Ultra-antifreeze, ultra-stretchable, transparent, and conductive hydrogel for multi-functional flexible electronics as strain sensor and triboelectric nanogenerator

Conductive hydrogels have become one of the most promising candidates for flexible electronics due to their excellent mechanical flexibility, durability of deformation, and good electrical conductivity. However, in real applications, severe environments occur frequently, such as extremely cold weather. General hydrogels always lack anti-freeze and anti-dehydration abilities. Consequently, the functions of electronic devices based on traditional hydrogels will quickly fail in extreme environments. Therefore, the development of environmentally robust hydrogels that can withstand extremely low temperatures, overcome dehydration, and ensure the stable operation of electronic devices has become increasingly important. Here, we report a kind of graphene oxide (GO) incorporated polyvinyl alcohol-polyacrylamide (PVA-PAAm) double network hydrogel (GPPD-hydrogel) which shows excellent anti-freeze ability. The GPPD-hydrogel exhibits not only good flexibility and ultra-high stretchability up to 2,000%, but ensures a high sensitivity when used as the strain sensor at −50 °C. More importantly, when serving as the electrode of a sandwich-structural triboelectric nanogenerator (TENG), the GPPD-hydrogel endows the TENG high and stable output performances even under −80 °C. Besides, the GPPD-hydrogel is demonstrated long-lasting moisture retention over 100 days. The GPPD-hydrogel provides a reliable and promising candidate for the new generation of wearable electronics.