Hoffmeister effect assisted the double-network cellulose hydrogel electrolyte with extreme environmental stability and enhanced conductivity for wearable devices and strain sensors

An ideal flexible sensor should possess excellent mechanical properties, outstanding electrochemical performance, and high environmental tolerance to ensure long-term applicability in wearable electronics. However, integrating these multifunctional properties remains a major challenge. Inspired by human skin tissue, this study develops a poly (acrylic acid)-TA@CNF (PTCCG-Na⁺) hydrogel with a hierarchical network via a hydrogen bond recombination strategy assisted by salting-out. The tannic acid-encapsulated cellulose nanofibers (TA@CNF), containing rigid crystalline regions and abundant hydrogen bonding sites, interact with glycerol and poly (acrylic acid) (PAA) to form a dynamic hydrogen bond network. This structure imparts the hydrogel with remarkable tensile performance (> 1300%), long-term cycling stability (> 2000 cycles), and broad environmental adaptability (−40 to 80°C). Additionally, NaCl and carbon nanotubes (CNTs) serve as physical reinforcement agents, providing additional physical crosslinking and synergistically enhancing the electrical conductivity (72.88 mS cm⁻¹) of the hydrogel. These combined features allow the hydrogel to be applied in wearable sensors for heart rate and pulse monitoring, as well as in supercapacitors (capacitance: 422.545 mF cm⁻² at 0.83 mA cm⁻²). This study presents a novel strategy for developing hydrogels with stable mechanical properties, exceptional environmental tolerance, and high conductivity.