Light-Induced Swelling-Responsive Conductive, Adhesive, and Stretchable Wireless Film Hydrogel as Electronic Artificial Skin

Light-induced wireless soft electronic skin hydrogels with excellent mechanical and electronic properties are important for several applications, such as soft robotics and intelligent wearable devices. Precise control of reversible stretchability and capacitive properties depending on intermolecular interaction and surface characteristics remains a challenge. Here, a thin-film hydrogel is designed based on titanium oxide (TiO2) polydopamine-perfluorosilica carbon dot-conjugated chitosan-polyvinyl alcohol-loaded tannic acid with controllable hydrophobic-hydrophilic transition in the presence of UV-vis light irradiation. The shifting of surface wettability from hydrophobic to hydrophilic by irradiation affects thin-film water permeability and swelling ratio. This allows the penetration of water into the matrix to change its mechanical strength, electronic properties, and adhesive behavior. Specifically, the hydrogel displays mechanical strain as high as 278% in response to light stimuli and demonstrates the ability to regain its initial state determining the elasticity of the fabricated material. Moreover, the thin-film hydrogel shows an increase in conductivity to 1.096 x 10(-3) and 1.026 x 10(-3) S cm(-1) when irradiated with UV and visible light, respectively. The hydrogel exhibits capacitive reversibility that follows finger motion which can be identified directly or remotely using wireless connection, indicative of its possible applications as an artificial electronic skin.