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마이크로채널 내에서 부착력 차이에 의한 유방암세포의 선별 및 농축
권건우(Keon Woo Kwon),박민철(Min Cheol Park),김필남(Pilnam Kim),황세연(Se Yon Hwang),이상호(Sang Ho Lee),김병규(Byungkyu Kim),서갑양(Kahp Y. Suh) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
A label-free microfluidic method for separation and enrichment of human breast cancer cells is presented using cell adhesion as a physical marker. To maximize the adhesion difference between human breast epithelial cells (MCF10A) and cancer cells (MCF7), flat or nanostructured polymer surfaces (400nm pillars, perpendicular, or parallel line) were constructed on the bottom of PDMS microfluidic channels using UVassisted capillary moulding. The adhesion of MCF10A and MCF7 on each channel was measured based on detachment assays where the adherent cells were counted with increasing flow rate after a pre-culture for a period of time (e.g., 1, 2, and 4 hrs). It was found that MCF10A cells show higher adhesion than MCF7 cells regardless of surface nanotopography. The optimum separation was found for 2 hours pre-culture on the 400nm perpendicular line pattern at a flow rate of 200 μl/min. The fraction of MCF7 cells was increased from 0.36 ± 0.04 to 0.83 ± 0.04 under these optimized conditions.
마이크로 채널 내에서 세포의 크기 및 위치에 따른 전단응력의 해석
조혜성(Hye-Sung Cho),이성훈(Sung-Hoon Lee),박민철(Min-Cheol Park),권건우(Keon-Woo Kwon),서갑양(Kahp-Yang Suh) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
We present simple functions of shear stress on an adherent cell trapped within narrow microchannel. There are many cell traps or docking methods in micro fluidic applications, but we classify the cell docking methods into three types by trapped cell position in microchannel and perform several computational fluid dynamics simulations. Based upon the cell radius R, channel height H, channel length L, we define the dimensionless geometric factor (G.F) as maximum shear stress over wall shear stress(τ<SUB>max</SUB> /τ<SUB>wall</SUB>). In here, the wall shear stress τ<SUB>wall</SUB> and the maximum shear stress τ<SUB>max</SUB> are linearly proportional to inlet average velocity. So G.F is not dependent on inlet average velocity. Finally we can calculate the maximum shear stress very simply as a function of inlet velocity and G.F. This study shows that the maximum shear stress on a cell can be decreased by 10?¹ using well-shape-geometry docking. All analysis performed by COMSOL Multiphysics 3.3 A.
A simple method for fabricating zinc oxide nanostructures using capillary lithography
박지원(Jee Won Park),김재관(Jae Kwan Kim),박민철(Min Cheol Park),권건우(Keon Woo Kwon),서갑양(Kahp Y. Suh) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
We present a simple solvent-assisted capillary molding method to fabricate zinc oxide (ZnO) nanostructures using an ultraviolet (UV) curable polyurethane acrylate (PUA) mold. A thin film of the ZnO sol-gel precursor solution in methyl alcohol was prepared by spin coating on a solid substrate and subsequently a nanopatterned PUA mold was brought in conformal contact with the substrate under a slight physical pressure (~ 3.5 bar). After annealing at 230 ℃ for 4 hrs, well-defined ZnO nanostructures formed with feature size down to ~ 50 ㎚ aided by capillary rise and solvent evaporation. It was found that the height of capillary rise highly depended on the applied pressure. A simple experimental setup was devised to examine the effects of pressure, revealing that the optimum pressure ranged from 3.5 to 5 bars. Also, ZnO nanorods could be selectively grown on the patterned regions using the seed layer as a pseudocatalyst when the width of seed layer was larger than ~ 200 ㎚.
dewetting을 이용한 고해상도 비평면 인쇄 기술 기발
곽문규(Moon Kyu Kwak),신규호(Kyu Ho Shin),윤응률(Eung Yeoul Yoon),박민철(Min Cheol Park),권건우(Keon Woo Kwon),서갑양(Kahp Y. Suh) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
We present here a simple dewetting-assisted flexographic printing method for potential applications to roll-to-roll or plate-to-roll pattern transfer. By controlling dewetting of a thin, conductive ink material with a patterned rubbery mold such as polydimethyl siloxane (PDMS). the liquid ink layer is broken and then selectively wets the protruding part of mold with good pattern uniformity. Subsequently, a resist (e.g., SU-8)-coated aluminum cylinder is brought in contact with the selectively ink-coated PDMS mold, resulting in a pattern transfer to the target substrate without collapse or merging of neighboring features. Using this method. conductive metal lines of silver ink are fabricated on a 300 ㎜-cylindrical surface with the resolution of~20 ㎛ and the sheet resistance less than~4.3 _ after 10 repeated transfer cycles.