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Open AccessArticle

A Numerical Study of an Ellipsoidal Nanoparticles under High Vacuum Using the DSMC Method

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Jinwoo Jang

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Youngwoo Son

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Sanghwan Lee

Micromachines 2023, 14(4), 778; https://doi.org/10.3390/mi14040778 - 30 Mar 2023

Viewed by 412

Abstract

The semiconductor and display manufacturing process requires high precision. Therefore, inside the equipment, fine impurity particles affect the yield rate of production. However, since most manufacturing processes are performed under high-vacuum conditions, it is difficult to estimate particle flow with conventional analytical tools. [...] Read more.

The semiconductor and display manufacturing process requires high precision. Therefore, inside the equipment, fine impurity particles affect the yield rate of production. However, since most manufacturing processes are performed under high-vacuum conditions, it is difficult to estimate particle flow with conventional analytical tools. In this study, high-vacuum flow was analyzed using the direct simulation Monte Carlo (DSMC) method, and various forces acting on fine particles in a high-vacuum flow field were calculated. To compute the computationally intensive DSMC method, GPU-based computer unified device architecture (CUDA) technology was used. The force acting on the particles in the high-vacuum rarefied gas region was verified using the results of previous studies, and the results were derived for the difficult-to-experiment region. An ellipsoid shape with an aspect ratio rather than a spherical shape was also analyzed. The change in drag force according to various aspect ratios was analyzed and compared with the results of the spherical shape under the same flow conditions. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessFeature PaperEditor’s ChoiceArticle

Electrically Inspired Flexible Electrochemical Film Power Supply for Long-Term Epidermal Sensors

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Micromachines 2023, 14(3), 650; https://doi.org/10.3390/mi14030650 - 13 Mar 2023

Viewed by 564

Abstract

This paper, for the first time, reports an electrically inspired flexible electrochemical film power supply for long-term epidermal sensors. This device can periodically provide electrical power for several hours after a short-time electrical activation. The electrical activation makes acetylcholine, which is infused into [...] Read more.

This paper, for the first time, reports an electrically inspired flexible electrochemical film power supply for long-term epidermal sensors. This device can periodically provide electrical power for several hours after a short-time electrical activation. The electrical activation makes acetylcholine, which is infused into the subcutaneous tissue by iontophoresis. The interstitial fluid (ISF) with glucose molecules is then permeated autonomously for several hours. At this period, the device can provide electrical power. The electrical power is generated from the catalyzing reaction between the glucose oxidase immobilized on the anode and the permeated glucose molecules. After the ISF permeation stops, we give a short-time electrical activation to provide electrical power for several hours again. The power supply is flexible, which makes it adaptively conform to skin. The episodic short-time electrical activation can be enabled by an integrated small film lithium-ion battery. This method extends the service life of a lithium-ion battery 10-fold and suggests the application of small lithium-ion batteries for long-term epidermal sensors. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Design and Simulated Electrical Properties of a Proposed Implanted-Epi Silicon 3D-Spherical Electrode Detector

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Micromachines 2023, 14(3), 551; https://doi.org/10.3390/mi14030551 - 26 Feb 2023

Viewed by 600

Abstract

A new type of 3D electrode detector, named here as the Implanted-Epi Silicon 3D-Spherical Electrode Detector, is proposed in this work. Epitaxial and ion implantation processes can be used in this new detector, allowing bowl-shaped electrodes to penetrate the silicon completely. The distance [...] Read more.

A new type of 3D electrode detector, named here as the Implanted-Epi Silicon 3D-Spherical Electrode Detector, is proposed in this work. Epitaxial and ion implantation processes can be used in this new detector, allowing bowl-shaped electrodes to penetrate the silicon completely. The distance between the bowl cathode and the central collection electrode is basically the same, thus the total depletion voltage of Implanted-Epi Silicon 3D-Spherical Electrode Detectors is no longer directively correlated with the thickness of the silicon wafer, but only related to the electrode spacing. In this work, we model the device physics of this new structure and use a simulation program to conduct a systematic 3D simulation of its electrical characteristics, including electric potential and electric field distributions, electron concentration profile, leakage current, and capacitance, and compare it to the traditional 3D detectors. The theoretical and simulation study found that the internal electric potential of the new detector was smooth and no potential saddle point was found. The electric field is also uniform, and there is no zero field and a low electric field area. Compared with the traditional silicon 3D electrode detectors, the full depletion voltage is greatly reduced and the charge collection efficiency is improved. As a large electrode spacing (up to 500 μm) can be realized in the Implanted-Epi Silicon 3D-Spherical Electrode Detector thanks to their advantage of a greatly reduced full depletion voltage, detectors with large pixel cells (and thus small dead volume) can be developed for applications in photon science (X-ray, among others). Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Rubik’s Cube as Reconfigurable Microfluidic Platform for Rapid Setup and Switching of Analytical Devices

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Micromachines 2022, 13(12), 2054; https://doi.org/10.3390/mi13122054 - 24 Nov 2022

Viewed by 1068

Abstract

Microfluidics technology plays an important role in modern analytical instruments, while the modular design of microfluidics facilitates the reconfiguration of analytical instrument functions, making it possible to deploy on-demand systems in the field. However, modular design also faces the challenges such as connection [...] Read more.

