Micromachines

15 pages, 4059 KiB

Open AccessArticle

An Improved Algorithm to Extract Moiré Fringe Phase for Wafer-Mask Alignment in Nanoimprint Lithography

by Feifan Xu, Yinye Ding, Wenhao Chen and Haojie Xia

Micromachines 2024, 15(12), 1408; https://doi.org/10.3390/mi15121408 - 22 Nov 2024

This paper proposes an improved algorithm based on the phase extraction of the Moiré fringe for wafer-mask alignment in nanoimprint lithography. The algorithm combines the strengths of the two-dimensional fast Fourier transform (2D-FFT) and two-dimensional window Fourier filtering (2D-WFF) to quickly and accurately [...] Read more.

This paper proposes an improved algorithm based on the phase extraction of the Moiré fringe for wafer-mask alignment in nanoimprint lithography. The algorithm combines the strengths of the two-dimensional fast Fourier transform (2D-FFT) and two-dimensional window Fourier filtering (2D-WFF) to quickly and accurately extract the fundamental frequencies of interest, eliminate noise in the fundamental frequency band by using the threshold of the local spectrum, and effectively suppress spectral leakage by using a Gaussian window with outstanding sidelobe characteristics while overcoming their limitations, such as avoiding the time-consuming parameter adjustment. The phase extraction accuracy determines the misalignment measurement accuracy, and the alignment accuracy is enhanced to the nanometer level, which is 15.8% and 6.6% higher than 2D-FFT and 2D-WFF, respectively. The results of simulations and experiments confirm the feasibility and rationality of the algorithm. Full article

(This article belongs to the Section E：Engineering and Technology)

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17 pages, 3550 KiB

Open AccessArticle

A High-Precision Temperature Compensation Method for TMR Weak Current Sensors Based on FPGA

by Jie Wu, Ke Zhou, Qingren Jin, Baihua Lu, Zhenhu Jin and Jiamin Chen

Micromachines 2024, 15(12), 1407; https://doi.org/10.3390/mi15121407 - 22 Nov 2024

Abstract

Tunnel magnetoresistance (TMR) sensors, known for their high sensitivity, efficiency, and compact size, are ideal for detecting weak currents, particularly leakage currents in smart grids. However, temperature variations can negatively impact their accuracy. This work investigates the effects of temperature variations on measurement [...] Read more.

Tunnel magnetoresistance (TMR) sensors, known for their high sensitivity, efficiency, and compact size, are ideal for detecting weak currents, particularly leakage currents in smart grids. However, temperature variations can negatively impact their accuracy. This work investigates the effects of temperature variations on measurement accuracy. We analyzed the operating principles and temperature characteristics of TMR sensors and proposed a high-precision, software-based temperature compensation method using cubic spline interpolation combined with polynomial regression and zero-point self-calibration. Additionally, a field-programmable gate array (FPGA)-based temperature compensation circuit was designed and implemented. An experimental platform was established to comprehensively evaluate the sensor’s performance under various temperature conditions. Experimental results demonstrate that this method significantly enhances the sensor’s temperature stability, reduces the sensitivity temperature drift coefficient, and improves zero-point drift stability, outperforming other compensation methods. After compensation, the sensor’s measurement accuracy in complex temperature environments is substantially improved, enabling effective weak current detection in smart grids across diverse environments. Full article

(This article belongs to the Section A：Physics)

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13 pages, 5282 KiB

Open AccessArticle

Parallel Farby–Perot Interferometers in an Etched Multicore Fiber for Vector Bending Measurements

by Kang Wang, Wei Ji, Cong Xiong, Caoyuan Wang, Yu Qin, Yichun Shen and Limin Xiao

Micromachines 2024, 15(12), 1406; https://doi.org/10.3390/mi15121406 - 21 Nov 2024

Abstract

Vector bending sensors can be utilized to detect the bending curvature and direction, which is essential for various applications such as structural health monitoring, mechanical deformation measurement, and shape sensing. In this work, we demonstrate a temperature-insensitive vector bending sensor via parallel Farby–Perot [...] Read more.

