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Micromachines
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Feature Papers of Micromachines in Materials and Processing 2021
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Feature Papers of Micromachines in Materials and Processing 2021

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D：Materials and Processing".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 68398

Special Issue Editor

Dr. Mehmet Remzi Dokmeci

grade E-Mail Website
Guest Editor
Terasaki Institute for Biomedical Innovation, 1018 Westwood Blvd, Los Angeles, CA 90024, USA
Interests: bio-micro-electro-mechanical systems (BioMEMS); biomedical and implantable devices; biosensors; organs-on-a-chip; micro- and nanosensors for monitoring organs-on-a-chip; flexible electronics and sensors for wound healing; packaging and encapsulation of implantable devices; biomaterials; biofabrication
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues,

We are pleased to announce the Special Issue entitled "Feature Papers of Micromachines in Materials and Processing 2021." In the past several years, we have worked in conjunction with excellent scholars and research groups to publish several high-impact high-quality manuscripts which have received a large number of views and citations. Our goal is to publish the latest scientific and technological advances in areas related to micro/nanofabrication with applications in biomedical sciences and biology, materials, semiconductors, photonics, and energy, which we hope will make great contributions to the scientific community.

This Special Issue will be a collection of high-quality papers from excellent scholars around the world. Both original research articles and comprehensive review papers are welcome. The papers will be published, free of charge, with full open access after peer review to benefit both authors and readers.

You are welcome to send short proposals for submissions of feature papers to our Editorial Office (mars.tu@mdpi.com) before the submission. The proposals will first be evaluated by the editors. Please note that selected full papers will still be subjected to a thorough and rigorous peer review.

We look forward to receiving your excellent work.

Prof. Dr. Mehmet Remzi Dokmeci
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Biomedical microdevices
  • Micro/nanofabrication
  • BioMEMS
  • Organs-on-a-chip
  • Minimally invasive devices
  • Wearable devices
  • Biosensors
  • 3D bioprinting
  • MEMS and CMOS technologies
  • Artificial Intelligence with applications to micro/nanofabrication and sensors

Published Papers (27 papers)

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13 pages, 1390 KiB  
Article
Detecting the Knowledge Domains of Compound Semiconductors
by Qian-Yo Lee, Chiyang James Chou, Ming-Xuan Lee and Yen-Chun Lee
Micromachines 2022, 13(3), 476; https://doi.org/10.3390/mi13030476 - 20 Mar 2022
Cited by 1 | Viewed by 2069
Abstract
The development of compound semiconductors (CS) has received extensive attention worldwide. This study aimed to detect and visualize CS knowledge domains for quantifying CS research patterns and emerging trends through a scientometric review based on the literature between 2011 and 2020 by using [...] Read more.
The development of compound semiconductors (CS) has received extensive attention worldwide. This study aimed to detect and visualize CS knowledge domains for quantifying CS research patterns and emerging trends through a scientometric review based on the literature between 2011 and 2020 by using CiteSpace. The combined dataset of 24,622 bibliographic records were collected through topic searches and citation expansion to ensure adequate coverage of the field. While research in “solar cell” and “perovskite tandem” appears to be the two most distinctive knowledge domains in the CS field, research related to thermoelectric materials has grown at a respectable pace. Most notably, the deep connections between “thermoelectric material” and “III-Sb nanowire (NW)” research have been demonstrated. A rapid adaptation of black phosphorus (BP) field-effect transistors (FETs) and gallium nitride (GaN) transistors in the CS field is also apparent. Innovative strategies have focused on the opto-electronics with engineered functionalities, the design, synthesis and fabrication of perovskite tandem solar cells, the growing techniques of Sb-based III–V NWs, and the thermal conductivity of boron arsenide (BAs). This study revealed how the development trends and research areas in the CS field advance over time, which greatly help us to realize its knowledge domains. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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18 pages, 9979 KiB  
Article
The Uses of a Dual-Band Corrugated Circularly Polarized Horn Antenna for 5G Systems
by Chih-Kai Liu, Wei-Yuan Chiang, Pei-Zong Rao, Pei-Hsiu Hung, Shih-Hung Chen, Chiung-An Chen, Liang-Hung Wang, Patricia Angela R. Abu and Shih-Lun Chen
Micromachines 2022, 13(2), 289; https://doi.org/10.3390/mi13020289 - 11 Feb 2022
Cited by 4 | Viewed by 2344
Abstract
This paper presents the development of a wide-beam width, dual-band, omnidirectional antenna for the mm-wave band used in 5G communication systems for indoor coverage. The 5G indoor environment includes features of wide space and short range. Additionally, it needs to function well under [...] Read more.
This paper presents the development of a wide-beam width, dual-band, omnidirectional antenna for the mm-wave band used in 5G communication systems for indoor coverage. The 5G indoor environment includes features of wide space and short range. Additionally, it needs to function well under a variety of circumstances in order to carry out its diverse set of network applications. The waveguide antenna has been designed to be small enough to meet the requirements of mm-wave band and utilizes a corrugated horn to produce a wide beam width. Additionally, it is small enough to integrate with 5G communication products and is easy to manufacture. This design is simple enough to have multi-feature antenna performance and is more useful for the femtocell repeater. The corrugated circularly polarized horn antenna has been designed for two frequency bands; namely, 26.5–30 GHz for the low band and 36–40 GHz for high band. The results of this study show that return-loss is better than 18 dB for both low and high band. The peak gain is 6.1 dBi for the low band and 8.7 dBi for the high band. The beam width is 105 degrees and 77 degrees for the low band and the high band, respectively. The axial ratio is less than 5.2 dB for both low and high band. Generally, traditional circularly polarized antennas cannot meet the requirements for broadband. The designs for the antennas proposed here can meet the requirements of FR2 bandwidths. This feature limits axial ratio performance. The measurement error in the current experiment comes from the high precision control on the size of the ridge. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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11 pages, 3803 KiB  
Article
Diffusion-Induced Stress in Commercial Graphite Electrodes during Multiple Cycles Measured by an In Situ Method
by Dawei Li, Guanglin Zhu, Huibing Liu and Yikai Wang
Micromachines 2022, 13(1), 142; https://doi.org/10.3390/mi13010142 - 17 Jan 2022
Cited by 7 | Viewed by 2000
Abstract
The cyclic stress evolution induced by repeated volume variation causes mechanical degradation and damage to electrodes, resulting in reduced performance and lifetime of LIBs. To probe the electro-chemo-mechanical coupled degradation, we conducted in situ measurements of Young’s modulus and stress evolution of commercial [...] Read more.
