• 설비공학논문집
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• 제27권2호
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• pp.75-80
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• 2015

The effect of inlet mixer geometries on the two-phase flow patterns in square micro-channel with $600{\times}600{\mu}m$ was investigated experimentally in this paper. The 4 different mixer configurations based on the Y, Impacting, and two T types (gas and liquid inlets were switched) were used. The test fluids were nitrogen and water. The liquid and gas superficial velocities were 0.01~10 m/s and 0.1~100 m/s, respectively. Several distinctive flow patterns, namely, annular, slug-annular, slug, slug-bubbly, bubbly, and churn flow could be seen. The flow pattern maps for each mixer were suggested, and it can be concluded that two-phase flow patterns are not very sensitive to the mixer geometries. But the mixing behaviors of gas and liquid for each mixer were different for slug and bubbly flow. Thus, the characteristics of slug and bubble for each case were not same.

• 설비공학논문집
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• 제27권10호
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• pp.520-526
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• 2015

The characteristics of gas-liquid Taylor (Slug) flow in a square micro-channel of $600{\sim}600{{\mu}m}$ were investigated experimentally in this paper. The test fluids were nitrogen and water. The liquid and gas superficial velocities were 0.01~3 m/s and 0.1~3 m/s, respectively. Bubble and liquid slug length, bubble velocity, and frequency were measured by analyzing optical images using a high speed camera. Bubble length decreased with higher liquid flow rate, which increased dramatically with higher gas flow rate. However, slug length did not vary with changes in inlet liquid conditions. Additionally, bubble velocities and frequencies increased with higher liquid and gas flow rates. It was found that measured bubble lengths were in good agreement with the empirical models in the existing literature, but slug lengths were not.

• Korean Chemical Engineering Research
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• 제56권5호
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• pp.761-766
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• 2018

액적-기반 미세유체장치는 물질 합성 및 초고속 대용량 스크리닝 등 다양한 응용분야에서 변형 가능한 새로운 접근법을 이끌어 냈다. 그러나 단일의 액적생성기를 이용한 액적의 생성 속도가 매우 낮기 때문에 이를 상용화 하기 위해서는 생산속도를 높이기 위한 노력이 필요하다. 본 연구는 단일의 유동-집속 생성기를 병렬로 연결하여 단분산성 액적의 생성 속도를 높이는 방법에 관한 것이다. 이러한 액적생성기를 갖는 미세유체장치를 제작하기 위해 본 연구에서는 양면 임프린팅 방법을 이용하여 단층 엘라스토머 조각에3차원의 마이크로 채널을 갖는 3D 모놀리식 탄성중합체 장치(monolithic elastomer device, 3D MED)를 제작 할 수 있다. 이렇게 제작된 8개의 액적생성기가 연결된 3D MED를 이용하여 연속상과 분산상의 유체를 조절하여 단분산성 액적의 형성속도가 향상되었음을 증명하였다. 따라서 본 미세유체시스템을 사용하여 다양한 재료 또는 세포들을 함유하는 단분산성 액적을 형성하여 마이크로입자 제조 및 스크리닝 시스템과 같은 넓은 분야에 활용될 수 있을 것으로 기대된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1534-1539
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• 2004

This experiment has been carried out to measure the process of droplet formation between water phase fluid(PVA 3%) and organic phase fluid(oil) and vector fields measured by a Dynamic Micro-PIV method in the inside of a droplet while generated. Droplet length controlled by changing flow rate conditions in microchannel. Water-in-oil(W/O) droplets successfully generated at a Y junction and cross microchannel. But oil-in-water(O/W) droplets could not be formed at a Y junction microchannel. That is, PVA 3% flow could not be detached from the PDMS surface and ran parallel with oil flow. When PVA 3% flow rate was constant, droplet length and time period decreased as oil flow rate increased, but droplet frequency increased. When PVA 3% and oil flow rate ratio was constant, droplet length and time period decreased as flow rate increased, but droplet frequency increased. All that case, Standard deviation of droplet formation have less than 5% at averaged droplet length and regular-sized droplets were reproducibly formed.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.80-84
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• 2005

Many important properties in colloidal systems are usually determined by surface charge ($\zeta$-potential) of the contacted solid surface. In this study, $\zeta$-potential of glass $\mu$-channel was evaluated from the electro-osmotic velocity distribution. The electro-osmotic velocity inside a glass $\mu$-channel was measured using a micro-PIV velocity field measurement technique. This evaluation method is more simple and easy to approach, compared with the traditional streaming potential technique. The $\zeta$-potential in the glass $\mu$-channel was measured for two different mole NaCl solutions. The effect of an anion surfactant, sodium dodecyl sulphate (SDS), on the electro-osmotic velocity and $\zeta$-potential in the glass surface was also studied. In the range of $0\∼6$mM, the surfactant SDS was added to NaCl solution in four different mole concentrations. As a result, the addition of SDS increases $\zeta$-potential in the surface of the glass $\mu$-channel. The measured $\zeta$-potential was found to vary from-260 to-70mV. When negatively charged particles were used, the flow direction was opposite compared with that of neutral particles. The $\zeta$-potential has a positive sign for the negative particles.

