Micromachines

10 pages, 2171 KiB

Open AccessArticle

A MEMS-Based Co-Oscillating Electrochemical Vector Hydrophone

by Anxiang Zhong, Mingwei Chen, Yulan Lu, Jian Chen, Deyong Chen and Junbo Wang

Micromachines 2022, 13(1), 143; https://doi.org/10.3390/mi13010143 - 17 Jan 2022

Cited by 1 | Viewed by 2435

Aiming at the development needs of low-frequency and high-sensitivity vector hydrophones, this paper has developed a micro-electro-mechanical system (MEMS) based co-oscillating electrochemical vector hydrophone. We obtained the optimized geometric parameters through simulation analysis of the diameter of the rubber membrane, the length of [...] Read more.

Aiming at the development needs of low-frequency and high-sensitivity vector hydrophones, this paper has developed a micro-electro-mechanical system (MEMS) based co-oscillating electrochemical vector hydrophone. We obtained the optimized geometric parameters through simulation analysis of the diameter of the rubber membrane, the length of the flow channel and the diameter of the flow holes. Based on the simulation results, electrodes were fabricated using MEMS technology, and were then assembled and tested. Device characterization was conducted, where the sensitivity and bandwidth were quantified as 0.5–150 Hz, −187 dB ref. 1 V/μPa, respectively. Compared with a previously reported co-oscillating vector hydrophone, the co-oscillating vector hydrophone developed in this article featured a lower working frequency band. Full article

(This article belongs to the Section C：Chemistry)

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11 pages, 3803 KiB

Open AccessArticle

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 9 | Viewed by 2538

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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12 pages, 2819 KiB

Open AccessArticle

Designing Sensitivity: A Comparative Analysis of Microelectrode Topologies for Electrochemical Oxygen Sensing in Biomedical Applications

by Daniel T. Bacheschi, Evan Z. Strittmatter, Sonya Sawtelle and Mohsen Nami

Micromachines 2022, 13(1), 141; https://doi.org/10.3390/mi13010141 - 17 Jan 2022

Cited by 3 | Viewed by 2425

Abstract

The monitoring of dissolved oxygen is a key parameter in many fields, namely the treatment and monitoring of various cerebral traumas. Leveraging existing manufacturing techniques, electrochemical sensors hold the potential for compact, simple, and scalable dissolved oxygen sensors. Past studies have focused on [...] Read more.

The monitoring of dissolved oxygen is a key parameter in many fields, namely the treatment and monitoring of various cerebral traumas. Leveraging existing manufacturing techniques, electrochemical sensors hold the potential for compact, simple, and scalable dissolved oxygen sensors. Past studies have focused on the general design of such sensors, but a comparative study on the impact of microelectrode geometries for cerebral applications has been forthcoming. We present here the results of a characterization study conducted across solid-state sensors with varying microelectrode geometries. The electrode structures were covered with a Nafion membrane and included variations of the classic interdigitated microelectrode array in addition to a circular microelectrode array variation. Voltage sweeps were conducted while monitoring the devices’ sensing current responses across a 50.3 mmHg change in dissolved oxygen within a deionized aqueous solution. Half of the devices were identified as ultramicroelectrode designs that presented a greater dependence on electrode spacing and topology. The ultramicroelectrode-style (UME) interdigitated electrode (IDE) topology presented the greatest signal response at 25.24 nA/mmHg, an approximate eight-fold improvement in sensitivity from a non-UME variation with a sensitivity of 2.98 nA/mmHg. The design presented a linear response from 8.3 mmHg to 58.6 mmHg with r² = 0.9743. The sensitivity improvement was attributed to the ultramicroelectrode structure’s amplifying diffusive feedback, which was enabled by the IDE topology and short electrode spacings. Full article

(This article belongs to the Special Issue Sensors for Brain Analytics)

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16 pages, 3723 KiB

Open AccessReview

A Review on Manufacturing and Post-Processing Technology of Vascular Stents

by Wei Jiang, Wenxiang Zhao, Tianfeng Zhou, Liang Wang and Tianyang Qiu

Micromachines 2022, 13(1), 140; https://doi.org/10.3390/mi13010140 - 16 Jan 2022

Cited by 28 | Viewed by 7635

Abstract

Percutaneous coronary intervention (PCI) with stent implantation is one of the most effective treatments for cardiovascular diseases (CVDs). However, there are still many complications after stent implantation. As a medical device with a complex structure and small size, the manufacture and post-processing technology [...] Read more.

Percutaneous coronary intervention (PCI) with stent implantation is one of the most effective treatments for cardiovascular diseases (CVDs). However, there are still many complications after stent implantation. As a medical device with a complex structure and small size, the manufacture and post-processing technology greatly impact the mechanical and medical performances of stents. In this paper, the development history, material, manufacturing method, and post-processing technology of vascular stents are introduced. In particular, this paper focuses on the existing manufacturing technology and post-processing technology of vascular stents and the impact of these technologies on stent performance is described and discussed. Moreover, the future development of vascular stent manufacturing technology will be prospected and proposed. Full article

(This article belongs to the Special Issue Advanced Biofabrication Technologies)

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18 pages, 2085 KiB

Open AccessReview

Microfluidic Approaches and Methods Enabling Extracellular Vesicle Isolation for Cancer Diagnostics

by Premanshu Kumar Singh, Aarti Patel, Anastasia Kaffenes, Catherine Hord, Delaney Kesterson and Shaurya Prakash

Micromachines 2022, 13(1), 139; https://doi.org/10.3390/mi13010139 - 16 Jan 2022

Cited by 12 | Viewed by 4063

Abstract

Advances in cancer research over the past half-century have clearly determined the molecular origins of the disease. Central to the use of molecular signatures for continued progress, including rapid, reliable, and early diagnosis is the use of biomarkers. Specifically, extracellular vesicles as biomarker [...] Read more.

