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AMOLED 제조공정에 사용되는 Fine Metal Mask 용 얇은 Invar 합금의 진동자를 이용한 펨토초 레이저 응용 홀 드릴링
최원석,김훈영,신영관,최준하,장원석,김재구,조성학,최두선,Choi, Won-Suk,Kim, Hoon-Young,Shin, Young-Gwan,Choi, Jun-ha,Chang, Won-Seok,Kim, Jae-Gu,Cho, Sung-Hak,Choi, Doo-Sun 한국금형공학회 2020 한국금형공학회지 Vol.14 No.3
One of display trends today is development of high pixel density. To get high PPI, a small size of pixel must be developed. RGB pixel is arranged by evaporation process which determines pixel size. Normally, a fine metal mask (FMM; Invar alloy) has been used for evaporation process and it has advantages such as good strength, and low thermal expansion coefficient at low temperature. A FMM has been manufactured by chemical etching which has limitation to controlling the pattern shape and size. One of alternative method for patterning FMM is laser micromachining. Femtosecond laser is normally considered to improve those disadvantages for laser micromachining process due to such short pulse duration. In this paper, a femtosecond laser drilling for thickness of 16 ㎛ FMM is examined. Additionally, we introduce experimental results for controlling taper angle of hole by vibration module adapted in laser system. We used Ti:Sapphire based femtosecond laser with attenuating optics, co-axial illumination, vision system, 3-axis linear stage and vibration module. By controlling vibration amplitude, entrance and exit diameters are controllable. Using vibrating objective lens, we can control taper angle when femtosecond laser hole drilling by moving focusing point. The larger amplitude of vibration we control, the smaller taper angle will be carried out.
극초단 펄스 레이저를 사용한 유리 내부의 필라멘테이션에 대한 실험적 연구
최원석,윤지욱,김주한,최지연,장원석,김재구,최두선,황경현,조성학,Choi, Won-Suk,Yoon, Ji-Wook,Kim, Joohan,Choi, Jiyeon,Chang, Won-Seok,Kim, Jae-Goo,Choi, Doo-Sun,Whang, Kyoung Hyun,Cho, Sung-Hak 한국레이저가공학회 2013 한국레이저가공학회지 Vol.16 No.1
We have successfully formed filament inside of a transparent soda-lime glass using a Ti:sapphire based femtosecond laser. To make filament form, keeping the laser intensity higher than critical intensity is essential. Also each of the machining parameters plays an important role for the formation of filament. In this paper, we study what parameter can possibly influence for formation of filament, and we introduce an application using filamentation by femtosecond laser for transparent material.
Thermal Aging Behavior of H-NBR/NBR Blend
최원석,김건완,도제성,유명우,류승훈,Choi, Won-Seok,Kim, Gun-Wan,Do, Je-Sung,Yoo, Myung-Ho,Ryu, Sung-Hun The Rubber Society of Korea 2011 엘라스토머 및 콤포지트 Vol. No.
본 연구는 H-NBR 함량 변화에 따른 H-NBR/NBR 블렌드의 열노화 거동에 대하여 살펴보았다. 이 때 가교제로는 dicumyl peroxide와 황 혼합물을 사용하였으며, 열노화에 따른 H-NBR/NBR 블렌드의 인장강도, 파괴신율, 경도 그리고 내마모성의 변화를 살펴보았다. H-NBR을 첨가함에 따라 인장강도는 증가하였으나 내마모성은 감소하는 현상을 나타내었다. 파괴신율과 경도는 H-NBR의 영향을 받지 않았다. 노화가 진행된 모든 시편은 초기 시편보다 낮은 인장강도, 파괴신율, 경도를 나타내었다. 그러나 H-NBR의 함량이 증가함에 따라 이러한 물성저하 속도가 감소함을 알 수 있었다. 즉 H-NBR 첨가에의해 열노화 특성이 향상됨을 알 수 있었다. 모든 NBR/H-NBR 블렌드는 노화시간이 증가함에 따라 내마모성이 감소하였으며, H-NBR을 첨가한 경우 내마모성의 저하가 상대적으로 낮음을 알 수 있었다. In the present investigation, thermal aging behavior of H-NBR/NBR blend with various H-NBR content was investigated. Mixture of dicumyl peroxide and sulfur were used as a curing agent. The influence of the thermal aging of the H-NBR/NBR blends on the solid state properties such as tensile strength, elongation at break, hardness and abrasion resistance was investigated. Tensile strength was increased with increasing H-NBR content, while abrasion resistance was decreased. Both elongation at break and hardness were not affected by the addition of H-NBR. The properties such as hardness, tensile strength and elongation at break of the aged samples were lower than unaged samples. However, the rate of deterioration of those properties was decreased by increasing the H-NBR content, which indicated that improved thermal aging behavior was obtained by the addition of H-NBR. Abrasion loss was increased with increasing aging time, but it became less by the addition of H-NBR addition.
라만 맵핑 방식을 사용한 다이아몬드상 카본박막의 미세구조변화에 관한 연구
최원석,Choi, Won-Seok 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.7
Hydrogenated Diamond-like carbon (DLC) films were prepared by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas. The wear track on the DLC films was examined after the ball-on disk (BOD) measurement with a Raman mapping method. The BOD measurement of the DLC films was performed for 1 to 3 hours with a 1-hour step time. The sliding traces on the hydrogenated DLC film after the BOD measurement were also observed using an optical microscope. The surface roughness and cross-sectional images of the wear track were obtained using an atomic force microscope (AFM). The novel Raman mapping method effectively shows the graphitization of DLC films of $300{\mu}m\times300{\mu}m$ area according to the sliding time by G-peak positions (intensities) and $I_D/I_G$ ratios.
