Micromachines

15 pages, 14093 KiB

Open AccessArticle

Integrating Multiple Hierarchical Parameters to Achieve the Self-Compensation of Scale Factor in a Micro-Electromechanical System Gyroscope

by Rui Zhou, Rang Cui, Daren An, Chong Shen, Yu Bai and Huiliang Cao

Micromachines 2024, 15(11), 1385; https://doi.org/10.3390/mi15111385 (registering DOI) - 16 Nov 2024

Abstract

The scale factor of thermal sensitivity serves as a crucial performance metric for micro-electromechanical system (MEMS) gyroscopes, and is commonly employed to assess the temperature stability of inertial sensors. To improve the temperature stability of the scale factor of MEMS gyroscopes, a self-compensation [...] Read more.

The scale factor of thermal sensitivity serves as a crucial performance metric for micro-electromechanical system (MEMS) gyroscopes, and is commonly employed to assess the temperature stability of inertial sensors. To improve the temperature stability of the scale factor of MEMS gyroscopes, a self-compensation method is proposed. This is achieved by integrating the primary and secondary relevant parameters of the scale factor using the partial least squares regression (PLSR) algorithm. In this paper, a scale factor prediction model is presented. The model indicates that the resonant frequency and demodulation phase angle are the primary correlation terms of the scale factor, while the drive control voltage and quadrature feedback voltage are the secondary correlation terms of the scale factor. By employing a weighted fusion of correlated terms through PLSR, the scale factor for temperature sensitivity is markedly enhanced by leveraging the predicted results to compensate for the output. The results indicate that the maximum error of the predicted scale factor is 0.124% within the temperature range of −40 °C to 60 °C, and the temperature sensitivity of the scale factor decreases from 6180 ppm/°C to 9.39 ppm/°C. Full article

(This article belongs to the Special Issue MEMS Sensors and Actuators: Design, Fabrication and Applications)

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13 pages, 1043 KiB

Open AccessArticle

Quantum Channel Extreme Bandgap AlGaN HEMT

by Michael Shur, Grigory Simin, Kamal Hussain, Abdullah Mamun, M. V. S. Chandrashekhar and Asif Khan

Micromachines 2024, 15(11), 1384; https://doi.org/10.3390/mi15111384 (registering DOI) - 15 Nov 2024

Abstract

An extreme bandgap Al_0.64Ga_0.36N quantum channel HEMT with Al_0.87Ga_0.13N top and back barriers, grown by MOCVD on a bulk AlN substrate, demonstrated a critical breakdown field of 11.37 MV/cm—higher than the 9.8 MV/cm expected for [...] Read more.

An extreme bandgap Al_0.64Ga_0.36N quantum channel HEMT with Al_0.87Ga_0.13N top and back barriers, grown by MOCVD on a bulk AlN substrate, demonstrated a critical breakdown field of 11.37 MV/cm—higher than the 9.8 MV/cm expected for the channel’s Al_0.64Ga_0.36N material. We show that the fraction of this increase is due to the quantization of the 2D electron gas. The polarization field maintains electron quantization in the quantum channel even at low sheet densities, in contrast to conventional HEMT designs. An additional increase in the breakdown field is due to quantum-enabled real space transfer of energetic electrons into high-Al barrier layers in high electric fields. These results show the advantages of the quantum channel design for achieving record-high breakdown voltages and allowing for superior power HEMT devices. Full article

(This article belongs to the Special Issue RF and Power Electronic Devices and Applications)

11 pages, 1551 KiB

Open AccessArticle

Comparison of Interfaces Between In Situ Laser Beam Deposition Forming and Electron Beam Welding for Thick-Walled Titanium Alloy Structures

by Pingchuan Yang, Fei Li, Zongtao Zhu and Hui Chen

Micromachines 2024, 15(11), 1383; https://doi.org/10.3390/mi15111383 (registering DOI) - 15 Nov 2024

Abstract

An investigation was conducted on electron beam-welded and additively manufactured joints on a thick-walled titanium alloy utilizing in situ laser beam deposition and electron beam welding techniques. The surface morphology, microstructural characteristics, and mechanical properties of both joint types were comprehensively analyzed using [...] Read more.

An investigation was conducted on electron beam-welded and additively manufactured joints on a thick-walled titanium alloy utilizing in situ laser beam deposition and electron beam welding techniques. The surface morphology, microstructural characteristics, and mechanical properties of both joint types were comprehensively analyzed using stereomicroscopy, scanning electron microscopy (SEM), microhardness and tensile strength testing, and electron backscatter diffraction (EBSD) techniques. The electron-beam-welded joint exhibited distinct fusion and heat-affected zones, whereas the laser-beam-deposited joint exhibited a smoother surface that was free from excess spatter. Both joints featured a sharp microstructural boundary with a pronounced hardness gradient across the interface, lacking a gradual transition area. During tensile testing, both joint types demonstrated a mixed brittle-ductile fracture mode; however, the electron beam-welded joints surpassed the laser-beam-deposited joints in terms of tensile strength, achieving over 1183 MPa with an elongation of more than 7.3%, compared to 1123 MPa and 5.9% elongation, respectively. Full article

(This article belongs to the Special Issue Future Prospects of Additive Manufacturing)

12 pages, 1594 KiB

Open AccessReview

Exploring the Connection Between Nanomaterials and Neurodegenerative Disorders

by Sitansu Sekhar Nanda and Dong Kee Yi

Micromachines 2024, 15(11), 1382; https://doi.org/10.3390/mi15111382 - 15 Nov 2024

Abstract

Drug delivery, tissue engineering, and cell promotion in biomedical fields heavily rely on the use of nanomaterials (NMs). When they penetrate cells, NPs undergo degradation and initiate the generation of reactive oxygen species (ROS) by causing changes in the structures of organelles linked [...] Read more.