Vector bending sensors can be utilized to detect the bending curvature and direction, which is essential for various applications such as structural health monitoring, mechanical deformation measurement, and shape sensing. In this work, we demonstrate a temperature-insensitive vector bending sensor via parallel Farby–Perot interferometers (FPIs) fabricated by etching and splicing a multicore fiber (MCF). The parallel FPIs made in this simple and effective way exhibit significant interferometric visibility with a fringe contrast over 20 dB in the reflection spectra, which is 6 dB larger than the previous MCF-based FPIs. And such a device exhibits a curvature sensitivity of 0.207 nm/m⁻¹ with strong bending-direction discrimination. The curvature magnitude and orientation angle can be reconstructed through the dip wavelength shifts in two off-diagonal outer-core FPIs. The reconstruction results of nine randomly selected pairs of bending magnitudes and directions show that the average relative error of magnitude is ~4.5%, and the average absolute error of orientation angle is less than 2.0°. Furthermore, the proposed bending sensor is temperature-insensitive, with temperature at a lower sensitivity than 10 pm/°C. The fabrication simplicity, high interferometric visibility, compactness, and temperature insensitivity of the device may accelerate MCF-based FPI applications. Full article

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14 pages, 10563 KiB

Open AccessArticle

Study on the Abrasive Blasting Mechanism of Solder Welded 304V Wire in Vascular Intervention

by Yao Liu, Shaobo Zhai, Jinzhu Guo, Shiling Fu, Bin Shen, Zhigang Zhao and Qingwei Ding

Micromachines 2024, 15(12), 1405; https://doi.org/10.3390/mi15121405 - 21 Nov 2024

Abstract

The solder burrs on the 304V wire surface can easily scratch the vascular tissue during interventional treatment, resulting in complications such as medial tears, bleeding, dissection, and rupture. Abrasive blasting is often used to remove solder burr and obtain a smooth surface for [...] Read more.

The solder burrs on the 304V wire surface can easily scratch the vascular tissue during interventional treatment, resulting in complications such as medial tears, bleeding, dissection, and rupture. Abrasive blasting is often used to remove solder burr and obtain a smooth surface for the interventional device. This study conducted an abrasive blasting experiment to explore the effects of process parameters (air pressure, lift-off height, abrasive volume, and abrasive type) on processing time, surface roughness, and mechanical properties to reveal the material removal mechanism. The results indicated that the resin abrasive can remove the SAC burr and keep the 304V integrity due to the proper hardness and Young’s module. Impaction pits are the main material removal mode in abrasive blasting. The processing time decreases with the increase in air pressure. The surface roughness increases with the increase in abrasive volume. The primary and secondary factors affecting the surface roughness of the 304V wire after abrasive blasting are the abrasive type and air pressure, followed by the abrasive volume and lift-off height. Blasting leads to a decrease in yield strength, and Young’s modulus and the hardness of the abrasive will affect the tensile strength. This study lays a foundation for understanding abrasive blasting and different cutting mechanisms. Full article

(This article belongs to the Special Issue Recent Advances in Micro/Nano-Fabrication)

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16 pages, 22713 KiB

Open AccessArticle

Fully Integrated MEMS Micropump and Miniaturized Mass Flow Sensor as Basic Components for a Microdosing System

by Martin Seidl and Gabriele Schrag

Micromachines 2024, 15(12), 1404; https://doi.org/10.3390/mi15121404 - 21 Nov 2024

Abstract

Despite major advances in the field of actuator technology for microsystems, miniaturized microfluidic actuation systems for mobile devices are still not common in the market. We present a micropump concept and an associated mass flow sensor design, which, in combination, have the potential [...] Read more.

Despite major advances in the field of actuator technology for microsystems, miniaturized microfluidic actuation systems for mobile devices are still not common in the market. We present a micropump concept and an associated mass flow sensor design, which, in combination, have the potential to form the basis for an integrated microfluidic development platform for microfluidic systems in general and microdosing systems in particular. The micropump combines the use of active valves with an electrostatic drive principle for the pump membrane and the valves, respectively. With a size of only 1.86 mm × 1.86 mm × 0.3 mm, the first prototypes are capable of pumping gaseous media at flow rates of up to 110 μL/min. A specific feature of the presented micropump is that the pumping direction is perpendicular to the chip surface. The corresponding flow sensor combines the principle of hot-wire anemometry with a very small footprint of only 1.4 mm × 1.4 mm × 0.4 mm. The main innovation is that the hot wires are fixed inside a through-hole in the substrate of the microchip, so that the flow direction of the fluid to be measured is perpendicular to the chip surface, which enables direct integration with the presented micropump. Detection thresholds of around 10 μL/min and measuring ranges of up to 20 mL/min can be achieved with the first prototypes, without dedicated evaluation electronics. Full article

(This article belongs to the Special Issue Selected Papers from 5th International Conference on Microfluidic Handling Systems (MFHS2024))

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17 pages, 3759 KiB

Open AccessArticle

Robust Control Strategy of Acoustic Micro Robots Based on Fuzzy System

by Junjie Dong and Xingguang Duan

Micromachines 2024, 15(11), 1403; https://doi.org/10.3390/mi15111403 - 20 Nov 2024

Abstract

This study presents a robust control strategy for acoustic micro robots utilizing a novel interval type-three fuzzy system. Micro robots driven by acoustic forces face significant challenges in fluid environments due to complex nonlinearities, uncertainties, and disturbances. To address these issues, we propose [...] Read more.

