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11 pages, 2779 KiB

Open AccessArticle

Analysis of Von Kármán Swirling Flows Due to a Porous Rotating Disk Electrode

by James Visuvasam and Hammad Alotaibi

Micromachines 2023, 14(3), 582; https://doi.org/10.3390/mi14030582 - 28 Feb 2023

Cited by 2 | Viewed by 994

The study of Von Kármán swirling flow is a subject of active interest due to its applications in a wide range of fields, including biofuel manufacturing, rotating heat exchangers, rotating disc reactors, liquid metal pumping engines, food processing, electric power generating systems, designs [...] Read more.

The study of Von Kármán swirling flow is a subject of active interest due to its applications in a wide range of fields, including biofuel manufacturing, rotating heat exchangers, rotating disc reactors, liquid metal pumping engines, food processing, electric power generating systems, designs of multi-pore distributors, and many others. This paper focusses on investigating Von Kármán swirling flows of viscous incompressible fluid due to a rotating disk electrode. The model is based on a system of four coupled second-order non-linear differential equations. The purpose of the present communication is to derive analytical expressions of velocity components by solving the non-linear equations using the homotopy analysis method. Combined effects of the slip λ and porosity γ parameters are studied in detail. If either parameter is increased, all velocity components are reduced, as both have the same effect on the mean velocity profiles. The porosity parameter γ increases the moment coefficient at the disk surface, which monotonically decreases with the slip parameter λ. The analytical results are also compared with numerical solutions, which are in satisfactory agreement. Furthermore, the effects of porosity and slip parameters on velocity profiles are discussed. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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14 pages, 3191 KiB

Open AccessArticle

Laser-Patterned Alumina Mask and Mask-Less Dry Etch of Si for Light Trapping with Photonic Crystal Structures

by Jovan Maksimovic, Haoran Mu, Daniel Smith, Tomas Katkus, Mantas Vaičiulis, Ramūnas Aleksiejūnas, Gediminas Seniutinas, Soon Hock Ng and Saulius Juodkazis

Micromachines 2023, 14(3), 550; https://doi.org/10.3390/mi14030550 - 26 Feb 2023

Cited by 1 | Viewed by 1481

Abstract

Ultra-short 230 fs laser pulses of a 515 nm wavelength were tightly focused onto 700 nm focal spots and utilised in opening ∼0.4–1 μm holes in alumina Al₂O₃ etch masks with a 20–50 nm thickness. Such dielectric masks simplify the fabrication [...] Read more.

Ultra-short 230 fs laser pulses of a 515 nm wavelength were tightly focused onto 700 nm focal spots and utilised in opening ∼0.4–1 μm holes in alumina Al₂O₃ etch masks with a 20–50 nm thickness. Such dielectric masks simplify the fabrication of photonic crystal (PhC) light-trapping patterns for the above-Lambertian performance of high-efficiency solar cells. The conditions of the laser ablation of transparent etch masks and the effects sub-surface Si modifications were revealed by plasma etching, numerical modelling, and minority carrier lifetime measurements. Mask-less patterning of Si is proposed using fs laser direct writing for dry plasma etching of Si. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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8 pages, 3211 KiB

Open AccessArticle

On-State Current Degradation Owing to Displacement Defect by Terrestrial Cosmic Rays in Nanosheet FET

by Jonghyeon Ha, Gyeongyeop Lee, Hagyoul Bae, Kihyun Kim, Jin-Woo Han and Jungsik Kim

Micromachines 2022, 13(8), 1276; https://doi.org/10.3390/mi13081276 - 08 Aug 2022

Viewed by 1577

Abstract

Silicon displacement defects are caused by various effects. For instance, epitaxial crystalline silicon growth and ion implantation often result in defects induced by the fabrication process, whereas displacement damage is induced by terrestrial cosmic radiation. Clustered displacement damage reportedly reduces the on-state current [...] Read more.

