Self‐Powered Frequency‐Selective Acoustic Sensor Based on Bound States in the Continuum

Sound is a clean, renewable, and abundant energy source present ubiquitously in nature. However, it is often underutilized due to its low energy density in most environments. This study introduces a two-state system that supports a Friedrich-Wintgen bound state in the continuum (BIC), achieving an unprecedented enhancement in sound energy density-up to 1849 times the incident sound intensity. By integrating this BIC-supporting system with energy conversion mechanisms, such as piezoelectric films, high-performance acoustic energy harvesting and sensing is realized. As a proof-of-concept, a self-powered acoustic sensor system is developed. This sensor leverages the high-quality-factor nature of a BIC, providing exceptional passive frequency selectivity and the ability to activate a light-emitting diode (LED) at the target frequency of 501 Hz with an offset of only 4 Hz. This work represents a groundbreaking advancement in sound-energy enhancement, paving the way for BIC-induced acoustic harvesters and sensors, with promising applications in wireless sensor networks and the Internet of Things.