arrays for light modulation and light steering in which transmission through the substrate is required. A comprehensive comparison of the technical achievements of micromirror arrays and microshutter arrays is provided. The main focus of this paper is MEMS micromirror arrays for smart glass in building windows and façades. This technology utilizes millions of miniaturized and actuatable micromirrors on transparent substrates, enabling use with transmissive substrates such as smart windows for personalized daylight steering, energy saving, and heat management in buildings. For the first time, subfield-addressable MEMS micromirror arrays with an area of nearly 1 m2 are presented. The recent advancements in MEMS smart glass technology for daylight steering are discussed, focusing on aspects like the switching speed, scalability, transmission, lifetime study, and reliability of micromirror arrays. Finally, simulations demonstrating the potential yearly energy savings for investments in MEMS smart glazing are presented, including a comparison to traditional automated external blind systems in a model office room with definite user interactions throughout the year. Additionally, this platform technology with planarized MEMS elements can be used for laser safety goggles to shield pilots, tram, and bus drivers as well as security personal from laser threats, and is also presented in this paper. Full article
(This article belongs to the Collection Optical MEMS: Design, Fabrication, Control, Modeling and Developments)
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17 pages, 4684 KiB  
Article
Short-Circuit Performance Analysis of Commercial 1.7 kV SiC MOSFETs Under Varying Electrical Stress
by Shahid Makhdoom, Na Ren, Ce Wang, Yiding Wu, Hongyi Xu, Jiakun Wang and Kuang Sheng
Micromachines 2025, 16(1), 102; https://doi.org/10.3390/mi16010102 - 16 Jan 2025
Viewed by 570
Abstract
The short-circuit (SC) robustness of SiC MOSFETs is critical for high-power applications, yet 1.2 kV devices often struggle to meet the industry-standard SC withstand time (SCWT) under practical operating conditions. Despite growing interest in higher voltage classes, no prior study has systematically evaluated [...] Read more.
The short-circuit (SC) robustness of SiC MOSFETs is critical for high-power applications, yet 1.2 kV devices often struggle to meet the industry-standard SC withstand time (SCWT) under practical operating conditions. Despite growing interest in higher voltage classes, no prior study has systematically evaluated the SC performance of 1.7 kV SiC MOSFETs. This study provides the first comprehensive evaluation of commercially available 1.7 kV SiC MOSFETs, analyzing their SC performance under varying electrical stress conditions. Results indicate a clear trade-off between SC withstand time (SCWT) and drain-source voltage (VDS), with SCWT decreasing from 32 µs at 400 V to 4 µs at 1100 V. Under 600 V, a condition representative of practical use cases in many high-voltage applications, the devices achieved an SCWT of 12 µs, exceeding the industry-standard 10 µs benchmark—a threshold often unmet by 1.2 kV devices under similar conditions. Failure analysis revealed gate dielectric breakdown as the dominant failure mode at VDS ≤ 600 V, while thermal runaway was observed at higher voltages (VDS = 800 V and 1100 V). These findings underscore the critical importance of robust gate drive designs and effective thermal management. By surpassing the shortcomings of lower voltage classes, 1.7 kV SiC MOSFETs can be a more reliable, and efficient choice for operating at higher voltages in next-generation power systems. Full article
(This article belongs to the Special Issue Advances in GaN- and SiC-Based Electronics: Design and Applications)
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22 pages, 3052 KiB  
Article
A Low-Power General Matrix Multiplication Accelerator with Sparse Weight-and-Output Stationary Dataflow
by Peng Liu and Yu Wang
Micromachines 2025, 16(1), 101; https://doi.org/10.3390/mi16010101 - 16 Jan 2025
Viewed by 596
Abstract
General matrix multiplication (GEMM) in machine learning involves massive computation and data movement, which restricts its deployment on resource-constrained devices. Although data reuse can reduce data movement during GEMM processing, current approaches fail to fully exploit its potential. This work introduces a sparse [...] Read more.