Silicon displacement defects are caused by various effects. For instance, epitaxial crystalline silicon growth and ion implantation often result in defects induced by the fabrication process, whereas displacement damage is induced by terrestrial cosmic radiation. Clustered displacement damage reportedly reduces the on-state current (I_on) in ordinary MOSFETs. In the case of an extremely scaled device such as a nanosheet field-effect transistor (NS-FET), the impact of displacement defect size was analyzed on the basis of the NS dimensions related to the device characteristics. In this study, we investigated the effect of displacement defects on NS-FETs using technology computer-aided design; the simulation model included quantum transport effects. The geometrical conditions, temperatures, trap concentrations, and scattering models were considered as the variables for on-state current reduction. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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9 pages, 2338 KiB

Open AccessArticle

Tunable Dual-Wavelength with Twin-Pulse Dissipative Solitons in All-Normal Dispersion Yb-Doped Fiber Laser

by Xiaojun Zhu, Wen Liu, Yongquan Pan, Shuai Li, Guoan Zhang, Yancheng Ji, Li Zou, Zhipeng Liang and Juan Cao

Micromachines 2022, 13(7), 1049; https://doi.org/10.3390/mi13071049 - 30 Jun 2022

Cited by 2 | Viewed by 1312

Abstract

A tunable dual-wavelength with two separated twin-pulse dissipative solitons (DSs) of Yb-doped mode-locked fiber laser in the all-normal-dispersion (ANDi) regime is firstly reported and demonstrated in this paper. A Sagnac loop is used as an all-fiber format spectral filter in the laser cavity, [...] Read more.

A tunable dual-wavelength with two separated twin-pulse dissipative solitons (DSs) of Yb-doped mode-locked fiber laser in the all-normal-dispersion (ANDi) regime is firstly reported and demonstrated in this paper. A Sagnac loop is used as an all-fiber format spectral filter in the laser cavity, and stable twin-pulse DSs with different wavelength mode-locked lasers are achieved by the nonlinear polarization evolution (NPE) effect. By adjusting the polarization state of the Sagnac loop, the spectral ranges of the dual-wavelength can be tuned from 1031.3 nm to 1041.5 nm and from 1067.1 nm to 1080.9 nm, respectively. However, the pulse space between the two separated twin-pulse DSs is maintained, i.e., 41.63 ns. Furthermore, the twin-pulse can regress to the single-pulse when the pump power keeps dropping. It has been observed that the highest energy of the two twin-pulse DSs output is 23.36 nJ at a repetition rate of 2.282 MHz with a maximum pump power of 560 mW. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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12 pages, 4149 KiB

Open AccessArticle

Planar Optofluidic Integration of Ring Resonator and Microfluidic Channels

by Genni Testa, Gianluca Persichetti and Romeo Bernini

Micromachines 2022, 13(7), 1028; https://doi.org/10.3390/mi13071028 - 28 Jun 2022

Cited by 2 | Viewed by 1250

Abstract

We report an optofluidic hybrid silicon-polymer planar ring resonator with integrated microfluidic channels for efficient liquid delivery. The device features a planar architecture of intersecting liquid-core waveguides and microfluidic channels. A low-loss integration of microfluidic channels is accomplished by exploiting the interference pattern [...] Read more.

We report an optofluidic hybrid silicon-polymer planar ring resonator with integrated microfluidic channels for efficient liquid delivery. The device features a planar architecture of intersecting liquid-core waveguides and microfluidic channels. A low-loss integration of microfluidic channels is accomplished by exploiting the interference pattern created by the self-imaging effect in the multimode interference-based coupler waveguides. Numerical simulations have been performed in order to minimize the propagation losses along the ring loop caused by the integration of microfluidic channels. The device has been fabricated and optically characterized by measuring the quality factor, obtaining a value of 4 × 10³. This result is comparable with the quality factor of an optofluidic ring with the same optical layout but without integrated microfluidic channels, thus, confirming the suitability of the proposed approach for microfluidics integration in planar optofluidic design. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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10 pages, 2914 KiB

Open AccessArticle

Influence of Radiation-Induced Displacement Defect in 1.2 kV SiC Metal-Oxide-Semiconductor Field-Effect Transistors

by Gyeongyeop Lee, Jonghyeon Ha, Kihyun Kim, Hagyoul Bae, Chong-Eun Kim and Jungsik Kim

Micromachines 2022, 13(6), 901; https://doi.org/10.3390/mi13060901 - 07 Jun 2022

Cited by 3 | Viewed by 2057

Abstract

The effect of displacement defect on SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) due to radiation is investigated using technology computer-aided design (TCAD) simulation. The position, energy level, and concentration of the displacement defect are considered as variables. The transfer characteristics, breakdown voltage, and energy [...] Read more.

