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Micromachines, Volume 11, Issue 8 (August 2020) – 76 articles

Cover Story (view full-size image): The traditional design of an ultrasonic transducer (UT) mainly depends on the experience of the designers, as it is often a time-consuming and inefficient process. In this research, an efficient optimization design method for UT design is developed by combining an equivalent circuit model and particle swarm optimization algorithm. The developed optimization design method can effectively and promptly design a UT according to the desired performance, with a short development cycle and low cost, which will promote its applications in medical imaging and diagnosis. View this paper
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10 pages, 3801 KiB  
Article
Low Power Consumption 3D-Inverted Ridge Thermal Optical Switch of Graphene-Coated Polymer/Silica Hybrid Waveguide
by Yue Cao, Yunji Yi, Yue Yang, Baizhu Lin, Jiawen Lv, Haowen Zhao, Fei Wang and Daming Zhang
Micromachines 2020, 11(8), 783; https://doi.org/10.3390/mi11080783 - 18 Aug 2020
Cited by 1 | Viewed by 2254
Abstract
An inverted ridge 3D thermal optical (TO) switch of a graphene-coated polymer/silica hybrid waveguide is proposed. The side electrode structure is designed to reduce the mode loss induced by the graphene film and by heating the electrode. The graphene layer is designed to [...] Read more.
An inverted ridge 3D thermal optical (TO) switch of a graphene-coated polymer/silica hybrid waveguide is proposed. The side electrode structure is designed to reduce the mode loss induced by the graphene film and by heating the electrode. The graphene layer is designed to be located on the waveguide to assist in the conduction of heat produced by the electrode. The inverted ridge core is fabricated by etching and spin-coating processes, which can realize the flat surface waveguide. This core improves the transfer of the graphene layer and the compatibility of the fabrication processes. Because of the opposite thermal optical coefficient of polymer and silica and the high thermal conductivity of the graphene layer, the 3D hybrid TO switch with low power consumption and fast response time is obtained. Compared with the traditional TO switch without graphene film, the power consumption of the proposed TO switch is reduced by 41.43% at the wavelength of 1550 nm, width of the core layer (a) of 3 μm, and electrode distance (d) of 4 μm. The rise and fall times of the proposed TO switch are simulated to be 64.5 μs and 175 μs with a d of 4 μm, and a of 2 μm, respectively. Full article
(This article belongs to the Special Issue Graphene based Electronic Devices)
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16 pages, 8383 KiB  
Article
Random Access Addressing of MEMS Electrostatic Shutter Array for Multi-Object Astronomical Spectroscopy
by Xufeng Liu, Takuya Takahashi, Masahiro Konishi, Kentaro Motohara and Hiroshi Toshiyoshi
Micromachines 2020, 11(8), 782; https://doi.org/10.3390/mi11080782 - 17 Aug 2020
Cited by 4 | Viewed by 3493
Abstract
An extended version of cross-bar type addressing technique is developed for three-port electrostatic micro shutters arranged in an arrayed format. A microelectromechanical systems (MEMS) shutter blade suspended by a pair of torsion beams works as a movable electrode that is either attracted upwards [...] Read more.
An extended version of cross-bar type addressing technique is developed for three-port electrostatic micro shutters arranged in an arrayed format. A microelectromechanical systems (MEMS) shutter blade suspended by a pair of torsion beams works as a movable electrode that is either attracted upwards to the cover plate to close the aperture or retracted downwards into the through-hole to open it. Tri-state positioning of the shutter—i.e., open, rest, and close—is controlled by the hysteresis loop of the electrostatic pull-in and release behavior using the combination of the voltages applied to the shutter, the cover, and the substrate. Random access addressing of the shutters is demonstrated by a control system composed of MATLAB-coded Arduino electronics. The shutter array developed in this work is for a sub-cluster of a reconfigurable shutter array under development for a multi-object galactic astronomy. Full article
(This article belongs to the Special Issue Optical MEMS, Volume II)
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8 pages, 2200 KiB  
Article
Design and Analysis of a Slot Photonic Crystal Waveguide for Highly Sensitive Evanescent Field Absorption Sensing in Fluids
by Reyhaneh Jannesari, Gerald Pühringer, Thomas Grille and Bernhard Jakoby
Micromachines 2020, 11(8), 781; https://doi.org/10.3390/mi11080781 - 15 Aug 2020
Cited by 5 | Viewed by 2913
Abstract
The design and modeling of a highly sensitive sensor based on a slot photonic crystal waveguide (slot-PCWG) is presented. The structure consists of cylindrical air rods drilled in a dielectric slab on a triangular lattice, which are filled with SiO2. The [...] Read more.
The design and modeling of a highly sensitive sensor based on a slot photonic crystal waveguide (slot-PCWG) is presented. The structure consists of cylindrical air rods drilled in a dielectric slab on a triangular lattice, which are filled with SiO2. The waveguide is formed by removing elements from the regular photonic crystal grid in a row, and embedding a slot in the center position. This concept allows for a vast enhancement of the evanescent field ratio, leading to a strong overlap between the field of the waveguide mode and the analyte. In the present work, we show that the sensitivity at the constant slab thickness of the slot-PCWG modes is greatly enhanced, up to a factor of 7.6 compared with the corresponding PCWG modes or Si-slab WGs. The finite-difference time-domain (FDTD) technique and plane wave expansion (PWE) methods were used to study the dispersion and profile of the PCWG mode. The simulation results show the potential of this design, which will be fabricated and tested in the following steps of the project. Full article
(This article belongs to the Special Issue MFHS 2019)
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10 pages, 3031 KiB  
Article
Analysis of Current Variation with Work Function Variation in L-Shaped Tunnel-Field Effect Transistor
by Jang Hyun Kim, Hyun Woo Kim, Young Suh Song, Sangwan Kim and Garam Kim
Micromachines 2020, 11(8), 780; https://doi.org/10.3390/mi11080780 - 15 Aug 2020
Cited by 17 | Viewed by 3160
Abstract
In this paper, an investigation is performed to analyze the L-shaped tunnel field-effect transistor (TFET) depending on a gate work function variation (WFV) with help of technology computer-aided design (TCAD) simulation. Depending on the gate voltage, the three variations occur in transfer curves. [...] Read more.
