Dynamics of ultra-thin two-layer films

The development of instabilities under the joint action of the Van der Waals forces and Marangoni stresses in a two-layer film on a heated or cooled substrate, is considered. The problem is solved by means of a linear stability theory and nonlinear simulations. Nontrivial change of the droplet shape in the presence of the Marangoni effect, which manifests itself as the deformation of a “plateau” into an “inkpot”, is observed. The appearance of the threshold oscillations predicted by the linear stability theory is confirmed by nonlinear simulations. In the case of a lateral heating, the film instability leads typically to formation of droplets which are driven by the thermocapillary flow and coalesce in an anisotropic way.