Contact instability in adhesion and debonding of thin elastic films

Based on experiments and 3D simulations, we show that a soft elastic film during adhesion and debonding from a rigid flat surface undergoes morphological transitions to pillars, labyrinths, and cavities, all of which have the same lateral pattern length scale, lambda close to lambda/H similar to 3 for thick films, H > 1 mu m. The linear stability analysis and experiments show a new thin film regime where lambda/H approximate to 3 + 2 pi(lambda/3 mu H)(1/4) (gamma is surface tension, mu is shear modulus) because of a significant surface energy penalty (for example, lambda/H approximate to 6 for H = 200 nm; mu = 1 MPa).