Flow of thin films on patterned surfaces

We present fully nonlinear time-dependent simulations of the gravity driven flow of thin wetting liquid films. The computations of the flow down a homogeneous substrate show that the contact line where liquid, solid, and gas phase meet becomes unstable and develops patterns. These computations are extended to inhomogeneous surfaces, and show that inhomogeneity can induce instability of the fluid front. In particular, we analyze flow on patterned surfaces, where surface inhomogeneity is introduced in a controllable manner. We discuss the conditions that need to be satisfied so that surface patterns, lead to predictable selective wetting of the substrate. Applications of these results to technologically relevant flows are discussed.