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Micromachines, Volume 9, Issue 11 (November 2018)

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Open AccessArticle On-Chip Tunable Cell Rotation Using Acoustically Oscillating Asymmetrical Microstructures
Micromachines 2018, 9(11), 596; https://doi.org/10.3390/mi9110596 (registering DOI)
Received: 26 September 2018 / Revised: 31 October 2018 / Accepted: 8 November 2018 / Published: 14 November 2018
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Abstract
The precise rotational manipulation of cells and other micrometer-sized biological samples is critical to many applications in biology, medicine, and agriculture. We describe an acoustic-based, on-chip manipulation method that can achieve tunable cell rotation. In an acoustic field formed by the vibration of
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The precise rotational manipulation of cells and other micrometer-sized biological samples is critical to many applications in biology, medicine, and agriculture. We describe an acoustic-based, on-chip manipulation method that can achieve tunable cell rotation. In an acoustic field formed by the vibration of a piezoelectric transducer, acoustic streaming was generated using a specially designed, oscillating asymmetrical sidewall shape. We also studied the nature of acoustic streaming generation by numerical simulations, and our simulation results matched well with the experimental results. Trapping and rotation of diatom cells and swine oocytes were coupled using oscillating asymmetrical microstructures with different vibration modes. Finally, we investigated the relationship between the driving voltage and the speed of cell rotation, showing that the rotational rate achieved could be as large as approximately 1800 rpm. Using our device, the rotation rate can be effectively tuned on demand for single-cell studies. Our acoustofluidic cell rotation approach is simple, compact, non-contact, and biocompatible, permitting rotation irrespective of the optical, magnetic, or electrical properties of the specimen under investigation. Full article
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Open AccessArticle Remote Stimulation of Sciatic Nerve Using Cuff Electrodes and Implanted Diodes
Micromachines 2018, 9(11), 595; https://doi.org/10.3390/mi9110595 (registering DOI)
Received: 29 August 2018 / Revised: 5 November 2018 / Accepted: 12 November 2018 / Published: 14 November 2018
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Abstract
We demonstrate a method of neurostimulation using implanted, free-floating, inter-neural diodes. They are activated by volume-conducted, high frequency, alternating current (AC) fields and address the issue of instability caused by interconnect wires in chronic nerve stimulation. The aim of this study is to
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We demonstrate a method of neurostimulation using implanted, free-floating, inter-neural diodes. They are activated by volume-conducted, high frequency, alternating current (AC) fields and address the issue of instability caused by interconnect wires in chronic nerve stimulation. The aim of this study is to optimize the set of AC electrical parameters and the diode features to achieve wireless neurostimulation. Three different packaged Schottky diodes (1.5 mm, 500 µm and 220 µm feature sizes) were tested in vivo (n = 17 rats). A careful assessment of sciatic nerve activation as a function of diode–dipole lengths and relative position of the diode was conducted. Subsequently, free-floating Schottky microdiodes were implanted in the nerve (n = 3 rats) and stimulated wirelessly. Thresholds for muscle twitch responses increased non-linearly with frequency. Currents through implanted diodes within the nerve suffer large attenuations (~100 fold) requiring 1–2 mA drive currents for thresholds at 17 µA. The muscle recruitment response using electromyograms (EMGs) is intrinsically steep for subepineurial implants and becomes steeper as diode is implanted at increasing depths away from external AC stimulating electrodes. The study demonstrates the feasibility of activating remote, untethered, implanted microscale diodes using external AC fields and achieving neurostimulation. Full article
(This article belongs to the Special Issue Neural Microelectrodes: Design and Applications)
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Open AccessReview Ultrasonic Based Tissue Modelling and Engineering
Micromachines 2018, 9(11), 594; https://doi.org/10.3390/mi9110594 (registering DOI)
Received: 19 October 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 14 November 2018
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Abstract
Systems and devices for in vitro tissue modelling and engineering are valuable tools, which combine the strength between the controlled laboratory environment and the complex tissue organization and environment in vivo. Device-based tissue engineering is also a possible avenue for future explant culture
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Systems and devices for in vitro tissue modelling and engineering are valuable tools, which combine the strength between the controlled laboratory environment and the complex tissue organization and environment in vivo. Device-based tissue engineering is also a possible avenue for future explant culture in regenerative medicine. The most fundamental requirements on platforms intended for tissue modelling and engineering are their ability to shape and maintain cell aggregates over long-term culture. An emerging technology for tissue shaping and culture is ultrasonic standing wave (USW) particle manipulation, which offers label-free and gentle positioning and aggregation of cells. The pressure nodes defined by the USW, where cells are trapped in most cases, are stable over time and can be both static and dynamic depending on actuation schemes. In this review article, we highlight the potential of USW cell manipulation as a tool for tissue modelling and engineering. Full article
(This article belongs to the Special Issue Acoustofluidics in Medicine and Biology)
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Open AccessArticle Superhydrophobic Water-Solid Contact Triboelectric Generator by Simple Spray-On Fabrication Method
Micromachines 2018, 9(11), 593; https://doi.org/10.3390/mi9110593
Received: 26 October 2018 / Revised: 8 November 2018 / Accepted: 10 November 2018 / Published: 13 November 2018
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Abstract
Energy harvesting is a method of converting energy from ambient environment into useful electrical energy. Due to the increasing number of sensors and personal electronics, energy harvesting technologies from various sources are gaining attention. Among energy-harvesting technologies, triboelectric nanogenerator (TENG) was introduced as
