Autonomous shape-shifting soft structures are common in a wide variety of natural systems and scales: from cellular membranes of embryos, through plant leaves and up to invertebrates. These organisms utilize external energy sources to alter their shape via local plastic deformations, prescribing a dynamical intrinsic geometry. Even though their flexibility and versatility are desired properties in man-made structures, so far only rudimentary examples were fabricated, focusing mostly on uni-axial deformations triggered by external stimuli.

In this work we build a completely autonomous soft-tissue that periodically changes its shape due to intrinsic transport-processes fueled by chemicals from its environment. We use environmentally-sensitive gel with equilibrium volume that is coupled to the Belousov-Zhabotinsty (BZ) chemical reaction. This reaction in a two-dimensional medium generates spatio-temporal patterns, resulting in a sheet whose intrinsic geometry is non-uniform and changes over time. The outcome is a gel that utilizes chemicals in its environment to autonomously change its shape, similarly to biological organisms.

To account for the evolving intrinsic geometry, incompatible elastic models are used, allowing us to study and predict the evolving three-dimensional shape of the gel. The shape and the phase of the BZ-reaction are measured using a stereoscopy apparatus. The experimental results are also compared to numerical elastic solutions.