• 센서학회지
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• 제8권4호
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• pp.320-326
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• 1999

센서의 감지막 표면에 흡착되어 있는 이물질을 세척하기 위해 노즐 원리를 도입하여 소형 카트리지를 제작하였다. 세척용 노즐구조는 유동 해석 프로그램(CFD-ACE)의 검증을 통하여 소형 카트리지에 적합하도록 설계하였다. 미세가공기술을 이용하여 제작된 카트리지의 전체 크기는 약 $2.6\;cm{\times}1.5\;cm$이고 세척용 노즐의 크기는 $0.2\;mm{\times}600\;mm$이며, 측정에 필요한 시료의 양은 약 $20\;{\mu}l$이다. REFET과 의사기준전극을 이용한 차동증폭법을 사용하여 기준전극을 소형화하였다. 또한, 미세채널에서 기포로 인한 센서의 오동작을 감지하기 위해 채널 양단에 금속전극을 증착하였다. 제작된 카트리지에 pH-ISFET를 장착하여 노즐에 의한 세척효과를 조사하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1135-1140
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• 2009

The present study has been studied on a thermal and flow characteristic of the microchannel waterblock with pass variations in 8 samples. Results of a numerical analysis using the CFX-11 were compared with results of an experiment. Numerical analysis and experiment were conducted under an input power of 150 W, inlet temperature of $35^{\circ}C$ and mass flow rates of $0.7{\sim}2.0\;kg/min$. The numerical results showed reasonably good agreement with the experimental results within about $3{\sim}5%$. Also, the numerical results showed that the sample 2 types with the 2 pass gave better performance than the sample 1 types with the 1 pass from the viewpoints of heat transfer and pressure drop.

• 한국산업정보학회논문지
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• 제20권3호
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• pp.19-28
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• 2015

스마트폰의 영상정보처리에 기반한 현장 진단기기 개발을 목표로 입자계수용 형광 smartscope와 DC 모터로 제어되는 입자정렬 시스템을 제작하였다. 크기가 작고 저렴한 비용으로 비전문가도 쉽게 다룰 수 있는 smartscope는 LED, 볼렌즈, 형광필터가 설치된 어댑터가 스마트폰 카메라 앞에 장착되어 전용 애플리케이션으로 형광입자와 형광염색된 백혈구를 계수할 수 있었다. 모터는 안드로이드 스마트폰의 블루투스 무선통신 기능을 통해 제어되었다. 나선형 미세유동채널이 축을 중심으로 회전하는 동안 백혈구와 크기가 유사한 입자가 정렬되는 현상을 관찰하였다. 모터로 회전 방향과 속도가 조절되는 입자 정렬 시스템은 많은 시간이 소요되는 수작업을 최소화하고 시료 전처리 과정을 자동화할 수 있으므로, smartscope와 통합될 경우 스마트폰을 이용한 현장진단기기에 활용될 수 있을 것이다.

• 대한기계학회논문집B
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• 제31권4호
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• pp.320-329
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• 2007

Electrokinesis and dielectrophoresis are important transport phenomena produced by external electric field applied to a microchannel containing a conductive fluid. We developed a CFD code to predict electrokinetic and dielectrophoretic flows in a microchannel with a uniform circular post array. Using the code, we calculated particle velocities driven by electrokinesis and dielectrophoresis, and conducted Monte Carlo simulations to visualize the particle motions. The code was validated by comparing the results with those from previous studies in literature. At a low electric field, electrokinesis and diffusion is the dominant transport mechanism. At a moderate electric field, dielectrophoresis is balanced with electrokinesis and diffusion, resulting in flowing filaments of particles in the microchannels. However, dielectrophoresis overwhelms the flow at a high electric field and traps particles locally. These results provide useful insight for optimizing design parameters of a microfluidic chip for biochemical analysis, especially for development of on-chip sample pretreatment techniques using electrokinetic and dielectrophoretic effects.

• 한국가시화정보학회지
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• 제18권3호
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• pp.116-121
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• 2020

In this study, a single-phase analysis of droplet slug with different contact angles was performed based on the visualization of experimental results. Droplet slug - flowing between gases in a hydrophobic mini channel - moves with a triple contact line without a gas liquid film on the wall. The results show that the rotational flow inside the droplet occurred; this was compared and verified with the results of two-phase analysis. The pressure field shows pressure rise at the front and rear ends. The effective length - the section that satisfies the laminar flow condition - became shorter as the droplet velocity increased. The Choi's correlation for the effective length agrees with this analysis results with a slight difference. This difference is judged as the difference in the contact angle of the slug model.