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: closed (30 May 2024) | Viewed by 9408

Special Issue Editor


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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
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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

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Keywords

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

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Related Special Issue

Published Papers (7 papers)

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Research

16 pages, 4462 KiB  
Article
Wafer Level Vacuum Packaging of MEMS-Based Uncooled Infrared Sensors
by Gulsah Demirhan Aydin, Orhan Sevket Akar and Tayfun Akin
Micromachines 2024, 15(8), 935; https://doi.org/10.3390/mi15080935 - 23 Jul 2024
Viewed by 1018
Abstract
This paper introduces a cost-effective, high-performance approach to achieving wafer level vacuum packaging (WLVP) for MEMS-based uncooled infrared sensors. Reliable and hermetic packages for MEMS devices are achieved using a cap wafer that is formed using two silicon wafers, where one wafer has [...] Read more.
This paper introduces a cost-effective, high-performance approach to achieving wafer level vacuum packaging (WLVP) for MEMS-based uncooled infrared sensors. Reliable and hermetic packages for MEMS devices are achieved using a cap wafer that is formed using two silicon wafers, where one wafer has precise grating/moth-eye structures on both sides of a double-sided polished wafer for improved transmission of over 80% in the long-wave infrared (LWIR) wavelength region without the need for an AR coating, while the other wafer is used to form a cavity. The two wafers are bonded using Au-In transient liquid phase (TLP) bonding at low temperature to form the cap wafer, which is then bondelectrical and Electronics d to the sensor wafer using glass frit bonding at high temperature to activate the getter inside the cavity region. The bond quality is assessed using three methods, including He-leak tests, cap deflection, and Pirani vacuum gauges. Hermeticity is confirmed through He-leak tests according to MIL-STD 883, yielding values as low as 0.1 × 10−9 atm·cc/s. The average shear strength is measured as 23.38 MPa. The package pressure varies from 133–533 Pa without the getter usage to as low as 0.13 Pa with the getter usage. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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10 pages, 2861 KiB  
Article
A New Silicon Mold Process for Polydimethylsiloxane Microchannels
by Lung-Jieh Yang, Sameer Shaik, Neethish Kumar Unnam and Valliammai Muthuraman
Micromachines 2024, 15(7), 848; https://doi.org/10.3390/mi15070848 - 29 Jun 2024
Viewed by 736
Abstract
As an alternative to SU-8 soft lithography, a new silicon mold process of fabricating PDMS microchannel chips was proposed. A picosecond laser is used to cut through a 550 μm thick silicon wafer and generate the original microchannel pattern with a 50 μm [...] Read more.
As an alternative to SU-8 soft lithography, a new silicon mold process of fabricating PDMS microchannel chips was proposed. A picosecond laser is used to cut through a 550 μm thick silicon wafer and generate the original microchannel pattern with a 50 μm minimum feature size. This single-crystal silicon pattern, with the edge debris caused by laser cutting being trimmed off by a KOH solution and with the protection field oxide layer being removed by BOE afterwards, firmly resided on a glass substrate through the anodic bonding technique. Four-inch wafers with microchannel patterns as the PDMS mold cores were successfully bonded on Pyrex 7740 or Eagle XG glass substrates for the follow-up PDMS molding/demolding process. This new maskless process does not need a photolithography facility, but the laser cutting service must be provided by professional off-campus companies. One PDMS microchannel chip for particle separation was shown as an example of what can be achieved when using this new process. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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13 pages, 3044 KiB  
Article
Fiber Optic LSPR Sensing AFM1 in Milk with Enhanced Sensitivity by the Hot Spot Effect Based on Nanogap Construction
by Jiacong Li, Yuxin Ni, Wei Zhang, Elvige Laure Nteppe Nteppe, Yurong Li, Yeshun Zhang and Hui Yan
Micromachines 2024, 15(6), 779; https://doi.org/10.3390/mi15060779 - 13 Jun 2024
Cited by 1 | Viewed by 762
Abstract
The detection of the amount of aflatoxin M1 (AFM1) in milk is crucial for food safety. Here, we utilize a fiber optic (FO) localized surface plasmon resonance (LSPR) biosensor by constructing gold nanoparticle (AuNP) multimers, in which the nanogaps amplified the LSPR signal [...] Read more.
The detection of the amount of aflatoxin M1 (AFM1) in milk is crucial for food safety. Here, we utilize a fiber optic (FO) localized surface plasmon resonance (LSPR) biosensor by constructing gold nanoparticle (AuNP) multimers, in which the nanogaps amplified the LSPR signal by the hot spot effect, and achieved a highly sensitive detection of f AFM1. Through the optimization of parameter conditions for the fabrication of the sensor and detection system, a high performance result from the FO LSPR biosensor was obtained, and the method for AFM1 detection was established, with a wide detection range of 0.05–100 ng/mL and a low limit of detection (LOD) of 0.04 ng/mL, and it has been successfully validated with the actual sample milk. Therefore, it is a good strategy to fabricate highly sensitive FO LSPR sensors for detecting AFM1 by constructing AuNP multimers, and this approach is suitable for developing other biosensors. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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13 pages, 3202 KiB  
Article
Fluid Flow to Electricity: Capturing Flow-Induced Vibrations with Micro-Electromechanical-System-Based Piezoelectric Energy Harvester
by Jin Gu Kang, Hyeukgyu Kim, Sangwoo Shin and Beom Seok Kim
Micromachines 2024, 15(5), 581; https://doi.org/10.3390/mi15050581 - 27 Apr 2024
Cited by 1 | Viewed by 2636
Abstract
We introduce a micro-electromechanical system (MEMS) energy harvester, designed for capturing flow energy. Moving beyond traditional vibration-based energy harvesting, our approach incorporates a cylindrical oscillator mounted on an MEMS chip, effectively harnessing wind energy through flow-induced vibration (FIV). A highlight of our research [...] Read more.
We introduce a micro-electromechanical system (MEMS) energy harvester, designed for capturing flow energy. Moving beyond traditional vibration-based energy harvesting, our approach incorporates a cylindrical oscillator mounted on an MEMS chip, effectively harnessing wind energy through flow-induced vibration (FIV). A highlight of our research is the development of a comprehensive fabrication process, utilizing a 5.00 µm thick cantilever beam and piezoelectric film, optimized through advanced micromachining techniques. This process ensures the harvester’s alignment with theoretical predictions and enhances its operational efficiency. Our wind tunnel experiments confirmed the harvester’s capability to generate a notable electrical output, with a peak voltage of 2.56 mV at an 8.00 m/s wind speed. Furthermore, we observed a strong correlation between the experimentally measured voltage frequencies and the lift force frequency observed by CFD analysis, with dominant frequencies identified in the range of 830 Hz to 867 Hz, demonstrating the potential application in actual flow environments. By demonstrating the feasibility of efficient energy conversion from ambient wind, our research contributes to the development of sustainable energy solutions and low-power wireless electron devices. Full article
(This article belongs to the Special Issue MEMS Nano/Microfabrication)
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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 - 9 Dec 2023
Cited by 1 | Viewed by 1365
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 - 7 Dec 2023
Viewed by 986
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 1022
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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