Micromachines

21 pages, 7140 KiB

Open AccessArticle

Deep Learning-Assisted Smartphone-Based Electrochemiluminescence Visual Monitoring Biosensor: A Fully Integrated Portable Platform

by Manish Bhaiyya, Prakash Rewatkar, Amit Pimpalkar, Dravyansh Jain, Sanjeet Kumar Srivastava, Jitendra Zalke, Jayu Kalambe, Suresh Balpande, Pawan Kale, Yogesh Kalantri and Madhusudan B. Kulkarni

Micromachines 2024, 15(8), 1059; https://doi.org/10.3390/mi15081059 - 22 Aug 2024

Cited by 2 | Viewed by 4050

Abstract

A novel, portable deep learning-assisted smartphone-based electrochemiluminescence (ECL) cost-effective (~10$) sensing platform was developed and used for selective detection of lactate. Low-cost, fast prototyping screen printing and wax printing methods with paper-based substrate were used to fabricate miniaturized single-pair electrode ECL platforms. The [...] Read more.

A novel, portable deep learning-assisted smartphone-based electrochemiluminescence (ECL) cost-effective (~10$) sensing platform was developed and used for selective detection of lactate. Low-cost, fast prototyping screen printing and wax printing methods with paper-based substrate were used to fabricate miniaturized single-pair electrode ECL platforms. The lab-made 3D-printed portable black box served as a reaction chamber. This portable platform was integrated with a smartphone and a buck-boost converter, eliminating the need for expensive CCD cameras, photomultiplier tubes, and bulky power supplies. This advancement makes this platform ideal for point-of-care testing applications. Foremost, the integration of a deep learning approach served to enhance not just the accuracy of the ECL sensors, but also to expedite the diagnostic procedure. The deep learning models were trained (3600 ECL images) and tested (900 ECL images) using ECL images obtained from experimentation. Herein, for user convenience, an Android application with a graphical user interface was developed. This app performs several tasks, which include capturing real-time images, cropping them, and predicting the concentration of required bioanalytes through deep learning. The device’s capability to work in a real environment was tested by performing lactate sensing. The fabricated ECL device shows a good liner range (from 50 µM to 2000 µM) with an acceptable limit of detection value of 5.14 µM. Finally, various rigorous analyses, including stability, reproducibility, and unknown sample analysis, were conducted to check device durability and stability. Therefore, the developed platform becomes versatile and applicable across various domains by harnessing deep learning as a cutting-edge technology and integrating it with a smartphone. Full article

(This article belongs to the Special Issue Biosensors for Biomedical and Environmental Applications, Third Edition)

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13 pages, 3031 KiB

Open AccessCommunication

Enhancing Flexible Neural Probe Performance via Platinum Deposition: Impedance Stability under Various Conditions and In Vivo Neural Signal Monitoring

by Daerl Park, Hyeonyeong Jeong, Jungsik Choi, Juyeon Han, Honglin Piao, Jaehyun Kim, Seonghoon Park, Mingu Song, Dowoo Kim, Jaesuk Sung, Eunji Cheong and Heonjin Choi

Micromachines 2024, 15(8), 1058; https://doi.org/10.3390/mi15081058 - 22 Aug 2024

Viewed by 850

Abstract

Monitoring neural activity in the central nervous system often utilizes silicon-based microelectromechanical system (MEMS) probes. Despite their effectiveness in monitoring, these probes have a fragility issue, limiting their application across various fields. This study introduces flexible printed circuit board (FPCB) neural probes characterized [...] Read more.

Monitoring neural activity in the central nervous system often utilizes silicon-based microelectromechanical system (MEMS) probes. Despite their effectiveness in monitoring, these probes have a fragility issue, limiting their application across various fields. This study introduces flexible printed circuit board (FPCB) neural probes characterized by robust mechanical and electrical properties. The probes demonstrate low impedance after platinum coating, making them suitable for multiunit recordings in awake animals. This capability allows for the simultaneous monitoring of a large population of neurons in the brain, including cluster data. Additionally, these probes exhibit no fractures, mechanical failures, or electrical issues during repeated-bending tests, both during handling and monitoring. Despite the possibility of using this neural probe for signal measurement in awake animals, simply applying a platinum coating may encounter difficulties in chronic tests and other applications. Furthermore, this suggests that FPCB probes can be advanced by any method and serve as an appropriate type of tailorable neural probes for monitoring neural systems in awake animals. Full article

(This article belongs to the Special Issue Biosensors for Diagnostic and Detection Applications, 2nd Edition)

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(a) Schematic image of N32-1-b probe. (b) Schematic image of electro-deposition method of platinum. (c) Real image of electro-deposition method of platinum. Full article ">Figure 2
(a) Mechanical test device; (b) schematic image of mechanical test setting. (c) Real image of side view (left) and top view (right) of the initial state of the bending test. (d) Real image of side view (left) and top view (right) of the bending state of the bending test. Full article ">Figure 3
(a) SEM image of the electrode of N32-1-b probe (left). EDS mapping data for the same image (right). Orange for copper, and yellow for gold. (b) SEM image of the electrode of N32-1-b probe (left) after electrodeposition of platinum. EDS mapping data for the same image (right). Orange for copper, yellow for gold, and light blue for platinum. (c) Average impedance data of 32 channels from reference N32-1-b electrode (d) Average impedance data of 32 channels from platinum-coated N32-1-b electrode (e) Impedance distribution at 1 kHZ of reference N32-1-b electrode (left) and impedance distribution at 1 kHZ of platinum-coated N32-1-b electrode (right). ‘****’ indicates that the observed differences between the groups are highly statistically significant, with a p-value of less than 0.0001. Full article ">Figure 4
(a) Box plot of impedance data before mechanical test (0 times for red) and after mechanical test (250 times for green, 500 times for blue). The sample-by-sample variability and ANOVA test results are shown at the bottom. (b) Box plot of impedance data before thermal test (room temperature for red) and after thermal test (150 °C for green, 175 °C for blue). The sample-by-sample variability and ANOVA test result are shown at the bottom. (c) Box plot of impedance data before chemical test (neutral for red) and after chemical test (alkaline for green, acidic for blue). The sample-by-sample variability and ANOVA test result are shown at the bottom. ‘ns’ indicates that the observed differences between the groups are not statistically significant, with a p-value over than 0.05. ‘*’ indicates that the observed differences between the groups are statistically significant, with a p-value of less than 0.05. ‘****’ indicates that the observed differences between the groups are highly statistically significant, with a p-value of less than 0.0001. Full article ">Figure 5
Simultaneous single-unit recording from multiple neurons using the neural probe. (a) Schematic of neural recording using the probe (left) and example recording site (right). Orange, DiI Fluorescence in the VPm thalamus. (b) Representative clusters of putative action potentials recorded with the probe. (c) Autocorrelation of a unit spike times. (d) Representative spike waveforms of two units recorded from four adjacent electrode sites. (e) Raster plot of neural spikes from total of 19 units. (f) Schematic of firing recording in the VPm thalamus upon stimulation before and after whisker cutting (top); example of motor movements (middle) and spikes recorded in VPm (bottom). (g) Representative raster plots (top) and PSTH (bottom) of a responsive neuron before (left) and after (right) whisker cutting. Gray line—duration of motor movement. Note that whisker cutting abolished VPm spikes upon stimulation, indicating that the signals are indeed neuronal firings. Full article ">Figure 6
Single-unit recording in awake, head-fixed animal. (a) Probe implantation for awake, head-fixed recording. (b) Schematic illustration of head-fixed recording. (c) Representative activity clusters of 2 electrodes in an awake mouse after implantation. (d) Representative autocorrelogram of unit 1. (e) Representative spike waveforms of a unit recorded from four adjacent electrode sites at day 1 (top) and day 14 (bottom). (f) Representative plot of neural spikes from total of 14 units. The red line is the units 1 day after implantation, and the blue line is the units 14 days after implantation. Full article ">

21 pages, 3902 KiB

Open AccessBrief Report

Enhancing Magnetic Micro- and Nanoparticle Separation with a Cost-Effective Microfluidic Device Fabricated by Laser Ablation of PMMA

by Cristian F. Rodríguez, Paula Guzmán-Sastoque, Carolina Muñoz-Camargo, Luis H. Reyes, Johann F. Osma and Juan C. Cruz

Micromachines 2024, 15(8), 1057; https://doi.org/10.3390/mi15081057 - 22 Aug 2024

Cited by 1 | Viewed by 1416

Abstract

Superparamagnetic iron oxide micro- and nanoparticles have significant applications in biomedical and chemical engineering. This study presents the development and evaluation of a novel low-cost microfluidic device for the purification and hyperconcentration of these magnetic particles. The device, fabricated using laser ablation of [...] Read more.