Microfluidics technology plays an important role in modern analytical instruments, while the modular design of microfluidics facilitates the reconfiguration of analytical instrument functions, making it possible to deploy on-demand systems in the field. However, modular design also faces the challenges such as connection reliability and reconfiguration convenience. Inspired by the self-locking structure of the Rubik’s cube, a modular, reconfigurable microfluidic instrument architecture is proposed in this paper. The system has a self-locking structure of Rubik’s cube components and an O-ring-based alignment and sealing mechanism, which enables reliable interconnection and rapid rearrangement of microfluidic modules by simply rotating the faces of the microfluidic cube. In addition, the system is capable of integrating a variety of customized modules to perform analysis tasks. A proof-of-concept application of detecting multiple pollutants in water is demonstrated to show the reconfigurable characteristics of the system. The findings of this paper provide a new idea for the design of microfluidic analytical instrument architectures. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Diffusion-Slip Boundary Conditions for Isothermal Flows in Micro- and Nano-Channels

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Alwin Michael Tomy

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S. Kokou Dadzie

Micromachines 2022, 13(9), 1425; https://doi.org/10.3390/mi13091425 - 29 Aug 2022

Cited by 1 | Viewed by 1006

Abstract

Continuum description of flows in micro- and nano-systems requires ad hoc addition of effects such as slip at walls, surface diffusion, Knudsen diffusion and others. While all these effects are derived from various phenomenological formulations, a sound theoretical ground unifying these effects and [...] Read more.

Continuum description of flows in micro- and nano-systems requires ad hoc addition of effects such as slip at walls, surface diffusion, Knudsen diffusion and others. While all these effects are derived from various phenomenological formulations, a sound theoretical ground unifying these effects and observations is still lacking. In this paper, adopting the definition and existence of various type of flow velocities beyond that of the standard mass velocity, we suggest derivation of model boundary conditions that may systematically justify various diffusion process occurring in micro- and nano-flows where the classical continuum model breaks down. Using these boundary conditions in conjunction with the classical continuum flow equations we present a unified derivation of various expressions of mass flow rates and flow profiles in micro- and nano-channels that fit experimental data and provide new insights into these flow profiles. The methodology is consistent with recasting the Navier–Stokes equations and appears justified for both gas and liquid flows. We conclude that these diffusion type of boundary conditions may be more appropriate to use in simulating flows in micro- and nano-systems and may also be adapted as boundary condition models in other interfacial flow modelling. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

PMCHWT Solver Accelerated by Adaptive Cross Approximation for Efficient Computation of Scattering from Metal Nanoparticles

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Micromachines 2022, 13(7), 1086; https://doi.org/10.3390/mi13071086 - 08 Jul 2022

Viewed by 733

Abstract

An accelerated algorithm that can efficiently calculate the light scattering of a single metal nanoparticle was proposed. According to the equivalent principle, the method of moment (MoM) transforms the Poggio–Miller–Chang–Harrington–Wu–Tsai (PMCHWT) integral equations into linear algebraic equations, which are solved by the flexible [...] Read more.

An accelerated algorithm that can efficiently calculate the light scattering of a single metal nanoparticle was proposed. According to the equivalent principle, the method of moment (MoM) transforms the Poggio–Miller–Chang–Harrington–Wu–Tsai (PMCHWT) integral equations into linear algebraic equations, which are solved by the flexible generalized minimal residual solver (FGMRES). Each element of near field MoM impedance matrix was described by Rao–Wilton–Glisson (RWG) basis functions and calculated by double surface integrals. Due to the low-rank property, the adaptive cross approximation (ACA) algorithm based on the octree data structure was applied to compress the MoM impedance matrix of far field action leading to the significant reduction of solution time and memory. Numerical results demonstrated that the proposed method is both accurate and efficient. Compared with the traditional MoM, the ACA algorithm can significantly reduce the impedance matrix filling time and accelerate the scattering field’s computation from actual metal nanoparticles using PMCHWT integral equations. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessFeature PaperEditor’s ChoiceArticle

A Fiber-Based SPR Aptasensor for the In Vitro Detection of Inflammation Biomarkers

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Yu Hua

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Ridong Wang

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Dachao Li

Micromachines 2022, 13(7), 1036; https://doi.org/10.3390/mi13071036 - 29 Jun 2022

Cited by 2 | Viewed by 1315

Abstract

It is widely accepted that the abnormal concentrations of different inflammation biomarkers can be used for the early diagnosis of cardiovascular disease (CVD). Currently, many reported strategies, which require extra report tags or bulky detection equipment, are not portable enough for onsite inflammation [...] Read more.

