A Flexible Tough Hydrovoltaic Coating for Wearable Sensing Electronics

Abstract The lack of a strong binding mechanism between nanomaterials severely restricts the advantages of the evaporation‐driven hydrovoltaic effect in wearable sensing electronics. It is a challenging task to observably improve the mechanical toughness and flexibility of hydrovoltaic devices to match the wearable demand without abandoning the nanostructures and surface function. Here, a flexible tough polyacrylonitrile/alumina (PAN/Al₂O₃) hydrovoltaic coating with both good electricity generation (open‐circuit voltage, V_oc ≈ 3.18 V) and sensitive ion sensing (2285 V M⁻¹ for NaCl solutions in 10⁻⁴ to 10⁻³ m) capabilities is developed. The porous nanostructure composed of Al₂O₃ nanoparticles is firmly locked by the strong binding effect of PAN, giving a critical binding force 4 times that of Al₂O₃ film to easily deal with 9.92 m s⁻¹ strong water‐flow impact. Finally, skin‐tight and non‐contact device structures are proposed to achieve wearable multifunctional self‐powered sensing directly using sweat. The flexible tough PAN/Al₂O₃ hydrovoltaic coating breaks through the mechanical brittleness limitation and broadens the applications of the evaporation‐induced hydrovoltaic effect in self‐powered wearable sensing electronics.