Topology Optimization of Wide‐Frequency Tunable Phononic Crystal Resonators with a Reconstructable Point Defect

Abstract Phononic crystal (PnC) resonators and their dynamic regulation of wave transmission hold significant practical importance in the field of acoustic energy harvesting. However, the majority of existing PnC resonators are typically designed and manufactured for fixed frequencies and limited functionalities. Once these resonators are manufactured, achieving tunable characteristics becomes challenging. To address the challenge, this study presents a topology optimization strategy based on an efficient point defect diagonally movement reconstruction mechanism. For achieving the broadest tunable range for various resonators, the proposed strategy involves the use of gradient‐free topology optimization algorithm to successively design surrounding unit cells and point defects of the resonator, leading to the successful realization of tunable resonators with customized functions. Optimization results from several examples demonstrate a tunable defect‐band frequency range that covers almost the entire bandgap. Furthermore, this study explores the relationship between the resonant frequency and the diagonal moving distance of reconstruction mechanism. Both numerical simulations and experimental tests demonstrate the effectiveness of the proposed design strategy in creating PnC resonators with wide‐frequency tunable characteristics. It achieves real‐time automated movement of resonance frequency in response to changes in external sound sources, offering a novel approach for designing tunable energy harvesters within the engineering domain.