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Energy harvesting is a method of converting energy from ambient environment into useful electrical energy. Due to the increasing number of sensors and personal electronics, energy harvesting technologies from various sources are gaining attention. Among energy-harvesting technologies, triboelectric nanogenerator (TENG) was introduced as a device that can effectively generate electricity from mechanical motions by contact-electrification. Particularly, liquid-solid contact TENGs, which use the liquid itself as a triboelectric material, can overcome the inevitable friction wear between two solid materials. Using a commercial aerosol hydrophobic spray, liquid-solid contact TENGs, with a superhydrophobic surface (contact angle over 160°) can be easily fabricated with only a few coating processes. To optimize the fabrication process, the open-circuit voltage of sprayed superhydrophobic surfaces was measured depending on the number of coating processes. To demonstrate the simple fabrication and applicability of this technique on random 3D surfaces, a liquid-solid contact TENG was fabricated on the brim of a cap (its complicated surface structure is due to the knitted strings). This simple sprayed-on superhydrophobic surface can be a possible solution for liquid-solid contact TENGs to be mass produced and commercialized in the future. Full article
(This article belongs to the Special Issue Nanogenerators in Korea)
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Open AccessArticle Cell Density Detector Based on Light Beam Focusing
Micromachines 2018, 9(11), 592; https://doi.org/10.3390/mi9110592
Received: 17 October 2018 / Revised: 1 November 2018 / Accepted: 5 November 2018 / Published: 13 November 2018
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Abstract
Although the lab-on-a-chip system has been successfully applied in a wide variety of fields, the goal of achieving a cell counter with simple operation, low cost, and high accuracy still attracts continuous research efforts. In this paper, the authors explore a cell counter
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Although the lab-on-a-chip system has been successfully applied in a wide variety of fields, the goal of achieving a cell counter with simple operation, low cost, and high accuracy still attracts continuous research efforts. In this paper, the authors explore a cell counter based on light beam focusing to measure the density of adherent cells. In this sensor, the light emitted from the optical fibers is collimated by the collimating lens formed in polydimethylsiloxane (PDMS). The uniformly attached adherent cells act as a convex lens, focusing the collimated light propagated through them. The intensity of the focused light indicates the density of the adherent cells. For Hela cells, a detection limit of 8.3 × 104 cells/mL with a detection range from 0.1 × 106 cells/mL to 1.0 × 106 cells/mL is achieved. This sensor is particularly useful for drug screening, cell pathology analysis, and cancer pre-diagnosis. Full article
(This article belongs to the Special Issue Optofluidics 2018)
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Open AccessArticle Self-Lubricanting Slippery Surface with Wettability Gradients for Anti-Sticking of Electrosurgical Scalpel
Micromachines 2018, 9(11), 591; https://doi.org/10.3390/mi9110591
Received: 30 September 2018 / Revised: 6 November 2018 / Accepted: 8 November 2018 / Published: 13 November 2018
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Abstract
Soft tissue sticking on electrosurgical scalpels in minimally invasive surgery can increase the difficulty of operation and easily lead to medical malpractice. It is significant to develop new methods for anti-sticking of soft tissue on electrosurgical scalpels. Based on the characteristics of biomimetic
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Soft tissue sticking on electrosurgical scalpels in minimally invasive surgery can increase the difficulty of operation and easily lead to medical malpractice. It is significant to develop new methods for anti-sticking of soft tissue on electrosurgical scalpels. Based on the characteristics of biomimetic ultra-slippery surface, a self-lubricating slippery surface with wettability gradients on electrosurgical scalpel was designed and fabricated. Non-uniformly distributed cylindrical micro pillars, which constitute the wettability gradients, were prepared by an electrolytic etching process and the theoretic of the spontaneous liquid spreading process was analyzed. The silicophilic property of wettability gradients surface was modified by octadecyltrichlorosilane (OTS) self-assembling coat with biocompatible liquid lubricant dimethyl silicone oil. The contact angle of gradient’s surface at different temperatures was measured. The transportation behaviors of both water and dimethyl silicone oil on the wettability gradient’s surface were investigated; the results illustrate that the wettability gradient’s slippery surface can successfully self-lubricate from regions with low pillar density to regions with high pillar density, ascribed to the unbalanced Young’s force. The anti-sticking capability of the electrosurgical scalpel with self-lubricating slippery surface was tested. Both the adhesion force and adhesion mass under different cycles were calculated. The results suggest that the as-prepared slippery surface has excellent anti-sticking ability associated with better durability. Full article
(This article belongs to the Special Issue Microscale Surface Tension and Its Applications)
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Open AccessArticle Cell Injection Millirobot Development and Evaluation in Microfluidic Chip
Micromachines 2018, 9(11), 590; https://doi.org/10.3390/mi9110590
Received: 26 September 2018 / Revised: 25 October 2018 / Accepted: 8 November 2018 / Published: 13 November 2018
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Abstract
We propose an innovative design of millirobot, which can achieve donor cell suction, delivery, and injection in a mammalian oocyte on a microfluidic chip. The millirobot body contains a hollow space that produces suction and ejection forces for the injection of cell nuclei
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We propose an innovative design of millirobot, which can achieve donor cell suction, delivery, and injection in a mammalian oocyte on a microfluidic chip. The millirobot body contains a hollow space that produces suction and ejection forces for the injection of cell nuclei using a nozzle at the tip of the robot. Specifically, a controller changes the hollow volume by balancing the magnetic and elastic forces of a membrane along with the motion of stages in the XY plane. A glass capillary attached to the tip of the robot contains a nozzle that is able to absorb and inject cell nuclei. The millirobot provides three degrees of freedom and generates micronewton forces. We demonstrate the effectiveness of the proposed millirobot through an experiment of the absorption and ejection of 20-µm particles from the nozzle using magnetic control in a microfluidic chip. Full article
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Open AccessArticle Aluminum Patterned Electroplating from AlCl3–[EMIm]Cl Ionic Liquid towards Microsystems Application
Micromachines 2018, 9(11), 589; https://doi.org/10.3390/mi9110589
Received: 18 October 2018 / Accepted: 6 November 2018 / Published: 12 November 2018
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Abstract
Electroplating process is being used to deposit a relatively thick film of metallic materials for various microsystems applications, such as for the wafer-level bonding sealing frame and as a thermal actuator. Recently, the Al electroplating process from ionic liquid has been an attractive