Advances in cancer research over the past half-century have clearly determined the molecular origins of the disease. Central to the use of molecular signatures for continued progress, including rapid, reliable, and early diagnosis is the use of biomarkers. Specifically, extracellular vesicles as biomarker cargo holders have generated significant interest. However, the isolation, purification, and subsequent analysis of these extracellular vesicles remain a challenge. Technological advances driven by microfluidics-enabled devices have made the challenges for isolation of extracellular vesicles an emerging area of research with significant possibilities for use in clinical settings enabling point-of-care diagnostics for cancer. In this article, we present a tutorial review of the existing microfluidic technologies for cancer diagnostics with a focus on extracellular vesicle isolation methods. Full article

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

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3 pages, 145 KiB

Open AccessEditorial

Editorial for the Special Issue on Advanced Energy Conversion and Storage Microdevices

by Hee-Seok Kim

Micromachines 2022, 13(1), 138; https://doi.org/10.3390/mi13010138 - 16 Jan 2022

Viewed by 1436

Abstract

Advanced energy conversion and storage systems have attracted much attention in recent decades due to the increasing demand for energy and the environmental impacts of non-sustainable energy resources [...] Full article

(This article belongs to the Special Issue Advanced Energy Conversion and Storage Microdevices)

16 pages, 7459 KiB

Open AccessArticle

Quality Prediction and Control in Wire Arc Additive Manufacturing via Novel Machine Learning Framework

by Xinyi Xiao, Clarke Waddell, Carter Hamilton and Hanbin Xiao

Micromachines 2022, 13(1), 137; https://doi.org/10.3390/mi13010137 - 15 Jan 2022

Cited by 54 | Viewed by 4631

Abstract

Wire arc additive manufacturing (WAAM) is capable of rapidly depositing metal materials thus facilitating the fabrication of large-shape metal components. However, due to the multi-process-variability in the WAAM process, the deposited shape (bead width, height, depth of penetration) is difficult to predict and [...] Read more.

Wire arc additive manufacturing (WAAM) is capable of rapidly depositing metal materials thus facilitating the fabrication of large-shape metal components. However, due to the multi-process-variability in the WAAM process, the deposited shape (bead width, height, depth of penetration) is difficult to predict and control within the desired level. Ultimately, the overall build will not achieve a near-net shape and will further hinder the part from performing its functionality without post-processing. Previous research primarily utilizes data analytical models (e.g., regression model, artificial neural network (ANN)) to forwardly predict the deposition width and height variation based on single or cross-linked process variables. However, these methods cannot effectively determine the optimal printable zone based on the desired deposition shape due to the inability to inversely deduce from these data analytical models. Additionally, the process variables are intercorrelated, and the bead width, height, and depth of penetration are highly codependent. Therefore, existing analysis cannot grant a reliable prediction model that allows the deposition (bead width, height, and penetration height) to remain within the desired level. This paper presents a novel machine learning framework for quantitatively analyzing the correlated relationship between the process parameters and deposition shape, thus providing an optimal process parameter selection to control the final deposition geometry. The proposed machine learning framework can systematically and quantitatively predict the deposition shape rather than just qualitatively as with other existing machine learning methods. The prediction model can also present the complex process-quality relations, and the determination of the deposition quality can guide the WAAM to be more prognostic and reliable. The correctness and effectiveness of the proposed quantitative process-quality analysis will be validated through experiments. Full article

(This article belongs to the Special Issue Intelligent Additive/Subtractive Manufacturing)

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11 pages, 7404 KiB

Open AccessArticle

Minimized Triple-Band Eight-Element Antenna Array for 5G Metal-frame Smartphone Applications

by Jianlin Huang, Zhuoni Chen, Qibo Cai, Tian Hong Loh and Gui Liu

Micromachines 2022, 13(1), 136; https://doi.org/10.3390/mi13010136 - 15 Jan 2022

Cited by 12 | Viewed by 2115

Abstract

A multiple-input-multiple-output (MIMO) antenna array for triple-band 5G metal-frame smartphone applications is proposed in this paper. Each single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The dimension of the antenna element is only [...] Read more.

A multiple-input-multiple-output (MIMO) antenna array for triple-band 5G metal-frame smartphone applications is proposed in this paper. Each single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The dimension of the antenna element is only 6.5 mm × 7 mm (0.076 λ₀ × 0.082 λ₀, λ₀ is the free-space wavelength at the frequency of 3.5 GHz). The −6 dB impedance bandwidth of the proposed eight-antenna array can cover 3.3–3.8 GHz, 4.8–5 GHz, and 5.15–5.925 GHz. The evolution design and the analysis of the optimal parameters for a single antenna element are derived to investigate the principle of the antenna. The measured total efficiency is larger than 70%. The measured isolation is better than 13 dB. The measurements of the prototype agree well with the simulation results. Full article

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11 pages, 3976 KiB

Open AccessArticle

A Novel Bidirectional AlGaN/GaN ESD Protection Diode

by Bin Yao, Yijun Shi, Hongyue Wang, Xinbin Xu, Yiqiang Chen, Zhiyuan He, Qingzhong Xiao, Lei Wang, Guoguang Lu, Hao Li, Yun Huang and Bo Zhang

Micromachines 2022, 13(1), 135; https://doi.org/10.3390/mi13010135 - 15 Jan 2022

Cited by 6 | Viewed by 3066

Abstract

Despite the superior working properties, GaN-based HEMTs and systems are still confronted with the threat of a transient ESD event, especially for the vulnerable gate structure of the p-GaN or MOS HEMTs. Therefore, there is still an urgent need for a bidirectional ESD [...] Read more.

