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Micromachines
Volume 15
Issue 9
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Micromachines, Volume 15, Issue 9 (September 2024) – 117 articles

Cover Story (view full-size image): Inertial focusing-based Lab-on-Chip systems offer a promising solution for efficient cell sorting thus meeting the World Health Organization's ASSURED criteria (Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free, and Deliverable to end-users). This review explores how inertial focusing in spiral microchannels supports cell sorting, examining the effects of different cross-sectional geometries—rectangular, trapezoidal, triangular, and hybrid—on particle focusing and sorting efficiency. By balancing the primary and secondary flow forces, spiral channels enable high-throughput and efficient filtration across varying particle sizes. Additionally, this work addresses various materials and prototyping techniques, providing insights to guide the design and selection of spiral geometries and materials based on application-specific particles. View this paper
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12 pages, 2389 KiB  
Article
Scan-Rate-Dependent Ion Current Rectification in Bipolar Interfacial Nanopores
by Xiaoling Zhang, Yunjiao Wang, Jiahui Zheng, Chen Yang and Deqiang Wang
Micromachines 2024, 15(9), 1176; https://doi.org/10.3390/mi15091176 - 23 Sep 2024
Viewed by 824
Abstract
This study presents a theoretical investigation into the voltammetric behavior of bipolar interfacial nanopores due to the effect of potential scan rate (1–1000 V/s). Finite element method (FEM) is utilized to explore the current–voltage (I–V) properties of bipolar interfacial nanopores at different bulk [...] Read more.
This study presents a theoretical investigation into the voltammetric behavior of bipolar interfacial nanopores due to the effect of potential scan rate (1–1000 V/s). Finite element method (FEM) is utilized to explore the current–voltage (I–V) properties of bipolar interfacial nanopores at different bulk salt concentrations. The results demonstrate a strong impact of the scan rate on the I–V response of bipolar interfacial nanopores, particularly at relatively low concentrations. Hysteresis loops are observed in bipolar interfacial nanopores under specific scan rates and potential ranges and divided by a cross-point potential that remains unaffected by the scan rate employed. This indicates that the current in bipolar interfacial nanopores is not just reliant on the bias potential that is imposed but also on the previous conditions within the nanopore, exhibiting history-dependent or memory effects. This scan-rate-dependent current–voltage response is found to be significantly influenced by the length of the nanopore (membrane thickness). Thicker membranes exhibit a more pronounced scan-rate-dependent phenomenon, as the mass transfer of ionic species is slower relative to the potential scan rate. Additionally, unlike conventional bipolar nanopores, the ion current passing through bipolar interfacial nanopores is minimally affected by the membrane thickness, making it easier to detect. Full article
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14 pages, 2526 KiB  
Article
A Novel Nano-Spherical Tip for Improving Precision in Elastic Modulus Measurements of Polymer Materials via Atomic Force Microscopy
by Tianyu Fu, Paul C. Uzoma, Xiaolei Ding, Pengyuan Wu, Oleksiy Penkov and Huan Hu
Micromachines 2024, 15(9), 1175; https://doi.org/10.3390/mi15091175 - 22 Sep 2024
Viewed by 1400
Abstract
Micro-nano-scale mechanical properties are vital for engineering and biological materials. The elastic modulus is generally measured by processing the force–indentation curves obtained by atomic force microscopy (AFM). However, the measurement precision is largely affected by tip shape, tip wear, sample morphology, and the [...] Read more.
Micro-nano-scale mechanical properties are vital for engineering and biological materials. The elastic modulus is generally measured by processing the force–indentation curves obtained by atomic force microscopy (AFM). However, the measurement precision is largely affected by tip shape, tip wear, sample morphology, and the contact model. In such research, it has been found that the radius of the sharp tip increases due to wear during contact scanning, affecting elastic modulus calculations. For flat-ended tips, it is difficult to identify the contact condition, leading to inaccurate results. Our research team has invented a nano-spherical tip, obtained by implanting focused helium ions into a silicon microcantilever, causing it to expand into a silicon nanosphere. This nano-spherical tip has the advantages of sub-micro size and a smooth spherical surface. Comparative tests of the elastic modulus measurement were conducted on polytetrafluoroethylene (PTFE) and polypropylene (PP) using these three tips. Overall, the experimental results show that our nano-spherical tip with a consistent tip radius, symmetrical geometric shape, and resistance to wear and contamination can improve precision in elastic modulus measurements of polymer materials. Full article
(This article belongs to the Special Issue Micro/Nanostructures in Sensors and Actuators, 2nd Edition)
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10 pages, 1790 KiB  
Article
Stress Engineering of Magnetization Fluctuation and Noise Spectra in Low-Barrier Nanomagnets Used as Analog and Binary Stochastic Neurons
by Rahnuma Rahman and Supriyo Bandyopadhyay
Micromachines 2024, 15(9), 1174; https://doi.org/10.3390/mi15091174 - 22 Sep 2024
Viewed by 629
Abstract
A single-domain nanomagnet, shaped like a thin elliptical disk with small eccentricity, has a double-well potential profile with two degenerate energy minima separated by a small barrier of a few kT (k = Boltzmann constant and T = absolute temperature). [...] Read more.
A single-domain nanomagnet, shaped like a thin elliptical disk with small eccentricity, has a double-well potential profile with two degenerate energy minima separated by a small barrier of a few kT (k = Boltzmann constant and T = absolute temperature). The two minima correspond to the magnetization pointing along the two mutually anti-parallel directions along the major axis of the ellipse. At room temperature, the magnetization fluctuates randomly between the two minima, mimicking telegraph noise. This makes the nanomagnet act as a “binary” stochastic neuron (BSN) with the neuronal state encoded in the magnetization orientation. If the nanomagnet is magnetostrictive, then the barrier can be depressed further by applying (electrically generated) uniaxial stress along the ellipse’s major axis, thereby gradually eroding the double-well shape. When the barrier almost vanishes, the magnetization begins to randomly assume any arbitrary orientation (not just along the major axis), making the nanomagnet act as an “analog” stochastic neuron (ASN). The magnetization fluctuation then begins to increasingly resemble white noise. The full width at half maximum (FWHM) of the noise auto-correlation function decreases with increasing stress, as the fluctuation gradually transforms from telegraph noise to white noise. Consistent with this trend, the noise spectral density exhibits a 1/fβ spectrum (at high frequencies) with β decreasing from 2.00 to 1.88 with increasing stress. Stress can thus not only reconfigure a BSN to an ASN, which has its own applications, but it can also perform “noise engineering”, i.e., tune the auto-correlation function and power spectral density, having applications in signal processing. Full article
(This article belongs to the Special Issue Advances in Nanomagnets)
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14 pages, 4775 KiB  
Article
A Micromachined Silicon-on-Glass Accelerometer with an Optimized Comb Finger Gap Arrangement
by Jiacheng Li, Rui Feng, Xiaoyi Wang, Huiliang Cao, Keru Gong and Huikai Xie
Micromachines 2024, 15(9), 1173; https://doi.org/10.3390/mi15091173 - 22 Sep 2024
Viewed by 848
Abstract
This paper reports the design, fabrication, and characterization of a MEMS capacitive accelerometer with an asymmetrical comb finger arrangement. By optimizing the ratio of the gaps of a rotor finger to its two adjacent stator fingers, the sensitivity of the accelerometer is maximized [...] Read more.