Permeable FW-H 방법을 이용한 원형 실린더 주변의 난류유동소음해석
최원석,홍석윤,송지훈,권현웅,정철민,Choi, Woen-Sug,Hong, Suk-Yoon,Song, Jee-Hun,Kwon, Hyun-Wung,Jung, Chul-Min 해양환경안전학회 2014 海洋環境安全學會誌 Vol.20 No.6
난류유동에 의한 소음은 계산비용의 관점에서 음향 상사법을 이용하여 전산유체 기법과 결합해 다양한 해석모델이 연구되고 있다. FW-H 음향상사법을 이용한 유동소음해석의 연구가 활발히 이루어지고 있으나, 기존 문헌들의 결과에서는 계산비용의 관점에서 난류유동에 의한 소음성분을 생략하고 있다. 그러나, 최근의 연구에서 유동소음특성에 있어 난류소음의 중요성이 밝혀진바 있다. 본 논문에서는 RANS 난류모델과 투과성 경계면을 이용한 Permeable FW-H 음향상사법을 이용한 난류유동소음해석에 대해 연구하였다. 2D실린더에 대하여 직접적으로 변동압력을 추출하는 직접법과 난류성분을 고려하지 않은 FW-H 상사법, 또 난류소음의 성분을 포함하는 Permeable FW-H 방법의 경우를 비교하였다. Permeable FW-H 방법을 통해 일반적으로 적용되는 FW-H 방법에서 해석 불가능한 난류에 의한 소음의 영향을 기존의 FW-H 방법과 동일한 계산비용으로 예측할 수 있었고, 적절한 투과성 경계면 설정을 통해 높은 정확도의 해석이 가능했다. Permeable FW-H 방법을 통한 난류유동해석 절차를 확립하였으며, 그 유용성을 확인했다. Varieties of research on turbulent-induced noise is conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyze efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods, direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent-induced noise using permeable FW-H is established and its usability is shown.
Fetal Bovine Serum을 포함한 세포 배양액에 담근 Indium Tin Oxide 전극 계면의 전기화학적 특성
최원석,조성보,Choi, Won Seok,Cho, Sungbo 대한의용생체공학회 2013 의공학회지 Vol.34 No.1
For the biocompatibility test of implantable devices or for the sensitivity evaluation of biomedical sensors, it is required to understand the mechanism of the protein adsorption and the interaction between the adsorbed proteins and cells. In this study, the adsorption of proteins in a cell culture medium with fetal bovine serum onto an indium tin-oxide electrode was characterized by using linear sweep voltammetry and impedance spectroscopy. We immersed the fabricated ITO electrodes in the culture medium for 30, 60, or 90 min, and then measured the electrochemical properties of electrodes with 10 mM $Fe(CN){_6}^{3-/4-}$ and 0.1 M KCl electrolyte. With an increase of contacting time, the anodic peak current was decreased and the charge transfer resistance was increased. However, both parameters were recovered to the values before contact with the medium after the treatment of Trypsin/Ethylenediaminetetraacetic acid hydrolyzing proteins.
PECVD로 합성한 다이아몬드상 카본박막의 전기적 특성
최원석,박문기,홍병유,Choi, Won-Seok,Park, Mun-Gi,Hong, Byung-You 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.11
In addition to its similarity to genuine diamond film, diamond-like carbon (DLC) film has many advantages, including its wide band gap and variable refractive index. In this study, DLC films were prepared by the RF PECVD (Plasma Enhanced Chemical Vapor Deposition) method on silicon substrates using methane ($CH_4$) and hydrogen ($H_2$) gas. We examined the effects of the RF power on the electrical properties of the DLC films. The films were deposited at several RF powers ranging from 50 to 175 W in steps of 25 W. The leakage current of DLC films increased at higher deposition RF power. And the resistivities of DLC films grown at 50 W and 175 W were $5\times10^{11}$ ${\Omega}cm$ and $2.68\times10^{10}$ ${\Omega}cm$, respectively.
LC 공진형 압력 센서를 이용한 돼지 경골 동맥의 실시간 혈압 측정
최원석,김진태,정연호,Choi, Won-Seok,Kim, Jin-Tae,Joung, Yeun-Ho 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.6
We have developed an implantable wireless sensor for real time pressure monitoring of blood circulation system. MEMS (micro-electro-mechanical system) technology was adopted as a sensor development method. The sensor is composed of photolithographically patterned inductors and a distributed capacitor in gap between the inductors. A resulting LC resonant system produces its resonant frequency in range of 269 to 284 MHz at 740 mmHg. To read the resonant frequency changed by blood pressure variation, we developed a custom readout system based on a network analyzer functionality. The bench-top testing of the pressure sensors showed good mechanical and electrical functionality. A sensor was implanted into tibial artery of farm pig, and interrogated wirelessly with accurate readings of blood pressure. After 45 days, the sensor's electrical response and histopathology were studied with good frequency reading and biocompatibility.