Drug delivery, tissue engineering, and cell promotion in biomedical fields heavily rely on the use of nanomaterials (NMs). When they penetrate cells, NPs undergo degradation and initiate the generation of reactive oxygen species (ROS) by causing changes in the structures of organelles linked to mitochondria. Inside the cell, the excess production of ROS can initiate a chain reaction, along with the autophagy process that helps maintain ROS balance by discarding unnecessary materials. At present, there is no effective treatment for Alzheimer’s disease (AD), a progressive neurodegenerative disease. The use of NMs for siRNA delivery could become a promising treatment for AD and other CNS disorders. Recent research demonstrates that the use of combined NPs can induce autophagy in cells. This article emphasizes the importance of the shape of siRNA-encapsulated NMs in determining their efficiency in delivering and suppressing gene activity in the central nervous system. Because of its strict selectivity against foreign substances, the blood–brain barrier (BBB) significantly hinders the delivery of therapeutic agents to the brain. Conventional chemotherapeutic drugs are significantly less effective against brain cancers due to this limitation. As a result, NMs have become a promising approach for targeted drug delivery, as they can be modified to carry specific ligands that direct them to their intended targets. This review thoroughly examines the latest breakthroughs in using NMs to deliver bioactive compounds across the BBB, focusing on their use in cancer treatments. The review starts by examining the structure and functions of the BBB and BBTB, and then emphasizes the benefits that NMs offer. Full article

(This article belongs to the Section B3: Nanoparticles in Biomedicine)

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15 pages, 5787 KiB

Open AccessReview

A Review of Ku-Band GaN HEMT Power Amplifiers Development

by Jihoon Kim

Micromachines 2024, 15(11), 1381; https://doi.org/10.3390/mi15111381 - 15 Nov 2024

Abstract

This review article investigates the current status and advances in Ku-band gallium nitride (GaN) high-electron mobility transistor (HEMT) high-power amplifiers (HPAs), which are critical for satellite communications, unmanned aerial vehicle (UAV) systems, and military radar applications. The demand for high-frequency, high-power amplifiers is [...] Read more.

This review article investigates the current status and advances in Ku-band gallium nitride (GaN) high-electron mobility transistor (HEMT) high-power amplifiers (HPAs), which are critical for satellite communications, unmanned aerial vehicle (UAV) systems, and military radar applications. The demand for high-frequency, high-power amplifiers is growing, driven by the global expansion of high-speed data communication and enhanced national security requirements. First, we compare the main GaN HEMT process technologies employed in Ku-band HPA development, categorizing the HPAs into monolithic microwave integrated circuits (MMICs) and internally matched power amplifier modules (IM-PAMs) and examining their respective characteristics. Then, by reviewing the literature, we explore design topologies, major issues like oscillation prevention and bias circuits, and heat sink technologies for thermal management. Our findings indicate that silicon carbide (SiC) substrates with gate lengths of 0.25 μm and 0.15 μm are predominantly used, with ongoing developments enabling MMICs and IM-PAMs to achieve up to 100 W output power and 30% power-added efficiency. Notably, the performance of MMIC power amplifiers is advancing more rapidly than that of IM-PAMs, highlighting MMICs as a promising direction for achieving higher efficiency and integration in future Ku-band applications. This paper can provide insights into the overall key technologies for Ku-band GaN HPA design and future development directions. Full article

(This article belongs to the Special Issue Novel Power Amplifiers and Integrated Circuits: Design and Applications)

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22 pages, 5925 KiB

Open AccessArticle

Research on Energy Dissipation Mechanism of Cobweb-like Disk Resonator Gyroscope

by Huang Yi, Bo Fan, Feng Bu, Fang Chen and Xiao-Qing Luo

Micromachines 2024, 15(11), 1380; https://doi.org/10.3390/mi15111380 - 15 Nov 2024

Abstract

The micro disk resonator gyroscope is a micro-mechanical device with potential for navigation-grade applications, where the performance is significantly influenced by the quality factor, which is determined by various energy dissipation mechanisms within the micro resonant structure. To enhance the quality factor, these [...] Read more.

The micro disk resonator gyroscope is a micro-mechanical device with potential for navigation-grade applications, where the performance is significantly influenced by the quality factor, which is determined by various energy dissipation mechanisms within the micro resonant structure. To enhance the quality factor, these gyroscopes are typically enclosed in high-vacuum packaging. This paper investigates a wafer-level high-vacuum-packaged (<0.1 Pa) cobweb-like disk resonator gyroscope, presenting a systematic and comprehensive theoretical analysis of the energy dissipation mechanisms, including air damping, thermoelastic damping, anchor loss, and other factors. Air damping is analyzed using both a continuous fluid model and an energy transfer model. The analysis results are validated through quality factor testing on batch samples and temperature characteristic testing on individual samples. The theoretical results obtained using the energy transfer model closely match the experimental measurements, with a maximum error in the temperature coefficient of less than 2%. The findings indicate that air damping and thermoelastic damping are the predominant energy dissipation mechanisms in the cobweb-like disk resonant gyroscope under high-vacuum conditions. Consequently, optimizing the resonator to minimize thermoelastic and air damping is crucial for designing high-performance gyroscopes. Full article

