Topological rainbow trapping and broadband piezoelectric energy harvesting of acoustic waves in gradient phononic crystals with coupled interfaces

Abstract

Topological phononic crystals (PCs) offer an innovative method for manipulating acoustic or elastic waves. In this study, we introduce the gradient PC structures with coupled interfaces, specifically designed to achieve topological rainbow trapping and broadband acoustic energy harvesting. By leveraging the geometric symmetry of PC unit cells, we merge two PCs with distinct topological phases to create coupled topological interfaces. Gradient modulation of structural parameters along the coupled interfaces induces rainbow trapping, where acoustic waves are spatially separated by frequency. The numerical and experimental results indicate that the acoustic waves of various frequencies are halted and magnified at distinct locations within the coupled interfaces. Compared to the bare harvester, the topological PC energy harvester markedly increases output power across a range of excitation frequencies, with a maximum amplification ratio of 91 observed in experiments. Furthermore, the topological rainbow trapping is robust against random structural disorders. The coupled interfaces exhibit broadband and multimodal capabilities, holding potential for various applications including selective filtering and enhanced sensing.