(540h) Stretch-Activated Reprogrammable Shape-Morphing Composite Elastomers

Shape-morphing behaviors are widely found in the natural world, and biomimetic artificial shape-morphing devices have facilitated the construction of intelligent systems. In this work, we report a new class of shape-morphing elastomer activated by simple stretch-and-release, beyond the common sense that a stretched elastomer should recover its original shape after releasing the applied force. A simple binary-component material system of an elastomer network and a crystallizable small molecule is designed to realize our vision, requiring no complicated chemistries. The geometrically heterogeneous mechanical responses in a flat ordinary elastomer film can be repeatedly regulated by spatially patterning a crystallizable small molecule (paraffin in this work). Upon stretch-and-release, the recovery of the elastic network in the paraffin-rich region would be hindered by the jamming of broken hard paraffin pieces and hence residual strains should occur. Local elasticity-plasticity mismatches lead to plentiful flat-to-3D shape-morphing from basic configurations like bend, Gaussian curvature change, and origami to their complex combinations. We further demonstrate that combining the diffusion model and mechanics model provides good theoretical prediction of the stretch-activated behaviors. Furthermore, due to the physical nature of our process, the shape-morphing is reversible, reprogrammable.