Skin-like dual-network gelatin/chitosan/emodin organohydrogel sensors mediated by Hofmeister effect and Schiff base reaction.

ABSTRACT

Conductive gels have been extensively explored in the field of wearable electronics due to their excellent flexibility and deformability. Traditional gels constructed from synthetic networks pose risks to biosecurity due to residual monomers like acrylamide, while pure biological hydrogels are plagued by inadequate mechanical performance. This study explores an innovative strategy, employing a dual-network (DN) system with purely biological components, as a superior alternative to conventional synthetic networks. By integrating gelatin and chitosan, two natural polymers with inherent biocompatibility and advantageous biomedical properties, this approach successfully avoids the toxic risk of synthetic polymers. By utilizing emodin, a natural extract from Rheum officinale, as a cross-linking agent for chitosan by Schiff base reactions, and Hofmeister effect of gelatin induced by sodium carbonate, the DN gelatin/chitosan/emodin organohydrogels achieve ultrahigh tensile strength (up to 9.45 MPa), tunable moduli (ranging from 0.07 to 3.42 MPa), excellent toughness (∼9.64 MJ/m3), and high ionic conductivity (7.63 mS/cm). Remarkably, these conductive organohydrogels also exhibit high sensitivity (gauge factor up to 1.5) and ultrahigh linearity (R2 up to 0.9995), making them promising candidates for soft human-motion sensors capable of accurately detecting and monitoring human movements in real time with high sensitivity and durability.