A super-tough ionic conductive hydrogel with anti-freezing, water retention, and self-regenerated properties for self-powered flexible sensor

Flexible sensors based on hydrogels have been widely studied for their ability to detect physiological information and provide feedback through electrical signals. However, several shortcomings, such as weak mechanical properties, easy freezing and dehydration, and dependence on external energy drive, seriously limit their practical application. To overcome the above problems, a super-tough agarose/poly (N-hydroxyethyl acrylamide-co-acrylic acid)/Ca2+ double network (agarose/P(HEAA-co-AA)/Ca2+ DN) hydrogel is designed by combining the fully physically crosslinked DN strategy with metal-ion coordination effect. The obtained transparent hydrogels show high toughness (12.54 ± 0.48 MJ m−3), good ionic conductivity (10.18 ± 1.23 mS cm−1), low freezing point (below −80 °C), and water retention ability (the hydrogel could retain ≈102% of its original weight after long-term storage at 25 °C and 40%RH). Unlike conventional hydrogels that lose water in the natural environment, the dehydrated DN hydrogel can spontaneously capture water from the atmosphere to regenerate its initial mechanical and electrical performances. Based on the DN hydrogel, a self-powered flexible sensor is constructed by using triboelectric nanogenerate technology. The transparent and highly stretchable flexible sensor can not only spontaneously output voltage signals for the bending of fingers and tiny facial behavior, but also can be assembled into an intellectual electronic glove to achieve gesture recognition, showing great application potential in the wearable electronics field.