Superparamagnetic iron oxide micro- and nanoparticles have significant applications in biomedical and chemical engineering. This study presents the development and evaluation of a novel low-cost microfluidic device for the purification and hyperconcentration of these magnetic particles. The device, fabricated using laser ablation of polymethyl methacrylate (PMMA), leverages precise control over fluid dynamics to efficiently separate magnetic particles from non-magnetic ones. We assessed the device’s performance through Multiphysics simulations and empirical tests, focusing on the separation of magnetite nanoparticles from blue carbon dots and magnetite microparticles from polystyrene microparticles at various total flow rates (TFRs). For nanoparticle separation, the device achieved a recall of up to 93.3 ± 4% and a precision of 95.9 ± 1.2% at an optimal TFR of 2 mL/h, significantly outperforming previous models, which only achieved a 50% recall. Microparticle separation demonstrated an accuracy of 98.1 ± 1% at a TFR of 2 mL/h in both simulations and experimental conditions. The Lagrangian model effectively captured the dynamics of magnetite microparticle separation from polystyrene microparticles, with close agreement between simulated and experimental results. Our findings underscore the device’s robust capability in distinguishing between magnetic and non-magnetic particles at both micro- and nanoscales. This study highlights the potential of low-cost, non-cleanroom manufacturing techniques to produce high-performance microfluidic devices, thereby expanding their accessibility and applicability in various industrial and research settings. The integration of a continuous magnet, as opposed to segmented magnets in previous designs, was identified as a key factor in enhancing magnetic separation efficiency. Full article

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Computational domain and boundary conditions. (a) Computational domain, and mesh used for the simulation. (b) Microfluidic device manufactured in PMMA using laser ablation. The particle inlet is shown in green and labeled ‘1’, and the water buffer inlet, facilitating the washing and separation of magnetic from non-magnetic particles, is in blue and labeled ‘2’. The outlet, marked in red and denoted by ‘3’, is where non-magnetic particles exit first, followed by magnetic particles after the magnet is removed. Full article ">Figure 2
Manufacturing process of microfluidic devices using CO2 laser ablation in PMMA. (1) The microfluidic device is manufactured in AutoCAD (AutoDesk Inc., Mill Valley, CA, USA). (2) The design is transferred to a CO2 laser system for engraving and cutting. A 2 mm-thick PMMA sheet is engraved to a depth of 1 mm to create the microfluidic channels, while a 4 mm-thick PMMA sheet is cut to form the inlets and outlets. (3) Then, PMMA layers are cleaned with a 70% ethanol solution to remove any residues. (4) Next, layers are bonded using 96% ethanol, pressure, and heat at 110 °C for 3 min. (5) Finally, the inlets and outlets are assembled into the microfluidic device. Full article ">Figure 3
Synthesis and functionalization of magnetite micro- and nanoparticles. (a) Schematic of the magnetite micro- and nanoparticle synthesis using the coprecipitation technique. The process involves the preparation of an iron chloride solution, followed by the addition of NaOH. Rapid addition yields micro-sized particles (~2405 nm), while slow, dropwise addition results in nano-sized particles (~155 nm). (b) Silanization of magnetite nanoparticles to functionalize their surface and facilitate further modifications. (c) Subsequent labeling of silanized magnetite nanoparticles with rhodamine B (Rhod-B). (d) Synthesis of carbon dots through a separate process involving heating, sonication, and filtration, yielding purified carbon dots. Full article ">Figure 4
Evaluation of magnetic nanoparticle separation microfluidic device. (a) Simulated magnetic flux density distribution around the continuous magnet. (b) Distribution of the magnetic scalar potential across the microfluidic device, indicating areas of maximum potential (up to ±2 amperes). (c) Trajectory simulation of magnetic nanoparticles in the microfluidic channel, demonstrating their response to the applied magnetic field. (d) Photographic evidence of nanoparticle retention within the microfluidic device, aligning with areas of high magnetic flux density. (e) Comparative bar graph showcasing recall, precision, and accuracy metrics for nanoparticle separation at varying total flow rates (2, 20, and 200 mL/h), as obtained from both in silico simulations (dark shades) and experimental results (light shades). Full article ">Figure 5
Microparticle separation efficacy: (a) Fluorescence microscope images: non-magnetic polystyrene particles exhibit red fluorescence, while magnetite particles are non-fluorescent and visible in the transmitted BF (Bright Field) overlay. Scale-bar 50 <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> </semantics></math>. (b) Analysis of recall, precision, and accuracy, derived from the fluorescence microscope images, illustrating the device’s performance. Full article ">Figure 6
Microparticle sedimentation in microchannels: Bright Field and fluorescent images show minimal sedimentation of rhodamine B-labeled polystyrene microparticles, primarily in curved regions. The sedimentation is minimal and does not significantly obstruct the microchannel or impact the device’s functionality. Black arrows show the direction flow. Full article ">Figure 7
SWOT analysis of the magnetic separator microfluidic device. Strengths (S), weaknesses (W), opportunities (O), and threats (T). Full article ">

13 pages, 20047 KiB

Open AccessArticle

Bi-Directional and Operand-Controllable In-Memory Computing for Boolean Logic and Search Operations with Row and Column Directional SRAM (RC-SRAM)

by Han Xiao, Ruiyong Zhao, Yulan Liu, Yuanzhen Liu and Jing Chen

Micromachines 2024, 15(8), 1056; https://doi.org/10.3390/mi15081056 - 22 Aug 2024

Viewed by 785

Abstract

The von Neumann architecture is no longer sufficient for handling large-scale data. In-memory computing has emerged as the potent method for breaking through the memory bottleneck. A new 10T SRAM bitcell with row and column control lines called RC-SRAM is proposed in this [...] Read more.

The von Neumann architecture is no longer sufficient for handling large-scale data. In-memory computing has emerged as the potent method for breaking through the memory bottleneck. A new 10T SRAM bitcell with row and column control lines called RC-SRAM is proposed in this article. The architecture based on RC-SRAM can achieve bi-directional and operand-controllable logic-in-memory and search operations through different signal configurations, which can comprehensively respond to various occasions and needs. Moreover, we propose threshold-controlled logic gates for sensing, which effectively reduces the circuit area and improves accuracy. We validate the RC-SRAM with a 28 nm CMOS technology, and the results show that the circuits are not only full featured and flexible for customization but also have a significant increase in the working frequency. At VDD = 0.9 V and T = 25 °C, the bi-directional search frequency is up to 775 MHz and 567 MHz, and the speeds for row and column Boolean logic reach 759 MHz and 683 MHz. Full article

(This article belongs to the Special Issue Emerging Memory Materials and Devices)

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13 pages, 31150 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Innovative Integration of Dual Quantum Cascade Lasers on Silicon Photonics Platform

by Dongbo Wang, Harindra Kumar Kannojia, Pierre Jouy, Etienne Giraud, Kaspar Suter, Richard Maulini, David Gachet, Léo Hetier, Geert Van Steenberge and Bart Kuyken

Micromachines 2024, 15(8), 1055; https://doi.org/10.3390/mi15081055 - 22 Aug 2024

Viewed by 1497

Abstract

For the first time, we demonstrate the hybrid integration of dual distributed feedback (DFB) quantum cascade lasers (QCLs) on a silicon photonics platform using an innovative 3D self-aligned flip-chip assembly process. The QCL waveguide geometry was predesigned with alignment fiducials, enabling a sub-micron [...] Read more.

For the first time, we demonstrate the hybrid integration of dual distributed feedback (DFB) quantum cascade lasers (QCLs) on a silicon photonics platform using an innovative 3D self-aligned flip-chip assembly process. The QCL waveguide geometry was predesigned with alignment fiducials, enabling a sub-micron accuracy during assembly. Laser oscillation was observed at the designed wavelength of 7.2 μm, with a threshold current of 170 mA at room temperature under pulsed mode operation. The optical output power after an on-chip beam combiner reached sub-milliwatt levels under stable continuous wave operation at 15 °C. The specific packaging design miniaturized the entire light source by a factor of 100 compared with traditional free-space dual lasers module. Divergence values of 2.88 mrad along the horizontal axis and 1.84 mrad along the vertical axis were measured after packaging. Promisingly, adhering to i-line lithography and reducing the reliance on high-end flip-chip tools significantly lowers the cost per chip. This approach opens new avenues for QCL integration on silicon photonic chips, with significant implications for portable mid-infrared spectroscopy devices. Full article

(This article belongs to the Special Issue The 15th Anniversary of Micromachines)

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9 pages, 31124 KiB

Open AccessArticle

Fabrication of Two-Layer Microfluidic Devices with Porous Electrodes Using Printed Sacrificial Layers

by Kosuke Ino, An Konno, Yoshinobu Utagawa, Taiyo Kanno, Kazuyuki Iwase, Hiroya Abe and Hitoshi Shiku

Micromachines 2024, 15(8), 1054; https://doi.org/10.3390/mi15081054 - 22 Aug 2024

Viewed by 1052

Abstract

Two-layer microfluidic devices with porous membranes have been widely used in bioapplications such as microphysiological systems (MPS). Porous electrodes, instead of membranes, have recently been incorporated into devices for electrochemical cell analysis. Generally, microfluidic channels are prepared using soft lithography and assembled into [...] Read more.