This paper reports the design, fabrication, and characterization of a MEMS capacitive accelerometer with an asymmetrical comb finger arrangement. By optimizing the ratio of the gaps of a rotor finger to its two adjacent stator fingers, the sensitivity of the accelerometer is maximized for the same comb finger area. With the fingers’ length, width, and depth at 120 μm, 4 μm, and 45 μm, respectively, the optimized finger gap ratio is 2.5. The area of the proof mass is 750 μm × 560 μm, which leads to a theoretical thermomechanical noise of 9 μg/√Hz. The accelerometer has been fabricated using a modified silicon-on-glass (SOG) process, in which a groove is pre-etched into the glass to hold the metal electrode. This SOG process greatly improves the silicon-to-glass bonding yield. The measurement results show that the resonant frequency of the accelerometer is about 2.05 kHz, the noise floor is 28 μg/√Hz, and the nonlinearity is less than 0.5%. Full article
(This article belongs to the Special Issue MEMS Sensors and Actuators: Design, Fabrication and Applications)
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15 pages, 4110 KiB  
Review
Formation, Structure, Electronic, and Transport Properties of Nitrogen Defects in Graphene and Carbon Nanotubes
by Yoshitaka Fujimoto
Micromachines 2024, 15(9), 1172; https://doi.org/10.3390/mi15091172 - 22 Sep 2024
Viewed by 787
Abstract
The substitutional doping of nitrogen is an efficient way to modulate the electronic properties of graphene and carbon nanotubes (CNTs). Therefore, it could enhance their physical and chemical properties as well as offer potential applications. This paper provides an overview of the experimental [...] Read more.
The substitutional doping of nitrogen is an efficient way to modulate the electronic properties of graphene and carbon nanotubes (CNTs). Therefore, it could enhance their physical and chemical properties as well as offer potential applications. This paper provides an overview of the experimental and theoretical investigations regarding nitrogen-doped graphene and CNTs. The formation of various nitrogen defects in nitrogen-doped graphene and CNTs, which are identified by several observations, is reviewed. The electronic properties and transport characteristics for nitrogen-doped graphene and CNTs are also reviewed for the development of high-performance electronic device applications. Full article
(This article belongs to the Special Issue Advances in Carbon-Based Nanomaterials Applied Innovations)
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9 pages, 5465 KiB  
Article
Enhanced Hybrid Nanogenerator Based on PVDF-HFP and PAN/BTO Coaxially Structured Electrospun Nanofiber
by Jin-Uk Yoo, Dong-Hyun Kim, Eun-Su Jung, Tae-Min Choi, Hwa-Rim Lee and Sung-Gyu Pyo
Micromachines 2024, 15(9), 1171; https://doi.org/10.3390/mi15091171 - 21 Sep 2024
Cited by 1 | Viewed by 1017
Abstract
Nanogenerators have garnered significant interest as environmentally friendly and potential energy-harvesting systems. Nanogenerators can be broadly classified into piezo-, tribo-, and hybrid nanogenerators. The hybrid nanogenerator used in this experiment is a nanogenerator that uses both piezo and tribo effects. These hybrid nanogenerators [...] Read more.
Nanogenerators have garnered significant interest as environmentally friendly and potential energy-harvesting systems. Nanogenerators can be broadly classified into piezo-, tribo-, and hybrid nanogenerators. The hybrid nanogenerator used in this experiment is a nanogenerator that uses both piezo and tribo effects. These hybrid nanogenerators have the potential to be used in wearable electronics, health monitoring, IoT devices, and more. In addition, the versatility of the material application in electrospinning makes it an ideal complement to hybrid nanogenerators. However, despite their potential, several experimental variables, biocompatibility, and harvesting efficiency require improvement in the research field. In particular, maximizing the output voltage of the fibers is a significant challenge. Based on this premise, this study aims to characterize hybrid nanogenerators (HNGs) with varied structures and material combinations, with a focus on identifying HNGs that exhibit superior piezoelectric- and triboelectric-induced voltage. In this study, several HNGs based on coaxial structures were fabricated via electrospinning. PVDF-HFP and PAN, known for their remarkable electrospinning properties, were used as the primary materials. Six combinations of these two materials were fabricated and categorized into homo and hetero groups based on their composition. The output voltage of the hetero group surpassed that of the homo group, primarily because of the triboelectric-induced voltage. Specifically, the overall output voltage of the hetero group was higher. In addition, the combination group with the most favorable voltage characteristics combined PVDF-HFP@PAN(BTO) and PAN hollow, boasting an output voltage of approximately 3.5 V. Full article
(This article belongs to the Special Issue Micro Energy Harvesting Technologies and Their Applications)
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40 pages, 16237 KiB  
Review
A Comprehensive Review of Piezoelectric Ultrasonic Motors: Classifications, Characterization, Fabrication, Applications, and Future Challenges
by Sidra Naz and Tian-Bing Xu
Micromachines 2024, 15(9), 1170; https://doi.org/10.3390/mi15091170 - 21 Sep 2024
Viewed by 1974
Abstract
Piezoelectric ultrasonic motors (USMs) are actuators that use ultrasonic frequency piezoelectric vibration-generated waves to transform electrical energy into rotary or translating motion. USMs receive more attention because they offer distinct qualities over traditional magnet-coil-based motors, such as miniaturization, great accuracy, speed, non-magnetic nature, [...] Read more.
Piezoelectric ultrasonic motors (USMs) are actuators that use ultrasonic frequency piezoelectric vibration-generated waves to transform electrical energy into rotary or translating motion. USMs receive more attention because they offer distinct qualities over traditional magnet-coil-based motors, such as miniaturization, great accuracy, speed, non-magnetic nature, silent operation, straightforward construction, broad temperature operations, and adaptability. This review study focuses on the principle of USMs and their classifications, characterization, fabrication methods, applications, and future challenges. Firstly, the classifications of USMs, especially, standing-wave, traveling-wave, hybrid-mode, and multi-degree-of-freedom USMs, are summarized, and their respective functioning principles are explained. Secondly, finite element modeling analysis for design and performance predictions, conventional and nano/micro-fabrication methods, and various characterization methods are presented. Thirdly, their advantages, such as high accuracy, small size, and silent operation, and their benefits over conventional motors for the different specific applications are examined. Fourthly, the advantages and disadvantages of USMs are highlighted. In addition, their substantial contributions to a variety of technical fields like surgical robots and industrial, aerospace, and biomedical applications are introduced. Finally, their future prospects and challenges, as well as research directions in USM development, are outlined, with an emphasis on downsizing, increasing efficiency, and new materials. Full article
(This article belongs to the Special Issue Piezoelectric Actuators and Sensors: Materials, Devices and Applications, 2nd Edition)
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14 pages, 2847 KiB  
Article
Waveguide-Enhanced Nanoplasmonic Biosensor for Ultrasensitive and Rapid DNA Detection
by Devesh Barshilia, Akhil Chandrakanth Komaram, Lai-Kwan Chau and Guo-En Chang
Micromachines 2024, 15(9), 1169; https://doi.org/10.3390/mi15091169 - 21 Sep 2024
Viewed by 885
Abstract
DNA is fundamental for storing and transmitting genetic information. Analyzing DNA or RNA base sequences enables the identification of genetic disorders, monitoring gene expression, and detecting pathogens. Traditional detection techniques like polymerase chain reaction (PCR) and next-generation sequencing (NGS) have limitations, including complexity, [...] Read more.