This study presents a robust control strategy for acoustic micro robots utilizing a novel interval type-three fuzzy system. Micro robots driven by acoustic forces face significant challenges in fluid environments due to complex nonlinearities, uncertainties, and disturbances. To address these issues, we propose a control framework that combines fuzzy logic and sliding mode control to enhance the stability and trajectory tracking performance of micro robots under varying fluid conditions. The interval type-3 fuzzy logic system provides increased robustness by better handling external disturbances and uncertainties compared to the robustness of the traditional methods. The experimental results from one-dimensional, two-dimensional, and three-dimensional fluid cavities demonstrate that the proposed control method significantly improves tracking accuracy, reducing the errors in complex environments. This control framework offers promising potential for the precise manipulation of micro robots in biomedical applications and other microfluidic systems. The minimum trajectory tracking control mean square error is 12.82 μm. Full article

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11 pages, 3345 KiB

Open AccessArticle

Performance Improvement of TiO₂ Ultraviolet Photodetectors by Using Atomic Layer Deposited Al₂O₃ Passivation Layer

by Yao-Tsung Yang, Shih-Chin Lin, Ching-Chiun Wang, Ying-Rong Ho, Jian-Zhi Chen and Jung-Jie Huang

Micromachines 2024, 15(11), 1402; https://doi.org/10.3390/mi15111402 - 20 Nov 2024

Abstract

This study employed atomic layer deposition (ALD) to fabricate an Al₂O₃ passivation layer to optimize the performance of ultraviolet (UV) photodetectors with a TiO₂-nanorod-(NR)-containing active layer and a solid–liquid heterojunction (SLHJ). To reduce the processing time and enhance [...] Read more.

This study employed atomic layer deposition (ALD) to fabricate an Al₂O₃ passivation layer to optimize the performance of ultraviolet (UV) photodetectors with a TiO₂-nanorod-(NR)-containing active layer and a solid–liquid heterojunction (SLHJ). To reduce the processing time and enhance light absorption, a hydrothermal method was used to grow a relatively thick TiO₂-NR-containng working electrode. Subsequently, a 5-nm-thick Al₂O₃ passivation layer was deposited on the TiO₂ NRs through ALD, which has excellent step coverage, to reduce the surface defects in the TiO₂ NRs and improve the carrier transport efficiency. X-ray photoelectron spectroscopy revealed that the aforementioned layer reduced the defects in the TiO₂ NRs. Moreover, high-resolution transmission electron microscopy indicated that following the annealing treatment, Al, Ti, and O atoms diffused across the interface between the Al₂O₃ passivation layer and TiO₂ NRs, resulting in the binding of these atoms to form Al–Ti–O bonds. This process effectively filled the oxygen vacancies in TiO₂. Examination of the photodetector device revealed that the photocurrent-to-dark current ratio exhibited a difference of four orders of magnitude (10⁻⁴ to 10⁻⁸ A), with the switch-on and switch-off times being 0.46 and 3.84 s, respectively. These results indicate that the Al₂O₃ passivation layer deposited through ALD can enhance the photodetection performance of SLHJ UV photodetectors with a TiO₂ active layer. Full article

(This article belongs to the Special Issue Latest Advancements in Semiconductor Materials, Devices, and Systems)

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12 pages, 2488 KiB

Open AccessArticle

A Polycarbonate-Assisted Transfer Method for van der Waals Contacts to Magnetic Two-Dimensional Materials

by Kunlin Yang, Guorui Zhao, Yibin Zhao, Jie Xiao, Le Wang, Jiaqi Liu, Wenqing Song, Qing Lan, Tuoyu Zhao, Hai Huang, Jia-Wei Mei and Wu Shi

Micromachines 2024, 15(11), 1401; https://doi.org/10.3390/mi15111401 - 20 Nov 2024

Abstract

Magnetic two-dimensional (2D) materials have garnered significant attention for their potential to revolutionize 2D spintronics due to their unique magnetic properties. However, their air-sensitivity and highly insulating nature of the magnetic semiconductors present substantial challenges for device fabrication with effective contacts. In this [...] Read more.

