• 한국세라믹학회지
• /
• 제44권8호
• /
• pp.424-429
• /
• 2007

Novel conductive $CO_2$ membranes composed of dual phases, molten carbonates and electronic conducting ceramics, were investigated. As the microstructure control of electronic conducting ceramic supports is extremely important to keep the molten carbonates stable in the membranes by a capillary force applied by the pore structure of the supports, we have scrutinized the microstructure of the electronic conducting supports utilizing microscopic images and gas permeability measurement. From the evaluation of the electrical conductivities of the molten carbonates and the electronic conducting ceramic supports, we found that the ionic conductivity of the molten carbonates could determine $CO_2$ flux through the dual phase membranes if the surface exchange rate were relatively high enough.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.160-161
• /
• 2003

Thermocapillary convection is a surface tension driven flow due to a temperature gradient along an interface. It occurs during a crystal-growth process and therefore understanding the convection is important to material processing in microgravity. Although modelling of the float-zone crystal-growth process has been of interest for a few decades, most studies of liquid bridges assumed non-deformable flat surfaces. In reality, the surface profile, g(t,z), is unknown and should be obtained as a solution to the coupled transport equations along with the surface force balance. Here we report on a numerical study of axisymmetric thermocapillary convection in liquid bridges with deformable surfaces. The interface is determined as part of the complete solution. The influence of the capillary number (Ca), Reynolds number (Re), Prandtl number (Pr) and aspect ratio(Ar) on the dynamics is explored.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.118-120
• /
• 2003

The behavior of viscous fingerings caused by an external force is investigated by using a two­phase lattice Boltzmann method. The effects of the modified capillary number, the viscosity contrast, and the modified Darcy-Rayleigh number on the instability of interfaces are found. The calculated wave numbers are in good agreement with the theoretical ones in the range of wave numbers smaller than 10, but the calculated ones tend to become smaller than the theoretical ones in higher wave numbers.

• International Journal of Precision Engineering and Manufacturing
• /
• 제9권3호
• /
• pp.13-17
• /
• 2008

This paper deals with the directional mobility of droplets on structured surfaces. Structured surfaces were micro-patterned with rectangular lines and spaces of varying pitch and height in the sub-millimeter range. The material used was polydimethylsiloxane, which is hydrophobic and wettable by oil. First, we studied the effect of the structural design on the sliding angle of pure water or oil through experiments. For pure water droplets, we found that a wider pitch enhanced the directionality. On the other hand, oil droplets spread along the groove because of their low surface tension and strong capillary force. The directionality of the sliding angle of oil droplets was larger than that of pure water, especially when the groove was narrower and deeper. Second, we poured a large amount of liquid on the structure and evaluated the removal rate on the tilted surface. We found that a parallel structure enhanced the liquid mobility for both pure water and oil.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.589-592
• /
• 2008

For the system of a droplet on an insulator-coated electrode, the Lippmann-Young equation is derived by considering the deformation of interface near the three-phase contact line. The equation governing the deformation of interface, which describes the local balance of the Maxwell stress and the capillary pressure, is integrated along the interface. The integration leads to the Lippmann-Young equation which is shown to represent the macroscopic balance of horizontal force acting on entire meniscus. Young's angle is assumed to be not affected by the Maxwell stress. The meaning and validity of the assumption are discussed.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2006년도 춘계학술대회 논문집
• /
• pp.465-466
• /
• 2006

A single-wall carbon nanotube (SWCNT) has been studied as a material of Nano-Eletro-Mechanical-System (NEMS) device together with various nanowires. In order for oscillation of a multi-wall carbon nanotube (MWCNT) or a single-walled carbon nanotube (SWCNT) on plane surface, it needs suspension of a CNT across trench electrodes. So we propose fabrication method of a MWCNT resonator using dielectrophoresis and show successful results of suspeneded MWNT. Thin electrodes with large gaps could not suspend small diameter MWNT but thicker electrodes could. Thin MWNT could be suspended only when the electrode gap was reduced.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.922-929
• /
• 2006

In this study, flow characteristics of the FPN (Fountain Pen Nano-Lithography) using active membrane pumping are investigated. This FPN has integrated chamber, micro channel, and high capacity reservoir for continuous ink feed. The most important aspect in this probe provided control of fluid injection using active membrane pumping in chamber. The flow rates in channel by capillary force are theoretically analyzed, including the control of mass flow rates by deflection of membrane. The above results are compared with numerical simulations that calculated by commercial code, FLUENT. The velocity of fluid in micro channel shows linear behaviors. And the mass flows are proportional to the second order function of pumping pressure that is imposed to membrane.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권10호
• /
• pp.449-452
• /
• 2005

We fabricated an electrochemical detector (ECD) to catalyze redox reaction efficiently by electrodepositing Prussian blue (PB) on the indium tin oxide (ITO) electrode. Capillary electrophoresis (CE) and amperometric method were used. We investigated the PB surface properties by topography from atomic force microscopy (AFM). Also PB film thickness calibration with respect to deposition time and voltage was used to get better PB surFace. The PB thin film of dense and smooth surface could catalyze redox reaction efficiently. Comparing with CE-ECD microchip using bare-lTO electrode, proposed CE-ECD microchip using PB deposited electrode has shown better sensitivity by determining the detected peak current from the electropherograms while the concentration of tested analyzes was maintained the same. It is verified that detection limit can be lowered for 0.01 mM of dopamine and catechol respectively.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
• /
• pp.45-48
• /
• 2007

기존에 사용되는 피에조 타입의 센서는 추력의 측정 범위가 제한되어 있으므로 이를 개선하고자 레이져 변위측정기와 cantilever를 이용하여 변위 측정 장치를 개선하였고, 스테인레스 캐필러리를 이용하여 추력 모델을 만든 후 추력을 측정하였다. 이와 더불어 extrude shape의 노즐을 갖는 마이크로 추력 장치를 PMMA(Polymethyl methacrylate)를 이용하여 공정하였으며, 매니스커스의 형상 변화를 관찰하였다.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제14권2호
• /
• pp.66-75
• /
• 2006

The effect of antifreeze solution liquid film on the frost prevention is experimentally investigated. It is desirable that the antifreeze solution spreads widely on the heat exchanger surface forming thin liquid film to prevent frost nucleation while having small thermal resistance across the film. A porous layer coating technique is adopted to improve the wettability of the antifreeze solution on a parallel plate heat exchanger. The antifreeze solution spreads widely on the heat exchanger surface with $100{\mu}m$ thickness by the capillary force resulted from the porous structure. It is observed that the antifreeze solution liquid film prevents a parallel plate heat exchanger from frosting. The reductions of heat and mass transfer rate caused by the thin liquid film are only $1{\sim}2%$ compared with those for non-liquid film surface.