Molecular Dynamics Simulation of Micro-Droplet Motion on Solid Surface Induced by Temperature Gradient

Abstract

Motion of a nanoscale droplet on a solid wall with temperature gradient was numerically simulated by using the molecular dynamics method. The platinum (Pt) solid wall (fcc with surface of (1 1 1)) was composed, and the argon (Ar) droplet was formed on it. The number of Ar molecule was 1000, 2000, and 4000. The number of Pt atom was 8000 or 16000 for the semi-cylindrical droplet, and 32000 or 72000 for the hemispherical droplet. The mean wall temperature was 90 K, and the maximum temperature gradient was 2×109K/m. On the isothermal wall, the droplet stayed around the initial location with some fluctuation. When the temperature gradient was applied to the wall, the droplet clearly moved toward the lower temperature side. In the hemispherical droplet case, the velocity was larger for the stronger fluid-solid interaction case, that is, the higher wettability and the lower contact angle case. On the other hand, the semi-cylindrical droplet case did not show a definite tendency in the effect of the fluid-solid interaction intensity on the velocity. Within the present computational conditions, the imposition of the temperature gradient did not make a distinct difference in the profile of the time-averaged interaction force exerted on the fluid molecules by the solid molecules, when compared between low and high temperature sides.