Magnetic two-dimensional (2D) materials have garnered significant attention for their potential to revolutionize 2D spintronics due to their unique magnetic properties. However, their air-sensitivity and highly insulating nature of the magnetic semiconductors present substantial challenges for device fabrication with effective contacts. In this study, we introduce a polycarbonate (PC)-assisted transfer method that effectively forms van der Waals (vdW) contacts with 2D materials, streamlining the fabrication process without the need for additional lithography. This method is particularly advantageous for air-sensitive magnetic materials, as demonstrated in Fe₃GeTe₂. It also ensures excellent interface contact quality and preserves the intrinsic magnetic properties in magnetic semiconductors like CrSBr. Remarkably, this method achieves a contact resistance four orders of magnitude lower than that achieved with traditional thermally evaporated electrodes in thin-layer CrSBr devices and enables the observation of sharp magnetic transitions similar to those observed with graphene vdW contacts. Compatible with standard dry-transfer processes and scalable to large wafer sizes, our approach provides a straightforward and effective solution for developing complex magnetic heterojunction devices and expanding the applications of magnetic 2D materials. Full article

(This article belongs to the Special Issue 2D-Materials Based Fabrication and Devices)

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11 pages, 8301 KiB

Open AccessArticle

A 2-D Fully Polarized Van Atta Array Based on Wide-Beam Tri-Polarized Antennas

by Jicheng Pan, Lei Chen, Shuangdi Zhao and Tianling Zhang

Micromachines 2024, 15(11), 1400; https://doi.org/10.3390/mi15111400 - 20 Nov 2024

Abstract

This paper proposes a 2-D fully polarized Van Atta array, which consists of four tri-polarized antenna elements. The tri-polarized antenna element comprises a monopole antenna and a low-profile microstrip antenna that widens the beam by folding four electric walls. This configuration enables the [...] Read more.

This paper proposes a 2-D fully polarized Van Atta array, which consists of four tri-polarized antenna elements. The tri-polarized antenna element comprises a monopole antenna and a low-profile microstrip antenna that widens the beam by folding four electric walls. This configuration enables the Van Atta arrays to receive and transmit arbitrarily polarized incident waves over a wider range. The measurement results indicate that the proposed Van Atta array exhibits a −5 dB radar cross-section (RCS) greater than 95° when TE-polarized waves are incident and greater than 134° when TM-polarized waves are incident, significantly surpassing the 2-D dual-polarized array. Full article

(This article belongs to the Special Issue Microwave Passive Components, 2nd Edition)

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10 pages, 8354 KiB

Open AccessArticle

Replication of Leaf Surface Structures on Flat Phosphor-Converted LEDs for Enhanced Angular Color Uniformity

by Bing-Mau Chen, Chiu-Hsiang Chen, Shang-Ping Ying and Yu-Kang Chang

Micromachines 2024, 15(11), 1399; https://doi.org/10.3390/mi15111399 - 20 Nov 2024

Abstract

We explored the use of biomimetic structures, including those that mimic leaf structures, to enhance the angular color uniformity of flat phosphor-converted light-emitting diodes (pcLEDs). The distinct microstructures found on natural leaf surfaces, such as micro-scale bumps, ridges, and hierarchical patterns, have inspired [...] Read more.

We explored the use of biomimetic structures, including those that mimic leaf structures, to enhance the angular color uniformity of flat phosphor-converted light-emitting diodes (pcLEDs). The distinct microstructures found on natural leaf surfaces, such as micro-scale bumps, ridges, and hierarchical patterns, have inspired the design of artificial microstructures that can improve light extraction, scattering, and overall optical performance in LED applications. The effects of these leaf surface microstructures on the phosphor layer of flat pcLEDs were evaluated. An imprinting technique was employed to directly replicate the surface morphology structures from fresh plant leaves. The results indicated that this method provided excellent scattering capability and reduced the disparity in light output between blue and yellow light emissions from flat pcLEDs at various angles. Subsequently, uniform correlated color temperature in the flat pcLEDs was achieved, reducing the yellow ring effect. Furthermore, the availability of diverse wrinkle and surface patterns from a wide range of natural prototypes could reduce design costs compared with traditional mold fabrication, making the method suitable for application in mass production. Full article

(This article belongs to the Special Issue Innovative Progression of Light-Emitting Diodes (LED))

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12 pages, 2219 KiB

Open AccessArticle

Buckling Behavior Analysis of Kirigami Structure Under Tension

by Pengzhong Dai, Ziqi Li, Xiaoyang Zhang and Qingmin Yu

Micromachines 2024, 15(11), 1398; https://doi.org/10.3390/mi15111398 - 20 Nov 2024

Abstract

Flexible electronic technology has attracted great interest, where rigid and brittle semiconductor materials can withstand large deformation. In order to improve the stretchability of devices, many novel structures have been designed, such as the classical “wavy” structure, the island-bridge structure, and origami structures [...] Read more.

