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3차원 LIGA 미세구조물 제작을 위한 마이크로 액추에이터 내장형 X-선 마스크
이광철,이승섭,Lee, Kwang-Cheol,Lee, Seung-S. 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.10
We present a novel method for 3D microfabrication with LIGA process that utilizes a deep X-ray mask in which a micro-actuator is integrated. The integrated micro-actuator oscillates the X-ray absorber, which is formed on the shuttle mass of the micro-actuator, during X-ray exposures to modify the absorbed dose profile in X-ray resist, typically PMMA. 3D PMMA microstructures according to the modulated dose contour are revealed after GG development. An X-ray mask with integrated comb drive actuator is fabricated using deep reactive ion etching, absorber electroplating, and bulk micromachining with silicon-on-insulator (SOI) wafer. 1mm $\times$ 1 mm, 20 $\mu$m thick silicon shuttle mass as a mask blank is supported by four 1 mm long suspension beams and is driven by the comb electrodes. A 10 $\mu$m thick, 50 $\mu$m line and spaced gold absorber pattern is electroplated on the shuttle mass before the release step. The fundamental frequency and amplitude are around 3.6 kHz and 20 $\mu$m, respectively, for a do bias of 100 V and an ac bias of 20 $V_{p-p}$ (peak-peak). Fabricated PMMA microstructure shows 15.4 $\mu$m deep, S-shaped cross section in the case of 1.6 kJ $cm^{-3}$ surface dose and GG development at 35$^{\circ}C$ for 40 minutes.
Transparent Patch Antenna Using Silver Mesh Electrode
김동진(Dong Jin Kim),장효양(Hyoyang Jang),조문형(Munhyeong Jo),엄준성(Junseong Eom),이승섭(Seung S. Lee),이재흥(Jaeheung Lee) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.9
This study presents a transparent-patch antenna using a silver-mesh transparent electrode film with a high optical transmittance (87.7%), low haze (1.1%), and low sheet resistance (8.9 Ω/sq). The silver-mesh transparent electrode film is fabricated by using UV embossing and doctor blading without any high-temperature or vacuum processes. The UV resin pattern is transferred from a nickel mold to a plastic film, and then a silver paste is filled into the UV resin pattern. The transparent antenna patch and ground plane are obtained by repeating these processes on both sides of a single plastic film. The antenna patch is designed with a width of 44.8 mm and a height of 36.0 mm in order to obtain a resonant frequency at 2.45 GHz, which is a frequency of wireless LAN. As a result, the transparent-patch antenna has a reflection coefficient (S11 parameter) of -35.6 dB, a peak gain of -3.99 dBi, and a radiation efficiency of 6.2% at 2.45 GHz. Finally, a Wi-Fi router using the transparent-patch antenna is demonstrated.
온도 변화를 이용한 고분자 막 마이크로 액추에이터의 공진 주파수 튜닝
이승훈(Seung Hoon Lee),이석우(Seok Woo Lee),권혁준(Hyuk-Jun Kwon),이광철(Kwang-Cheol Lee),이승섭(Seung S. Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Resonant frequency tuning of micro devices is essential to achieve performance uniformity and high sensitivity. Previously reported frequency tuning methods using electrostatic force or mass deposition are not directly applicable to non-conducting polymer devices and have limitations such as dielectric breakdown or low tunable bandwidth. In this paper, thermally frequency-tunable microactuators with poly-dimethylsiloxane membranes are proposed. Permanent and/or nonpermanent frequency tunings are possible using a simple temperature control of the device. Resonant frequency and Q-factor variations of devices according to temperature change were studied using a micro heater and laser Doppler vibrometer. The initial resonant frequencies determined by polymer curing and hardening temperatures are reversibly tuned by thermal cycles. The measured resonant frequency of 9.7 ㎑ was tuned up by ~ 25% and Q-factor was increased from 14.5 to 27 as the micro heater voltage increased from 0 to 70 V.
