Journal Description
Micromachines
Micromachines
is a peer-reviewed, open access journal on the science and technology of small structures, devices and systems, published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), PubMed, PMC, Ei Compendex, dblp, and other databases.
- Journal Rank: JCR - Q2 (Chemistry, Analytical) / CiteScore - Q2 (Mechanical Engineering)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.1 days after submission; acceptance to publication is undertaken in 1.9 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Testimonials: See what our editors and authors say about Micromachines.
Impact Factor:
3.4 (2022);
5-Year Impact Factor:
3.3 (2022)
Latest Articles
Designing a Simple Electrochemical Genosensor for the Detection of Urinary PCA3, a Prostate Cancer Biomarker
Micromachines 2024, 15(5), 602; https://doi.org/10.3390/mi15050602 (registering DOI) - 29 Apr 2024
Abstract
This study investigates the feasibility of a simple electrochemical detection of Prostate Cancer Antigen 3 (PCA3) fragments extracted from patients’ urine, using a thiolated single-strand DNA probe immobilized on a gold surface without using a redox probe. To enhance the PCA3 recognition process,
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This study investigates the feasibility of a simple electrochemical detection of Prostate Cancer Antigen 3 (PCA3) fragments extracted from patients’ urine, using a thiolated single-strand DNA probe immobilized on a gold surface without using a redox probe. To enhance the PCA3 recognition process, we conducted a comparative analysis of the hybridization location using two thiolated DNA probes: Probe 1 targets the first 40 bases, while Probe 2 targets the fragment from bases 47 to 86. Hybridization with PCA3 followed, using square wave voltammetry. The limit of detection of the designed genosenors were of the order of (2.2 ng/mL), and (1.6 ng/mL) for Probes 1 and 2, respectively, and the subsequent sensitivities were of the order of (0.09 ± 0.01) µA−1 · µg−1 · mL and (0.10 ± 0.01) µA−1 · µg−1 · mL. Specificity tests were then conducted with the sensor functionalized with Probe 2, as it presents better analytical performances. The electrochemical results indicate that the designed sensor can clearly discriminate a complementary target from a non-complementary one. A further modeling of the calibration curves with the Power Law/Hill model indicates that the dissociation constant increases by one order of magnitude, confirming the ability of the designed sensor to perfectly discriminate complementary targets from non-complementary ones.
Full article
(This article belongs to the Special Issue Prospects and Challenges of Biosensors towards Diagnostics of the Diseases and Health Monitoring)
Open AccessArticle
Design of A Compact 2–6 GHz High-Efficiency and High-Gain GaN Power Amplifier
by
Yongchun Zhou, Shuai Wang, Junyan Dai, Jiang Luo and Qiang Cheng
Micromachines 2024, 15(5), 601; https://doi.org/10.3390/mi15050601 (registering DOI) - 29 Apr 2024
Abstract
In this paper, a novel wideband power amplifier (PA) operating in the 2–6 GHz frequency range is presented. The proposed PA design utilizes a combination technique consisting of a distributed equalization technique, multiplexing the power supply network and matching network technique, an LR
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In this paper, a novel wideband power amplifier (PA) operating in the 2–6 GHz frequency range is presented. The proposed PA design utilizes a combination technique consisting of a distributed equalization technique, multiplexing the power supply network and matching network technique, an LR dissipative structure, and an RC stability network technique to achieve significant bandwidth while maintaining superior gain flatness, high efficiency, high gain, and compact size. For verification, a three-stage PA using the combination technique is designed and implemented in a 0.25 μm GaN high-electron-mobility transistor (HEMT) process. The fabricated prototype demonstrates a saturated output power of 4 W, a power gain of 21 dB, a gain flatness of ±0.6 dB, a power-added efficiency of 39–46%, and a fractional bandwidth of 100% under the operating conditions of drain voltage 28 V (continuous wave) and gate voltage −2.6 V. Moreover, the chip occupies a compact size of only 2.51 mm × 1.97 mm.