DNA is fundamental for storing and transmitting genetic information. Analyzing DNA or RNA base sequences enables the identification of genetic disorders, monitoring gene expression, and detecting pathogens. Traditional detection techniques like polymerase chain reaction (PCR) and next-generation sequencing (NGS) have limitations, including complexity, high cost, and the need for advanced computational skills. Therefore, there is a significant demand for enzyme-free and amplification-free strategies for rapid, low-cost, and sensitive DNA detection. DNA biosensors, especially those utilizing plasmonic nanomaterials, offer a promising solution. This study introduces a novel DNA-functionalized waveguide-enhanced nanoplasmonic optofluidic biosensor using a nanogold-linked sorbent assay for enzyme-free and amplification-free DNA detection. Integrating plasmonic gold nanoparticles (AuNPs) with a glass planar waveguide (WG) and a microfluidic channel, fabricated through cost-effective, vacuum-free methods, the biosensor achieves specific detection of complementary target DNA sequences. Utilizing a sandwich architecture, AuNPs labeled with detection DNA probes enhance sensitivity by altering evanescent wave distribution and inducing plasmon resonance modes. The biosensor demonstrated exceptional performance in DNA detection, achieving a limit of detection (LOD) of 33.1 fg/mL (4.36 fM) with a rapid response time of approximately 8 min. This ultrasensitive, rapid, and cost-effective biosensor exhibits minimal background nonspecific adsorption, making it highly suitable for clinical applications and early disease diagnosis. The innovative design and fabrication processes offer significant advantages for mass production, presenting a viable tool for precise disease diagnostics and improved clinical outcomes. Full article
(This article belongs to the Special Issue Exploration and Application of Micro-Devices/Sensors in Analytical Chemistry)
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17 pages, 10664 KiB  
Article
Multi-Position Inertial Alignment Method for Underground Pipelines Using Data Backtracking Based on Single-Axis FOG/MIMU
by Jiachen Liu, Lu Wang, Yutong Zu and Yuanbiao Hu
Micromachines 2024, 15(9), 1168; https://doi.org/10.3390/mi15091168 - 21 Sep 2024
Viewed by 3368
Abstract
The inertial measurement method of pipelines utilizes a Micro-Electro-Mechanical Systems Inertial Measurement Unit (MIMU) to get the three-dimensional trajectory of underground pipelines. The initial attitude is significant for the inertial measurement method of pipelines. The traditional method to obtain the initial attitude uses [...] Read more.
The inertial measurement method of pipelines utilizes a Micro-Electro-Mechanical Systems Inertial Measurement Unit (MIMU) to get the three-dimensional trajectory of underground pipelines. The initial attitude is significant for the inertial measurement method of pipelines. The traditional method to obtain the initial attitude uses three-axis magnetometers to measure the Earth’s magnetic field. However, the magnetic field in urban underground pipelines is intricate, which leads to the initial attitude being inaccurate. To overcome this challenge, a novel multi-position initial alignment method based on data backtracking for a single-axis FOG and a three-axis Micro-Electro-Mechanical Inertial Measurement Unit (MIMU) is proposed. Firstly, the configuration of the sensors is determined. Secondly, according to the three-point support structure of the pipeline measuring instrument, a three-position alignment scheme is designed. Additionally, an initial alignment algorithm using the data backtracking method is developed. In this algorithm, a rough initial alignment is conducted by the data from single-axis FOG, and a fine initial alignment is conducted by the data from FOG/MIMU. Finally, an experiment was conducted to validate this method. The experiment results indicate that the pitch and roll angle errors are less than 0.05°, and the azimuth angle errors are less than 0.2°. This improved the precision of the 3-D trajectory of underground pipelines. Full article
(This article belongs to the Special Issue MEMS Nano/Micro Fabrication, 2nd Edition)
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20 pages, 7194 KiB  
Article
Deep Learning-Driven Prediction of Mechanical Properties of 316L Stainless Steel Metallographic by Laser Powder Bed Fusion
by Zhizhou Zhang, Paul Mativenga, Wenhua Zhang and Shi-qing Huang
Micromachines 2024, 15(9), 1167; https://doi.org/10.3390/mi15091167 - 21 Sep 2024
Viewed by 1059
Abstract
This study developed a new metallography–property relationship neural network (MPR-Net) to predict the relationship between the microstructure and mechanical properties of 316L stainless steel built by laser powder bed fusion (LPBF). The accuracy R2 of MPR-Net was 0.96 and 0.91 for tensile [...] Read more.
This study developed a new metallography–property relationship neural network (MPR-Net) to predict the relationship between the microstructure and mechanical properties of 316L stainless steel built by laser powder bed fusion (LPBF). The accuracy R2 of MPR-Net was 0.96 and 0.91 for tensile strength and Vickers hardness predictions, respectively, based on optical metallurgy images. Feature visualisation methods, such as gradient-weighted class activation mapping (Grad-CAM) and clustering, were employed to interpret the abstract features within the MPR-Net, providing insights into the molten pool morphology and grain formation mechanisms during the LPBF process. Experimental results showed that the optimal process parameters—190 W laser power and 700 mm/s scanning speed—yielded a maximum tensile strength of 762.83 MPa and a Vickers hardness of 253.07 HV0.2 with nearly full densification (99.97%). The study marks the first application of a convolutional neural network (MPR-Net) to predict the mechanical properties of 316L stainless steel samples manufactured through laser powder bed fusion (LPBF) based on metallography. It innovatively employs techniques such as gradient-weighted class activation mapping (Grad-CAM), spatial coherence testing, and clustering to provide deeper insights into the workings of the machine learning model, enhancing the interpretability of complex neural network decisions in material science. Full article
(This article belongs to the Special Issue Optical and Laser Material Processing)
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17 pages, 12419 KiB  
Article
Design of a Novel Microlens Array and Imaging System for Light Fields
by Yifeng Li, Pangyue Li, Xinyan Zheng, Huachen Liu, Yiran Zhao, Xueping Sun, Weiguo Liu and Shun Zhou
Micromachines 2024, 15(9), 1166; https://doi.org/10.3390/mi15091166 - 21 Sep 2024
Cited by 1 | Viewed by 1474
Abstract
Light field cameras are unsuitable for further acquisition of high-quality images due to their small depth of field, insufficient spatial resolution, and poor imaging quality. To address these issues, we proposed a novel four-focal-square microlens and light field system. A square aspheric microlens [...] Read more.