Flexible electronic technology has attracted great interest, where rigid and brittle semiconductor materials can withstand large deformation. In order to improve the stretchability of devices, many novel structures have been designed, such as the classical “wavy” structure, the island-bridge structure, and origami structures that achieve stretchability through creases. However, the stretchability of these structures is still not large enough. Inspired by traditional kirigami, the stretchability of devices is achieved by making various periodic cuts in the substrate while the devices are placed in the area around the cuts. The previous research mainly focused on the change in the electrical properties of the structure during the deformation process, and there were few studies on the mechanical mechanisms. Therefore, this paper studies the buckling behavior of the kirigami structure when the substrate is stretched, and its mechanism can provide guidance for practical applications. Full article

(This article belongs to the Special Issue Structural Analyses and Designs for Flexible/Stretchable Electronics, 3rd Edition)

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11 pages, 1777 KiB

Open AccessArticle

Study of Vertical Phototransistors Based on Integration of Inorganic Transistors and Organic Photodiodes

by Jui-Fen Chang, Ying-You Lin and Yu-Ming Li

Micromachines 2024, 15(11), 1397; https://doi.org/10.3390/mi15111397 - 20 Nov 2024

Abstract

We investigate the inorganic/organic hybrid vertical phototransistor (VPT) by integrating an atomic layer deposition-processed ZnO (ALD-ZnO) transistor with a prototype poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PC₆₁BM) blend organic photodiode (OPD) based on an encapsulated source electrode geometry, and discuss the [...] Read more.

We investigate the inorganic/organic hybrid vertical phototransistor (VPT) by integrating an atomic layer deposition-processed ZnO (ALD-ZnO) transistor with a prototype poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PC₆₁BM) blend organic photodiode (OPD) based on an encapsulated source electrode geometry, and discuss the device mechanism. Our preliminary studies on reference P3HT:PC₆₁BM OPDs show non-ohmic electron injection between the ALD-ZnO and P3HT:PC₆₁BM layers. However, the ALD-ZnO layer enables the accumulation of photogenerated holes under negative bias, which facilitates electron injection upon illumination and thereby enhances the external quantum efficiency (EQE). This mechanism underpins the photoresponse in the VPT. Furthermore, we demonstrate that the gate field in the VPT effectively modulates electron injection from the ALD-ZnO layer to the top OPD, resulting in the VPT operating as a non-ohmic OPD in the OFF state and as an ohmic OPD in the ON state. Benefiting from the unique transistor geometry and gate modulation capability, this hybrid VPT can achieve an EQE of 45,917%, a responsivity of 197 A/W, and a specific detectivity of 3.4 × 10¹² Jones under 532 nm illumination and low drain-source voltage (V_ds = 3 V) conditions. This transistor geometry also facilitates integration with various OPDs and the miniaturization of the ZnO channel area, offering an ideal basis for the development of highly efficient VPTs and high-resolution image sensors. Full article

(This article belongs to the Special Issue Future Prospects of Thin-Film Transistors and Their Applications, 2nd Edition)

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13 pages, 5261 KiB

Open AccessArticle

A High-Performance Micro Differential Pressure Sensor

by Xutao Fan, Lei Wang and Songsong Zhang

Micromachines 2024, 15(11), 1396; https://doi.org/10.3390/mi15111396 - 20 Nov 2024

Abstract

With the development of the micro electromechanical system (MEMS), which widely adopts micro differential pressure sensors (MDPSs), the demand for high-performance MDPSs had continuously increased. Pressure sensors realized using MEMS technology integrated with biomedical catheters are of significant importance in the detection and [...] Read more.

