Transition Wave Propagation in Hierarchical Phase-transforming Metamaterials

Mechanical metamaterials comprising coupled, multi-stable elements support the propagation of transition waves (i.e., topological solitons) that, upon passing, transform the local structural geometry from one stable configuration to another. Although structural hierarchy has been explored in the broader metamaterial literature, its affects multi-stable architectures have yet to be investigated in the context of transition wave propagation in phase-transforming metamaterials. In this presentation, we introduce structural hierarchy as an addition design parameter to the phase-transforming metamaterial platform, yielding unique results not found in the relevant literature, which exclusively comprises non-hierarchical systems. We find that the structural hierarchy inhomogeneously alters the energy landscape driving transition wave propagation, leading to direction-dependent propagation, non-circular domains, and a stabilizing affect applicable to domain patterning. Our results contribute to efforts of realized control over transition wave dynamics for potential applications, e.g., in locomotion of soft robotics, mechanical memory, and communication via mechanical waves.