Adhesion induced mesoscale instability patterns in thin PDMS-metal bilayers

Abstract

We show that the surface of a thin elastomer-metal (aluminum) hybrid bilayer becomes spontaneously patterned when brought in adhesive contact with a rigid surface. The self-organized surface patterns show three distinct morphological phases—columns, labyrinths, and holes—depending on the area of contact. The characteristic wavelength of these patterns is found to be 2.94±0.20 times the total film thickness, independent of the morphological phase and the surface properties of the contacting surface. Interestingly, the metal films 60–120nm thick showed the same scaling, but the bilayers with thicker metal films were completely stable. This observation demonstrates for the first time a “hard” transition to the instability as the elastic stiffness of the film is varied. We also report a protocol for alignment of the instability patterns and for transferring the metal patterns to another surface.