The cyclic stress evolution induced by repeated volume variation causes mechanical degradation and damage to electrodes, resulting in reduced performance and lifetime of LIBs. To probe the electro-chemo-mechanical coupled degradation, we conducted in situ measurements of Young’s modulus and stress evolution of commercial used graphite electrodes during multiple cycles. A bilayer graphite electrode cantilever is cycled galvanostatically in a custom cell, while the bending deformation of the bilayer electrode is captured by a CCD optical system. Combined with a mechanical model, Li-concentration-dependent elastic modulus and stress are derived from the curvature of the cantilever electrode. The results show that modulus, stress and strain all increase with the lithium concentration, and the stress transforms from compression to tension in the thickness direction. During multiple cycles, the modulus decreases with an increase in the cycle number at the same concentration. The maximum stress/strain of each cycle is maintained at almost same level, exhibiting a threshold that results from the co-interaction of concentration and damage. These findings provide basic information for modeling the degradation of LIBs. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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14 pages, 63197 KiB  
Article
A Microfabricated Bandpass Filter with Coarse-Tuning and Fine-Tuning Ability Based on IPD Process and PCB Artwork
by Junzhe Shen, Tian Qiang, Minjia Gao, Yangchuan Ma, Junge Liang and Yanfeng Jiang
Micromachines 2022, 13(1), 123; https://doi.org/10.3390/mi13010123 - 13 Jan 2022
Viewed by 1750
Abstract
In this paper, a bandpass filter (BPF) was developed utilizing GaAs-based integrated passive device technology which comprises an asymmetrical spiral inductor and an interleaved array capacitor, possessing two tuning modes: coarse-tuning and fine-tuning. By altering the number of layers and radius of the [...] Read more.
In this paper, a bandpass filter (BPF) was developed utilizing GaAs-based integrated passive device technology which comprises an asymmetrical spiral inductor and an interleaved array capacitor, possessing two tuning modes: coarse-tuning and fine-tuning. By altering the number of layers and radius of the GaAs substrate metal spheres, capacitance variation from 0.071 to 0.106 pF for coarse-tuning, and of 0.0015 pF for fine-tuning, can be achieved. Five air bridges were employed in the asymmetrical spiral inductor to save space, contributing to a compact chip area of 0.015λ0 × 0.018λ0. The BPF chip was installed on the printed circuit board artwork with Au bonding wire and attached to a die sink. Measured results demonstrate an insertion loss of 0.38 dB and a return loss of 21.5 dB at the center frequency of 2.147 GHz. Furthermore, under coarse-tuning mode, variation in the center frequency from 1.956 to 2.147 GHz and transmission zero frequency from 4.721 to 5.225 GHz can be achieved. Under fine-tuning mode, the minimum tuning value and the average tuning value of the proposed BPF can be accurate to 1.0 MHz and 4.7 MHz for the center frequency and 1.0 MHz and 12.8 MHz for the transmission zero frequency, respectively. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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10 pages, 2484 KiB  
Communication
Self-Assembled 1-Octadecanethiol Membrane on Pd/ZnO for a Selective Room Temperature Flexible Hydrogen Sensor
by Pawan Pathak and Hyoung Jin Cho
Micromachines 2022, 13(1), 26; https://doi.org/10.3390/mi13010026 - 26 Dec 2021
Cited by 3 | Viewed by 2437
Abstract
A layer of self-assembled 1-octadecanethiol was used to fabricate a palladium (Pd)/zinc oxide (ZnO) nanoparticle-based flexible hydrogen sensor with enhanced response and high selectivity at room temperature. A palladium film was first deposited using DC sputtering technique and later annealed to form palladium [...] Read more.
A layer of self-assembled 1-octadecanethiol was used to fabricate a palladium (Pd)/zinc oxide (ZnO) nanoparticle-based flexible hydrogen sensor with enhanced response and high selectivity at room temperature. A palladium film was first deposited using DC sputtering technique and later annealed to form palladium nanoparticles. The formation of uniform, surfactant-free palladium nanoparticles contributed to improved sensor response towards hydrogen gas at room temperature. The obtained sensor response was higher than for previously reported room temperature Pd/ZnO sensors. Furthermore, the use of the polymer membrane suppressed the sensor’s response to methane, moisture, ethanol, and acetone, resulting in the selective detection of hydrogen in the presence of the common interfering species. This study shows a viable low-cost fabrication pathway for highly selective room temperature flexible hydrogen sensors for hydrogen-powered vehicles and other clean energy applications. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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9 pages, 36682 KiB  
Article
Ultrafast Deep-Ultraviolet Laser-Induced Voltage Response of Pyrite
by Xuecong Liu, Yudong Li, Haoqiang Wu, Yawen Yu, Honglei Zhan, Xinyang Miao and Kun Zhao
Micromachines 2021, 12(12), 1555; https://doi.org/10.3390/mi12121555 - 13 Dec 2021
Cited by 5 | Viewed by 1838
Abstract
Ultrafast, high-sensitivity deep-ultraviolet (UV) photodetectors are crucial for practical applications, including optical communication, ozone layer monitoring, flame detection, etc. However, fast-response UV photodetectors based on traditional materials suffer from issues of expensive production processes. Here, we focused on pyrite with simultaneously cheap production [...] Read more.
Ultrafast, high-sensitivity deep-ultraviolet (UV) photodetectors are crucial for practical applications, including optical communication, ozone layer monitoring, flame detection, etc. However, fast-response UV photodetectors based on traditional materials suffer from issues of expensive production processes. Here, we focused on pyrite with simultaneously cheap production processes and ultrafast response speed. Nanoseconds photovoltaic response was observed under UV pulsed laser irradiation without an applied bias at room temperature. In addition, the response time of the laser-induced voltage (LIV) signals was ~20 ns, which was the same as the UV laser pulse width. The maximum value of the responsivity is 0.52 V/mJ and the minimum value of detectivity was about to ~1.4 × 1013 Jones. When there exists nonuniform illumination, a process of diffusion occurs by which the carriers migrate from the region of high concentration toward the region of low concentration. The response speed is limited by a factor of the diffusion of the carriers. With an increment in laser energy, the response speed of LIV is greatly improved. The high response speed combined with low-cost fabrication makes these UV photodetectors highly attractive for applications in ultrafast detection. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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15 pages, 2521 KiB  
Article
New Submicron Low Gate Leakage In0.52Al0.48As-In0.7Ga0.3As pHEMT for Low-Noise Applications
by Mohamed Fauzi Packeer Mohamed, Mohamad Faiz Mohamed Omar, Muhammad Firdaus Akbar Jalaludin Khan, Nor Azlin Ghazali, Mohd Hendra Hairi, Shaili Falina and Mohd Syamsul Nasyriq Samsol Baharin
Micromachines 2021, 12(12), 1497; https://doi.org/10.3390/mi12121497 - 30 Nov 2021
Cited by 1 | Viewed by 2124
Abstract
Conventional pseudomorphic high electron mobility transistor (pHEMTs) with lattice-matched InGaAs/InAlAs/InP structures exhibit high mobility and saturation velocity and are hence attractive for the fabrication of three-terminal low-noise and high-frequency devices, which operate at room temperature. The major drawbacks of conventional pHEMT devices are [...] Read more.