탄소 기반의 고주파 나노 역학 공진기의 제작 및 동역학적 특성에 대한 연구
이승훈(Seung Hoon Lee),민범기(Bumki Min),이광철(Kwang-Cheol Lee),박세일(Se Il Park),이승섭(Seung S. Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Nanomechanical resonators have attracted much attention in the last decade due to superior performance with high sensitivity and high oscillation frequency. In this paper, we propose carbon-based high frequency nanomechanical resonators by utilizing pyrolyzed carbon layers with embedded single walled carbonnanotube (swCNT) layers. SwCNTs are used as a reinforcement material and also lower the density of the resonator. Dynamic behaviors of the fabricated resonators, including fundamental frequency, Q-factor, and frequency tuning characteristics were investigated using magnetomotive dynamic flexural measurements. We believe that the carbon-based nanomechanical resonators have promising applications in sensitive nanodevices with low power consumption. These materials are also ideal because of the low-cost batch processing capability and could be an alternative for silicon-based nanodevices.
표면처리된 탄소 마이크로니들을 이용한 초소수성 표면 제조
이정아(Jung A Lee),이석우(Seok Woo Lee),이승섭(Seung S. Lee),박세일(Se Il Park),이광철(Kwang-Cheol Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
This paper reports a fabrication method of high aspect ratio (HAR) carbon microneedle arrays with controlled geometry and a creation of a superhydrophobic surface utilizing HMDS (hexamethyldisilazane)-modified carbon microneedles. Carbon microneedles are obtained through lithography and thermal treatment, which have aspect ratios greater than ten and nanoscale tips by volume shrinkage during pyrolysis of the fabricated SU-8 microneedles. We also stuied the wetting property of carbon microneedle arrays with different base diameters and spacing between needles and created an extremely water-repellent surface using HMDS-treated carbon microneedles. The proposed surface will be of great interest in self-cleaning, low-drag microfluidics, and lab-on-a-chip.
〈학술논문〉 비틀림 셀프 펌핑 스프링이 내재된 π-형상 파라메트릭 공진기 개발
김진하(Jin Ha Kim),이승훈(Seung Hoon Lee),이정아(Jung A Lee),심승보(Seung-Bo Shim),이광철(Kwang-Cheol Lee),이승섭(Seung S. Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Mechanically pumped parametric resonators have advantages in size minimizing and sensitivity increasing of sensors, but only limited studies have been done, despite its potential capabilities. Here we report new π-shape parametric resonators - constructed with operating cantilevers and pumping beams - in which torsional self pumping springs are included. Zero-displacement points of pumping beams are identified using areal calculation method to contribute only torsional pumping. Suggested nanocantilevers are fabricated by simple patterning and etching process. Resonance frequencies of operating cantilevers and pumping beams are measured, and the measured resonance frequencies are compared with vibration modes simulation results. We perform DC tuning for resonance frequency matching. The suggested design of resonator establishes development very small and high sensitivity sensors.
이성근,이광철,이승섭,Lee, Sung-Keun,Lee, Kwang-Cheol,Lee, Seung-S. 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11
Microlenses and microlens arrays are fabricated using a novel fabrication technology based on the exposure of a resist (usually PMMA) to deep X-rays and subsequent thermal treatment. The fabrication technology is very simple and produces microlenses and microlens arrays with good surface roughness (less than 1 nm). The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses is produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. The geometry of the microlens is determined by parameters such as the X-ray dose applied to the PMMA, the diameter of the microlens, along with the heating temperature, heating time, and cooling rate in the thermal treatment. Microlenses are produced with diameters ranging from 30 to 1500 ${\mu}{\textrm}{m}$. The modified LIGA process is used not only to construct hemispherical microlenses but also structures that are rectangular-shaped, star-shaped, etc.
마이크로 채널 충전 과정의 유동 현상(I) - 유동 가시화 실험 -
김동성,이광철,권태헌,이승섭,Kim, Dong-Sung,Lee, Kwang-Cheol,Kwon, Tai-Hun,Lee, Seung-S. 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.10
Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in micro-system industries, in particular the bio-application industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, Part 1, an experimental investigation has been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness (40um,30um and 2011m) were fabricated using SU-8 on silicon wafer substrate. And a flow visualization system was developed to observe the filling flow into the micro-channels. Experimental flow observations are extensively made to find the effects of pressure, inertia force, viscous force and surface tension. A dimensional analysis for experimental results was carried out and several relationships A dimensionless parameters are obtained.