Super-adhesive and highly sensitive conductive hydrogel based on halometallate ionic liquid for flexible electronic devices

Hydrogels are widely used as functional smart materials in wearable electronics and other applications. However, limitations in certain properties restrict their broader utility. In this paper, halometallate ionic liquids, synthesized by combining ionic liquids (ILs) with metal Zn salts, were incorporated into glycerol to create supramolecular liquids. These served as functional auxiliaries for a composite hydrogel synthesized by combining a p(AM-co-HEMA) copolymer network with a macromolecular carboxymethylcellulose (CMC) interpenetrating network. Meanwhile, lignin nanoparticles (LNPs) facilitated the redox reactions with Zn ions and accelerated free radical polymerization. The composite hydrogel, exhibiting tunable mechanical properties due to abundant metal coordination and hydrogen bonding, demonstrates high tensile elongation at break (1300 %), excellent adhesion (462.3 kPa), freezing resistance (−60 °C), high moisture retention, significant temperature sensitivity (TCR = −11.47 %/°C at 20–35 °C), and good electrical conductivity (1.56 S/m). Its high sensitivity (gauge factor, GF = 5.78; pressure sensitivity = 13.74 kPa −1 ) and fast response time (0.1 s) further enhance its capabilities. Consequently, these multifunctional hydrogels find applications in strain, pressure, and temperature sensors, as well as in capacitive pens and energy generation. This research offers a pathway for integrating hydrogel-based electronics into intelligent human-computer interaction, information transmission, health monitoring, and traffic detection systems.