Buckling-Pattern-Based Characterization of Stiff Membrane on Soft Film

Stiff and soft bilayer systems are commonly used in industrial and biological applications. A classical stiff/soft bilayer film is an oxygen-plasma-treated polydimethylsiloxane (PDMS) film. After treatment, the PDMS film surface is oxidized, and then the stiff oxide surface layer and residual soft PDMS layer jointly constitute bilayer films, which are crucial materials in the fields of flexible electronics and buckling behavior studies. However, the oxidized surface layer is not properly recognized because of the complexity of the oxidization transition induced by the oxygen plasma. Here, its atomic composition and ratio are experimentally determined. A calculation approach to calculate its thickness and modulus based on the buckling behaviors of bilayer films is proposed. An accurate modulus of the oxide layer, 34.6 GPa, is obtained. Furthermore, this method can be used to characterize various stiff films in bilayer systems, which shows great potential for applications in many fields.