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Micromachines, Volume 16, Issue 2 (February 2025) – 86 articles

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18 pages, 5900 KiB  
Article
Research on Deflection and Stress Analyses and the Improvement of the Removal Uniformity of Silicon in a Single-Sided Polishing Machine Under Pressure
by Guoqing Ye and Zhenqiang Yao
Micromachines 2025, 16(2), 198; https://doi.org/10.3390/mi16020198 (registering DOI) - 8 Feb 2025
Abstract
The chemical–mechanical polishing (CMP) of silicon wafers involves high-precision surface machining after double-sided lapping. Silicon wafers are subjected to chemical corrosion and mechanical removal under pressurized conditions. The multichip CMP process for 4~6-inch silicon wafers, such as those in MOSFETs (Metal Oxide Semiconductor [...] Read more.
The chemical–mechanical polishing (CMP) of silicon wafers involves high-precision surface machining after double-sided lapping. Silicon wafers are subjected to chemical corrosion and mechanical removal under pressurized conditions. The multichip CMP process for 4~6-inch silicon wafers, such as those in MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated-Gate Bipolar Transistors), and MEMS (Micro-Electromechanical System) field materials, is conducted to maintain multiple chips to improve efficiency and improve polish removal uniformity; that is, the detected TTV (total thickness variation) gradually increases from 10 μm to less than 3 μm. In this work, first, a mathematical model for calculating the small deflection of silicon wafers under pressure is established, and the limit values under two boundary conditions of fixed support and simple support are calculated. Moreover, the removal uniformity of the silicon wafers is improved by improving the uniformity of the wax-coated adhesion state and adjusting the boundary conditions to reflect a fixed support state. Then, the stress distribution of the silicon wafers under pressure is simulated, and the calculation methods for measuring the TTV of the silicon wafers and the uniformity measurement index are described. Stress distribution is changed by changing the size of the pressure ring to achieve the purpose of removing uniformity. This study provides a reference for improving the removal uniformity of multichip silicon wafer chemical–mechanical polishing. Full article
(This article belongs to the Special Issue Functional Materials and Microdevices, 2nd Edition)
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3 pages, 136 KiB  
Editorial
Research Progress on Insulated Gate Bipolar Transistor (IGBT) Modules
by Peisheng Liu and Yaohui Deng
Micromachines 2025, 16(2), 197; https://doi.org/10.3390/mi16020197 (registering DOI) - 8 Feb 2025
Abstract
With the rapid advancement of social productivity and technological innovation, the insulated gate bipolar transistor (IGBT) has emerged as a cornerstone in modern power electronic devices [...] Full article
(This article belongs to the Special Issue Insulated Gate Bipolar Transistor (IGBT) Modules)
14 pages, 37756 KiB  
Article
Optimized Phase-Generated Carrier Demodulation Algorithm for Membrane-Free Fabry-Pérot Acoustic Sensor with High Sensitivity
by Yang Yang, Xinyu Zhao, Yongqiu Zheng, Juan Cui, Dongqing Zhao, Zhixuan Zheng, Yan Cao and Chenyang Xue
Micromachines 2025, 16(2), 196; https://doi.org/10.3390/mi16020196 (registering DOI) - 8 Feb 2025
Viewed by 111
Abstract
Demodulation of fiber optic Fabry–Pérot (F-P) acoustic sensors with high sensitivity and a large dynamic range continues to pose significant challenges. In this paper, we propose an advanced phase-generated carrier (PGC) demodulation algorithm, applied innovatively to membrane-free F-P acoustic sensors operating under high [...] Read more.
Demodulation of fiber optic Fabry–Pérot (F-P) acoustic sensors with high sensitivity and a large dynamic range continues to pose significant challenges. In this paper, we propose an advanced phase-generated carrier (PGC) demodulation algorithm, applied innovatively to membrane-free F-P acoustic sensors operating under high sound pressure. The algorithm optimizes acoustic demodulation results by adjusting the mixing phase delay, achieving the best signal to noise and distortion ratio (SINAD) and total harmonic distortion (THD) (<1%). Additionally, by introducing the cosine component of the acoustic signal obtained directly after filtering the interference signal, into the demodulation algorithm process, the sensitivity of the sensor at high sound pressure is significantly improved. The experimental results show that the ameliorated algorithm obtains a demodulation sensitivity of 34.95 μrad/Pa and a THD of 0.87%, both of which are superior to traditional PGC demodulation algorithms under the same experimental conditions. At the same time, the minimum detectable sound pressure of 129.73 mPa/Hz1/2 was obtained, and the sound pressure tested in the experiment at a frequency of 1 kHz was as high as 3169.78 Pa (164 dB). With the proposed algorithm, the flatness of the frequency response is ±0.82 dB from 100 Hz to 33 kHz, and a dynamic range of up to 102.6 dB was obtained, making it relevant in the field of aerospace acoustic measurements. Full article
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18 pages, 4880 KiB  
Article
Design, Analysis, and Simulation of a MEMS Tuning Fork Gyroscope with a Mechanical Amplification Structure
by Haotian Hu, Benedetta Calusi, Alvise Bagolini and Maria F. Pantano
Micromachines 2025, 16(2), 195; https://doi.org/10.3390/mi16020195 (registering DOI) - 8 Feb 2025
Viewed by 110
Abstract
This paper describes a novel micro-electro-mechanical system (MEMS) tuning fork gyroscope (TFG) design that employs a chevron-shaped displacement mechanism to amplify the displacement generated by the Coriolis force, thereby increasing the TFG’s mechanical sensitivity. This approach was evaluated using both theoretical modeling and [...] Read more.
This paper describes a novel micro-electro-mechanical system (MEMS) tuning fork gyroscope (TFG) design that employs a chevron-shaped displacement mechanism to amplify the displacement generated by the Coriolis force, thereby increasing the TFG’s mechanical sensitivity. This approach was evaluated using both theoretical modeling and finite element analysis (FEA), and the results showed a high degree of agreement between the two methods. A conventional TFG having a comparable area was also designed and analyzed for comparison purposes. By introducing the displacement amplification mechanism, the proposed MEMS TFG design provides an output displacement about 2.5 times higher than the conventional design, according to the computation, without increasing the device footprint. Theoretical analysis and FEA on the TFG with amplification and a conventional TFG confirmed that the amplified displacement significantly improves the mechanical sensitivity of the gyroscope compared to conventional TFG designs. Full article
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76 pages, 5996 KiB  
Review
From Present Innovations to Future Potential: The Promising Journey of Lithium-Ion Batteries
by Pooya Parvizi, Milad Jalilian, Alireza Mohammadi Amidi, Mohammad Reza Zangeneh and Jordi-Roger Riba
Micromachines 2025, 16(2), 194; https://doi.org/10.3390/mi16020194 (registering DOI) - 7 Feb 2025
Viewed by 601
Abstract
Lithium-ion batteries (LIBs) have become integral to modern technology, powering portable electronics, electric vehicles, and renewable energy storage systems. This document explores the complexities and advancements in LIB technology, highlighting the fundamental components such as anodes, cathodes, electrolytes, and separators. It delves into [...] Read more.