In this paper, an investigation is performed to analyze the L-shaped tunnel field-effect transistor (TFET) depending on a gate work function variation (WFV) with help of technology computer-aided design (TCAD) simulation. Depending on the gate voltage, the three variations occur in transfer curves. The first one is the on-state current (ION) variation, the second one is the hump current (IHUMP) variation, and the last one is ambipolar current (IAMB) variation. According to the simulation results, the ION variation is sensitive depending on the size of the tunneling region and could be reduced by increasing the tunneling region. However, the IHUMP and IAMB variations are relatively irrelevant to the size of the tunneling region. In order to analyze the cause of this difference, we investigated the band-to-band tunneling (BTBT) rate according to WFV cases. The results show that when ION is formed in L-shaped TFET, the BTBT rate relies on the WFV in the whole region of the gate because the tunnel barrier is formed in the entire area where the source and the gate meet. On the other hand, when the IHUMP and IAMB are formed in L-shaped TFET, the BTBT rate relies on the WFV in the edge of the gate. Full article
(This article belongs to the Special Issue NANO KOREA 2020)
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28 pages, 3634 KiB  
Review
2D Nanomaterial-Based Surface Plasmon Resonance Sensors for Biosensing Applications
by Sachin Singh, Pravin Kumar Singh, Ahmad Umar, Pooja Lohia, Hasan Albargi, L. Castañeda and D. K. Dwivedi
Micromachines 2020, 11(8), 779; https://doi.org/10.3390/mi11080779 - 15 Aug 2020
Cited by 81 | Viewed by 5464
Abstract
The absorption and binding energy of material plays an important role with a large surface area and conductivity for the development of any sensing device. The newly grown 2D nanomaterials like black phosphorus transition metal dichalcogenides (TMDCs) or graphene have excellent properties for [...] Read more.
The absorption and binding energy of material plays an important role with a large surface area and conductivity for the development of any sensing device. The newly grown 2D nanomaterials like black phosphorus transition metal dichalcogenides (TMDCs) or graphene have excellent properties for sensing devices’ fabrication. This paper summarizes the progress in the area of the 2D nanomaterial-based surface plasmon resonance (SPR) sensor during last decade. The paper also focuses on the structure of Kretschmann configuration, the sensing principle of SPR, its characteristic parameters, application in various fields, and some important recent works related to SPR sensors have also been discussed, based on the present and future scope of this field. The present paper provides a platform for researchers to work in the field of 2D nanomaterial-based SPR sensors. Full article
(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application, Volume II)
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17 pages, 2591 KiB  
Article
Simulation and Optimization of Electromagnetic Absorption of Polycarbonate/CNT Composites Using Machine Learning
by Lakhdar Sidi Salah, Mohamed Chouai, Yann Danlée, Isabelle Huynen and Nassira Ouslimani
Micromachines 2020, 11(8), 778; https://doi.org/10.3390/mi11080778 - 15 Aug 2020
Cited by 16 | Viewed by 3642
Abstract
Electronic devices that transmit, distribute, or utilize electrical energy create electromagnetic interference (EMI) that can lead to malfunctioning and degradation of electronic devices. EMI shielding materials block the unwanted electromagnetic waves from reaching the target material. EMI issues can be solved by using [...] Read more.
Electronic devices that transmit, distribute, or utilize electrical energy create electromagnetic interference (EMI) that can lead to malfunctioning and degradation of electronic devices. EMI shielding materials block the unwanted electromagnetic waves from reaching the target material. EMI issues can be solved by using a new family of building blocks constituted of polymer and nanofillers. The electromagnetic absorption index of this material is calculated by measuring the “S-parameters”. In this article, we investigated the use of artificial intelligence (AI) in the EMI shielding field by developing a new system based on a multilayer perceptron neural network designed to predict the electromagnetic absorption of polycarbonate-carbon nanotubes composites films. The proposed system included 15 different multilayer perception (MLP) networks; each network was specialized to predict the absorption value of a specific category sample. The selection of appropriate networks was done automatically, using an independent block. Optimization of the hyper-parameters using hold-out validation was required to ensure the best results. To evaluate the performance of our system, we calculated the similarity error, precision accuracy, and calculation time. The results obtained over our database showed clearly that the system provided a very good result with an average accuracy of 99.7997%, with an overall average calculation time of 0.01295 s. The composite based on polycarbonate−5 wt.% carbon nanotube was found to be the ultimate absorber over microwave range according to Rozanov formalism. Full article
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16 pages, 13677 KiB  
Article
Effects of Bonding Parameters on Free Air Ball Properties and Bonded Strength of Ag-10Au-3.6Pd Alloy Bonding Wire
by Jun Cao, Junchao Zhang, John Persic and Kexing Song
Micromachines 2020, 11(8), 777; https://doi.org/10.3390/mi11080777 - 14 Aug 2020
Cited by 8 | Viewed by 3940
Abstract
Free air ball (FAB) and bonded strength were performed on an Ag-10Au-3.6Pd alloy bonding wire (diameter of 0.025 mm) for different electronic flame-off (EFO) currents, times and bonding parameters. The effects of the EFO and bonding parameters on the characteristics of the FAB [...] Read more.
