Self-organized microstructures in thin bilayers on chemically patterned substrates

Abstract

A long-wave nonlinear analysis of the instabilities engendered by van der Waals forces in a thin (<100 nm) viscous bilayer resting on a chemically heterogeneous patterned substrate is presented. Dewetting behavior of thin bilayers is correlated to the macroscopic wetting properties of the two fluids. The chemical potential gradients created by the microdomains of differing wettability can lead to a variety of ordered patterns in an unstable dewetting bilayer. For example, periodic stripes and checkerboard chemical patterns can engender interesting ordered morphologies such as arrays of open or closed channels, membranes with ordered porosity, and embedded or encapsulated microdroplets. We also show that thin bilayers can also be used as a tool for (i) transfer or replication of ordered patterns from the interface of the buried lower layer to the more accessible free surface of the upper layer and (ii) generation of micromolds for patterning applications.