Acoustic energy harvesting based on Friedrich–Wintgen bound state in the continuum with bridged near-field coupling

In this work, we have designed and fabricated a symmetry-protected acoustic bound state in the continuum (QBIC) metamaterial that allows for simple modulation, with its operating frequency precisely controlled through the coupling coefficient κ. Due to the extremely high Q factor of QBIC, propagating waves can be converted into bound states, allowing for efficient localization of acoustic waves and energy harvesting. Subsequently, a piezoelectric composite sheet (PCS) is placed in the antenna region for acoustic energy collection. Numerical simulations and experimental results confirm that the sound pressure is amplified by 12 times compared to the incident wave, and the output power of a single PCS is increased by 50 times. Our work provides a simple and efficient energy-harvesting method with low directional requirements for the incident waves, demonstrating strong potential for practical applications.