Free air ball (FAB) and bonded strength were performed on an Ag-10Au-3.6Pd alloy bonding wire (diameter of 0.025 mm) for different electronic flame-off (EFO) currents, times and bonding parameters. The effects of the EFO and bonding parameters on the characteristics of the FAB as well as the bonded strength were investigated using scanning electron microscopy. The results showed that, for a constant EFO time, the FAB of the Ag-10Au-3.6Pd alloy bonding wire transitioned from a pointed defined ball to an oval one, then to a perfectly shaped one, and finally to a golf ball with an increase in the EFO current. On the other hand, when the EFO current was constant and the EFO time was increased, the FAB changed from a small ball to a perfect one, then to a large one, and finally to a golf ball. The FAB exhibited the optimal geometry at an EFO current of 0.030 A and EFO time of 0.8 ms. Further, in the case of the Ag-10Au-3.6Pd alloy bonding wire, for an EFO current of 0.030 A, the FAB diameter exhibited a nonlinear relationship with the EFO time, which could be expressed by a quadratic function. Finally, the bonded strength decreased when the bonding power and force were excessively high, causing the ball bond to overflow. This led to the formation of neck cracks and decrease in the bonded strength. On the other hand, the bonded strength was insufficiently when the bonding power and force were small. The bonded strength was of the desired level when the bonding power and force were 70 mW and 0.60 N (for the ball bonded) and 95 mW and 0.85 N (for the wedge bonded), respectively. Full article
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4 pages, 169 KiB  
Editorial
Editorial on the Special Issue on Microelectrode Arrays and Application to Medical Devices
by Alinaghi Salari and Colin Dalton
Micromachines 2020, 11(8), 776; https://doi.org/10.3390/mi11080776 - 14 Aug 2020
Cited by 1 | Viewed by 1625
Abstract
In this editorial note, we briefly review the major findings of the 10 articles published in the Special Issue on microelectrode arrays and application to medical devices [...] Full article
(This article belongs to the Special Issue Microelectrode Arrays and Application to Medical Devices)
13 pages, 9179 KiB  
Article
Effect of the Lapping Platen Groove Density on the Characteristics of Microabrasive-Based Lapping
by Taekyung Lee, Haedo Jeong, Sangjik Lee, Doyeon Kim and Hyoungjae Kim
Micromachines 2020, 11(8), 775; https://doi.org/10.3390/mi11080775 - 14 Aug 2020
Cited by 4 | Viewed by 3401
Abstract
Microabrasive-based lapping is widely used in the manufacturing of single-crystal substrates such as sapphire, SiC, and GaN. Although many studies have been conducted to improve the lapping process characteristics, most of them focused on process conditions or consumables. In this study, the effect [...] Read more.
Microabrasive-based lapping is widely used in the manufacturing of single-crystal substrates such as sapphire, SiC, and GaN. Although many studies have been conducted to improve the lapping process characteristics, most of them focused on process conditions or consumables. In this study, the effect of the lapping platen groove density on the lapping characteristics was studied using a sapphire substrate. Groove density was defined as the ratio of groove width to groove pitch, and the displacement of the lapping head was measured to calculate the oil film thickness. It was confirmed that, for groove densities below 0.30, hydroplaning occurs when the oil film thickness increases. When the oil film thickness is larger than the abrasive particle size, the material removal rate is low because the abrasive does not participate in the lapping process. When the oil film was developed, the experimental results showed a high surface roughness and poor flatness of the substrate, as only large abrasive particles participated in the lapping process. Therefore, to improve the lapping characteristics, it is important to reduce the groove density by reducing the groove pitch, which prevents the development of the oil film. Full article
(This article belongs to the Section E:Engineering and Technology)
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27 pages, 8705 KiB  
Review
Nanotechnology-Assisted Isolation and Analysis of Circulating Tumor Cells on Microfluidic Devices
by Jie Cheng, Yang Liu, Yang Zhao, Lina Zhang, Lingqian Zhang, Haiyang Mao and Chengjun Huang
Micromachines 2020, 11(8), 774; https://doi.org/10.3390/mi11080774 - 14 Aug 2020
Cited by 33 | Viewed by 5548
Abstract
Circulating tumor cells (CTCs), a type of cancer cell that spreads from primary tumors into human peripheral blood and are considered as a new biomarker of cancer liquid biopsy. It provides the direction for understanding the biology of cancer metastasis and progression. Isolation [...] Read more.
Circulating tumor cells (CTCs), a type of cancer cell that spreads from primary tumors into human peripheral blood and are considered as a new biomarker of cancer liquid biopsy. It provides the direction for understanding the biology of cancer metastasis and progression. Isolation and analysis of CTCs offer the possibility for early cancer detection and dynamic prognosis monitoring. The extremely low quantity and high heterogeneity of CTCs are the major challenges for the application of CTCs in liquid biopsy. There have been significant research endeavors to develop efficient and reliable approaches to CTC isolation and analysis in the past few decades. With the advancement of microfabrication and nanomaterials, a variety of approaches have now emerged for CTC isolation and analysis on microfluidic platforms combined with nanotechnology. These new approaches show advantages in terms of cell capture efficiency, purity, detection sensitivity and specificity. This review focuses on recent progress in the field of nanotechnology-assisted microfluidics for CTC isolation and detection. Firstly, CTC isolation approaches using nanomaterial-based microfluidic devices are summarized and discussed. The different strategies for CTC release from the devices are specifically outlined. In addition, existing nanotechnology-assisted methods for CTC downstream analysis are summarized. Some perspectives are discussed on the challenges of current methods for CTC studies and promising research directions. Full article
(This article belongs to the Special Issue Microfluidics for Cells and Other Organisms, Volume II)
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18 pages, 9797 KiB  
Article
Modifying Wicking Speeds in Paper-Based Microfluidic Devices by Laser-Etching
by Brent Kalish, Mick Kyle Tan and Hideaki Tsutsui
Micromachines 2020, 11(8), 773; https://doi.org/10.3390/mi11080773 - 14 Aug 2020
Cited by 18 | Viewed by 3411
Abstract
Paper-based microfluidic devices are an attractive platform for developing low-cost, point-of-care diagnostic tools. As paper-based devices’ detection chemistries become more complex, more complicated devices are required, often entailing the sequential delivery of different liquids or reagents to reaction zones. Most research into flow [...] Read more.
Paper-based microfluidic devices are an attractive platform for developing low-cost, point-of-care diagnostic tools. As paper-based devices’ detection chemistries become more complex, more complicated devices are required, often entailing the sequential delivery of different liquids or reagents to reaction zones. Most research into flow control has been focused on introducing delays. However, delaying the flow can be problematic due to increased evaporation leading to sample loss. We report the use of a CO2 laser to uniformly etch the surface of the paper to modify wicking speeds in paper-based microfluidic devices. This technique can produce both wicking speed increases of up to 1.1× faster and decreases of up to 0.9× slower. Wicking speeds can be further enhanced by etching both sides of the paper, resulting in wicking 1.3× faster than unetched channels. Channels with lengthwise laser-etched grooves were also compared to uniformly etched channels, with the most heavily grooved channels wicking 1.9× faster than the fastest double-sided etched channels. Furthermore, sealing both sides of the channel in packing tape results in the most heavily etched channels, single-sided, double-sided, and grooved, wicking over 13× faster than unetched channels. By selectively etching individual channels, different combinations of sequential fluid delivery can be obtained without altering any channel geometry. Laser etching is a simple process that can be integrated into the patterning of the device and requires no additional materials or chemicals, enabling greater flow control for paper-based microfluidic devices. Full article
(This article belongs to the Special Issue X-fluidics at the Micro/Nanoscale)
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14 pages, 4680 KiB  
Article
Influence of Non-Structural Parameters on Dual Parallel Jet Characteristics of Porous Nozzles
by Jin Zhang, Ruiqi Lv, Qifan Yang, Baolei Liu and Ying Li
Micromachines 2020, 11(8), 772; https://doi.org/10.3390/mi11080772 - 14 Aug 2020
Cited by 2 | Viewed by 2495
Abstract
As an important actuator of the dual parallel jet, the porous nozzle has some non-structural parameters (such as inlet pressure, nozzle spacing ratio, etc.) which have a significant influence on energy transport, chemical combustion and pollutant generation. The research on the microfluidic state [...] Read more.