Full article
(This article belongs to the Special Issue Future of RF/Microwave Filtering and Memristive Devices in Nowadays Mobile Networks)
Open AccessArticle
Research on the Influence of Carbon Sources and Buffer Layers on the Homogeneous Epitaxial Growth of 4H-SiC
by
Weilong Yuan, Yicheng Pei, Yunkai Li, Ning Guo, Xiuhai Zhang and Xingfang Liu
Micromachines 2024, 15(5), 600; https://doi.org/10.3390/mi15050600 (registering DOI) - 29 Apr 2024
Abstract
In this study, a 4H-SiC homoepitaxial layer was grown on a 150 mm 4° off-axis substrate using a horizontal hot wall chemical vapor deposition reactor. Comparing C3H8 and C2H4 as C sources, the sample grown with C
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In this study, a 4H-SiC homoepitaxial layer was grown on a 150 mm 4° off-axis substrate using a horizontal hot wall chemical vapor deposition reactor. Comparing C3H8 and C2H4 as C sources, the sample grown with C2H4 exhibited a slower growth rate and lower doping concentration, but superior uniformity and surface roughness compared to the C3H8-grown sample. Hence, C2H4 is deemed more suitable for commercial epitaxial wafer growth. Increasing growth pressure led to decreased growth rate, worsened thickness uniformity, reduced doping concentration, deteriorated uniformity, and initially improved and then worsened surface roughness. Optimal growth quality was observed at a lower growth pressure of 40 Torr. Furthermore, the impact of buffer layer growth on epitaxial quality varied significantly based on different C/Si ratios, emphasizing the importance of selecting the appropriate conditions for subsequent device manufacturing.
Full article
(This article belongs to the Section D1: Semiconductor Devices)
Open AccessArticle
Fabrication of Perfluoropolyether Microfluidic Devices Using Laser Engraving for Uniform Droplet Production
by
Eun Seo Kim, Mincheol Cho, Inseong Choi and Sung-Wook Choi
Micromachines 2024, 15(5), 599; https://doi.org/10.3390/mi15050599 (registering DOI) - 29 Apr 2024
Abstract
A perfluoropolyether (PFPE)-based microfluidic device with cross-junction microchannels was fabricated with the purpose of producing uniform droplets. The microchannels were developed using CO2 laser engraving. PFPE was chosen as the main material because of its excellent solvent resistance. Polyethylene glycol diacrylate (PEGDA)
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A perfluoropolyether (PFPE)-based microfluidic device with cross-junction microchannels was fabricated with the purpose of producing uniform droplets. The microchannels were developed using CO2 laser engraving. PFPE was chosen as the main material because of its excellent solvent resistance. Polyethylene glycol diacrylate (PEGDA) was mixed with PFPE to improve the hydrophilic properties of the inner surface of the microchannels. The microchannels of the polydimethylsiloxane microfluidic device had a blackened and rough surface after laser engraving. By contrast, the inner surface of the microchannels of the PFPE-PEGDA microfluidic device exhibited a smooth surface. The lower power and faster speed of the laser engraving resulted in the development of microchannels with smaller dimensions, less than 30 μm in depth. The PFPE and PFPE-PEGDA microfluidic devices were used to produce uniform water and oil droplets, respectively. We believe that such a PFPE-based microfluidic device with CO2-laser-engraved microchannels can be used as a microfluidic platform for applications in various fields, such as biological and chemical analysis, extraction, and synthesis.
Full article
(This article belongs to the Collection Lab-on-a-Chip)
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Open AccessArticle
Skin Electrodes Based on TPU Fiber Scaffolds with Conductive Nanocomposites with Stretchability, Breathability, and Washability
by
Zijia Zhao, Chaopeng Yang and Dongchan Li
Micromachines 2024, 15(5), 598; https://doi.org/10.3390/mi15050598 (registering DOI) - 29 Apr 2024
Abstract
In the context of an aging population and escalating work pressures, cardiovascular diseases pose increasing health risks. Electrocardiogram (ECG) monitoring presents a preventive tool, but conventional devices often compromise comfort. This study proposes an approach using Ag NW/TPU composites for flexible and breathable
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In the context of an aging population and escalating work pressures, cardiovascular diseases pose increasing health risks. Electrocardiogram (ECG) monitoring presents a preventive tool, but conventional devices often compromise comfort. This study proposes an approach using Ag NW/TPU composites for flexible and breathable epidermal electronics. In this new structure, TPU fibers are used to support Ag NWs/TPU nanocomposites. The TPU fiber-reinforced Ag NW/TPU (TFRAT) nanocomposites exhibit excellent conductivity, stretchability, and electromechanical durability. The composite ensures high steam permeability, maintaining stable electrical performance after washing cycles. Employing this technology, a flexible ECG detection system is developed, augmented with a convolutional neural network (CNN) for automated signal analysis. The experimental results demonstrate the system’s reliability in capturing physiological signals. Additionally, a CNN model trained on ECG data achieves over 99% accuracy in diagnosing arrhythmias. This study presents TFRAT as a promising solution for wearable electronics, offering both comfort and functionality in long-term epidermal applications, with implications for healthcare and beyond.