(This article belongs to the Special Issue Advances in MEMS Inertial Sensors)

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15 pages, 4488 KiB

Open AccessArticle

Multi-Frame Vibration MEMS Gyroscope Temperature Compensation Based on Combined GWO-VMD-TCN-LSTM Algorithm

by Ao Li, Ke Cui, Daren An, Xiaoyi Wang and Huiliang Cao

Micromachines 2024, 15(11), 1379; https://doi.org/10.3390/mi15111379 - 15 Nov 2024

Abstract

This paper presents a temperature compensation model for the Multi-Frame Vibration MEMS Gyroscope (DMFVMG) based on Grey Wolf Optimization Variational Mode Decomposition (GWO-VMD) for denoising and a combination of the Temporal Convolutional Network (TCN) and the Long Short-Term Memory (LSTM) network for temperature [...] Read more.

This paper presents a temperature compensation model for the Multi-Frame Vibration MEMS Gyroscope (DMFVMG) based on Grey Wolf Optimization Variational Mode Decomposition (GWO-VMD) for denoising and a combination of the Temporal Convolutional Network (TCN) and the Long Short-Term Memory (LSTM) network for temperature drift prediction. Initially, the gyroscope output signal was denoised using GWO-VMD, retaining the useful signal components and eliminating noise. Subsequently, the denoised signal was utilized to predict temperature drift using the TCN-LSTM model. The experimental results demonstrate that the compensation model significantly enhanced the gyroscope’s performance across various temperatures, reducing the rate random wander from 102.929°/h/√Hz to 17.6903°/h/√Hz and the bias instability from 63.70°/h to 1.38°/h, with reductions of 82.81% and 97.83%, respectively. This study validates the effectiveness and superiority of the proposed temperature compensation model. Full article

(This article belongs to the Special Issue MEMS Sensors and Actuators: Design, Fabrication and Applications)

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14 pages, 4040 KiB

Open AccessArticle

Analysis of the Radial Force of a Piezoelectric Actuator with Interdigitated Spiral Electrodes

by Yateng Wang, Tianxing Ren, Yuan Ren, Ruijie Gu and Yonggang Liu

Micromachines 2024, 15(11), 1378; https://doi.org/10.3390/mi15111378 - 15 Nov 2024

Abstract

The actuator is a critical component of the micromanipulator. By utilizing the properties of expansion and contraction, the piezoelectric actuator enables the manipulator to handle and grasp miniature objects during micromanipulation. However, in piezoelectric ceramic disc actuators with conventional surface electrode configurations, the [...] Read more.

The actuator is a critical component of the micromanipulator. By utilizing the properties of expansion and contraction, the piezoelectric actuator enables the manipulator to handle and grasp miniature objects during micromanipulation. However, in piezoelectric ceramic disc actuators with conventional surface electrode configurations, the actuating force generated in the radial direction is relatively limited. When used as the actuation element of the manipulator, achieving regulation over a wide range of operating strokes becomes challenging. Therefore, altering the electrode structure is necessary to generate a greater radial force, thus enhancing the positioning and grasping capabilities of the operating arm. This paper investigates a piezoelectric actuator with interdigitated spiral electrodes, featuring a constant pitch between adjacent electrodes. The radial force was tested under mechanical clamping conditions, and the influence of the electrical signal was examined. The characteristics of the electrode structure were described, and the working principles of the piezoelectric actuators were analyzed. Theoretical equations were derived for the macroscopic characterization of the radial clamping force of the actuator, based on the piezoelectric constitutive equation, geometric principles, and Bond matrix transformation relationships. A finite element model was developed, reflecting the features of the electrode structure, and finite element simulations were employed to verify the theoretical equations for radial force. To prepare the samples, encircled interdigitated spiral electrode lines were printed on the PZT-52 piezoelectric ceramic disc using a screen printing method. The clamping force experimental platform was established, and experiments on the clamping radial force were conducted with electrical signals of varying waveforms, frequencies, and voltages. The experimental results show that the piezoelectric ceramic disc actuator with an interdigitated spiral electrode line structure, when excited by a stable sine wave operating at 200 V and 0.2 Hz, generated a peak force of 0.37 N. It was 1.76 times greater than that produced by a previously utilized piezoelectric disc with conventional electrode structures. Full article

(This article belongs to the Special Issue Soft Actuators: Design, Fabrication and Applications, 2nd Edition)

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16 pages, 14457 KiB

Open AccessArticle

ScAlN PMUTs Based on Flexurally Suspended Membrane for Long-Range Detection

by Shutao Yao, Wenling Shang, Guifeng Ta, Jinyan Tao, Haojie Liu, Xiangyong Zhao, Jianhe Liu, Bin Miao and Jiadong Li

Micromachines 2024, 15(11), 1377; https://doi.org/10.3390/mi15111377 - 14 Nov 2024

Abstract

Piezoelectric micromachined ultrasonic transducers (PMUTs) have been widely applied in distance sensing applications. However, the rapid movement of miniature robots in complex environments necessitates higher ranging capabilities from sensors, making the enhancement of PMUT sensing distance critically important. In this paper, a scandium-doped [...] Read more.