Two-layer microfluidic devices with porous membranes have been widely used in bioapplications such as microphysiological systems (MPS). Porous electrodes, instead of membranes, have recently been incorporated into devices for electrochemical cell analysis. Generally, microfluidic channels are prepared using soft lithography and assembled into two-layer microfluidic devices. In addition to soft lithography, three-dimensional (3D) printing has been widely used for the direct fabrication of microfluidic devices because of its high flexibility. However, this technique has not yet been applied to the fabrication of two-layer microfluidic devices with porous electrodes. This paper proposes a novel fabrication process for this type of device. In brief, Pluronic F-127 ink was three-dimensionally printed in the form of sacrificial layers. A porous Au electrode, fabricated by sputtering Au on track-etched polyethylene terephthalate membranes, was placed between the top and bottom sacrificial layers. After covering with polydimethylsiloxane, the sacrificial layers were removed by flushing with a cold solution. To the best of our knowledge, this is the first report on the sacrificial approach-based fabrication of two-layer microfluidic devices with a porous electrode. Furthermore, the device was used for electrochemical assays of serotonin and could successfully measure concentrations up to 5 µM. In the future, this device can be used for MPS applications. Full article

(This article belongs to the Special Issue Microelectrodes and Microdevices for Electrochemical Applications)

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Schematic of the fabrication process of the two-layer microfluidics device with the porous electrode. Pluronic F-127 was used as the sacrificial ink. (i) Preparation of a cured PDMS film as the 1st layer. (ii) Printing of the sacrificial layer of the Pluronic F-127 ink for the bottom channel. (iii) Pouring the uncured PDMS up to the height of the bottom channel. (iv) Setting the porous Au electrode on the device. The PET porous membrane side is at the top. (v) Printing of the sacrificial layer of the Pluronic F-127 ink for the top channel. (vi) Pouring the uncured PDMS to fill the entire area. (vii) Curing the PDMS layers. (viii) Flushing out the sacrificial layers. Full article ">Figure 2
Porous Au electrode. (a) Schematic illustration and bright-field images of the (b) top and (c) cross-section of the porous electrodes. Full article ">Figure 3
Two-layer microfluidic devices with porous electrodes using the proposed strategy. (a) Fabrication process. (i) Setting the 1st PDMS layer. (ii) Printing the bottom channel using the Pluronic F-127 ink. (iii) Preparing the 2nd PDMS layer and setting the porous electrode membrane. (iv) Printing the top channel using the Pluronic F-127 ink. (v) Preparing the 3rd PDMS layer. (vi) Flushing out the sacrificial layers and cutting the device to be removed from the dish. (b) Cross-sectional image of the two-layer microfluidic device with the porous electrode. (c) Time-course images of the device at 0, 5, and 10 s after introducing the blue ink. Full article ">Figure 4
CV of ferrocenemethanol using the porous electrode in the device. (a) Cyclic voltammograms of 0, 0.125, 0.25, 0.5, and 1 mM ferrocenemethanol in PBS with 0.1 M KCl. Scan rate: 100 mV/s. (b) Calibration plots using the peak currents of the cyclic voltammograms. Full article ">Figure 5
CV of serotonin using the porous electrode (a,b) before and (c,d) after incorporating it into the device. (a,c) Cyclic voltammograms of 0, 5, 10, 20, and 30 µM serotonin in PBS. Scan rate: 100 mV/s. The results were obtained from the 2nd CV scan. (b,d) Calibration plots of the cyclic voltammograms using the currents at 0.5 V. Full article ">

16 pages, 6988 KiB

Open AccessArticle

Online Handwriting Recognition Method with a Non-Inertial Reference Frame Based on the Measurement of Linear Accelerations and Differential Geometry: An Alternative to Quaternions

by Griselda Stephany Abarca Jiménez, Carmen Caritina Muñoz Garnica, Mario Alfredo Reyes Barranca, Jesús Mares Carreño, Manuel Vladimir Vega Blanco and Francisco Gutiérrez Galicia

Micromachines 2024, 15(8), 1053; https://doi.org/10.3390/mi15081053 - 21 Aug 2024

Viewed by 741

Abstract

This work describes a mathematical model for handwriting devices without a specific reference surface (SRS). The research was carried out on two hypotheses: the first considers possible circular segments that could be made during execution for the reconstruction of the trace, and the [...] Read more.

This work describes a mathematical model for handwriting devices without a specific reference surface (SRS). The research was carried out on two hypotheses: the first considers possible circular segments that could be made during execution for the reconstruction of the trace, and the second is the combination of lines and circles. The proposed system has no flat reference surface, since the sensor is inside the pencil that describes the trace, not on the surface as in tablets or cell phones. An inertial sensor was used for the measurements, in this case, a commercial Micro-Electro Mechanical sensor of linear acceleration. The tracking device is an IMU sensor and a processing card that allows inertial measurements of the pen during on-the-fly tracing. It is essential to highlight that the system has a non-inertial reference frame. Comparing the two proposed models shows that it is possible to construct shapes from curved lines and that the patterns obtained are similar to what is recognized; this method provides an alternative to quaternion calculus for poorly specified orientation problems. Full article

(This article belongs to the Special Issue Accelerometer and Magnetometer: From Fundamentals to Applications, 2nd Edition)

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Graphical abstract

17 pages, 12176 KiB

Open AccessArticle

Fabrication of Medium Mn Advanced High-Strength Steel with Excellent Mechanical Properties by Friction Stir Processing

by Yonggang Yang, Wangnan Zuo, Yu Liu, Yunzong Ge, Zhiqiang Yang, Jiansheng Han and Zhenli Mi

Micromachines 2024, 15(8), 1052; https://doi.org/10.3390/mi15081052 - 21 Aug 2024

Viewed by 788

Abstract

Friction stir processing (FSP) manufacturing technology was used to fabricate medium Mn advanced high-strength steel in this study. The mechanical properties and microstructure of the steel fabricated using FSP were investigated. The steel obtained a total elongation of 35.1% and a tensile strength [...] Read more.

Friction stir processing (FSP) manufacturing technology was used to fabricate medium Mn advanced high-strength steel in this study. The mechanical properties and microstructure of the steel fabricated using FSP were investigated. The steel obtained a total elongation of 35.1% and a tensile strength of 1034.6 MPa, which is about 59% higher than that of the steel without FSP. After FSP, a gradient structure occurs along the thickness direction. Specifically, across the thickness direction from the base material zone to the transition zone and finally to the stirring zone, both the grain size and austenite fraction decrease while the dislocation density increases, which results from the simultaneous effect of severe plastic deformation and recrystallization during FSP. Due to the gradient structure, an obvious difference in the strain across the thickness direction of the steel occurs during the deformation process, resulting in significant hetero-deformation-induced (HDI) strengthening. The deformation mechanism analysis reveals that HDI strengthening and dislocation strengthening are the main factors in the improvement in the strength–ductility balance. The obtained knowledge sheds light on the process of fabricating medium Mn steels with excellent properties using FSP manufacturing technology. Full article

(This article belongs to the Special Issue Advanced Manufacturing Technology and Systems, 3rd Edition)

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11 pages, 705 KiB

Open AccessArticle

A Broadband MS-Based Circularly Polarized Antenna Array Using Sequential-Phase Feeding Network

by Hung Pham-Duy, Dat Nguyen-Tien, Thanh Nguyen-Ngoc, Duc-Nguyen Tran-Viet, Thai Nguyen-Dinh, Tuyen Danh Pham and Hung Tran-Huy

Micromachines 2024, 15(8), 1051; https://doi.org/10.3390/mi15081051 - 20 Aug 2024

Viewed by 801

Abstract

This paper introduces the design of a circularly polarized metasurface-based antenna array for C-band satellite applications that owns broadband operation and high gain characteristics. The single radiating element comprises a Y-shape patch and an above-placed 2 × 2 unit-cell metasurface. Further improvement in [...] Read more.

This paper introduces the design of a circularly polarized metasurface-based antenna array for C-band satellite applications that owns broadband operation and high gain characteristics. The single radiating element comprises a Y-shape patch and an above-placed 2 × 2 unit-cell metasurface. Further improvement in operating bandwidth and broadside gain is achieved by arranging four single elements in a 2 × 2 configuration and a sequential-phase feed network. A prototype has been fabricated and measured to validate the feasibility of the proposed antenna array. The measured operating bandwidth is 20% (4.50–5.50 GHz), which is an overlap between a −10 dB impedance bandwidth of 29.8% (4.50–5.99 GHz) and a 3 dB axial ratio bandwidth of 20% (4.50–5.50 GHz). Across this operating band, the peak broadside gain is 10.5 dBi. Compared with the recently published studies, the proposed array is a prominent design for producing a wide operating bandwidth and relatively high gains while maintaining the overall compact dimensions. Full article

(This article belongs to the Special Issue Micro and Smart Devices and Systems, 3rd Edition)

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17 pages, 15283 KiB

Open AccessArticle

Development of a Fast Positioning Platform with a Large Stroke Based on a Piezoelectric Actuator for Precision Machining

by Gaofeng Hu, Wendong Xin, Min Zhang, Guangjun Chen, Jia Man and Yanling Tian

Micromachines 2024, 15(8), 1050; https://doi.org/10.3390/mi15081050 - 19 Aug 2024

Cited by 1 | Viewed by 859

Abstract

In this paper, a fast positioning platform (FPP) is proposed, able to meet simultaneously the requirements of large stroke and high frequency response, developed based on a PZT (piezoelectric actuator) and a quad-parallel flexible mechanism, for application in precision machining. The FPP is [...] Read more.