As an important actuator of the dual parallel jet, the porous nozzle has some non-structural parameters (such as inlet pressure, nozzle spacing ratio, etc.) which have a significant influence on energy transport, chemical combustion and pollutant generation. The research on the microfluidic state of the porous nozzle dual parallel jet, however, remains insufficient because of its microjet pattern and complex intersection process. In this paper, the authors used numerical simulation and an experimental method to clarify the influence of porous nozzles’ non-structural parameters on dual parallel jet characteristics. The results show that the inlet pressure only changes the pressure peak value on the parallel jet axis; the starting point (SP) and peak point (PP) on the parallel jet axis, which are located at Xsp = 22 mm and Xpp = 75 mm, respectively, are not changed; and with the increase in the nozzle spacing ratio, the merging points (MPs) on the parallel jet axis are Xmp = 25 mm, 32 mm and 59 mm, respectively. The merging point and the combined point move to a farther distance and the inner deflection angle of the jet is weakened. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)
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16 pages, 7194 KiB  
Article
Generating Convergent Laguerre-Gaussian Beams Based on an Arrayed Convex Spiral Phaser Fabricated by 3D Printing
by Chang Liu, Chai Hu, Dong Wei, Mingce Chen, Jiashuo Shi, Haiwei Wang, Changsheng Xie and Xinyu Zhang
Micromachines 2020, 11(8), 771; https://doi.org/10.3390/mi11080771 - 13 Aug 2020
Cited by 3 | Viewed by 2204
Abstract
A convex spiral phaser array (CSPA) is designed and fabricated to generate typical convergent Laguerre-Gaussian (LG) beams. A type of 3D printing technology based on the two-photon absorption effect is used to make the CSPAs with different featured sizes, which present a structural [...] Read more.
A convex spiral phaser array (CSPA) is designed and fabricated to generate typical convergent Laguerre-Gaussian (LG) beams. A type of 3D printing technology based on the two-photon absorption effect is used to make the CSPAs with different featured sizes, which present a structural integrity and fabricating accuracy of ~200 nm according to the surface topography measurements. The light field vortex characteristics of the CSPAs are evaluated through illuminating them by lasers with different central wavelength such as 450 nm, 530 nm and 650 nm. It should be noted that the arrayed light fields out from the CSPA are all changed from a clockwise vortex orientation to a circular distribution at the focal plane and then a counterclockwise vortex orientation. The circular light field is distributed 380–400 μm away from the CSPA, which is close to the 370 μm of the focal plane design. The convergent LG beams can be effectively shaped by the CASPs produced. Full article
(This article belongs to the Special Issue Optical MEMS, Volume II)
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17 pages, 4661 KiB  
Article
Development of Fully Flexible Tactile Pressure Sensor with Bilayer Interlaced Bumps for Robotic Grasping Applications
by Lingfeng Zhu, Yancheng Wang, Deqing Mei and Chengpeng Jiang
Micromachines 2020, 11(8), 770; https://doi.org/10.3390/mi11080770 - 12 Aug 2020
Cited by 18 | Viewed by 5089
Abstract
Flexible tactile sensors have been utilized in intelligent robotics for human-machine interaction and healthcare monitoring. The relatively low flexibility, unbalanced sensitivity and sensing range of the tactile sensors are hindering the accurate tactile information perception during robotic hand grasping of different objects. This [...] Read more.
Flexible tactile sensors have been utilized in intelligent robotics for human-machine interaction and healthcare monitoring. The relatively low flexibility, unbalanced sensitivity and sensing range of the tactile sensors are hindering the accurate tactile information perception during robotic hand grasping of different objects. This paper developed a fully flexible tactile pressure sensor, using the flexible graphene and silver composites as the sensing element and stretchable electrodes, respectively. As for the structural design of the tactile sensor, the proposed bilayer interlaced bumps can be used to convert external pressure into the stretching of graphene composites. The fabricated tactile sensor exhibits a high sensing performance, including relatively high sensitivity (up to 3.40% kPa−1), wide sensing range (200 kPa), good dynamic response, and considerable repeatability. Then, the tactile sensor has been integrated with the robotic hand finger, and the grasping results have indicated the capability of using the tactile sensor to detect the distributed pressure during grasping applications. The grasping motions, properties of the objects can be further analyzed through the acquired tactile information in time and spatial domains, demonstrating the potential applications of the tactile sensor in intelligent robotics and human-machine interfaces. Full article
(This article belongs to the Special Issue Graphene based Electronic Devices)
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17 pages, 3579 KiB  
Article
Combined Ammonia and Electron Processing of a Carbon-Rich Ruthenium Nanomaterial Fabricated by Electron-Induced Deposition
by Markus Rohdenburg, Johannes E. Fröch, Petra Martinović, Charlene J. Lobo and Petra Swiderek
Micromachines 2020, 11(8), 769; https://doi.org/10.3390/mi11080769 - 12 Aug 2020
Cited by 5 | Viewed by 3143
Abstract
Ammonia (NH3)-assisted purification of deposits fabricated by focused electron beam-induced deposition (FEBID) has recently been proven successful for the removal of halide contaminations. Herein, we demonstrate the impact of combined NH3 and electron processing on FEBID deposits containing hydrocarbon contaminations [...] Read more.
