Modelling pinching dynamics in thin films of binary mixtures

In binary mixtures, the lifetimes of surface bubbles can be five orders of magnitude longer than those in pure liquids because of slightly different compositions of the bulk and the surfaces, leading to a thickness-dependent surface tension of thin films. Taking advantage of the resulting simple surface rheology, we derive the equations describing the thickness, flow velocity and surface tension of a single liquid film, using thermodynamics of ideal solutions and thin film mechanics. Numerical resolution shows that, after a first step of tension equilibration, the Laplace-pressure-driven flow is associated with a flow at the interface driven by an induced Marangoni stress. The resulting parabolic flow with mobile interfaces in the film further leads to its pinching, eventually causing its rupture. Our model paves the way for a better understanding of the rupture dynamics of liquid films of binary mixtures.