Lithium-ion batteries (LIBs) have become integral to modern technology, powering portable electronics, electric vehicles, and renewable energy storage systems. This document explores the complexities and advancements in LIB technology, highlighting the fundamental components such as anodes, cathodes, electrolytes, and separators. It delves into the critical interplay of these components in determining battery performance, including energy density, cycling stability, and safety. Moreover, the document addresses the significant sustainability challenges posed by the widespread adoption of LIBs, focusing on resource depletion and environmental impact. Various recycling practices, including hydrometallurgy, pyrometallurgy, and direct recycling, are evaluated for their efficiency in metal recovery and ecological footprint. The advancements in recycling technologies aim to mitigate the adverse effects of LIB waste, emphasizing the need for sustainable and scalable solutions. The research underscores the importance of ongoing innovation in electrode materials and recycling methodologies, reminding us of our responsibility and commitment to finding and implementing these solutions, as this continuous improvement is crucial to enhance the performance, safety, and sustainability of LIBs, ensuring their continued relevance in the evolving energy storage landscape. Full article
(This article belongs to the Special Issue Nanotechnology in Li-Ion Batteries and Beyond)
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13 pages, 2045 KiB  
Article
A Hardware Accelerator for Real-Time Processing Platforms Used in Synthetic Aperture Radar Target Detection Tasks
by Yue Zhang, Yunshan Tang, Yue Cao and Zhongjun Yu
Micromachines 2025, 16(2), 193; https://doi.org/10.3390/mi16020193 - 7 Feb 2025
Viewed by 236
Abstract
The deep learning object detection algorithm has been widely applied in the field of synthetic aperture radar (SAR). By utilizing deep convolutional neural networks (CNNs) and other techniques, these algorithms can effectively identify and locate targets in SAR images, thereby improving the accuracy [...] Read more.
The deep learning object detection algorithm has been widely applied in the field of synthetic aperture radar (SAR). By utilizing deep convolutional neural networks (CNNs) and other techniques, these algorithms can effectively identify and locate targets in SAR images, thereby improving the accuracy and efficiency of detection. In recent years, achieving real-time monitoring of regions has become a pressing need, leading to the direct completion of real-time SAR image target detection on airborne or satellite-borne real-time processing platforms. However, current GPU-based real-time processing platforms struggle to meet the power consumption requirements of airborne or satellite applications. To address this issue, a low-power, low-latency deep learning SAR object detection algorithm accelerator was designed in this study to enable real-time target detection on airborne and satellite SAR platforms. This accelerator proposes a Process Engine (PE) suitable for multidimensional convolution parallel computing, making full use of Field-Programmable Gate Array (FPGA) computing resources to reduce convolution computing time. Furthermore, a unique memory arrangement design based on this PE aims to enhance memory read/write efficiency while applying dataflow patterns suitable for FPGA computing to the accelerator to reduce computation latency. Our experimental results demonstrate that deploying the SAR object detection algorithm based on Yolov5s on this accelerator design, mounted on a Virtex 7 690t chip, consumes only 7 watts of dynamic power, achieving the capability to detect 52.19 512 × 512-sized SAR images per second. Full article
(This article belongs to the Section E:Engineering and Technology)
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13 pages, 1878 KiB  
Article
Integrated Device for Cancer Nucleic Acid Biomarker Detection at Body Temperature
by Chang Chen, Bin Wu, Xuesong Li, Yuhang Jin, Hangyu Zhang, Bo Liu, Zhengyao Zhang and Na Li
Micromachines 2025, 16(2), 192; https://doi.org/10.3390/mi16020192 - 7 Feb 2025
Viewed by 187
Abstract
The quantitative analysis of nucleic acid markers is extensively utilized in cancer detection. However, it faces significant challenges, such as the need for specialized detection devices and the inherent complexity of testing procedures. To address these issues, this study proposes a simplified, rapid, [...] Read more.
The quantitative analysis of nucleic acid markers is extensively utilized in cancer detection. However, it faces significant challenges, such as the need for specialized detection devices and the inherent complexity of testing procedures. To address these issues, this study proposes a simplified, rapid, and user-friendly platform for cancer nucleic acid marker detection. We firstly designed a polydimethylsiloxane (PDMS) device for the isothermal amplification reaction of nucleic acid biomarkers based on reverse-transcription recombinase-aided amplification (RT-RAA) technology. Specifically, three potential cancer nucleic acid biomarkers, carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), and prostate cancer antigen 3 (PCA3) were amplified from human serum or urine samples in the PDMS device at body temperature. The reaction chamber was directly integrated with nucleic acid test strips labeled with colloidal gold nanoparticles, allowing for the visual observation of the detection results for the amplification products. The optimal reaction conditions, such as pH, reaction time, antibody, and streptavidin concentration, were defined after a series of optimization studies. The findings demonstrated that the optimal RT-RAA reaction time was 20 min, the primary antibodies were labeled with colloidal gold to the greatest extent at pH 8.5, and the optimal concentrations of secondary antibody and streptavidin were 1.0 mg/mL and 0.5 mg/mL, respectively. Furthermore, this novel detection approach could not only exhibit excellent sensitivity and specificity but also show high accuracy for the analysis of nucleic acid biomarkers in both clinical serum and urine samples. Therefore, the simplified and more convenient operation platform provides a new insight for the semi-quantitative analysis of cancer nucleic acid biomarkers and the rapid screening of early cancer, thereby offering a promising alternative to oncological point-of-care testing (POCT) diagnostics. Full article
23 pages, 10686 KiB  
Article
Impact of Layer Materials, Their Thicknesses, and Their Reflectivities on Emission Color and NVIS Compatibility in OLED Devices for Avionic Display Applications
by Esin Uçar, Alper Ülkü, Halil Mert Kaya, Ramis Berkay Serin, Rifat Kaçar, Ahmet Yavuz Oral and Ebru Menşur
Micromachines 2025, 16(2), 191; https://doi.org/10.3390/mi16020191 - 7 Feb 2025
Viewed by 289
Abstract
Organic Light Emitting Diode (OLED) technology is preferred in modern display applications due to its superior efficiency, color quality, and flexibility. It also carries a high potential of applicability in military displays where emission color tuning is required for MIL-STD-3009 Night Vision Imaging [...] Read more.