In this paper, a fast positioning platform (FPP) is proposed, able to meet simultaneously the requirements of large stroke and high frequency response, developed based on a PZT (piezoelectric actuator) and a quad-parallel flexible mechanism, for application in precision machining. The FPP is driven by a high-stiffness PZT and guided by a flexible hinge-based mechanism with a quad-parallel flexible hinge. The proposed quad-parallel flexible hinge mechanism can provide excellent planar motion capability with high stiffness and good guiding performance, thus guaranteeing outstanding dynamics characteristics. The mechanical model was established, the input and output characteristics of the FPP were analyzed, and the working range (output displacement and frequency) of the FPP was determined. Based on the mechanical model and the input and output characteristics of the FPP, the design method is described for of the proposed FPP, which is capable of achieving a large stroke while responding at a high frequency. The characteristics of the FPP were investigated using finite element analysis (FEA). Experiments were conducted to examine the performance of the FPP; the natural frequency of the FPP was 1315.6 Hz, while the maximum output displacement and the motion resolution of the FPP in a static state were 53.13 μm and 5 nm, respectively. Step response testing showed that under a step magnitude of 50 μm, the stabilization times for the falling and rising edges of the moving platform were 37 ms and 26 ms, respectively. The tracking errors were about ±1.96 μm and ±0.59 μm when the amplitude and frequency of the signal were 50 μm, 50 Hz and 10 μm, 200 Hz, respectively. The FPP showed excellent performance in terms of fast response and output displacement. The cutting test results indicated that compared with the uncontrolled condition, the values of surface roughness under controlled conditions decreased by 23.9% and 12.7% when the cutting depths were 5 μm and 10 μm, respectively. The developed FPP device has excellent precision machining performance. Full article

(This article belongs to the Special Issue Research Progress of Ultra-Precision Micro-nano Machining)

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24 pages, 5248 KiB

Open AccessArticle

Resonant MEMS Accelerometer with Low Cross-Axis Sensitivity—Optimized Based on BP and NSGA-II Algorithms

by Jiaqi Miao, Pinghua Li, Mingchen Lv, Suzhen Nie, Yang Liu, Ruimei Liang, Weijiang Ma and Xuye Zhuang

Micromachines 2024, 15(8), 1049; https://doi.org/10.3390/mi15081049 - 18 Aug 2024

Cited by 1 | Viewed by 4049

Abstract

This article proposes a low cross-axis sensitivity resonant MEMS(Micro-Electro-Mechanical Systems) accelerometer that is optimized based on the BP and NSGA-II algorithms. When resonant accelerometers are used in seismic monitoring, automotive safety systems, and navigation applications, high immunity and low cross-axis sensitivity are required. [...] Read more.

This article proposes a low cross-axis sensitivity resonant MEMS(Micro-Electro-Mechanical Systems) accelerometer that is optimized based on the BP and NSGA-II algorithms. When resonant accelerometers are used in seismic monitoring, automotive safety systems, and navigation applications, high immunity and low cross-axis sensitivity are required. To improve the high immunity of the accelerometer, a coupling structure is introduced. This structure effectively separates the symmetric and antisymmetric mode frequencies of the DETF resonator and prevents mode coupling. To obtain higher detection accuracy and low cross-axis sensitivity, a decoupling structure is introduced. To find the optimal dimensional parameters of the decoupled structure, the BP and NSGA-II algorithms are used to optimize the dimensional parameters of the decoupled structure. The optimized decoupled structure has an axial stiffness of 6032.21 N/m and a transverse stiffness of 6.29 N/m. The finite element analysis results show that the sensitivity of the accelerometer is 59.1 Hz/g (Y-axis) and 59 Hz/g (X-axis). Cross-axis sensitivity is 0.508% (Y-axis) and 0.339% (X-axis), which is significantly lower than most resonant accelerometers. The coupling structure and optimization method proposed in this paper provide a new solution for designing resonant accelerometers with high interference immunity and low cross-axis sensitivity. Full article

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3 pages, 157 KiB

Open AccessEditorial

Editorial for the Special Issue on Exploring IoT Sensors and Their Applications: Advancements, Challenges, and Opportunities in Smart Environments

by Lei Jing, Yoshinori Matsumoto and Zhan Zhang

Micromachines 2024, 15(8), 1048; https://doi.org/10.3390/mi15081048 - 18 Aug 2024

Viewed by 3909

Abstract

As the editor of the Special Issue on “Exploring IoT Sensors and Their Applications: Advancements, Challenges, and Opportunities in Smart Environments”, I am delighted to present this collection of groundbreaking research that addresses the emerging needs and challenges in the field of IoT [...] Read more.

As the editor of the Special Issue on “Exploring IoT Sensors and Their Applications: Advancements, Challenges, and Opportunities in Smart Environments”, I am delighted to present this collection of groundbreaking research that addresses the emerging needs and challenges in the field of IoT sensors and smart environments [...] Full article

(This article belongs to the Special Issue Exploring IoT Sensors and Their Applications: Advancements, Challenges, and Opportunities in Smart Environments)

14 pages, 4787 KiB

Open AccessArticle

Design and Fabrication of Tryptophan Sensor Using Voltammetric Method

by Mohd Quasim Khan, Khursheed Ahmad and Rais Ahmad Khan

Micromachines 2024, 15(8), 1047; https://doi.org/10.3390/mi15081047 - 18 Aug 2024

Viewed by 869

Abstract

L-tryptophan is an amino acid that significantly impacts metabolic activity in both humans and herbivorous animals. It is also known as a precursor for melatonin and serotonin, and its levels must be regulated in the human body. Therefore, there is a need to [...] Read more.

L-tryptophan is an amino acid that significantly impacts metabolic activity in both humans and herbivorous animals. It is also known as a precursor for melatonin and serotonin, and its levels must be regulated in the human body. Therefore, there is a need to develop a cost-effective, simple, sensitive, and selective method for detecting L-tryptophan. Herein, we report the fabrication of an L-tryptophan sensor using a nickel-doped tungsten oxide ceramic-modified electrode. The Ni-WO₃ was synthesized using simple strategies and characterized by various advanced techniques such as powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoelectron X-ray spectroscopy. Furthermore, a glassy carbon electrode was modified with the synthesized Ni-WO₃ and explored as the L-tryptophan (L-TRP) sensor. Cyclic voltammetry and differential pulse voltammetry were used to investigate the sensing ability of the modified electrode (Ni-WO₃/GC). The Ni-WO₃/GC exhibited an excellent limit of detection of 0.4 µM with a good dynamic linear range. The Ni-WO₃/GC also demonstrated excellent selectivity in the presence of various electroactive molecules. The Ni-WO₃/GC also showed decent reproducibility, repeatability, stability, and storage stability. This work proposes the fabrication of novel Ni-WO₃/GC for the sensing of L-tryptophan. So far, no report is available on the use of Ni-WO₃/GC for the sensing of L-TRP. This is the first report on the use of Ni-WO₃/GC for the sensing of L-TRP sensing applications. Full article

(This article belongs to the Special Issue Biosensors for Biomedical and Environmental Applications, Third Edition)

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14 pages, 2513 KiB

Open AccessArticle

Electromigration Analysis for Interconnects Using Improved Graph Convolutional Network with Edge Feature Aggregation

by Ruqing Ye and Xiaoming Chen

Micromachines 2024, 15(8), 1046; https://doi.org/10.3390/mi15081046 - 18 Aug 2024

Viewed by 960

Abstract

Electromigration (EM) is a critical reliability issue in integrated circuits and is becoming increasingly significant as fabrication technology nodes continue to advance. The analysis of the hydrostatic stress, which is paramount in electromigration studies, typically involves solving complex physical equations (partial differential equations, [...] Read more.

Electromigration (EM) is a critical reliability issue in integrated circuits and is becoming increasingly significant as fabrication technology nodes continue to advance. The analysis of the hydrostatic stress, which is paramount in electromigration studies, typically involves solving complex physical equations (partial differential equations, or PDEs in this case), which is time consuming, inefficient and not practical for full-chip EM analysis. In this paper, a novel approach is proposed, conceptualizing circuit interconnect trees as a graph within a graph neural network framework. Using finite element solution software, ground truth hydrostatic stress values were obtained to construct a dataset of interconnected trees with hydrostatic stress values for each node. An improved Graph Convolutional Network (GCN) augmented with edge feature aggregation and attention mechanism was then trained employing the dataset, yielding a model capable of predicting hydrostatic stress values for nodes in an interconnect tree. The results show that our model demonstrated a 15% improvement in the Root Mean Square Error (RMSE) compared to the original GCN model and improved the solution speed greatly compared to traditional finite element software. Full article

(This article belongs to the Special Issue Emerging Packaging and Interconnection Technology)

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23 pages, 6560 KiB

Open AccessArticle

Development of a Portable Residual Chlorine Detection Device with a Combination of Microfluidic Chips and LS-BP Algorithm to Achieve Accurate Detection of Residual Chlorine in Water

by Tongfei Wang, Jiping Niu, Haoran Pang, Xiaoyu Meng, Ruqian Sun and Jiaqing Xie

Micromachines 2024, 15(8), 1045; https://doi.org/10.3390/mi15081045 - 18 Aug 2024

Viewed by 966

Abstract

Chlorine is widely used for sterilization and disinfection of water, but the presence of excess residual chlorine in water poses a substantial threat to human health. At present, there is no portable device which can achieve accurate, rapid, low-cost, and convenient detection of [...] Read more.