Despite the superior working properties, GaN-based HEMTs and systems are still confronted with the threat of a transient ESD event, especially for the vulnerable gate structure of the p-GaN or MOS HEMTs. Therefore, there is still an urgent need for a bidirectional ESD protection diode to improve the ESD robustness of a GaN power system. In this study, an AlGaN/GaN ESD protection diode with bidirectional clamp capability was proposed and investigated. Through the combination of two floating gate electrodes and two pF-grade capacitors connected in parallel between anode or cathode electrodes and the adjacent floating gate electrodes (C_GA (C_GC)), the proposed diode could be triggered by a required voltage and possesses a high secondary breakdown current (I_S) in both forward and reverse transient ESD events. Based on the experimental verification, it was found that the bidirectional triggering voltages (V_trig) and I_S of the proposed diode were strongly related to C_GA (C_GC). With C_GA (C_GC) increasing from 5 pF to 25 pF, V_trig and I_S decreased from ~18 V to ~7 V and from ~7 A to ~3 A, respectively. The diode’s high performance demonstrated a good reference for the ESD design of a GaN power system. Full article

(This article belongs to the Special Issue GaN-Based Semiconductor Devices)

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9 pages, 1263 KiB

Open AccessArticle

Thermodynamic Modeling of Solvent-Assisted Lipid Bilayer Formation Process

by Hongmei Xu, Hyunhyuk Tae, Nam-Joon Cho, Changjin Huang and K. Jimmy Hsia

Micromachines 2022, 13(1), 134; https://doi.org/10.3390/mi13010134 - 15 Jan 2022

Cited by 6 | Viewed by 2536

Abstract

The solvent-assisted lipid bilayer (SALB) formation method provides a simple and efficient, microfluidic-based strategy to fabricate supported lipid bilayers (SLBs) with rich compositional diversity on a wide range of solid supports. While various studies have been performed to characterize SLBs formed using the [...] Read more.

The solvent-assisted lipid bilayer (SALB) formation method provides a simple and efficient, microfluidic-based strategy to fabricate supported lipid bilayers (SLBs) with rich compositional diversity on a wide range of solid supports. While various studies have been performed to characterize SLBs formed using the SALB method, relatively limited work has been carried out to understand the underlying mechanisms of SALB formation under various experimental conditions. Through thermodynamic modeling, we studied the experimental parameters that affect the SALB formation process, including substrate surface properties, initial lipid concentration, and temperature. It was found that all the parameters are critically important to successfully form high-quality SLBs. The model also helps to identify the range of parameter space within which conformal, homogeneous SLBs can be fabricated, and provides mechanistic guidance to optimize experimental conditions for lipid membrane-related applications. Full article

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

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11 pages, 2525 KiB

Open AccessArticle

An Analytical Energy Harvester Model for Interdigitated Ring Electrode on Circular Elastic Membrane

by Hua-Ju Shih and Kuo-Ching Chen

Micromachines 2022, 13(1), 133; https://doi.org/10.3390/mi13010133 - 15 Jan 2022

Viewed by 1917

Abstract

Energy harvesters are devices that accumulate ambient vibrational energy from the environment, and for the time being, variable capacitance is the most widely used mechanism. Various designs were proposed to increase the power of such devices, and in particular, the interdigitated electrode (IDE) [...] Read more.

Energy harvesters are devices that accumulate ambient vibrational energy from the environment, and for the time being, variable capacitance is the most widely used mechanism. Various designs were proposed to increase the power of such devices, and in particular, the interdigitated electrode (IDE) pattern is the mainstream. Nevertheless, most IDE designs focus merely on the parallel-type vibrations of electrodes. In this study, the performance of a novel harvester, which combined circular membrane and interdigitated ring electrodes (IRE), was investigated. This design allows the device to collect energy from the rotational structure motions of electrodes through the vibrating membrane. Besides, the circular structure provides a dense capacitive arrangement that is higher than that of the arrangement obtained using regular rectangular chips. The IRE diagram is composed of many capacitive rings, each of which harvests vibrated energy simultaneously. Three gaps (1, 10, and 100 μm) of the ring are investigated for the first four vibrational modes of the membrane to understand the effect of energy output. It is found that the energy outputs are approximately the same for the three gaps; however, rings with a wider gap are easier to manufacture in MEMS. Full article

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17 pages, 6054 KiB

Open AccessArticle

Evaluation and Optimization of a Cross-Rib Micro-Channel Heat Sink

by Haiying Chen, Chuan Chen, Yunyan Zhou, Chenglin Yang, Gang Song, Fengze Hou, Binbin Jiao and Ruiwen Liu

Micromachines 2022, 13(1), 132; https://doi.org/10.3390/mi13010132 - 14 Jan 2022

Cited by 10 | Viewed by 3221

Abstract

This article presents a novel cross-rib micro-channel (MC-CR) heat sink to make fluid self-rotate. For a thermal test chip (TTC) with 100 w/cm², the cross-ribs micro-channel were compared with the rectangular (MC-R) and horizontal rib micro-channel (MC-HR) heat sinks. The results [...] Read more.