Ammonia (NH3)-assisted purification of deposits fabricated by focused electron beam-induced deposition (FEBID) has recently been proven successful for the removal of halide contaminations. Herein, we demonstrate the impact of combined NH3 and electron processing on FEBID deposits containing hydrocarbon contaminations that stem from anionic cyclopentadienyl-type ligands. For this purpose, we performed FEBID using bis(ethylcyclopentadienyl)ruthenium(II) as the precursor and subjected the resulting deposits to NH3 and electron processing, both in an environmental scanning electron microscope (ESEM) and in a surface science study under ultrahigh vacuum (UHV) conditions. The results provide evidence that nitrogen from NH3 is incorporated into the carbon content of the deposits which results in a covalent nitride material. This approach opens a perspective to combine the promising properties of carbon nitrides with respect to photocatalysis or nanosensing with the unique 3D nanoprinting capabilities of FEBID, enabling access to a novel class of tailored nanodevices. Full article
(This article belongs to the Special Issue Nanofabrication with Focused Electron/Ion Beam Induced Processing)
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12 pages, 7149 KiB  
Article
Experimental Flight Patterns Evaluation for a UAV-Based Air Pollutant Sensor
by João Otávio Araujo, João Valente, Lammert Kooistra, Sandra Munniks and Ruud J. B. Peters
Micromachines 2020, 11(8), 768; https://doi.org/10.3390/mi11080768 - 11 Aug 2020
Cited by 12 | Viewed by 3261
Abstract
The use of drones in combination with remote sensors have displayed increasing interest over the last years due to its potential to automate monitoring processes. In this study, a novel approach of a small flying e-nose is proposed by assembling a set of [...] Read more.
The use of drones in combination with remote sensors have displayed increasing interest over the last years due to its potential to automate monitoring processes. In this study, a novel approach of a small flying e-nose is proposed by assembling a set of AlphaSense electrochemical-sensors to a DJI Matrix 100 unmanned aerial vehicle (UAV). The system was tested on an outdoor field with a source of NO2. Field tests were conducted in a 100 m2 area on two dates with different wind speed levels varying from low (0.0–2.9m/s) to high (2.1–5.3m/s), two flight patterns zigzag and spiral and at three altitudes (3, 6 and 9 m). The objective of this study is to evaluate the sensors responsiveness and performance when subject to distinct flying conditions. A Wilcoxon rank-sum test showed significant difference between flight patterns only under High Wind conditions, with Spiral flights being slightly superior than Zigzag. With the aim of contributing to other studies in the same field, the data used in this analysis will be shared with the scientific community. Full article
(This article belongs to the Special Issue Development of Innovative Sensor Platforms for Field Analysis)
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11 pages, 12410 KiB  
Article
A Novel Electroporation System for Living Cell Staining and Membrane Dynamics Interrogation
by Yuanjun Zhang, Zishen Yan, Xingyu Xia and Yuan Lin
Micromachines 2020, 11(8), 767; https://doi.org/10.3390/mi11080767 - 11 Aug 2020
Cited by 5 | Viewed by 3007
Abstract
A novel electroporation system was developed to introduce transient membrane pores to cells in a spatially and temporally controlled manner, allowing us to achieve fast electrotransfection and live cell staining as well as to systematically interrogate the dynamics of the cell membrane. Specifically, [...] Read more.
A novel electroporation system was developed to introduce transient membrane pores to cells in a spatially and temporally controlled manner, allowing us to achieve fast electrotransfection and live cell staining as well as to systematically interrogate the dynamics of the cell membrane. Specifically, using this platform, we showed that both reversible and irreversible electroporation could be induced in the cell population, with nano-sized membrane pores in the former case being able to self-reseal in ~10 min. In addition, green fluorescent protein(GFP)-vinculin plasmid and 543 phalloidin have been delivered successively into fibroblast cells, which enables us to monitor the distinct roles of vinculin and F-actin in cell adhesion and migration as well as their possible interplay during these processes. Compared to conventional bulk electroporation and staining methods, the new system offers advantages such as low-voltage operation, cellular level manipulation and testing, fast and adjustable transfection/staining and real-time monitoring; the new system therefore could be useful in different biophysical studies in the future. Full article
(This article belongs to the Special Issue Microfluidic Machines)
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16 pages, 6844 KiB  
Article
Force Prediction and Cutting-Parameter Optimization in Micro-Milling Al7075-T6 Based on Response Surface Method
by Menghua Zhou, Yinghua Chen and Guoqing Zhang
Micromachines 2020, 11(8), 766; https://doi.org/10.3390/mi11080766 - 11 Aug 2020
Cited by 16 | Viewed by 2577
Abstract
Optimization of cutting parameters in micro-milling is an important measure to improve surface quality and machining efficiency of the workpiece. Investigation of micro-milling forces prediction plays a positive role in improving machining capacity. To predict micro-milling forces and optimize micro-milling cutting parameters (per-feed [...] Read more.
Optimization of cutting parameters in micro-milling is an important measure to improve surface quality and machining efficiency of the workpiece. Investigation of micro-milling forces prediction plays a positive role in improving machining capacity. To predict micro-milling forces and optimize micro-milling cutting parameters (per-feed tooth (fz), axial cutting depth (ap), spindle speed (n) and tool extended length (l)), a rotatable center composite experiment of micro-milling straight micro-groove in the workpiece of Al7075-T6 were designed, based on second-order response surface methods. According to the experiment results, the least square method was used to estimate the regression coefficient corresponding to the cutting parameters. Simultaneously, the response prediction model of micro-milling was established and successfully coincide the predicted values with the experiment values. The significance of the regression equation was tested by analysis of variance, and the influence of micro-milling cutting parameters on force and top burrs morphology was studied. The experiment results show that in a specific range of cutting parameters, ap and fz have a significant linear relation with the micro-milling force and the top burrs width. According to the optimal response value, the optimized cutting parameters for micro-milling obtained as: n is 11,393 r/min, fz is 6 µm/z, ap is 11 μm and l is 20.8 mm. The research results provide a useful reference for the selection of cutting parameters for micro-milling. Full article
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14 pages, 9703 KiB  
Article
A Novel Stick-Slip Nanopositioning Stage Integrated with a Flexure Hinge-Based Friction Force Adjusting Structure
by Junhui Zhu, Peng Pan, Yong Wang, Sen Gu, Rongan Zhai, Ming Pang, Xinyu Liu and Changhai Ru
Micromachines 2020, 11(8), 765; https://doi.org/10.3390/mi11080765 - 11 Aug 2020
Cited by 3 | Viewed by 3138
Abstract
The piezoelectrically-actuated stick-slip nanopositioning stage (PASSNS) has been applied extensively, and many designs of PASSNSs have been developed. The friction force between the stick-slip surfaces plays a critical role in successful movement of the stage, which influences the load capacity, dynamic performance, and [...] Read more.