Piezoelectric micromachined ultrasonic transducers (PMUTs) have been widely applied in distance sensing applications. However, the rapid movement of miniature robots in complex environments necessitates higher ranging capabilities from sensors, making the enhancement of PMUT sensing distance critically important. In this paper, a scandium-doped aluminum nitride (ScAlN) PMUT based on a flexurally suspended membrane is proposed. Unlike the traditional fully clamped design, the PMUT incorporates a partially clamped membrane, thereby extending the vibration displacement and enhancing the output sound pressure. Experimental results demonstrate that at a resonant frequency of 78 kHz, a single PMUT generates a sound pressure level (SPL) of 112.2 dB at a distance of 10 mm and achieves a high receiving sensitivity of 12.3 mV/Pa. Distance testing reveals that a single PMUT equipped with a horn can achieve a record-breaking distance sensing range of 11.2 m when used alongside a device capable of simultaneously transmitting and receiving ultrasound signals. This achievement is significant for miniaturized and integrated applications that utilize ultrasound for long-range target detection. Full article

(This article belongs to the Special Issue MEMS Ultrasonic Transducers)

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16 pages, 9416 KiB

Open AccessArticle

An Image Processing Approach to Quality Control of Drop-on-Demand Electrohydrodynamic (EHD) Printing

by Yahya Tawhari, Charchit Shukla and Juan Ren

Micromachines 2024, 15(11), 1376; https://doi.org/10.3390/mi15111376 - 14 Nov 2024

Abstract

Droplet quality in drop-on-demand (DoD) Electrohydrodynamic (EHD) inkjet printing plays a crucial role in influencing the overall performance and manufacturing quality of the operation. The current approach to droplet printing analysis involves manually outlining/labeling the printed dots on the substrate under a microscope [...] Read more.

Droplet quality in drop-on-demand (DoD) Electrohydrodynamic (EHD) inkjet printing plays a crucial role in influencing the overall performance and manufacturing quality of the operation. The current approach to droplet printing analysis involves manually outlining/labeling the printed dots on the substrate under a microscope and then using microscope software to estimate the dot sizes by assuming the dots have a standard circular shape. Therefore, it is prone to errors. Moreover, the dot spacing information is missing, which is also important for EHD DoD printing processes, such as manufacturing micro-arrays. In order to address these issues, the paper explores the application of feature extraction methods aimed at identifying characteristics of the printed droplets to enhance the detection, evaluation, and delineation of significant structures and edges in printed images. The proposed method involves three main stages: (1) image pre-processing, where edge detection techniques such as Canny filtering are applied for printed dot boundary detection; (2) contour detection, which is used to accurately quantify the dot sizes (such as dot perimeter and area); and (3) centroid detection and distance calculation, where the spacing between neighboring dots is quantified as the Euclidean distance of the dot geometric centers. These stages collectively improve the precision and efficiency of EHD DoD printing analysis in terms of dot size and spacing. Edge and contour detection strategies are implemented to minimize edge discrepancies and accurately delineate droplet perimeters for quality analysis, enhancing measurement precision. The proposed image processing approach was first tested using simulated EHD printed droplet arrays with specified dot sizes and spacing, and the achieved quantification accuracy was over 98% in analyzing dot size and spacing, highlighting the high precision of the proposed approach. This approach was further demonstrated through dot analysis of experimentally EHD-printed droplets, showing its superiority over conventional microscope-based measurements. Full article

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Overview of the proposed framework for DoD EHD printing analysis. (a) The proposed method takes a microscope image of printed droplets as the input, outputs the detection results, and calculates the spacing of the dot size (area). (b) Visual analysis of the printing quality provides size distribution of the printed dots. The x-axis represents the three categories of dot size range, and the y-axis indicates the percentage within each size category. Full article ">Figure 2
An image (a) is used as input for the pre-proposed method; (b) is the image after applying a Gaussian filter; (c) is the image after applying Canny edge detection; (d) is the image after applying dilation and morphological closing. Full article ">Figure 3
Line dot printing pattern. (a) original pattern. (b) processed pattern. Full article ">Figure 4
Distance Quantification Analysis. Full article ">Figure 5
Circular dot printing pattern. (a) original pattern. (b) processed pattern. Full article ">Figure 6
Experimental EHD DoD print result analysis. (a) The origin image of the printed droplet. (b) The printed droplet was analyzed offline using a manual microscope approach. (c) The analyzed image using the the proposed approach. (d) Detailed comparison of the two analysis methods. Full article ">

12 pages, 2475 KiB

Open AccessArticle

Effect of Hot Junction Size on the Temperature Measurement of Proton Exchange Membrane Fuel Cells Using NiCr/NiSi Thin-Film Thermocouple Sensors

by Huijin Guo, Zhihui Liu, Tengda Guo, Yi Sun, Kai Shen, Bi Wang, Yongjun Cheng, Yuming Wang, Tiancai Ma, Zixi Wang and Wanyu Ding

Micromachines 2024, 15(11), 1375; https://doi.org/10.3390/mi15111375 - 14 Nov 2024

Abstract

In the process of using thin-film thermocouples for contact measurement of the reaction temperature in proton exchange membrane fuel cells (PEMFC), the impact of thin-film thermocouple volume on the system’s reaction temperature field variation, reaction efficiency, and the lifespan of thermocouples under these [...] Read more.

