Manipulating energy flows in non-periodic mechanical metamaterials

Energy focusing, mechanical signal processing, cloaking and guiding of nonlinear elastic waves are all examples of complex dynamic tasks requiring effective control of the energy flow in a material domain. As no single periodic architecture can perform such tasks, a rational way to efficiently navigate non-periodic design spaces is necessary to discover optimal material structures. In the context of mechanical metamaterials, we present a design framework for the automated discovery of non-periodic architectures that are optimized for a single task as well as multiple concurrent tasks. Specifically, we show how dynamic material responses can be effectively tailored to achieve energy focusing, energy routing along arbitrary paths, dynamic protection, and shock absorption. The design framework is based on an inverse design approach powered by automatic differentiation of the forward solution to the nonlinear dynamical system. The versatility of the method paves the way for the development of metamaterial-based soft robotic systems endowed with energy harvesting and signal processing capabilities.