The piezoelectrically-actuated stick-slip nanopositioning stage (PASSNS) has been applied extensively, and many designs of PASSNSs have been developed. The friction force between the stick-slip surfaces plays a critical role in successful movement of the stage, which influences the load capacity, dynamic performance, and positioning accuracy of the PASSNS. Toward solving the influence problems of friction force, this paper presents a novel stick-slip nanopositioning stage where the flexure hinge-based friction force adjusting unit was employed. Numerical analysis was conducted to estimate the static performance of the stage, a dynamic model was established, and simulation analysis was performed to study the dynamic performance of the stage. Further, a prototype was manufactured and a series of experiments were carried out to test the performance of the stage. The results show that the maximum forward and backward movement speeds of the stage are 1 and 0.7 mm/s, respectively, and the minimum forward and backward step displacements are approximately 11 and 12 nm, respectively. Compared to the step displacement under no working load, the forward and backward step displacements only increase by 6% and 8% with a working load of 20 g, respectively. And the load capacity of the PASSNS in the vertical direction is about 72 g. The experimental results confirm the feasibility of the proposed stage, and high accuracy, high speed, and good robustness to varying loads were achieved. These results demonstrate the great potential of the developed stage in many nanopositioning applications. Full article
(This article belongs to the Section E:Engineering and Technology)
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12 pages, 5955 KiB  
Article
Curvature-Modulated Si Spherical Cap-Like Structure Fabricated by Multistep Ring Edge Etching
by Tieying Ma, Jiachen Wang and Dabo Li
Micromachines 2020, 11(8), 764; https://doi.org/10.3390/mi11080764 - 10 Aug 2020
Cited by 5 | Viewed by 2228
Abstract
To create approximately spherical structures with curved sidewalls, this paper presents a method for building a series of decreasing slopes along the sidewall of a circular truncated cone. The multistep ring-edge etching technology of first reducing the concentric mask and then cutting the [...] Read more.
To create approximately spherical structures with curved sidewalls, this paper presents a method for building a series of decreasing slopes along the sidewall of a circular truncated cone. The multistep ring-edge etching technology of first reducing the concentric mask and then cutting the top off to create a mesa shape can be used to form the slopes. This wet-etching method avoids the constraints of crystallographic properties with surfactant-added Tetramethylammonium hydroxide (TMAH), enabling the manufacture of successive given inclination angles, the precise modulation of the spherical curvature by reduction design of concentric masks, and the setting of etching time. The newly approximated spherical Si microstructure patterns can be used for microlenses, quartz crystal resonators, micropulleys, and other applications. The present research is an approach to fabricate advanced microelectromechanical systems (MEMS) curved-surface structures, extending the range of 3D structures fabricated by silicon wet etching. Full article
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13 pages, 2426 KiB  
Article
Study of Ultrasonic Near-Field Region in Ultrasonic Liquid-Level Monitoring System
by Wanjia Gao, Wenyi Liu, Yanjun Hu and Jun Wang
Micromachines 2020, 11(8), 763; https://doi.org/10.3390/mi11080763 - 10 Aug 2020
Cited by 19 | Viewed by 3811
Abstract
In the method of monitoring the liquid level based on ultrasonic impedance, the near-field effect can seriously affect the validity of the results. In this paper, we explore the factors affecting the length of the ultrasonic near field. Based on that, we propose [...] Read more.
In the method of monitoring the liquid level based on ultrasonic impedance, the near-field effect can seriously affect the validity of the results. In this paper, we explore the factors affecting the length of the ultrasonic near field. Based on that, we propose the optimal length and the minimum length of the buffer block to avoid the near field. The evaluations show that when the parameters of the ultrasonic probe are 15 mm in diameter, 1 MHz in frequency, and ±15 V in emitted ultrasonic wave amplitude, the best results are obtained when the length of the buffer block is 22 mm. When the probe diameter is 10 mm, the buffer block length should be ≥5 mm to ensure the validity of the measured results. The evaluation precision is 1 mm. This research can effectively avoid the blind area of emitted waves when using ultrasonic to measure the liquid level. It provides an effective basis for the selection and design of ultrasonic probes. Full article
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11 pages, 2631 KiB  
Article
Photo-Cleavable Peptide-Poly(Ethylene Glycol) Conjugate Surfaces for Light-Guided Control of Cell Adhesion
by Satoshi Yamaguchi, Yumi Takasaki, Shinya Yamahira and Teruyuki Nagamune
Micromachines 2020, 11(8), 762; https://doi.org/10.3390/mi11080762 - 8 Aug 2020
Cited by 8 | Viewed by 2939
Abstract
Photo-responsive cell attachment surfaces can simplify patterning and recovery of cells in microdevices for medicinal and pharmaceutical research. We developed a photo-responsive surface for controlling the attachment and release of adherent cells on a substrate under light-guidance. The surface comprises a poly(ethylene glycol) [...] Read more.
Photo-responsive cell attachment surfaces can simplify patterning and recovery of cells in microdevices for medicinal and pharmaceutical research. We developed a photo-responsive surface for controlling the attachment and release of adherent cells on a substrate under light-guidance. The surface comprises a poly(ethylene glycol) (PEG)-based photocleavable material that can conjugate with cell-adhesive peptides. Surface-bound peptides were released by photocleavage in the light-exposed region, where the cell attachment was subsequently suppressed by the exposed PEG. Simultaneously, cells selectively adhered to the peptide surface at the unexposed microscale region. After culture, the adhered and spread cells were released by exposure to a light with nontoxic dose level. Thus, the present surface can easily create both cell-adhesive and non-cell-adhesive regions on the substrate by single irradiation of the light pattern, and the adhered cells were selectively released from the light-exposed region on the cell micropattern without damage. This study shows that the photo-responsive surface can serve as a facile platform for the remote-control of patterning and recovery of adherent cells in microdevices. Full article
(This article belongs to the Special Issue Micro and Nano Devices for Cell Analysis)
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11 pages, 1543 KiB  
Article
Core-Shell Beads as Microreactors for Phylogrouping of E. coli Strains
by Lena Gorgannezhad, Kamalalayam Rajan Sreejith, Melody Christie, Jing Jin, Chin Hong Ooi, Mohammad Katouli, Helen Stratton and Nam-Trung Nguyen
Micromachines 2020, 11(8), 761; https://doi.org/10.3390/mi11080761 - 7 Aug 2020
Cited by 9 | Viewed by 2932
Abstract
Multiplex polymerase chain reaction (PCR) is an effective tool for simultaneous detection of target genes. Nevertheless, their use has been restricted due to the intrinsic interference between primer pairs. Performing several single PCRs in an array format instead of a multiplex PCR is [...] Read more.