In the process of using thin-film thermocouples for contact measurement of the reaction temperature in proton exchange membrane fuel cells (PEMFC), the impact of thin-film thermocouple volume on the system’s reaction temperature field variation, reaction efficiency, and the lifespan of thermocouples under these conditions is not thoroughly studied. Using magnetron sputtering technology, NiCr/NiSi thin-film thermocouples (NiCr/NiSi TFTCs) with different junction sizes were fabricated on the proton exchange membrane (PEM). These NiCr/NiSi TFTCs exhibit excellent compactness, with thickness and planar dimensions in the micrometer range. When PEMFCs are equipped with built-in NiCr/NiSi TFTCs of different hot junction sizes, the time required for the system to reach a steady state varies with the size of the hot junction, with smaller hot junction sizes reaching a steady state more quickly. In a 500-h continuous operation test, the failure rates of NiCr/NiSi TFTCs also vary based on the hot junction size. Both smaller and larger hot junction sizes have relatively higher failure rates, whereas medium-sized junctions have a lower failure rate. These extensive and repetitive comparative experiments provide significant reference value for the size design of TFTCs operating inside PEMFCs, promoting both industrial production and scientific research. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications, 2nd Edition)

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Schematic diagram of the NiCr/NiSi thin-film thermocouple position on the PEM. Full article ">Figure 2
Static and dynamic calibration system structure diagram. Full article ">Figure 3
The effect of different hot point two-dimensional sizes on the response time and temperature measurement accuracy of NiCr/NiSi TFTCs temperature measurement systems. Full article ">Figure 4
(a) The ratio of failed NiCr/NiSi TFTCs to the total number for each hot junction size. (b) The damage location diagram of failed NiCr/NiSi TFTCs. Full article ">Figure 5
Basic characteristics of NiCr and NiSi thin films: (a) XRD patterns of NiCr thin films, NiCr target material, and the standard XRD pattern of Ni91Cr9 (wt.%); XRD patterns of NiSi thermoelectric electrodes, NiSi target material, and the standard XRD pattern of Ni94Si6 (wt.%). (b) EDS spectrum of the NiCr thin film. (c) EDS spectrum of the NiSi thin film. Full article ">Figure 6
The effect of NiCr/NiSi TFTCs with different hot spot sizes on the I-V and I-P polarization curves of PEMFC. Full article ">Figure 7
The calculation results of the benefit coefficient for different junction sizes. Full article ">

11 pages, 1223 KiB

Open AccessArticle

Open-End Control of Neurite Outgrowth Lengths with Steep Bending Confinement Microchannel Patterns for Miswiring-Free Neuronal Network Formation

by Naoya Takada, Soya Hagiwara, Nanami Abe, Ryohei Yamazaki, Kazuhiro Tsuneishi and Kenji Yasuda

Micromachines 2024, 15(11), 1374; https://doi.org/10.3390/mi15111374 - 14 Nov 2024

Abstract

Wiring technology to control the length and direction of neurite outgrowth and to connect them is one of the most crucial development issues for forming single-cell-based neuronal networks. However, with current neurite wiring technology, it has been difficult to stop neurite extension at [...] Read more.

Wiring technology to control the length and direction of neurite outgrowth and to connect them is one of the most crucial development issues for forming single-cell-based neuronal networks. However, with current neurite wiring technology, it has been difficult to stop neurite extension at a specific length and connect it to other neurites without causing miswiring due to over-extension. Here, we examined a novel method of wiring neurites without miswiring by controlling the length of neurites in open-ended bending microchannel arrays connected beyond the maximum bending angle of neurite outgrowth. First, we determined the maximum bending angle of neurite elongation to pass through the bending point of a bending microfluidic channel; the maximum angle (the critical angle) was 90°. Next, we confirmed the control of neurite outgrowth length in open-ended microchannels connected at 120°, an angle beyond the maximum bending angle. The neurites stopped when elongated to the bend point, and no further elongation was observed. Finally, we observed that in bending microchannel arrays connected at an angle of 120°, two neurite outgrowths stopped and contacted each other without crossing over the bend point. The results show that the steep bending connection pattern is a robust open-end neurite wiring technique that prevents over-extension and miswiring. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Biology and Biomedicine 2024)

