RUPTURE OF THIN LIQUID FILMS DUE TO SPONTANEOUS FLUCTUATIONS IN THICKNESS

The surfaces of thin liquid films are slightly corrugated because of thermal fluctuations. These corrugations show up in the light scattered by these films. It can be shown that corrugations having wavelengths larger than a critical wavelength will grow spontaneously, because of the action of van der Waals forces, and will cause the film to become rapidly thinner and break (or be stabilized as a black film, if sufficiently strong repulsive forces keep the two faces of the film separated). The critical wavelength ⋀crit = [-2π2γ/(d2G/dh2)]1/2, in which γ is the surface tension, G the Gibbs energy of interaction among the molecules per unit area of the film, and h the thickness of the film. The rate at which fluctuations above the critical wavelength grow depends on the viscosity of the liquid, and it can be shown that the combination of regular drainage and spontaneous growth of fluctuations leads to a critical thickness and a lifetime for the film of the same order as those found in experiments. © 1968, American Chemical Society. All rights reserved.