A vortex-induction underwater energy harvester based on Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ single crystal macro-fiber composites

Various wireless sensors in the Internet of Things (IoT) systems have been adopted in ocean exploration, with increasing energy supply concern. Regarding the marine environment, self-powered sensors utilizing ambient flow and wave energy can increase maintainability with a long lifespan. However, the current underwater piezoelectric energy harvesters made of piezoelectric ceramics suffer from low power density (<0.5 mW cm−3 m−1 s). In this paper, we proposed a vortex-induction underwater piezoelectric energy harvester based on a Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) single crystal macro-fiber composite (MFC). The single crystal MFC shows mechanical flexibility in which the volume fraction of the piezoelectric phase is 70%. Regarding the structure design, a bicylinder configuration with a ladder-shaped cantilever is employed for decreasing the resonant frequency of the underwater piezoelectric energy harvester and enhancing vortex force during fluid–structure interaction process. The designed underwater energy harvester exhibits a high output voltage of 54 Vpp at 0.9 m/s flow in the designed underwater energy harvesting test platform. Due to the high figure-of-merit d 32 × g 32 (7.65 × 10−11 m2/N) of the single crystal, the maximum output power reaches 62 μW under the flow speed of 0.9 m/s. The normalized power density is 1.1 mW cm−3 m−1 s, being 2.3 times larger than that of the state-of-the-art PZT ceramics-based underwater energy harvester. This work will help to mitigate the energy crisis of the IoT system, promoting the development of underwater equipment.