Micromachines

10 pages, 3820 KiB

Open AccessArticle

The Electric-Field-Driven Fusion Jetting 3D Printing for Fabricating High Resolution Polylactic Acid/Multi-Walled Carbon Nanotube Composite Micro-Scale Structures

by Xiaoqiang Li, Guangming Zhang, Wenhai Li, Zun Yu, Kun Yang and Hongbo Lan

Micromachines 2020, 11(12), 1132; https://doi.org/10.3390/mi11121132 - 21 Dec 2020

Cited by 10 | Viewed by 2818

Abstract

Existing 3D printing techniques are still facing the challenge of low resolution for fabricating polymer matrix composites, inhibiting the wide engineering applications for the biomedical engineering (biomimetic scaffolds), micro fuel cells, and micro-electronics. In order to achieve high resolution fabrication of polylactic acid [...] Read more.

Existing 3D printing techniques are still facing the challenge of low resolution for fabricating polymer matrix composites, inhibiting the wide engineering applications for the biomedical engineering (biomimetic scaffolds), micro fuel cells, and micro-electronics. In order to achieve high resolution fabrication of polylactic acid (PLA)/multi-walled carbon nanotube (MWCNT) composites, this paper presents an electric-field-driven (EFD) fusion jetting 3D printing method by combining the mixing effect and material feeding of the micro-screw and the necking effect of Taylor cone by the EFD. The effects of main process parameters (the carbon loading, the voltage, the screw speed, and the printing speed) on the line width and the printing quality were studied and optimized. To demonstrate the printing capability of this proposed method, meshes with line width of 30 µm to 100 μm and 1 wt.% to 5 wt.% MWCNT for the application of conductive biomimetic scaffold and the anisotropic flexible meshes were prepared. The electrical properties were investigated to present the frequency dependence of the alternating current conductivity and the dielectric loss (tanδ), and the microstructures of printed structures demonstrated the uniformly dispersed MWCNT in PLA matrix. Therefore, it provides a new solution to fabricate micro-scale structures of composite materials, especially the 3D conductive biomimetic scaffolds. Full article

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13 pages, 3466 KiB

Open AccessArticle

AlGaN/GaN on SiC Devices without a GaN Buffer Layer: Electrical and Noise Characteristics

by Justinas Jorudas, Artūr Šimukovič, Maksym Dub, Maciej Sakowicz, Paweł Prystawko, Simonas Indrišiūnas, Vitalij Kovalevskij, Sergey Rumyantsev, Wojciech Knap and Irmantas Kašalynas

Micromachines 2020, 11(12), 1131; https://doi.org/10.3390/mi11121131 - 20 Dec 2020

Cited by 21 | Viewed by 5294

Abstract

We report on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping [...] Read more.

We report on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping effects. Fabricated Schottky barrier diodes (SBDs) demonstrated an ideality factor n at approximately 1.7 and breakdown voltages (fields) up to 780 V (approximately 0.8 MV/cm). Hall measurements revealed a thermally stable electron density at N_2DEG = 1 × 10¹³ cm⁻² of two-dimensional electron gas in the range of 77–300 K, with mobilities μ = 1.7 × 10³ cm²/V∙s and μ = 1.0 × 10⁴ cm²/V∙s at 300 K and 77 K, respectively. The maximum drain current and the transconductance were demonstrated to be as high as 0.5 A/mm and 150 mS/mm, respectively, for the transistors with gate length L_G = 5 μm. Low-frequency noise measurements demonstrated an effective trap density below 10¹⁹ cm⁻³ eV⁻¹. RF analysis revealed f_T and f_max values up to 1.3 GHz and 6.7 GHz, respectively, demonstrating figures of merit f_T × L_G up to 6.7 GHz × µm. These data further confirm the high potential of a GaN–SiC hybrid material for the development of thin high electron mobility transistors (HEMTs) and SBDs with improved thermal stability for high-frequency and high-power applications. Full article

(This article belongs to the Special Issue Wide Bandgap Based Devices: Design, Fabrication and Applications, Volume II)

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13 pages, 5044 KiB

Open AccessArticle

Q-Factor Enhancement of Thin-Film Piezoelectric-on-Silicon MEMS Resonator by Phononic Crystal-Reflector Composite Structure

by Jiacheng Liu, Temesgen Bailie Workie, Ting Wu, Zhaohui Wu, Keyuan Gong, Jingfu Bao and Ken-ya Hashimoto

Micromachines 2020, 11(12), 1130; https://doi.org/10.3390/mi11121130 - 20 Dec 2020

Cited by 16 | Viewed by 3858

Abstract

Thin-film piezoelectric-on-silicon (TPoS) microelectromechanical (MEMS) resonators are required to have high Q-factor to offer satisfactory results in their application areas, such as oscillator, filter, and sensors. This paper proposed a phononic crystal (PnC)-reflector composite structure to improve the Q factor of TPoS resonators. [...] Read more.

Thin-film piezoelectric-on-silicon (TPoS) microelectromechanical (MEMS) resonators are required to have high Q-factor to offer satisfactory results in their application areas, such as oscillator, filter, and sensors. This paper proposed a phononic crystal (PnC)-reflector composite structure to improve the Q factor of TPoS resonators. A one-dimensional phononic crystal is designed and deployed on the tether aiming to suppress the acoustic leakage loss as the acoustic wave with frequency in the range of the PnC is not able to propagate through it, and a reflector is fixed on the anchoring boundaries to reflect the acoustic wave that lefts from the effect of the PnC. Several 10 MHz TPoS resonators are fabricated and tested from which the Q-factor of the proposed 10 MHz TPoS resonator which has PnC-reflector composite structure on the tether and anchoring boundaries achieved offers a loaded Q-factor of 4682 which is about a threefold improvement compared to that of the conventional resonator which is about 1570. Full article

(This article belongs to the Special Issue Piezoelectric Thin Film MEMS)

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12 pages, 3606 KiB

Open AccessArticle

Continuous Determination of Glucose Using a Membraneless, Microfluidic Enzymatic Biofuel Cell

by Haroon Khan, Jin Ho Choi, Asad Ullah, Young Ho Kim and Gyu Man Kim

Micromachines 2020, 11(12), 1129; https://doi.org/10.3390/mi11121129 - 20 Dec 2020

Cited by 10 | Viewed by 3064

Abstract

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped [...] Read more.

