PVA‐based Hydrogel Materials for Underwater Energy Storage and Underwater Sensing

Abstract As human exploration of marine continues to expand, the demand for underwater devices is also increasing. The unique properties of hydrogel materials make them well‐suited for underwater applications. We propose a multi‐functional polyvinyl alcohol (PVA) – NaCl @ Polyaniline (PANI) (PNP) hydrogel, which is characterized by easy fabrication, integrated structure, and flexibility, and can be directly applied in the fields of underwater energy storage and underwater sensing. Solid‐state supercapacitors fabricated by the PNP hydrogel, due to integrated and all‐solid‐state design, can be charged and discharged underwater without encapsulation. What's more, the PNP supercapacitor can maintain a capacitance retention rate of over 90 % after 5,000 cycles in simulated seawater, eliminating concerns about the hydrogel's dehydration when used underwater. The PNP hydrogel with an integrated three‐layer structure can also be applied to the capacitive pressure sensors, which can also be directly used in underwater environments without the need for encapsulation, significantly reducing the structural complexity and preparation steps of the device. Finally, we demonstrate a “supercapacitor module” with a voltage window greater than 1.6 V created by directly connecting multiple PNP supercapacitors in series, as well as an underwater intelligent glove, providing new solutions for underwater energy storage and underwater wearable sensing applications.