Preparation of degradable, biocompatible, conductive and multifunctional chitosan/thiol-functionalized graphene nanocomposite hydrogel via click chemistry for human motion sensing

As an auspicious multifunctional material, hydrogels have engendered a huge surge of interest worldwide because of their undeniable applications, particularly in wearable sensor fields. However, it has been a great challenge to simultaneously integrate flexibility, high electrical conductivity, strain sensitivity, self-healing property, biodegradability and non-drying property into a single hydrogel. In this work, the conductive biodegradable nanocomposite hydrogels based on chitosan (CS) and thiol-functionalized graphene oxide (GSH) were presented via "thiol-ene" click reaction. Remarkably, the compressive modulus and shape recovery of the nanocomposite hydrogels, totally increased by more than 400% and 300%, respectively, in comparison with the CS hydrogel. Furthermore, benefiting from the electroactive pathway generated by GSH in the hydrogel network, the flexible hydrogel sensors indicated strain sensitivity and the electrical conductivity of the obtained nanocomposite hydrogels reached 0.35 S/m. These excellent properties were demonstrated by human activity monitoring device in real time. Also, cytocompatibility of the hydrogels was also confirmed using L929 fibroblast cells. The fast gelation method proposed in this paper would be promising in fabricating smart conductive sensors used for biomedical diagnostics and wearable electronics.