General matrix multiplication (GEMM) in machine learning involves massive computation and data movement, which restricts its deployment on resource-constrained devices. Although data reuse can reduce data movement during GEMM processing, current approaches fail to fully exploit its potential. This work introduces a sparse GEMM accelerator with a weight-and-output stationary (WOS) dataflow and a distributed buffer architecture. It processes GEMM in a compressed format and eliminates on-chip transfers of both weights and partial sums. Furthermore, to map the compressed GEMM of various sizes onto the accelerator, an adaptable mapping scheme is designed. However, the irregular sparsity of weight matrices makes it difficult to store them in local buffers with the compressed format; denser vectors can exceed the buffer capacity, while sparser vectors may lead to the underutilization of buffers. To address this complication, this work also proposes an offline sparsity-aware shuffle strategy for weights, which balances the utilization of distributed buffers and minimizes buffer waste. Finally, a low-cost sparse computing method is applied to the WOS dataflow with globally shared inputs to achieve high computing throughput. Experiments with an FPGA show that the proposed accelerator achieves 1.73× better computing efficiency and 1.36× higher energy efficiency than existing approaches. Full article
(This article belongs to the Section E：Engineering and Technology)
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23 pages, 8668 KiB  
Article
Tribological and Structural Properties of Copper-Coated 3D-Printed Parts from Biodegradable Polymers
by Mihaela Feraru (Ilie), Simona-Nicoleta Mazurchevici, Nicoleta-Monica Lohan, Marcelin Benchea, Fabian Cezar Lupu and Dumitru Nedelcu
Micromachines 2025, 16(1), 100; https://doi.org/10.3390/mi16010100 - 16 Jan 2025
Viewed by 609
Abstract
This manuscript highlights the behavior of biodegradable polymers (PLA and HD PLA Green) coated with two distinct bronze alloy powders, Metco 51F-NS (Cu 9.5Al 1.2Fe) and Metco 445 (Cu 9.5Al). The coating was realized on printed samples by using the Atmospheric Plasma Spray [...] Read more.
This manuscript highlights the behavior of biodegradable polymers (PLA and HD PLA Green) coated with two distinct bronze alloy powders, Metco 51F-NS (Cu 9.5Al 1.2Fe) and Metco 445 (Cu 9.5Al). The coating was realized on printed samples by using the Atmospheric Plasma Spray (APS) technique. The current investigation will explain the results related to the surface quality, micro-structure, morphology, and thermal and tribological properties. Thus, from a structural point of view, the most uniform deposition was obtained in the case of composite powder Metco 51F-NS. The thermal behavior of the samples coated with copper-based powder achieved stability up to temperatures slightly above 200 °C, with carbonization of the matrix structure taking place around 350 °C. The micro-indentation and scratch analysis responses were significantly influenced by the semicrystalline structure of the samples and the presence of the powder compounds. Based on the increased characteristics of the coated samples, the authors of the present paper consider that parts made of biodegradable polymers and coated with copper microparticles are appropriate for some applications which take place in adverse operating conditions. Full article
(This article belongs to the Special Issue Micro- and Nanotechnologies: Materials, Manufacturing and Applications)
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11 pages, 2585 KiB  
Article
Narrow Linewidth All-Optical Microwave Oscillator Based on Torsional Radial Acoustic Modes of Single-Mode Fiber
by Wen Wang, Wenjun He, Xinyue Fang, Yi Liu, Yajun You, Mingxing Li, Lei Yu, Qing Yan, Yafei Hou, Jian He and Xiujian Chou
Micromachines 2025, 16(1), 97; https://doi.org/10.3390/mi16010097 - 15 Jan 2025
Viewed by 524
Abstract
A Hz level narrow linewidth all-optical microwave oscillator based on the torsional radial acoustic modes (TR2,m) of a single-mode fiber (SMF) is proposed and validated. The all-optical microwave oscillator consists of a 20 km SMF main ring cavity and a 5 [...] Read more.