Chlorine is widely used for sterilization and disinfection of water, but the presence of excess residual chlorine in water poses a substantial threat to human health. At present, there is no portable device which can achieve accurate, rapid, low-cost, and convenient detection of residual chlorine in water. Therefore, it is necessary to develop a device that can perform accurate, rapid, low-cost, and convenient detection of residual chlorine in water. In this study, a portable residual chlorine detection device was developed. A microfluidic chip was studied to achieve efficient mixing of two-phase flow. This microfluidic chip was used for rapid mixing of reagents in the portable residual chlorine detection device, reducing the consumption of reagents, detection time, and device volume. A deep learning algorithm was proposed for predicting residual chlorine concentration in water, achieving precise detection. Firstly, the microfluidic chip structure for detecting mixed reagents was optimized, and the microfluidic chip was fabricated by a 3D-printing method. Secondly, a deep learning (LS-BP) algorithm was constructed and proposed for predicting residual chlorine concentration in water, which can realize dual-channel signal reading. Thirdly, the corresponding portable residual chlorine detection device was developed, and the detection device was compared with residual chlorine detection devices and methods in other studies. The comparison results indicate that the portable residual chlorine detection device has high detection accuracy, fast detection speed, low cost, and good convenience. The excellent performance of the portable residual chlorine detection device makes it suitable for detecting residual chlorine in drinking water, swimming pool water, aquaculture and other fields. Full article

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

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12 pages, 5666 KiB

Open AccessArticle

Research on the Key Technology of a Fluorescence Detection Device Using the RT-LAMP Method for Instant Detection

by Hongzhuang Guo, Ping Gong, Tingting Sun, Xin Wang and Hao Zhang

Micromachines 2024, 15(8), 1044; https://doi.org/10.3390/mi15081044 - 18 Aug 2024

Viewed by 784

Abstract

As of 31 October 2023, there have been 771,795,258 confirmed cases of COVID-19 globally. Developing simple, portable, and reliable testing devices has become increasingly important. This paper presents a point-of-care testing (POCT) device for COVID-19 based on the dual-excitation fluorescence RT-LAMP method, which [...] Read more.

As of 31 October 2023, there have been 771,795,258 confirmed cases of COVID-19 globally. Developing simple, portable, and reliable testing devices has become increasingly important. This paper presents a point-of-care testing (POCT) device for COVID-19 based on the dual-excitation fluorescence RT-LAMP method, which is derived from the principles of RT-LAMP-based COVID-19 detection kits available in the market. The key design solutions of the device were simulated and modeled. Key performance metrics such as detection repeatability and linearity were validated. Comparative experiments with the RT-qPCR detection method were conducted to verify the accuracy and reliability of the device. Additionally, the device’s detection sensitivity and accuracy were assessed. Experimental results show that the repeatability coefficient of variation (CV) value is ≤0.09%; the linearity R² for the FAM channel is 0.9977 and that for the HEX channel is 0.9899; it exhibits good anti-interference performance, with negligible cross-channel interference; the temperature stability is ±0.062 °C, the temperature accuracy is less than 0.2 °C, and there is no significant temperature overshoot during the heating process. Compared with the real-time quantitative PCR (RT-qPCR) instrument, the positive agreement rate is 100% and the negative agreement rate is 95.0%. This research provides a foundational basis for the development of equipment for the prevention of infectious diseases and clinical diagnostics. Full article

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11 pages, 4595 KiB

Open AccessCommunication

Nonlinear Optical Response of Au/CsPbI₃ Quantum Dots and Its Laser Modulation Characteristics at 2.7 μm

by Mengqi Lv, Jin Zhao, Leilei Guo, Yanxu Zhang, Qiuling Zhao, Lihua Teng, Maorong Wang, Shuaiyi Zhang and Xia Wang

Micromachines 2024, 15(8), 1043; https://doi.org/10.3390/mi15081043 - 18 Aug 2024

Viewed by 890

Abstract

A passively Q-switched Er:YAP laser of 2.7 µm, utilizing Au-doped CsPbI₃ quantum dots (QDs) as a saturable absorber (SA), was realized. It was operated stably with a minimum pulse width of 185 ns and a maximum repetition rate of 480 kHz. The [...] Read more.

A passively Q-switched Er:YAP laser of 2.7 µm, utilizing Au-doped CsPbI₃ quantum dots (QDs) as a saturable absorber (SA), was realized. It was operated stably with a minimum pulse width of 185 ns and a maximum repetition rate of 480 kHz. The maximum pulse energy and the maximum peak power were 0.6 μJ and 2.9 W, respectively, in the Q-switched operation. The results show that the CsPbI₃ QDs SA exhibits remarkable laser modulation properties at ~3 μm. Full article

(This article belongs to the Special Issue Optical and Laser Material Processing)

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11 pages, 8347 KiB

Open AccessArticle

Study on 1550 nm Human Eye-Safe High-Power Tunnel Junction Quantum Well Laser

by Qi Wu, Dongxin Xu, Xuehuan Ma, Zaijin Li, Yi Qu, Zhongliang Qiao, Guojun Liu, Zhibin Zhao, Lina Zeng, Hao Chen, Lin Li and Lianhe Li

Micromachines 2024, 15(8), 1042; https://doi.org/10.3390/mi15081042 - 17 Aug 2024

Viewed by 911

Abstract

Falling within the safe bands for human eyes, 1550 nm semiconductor lasers have a wide range of applications in the fields of LIDAR, fast-ranging long-distance optical communication, and gas sensing. The 1550 nm human eye-safe high-power tunnel junction quantum well laser developed in [...] Read more.

Falling within the safe bands for human eyes, 1550 nm semiconductor lasers have a wide range of applications in the fields of LIDAR, fast-ranging long-distance optical communication, and gas sensing. The 1550 nm human eye-safe high-power tunnel junction quantum well laser developed in this paper uses three quantum well structures connected by two tunnel junctions as the active region; photolithography and etching were performed to form two trenches perpendicular to the direction of the epitaxial layer growth with a depth exceeding the tunnel junction, and the trenches were finally filled with oxides to reduce the extension current. Finally, a 1550 nm InGaAlAs quantum well laser with a pulsed peak power of 31 W at 30 A (10 KHz, 100 ns) was realized for a single-emitter laser device with an injection strip width of 190 μm, a ridge width of 300 μm, and a cavity length of 2 mm, with a final slope efficiency of 1.03 W/A, and with a horizontal divergence angle of about 13° and a vertical divergence angle of no more than 30°. The device has good slope efficiency, and this 100 ns pulse width can be effectively applied in the fields of fog-transparent imaging sensors and fast headroom ranging radar areas. Full article

(This article belongs to the Special Issue III-V Optoelectronics and Semiconductor Process Technology)

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InAlAs-InP tunnel junction: (a) energy band diagram of tunnel junction (The black lines represent the Ec and Ev, the blue line represents the Ef, and the red lines represent the tunnel junction region.); (b) I–V curve of tunnel junctions at room temperature. Full article ">Figure 2
Structure diagram of 1550 nm semiconductor laser: (a) cross-section of a dual-channel structured tunnel junction semiconductor laser chip; (b) single-emitter laser device structure; (c) SEM image of the exit surface of the device. Full article ">Figure 3
Test results for 1550 nm eye-safe pulse semiconductor laser: (a) P-I-V diagram; (b) a wavelength shift caused by temperature changes; (c) light emission spectrum. Full article ">Figure 4
Spot test for 1550 nm laser. (a) The laser spot at the luminescent surface of the device under a metallurgical microscope; (b) devices for testing laser spots. Full article ">Figure 5
Far-field pattern for 1550 nm laser. (a) Uncollimated; (b) compression along the fast-axis direction with a 200 μm diameter microlens; (c) far-field divergence angles of a 1550 nm laser at 10 W. Full article ">Figure 5 Cont.
Far-field pattern for 1550 nm laser. (a) Uncollimated; (b) compression along the fast-axis direction with a 200 μm diameter microlens; (c) far-field divergence angles of a 1550 nm laser at 10 W. Full article ">

26 pages, 6398 KiB

Open AccessReview

A Systematic Review of Modeling and Simulation for Precision Diamond Wire Sawing of Monocrystalline Silicon

by Ansheng Li, Hongyan Wang, Shunchang Hu, Yu Zhou, Jinguang Du, Lianqing Ji and Wuyi Ming

Micromachines 2024, 15(8), 1041; https://doi.org/10.3390/mi15081041 - 17 Aug 2024

Viewed by 905

Abstract

Precision processing of monocrystalline silicon presents significant challenges due to its unique crystal structure and chemical properties. Effective modeling and simulation are essential for advancing the understanding of the manufacturing process, optimizing design, and refining production parameters to enhance product quality and performance. [...] Read more.

Precision processing of monocrystalline silicon presents significant challenges due to its unique crystal structure and chemical properties. Effective modeling and simulation are essential for advancing the understanding of the manufacturing process, optimizing design, and refining production parameters to enhance product quality and performance. This review provides a comprehensive analysis of the modeling and simulation techniques applied in the precision machining of monocrystalline silicon using diamond wire sawing. Firstly, the principles of mathematical analytical model, molecular dynamics, and finite element methods as they relate to monocrystalline silicon processing are outlined. Subsequently, the review explores how mathematical analytical models address force-related issues in this context. Molecular dynamics simulations provide valuable insights into atomic-scale processes, including subsurface damage and stress distribution. The finite element method is utilized to investigate temperature variations and abrasive wear during wire cutting. Furthermore, similarities, differences, and complementarities among these three modeling approaches are examined. Finally, future directions for applying these models to precision machining of monocrystalline silicon are discussed. Full article

(This article belongs to the Section D：Materials and Processing)

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15 pages, 66581 KiB

Open AccessArticle

The Impact of Titanium Hydroxyapatite Doping on the Mechanical and Biological Properties of Photocured Resin

by Xiaopan Li, Chao Yao, Junfu Shen, Siqi Zhu, Yiyun Kong, Chun Yao, Yuankai Zhou and Jing Xia

Micromachines 2024, 15(8), 1040; https://doi.org/10.3390/mi15081040 - 16 Aug 2024

Viewed by 1321

Abstract

Photocured resin materials are widely used in various fields, such as 3D printing, medical applications, and dentistry. However, the strength, wear resistance, and antibacterial properties of photocured resin are relatively limited, rendering it susceptible to potential failures. In this recent study, photocured composite [...] Read more.