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped microchannel. The microchannel was produced with polydimethylsiloxane (PDMS) using soft lithography, while the MWCNT electrodes were replicated via a PDMS stencil on indium tin oxide (ITO) glass. Moreover, the electrodes were modified with glucose oxidase and laccase by direct covalent bonding. The device was studied at different MWCNT deposition amounts and electrolyte flow rates to achieve optimum settings. The experimental results demonstrated that glucose could be determined linearly up to a concentration of 4 mM at a sensitivity of 31 mV∙mM⁻¹cm⁻². Full article

(This article belongs to the Special Issue Nanomaterials Based Electrochemical Sensors)

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11 pages, 6028 KiB

Open AccessArticle

Ti Alloyed α-Ga₂O₃: Route towards Wide Band Gap Engineering

by Armin Barthel, Joseph Roberts, Mari Napari, Martin Frentrup, Tahmida Huq, András Kovács, Rachel Oliver, Paul Chalker, Timo Sajavaara and Fabien Massabuau

Micromachines 2020, 11(12), 1128; https://doi.org/10.3390/mi11121128 - 20 Dec 2020

Cited by 20 | Viewed by 5920

Abstract

The suitability of Ti as a band gap modifier for

α

-Ga₂O₃ was investigated, taking advantage of the isostructural

α

phases and high band gap difference between Ti₂O₃ and Ga₂O₃. Films of (Ti,Ga) [...] Read more.

The suitability of Ti as a band gap modifier for

α

-Ga₂O₃ was investigated, taking advantage of the isostructural

α

phases and high band gap difference between Ti₂O₃ and Ga₂O₃. Films of (Ti,Ga)₂O₃ were synthesized by atomic layer deposition on sapphire substrates, and characterized to determine how crystallinity and band gap vary with composition for this alloy. We report the deposition of high quality

α

-(Ti_xGa_1−x)₂O₃ films with x = 3.7%. For greater compositions the crystalline quality of the films degrades rapidly, where the corundum phase is maintained in films up to x = 5.3%, and films containing greater Ti fractions being amorphous. Over the range of achieved corundum phase films, that is 0% ≤ x ≤ 5.3%, the band gap energy varies by ∼270 meV. The ability to maintain a crystalline phase at low fractions of Ti, accompanied by a modification in band gap, shows promising prospects for band gap engineering and the development of wavelength specific solar-blind photodetectors based on

α

-Ga₂O₃. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor Based Solar-Blind Photodetectors)

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13 pages, 2632 KiB

Open AccessArticle

Upscaling Inverted Perovskite Solar Cells: Optimization of Laser Scribing for Highly Efficient Mini-Modules

by Francesco Di Giacomo, Luigi A. Castriotta, Felix U. Kosasih, Diego Di Girolamo, Caterina Ducati and Aldo Di Carlo

Micromachines 2020, 11(12), 1127; https://doi.org/10.3390/mi11121127 - 20 Dec 2020

Cited by 50 | Viewed by 12102

Abstract

The upscaling of perovskite solar cells is one of the challenges that must be addressed to pave the way toward the commercial development of this technology. As for other thin-film photovoltaic technologies, upscaling requires the fabrication of modules composed of series-connected cells. In [...] Read more.

The upscaling of perovskite solar cells is one of the challenges that must be addressed to pave the way toward the commercial development of this technology. As for other thin-film photovoltaic technologies, upscaling requires the fabrication of modules composed of series-connected cells. In this work we demonstrate for the first time the interconnection of inverted modules with NiO_x using a UV ns laser, obtaining a 10.2 cm² minimodule with a 15.9% efficiency on the active area, the highest for a NiO_x based perovskite module. We use optical microscopy, energy-dispersive X-ray spectroscopy, and transfer length measurement to optimize the interconnection. The results are implemented in a complete electrical simulation of the cell-to-module losses to evaluate the experimental results and to provide an outlook on further development of single junction and multijunction perovskite modules. Full article

(This article belongs to the Special Issue Large Area Solar Cells, LEDs and Photodetectors Based on Organometal Halide Perovskite)

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23 pages, 10912 KiB

Open AccessArticle

Manufacturability and Stress Issues in 3D Silicon Detector Technology at IMB-CNM

by David Quirion, Maria Manna, Salvador Hidalgo and Giulio Pellegrini

Micromachines 2020, 11(12), 1126; https://doi.org/10.3390/mi11121126 - 18 Dec 2020

Cited by 17 | Viewed by 9179

Abstract

This paper provides an overview of 3D detectors fabrication technology developed in the clean room of the Microelectronics Institute of Barcelona (IMB-CNM). Emphasis is put on manufacturability, especially on stress and bow issues. Some of the technological solutions proposed at IMB-CNM to improve [...] Read more.

This paper provides an overview of 3D detectors fabrication technology developed in the clean room of the Microelectronics Institute of Barcelona (IMB-CNM). Emphasis is put on manufacturability, especially on stress and bow issues. Some of the technological solutions proposed at IMB-CNM to improve manufacturability are presented. Results and solutions from other research institutes are also mentioned. Analogy with through-silicon-via technology is drawn. This article aims at giving hints of the technology improvements implemented to upgrade from a R&D process to a mature technology. Full article

(This article belongs to the Special Issue 3D Pixel Sensors and Detectors)

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25 pages, 5863 KiB

Open AccessReview

Recent Studies on Supercapacitors with Next-Generation Structures

by Juho Sung and Changhwan Shin

Micromachines 2020, 11(12), 1125; https://doi.org/10.3390/mi11121125 - 18 Dec 2020

Cited by 51 | Viewed by 6883

Abstract

Supercapacitors have shown great potential as a possible solution to the increasing global demand for next-generation energy storage systems. Charge repositioning is based on physical or chemical mechanisms. There are three types of supercapacitors—the electrochemical double layer, the pseudocapacitor, and a hybrid of [...] Read more.

Supercapacitors have shown great potential as a possible solution to the increasing global demand for next-generation energy storage systems. Charge repositioning is based on physical or chemical mechanisms. There are three types of supercapacitors—the electrochemical double layer, the pseudocapacitor, and a hybrid of both. Each type is further subdivided according to the material used. Herein, a detailed overview of the working mechanism as well as a new method for capacitance enhancement are presented. Full article

(This article belongs to the Special Issue Novel Energy Storage Devices based on Carbon and Oxide Nanostructures)

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14 pages, 6381 KiB

Open AccessArticle

Thermoelectrically-Cooled InAs/GaSb Type-II Superlattice Detectors as an Alternative to HgCdTe in a Real-Time Mid-Infrared Backscattering Spectroscopy System

by Raphael Müller, Marko Haertelt, Jasmin Niemasz, Klaus Schwarz, Volker Daumer, Yuri V. Flores, Ralf Ostendorf and Robert Rehm

Micromachines 2020, 11(12), 1124; https://doi.org/10.3390/mi11121124 - 18 Dec 2020

Cited by 15 | Viewed by 3621

Abstract

We report on the development of thermoelectrically cooled (TE-cooled) InAs/GaSb type-II superlattice (T2SL) single element infrared (IR) photodetectors and exemplify their applicability for real-time IR spectroscopy in the mid-infrared in a possible application. As the European Union’s Restriction of Hazardous Substances (RoHS) threatens [...] Read more.

