• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.385-390
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• 2011

In this study, we developed a micromixer based on the non-equilibrium electrokinetics at the junction of a microchannel and nanochannel. Two fluid streams were mixed by an electro-osmotic flow and a vortex flow created as a result of the non-equilibrium electrokinetics at the junction of the microchannel and nanochannel. Initially, the microchannel was fabricated using Polydimethylsiloxane (PDMS) by the general soft lithography process and the nanochannel was created at a specific position on the microchannel by applying a high voltage. To evaluate the mixing performance of the micromixer, fluorescent distribution was analyzed by using the fluorescent dye, Rhodamine B. About 90% mixing was achieved with this novel micromixer, and this micromixer can be used in microsystems for biochemical sample analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.114-121
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• 2013

In order to estimate the efficiency of an evaporative heat exchanger having mini channel, the equations to calculate heat exchanger properties, those are air temperatures and water temperatures etc, are derived from the governing equations based on the Navier-Stokes equation, even though there are several assumptions to make problem simplify. There are three heat transfer zones at the mini channel heat exchanger depending on the water condition. So, there are three governing equations and solutions to calculate the properties. As the results of this study, the equations to calculate a saturation point and a dry point are derived to evaluate an evaporative heat exchanger having micro channel. It is supposed to predict and evaluate the performance of a mini channel heat exchanger with evaporation of liquid.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.77-82
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• 2010

Our study aims to understand the flow of liquid in an open-top rectangular microchannel that can be used in micro total analysis systems ($\mu$-TAS) because it has advantages in terms of light transmission and energy efficiency. We measured the liquid velocity using particle tracking technique and conducted a simulation with computational fluid dynamics by altering the area of channel cross section and channel length for the capillary-driven flow in the open-top rectangular microchannel. When liquid water drops to an entrance of the fabricated microchannel with a height of 20 μm and a width of 20 ${\mu}m$, it flows along the microchannel by only capillary force. In the wetting behavior of the liquid, important parameters of this flow are channel size, contact angle and liquid properties such as surface tension and viscosity, which are used to control the flow of liquid in the microchannel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.89-95
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• 2012

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.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.54.2-54.2
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• 2005

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.47-53
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• 2015

In this paper, a novel fluid controlled phase tunable line using inkjet printed microfluidic composite right/left-handed(CRLH) transmission line(TL) is proposed. A CRLH-TL prototype has been inkjet-printed on a paper substrate using silver nano particle ink. In addition, a laser-etched microfluidic channel in poly methyl methacrylate(PMMA) has been integrated with the CRLH TL using inkjet-printed SU-8 as a bonding material. The proposed TL provides excellent phase-tuning capability that is dependent on the different fluidic materials used. As the fluid is changed, the proposed TL can have negative-phase, zero-phase, and positive-phase characteristics at 900 MHz and reflection coefficient is maintained to below -10 dB. The performance of the proposed TL is successfully validated using simulation and measurement results.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.437-446
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• 2006

A fabrication method fur high-aspect-ratio microchannels in stainless steel using laser-assisted thermochemical wet etching is reported in this paper. The fabrication of deep microchannels with an aspect ratio over ten is realized by applying a multiple etching process with an optimization of process conditions. The cross-sectional profile of the microchannels can be adjusted between rectangular and triangular shapes by properly controlling laser power and etchant concentration. Excellent dimensional uniformity is achieved among the channels with little heat-affected area. Microchannels with a width ranging from 15 to $50{\mu}m$ can be fabricated with an aspect ratio of ten and a pitch of 150 m or smaller. The effects of process variables such as laser power, scan speed, and etchant concentration on the fabrication results, including etch width, depth, and cross-sectional profile are closely examined.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.69-71
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• 2001

본 논문에서는 FACS(fluorescence activated cell sorting)의 초소형화를 위한 미세 유체소자들을 플라스틱 기판에 집적하여 제작하고 전기삼투를 이용해서 세포가 일렬로 이송되는 특성을 시험한다. 제작된 미세 유체 소자는 유리 하부 기판과 플라스틱 상부 기판 및 전원장치로 구성된다. 상부기판은 세포를 주입하기 위한 샘플 측 레저버와 세포를 운반 및 일렬 이송이 가능하게 하는 버퍼를 저장할 두 개의 레저버가 있고 이들이 배출되는 레저버로 구성된다. 마이크로머시닝 기술을 이용하여 실리콘 기판 위에 미세 채널 몰드를 제작한 후 PDMS(polydimethylsiloxane)로 주물을 제작한다. $O_2$ 플라즈마를 이용하여 유리 기판과 PDMS 주물을 접합하며 제작된 채널에 적색 잉크와 bead를 샘플 측에 충전하고 버퍼 측에 sodium borate를 충전한 후 전기삼투로 구동시킨다. bead가 일렬로 이송되도록 전장을 조절하고 이때의 유속과 유량을 측정한다. 다양한 전장에 따른 실험을 통하여 채널의 구조를 최적화한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.85-85
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• 2003

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1281_1282
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• 2009

ICP-CVD를 이용하여 inverted staggered 구조를 갖는 미세결정 실리콘 (Nanocrystalline Silicon, nc-Si) 박막 트랜지스터(Thin Film Transistor, TFT)를 제작하였다. 또한, 소자의 특성과 전기적 안정성을 평가하였다. 실험 결과는 짧은 채널 길이를 갖는 nc-Si TFT가 긴 채널 길이의 소자보다 같은 드레인 전압 바이어스 하에서 덜 열화 됨을 알 수 있었다. 이는 드레인 전압 바이어스 하에서의 낮은 채널 캐리어 농도는 적은 defect state를 만들기 때문으로 짧은 채널 길이의 TFT가 긴 채널 길이의 TFT보다 $V_{TH}$ 열화가 적었다. 이러한 결과는 짧은 채널 길이의 nc-Si TFT가 디스플레이 분야에 있어 다양하게 응용될 것으로 기대된다.