Slip between a liquid and a solid: D.M. Tolstoi's (1952) theory reconsidered

Abstract Tolstoi's molecular-kinetic theory of slip between a liquid and a solid is reviewed and extended to take account of liquid adsorption at the solid surface. The theory links slip with wettability and predicts that slip will occur only with poorly wetting liquids, i.e., those for which the equilibrium contact angle, θ0, is greater than zero. This prediction appears to be borne out by experiment, but the magnitude of the effect remains uncertain. The new analysis shows that for liquids that completely wet the solid (θ0= 0) and are strongly adsorbed, the theoretical “no-slip” plane will lie in the liquid. Recent experiments suggest that the distance between the no-slip plane and the solid surface may be no more than a molecular diameter. In the absence of precise experimental data such as this, the choice of the hydrodynamic interface is arbitrary and becomes fixed only by convention.