Ultra-stretchable dual-network ionic hydrogel strain sensor with moistening and anti-freezing ability

Ionic hydrogel strain sensors are widely used in wearable electronic devices because of their excellent stretchability and responsiveness. However, ordinary ionic hydrogels are easy to dry during working under low temperatures, which severely limit their service life and application areas. Herein, we constructed a dual-network ionic conductive hydrogel based on the alginate/polyacrylamide dual-network hydrogel via solvent replacement treatment, which can be further applied as the wearable strain sensors. The solvent replacement process is by soaking the dual-network hydrogel in LiCl/CaCl2/glycerin/water solution, in which divalent cations Ca2+ ions cross-linking with the alginate chain to further toughen the dual-network, thus obtaining high stress of ~0.81 MPa and a high ionic conductivity (>19.4 mS/cm), and the mixed salt solution of glycerin/water provides excellent moisture for >30 days and frost resistance even under −80 °C ultralow temperature. Impressively, the resulting hydrogel sensor demonstrates excellent sensitivity and cyclic stability in detecting tensile deformation and human motion in a range of sizes. This work provides a feasible method for the construction of high-strength, moisturizing, antifreeze, and durable hydrogel sensors with high sensitivity and a wide range of detection capabilities, and provides a new idea for the application of electronic skin and intelligent wearable devices.