Full article
(This article belongs to the Special Issue Flexible and Wearable Sensors, 3rd Edition)
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Open AccessArticle
Improved Test Fixture for Collecting Microcontact Performance and Reliability Data
by
Turja Nandy, Ronald A. Coutu, Jr. and Rafee Mahbub
Micromachines 2024, 15(5), 597; https://doi.org/10.3390/mi15050597 (registering DOI) - 29 Apr 2024
Abstract
Microelectromechanical systems (MEMS) ohmic contact switches are considered to be a promising candidate for wireless communication applications. The longevity of MEMS switches is directly related to the reliability and performance of microcontacts. In this work, an improved microcontact test fixture with high actuation
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Microelectromechanical systems (MEMS) ohmic contact switches are considered to be a promising candidate for wireless communication applications. The longevity of MEMS switches is directly related to the reliability and performance of microcontacts. In this work, an improved microcontact test fixture with high actuation rates (KHz) and highly precise position control (nm) and force (nN) control was developed. Here, we collected microcontact performance data from initial contact tests (ICT) and microcontact reliability data from cold switched tests (CST). To perform these tests with our test fixture, we fabricated MEMS microcontact test structures with relatively high Young’s modulus electroplated Nickel (Ni)-based, fixed–fixed beam structure with Au/RuO2 bimetallic microcontacts. These structures were characterized for forces ranging from 200–1000 µN in ICT tests. In a CST test, the tested microcontact survived more than 200 million cycles at a 1 KHz cycle rate, with a stable contact resistance value ranging between 3.8–5.2 Ω. These experiments validate the potentiality of our microcontact test fixture, and will facilitate further investigation on advanced microcontacts to enhance the MEMS switch’s reliability.
Full article
(This article belongs to the Special Issue Feature Papers from Micromachines Reviewers 2023)
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Open AccessArticle
Design and Growth of Low Resistivity P-Type AlGaN Superlattice Structure
by
Yang Liu, Xiaowei Zhou, Peixian Li, Bo Yang and Zhuang Zhao
Micromachines 2024, 15(5), 596; https://doi.org/10.3390/mi15050596 (registering DOI) - 29 Apr 2024
Abstract
This work investigated the impact of periodic thickness and doping region on the doping efficiency of the P-type AlGaN superlattice. In this paper, the band structure of the simulated superlattice was analyzed. The superlattice structure of Al0.1Ga0.3N/Al0.4Ga
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This work investigated the impact of periodic thickness and doping region on the doping efficiency of the P-type AlGaN superlattice. In this paper, the band structure of the simulated superlattice was analyzed. The superlattice structure of Al0.1Ga0.3N/Al0.4Ga0.6N, and the AlGaN buffer on the sapphire substrate, achieved a resistivity of ~3.3 Ω·cm. The results indicate that barrier doping and low periodic thickness offer significant advantages in introducing a reduction of the resistivity of P-type AlGaN superlattice structures.
Full article
(This article belongs to the Special Issue Recent Advances in Emerging Transistor Technologies and Their Applications)
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Open AccessArticle
Modulation Steering Motion by Quantitative Electrical Stimulation in Pigeon Robots
by
Mingxuan Bi, Huimin Zhang, Yaohong Ma, Hao Wang, Wenbo Wang, Yuan Shi, Wenlong Sheng, Qiushun Li, Guangheng Gao and Lei Cai
Micromachines 2024, 15(5), 595; https://doi.org/10.3390/mi15050595 (registering DOI) - 29 Apr 2024
Abstract
The pigeon robot has attracted significant attention in the field of animal robotics thanks to its outstanding mobility and adaptive capability in complex environments. However, research on pigeon robots is currently facing bottlenecks, and achieving fine control over the motion behavior of pigeon
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The pigeon robot has attracted significant attention in the field of animal robotics thanks to its outstanding mobility and adaptive capability in complex environments. However, research on pigeon robots is currently facing bottlenecks, and achieving fine control over the motion behavior of pigeon robots through brain–machine interfaces remains challenging. Here, we systematically quantify the relationship between electrical stimulation and stimulus-induced motion behaviors, and provide an analytical method to demonstrate the effectiveness of pigeon robots based on electrical stimulation. In this study, we investigated the influence of gradient voltage intensity (1.2–3.0 V) on the indoor steering motion control of pigeon robots. Additionally, we discussed the response time of electrical stimulation and the effective period of the brain–machine interface. The results indicate that pigeon robots typically exhibit noticeable behavioral responses at a 2.0 V voltage stimulus. Increasing the stimulation intensity significantly controls the steering angle and turning radius (p < 0.05), enabling precise control of pigeon robot steering motion through stimulation intensity regulation. When the threshold voltage is reached, the average response time of a pigeon robot to the electrical stimulation is 220 ms. This study quantifies the role of each stimulation parameter in controlling pigeon robot steering behavior, providing valuable reference information for the precise steering control of pigeon robots. Based on these findings, we offer a solution for achieving precise control of pigeon robot steering motion and contribute to solving the problem of encoding complex trajectory motion in pigeon robots.