Photocured resin materials are widely used in various fields, such as 3D printing, medical applications, and dentistry. However, the strength, wear resistance, and antibacterial properties of photocured resin are relatively limited, rendering it susceptible to potential failures. In this recent study, photocured composite resins incorporating titanium-doped hydroxyapatite (Ti-HAp) were fabricated to investigate their mechanical and biological properties. It was found that the hardness and wear resistance increased with the addition of an appropriate amount of hydroxyapatite (HAp). Specifically, the 6wt%HAp resin demonstrated superior hardness. Compared with the 6wt%HAp resin, the acid resistance and wear resistance improved when an appropriate amount of Ti-HAp was added. Notably, the resin containing 0.56%Ti-HAp demonstrated superior wear resistance. Additionally, the antibacterial performance improved with higher titanium (Ti) content, showcasing a 71.9% improvement in the resin containing 1.37%Ti-HAp compared with the 6wt%HAp resin, alongside commendable remineralization capabilities. In summary, the Ti-HAp composite resin showed enhanced mechanical and biological properties, meeting clinical standards in terms of mechanical and antibacterial properties. Full article

(This article belongs to the Special Issue Advanced Biomanufacturing for Biomedical Engineering Applications, 2nd Edition)

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18 pages, 9544 KiB

Open AccessArticle

Design, Modeling, and Testing of a Long-Stroke Fast Tool Servo Based on Corrugated Flexure Units

by Ning Chen, Zhichao Wen, Jiateng Rong, Chuan Tian and Xianfu Liu

Micromachines 2024, 15(8), 1039; https://doi.org/10.3390/mi15081039 - 15 Aug 2024

Viewed by 720

Abstract

To further enhance the performance of the fast tool servo (FTS) system in terms of stroke, load capacity, and application area, this paper proposes a novel fast tool servo device driven by a voice coil motor (VCM), based on a three-segment uniform corrugated [...] Read more.

To further enhance the performance of the fast tool servo (FTS) system in terms of stroke, load capacity, and application area, this paper proposes a novel fast tool servo device driven by a voice coil motor (VCM), based on a three-segment uniform corrugated flexure (CF) guiding mechanism, with a large stroke, high accuracy, and high dynamics. To describe the unified static characteristics of such device, the compliance matrix method is applied to establish its model, where the influence of CF beam structural parameters on the FTS device is investigated in detail. Furthermore, resolution and positioning accuracy tests are conducted to validate the features of the system. The testing results indicate that the maximum stroke of the FTS device is up to 3.5 mm and the positioning resolution values are 3.6 μm and 2.4 μm for positive and negative stroke, respectively, which further verifies the device’s effectiveness and promising application prospect in ultra-precision microstructure machining. Full article

(This article belongs to the Special Issue Micro and Smart Devices and Systems, 3rd Edition)

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11 pages, 3010 KiB

Open AccessArticle

The Performance and Fabrication of 3D Variable Cross-Section Channel for Passive Microfluidic Control

by Wenjie Qian, Zhou Zhou, Qing Wang, Wei Shi, Manman Xu and Daoheng Sun

Micromachines 2024, 15(8), 1038; https://doi.org/10.3390/mi15081038 - 15 Aug 2024

Viewed by 771

Abstract

Passive fluid control has mostly been used for valves, pumps, and mixers in microfluidic systems. The basic principle is to generate localized losses in special channel structures, such as branches, grooves, or spirals. The flow field in two-dimensional space can be easily calculated [...] Read more.

Passive fluid control has mostly been used for valves, pumps, and mixers in microfluidic systems. The basic principle is to generate localized losses in special channel structures, such as branches, grooves, or spirals. The flow field in two-dimensional space can be easily calculated using the typical Stokes formula, but it is challenging in three-dimensional space. Moreover, the flow field with periodic variable cross-sections channeled of polyhedral units has been neglected in this research field due to previous limitations in manufacturing technology. With the continuous progress of 3D printing technology, the field of microfluidic devices ushered in a new era of manufacturing three-dimensional irregular channels. In this study, we present finite analysis results for a periodic nodular-like channel. The experiments involve variations in the Reynold number (Re), periodic frequency, and comparative analyses with conventional structures. The findings indicate that this variable 3D cross-section structure can readily achieve performance comparable to other passive fluid control methods in valve applications. A 3D model of the periodic tetrahedron channel was fabricated using 3D printing to validate these conclusions. This research has the potential to significantly enhance the performance of passive fluid control units that have long been constrained by manufacturing dimensions. Full article

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Flow field characteristics utilized in the current study: (a) streamline field of symmetric and asymmetric elements; (b) cross-sectional view of the variable cross-section channel. Full article ">Figure 2
Simulation of pressure drop for typical solid elements: (a) the simulation model consists of diffuser/nozzle or tetrahedron elements; (b) comparison of pressure drop among tetrahedron, cylinder, and plane structures; (c) nonlinear distribution of pressure drop along different edges of a tetrahedron element leading to the formation of local vortices in the flow field. Full article ">Figure 3
Fabrication and testing of a valve array: (a) a 3D-printed nodal solid architecture consisting of eight elements with a cross section of 500 μm; (b) a C-type array of 3 × 6 valves (the green and red lines indicate the direction in which the liquid flows in and out, respectively); (c) microscopic image of the 3D printed device; (d) flow behavior at 30 μL/s, demonstrating selective flow through the valves in the network. Full article ">Figure 4
Comparative modeling of positive and negative flow differences: (a) 3D printing runner modeling; (b) forward and reverse total flow test. Full article ">Figure 5
Specificity of one-way flow conduction of a tetrahedron element: (a) diodicity curve and the stream line field for Re = 10~200 and angle = 60°; (b) diodicity versus Reynolds number and diffuse angle. Full article ">Figure 6
Specificity of one-way flow conduction of the diffuser/nozzle element. (a) The diodicity curve and the stream line field in the case of Re = 0.5 to 60 and angle = 60°; (b) the diodicity versus Reynolds number and diffusion angle. Full article ">Figure 7
Simulated data on diode characteristics and their influencing factors in an array arrangement: (a) the diodicity versus nodes number; (b) the diodicity versus f in the case of a tetrahedron element; (c) the diodicity versus f in the case of a diffuser/nozzle element; (d) the diodicity versus Re in the case of a rotation diffuser/nozzle element. Full article ">

18 pages, 4465 KiB

Open AccessArticle

Development of a Microbioreactor for Bacillus subtilis Biofilm Cultivation

by Mojca Seručnik, Iztok Dogsa, Lan Julij Zadravec, Ines Mandic-Mulec and Polona Žnidaršič-Plazl

Micromachines 2024, 15(8), 1037; https://doi.org/10.3390/mi15081037 - 15 Aug 2024

Viewed by 1040

Abstract

To improve our understanding of Bacillus subtilis growth and biofilm formation under different environmental conditions, two versions of a microfluidic reactor with two channels separated by a polydimethylsiloxane (PDMS) membrane were developed. The gas phase was introduced into the channel above the membrane, [...] Read more.

To improve our understanding of Bacillus subtilis growth and biofilm formation under different environmental conditions, two versions of a microfluidic reactor with two channels separated by a polydimethylsiloxane (PDMS) membrane were developed. The gas phase was introduced into the channel above the membrane, and oxygen transfer from the gas phase through the membrane was assessed by measuring the dissolved oxygen concentration in the liquid phase using a miniaturized optical sensor and oxygen-sensitive nanoparticles. B. subtilis biofilm formation was monitored in the growth channels of the microbioreactors, which were designed in two shapes: one with circular extensions and one without. The volumes of these microbioreactors were (17 ± 4) μL for the reactors without extensions and (28 ± 4) μL for those with extensions. The effect of microbioreactor geometry and aeration on B. subtilis biofilm growth was evaluated by digital image analysis. In both microbioreactor geometries, stable B. subtilis biofilm formation was achieved after 72 h of incubation at a growth medium flow rate of 1 μL/min. The amount of oxygen significantly influenced biofilm formation. When the culture was cultivated with a continuous air supply, biofilm surface coverage and biomass concentration were higher than in cultivations without aeration or with a 100% oxygen supply. The channel geometry with circular extensions did not lead to a higher total biomass in the microbioreactor compared to the geometry without extensions. Full article

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

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16 pages, 16781 KiB

Open AccessArticle

Multi-Channel Microscale Nerve Cuffs for Spatially Selective Neuromodulation

by Morgan Riley, FNU Tala, Katherine J. Johnson and Benjamin C. Johnson

Micromachines 2024, 15(8), 1036; https://doi.org/10.3390/mi15081036 - 15 Aug 2024

Viewed by 926

Abstract

Peripheral nerve modulation via electrical stimulation shows promise for treating several diseases, but current approaches lack selectivity, leading to side effects. Exploring selective neuromodulation with commercially available nerve cuffs is impractical due to their high cost and limited spatial resolution. While custom cuffs [...] Read more.