Multiplex polymerase chain reaction (PCR) is an effective tool for simultaneous detection of target genes. Nevertheless, their use has been restricted due to the intrinsic interference between primer pairs. Performing several single PCRs in an array format instead of a multiplex PCR is a simple way to overcome this obstacle. However, there are still major technical challenges in designing a new generation of single PCR microreactors with a small sample volume, rapid thermal cycling, and no evaporation during amplification. We report a simple and robust core-shell bead array for a series of single amplifications. Four core-shell beads with a polymer coating and PCR mixture were synthesized using liquid marble formation and subsequent photo polymerization. Each bead can detect one target gene. We constructed a customised system for thermal cycling of these core-shell beads. Phylogrouping of the E. coli strains was carried out based on the fluorescent signal of the core-shell beads. This platform can be a promising alternative for multiplex nucleic acid analyses due to its simplicity and high throughput. The platform reported here also reduces the cycling time and avoids evaporation as well as contamination of the sample during the amplification process. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Biology and Biomedicine 2020)
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5 pages, 181 KiB  
Editorial
Editorial for the Special Issue on Nonlinear Photonics Devices
by Luigi Sirleto and Giancarlo C. Righini
Micromachines 2020, 11(8), 760; https://doi.org/10.3390/mi11080760 - 7 Aug 2020
Viewed by 1976
Abstract
There is some incertitude on the creation of the term “photonics” and some ambiguity about its frontiers (and differences with respect to optoelectronics and electro-optics) [...] Full article
(This article belongs to the Special Issue Nonlinear Photonics Devices)
16 pages, 5299 KiB  
Article
The Mechanism of Layer Stacked Clamping (LSC) for Polishing Ultra-Thin Sapphire Wafer
by Zhixiang Chen, Linlin Cao, Julong Yuan, Binghai Lyu, Wei Hang and Jiahuan Wang
Micromachines 2020, 11(8), 759; https://doi.org/10.3390/mi11080759 - 6 Aug 2020
Cited by 6 | Viewed by 2867
Abstract
Double-sides polishing technology has the advantages of high flatness and parallelism, and high polishing efficiency. It is the preferred polishing method for the preparation of ultra-thin sapphire wafer. However, the clamping method is a fundamental problem which is currently difficult to solve. In [...] Read more.
Double-sides polishing technology has the advantages of high flatness and parallelism, and high polishing efficiency. It is the preferred polishing method for the preparation of ultra-thin sapphire wafer. However, the clamping method is a fundamental problem which is currently difficult to solve. In this paper, a layer stacked clamping (LSC) method of ultra-thin sapphire wafer which was used on double-sides processing was proposed and the clamping mechanism of layer stacked clamping (LSC) was studied. Based on the rough surface contact model of fractal theory, combining the theory of van der Waals force and capillary force, the adhesion model of the rough surfaces was constructed, and the reliability of the model was verified through experiments. Research has found that after displacement between the two surfaces the main force of the adhesion force is capillary force. The capillary force decreases with the increasing of surface roughness, droplet volume, and contact angle. For an ultra-thin sapphire wafer with a diameter of 50.8 mm and a thickness of 0.17 mm, more than 1.4 N of normal adhesion force can be generated through the LSC method. Through the double-sides polishing experiment using the LSC method, an ultra-thin sapphire wafer with an average surface roughness (Ra) of 1.52 nm and a flatness (PV) of 0.968 μm was obtained. Full article
(This article belongs to the Section E:Engineering and Technology)
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13 pages, 3666 KiB  
Article
Comparison of Swing and Tilting Check Valves Flowing Compressible Fluids
by Zhi-xin Gao, Ping Liu, Yang Yue, Jun-ye Li and Hui Wu
Micromachines 2020, 11(8), 758; https://doi.org/10.3390/mi11080758 - 6 Aug 2020
Cited by 8 | Viewed by 4983
Abstract
Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum [...] Read more.
Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum Mach number under small valve openings, the dynamic opening time, and the hydrodynamic moment acting on the valve disc are chosen to evaluate the difference between the two types of check valves. Results show that the maximum Mach number increases with the decrease in the valve opening and the increase in the mass flow rate, and the Mach number and the pressure difference in the tilting check valve are higher. In the swing check valve, the hydrodynamic moment is higher and the valve opening time is shorter. Furthermore, the valve disc is more stable for the swing check valve, and there is a periodical oscillation of the valve disc in the tilting check valve under a small mass flow rate. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)
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18 pages, 1621 KiB  
Article
Start-Up Electroosmotic Flow of Multi-Layer Immiscible Maxwell Fluids in a Slit Microchannel
by Juan Escandón, David Torres, Clara Hernández and René Vargas
Micromachines 2020, 11(8), 757; https://doi.org/10.3390/mi11080757 - 5 Aug 2020
Cited by 8 | Viewed by 2643
Abstract
In this investigation, the transient electroosmotic flow of multi-layer immiscible viscoelastic fluids in a slit microchannel is studied. Through an appropriate combination of the momentum equation with the rheological model for Maxwell fluids, an hyperbolic partial differential equation is obtained and semi-analytically solved [...] Read more.