Full article
(This article belongs to the Special Issue Intelligent Bioelectronics and Neural Interfaces)
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Flexible Peripheral Nerve Interfacing Electrode for Joint Position Control in Closed-Loop Neuromuscular Stimulation
by
Sia Kim and Kang-Il Song
Micromachines 2024, 15(5), 594; https://doi.org/10.3390/mi15050594 (registering DOI) - 29 Apr 2024
Abstract
Addressing peripheral nerve disorders with electronic medicine poses significant challenges, especially in replicating the dynamic mechanical properties of nerves and understanding their functionality. In the field of electronic medicine, it is crucial to design a system that thoroughly understands the functions of the
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Addressing peripheral nerve disorders with electronic medicine poses significant challenges, especially in replicating the dynamic mechanical properties of nerves and understanding their functionality. In the field of electronic medicine, it is crucial to design a system that thoroughly understands the functions of the nervous system and ensures a stable interface with nervous tissue, facilitating autonomous neural adaptation. Herein, we present a novel neural interface platform that modulates the peripheral nervous system using flexible nerve electrodes and advanced neuromodulation techniques. Specifically, we have developed a surface-based inverse recruitment model for effective joint position control via direct electrical nerve stimulation. Utilizing barycentric coordinates, this model constructs a three-dimensional framework that accurately interpolates inverse isometric recruitment values across various joint positions, thereby enhancing control stability during stimulation. Experimental results from rabbit ankle joint control trials demonstrate our model’s effectiveness. In combination with a proportional–integral–derivative (PID) controller, it shows superior performance by achieving reduced settling time (less than 1.63 s), faster rising time (less than 0.39 s), and smaller steady-state error (less than 3 degrees) compared to the legacy model. Moreover, the model’s compatibility with recent advances in flexible interfacing technologies and its integration into a closed-loop controlled functional neuromuscular stimulation (FNS) system highlight its potential for precise neuroprosthetic applications in joint position control. This approach marks a significant advancement in the management of neurological disorders with advanced neuroprosthetic solutions.
Full article
(This article belongs to the Special Issue Intelligent Bioelectronics and Neural Interfaces)
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Open AccessArticle
A Microwave Photonic 2 × 2 IBFD–MIMO Communication System with Narrowband Self-Interference Cancellation
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Ying Ma, Fangjing Shi and Yangyu Fan
Micromachines 2024, 15(5), 593; https://doi.org/10.3390/mi15050593 (registering DOI) - 29 Apr 2024
Abstract
Combined in-band full duplex-multiple input multiple output (IBFD–MIMO) technology can significantly improve spectrum efficiency and data throughput, and has broad application prospects in communications, radar, the Internet of Things (IoT), and other fields. Targeting the self-interference (SI) issue in microwave photonic-based IBFD–MIMO communication
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Combined in-band full duplex-multiple input multiple output (IBFD–MIMO) technology can significantly improve spectrum efficiency and data throughput, and has broad application prospects in communications, radar, the Internet of Things (IoT), and other fields. Targeting the self-interference (SI) issue in microwave photonic-based IBFD–MIMO communication systems, a microwave photonic self-interference cancellation (SIC) method applied to the narrowband 2 × 2 IBFD–MIMO communication system was proposed, simulated, and analyzed. An interleaver was used to construct a polarization multiplexing dual optical frequency comb with a frequency shifting effect, generating a dual-channel reference interference signal. The programmable spectrum processor was employed for filtering, attenuation, and phase-shifting operations, ensuring amplitude and phase matching to eliminate the two self-interference (SI) signals. The simulation results show that the single-frequency SIC depth exceeds 45.8 dB, and the narrowband SIC depth under 30 MHz bandwidth exceeds 32.7 dB. After SIC, the desired signal, employing a 4QAM modulation format, can be demodulated with an error vector magnitude (EVM) as low as 4.7%. Additionally, further channel expansion and system performance optimization are prospected.
