Bending and twisting of soft materials by non-homogenous swelling

Soft materials such as biological tissues and gels undergo morphological changes, motion, and instabilities when subjected to external stimuli. We examine how thin elastic plates undergo rapid bending and buckling instabilities after non-homogenous exposure to a favorable solvent that swells the network. An unconstrained beam bends along its length, while a circular disc bends and buckles with multiple curvatures. In the case of a disc, a large-amplitude transverse travelling wave rotates azimuthally around the disc. We provide theoretical interpretations inspired by the complementary thermal expansion problem of transient shape changes triggered by non-homogenous time-dependent heating, which allows collapse of time-dependent swelling data onto universal curves. Control of dynamical, swelling-induced shape changes provides new directions for the utilization of soft materials.