Peripheral nerve modulation via electrical stimulation shows promise for treating several diseases, but current approaches lack selectivity, leading to side effects. Exploring selective neuromodulation with commercially available nerve cuffs is impractical due to their high cost and limited spatial resolution. While custom cuffs reported in the literature achieve high spatial resolutions, they require specialized microfabrication equipment and significant effort to produce even a single design. This inability to rapidly and cost-effectively prototype novel cuff designs impedes research into selective neuromodulation therapies in acute studies. To address this, we developed a reproducible method to easily create multi-channel epineural nerve cuffs for selective fascicular neuromodulation. Leveraging commercial flexible printed circuit (FPC) technology, we created cuffs with high spatial resolution (50 μm) and customizable parameters like electrode size, channel count, and cuff diameter. We designed cuffs to accommodate adult mouse or rat sciatic nerves (300–1500 μm diameter). We coated the electrodes with PEDOT:PSS to improve the charge injection capacity. We demonstrated selective neuromodulation in both rats and mice, achieving preferential activation of the tibialis anterior (TA) and lateral gastrocnemius (LG) muscles. Selectivity was confirmed through micro-computed tomography (μCT) and quantified through a selectivity index. These results demonstrate the potential of this fabrication method for enabling selective neuromodulation studies while significantly reducing production time and costs compared to traditional approaches. Full article

(This article belongs to the Special Issue Neural Interface: From Material to System)

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15 pages, 4535 KiB

Open AccessArticle

Study on the Performance of Deep Red to Near-Infrared pc-LEDs by the Simulation Method Considering the Distribution of Phosphor Particles

by Chenghang Li, Zikeng Fang, Ying Yan, Henan Li, Xiang Luo, Xuyue Wang and Ping Zhou

Micromachines 2024, 15(8), 1035; https://doi.org/10.3390/mi15081035 - 15 Aug 2024

Viewed by 799

Abstract

Effectively utilizing deep red to near-infrared (DR-NIR) phosphors to achieve the optimal performance of NIR phosphor-converted white LEDs (DR-NIR pc-wLEDs) is currently a research hotspot. In this study, an optical model of DR-NIR pc-wLEDs with virtual multilayer fluorescent films was established based on [...] Read more.

Effectively utilizing deep red to near-infrared (DR-NIR) phosphors to achieve the optimal performance of NIR phosphor-converted white LEDs (DR-NIR pc-wLEDs) is currently a research hotspot. In this study, an optical model of DR-NIR pc-wLEDs with virtual multilayer fluorescent films was established based on the Monte Carlo ray-tracing method. Different gradient distributions of the particles were assigned within the fluorescent film to explore their impact on the optical performance of pc-LEDs. The results show that, for the case with single-type particles, distributing more DR-NIR particles far from the blue LED chip increased the overall radiant power. The distribution of more DR-NIR particles near the chip increased the conversion ratio from blue to DR-NIR light. The ratio of the 707 nm fluorescence emission intensity to the 450 nm excitation light intensity increased from 1:0.51 to 1:0.28. For multiple-type particles, changes in the gradient distribution resulted in dual-nature changes, leading to a deterioration in the color rendering index and an increase in the correlated color temperature, while also improving the DR-NIR band ratio. The reabsorption caused by the partial overlap between the excitation band of the DR-NIR particles and the emission band of the other particles enhanced the radiant power at 707 nm. Distributing DR-NIR phosphor particles closer to the chip effectively amplified this effect. The proposed model and its results provide a solution for the forward design of particle distributions in fluorescent films to improve the luminous performance of DR-NIR pc-wLEDs. Full article

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13 pages, 2230 KiB

Open AccessArticle

A Droplet-Based Microfluidic Platform for High-Throughput Culturing of Yeast Cells in Various Conditions

by Min-Chieh Yu and Yung-Shin Sun

Micromachines 2024, 15(8), 1034; https://doi.org/10.3390/mi15081034 - 15 Aug 2024

Viewed by 1420

Abstract

Yeast plays a significant role in a variety of fields. In particular, it is extensively used as a model organism in genetics and cellular biology studies, and is employed in the production of vaccines, pharmaceuticals, and biofuels. Traditional “bulk”-based studies on yeast growth [...] Read more.

Yeast plays a significant role in a variety of fields. In particular, it is extensively used as a model organism in genetics and cellular biology studies, and is employed in the production of vaccines, pharmaceuticals, and biofuels. Traditional “bulk”-based studies on yeast growth often overlook cellular variability, emphasizing the need for single-cell analysis. Micro-droplets, tiny liquid droplets with high surface-area-to-volume ratios, offer a promising platform for investigating single or a small number of cells, allowing precise control and monitoring of individual cell behaviors. Microfluidic devices, which facilitate the generation of micro-droplets, are advantageous due to their reduced volume requirements and ability to mimic in vivo micro-environments. This study introduces a custom-designed microfluidic device to encapsulate yeasts in micro-droplets under various conditions in a parallel manner. The results reveal that optimal glucose concentrations promoted yeast growth while cycloheximide and Cu²⁺ ions inhibited it. This platform enhances yeast cultivation strategies and holds potential for high-throughput single-cell investigations in more complex organisms. Full article

(This article belongs to the Special Issue Microfluidic Chips for Biomedical Applications)

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Designs of the (a) generation and (b) observation chips. Scale bar = 1 cm. In (b), A: observation area; B: raised reservoir for oil storage; C: elevated space for droplet storage. Full article ">Figure 2
Pictures showing (a) the generation and observation chips, (b) the two chips connected, and (c) the yeast-encapsulated droplets (scale bar = 100 μm). Full article ">Figure 3
(a) Images of droplets in five channels of the observation chip. (b) Mean diameters with SDs of the droplets in these channels. Full article ">Figure 4
The growth of S. cerevisiae cells when cultured in different concentrations of glucose. T-tests were performed with ns: not significant difference (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001. Full article ">Figure 5
The growth of S. cerevisiae cells when cultured in different concentrations of cycloheximide. T-tests were performed with ns: not significant difference (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001. Full article ">Figure 6
The growth of S. cerevisiae cells when cultured in different concentrations of Cu2+. T-tests were performed with ns: not significant difference (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001. Full article ">Figure 7
The growth of S. cerevisiae cells when cultured in different initial concentrations. T-tests were performed with ns: not significant difference (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001. Full article ">

13 pages, 3358 KiB

Open AccessArticle

Optimization of Hot Embossing Condition Using Taguchi Method and Evaluation of Microchannels for Flexible On-Chip Proton-Exchange Membrane Fuel Cell

by Yubo Huang, Han Gao, Zhiheng Wu, Hongyang Xiao, Cao Xia, Yuanlin Xia and Zhuqing Wang

Micromachines 2024, 15(8), 1033; https://doi.org/10.3390/mi15081033 - 14 Aug 2024

Viewed by 1011

Abstract

Hot embossing is a manufacturing technique used to create microchannels on polymer substrates. In recent years, microchannel fabrication technology based on hot embossing has attracted considerable attention due to its convenience and low cost. A new evaluation method of microchannels, as well as [...] Read more.

Hot embossing is a manufacturing technique used to create microchannels on polymer substrates. In recent years, microchannel fabrication technology based on hot embossing has attracted considerable attention due to its convenience and low cost. A new evaluation method of microchannels, as well as an approach to obtaining optimal hot embossing conditions based on the Taguchi method, is proposed in this paper to fabricate precise microchannels for a flexible proton-exchange membrane fuel cell (PEMFC). Our self-made hot embossing system can be used to fabricate assorted types of micro-channel structures on polymer substrates according to various applications, whose bottom width, top width, height and cross-sectional area vary in the aims of different situations. In order to obtain a high effective filling ratio, a new evaluation method is presented based on the four parameters of channel structures, and the Taguchi method is utilized to arrange three main factors (temperature, force and time) affecting the hot embossing in orthogonal arrays, quickly finding the optimal condition for the embossing process. The evaluation method for microchannels proposed in this paper, compared to traditional evaluation methods, incorporates the area factor, providing a more comprehensive assessment of the fabrication completeness of the microchannels. Additionally, it allows for the quick and simple identification of optimal conditions. The experimental results indicate that after determining the optimal embossing temperature, pressure and time using the Taguchi method, the effective filling rate remains above 95%, thereby enhancing the power density. Through variance analysis, it was found that temperature is the most significant factor affecting the hot embossing of microchannels. The high filling rate makes the process suitable for PEMFCs. The results demonstrate that under optimized process conditions, a self-made hot embossing system can effectively fabricate columnar structure microchannels for PEMFCs. Full article

(This article belongs to the Special Issue JCK MEMS/NEMS 2024)

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Schematic of a new concept planar micro-PEMFC. Full article ">Figure 2
The self-made micro-hot-embossing system and the self-made hot embossing equipment in comparison with the commercial product: (a) the mold of the self-made hot embossing equipment; (b) a physical drawing of the self-made hot embossing equipment; (c) a comparison of the heating times between the self-made hot embossing equipment and a commercial product; (d) a comparison of the cooling times between the self-made hot embossing equipment and a commercial product. Full article ">Figure 3
The processes of hot embossing and the substrate polymer and master mold used in hot embossing processes and the cross-section structures of the master mold and the substrate polymer: (a) the processes of hot embossing; (b) the temperature and force acting stages in the hot embossing process; (c) the structures of the substrate polymer before and after the embossing process; (d) the structures of the master mold before and after the embossing process; (e) the cross-section structures of the substrate polymer; and (f) the cross-section structures of the master mold. Full article ">Figure 4
Three main factors arranged by orthogonal arrays using the Taguchi method. Full article ">Figure 5
Effective filling ratio for different levels of embossing temperature, embossing force and embossing time, and the proportion of the influence of the factors and error on the experimental results: (a) effective filling ratio for different levels of embossing temperature; (b) effective filling ratio for different levels of embossing time; (c) effective filling ratio for different levels of embossing force; and (d) the proportion of the influence of the factors and errors on the experimental results. Full article ">Figure 6
Test results for under the optimal conditions: (a) the effective filling ratio for repeating the experiments 10 times; (b) the average effective filling ratio for repeating the experiments 10 times; (c) the effective filling ratio of mold II for repeating the experiments 5 times; and (d) the average effective filling ratio of mold II for repeating the experiments 5 times. Full article ">

15 pages, 7964 KiB

Open AccessArticle

Optimal Motion Control of a Capsule Endoscope in the Stomach Utilizing a Magnetic Navigation System with Dual Permanent Magnets

by Suhong Bae, Junhyoung Kwon, Jongyul Kim and Gunhee Jang

Micromachines 2024, 15(8), 1032; https://doi.org/10.3390/mi15081032 - 14 Aug 2024

Viewed by 1094

Abstract

We propose a method to control the motion of a capsule endoscope (CE) in the stomach utilizing either a single external permanent magnet (EPM) or dual EPMs to extend the examination of the upper gastrointestinal tract. When utilizing the conventional magnetic navigational system [...] Read more.