We report on the development of thermoelectrically cooled (TE-cooled) InAs/GaSb type-II superlattice (T2SL) single element infrared (IR) photodetectors and exemplify their applicability for real-time IR spectroscopy in the mid-infrared in a possible application. As the European Union’s Restriction of Hazardous Substances (RoHS) threatens the usage of the state-of-the-art detector material mercury cadmium telluride (MCT), RoHS-compatible alternatives to MCT have to be established for IR detection. We use bandgap engineered InAs/GaSb T2SLs to tailor the temperature-dependent bandgap energy for detection throughout the required spectral range. Molecular beam epitaxy of superlattice samples is performed on GaAs substrates with a metamorphic GaAsSb buffer layer. Photolithographic processing yields laterally-operated T2SL photodetectors. Integrated in a TE-cooled IR detector module, such T2SL photodetectors can be an alternative to MCT photodetectors for spectroscopy applications. Here, we exemplify this by exchanging a commercially available MCT-based IR detector module with our T2SL-based IR detector module in a real-time mid-infrared backscattering spectroscopy system for substance identification. The key detector requirements imposed by the spectroscopy system are a MHz-bandwidth, a broad spectral response, and a high signal-to-noise ratio, all of which are covered by the reported T2SL-based IR detector module. Hence, in this paper, we demonstrate the versatility of TE-cooled InAs/GaSb T2SL photodetectors and their applicability in an IR spectroscopy system. Full article

(This article belongs to the Special Issue Semiconductor Infrared Devices and Applications)

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13 pages, 3597 KiB

Open AccessArticle

A Lipid-Bilayer-On-A-Cup Device for Pumpless Sample Exchange

by Yoshihisa Ito, Yusuke Izawa, Toshihisa Osaki, Koki Kamiya, Nobuo Misawa, Satoshi Fujii, Hisatoshi Mimura, Norihisa Miki and Shoji Takeuchi

Micromachines 2020, 11(12), 1123; https://doi.org/10.3390/mi11121123 - 18 Dec 2020

Cited by 2 | Viewed by 3727

Abstract

Lipid-bilayer devices have been studied for on-site sensors in the fields of diagnosis, food and environmental monitoring, and safety/security inspection. In this paper, we propose a lipid-bilayer-on-a-cup device for serial sample measurements using a pumpless solution exchange procedure. The device consists of a [...] Read more.

Lipid-bilayer devices have been studied for on-site sensors in the fields of diagnosis, food and environmental monitoring, and safety/security inspection. In this paper, we propose a lipid-bilayer-on-a-cup device for serial sample measurements using a pumpless solution exchange procedure. The device consists of a millimeter-scale cylindrical cup with vertical slits which is designed to steadily hold an aqueous solution and exchange the sample by simply fusing and splitting the solution with an external solution. The slit design was experimentally determined by the capabilities of both the retention and exchange of the solution. Using the optimized slit, a planar lipid bilayer was reconstituted with a nanopore protein at a microaperture allocated to the bottom of the cup, and the device was connected to a portable amplifier. The solution exchangeability was demonstrated by observing the dilution process of a blocker molecule of the nanopore dissolved in the cup. The pumpless solution exchange by the proposed cup-like device presents potential as a lipid-bilayer system for portable sensing applications. Full article

(This article belongs to the Special Issue Lipid Bilayers on Chip)

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16 pages, 4926 KiB

Open AccessArticle

Numerical Study of T-Shaped Micromixers with Vortex-Inducing Obstacles in the Inlet Channels

by Chih-Yang Wu and Bing-Hao Lai

Micromachines 2020, 11(12), 1122; https://doi.org/10.3390/mi11121122 - 18 Dec 2020

Cited by 19 | Viewed by 3026

Abstract

To enhance fluid mixing, a new approach for inlet flow modification by adding vortex-inducing obstacles (VIOs) in the inlet channels of a T-shaped micromixer is proposed and investigated in this work. We use a commercial computational fluid dynamics code to calculate the pressure [...] Read more.

To enhance fluid mixing, a new approach for inlet flow modification by adding vortex-inducing obstacles (VIOs) in the inlet channels of a T-shaped micromixer is proposed and investigated in this work. We use a commercial computational fluid dynamics code to calculate the pressure and the velocity vectors and, to reduce the numerical diffusion in high-Peclet-number flows, we employ the particle-tracking simulation with an approximation diffusion model to calculate the concentration distribution in the micromixers. The effects of geometric parameters, including the distance between the obstacles and the angle of attack of the obstacles, on the mixing performance of micromixers are studied. From the results, we can observe the following trends: (i) the stretched contact surface between different fluids caused by antisymmetric VIOs happens for the cases with the Reynolds number (Re) greater than or equal to 27 and the enhancement of mixing increases with the increase of Reynolds number gradually, and (ii) the onset of the engulfment flow happens at

R e \approx 125

in the T-shaped mixer with symmetric VIOs or at

R e \approx 140

in the standard planar T-shaped mixer and results in a sudden increase of the degree of mixing. The results indicate that the early initiation of transversal convection by either symmetric or antisymmetric VIOs can enhance fluid mixing at a relatively lower Re. Full article

(This article belongs to the Special Issue Analysis, Design and Fabrication of Micromixers)

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10 pages, 2394 KiB

Open AccessArticle

Dielectrophoresis Response of Water-in-Oil-in-Water Double Emulsion Droplets with Singular or Dual Cores

by Tianyi Jiang, Yankai Jia, Haizhen Sun, Xiaokang Deng, Dewei Tang and Yukun Ren

Micromachines 2020, 11(12), 1121; https://doi.org/10.3390/mi11121121 - 17 Dec 2020

Cited by 9 | Viewed by 3814

Abstract

Microfluidic technologies have enabled generation of exquisite multiple emulsion droplets, which have been used in many fields, including single-cell assays, micro-sized chemical reactions, and material syntheses. Electrical controlling is an important technique for droplet manipulation in microfluidic systems, but the dielectrophoretic behaviors of [...] Read more.

