Feature Papers of Micromachines in Engineering and Technology 2021

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E:Engineering and Technology".

Deadline for manuscript submissions: closed (15 December 2021) | Viewed by 33600

Special Issue Editor

Special Issue Information

Dear Colleague,

We are pleased to announce the Special Issue entitled “Feature Papers of Micromachines in Engineering and Technology 2021”. In recent years, we have cooperated with many excellent scholars/scientific groups and published several very important high-level works that have already received numerous citations, according to Web of Science data. We aim to introduce new insights into the scientific developments and cutting-edge technology related to micromachines in the engineering and technology fields, which will make a great contribution to the community.

This Special Issue will be a collection of high-quality papers by outstanding scholars from 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 ([email protected]) before submission. These will undergo a preliminary evaluation by our 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. Stephen Edward Saddow
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

  • Micro/nano fabrication and manufacturing: deposition, lithography, patterning, etching, surface micromachining, bulk micromachining, laser fabrication, biofabrication, 3D printing, self-assembly, etc
  • Design and optimization principles of micro- and nanosystems
  • Micro- nanosystems and advanced technologies for engineering applications: resources engineering, civil engineering, advanced manufacturing engineering, environmental engineering, bioengineering, electronic system (including electrical circuits and devices, transistors, capacitors, inductors, resistors, diodes, insulators and conductors) engineering, etc.

Related Special Issue

Published Papers (10 papers)

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Research

Jump to: Review

12 pages, 2881 KiB  
Article
Three-Dimensional Kidney-on-a-Chip Assessment of Contrast-Induced Kidney Injury: Osmolality and Viscosity
by Kipyo Kim, Beomgyun Jeong, Yun-Mi Lee, Hyung-Eun Son, Ji-Young Ryu, Seokwoo Park, Jong Cheol Jeong, Ho Jun Chin and Sejoong Kim
Micromachines 2022, 13(5), 688; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13050688 - 28 Apr 2022
Cited by 6 | Viewed by 2372
Abstract
Increased viscosity of concentrated contrast media (CM) in the renal tubules can perturb renal hemodynamics and have a detrimental effect on tubular epithelial cells. However, the effects of viscosity on contrast-induced nephropathy (CIN) remain poorly understood. Conventional in vitro culture studies do not [...] Read more.
Increased viscosity of concentrated contrast media (CM) in the renal tubules can perturb renal hemodynamics and have a detrimental effect on tubular epithelial cells. However, the effects of viscosity on contrast-induced nephropathy (CIN) remain poorly understood. Conventional in vitro culture studies do not reflect the rheological properties of CM. Therefore, we investigated the effects of CM viscosity on renal tubules using a kidney-on-a-chip and two different types of CM. Renal proximal tubule epithelial cells (RPTEC) were cultured in a three-dimensional microfluidic culture platform under bidirectional fluid shear stress. We treated the RPTEC with two types of CM: low- (LOCM, iopromide) and iso-osmolar contrast media (IOCM, iodixanol). Renal tubular cell injury induced by LOCM and IOCM was examined under different iodine concentrations (50–250 mgI/mL) and shear-stress conditions. LOCM showed a significant dose-dependent cytotoxic effect, which was significantly higher than that of IOCM under static and low-to-moderate shear stress conditions. However, high shear-stress resulted in reduced cell viability in IOCM; no difference between IOCM and LOCM was found under high shear-stress conditions. The cytotoxic effects were pronounced at a mean shear stress of 1 dyn/cm2 or higher. The high viscosity of IOCM slowed the fluid flow rate and augmented fluid shear-stress. We suggest an alternative in vitro model of CIN using the three-dimensional kidney-on-a-chip. Our results indicate a vital role of viscosity-induced nephrotoxicity under high shear-stress conditions, contrary to the findings of conventional in vitro studies. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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16 pages, 2693 KiB  