Light field cameras are unsuitable for further acquisition of high-quality images due to their small depth of field, insufficient spatial resolution, and poor imaging quality. To address these issues, we proposed a novel four-focal-square microlens and light field system. A square aspheric microlens array with four orthogonal focal lengths was designed, in which the aperture of a single lens was 100 μm. The square arrangement improves pixel utilization, the four focal lengths increase the depth of field, and the aspheric improves image quality. The simulations demonstrate pixel utilization rates exceeding 90%, depth-of-field ranges 6.57 times that of a single focal length, and image quality is significantly improved. We have provided a potential solution for improving the depth of field and image quality of the light field imaging system. Full article
(This article belongs to the Section E：Engineering and Technology)
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12 pages, 2071 KiB  
Article
The Side-Release Method Measures the High-Pressure Sound Velocity of Iron Using Line-Spatially Resolved DISAR
by Long Chen, Cangli Liu, Longhuang Tang, Heli Ma, Xing Jia, Tianjiong Tao, Shenggang Liu, Yongchao Chen, Xiang Wang, Jian Wu, Chengjun Li, Dameng Liu, Jidong Weng and Huan Liu
Micromachines 2024, 15(9), 1165; https://doi.org/10.3390/mi15091165 - 20 Sep 2024
Viewed by 765
Abstract
The study of high-pressure sound velocity is an important part of shock wave physics, and the study of ultra-high pressure sound velocity of iron is of great significance to many research fields such as geophysics, solid state physics, and crystallography. At present, the [...] Read more.
The study of high-pressure sound velocity is an important part of shock wave physics, and the study of ultra-high pressure sound velocity of iron is of great significance to many research fields such as geophysics, solid state physics, and crystallography. At present, the measurement of sound velocity is usually carried out by the catch-up sparse wave method and windowed VISAR technology, which is complex in structure and not highly adaptable. In particular, for the ultra-high pressure sonic velocity measurement of metals, it is limited by the loading platform and window materials and cannot realize the high temperature and high-pressure environment of the earth’s inner core. In this paper, the sound velocity measurement of iron under high temperature and high-pressure environment (78 GPa) is realized based on the two-stage light gas cannon experimental platform. The side-side sparse wave method was used to establish a coupling model of high-spatially resolved optical group and fiber bundle. A multiplexed all-fiber laser interferometry velocity measurement system (DISAR) was built, and the spatial resolution was better than 20 μm. In this paper, we will provide a feasible route for a method for measuring the high spatiotemporal resolution velocity. Full article
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18 pages, 7139 KiB  
Article
An FPGA-Based YOLOv5 Accelerator for Real-Time Industrial Vision Applications
by Zhihong Yan, Bingqian Zhang and Dong Wang
Micromachines 2024, 15(9), 1164; https://doi.org/10.3390/mi15091164 - 19 Sep 2024
Viewed by 1583
Abstract
The You Only Look Once (YOLO) object detection network has garnered widespread adoption in various industries, owing to its superior inference speed and robust detection capabilities. This model has proven invaluable in automating production processes such as material processing, machining, and quality inspection. [...] Read more.
The You Only Look Once (YOLO) object detection network has garnered widespread adoption in various industries, owing to its superior inference speed and robust detection capabilities. This model has proven invaluable in automating production processes such as material processing, machining, and quality inspection. However, as market competition intensifies, there is a constant demand for higher detection speed and accuracy. Current FPGA accelerators based on 8-bit quantization have struggled to meet these increasingly stringent performance requirements. In response, we present a novel 4-bit quantization-based neural network accelerator for the YOLOv5 model, designed to enhance real-time processing capabilities while maintaining high detection accuracy. To achieve effective model compression, we introduce an optimized quantization scheme that reduces the bit-width of the entire YOLO network—including the first layer—to 4 bits, with only a 1.5% degradation in mean Average Precision (mAP). For the hardware implementation, we propose a unified Digital Signal Processor (DSP) packing scheme, coupled with a novel parity adder tree architecture that accommodates the proposed quantization strategies. This approach efficiently reduces on-chip DSP utilization by 50%, offering a significant improvement in performance and resource efficiency. Experimental results show that the industrial object detection system based on the proposed FPGA accelerator achieves a throughput of 808.6 GOPS and an efficiency of 0.49 GOPS/DSP for YOLOv5s on the ZCU102 board, which is 29% higher than a commercial FPGA accelerator design (Xilinx’s Vitis AI). Full article
(This article belongs to the Special Issue FPGA Applications and Future Trends)
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8 pages, 1480 KiB  
Communication
Exploration of a Novel Electric-Fuse Device with a Simple Structure of Ni Metal on a SiO2 Dielectric for Electrostatic Discharge Protection under a Human Body Model
by He Guan, Jiaying Li, Yangchao Chen, Yongchuan Tang and Yunshuo Li
Micromachines 2024, 15(9), 1163; https://doi.org/10.3390/mi15091163 - 19 Sep 2024
Viewed by 697
Abstract
On-chip electrostatic discharge (ESD) protection poses a challenge in the chip fabrication process. In this study, a novel electric fuse (E-fuse) device featuring a simple structure of Ni metal on a SiO2 dielectric for ESD protection was proposed, and the physical mechanism [...] Read more.
On-chip electrostatic discharge (ESD) protection poses a challenge in the chip fabrication process. In this study, a novel electric fuse (E-fuse) device featuring a simple structure of Ni metal on a SiO2 dielectric for ESD protection was proposed, and the physical mechanism of its operation was investigated in detail. Experimental evaluations, utilizing transmission line pulse (TLP) testing and fusing performance analyses, reveal that the E-fuse, constructed with a Ni metal layer measuring 5 μm in width, 100 μm in length, and 5 nm in thickness, achieved a significant ESD protection voltage of 251 V (VHBM) and demonstrates low-voltage fusing at a bias voltage of 7 V. Compared to traditional ESD protection devices, the E-fuse boasts a smaller size and removability. To assess fusing performance, devices of varying sizes were tested using a fusing lifetime model. This study supports both theoretical and empirical evidence, enabling the adoption of cost-effective, straightforward E-fuse devices for ESD protection. Full article
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21 pages, 5975 KiB  
Article
High-Precision Measurement of Microscales Based on Optoelectronics and Image Integration Method
by Yanlong Zhu, Yinbao Cheng, Hongtang Gao, Shuanghua Sun, Xudong Zhang, Liang Xue, Jiangwen Tang and Yingqi Tang
Micromachines 2024, 15(9), 1162; https://doi.org/10.3390/mi15091162 - 17 Sep 2024
Viewed by 792
Abstract
Currently, there are various types of microscales and the conventional line detection system usually has only one detection method, which is difficult to adapt to the diverse calibration needs of microscales. This article investigates the high-precision measurement method of a microscale based on [...] Read more.