Conventional pseudomorphic high electron mobility transistor (pHEMTs) with lattice-matched InGaAs/InAlAs/InP structures exhibit high mobility and saturation velocity and are hence attractive for the fabrication of three-terminal low-noise and high-frequency devices, which operate at room temperature. The major drawbacks of conventional pHEMT devices are the very low breakdown voltage (<2 V) and the very high gate leakage current (∼1 mA/mm), which degrade device and performance especially in monolithic microwave integrated circuits low-noise amplifiers (MMIC LNAs). These drawbacks are caused by the impact ionization in the low band gap, i.e., the InxGa(1−x)As (x = 0.53 or 0.7) channel material plus the contribution of other parts of the epitaxial structure. The capability to achieve higher frequency operation is also hindered in conventional InGaAs/InAlAs/InP pHEMTs, due to the standard 1 μm flat gate length technology used. A key challenge in solving these issues is the optimization of the InGaAs/InAlAs epilayer structure through band gap engineering. A related challenge is the fabrication of submicron gate length devices using I-line optical lithography, which is more cost-effective, compared to the use of e-Beam lithography. The main goal for this research involves a radical departure from the conventional InGaAs/InAlAs/InP pHEMT structures by designing new and advanced epilayer structures, which significantly improves the performance of conventional low-noise pHEMT devices and at the same time preserves the radio frequency (RF) characteristics. The optimization of the submicron T-gate length process is performed by introducing a new technique to further scale down the bottom gate opening. The outstanding achievements of the new design approach are 90% less gate current leakage and 70% improvement in breakdown voltage, compared with the conventional design. Furthermore, the submicron T-gate length process also shows an increase of about 58% and 33% in fT and fmax, respectively, compared to the conventional 1 μm gate length process. Consequently, the remarkable performance of this new design structure, together with a submicron gate length facilitatesthe implementation of excellent low-noise applications. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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21 pages, 52334 KiB  
Article
Design of Planar Array Transducers Based on Connected 1–3 Piezoelectric Composites
by Jiacheng Wang, Chao Zhong, Shaohua Hao, Ning Lv and Likun Wang
Micromachines 2021, 12(11), 1417; https://doi.org/10.3390/mi12111417 - 18 Nov 2021
Cited by 2 | Viewed by 2518
Abstract
To improve the transmission performance and preparation of a transducer array, two planar array transducers based on connected 1–3 piezoelectric composites as a matrix were designed. Each transducer contained 25 array elements with a gap of 1 mm between them. The length, width [...] Read more.
To improve the transmission performance and preparation of a transducer array, two planar array transducers based on connected 1–3 piezoelectric composites as a matrix were designed. Each transducer contained 25 array elements with a gap of 1 mm between them. The length, width and height of each array element were 1 mm, 26 mm and 5 mm, respectively. Two kinds of array transducers were tested through finite element simulation and experiments. The array transducer prototype was fabricated based on two kinds of composite materials, and the fabrication cycle was short. Our results show that the maximum transmission voltage response of the two-phase 1–3 full array driver is up to 179 dB at 200–400 kHz and the acoustic radiation intensity can be increased by up to 22% compared with the traditional splicing transducer array. It is suitable for short-range target positioning and measurement. Moreover, in the single element mode, the beam of the three-phase 1–3 transducer has no sidelobe and a single element −3 dB beam width of up to 91°. Furthermore, the beam width of the two-phase 1–3 type is 54°, and the acoustic radiation breadth is improved by 40.6%. The three-phase 1–3 type array transducer has the characteristics of concentrated acoustic transmission energy of the whole array, and its −3 dB beam width is 3.5°. The beam width decreased by 12.5%, indicating that the three-phase 1–3 type transducer is suitable for short-range target detection and perception. The two array transducers have their own advantages in transmitting the voltage response and beam width, which must be selected on the basis of the requirements of practical applications. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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13 pages, 2838 KiB  
Article
Polycarbonate Masters for Soft Lithography
by Filippo Amadeo, Prithviraj Mukherjee, Hua Gao, Jian Zhou and Ian Papautsky
Micromachines 2021, 12(11), 1392; https://doi.org/10.3390/mi12111392 - 13 Nov 2021
Cited by 4 | Viewed by 3009
Abstract
Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to its simplicity and low cost. The approach relies on casting of elastomers, such as polydimethylsiloxane (PDMS), on masters fabricated from photoresists on silicon substrates. These masters, however, [...] Read more.
Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to its simplicity and low cost. The approach relies on casting of elastomers, such as polydimethylsiloxane (PDMS), on masters fabricated from photoresists on silicon substrates. These masters, however, can be expensive, complicated to fabricate, and fragile. Here we describe an optimized replica molding approach to preserve the original masters by heat molding of polycarbonate (PC) sheets on PDMS molds. The process is faster and simpler than previously reported methods and does not result in a loss of resolution or aspect ratio for the features. The generated PC masters were used to successfully replicate a wide range of microfluidic devices, including rectangular channels with aspect ratios from 0.025 to 7.3, large area spiral channels, and micropost arrays with 5 µm spacing. Moreover, fabrication of rounded features, such as semi-spherical microwells, was possible and easy. Quantitative analysis of the replicated features showed variability of <2%. The approach is low cost, does not require cleanroom setting or hazardous chemicals, and is rapid and simple. The fabricated masters are rigid and survive numerous replication cycles. Moreover, damaged or missing masters can be easily replaced by reproduction from previously cast PDMS replicas. All of these advantages make the PC masters highly desirable for long-term preservation of soft lithography masters for microfluidic devices. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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13 pages, 3121 KiB  
Article
Suspended Silicon Waveguide with Sub-Wavelength Grating Cladding for Optical MEMS in Mid-Infrared
by Qifeng Qiao, Haoyang Sun, Xinmiao Liu, Bowei Dong, Ji Xia, Chengkuo Lee and Guangya Zhou
Micromachines 2021, 12(11), 1311; https://doi.org/10.3390/mi12111311 - 26 Oct 2021
Cited by 9 | Viewed by 3121
Abstract
Mid-infrared (MIR) photonics are generating considerable interest because of the potential applications in spectroscopic sensing, thermal imaging, and remote sensing. Silicon photonics is believed to be a promising solution to realize MIR photonic integrated circuits (PICs). The past decade has seen a huge [...] Read more.