We propose a method to control the motion of a capsule endoscope (CE) in the stomach utilizing either a single external permanent magnet (EPM) or dual EPMs to extend the examination of the upper gastrointestinal tract. When utilizing the conventional magnetic navigational system (MNS) with a single EPM to generate tilting and rotational motions of the CE, undesired translational motion of the CE may prevent accurate examination. We analyzed the motion of the CE by calculating the magnetic torque and magnetic force applied to the CE using the point-dipole approximation model. Using the proposed model, we propose a method to determine the optimal position and orientation of the EPM to generate tilting and rotational motions without undesired translational motion of the CE. Furthermore, we optimized the weight of dual EPMs to develop a lightweight MNS. We prototyped the proposed MNS and experimentally verified that the developed MNS can generate tilting and rotational motions of the CE without any translational motion. Full article

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

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16 pages, 4845 KiB

Open AccessArticle

Fabrication of Porous Collagen Scaffolds Containing Embedded Channels with Collagen Membrane Linings

by Neda Fakhri, Arezoo Khalili, Terry Sachlos and Pouya Rezai

Micromachines 2024, 15(8), 1031; https://doi.org/10.3390/mi15081031 - 14 Aug 2024

Viewed by 1028

Abstract

Tissues and organs contain an extracellular matrix (ECM). In the case of blood vessels, endothelium cells are anchored to a specialized basement membrane (BM) embedded inside the interstitial matrix (IM). We introduce a multi-structural collagen-based scaffold with embedded microchannels that mimics in vivo [...] Read more.

Tissues and organs contain an extracellular matrix (ECM). In the case of blood vessels, endothelium cells are anchored to a specialized basement membrane (BM) embedded inside the interstitial matrix (IM). We introduce a multi-structural collagen-based scaffold with embedded microchannels that mimics in vivo structures within vessels. Our scaffold consists of two parts, each containing two collagen layers, i.e., a 3D porous collagen layer analogous to IM lined with a thin 2D collagen film resembling the BM. Enclosed microchannels were fabricated using contact microprinting. Microchannel test structures with different sizes ranging from 300 to 800 µm were examined for their fabrication reproducibility. The heights and perimeters of the fabricated microchannels were ~20% less than their corresponding values in the replication PDMS mold; however, microchannel widths were significantly closer to their replica dimensions. The stiffness, permeability, and pore size properties of the 2D and 3D collagen layers were measured. The permeability of the 2D collagen film was negligible, making it suitable for mimicking the BM of large blood vessels. A leakage test at various volumetric flow rates applied to the microchannels showed no discharge, thereby verifying the reliability of the proposed integrated 2D/3D collagen parts and the contact printing method used for bonding them in the scaffold. In the future, multi-cell culturing will be performed within the 3D porous collagen and against the 2D membrane inside the microchannel, hence preparing this scaffold for studying a variety of blood vessel–tissue interfaces. Also, thicker collagen scaffold tissues will be fabricated by stacking several layers of the proposed scaffold. Full article

(This article belongs to the Special Issue Interfacial Physics, Healthcare and Medicine: Microfluidics and Nanofluidics)

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Schematic diagrams of the proposed collagen scaffold simulating 3D porous tissues with embedded microchannels that have inner-wall 2D membrane linings. (a) The final scaffold with an embedded microchannel connected to inlet and outlet tubing. (b) Close-up cross-sectional view of the microchannel with the 2D BM lining embedded inside the 3D porous IM, which was formed by bonding two collagen layers. (Created with <a href="http://BioRender.com" target="_blank">BioRender.com</a>.) Full article ">Figure 2
A schematic diagram showing (a–j) the fabrication procedure of the collagen microchannels and (k–m) the contact printing method for bonding the patterned collagen with a second flat collagen layer. (Created with <a href="http://BioRender.com" target="_blank">BioRender.com</a>). Full article ">Figure 3
Properties of the 2D collagen film. (a) Thickness of the 2D collagen film corresponding to different mass values of collagen per unit area used for fabrication. A solid red line is fitted to the experimental results to assess the linearity of the collagen’s response. (b) Tensile stress vs. strain curves for 2D collagen films in dry and hydrated states. (c) The stiffness of the 2D collagen films under low strains for the dry and hydrated states. The p-value is less than 0.01 (**) for n = 3 data in each group. Error bars show the standard deviations (SD) of the experiments in three trials. Full article ">Figure 4
SEM images of 3D porous collagen scaffolds and the corresponding pore size distributions. Porous collagen scaffolds were fabricated using freezing temperatures of (a) −80 °C and (b) −20 °C; scale bar: 1 mm. SEM images of a single pore in porous collagen fabricated using freezing temperatures of (c) −80 °C and (d) −20 °C; scale bar: 100 μm. Pore size distribution for collagen scaffolds fabricated using freezing temperatures of (e) −80 °C and (f) −20 °C. (g) Bar plot for the average pore wall thicknesses for fabricated collagens using different freezing temperatures (**: p-value < 0.01). Full article ">Figure 5
Mechanical properties of dry and hydrated collagen scaffolds fabricated using freezing temperatures of −20 and −80 °C: (a) tensile stress–strain curves, (b) stiffness under low strain, (c) tensile-stress curves for collagen scaffolds fabricated using a −20 °C freezing temperature, and (d) stiffness under low strain for dry and hydrated collagen scaffolds based on the curves in panel (c). ***: p-value < 0.001 for n = 3 data in each group. Error bars show the standard deviations (SD) of the experiments in three trials. Full article ">Figure 6
Collagen microchannels with different sizes and comparison between channel sizes in the collagen and channel sizes in the master mold. (a) Cross-sectional view of six parallel test microchannels ranging from 300 μm to 1.5 mm in width and height; the respective plots show (b) the width (WCollagen), (c) the height (HCollagen), and (d) the perimeter (PCollagen) of collagen microchannels versus the corresponding dimensions of their PDMS replica master molds; (e) shrinkage of the collagen channels based on changes in the perimeter of the collagen compared to the master mold. The solid red lines are fitted lines based on the experimental data. Full article ">Figure 7
Fabricated enclosed microchannels: (a) cross-sectional view of the final collagen scaffold; (b) final collagen microchannel with embedded needles as inputs and outputs; (c) top-view and (d) side-view SEM images of the fabricated collagen scaffold containing microchannels based on the integration of 2D collagen film and a 3D scaffold; (e) top-view and (f) side-view SEM images of the fabricated collagen scaffold containing microchannels without the 2D collagen film; (g) the ratio of outflow rates to inflow rates with different flow rates when the 2D collagen membrane was used (shown in orange) and when no 2D BM was used (shown in blue). Full article ">

33 pages, 13709 KiB

Open AccessReview

Recent Developments in Mechanical Ultraprecision Machining for Nano/Micro Device Manufacturing

by Tirimisiyu Olaniyan, Nadimul Faisal and James Njuguna

Micromachines 2024, 15(8), 1030; https://doi.org/10.3390/mi15081030 - 14 Aug 2024

Viewed by 5096

Abstract

The production of many components used in MEMS or NEMS devices, especially those with com-plex shapes, requires machining as the best option among manufacturing techniques. Ultraprecision machining is normally employed to achieve the required shapes, dimensional accuracy, or improved surface quality in most [...] Read more.

The production of many components used in MEMS or NEMS devices, especially those with com-plex shapes, requires machining as the best option among manufacturing techniques. Ultraprecision machining is normally employed to achieve the required shapes, dimensional accuracy, or improved surface quality in most of these devices and other areas of application. Compared to conventional machining, ultraprecision machining involves complex phenomenal processes that require extensive investigations for a better understanding of the material removal mechanism. Materials such as semiconductors, composites, steels, ceramics, and polymers are commonly used, particularly in devices designed for harsh environments or applications where alloyed metals may not be suitable. However, unlike alloyed metals, materials like semiconductors (e.g., silicon), ceramics (e.g., silicon carbide), and polymers, which are typically brittle and/or hard, present significant challenges. These challenges include achieving precise surface integrity without post-processing, managing the ductile-brittle transition, and addressing low material removal rates, among others. This review paper examines current research trends in mechanical ultraprecision machining and sustainable ultraprecision machining, along with the adoption of molecular dynamics simulation at the micro and nano scales. The identified challenges are discussed, and potential solutions for addressing these challenges are proposed. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials: Synthesis, Characterization and Device Applications)

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Micromachines, Volume 15, Issue 8 (August 2024) – 125 articles

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