A Flexible Tough Hydrovoltaic Coating for Wearable Sensing Electronics

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/Al₂ O₃ ) 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 Al₂ O₃ nanoparticles is firmly locked by the strong binding effect of PAN, giving a critical binding force 4 times that of Al₂ O₃ 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/Al₂ O₃ hydrovoltaic coating breaks through the mechanical brittleness limitation and broadens the applications of the evaporation-induced hydrovoltaic effect in self-powered wearable sensing electronics.