Pattern formation in hot embossing of thin polymer films

We have investigated pattern formation of thin PMMA films during both hot embossing and demoulding of micro- and nanostructures. During filling of the stamp cavities, compressive and capillary effects were observed, and under certain conditions periodic patterns with characteristic length scales formed. In unstructured stamp regions the form of these patterns is affected by local differences in the pressure. For structured stamps, the self-assembly is strongly influenced by the size and the shape of the stamp cavities. Rapid expansion of trapped air resulted in viscous fingering patterns and a dewetting behaviour of the polymer could be observed.