The effect of displacement defect on SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) due to radiation is investigated using technology computer-aided design (TCAD) simulation. The position, energy level, and concentration of the displacement defect are considered as variables. The transfer characteristics, breakdown voltage, and energy loss of a double-pulse switching test circuit are analyzed. Compared with the shallow defect energy level, the deepest defect energy level with E_C − 1.55 eV exhibits considerable degradation. The on-current decreases by 54% and on-resistance increases by 293% due to the displacement defect generated at the parasitic junction field-effect transistor (JFET) region next to the P-well. Due to the existence of a defect in the drift region, the breakdown voltage increased up to 21 V. In the double-pulse switching test, the impact of displacement defect on the power loss of SiC MOSFETs is negligible. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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20 pages, 5124 KiB

Open AccessArticle

Single-Pixel Near-Infrared 3D Image Reconstruction in Outdoor Conditions

by C. Osorio Quero, D. Durini, J. Rangel-Magdaleno, J. Martinez-Carranza and R. Ramos-Garcia

Micromachines 2022, 13(5), 795; https://doi.org/10.3390/mi13050795 - 20 May 2022

Cited by 9 | Viewed by 2702

Abstract

In the last decade, the vision systems have improved their capabilities to capture 3D images in bad weather scenarios. Currently, there exist several techniques for image acquisition in foggy or rainy scenarios that use infrared (IR) sensors. Due to the reduced light scattering [...] Read more.

In the last decade, the vision systems have improved their capabilities to capture 3D images in bad weather scenarios. Currently, there exist several techniques for image acquisition in foggy or rainy scenarios that use infrared (IR) sensors. Due to the reduced light scattering at the IR spectra it is possible to discriminate the objects in a scene compared with the images obtained in the visible spectrum. Therefore, in this work, we proposed 3D image generation in foggy conditions using the single-pixel imaging (SPI) active illumination approach in combination with the Time-of-Flight technique (ToF) at 1550 nm wavelength. For the generation of 3D images, we make use of space-filling projection with compressed sensing (CS-SRCNN) and depth information based on ToF. To evaluate the performance, the vision system included a designed test chamber to simulate different fog and background illumination environments and calculate the parameters related to image quality. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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13 pages, 3762 KiB

Open AccessArticle

Optofluidic Particle Manipulation Platform with Nanomembrane

by Zachary J. Walker, Tanner Wells, Ethan Belliston, Sage Romney, Seth B. Walker, Mohammad Julker Neyen Sampad, S M Saiduzzaman, Ravipa Losakul, Holger Schmidt and Aaron R. Hawkins

Micromachines 2022, 13(5), 721; https://doi.org/10.3390/mi13050721 - 30 Apr 2022

Cited by 2 | Viewed by 1744

Abstract

We demonstrate a method for fabricating and utilizing an optofluidic particle manipulator on a silicon chip that features a 300 nm thick silicon dioxide membrane as part of a microfluidic channel. The fabrication method is based on etching silicon channels and converting the [...] Read more.

