Ultra-strong adhesive, self-healing and electroactive bio-based hydrogels for the on-demand fabrication of sandwich-inspired smart electronic sensing floors

Bio-based adhesive electroactive hydrogels as electronics are of significant research interest in health monitoring systems, wearable devices and smart home systems. Herein, a series of ultra-strong adhesive, self-healable and electroactive nanocomposite hydrogels (CAM-Gels) driven by integrated molecular-chain entanglements, hydrogen bonds, chelation and electrostatic interactions was nano-engineered by compounding biomass gelatin (Gel) and chitosan (CS), acrylamide (AM), multi-walled carbon nanotubes (MWCNTs) and FeCl3 though a simple one-pot method as a conductive adhesive layer for the bio-fabrication of a brand new sandwich-inspired leather-based smart electronic sensing floor (e-floor). Comprehensive experiments showed that the integration of abundant active groups and cohesion among the constituents endowed CAM-Gels with desired adhesive ability towards various substrates. Exhilaratingly, CAM-Gels exhibited ultra-strong adhesive strength on natural hydrogenoid skin, superior to that of currently reported polyurethane adhesives, bio-based adhesives and mussel-inspired adhesives. Owing to the dynamic reversible physical crosslinking, CAM-Gels showed on-demand self-healing ability. Moreover, CAM-Gels presented the accurate real-time monitoring of comprehensive large- and small-scale human activities, demonstrating its significant potential for sensor electronics. Furthermore, the proposed leather-based e-floor exhibited a repeatable and regular electrical signal as expected, substantiating that the e-floor can be used for accurately tracking people's daily activities. The e-floor breaks new ground for leather-based electronics, which will have potential applications in smart homes.