Mid-infrared (MIR) photonics are generating considerable interest because of the potential applications in spectroscopic sensing, thermal imaging, and remote sensing. Silicon photonics is believed to be a promising solution to realize MIR photonic integrated circuits (PICs). The past decade has seen a huge growth in MIR PIC building blocks. However, there is still a need for the development of MIR reconfigurable photonics to enable powerful on-chip optical systems and new functionalities. In this paper, we present an MIR (3.7~4.1 μm wavelength range) MEMS reconfiguration approach using the suspended silicon waveguide platform on the silicon-on-insulator. With the sub-wavelength grating claddings, the photonic waveguide can be well integrated with the MEMS actuator, thus offering low-loss, energy-efficient, and effective reconfiguration. We present a simulation study on the waveguide design and depict the MEMS-integration approach. Moreover, we experimentally report the suspended waveguide with propagation loss (−2.9 dB/cm) and bending loss (−0.076 dB each). The suspended waveguide coupler is experimentally investigated. In addition, we validate the proposed optical MEMS approach using a reconfigurable ring resonator design. In conclusion, we experimentally demonstrate the proposed waveguide platform’s capability for MIR MEMS-reconfigurable photonics, which empowers the MIR on-chip optical systems for various applications. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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19 pages, 8151 KiB  
Article
Experimental Optimization of Process Parameters in CuNi18Zn20 Micromachining
by Andrea Abeni, Alessandro Metelli, Cristian Cappellini and Aldo Attanasio
Micromachines 2021, 12(11), 1293; https://doi.org/10.3390/mi12111293 - 21 Oct 2021
Cited by 7 | Viewed by 1698
Abstract
Ultraprecision micromachining is a technology suitable to fabricate miniaturized and complicated 3-dimensional microstructures and micromechanisms. High geometrical precision and elevated surface finishing are both key requirements in several manufacturing sectors. Electronics, biomedicals, optics and watchmaking industries are some of the fields where micromachining [...] Read more.
Ultraprecision micromachining is a technology suitable to fabricate miniaturized and complicated 3-dimensional microstructures and micromechanisms. High geometrical precision and elevated surface finishing are both key requirements in several manufacturing sectors. Electronics, biomedicals, optics and watchmaking industries are some of the fields where micromachining finds applications. In the last years, the integration between product functions, the miniaturization of the features and the increasing of geometrical complexity are trends which are shared by all the cited industrial sectors. These tendencies implicate higher requirements and stricter geometrical and dimensional tolerances in machining. From this perspective, the optimization of the micromachining process parameters assumes a crucial role in order to increase the efficiency and effectiveness of the process. An interesting example is offered by the high-end horology field. The optimization of micro machining is indispensable to achieve excellent surface finishing combined with high precision. The cost-saving objective can be pursued by limiting manual post-finishing and by complying the very strict quality standards directly in micromachining. A micro-machining optimization technique is presented in this a paper. The procedure was applied to manufacturing of main-plates and bridges of a wristwatch movement. Cutting speed, feed rate and depth of cut were varied in an experimental factorial plan in order to investigate their correlation with some fundamental properties of the machined features. The dimensions, the geometry and the surface finishing of holes, pins and pockets were evaluated as results of the micromachining optimization. The identified correlations allow to manufacture a wristwatch movement in conformity with the required technical characteristics and by considering the cost and time constraints. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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18 pages, 2233 KiB  
Article
Improved Biomedical Properties of Polydopamine-Coated Carbon Nanotubes
by Sahin Demirci, Mehtap Sahiner, Selin Sagbas Suner and Nurettin Sahiner
Micromachines 2021, 12(11), 1280; https://doi.org/10.3390/mi12111280 - 20 Oct 2021
Cited by 10 | Viewed by 2446
Abstract
Carbon nanotubes (CNTs) due to their outstanding mechanical, thermal, chemical, and optical properties were utilized as a base material and were coated with polydopamine (PDA) (PDA@CNT) via the simple self-polymerization of dopamine (DA). Then, PDA@CNT coatings of up to five layers were examined [...] Read more.
Carbon nanotubes (CNTs) due to their outstanding mechanical, thermal, chemical, and optical properties were utilized as a base material and were coated with polydopamine (PDA) (PDA@CNT) via the simple self-polymerization of dopamine (DA). Then, PDA@CNT coatings of up to five layers were examined for potential biomedical applications. The success of multiple coating of CNTs with PDA was confirmed via increased weight loss values with the increased number of PDA coatings of CNTs at 500 °C by thermogravimetric analysis. The surface area of bare CNTs was measured as 263.9 m2/g and decreased to 197.0 m2/g after a 5th coating with PDA. Furthermore, the antioxidant activities of CNT and PDA@CNTs were determined via total flavonoid content (TFC), total phenol content (TPC), and Fe(III)-reducing antioxidant power (FRAP) tests, revealing the increased antioxidant ability of PDA@CNTs with the increasing numbers of PDA coatings. Moreover, a higher inhibition percentage of the activity of the alpha-glucosidase enzyme with 95.1 ± 2.9% inhibition at 6 mg/mL PDA-1st@CNTs concentration was found. The CNT and PDA@CNTs exhibited blood compatibility, less than a 2.5% hemolysis ratio, and more than 85% blood clotting indexes. The minimum inhibition concentration (MIC) of PDA-5th@CNTs against E. coli and S. aureus bacteria was determined as 10 mg/mL. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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11 pages, 4573 KiB  
Article
Synthesis of Single-Crystal Graphene on Copper Foils Using a Low-Nucleation-Density Region in a Quartz Boat
by Kaiqiang Yang, Jianlong Liu, Ruirui Jiang, Yubin Gong, Baoqing Zeng, Zichuan Yi, Qingguo Gao, Jianjun Yang, Feng Chi and Liming Liu
Micromachines 2021, 12(10), 1236; https://doi.org/10.3390/mi12101236 - 12 Oct 2021
Cited by 2 | Viewed by 1963
Abstract
The nucleation of graphene at different locations in the quartz boat was studied, and the lowest nucleation density of graphene in the quartz boat was found. The nucleation density of graphene is the lowest at the bottom of the quartz boat near the [...] Read more.
