Antifreezing, Antidrying, and Conductive Hydrogels for Electronic Skin Applications at Ultralow Temperatures

Although conductive hydrogel-based flexible electronic devices have superb flexibility and high conductivities, they tend to malfunction in dry or frigid areas. Herein, an ultralow-temperature tolerant, antidrying, and conductive composite hydrogel is designed for electronic skin applications on the basis of the synergy of double-cross-linked polymer networks, Hofmeister effect, and electrostatic interaction and fabricated by in situ free radical polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylic acid in the presence of poly(vinyl alcohol) and conductive MXene sheets, followed by impregnation with LiCl. Thanks to the synergy of LiCl and the charged polar terminal groups of the synthesized polymers, the composite hydrogel can not only bear an ultralow temperature of -80 °C without freezing but also maintain its original mass. Meanwhile, the resultant hydrogel possesses satisfactory self-regeneration ability benefiting from the moisturizing effect of LiCl. The conductive network of MXene sheets greatly improves the ionic conductivity of the hydrogel at low temperatures, exhibiting an ionic conductivity of 1.4 S m