With the development of the micro electromechanical system (MEMS), which widely adopts micro differential pressure sensors (MDPSs), the demand for high-performance MDPSs had continuously increased. Pressure sensors realized using MEMS technology integrated with biomedical catheters are of significant importance in the detection and treatment of various biological diseases. Biomedical catheters used in low-Fr applications (1Fr = 0.33 mm outer diameter) require miniaturized sensors that do not compromise their performance. For instance, catheters (5Fr) used for central venous pressure (CVP) monitoring require the integration of high-performance sensors with total dimensions smaller than 1.65 mm along at least two directions (length, width, or height). In this paper, a silicon-on-insulator (SOI)-based MDPS was designed and fabricated for micro-pressure detection in the range of 0–1 kPa. The dimension of the sensor is only 1 mm × 1 mm × 0.4 mm, with a sensitivity of 3.401 mV/V/kPa at room temperature, nonlinearity of 0.376% FS (full scale), and an overall accuracy of 0.59% FS. The sensor operates normally when the temperature is even increased to 160 °C, and its temperature coefficient of zero output (TCO) and temperature coefficient of sensitivity (TCS) are 0.093% FS/°C and −0.144% FS/°C. The dimension and performance results of this MDPS demonstrate its potential to play a significant role in biomedical catheters. In addition, it is fabricated using an 8-inch MEMS process, which significantly reduces the cost. Full article

(This article belongs to the Special Issue Acoustic Transducers and Their Applications, 2nd Edition)

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13 pages, 2311 KiB

Open AccessArticle

Multifunctional Downhole Drilling Motor Speed Sensor Based on Triboelectric Nanogenerator

by Yanbo Zhang, Shida Su, Lei Zhang, Yulin Gao and Chuan Wu

Micromachines 2024, 15(11), 1395; https://doi.org/10.3390/mi15111395 - 18 Nov 2024

Abstract

The measurement of downhole drilling motor rotational speed is crucial for optimizing drilling operations, improving work efficiency, and preventing equipment failures. However, traditional downhole rotational speed sensors suffer from power supply limitations, which can increase drilling costs. To address this issue, this study [...] Read more.

The measurement of downhole drilling motor rotational speed is crucial for optimizing drilling operations, improving work efficiency, and preventing equipment failures. However, traditional downhole rotational speed sensors suffer from power supply limitations, which can increase drilling costs. To address this issue, this study presents a novel multifunctional rotational speed sensor based on triboelectric nanogenerator (TENG) technology, enabling the self-powered measurement of rotational speed, direction, and angle. Our experimental results demonstrate that the sensor operates stably within a temperature range of 0 to 150 °C and a humidity range of 0 to 90%. It achieves rotational speed measurement with an accuracy of less than 2.5% error within a range of 0 to 1000 rpm, angular measurement with a resolution of 60 degrees and an error of less than 2% within a range of 0 to 360 degrees, and rotational direction measurement. Furthermore, the sensor exhibits self-powered functionality, achieving a maximum power output of 29.1 μW when the external load is 10 MΩ. Compared to conventional rotational speed sensors, this sensor possesses the unique advantage of integrating the measurement of rotational speed, angle, and direction, while simultaneously harnessing downhole working conditions for self-power generation. These characteristics make it highly suitable for practical downhole environments. Full article

(This article belongs to the Special Issue Emerging Applications of Triboelectric Effects/Materials)

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15 pages, 5497 KiB

Open AccessArticle

Spatial Discrimination Limit Analysis of Macrophage Phagocytosis Between Target Antigens and Non-Target Objects Using Microcapillary Manipulation Assay

by Maiha Ando, Dan Horonushi, Haruka Yuki, Shinya Kato, Amane Yoshida and Kenji Yasuda

Micromachines 2024, 15(11), 1394; https://doi.org/10.3390/mi15111394 - 18 Nov 2024

Abstract

During phagocytosis, the FcGR–IgG bond is thought to be necessary to promote cell-membrane extension as the zipper mechanism. However, does this zipper mechanism provide a spatial antigen discrimination capability that allows macrophages to selectively phagocytose only antigens, especially for clusters with a mixture [...] Read more.

During phagocytosis, the FcGR–IgG bond is thought to be necessary to promote cell-membrane extension as the zipper mechanism. However, does this zipper mechanism provide a spatial antigen discrimination capability that allows macrophages to selectively phagocytose only antigens, especially for clusters with a mixture of antigens and non-antigens? To elucidate the ability and limitation of the zipper mechanism, we fed a coupled 2 μm IgG-coated and 4.5 μm non-coated polystyrene bead mixtures to macrophages and observed their phagocytosis. Macrophage engulfed the mixed clusters, including the 4.5 μm non-coated polystyrene part, indicating that the non-coated particles can be engulfed even without the zipper mechanism as far as coupled to the opsonized particles. In contrast, when the non-opsonized particle part was held by the microcapillary manipulation assay, macrophages pinched off the non-coated polystyrene particle part and internalized the opsonized particle part only. The results suggest that (1) an IgG-coated surface is needed to anchor phagocytosis by cell-membrane protrusion; however, (2) once the antibody-dependent cell phagocytosis is started, phagocytosis can proceed with the uncoated objects as the followers of the internalizing opsonized particles even without the support of the zipper mechanism. They may also indicate the concern of misleading the immune system to target unexpected objects because of their aggregation with target pathogens and the possibility of new medical applications to capture the non-opsonized target objects by the aggregation with small antigens to activate an immune response. Full article

