Elastocapillary Crease

A material under compression often forms creases. When the material is elastic and soft, the nucleation of creases depends on both elasticity and capillarity. Here we introduce a model of elastocapillary creases. The model assumes that the surface tension remains constant on the free surface, but may change upon self-contact. In particular, surface tension vanishes upon self-contact for a pristine surface of elastomers and gels. The model predicts that the nucleation of creases depends on the sizes of surface defects relative to the elastocapillary length, and happens over a well-defined range of strains, instead of a specific strain. The loss of surface tension upon self-contact lowers the energy barrier for nucleation, and widens the range of nucleation strains for materials of any thickness relative to the elastocapillary length. We test this model by conducting experiments with materials of various elastocapillary lengths, along with the data available in the literature.