The nucleation of graphene at different locations in the quartz boat was studied, and the lowest nucleation density of graphene in the quartz boat was found. The nucleation density of graphene is the lowest at the bottom of the quartz boat near the gas inlet side. Based on the above results, a simple and reproducible way is proposed to significantly suppress the nucleation density of graphene on the copper foil during the chemical vapor deposition process. Placing the copper foil with an area of 1.3 cm × 1 cm in the middle of the bottom of the quartz boat or further back, and placing two copper pockets in front of the copper foil, an ultra-low nucleation density of ~42 nucleus/cm2 was achieved on the back of the copper foil. Single-crystal monolayer graphene with a lateral size of 800 μm can be grown on the back of copper foils after 60 min of growth. Raman spectroscopy revealed the single-crystal graphene to be in uniform monolayers with a low D-band intensity. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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25 pages, 76358 KiB  
Article
Design and Experimental Investigations of Shape and Attitude Carding System for the Wires of Micro Coreless Motor Winding
by Yuezong Wang, Liuqian Wang and Jiqiang Chen
Micromachines 2021, 12(10), 1140; https://doi.org/10.3390/mi12101140 - 23 Sep 2021
Viewed by 1981
Abstract
The shape and attitude (S&A) of the electrode wire are important characteristics of micro coreless motor winding. The purpose of this paper is to present the design of a robotic micro-manipulation system for micro wire carding with arbitrary S&A, which can be used [...] Read more.
The shape and attitude (S&A) of the electrode wire are important characteristics of micro coreless motor winding. The purpose of this paper is to present the design of a robotic micro-manipulation system for micro wire carding with arbitrary S&A, which can be used as the pretreatment system for wire micro-gripper systems. The system is based on the principle of flexible carding, and uses nylon, bristle, nanometer-silk and wool as materials for the brushing micro-manipulator. The trajectory of the brushing micro-manipulator is designed, and the S&A of the electrode wires are straightened through the combined motion mode of horizontal and vertical brushing micro-manipulators. The experimental results show that the material of the brushing micro-manipulator has a great impact on the carding quality. Nanometer-silk material is more suitable for horizontal brushing micro-manipulators, and wool material is more suitable for vertical brushing micro-manipulators. The geometric dimension of the brushing micro-manipulator also affects the carding quality. When the diameter is in the range of 1 mm, the carding effect of the horizontal brushing micro-manipulator with a length of 4.9–8 mm is better. The system can realize the automatic carding of flexible electrode wires with arbitrary S&A, and it will not damage the structure of wires in the process. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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13 pages, 6564 KiB  
Article
Investigation on Bidirectional Pulse Electrochemical Micromachining of Micro Dimples
by Zhouzhi Gu, Xiaolei Chen, Zhongzheng Xu, Zhisen Ye and Guojun Li
Micromachines 2021, 12(9), 1108; https://doi.org/10.3390/mi12091108 - 15 Sep 2021
Cited by 2 | Viewed by 1676
Abstract
Through-mask electrochemical micromachining (TMEMM) is a promising method to prepare micro dimples on the surface of metallic parts. However, the workpiece is machined one by one in traditional TMEMM. This paper introduced bidirectional pulse to TMEMM to improve the machining efficiency. Two masked [...] Read more.
Through-mask electrochemical micromachining (TMEMM) is a promising method to prepare micro dimples on the surface of metallic parts. However, the workpiece is machined one by one in traditional TMEMM. This paper introduced bidirectional pulse to TMEMM to improve the machining efficiency. Two masked workpieces were placed face to face, and connected to the ends of the bidirectional pulse power supply. Along with the change of the pulse direction, the polarities of the two workpieces were interchanged periodically, and micro dimples could be prepared on both workpieces at one time. The simulation and experiment results indicated that with bidirectional pulse mode, micro dimples with same the profile can be prepared on two workpieces at one time, and the dimension of micro dimple was smaller than that with unidirectional pulse mode. In bidirectional pulse current, the pulse frequency and pulse duty cycle played an important role on the preparation of micro dimple. With high pulse frequency and low pulse duty cycle, it is useful to reduce the undercut of micro dimple and improve the machining localization. With the pulse duty cycle of 20% and pulse frequency of 10 kHz, micro dimples with etch factor (EF) of 3 were well prepared on both workpieces surface. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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23 pages, 3269 KiB  
Article
Light Scattering Calculations for Spherical Metallic Nanoparticles (Ag, Au) Coated by TCO (AZO, ITO, PEDOT:PSS) Shell
by Francesco Ruffino
Micromachines 2021, 12(9), 1050; https://doi.org/10.3390/mi12091050 - 30 Aug 2021
Cited by 1 | Viewed by 2077
Abstract
Ag and Au nanostructures became increasingly interesting due to their localized surface plasmon resonance properties. These properties can be successfully exploited in order to enhance the light trapping in solar cell devices by appropriate light scattering phenomena. In solar cell applications, the Ag [...] Read more.
Ag and Au nanostructures became increasingly interesting due to their localized surface plasmon resonance properties. These properties can be successfully exploited in order to enhance the light trapping in solar cell devices by appropriate light scattering phenomena. In solar cell applications, the Ag or Au nanoparticles are, usually, supported on or embedded in a thin transparent conductive oxide layer, mainly AZO and ITO for inorganic solar cells and PEDOT:PSS for organic solar cells. However, the light scattering properties strongly depend on the shape and size of the metal nanostructures and on the optical properties of the surrounding environment. Therefore, the systems need to be well designed to maximize scattering and minimize the light absorption within the metal nanoparticles. In this regard, this work reports, in particular, results concerning calculations, by using the Mie theory, of the angle-dependent light scattering intensity (I(θ)) for spherical Ag and Au nanoparticles coated by a shell of AZO or ITO or PEDOT:PSS. I(θ) and scattering efficiency Qscatt for the spherical core–shell nanoparticles are calculated by changing the radius R of the spherical core (Ag or Au) and the thickness d of the shell (AZO, ITO, or PEDOT:PSS). For each combination of core–shell system, the evolution of I(θ) and Qscatt with the core and shell sizes is drawn and comparisons between the various types of systems is drawn at parity of core and shell sizes. For simplicity, the analysis is limited to spherical core–shell nanoparticles so as to use the Mie theory and to perform analytically exact calculations. However, the results of the present work, even if simplified, can help in establishing the general effect of the core and shell sizes on the light scattering properties of the core–shell nanoparticles, essential to prepare the nanoparticles with desired structure appropriate to the application. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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10 pages, 3244 KiB  
Article
Effect of Sputtering Oxygen Partial Pressure on the Praseodymium-Doped InZnO Thin Film Transistor Using Microwave Photoconductivity Decay Method
by Huansong Tang, Kuankuan Lu, Zhuohui Xu, Honglong Ning, Dengming Yao, Xiao Fu, Huiyun Yang, Dongxiang Luo, Rihui Yao and Junbiao Peng
Micromachines 2021, 12(9), 1044; https://doi.org/10.3390/mi12091044 - 29 Aug 2021
Cited by 2 | Viewed by 2083
Abstract
The praseodymium-doped indium-zinc-oxide (PrIZO) thin film transistor (TFT) shows broad application prospects in the new generation of display technologies due to its high performance and high stability. However, traditional device performance evaluation methods need to be carried out after the end of the [...] Read more.
