Reprogrammable flexible mechanical metamaterials

Mechanical metamaterials are artificial structures with structure-dependent properties. They often harness zero-energy deformation modes. We address this limitation using a flexible material, called light-responsive shape-memory polydimethylsiloxane (SM-PDMS), to introduce reprogrammability into flexible mechanical metamaterials. Assisted by the crystal-amorphous transition of the shape-memory (SM) polymer, we designed three different flexible metamaterials with distinctive deformation modes: auxetic SM-PDMS, chiral SM-PDMS, and buckling-induced SM-PDMS. Their deformation modes can be reprogrammed into inverse responses through local light stimulations: from expansion to shrinkage, clockwise twist to counterclockwise, and clockwise rotation to counterclockwise, respectively. Finally, we demonstrated the application of harnessing buckling-induced SM-PDMS to make a soft actuator with a reprogrammable preferred locomotion direction. Although we focus on reprogramming flexible metamaterials using the light-induced SM effect, our strategy can be easily extended to other structures and smart materials. Furthermore, our designed flexible metamaterials have the potential for different applications, such as soft robots, actuation, adaptive safety, and sports equipment.