Mesoscopic Dynamics of Fluid in the vicinity of Moving Solid-Liquid-Gas Boundary Line (Contact Line)

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A series of study were carried out with a special interest on the dynamics of the fluid in the vicinity of the boundary line of three phases; solid-liquid-gas interface. A spreading droplet on a solid substrate is accompanied with the movement of a visible boundary line so-called 'macroscopic contact line.' Existing studies have indicated there exits a thin liquid film known as 'precursor film' ahead of the macroscopic contact line of the droplet. The present authors focused on the early stage of spreading and dedicated their special effort to detect the advancing edge of the precursor film by applying an interferometer with a high-speed camera and by noise cancellation of using time-frequency analysis of brightness variation. The authors estimated the precursor film length for comparison with theoretical predictions, and also investigated the effect of changing viscosity on the precursor film by using the present method of detection. In addition, wetting/dewetting process was investigated on a microscopic point of view; a numerical simulation by classical molecular dynamics was conducted to evaluate an instability arosen on a nanometer-scale liquid culumn. The target geometries were (1) liquid column on a sold surface and (2) liquid column wrapping a thin wire. The authors focused on Rayleigh-Plateau-like instabilityemerging on the liquid column in the deformation process.