The praseodymium-doped indium-zinc-oxide (PrIZO) thin film transistor (TFT) shows broad application prospects in the new generation of display technologies due to its high performance and high stability. However, traditional device performance evaluation methods need to be carried out after the end of the entire preparation process, which leads to the high-performance device preparation process that takes a lot of time and costs. Therefore, there is a lack of effective methods to optimize the device preparation process. In this paper, the effect of sputtering oxygen partial pressure on the properties of PrIZO thin film was studied, and the quality of PrIZO thin film was quickly evaluated by the microwave photoconductivity decay (µ-PCD) method. The μ-PCD results show that as the oxygen partial pressure increases, the peak first increases and then decreases, while the D value shows the opposite trend. The quality of PrIZO thin film prepared under 10% oxygen partial pressure is optimal due to its low localized defect states. The electric performance of PrIZO TFTs prepared under different oxygen partial pressures is consistent with the μ-PCD results. The optimal PrIZO TFT prepared under 10% oxygen partial pressure exhibits good electric performance with a threshold voltage (Vth) of 1.9 V, a mobility (µsat) of 24.4 cm2·V−1·s−1, an Ion/Ioff ratio of 2.03 × 107, and a subthreshold swing (SS) of 0.14 V·dec−1. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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12 pages, 2657 KiB  
Article
High-Precision Fabrication of Micro Monolithic Tungsten Ball Tips via Arc Discharge and the Taguchi Method
by Zhen-Ying Cheng, Pan Yao, Yong-Jun Wang, Chen Chen, Li-Juan Chen, Rui-Jun Li and Qiang-Xian Huang
Micromachines 2021, 12(9), 1042; https://doi.org/10.3390/mi12091042 - 29 Aug 2021
Cited by 3 | Viewed by 1521
Abstract
A micro ball tip is a core component of high precision coordinate measuring machines. The present micro ball tips cannot satisfy the high-precision measuring requirements of high aspect ratio microstructures due to their large diameter and low accuracy. In the previous study, we [...] Read more.
A micro ball tip is a core component of high precision coordinate measuring machines. The present micro ball tips cannot satisfy the high-precision measuring requirements of high aspect ratio microstructures due to their large diameter and low accuracy. In the previous study, we fabricated a micro monolithic tungsten ball tip by using arc discharge and surface tension principles. However, the fabrication success rate of forming a micro ball tip is less than 10%. In the present study, the Taguchi method has been applied to increase the fabrication success rate, and it has increased to 57.5%. The output response is evaluated in terms of the diameter, roundness, and center offset of the tungsten probe ball tips. The smaller-the-better signal-to-noise ratio is applied to analyze the influence of various parameters. The proposed parameters can be used to increase the fabrication success rate and accuracy of the monolithic probe ball tip. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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17 pages, 3445 KiB  
Article
Optimisation of Lapping Process Parameters for Single-Crystal 4H–SiC Using Orthogonal Experiments and Grey Relational Analysis
by Jiayun Deng, Qiusheng Yan, Jiabin Lu, Qiang Xiong and Jisheng Pan
Micromachines 2021, 12(8), 910; https://doi.org/10.3390/mi12080910 - 30 Jul 2021
Cited by 10 | Viewed by 2859
Abstract
Lapping is one of the standard essential methods to realise the global planarization of SiC and other semiconductor substrates. It is necessary to deeply study the mechanism to obtain SiC lapping process parameters with a strong comprehensive lapping performance (i.e., high material removal [...] Read more.
Lapping is one of the standard essential methods to realise the global planarization of SiC and other semiconductor substrates. It is necessary to deeply study the mechanism to obtain SiC lapping process parameters with a strong comprehensive lapping performance (i.e., high material removal rate (MRRm), small surface roughness (Ra), and low total thickness variation (TTV)). The effects of the lapping process parameters and their interactions on lapping performance for SiC were investigated using orthogonal experiments; the effects on the MRRm, Ra, TTV, and optimal parameters under the conditions of a single evaluation index were investigated using intuitive analysis (range analysis, variance analysis, and effect curve analysis). The entropy value method and grey relational analysis were used to transform the multi-evaluation-index optimisation into a single-index optimisation about the grey relational grade (GRG) and to comprehensively evaluate the lapping performance of each process parameter. The results showed that the lapping plate types, abrasive size, and their interaction effect had the most significant effects on MRRm and Ra, with a contribution of over 85%. The interaction between the lapping plate types and abrasive size was also found to have the most significant effect on TTV, with a contribution of up to 51.07%. As the lapping plate’s hardness and abrasive size increased, the MRRm and Ra also gradually increased. As the lapping normal-pressure increased, MRRm increased, Ra gradually decreased, and TTV first decreased and then increased. MRRm, Ra, and TTV first increased and then decreased with increasing abrasive concentration. Compared to the optimisation results obtained by intuitive analysis, the process parameter optimised by the grey relational analysis resulted in a smooth surface with an MRRm of 90.2 μm/h, an Ra of 0.769 nm, and a TTV of 3 μm, with a significant improvement in the comprehensive lapping performance. This study reveals that a combination of orthogonal experiments and grey relational analysis can provide new ideas for optimising the process parameters of SiC. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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14 pages, 4518 KiB  
Article
Design Approach for Reducing Cross-Axis Sensitivity in a Single-Drive Multi-Axis MEMS Gyroscope
by Hussamud Din, Faisal Iqbal and Byeungleul Lee
Micromachines 2021, 12(8), 902; https://doi.org/10.3390/mi12080902 - 29 Jul 2021
Cited by 4 | Viewed by 2973
Abstract
In this paper, a new design technique is presented to estimate and reduce the cross-axis sensitivity (CAS) in a single-drive multi-axis microelectromechanical systems (MEMS) gyroscope. A simplified single-drive multi-axis MEMS gyroscope, based on a mode-split approach, was analyzed for cross-axis sensitivity using COMSOL [...] Read more.
