Ultra-stretchable and anti-freezing conductive organohydrogel reinforced with ionic clusters for wearable strain sensors

Abstract

Ionic conductive hydrogels have attracted extensive attention as a substitute for traditional rigid metal conductors, especially in wearable electronic devices. However, to prolong the service life of ionic conductive hydrogel-based devices, the development of highly elastic ionic conductive hydrogels that can remain good performance under extreme environmental conditions (below 0 °C or dry) is still facing great challenges. Herein, a novel double-network (DN) organohydrogel with high tensile strength (~0.9 MPa), elongation at break (~1097%), compressive strength (~6.96 MPa), toughness (~4.75 MJ m−3), transparency (~97%), anti-freezing and ionic conductivity (1.07 mS cm−1) is prepared by photoinitiation polymerization, complexation of transition metal ions, and solvent exchange method using polyacrylamide (PAM) and sodium carboxymethyl cellulose (CMCNa) in dimethyl sulfoxide-water binary solvent system. It is noteworthy that the DN gel design is more compact, and zinc carboxylate complexes composed of CMCNa and Zn2+ form nanoscale metal ionic clusters through coulomb force interaction in the binary solvent environment, which proves the synergistic effect on mechanical properties and conductivity. Moreover, the prepared organohydrogels used as strain sensors have obvious recovery effect, flexibility, high sensitivity (GF=4.38) and stable electrical properties (0.6 mS cm−1 at 30 °C) under the temperature range (−20 to 60 °C). Combined with the above advantages, this conductive organohydrogel promotes the application prospect in different fields, such as soft robots, human-machine interaction, artificial sensors, ionic skin, and optical electronics devices, energy-storage devices, and so on.