Full article
(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)
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Open AccessArticle
Flexible Thermoelectric Device Based on Protrusion-Structured Liquid Metal Elastomer for Gravity Heat Pipe
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Xiaogang Zhang, Xinghua Zhang, Shaocheng Ge, Bailin Zhang, Dongguang Zhang and Jiayi Yang
Micromachines 2024, 15(5), 592; https://doi.org/10.3390/mi15050592 (registering DOI) - 29 Apr 2024
Abstract
Monitoring the temperature of the coal gangue mountains is fundamental to preventing their spontaneous combustion. However, the existing temperature monitoring systems fail to achieve stable, pollution-free temperature monitoring without affecting vegetation growth in these mountains. To address this issue, this work proposes a
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Monitoring the temperature of the coal gangue mountains is fundamental to preventing their spontaneous combustion. However, the existing temperature monitoring systems fail to achieve stable, pollution-free temperature monitoring without affecting vegetation growth in these mountains. To address this issue, this work proposes a flexible thermoelectric device (FTD) based on a protrusion-structured liquid metal elastomer (LME). Utilizing a high-thermal-conductivity LME, the FTD adheres closely to the surface of the gravity heat pipe (GHP), ensuring compatibility between FTD and the curved surface of the GHP. Simultaneously, employing a low-thermal-conductivity elastomer helps concentrate heat onto FTD, thereby enhancing thermoelectric power generation efficiency. Additionally, the impact of the shape, size, and height of the protrusion structure at the cold end of the GHP on its efficiency was also investigated. The practical application of FTD on GHP was demonstrated.
Full article
(This article belongs to the Special Issue Energy Harvesters and Self-Powered Sensors for Smart Electronics, 3rd Edition)
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Open AccessArticle
Synthesis and Characterization of 2D Ternary Compound TMD Materials Ta3VSe8
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Yuanji Ma, Yuhan Du, Wenbin Wu, Zeping Shi, Xianghao Meng and Xiang Yuan
Micromachines 2024, 15(5), 591; https://doi.org/10.3390/mi15050591 (registering DOI) - 28 Apr 2024
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) are garnering considerable scientific interest, prompting discussion regarding their prospective applications in the fields of nanoelectronics and spintronics while also fueling groundbreaking discoveries in phenomena such as the fractional quantum anomalous Hall effect (FQAHE) and exciton dynamics.
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Two-dimensional (2D) transition metal dichalcogenides (TMDs) are garnering considerable scientific interest, prompting discussion regarding their prospective applications in the fields of nanoelectronics and spintronics while also fueling groundbreaking discoveries in phenomena such as the fractional quantum anomalous Hall effect (FQAHE) and exciton dynamics. The abundance of binary compound TMDs, such as MX2 (M = Mo, W; X = S, Se, Te), has unlocked myriad avenues of exploration. However, the exploration of ternary compound TMDs remains relatively limited, with notable examples being Ta2NiS5 and Ta2NiSe5. In this study, we report the synthesis of a new 2D ternary compound TMD materials, Ta3VSe8, employing the chemical vapor transport (CVT) method. The as-grown bulk crystal is shiny and can be easily exfoliated. The crystal quality and structure are verified by X-ray diffraction (XRD), while the surface morphology, stoichiometric ratio, and uniformity are determined by scanning electron microscopy (SEM). Although the phonon property is found stable at different temperatures, magneto-resistivity evolves. These findings provide a possible approach for the realization and exploration of ternary compound TMDs.
Full article
(This article belongs to the Special Issue Devices Based on Two-Dimensional Materials: Materials and Fabrication)
Open AccessArticle
Mechanical Characterization of the Erythrocyte Membrane Using a Capacitor-Based Technique
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Doriana Dorta, Carlos Plazaola, Jafeth Carrasco, Maria F. Alves-Rosa, Lorena M. Coronado, Ricardo Correa, Maytee Zambrano, Braulio Gutiérrez-Medina, Erick Sarmiento-Gómez, Carmenza Spadafora and Guadalupe Gonzalez
Micromachines 2024, 15(5), 590; https://doi.org/10.3390/mi15050590 (registering DOI) - 28 Apr 2024
Abstract
Pathological processes often change the mechanical properties of cells. Increased rigidity could be a marker of cellular malfunction. Erythrocytes are a type of cell that deforms to squeeze through tiny capillaries; changes in their rigidity can dramatically affect their functionality. Furthermore, differences in
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Pathological processes often change the mechanical properties of cells. Increased rigidity could be a marker of cellular malfunction. Erythrocytes are a type of cell that deforms to squeeze through tiny capillaries; changes in their rigidity can dramatically affect their functionality. Furthermore, differences in the homeostatic elasticity of the cell can be used as a tool for diagnosis and even for choosing the adequate treatment for some illnesses. More accurate types of equipment needed to study biomechanical phenomena at the single-cell level are very costly and thus out of reach for many laboratories around the world. This study presents a simple and low-cost technique to study the rigidity of red blood cells (RBCs) through the application of electric fields in a hand-made microfluidic chamber that uses a capacitor principle. As RBCs are deformed with the application of voltage, cells are observed under a light microscope. From mechanical force vs. deformation data, the elastic constant of the cells is determined. The results obtained with the capacitor-based method were compared with those obtained using optical tweezers, finding good agreement. In addition, P. falciparum-infected erythrocytes were tested with the electric field applicator. Our technique provides a simple means of testing the mechanical properties of individual cells.
