A multifunctional graphene-integrated double-network nanocomposite hydrogel for dual strain-temperature wearable sensing

Abstract

Inspired by the natural sensing capabilities of human skin, flexible and stretchable materials such as hydrogels have emerged as vital platforms for skin-interfaced and wearable electronics. A double-network chitosan/modified polyethylene glycol/graphene (Cs./mPEG/G) nanocomposite hydrogel is developed as a flexible, multifunctional platform for dual strain-temperature sensing. By leveraging the balanced mechanical properties of the double-network hydrogel and the exceptional electrical conductivity of graphene, the nanocomposite hydrogel possesses strong mechanical resilience and reliable electrical conductivity at strains up to 350%. The sensor effectively tracks various body movements with a gauge factor of 13.8 and maintains cyclic electromechanical stability for over 500 stretching cycles. Additionally, the chitosan-based polymer network exhibits self-adhesion properties due to its terminal hydroxyl and amino groups, which facilitate hydrogen bonding with surfaces such as plastic, rubber, glass, metal, and human tissues. Most importantly, the hydrogel sensor attached to wrists, fingers, elbows, or ankles delivers stable ΔR/R₀ dynamic pulses during movement and detects fever-range temperature changes within 37.5–40 °C in real time, with a linear thermoresistive response and an ultrahigh temperature coefficient of resistance of -5.62% °C⁻¹. These results highlight the potential of the hydrogel nanocomposite as a high-performance dual strain-temperature tactile sensor for wearable healthcare devices and flexible electronics.