In this investigation, the transient electroosmotic flow of multi-layer immiscible viscoelastic fluids in a slit microchannel is studied. Through an appropriate combination of the momentum equation with the rheological model for Maxwell fluids, an hyperbolic partial differential equation is obtained and semi-analytically solved by using the Laplace transform method to describe the velocity field. In the solution process, different electrostatic conditions and electro-viscous stresses have to be considered in the liquid-liquid interfaces due to the transported fluids content buffer solutions based on symmetrical electrolytes. By adopting a dimensionless mathematical model for the governing and constitutive equations, certain dimensionless parameters that control the start-up of electroosmotic flow appear, as the viscosity ratios, dielectric permittivity ratios, the density ratios, the relaxation times, the electrokinetic parameters and the potential differences. In the results, it is shown that the velocity exhibits an oscillatory behavior in the transient regime as a consequence of the competition between the viscous and elastic forces; also, the flow field is affected by the electrostatic conditions at the liquid-liquid interfaces, producing steep velocity gradients, and finally, the time to reach the steady-state is strongly dependent on the relaxation times, viscosity ratios and the number of fluid layers. Full article
(This article belongs to the Special Issue Electrokinetics in Micro-/nanofluidic Devices)
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12 pages, 1376 KiB  
Article
Parallel-Channel Electrotaxis and Neuron Screening of Caenorhabditis elegans
by Khaled Youssef, Daphne Archonta, Terrance Kubiseski, Anurag Tandon and Pouya Rezai
Micromachines 2020, 11(8), 756; https://doi.org/10.3390/mi11080756 - 4 Aug 2020
Cited by 8 | Viewed by 3340
Abstract
In this paper, we report a novel microfluidic method to conduct a Caenorhabditis elegans electrotaxis movement assay and neuronal imaging on up to 16 worms in parallel. C. elegans is a model organism for neurodegenerative disease and movement disorders such as Parkinson’s disease [...] Read more.
In this paper, we report a novel microfluidic method to conduct a Caenorhabditis elegans electrotaxis movement assay and neuronal imaging on up to 16 worms in parallel. C. elegans is a model organism for neurodegenerative disease and movement disorders such as Parkinson’s disease (PD), and for screening chemicals that alleviate protein aggregation, neuronal death, and movement impairment in PD. Electrotaxis of C. elegans in microfluidic channels has led to the development of neurobehavioral screening platforms, but enhancing the throughput of the electrotactic behavioral assay has remained a challenge. Our device consisted of a hierarchy of tree-like channels for worm loading into 16 parallel electrotaxis screening channels with equivalent electric fields. Tapered channels at the ends of electrotaxis channels were used for worm immobilization and fluorescent imaging of neurons. Parallel electrotaxis of worms was first validated against established single-worm electrotaxis phenotypes. Then, mutant screening was demonstrated using the NL5901 strain, carrying human α-synuclein in the muscle cells, by showing the associated electrotaxis defects in the average speed, body bend frequency (BBF), and electrotaxis time index (ETI). Moreover, chemical screening of a PD worm model was shown by exposing the BZ555 strain, expressing green fluorescence protein (GFP) in the dopaminergic neurons (DNs), to 6-hydroxydopamine neurotoxin. The neurotoxin-treated worms exhibited a reduction in electrotaxis swimming speed, BBF, ETI, and DNs fluorescence intensity. We envision our technique to be used widely in C. elegans-based movement disorder assays to accelerate behavioral and cellular phenotypic investigations. Full article
(This article belongs to the Special Issue Organisms-on-Chips)
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21 pages, 6399 KiB  
Article
A Mobility Aware Binary Tree Algorithm to Resolve RFID Jam and Bottleneck Problems in a Next Generation Specimen Management System
by Yen-Hung Chen, Yen-An Chen and Shu-Rong Huang
Micromachines 2020, 11(8), 755; https://doi.org/10.3390/mi11080755 - 4 Aug 2020
Cited by 3 | Viewed by 2403
Abstract
Hospitals are continuously working to reduce delayed analysis and specimen errors during transfers from testing stations to clinical laboratories. Radio-frequency identification (RFID) tags, which provide automated specimen labeling and tracking, have been proposed as a solution to specimen management that reduces human resource [...] Read more.
Hospitals are continuously working to reduce delayed analysis and specimen errors during transfers from testing stations to clinical laboratories. Radio-frequency identification (RFID) tags, which provide automated specimen labeling and tracking, have been proposed as a solution to specimen management that reduces human resource costs and analytic delays. Conventional RFID solutions, however, confront the problem of traffic jams and bottlenecks on the conveyor belts that connect testing stations with clinical laboratories. This mainly results from methods which assume that the arrival rate of specimens to laboratory RFID readers is fixed/stable, which is unsuitable and impractical in the real world. Previous RFID algorithms have attempted to minimize the time required for tag identification without taking the dynamic arrival rates of specimens into account. Therefore, we propose a novel RFID anti-collision algorithm called the Mobility Aware Binary Tree Algorithm (MABT), which can be used to improve the identification of dynamic tags within the reader’s coverage area and limited dwell time. Full article
(This article belongs to the Special Issue Next Generation RFID Transponders)
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24 pages, 2014 KiB  
Review
Recent Advances and Perceptive Insights into Powder-Mixed Dielectric Fluid of EDM
by Asarudheen Abdudeen, Jaber E. Abu Qudeiri, Ansar Kareem, Thanveer Ahammed and Aiman Ziout
Micromachines 2020, 11(8), 754; https://doi.org/10.3390/mi11080754 - 31 Jul 2020
Cited by 56 | Viewed by 5592
Abstract
Electrical discharge machining (EDM) is an advanced machining method which removes metal by a series of recurring electrical discharges between an electrode and a conductive workpiece, submerged in a dielectric fluid. Even though EDM techniques are widely used to cut hard materials, low [...] Read more.
Electrical discharge machining (EDM) is an advanced machining method which removes metal by a series of recurring electrical discharges between an electrode and a conductive workpiece, submerged in a dielectric fluid. Even though EDM techniques are widely used to cut hard materials, low efficiency and high tool wear remain remarkable challenges in this process. Various studies, such as mixing different powders to dielectric fluids, are progressing to improve their efficiency. This paper reviews advances in the powder-mixed EDM process. Furthermore, studies about various powders used for the process and its comparison are carried out. This review looks at the objectives of achieving a more efficient metal removal rate, reduction in tool wear, and improved surface quality of the powder-mixed EDM process. Moreover, this paper helps researchers select suitable powders which are exhibiting better results and identifying different aspects of powder-mixed dielectric fluid of EDM. Full article
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