Organic Light Emitting Diode (OLED) technology is preferred in modern display applications due to its superior efficiency, color quality, and flexibility. It also carries a high potential of applicability in military displays where emission color tuning is required for MIL-STD-3009 Night Vision Imaging Systems (NVISs), as compatibility is critical. Herein, we report the effects of different OLED device layer materials and thicknesses such as the hole injection layer (HIL), hole transport layer (HTL), and electron transport layer (ETL) on the color coordinates, luminance, and efficiency of OLED devices designed for night vision (NVIS) compatibility. In this study, simulation tools like SETFOS® (Semi-conducting Emissive Thin Film Optics Simulator), MATLAB®, and LightTools® (Illumination Design Software) were used to verify and validate the luminance, luminance efficiency, and chromaticity coordinates of the proposed NVIS-OLED devices. We modeled the OLED device using SETFOS®, then the selection of materials for each layer for an optimal electron–hole balance was performed in the same tool. The effective reflectivity of multiple OLED layers was determined in MATLAB® in addition to an optimal device efficiency calculation in SETFOS®. The optical validation of output luminance and luminous efficiency was performed in LightTools®. Through a series of simulations for a green-emitting OLED device, we observed significant shifts in color coordinates, particularly towards the yellow spectrum, when the ETL materials and their thicknesses varied between 1 nm and 200 nm, whereas a change in the thickness of the HIL and HTL materials had a negligible impact on the color coordinates. While the critical role of ETL in color tuning and the emission characteristics of OLEDs is highlighted, our results also suggested a degree of flexibility in material selection for the HIL and HTL, as they minimally affected the color coordinates of emission. We validated via a combination of SETFOS®, MATLAB®, and LightTools® that when the ETL (3TPYMB) material thickness is optimized to 51 nm, the cathode reflectivity via the ETL-EIL stack became the minimum enabling output luminance of 3470 cd/m2 through our emissive layer within the Glass/ITO/MoO3/TAPC/(CBP:Ir(ppy)3)/3TPYMB/LiF/Aluminum OLED stack architecture, also yielding 34.73 cd/A of current efficiency under 10 mA/cm2 of current density. We infer that when stack layer thicknesses are optimized with respect to their reflectivity properties, better performances are achieved. Full article
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20 pages, 5569 KiB  
Review
Design and Fabrication of Microelectrodes for Dielectrophoresis and Electroosmosis in Microsystems for Bio-Applications
by Mengren Wu, Zijian Liu and Yuan Gao
Micromachines 2025, 16(2), 190; https://doi.org/10.3390/mi16020190 - 7 Feb 2025
Viewed by 377
Abstract
Microfluidic technology has emerged as a multidisciplinary field, integrating fluid dynamics, electronics, materials science, etc., enabling precise manipulation of small volumes of fluids and particles for various bio-applications. Among the forms of energy integrated into microfluidic systems, electric fields are particularly advantageous for [...] Read more.
Microfluidic technology has emerged as a multidisciplinary field, integrating fluid dynamics, electronics, materials science, etc., enabling precise manipulation of small volumes of fluids and particles for various bio-applications. Among the forms of energy integrated into microfluidic systems, electric fields are particularly advantageous for achieving precise control at the microscale. This review focuses on the design and fabrication of microelectrodes that drive electrokinetic phenomena, dielectrophoresis (DEP) and electroosmotic flow (EOF), key techniques for particle and fluid manipulation in microfluidic devices. DEP relies on non-uniform electric fields to manipulate particles based on their dielectric properties, while EOF utilizes uniform electric fields to generate consistent fluid flow across microchannels. Advances in microelectrode fabrication, including photolithography, soft lithography, and emerging non-cleanroom techniques, are discussed. Additionally, the review explores innovative approaches such as rapid prototyping, contactless electrodes, and three-dimensional structures, along with material considerations like conductive polymers and carbon composites. The review discusses the role of microelectrodes in enhancing device functionality, scalability, and reliability. The paper also identifies challenges, including the need for improved fabrication reproducibility and multifunctional integration. Finally, potential future research directions are proposed to further optimize DEP- and EOF-based microsystems for advanced biomedical and diagnostic applications. Full article
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7 pages, 713 KiB  
Editorial
Editorial for the Special Issue on MEMS/NEMS Devices and Applications, 2nd Edition
by Yao-Chuan Tsai, Pin-Chun Huang and Ching-Liang Dai
Micromachines 2025, 16(2), 189; https://doi.org/10.3390/mi16020189 - 7 Feb 2025
Viewed by 307
Abstract
Microelectromechanical systems (MEMSs) and nanoelectromechanical systems (NEMSs) are revolutionary technologies that merge mechanical and electronic components on microscopic and nanoscopic scales [...] Full article
(This article belongs to the Special Issue MEMS/NEMS Devices and Applications, 2nd Edition)
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15 pages, 6026 KiB  
Article
A 3.3 kV SiC Semi-Superjunction MOSFET with Trench Sidewall Implantations
by Marco Boccarossa, Kyrylo Melnyk, Arne Benjamin Renz, Peter Michael Gammon, Viren Kotagama, Vishal Ajit Shah, Luca Maresca, Andrea Irace and Marina Antoniou
Micromachines 2025, 16(2), 188; https://doi.org/10.3390/mi16020188 - 6 Feb 2025
Viewed by 261
Abstract
Superjunction (SJ) technology offers a promising solution to the challenges faced by silicon carbide (SiC) Metal Oxide Semiconductor Field-Effect Transistors (MOSFETs) operating at high voltages (>3 kV). However, the fabrication of SJ devices presents significant challenges due to fabrication complexity. This paper presents [...] Read more.
Superjunction (SJ) technology offers a promising solution to the challenges faced by silicon carbide (SiC) Metal Oxide Semiconductor Field-Effect Transistors (MOSFETs) operating at high voltages (>3 kV). However, the fabrication of SJ devices presents significant challenges due to fabrication complexity. This paper presents a comprehensive analysis of a feasible and easy-to-fabricate semi-superjunction (SSJ) design for 3.3 kV SiC MOSFETs. The proposed approach utilizes trench etching and sidewall implantation, with a tilted trench to facilitate the implantation process. Through Technology Computer-Aided Design (TCAD) simulations, we investigate the effects of the p-type sidewall on the charge balance and how it affects key performance characteristics, such as breakdown voltage (BV) and on-state resistance (RDS-ON). In particular, both planar gate (PSSJ) and trench gate (TSSJ) designs are simulated to evaluate their performance improvements over conventional planar MOSFETs. The PSSJ design achieves a 2.5% increase in BV and a 48.7% reduction in RDS-ON, while the TSSJ design further optimizes these trade-offs, with a 3.1% improvement in BV and a significant 64.8% reduction in RDS-ON compared to the benchmark. These results underscore the potential of tilted trench SSJ designs to significantly enhance the performance of SiC SSJ MOSFETs for high-voltage power electronics while simplifying fabrication and lowering costs. Full article
(This article belongs to the Special Issue SiC Based Miniaturized Devices, 3rd Edition)
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19 pages, 2366 KiB  
Review
Electro-Elastic Instability and Turbulence in Electro-osmotic Flows of Viscoelastic Fluids: Current Status and Future Directions
by Chandi Sasmal
Micromachines 2025, 16(2), 187; https://doi.org/10.3390/mi16020187 - 4 Feb 2025
Viewed by 420
Abstract
The addition of even minute amounts of solid polymers, measured in parts per million (ppm), into a simple Newtonian fluid like water significantly alters the flow behavior of the resulting polymer solutions due to the introduction of fluid viscoelasticity. This viscoelastic behavior, which [...] Read more.