Currently, there are various types of microscales and the conventional line detection system usually has only one detection method, which is difficult to adapt to the diverse calibration needs of microscales. This article investigates the high-precision measurement method of a microscale based on optoelectronics and the image integration method to solve the diversified calibration needs of microscales. The automatic measurement and processing system integrates two methods: the photoelectric signal measurement method and the photoelectric image measurement method. This article studies the smooth motion method based on ordinary linear guides, investigates the method of reducing the cosine error of a small-range interference length measurement, proposes an image-based line positioning method, and studies the edge and center recognition algorithms of the line. According to the experimental data, the system’s measurement accuracy was analyzed using the photoelectric signal measurement method to measure the 1 mm microscale, the maximum difference from the reference value was 0.105 μm, the standard uncertainty was 0.068 μm, and the absolute value of normalized error was less than 1. The accuracy of the image measurement method to measure the 1 mm microscale was consistent with that of the photoelectric signal method. The results show good consistency in the measurement results between the two methods of the integrated measurement system. The photoelectric signal method has the technical characteristics of high measurement efficiency and high accuracy, while the pixel-based measurement of the image method has two-dimensional measurement characteristics, which can realize measurements that cannot be realized by the photoelectric signal method; therefore, the measurement system of optoelectronics and image integration is characterized by high precision and a wide range of measurement adaptations. Full article
(This article belongs to the Special Issue Precision Optical Manufacturing and Processing)
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13 pages, 16375 KiB  
Article
Laser-Induced Periodic Surface Structures and Their Application for Gas Sensing
by Johann Zehetner, Ivan Hotovy, Vlastimil Rehacek, Ivan Kostic, Miroslav Mikolasek, Dana Seyringer and Fadi Dohnal
Micromachines 2024, 15(9), 1161; https://doi.org/10.3390/mi15091161 - 17 Sep 2024
Viewed by 3466
Abstract
Semiconducting metal oxides are widely used for solar cells, photo-catalysis, bio-active materials and gas sensors. Besides the material properties of the semiconductor being used, the specific surface topology of the sensors determines device performance. This study presents different approaches for increasing the sensing [...] Read more.
Semiconducting metal oxides are widely used for solar cells, photo-catalysis, bio-active materials and gas sensors. Besides the material properties of the semiconductor being used, the specific surface topology of the sensors determines device performance. This study presents different approaches for increasing the sensing area of semiconducting metal oxide gas sensors. Micro- and nanopatterned laser-induced periodic surface structures (LIPSSs) are generated on silicon, Si/SiO2 and glass substrates. The surface morphologies of the fabricated samples are examined by FE SEM. We selected the nanostructuring and characterization of nanostructured source Ni/Au and Ti/Au films prepared on glass using laser ablation as the most suitable of the investigated approaches. Surface structures produced on glass by backside ablation provide 100 nm features with a high surface area; they are also transparent and have high resistivity. The value of the hydrogen sensitivity in the range concentrations from 100 to 500 ppm was recorded using transmittance measurements to be twice as great for the nanostructured target TiO2/Au as compared to the NiO/Au. It was found that such transparent materials present additional possibilities for producing optical gas sensors. Full article
(This article belongs to the Special Issue Ultrafast Laser Micro- and Nanoprocessing, 2nd Edition)
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10 pages, 1639 KiB  
Article
One-Step Dry-Etching Fabrication of Tunable Two-Hierarchical Nanostructures
by Xu Ji, Bo Wang, Zhongshan Zhang, Yuan Xiang, Haifang Yang, Ruhao Pan and Junjie Li
Micromachines 2024, 15(9), 1160; https://doi.org/10.3390/mi15091160 - 17 Sep 2024
Viewed by 891
Abstract
Two-hierarchical nanostructures, characterized by two distinct configurations along the height direction, exhibit immense potential for applications in various fields due to their significantly enhanced controllable degree compared to single-order structures. However, due to the limitations imposed by planar technology, the realization of two-hierarchical [...] Read more.
Two-hierarchical nanostructures, characterized by two distinct configurations along the height direction, exhibit immense potential for applications in various fields due to their significantly enhanced controllable degree compared to single-order structures. However, due to the limitations imposed by planar technology, the realization of two-hierarchical nanostructures encounters huge challenges. In this work, we developed a one-step etching method based on inductively coupled plasma reactive ion etching for two-hierarchical nanostructures. Thanks to the shrinking effect of the Cr mask and the generation of a passivation layer during etching, the target materials experienced two different states from vertical etching to shrink etching. Consequently, the achieved two-hierarchical nanostructure configuration features a cross-section of an upper triangle and a lower rectangle, showing higher controllable degrees compared to the one-order ones. Both the mask pattern and etching parameters play crucial roles, by which two-hierarchical structures with diversiform shapes can be constructed controllably. This method for two-hierarchical nanostructures offers advantages including excellent control over structural properties, high processing efficiency, uniformity across large areas, and universality in materials. This developed strategy not only presents a simple and rapid nanofabrication platform for realizing optoelectronic devices, but also provides innovative ideas for designing the next generation of high-performance devices. Full article
(This article belongs to the Special Issue The 15th Anniversary of Micromachines)
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27 pages, 4805 KiB  
Article
Actuators with Two Double Gimbal Magnetically Suspended Control Moment Gyros for the Attitude Control of the Satellites
by Romulus Lungu, Alexandru-Nicolae Tudosie, Mihai-Aureliu Lungu and Nicoleta-Claudia Crăciunoiu
Micromachines 2024, 15(9), 1159; https://doi.org/10.3390/mi15091159 - 16 Sep 2024
Viewed by 681
Abstract
The paper proposes a novel automatic control system for the attitude of the mini-satellites equipped with an actuator having N = 2 DGMSCMGs (Double Gimbal Magnetically Suspended Control Moment Gyros) in parallel and orthogonal configuration, as well as a DGMSCMG-type sensor for the [...] Read more.
The paper proposes a novel automatic control system for the attitude of the mini-satellites equipped with an actuator having N = 2 DGMSCMGs (Double Gimbal Magnetically Suspended Control Moment Gyros) in parallel and orthogonal configuration, as well as a DGMSCMG-type sensor for the measurement of the satellite absolute angular rate. The proportional-derivative controller, designed based on the Lyapunov-functions theory, elaborates the control law according to which the angular rates applied to the servo systems for the actuation of the DGMSCMGs gyroscopic gimbals are computed. The gimbal’s angular rates create gyroscopic couples acting on the satellite in order to control its attitude with respect to the local orbital frame. The new proposed control architecture was software implemented and validated, and the analysis of the obtained results proved the cancellation of the convergence errors and excellent angular rate precision. Full article
(This article belongs to the Special Issue Advances in Sensors, Algorithms and Machines for Intelligent Micro- and Nano-Systems)
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10 pages, 4095 KiB  
Article
Improvement of Single Event Transient Effects for a Novel AlGaN/GaN High Electron-Mobility Transistor with a P-GaN Buried Layer and a Locally Doped Barrier Layer
by Juan Xiong, Xintong Xie, Jie Wei, Shuxiang Sun and Xiaorong Luo
Micromachines 2024, 15(9), 1158; https://doi.org/10.3390/mi15091158 - 16 Sep 2024
Viewed by 876
Abstract
In this paper, a novel AlGaN/GaN HEMT structure with a P-GaN buried layer in the buffer layer and a locally doped barrier layer under the gate (PN-HEMT) is proposed to enhance its resistance to single event transient (SET) effects while also overcoming the [...] Read more.
