Graphene oxide-based composite organohydrogels with high strength and low temperature resistance for strain sensors

In recent years, a rapid development of polymeric hydrogel-based sensors has been witnessed. However, conventional hydrogels often exhibit poor mechanical properties. Additionally, the use of these sensors at temperatures <0 °C is limited due to the freezing of the water molecules in the hydrogel matrix. In this study, graphene oxide/poly(acrylamide-co-N-(3-amino propyl)methacrylamide) [poly(AAm-co-APMA)/GO] hydrogels have been synthesized by UV photo-initiation polymerization. Subsequently, the poly(AAm-co-APMA)/GO-Gly (PAAG-Gly) organohydrogels were obtained by glycerol replacement. GO and glycerol had multiple interactions with the polymer chains, which endowed the physically crosslinked organohydrogel with a high fracture stress of up to 782.9 ± 38.6 kPa. Also, the glycerol molecules formed hydrogen bonds with the water molecules, thus inhibiting the formation of ice crystals. After storage at -20 °C for 24 h, the PAAG-Gly organohydrogels retained their superior mechanical properties, adhesion strength, and electrical conductivity. Once the cut surfaces of the organohydrogel were contacted, the conductive path was rapidly self-healed. Moreover, the PAAG-Gly organohydrogels exhibited excellent cytocompatibility. At 100% strain, the gauge factor of the organohydrogel-based sensor reached 4.22. The organohydrogel-based sensor revealed the capability to monitor human motions, such as finger, wrist and knee movements.