The addition of even minute amounts of solid polymers, measured in parts per million (ppm), into a simple Newtonian fluid like water significantly alters the flow behavior of the resulting polymer solutions due to the introduction of fluid viscoelasticity. This viscoelastic behavior, which arises due to the stretching and relaxation phenomena of polymer molecules, leads to complex flow dynamics that are starkly different from those seen in simple Newtonian fluids under the same conditions. In addition to polymer solutions, many other fluids, routinely used in various industries and our daily lives, exhibit viscoelastic properties, including emulsions; foams; suspensions; biological fluids such as blood, saliva, and cerebrospinal fluid; and suspensions of biomolecules like DNA and proteins. In various microfluidic platforms, these viscoelastic fluids are often transported using electro-osmotic flows (EOFs), where an electric field is applied to control fluid movement. This method provides more precise and accurate flow control compared to pressure-driven techniques. However, several experimental and numerical studies have shown that when either the applied electric field strength or the fluid elasticity exceeds a critical threshold, the flow in these viscoelastic fluids becomes unstable and asymmetric due to the development of electro-elastic instability (EEI). These instabilities are driven by the normal elastic stresses in viscoelastic fluids and are not observed in Newtonian fluids under the same conditions, where the flow remains steady and symmetric. As the electric field strength or fluid elasticity is further increased, these instabilities can transition into a more chaotic and turbulent-like flow state, referred to as electro-elastic turbulence (EET). This article comprehensively reviews the existing literature on these EEI and EET phenomena, summarizing key findings from both experimental and numerical studies. Additionally, this article presents a detailed discussion of future research directions, emphasizing the need for further investigations to fully understand and harness the potential of EEI and EET in various practical applications, particularly in microscale flow systems where better flow control and increased transport rates are essential. Full article
(This article belongs to the Collection Micro/Nanoscale Electrokinetics)
16 pages, 2258 KiB  
Article
Design and Fabrication of a Piezoelectric Bimorph Microphone with High Reliability and Dynamic Range Based on Al0.8Sc0.2N
by Ruixiang Yan, Yucheng Ji, Anyuan Liu, Lei Wang and Songsong Zhang
Micromachines 2025, 16(2), 186; https://doi.org/10.3390/mi16020186 - 4 Feb 2025
Viewed by 479
Abstract
With the development of technology, MEMS microphones, which are small-sized and highly uniform, have been applied extensively. To improve their reliability in extreme environment and overcome the constraints of traditional microphones, this article presents a piezoelectric bimorph MEMS microphone using [...] Read more.
With the development of technology, MEMS microphones, which are small-sized and highly uniform, have been applied extensively. To improve their reliability in extreme environment and overcome the constraints of traditional microphones, this article presents a piezoelectric bimorph MEMS microphone using Al0.8Sc0.2N. In the article, the high robustness of piezoelectric microphones and the reasons for choosing Al0.8Sc0.2N as piezoelectric materials are described. The sensitivity of an Al0.8Sc0.2N-based piezoelectric bimorph compared with the traditional structure are revealed through FEA. Subsequently, a lumped element microphone model is constructed and all noise sources are evaluated comprehensively. The difference in output noise caused by different structures is calculated. The designed piezoelectric microphone, which comprises eight triangular cantilever beams, was fabricated on a chip with an area of 900 μm × 900 μm. The sensitivity of the designed microphone achieves 1.68 mV/Pa, with a noise floor of −110 dBA and SNR of 54.5 dB. The acoustic overload point of the microphone stands at 147 dB SPL, and following the impact test, the survival rate was 100%. Compared to traditional MEMS microphones, the microphone achieves a dynamic range of 107.5 dB. Full article
(This article belongs to the Section A:Physics)
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16 pages, 3723 KiB  
Article
Real-Time 0.89 THz Terahertz Imaging with High-Electron-Mobility Transistor Detector and Hydrogen Cyanide Laser for Non-Destructive Nut Detection
by Nu Zhang, Haiqing Liu, Huihui Yan, Hongbei Wang, Jiaxing Xie, Yinxian Jie and Damao Yao
Micromachines 2025, 16(2), 185; https://doi.org/10.3390/mi16020185 - 4 Feb 2025
Viewed by 413
Abstract
We present a method for real-time terahertz imaging that employs a hydrogen cyanide (HCN) laser as a terahertz source at 0.89 THz and an AlGaN/GaN high-electron-mobility transistor (HEMT) terahertz detector as a camera. We developed an HCN laser and constructed a transmission imaging [...] Read more.
We present a method for real-time terahertz imaging that employs a hydrogen cyanide (HCN) laser as a terahertz source at 0.89 THz and an AlGaN/GaN high-electron-mobility transistor (HEMT) terahertz detector as a camera. We developed an HCN laser and constructed a transmission imaging system based on it. This combination utilizes a high-power HCN laser with a highly sensitive terahertz detector, enabling practical applications of real-time terahertz imaging. A resolution test plane was produced to determine that the system could achieve a lateral resolution of 2 mm, and real-time terahertz imaging was carried out on Siemens star, pistachios, and sunflower seeds. The results demonstrate that the hidden structures inside nuts can be observed by terahertz imaging. Through our analysis of terahertz images of both sunflower seeds and pine nuts, we successfully assessed their fullness and demonstrated the capability to distinguish between full and unfilled nuts. These findings validate the potential of this technique for future applications in nut detection. We discuss the limitations of the current setup, potential improvements, and possible applications, and we outline the introduction of aspherical lenses and terahertz transmission tomography. Full article
(This article belongs to the Section E:Engineering and Technology)
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11 pages, 13085 KiB  
Article
Mechanism of OH*-Modified 4H-SiC Surface with Scratches Based on ReaxFF MD Simulation
by Dongxiao Yan, Hui Huang, Mingpu Xue and Nian Duan
Micromachines 2025, 16(2), 184; https://doi.org/10.3390/mi16020184 - 3 Feb 2025
Viewed by 470
Abstract
OH* generated through plasma catalysis offers several advantages, including a long survival time, high modification efficiency, and environmental friendliness. Consequently, a plasma-assisted polishing technology has rapidly developed. Previous studies exploring the interaction mechanism between OH* and 4H-SiC have often assumed flat surfaces. However, [...] Read more.
OH* generated through plasma catalysis offers several advantages, including a long survival time, high modification efficiency, and environmental friendliness. Consequently, a plasma-assisted polishing technology has rapidly developed. Previous studies exploring the interaction mechanism between OH* and 4H-SiC have often assumed flat surfaces. However, in the surface modification experiments on 4H-SiC, the actual surface morphology was not flat but contained numerous scratches. Therefore, this study investigated the interaction mechanism of OH* on an uneven surface using reactive force field molecular dynamics (ReaxFF MD) simulations. The results show that in the low-speed OH* modification process, the adsorption effect leads to a thicker modified layer at higher locations than at lower locations. The resulting modified layer can be removed by soft abrasive mechanical polishing to achieve surface flatness, but there will be a modified layer on the surface, which needs to be modified and polished several times. In contrast, during high-speed OH* modification, high-speed particle bombardment causes more Si-O bonds to diffuse into the scratches, resulting in the formation of a flat bonding layer with surface planarization achieved after a single polishing step. The interaction mechanism of OH* with the uneven surface at different speeds, as obtained through ReaxFF MD, provides a theoretical foundation for subsequent polishing experiments. Full article
(This article belongs to the Section E:Engineering and Technology)
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14 pages, 968 KiB  
Article
Fano Resonant Sensing in MIM Waveguide Structures Based on Multiple Circular Split-Ring Resonant Cavities
by Wenjing Wang, Shaoze Zhang and Huiliang Cao
Micromachines 2025, 16(2), 183; https://doi.org/10.3390/mi16020183 - 3 Feb 2025
Viewed by 410
Abstract
In this work, a non-through metal–insulator–metal (MIM) waveguide capable of exciting three Fano resonances was designed and numerically studied using the finite element method. Fano resonances are achieved through the interaction between the modes of multiple circular split-ring resonator cavities and the waveguide. [...] Read more.