In this paper, a novel AlGaN/GaN HEMT structure with a P-GaN buried layer in the buffer layer and a locally doped barrier layer under the gate (PN-HEMT) is proposed to enhance its resistance to single event transient (SET) effects while also overcoming the degradation of other characteristics. The device operation mechanism and characteristics are investigated by TCAD simulation. The results show that the peak electric field and impact ionization at the gate edges are reduced in the PN-HEMT due to the introduced P-GaN buried layer in the buffer layer. This leads to a decrease in the peak drain current (Ipeak) induced by the SET effect and an improvement in the breakdown voltage (BV). Additionally, the locally doped barrier layer provides extra electrons to the channel, resulting in higher saturated drain current (ID,sat) and maximum transconductance (gmax). The Ipeak of the PN-HEMT (1.37 A/mm) is 71.8% lower than that of the conventional AlGaN/GaN HEMT (C-HEMT) (4.85 A/mm) at 0.6 pC/µm. Simultaneously, ID,sat and BV are increased by 21.2% and 63.9%, respectively. Therefore, the PN-HEMT enhances the hardened SET effect of the device without sacrificing other key characteristics of the AlGaN/GaN HEMT. Full article
(This article belongs to the Special Issue Advances in GaN- and SiC-Based Electronics: Design and Applications)
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11 pages, 3519 KiB  
Article
Optimization of Non-Alloyed Backside Ohmic Contacts to N-Face GaN for Fully Vertical GaN-on-Silicon-Based Power Devices
by Youssef Hamdaoui, Sofie S. T. Vandenbroucke, Sondre Michler, Katir Ziouche, Matthias M. Minjauw, Christophe Detavernier and Farid Medjdoub
Micromachines 2024, 15(9), 1157; https://doi.org/10.3390/mi15091157 - 15 Sep 2024
Viewed by 1272
Abstract
In the framework of fully vertical GaN-on-Silicon device technology development, we report on the optimization of non-alloyed ohmic contacts on the N-polar n+-doped GaN face backside layer. This evaluation is made possible by using patterned TLMs (Transmission Line Model) through direct laser writing [...] Read more.
In the framework of fully vertical GaN-on-Silicon device technology development, we report on the optimization of non-alloyed ohmic contacts on the N-polar n+-doped GaN face backside layer. This evaluation is made possible by using patterned TLMs (Transmission Line Model) through direct laser writing lithography after locally removing the substrate and buffer layers in order to access the n+-doped backside layer. As deposited non-alloyed metal stack on top of N-polar orientation GaN layer after buffer layers removal results in poor ohmic contact quality. To significantly reduce the related specific contact resistance, an HCl treatment is applied prior to metallization under various time and temperature conditions. A 3 min HCl treatment at 70 °C is found to be the optimum condition to achieve thermally stable high ohmic contact quality. To further understand the impact of the wet treatment, SEM (Scanning Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy) analyses were performed. XPS revealed a decrease in Ga-O concentration after applying the treatment, reflecting the higher oxidation susceptibility of the N-polar face compared to the Ga-polar face, which was used as a reference. SEM images of the treated samples show the formation of pyramids on the N-face after HCl treatment, suggesting specific wet etching planes of the GaN crystal from the N-face. The size of the pyramids is time-dependent; thus, increasing the treatment duration results in larger pyramids, which explains the degradation of ohmic contact quality after prolonged high-temperature HCl treatment. Full article
(This article belongs to the Special Issue Wide Bandgap Based Devices: Design, Fabrication and Applications, 4th Edition)
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16 pages, 5590 KiB  
Article
Corrosion Behavior and Biological Properties of ZK60/HA Composites Prepared by Laser Powder Bed Fusion
by Cijun Shuai, Cheng Chen, Zhenyu Zhao and Youwen Yang
Micromachines 2024, 15(9), 1156; https://doi.org/10.3390/mi15091156 - 15 Sep 2024
Viewed by 850
Abstract
Magnesium alloy ZK60 shows great promise as a medical metal material, but its corrosion resistance in the body is inadequate. Hydroxyapatite (HA), the primary inorganic component of human and animal bones, can form chemical bonds with body tissues at the interface, promoting the [...] Read more.
Magnesium alloy ZK60 shows great promise as a medical metal material, but its corrosion resistance in the body is inadequate. Hydroxyapatite (HA), the primary inorganic component of human and animal bones, can form chemical bonds with body tissues at the interface, promoting the deposition of phosphorus products and creating a dense calcium and phosphorus layer. To enhance the properties of ZK60, HA was added to create HA/ZK60 composite materials. These composites, fabricated using the advanced technique of LPBF, demonstrated superior corrosion resistance and enhanced bone inductive capabilities compared to pristine ZK60. Notably, the incorporation of 3 wt% led to a significant reduction in bulk porosity, achieving a value of 0.8%. The Ecorr value increased from −1.38 V to −1.32 V, while the minimum Icorr value recorded at 33.9 μA·cm−2. Nano-HA achieved the lowest volumetric porosity and optimal corrosion resistance. Additionally, these composites significantly promoted osteogenic differentiation in bone marrow stromal cells (BMSCs), as evidenced by increased alkaline phosphatase (ALP) activity and robust calcium nodule formation, highlighting their excellent biocompatibility and osteo-inductive potential. However, when increasing the HA content to 6 wt%, the bulk porosity rose significantly to 3.3%. The Ecorr value was −1.3 V, with the Icorr value being approximately 50 μA·cm−2. This increase in porosity and weaker interfacial bonding, ultimately accelerated electrochemical corrosion. Therefore, a carefully balanced amount of HA significantly enhances the performance of the ZK60 magnesium alloy, while excessive amounts can be detrimental. Full article
(This article belongs to the Special Issue Laser Additive Manufacturing of Metallic Materials, 2nd Edition)
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16 pages, 10385 KiB  
Article
Laser Direct Writing of Setaria Virids-Inspired Hierarchical Surface with TiO2 Coating for Anti-Sticking of Soft Tissue
by Qingxu Zhang, Yanyan Yang, Shijie Huo, Shucheng Duan, Tianao Han, Guang Liu, Kaiteng Zhang, Dengke Chen, Guang Yang and Huawei Chen
Micromachines 2024, 15(9), 1155; https://doi.org/10.3390/mi15091155 - 15 Sep 2024
Viewed by 965
Abstract
In minimally invasive surgery, the tendency for human tissue to adhere to the electrosurgical scalpel can complicate procedures and elevate the risk of medical accidents. Consequently, the development of an electrosurgical scalpel with an anti-sticking coating is critically important. Drawing inspiration from nature, [...] Read more.
In minimally invasive surgery, the tendency for human tissue to adhere to the electrosurgical scalpel can complicate procedures and elevate the risk of medical accidents. Consequently, the development of an electrosurgical scalpel with an anti-sticking coating is critically important. Drawing inspiration from nature, we identified that the leaves of Setaria Virids exhibit exceptional non-stick properties. Utilizing this natural surface texture as a model, we designed and fabricated a specialized anti-sticking surface for electrosurgical scalpels. Employing nanosecond laser direct writing ablation technology, we created a micro-nano textured surface on the high-frequency electrosurgical scalpel that mimics the structure found on Setaria Virids leaves. Subsequently, a TiO2 coating was deposited onto the ablated scalpel surface via magnetron sputtering, followed by plasma-induced hydrophobic modification and treatment with octadecyltrichlorosilane (OTS) to enhance the surface’s affinity for silicone oil, thereby constructing a self-lubricating and anti-sticking surface. The spreading behavior of deionized water, absolute ethanol, and dimethyl silicone oil on this textured surface is investigated to confirm the effectiveness of the self-lubrication mechanism. Furthermore, the sticking force and quality are compared between the anti-sticking electrosurgical scalpel and a standard high-frequency electrosurgical scalpel to demonstrate the efficacy of the nanosecond laser-ablated micro-nano texture in preventing sticking. The findings indicate that the self-lubricating anti-sticking surface fabricated using this texture exhibits superior anti-sticking properties. Full article
(This article belongs to the Special Issue Recent Advances in Micro/Nano-Fabrication)
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12 pages, 4905 KiB  
Article
Research on the Magnetorheological Finishing Technology of a High-Steepness Optical Element Based on the Virtual-Axis and Spiral Scanning Path
by Chihao Chen, Chaoliang Guan, Meng Liu, Yifan Dai and Hao Hu
Micromachines 2024, 15(9), 1154; https://doi.org/10.3390/mi15091154 - 15 Sep 2024
Viewed by 743
Abstract
Magnetorheological finishing (MRF) of aspherical optical elements usually requires the coordination between the translational axes and the oscillating axes of the machine tool to realize the processing. For aspheric optical elements whose steepness exceeds the machining stroke of the equipment, there is still [...] Read more.