A Hz level narrow linewidth all-optical microwave oscillator based on the torsional radial acoustic modes (TR2,m) of a single-mode fiber (SMF) is proposed and validated. The all-optical microwave oscillator consists of a 20 km SMF main ring cavity and a 5 km SMF sub ring cavity. The main ring cavity provides forward stimulated Brillouin scattering gain and utilizes a nonlinear polarization rotation effect to achieve TR2,7 mode locking. By combining the sub ring cavity with the main ring cavity and utilizing the Vernier effect, the TR2,7 mode microwave photonic single longitudinal mode (SLM) output can be ensured. Meanwhile, the 6.281 Hz narrow linewidth of the TR2,7 mode is achieved by reducing the intrinsic linewidth of the passive resonant cavity. The acoustic mode suppression ratio and side mode suppression ratio of the TR2,7 mode were 43 dB and 54 dB, respectively. The power and frequency fluctuations of within 40 min were approximately ±0.49 dB and ±0.187 kHz, indicating good stability. At a frequency offset of 10 kHz, the TR2,7 mode had a low phase noise value of −110 dBc/Hz. This solution can be used in various fields, such as high-precision radar detection, long-distance optical communication, and high-performance fiber optic sensing. Full article
(This article belongs to the Special Issue Fiber-Optic Technologies for Communication and Sensing)
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14 pages, 3285 KiB  
Article
Design of Interface ASIC with Power-Saving Switches for Capacitive Accelerometers
by Juncheng Cai, Yongbin Cai, Xiangyu Li, Shanshan Wang, Xiaowei Zhang, Xinpeng Di and Pengjun Wang
Micromachines 2025, 16(1), 96; https://doi.org/10.3390/mi16010096 - 15 Jan 2025
Viewed by 571
Abstract
High-precision, low-power MEMS accelerometers are extensively utilized across civilian applications. Closed-loop accelerometers employing switched-capacitor (SC) circuit topologies offer notable advantages, including low power consumption, high signal-to-noise ratio (SNR), and excellent linearity. Addressing the critical demand for high-precision, low-power MEMS accelerometers in modern geophones, [...] Read more.
High-precision, low-power MEMS accelerometers are extensively utilized across civilian applications. Closed-loop accelerometers employing switched-capacitor (SC) circuit topologies offer notable advantages, including low power consumption, high signal-to-noise ratio (SNR), and excellent linearity. Addressing the critical demand for high-precision, low-power MEMS accelerometers in modern geophones, this work focuses on the design and implementation of closed-loop interface ASICs (Application-Specific Integrated Circuits). The proposed interface circuit, based on switched-capacitor modulation technology, incorporates a low-noise charge amplifier, sample-and-hold circuit, integrator, and clock divider circuit. To minimize average power consumption, a switched operational amplifier (op-amp) technique is adopted, which temporarily disconnects idle op-amps from the power supply. Additionally, a class-AB output stage is employed to enhance the dynamic range of the circuit. The design was realized using a standard 0.35 μm CMOS process, culminating in the completion of layout design and small-scale engineering fabrication. The performance of the MEMS accelerometers was evaluated under a 3.3 V power supply, achieving a power consumption of 3.3 mW, an accelerometer noise density below 1 μg/√Hz, a sensitivity of 1.65 V/g, a measurement range of ±1 g, a nonlinearity of 0.15%, a bandwidth of 300 Hz, and a bias stability of approximately 36 μg. These results demonstrate the efficacy of the proposed design in meeting the stringent requirements of high-precision MEMS accelerometer applications. Full article
(This article belongs to the Special Issue MEMS Inertial Device, 2nd Edition)
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22 pages, 7907 KiB  
Article
The Impact of Targeted Therapies on Red Blood Cell Aggregation in Patients with Chronic Lymphocytic Leukemia Evaluated Using Software Image Flow Analysis
by Anika Alexandrova-Watanabe, Emilia Abadjieva, Lidia Gartcheva, Ariana Langari, Miroslava Ivanova, Margarita Guenova, Tihomir Tiankov, Velichka Strijkova, Sashka Krumova and Svetla Todinova
Micromachines 2025, 16(1), 95; https://doi.org/10.3390/mi16010095 - 15 Jan 2025
Viewed by 637
Abstract
Chronic lymphocytic leukemia (CLL), the most common type of leukemia, remains incurable with conventional therapy. Despite advances in therapies targeting Bruton’s tyrosine kinase and anti-apoptotic protein BCL-2, little is known about their effect on red blood cell (RBC) aggregation in blood flow. In [...] Read more.