In this work, a non-through metal–insulator–metal (MIM) waveguide capable of exciting three Fano resonances was designed and numerically studied using the finite element method. Fano resonances are achieved through the interaction between the modes of multiple circular split-ring resonator cavities and the waveguide. The effect of coupling between different resonators on the Fano resonance peaks is investigated. Independent tuning of the Fano resonance wavelength and transmission rate is accomplished by modifying the structural rotation angle and geometric parameters. After optimizing these parameters, the structure achieves an optimal refractive index sensitivity of 946.88 nm/RIU and a figure of merit of 99.17. The proposed structure holds potential for guiding the design of nanosensors. Full article
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18 pages, 13776 KiB  
Article
Dynamic Response and Energy Conversion of Coupled Cantilevers with Dual Piezoelectric–Triboelectric Harvesting Mechanisms
by Mohammad Alghamaz, Leila Donyaparastlivari and Alwathiqbellah Ibrahim
Micromachines 2025, 16(2), 182; https://doi.org/10.3390/mi16020182 - 31 Jan 2025
Viewed by 577
Abstract
This study presents a Hybrid Piezoelectric–Triboelectric Energy Harvester (HPTEH) composed of two coupled cantilever beams, designed to enhance energy generation and broaden bandwidth by combining piezoelectric and triboelectric mechanisms. A theoretical 2-DOF lumped model was developed and validated with experimental results, demonstrating good [...] Read more.
This study presents a Hybrid Piezoelectric–Triboelectric Energy Harvester (HPTEH) composed of two coupled cantilever beams, designed to enhance energy generation and broaden bandwidth by combining piezoelectric and triboelectric mechanisms. A theoretical 2-DOF lumped model was developed and validated with experimental results, demonstrating good agreement. Experimental findings reveal that Beam I exhibits a softening effect, with resonance frequencies shifting to lower values and increased displacement amplitudes under higher excitation levels due to material nonlinearities and strain-induced voltage generation. Beam II, in contrast, displays a hardening effect, with resonance frequencies increasing as triboelectric interactions enhance stiffness at higher excitation levels. Coupling dynamics reveal asymmetry, with Beam I significantly influencing Beam II in the higher frequency range, while Beam II’s impact on Beam I remains minimal. Phase portraits highlight the dynamic coupling and energy transfer between the beams, particularly near their natural frequencies of 18.6 Hz and 40.6 Hz, demonstrating complex interactions and energy exchange across a broad frequency range. The synergistic interplay between triboelectric and piezoelectric mechanisms allows the HPTEH to efficiently harvest energy across a wider spectrum, underscoring its potential for advanced energy applications in diverse vibrational environments. Full article
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23 pages, 5559 KiB  
Review
Propulsion Mechanisms in Magnetic Microrobotics: From Single Microrobots to Swarms
by Lanlan Jia, Guangfei Su, Mengyu Zhang, Qi Wen, Lihong Wang and Junyang Li
Micromachines 2025, 16(2), 181; https://doi.org/10.3390/mi16020181 - 31 Jan 2025
Viewed by 584
Abstract
Microrobots with different structures can exhibit multiple propulsion mechanisms under external magnetic fields. Swarms dynamically assembled by microrobots inherit the advantages of single microrobots, such as degradability and small dimensions, while also offering benefits like scalability and high flexibility. With control of magnetic [...] Read more.
Microrobots with different structures can exhibit multiple propulsion mechanisms under external magnetic fields. Swarms dynamically assembled by microrobots inherit the advantages of single microrobots, such as degradability and small dimensions, while also offering benefits like scalability and high flexibility. With control of magnetic fields, these swarms demonstrate diverse propulsion mechanisms and can perform precise actions in complex environments. Therefore, the relationship between single microrobots and their swarms is a significant area of study. This paper reviews the relationship between single microrobots and swarms by examining the structural design, control methods, propulsion mechanisms, and practical applications. At first, we introduce the structural design of microrobots, including materials and manufacturing methods. Then, we describe magnetic field generation systems, including gradient, rotating, and oscillating magnetic fields, and their characteristics. Next, we analyze the propulsion mechanisms of individual microrobots and the way microrobots dynamically assemble into a swarm under an external magnetic field, which illustrates the relationship between single microrobots and swarms. Finally, we discuss the application of different swarm propulsion mechanisms in water purification and targeted delivery, summarize current challenges and future work, and explore future directions. Full article
(This article belongs to the Special Issue Magnetic Microrobots for Biomedical Applications, Second Edition)
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14 pages, 5253 KiB  
Article
Research on Monitoring Methods for Electrostatic Discharge Pulses in Spacecraft Dielectric Materials
by Hong Yin, Cunhui Li, Chengxuan Zhao, Xiaogang Qin, Xiaojin Lu, Xuan Wen, Liang Shi, Qing Liu, Jun Wang, Hanwu Jia and Shengsheng Yang
Micromachines 2025, 16(2), 180; https://doi.org/10.3390/mi16020180 - 31 Jan 2025
Viewed by 490
Abstract
Space particle radiation induces charging and discharging phenomena in spacecraft dielectric materials, leading to electrostatic discharge (ESD) and electromagnetic pulses (EMP), which pose significant risks to spacecraft electronic systems by causing interference and potential damage. Accurate and timely monitoring of these phenomena, combined [...] Read more.
