Liquid Dielectric‐Mediated Interfacial Switching Enables Packaging‐Free Triboelectric Nanogenerator for Underwater Energy Harvesting

ABSTRACT The development of triboelectric nanogenerators (TENGs) for underwater applications has been persistently challenged by the fundamental conflict between packaging‐dependent pressure resistance and the need for adaptive, efficient energy conversion in water environments. Here, we propose a liquid dielectric (LD)‐mediated interfacial switching strategy that enables an underwater packaging‐free TENG (UPF‐TENG) based on a movable core–shell structure. By introducing a functional ball impregnated with LD into a shell with deflector holes, dynamic and reversible switching between solid–water and solid‐LD interfaces can be realized, which effectively disrupts the electric double‐layer shielding effect while maintaining intrinsic pressure adaptability. The microscopic mechanism by which LD drives water on solid surfaces was verified through molecular dynamics simulations. Systematic optimization of the LD's properties and the porous carrier matrix ensures efficient and stable charge transfer. The UPF‐TENG exhibits multimodal responsiveness to various flow patterns, which simultaneously enable energy harvesting and flow sensing. Based on the movable core–shell structure with deflector holes designed, the UPF‐TENG may achieve pressure adaptation and operation in the full‐ocean depth environment. This work also establishes a new paradigm for underwater energy harvesting through active liquid‐phase interface control and provides a viable technology for sustainable power solutions in deep‐sea exploration and monitoring systems.