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_1/2Nb_1/2)O₃−Pb(Mg_1/3Nb_2/3)O₃−PbTiO₃ (PIN-PMN-PT) relaxor ferroelectric crystal with high piezoelectric coefficient (d₃₃≈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.