Space particle radiation induces charging and discharging phenomena in spacecraft dielectric materials, leading to electrostatic discharge (ESD) and electromagnetic pulses (EMP), which pose significant risks to spacecraft electronic systems by causing interference and potential damage. Accurate and timely monitoring of these phenomena, combined with a comprehensive understanding of their underlying mechanisms, is critical for developing effective protection strategies against satellite charging effects. Addressing in-orbit monitoring requirements, this study proposes the design of a compact sleeve monopole antenna. Through simulations, the relationships between the antenna’s design parameters and its voltage standing wave ratio (VSWR) are analyzed alongside its critical performance characteristics, including frequency band, gain, radiation pattern, and matching circuit. The proposed antenna demonstrates operation within a frequency range of (28.73–31.25) MHz (VSWR < 2), with a center frequency of 30 MHz and a relative bandwidth of 8.4%. Performance evaluations and simulation-based experiments reveal that the antenna can measure pulse signals with electric field strengths ranging from (−1000 to −80) V/m and (80 to 1000) V/m, centered at 25.47 MHz. It reliably monitors discharge pulses generated by electron irradiation on spacecraft-grade FR4 (Flame-Retardant 4) dielectric materials, providing technical support for the engineering application of discharge research in space environments. Full article
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9 pages, 1300 KiB  
Article
Production of Uniform Droplets and Lipid Nanoparticles Using Perfluoropolyether-Based Microfluidic Devices
by Mincheol Cho, Eun Seo Kim, Tae-Kyung Ryu, Inseong Choi and Sung-Wook Choi
Micromachines 2025, 16(2), 179; https://doi.org/10.3390/mi16020179 - 31 Jan 2025
Viewed by 569
Abstract
Microfluidic devices are greatly affected by the materials used. The materials used in previous studies had problems in various aspects, such as processing, adsorption, and price. This study will investigate the materials needed to overcome such problems. Various microfluidic devices based on the [...] Read more.
Microfluidic devices are greatly affected by the materials used. The materials used in previous studies had problems in various aspects, such as processing, adsorption, and price. This study will investigate the materials needed to overcome such problems. Various microfluidic devices based on the perfluorinated compound perfluoropolyether (PFPE) were fabricated and mixed with hydrophilic and amphiphilic monomers, including poly(ethylene glycol) diacrylate, polyethylene glycol monomethacrylate, poly(ethylene glycol) methyl ether methacrylate, acrylic acid, and 2-hydroxyethyl methacrylate. A PFPE-based sheet with a repeating structure of hydrophobic and hydrophilic groups was fabricated. Thus, the hydrophilicity of highly hydrophobic PFPE was enhanced. The fluidic channel was engraved on a PFPE-based sheet using laser cutting and a fabricated microfluidic device. The channels of microfluidic devices are micro-scale (100 µm~300 µm). The lipid nanoparticles and droplets generated through the microfluidic device demonstrated uniform particles continuously. Full article
(This article belongs to the Special Issue Microfluidic Nanoparticle Synthesis)
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25 pages, 6634 KiB  
Article
Development of Visibly Opaque Polyolefin Sheets While Preserving Infrared-Light Transparency
by Md. Saiful Hoque, Mehnab Ali, Xiaoruo Sun, Asad Asad, Patricia I. Dolez, James David Hogan and Dan Sameoto
Micromachines 2025, 16(2), 178; https://doi.org/10.3390/mi16020178 - 31 Jan 2025
Viewed by 551
Abstract
This study focused on developing pigmented linear low-density polyethylene (LLDPE) sheets while preserving their mechanical properties and infrared (IR) transparency. Six pigments—ZnO, ZnS, TiO2, FeO yellow, FeO light brown, and FeO dark brown—were each mixed with polyethylene (PE) wax in a [...] Read more.
This study focused on developing pigmented linear low-density polyethylene (LLDPE) sheets while preserving their mechanical properties and infrared (IR) transparency. Six pigments—ZnO, ZnS, TiO2, FeO yellow, FeO light brown, and FeO dark brown—were each mixed with polyethylene (PE) wax in a 1:1 ratio and blended with LLDPE at concentrations of 1, 3, and 5 wt%. Tensile strength tests showed minimal changes at lower pigment concentrations, with values near that of pure LLDPE (14 MPa), and slight reductions at 5 wt%. IR transparency tests, conducted using both direct and reflected heat sources, showed that white-pigmented sheets maintained over 85% transparency, while colored pigments exhibited slightly reduced IR transmittance, ranging from 70% to 91%. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that the critical IR transparency range of 8–12 μm remained unaffected with both pure and pigmented sheets. On the other hand, ultraviolet–visible (UV–VIS) testing showed that white-pigmented sheets experienced enhanced visible-light absorption with increasing pigment concentration and thickness, while color-pigmented sheets exhibited high opacity. Additionally, micro-structuring was performed on the LLDPE sheets to further modify their IR properties, which resulted in effective scattering of IR radiation. These findings highlight the potential of pigmented LLDPE sheets for applications requiring both visual opacity and IR transparency, such as thermal management and camouflage, as well as applications requiring tunable IR properties. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2024)
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22 pages, 7934 KiB  
Article
Research on a New Method of Macro–Micro Platform Linkage Processing for Large-Format Laser Precision Machining
by Longjie Xiong, Haifeng Ma, Zheng Sun, Xintian Wang, Yukui Cai, Qinghua Song and Zhanqiang Liu
Micromachines 2025, 16(2), 177; https://doi.org/10.3390/mi16020177 - 31 Jan 2025
Viewed by 403
Abstract
In recent years, the macro–micro structure (servo platform for macro motion and galvanometer for micro motion) composed of a galvanometer and servo platform has been gradually applied to laser processing in order to address the increasing demand for high-speed, high-precision, and large-format precision [...] Read more.
In recent years, the macro–micro structure (servo platform for macro motion and galvanometer for micro motion) composed of a galvanometer and servo platform has been gradually applied to laser processing in order to address the increasing demand for high-speed, high-precision, and large-format precision machining. The research in this field has evolved from step-and-scan methods to linkage processing methods. Nevertheless, the existing linkage processing methods cannot make full use of the field-of-view (FOV) of the galvanometer. In terms of motion distribution, the existing methods are not suitable for continuous micro segments and generate the problem that the distribution parameter can only be obtained through experience or multiple experiments. In this research, a new laser linkage processing method for global trajectory smoothing of densely discretized paths is proposed. The proposed method can generate a smooth trajectory of the servo platform with bounded acceleration by the finite impulse response (FIR) filter under the global blending error constrained by the galvanometer FOV. Moreover, the trajectory of the galvanometer is generated by vector subtraction, and the motion distribution of macro–micro structure is accurately realized. Experimental verification is carried out on an experimental platform composed of a three-axis servo platform, a galvanometer, and a laser. Simulation experiment results indicate that the processing efficiency of the proposed method is improved by 79% compared with the servo platform processing only and 55% compared with the previous linkage processing method. Furthermore, the method can be successfully utilized on experimental platforms with good tracking performance. In summary, the proposed method adeptly balances efficiency and quality, rendering it particularly suitable for laser precision machining applications. Full article
(This article belongs to the Section E:Engineering and Technology)
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25 pages, 42288 KiB  
Article
An Analysis of Arrays with Irregular Apertures in MEMS Smart Glasses for the Improvement of Clear View
by Roland Donatiello, Mustaqim Siddi Que Iskhandar, Md Kamrul Hasan, Philipp Kästner, Muhammad Hasnain Qasim, Jiahao Chen, Shilby Baby, Basma Elsaka, Guilin Xu and Hartmut Hillmer
Micromachines 2025, 16(2), 176; https://doi.org/10.3390/mi16020176 - 31 Jan 2025
Viewed by 555
Abstract
An innovative glass substrate surface technology including integrated micro-electro-mechanical systems (MEMS) is presented as an advanced light modulation, heat control, and energy management system. This smart technology is based on millions of metallic micromirrors per square meter fabricated on the glass surface, which [...] Read more.
