Bistable Multi-Layer Triboelectric Nanogenerator for Harvesting Random and Ultra-Low-Frequency Vibration Energy with Increased Charge Transfer.

Approximately 70% of the Earth's surface is covered by seawater, making the ocean ideal for harvesting energy. Triboelectric nanogenerators (TENGs), due to their low cost and simple structure, are well-suited for capturing ocean energy. However, their low charge transfer under weak inputs limits efficiency in harvesting random and ultra-low-frequency wave energy. This paper proposes a novel bistable multi-layer TENG (BM-TENG) to address this challenge for self-powered wireless sensing and lighting. Simulations and experiments demonstrate that both in intra-well and inter-well motions, the bistable mechanism enhances the dynamic responses and thus the power output by up to 48%. Furthermore, the multi-layer design within the constrained structure significantly boosts the power density. Experimental results show 730 V peak-to-peak open-circuit voltage and 5 mW maximum power in a three-layer BM-TENG under the excitation of 0.6 Hz and 0.18 g. The normalized power density of the proposed device is 54.9 Wm·Hz, surpassing the state-of-the-art results in literature. The application test shows that BM-TENG can successfully power 296 LEDs for ocean warning lighting, and power Bluetooth wireless sensors for monitoring marine environmental variables. This work introduces a novel and highly efficient self-powered sensing technique for advancements in marine Internet of Things (IoT) systems.