This article presents a novel cross-rib micro-channel (MC-CR) heat sink to make fluid self-rotate. For a thermal test chip (TTC) with 100 w/cm², the cross-ribs micro-channel were compared with the rectangular (MC-R) and horizontal rib micro-channel (MC-HR) heat sinks. The results show that, with the cross-rib micro-channel, the junction temperature of the thermal test chip was 336.49 K, and the pressure drop was 22 kPa. Compared with the rectangular and horizontal ribs heat sink, the cross-rib micro-channel had improvements of 28.6% and 14.3% in cooling capability, but the pressure drop increased by 10.7-fold and 5.5-fold, respectively. Then, the effects of the aspect ratio (λ) of micro-channel in different flow rates were studied. It was found that the aspect ratio and cooling performance were non-linear. To reduce the pressure drop, the inclination (α) and spacing (S) of the cross-ribs were optimized. When α = 30°, S = 0.1 mm, and λ = 4, the pressure drop was reduced from 22 kPa to 4.5 kPa. In addition, the heat dissipation performance of the rectangular, staggered fin (MC-SF), staggered rib (MC-SR) and cross-rib micro-channels were analyzed in the condition of the same pressure drop, MC-CR still has superior heat dissipation performance. Full article

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16 pages, 4031 KiB

Open AccessFeature PaperArticle

Perfusion System for Modification of Luminal Contents of Human Intestinal Organoids and Realtime Imaging Analysis of Microbial Populations

by Nicholas J. Ginga, Raleigh Slyman, Ge-Ah Kim, Eric Parigoris, Sha Huang, Veda K. Yadagiri, Vincent B. Young, Jason R. Spence and Shuichi Takayama

Micromachines 2022, 13(1), 131; https://doi.org/10.3390/mi13010131 - 14 Jan 2022

Cited by 8 | Viewed by 3576

Abstract

Intestinal organoids are 3D cell structures that replicate some aspects of organ function and are organized with a polarized epithelium facing a central lumen. To enable more applications, new technologies are needed to access the luminal cavity and apical cell surface of organoids. [...] Read more.

Intestinal organoids are 3D cell structures that replicate some aspects of organ function and are organized with a polarized epithelium facing a central lumen. To enable more applications, new technologies are needed to access the luminal cavity and apical cell surface of organoids. We developed a perfusion system utilizing a double-barrel glass capillary with a pressure-based pump to access and modify the luminal contents of a human intestinal organoid for extended periods of time while applying cyclic cellular strain. Cyclic injection and withdrawal of fluorescent FITC-Dextran coupled with real-time measurement of fluorescence intensity showed discrete changes of intensity correlating with perfusion cycles. The perfusion system was also used to modify the lumen of organoids injected with GFP-expressing E. coli. Due to the low concentration and fluorescence of the E. coli, a novel imaging analysis method utilizing bacteria enumeration and image flattening was developed to monitor E. coli within the organoid. Collectively, this work shows that a double-barrel perfusion system provides constant luminal access and allows regulation of luminal contents and luminal mixing. Full article

(This article belongs to the Special Issue Microengineered Physiological Systems for Disease Modeling and Drug Testing)

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20 pages, 11405 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Dynamic Modeling and Experimental Validation of a Water Hydraulic Soft Manipulator Based on an Improved Newton—Euler Iterative Method

by Yinglong Chen, Qiang Sun, Qiang Guo and Yongjun Gong

Micromachines 2022, 13(1), 130; https://doi.org/10.3390/mi13010130 - 14 Jan 2022

Cited by 16 | Viewed by 5913

Abstract

Compared with rigid robots, soft robots have better adaptability to the environment because of their pliability. However, due to the lower structural stiffness of the soft manipulator, the posture of the manipulator is usually decided by the weight and the external load under [...] Read more.

Compared with rigid robots, soft robots have better adaptability to the environment because of their pliability. However, due to the lower structural stiffness of the soft manipulator, the posture of the manipulator is usually decided by the weight and the external load under operating conditions. Therefore, it is necessary to conduct dynamics modeling and movement analysis of the soft manipulator. In this paper, a fabric reinforced soft manipulator driven by a water hydraulic system is firstly proposed, and the dynamics of both the soft manipulator and hydraulic system are considered. Specifically, a dynamic model of the soft manipulator is established based on an improved Newton–Euler iterative method, which comprehensively considers the influence of inertial force, elastic force, damping force, as well as combined bending and torsion moments. The dynamics of the water hydraulic system consider the effects of cylinder inertia, friction, and water response. Finally, the accuracy of the proposed dynamic model is verified by comparing the simulation results with the experimental data about the steady and dynamic characteristics of the soft manipulator under various conditions. The results show that the maximum sectional error is about 0.0245 m and that the maximum cumulative error is 0.042 m, which validate the effectiveness of the proposed model. Full article

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

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9 pages, 2327 KiB

Open AccessArticle

Improvement of Crystal Quality of AlN Films with Different Polarities by Annealing at High Temperature

by Yang Yue, Maosong Sun, Jie Chen, Xuejun Yan, Zhuokun He, Jicai Zhang and Wenhong Sun

Micromachines 2022, 13(1), 129; https://doi.org/10.3390/mi13010129 - 14 Jan 2022

Cited by 11 | Viewed by 2431

Abstract

High-quality AlN film is a key factor affecting the performance of deep-ultraviolet optoelectronic devices. In this work, high-temperature annealing technology in a nitrogen atmosphere was used to improve the quality of AlN films with different polarities grown by magnetron sputtering. After annealing at [...] Read more.

High-quality AlN film is a key factor affecting the performance of deep-ultraviolet optoelectronic devices. In this work, high-temperature annealing technology in a nitrogen atmosphere was used to improve the quality of AlN films with different polarities grown by magnetron sputtering. After annealing at 1400–1650 °C, the crystal quality of the AlN films was improved. However, there was a gap between the quality of non-polar and polar films. In addition, compared with the semi-polar film, the quality of the non-polar film was more easily improved by annealing. The anisotropy of both the semi-polar and non-polar films decreased with increasing annealing temperature. The results of Raman spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the annihilation of impurities and grain boundaries during the annealing process were responsible for the improvement of crystal quality and the differences between the films with different polarities. Full article

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

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14 pages, 4197 KiB

Open AccessArticle

Preparation of Fe₃O₄@PDA@Au@GO Composite as SERS Substrate and Its Application in the Enrichment and Detection for Phenanthrene

by Junyu Liu, Yiwei Liu, Yida Cao, Shihua Sang, Liang Guan, Yinyin Wang and Jian Wang

Micromachines 2022, 13(1), 128; https://doi.org/10.3390/mi13010128 - 14 Jan 2022

Cited by 8 | Viewed by 2777

Abstract

In this study, highly active Fe₃O₄@PDA@Au@GO surface-enhanced Raman spectroscopy (SERS) active substrate was synthesized for application in the enrichment and detection of trace polycyclic aromatic hydrocarbons (PAHs) in the environment. The morphology and structure were characterized by transmission electron [...] Read more.

