Push, snap, pull, and buckle: A material design framework enabled by cooperating active and geometrically nonlinear passive microstructures

Many active materials have properties that make them challenging to design with or limit their utility, including having combinations of nonlinear, viscous, slow, or small responses. In this work, we show that by designing metamaterial unit cells that have separately active and, specifically geometrically nonlinear, passive elements, many of these drawbacks can be mitigated and enhanced performance enabled (specifically, large, rapid, and resettable shape change). This separation between active and passive elements is advantageous, in that the complex active materials can be assigned only where needed, with the simplest geometries and functions. The use of geometric nonlinearity in passive elements is helpful as it provides mechanisms for augmented performance and further simplifies the role of the active elements. While all elements of the microstructural motifs used herein have been previously seen elsewhere, we suggest that the contribution provided here is a conceptual design approach that may be used more broadly for enabling new types of high-performing, stimuli-responsive metamaterials.