Microfluidic technologies have enabled generation of exquisite multiple emulsion droplets, which have been used in many fields, including single-cell assays, micro-sized chemical reactions, and material syntheses. Electrical controlling is an important technique for droplet manipulation in microfluidic systems, but the dielectrophoretic behaviors of multiple emulsion droplets in electrical fields are rarely studied. Here, we report on the dielectrophoresis response of double emulsion droplets in AC electric fields in microfluidic channel. A core-shell model is utilized for analyzing the polarization of droplet interfaces and the overall dielectrophoresis (DEP) force. The water-in-oil-in-water droplets, generated by glass capillary devices, experience negative DEP at low field frequency. At high frequency, however, the polarity of DEP is tunable by adjusting droplet shell thickness or core conductivity. Then, the behavior of droplets with two inner cores is investigated, where the droplets undergo rotation before being repelled or attracted by the strong field area. This work should benefit a wide range of applications that require manipulation of double emulsion droplets by electric fields. Full article

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

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9 pages, 2817 KiB

Open AccessArticle

A New 3D Printing System of Poly(3,4-ethylenedioxythiophene) for Realizing a High Electrical Conductivity and Fine Processing Resolution

by Katsumi Yamada and Junji Sone

Micromachines 2020, 11(12), 1120; https://doi.org/10.3390/mi11121120 - 17 Dec 2020

Cited by 3 | Viewed by 2275

Abstract

Micro-nano 3D printing of the conductive 3,4-ethylenedioxythiophene polymer (PEDOT) was performed in this study. An oil immersion objective lens was introduced into the 3D photofabrication system using a femtosecond pulsed laser as the light source. As a result, the processing resolution in the [...] Read more.

Micro-nano 3D printing of the conductive 3,4-ethylenedioxythiophene polymer (PEDOT) was performed in this study. An oil immersion objective lens was introduced into the 3D photofabrication system using a femtosecond pulsed laser as the light source. As a result, the processing resolution in the horizontal and vertical directions was improved in comparison to our previous study. A relatively high electrical conductivity (3500 S/cm) was found from the obtained 3D PEDOT micro-structures. It is noteworthy that the high conductivity of the PEDOT was obtained in the mixed state with an insulating Nafion sheet. Full article

(This article belongs to the Special Issue 3D Printing Fabrication of Small Components)

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23 pages, 7732 KiB

Open AccessArticle

Multiphysics Simulator for the IPMC Actuator: Mathematical Model, Finite Difference Scheme, Fast Numerical Algorithm, and Verification

by Anton P. Broyko, Ivan K. Khmelnitskiy, Eugeny A. Ryndin, Andrey V. Korlyakov, Nikolay I. Alekseyev and Vagarshak M. Aivazyan

Micromachines 2020, 11(12), 1119; https://doi.org/10.3390/mi11121119 - 17 Dec 2020

Cited by 5 | Viewed by 2939

Abstract

The article is devoted to the development and creation of a multiphysics simulator that can, on the one hand, simulate the most significant physical processes in the IPMC actuator, and on the other hand, unlike commercial products such as COMSOL, can use computing [...] Read more.

The article is devoted to the development and creation of a multiphysics simulator that can, on the one hand, simulate the most significant physical processes in the IPMC actuator, and on the other hand, unlike commercial products such as COMSOL, can use computing resources economically. The developed mathematical model is an adjoint differential equation describing the transport of charged particles and water molecules in the ion-exchange membrane, the electrostatic field inside, and the mechanical deformation of the actuator. The distribution of the electrostatic potential in the interelectrode space is located by means of the solution of the Poisson equation with the Dirichlet boundary conditions, where the charge density is a function of the concentration of cations inside the membrane. The cation distribution was obtained by means of the solution of the equation system, in which the fluxes of ions and water molecules are described by the modified Nernst-Planck equations with boundary conditions of the third kind (the Robin problem). The cantilever beam forced oscillation equation in the presence of resistance (allowing for dissipative processes) with assumptions of elasticity theory was used to describe the actuator motion. A combination of the following computational methods was used as a numerical algorithm for the solution: the Poisson equation was solved by a direct method, the modified Nernst-Planck equations were solved by the Newton-Raphson method, and the mechanical oscillation equation was solved using an explicit scheme. For this model, a difference scheme has been created and an algorithm has been described, which can be implemented in any programming language and allows for fast computational experiments. On the basis of the created algorithm and with the help of the obtained experimental data, a program has been created and the verification of the difference scheme and the algorithm has been performed. Model parameters have been determined, and recommendations on the ranges of applicability of the algorithm and the program have been given. Full article

(This article belongs to the Special Issue Soft Robotics: Design, Fabrication, Modeling, Control and Applications)

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11 pages, 16756 KiB

Open AccessArticle

A New 3D Cultured Liver Chip and Real-Time Monitoring System Based on Microfluidic Technology

by Yao Zhang, Ning Yang, Liangliang Xie, Fangyu Shu, Qian Shi and Naila Shaheen

Micromachines 2020, 11(12), 1118; https://doi.org/10.3390/mi11121118 - 16 Dec 2020

Cited by 8 | Viewed by 3168

Abstract

In vitro models of the liver have a good simulation of the micro-liquid environment inside the human liver and the communication between cell tissues, which provides an important research tool for drug research and liver disease treatment. In this paper, we designed a [...] Read more.

In vitro models of the liver have a good simulation of the micro-liquid environment inside the human liver and the communication between cell tissues, which provides an important research tool for drug research and liver disease treatment. In this paper, we designed a 3D liver chip and real-time monitoring system based on microfluidic technology. The in vitro model of the liver on the chip was established by the three-dimensional microfluidic chip pipeline and the corresponding microwell array. Meanwhile, the culture medium is continuously injected on the chip, and the electrochemical impedance spectroscopy and near-infrared spectroscopy of the liver chip are recorded and analyzed from day one to day five. When the 3D cultured liver chip in vitro model reached a certain period and stabilized, paracetamol with varying gradients of concentration was applied to the cultured cells for drug resistance testing. The experimental results show that the liver chip and its monitoring system designed in this paper can maintain 100% cell viability of hepatocytes in vitro for a long time. Furthermore, it can meet the requirements of measurement technologies such as electrical impedance measurement and near-infrared spectroscopy in real-time, providing a stable culture platform for the further study of organ chips. Full article

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21 pages, 3175 KiB

Open AccessArticle

A New MIMU/GNSS Ultra-Tightly Coupled Integration Architecture for Mitigating Abrupt Changes of Frequency Tracking Errors

by Shiming Liu, Sihai Li, Qiangwen Fu, Yuanbo Tao and Feng Wu

Micromachines 2020, 11(12), 1117; https://doi.org/10.3390/mi11121117 - 16 Dec 2020

Cited by 3 | Viewed by 1954

Abstract

We present a new ultra-tightly coupled (UTC) integration architecture of a micro-electromechanical inertial measurement unit (MIMU) and global navigation satellite system (GNSS) to reduce the performance degradation caused by abrupt changes of frequency tracking errors. A large frequency error will lead to a [...] Read more.