In this paper, a new design technique is presented to estimate and reduce the cross-axis sensitivity (CAS) in a single-drive multi-axis microelectromechanical systems (MEMS) gyroscope. A simplified single-drive multi-axis MEMS gyroscope, based on a mode-split approach, was analyzed for cross-axis sensitivity using COMSOL Multiphysics. A design technique named the “ratio-matching method” of drive displacement amplitudes and sense frequency differences ratios was proposed to reduce the cross-axis sensitivity. Initially, the cross-axis sensitivities in the designed gyroscope for x and y-axis were calculated to be 0.482% and 0.120%, respectively, having an average CAS of 0.301%. Using the proposed ratio-matching method and design technique, the individual cross-axis sensitivities in the designed gyroscope for x and y-axis were reduced to 0.018% and 0.073%, respectively. While the average CAS was reduced to 0.045%, showing a reduction rate of 85.1%. Moreover, the proposed ratio-matching method for cross-axis sensitivity reduction was successfully validated through simulations by varying the coupling spring position and sense frequency difference variation analyses. Furthermore, the proposed methodology was verified experimentally using fabricated single-drive multi-axis gyroscope. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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11 pages, 1112 KiB  
Article
Design and Adoption of Low-Cost Point-of-Care Diagnostic Devices: Syrian Case
by M. Munzer Alseed, Hamzah Syed, Mehmet Cengiz Onbasli, Ali K. Yetisen and Savas Tasoglu
Micromachines 2021, 12(8), 882; https://doi.org/10.3390/mi12080882 - 27 Jul 2021
Cited by 1 | Viewed by 2689
Abstract
Civil wars produce immense humanitarian crises, causing millions of individuals to seek refuge in other countries. The rate of disease prevalence has inclined among the refugees, increasing the cost of healthcare. Complex medical conditions and high numbers of patients at healthcare centers overwhelm [...] Read more.
Civil wars produce immense humanitarian crises, causing millions of individuals to seek refuge in other countries. The rate of disease prevalence has inclined among the refugees, increasing the cost of healthcare. Complex medical conditions and high numbers of patients at healthcare centers overwhelm the healthcare system and delay diagnosis and treatment. Point-of-care (PoC) testing can provide efficient solutions to high equipment cost, late diagnosis, and low accessibility of healthcare services. However, the development of PoC devices in developing countries is challenged by several barriers. Such PoC devices may not be adopted due to prejudices about new technologies and the need for special training to use some of these devices. Here, we investigated the concerns of end users regarding PoC devices by surveying healthcare workers and doctors. The tendency to adopt PoC device changes is based on demographic factors such as work sector, education, and technology experience. The most apparent concern about PoC devices was issues regarding low accuracy, according to the surveyed clinicians. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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20 pages, 5253 KiB  
Article
Morphological and Compositional Studies on Al/Ti/TiN/Si, Al/TiN/Si, Al/W/Si, Al/WN/Si Systems to Test the Diffusion Barrier Properties of Nanoscale-Thick Layers between Al and Si
by Maria Censabella, Cristina Drago, Brunella Cafra, Paolo Badalà, Anna Bassi, Giovanni Piccitto, Salvatore Mirabella, Maria Grazia Grimaldi and Francesco Ruffino
Micromachines 2021, 12(8), 849; https://doi.org/10.3390/mi12080849 - 21 Jul 2021
Cited by 3 | Viewed by 2116
Abstract
In this work, an investigation of the properties of nanoscale-thick Ti/TiN, TiN, W, WN layers as diffusion barriers between Si and Al is carried out in view of Si-based electronic applications. Heat treatments were performed on the samples to activate interdiffusion between Si [...] Read more.
In this work, an investigation of the properties of nanoscale-thick Ti/TiN, TiN, W, WN layers as diffusion barriers between Si and Al is carried out in view of Si-based electronic applications. Heat treatments were performed on the samples to activate interdiffusion between Si and Al. Changing annealing time and temperature, each sample was morphologically characterized by scanning electron microscopy and atomic force microscopy and compositionally characterized by Rutherford backscattering analysis. The aim is to evaluate the efficiency of the layers as diffusion barriers between Si and Al and, at the same time, to evaluate the surface morphological changes upon annealing processes. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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13 pages, 2464 KiB  
Article
Power Dissipation of an Inductively Coupled Plasma Torch under E Mode Dominated Regime
by Nan Yu, Renaud Jourdain, Mustapha Gourma, Fangda Xu, Adam Bennett and Fengzhou Fang
Micromachines 2021, 12(7), 834; https://doi.org/10.3390/mi12070834 - 18 Jul 2021
Cited by 8 | Viewed by 4519
Abstract
This paper focuses on the power dissipation of a plasma torch used for an optical surface fabrication process. The process utilizes an inductively coupled plasma (ICP) torch that is equipped with a De-Laval nozzle for the delivery of a highly collimated plasma jet. [...] Read more.
This paper focuses on the power dissipation of a plasma torch used for an optical surface fabrication process. The process utilizes an inductively coupled plasma (ICP) torch that is equipped with a De-Laval nozzle for the delivery of a highly collimated plasma jet. The plasma torch makes use of a self-igniting coil and an intermediate co-axial tube made of alumina. The torch has a distinctive thermal and electrical response compared to regular ICP torches. In this study, the results of the power dissipation investigation reveal the true efficiency of the torch and discern its electrical response. By systematically measuring the coolant parameters (temperature change and flow rate), the power dissipation is extrapolated. The radio frequency power supply is set to 800 W, E mode, throughout the research presented in this study. The analytical results of power dissipation, derived from the experiments, show that 15.4% and 33.3% are dissipated by the nozzle and coil coolant channels, respectively. The experiments also enable the determination of the thermal time constant of the plasma torch for the entire range of RF power. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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12 pages, 3804 KiB  
Article
Development of a 3-DOF Flexible Micro-Motion Platform Based on a New Compound Lever Amplification Mechanism
by Fangni Cui, Yangmin Li and Junnan Qian
Micromachines 2021, 12(6), 686; https://doi.org/10.3390/mi12060686 - 11 Jun 2021
Cited by 9 | Viewed by 2774
Abstract
In this paper, a flexible micro-operation platform with three degrees of freedom, large stroke, and high precision is designed to meet the higher demands in the fields of biological engineering and medicine. The platform adopts a compound lever mechanism. The theoretical magnification of [...] Read more.