It is widely accepted that the abnormal concentrations of different inflammation biomarkers can be used for the early diagnosis of cardiovascular disease (CVD). Currently, many reported strategies, which require extra report tags or bulky detection equipment, are not portable enough for onsite inflammation biomarker detection. In this work, a fiber-based surface plasmon resonance (SPR) biosensor decorated with DNA aptamers, which were specific to two typical inflammation biomarkers, C-reactive protein (CRP) and cardiac troponin I (cTn-I), was developed. By optimizing the surface concentration of the DNA aptamer, the proposed sensor could achieve a limit of detection (LOD) of 1.7 nM (0.204 μg/mL) and 2.5 nM (57.5 ng/mL) to CRP and cTn-I, respectively. Additionally, this biosensor could also be used to detect other biomarkers by immobilizing corresponding specific DNA aptamers. Integrated with a miniaturized spectral analysis device, the proposed sensor could be applied for constructing a portable instrument to provide the point of care testing (POCT) for CVD patients. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Influence of Surface Tension on Dynamic Characteristics of Single Bubble in Free-Field Exposed to Ultrasound

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Micromachines 2022, 13(5), 782; https://doi.org/10.3390/mi13050782 - 17 May 2022

Cited by 1 | Viewed by 1314

Abstract

The motion of bubbles in an ultrasonic field is a fundamental physical mechanism in most applications of acoustic cavitation. In these applications, surface-active solutes, which could lower the surface tension of the liquid, are always utilized to improve efficiency by reducing the cavitation [...] Read more.

The motion of bubbles in an ultrasonic field is a fundamental physical mechanism in most applications of acoustic cavitation. In these applications, surface-active solutes, which could lower the surface tension of the liquid, are always utilized to improve efficiency by reducing the cavitation threshold. This paper examines the influence of liquids’ surface tension on single micro-bubbles motion in an ultrasonic field. A novel experimental system based on high-speed photography has been designed to investigate the temporary evolution of a single bubble in the free-field exposed to a 20.43 kHz ultrasound in liquids with different surface tensions. In addition, the R-P equations in the liquid with different surface tension are solved. It is found that the influences of the surface tension on the bubble dynamics are obvious, which reflect on the changes in the maximum size and speed of the bubble margin during bubble oscillating, as well as the weaker stability of the bubble in the liquid with low surface tension, especially for the oscillating bubble with higher speed. These effects of the surface tension on the bubble dynamics can explain the mechanism of surfactants for promoting acoustic cavitation in numerous application fields. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Effect of Wind-Induced Vibration on Measurement Range of Microcantilever Anemometer

by

Yizhou Ye

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Shu Wan

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Xuefeng He

Micromachines 2022, 13(5), 720; https://doi.org/10.3390/mi13050720 - 30 Apr 2022

Viewed by 921

Abstract

In this paper, the effect of wind-induced vibration on measurement range of microcantilever anemometer is investigated for the first time. The microcantilever anemometer is composed of a flexible substrate and a piezoresistor. The wind speed can be detected through the airflow-induced deformation in [...] Read more.

In this paper, the effect of wind-induced vibration on measurement range of microcantilever anemometer is investigated for the first time. The microcantilever anemometer is composed of a flexible substrate and a piezoresistor. The wind speed can be detected through the airflow-induced deformation in the flexible substrate. Previous work indicated that the flexible substrate vibrates violently once the wind speed exceeds a critical value, resulting in severe output jitter. This wind-induced vibration limits the measurement range of the anemometer, and the relationship between the anemometer measurement range and its structural parameters has not been explored systematically. Therefore, this paper aims to reveal this relationship theoretically and experimentally, demonstrating that a shorter and thicker cantilever with larger stiffness can effectively suppress the wind-induced vibration, leading to the critical speed rising. By eliminating the wind-induced vibration, the measurement range of the microcantilever anemometer can be increased by up to 697%. These results presented in this paper can pave the way for the design and fabrication of wide-range mechanical anemometers. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Variable Range Hopping Model Based on Gaussian Disordered Organic Semiconductor for Seebeck Effect in Thermoelectric Device

by

Ying Zhao

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Jiawei Wang

Micromachines 2022, 13(5), 707; https://doi.org/10.3390/mi13050707 - 29 Apr 2022

Cited by 2 | Viewed by 1306

Abstract

We investigate the carrier concentration dependent Seebeck coefficient in Gaussian disordered organic semiconductors (GD-OSs) for thermoelectric device applications. Based on the variable-range hopping (VRH) theory, a general model predicting the Seebeck effect is developed to reveal the thermoelectric properties in GD-OSs. The proposed [...] Read more.