An innovative glass substrate surface technology including integrated micro-electro-mechanical systems (MEMS) is presented as an advanced light modulation, heat control, and energy management system. This smart technology is based on millions of metallic micromirrors per square meter fabricated on the glass surface, which are arranged in arrays and electrostatically actuated. The smart window application exploits an elaborate MEMS glass technology for active daylight steering and energy management in buildings, enabling energy saving, CO2 emission reduction, a positive health impact, and improved well-being. When light interacts with a glass substrate that has regular, repetitive patterning at the microscopic scale on its surface, these microstructures can cause the diffraction of the transmitted light, resulting in the potential deterioration of the view quality through the smart glass. A reduction in optical artifacts for improved clear view is presented by using irregular geometric micromirror apertures. Several non-periodic, irregular micromirror aperture designs are compared with corresponding periodic regular designs. For each considered aperture geometry, the irregular array reveals a reduction in optical artifacts and, therefore, by far a clearer view than the corresponding regular array. A systematic and comprehensive study was conducted through design, simulation, technological fabrication, experimental characterization, and analysis. Full article
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15 pages, 13367 KiB  
Article
Effect of Alloying and Reinforcing Nanocomposites on the Mechanical, Tribological, and Wettability Properties of Pulse-Electrodeposited Ni Coatings
by Aashish John, Adil Saeed and Zulfiqar Ahmad Khan
Micromachines 2025, 16(2), 175; https://doi.org/10.3390/mi16020175 - 31 Jan 2025
Viewed by 496
Abstract
Research into the introduction of alloying and reinforcing nanocomposites into nickel (Ni) coatings has been motivated by the need for tribologically superior coatings that will improve energy efficiency. Using pulse electrodeposition, this work investigates the effects of adding cobalt (Co) as the alloying [...] Read more.
Research into the introduction of alloying and reinforcing nanocomposites into nickel (Ni) coatings has been motivated by the need for tribologically superior coatings that will improve energy efficiency. Using pulse electrodeposition, this work investigates the effects of adding cobalt (Co) as the alloying nanoparticle and silicon carbide (SiC), zirconium oxide (ZrO2), and aluminium oxide (Al2O3) as reinforcing nanocomposites to Ni coatings. The surface properties, mechanical strength, nanotribological behaviour, and wettability of these coatings were analysed. Surface characteristics were evaluated by the use of a Scanning Electron Microscope, revealing a grain dimension reduction of approximately ~7–43% compared to pristine Ni coatings. When alloying and reinforcing nanocomposites were added to Ni coatings, nanoindentation research showed that there was an increase in nanohardness of ~12% to ~69%. This resulted in an improvement in the tribological performance from approximately 2% to 65%.The hydrophilic nature of Ni coatings was observed with wettability analysis. This study demonstrates that nanocomposite reinforcement can be used to customise Ni coatings for applications that require exceptional tribological performance. The results point to the use of Ni-Co coatings for electronics and aerospace sectors, with more improvements possible with the addition of reinforcing nanoparticles. Full article
(This article belongs to the Section D:Materials and Processing)
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25 pages, 3015 KiB  
Review
Magnetic Polymeric Conduits in Biomedical Applications
by Sayan Ganguly and Shlomo Margel
Micromachines 2025, 16(2), 174; https://doi.org/10.3390/mi16020174 - 31 Jan 2025
Viewed by 445
Abstract
Magnetic polymeric conduits are developing as revolutionary materials in regenerative medicine, providing exceptional benefits in directing tissue healing, improving targeted medication administration, and facilitating remote control via external magnetic fields. The present article offers a thorough examination of current progress in the design, [...] Read more.
Magnetic polymeric conduits are developing as revolutionary materials in regenerative medicine, providing exceptional benefits in directing tissue healing, improving targeted medication administration, and facilitating remote control via external magnetic fields. The present article offers a thorough examination of current progress in the design, construction, and functionalization of these hybrid systems. The integration of magnetic nanoparticles into polymeric matrices confers distinctive features, including regulated alignment, improved cellular motility, and targeted medicinal delivery, while preserving structural integrity. Moreover, the incorporation of multifunctional attributes, such as electrical conductivity for cerebral stimulation and optical characteristics for real-time imaging, expands their range of applications. Essential studies indicate that the dimensions, morphology, surface chemistry, and composition of magnetic nanoparticles significantly affect their biocompatibility, degrading characteristics, and overall efficacy. Notwithstanding considerable advancements, issues concerning long-term biocompatibility, biodegradability, and scalability persist, in addition to the must for uniform regulatory frameworks to facilitate clinical translation. Progress in additive manufacturing and nanotechnology is overcoming these obstacles, facilitating the creation of dynamic and adaptive conduit structures designed for particular biomedical requirements. Magnetic polymeric conduits, by integrating usefulness and safety, are set to transform regenerative therapies, presenting a new avenue for customized medicine and advanced healthcare solutions. Full article
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18 pages, 22335 KiB  
Review
Research Progress on Laser-Assisted Precision Machining Technology
by Qimeng Liu, Jie Liu, Zhe Ming, Bo Cui and Jian Wang
Micromachines 2025, 16(2), 173; https://doi.org/10.3390/mi16020173 - 31 Jan 2025
Viewed by 389
Abstract
As a revolutionary advanced manufacturing technology, the core of laser-assisted machining technology lies in the innovation of traditional machining technology. It uses a laser to precisely modify the surface of the workpiece material through clever integration. This process can lead to significant changes [...] Read more.
As a revolutionary advanced manufacturing technology, the core of laser-assisted machining technology lies in the innovation of traditional machining technology. It uses a laser to precisely modify the surface of the workpiece material through clever integration. This process can lead to significant changes in the microstructure, thermodynamic properties, and physical properties of the workpiece’s cutting layer, greatly facilitating the removal of material by the cutting tool. Especially for difficult-to-process materials, this technology can effectively solve the processing problems they face. This not only improves the processing accuracy, but also ensures the processing quality, making it possible to process difficult-to-process materials with high precision and high quality. This article comprehensively summarizes the latest research progress in laser-assisted precision machining technology and deeply summarizes the specific mechanism of laser-assisted machining technology on the surface of workpiece materials. The influence of laser-assisted machining technology on the cutting characteristics of machining materials is elaborated in detail, providing a theoretical basis for the application of this technology. Finally, the future development direction of laser-assisted machining technology is prospected. Full article
(This article belongs to the Special Issue Advances in Digital Manufacturing and Nano Fabrication)
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18 pages, 2368 KiB  
Article
Hydrogen Production from Chemical Hydrides via Porous Carbon Particle Composite Catalyst Embedding of Metal Nanoparticles
by Sahin Demirci, Osman Polat and Nurettin Sahiner
Micromachines 2025, 16(2), 172; https://doi.org/10.3390/mi16020172 - 31 Jan 2025
Viewed by 385
Abstract
Porous carbon particles (PCPs) prepared from sucrose via the hydrothermal method and its modified forms with polyethyleneimine (PEI) as PCP-PEI were used as templates as in situ metal nanoparticles as M@PCP and M@PCP-PEI (M:Co, Ni, or Cu), respectively. The prepared M@PCP and M@PCP-PEI [...] Read more.
