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Injection Molded Plastic Lens for Relay Lens System and Optical Imaging Probe
라문우,박상민,김원경,이창호,김철홍,김동성 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.8
In this study, we designed, fabricated and characterized a plastic lens which can be used as an optical compartment of a relay lens system for a disposable endoscope or an imaging probe for optical-resolution photoacoustic microscopy (OR-PAM). Cost-effective injection molding using polycarbonate (PC) as a material was conducted for the mass production of the PC lens. The effects of important processing parameters, i.e. mold temperature, injection speed, packing pressure and packing time, on the transcription quality of the PC lenses were investigated quantitatively using the design of experiments based on the Taguchi method. Optical performances, i.e., focal length and birefringence, were evaluated to determine the optimal injection molding condition for the replication. The PC lenses facilitated the feasibility of developing a disposable length-adjustable endoscope comprising a relay lens system. The PC lens was also applied to an optical imaging probe in an OR-PAM for in vivo observation of mouse micro-vasculatures.
연속 구배형 전도성 표면 구현을 위한 탄성중합체 코팅에 관한 연구
라문우,윤길상,박성제,La, Moon-Woo,Yoon, Gil-Sang,Park, Sung-Jea 한국금형공학회 2019 한국금형공학회지 Vol.13 No.3
Recently, studies on the development of flexible electronic devices by combining flexible materials and a conductor have been actively performed as interest in wearable devices. Especially, carbon nanotubes (CNT) or graphene coating have been used to construct a circuit to induce improvement in flexibility and rigidity. Various technologies have been developed in the surface coating of conductive materials, which are key to the manufacture of flexible electronic devices. Surface coating products with 3D coating and micro-patterns have been proposed through electrospinning, electrification, and 3D printing technologies. As a result of this advanced surface coating technology, there is a growing interest in manufacturing gradient conductive surfaces. Gradient surfaces have the advantage that they are adapted to apply a gentle change or to inspect optimum conditions in a particular region by imparting continuously changing properties. In this study, we propose a manufacturing technique to produce a continuous gradient conductive surface by combining a partial stretching of elastomer and a conductive material coating, and introduce experimental results to confirm its performance.
국부 가열 금형을 이용한 플라스틱 나노 구조표면 사출성형 연구
라문우,박장민,김동언 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.4
In this study, we fabricated and characterized a nanostructured surface based on a plastic injection molding with a local mold heating (LMH) system. A metal mold core with a closed packed nano convex array (CVA) was achieved by integrated engineering procedures: (1) master template fabrication by anodic aluminum oxidation (AAO), (2) nickel electroforming (NE) process, and (3) post-processing by precision machining. The nickel mold core was utilized to replicate a surface with a closed packed nano concave-array (CCA) based on injection molding using cyclic olefin copolymer (COC) as a plastic material. In particular, an LMH system was introduced to enhance transcription quality of the nano structures by delaying solidification of molten polymer near the surface of the mold core.
광반응사출성형 시 캐비티 엣지에서 발생하는 미세누출현상에 관한 해석적 연구
라문우,La, Moon-woo 한국금형공학회 2016 한국금형공학회지 Vol.10 No.3
Despite technological advance, there have been several troubles in photo reaction injection molding (photo RIM) to produce ultra thin light guide panels (LGPs). In this study, micro leakage problem at cavity edge during photo RIM was investigated numerically. In order to obtain optimal processing conditions, we regulated inlet pressure of injected resin at the cavity edge and figured out micro leakage behaviors. At low inlet pressure (less than 100 Pa), though the micro leakage problem was not occurred, another problem, short shot due to not enough driving force, was appeared More than 1,000 Pa of the inlet pressure, injected resin was rapidly leaked through the micro gap at the cavity edge. Finally, we obtained optimal inlet pressure around 600 ~ 1,000 Pa. At this region, injected resin fully filled the cavity without micro leakage behavior. Based on the present study, further comparative investigations with experimental photo RIM should be performed to find optimal processing conditions for produce ultra thin LGPs.
부피가 다른 두 유체의 효과적인 유동제어를 위한 미세채널
라문우(Moonwoo La),호재윤(Jae-Yun Ho),김동성(Dong Sung Kim) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.1
본 연구에서는 부피가 다른 두 유체의 효과적인 유동제어를 위하여 Stokes 유동 방정식을 기반으로 설계된 미세채널을 제안한다. 부피가 다른 두 유체가 압력 구동에 의하여 주입구를 통과하는 과정에서, 두 유동이 동시에 만나 주어진 부피비를 유지하며 흘러나간 후에 일시에 끝날 수 있도록 주입구의 폭과 길이를 조절하였다. 디자인된 미세채널은 비압축성, 뉴턴 유체의 과도상태 유동에 대한 전산유체역학 모사를 수행하였다. 또한, 소프트리소그래피를 통해 미세유체칩을 제작하고, 압력 구동에 의한 부피가 다른 두 유체의 유동 특성을 평가하였다. In this paper, microchannels for the flow control of two fluids with different volumes have been designed, fabricated, and verified. The dimensions of the inlets were determined based on the Stokes equation in order to realize that the flow of the two fluids meet at the same time, and to maintain a certain configuration when the flows passed through each inlet channel. The designed microchannels were confirmed using computational fluid dynamics simulation for the incompressible, Newtonian, and transient flows. In addition, a microfluidic system containing the designed microchannels was fabricated by soft lithography, and the pressure-driven flows of the two fluids were characterized by microfluidic experiments.