We demonstrate a method for fabricating and utilizing an optofluidic particle manipulator on a silicon chip that features a 300 nm thick silicon dioxide membrane as part of a microfluidic channel. The fabrication method is based on etching silicon channels and converting the walls to silicon dioxide through thermal oxidation. Channels are encapsulated by a sacrificial polymer which fills the length of the fluid channel by way of spontaneous capillary action. The sacrificial material is then used as a mold for the formation of a nanoscale, solid-state, silicon dioxide membrane. The hollow channel is primarily used for fluid and particle transport but is capable of transmitting light over short distances and utilizes radiation pressure for particle trapping applications. The optofluidic platform features solid-core ridge waveguides which can direct light on and off of the silicon chip and intersect liquid channels. Optical loss values are characterized for liquid and solid-core structures and at interfaces. Estimates are provided for the optical power needed to trap particles of various sizes. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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8 pages, 1636 KiB

Open AccessArticle

Ultrathin Optics-Free Spectrometer with Monolithically Integrated LED Excitation

by Tuba Sarwar and Pei-Cheng Ku

Micromachines 2022, 13(3), 382; https://doi.org/10.3390/mi13030382 - 27 Feb 2022

Cited by 1 | Viewed by 1729

Abstract

A semiconductor spectrometer chip with a monolithically integrated light-emitting diode was demonstrated. The spectrometer design was based on a computational reconstruction algorithm and a series of absorptive spectral filters directly built in to the photodetectors’ active regions. The result is the elimination of [...] Read more.

A semiconductor spectrometer chip with a monolithically integrated light-emitting diode was demonstrated. The spectrometer design was based on a computational reconstruction algorithm and a series of absorptive spectral filters directly built in to the photodetectors’ active regions. The result is the elimination of the need to employ external optics to control the incident angle of light. In the demonstration, an array of gallium nitride (GaN) based photodetectors with wavelength selectivity generated via the principle of local strain engineering were designed and fabricated. Additionally, a GaN based LED was monolithically integrated. An optical blocking structure was used to suppress the LED-photodetector interference and was shown to be essential for the spectroscopic functionality. A proof of concept using a reflection spectroscopy configuration was experimentally conducted to validate the feasibly of simultaneously operating the LED excitation light source and the photodetectors. Spectral reconstruction using a non-negative least squares (NNLS) algorithm enhanced with orthogonal matching pursuit was shown to reconstruct the signal from the reflection spectroscopy. Optics-free operation was also demonstrated. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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9 pages, 1836 KiB

Open AccessArticle

Determination of the Dielectrophoretic Force Induced by the Photovoltaic Effect on Lithium Niobate

by Alessio Meggiolaro, Sebastian Cremaschini, Davide Ferraro, Annamaria Zaltron, Mattia Carneri, Matteo Pierno, Cinzia Sada and Giampaolo Mistura

Micromachines 2022, 13(2), 316; https://doi.org/10.3390/mi13020316 - 18 Feb 2022

Cited by 7 | Viewed by 1877

Abstract

The actuation of droplets on a surface is extremely relevant for microfluidic applications. In recent years, various methodologies have been used. A promising solution relies on iron-doped lithium niobate crystals that, when illuminated, generate an evanescent electric field in the surrounding space due [...] Read more.

The actuation of droplets on a surface is extremely relevant for microfluidic applications. In recent years, various methodologies have been used. A promising solution relies on iron-doped lithium niobate crystals that, when illuminated, generate an evanescent electric field in the surrounding space due to the photovoltaic effect. This field can be successfully exploited to control the motion of water droplets. Here, we present an experimental method to determine the attractive force exerted by the evanescent field. It consists of the analysis of the elongation of a pendant droplet and its detachment from the suspending syringe needle, caused by the illumination of an iron-doped lithium niobate crystal. We show that this interaction resembles that obtained by applying a voltage between the needle and a metallic substrate, and a quantitative investigation of these two types of actuation yields similar results. Pendant droplet tensiometry is then demonstrated to offer a simple solution for quickly mapping out the force at different distances from the crystal, generated by the photovoltaic effect and its temporal evolution, providing important quantitative data for the design and characterization of optofluidic devices based on lithium niobate crystals. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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7 pages, 1155 KiB

Open AccessArticle

Light-Induced Dynamic Holography

by Daniele Eugenio Lucchetta, Andrea Di Donato, Melania Paturzo, Gautam Singh and Riccardo Castagna

Micromachines 2022, 13(2), 297; https://doi.org/10.3390/mi13020297 - 14 Feb 2022

Cited by 6 | Viewed by 1583

Abstract

Holographic photomobile polymers (H-PMP) are a novel class of photomobile materials in which holograms can be optically recorded. They can be used in a large variety of applications, including optical switches and color selectors. In this work, we show one of the most [...] Read more.