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Electroplating process is being used to deposit a relatively thick film of metallic materials for various microsystems applications, such as for the wafer-level bonding sealing frame and as a thermal actuator. Recently, the Al electroplating process from ionic liquid has been an attractive deposition method for anti-corrosion coatings. To extend the utilization of the film, in particular for microsystems application, a microstructure formation by patterned electroplating of Al from AlCl 3 –1-ethyl-3-methylimidazolium chloride ((EMIm)Cl) ionic liquid is investigated in this study. The influences of each deposition parameters to the electroplating process as well as the resulting surface morphology are evaluated. Electroplated Al deposits on both Au and Al seed layers are both studied. It is also found that a recurrent galvanic pulse plating process yields in a higher current efficiency. Finally, Al electroplating on a 2 µm-trenched 100 mm-wafer is also demonstrated. Full article
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Open AccessArticle Microfluidic Analyzer Enabling Quantitative Measurements of Specific Intracellular Proteins at the Single-Cell Level
Micromachines 2018, 9(11), 588; https://doi.org/10.3390/mi9110588
Received: 12 October 2018 / Revised: 2 November 2018 / Accepted: 8 November 2018 / Published: 12 November 2018
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Abstract
This paper presents a microfluidic instrument capable of quantifying single-cell specific intracellular proteins, which are composed of three functioning modules and two software platforms. Under the control of a LabVIEW platform, a pressure module flushed cells stained with fluorescent antibodies through a microfluidic
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This paper presents a microfluidic instrument capable of quantifying single-cell specific intracellular proteins, which are composed of three functioning modules and two software platforms. Under the control of a LabVIEW platform, a pressure module flushed cells stained with fluorescent antibodies through a microfluidic module with fluorescent intensities quantified by a fluorescent module and translated into the numbers of specific intracellular proteins at the single-cell level using a MATLAB platform. Detection ranges and resolutions of the analyzer were characterized as 896.78–6.78 × 105 and 334.60 nM for Alexa 488, 314.60–2.11 × 105 and 153.98 nM for FITC, and 77.03–5.24 × 104 and 37.17 nM for FITC-labelled anti-beta-actin antibodies. As a demonstration, the numbers of single-cell beta-actins of two paired oral tumor cell types and two oral patient samples were quantified as: 1.12 ± 0.77 × 106/cell (salivary adenoid cystic carcinoma parental cell line (SACC-83), ncell = 13,689) vs. 0.90 ± 0.58 × 105/cell (salivary adenoid cystic carcinoma lung metastasis cell line (SACC-LM), ncell = 15,341); 0.89 ± 0.69 × 106/cell (oral carcinoma cell line (CAL 27), ncell = 7357) vs. 0.93 ± 0.69 × 106/cell (oral carcinoma lymphatic metastasis cell line (CAL 27-LN2), ncell = 6276); and 0.86 ± 0.52 × 106/cell (patient I) vs. 0.85 ± 0.58 × 106/cell (patient II). These results (1) validated the developed analyzer with a throughput of 10 cells/s and a processing capability of ~10,000 cells for each cell type, and (2) revealed that as an internal control in cell analysis, the expressions of beta-actins remained stable in oral tumors with different malignant levels. Full article
(This article belongs to the Special Issue Microfluidics for Cell and Other Organisms)
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Open AccessArticle Characterizing Longitudinal Changes in the Impedance Spectra of In-Vivo Peripheral Nerve Electrodes
Micromachines 2018, 9(11), 587; https://doi.org/10.3390/mi9110587
Received: 6 October 2018 / Revised: 2 November 2018 / Accepted: 5 November 2018 / Published: 12 November 2018
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Abstract
Characterizing the aging processes of electrodes in vivo is essential in order to elucidate the changes of the electrode–tissue interface and the device. However, commonly used impedance measurements at 1 kHz are insufficient for determining electrode viability, with measurements being prone to false
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Characterizing the aging processes of electrodes in vivo is essential in order to elucidate the changes of the electrode–tissue interface and the device. However, commonly used impedance measurements at 1 kHz are insufficient for determining electrode viability, with measurements being prone to false positives. We implanted cohorts of five iridium oxide (IrOx) and six platinum (Pt) Utah arrays into the sciatic nerve of rats, and collected the electrochemical impedance spectroscopy (EIS) up to 12 weeks or until array failure. We developed a method to classify the shapes of the magnitude and phase spectra, and correlated the classifications to circuit models and electrochemical processes at the interface likely responsible. We found categories of EIS characteristic of iridium oxide tip metallization, platinum tip metallization, tip metal degradation, encapsulation degradation, and wire breakage in the lead. We also fitted the impedance spectra as features to a fine-Gaussian support vector machine (SVM) algorithm for both IrOx and Pt tipped arrays, with a prediction accuracy for categories of 95% and 99%, respectively. Together, this suggests that these simple and computationally efficient algorithms are sufficient to explain the majority of variance across a wide range of EIS data describing Utah arrays. These categories were assessed over time, providing insights into the degradation and failure mechanisms for both the electrode–tissue interface and wire bundle. Methods developed in this study will allow for a better understanding of how EIS can characterize the physical changes to electrodes in vivo. Full article
(This article belongs to the Special Issue Neural Microelectrodes: Design and Applications)
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Open AccessArticle Rapid Simultaneous Determination of Paraquat and Creatinine in Human Serum Using a Piece of Paper
Micromachines 2018, 9(11), 586; https://doi.org/10.3390/mi9110586
Received: 13 October 2018 / Revised: 3 November 2018 / Accepted: 9 November 2018 / Published: 12 November 2018
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Abstract
Paraquat intoxication is characterized by acute kidney injury and multi-organ failure, causing substantial mortality and morbidity. This study aims to develop a 2-in-1 paper-based analytical device to detect the concentrations of paraquat and creatinine in human serum, which can help clinicians diagnose patients
