• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.325-335
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• 2014

원자 힘 현미경 (Atomic Force Microscopy, AFM) 탐침과 표면 사이의 좁은 공간에서 형성되는 나노미터 크기의 메니스커스는 AFM으로 측정하는 표면 이미지에 영향을 주는 것으로 알려져 있다. 본 연구에서는 격자 기체 기반의 몬테카를로 방법을 이용하여 계의 상대습도 변화에 따른 시스템의 크기와 표면의 곡률이 메니스커스의 모양 및 이로 인해 발생하는 모세관 힘에 미치는 영향을 알아 보았다. 일반적으로 시스템의 크기가 작을수록, 표면의 곡률이 클수록 (표면이 거칠수록), 메니스커스 폭은 좁아지고 모세관 힘이 줄어드는 것을 확인 하였다.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.167-177
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• 2013

원자 힘 현미경(Atomic Force Microscopy, AFM) 탐침과 표면 사이의 좁은 틈에서 형성되는 나노미터 크기의 물 메니스커스는 AFM을 사용하여 측정하는 이미지에 영향을 주는 것으로 알려져 있다. 본 연구에서는 격자 기체 기반의 몬테카를로 시뮬레이션을 이용하여 탐침의 곡률과 결합 에너지 특성이 메니스커스의 형상과 그로 인해 발생하는 모세관 힘에 어떠한 영향을 미치는지 알아보았다. 일반적으로 탐침의 곡률이 커질수록, 친수성이 작아질수록 메니스커스 폭은 좁아지고 모세관 힘이 줄어드는 것을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.823-829
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• 2014

In the present study, simple models were proposed to predict the capillary-driven flow length in a surfactant-added poly(dimethylsiloxane) (PDMS) rectangular microchannel. Owing to the hydrophobic nature of PDMS, it is difficult to transport water in a conventional PDMS microchannel by means of the capillary force alone. To overcome this problem, microchannels with a hydrophilic surface were fabricated using surfactant-added PDMS. By measuring the contact angle change on the surfactant-added PDMS surface, the behavior was investigated to establish a simple model. In order to predict the filling length induced by the capillary force, the Washburn equation was modified in the present study. From the investigation, it was found that the initial rate-of-change of the contact angle affected the filling length. Simple models were developed for three representative cases, and these can be useful tools in designing microfluidic manufacturing techniques including MIcroMolding In Capillaries (MIMIC).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.47-54
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• 2012

We developed a novel method of fluidic self-assembly to replace the conventional pick-and-place method. This method is cheaper and more effective than the previous method. For this research, we compared mathematical models with experimental results using the parameters of the drag force, the capillary force, and the restoring force for effective chip assembly, and the results for the alignment to the substrate. We obtained a 96.5% attach rate and $5^{\circ}$-misalignment to the substrate in a 500 ${\mu}m$ solder ball.

• 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.

• Journal for History of Mathematics
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• v.21 no.3
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• pp.1-30
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• 2008

The success of Newton's Gravitational Theory has influenced the theory of capillarity, beginning in the early nineteenth century, by providing a major model of molecular attraction. He used the equation of the attraction of spheroids, which is expressed by second order partial differential equations, to utilize this analogy as the same kind of a particle's force, between gravitational, refractive force of light, and capillarity. The solution of the differential equation corresponds to the geometrical figure of the vessel and the contact angle which is made by the fluid. Unknown abstract functions $\varphi(f)$ represent interaction forces between molecules, giving their potential functions. By conducting several kinds of experimental conditions, it was found that the height of the ascending fluid in the tube is inversely proportional to the rayon of the tube or the distance of the plate. This model is an essential element in the theory of capillarity. Laplace has brought Newtonian mechanics to completion, which relates to the standard model of gravitational theory. Laplace-Young's equation of capillarity is applicable to minimal surfaces in mathematics, to surface tensional phenomena in physics, and to soap bubble experiments.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06d
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• pp.9-12
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• 1998

공기경계층을 갖는 유리평판에서 힘의 크기가 10N이고 상승시간이 약 280ns 인 경사 점하중이 인가된 경우에 대하여 진앙점에서 입자 변위와 입자 속도를 계산하였다. 이론적으로 계산된 수직성분이 입자속도가 PZT변환자에 입사한다고 가정하여 PZT 변환자의 과도 응답특성을 Mason 등가회로와 격자점을 이용하여 계산하였다. 유리모세관의 파과시에 방출괴는 과도탄성파를 이용하여 유리평판의 진앙점에서 PZT 변환기의 응답을 조사하였고, 이론과 비교한 결과 상당히 일치하였다. 이를 이용하여 음향방출 시스템인 발생원, 전파매질, 변환자 및 신호분석시스템을 수학적으로 모형화할 수 있는 기초를 마련하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.465-466
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• 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.

• Journal of Conservation Science
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• v.23
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• pp.1-10
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• 2008

Consolidants based on tetraethoxysilane (TEOS) such as alkoxysilanes have been widely used for the consolidation of decaying stone heritages. Low-viscosity alkoxysilanes penetrate inside the decaying stone and polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the material. However, TEOS-based consolidants suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developed capillary force, which is typical for TEOS-based consolidants. We prepared new consolidants TEOS-based consolidants containing flexible (3-glycidoxypropyl)trimethoxysilane (GPTMS) and silica nanoparticles (or polyhedral oligomeric silsesquioxanes (POSS)) in order to reduce capillary force development during gel drying. Since the consolidants should have a good interaction with the component of the stone in order to connect the isolate grains of decaying stone, the adhesion interaction of the developed consolidants on the surface of the granite was macroscopically investigated by the ISO 2409 cross cutting test. The adhesion interaction decreased with the addition of silica nanoparticle and POSS while it increased with the addition of GPTMS in TEOS solution.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.1-11
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• 2002

A mathematical model is proposed to analyze the force; acting on the hard contact lens fitted on the cornea. The model incorporates the nonlinear equations and their numerical solution program, based on the formulations of surface tension force arising from the capillary action in the tear-film layer between the lens and cornea. The model simulates how the adhesion between lens and cornea varies according to the base curves and diameters of the lenses. When the spherical lens is fitted on the spherical cornea it is to rotate downward due to the weight of lens itself until it reaches an equilibrium position along the cornea where the counter(upward) moment caused by net force between the upper and lower portion of the periphery of lens. It is found that both the adhesion and displacement of lens along the cornea, where the gravity of lens balances the capillary-induced upward force, increases rapidly as the base curve of lens increases, i.e., as the lens gets flatter, while the increase in the diameter of lenses has resulted in the less increase in the rotation and adhesion. With the base curve and diameters of lenses being remained constant the increase in surface tension of tear film yields the increase in the adhesion between the cornea and lens while the initial rotation of lens is inversely proportional to the surface tension of the tear film.