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Fabrication of angled single neurite elongation patterns in agarose microstructures. (A) Schematic drawing of angled agarose microchannels fabrication procedure in a thin agarose layer on the cultivation dish. First, a thin agarose layer is coated on the poly-D-lysine colated cultivation dish. Then, the focused infrared laser is applied to the agarose layer to melt a portion of the agarose for the microchamber and angled microchannel formation. A hippocampal cell is set in the microchamber. Finally, the elongation of neurite in the angled microchannel was observed. (B) Schematic images of the microchamber and angled microchannel for single neurite elongation observation. Left, design of the microchamber and angled microchannel pattern. Right, a neuron is placed in the microchamber, and the elongated neurite is elongated in the angled microchannel. (C) Micrographs of the microchamber and the 45° angled bending microchannel before (left) and after the neurite elongation cultivation started (day 3) (right). Bar, 50 μm. Full article ">Figure 2
Ability of single neurite elongations in various bending angles. (A) Neurite elongations in the various bending microchannels from 20° to 120° bending angles. Neurites in the bending angles larger than 90° stopped their elongation at the bending point. To confirm that they had stopped, two micrographs were compared: left, the day elongation stopped; right, a day after to confirm their stopping. (B) Summary of bending angle dependence of neurite elongations. (C) Observation of the neurite outgrowth until six days (day 8) after its elongation stopped at the 90° bending point (day 2). White arrows indicate the position of the neurite tips. Bars, 50 μm. Full article ">Figure 3
Effect of bending angles for single neurite differentiation. (Left), bending angles. (Middle), phase-contrast images of neurons and their neurites in the microchambers and the bending microchannels. (Right), fluorescent images of immunostained neurons and neurites: neurons and neurites were fixed on day 2 (45°) or day 3 (50° and 90°) after the cultivation started, and were immunostained for Tau-1 to indicate axons (red) and for MAP-2 to indicate cell bodies and dendrites (green). The white arrows show the positions of the elongated neurite tips. Bar, 50 μm. Full article ">Figure 4
Neurite outgrowth length control using angled bending shapes of open-end microtunnel structure. (A,B) Phase-contrast images of neurites elongated from single neurons in the 120° steep bending open-end microchannel series. Microchamber diameter, 20 μm; microchannel lengths, 110 μm (left side), and 30 μm (right side). Bar, 50 μm. Full article ">Figure 5
Connection of length-controlled neurites using 120° steep bending microchannel series. (A,B) Phase-contrast images of neurites elongated from neurons in the 120° steep bending open-end microchannel series. (C) A fluorescent image of immunostained neurons and neurites of (B) neurons and neurites were fixed on day 4 and immunostained for Tau-1 to indicate axons (red) and for MAP-2 to indicate cell bodies and dendrites (green). (D) A magnified fluorescent image of immunostained neurons and neurites of (C) with 40× obj. lens. Bars, 50 μm. Full article ">

23 pages, 4958 KiB

Open AccessArticle

Magnetic Actuation for Wireless Capsule Endoscopy in a Large Workspace Using a Mobile-Coil System

by Xiao Li, Detian Zeng, Han Xu, Qi Zhang and Bin Liao

Micromachines 2024, 15(11), 1373; https://doi.org/10.3390/mi15111373 - 14 Nov 2024

Abstract

Current wireless capsule endoscopy (WCE) is limited in the long examination time and low flexibility since the capsule is passively moved by the natural peristalsis. Efforts have been made to facilitate the active locomotion of WCE using magnetic actuation and localization technologies. This [...] Read more.

Current wireless capsule endoscopy (WCE) is limited in the long examination time and low flexibility since the capsule is passively moved by the natural peristalsis. Efforts have been made to facilitate the active locomotion of WCE using magnetic actuation and localization technologies. This work focuses on the motion control of the robotic capsule under magnetic actuation in a complex gastrointestinal (GI) tract environment in order to improve the efficiency and accuracy of its motion in dynamic, complex environments. Specifically, a magnetic actuation system based on a four-electromagnetic coil module is designed, and a control strategy for the system is proposed. In particular, the proportional–integral–derivative (PID) control parameters and current values are optimized online and in real time using the adaptive particle swarm optimization (APSO) algorithm. In this paper, both simulations and real-world experiments were conducted using acrylic plates with irregular shapes to simulate the GI tract environment for evaluation. The results demonstrate the potential of the proposed control methods to realize the accurate and efficient inspection of the intestine using active WCE. The methods presented in this paper can be integrated with current WCE to improve the diagnostic accuracy and efficiency of the GI tract. Full article

(This article belongs to the Topic Micro-Mechatronic Engineering)

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18 pages, 11355 KiB

Open AccessArticle

Denoising Phase-Unwrapped Images in Laser Imaging via Statistical Analysis and DnCNN

by Yibo Xie, Jin Cheng, Shun Zhou, Qing Fan, Yue Jia, Jingjin Xiao and Weiguo Liu

Micromachines 2024, 15(11), 1372; https://doi.org/10.3390/mi15111372 - 14 Nov 2024

Abstract

Three-dimensional imaging plays a crucial role at the micro-scale in fields such as precision manufacturing and materials science. However, image noise significantly impacts the accuracy of point cloud reconstruction, making image denoising techniques a widely discussed topic. Statistical analysis of laser imaging noise [...] Read more.

Three-dimensional imaging plays a crucial role at the micro-scale in fields such as precision manufacturing and materials science. However, image noise significantly impacts the accuracy of point cloud reconstruction, making image denoising techniques a widely discussed topic. Statistical analysis of laser imaging noise has led to the conclusion that logarithmically transformed noise follows a Gumbel distribution. A corresponding neural network training set was developed to address the challenges of difficult data collection and the scarcity of phase-unwrapped image datasets. Building on this foundation, a phase-unwrapped image denoising method based on the Denoising Convolutional Neural Network (DnCNN) is proposed. This method aims to achieve three-dimensional filtering by performing two-dimensional image denoising. Experimental results show a significant reduction in the Cloud-to-Mesh Distance (C2M) statistics of the corresponding point clouds before and after planar filtering. Specifically, the statistic at 97.5% of the 2σ principle decreases from 0.8782 mm to 0.3384 mm, highlighting the effectiveness of the filtering algorithm in improving the planar fit. Moreover, the DnCNN method exhibits exceptional denoising performance when applied to real-world target data, such as plaster statues with complex depth variations and PCBs made from different materials, thereby enhancing accuracy and reliability in point cloud reconstruction. This study provides valuable insights into phase-unwrapped image noise suppression in laser imaging, particularly in micro-scale applications where precision is critical. Full article

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13 pages, 945 KiB

Open AccessArticle

Inverse Tesla Valve as Micromixer for Water Purification

by Christos Liosis, George Sofiadis, Evangelos Karvelas, Theodoros Karakasidis and Ioannis Sarris

Micromachines 2024, 15(11), 1371; https://doi.org/10.3390/mi15111371 - 14 Nov 2024

Abstract

Contaminated water has remained an unsolved problem for decades, particularly when the contamination derived from heavy metals. A possible solution is to mix the contaminated water with magnetic nanoparticles so that an adsorption process can take place. In that frame, Tesla valve micromixer [...] Read more.

