Self‐Powered Underwater Acoustic Beacon System Enabled by Dual Bluff Body Energy Harvester with Relaxor Ferroelectric Crystals

As a critical device for underwater communication, underwater acoustic beacons face significant technical challenges in energy supply and signal transmission. In this study, a self‐powered underwater acoustic beacon system is developed. In the self‐powered module, a piezoelectric energy harvester (PEH) with a dual bluff body variable‐stiffness cantilever structure is introduced. It is based on Pb(In 1/2 Nb 1/2 )O 3 −Pb(Mg 1/3 Nb 2/3 )O 3 −PbTiO 3 (PIN‐PMN‐PT) relaxor ferroelectric crystal with high piezoelectric coefficient ( d 33 ≈2082 pC N −1 ). By enhancing vortex‐induced forces via the Karman vortex street effect, it achieves 117.8 V PP output voltage and 11.52 mW cm − 3 power density at a flow velocity of 1 m s −1 . These values are more than 10 times higher than traditional cantilever designs (≈10 V PP and 1 mW cm − 3 ). In the underwater acoustic beacon module, a PIN‐PMN‐PT‐based underwater acoustic transducer is designed. It leverages the high piezoelectric performance of the single crystal, along with optimized matching layers and circuit design. Compared to ceramic counterparts, it achieves a 2.58–10.81 dB higher transmitting voltage response and a 4.68–12.51 dB higher receiving voltage sensitivity, while its −6 dB bandwidth is expanded by 2–8 kHz. Experimental sea trials validate its efficient energy harvesting and long‐term operation, offering a maintenance‐free solution for long‐distance underwater communication.