Superior low-temperature tolerant, self-adhesive and antibacterial hydrogels for wearable sensors and communication devices

Hydrogel-based sensors have drawn wide attention in the fields of medical monitoring, electronic skin, human–machine interfaces, and so forth. So far, although the research on hydrogel-based sensors has made great progress, there are still some problems hindering their further development, such as poor mechanical flexibility, inadequate anti-freezing capability, and weak self-adhesive and antibacterial properties. Herein, a multipurpose hydrogel (GG/PAAm/PA/LiCl) is facilely prepared by the thermally initiated radical polymerization method. The natural guar gum (GG) and chemically cross-linked polyacrylamide (PAAm) chain-based dual-network structures endow the hydrogel with excellent stretchability (2102%) and tensile strength (117 kPa). Meanwhile, the hydrogel exhibits extraordinary low-temperature tolerance due to the synergistic effects of phytic acid (PA) and lithium chloride (LiCl), which can basically maintain its original mechanical properties even after being stored at −50 °C for 15 days. Moreover, the introduction of natural biomolecule PA has also contributed to the superior self-adhesive property and prominent antibacterial activity. Furthermore, the as-prepared hydrogel can be served as a strain sensor with wide sensing range (5–500%) and remarkable signal stability (800 cycles at 200% strain), which displays attractive application prospects in rehabilitation training monitoring and information transmission. Owing to the outstanding anti-freezing capability, the hydrogel-based sensor is also capable of precisely sensing the bending movements of a prosthetic finger under an extreme weather condition of −50 °C. This work provides a new horizon to develop extraordinary freezing-tolerant hydrogels with multiple properties for future wearable electronics and artificial intelligence.