Article
Numerical Study on Flow and Heat Transfer Characteristics of Trapezoidal Printed Circuit Heat Exchanger
by Yuxuan Ji, Kaixiang Xing, Kefa Cen, Mingjiang Ni, Haoran Xu and Gang Xiao
Micromachines 2021, 12(12), 1589; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12121589 - 20 Dec 2021
Cited by 6 | Viewed by 2541
Abstract
Printed circuit heat exchanger (PCHE) is a promising regenerative device in the sCO2 power cycle, with the advantages of a large specific surface area and compact structure. Its tiny and complex flow channel structure brings enhanced heat transfer performance, while increasing pressure [...] Read more.
Printed circuit heat exchanger (PCHE) is a promising regenerative device in the sCO2 power cycle, with the advantages of a large specific surface area and compact structure. Its tiny and complex flow channel structure brings enhanced heat transfer performance, while increasing pressure drop losses. It is, thus, important to balance heat transfer and flow resistance performances with the consideration of sCO2 as the working agent. Herein, three-dimensional models are built with a full consideration of fluid flow and heat transfer fields. A trapezoidal channel is developed and its thermal–hydraulic performances are compared with the straight, the S-shape, and the zigzag structures. Nusselt numbers and the Fanning friction factors are analyzed with respect to the changes in Reynolds numbers and structure geometric parameters. A sandwiched structure that couples two hot channels with one cold channel is further designed to match the heat transfer capacity and the velocity of sCO2 flows between different sides. Through this novel design, we can reduce the pressure drop by 75% and increase the regenerative efficiency by 5%. This work can serve as a solid reference for the design and applications of PCHEs. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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13 pages, 2955 KiB  
Article
Mechano-Triboelectric Analysis of Surface Charge Generation on Replica-Molded Elastomeric Nanodomes
by Myung Gi Ji, Mohammed Bazroun, In Ho Cho, W. Dennis Slafer, Rana Biswas and Jaeyoun Kim
Micromachines 2021, 12(12), 1460; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12121460 - 27 Nov 2021
Cited by 3 | Viewed by 1678
Abstract
Replica molding-based triboelectrification has emerged as a new and facile technique to generate nanopatterned tribocharge on elastomer surfaces. The “mechano-triboelectric charging model” has been developed to explain the mechanism of the charge formation and patterning process. However, this model has not been validated [...] Read more.
Replica molding-based triboelectrification has emerged as a new and facile technique to generate nanopatterned tribocharge on elastomer surfaces. The “mechano-triboelectric charging model” has been developed to explain the mechanism of the charge formation and patterning process. However, this model has not been validated to cover the full variety of nanotexture shapes. Moreover, the experimental estimation of the tribocharge’s surface density is still challenging due to the thick and insulating nature of the elastomeric substrate. In this work, we perform experiments in combination with numerical analysis to complete the mechano-triboelectrification charging model. By utilizing Kelvin probe force microscopy (KPFM) and finite element analysis, we reveal that the mechano-triboelectric charging model works for replica molding of both recessed and protruding nanotextures. In addition, by combining KPFM with numerical electrostatic modeling, we improve the accuracy of the surface charge density estimation and cross-calibrate the result against that of electrostatic force microscopy. Overall, the regions which underwent strong interfacial friction during the replica molding exhibited high surface potential and charge density, while those suffering from weak interfacial friction exhibited low values on both. These multi-physical approaches provide useful and important tools for comprehensive analysis of triboelectrification and generation of nanopatterned tribocharge. The results will widen our fundamental understanding of nanoscale triboelectricity and advance the nanopatterned charge generation process for future applications. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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Review