Magnetorheological finishing (MRF) of aspherical optical elements usually requires the coordination between the translational axes and the oscillating axes of the machine tool to realize the processing. For aspheric optical elements whose steepness exceeds the machining stroke of the equipment, there is still no better method to achieve high-precision and high-efficiency error convergence. To solve this problem, an MRF method combining virtual-axis technology and a spiral scanning path is proposed in this paper. Firstly, the distribution law of the magnetic induction intensity inside the polishing wheel is analyzed by simulation, the stability of the removal efficiency of the removal function within the ±7∘ angle of the normal angle of the polishing wheel is determined, and MRF is expanded from traditional single-point processing to circular arc segment processing. Secondly, the spiral scanning path is proposed for aspherical rotational symmetric optical elements, which can reduce the requirements of the number of machine tool axes and the dynamic performance of machine tools. Finally, an aspherical fused silica optical element with a curvature radius of 400 mm, K value of −1, and aperture of 100 mm is processed. The PV value of this optical element converges from 189.2 nm to 24.85 nm, and the RMS value converges from 24.85 nm to 5.74 nm. The experimental results show that the proposed combined process has the ability to modify curved optical elements and can be applied to ultra-precision machining of high-steepness optical elements. Full article
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19 pages, 6389 KiB  
Article
A Breast Tumor Monitoring Vest with Flexible UWB Antennas—A Proof-of-Concept Study Using Realistic Breast Phantoms
by Rakshita Dessai, Daljeet Singh, Marko Sonkki, Jarmo Reponen, Teemu Myllylä, Sami Myllymäki and Mariella Särestöniemi
Micromachines 2024, 15(9), 1153; https://doi.org/10.3390/mi15091153 - 14 Sep 2024
Viewed by 982
Abstract
Breast cancers can appear and progress rapidly, necessitating more frequent monitoring outside of hospital settings to significantly reduce mortality rates. Recently, there has been considerable interest in developing techniques for portable, user-friendly, and low-cost breast tumor monitoring applications, enabling frequent and cost-efficient examinations. [...] Read more.
Breast cancers can appear and progress rapidly, necessitating more frequent monitoring outside of hospital settings to significantly reduce mortality rates. Recently, there has been considerable interest in developing techniques for portable, user-friendly, and low-cost breast tumor monitoring applications, enabling frequent and cost-efficient examinations. Microwave technique-based breast cancer detection, which is based on differential dielectric properties of malignant and healthy tissues, is regarded as a promising solution for cost-effective breast tumor monitoring. This paper presents the development process of the first proof-of-concept of a breast tumor monitoring vest which is based on the microwave technique. Two unique vests are designed and evaluated on realistic 3D human tissue phantoms having different breast density types. Additionally, the measured results are verified using simulations carried out on anatomically realistic voxel models of the electromagnetic simulations. The radio channel characteristics are evaluated and analyzed between the antennas embedded in the vest in tumor cases and reference cases. Both measurements and simulation results show that the proposed vest can detect tumors even if only 1 cm in diameter. Additionally, simulation results show detectability with 0.5 cm tumors. It is observed that the detectability of breast tumors depends on the frequency, antenna selection, size of the tumors, and breast types, causing differences of 0.5–30 dB in channel responses between the tumorous and reference cases. Due to simplicity and cost-efficiency, the proposed channel analysis-based breast monitoring vests can be used for breast health checks in smaller healthcare centers and for user-friendly home monitoring which can prove beneficial in rural areas and developing countries. Full article
(This article belongs to the Special Issue Biomaterials, Biodevices and Tissue Engineering, Second Edition)
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18 pages, 36209 KiB  
Review
Application of Metal Halide Perovskite in Internet of Things
by Zhihao Chai, Hui Lin, Hang Bai, Yixiang Huang, Zhen Guan, Fangze Liu and Jing Wei
Micromachines 2024, 15(9), 1152; https://doi.org/10.3390/mi15091152 - 14 Sep 2024
Viewed by 986
Abstract
The Internet of Things (IoT) technology connects the real and network worlds by integrating sensors and internet technology, which has greatly changed people’s lifestyles, showing its broad application prospects. However, traditional materials for the sensors and power components used in the IoT limit [...] Read more.
The Internet of Things (IoT) technology connects the real and network worlds by integrating sensors and internet technology, which has greatly changed people’s lifestyles, showing its broad application prospects. However, traditional materials for the sensors and power components used in the IoT limit its development for high-precision detection, long-term endurance, and multi-scenario applications. Metal halide perovskite, with unique advantages such as excellent photoelectric properties, an adjustable bandgap, flexibility, and a mild process, exhibits enormous potential to meet the requirements for IoT development. This paper provides a comprehensive review of metal halide perovskite’s application in sensors and energy supply modules within IoT systems. Advances in perovskite-based sensors, such as for gas, humidity, photoelectric, and optical sensors, are discussed. The application of indoor photovoltaics based on perovskite in IoT systems is also discussed. Lastly, the application prospects and challenges of perovskite-based devices in the IoT are summarized. Full article
(This article belongs to the Special Issue Prospective Outlook on Perovskite Materials and Devices)
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15 pages, 7305 KiB  
Article
Contact Hole Shrinkage: Simulation Study of Resist Flow Process and Its Application to Block Copolymers
by Sang-Kon Kim
Micromachines 2024, 15(9), 1151; https://doi.org/10.3390/mi15091151 - 13 Sep 2024
Viewed by 1079
Abstract
For vertical interconnect access (VIA) in three-dimensional (3D) structure chips, including those with high bandwidth memory (HBM), shrinking contact holes (C/Hs) using the resist flow process (RFP) represents the most promising technology for low- [...] Read more.