We present a new ultra-tightly coupled (UTC) integration architecture of a micro-electromechanical inertial measurement unit (MIMU) and global navigation satellite system (GNSS) to reduce the performance degradation caused by abrupt changes of frequency tracking errors. A large frequency error will lead to a decrease in the carrier-to-noise ratio (C/N₀) estimate and an increase in the code discriminator estimation error. The disruptive effects of frequency errors on the estimation of C/N₀ and on the code discriminator are quantitatively evaluated via theoretical analyses and Monte Carlo simulations. The new MIMU/GNSS UTC architecture introduces a large frequency error detector and a refined frequency processor based on a retuned frequency in each tracking channel. In addition, an adaptive channel prefilter with multiple fading factors is introduced as an alternate to the conventional prefilter. Numerical simulations based on a highly dynamic trajectory are used to assess performance. The simulation results show that when there is an abrupt step change in the frequency tracking error, the new UTC architecture can effectively suppress the divergence of navigation solutions and the loss of tracking lock, and can significantly reduce the deviation of the C/N₀ estimation. Full article

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

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29 pages, 3340 KiB

Open AccessReview

Overview of Power Electronic Switches: A Summary of the Past, State-of-the-Art and Illumination of the Future

by Immanuel N. Jiya and Rupert Gouws

Micromachines 2020, 11(12), 1116; https://doi.org/10.3390/mi11121116 - 16 Dec 2020

Cited by 19 | Viewed by 12030

Abstract

As the need for green and effective utilization of energy continues to grow, the advancements in the energy and power electronics industry are constantly driven by this need, as both industries are intertwined for obvious reasons. The developments in the power electronics industry [...] Read more.

As the need for green and effective utilization of energy continues to grow, the advancements in the energy and power electronics industry are constantly driven by this need, as both industries are intertwined for obvious reasons. The developments in the power electronics industry has over the years hinged on the progress of the semiconductor device industry. The semiconductor device industry could be said to be on the edge of a turn into a new era, a paradigm shift from the conventional silicon devices to the wide band gap semiconductor technologies. While a lot of work is being done in research and manufacturing sectors, it is important to look back at the past, evaluate the current progress and look at the prospects of the future of this industry. This paper is unique at this time because it seeks to give a good summary of the past, the state-of-the-art, and highlight the opportunities for future improvements. A more or less ‘forgotten’ power electronic switch, the four-quadrant switch, is highlighted as an opportunity waiting to be exploited as this switch presents a potential for achieving an ideal switch. Figures of merit for comparing semiconductor materials and devices are also presented in this review. Full article

(This article belongs to the Special Issue Power Electronics and Sensors)

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20 pages, 48006 KiB

Open AccessArticle

Functional Analysis Validation of Micro and Conventional Injection Molding Machines Performances Based on Process Precision and Accuracy for Micro Manufacturing

by Matteo Calaon, Federico Baruffi, Gualtiero Fantoni, Ilenia Cirri, Marco Santochi, Hans Nørgaard Hansen and Guido Tosello

Micromachines 2020, 11(12), 1115; https://doi.org/10.3390/mi11121115 - 16 Dec 2020

Cited by 12 | Viewed by 3712

Abstract

Micro polymer parts can be usually manufactured either by conventional injection moulding (IM) or by micro-injection moulding (µIM). In this paper, functional analysis was used as a tool to investigate the performances of IM and µIM used to manufacture the selected industrial component. [...] Read more.

Micro polymer parts can be usually manufactured either by conventional injection moulding (IM) or by micro-injection moulding (µIM). In this paper, functional analysis was used as a tool to investigate the performances of IM and µIM used to manufacture the selected industrial component. The methodology decomposed the production cycle phases of the two processes and attributed functions to parts features of the two investigated machines. The output of the analysis was aimed to determine casual chains leading to the final outcome of the process. Experimental validation of the functional analysis was carried out moulding the same micro medical part in thermoplastic elastomer (TPE) material using the two processes by means of multi-cavity moulds. The produced batches were assessed using a precision scale and a high accuracy optical instrument. The measurement results were compared using capability indexes. The data-driven comparison identified and quantified the correlations between machine design and part quality, demonstrating that the µIM machine technology better meets the accuracy and precision requirements typical of micro manufacturing productions. Full article

(This article belongs to the Special Issue Latest Advancements in Micro Nano Molding Technologies – Process Developments and Optimization, Materials, Applications, Key Enabling Technologies)

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16 pages, 5947 KiB

Open AccessArticle

Fabrication and Characterization of MoS₂/h-BN and WS₂/h-BN Heterostructures

by Tao Han, Hongxia Liu, Shupeng Chen, Yanning Chen, Shulong Wang and Zhandong Li

Micromachines 2020, 11(12), 1114; https://doi.org/10.3390/mi11121114 - 16 Dec 2020

Cited by 15 | Viewed by 4913

Abstract

The general preparation method of large-area, continuous, uniform, and controllable vdW heterostructure materials is provided in this paper. To obtain the preparation of MoS₂/h-BN and WS₂/h-BN heterostructures, MoS₂ and WS₂ material are directly grown on the insulating [...] Read more.

The general preparation method of large-area, continuous, uniform, and controllable vdW heterostructure materials is provided in this paper. To obtain the preparation of MoS₂/h-BN and WS₂/h-BN heterostructures, MoS₂ and WS₂ material are directly grown on the insulating h-BN substrate by atmospheric pressure chemical vapor deposition (APCVD) method, which does not require any intermediate transfer steps. The test characterization of MoS₂/h-BN and WS₂/h-BN vdW heterostructure materials can be accomplished by optical microscope, AFM, Raman and PL spectroscopy. The Raman peak signal of h-BN material is stronger when the h-BN film is thicker. Compared to the spectrum of MoS₂ or WS₂ material on SiO₂/Si substrate, the Raman and PL spectrum peak positions of MoS₂/h-BN heterostructure are blue-shifted, which is due to the presence of local strain, charged impurities and the vdW heterostructure interaction. Additionally, the PL spectrum of WS₂ material shows the strong emission peak at 1.96 eV, while the full width half maximum (FWHM) is only 56 meV. The sharp emission peak indicates that WS₂/h-BN heterostructure material has the high crystallinity and clean interface. In addition, the peak position and shape of IPM mode characteristic peak are not obvious, which can be explained by the Van der Waals interaction of WS₂/h-BN heterostructure. From the above experimental results, the preparation method of heterostructure material is efficient and scalable, which can provide the important support for the subsequent application of TMDs/h-BN heterostructure in nanoelectronics and optoelectronics. Full article

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

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11 pages, 2981 KiB

Open AccessArticle

Electrowetting-on-Dielectric Based Economical Digital Microfluidic Chip on Flexible Substrate by Inkjet Printing

by He Wang and Liguo Chen

Micromachines 2020, 11(12), 1113; https://doi.org/10.3390/mi11121113 - 16 Dec 2020

Cited by 11 | Viewed by 3923

Abstract

In order to get rid of the dependence on expensive photolithography technology and related facilities, an economic and simple design and fabrication technology for digital microfluidics (DMF) is proposed. The electrodes pattern was generated by inkjet printing nanosilver conductive ink on the flexible [...] Read more.

