Mineralized Soft and Elastic Polymer Dot Hydrogel for a Flexible Self-Powered Electronic Skin Sensor

We propose an integrated, self-powered, flexible electronic skin device containing an alginate-derived polymer dot (A-PD)-incorporated mineralized hydrogel-based energy storage unit and a chitosan-derived n-type carbon dot (N-CD)-based solar cell for an energy-harvesting unit. This study demonstrates a unique architecture of mineralized hydrogel comprising A-PD-incorporated poly(acrylic acid) (PAA)/CaCO₃/laponite containing soft and sensitive layers, deposited with a polyaniline electrode to serve as an energy storage unit. The self-assembly was achieved through the ionic cross-linking between A-PD and PAA driven by the mineralization process, resulting in excellent dimensional stability and improved mechanical properties of the hydrogel. The sp² carbon-rich A-PD enhances the electrochemical performance and the overall photon-to-electrical conversion and storage efficiency for self-powered devices by the formation of the bridge of electrons between the ionized polymer and metal ion. The capacitive sensor developed in this study exhibits high sensitivity in detecting small pressure changes, such as the falling of small water droplets. The self-powered sensing device can detect and monitor various human motions continuously by harvesting light energy from outdoor sunlight. Furthermore, the energy-autonomous device exhibits unique responses for handwriting characters stably and repeatedly. The proposed system may be applicable to human-machine interfaces, biomonitoring systems, secure communication, and wearable devices.