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

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/H2O/IGZO structure delivers a peak short-circuit current density up to 2.3 mu A cm(-2), a peak open-circuit voltage up to 620 mV, and a power density up to 0.1 mu W 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 x 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.