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Micromachines
Special Issues
MEMS Nano/Microfabrication
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MEMS Nano/Microfabrication

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

Deadline for manuscript submissions: 30 May 2024 | Viewed by 2583

Special Issue Editor

Dr. Donghwi Lee

E-Mail Website
Guest Editor
Department of Mechanical System Engineering, Jeonbuk National University, Jeonju 54896, Republic of Korea
Interests: nano/microfabrication; two-phase heat transfer; bubble visualization; nuclear engineering; thermal hydraulics

Special Issue Information

Dear Colleagues,

In order to use nano/microstructures in industrial applications, nano/microfabrication has been extensively studied over the past decade. Microscale structures are mainly manufactured using photolithography-based microelectromechanical systems (MEMSs). In contrast, nanoscale structures are fabricated using two different approaches: top-down methods (wet/dry etching, etc.) and bottom-up methods (vapor–liquid–solid (VLS), template-assisted electrodeposition, etc.). Nano/microstructures are produced using these methods for various engineering applications. For example, they can be used for drag reduction, anti-biofouling, anti-corrosion, anti-fogging, anti-frosting, and anti-icing through the control of the hydrophilicity of the surface in material engineering. Some of their other applications include high-performance sensors in electronic engineering (e.g., gas sensors and biosensors), owing to their large surface area and high sensitivity. Similarly, in mechanical engineering, they can be adopted for device-cooling applications (e.g., for enhanced cooling surfaces in computer chips, data centers, and nuclear fuel core cooling) due to their large surface area. This Special Issue will cover topics ranging from nano/microfabrication methods to their engineering applications and seeks to showcase research papers, communications, and review articles that focus on (1) novel nano/microfabrication methods and (2) new developments applying nano/microstructures in various engineering fields (e.g., mechanics, materials, and electronics).

We look forward to receiving your submissions.

Dr. Donghwi Lee
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 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

  • nano/micro fabrication
  • Microelectromechanical Systems (MEMS)
  • sensor and actuator
  • surface wettability
  • single-phase heat transfer
  • two-phase heat transfer
  • device cooling

Published Papers (3 papers)

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Research

17 pages, 4375 KiB  
Article
Numerical Study of Flow and Heat Transfer Characteristics for Al2O3 Nanofluid in a Double-Pipe Helical Coil Heat Exchanger
by Hyeon Taek Nam, Sumin Lee, Minsuk Kong and Seungro Lee
Micromachines 2023, 14(12), 2219; https://doi.org/10.3390/mi14122219 - 09 Dec 2023
Cited by 1 | Viewed by 793
Abstract
To numerically investigate the flow and heat transfer characteristics of a water/Al2O3 nanofluid in a double-pipe helical coil heat exchanger, we simulated a two-phase Eulerian model to predict the heat transfer coefficient, Nusselt number, and pressure drop at various concentrations [...] Read more.
To numerically investigate the flow and heat transfer characteristics of a water/Al2O3 nanofluid in a double-pipe helical coil heat exchanger, we simulated a two-phase Eulerian model to predict the heat transfer coefficient, Nusselt number, and pressure drop at various concentrations (i.e., volume fraction) and under diverse flow rates at the steady state. In this simulation, we used the k-epsilon turbulence model with an enhanced wall treatment method. The performance factor of the nanofluid was evaluated by accounting for the heat transfer and pressure drop characteristics. As a result, the heat transfer was enhanced by increasing the nanofluid concentration. The 1.0 vol.% nanofluid (i.e., the highest concentration) showed a heat transfer coefficient 1.43 times greater than water and a Nusselt number of 1.38 times greater than water. The pressure drop of nanofluids was greater than that of water due to the increased density and viscosity induced using nanoparticles. Based on the relationship between the Nusselt number and pressure drop, the 1.0 vol.% nanofluid was calculated to have a performance factor of 1.4 relative to water, indicating that the enhancement rate in heat transfer performance was greater than that in the pressure drop. In conclusion, the Al2O3 nanofluid shows potential as an enhanced working fluid in diverse heat transfer applications. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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17 pages, 4602 KiB  
Article
MEMS Electrostatically Driven Coupled Beam Filter Banks
by Richard Syms and Adam Bouchaala
Micromachines 2023, 14(12), 2214; https://doi.org/10.3390/mi14122214 - 07 Dec 2023
Viewed by 659
Abstract
MEMS bandpass filters based on electrostatically driven, mechanically coupled beams with in-plane motion have been demonstrated up to the VHF band. Filters higher than second order with parallel plate drives have inherent tuning difficulties, which may be resolved by adding mass-loaded beams to [...] Read more.
MEMS bandpass filters based on electrostatically driven, mechanically coupled beams with in-plane motion have been demonstrated up to the VHF band. Filters higher than second order with parallel plate drives have inherent tuning difficulties, which may be resolved by adding mass-loaded beams to the ends of the array. These beams deflect for DC voltages, and thus allow synchronized electrostatic tuning, but do not respond to in-band AC voltages and hence do not interfere with dynamic synchronization. Additional out-of-band responses may be damped, leaving the desired response. The principle is extended here to close-packed banks of filters, with adjacent arrays sharing mass-loaded beams that localize modes to sub-arrays. The operating principles are explained using a lumped element model (LEM) of the equations of motion in terms of resonant modes and the reflection of acoustic waves at discontinuities. Performance is simulated using the LEM and verified using the more realistic stiffness matrix method (SMM) for banks of up to eight filters. Similar or dissimilar filters may be combined in a compact arrangement, and the method may be extended to higher order resonances and alternative coupled resonator systems. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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12 pages, 6728 KiB  
Article
Performance Improvement of an STS304-Based Dispensing Needle via Electrochemical Etching
by Yong-Taek Kwon, Sanghyun Jeon, Jun Lee, Juheon Kim, Sangmin Lee and Hyungmo Kim
Micromachines 2023, 14(12), 2183; https://doi.org/10.3390/mi14122183 - 30 Nov 2023
Viewed by 634
Abstract
In this study, we explored the formation of micro-/nanosized porous structures on the surface of a needle composed of STS304 and examined the effect of conventional needles and needles capable of liquid ejection. Aqua regia, composed of HCl and HNO3, was [...] Read more.
In this study, we explored the formation of micro-/nanosized porous structures on the surface of a needle composed of STS304 and examined the effect of conventional needles and needles capable of liquid ejection. Aqua regia, composed of HCl and HNO3, was electrochemically etched to form appropriately sized micro-/nanoporous structures. We observed that when dispensing liquids with low surface tension, they do not immediately fall downward but instead spread over the exterior surface of the needle before falling. We found that the extent of spreading on the surface is influenced by an etched porous structure. Furthermore, to analyze the effect of surface tension differences, we dispensed liquids with varying surface tensions using etched needles. Through the analysis, it was confirmed that, despite the low surface tension, the ejected droplet volume and speed could be stably maintained on the etched needle. This indicates that the spreading phenomenon of the liquid on the needle surface just before ejection can be controlled by the micro/nanoporous structure. We anticipate that these characteristics of etched needles could be utilized in industries where precision dispensing of low-surface-tension liquids is essential. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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