In this study, highly active Fe₃O₄@PDA@Au@GO surface-enhanced Raman spectroscopy (SERS) active substrate was synthesized for application in the enrichment and detection of trace polycyclic aromatic hydrocarbons (PAHs) in the environment. The morphology and structure were characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and UV–visible absorption spectrum (UV–vis spectra). The effect of each component of Fe₃O₄@PDA@Au@GO nanocomposites on SERS was explored, and it was found that gold nanoparticles (Au NPs) are crucial to enhance the Raman signal based on the electromagnetic enhancement mechanism, and apart from enriching the PAHs through π–π interaction, graphene oxide (GO) also generates strong chemical enhancement of Raman signals, and polydopamine (PDA) can prevent Au from shedding and agglomeration. The existence of Fe3O4 aided the quick separation of substrate from the solutions, which greatly simplified the detection procedure and facilitated the reuse of the substrate. The SERS active substrate was used to detect phenanthrene in aqueous solution with a detection limit of 10⁻⁷ g/L (5.6 × 10⁻¹⁰ mol/L), which is much lower than that of ordinary Raman, it is promising for application in the enrichment and detection of trace PAHs. Full article

(This article belongs to the Special Issue Directed Self-Assembly of Micro- and Nanoparticles)

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17 pages, 7103 KiB

Open AccessArticle

Estimation of Position and Size of a Contaminant in Aluminum Casting Using a Thin-Film Magnetic Sensor

by Tomoo Nakai

Micromachines 2022, 13(1), 127; https://doi.org/10.3390/mi13010127 - 14 Jan 2022

Cited by 5 | Viewed by 1645

Abstract

Advanced manufacturing processes require an in-line full inspection system. A nondestructive inspection system able to detect a contaminant such as tool chipping was utilized for the purpose of detecting a defective product as well as damaged machine tools used to fabricate the product. [...] Read more.

Advanced manufacturing processes require an in-line full inspection system. A nondestructive inspection system able to detect a contaminant such as tool chipping was utilized for the purpose of detecting a defective product as well as damaged machine tools used to fabricate the product. In a previous study, a system able to detect magnetic tool steel chipping in conductive material such as aluminum was developed and tested. In this study, a method of position and size estimation for magnetic chipping was investigated and is described. An experimental confirmation of the proposed method was also carried out using an actual prototype system. Full article

(This article belongs to the Special Issue Selected Papers from the 12th Symposium on Micro-Nano Science and Technology on Micromachines)

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13 pages, 1605 KiB

Open AccessArticle

A Novel Distribution for Representation of 6D Pose Uncertainty

by Lei Zhang, Huiliang Shang and Yandan Lin

Micromachines 2022, 13(1), 126; https://doi.org/10.3390/mi13010126 - 13 Jan 2022

Cited by 12 | Viewed by 2639

Abstract

The 6D Pose estimation is a crux in many applications, such as visual perception, autonomous navigation, and spacecraft motion. For robotic grasping, the cluttered and self-occlusion scenarios bring new challenges to the this field. Currently, society uses CNNs to solve this problem. The [...] Read more.

The 6D Pose estimation is a crux in many applications, such as visual perception, autonomous navigation, and spacecraft motion. For robotic grasping, the cluttered and self-occlusion scenarios bring new challenges to the this field. Currently, society uses CNNs to solve this problem. The CNN models will suffer high uncertainty caused by the environmental factors and the object itself. These models usually maintain a Gaussian distribution, which is not suitable for the underlying manifold structure of the pose. Many works decouple rotation from the translation and quantify rotational uncertainty. Only a few works pay attention to the uncertainty of the 6D pose. This work proposes a distribution that can capture the uncertainty of the 6D pose parameterized by the dual quaternions, meanwhile, the proposed distribution takes the periodic nature of the underlying structure into account. The presented results include the normalization constant computation and parameter estimation techniques of the distribution. This work shows the benefits of the proposed distribution, which provides a more realistic explanation for the uncertainty in the 6D pose and eliminates the drawback inherited from the planar rigid motion. Full article

(This article belongs to the Special Issue Soft Robotics: Challenges and Perspectives)

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11 pages, 26608 KiB

Open AccessArticle

Pressure-Responsive Conductive Poly(vinyl alcohol) Composites Containing Waste Cotton Fibers Biochar

by Mattia Bartoli, Daniele Torsello, Erik Piatti, Mauro Giorcelli, Amelia Carolina Sparavigna, Massimo Rovere, Gianluca Ghigo and Alberto Tagliaferro

Micromachines 2022, 13(1), 125; https://doi.org/10.3390/mi13010125 - 13 Jan 2022

Cited by 17 | Viewed by 2234

Abstract

The development of responsive composite materials is among the most interesting challenges in contemporary material science and technology. Nevertheless, the use of highly expensive nanostructured fillers has slowed down the spread of these smart materials in several key productive sectors. Here, we propose [...] Read more.