In order to get rid of the dependence on expensive photolithography technology and related facilities, an economic and simple design and fabrication technology for digital microfluidics (DMF) is proposed. The electrodes pattern was generated by inkjet printing nanosilver conductive ink on the flexible Polyethylene terephthalate (PET) substrate with a 3D circuit board printer, food wrap film was attached to the electrode array to act as the dielectric layer and Teflon^® AF was sprayed to form a hydrophobic layer. The PET substrate and food wrap film are low cost and accessible to general users. The proposed flexible DMF chips can be reused for a long time by replacing the dielectric film coated with hydrophobic layer. The resolution and conductivity of silver traces and the contact angle and velocity of the droplets were evaluated to demonstrate that the proposed technology is comparable to the traditional DMF fabrication process. As far as the rapid prototyping of DMF is concerned, this technology has shown very attractive advantages in many aspects, such as fabrication cost, fabrication time, material selection and mass production capacity, without sacrificing the performance of DMF. The flexible DMF chips have successfully implemented basic droplet operations on a square and hexagon electrode array. Full article

(This article belongs to the Special Issue Droplet-Based Microfluidic Devices)

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11 pages, 13308 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Patterning Biological Gels for 3D Cell Culture inside Microfluidic Devices by Local Surface Modification through Laminar Flow Patterning

by Joshua Loessberg-Zahl, Jelle Beumer, Albert van den Berg, Jan C. T. Eijkel and Andries D. van der Meer

Micromachines 2020, 11(12), 1112; https://doi.org/10.3390/mi11121112 - 16 Dec 2020

Cited by 11 | Viewed by 5803

Abstract

Microfluidic devices are used extensively in the development of new in vitro cell culture models like organs-on-chips. A typical feature of such devices is the patterning of biological hydrogels to offer cultured cells and tissues a controlled three-dimensional microenvironment. A key challenge of [...] Read more.

Microfluidic devices are used extensively in the development of new in vitro cell culture models like organs-on-chips. A typical feature of such devices is the patterning of biological hydrogels to offer cultured cells and tissues a controlled three-dimensional microenvironment. A key challenge of hydrogel patterning is ensuring geometrical confinement of the gel, which is generally solved by inclusion of micropillars or phaseguides in the channels. Both of these methods often require costly cleanroom fabrication, which needs to be repeated even when only small changes need be made to the gel geometry, and inadvertently expose cultured cells to non-physiological and mechanically stiff structures. Here, we present a technique for facile patterning of hydrogel geometries in microfluidic chips, but without the need for any confining geometry built into the channel. Core to the technique is the use of laminar flow patterning to create a hydrophilic path through an otherwise hydrophobic microfluidic channel. When a liquid hydrogel is injected into the hydrophilic region, it is confined to this path by the surrounding hydrophobic regions. The various surface patterns that are enabled by laminar flow patterning can thereby be rendered into three-dimensional hydrogel structures. We demonstrate that the technique can be used in many different channel geometries while still giving the user control of key geometric parameters of the final hydrogel. Moreover, we show that human umbilical vein endothelial cells can be cultured for multiple days inside the devices with the patterned hydrogels and that they can be stimulated to migrate into the gel under the influence of trans-gel flows. Finally, we demonstrate that the patterned gels can withstand trans-gel flow velocities in excess of physiological interstitial flow velocities without rupturing or detaching. This novel hydrogel-patterning technique addresses fundamental challenges of existing methods for hydrogel patterning inside microfluidic chips, and can therefore be applied to improve design time and the physiological realism of microfluidic cell culture assays and organs-on-chips. Full article

(This article belongs to the Special Issue Microfluidics: Tissue Chips and Microphysiological Systems)

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11 pages, 4728 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Femtosecond Laser Direct Writing of Integrated Photonic Quantum Chips for Generating Path-Encoded Bell States

by Meng Li, Qian Zhang, Yang Chen, Xifeng Ren, Qihuang Gong and Yan Li

Micromachines 2020, 11(12), 1111; https://doi.org/10.3390/mi11121111 - 15 Dec 2020

Cited by 18 | Viewed by 4165

Abstract

Integrated photonic quantum chip provides a promising platform to perform quantum computation, quantum simulation, quantum metrology and quantum communication. Femtosecond laser direct writing (FLDW) is a potential technique to fabricate various integrated photonic quantum chips in glass. Several quantum logic gates fabricated by [...] Read more.

Integrated photonic quantum chip provides a promising platform to perform quantum computation, quantum simulation, quantum metrology and quantum communication. Femtosecond laser direct writing (FLDW) is a potential technique to fabricate various integrated photonic quantum chips in glass. Several quantum logic gates fabricated by FLDW have been reported, such as polarization and path encoded quantum controlled-NOT (CNOT) gates. By combining several single qubit gates and two qubit gates, the quantum circuit can realize different functions, such as generating quantum entangled states and performing quantum computation algorithms. Here we demonstrate the FLDW of integrated photonic quantum chips composed of one Hadamard gate and one CNOT gate for generating all four path-encoded Bell states. The experimental results show that the average fidelity of the reconstructed truth table reaches as high as 98.8

\pm

0.3%. Our work is of great importance to be widely applied in many quantum circuits, therefore this technique would offer great potential to fabricate more complex circuits to realize more advanced functions. Full article

(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)

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19 pages, 5207 KiB

Open AccessArticle

Enhancement of Fluid Mixing with U-Shaped Channels on a Rotating Disc

by Chi-Wei Hsu, Po-Tin Shih and Jerry M. Chen

Micromachines 2020, 11(12), 1110; https://doi.org/10.3390/mi11121110 - 15 Dec 2020

Cited by 11 | Viewed by 3291

Abstract

In this study, centrifugal microfluidics with a simple geometry of U-shaped structure was designed, fabricated and analyzed to attain rapid and efficient fluid mixing. Visualization experiments together with numerical simulations were carried out to investigate the mixing behavior for the microfluidics with single, [...] Read more.