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21 pages, 1683 KiB  
Review
Temperature-to-Digital Converters’ Evolution, Trends and Techniques across the Last Two Decades: A Review
by Antonio Aprile, Edoardo Bonizzoni and Piero Malcovati
Micromachines 2022, 13(11), 2025; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13112025 - 19 Nov 2022
Cited by 5 | Viewed by 2022
Abstract
This paper presents an extensive review of the main highlights in the Temperature-to-Digital Converters (TDCs) field, which has gained importance and research interest throughout the last two decades. The key techniques and approaches that have led to the evolution of this kind of [...] Read more.
This paper presents an extensive review of the main highlights in the Temperature-to-Digital Converters (TDCs) field, which has gained importance and research interest throughout the last two decades. The key techniques and approaches that have led to the evolution of this kind of systems are presented and compared; their peculiarities are identified in order to highlight the pros and cons of the different design methods, and the main trade-offs are extracted from this analysis. Finally, the trends that have emerged from the performance evaluation of the large amount of published works in this field are identified with the purpose of providing a directional view of the past, present and future features of these devices. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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34 pages, 7572 KiB  
Review
Advances in Soft and Dry Electrodes for Wearable Health Monitoring Devices
by Hyeonseok Kim, Eugene Kim, Chanyeong Choi and Woon-Hong Yeo
Micromachines 2022, 13(4), 629; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13040629 - 16 Apr 2022
Cited by 33 | Viewed by 5837
Abstract
Electrophysiology signals are crucial health status indicators as they are related to all human activities. Current demands for mobile healthcare have driven considerable interest in developing skin-mounted electrodes for health monitoring. Silver-Silver chloride-based (Ag-/AgCl) wet electrodes, commonly used in conventional clinical practice, provide [...] Read more.
Electrophysiology signals are crucial health status indicators as they are related to all human activities. Current demands for mobile healthcare have driven considerable interest in developing skin-mounted electrodes for health monitoring. Silver-Silver chloride-based (Ag-/AgCl) wet electrodes, commonly used in conventional clinical practice, provide excellent signal quality, but cannot monitor long-term signals due to gel evaporation and skin irritation. Therefore, the focus has shifted to developing dry electrodes that can operate without gels and extra adhesives. Compared to conventional wet electrodes, dry ones offer various advantages in terms of ease of use, long-term stability, and biocompatibility. This review outlines a systematic summary of the latest research on high-performance soft and dry electrodes. In addition, we summarize recent developments in soft materials, biocompatible materials, manufacturing methods, strategies to promote physical adhesion, methods for higher breathability, and their applications in wearable biomedical devices. Finally, we discuss the developmental challenges and advantages of various dry electrodes, while suggesting research directions for future studies. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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21 pages, 7337 KiB  
Review
Silicon Carbide Technology for Advanced Human Healthcare Applications
by Stephen E. Saddow
Micromachines 2022, 13(3), 346; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13030346 - 22 Feb 2022
Cited by 23 | Viewed by 3759
Abstract
Silicon carbide (SiC) is a highly robust semiconductor material that has the potential to revolutionize implantable medical devices for human healthcare, such as biosensors and neuro-implants, to enable advanced biomedical therapeutic applications for humans. SiC is both bio and hemocompatible, and is already [...] Read more.
Silicon carbide (SiC) is a highly robust semiconductor material that has the potential to revolutionize implantable medical devices for human healthcare, such as biosensors and neuro-implants, to enable advanced biomedical therapeutic applications for humans. SiC is both bio and hemocompatible, and is already commercially used for long-term human in vivo applications ranging from heart stent coatings and dental implants to short-term diagnostic applications involving neural implants and sensors. One challenge facing the medical community today is the lack of biocompatible materials which are inherently smart or, in other words, capable of electronic functionality. Such devices are currently implemented using silicon technology, which either has to be hermetically sealed so it does not directly interact with biological tissue or has a short lifetime due to instabilities in vivo. Long-term, permanently implanted devices such as glucose sensors, neural interfaces, smart bone and organ implants, etc., require a more robust material that does not degrade over time and is not recognized and rejected as a foreign object by the inflammatory response. SiC has displayed these exceptional material properties, which opens up a whole new host of applications and allows for the development of many advanced biomedical devices never before possible for long-term use in vivo. This paper is a review of the state-of-the art and discusses cutting-edge device applications where SiC medical devices are poised to translate to the commercial marketplace. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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42 pages, 3851 KiB  
Review
Application of Microfluidic Systems for Breast Cancer Research
by Zachary D. Frankman, Linan Jiang, Joyce A. Schroeder and Yitshak Zohar
Micromachines 2022, 13(2), 152; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13020152 - 20 Jan 2022
Cited by 6 | Viewed by 4455
Abstract
Cancer is a disease in which cells in the body grow out of control; breast cancer is the most common cancer in women in the United States. Due to early screening and advancements in therapeutic interventions, deaths from breast cancer have declined over [...] Read more.
