Experimental evidence for a large slip effect at a nonwetting fluid-solid interface

It is shown that the, flow of a simple Newtonian liquid near a hard wall can be affected by the chemical nature of this wall. We have studied with a surface force apparatus (SFA) the hydrodynamic force between a sphere and a plane immersed in glycerol. The drainage of the thin film is different on a hydrophobic plane and a hydrophilic one. This effect can be interpreted, when the film is not too thin, by the existence of a slipping velocity at the boundary between the liquid and the hydrophobic solid. The slipping length is about 65 times, the glycerol molecular size.