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Paraquat intoxication is characterized by acute kidney injury and multi-organ failure, causing substantial mortality and morbidity. This study aims to develop a 2-in-1 paper-based analytical device to detect the concentrations of paraquat and creatinine in human serum, which can help clinicians diagnose patients with paraquat poisoning in a more rapid and geographically unrestricted manner. The procedure involves fabrication of a paper-based analytical device, i.e., printing of design on a filter paper, heating of wax-printed micro zone plates so as molten wax diffusing into and completely through the paper to the other side, forming hydrophobic boundaries that could act as detection zones for the paraquat colorimetric assay, and finally analysis using ImageJ software. The paper employed a colorimetric sodium dithionite assay to indicate the paraquat level in a buffer or human serum system in less than 10 min. In this study, colorimetric changes into blue color could be observed by the naked eye. By curve fitting models of sodium dithionite in normal human serum, we evaluated the serum paraquat levels for five paraquat patients. In the sodium dithionate assay, the measured serum paraquat concentrations in patients 1–5 were 22.59, 5.99, 26.52, 35.19 and 25.00 ppm, respectively. On the other hand, by curve fitting models of the creatinine assay in normal human serum, the measured serum creatinine concentrations were 16.10, 12.92, 13.82, 13.58 and 12.20 ppm, respectively. We found that the analytical performance of this device can compete with the standard of Clinical Laboratory of Chang Gung Memorial Hospital, with a less complicated sample preparation process and more rapid results. In conclusion, this 2-in-1 paper-based analytical device has the advantage of being simple and cheap, enabling rapid detection of paraquat intoxication as well as assessment of renal prognosis. Full article
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Open AccessArticle Parametric Analysis and Optimization of Radially Layered Cylindrical Piezoceramic/Epoxy Composite Transducers
Micromachines 2018, 9(11), 585; https://doi.org/10.3390/mi9110585
Received: 8 October 2018 / Revised: 28 October 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
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Abstract
Radially layered cylindrical piezoceramic/epoxy composite transducers have been designed by integrating the excellent performance of piezoelectric/polymer composites and the radial radiation ability of cylindrical configurations, which are promising in developing novel ultrasonic and underwater sound techniques. Our previous study has explored the effects
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Radially layered cylindrical piezoceramic/epoxy composite transducers have been designed by integrating the excellent performance of piezoelectric/polymer composites and the radial radiation ability of cylindrical configurations, which are promising in developing novel ultrasonic and underwater sound techniques. Our previous study has explored the effects of the external resistance on the electromechanical characteristics of the transducer, and obtained some valuable findings. To clearly understand the electromechanical characteristics of the transducer and to guide the device design, in this paper, parametric analysis was performed to reveal the effects of multiple key factors on the electromechanical characteristics. These factors include material parameters of epoxy layers, piezoceramic material types, and locations of piezoceramic rings. In order to better analyze the influence of these factors, a modified theoretical model, in which every layer has different geometric and material parameters, was developed based on the model given in the previous work. Furthermore, the reliability of the model was validated by the ANSYS simulation results and the experimental results. The present investigation provides some helpful guidelines to design and optimize the radially layered cylindrical piezoceramic/epoxy composite transducers. Full article
(This article belongs to the Special Issue Piezoelectric Transducers: Materials, Devices and Applications)
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Open AccessReview Recent Progress on Photoacoustic Imaging Enhanced with Microelectromechanical Systems (MEMS) Technologies
Micromachines 2018, 9(11), 584; https://doi.org/10.3390/mi9110584
Received: 12 October 2018 / Revised: 5 November 2018 / Accepted: 6 November 2018 / Published: 8 November 2018
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Abstract
Photoacoustic imaging (PAI) is a new biomedical imaging technology currently in the spotlight providing a hybrid contrast mechanism and excellent spatial resolution in the biological tissues. It has been extensively studied for preclinical and clinical applications taking advantage of its ability to provide
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Photoacoustic imaging (PAI) is a new biomedical imaging technology currently in the spotlight providing a hybrid contrast mechanism and excellent spatial resolution in the biological tissues. It has been extensively studied for preclinical and clinical applications taking advantage of its ability to provide anatomical and functional information of live bodies noninvasively. Recently, microelectromechanical systems (MEMS) technologies, particularly actuators and sensors, have contributed to improving the PAI system performance, further expanding the research fields. This review introduces cutting-edge MEMS technologies for PAI and summarizes the recent advances of scanning mirrors and detectors in MEMS. Full article
(This article belongs to the Special Issue MEMS Technology for Biomedical Imaging Applications)
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Open AccessArticle A Mechanically-Adaptive Polymer Nanocomposite-Based Intracortical Probe and Package for Chronic Neural Recording
Micromachines 2018, 9(11), 583; https://doi.org/10.3390/mi9110583
Received: 14 September 2018 / Revised: 19 October 2018 / Accepted: 2 November 2018 / Published: 8 November 2018
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Abstract
Mechanical, materials, and biological causes of intracortical probe failure have hampered their utility in basic science and clinical applications. By anticipating causes of failure, we can design a system that will prevent the known causes of failure. The neural probe design was centered
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Mechanical, materials, and biological causes of intracortical probe failure have hampered their utility in basic science and clinical applications. By anticipating causes of failure, we can design a system that will prevent the known causes of failure. The neural probe design was centered around a bio-inspired, mechanically-softening polymer nanocomposite. The polymer nanocomposite was functionalized with recording microelectrodes using a microfabrication process designed for chemical and thermal process compatibility. A custom package based upon a ribbon cable, printed circuit board, and a 3D-printed housing was designed to enable connection to external electronics. Probes were implanted into the primary motor cortex of Sprague-Dawley rats for 16 weeks, during which regular recording and electrochemical impedance spectroscopy measurement sessions took place. The implanted mechanically-softening probes had stable electrochemical impedance spectra across the 16 weeks and single units were recorded out to 16 weeks. The demonstration of chronic neural recording with the mechanically-softening probe suggests that probe architecture, custom package, and general design strategy are appropriate for long-term studies in rodents. Full article
(This article belongs to the Special Issue Neural Microelectrodes: Design and Applications)
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Open AccessArticle The Balancing Act in Ferroelectric Transistors: How Hard Can It Be?