The development of responsive composite materials is among the most interesting challenges in contemporary material science and technology. Nevertheless, the use of highly expensive nanostructured fillers has slowed down the spread of these smart materials in several key productive sectors. Here, we propose a new piezoresistive PVA composite containing a cheap, conductive, waste-derived, cotton biochar. We evaluated the electromagnetic properties of the composites under both AC and DC regimes and as a function of applied pressure, showing promisingly high conductivity values by using over 20 wt.% filler loading. We also measured the conductivity of the waste cotton biochar from 20 K up to 350 K observing, for the first time, hopping charge transport in biochar materials. Full article

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8 pages, 3669 KiB

Open AccessArticle

Power Reduction in Punch-Through Current-Based Electro-Thermal Annealing in Gate-All-Around FETs

by Min-Kyeong Kim, Yang-Kyu Choi and Jun-Young Park

Micromachines 2022, 13(1), 124; https://doi.org/10.3390/mi13010124 - 13 Jan 2022

Cited by 4 | Viewed by 1945

Abstract

Device guidelines for reducing power with punch-through current annealing in gate-all-around (GAA) FETs were investigated based on three-dimensional (3D) simulations. We studied and compared how different geometric dimensions and materials of GAA FETs impact heat management when down-scaling. In order to maximize power [...] Read more.

Device guidelines for reducing power with punch-through current annealing in gate-all-around (GAA) FETs were investigated based on three-dimensional (3D) simulations. We studied and compared how different geometric dimensions and materials of GAA FETs impact heat management when down-scaling. In order to maximize power efficiency during electro-thermal annealing (ETA), applying gate module engineering was more suitable than engineering the isolation or source drain modules. Full article

(This article belongs to the Special Issue Recent Advances in Thin Film Electronic Devices)

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14 pages, 63197 KiB

Open AccessArticle

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 2095

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, 3100 KiB

Open AccessArticle

A Novel Dye-Sensitized Solar Cell Structure Based on Metal Photoanode without FTO/ITO

by Jianjun Yang, Xiaobao Yu, Yaxin Li, Guilin Cheng, Zichuan Yi, Zhi Zhang, Feng Chi and Liming Liu

Micromachines 2022, 13(1), 122; https://doi.org/10.3390/mi13010122 - 13 Jan 2022

Cited by 8 | Viewed by 2381

Abstract

Traditional dye-sensitized solar cells (DSSC) use FTO/ITO containing expensive rare elements as electrodes, which are difficult to meet the requirements of flexibility. A new type of flexible DSSC structure with all-metal electrodes without rare elements is proposed in this paper. Firstly, a light-receiving [...] Read more.

Traditional dye-sensitized solar cells (DSSC) use FTO/ITO containing expensive rare elements as electrodes, which are difficult to meet the requirements of flexibility. A new type of flexible DSSC structure with all-metal electrodes without rare elements is proposed in this paper. Firstly, a light-receiving layer was prepared outside the metal photoanode with small holes to realize the continuous oxidation-reduction reaction in the electrolyte; Secondly, the processing technology of the porous titanium dioxide (TiO₂) film was analyzed. By testing the J–V characteristics, it was found that the performance is better when the heating rate is slow. Finally, the effects of different electrode material combinations were compared through experiments. Our results imply that in the case of all stainless-steel electrodes, the open-circuit voltage can reach 0.73 V, and in the case of a titanium photoanode, the photoelectric conversion efficiency can reach 3.86%. Full article

(This article belongs to the Special Issue Micro and Smart Devices and Systems)

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12 pages, 8675 KiB

Open AccessArticle

A Circularly Polarized Implantable Rectenna for Microwave Wireless Power Transfer

by Chao Xu, Yi Fan and Xiongying Liu

Micromachines 2022, 13(1), 121; https://doi.org/10.3390/mi13010121 - 12 Jan 2022

Cited by 10 | Viewed by 2328

Abstract

A circularly polarized implantable antenna integrated with a voltage-doubled rectifier (abbr., rectenna) is investigated for microwave wireless power transfer in the industrial, scientific, and medical (ISM) band of 2.4–2.48 GHz. The proposed antenna is miniaturized with the dimensions of 7.5 mm × 7.5 [...] Read more.

A circularly polarized implantable antenna integrated with a voltage-doubled rectifier (abbr., rectenna) is investigated for microwave wireless power transfer in the industrial, scientific, and medical (ISM) band of 2.4–2.48 GHz. The proposed antenna is miniaturized with the dimensions of 7.5 mm × 7.5 mm × 1.27 mm by etching four C-shaped open slots on the patch. A rectangular slot truncated diagonally is cut to improve the circular polarization performance of the antenna. The simulated impedance bandwidth in a three-layer phantom is 30.4% (1.9–2.58 GHz) with |S₁₁| below −10 dB, and the 3-dB axial-ratio bandwidth is 16.9% (2.17–2.57 GHz). Furthermore, a voltage-doubled rectifier circuit that converts RF power to DC power is designed on the back of the antenna. The simulated RF-to-DC conversion efficiency can be up to 45% at the input power of 0 dBm. The proposed rectenna was fabricated and measured in fresh pork to verify the simulated results and evaluate the performance of wireless power transfer. Full article

(This article belongs to the Special Issue Smart Implants)

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9 pages, 1980 KiB

Open AccessArticle

Graphitisation of Waste Carbon Powder with Femtosecond Laser Annealing

by Lucas Lum, Chong-Wei Tan, Chun Fei Siah, Kun Liang and Beng Kang Tay

Micromachines 2022, 13(1), 120; https://doi.org/10.3390/mi13010120 - 12 Jan 2022

Viewed by 1968

Abstract

Graphitisation of structural characteristics and improvement in electrical conductivity was reported onto waste carbon powder through femtosecond laser annealing. Raman spectroscopy on the carbon powder pre- and post-annealing showed a shift from amorphous-like carbon to graphitic-like carbon, which can be explained by the [...] Read more.