(This article belongs to the Section B：Biology and Biomedicine)

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21 pages, 5645 KiB

Open AccessArticle

Design, Testing, and Validation of a Soft Robotic Sensor Array Integrated with Flexible Electronics for Mapping Cardiac Arrhythmias

by Abdellatif Ait Lahcen, Michael Labib, Alexandre Caprio, Mohsen Annabestani, Lina Sanchez-Botero, Weihow Hsue, Christopher F. Liu, Simon Dunham and Bobak Mosadegh

Micromachines 2024, 15(11), 1393; https://doi.org/10.3390/mi15111393 - 18 Nov 2024

Abstract

Cardiac mapping is a crucial procedure for diagnosing and treating cardiac arrhythmias. Still, current clinical techniques face limitations including insufficient electrode coverage, poor conformability to complex heart chamber geometries, and high costs. This study explores the design, testing, and validation of a 64-electrode [...] Read more.

Cardiac mapping is a crucial procedure for diagnosing and treating cardiac arrhythmias. Still, current clinical techniques face limitations including insufficient electrode coverage, poor conformability to complex heart chamber geometries, and high costs. This study explores the design, testing, and validation of a 64-electrode soft robotic catheter that addresses these challenges in cardiac mapping. A dual-layer flexible printed circuit board (PCB) was designed and integrated with sensors into a soft robotic sensor array (SRSA) assembly. Design considerations included flex PCB layout, routing, integration, conformity to heart chambers, sensor placement, and catheter durability. Rigorous SRSA in vitro testing evaluated the burst/leakage pressure, block force for electrode contact, mechanical integrity, and environmental resilience. For in vivo validation, a porcine model was used to demonstrate the successful deployment, conformability, and acquisition of electrograms in both the ventricles and atria. This catheter-deployable SRSA represents a meaningful step towards translating the integration of soft robotic actuators and stretchable electronics for clinical use, showcasing the unique mechanical and electrical performance that these designs enable. The high-density electrode array enabled rapid 2 s data acquisition with detailed spatial and temporal resolution, as illustrated by the clear and consistent cardiac signals recorded across all electrodes. The future of this work will lie in enabling high-density, anatomically conformable devices for detailed cardiac mapping to guide ablation therapy and other interventions. Full article

(This article belongs to the Section B：Biology and Biomedicine)

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20 pages, 5507 KiB

Open AccessArticle

Analysis of Entropy Generation for Mass and Thermal Mixing Behaviors in Non-Newtonian Nano-Fluids of a Crossing Micromixer

by Ayache Lakhdar, Jribi Skander, Naas Toufik Tayeb, Telha Mostefa, Shakhawat Hossain and Sun Min Kim

Micromachines 2024, 15(11), 1392; https://doi.org/10.3390/mi15111392 - 17 Nov 2024

Abstract

This work’s objective is to investigate the laminar steady flow characteristics of non-Newtonian nano-fluids in a developed chaotic microdevice known as a two-layer crossing channels micromixer (TLCCM). The continuity equation, the 3D momentum equations, and the species transport equations have been solved numerically [...] Read more.

This work’s objective is to investigate the laminar steady flow characteristics of non-Newtonian nano-fluids in a developed chaotic microdevice known as a two-layer crossing channels micromixer (TLCCM). The continuity equation, the 3D momentum equations, and the species transport equations have been solved numerically at low Reynolds numbers with the commercial CFD software Fluent. A procedure has been verified for non-Newtonian flow in studied geometry that is continuously heated. Secondary flows and thermal mixing performance with two distinct intake temperatures of nano-shear thinning fluids is involved. For an extensive range of Reynolds numbers (0.1 to 25), the impact of fluid characteristics and various concentrations of Al₂O₃ nanoparticles on thermal mixing capabilities and pressure drop were investigated. The simulation for performance enhancement was run using a power-law index (n) at intervals of different nanoparticle concentrations (0.5 to 5%). At high nano-fluid concentrations, our research findings indicate that hydrodynamic and thermal performances are considerably improved for all Reynolds numbers because of the strong chaotic flow. The mass fraction visualization shows that the suggested design has a fast thermal mixing rate that approaches 0.99%. As a consequence of the thermal and hydrodynamic processes, under the effect of chaotic advection, the creation of entropy governs the second law of thermodynamics. Thus, with the least amount of friction and thermal irreversibilities compared to other studied geometries, the TLCCM arrangement confirmed a significant enhancement in the mixing performance. Full article