Chronic lymphocytic leukemia (CLL), the most common type of leukemia, remains incurable with conventional therapy. Despite advances in therapies targeting Bruton’s tyrosine kinase and anti-apoptotic protein BCL-2, little is known about their effect on red blood cell (RBC) aggregation in blood flow. In this study, we applied a microfluidic device and a newly developed Software Image Flow Analysis to assess the extent of RBC aggregation in CLL patients and to elucidate the hemorheological effects of the commonly applied therapeutics Obinutuzumab/Venetoclax and Ibrutinib. The results revealed that, in RBC samples from untreated CLL patients, complex 3D clusters of large RBC aggregates are formed, and their number is significantly increased compared to healthy control samples. The application of the Obinutuzumab/Venetoclax combination did not affect this aspect of RBCs’ rheological behavior. In contrast, targeted therapy with Ibrutinib preserves the aggregation state of CLL RBCs to levels seen in healthy controls, demonstrating that Ibrutinib mitigates the alterations in the rheological properties of RBCs associated with CLL. Our findings highlight the alterations in RBC aggregation in CLL and the impact of different targeted therapies on RBCs’ rheological properties, which is critical for predicting the potential complications and side effects of CLL treatments, particularly concerning blood flow dynamics. Full article
(This article belongs to the Special Issue Interfacial Physics, Healthcare and Medicine: Microfluidics and Nanofluidics)
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13 pages, 4909 KiB  
Article
Design and Application of Uniaxially Sensitive Stress Sensor
by Kaituo Wu, Zixun Xiang, Xinbo Lu, Yichao Yan, Chunyang Wu, Tao Wang and Wanli Zhang
Micromachines 2025, 16(1), 94; https://doi.org/10.3390/mi16010094 - 15 Jan 2025
Viewed by 425
Abstract
Current stress sensors for microsystems face integration challenges and complex signal decoding. This paper proposes a real-time uniaxially sensitive stress sensor. It is obtained by simple combinations of bar resistors using their sensitivity differences in different axes. With the aid of a Wheatstone [...] Read more.
Current stress sensors for microsystems face integration challenges and complex signal decoding. This paper proposes a real-time uniaxially sensitive stress sensor. It is obtained by simple combinations of bar resistors using their sensitivity differences in different axes. With the aid of a Wheatstone bridge, the sensor can measure the uniaxial stress magnitude by simple calibration of the stress against the output voltage and detect the bidirectional stress magnitude and direction in a micro-zone by simple rotation. The theoretical sensitivity obtained from simulation is 0.087 mV/V·MPa when the X-bridge is stressed in the X-direction under 1 V of excitation, and the test sensitivity of the X-bridge prepared in this paper is 0.1 mV/V·MPa. The design is structurally and procedurally simple, exhibits better temperature stability, and reduces interface requirements, making it suitable for the health monitoring of multi-chip microsystem chips. Full article
(This article belongs to the Special Issue Acoustic Transducers and Their Applications, 2nd Edition)
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15 pages, 2859 KiB  
Article
A Microfluidic-Based Cell-Stretching Culture Device That Allows for Easy Preparation of Slides for Observation with High-Magnification Objective Lenses
by Momoko Kato and Kae Sato
Micromachines 2025, 16(1), 93; https://doi.org/10.3390/mi16010093 - 15 Jan 2025
Viewed by 641
Abstract
Microfluidic-based cell-stretching devices are vital for studying the molecular pathways involved in cellular responses to mechanobiological processes. Accurate evaluation of these responses requires detailed observation of cells cultured in this cell-stretching device. This study aimed to develop a method for preparing microscope slides [...] Read more.
Microfluidic-based cell-stretching devices are vital for studying the molecular pathways involved in cellular responses to mechanobiological processes. Accurate evaluation of these responses requires detailed observation of cells cultured in this cell-stretching device. This study aimed to develop a method for preparing microscope slides to enable high-magnification imaging of cells in these devices. The key innovation is creating a peelable bond between the cell culture membrane and the upper channel, allowing for easy removal of the upper layer and precise cutting of the membrane for high-magnification microscopy. Using the fabricated device, OP9 cells (15,000 cells/channel) were stretched, and the effects of focal adhesion proteins and the intracellular distribution of YAP1 were examined under a fluorescence microscope with 100× and 60× objectives. Stretch stimulation increased integrinβ1 expression and promoted integrin–vinculin complex formation by approximately 1.4-fold in OP9 cells. Furthermore, YAP1 nuclear localization was significantly enhanced (approximately 1.3-fold) during stretching. This method offers a valuable tool for researchers using microfluidic-based cell-stretching devices. The advancement of imaging techniques in microdevice research is expected to further drive progress in mechanobiology research. Full article
(This article belongs to the Special Issue Recent Advances in Lab-on-a-Chip and Their Biomedical Applications)
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14 pages, 3900 KiB  
Article
Dual-Mode Textile Sensor Based on PEDOT:PSS/SWCNTs Composites for Pressure–Temperature Detection
by Ying Wang, Qingchao Zhang and Zhidong Zhang
Micromachines 2025, 16(1), 92; https://doi.org/10.3390/mi16010092 - 14 Jan 2025
Viewed by 595
Abstract
As an innovative branch of electronics, intelligent electronic textiles (e-textiles) have broad prospects in applications such as e-skin, human–computer interaction, and smart homes. However, it is still a challenge to distinguish multiple stimuli in the same e-textile. Herein, we propose a dual-parameter smart [...] Read more.
