Origin of contact line slip on the substrate: A microscopic approach

Abstract

The no-slip condition of the viscous flow theory on the contact line is violated, where an interface between two fluids reaches the solid surface. Despite over a century of the scientific research, slip on the contact line is an issue that is still being debated. In this paper we present a theoretical discussion of the slip origin. The basic assumption is that the mechanism of slippage for liquid and gas on the wall is same. The idea is that, on the contact line, the tangential velocity of liquid molecules after collision with the surface by liquid and gas molecules is not diminished sufficiently, and this provides a way for liquid molecules to slip on the surface. In addition, from contact line toward liquid phase, with the increase in the number of liquid molecules and the collisions, the tangential velocity of the molecules decrease gradually and the no-slip state is dominated.