Programmable metastructures featuring adaptable stiffness based on local bistability

We present a novel class of programmable structures displaying large stiffness adaptability from local changes of shape. We connect a series of locally bistable semi-spherical shells (domes) within structural element geometries to create highly programmable properties. We demonstrate the property programmability by manufacturing and testing the dome patterned metasheets and beam-like metastructures, the properties of which are adapted by changing the local state of individual domes. We present bending and in-plane stiffness curves characterizing the global response as a function of the local unit cell states. Our results reveal extreme adaptability of properties ranging from high stiffness to high compliance as a result of the local changes of stable states. The properties of the metastructures depend on the local bistable state adopted by the domes and the global connectivity of the metastructures, thus departing from constraints imposed by specific constitute material choice for obtaining adaptability. We demonstrate the applicability of these metastructures in compliant/soft robotics particularly to enable stiffening without compromising on shape reconfiguration, all while using a simplified single input control to shift between stable states.