Meso-patterning of thin polymer films by controlled dewetting: from nano-droplet arrays to membranes.

Controlled dewetting of thin polymer films on physically heterogeneous substrates is employed as a new soft lithography route to obtain various types of ordered meso-scale structures, including nano-membranes and ordered arrays of nano-droplets. Dewetting of a thin polymer film on a defect free homogeneous surface occurs by a randomly placed collection of holes and droplets with a well-defined spacing. In contrast, on a physically patterned surface, strong influence of the underlying pattern is observed on the dewetting pathways as well as on the ordering and size of the resulting meso-scale structures. The imposed periodicity of the substrate pattern vis-à-vis the spinodal length scale of dewetting provides a powerful tool for the morphology and size control. The thickness of the film and the kinetics of dewetting are the other important parameters that govern the morphology of the resulting structures.