(This article belongs to the Collection Micromixers: Analysis, Design and Fabrication)

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13 pages, 2708 KiB

Open AccessArticle

Fused Deposition Modeling of Chemically Resistant Microfluidic Chips in Polyvinylidene Fluoride

by Christof Rein, Leonhard Hambitzer, Zahra Soraya, Han Zhang, Henning J. Jessen, Frederik Kotz-Helmer and Bastian E. Rapp

Micromachines 2024, 15(11), 1391; https://doi.org/10.3390/mi15111391 - 17 Nov 2024

Abstract

Fused deposition modeling (FDM) is well suited for microfluidic prototyping due to its low investment cost and a wide range of accessible materials. Nevertheless, most commercial FDM materials exhibit low chemical and thermal stability. This reduces the scope of applications and limits their [...] Read more.

Fused deposition modeling (FDM) is well suited for microfluidic prototyping due to its low investment cost and a wide range of accessible materials. Nevertheless, most commercial FDM materials exhibit low chemical and thermal stability. This reduces the scope of applications and limits their use in research and development, especially for on-chip chemical synthesis. In this paper, we present FDM fabrication of microfluidic chips with polyvinylidene fluoride (PVDF) for applications that require high thermal or chemical resistance. Embedded microchannels with a minimum channel width and heights of ~200 µm × 200 µm were fabricated, and the resistance against common solvents was analyzed. A procedure was developed to increase the optical transmission to result in translucent components by printing on glass. Chips for fluid mixing were printed, as well as microreactors that were packed with a catalytically active phase and used for acetal deprotection with a conversion of more than 99%. By expanding the use of fluorinated polymers to FDM printing, previously challenging microfluidic applications will be conducted with ease at the lab scale. Full article

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12 pages, 21486 KiB

Open AccessArticle

Laser Cutting of Non-Woven Fabric Using UV Nanosecond Pulsed Laser

by Jiajun Fu, Chao Liu, Runhan Zhao, Huixin Wang, Zhongjie Yu and Qinghua Wang

Micromachines 2024, 15(11), 1390; https://doi.org/10.3390/mi15111390 - 17 Nov 2024

Abstract

The efficient cutting of non-woven fabric shows great significance to the development of the textile industry. In recent years, laser cutting technology has been widely applied in the clothing industry due to its high efficiency and cutting quality. In this work, a UV [...] Read more.

The efficient cutting of non-woven fabric shows great significance to the development of the textile industry. In recent years, laser cutting technology has been widely applied in the clothing industry due to its high efficiency and cutting quality. In this work, a UV nanosecond pulsed laser with a wavelength of 355 nm and a max power of 6.5 W is used to cut non-woven fabric with a thickness of 0.15 mm. The variation of kerf width, surface morphology, and chemical contents are investigated under different laser processing parameters, and the optimal processing parameter is determined. The experimental results demonstrate that the degree of crystallization and chemical composition of the kerf on the non-woven fabric surface is significantly influenced by laser cutting parameters such as laser scanning speed (from 100 to 700 mm/s) and frequency (from 20 to 70 kHz). The scanning speed of 500 mm/s and frequency of 30 kHz are considered the best parameters for achieving abundant energy for the complete and efficient cutting of non-woven fabric. In addition, the level of carbonization and oxidation reaches a relatively low value, and the kerf width is 0.214 mm, which is considered a reasonable value under the optimal processing parameters, showing high cutting quality. Furthermore, the effect of different cutting treatments on surface morphology and chemical contents is also studied. The experimental results present that the non-woven fabric cut by laser possesses a flat kerf, showing a similar effect to that of scissor cutting. Moreover, due to the programmability of laser processing patterns, it is possible to create more intricate designs on non-woven fabric. This facilitates the application and promotion of laser-cut non-woven fabrics. These results can provide a certain reference for laser cutting in the textile industry and are expected to allow for the cutting of high-quality kerf with low carbonization and oxidation. Full article

(This article belongs to the Special Issue Advancement of Laser Technology from Materials Processing to Nano/Micro Fabrications)

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