Micromachines 2018, 9(11), 582; https://doi.org/10.3390/mi9110582
Received: 19 October 2018 / Revised: 31 October 2018 / Accepted: 5 November 2018 / Published: 7 November 2018
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Abstract
For some years now, the ever continuing dimensional scaling has no longer been considered to be sufficient for the realization of advanced CMOS devices. Alternative approaches, such as employing new materials and introducing new device architectures, appear to be the way to go
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For some years now, the ever continuing dimensional scaling has no longer been considered to be sufficient for the realization of advanced CMOS devices. Alternative approaches, such as employing new materials and introducing new device architectures, appear to be the way to go forward. A currently hot approach is to employ ferroelectric materials for obtaining a positive feedback in the gate control of a switch. This work elaborates on two device architectures based on this approach: the negative-capacitance and the piezoelectric field-effect transistor, i.e., the NC-FET (negative-capacitance field-effect transistor), respectively π -FET. It briefly describes their operation principle and compares those based on earlier reports. For optimal performance, the adopted ferroelectric material in the NC-FET should have a relatively wide polarization-field loop (i.e., “hard” ferroelectric material). Its optimal remnant polarization depends on the NC-FET architecture, although there is some consensus in having a low value for that (e.g., HZO (Hafnium-Zirconate)). π -FET is the piezoelectric coefficient, hence its polarization-field loop should be as high as possible (e.g., PZT (lead-zirconate-titanate)). In summary, literature reports indicate that the NC-FET shows better performance in terms of subthreshold swing and on-current. However, since its operation principle is based on a relatively large change in polarization the maximum speed, unlike in a π -FET, forms a big issue. Therefore, for future low-power CMOS, a hybrid solution is proposed comprising both device architectures on a chip where hard ferroelectric materials with a high piezocoefficient are used. Full article
(This article belongs to the Special Issue Miniaturized Transistors)
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Open AccessArticle A Novel One-Transistor Dynamic Random-Access Memory (1T DRAM) Featuring Partially Inserted Wide-Bandgap Double Barriers for High-Temperature Applications
Micromachines 2018, 9(11), 581; https://doi.org/10.3390/mi9110581
Received: 1 October 2018 / Revised: 4 November 2018 / Accepted: 5 November 2018 / Published: 7 November 2018
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Abstract
These days, the demand on electronic systems operating at high temperature is increasing owing to bursting interest in applications adaptable to harsh environments on earth, as well as in the unpaved spaces in the universe. However, research on memory technologies suitable to high-temperature
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These days, the demand on electronic systems operating at high temperature is increasing owing to bursting interest in applications adaptable to harsh environments on earth, as well as in the unpaved spaces in the universe. However, research on memory technologies suitable to high-temperature conditions have been seldom reported yet. In this work, a novel one-transistor dynamic random-access memory (1T DRAM) featuring the device channel with partially inserted wide-bandgap semiconductor material toward the high-temperature application is proposed and designed, and its device performances are investigated with an emphasis at 500 K. The possibilities of the program operation by impact ionization and the erase operation via drift conduction by a properly high drain voltage have been verified through a series of technology computer-aided design (TCAD) device simulations at 500 K. Analyses of the energy-band structures in the hold state reveals that the electrons stored in the channel can be effectively confined and retained by the surrounding thin wide-bandgap semiconductor barriers. Additionally, for more realistic and practical claims, transient characteristics of the proposed volatile memory device have been closely investigated quantifying the programming window and retention time. Although there is an inevitable degradation in state-1/state-0 current ratio compared with the case of room-temperature operation, the high-temperature operation capabilities of the proposed memory device at 500 K have been confirmed to fall into the regime permissible for practical use. Full article
(This article belongs to the Special Issue Wide Bandgap Semiconductor Based Micro/Nano Devices)
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Open AccessReview Recent Developments for Flexible Pressure Sensors: A Review
Micromachines 2018, 9(11), 580; https://doi.org/10.3390/mi9110580
Received: 5 September 2018 / Revised: 26 October 2018 / Accepted: 2 November 2018 / Published: 7 November 2018
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Abstract
Flexible pressure sensors are attracting great interest from researchers and are widely applied in various new electronic equipment because of their distinct characteristics with high flexibility, high sensitivity, and light weight; examples include electronic skin (E-skin) and wearable flexible sensing devices. This review
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Flexible pressure sensors are attracting great interest from researchers and are widely applied in various new electronic equipment because of their distinct characteristics with high flexibility, high sensitivity, and light weight; examples include electronic skin (E-skin) and wearable flexible sensing devices. This review summarizes the research progress of flexible pressure sensors, including three kinds of transduction mechanisms and their respective research developments, and applications in the fields of E-skin and wearable devices. Furthermore, the challenges and development trends of E-skin and wearable flexible sensors are also briefly discussed. Challenges of developing high extensibility, high sensitivity, and flexible multi-function equipment still exist at present. Exploring new sensing mechanisms, seeking new functional materials, and developing novel integration technology of flexible devices will be the key directions in the sensors field in future. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle High Performance Seesaw Torsional CMOS-MEMS Relay Using Tungsten VIA Layer
Micromachines 2018, 9(11), 579; https://doi.org/10.3390/mi9110579
Received: 28 September 2018 / Revised: 23 October 2018 / Accepted: 1 November 2018 / Published: 7 November 2018
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Abstract
In this paper, a seesaw torsional relay monolithically integrated in a standard 0.35 μm complementary metal oxide semiconductor (CMOS) technology is presented. The seesaw relay is fabricated using the Back-End-Of-Line (BEOL) layers available, specifically using the tungsten VIA3 layer of a 0.35 μm
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In this paper, a seesaw torsional relay monolithically integrated in a standard 0.35 μm complementary metal oxide semiconductor (CMOS) technology is presented. The seesaw relay is fabricated using the Back-End-Of-Line (BEOL) layers available, specifically using the tungsten VIA3 layer of a 0.35 μm CMOS technology. Three different contact materials are studied to discriminate which is the most adequate as a mechanical relay. The robustness of the relay is proved, and its main characteristics as a relay for the three different contact interfaces are provided. The seesaw relay is capable of a double hysteretic switching cycle, providing compactness for mechanical logic processing. The low contact resistance achieved with the TiN/W mechanical contact with high cycling life time is competitive in comparison with the state-of-the art. Full article
(This article belongs to the Special Issue Development of CMOS-MEMS/NEMS Devices)
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Open AccessArticle Research on a 3-DOF Motion Device Based on the Flexible Mechanism Driven by the Piezoelectric Actuators
Micromachines 2018, 9(11), 578; https://doi.org/10.3390/mi9110578
Received: 5 September 2018 / Revised: 25 October 2018 / Accepted: 29 October 2018 / Published: 6 November 2018
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Abstract
This paper describes the innovative design of a three-dimensional (3D) motion device based on a flexible mechanism, which is used primarily to produce accurate and fast micro-displacement. For example, the rapid contact and separation of the tool and the workpiece are realized by
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This paper describes the innovative design of a three-dimensional (3D) motion device based on a flexible mechanism, which is used primarily to produce accurate and fast micro-displacement. For example, the rapid contact and separation of the tool and the workpiece are realized by the operation of the 3D motion device in the machining process. This paper mainly concerns the device performance. A theoretical model for the static performance of the device was established using the matrix-based compliance modeling (MCM) method, and the static characteristics of the device were numerically simulated by finite element analysis (FEA). The Lagrangian principle and the finite element analysis method for device dynamics are used for prediction to obtain the natural frequency of the device. Under no-load conditions, the dynamic response performance and linear motion performance of the three directions were tested and analyzed with different input signals, and three sets of vibration trajectories were obtained. Finally, the scratching experiment was carried out. The detection of the workpiece reveals a pronounced periodic texture on the surface, which verifies that the vibration device can generate an ideal 3D vibration trajectory. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle Design and Analysis of a High-Gain and Robust Multi-DOF Electro-thermally Actuated MEMS Gyroscope
Micromachines 2018, 9(11), 577; https://doi.org/10.3390/mi9110577
Received: 30 September 2018 / Revised: 24 October 2018 / Accepted: 1 November 2018 / Published: 5 November 2018
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Abstract
This paper presents the design and analysis of a multi degree of freedom (DOF) electro-thermally actuated non-resonant MEMS gyroscope with a 3-DOF drive mode and 1-DOF sense mode system. The 3-DOF drive mode system consists of three masses coupled together using suspension beams.