For vertical interconnect access (VIA) in three-dimensional (3D) structure chips, including those with high bandwidth memory (HBM), shrinking contact holes (C/Hs) using the resist flow process (RFP) represents the most promising technology for low-k1 (where CD=k1λ/NA,CD is the critical dimension, λ is wavelength, and NA is the numerical aperture). This method offers a way to reduce dimensions without additional complex process steps and is independent of optical technologies. However, most empirical models are heuristic methods and use linear regression to predict the critical dimension of the reflowed structure but do not account for intermediate shapes. In this research, the resist flow process (RFP) was modeled using the evolution method, the finite-element method, machine learning, and deep learning under various reflow conditions to imitate experimental results. Deep learning and machine learning have proven to be useful for physical optimization problems without analytical solutions, particularly for regression and classification tasks. In this application, the self-assembly of cylinder-forming block copolymers (BCPs), confined in prepatterns of the resist reflow process (RFP) to produce small contact hole (C/H) dimensions, was described using the self-consistent field theory (SCFT). This research paves the way for the shrink modeling of the enhanced resist reflow process (RFP) for random contact holes (C/Hs) and the production of smaller contact holes. Full article
(This article belongs to the Special Issue Recent Advances in Micro/Nano-Fabrication)
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10 pages, 2956 KiB  
Article
Preparation and Properties Study of CsPbX3@PMMA Luminescent Resin
by Xinqiang Ma, Shengying Fan, Wenwen Yang, Jiajie Wei, Xiaolei Wang, Jincheng Ni, Wei Cheng and Qinhe Zhang
Micromachines 2024, 15(9), 1150; https://doi.org/10.3390/mi15091150 - 13 Sep 2024
Viewed by 711
Abstract
Perovskite as an emerging semiconductor luminescent material has attracted widespread attention due to its simple preparation, high luminescence quantum yield, high color purity, tunable spectrum, and ability to cover the entire visible light band. However, due to the influence of water or other [...] Read more.
Perovskite as an emerging semiconductor luminescent material has attracted widespread attention due to its simple preparation, high luminescence quantum yield, high color purity, tunable spectrum, and ability to cover the entire visible light band. However, due to the influence of water or other highly polar solvents, oxygen, temperature, and radiation, perovskite nanocrystals will aggregate or collapse in the lattice, eventually leading to luminescence quenching. This study starts from the postprocessing of perovskite, uses methyl methacrylate as the monomer and TPO as the photoinitiator, and encapsulates the perovskite powder prepared by the hot injection method through ultraviolet light initiation. A method is proposed to improve the luminescence and crystal structure stability of perovskite. By eliminating the influence of environmental factors on perovskite nanocrystals through the dense structure formed by organic polymers, the resistance of perovskite to strong polar solvents such as water will be greatly improved, and it has great potential in the protection of perovskite. Finally, by changing the proportion of halogen elements in the perovskite resin to change the color of the luminescent resin, a fluorescent coating emitting light in all visible light bands is prepared. Fluorescent coatings are widely used in life and industry fields such as plastics, sol, and paper. Full article
(This article belongs to the Special Issue Optical and Laser Material Processing)
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3 pages, 163 KiB  
Editorial
Editorial for the Special Issue on Methodology, Microfabrication and Applications of Advanced Sensing and Smart Systems
by Luyu Jia, Shanling Ji, Yuze Gao, Haiying Wen and Jianxiong Zhu
Micromachines 2024, 15(9), 1149; https://doi.org/10.3390/mi15091149 - 13 Sep 2024
Viewed by 3171
Abstract
Smart sensing and advanced systems have played crucial roles in the modern industrialization of society, which has led to many sensors being used in fabrication methodologies for various applications, such as in medical equipment [...] Full article
(This article belongs to the Special Issue Methodology, Microfabrication and Applications of Advanced Sensing and Smart Systems)
11 pages, 3101 KiB  
Article
Influence of the Bias Voltage on Effective Electron Velocity in AlGaN/GaN High Electron Mobility Transistors
by Guangyuan Jiang, Peng Cui, Chen Fu, Yuanjie Lv, Ming Yang, Qianding Cheng, Yang Liu and Guangyuan Zhang
Micromachines 2024, 15(9), 1148; https://doi.org/10.3390/mi15091148 - 13 Sep 2024
Viewed by 796
Abstract
The small-signal S parameters of the fabricated double-finger gate AlGaN/GaN high electron mobility transistors (HEMTs) were measured at various direct current quiescent operating points (DCQOPs). Under active bias conditions, small-signal equivalent circuit (SSEC) parameters such as Rs and Rd, and [...] Read more.
The small-signal S parameters of the fabricated double-finger gate AlGaN/GaN high electron mobility transistors (HEMTs) were measured at various direct current quiescent operating points (DCQOPs). Under active bias conditions, small-signal equivalent circuit (SSEC) parameters such as Rs and Rd, and intrinsic parameters were extracted. Utilizing fT and the SSEC parameters, the effective electron velocity (νe−eff) and intrinsic electron velocity (νe−int) corresponding to each gate bias (VGS) were obtained. Under active bias conditions, the influence mechanism of VGS on νe−eff was systematically studied, and an expression was established that correlates νe−eff, νe−int, and bias-dependent parasitic resistances. Through the analysis of the main scattering mechanisms in AlGaN/GaN HEMTs, it has been discovered that the impact of VGS on νe−eff should be comprehensively analyzed from the aspects of νe−int and parasitic resistances. On the one hand, changes in VGS influence the intensity of polar optical phonon (POP) scattering and polarization Coulomb field (PCF) scattering, which lead to changes in νe−int dependent on VGS. The trend of νe−int with changes in VGS plays a dominant role in determining the trend of νe−eff with changes in VGS. On the other hand, both POP scattering and PCF scattering affect νe−eff through their impact on parasitic resistance. Since there is a difference in the additional scattering potential corresponding to the additional polarization charges (APC) between the gate-source/drain regions and the region under the gate, the mutual effects of PCF scattering on the under-gate electron system and the gate-source/drain electron system should be considered when adjusting the PCF scattering intensity through device structure optimization to improve linearity. This study contributes to a new understanding of the electron transport mechanisms in AlGaN/GaN HEMTs and provides a novel theoretical basis for improving device performance. Full article
(This article belongs to the Section D1: Semiconductor Devices)
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19 pages, 11484 KiB  
Communication
Analysis of Vibration Characteristics of Spatial Non-Uniform Tensioned Thin-Film Structures Based on the Absolute Nodal Coordinate Formulation
by Peng Sun, Jin Huang, Jiaying Zhang, Fanbo Meng and Pengbing Zhao
Micromachines 2024, 15(9), 1147; https://doi.org/10.3390/mi15091147 - 12 Sep 2024
Viewed by 663
Abstract
Due to their lightweight characteristics, spatial thin-film structures can generate vibrations far exceeding their film thickness when subjected to external loads, which has become a key factor limiting their performance. This study examines the vibration characteristics of tensioned membrane structures with non-uniform elements [...] Read more.
Due to their lightweight characteristics, spatial thin-film structures can generate vibrations far exceeding their film thickness when subjected to external loads, which has become a key factor limiting their performance. This study examines the vibration characteristics of tensioned membrane structures with non-uniform elements subjected to impacts in air, leveraging the Absolute Nodal Coordinate Formulation (ANCF). This model takes into account the wrinkling deformation of thin films under pre-tension and incorporates it into the dynamic equation derived using the absolute node coordinate method. A detailed discussion was conducted on the influence of non-uniform elements, situated at different locations and side lengths, on the vibration characteristics of the thin film. The analytical results obtained from the vibration model were compared with the experimental results, validating the effectiveness of the vibration model. This provides a theoretical foundation for the subsequent vibration control of thin films. Full article
(This article belongs to the Section E：Engineering and Technology)
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