Graphitisation of structural characteristics and improvement in electrical conductivity was reported onto waste carbon powder through femtosecond laser annealing. Raman spectroscopy on the carbon powder pre- and post-annealing showed a shift from amorphous-like carbon to graphitic-like carbon, which can be explained by the three-stage model. Electrical I-V probing of the samples revealed an increase in conductivity by up to 90%. An increase in incident laser power was found to be correlated to an increase in conductivity. An average incident laser power of 0.104 W or less showed little to no change in electrical characteristics, while an average incident laser power of greater than 1.626 W had a destructive effect on the carbon powder, shown through the reduction in powder. The most significant improvement in electrical conductivity has been observed at laser powers ranging from 0.526 to 1.286 W. To conclude, the graphitisation of waste carbon powder is possible using post-process femtosecond laser annealing to alter its electrical conductivity for future applications. Full article

(This article belongs to the Special Issue Recent Advances in Nanotechnology and Nanomaterials)

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29 pages, 12493 KiB

Open AccessReview

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 39 | Viewed by 7231

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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14 pages, 4470 KiB

Open AccessArticle

Acoustic Performance Study of Fiber-Optic Acoustic Sensors Based on Fabry–Pérot Etalons with Different Q Factors

by Jiamin Chen, Chenyang Xue, Yongqiu Zheng, Jiandong Bai, Xinyu Zhao, Liyun Wu and Yuan Han

Micromachines 2022, 13(1), 118; https://doi.org/10.3390/mi13010118 - 12 Jan 2022

Cited by 5 | Viewed by 2766

Abstract

The ideal development direction of the fiber-optic acoustic sensor (FOAS) is toward broadband, a high sensitivity and a large dynamic range. In order to further promote the acoustic detection potential of the Fabry–Pérot etalon (FPE)-based FOAS, it is of great significance to study [...] Read more.

The ideal development direction of the fiber-optic acoustic sensor (FOAS) is toward broadband, a high sensitivity and a large dynamic range. In order to further promote the acoustic detection potential of the Fabry–Pérot etalon (FPE)-based FOAS, it is of great significance to study the acoustic performance of the FOAS with the quality (Q) factor of FPE as the research objective. This is because the Q factor represents the storage capability and loss characteristic of the FPE. The three FOASs with different Q factors all achieve a broadband response from 20 Hz to 70 kHz with a flatness of

\pm

2 dB, which is consistent with the theory that the frequency response of the FOAS is not affected by the Q factor. Moreover, the sensitivity of the FOAS is proportional to the Q factor. When the Q factor is

1.04 \times 10^{6}

, the sensitivity of the FOAS is as high as 526.8 mV/Pa. Meanwhile, the minimum detectable sound pressure of

347.33 μ Pa / {Hz}^{1 / 2}

is achieved. Furthermore, with a Q factor of

0.27 \times 10^{6}

, the maximum detectable sound pressure and dynamic range are 152.32 dB and 107.2 dB, respectively, which is greatly improved compared with two other FOASs. Separately, the FOASs with different Q factors exhibit an excellent acoustic performance in weak sound detection and high sound pressure detection. Therefore, different acoustic detection requirements can be met by selecting the appropriate Q factor, which further broadens the application range and detection potential of FOASs. Full article

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13 pages, 5378 KiB

Open AccessArticle

Continuous Particle Separation Driven by 3D Ag-PDMS Electrodes with Dielectric Electrophoretic Force Coupled with Inertia Force

by Xiaohong Li, Junping Duan, Zeng Qu, Jiayun Wang, Miaomiao Ji and Binzhen Zhang

Micromachines 2022, 13(1), 117; https://doi.org/10.3390/mi13010117 - 12 Jan 2022

Cited by 6 | Viewed by 2468

Abstract

Cell separation has become @important in biological and medical applications. Dielectrophoresis (DEP) is widely used due to the advantages it offers, such as the lack of a requirement for biological markers and the fact that it involves no damage to cells or particles. [...] Read more.

Cell separation has become @important in biological and medical applications. Dielectrophoresis (DEP) is widely used due to the advantages it offers, such as the lack of a requirement for biological markers and the fact that it involves no damage to cells or particles. This study aimed to report a novel approach combining 3D sidewall electrodes and contraction/expansion (CEA) structures to separate three kinds of particles with different sizes or dielectric properties continuously. The separation was achieved through the interaction between electrophoretic forces and inertia forces. The CEA channel was capable of sorting particles with different sizes due to inertial forces, and also enhanced the nonuniformity of the electric field. The 3D electrodes generated a non-uniform electric field at the same height as the channels, which increased the action range of the DEP force. Finite element simulations using the commercial software, COMSOL Multiphysics 5.4, were performed to determine the flow field distributions, electric field distributions, and particle trajectories. The separation experiments were assessed by separating 4 µm polystyrene (PS) particles from 20 µm PS particles at different flow rates by experiencing positive and negative DEP. Subsequently, the sorting performances of the 4 µm PS particles, 20 µm PS particles, and 4 µm silica particles with different solution conductivities were observed. Both the numerical simulations and the practical particle separation displayed high separating efficiency (separation of 4 µm PS particles, 94.2%; separation of 20 µm PS particles, 92.1%; separation of 4 µm Silica particles, 95.3%). The proposed approach is expected to open a new approach to cell sorting and separating. Full article

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17 pages, 4794 KiB

Open AccessArticle

An MHD Fluid Flow over a Porous Stretching/Shrinking Sheet with Slips and Mass Transpiration

by A. B. Vishalakshi, U. S. Mahabaleshwar and Ioannis E. Sarris

Micromachines 2022, 13(1), 116; https://doi.org/10.3390/mi13010116 - 12 Jan 2022

Cited by 40 | Viewed by 2580

Abstract

In the present paper, an MHD three-dimensional non-Newtonian fluid flow over a porous stretching/shrinking sheet in the presence of mass transpiration and thermal radiation is examined. This problem mainly focusses on an analytical solution; graphene water is immersed in the flow of a [...] Read more.

