Flexible Liquid‐Based Continuous Direct‐Current Tribovoltaic Generators Enable Self‐Powered Multi‐Modal Sensing

Abstract

Abstract Flexible tribovoltaic direct‐current (DC) generators are urgently expected by wearable applications. Traditional rigid contact‐separation type tribovoltaic DC generators normally have non‐ignorable friction loss and cannot sustain outstanding outputs. This hinders their serviceability in continuous motion scenarios. Here, flexible liquid‐based DC generators (FLGs) with metal‐liquid‐semiconductor indium gallium zinc oxide (IGZO) stack structures are reported. The FLG with Pt/H 2 O/IGZO structure delivers a peak short‐circuit current density up to 2.3 µA cm −2 , a peak open‐circuit voltage up to 620 mV, and a power density up to 0.1 µW cm −2 . The differences in the properties of different liquid–solid interfaces are studied by density functional theory, showing that the bond formation, charge‐transfer‐induced dipole electric field at the solid‐liquid interface, and the built‐in electric field are responsible for the generation and separation of electron‐hole pairs to form continuous DC. The proposed FLG can keep excellent performance even after >5 × 10 4 shaking cycles or exposing to ambient conditions for 30 days, showing extraordinary stability. Besides charging capacitors or driving LEDs, the FLG is further demonstrated to work for self‐powered multifunctional sensing, enabling pressure, position‐posture, or temperature detections. This design offers potential solutions and novel possibilities for next‐generation self‐powered wearable electronics.