Contaminated water has remained an unsolved problem for decades, particularly when the contamination derived from heavy metals. A possible solution is to mix the contaminated water with magnetic nanoparticles so that an adsorption process can take place. In that frame, Tesla valve micromixer and

{Fe}_{3} O_{4}

magnetic nanoparticles were selected to perform simulations for encounter maximum mixing efficiency. These simulations focus on inlet velocities ratios between contaminated water and nanoparticles and inlet rates of nanoparticles. The maximum mixing efficiency was 44% for the inverse double Tesla micromixer found for the combination of

{Fe}_{3} O_{4}

nanoparticles as the inlet rate and with inlet velocity ratios of

\frac{V_{p}}{V_{c}} = 10

. Full article

(This article belongs to the Special Issue Advanced Micromixing Technology)

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12 pages, 5351 KiB

Open AccessArticle

A Study on Regulating the Residual Stress of Electroplated Cu by Manipulating the Nanotwin Directions

by Gangli Yang, Tailong Shi, Liu Chang, Hongjia Zhu, Dongyu Tong, Wending Yang, Zeyuan Li and Liyi Li

Micromachines 2024, 15(11), 1370; https://doi.org/10.3390/mi15111370 - 14 Nov 2024

Abstract

Glass substrate, a new type of substrate with excellent mechanical and electrical properties of glass itself, has great potential to become an ideal platform for heterogeneous integration in chiplet systems for high-performance computing applications. The residual stress of the metal layer generated on [...] Read more.

Glass substrate, a new type of substrate with excellent mechanical and electrical properties of glass itself, has great potential to become an ideal platform for heterogeneous integration in chiplet systems for high-performance computing applications. The residual stress of the metal layer generated on the glass surface during the electroplating process is one of the major bottlenecks of glass packaging technologies, resulting in glass-metal layer delamination and glass breakage. This paper demonstrated for the first time a method to regulate the residual stress by manipulating the nanotwin directions of the electroplated Cu. The experimental results show that nanotwins with three different directions (non-directional, vertical, and horizontal) can be manipulated by controlling electroplating conditions (concentration of Cl⁻ and gelatin, stirring speed). The orientations of non-directional, vertical, and horizontal nanotwinned Cu are non-oriented, 110 and 111, respectively. After electroplating, the 111-oriented nanotwinned Cu has the smallest residual stress (39.7 MPa). Annealing can significantly reduce the residual stress of nanotwinned Cu, which has been attributed to the decrease in the geometric necessity dislocation density. 110-oriented nanotwinned Cu had drastic recrystallization, while 111-oriented nanotwinned Cu and non-oriented nanotwinned Cu had only slight recrystallization. After annealing, the residual stress of 111-nt-Cu remains the lowest (29.1 MPa). Full article

(This article belongs to the Special Issue Two-Dimensional Materials for Electronic and Optoelectronic Devices)

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22 pages, 4972 KiB

Open AccessArticle

The Optical Forces and Torques Exerted by Airy Light-Sheet on Magnetic Particles Utilized for Targeted Drug Delivery

by Ningning Song, Shiguo Chen, Hao Wang, Xinbo He, Bing Wei, Renxian Li, Shu Zhang and Lei Xu

Micromachines 2024, 15(11), 1369; https://doi.org/10.3390/mi15111369 - 12 Nov 2024

Abstract

The remarkable properties of magnetic nanostructures have sparked considerable interest within the biomedical domain, owing to their potential for diverse applications. In targeted drug delivery systems, therapeutic molecules can be loaded onto magnetic nanocarriers and precisely guided and released within the body with [...] Read more.

The remarkable properties of magnetic nanostructures have sparked considerable interest within the biomedical domain, owing to their potential for diverse applications. In targeted drug delivery systems, therapeutic molecules can be loaded onto magnetic nanocarriers and precisely guided and released within the body with the assistance of an externally applied magnetic field. However, conventional external magnetic fields generated by permanent magnets or electromagnets are limited by finite magnetic field gradients, shallow penetration depths, and low precision. The novel structured light field known as the Airy light-sheet possesses unique characteristics such as non-diffraction, self-healing, and self-acceleration, which can potentially overcome the limitations of traditional magnetic fields to some extent. While existing studies have primarily focused on the manipulation of dielectric particles by Airy light-sheet, comprehensive analyses exploring the intricate interplay between Airy light-sheet and magnetic nanostructures are currently lacking in the literature, with only preliminary theoretical discussions available. This study systematically explores the mechanical response of magnetic spherical particles under the influence of Airy light-sheet, including radiation forces and spin torques. Furthermore, we provide an in-depth analysis of the effects of particle size, permittivity, permeability, and incident light-sheet parameters on the mechanical effects. Our research findings not only offer new theoretical guidance and practical references for the application of magnetic nanoparticles in biomedicine but also provide valuable insights for the manipulation of other types of micro/nanoparticles using structured light fields. Full article

(This article belongs to the Section B5: Drug Delivery System)

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26 pages, 6673 KiB

Open AccessReview

Neural Network Methods in the Development of MEMS Sensors

by Yan Liu, Mingda Ping, Jizhou Han, Xiang Cheng, Hongbo Qin and Weidong Wang

Micromachines 2024, 15(11), 1368; https://doi.org/10.3390/mi15111368 - 12 Nov 2024

Abstract

As a kind of long-term favorable device, the microelectromechanical system (MEMS) sensor has become a powerful dominator in the detection applications of commercial and industrial areas. There have been a series of mature solutions to address the possible issues in device design, optimization, [...] Read more.