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This paper presents the design and analysis of a multi degree of freedom (DOF) electro-thermally actuated non-resonant MEMS gyroscope with a 3-DOF drive mode and 1-DOF sense mode system. The 3-DOF drive mode system consists of three masses coupled together using suspension beams. The 1-DOF system consists of a single mass whose motion is decoupled from the drive mode using a decoupling frame. The gyroscope is designed to be operated in the flat region between the first two resonant peaks in drive mode, thus minimizing the effect of environmental and fabrication process variations on device performance. The high gain in the flat operational region is achieved by tuning the suspension beams stiffness. A detailed analytical model, considering the dynamics of both the electro-thermal actuator and multi-mass system, is developed. A parametric optimization is carried out, considering the microfabrication process constraints of the Metal Multi-User MEMS Processes (MetalMUMPs), to achieve high gain. The stiffness of suspension beams is optimized such that the sense mode resonant frequency lies in the flat region between the first two resonant peaks in the drive mode. The results acquired through the developed analytical model are verified with the help of 3D finite element method (FEM)-based simulations. The first three resonant frequencies in the drive mode are designed to be 2.51 kHz, 3.68 kHz, and 5.77 kHz, respectively. The sense mode resonant frequency is designed to be 3.13 kHz. At an actuation voltage of 0.2 V, the dynamically amplified drive mode gain in the sense mass is obtained to be 18.6 µm. With this gain, a capacitive change of 28.11   f F and 862.13   f F is achieved corresponding to the sense mode amplitude of 0.15   μ m and 4.5   μ m at atmospheric air pressure and in a vacuum, respectively. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle Development of Flexible Robot Skin for Safe and Natural Human–Robot Collaboration
Micromachines 2018, 9(11), 576; https://doi.org/10.3390/mi9110576
Received: 9 October 2018 / Revised: 31 October 2018 / Accepted: 3 November 2018 / Published: 5 November 2018
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Abstract
For industrial manufacturing, industrial robots are required to work together with human counterparts on certain special occasions, where human workers share their skills with robots. Intuitive human–robot interaction brings increasing safety challenges, which can be properly addressed by using sensor-based active control technology.
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For industrial manufacturing, industrial robots are required to work together with human counterparts on certain special occasions, where human workers share their skills with robots. Intuitive human–robot interaction brings increasing safety challenges, which can be properly addressed by using sensor-based active control technology. In this article, we designed and fabricated a three-dimensional flexible robot skin made by the piezoresistive nanocomposite based on the need for enhancement of the security performance of the collaborative robot. The robot skin endowed the YuMi robot with a tactile perception like human skin. The developed sensing unit in the robot skin showed the one-to-one correspondence between force input and resistance output (percentage change in impedance) in the range of 0–6.5 N. Furthermore, the calibration result indicated that the developed sensing unit is capable of offering a maximum force sensitivity (percentage change in impedance per Newton force) of 18.83% N−1 when loaded with an external force of 6.5 N. The fabricated sensing unit showed good reproducibility after loading with cyclic force (0–5.5 N) under a frequency of 0.65 Hz for 3500 cycles. In addition, to suppress the bypass crosstalk in robot skin, we designed a readout circuit for sampling tactile data. Moreover, experiments were conducted to estimate the contact/collision force between the object and the robot in a real-time manner. The experiment results showed that the implemented robot skin can provide an efficient approach for natural and secure human–robot interaction. Full article
(This article belongs to the Special Issue Printed Flexible and Stretchable Electronics)
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Open AccessArticle Investigations of the Effects of Geometric Imperfections on the Nonlinear Static and Dynamic Behavior of Capacitive Micomachined Ultrasonic Transducers
Micromachines 2018, 9(11), 575; https://doi.org/10.3390/mi9110575
Received: 30 September 2018 / Revised: 30 October 2018 / Accepted: 1 November 2018 / Published: 5 November 2018
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Abstract
In order to investigate the effects of geometric imperfections on the static and dynamic behavior of capacitive micomachined ultrasonic transducers (CMUTs), the governing equations of motion of a circular microplate with initial defection have been derived using the von Kármán plate theory while
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In order to investigate the effects of geometric imperfections on the static and dynamic behavior of capacitive micomachined ultrasonic transducers (CMUTs), the governing equations of motion of a circular microplate with initial defection have been derived using the von Kármán plate theory while taking into account the mechanical and electrostatic nonlinearities. The partial differential equations are discretized using the differential quadrature method (DQM) and the resulting coupled nonlinear ordinary differential equations (ODEs) are solved using the harmonic balance method (HBM) coupled with the asymptotic numerical method (ANM). It is shown that the initial deflection has an impact on the static behavior of the CMUT by increasing its pull-in voltage up to 45%. Moreover, the dynamic behavior is affected by the initial deflection, enabling an increase in the resonance frequencies and the bistability domain and leading to a change of the frequency response from softening to hardening. This model allows MEMS designers to predict the nonlinear behavior of imperfect CMUT and tune its bifurcation topology in order to enhance its performances in terms of bandwidth and generated acoustic power while driving the microplate up to 80% beyond its critical amplitude. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle Research on the Relationship between Cutting Force and Machined Surface Quality in Micro Ball End-Milling of Potassium Dihydrogen Phosphate Crystal
Micromachines 2018, 9(11), 574; https://doi.org/10.3390/mi9110574
Received: 7 October 2018 / Revised: 30 October 2018 / Accepted: 2 November 2018 / Published: 5 November 2018
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Abstract
Potassium dihydrogen phosphate (KDP or KH2PO4) crystal is widely used as terminal frequency converters in inertial confinement fusion (ICF). However, KDP crystal is a typical difficult-to-cut optical crystal with the characteristic of soft-brittle. In this work, the relationship between