In this study, centrifugal microfluidics with a simple geometry of U-shaped structure was designed, fabricated and analyzed to attain rapid and efficient fluid mixing. Visualization experiments together with numerical simulations were carried out to investigate the mixing behavior for the microfluidics with single, double and triple U-shaped structures, where each of the U-structures consisted of four consecutive 90° bends. It is found that the U-shaped structure markedly enhances mixing by transverse secondary flow that is originated from the Coriolis-induced vortices and further intensified by the Dean force generated as the stream turns along the 90° bends. The secondary flow becomes stronger with increasing rotational speed and with more U-shaped structures, hence higher mixing performance. The mixing efficiency measured for the three types of mixers shows a sharp increase with increasing rotational speed in the lower range. As the rotational speed further increases, nearly complete mixing can be achieved at 600 rpm for the triple-U mixer and at 720 rpm for the double-U mixer, while a maximum efficiency level of 83–86% is reached for the single-U mixer. The simulation results that reveal detailed characteristics of the flow and concentration fields are in good agreement with the experiments. Full article

(This article belongs to the Special Issue Analysis, Design and Fabrication of Micromixers)

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12 pages, 4129 KiB

Open AccessArticle

Plasmonic Hybrids of MoS₂ and 10-nm Nanogap Arrays for Photoluminescence Enhancement

by Yang Yang, Ruhao Pan, Shibing Tian, Changzhi Gu and Junjie Li

Micromachines 2020, 11(12), 1109; https://doi.org/10.3390/mi11121109 - 15 Dec 2020

Cited by 11 | Viewed by 3248

Abstract

Monolayer MoS₂ has attracted tremendous interest, in recent years, due to its novel physical properties and applications in optoelectronic and photonic devices. However, the nature of the atomic-thin thickness of monolayer MoS₂ limits its optical absorption and emission, thereby hindering its [...] Read more.

Monolayer MoS₂ has attracted tremendous interest, in recent years, due to its novel physical properties and applications in optoelectronic and photonic devices. However, the nature of the atomic-thin thickness of monolayer MoS₂ limits its optical absorption and emission, thereby hindering its optoelectronic applications. Hybridizing MoS₂ by plasmonic nanostructures is a critical route to enhance its photoluminescence. In this work, the hybrid nanostructure has been proposed by transferring the monolayer MoS₂ onto the surface of 10-nm-wide gold nanogap arrays fabricated using the shadow deposition method. By taking advantage of the localized surface plasmon resonance arising in the nanogaps, a photoluminescence enhancement of ~20-fold was achieved through adjusting the length of nanogaps. Our results demonstrate the feasibility of a giant photoluminescence enhancement for this hybrid of MoS₂/10-nm nanogap arrays, promising its further applications in photodetectors, sensors, and emitters. Full article

(This article belongs to the Special Issue 2D Nanomaterials Processing and Integration in Miniaturized Devices)

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10 pages, 3284 KiB

Open AccessArticle

Improving the Detection Ability of Inductive Micro-Sensor for Non-Ferromagnetic Wear Debris

by Man Wang, Haotian Shi, Hongpeng Zhang, Dian Huo, Yucai Xie and Jun Su

Micromachines 2020, 11(12), 1108; https://doi.org/10.3390/mi11121108 - 15 Dec 2020

Cited by 9 | Viewed by 2586

Abstract

The inductive debris sensor has been studied because of its wide application prospects in mechanical health monitoring. In order to ensure a high-precision detection performance, a comprehensive method to improve the detection sensitivity and detection ability of the inductive sensor for non-ferromagnetic metal [...] Read more.

The inductive debris sensor has been studied because of its wide application prospects in mechanical health monitoring. In order to ensure a high-precision detection performance, a comprehensive method to improve the detection sensitivity and detection ability of the inductive sensor for non-ferromagnetic metal debris is proposed. Based on the characteristics of the eddy current inside the metal, the change of the coil impedance caused by the metal debris is increased by enhancing the magnetic field strength and selecting the optimal excitation frequency. The impedance detection method involving inductance and resistance parameters is used to improve the detection limit of non-ferromagnetic metal debris. The experimental results verify that the magnetic field in the detection region can be enhanced by adding a silicon steel strip (paramagnetic material) in the central hole of the coil, thereby greatly improving the detection sensitivity of the inductive sensor, and the concentrated distribution of the magnetic field avoids the double-peak signals generated by a single particle. The characteristics of the signal amplitude of non-ferromagnetic debris with excitation frequency are studied. Higher inductance, resistance amplitudes, and signal-to-noise ratio (SNR) can be obtained by using a high-frequency alternating current. Compared with inductance parameter detection, resistance parameter detection can detect smaller non-ferromagnetic debris. Combining the detection results of the inductance and resistance parameters can effectively improve the sensor’s ability to detect non-ferromagnetic debris. Full article

(This article belongs to the Special Issue MEMS/NEMS Sensors: Fabrication and Application, Volume III)

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15 pages, 4307 KiB

Open AccessArticle

Propulsion Mechanism of Flexible Microbead Swimmers in the Low Reynolds Number Regime

by Yan-Hom Li and Shao-Chun Chen

Micromachines 2020, 11(12), 1107; https://doi.org/10.3390/mi11121107 - 15 Dec 2020

Cited by 2 | Viewed by 2544

Abstract

A propulsion mechanism for a flexible microswimmer constructed from superparamagnetic microbeads with different diameters and subjected to an oscillating field was studied experimentally and theoretically herein. Various types of artificial swimmers with different bending patterns were fabricated to determine the flexibility and an [...] Read more.

A propulsion mechanism for a flexible microswimmer constructed from superparamagnetic microbeads with different diameters and subjected to an oscillating field was studied experimentally and theoretically herein. Various types of artificial swimmers with different bending patterns were fabricated to determine the flexibility and an effective waveform for a planar beating flagellum. Waveform evolutions for various swimmer configurations were studied to determine the flexible mechanism of the swimmers. A one-armed microswimmer can propel itself only if the friction of its wavelike body is anisotropic. A swimmer with a larger head and a stronger magnetic dipole moment with a flexible tail allows the bending wave to propagate from the head toward the tail to generate forward thrust. The oscillating head and tail do not simultaneously generate positive thrust all the time within a period of oscillation. To increase the propulsion for a bending swimmer, this study proposes a novel configuration for a microbead swimmer that ensures better swimming efficiency. The ratio of the oscillation amplitude of the head to the length of the swimmer (from 0.26 to 0.28) produces a faster swimmer. On the other hand, the swimmer is propelled more effectively if the ratio of the oscillation amplitude of the tail to the length of the swimmer is from 0.29 to 0.33. This study determined the optimal configuration for a flexible microbead swimmer that generates the greatest propulsion in a low Reynolds number environment. Full article

(This article belongs to the Special Issue Advances in Microswimmers)

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15 pages, 4527 KiB

Open AccessArticle

Scale-Up Studies for Co/Ni Separations in Intensified Reactors

by Dimitrios Tsaoulidis, Milan Mamtora, Marta Mayals Gañet, Eduardo Garciadiego-Ortega and Panagiota Angeli

Micromachines 2020, 11(12), 1106; https://doi.org/10.3390/mi11121106 - 15 Dec 2020

Cited by 3 | Viewed by 3597

Abstract

In this paper, the effect of the scalability of small-scale devices on the separation of Co(II) from a binary Co(II)/Ni(II) mixture in a nitric acid solution by an organic Cyanex 272/TBP/kerosene (Exxsol D80) phase is studied. In particular, circular channels with diameters of [...] Read more.