Porous carbon particles (PCPs) prepared from sucrose via the hydrothermal method and its modified forms with polyethyleneimine (PEI) as PCP-PEI were used as templates as in situ metal nanoparticles as M@PCP and M@PCP-PEI (M:Co, Ni, or Cu), respectively. The prepared M@PCP and M@PCP-PEI composites were used as catalysts in the hydrolysis of NaBH4 and NH3BH3 to produce hydrogen (H2). The amount of Co nanoparticles within the Co@PCP-PEI structure was steadily increased via multiple loading/reducing cycles, e.g., from 29.8 ± 1.1 mg/g at the first loading/reducing cycles to 44.3 ± 4.9 mg/g after the third loading/reducing cycles. The Co@PCP-PEI catalyzed the hydrolysis of NaBH4 within 120 min with 251 ± 1 mL H2 production and a 100% conversion ratio with a 3.8 ± 0.3 mol H2/(mmol cat·min) turn-over frequency (TOF) and a lower activation energy (Ea), 29.3 kJ/mol. In addition, the Co@PCP-PEI-catalyzed hydrolysis of NH3BH3 was completed in 28 min with 181 ± 1 mL H2 production at 100% conversion with a 4.8 ± 0.3 mol H2/(mmol cat·min) TOF value and an Ea value of 32.5 kJ/mol. Moreover, Co@PCP-PEI composite catalysts were afforded 100% activity up to 7 and 5 consecutive uses in NaBH4 and NH3B3 hydrolysis reactions, respectively, with all displaying 100% conversions for both hydrolysis reactions in the 10 successive uses of the catalyst. Full article
(This article belongs to the Section C:Chemistry)
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14 pages, 13945 KiB  
Article
S-Bend and Y Waveguide Architectures in Germanate Glasses Irradiated by Femtosecond Laser
by Thiago Vecchi Fernandes, Camila Dias da Silva Bordon, Niklaus Ursus Wetter, Wagner de Rossi and Luciana Reyes Pires Kassab
Micromachines 2025, 16(2), 171; https://doi.org/10.3390/mi16020171 - 31 Jan 2025
Viewed by 470
Abstract
This study is focused on the fabrication and characterization of various dual waveguides through femtosecond (fs) laser irradiation of GeO2-based glass samples. The objective of the present work is to develop diverse waveguide configurations, namely straight, S-bend and Y-shaped waveguides within [...] Read more.
This study is focused on the fabrication and characterization of various dual waveguides through femtosecond (fs) laser irradiation of GeO2-based glass samples. The objective of the present work is to develop diverse waveguide configurations, namely straight, S-bend and Y-shaped waveguides within GeO2–PbO glasses embedded with silver nanoparticles, utilizing a double-guide platform, for photonic applications such as resonant rings and beam splitters. Enhanced guidance was observed with a larger radius of curvature (80 mm) among the two distinct S-bend waveguides produced. The maximum relative propagation loss was recorded for the S-bend waveguide with a 40 mm radius, while the minimum loss was noted for the Y-shaped waveguide. In the latter configuration, with an opening angle of 5° and a separation of 300 µm between the two arms, an output power ratio of 50.5/49.5 between the left and right arms indicated promising potential for beam splitter applications. During the study, the quality factor (M2) of the proposed architectures was measured and the 80 mm S-bend configuration presented the best symmetry between the x and y axes; in the case of the Y configuration the similarity between the M2 values in both axes, for the first and second arms, indicates comparable light guidance. Full article
(This article belongs to the Special Issue Laser Micro/Nano Fabrication, Second Edition)
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12 pages, 2132 KiB  
Article
A Versatile SAW Sensor-Based Modular and Portable Platform for a Multi-Sensor Device
by Ángel López-Luna, Patricia Arroyo, Daniel Matatagui, Carlos Sánchez-Vicente and Jesús Lozano
Micromachines 2025, 16(2), 170; https://doi.org/10.3390/mi16020170 - 31 Jan 2025
Viewed by 485
Abstract
This study presents the development and characterization of a novel electronic nose system based on customized surface acoustic wave (SAW) sensors. The system includes four sensors, customized with different custom polymer coatings, in order to detect volatile organic compounds (VOCs). The main innovation [...] Read more.
This study presents the development and characterization of a novel electronic nose system based on customized surface acoustic wave (SAW) sensors. The system includes four sensors, customized with different custom polymer coatings, in order to detect volatile organic compounds (VOCs). The main innovation lies in the design of a robust and versatile switching electronics system that allows for the integration of the SAW sensors into portable systems, as well as interoperability with other gas sensor technologies. The system includes a modular architecture that allows multiple sensor arrays to be combined to improve the selectivity and discrimination of complex gas mixtures. To verify the proper performance of the system and the detection capability of the manufactured sensors, experimental laboratory tests have been carried out. Specifically, ethanol and acetone measurements up to a 2000 ppm concentration have been performed. These preliminary experimental results demonstrate the capability of the SAW sensors with different response patterns across the sensor array. In particular, the sensor made with the polyvinyl acetate polymer exhibits high sensitivity to both VOCs. Full article
(This article belongs to the Section E:Engineering and Technology)
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14 pages, 4601 KiB  
Article
Modeling and Analysis of Vibration Coupling in Differential Common-Based MEMS Resonators
by Jing Zhang, Zhuo Yang, Tianhao Wu, Zhichao Yao, Chen Lin and Yan Su
Micromachines 2025, 16(2), 169; https://doi.org/10.3390/mi16020169 - 30 Jan 2025
Viewed by 436
Abstract
In differential MEMS resonant sensors, a pair of resonators are interconnected with other structural components while sharing a common substrate. This leads to mutual coupling of vibration energy between resonators, interfering with their frequency outputs and affecting the sensor’s static performance. This paper [...] Read more.
In differential MEMS resonant sensors, a pair of resonators are interconnected with other structural components while sharing a common substrate. This leads to mutual coupling of vibration energy between resonators, interfering with their frequency outputs and affecting the sensor’s static performance. This paper aims to model and analyze the vibration coupling phenomena in differential common-based MEMS resonators (DCMR). A mechanical model of the DCMR structure was established and refined through finite element simulation analysis. Theoretical calculations yielded vibration coupling curves for two typical silicon resonant accelerometer (SRA) structures containing DCMR: SRA-V1 and SRA-V2, with coupling stiffness values of 2.361 × 10−4 N/m and 1.370 × 10−2 N/m, respectively. An experimental test system was constructed to characterize the vibration coupling behavior. The results provided coupling amplitude-frequency characteristic curves and coupling stiffness values (7.073 × 10−4 N/m and 1.068 × 10−2 N/m for SRA-V1 and SRA-V2, respectively) that validated the theoretical analysis and computational model. This novel approach enables effective evaluation of coupling intensity between 5resonators and provides a theoretical foundation for optimizing device structural designs. Full article
(This article belongs to the Special Issue Advances in MEMS Inertial Sensors)
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