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Potassium dihydrogen phosphate (KDP or KH2PO4) crystal is widely used as terminal frequency converters in inertial confinement fusion (ICF). However, KDP crystal is a typical difficult-to-cut optical crystal with the characteristic of soft-brittle. In this work, the relationship between cutting force and processed surface quality in micro ball end-milling of KDP crystal with various depth of cut and spindle speed is studied by carried out the micro-milling experiments. Fast Fourier Transform (FFT) algorithm is used to diagnose the recorded cutting force. The periodic change of cutting force and the cutting force after filtering noises can be got through FFT analysis. Through calculating the correlation coefficients between the static component of thrust force and roughness value Ra of machined grooves, as well as the peak-valley (P-V) value of thrust force and dimensional error of machined grooves, the roughness value Ra and dimensional error of machined grooves would be predicted by monitoring the static component and P-V value of the thrust force, respectively. The relatively large spindle speed helps to reduce the roughness value Ra. The spindle speed with moderate value is recommended to reduce the dimensional error of machined groove because the dimensional error of machined groove will increase when the spindle speed is small enough (causing brittle cutting) or large enough (reducing cutting stability). Full article
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Open AccessArticle An Improved UU-MESFET with High Power Added Efficiency
Micromachines 2018, 9(11), 573; https://doi.org/10.3390/mi9110573
Received: 25 September 2018 / Revised: 24 October 2018 / Accepted: 30 October 2018 / Published: 5 November 2018
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An improved ultrahigh upper gate 4H-SiC metal semiconductor field effect transistor (IUU-MESFET) is proposed in this paper. The structure is obtained by modifying the ultrahigh upper gate height h of the ultrahigh upper gate 4H-SiC metal semiconductor field effect transistor (UU-MESFET) structure, and
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An improved ultrahigh upper gate 4H-SiC metal semiconductor field effect transistor (IUU-MESFET) is proposed in this paper. The structure is obtained by modifying the ultrahigh upper gate height h of the ultrahigh upper gate 4H-SiC metal semiconductor field effect transistor (UU-MESFET) structure, and the h is 0.1 μm and 0.2 μm for the IUU-MESFET and UU-MESFET, respectively. Compared with the UU-MESFET, the IUU-MESFET structure has a greater threshold voltage and trans-conductance, and smaller breakdown voltage and saturation drain current, and when the ultrahigh upper gate height h is 0.1 μm, the relationship between these parameters is balanced, so as to solve the contradictory relationship that these parameters cannot be improved simultaneously. Therefore, the power added efficiency (PAE) of the IUU-MESFET structure is increased from 60.16% to 70.99% compared with the UU-MESFET, and advanced by 18%. Full article
(This article belongs to the Special Issue Wide Bandgap Semiconductor Based Micro/Nano Devices)
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Open AccessArticle Fabrication, Experiments, and Analysis of an LBM Additive-Manufactured Flexure Parallel Mechanism
Micromachines 2018, 9(11), 572; https://doi.org/10.3390/mi9110572
Received: 15 September 2018 / Revised: 31 October 2018 / Accepted: 1 November 2018 / Published: 5 November 2018
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Abstract
Additive manufacturing technology has advantages for realizing complex monolithic structures, providing huge potential for developing advanced flexure mechanisms for precision manipulation. However, the characteristics of flexure hinges fabricated by laser beam melting (LBM) additive manufacturing (AM) are currently little known. In this paper,
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Additive manufacturing technology has advantages for realizing complex monolithic structures, providing huge potential for developing advanced flexure mechanisms for precision manipulation. However, the characteristics of flexure hinges fabricated by laser beam melting (LBM) additive manufacturing (AM) are currently little known. In this paper, the fabrication and characterization of a flexure parallel mechanism through the LBM process are reported for the first time to demonstrate the development of this technique. The geometrical accuracy of the additive-manufactured flexure mechanism was evaluated by three-dimensional scanning. The stiffness characteristics of the flexure mechanism were investigated through finite element analysis and experimental tests. The effective hinge thickness was determined based on the parameters study of the flexure parallel mechanism. The presented results highlight the promising outlook of LBM flexure parts for developing novel nanomanipulation platforms, while additional attention is required for material properties and manufacturing errors. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle Investigation on the I–V Kink Effect in Large Signal Modeling of AlGaN/GaN HEMTs
Micromachines 2018, 9(11), 571; https://doi.org/10.3390/mi9110571
Received: 26 September 2018 / Revised: 28 October 2018 / Accepted: 2 November 2018 / Published: 5 November 2018
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Abstract
The effect brought by the I–V kink effect on large signal performance of AlGaN/GaN high electron mobility transistors (HEMTs) was investigated in this paper. An improved compact model was proposed to accurately characterize the I–V kink effect. The bias dependence of the I–V
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The effect brought by the I–V kink effect on large signal performance of AlGaN/GaN high electron mobility transistors (HEMTs) was investigated in this paper. An improved compact model was proposed to accurately characterize the I–V kink effect. The bias dependence of the I–V kink effect has also been taken into consideration. AlGaN/GaN HEMTs with different gate width were utilized to validate the proposed model. Built on the proposed model, the effect brought by the I–V kink effect on large signal performance has been studied. Results show that the I–V kink effect will lead to the degradation of characteristics, including output power, gain, and power-added efficiency at the saturation region. Furthermore, the influence of the I–V kink effect was found to be related with the input power and the static bias point in this work. The time domain waveform and AC dynamic load line were used for validation of results based on simulation. The consequences of this paper will be useful for the optimization of practical circuit design. Full article
(This article belongs to the Special Issue Wide Bandgap Semiconductor Based Micro/Nano Devices)
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Open AccessArticle Reduction of Parasitic Capacitance of A PDMS Capacitive Force Sensor