Cancer is a disease in which cells in the body grow out of control; breast cancer is the most common cancer in women in the United States. Due to early screening and advancements in therapeutic interventions, deaths from breast cancer have declined over time, although breast cancer remains the second leading cause of cancer death among women. Most deaths are due to metastasis, as cancer cells from the primary tumor in the breast form secondary tumors in remote sites in distant organs. Over many years, the basic biological mechanisms of breast cancer initiation and progression, as well as the subsequent metastatic cascade, have been studied using cell cultures and animal models. These models, although extremely useful for delineating cellular mechanisms, are poor predictors of physiological responses, primarily due to lack of proper microenvironments. In the last decade, microfluidics has emerged as a technology that could lead to a paradigm shift in breast cancer research. With the introduction of the organ-on-a-chip concept, microfluidic-based systems have been developed to reconstitute the dominant functions of several organs. These systems enable the construction of 3D cellular co-cultures mimicking in vivo tissue-level microenvironments, including that of breast cancer. Several reviews have been presented focusing on breast cancer formation, growth and metastasis, including invasion, intravasation, and extravasation. In this review, realizing that breast cancer can recur decades following post-treatment disease-free survival, we expand the discussion to account for microfluidic applications in the important areas of breast cancer detection, dormancy, and therapeutic development. It appears that, in the future, the role of microfluidics will only increase in the effort to eradicate breast cancer. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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40 pages, 10660 KiB  
Review
The Rise of the OM-LoC: Opto-Microfluidic Enabled Lab-on-Chip
by Harry Dawson, Jinane Elias, Pascal Etienne and Sylvie Calas-Etienne
Micromachines 2021, 12(12), 1467; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12121467 - 28 Nov 2021
Cited by 8 | Viewed by 2551
Abstract
The integration of optical circuits with microfluidic lab-on-chip (LoC) devices has resulted in a new era of potential in terms of both sample manipulation and detection at the micro-scale. On-chip optical components increase both control and analytical capabilities while reducing reliance on expensive [...] Read more.
The integration of optical circuits with microfluidic lab-on-chip (LoC) devices has resulted in a new era of potential in terms of both sample manipulation and detection at the micro-scale. On-chip optical components increase both control and analytical capabilities while reducing reliance on expensive laboratory photonic equipment that has limited microfluidic development. Notably, in-situ LoC devices for bio-chemical applications such as diagnostics and environmental monitoring could provide great value as low-cost, portable and highly sensitive systems. Multiple challenges remain however due to the complexity involved with combining photonics with micro-fabricated systems. Here, we aim to highlight the progress that optical on-chip systems have made in recent years regarding the main LoC applications: (1) sample manipulation and (2) detection. At the same time, we aim to address the constraints that limit industrial scaling of this technology. Through evaluating various fabrication methods, material choices and novel approaches of optic and fluidic integration, we aim to illustrate how optic-enabled LoC approaches are providing new possibilities for both sample analysis and manipulation. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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27 pages, 4129 KiB  
Review
Gold–Carbon Nanocomposites for Environmental Contaminant Sensing
by Shahrooz Rahmati, William Doherty, Arman Amani Babadi, Muhamad Syamim Akmal Che Mansor, Nurhidayatullaili Muhd Julkapli, Volker Hessel and Kostya (Ken) Ostrikov
Micromachines 2021, 12(6), 719; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12060719 - 19 Jun 2021
Cited by 12 | Viewed by 2735
Abstract
The environmental crisis, due to the rapid growth of the world population and globalisation, is a serious concern of this century. Nanoscience and nanotechnology play an important role in addressing a wide range of environmental issues with innovative and successful solutions. Identification and [...] Read more.
The environmental crisis, due to the rapid growth of the world population and globalisation, is a serious concern of this century. Nanoscience and nanotechnology play an important role in addressing a wide range of environmental issues with innovative and successful solutions. Identification and control of emerging chemical contaminants have received substantial interest in recent years. As a result, there is a need for reliable and rapid analytical tools capable of performing sample analysis with high sensitivity, broad selectivity, desired stability, and minimal sample handling for the detection, degradation, and removal of hazardous contaminants. In this review, various gold–carbon nanocomposites-based sensors/biosensors that have been developed thus far are explored. The electrochemical platforms, synthesis, diverse applications, and effective monitoring of environmental pollutants are investigated comparatively. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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19 pages, 7724 KiB  
Review
Thermal Sensors for Contactless Temperature Measurements, Occupancy Detection, and Automatic Operation of Appliances during the COVID-19 Pandemic: A Review
by Elisabetta Moisello, Piero Malcovati and Edoardo Bonizzoni
Micromachines 2021, 12(2), 148; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020148 - 03 Feb 2021
Cited by 30 | Viewed by 4562
Abstract
The worldwide spread of COVID-19 has forced us to adapt to a new way of life made of social distancing, avoidance of physical contact and temperature checks before entering public places, in order to successfully limit the virus circulation. The role of technology [...] Read more.
The worldwide spread of COVID-19 has forced us to adapt to a new way of life made of social distancing, avoidance of physical contact and temperature checks before entering public places, in order to successfully limit the virus circulation. The role of technology has been fundamental in order to support the required changes to our lives: thermal sensors, in particular, are especially suited to address the needs arisen during the pandemic. They are, in fact, very versatile devices which allow performing contactless human body temperature measurements, presence detection and people counting, and automation of appliances and systems, thus avoiding the need to touch them. This paper reviews the theory behind thermal detectors, considering the different types of sensors proposed during the last ten years, while focusing on their possible employment for COVID-19 related applications. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Engineering and Technology 2021)
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