As an innovative branch of electronics, intelligent electronic textiles (e-textiles) have broad prospects in applications such as e-skin, human–computer interaction, and smart homes. However, it is still a challenge to distinguish multiple stimuli in the same e-textile. Herein, we propose a dual-parameter smart e-textile that can detect human pulse and body temperature in real time, with high performance and no signal interference. The doping of SWCNTs in PEDOT:PSS improves the electrical conductivity and Seebeck coefficient of the prepared composites, which results in excellent pressure and temperature-sensing properties of the PEDOT:PSS/SWCNTs/CS@PET-textile (PSCP) sensor. The dual-mode sensor has high sensitivity (32.4 kPa−1), fast response time (~21 ms), and excellent durability (>2000 times) in pressure detection. Concurrently, this sensor maintains a high Seebeck coefficient of 25 μV/K in the 0–120 K temperature range with a tremendous linear relationship. Based on impressive dual-mode sensing characteristics and independent temperature-difference- and pressure-sensing mechanisms, smart e-textile sensors realize the real-time simultaneous monitoring of weak pulse signals and human body temperature, showing great potential in medical healthcare. In addition, the potential energy is excited by the temperature gradient between the human skin and the environment, which provides a novel idea for wearable self-powered devices. Full article
(This article belongs to the Special Issue Flexible and Wearable Sensors, 3rd Edition)
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21 pages, 10698 KiB  
Article
A High-Precision Micro-Roll Forming Facility for Fuel Cell Metal Bipolar Plate Production
by Matthias Weiss, Peng Zhang and Michael Pereira
Micromachines 2025, 16(1), 91; https://doi.org/10.3390/mi16010091 - 14 Jan 2025
Viewed by 628
Abstract
The metal bipolar plate is a critical component of the hydrogen fuel cell stack used in proton exchange membrane fuel cells. Bipolar plates must have high accuracy micro-channels with a high aspect ratio (AR) between the channel depth and the half [...] Read more.
The metal bipolar plate is a critical component of the hydrogen fuel cell stack used in proton exchange membrane fuel cells. Bipolar plates must have high accuracy micro-channels with a high aspect ratio (AR) between the channel depth and the half periodic width to achieve optimal cell performance. Conventional forming methods, such as micro-stamping, hydroforming, and rubber pad forming, cannot achieve these high ARs given that in these processes, material deformation is dominated by stretch deformation. In micro-roll forming the major deformation mode is bending, and this enables production of channels with higher ARs than is currently possible. However, micro-roll forming uses multiple sets of forming roll stands to form the part and this leads to technological challenges related to tool alignment and roll tool precision that must be overcome before widespread application can be achieved. This study presents a new methodology to achieve tight tool tolerances when producing micro-roll tooling by utilizing wire-EDM and micro-turning techniques. This is combined with a new micro-roll former design that enables high-precision tool alignment across multiple roll stations. Proof of concept is provided through micro-roll forming trials performed on ultra-thin titanium sheets that show that the proposed technology can achieve tight dimensional tolerances in the sub-millimeter scale that suits bipolar plate applications. Full article
(This article belongs to the Special Issue Microforming Technology and Its Applications)
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14 pages, 1880 KiB  
Article
Trench MOS Schottky Diodes: A Physics-Based Analytical Model Approach to Charge Sharing
by Mohammed Tanvir Quddus, Alvaro D. Latorre-Rey, Zeinab Ramezani and Mihir Mudholkar
Micromachines 2025, 16(1), 90; https://doi.org/10.3390/mi16010090 - 14 Jan 2025
Viewed by 521
Abstract
Trench MOS Barrier Schottky (TMBS) rectifiers offer superior static and dynamic electrical characteristics when compared with planar Schottky rectifiers for a given active die size. The unique structure of TMBS devices allows for efficient manipulation of the electric field, enabling higher doping concentrations [...] Read more.
