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, Voc ≈ 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.