Gravity induced crease-to-wrinkle transition in soft materials

Creasing and wrinkling instability are two distinct surface instability modes characterized by localized singular folds and continuous smooth undulations, respectively. In this article, we show that the surface of a soft elastomer may develop wrinkles or creases under compression and the action of gravitational force, depending on the magnitude of gravitational force. Using linear perturbation analysis and numerical calculations, we establish a phase map with respective creasing domain, wrinkling domain and the domain of homogenous deformation.When the gravitational force is small, the surface of the elastomer forms creases when the compressive strain is beyond a critical value, while the surface of the elastomer forms wrinkles under compression when the gravitation force is large.