Full article
(This article belongs to the Special Issue Measurement and Standardization in Microfluidic Devices: Fabrication and Testing)
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Open AccessArticle
A Micro Bridge-Wing-Thickened Low-Energy Exploding Foil Initiator Chip
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Pengfei Xue, Heng Hu, Tao Wang, Peng Xiong, Mingyu Li and Qingxuan Zeng
Micromachines 2024, 15(5), 589; https://doi.org/10.3390/mi15050589 (registering DOI) - 28 Apr 2024
Abstract
To enhance the energy efficiency of exploding foil initiator systems (EFIs) and mitigate energy loss due to ablation in the bridge-wing regions, a low-energy bridge-wing-thickened EFI chip was designed and fabricated. Computational analysis revealed that increasing the thickness of the bridge flanks significantly
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To enhance the energy efficiency of exploding foil initiator systems (EFIs) and mitigate energy loss due to ablation in the bridge-wing regions, a low-energy bridge-wing-thickened EFI chip was designed and fabricated. Computational analysis revealed that increasing the thickness of the bridge flanks significantly reduces ablation within the bridge region during the electrical explosion. The refinement of the design led to the adoption of a bridge flank thickness of 19 μm, with the bridge area dimensions specified as 0.25 mm × 0.25 mm × 4 μm. This bridge-wing-thickened EFI chip was produced by employing micro-electro-mechanical systems (MEMS) technology and underwent rigorous performance evaluations. The empirical results closely matched the computational predictions, thereby corroborating the precision of the proposed model in simulating the temperature distribution seen during the explosion process. Notably, this enhanced EFI design achieves a flyer velocity of 3800 m/s at a condition of 900 V/0.22 μF, signifying a significant advancement in EFI system efficiency and performance.
Full article
(This article belongs to the Section E:Engineering and Technology)
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A Novel Dual-Band Circularly Polarized Wearable Antenna
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Yu Dong, Hong Lu and Xing Chen
Micromachines 2024, 15(5), 588; https://doi.org/10.3390/mi15050588 (registering DOI) - 28 Apr 2024
Abstract
A circularly polarized wearable antenna operating in the 2.45/5.8 GHz ISM dual bands is proposed, which consists of a coplanar waveguide-fed rectangular monopole antenna and two parasitic branches. The monopole rectangular radiation patch can generate 2.45 and 7 GHz frequency bands and has
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A circularly polarized wearable antenna operating in the 2.45/5.8 GHz ISM dual bands is proposed, which consists of a coplanar waveguide-fed rectangular monopole antenna and two parasitic branches. The monopole rectangular radiation patch can generate 2.45 and 7 GHz frequency bands and has linear polarization characteristics. By adding L-shaped parasitic branches and L-like grounded branches on both sides of the monopole, the 7 GHz operating frequency band can be moved to the 5.8 GHz frequency band, and circular polarization characteristics can be achieved in both the 2.45 and 5.8 GHz frequency bands. The size of the antenna is 48.7 mm × 42.1 mm × 1.016 mm. The simulated −10 dB impedance bandwidths of the antenna are 1.8–2.66 GHz and 5.48–6.98 GHz, respectively. The 3 dB axial ratio bandwidths are 2.34–2.67 GHz and 5.58–6.39 GHz, respectively, and it has dual-band circular polarization characteristics. In addition, the radiation characteristics of the antenna and its safety performance near the human body were analyzed. The antenna prototype has been constructed, and the measurement and simulation results have good consistency. The proposed antenna is suitable for application in wearable devices.