We investigate the carrier concentration dependent Seebeck coefficient in Gaussian disordered organic semiconductors (GD-OSs) for thermoelectric device applications. Based on the variable-range hopping (VRH) theory, a general model predicting the Seebeck effect is developed to reveal the thermoelectric properties in GD-OSs. The proposed model could interpret the experimental data on carrier concentration- and temperature-dependence of the Seebeck coefficient, including various kinds of conducting polymer film and small molecule based field-effect transistors (FETs). Compared with the conventional Mott’s VRH and mobility edge model, our model has a much better description of the relationship between the Seebeck coefficient and conductivity. The model could deepen our insight into charge transport in organic semiconductors and provide instructions for the optimization of thermoelectric device performance in a disordered system. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessArticle

Fast and Accurate Prediction of Light Scattering from Plasmonic Nanoarrays in Multiple Directions

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Micromachines 2022, 13(4), 613; https://doi.org/10.3390/mi13040613 - 14 Apr 2022

Cited by 1 | Viewed by 940

Abstract

The method of moments (MoM) is an efficient electromagnetic numerical method for the accurate prediction of light scattering from plasmonic nanostructures. In practice, the light-scattering properties in different incident directions are often concerning. However, traditional MoM generally resorts to the iterative method, which [...] Read more.

The method of moments (MoM) is an efficient electromagnetic numerical method for the accurate prediction of light scattering from plasmonic nanostructures. In practice, the light-scattering properties in different incident directions are often concerning. However, traditional MoM generally resorts to the iterative method, which suffers from the problems of convergence rate and redundant computations for multiple incident excitations. Nanoarray structures will further aggravate these problems due to a large number of unknowns. In this article, an efficient numerical method based on MoM and a hierarchical matrix (H-matrix) algorithm is proposed to solve these problems. Numerical experiments demonstrate the efficiency and accuracy of the proposed method for the prediction of light scattering from plasmonic nanoarrays in multiple directions. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Review

Jump to: Research

Open AccessReview

Modular Microfluidics: Current Status and Future Prospects

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Micromachines 2022, 13(8), 1363; https://doi.org/10.3390/mi13081363 - 22 Aug 2022

Cited by 7 | Viewed by 1840

Abstract

This review mainly studies the development status, limitations, and future directions of modular microfluidic systems. Microfluidic technology is an important tool platform for scientific research and plays an important role in various fields. With the continuous development of microfluidic applications, conventional monolithic microfluidic [...] Read more.

This review mainly studies the development status, limitations, and future directions of modular microfluidic systems. Microfluidic technology is an important tool platform for scientific research and plays an important role in various fields. With the continuous development of microfluidic applications, conventional monolithic microfluidic chips show more and more limitations. A modular microfluidic system is a system composed of interconnected, independent modular microfluidic chips, which are easy to use, highly customizable, and on-site deployable. In this paper, the current forms of modular microfluidic systems are classified and studied. The popular fabrication techniques for modular blocks, the major application scenarios of modular microfluidics, and the limitations of modular techniques are also discussed. Lastly, this review provides prospects for the future direction of modular microfluidic technologies. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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Open AccessReview

Development and Application of SAW Filter

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Pu Chen

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Guangxi Li

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Zhiyuan Zhu

Micromachines 2022, 13(5), 656; https://doi.org/10.3390/mi13050656 - 20 Apr 2022

Cited by 5 | Viewed by 2817

Abstract

With the in-depth advancement of the fifth generation (5G) mobile communication technology, the technical requirements for filters are also constantly improving. Surface acoustic wave (SAW) filters are widely used in home TV, mobile communications, radio frequency filters and radar due to their simple [...] Read more.

With the in-depth advancement of the fifth generation (5G) mobile communication technology, the technical requirements for filters are also constantly improving. Surface acoustic wave (SAW) filters are widely used in home TV, mobile communications, radio frequency filters and radar due to their simple structure, few mask layers, easy miniaturization, and low cost. Through the continuous improvement of communication technology, SAW has developed into various high-performance acoustic filters from bulk SAW with the support of some new architectures, new materials and advanced modeling techniques. This paper analyzes and reviews the research situation of SAW filter technology. Full article

(This article belongs to the Special Issue Physics in Micro/Nano Devices: From Fundamental to Application)

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