Intrinsic conductive cellulose nanofiber induce room-temperature reversible and robust polyvinyl alcohol hydrogel for multifunctional self-healable biosensors

Polyvinyl alcohol (PVA) hydrogels are widely used for flexible sensors by adding various conductive substances due to their excellent mechanical properties and self-healing properties. However, most of the conductive substances added to PVA hydrogel sensors are currently complicated to prepare, costly, and environmentally unfriendly. Herein, to overcome this challenge, we successfully prepared intrinsic conductive cellulose nanofiber (G-CNF) by simply applying sulfuric acid and a low-energy water bath with heat treatment, and obtained a powerful multifunctional self-healing PGC hydrogel biosensor using dynamic chemical cross-linking of PVA and borax with glycerol and G-CNF. The obtained PGC hydrogels have excellent mechanical properties (strain: 950%), good adhesion ability, robust self-healing properties, and room-temperature reversibility, due to the presence of conductive networks and hydrogen bonds within PGC hydrogel. Especially, PGC hydrogels with the graphene structured G-CNF have a fast response to various signals and good stability with gauge factor (GF) values up to 1.83, as well as a sensitive response to temperature (temperature coefficient of resistance (TCR) up to 1.9), which can be designed as a variety of biosensors, such as human motion monitoring, information encryption/transmission, and real-time temperature monitoring biosensors. Thus, PGC hydrogels as multifunctional self-healing hydrogel biosensors pave the way for the development of flexible biosensors in wearable devices, human—computer interaction, and artificial-related applications.