Full article
(This article belongs to the Special Issue Advanced Antenna System: Structural Analysis, Design and Application)
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Open AccessArticle
Motor Behavior Regulation of Rat Robots Using Integrated Electrodes Stimulated by Micro-Nervous System
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Jiabing Huo, Le Zhang, Xiangyu Luo, Yongkang Rao, Peili Cao, Xiaojuan Hou, Jian He, Jiliang Mu, Wenping Geng, Haoran Cui, Rui Cheng and Xiujian Chou
Micromachines 2024, 15(5), 587; https://doi.org/10.3390/mi15050587 (registering DOI) - 28 Apr 2024
Abstract
As a cutting-edge technology, animal robots based on living organisms are being extensively studied, with potential for diverse applications in the fields of neuroscience, national security, and civil rescue. However, it remains a significant challenge to reliably control the animal robots with the
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As a cutting-edge technology, animal robots based on living organisms are being extensively studied, with potential for diverse applications in the fields of neuroscience, national security, and civil rescue. However, it remains a significant challenge to reliably control the animal robots with the objective of protecting their long-term survival, and this has seriously hindered their practical implementation. To address this issue, this work explored the use of a bio-friendly neurostimulation system that includes integrated stimulation electrodes together with a remote wireless stimulation circuit to control the moving behavior of rat robots. The integrated electrodes were implanted simultaneously in four stimulation sites, including the medial forebrain bundle (MFB) and primary somatosensory cortex, barrel field (S1BF). The control system was able to provide flexibility in adjusting the following four stimulation parameters: waveform, amplitude, frequency, and duration time. The optimized parameters facilitated the successful control of the rat’s locomotion, including forward movement and left and right turns. After training for a few cycles, the rat robots could be guided along a designated route to complete the given mission in a maze. Moreover, it was found that the rat robots could survive for more than 20 days with the control system implanted. These findings will ensure the sustained and reliable operation of the rat robots, laying a robust foundation for advances in animal robot regulation technology.
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(This article belongs to the Collection Women in Micromachines)
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Design, Fabrication, and Characterization of a Planar Three-Electrode Trigger Switch Based on Flexible Printed Circuit Process
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Pengfei Xue, Peng Xiong, Heng Hu, Tao Wang, Mingyu Li and Qingxuan Zeng
Micromachines 2024, 15(5), 586; https://doi.org/10.3390/mi15050586 (registering DOI) - 28 Apr 2024
Abstract
An exploding foil initiator system (EFIs) is essential in modern weaponry for its safety and reliability. As the main component of EFIs, the performance of the switch is critical to EFIs. In this study, a planar three-electrode trigger switch was designed and fabricated
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An exploding foil initiator system (EFIs) is essential in modern weaponry for its safety and reliability. As the main component of EFIs, the performance of the switch is critical to EFIs. In this study, a planar three-electrode trigger switch was designed and fabricated using the Flexible Printed Circuits (FPC) process. Subsequently, the performance of the FPC switch was tested. The results show that the self-breakdown voltage of the FPC switch is stable. In addition, an FPF switch with a 0.6 mm main electrode gap demonstrated consistency, with delay times below 31.75 ns, and a jitter ranging from 1.7 ns to 10.94 ns at 900 V to 1200 V, evidencing the FPC switches’ reliability and uniform performance across various voltages. Compared to the Micro-Electro-Mechanical Systems (MEMS) switches of similar dimensions, the FPC switches achieved a faster high-current attainment with less inductance, showing a 5% reduction in loop inductance. The repetitive testing results demonstrate that the FPC switch maintains consistent output performance, with stable peak currents, peak current time, and delay time over 50 action cycles, highlighting its repeatability. The FPC switch was assembled with an EFI chip and capacitor into an integrated system, which was subsequently able to successfully detonate HNS-IV at 1000 V/0.22 μF, proving the FPC switch’s potential in low inductance applications.
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(This article belongs to the Section E:Engineering and Technology)
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Band 40/41 Surface Acoustic Wave Filters on 42°YX-Lithium Tantalate Substrate with Suppression of Transverse Leakage
by
Qiang Xiao, Zihang Gao, Mengqun Chu, Zeyu Zheng, Xuesong Du, Chengji Hu, Hongzhi Pan, Hualin Li, Jiahe Dong, Zhenglin Chen, Huazhi Chen, Chuan Lu, Mi Tang, Yanping Fan and Jinyi Ma
Micromachines 2024, 15(5), 585; https://doi.org/10.3390/mi15050585 (registering DOI) - 28 Apr 2024
Abstract
The transverse leakage of leaky surface acoustic waves (LSAWs) occurs on 42°YX-lithium tantalate substrates (42LT), which increases the insertion loss, narrows the bandwidth and flattens the roll-off of band 40/41 SAW filters and duplexers. In this work, LSAW characteristics with different metal materials
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The transverse leakage of leaky surface acoustic waves (LSAWs) occurs on 42°YX-lithium tantalate substrates (42LT), which increases the insertion loss, narrows the bandwidth and flattens the roll-off of band 40/41 SAW filters and duplexers. In this work, LSAW characteristics with different metal materials and thicknesses are calculated by the finite element method (FEM), which determines the IDT material and thickness used for band 40/41 SAW filter design. To deeply understand transverse leakage and suppress it, the effects of different gap and dummy lengths on transverse leakage are simulated and discussed. Then, a new technique of using a wider dummy without any additional lithographic or depositing processes is proposed to suppress the leakage. Its effectiveness is validated by both simulations and experiments. Then, the technique is extended to applications of band 40 and 41 SAW filters. The experimental results show that with the wider dummy structure, the band 40 and 41 SAW filters achieve a more than 0.2 dB improvement in the insertion loss, a wider bandwidth and a steeper roll-off characteristic. This technique may also be extended to the other band SAW filter applications.