Micromachines 2018, 9(11), 570; https://doi.org/10.3390/mi9110570
Received: 27 August 2018 / Revised: 23 October 2018 / Accepted: 29 October 2018 / Published: 3 November 2018
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Abstract
Polymer-based flexible micro electro mechanical systems (MEMS) tactile sensors have been widely studied for a variety of applications, such as medical and robot fields. The small size and flexibility are of great advantage in terms of accurate measurement and safety. Polydimethylsiloxane (PDMS) is
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Polymer-based flexible micro electro mechanical systems (MEMS) tactile sensors have been widely studied for a variety of applications, such as medical and robot fields. The small size and flexibility are of great advantage in terms of accurate measurement and safety. Polydimethylsiloxane (PDMS) is often used as the flexible structural material. However, the sensors are likely subject to large parasitic capacitance noise. The smaller dielectric constant leads to smaller influences of parasitic capacitance and a larger signal-to-noise ratio. In this study, the sensor underwent ultraviolet (UV) exposure, which changes Si–CH3 bonds in PDMS to Si–O, makes PDMS nanoporous, and leads to a low dielectric constant. In addition, we achieved further reduction of the dielectric constant of PDMS by washing it with an ethanol–toluene buffer solution after UV exposure. This simple but effective method can be readily applicable to improve the signal-to-noise ratio of PDMS-based flexible capacitive sensors. In this study, we propose reduction techniques for the dielectric constant of PDMS and applications for flexible capacitive force sensors. Full article
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Open AccessArticle Transfer Tiling of Nanostructures for Large-Area Fabrication
Micromachines 2018, 9(11), 569; https://doi.org/10.3390/mi9110569
Received: 23 October 2018 / Accepted: 1 November 2018 / Published: 3 November 2018
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Abstract
The fabrication of nanoscale patterns over a large area has been considered important but difficult, because there are few ways to satisfy both conditions. Previously, visually tolerable tiling (VTT) for fabricating nanopatterns for optical applications has been reported as a candidate for large
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The fabrication of nanoscale patterns over a large area has been considered important but difficult, because there are few ways to satisfy both conditions. Previously, visually tolerable tiling (VTT) for fabricating nanopatterns for optical applications has been reported as a candidate for large area fabrication. The essence of VTT is the inevitable stitching of the nanoscale optical component, which is not seen by the naked eye if the boundary is very narrow while the tiles are overlapped. However, it had been difficult to control the shape of the spread of liquid prepolymers in the previous work, and there was room for the development of tiling. Here, we propose a method for transferring various shapes of tiles, which can be defined with a shadow mask. The method of using a transparent shadow mask can provide a wide process window, because it allows the spreading of a liquid prepolymer to be more easily controlled. We optimize the coating condition of a liquid prepolymer and the ultraviolet (UV) exposure time. Using this method, we can attach tiles of various shapes without a significant visible trace in the overlapped region. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle Cutting Performance of Different Coated Micro End Mills in Machining of Ti-6Al-4V
Micromachines 2018, 9(11), 568; https://doi.org/10.3390/mi9110568
Received: 26 August 2018 / Revised: 27 October 2018 / Accepted: 29 October 2018 / Published: 2 November 2018
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Abstract
Tool wear is a significant issue for the application of micro end mills. This can be significantly improved by coating materials on tool surfaces. This paper investigates the effects of different coating materials on tool wear in the micro milling of Ti-6Al-4V. A
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Tool wear is a significant issue for the application of micro end mills. This can be significantly improved by coating materials on tool surfaces. This paper investigates the effects of different coating materials on tool wear in the micro milling of Ti-6Al-4V. A series of cutting experiments were conducted. The tool wear and workpiece surface morphology were investigated by analyzing the wear of the end flank surface and the total cutting edge. It was found that, without coating, serious tool wear and breakage occurred easily during milling. However, AlTiN-based and AlCrN-based coatings could highly reduce cutting edge chipping and flank wear. Specifically, The AlCrN-based coated mill presented less fracture resistance. For TiN coated micro end mill, only slight cutting edge chipping occurred. Compared with other types of tools, the AlTiN-based coated micro end mill could maximize tool life, bringing about an integrated cutting edges with the smallest surface roughness. In short, the AlTiN-based coating material is recommended for the micro end mill in the machining of Ti-6Al-4V. Full article
(This article belongs to the Section A:Physics)
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Open AccessArticle Design and Analysis of the Elastic-Beam Delaying Mechanism in a Micro-Electro-Mechanical Systems Device
Micromachines 2018, 9(11), 567; https://doi.org/10.3390/mi9110567
Received: 17 October 2018 / Revised: 31 October 2018 / Accepted: 31 October 2018 / Published: 2 November 2018
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The delaying mechanism is an important part of micro-electro-mechanical systems (MEMS) devices. However, very few mechanical delaying mechanisms are available. In this paper, an elastic-beam delaying mechanism has been proposed innovatively through establishing a three-dimensional model of an elastic-beam delay mechanism, establishing the
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The delaying mechanism is an important part of micro-electro-mechanical systems (MEMS) devices. However, very few mechanical delaying mechanisms are available. In this paper, an elastic-beam delaying mechanism has been proposed innovatively through establishing a three-dimensional model of an elastic-beam delay mechanism, establishing the force and the parameters of an elastic-beam delay mechanism, deriving the mathematical model according to the rigid dynamic mechanics theory, establishing the finite element model by using Ls-dyna solver of the Ansys software, and carrying out the centrifugal test. Simulation and test results match theoretical results quite well. It is believed that the elastic-beam delaying mechanism is quite effective and useful to slow the speed of the movable part in MEMS devices. Full article
(This article belongs to the Special Issue MEMS Accelerometers)
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