Film stratification in the presence of colloidal particles

This is probably the first study about the drainage of curved liquid films in the presence of colloidal particles. The systems did not contain any sur factant. In the presence of monodispersed colloidal particles, thinning occ urs in a stepwise manner (stratification). It has been shown that the size of the film is an important parameter in the stepwise thinning process. Thi s investigation found a critical film size below which at least one layer o f particles stays in the film at equilibrium; a "spot" ia thinner section o f the film), even if formed, does not expand and is in equilibrium with the film. The area of the spot expands linearly with time. The rate of spot-ar ea expansion increases linearly with the film perimeter and can be increase d or decreased merely by changing the film size. The stepwise film thinning and the effects of film size and particle concentration on film stability are discussed on the basis of the diffusive-osmotic mechanism.