MECHANICAL ANALYSIS OF A DROPLET SPREADING ON THE DISCRETE TEXTURED SURFACES

The spreading of a droplet on a solid surface is of obvious importance in a number of practical situations, such as lubrication and coating.In this paper, droplet spreading behaviors on the surfaces with four discrete textures were studied through numerical simulations and wetting experiments.Mechanical analysis on the movement of triple contact line was conducted from interface mechanics in micro-scale.We also introduce a new parameter, texture wetting factor θ^*, to characterize the influence of texture type on wettability.Results show that the discrete textures on the substrates provide excess contact area between liquid and solid, and the spreading fringe partly penetrates into the space among the textures, which leads to the increase of curvature, and the increase of Laplace pressure in the droplet provides excess driving force and accelerates the liquid as it approaches.Droplet on the grooved surface shows spreading anisotropy.In addition, simulation analysis indicates that the pinning effect of contact line has a close relationship with surface roughness and texture type, the greater the surface roughness, the greater the pinning effect, and the pinning effect on the grooved surface also shows directivity.