Holographic photomobile polymers (H-PMP) are a novel class of photomobile materials in which holograms can be optically recorded. They can be used in a large variety of applications, including optical switches and color selectors. In this work, we show one of the most important properties of the photomobile film, which is the photophobicity of the unpolymerized parts of the photomobile mixture. In order to investigate this property, we recorded a transmission phase grating on an H-PMP film, and used a different experimental technique to measure the diffraction efficiency, surface tension, and mixture properties. The results allowed for a better understanding of the mechanism of the light-controlled bending observed in these compounds. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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Review

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29 pages, 10834 KiB

Open AccessReview

Acoustic Wake-Up Technology for Microsystems: A Review

by Deng Yang and Jiahao Zhao

Micromachines 2023, 14(1), 129; https://doi.org/10.3390/mi14010129 - 03 Jan 2023

Cited by 4 | Viewed by 2281

Abstract

Microsystems with capabilities of acoustic signal perception and recognition are widely used in unattended monitoring applications. In order to realize long-term and large-scale monitoring, microsystems with ultra-low power consumption are always required. Acoustic wake-up is one of the solutions to effectively reduce the [...] Read more.

Microsystems with capabilities of acoustic signal perception and recognition are widely used in unattended monitoring applications. In order to realize long-term and large-scale monitoring, microsystems with ultra-low power consumption are always required. Acoustic wake-up is one of the solutions to effectively reduce the power consumption of microsystems, especially for monitoring sparse events. This paper presents a review of acoustic wake-up technologies for microsystems. Acoustic sensing, acoustic recognition, and system working mode switching are the basis for constructing acoustic wake-up microsystems. First, state-of-the-art MEMS acoustic transducers suitable for acoustic wake-up microsystems are investigated, including MEMS microphones, MEMS hydrophones, and MEMS acoustic switches. Acoustic transducers with low power consumption, high sensitivity, low noise, and small size are attributes needed by the acoustic wake-up microsystem. Next, acoustic features and acoustic classification algorithms for target and event recognition are studied and summarized. More acoustic features and more computation are generally required to achieve better recognition performance while consuming more power. After that, four different system wake-up architectures are summarized. Acoustic wake-up microsystems with absolutely zero power consumption in sleep mode can be realized in the architecture of zero-power recognition and zero-power sleep. Applications of acoustic wake-up microsystems are then elaborated, which are closely related to scientific research and our daily life. Finally, challenges and future research directions of acoustic wake-up microsystems are elaborated. With breakthroughs in software and hardware technologies, acoustic wake-up microsystems can be deployed for ultra-long-term and ultra-large-scale use in various fields, and play important roles in the Internet of Things. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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24 pages, 6861 KiB

Open AccessReview

Development of Electrostatic Microactuators: 5-Year Progress in Modeling, Design, and Applications

by Inga Morkvenaite-Vilkonciene, Vytautas Bucinskas, Jurga Subaciute-Zemaitiene, Ernestas Sutinys, Darius Virzonis and Andrius Dzedzickis

Micromachines 2022, 13(8), 1256; https://doi.org/10.3390/mi13081256 - 04 Aug 2022

Cited by 12 | Viewed by 3177

Abstract

The implementation of electrostatic microactuators is one of the most popular technical solutions in the field of micropositioning due to their versatility and variety of possible operation modes and methods. Nevertheless, such uncertainty in existing possibilities creates the problem of choosing suitable methods. [...] Read more.

The implementation of electrostatic microactuators is one of the most popular technical solutions in the field of micropositioning due to their versatility and variety of possible operation modes and methods. Nevertheless, such uncertainty in existing possibilities creates the problem of choosing suitable methods. This paper provides an effort to classify electrostatic actuators and create a system in the variety of existing devices. Here is overviewed and classified a wide spectrum of electrostatic actuators developed in the last 5 years, including modeling of different designs, and their application in various devices. The paper provides examples of possible implementations, conclusions, and an extensive list of references. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)

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