Creasing-wrinkling transition in elastomer films under electric fields.

Creasing and wrinkling are different types of instabilities on material surfaces characterized by localized singular folds and continuously smooth undulation, respectively. While it is known that electric fields can induce both types of instabilities in elastomer films bonded on substrates, the relation and transition between the field-induced instabilities have not been analyzed or understood. We show that the surface energy, modulus, and thickness of the elastomer determine the types, critical fields, and wavelengths of the instabilities. By independently varying these parameters of elastomers under electric fields, our experiments demonstrate transitions between creases with short wavelengths and wrinkles with long wavelengths. We further develop a unified theoretical model that accounts for both creasing and wrinkling instabilities induced by electric fields and predicts their transitions. The experimental data agree well with the theoretical model.