In this paper, a flexible micro-operation platform with three degrees of freedom, large stroke, and high precision is designed to meet the higher demands in the fields of biological engineering and medicine. The platform adopts a compound lever mechanism. The theoretical magnification of the mechanism is 9.627, the simulation magnification is 10.111, and the error is 5.02%. The platform uses a piezoelectric ceramic driver to increase the output stroke to obtain a larger movement space. The composite lever mechanism and new micro-operating platform are studied by theoretical calculation and finite element simulation. The results show that the new flexible micro-operating platform based on the composite lever mechanism has good motion decoupling and high precision. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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10 pages, 4008 KiB  
Article
High-Consistency Optical Fiber Fabry–Perot Pressure Sensor Based on Silicon MEMS Technology for High Temperature Environment
by Fei Feng, Pinggang Jia, Jiang Qian, Zhengpeng Hu, Guowen An and Li Qin
Micromachines 2021, 12(6), 623; https://doi.org/10.3390/mi12060623 - 28 May 2021
Cited by 10 | Viewed by 3531
Abstract
This paper proposes a high-temperature optical fiber Fabry–Perot pressure sensor based on the micro-electro-mechanical system (MEMS). The sensing structure of the sensor is composed of Pyrex glass wafer and silicon wafer manufactured by mass micromachining through anodic bonding process. The separated sensing head [...] Read more.
This paper proposes a high-temperature optical fiber Fabry–Perot pressure sensor based on the micro-electro-mechanical system (MEMS). The sensing structure of the sensor is composed of Pyrex glass wafer and silicon wafer manufactured by mass micromachining through anodic bonding process. The separated sensing head and the gold-plated fiber are welded together by a carbon dioxide laser to form a fiber-optic Fabry–Perot high temperature pressure sensor, which uses a four-layer bonding technology to improve the sealing performance of the Fabry–Perot cavity. The test system of high temperature pressure sensor is set up, and the experimental data obtained are calculated and analyzed. The experimental results showed that the maximum linearity of the optical fiber pressure sensor was 1% in the temperature range of 20–400 °C. The pressure sensor exhibited a high linear sensitivity of about 1.38 nm/KPa at room temperature at a range of pressures from approximarely 0-to 1 MPa. The structure of the sensor is characterized by high consistency, which makes the structure more compact and the manufacturing process more controllable. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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10 pages, 2528 KiB  
Article
A Study of Nanosilver Colloid Prepared by Electrical Spark Discharge Method and Its Antifungal Control Benefits
by Kuo-Hsiung Tseng, Meng-Yun Chung, Juei-Long Chiu, Chao-Heng Tseng and Chao-Yun Liu
Micromachines 2021, 12(5), 503; https://doi.org/10.3390/mi12050503 - 30 Apr 2021
Cited by 1 | Viewed by 1600
Abstract
This is a study of an antimicrobial test, including yeast, Aspergillus Niger, and Aspergillus Flavus, on a nanosilver colloid solution. The antibiosis is compared with a standard silver ion solution at the same concentration as in the experimental process. This study [...] Read more.
This is a study of an antimicrobial test, including yeast, Aspergillus Niger, and Aspergillus Flavus, on a nanosilver colloid solution. The antibiosis is compared with a standard silver ion solution at the same concentration as in the experimental process. This study proved that the nanosilver colloid prepared by the electrical spark discharge method (ESDM) is free of any chemical additives, has a microbial control effect, and that the effect is much better than the Ag+ standard solution at the same concentration. 3M Count Plate (YM) is used to test and observe the colony counts. The microbial control test for yeast, Aspergillus Niger, and Aspergillus Flavus is implemented in the nanosilver colloid. In addition to Aspergillus flavus, an Ag+ concentration of 16 ppm is enough to inhibit the growth of the samples. At the same concentration, the nanosilver colloid has a much better microbial control effect than the Ag+ standard solution, which may be because the nanoparticle can release Ag+ continuously, so the solution using the ESDM has a more significant microbial control effect. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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Review

Jump to: Research

29 pages, 12493 KiB  
Review
Graphene as a Piezoresistive Material in Strain Sensing Applications
by Farid Sayar Irani, Ali Hosseinpour Shafaghi, Melih Can Tasdelen, Tugce Delipinar, Ceyda Elcin Kaya, Guney Guven Yapici and Murat Kaya Yapici
Micromachines 2022, 13(1), 119; https://doi.org/10.3390/mi13010119 - 12 Jan 2022
Cited by 27 | Viewed by 5777
Abstract
High accuracy measurement of mechanical strain is critical and broadly practiced in several application areas including structural health monitoring, industrial process control, manufacturing, avionics and the automotive industry, to name a few. Strain sensors, otherwise known as strain gauges, are fueled by various [...] Read more.
High accuracy measurement of mechanical strain is critical and broadly practiced in several application areas including structural health monitoring, industrial process control, manufacturing, avionics and the automotive industry, to name a few. Strain sensors, otherwise known as strain gauges, are fueled by various nanomaterials, among which graphene has attracted great interest in recent years, due to its unique electro-mechanical characteristics. Graphene shows not only exceptional physical properties but also has remarkable mechanical properties, such as piezoresistivity, which makes it a perfect candidate for strain sensing applications. In the present review, we provide an in-depth overview of the latest studies focusing on graphene and its strain sensing mechanism along with various applications. We start by providing a description of the fundamental properties, synthesis techniques and characterization methods of graphene, and then build forward to the discussion of numerous types of graphene-based strain sensors with side-by-side tabular comparison in terms of figures-of-merit, including strain range and sensitivity, otherwise referred to as the gauge factor. We demonstrate the material synthesis, device fabrication and integration challenges for researchers to achieve both wide strain range and high sensitivity in graphene-based strain sensors. Last of all, several applications of graphene-based strain sensors for different purposes are described. All in all, the evolutionary process of graphene-based strain sensors in recent years, as well as the upcoming challenges and future directions for emerging studies are highlighted. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Materials and Processing 2021)
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