Terraced spreading of nanofilms under a nonmonotonic disjoining pressure

Abstract

A thin (∼nanometer) film of a viscous, essentially nonvolatile liquid spreads over a substrate controlled by the disjoining pressure Π(h) exerted by the two interfaces on one another. Such films are commonly used as hard disk lubricants in the magnetic recording industry. Macroscopic nonuniformities in the film caused by a perturbation of the uniformly spread state flow away and the film is "healed" in a time frame governed by the appropriate hydrodynamic equations. Lubrication theory may be used to derive a diffusion equation for the local film height h(x,t) as a function of position and time which shows that an effective height-dependent diffusion coefficient D(h)=-[h3/3μBξ(h)][dΠ(h)/dh] c..