As a kind of long-term favorable device, the microelectromechanical system (MEMS) sensor has become a powerful dominator in the detection applications of commercial and industrial areas. There have been a series of mature solutions to address the possible issues in device design, optimization, fabrication, and output processing. The recent involvement of neural networks (NNs) has provided a new paradigm for the development of MEMS sensors and greatly accelerated the research cycle of high-performance devices. In this paper, we present an overview of the progress, applications, and prospects of NN methods in the development of MEMS sensors. The superiority of leveraging NN methods in structural design, device fabrication, and output compensation/calibration is reviewed and discussed to illustrate how NNs have reformed the development of MEMS sensors. Relevant issues in the usage of NNs, such as available models, dataset construction, and parameter optimization, are presented. Many application scenarios have demonstrated that NN methods can enhance the speed of predicting device performance, rapidly generate device-on-demand solutions, and establish more accurate calibration and compensation models. Along with the improvement in research efficiency, there are also several critical challenges that need further exploration in this area. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors and Actuators, 2nd Edition)

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9 pages, 4045 KiB

Open AccessArticle

A Laterally Excited Bulk Acoustic Wave Resonator Based on LiNbO₃ with Arc-Shaped Electrodes

by Jieyu Liu, Wenjuan Liu, Zhiwei Wen, Min Zeng and Chengliang Sun

Micromachines 2024, 15(11), 1367; https://doi.org/10.3390/mi15111367 - 12 Nov 2024

Abstract

High frequency and large bandwidth are growing trends in communication radio-frequency devices. The LiNbO₃ thin film material is expected to become the preferred piezoelectric material for high coupling resonators in the 5G frequency band due to its ultra-high piezoelectric coefficient and low [...] Read more.

High frequency and large bandwidth are growing trends in communication radio-frequency devices. The LiNbO₃ thin film material is expected to become the preferred piezoelectric material for high coupling resonators in the 5G frequency band due to its ultra-high piezoelectric coefficient and low loss characteristics. The main mode of laterally excited bulk acoustic wave resonators (XBAR) have an ultra-high sound velocity, which enables high-frequency applications. However, the interference of spurious modes is one of the main reasons hindering the widespread application of XBAR. In this paper, a Z-cut LiNbO₃ thin film-based XBAR with arc-shaped electrodes is presented. We investigate the electric field distribution of the XBAR, while the irregular boundary of the arc-shaped electrodes affects the electric field between the existing interdigital transducers (IDTs). The mode shapes and impedance response of the XBAR with arc-shaped electrodes and the XBARs with traditional IDTs are compared in this work. The fabricated XBAR on a 350 nm Z-cut LiNbO₃ thin film with arc-shaped electrodes operating at over 5 GHz achieves a high effective electromechanical coupling coefficient of 29.8% and the spurious modes are well suppressed. This work promotes an XBAR with an optimized electrode design to further achieve the desired performance. Full article

(This article belongs to the Special Issue Piezoelectric Devices and System in Micromachines)

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Figure 1
Two-dimensional cross-sectional view of XBARs (a) with IDT electrodes and (b) with arc-shaped electrodes. (c) The cross-sectional view of a XBAR based on a Z-cut LiNbO3 thin film. Full article ">Figure 2
(a) The schematic of hexagonal unit cell of Z-cut LiNbO3. Dispersive diagrams for propagation on the x-axis for the real part of propagation constant (b) while the frequency domain is 0.1–3.5 GHz, (c) while the frequency domain is 3.5–5.5 GHz and (d) while the frequency domain is 5.5–6.5 GHz. (e) The total displacements of different mode shapes while kx = 0 (1/m). Full article ">Figure 3
Process flows of XBAR: (a) The schematic diagram of LNOI wafer. (b) Definition of top electrode. (c) DRIE back surface Si. (d) Suspend the resonator using BOE. Full article ">Figure 4
The microscope images of (a) device with IDT electrodes and (b) device with arc-shaped electrodes. Full article ">Figure 5
The SEM pictures of the fabricated XBARs (a) with arc-shaped electrodes and (b) with IDT electrodes. Measured impedance responses of XBARs (c) with arc-shaped electrodes and (d) with IDT electrodes. Full article ">Figure 6
Simulated impedance curve of XBARs (a) with IDT electrodes and (b) with arc-shaped electrodes. Full article ">Figure 7
Schematic diagram of acoustic wave propagation between adjacent (a) IDT electrodes and (b) arc-shaped electrodes. Simulated electric field distributions of XBARs (c) with IDT electrodes and (d) with arc-shaped electrodes. Full article ">Figure 8
Impedance curve of arc-shaped electrode XBAR when a = 10 μm and (a) b = 2 μm; (b) b = 5 μm; (c) b = 7.5 μm; (d) b = 10 μm. Full article ">

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