In this paper, the effect of the scalability of small-scale devices on the separation of Co(II) from a binary Co(II)/Ni(II) mixture in a nitric acid solution by an organic Cyanex 272/TBP/kerosene (Exxsol D80) phase is studied. In particular, circular channels with diameters of 1, 2, and 3.2 mm are considered. The results were compared against those from a confined impinging-jets (CIJ) cell with a main channel diameter of 3.2 mm. The effects of total flowrate, residence time, Cyanex 272 concentration, and flowrate ratio on the mass transfer performance were investigated. It was found that at increased channel size, the throughputs were also increased but the extraction percentages remained the same. Higher extraction percentages were obtained by using the CIJ configuration at short residence times. However, for longer residence times, the mass transfer coefficients were similar and capillary channels should be preferred over the CIJ because of the ease of separation of the two phases at the end of the unit. The overall mass transfer coefficients ranged between 0.02 and 0.14 s⁻¹ for the capillary channels during plug flow and between 0.05 and 0.45 s⁻¹ for the CIJ cells during dispersed flow. Full article

(This article belongs to the Special Issue Micro Process-Devices)

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14 pages, 878 KiB

Open AccessArticle

Geometric Understanding of Local Fluctuation Distribution of Conduction Time in Lined-Up Cardiomyocyte Network in Agarose-Microfabrication Multi-Electrode Measurement Assay

by Kazufumi Sakamoto, Shota Aoki, Yuhei Tanaka, Kenji Shimoda, Yoshitsune Hondo and Kenji Yasuda

Micromachines 2020, 11(12), 1105; https://doi.org/10.3390/mi11121105 - 14 Dec 2020

Cited by 4 | Viewed by 2468

Abstract

We examined characteristics of the propagation of conduction in width-controlled cardiomyocyte cell networks for understanding the contribution of the geometrical arrangement of cardiomyocytes for their local fluctuation distribution. We tracked a series of extracellular field potentials of linearly lined-up human embryonic stem (ES) [...] Read more.

We examined characteristics of the propagation of conduction in width-controlled cardiomyocyte cell networks for understanding the contribution of the geometrical arrangement of cardiomyocytes for their local fluctuation distribution. We tracked a series of extracellular field potentials of linearly lined-up human embryonic stem (ES) cell-derived cardiomyocytes and mouse primary cardiomyocytes with 100 kHz sampling intervals of multi-electrodes signal acquisitions and an agarose microfabrication technology to localize the cardiomyocyte geometries in the lined-up cell networks with 100–300 μm wide agarose microstructures. Conduction time between two neighbor microelectrodes (300 μm) showed Gaussian distribution. However, the distributions maintained their form regardless of its propagation distances up to 1.5 mm, meaning propagation diffusion did not occur. In contrast, when Quinidine was applied, the propagation time distributions were increased as the faster firing regulation simulation predicted. The results indicate the “faster firing regulation” is not sufficient to explain the conservation of the propagation time distribution in cardiomyocyte networks but should be expanded with a kind of community effect of cell networks, such as the lower fluctuation regulation. Full article

(This article belongs to the Special Issue Biosensors and MEMS-based Diagnostic Applications)

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15 pages, 32578 KiB

Open AccessArticle

Experimental Investigation on Laser Assisted Diamond Turning of Binderless Tungsten Carbide by In-Process Heating

by Kaiyuan You, Fengzhou Fang, Guangpeng Yan and Yue Zhang

Micromachines 2020, 11(12), 1104; https://doi.org/10.3390/mi11121104 - 14 Dec 2020

Cited by 35 | Viewed by 3369

Abstract

Binderless tungsten carbide (WC) finds widespread applications in precision glass molding (PGM). Grinding and polishing are the main processes to realize optical surface finish on binderless WC mold inserts. The laser assisted turning (LAT) by in-process heating is an efficient method to enhance [...] Read more.

Binderless tungsten carbide (WC) finds widespread applications in precision glass molding (PGM). Grinding and polishing are the main processes to realize optical surface finish on binderless WC mold inserts. The laser assisted turning (LAT) by in-process heating is an efficient method to enhance the machinability of hard and brittle materials. In this paper, laser heating temperature was pre-calculated by the finite element analysis, and was utilized to facilitate laser power selection. The effects of rake angle, depth of cut, feed rate, and laser power are studied experimentally using the Taguchi method. The variance, range, and signal-to-noise ratio analysis methods are employed to evaluate the effects of the factors on the surface roughness. Based on the self-developed LAT system, binderless WC mold inserts with mirror finished surfaces are machined using the optimal parameters. PGM experiments of molding glass lenses for practical application are conducted to verify the machined mold inserts quality. The experiment results indicate that both the mold inserts and molded lenses with the required quality are achieved. Full article

(This article belongs to the Special Issue Advances in Micro and Nano Manufacturing: Process Modeling and Applications)

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11 pages, 3162 KiB

Open AccessArticle

Highly-Sensitive Textile Pressure Sensors Enabled by Suspended-Type All Carbon Nanotube Fiber Transistor Architecture

by Jae Sang Heo, Keon Woo Lee, Jun Ho Lee, Seung Beom Shin, Jeong Wan Jo, Yong Hoon Kim, Myung Gil Kim and Sung Kyu Park

Micromachines 2020, 11(12), 1103; https://doi.org/10.3390/mi11121103 - 14 Dec 2020

Cited by 10 | Viewed by 2966

Abstract

Among various wearable health-monitoring electronics, electronic textiles (e-textiles) have been considered as an appropriate alternative for a convenient self-diagnosis approach. However, for the realization of the wearable e-textiles capable of detecting subtle human physiological signals, the low-sensing performances still remain as a challenge. [...] Read more.

Among various wearable health-monitoring electronics, electronic textiles (e-textiles) have been considered as an appropriate alternative for a convenient self-diagnosis approach. However, for the realization of the wearable e-textiles capable of detecting subtle human physiological signals, the low-sensing performances still remain as a challenge. In this study, a fiber transistor-type ultra-sensitive pressure sensor (FTPS) with a new architecture that is thread-like suspended dry-spun carbon nanotube (CNT) fiber source (S)/drain (D) electrodes is proposed as the first proof of concept for the detection of very low-pressure stimuli. As a result, the pressure sensor shows an ultra-high sensitivity of ~3050 Pa⁻¹ and a response/recovery time of 258/114 ms in the very low-pressure range of <300 Pa as the fiber transistor was operated in the linear region (V_DS = −0.1 V). Also, it was observed that the pressure-sensing characteristics are highly dependent on the contact pressure between the top CNT fiber S/D electrodes and the single-walled carbon nanotubes (SWCNTs) channel layer due to the air-gap made by the suspended S/D electrode fibers on the channel layers of fiber transistors. Furthermore, due to their remarkable sensitivity in the low-pressure range, an acoustic wave that has a very tiny pressure could be detected using the FTPS. Full article

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