Full article
(This article belongs to the Special Issue Surface and Bulk Acoustic Wave Resonators: Materials, Design and Fabrication)
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Open AccessArticle
A Dual-Band 8-Antenna Array Design for 5G/WiFi 5 Metal-Frame Smartphone Applications
by
Huiyang Li, Shanshan Xiao, Lefei He, Qibo Cai and Gui Liu
Micromachines 2024, 15(5), 584; https://doi.org/10.3390/mi15050584 (registering DOI) - 28 Apr 2024
Abstract
This paper presents a dual-band 8-port multiple-input multiple-output (MIMO) antenna specifically designed for fifth-generation (5G) smartphones, featuring two open-slot metal frames. To enhance impedance matching and improve isolation between adjacent antenna elements, each antenna element employed a coupling feed. All simulation results in
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This paper presents a dual-band 8-port multiple-input multiple-output (MIMO) antenna specifically designed for fifth-generation (5G) smartphones, featuring two open-slot metal frames. To enhance impedance matching and improve isolation between adjacent antenna elements, each antenna element employed a coupling feed. All simulation results in this paper come from Ansys HFSS. The operational frequency bands of the proposed antenna spanned 3.36–4.2 GHz for the lower band and 4.37–5.95 GHz for the higher band, covering 5G New Radio (NR) bands N78 (3.4–3.6 GHz) and N79 (4.4–4.9 GHz), as well as WiFi 5 (5.15–5.85 GHz). Notably, the antenna demonstrated outstanding isolation exceeding 16.5 dB within the specified operating bands. The exceptional performance positions the proposed antenna as a promising candidate for integration into 5G metal-frame smartphones.
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(This article belongs to the Special Issue Recent Advancements in Flexible, Reconfigurable and Wearable Antennas for 5G and Beyond)
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Open AccessArticle
Effect of Geometrical Parameters on the Mechanical Performance of Bamboo-Inspired Gradient Hollow-Strut Octet Lattice Structure Fabricated by Additive Manufacturing
by
Junxian Ge, Yu Song, Zhenyu Chen, Yuhao Zhuo, Tongzheng Wei, Chen Ge, Yuang Cheng, Ming Liu and Qingbo Jia
Micromachines 2024, 15(5), 583; https://doi.org/10.3390/mi15050583 (registering DOI) - 28 Apr 2024
Abstract
Hollow-strut metal lattice structures are currently attracting extensive attention due to their excellent mechanical performance. Inspired by the node structure of bamboo, this study aimed to investigate the mechanical performance of the gradient hollow-strut octet lattice structure fabricated by laser powder bed fusion
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Hollow-strut metal lattice structures are currently attracting extensive attention due to their excellent mechanical performance. Inspired by the node structure of bamboo, this study aimed to investigate the mechanical performance of the gradient hollow-strut octet lattice structure fabricated by laser powder bed fusion (LPBF). The effect of geometrical parameters on the yield strength, Young’s modulus and energy absorption of the designed octet unit cells were studied and optimized by FEA analysis. The hollow-strut geometrical parameters that deliver the best mechanical property combinations were identified, and the corresponding unit cells were then redesigned into the 3 × 3 × 3 type lattice structures for experimental evaluations. Compression tests confirmed that the designed gradient hollow-strut octet lattice structures demonstrated superior mechanical properties and deformation stability than their solid-strut lattice structure counterparts. The underlying deformation mechanism analysis revealed that the remarkably enhanced bending strength of the gradient hollow-strut lattice structure made significant contributions to its mechanical performance improvement. This study is envisaged to shed light on future hollow-strut metal lattice structure design for lightweight applications, with the final aim of enhancing the component’s mechanical properties and/or lowering its density as compared with the solid-strut lattice structures.
Full article
(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)
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