Trench MOS Barrier Schottky (TMBS) rectifiers offer superior static and dynamic electrical characteristics when compared with planar Schottky rectifiers for a given active die size. The unique structure of TMBS devices allows for efficient manipulation of the electric field, enabling higher doping concentrations in the drift region and thus achieving a lower forward voltage drop (VF) and reduced leakage current (IR) while maintaining high breakdown voltage (BV). While the use of trenches to push electric fields away from the mesa surface is a widely employed concept for vertical power devices, a significant gap exists in the analytical modeling of this effect, with most prior studies relying heavily on computationally intensive numerical simulations. This paper introduces a new physics-based analytical model to elucidate the behavior of electric field and potential in the mesa region of a TMBS rectifier in reverse bias. Our model leverages the concept of shared charge between the Schottky and MOS junctions, capturing how electric field distribution is altered in response to trench geometry and bias conditions. This shared charge approach not only simplifies the analysis of electric field distribution but also reveals key design parameters, such as trench depth, oxide thickness, and doping concentration, that influence device performance. This model employs the concept of shared charge between the vertical Schottky and MOS junction. Additionally, it provides a detailed view of the electric field suppression mechanism in the TMBS device, highlighting the significant effects of the inversion charge on the MOS interface. By comparing our analytical results with TCAD simulations, we demonstrate strong agreement, underscoring the model’s accuracy and its potential to serve as a more accessible alternative to resource-intensive simulations. This work contributes to a valuable tool for TMBS device design, offering insights into electric field management that support high-efficiency, high-voltage applications, including power supplies, automotive electronics, and renewable energy systems. Full article
(This article belongs to the Special Issue Recent Advances and Challenges in Nanoscale and Microscale Semiconductor Devices)
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25 pages, 2945 KiB  
Review
Leadless Pacing: Current Status and Ongoing Developments
by Richard G. Trohman
Micromachines 2025, 16(1), 89; https://doi.org/10.3390/mi16010089 - 14 Jan 2025
Viewed by 590
Abstract
Although significant strides have been made in cardiac pacing, the field is still evolving. While transvenous permanent pacing is highly effective in the management of bradyarrhythmias, it is not risk free and may result in significant morbidity and, rarely, mortality. Transvenous leads are [...] Read more.
Although significant strides have been made in cardiac pacing, the field is still evolving. While transvenous permanent pacing is highly effective in the management of bradyarrhythmias, it is not risk free and may result in significant morbidity and, rarely, mortality. Transvenous leads are often the weakest link in a pacing system. They may dislodge, fracture, or suffer breaches in their insulation. This review was undertaken to clarify leadless risks, benefits, and alternatives to transvenous cardiac pacing for bradyarrhythmias and heart failure management. In order to clarify the role(s) of leadless pacing, this narrative review was undertaken by searching MEDLINE to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and review articles, as well as other clinically relevant reports and studies. The search was limited to English-language reports published between 1932 and 2024. Leadless pacing was searched using the terms Micra™, Nanostim™, AVEIR™, single-chamber leadless pacemaker, dual-chamber leadless pacemaker, cardiac resynchronization therapy (CRT), cardiac physiological pacing (CPP) and biventricular pacing (BiV). Google and Google Scholar, as well as bibliographies of identified articles were also reviewed for additional references. The advantages and limitations of leadless pacing as well as options that are under investigation are discussed in detail. Full article
(This article belongs to the Special Issue Feature Reviews in Micromachines 2024)
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9 pages, 4231 KiB  
Communication
A Low-Profile Balanced Dielectric Resonator Filtering Power Divider with Isolation
by Rong Cai, Chuan Shao and Kai Xu
Micromachines 2025, 16(1), 88; https://doi.org/10.3390/mi16010088 - 14 Jan 2025
Viewed by 459
Abstract
A balanced dielectric resonator filtering power divider with isolation performance is proposed. By using the coupling of the TE111y modes between three rectangle dielectric resonators, combined with balanced feed structures, the differential-mode filtering and power dividing functions, as well as [...] Read more.
A balanced dielectric resonator filtering power divider with isolation performance is proposed. By using the coupling of the TE111y modes between three rectangle dielectric resonators, combined with balanced feed structures, the differential-mode filtering and power dividing functions, as well as the common-mode suppression were achieved effectively. Additionally, by technically utilizing the hollow structure of the stacked substrates, isolation resistor structures are introduced at the two output ports to improve the isolation level of the power divider. It can solve the problem of traditional metal-cavity dielectric resonator filter power dividers being unable to add isolation structures due to structural reasons. Compared with the reported dielectric resonator filtering power dividers, the proposed one has the characters of a lower profile and high isolation. For demonstration, one dielectric resonator filtering power divider was fabricated and measured at 11.65 GHz with the profile of 0.66 λg and an isolation higher than 15 dB. The simulation results are in good agreement with the measured results. Full article
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12 pages, 7074 KiB  
Article
An X-Band Class-J GaN MMIC Power Amplifier with Well-Designed In-Band Output Power Flatness
by Bangjie Zheng, Zhiqun Cheng, Zhiwei Zhang, Ruizhe Zhang, Tingwei Gong and Chao Le
Micromachines 2025, 16(1), 87; https://doi.org/10.3390/mi16010087 - 13 Jan 2025
Viewed by 541
Abstract
This paper presents an X-band high-power GaN MMIC power amplifier (PA). To balance efficiency, output power, and saturated power flatness, the load-line theory is employed to analyze and validate the power variation trends within an extended continuous Class B/J (CCBJ) impedance space. Theoretical [...] Read more.
