Stable, recyclable, hybrid ionic-electronic conductive hydrogels with non-covalent networks enhanced by bagasse cellulose nanofibrils for wearable sensors

Conductive hydrogels are utilized in flexible sensors due to their high-water content, excellent elasticity, and shape controllability. However, the sharp increase in resistance of this material under enormous strain leads to instability in the sensing process. This study presents a straightforward method for creating a stable, recyclable, hybrid ionic-electronic conductive (HIEC) hydrogel via a simple one-pot strategy using polyvinyl alcohol (PVA), bagasse cellulose nanofibrils (CNF), and graphene(G) with sodium dodecylbenzene sulfonate (SDBS). The SDBS/G hemimicelles are formed through hydrophobic and π-π stacking interactions between SDBS and G, enhancing the dispersibility of G. Then SDBS/G hemimicelles were integrated into a non-covalent cross-linking network from CNF and PVA, which ensures recyclability and stability. The CNF-PVA-Graphene (CPG) hydrogel exhibited high and stable sensing sensitivity (average gauge factor up to 1.99), high conductivity (0.36 S/m), low graphene concentration (0.16  wt %), low detection limit (1 %), and fast response time (0.17 s). The sensor can detect large (wrist and knee) and small (pulse and laryngeal prominence) body movements. After recycling, the hydrogel sensors maintained high conductivity sensitivity (average gauge factor up to 1.01) and good tensile properties (360 % strain). This study introduces a new approach of hybrid conductive biomass-based hydrogel sensors for precisely monitoring human movements.