Deep-sea self-powered system based on pressure-adaptive balloon triboelectric nanogenerator.

Triboelectric nanogenerators (TENGs), which operate independently of sunlight or fuel, can effectively harvest deep-sea mechanical energy (such as ocean currents and fluctuations) to power long-term low-energy electronic devices, forming self-powered systems. However, structural design for deep-sea equipment remains a significant challenge due to extreme depth and pressure conditions. Here, we demonstrate that a simple balloon structure can meet the corresponding design requirements in a low-cost manner. Through the expansion and contraction of the balloon in response to pressure variations, the nanogenerator integrated on the inner surface of the balloon achieves contact-separation motion. Quasi-hydrostatic pressure introduces no additional shear stress, and the normal stresses cancel each other out, enabling the thin-walled balloon to withstand immense water pressure. By presetting the gas volume, the operating depth of the device can be tuned, while reducing buoyancy-induced restraint requirements, thereby enhancing deployment stability. The excellent airtightness of the balloon ensures that humidity does not interfere with TENG operation. The device has been demonstrated to effectively harvest energy over short-term tests. This study provides a proof-of-concept validation of a pressure-adaptive balloon TENG for underwater energy harvesting at moderate pressures. Finite element simulations suggest the potential scalability of this design to greater depths, contributing to the advancement of TENGs for extreme marine environments.