This paper presents an X-band high-power GaN MMIC power amplifier (PA). To balance efficiency, output power, and saturated power flatness, the load-line theory is employed to analyze and validate the power variation trends within an extended continuous Class B/J (CCBJ) impedance space. Theoretical constant power contours are plotted within this space. An L-C impedance matching network is used to match the amplifier’s output impedance to the overlapping region of the 0.5 dB constant power contour and the CCBJ impedance space, significantly improving the in-band power flatness of the PA based on the CCBJ design approach. Additionally, an RC parallel structure is integrated into the interstage matching network to maximize gain while ensuring stability. The proposed PA, implemented using a 0.25 µm commercial GaN process, achieves a saturated output power of 47–47.6 dBm with in-band fluctuations within ± 0.3 dB, a power gain of 27.0–27.8 dB, and an efficiency of 40–45.5% across the X-band. Full article
(This article belongs to the Special Issue Novel Power Amplifiers and Integrated Circuits: Design and Applications)
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13 pages, 4773 KiB  
Article
Research on Helical Electrode Electrochemical Drilling Assisted by Anode Vibration for Jet Micro-Hole Arrays on Tube Walls
by Tao Yang, Yikai Xiao, Yusen Hang, Xiujuan Wu and Weijing Kong
Micromachines 2025, 16(1), 86; https://doi.org/10.3390/mi16010086 - 13 Jan 2025
Viewed by 486
Abstract
The electrochemical cutting technique, utilizing electrolyte flushing through micro-hole arrays in the radial direction of a tube electrode, offers the potential for cost-effective and high-surface-integrity machining of large-thickness, straight-surface structures of difficult-to-cut materials. However, fabricating the array of jet micro-holes on the tube [...] Read more.
The electrochemical cutting technique, utilizing electrolyte flushing through micro-hole arrays in the radial direction of a tube electrode, offers the potential for cost-effective and high-surface-integrity machining of large-thickness, straight-surface structures of difficult-to-cut materials. However, fabricating the array of jet micro-holes on the tube electrode sidewall remains a significant challenge, limiting the broader application of this technology. To enhance the efficiency and quality of machining these jet micro-holes on the tube sidewall, a helical electrode electrochemical drilling method assisted by anode vibration has been proposed. The influence of parameters, such as the rotational direction and speed of the helical electrode, as well as the vibration amplitude and frequency of the workpiece, on the machining results was investigated using fluid field simulation and machining experiments. It was found that these auxiliary movements could facilitate the renewal of electrolytes within the machining gap, thereby enhancing the efficiency and quality of electrochemical drilling. Using the optimized machining parameters, an array of 10 jet micro-holes with a diameter of 200 μm was machined on the metal tube sidewall. Electrochemical cutting with radial electrolyte flushing tests were then performed through these micro-holes. Full article
(This article belongs to the Special Issue Ultra-Precision Machining of Difficult-to-Machine Materials)
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17 pages, 9246 KiB  
Article
Simulation and Experimental Study of the Single-Pulse Femtosecond Laser Ablation Morphology of GaN Films
by Mingyuan Wang, Tong Zhang, Yanping Yuan, Zhiyong Wang, Yanlei Liu and Lin Chen
Micromachines 2025, 16(1), 85; https://doi.org/10.3390/mi16010085 - 13 Jan 2025
Viewed by 542
Abstract
Gallium nitride (GaN) exhibits distinctive physical and chemical properties that render it indispensable in a multitude of electronic and optoelectronic devices. Given that GaN is a typical hard and brittle material that is difficult to machine, femtosecond laser technology provides an effective and [...] Read more.