In the present paper, an MHD three-dimensional non-Newtonian fluid flow over a porous stretching/shrinking sheet in the presence of mass transpiration and thermal radiation is examined. This problem mainly focusses on an analytical solution; graphene water is immersed in the flow of a fluid to enhance the thermal efficiency. The given non-linear PDEs are mapped into ODEs via suitable transformations, then the solution is obtained in terms of incomplete gamma function. The momentum equation is analyzed, and to derive the mass transpiration analytically, this mass transpiration is used in the heat transfer analysis and to find the analytical results with a Biot number. Physical significance parameters, including volume fraction, skin friction, mass transpiration, and thermal radiation, can be analyzed with the help of graphical representations. We indicate the unique solution at stretching sheet and multiple solution at shrinking sheet. The physical scenario can be understood with the help of different physical parameters, namely a Biot number, magnetic parameter, inverse Darcy number, Prandtl number, and thermal radiation; these physical parameters control the analytical results. Graphene nanoparticles are used to analyze the present study, and the value of the Prandtl number is fixed to 6.2. The graphical representations help to discuss the results of the present work. This problem is used in many industrial applications such as Polymer extrusion, paper production, metal cooling, glass blowing, etc. At the end of this work, we found that the velocity and temperature profile increases with the increasing values of the viscoelastic parameter and solid volume fraction; additionally, efficiency is increased for higher values of thermal radiation. Full article

(This article belongs to the Special Issue Micro/Nanofluids in Magnetic/Electric Fields)

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11 pages, 3961 KiB

Open AccessArticle

A Low Cost Fe₃O₄–Activated Biochar Electrode Sensor by Resource Utilization of Excess Sludge for Detecting Tetrabromobisphenol A

by Suxing Luo, Meizhi Yang, Yuanhui Wu, Jiang Li, Jun Qin and Feng Feng

Micromachines 2022, 13(1), 115; https://doi.org/10.3390/mi13010115 - 11 Jan 2022

Cited by 14 | Viewed by 1972

Abstract

Owing to its ubiquity in natural water systems and the high toxicity of its accumulation in the human body, it is essential to develop simple and low-cost electrochemical sensors for the determination of 3,3′,5,5′-tetrabromobisphenol A (TBBPA). In this work, Fe₃O₄ [...] Read more.

Owing to its ubiquity in natural water systems and the high toxicity of its accumulation in the human body, it is essential to develop simple and low-cost electrochemical sensors for the determination of 3,3′,5,5′-tetrabromobisphenol A (TBBPA). In this work, Fe₃O₄–activated biochar, which is based on excess sludge, was prepared and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and BET analysis to analyze its basic features. Subsequently, it was used to fabricate an electrochemical sensor for the detection of TBBPA. The electrochemical test results revealed that the Fe₃O₄–activated biochar film exhibited a larger active surface area, a lower charge transfer resistance and a higher accumulation efficiency toward TBBPA. Consequently, the peak current of TBBPA was significantly enhanced on the surface of the Fe₃O₄–activated biochar. The TBBPA sensing platform developed using the Fe₃O₄–activated biochar composite film, with relatively a lower detection limit (3.2 nM) and a wider linear range (5–1000 nM), was successfully utilized to determine TBBPA levels in water samples. In summary, the effective application of Fe₃O₄–activated biochar provided eco-friendly and sustainable materials for the development of a desirable high-sensitivity sensor for TBBPA detection. Full article

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26 pages, 11984 KiB

Open AccessReview

A Survey on Analog-to-Digital Converter Integrated Circuits for Miniaturized High Resolution Ultrasonic Imaging System

by Dongdong Chen, Xinhui Cui, Qidong Zhang, Di Li, Wenyang Cheng, Chunlong Fei and Yintang Yang

Micromachines 2022, 13(1), 114; https://doi.org/10.3390/mi13010114 - 11 Jan 2022

Cited by 15 | Viewed by 5003

Abstract

As traditional ultrasonic imaging systems (UIS) are expensive, bulky, and power-consuming, miniaturized and portable UIS have been developed and widely utilized in the biomedical field. The performance of integrated circuits (ICs) in portable UIS obviously affects the effectiveness and quality of ultrasonic imaging. [...] Read more.

As traditional ultrasonic imaging systems (UIS) are expensive, bulky, and power-consuming, miniaturized and portable UIS have been developed and widely utilized in the biomedical field. The performance of integrated circuits (ICs) in portable UIS obviously affects the effectiveness and quality of ultrasonic imaging. In the ICs for UIS, the analog-to-digital converter (ADC) is used to complete the conversion of the analog echo signal received by the analog front end into digital for further processing by a digital signal processing (DSP) or microcontroller unit (MCU). The accuracy and speed of the ADC determine the precision and efficiency of UIS. Therefore, it is necessary to systematically review and summarize the characteristics of different types of ADCs for UIS, which can provide valuable guidance to design and fabricate high-performance ADC for miniaturized high resolution UIS. In this paper, the architecture and performance of ADC for UIS, including successive approximation register (SAR) ADC, sigma-delta (Σ-∆) ADC, pipelined ADC, and hybrid ADC, have been systematically introduced. In addition, comparisons and discussions of different types of ADCs are presented. Finally, this paper is summarized, and presents the challenges and prospects of ADC ICs for miniaturized high resolution UIS. Full article

(This article belongs to the Special Issue Low-Power Circuits for Internet-of-Things)

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