Gallium nitride (GaN) exhibits distinctive physical and chemical properties that render it indispensable in a multitude of electronic and optoelectronic devices. Given that GaN is a typical hard and brittle material that is difficult to machine, femtosecond laser technology provides an effective and convenient tool for processing such materials. However, GaN undergoes complex physical and chemical changes during high-power ablation, which poses a challenge to high-precision processing with controllable geometry. In this study, the quantitative relationship between the parameters of a single-pulse femtosecond laser and GaN ablation morphology was investigated using isotherm distribution. A multiphysics model using COMSOL Multiphysics® was developed to generate the isothermal distributions. Experiments were conducted on the femtosecond laser ablation of GaN at various single-pulse energies, and the resulting ablation morphologies were compared with the predictions from the multiphysics model. The comparison demonstrated that the calculated isotherm distribution accurately predicted not only the ablation diameter and depth but also the crater shape across a broad range of laser fluences. The predicted errors of the ablation diameters and depths were within 4.71% and 10.9%, respectively. The root mean square error (RMSE) and coefficient of determination (R2) were employed to evaluate the prediction errors associated with the crater shapes, which fell within the range of 0.018–0.032 μm and 0.77–0.91, respectively. This study can provide an important reference for utilizing femtosecond lasers in the precise ablation of GaN to achieve desired geometries. Full article
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25 pages, 12422 KiB  
Article
Effects of Machining Parameters on Abrasive Flow Machining of Single Crystal γ-TiAl Alloy Based on Molecular Dynamics
by Junye Li, Chao Song, Xin Du, Hongcai Xie, Jinghe Zhao and Ying Chen
Micromachines 2025, 16(1), 84; https://doi.org/10.3390/mi16010084 - 13 Jan 2025
Viewed by 550
Abstract
Observing the intricate microstructure changes in abrasive flow machining with traditional experimental methods is difficult. Molecular dynamics simulations are used to look at the process of abrasive flow processing from a microscopic scale in this work. A molecular dynamics model for micro-cutting a [...] Read more.
Observing the intricate microstructure changes in abrasive flow machining with traditional experimental methods is difficult. Molecular dynamics simulations are used to look at the process of abrasive flow processing from a microscopic scale in this work. A molecular dynamics model for micro-cutting a single crystal γ-TiAl alloy with a rough surface in a fluid medium environment is constructed, which is more realistic. The evolution of material removal, cutting force, temperature, energy, and dislocation during micro-cutting are analyzed. The impact of cutting depth, abrasive particle sizes, and abrasive material on the micro-cutting process are analyzed. The analysis shows that the smaller cutting depth and abrasive particle sizes are beneficial to obtain a better machining surface, and the cubic boron nitride (CBN) abrasive is an effective substitute material for diamonds. The purpose of this study is to provide unique insights for improving the material removal rate and subsurface quality by adjusting machining parameters in actual abrasive flow precision machining. Full article
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11 pages, 3416 KiB  
Article
Efficient Particle Manipulation Using Contraction–Expansion Microchannels Embedded with Hook-Shaped Arrays
by Di Huang, Yan Zhao, Chao Cao and Jiyun Zhao
Micromachines 2025, 16(1), 83; https://doi.org/10.3390/mi16010083 - 13 Jan 2025
Viewed by 558
Abstract
Inertial microfluidics, as an efficient method for the manipulation of micro-/nanoparticles, has garnered significant attention due to its advantages of high throughput, structural simplicity, no need for external fields, and sheathless operation. Common structures include straight channels, contraction–expansion array (CEA) channels, spiral channels, [...] Read more.
Inertial microfluidics, as an efficient method for the manipulation of micro-/nanoparticles, has garnered significant attention due to its advantages of high throughput, structural simplicity, no need for external fields, and sheathless operation. Common structures include straight channels, contraction–expansion array (CEA) channels, spiral channels, and serpentine channels. In this study, we developed a CEA channel embedded with hook-shaped microstructures to modify the characteristics of vortices. Through experimental studies, we investigated the particles’ migration mechanisms within the proposed structure. The findings indicated that, in comparison to conventional rectangular microstructures, the particles within the hook-shaped microstructured CEA channels experienced a more pronounced influence from inertial lift forces. Moreover, the magnitude of the second flow within the novel configuration was directly proportional to the channel width, the length of the expansion segment, and the embedding depth of the microstructure. The innovative structure was subsequently employed for particle trapping, focusing, and separation. The experimental outcomes revealed focusing efficiency of up to 99.1% and sorting efficiency of up to 97%. This research holds the potential to enhance the foundational theory of Dean flows and broaden the application spectrum of inertial contraction–expansion microfluidic chips. Full article
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