Advanced wearable strain sensors: Ionic double network hydrogels with exceptional stretchability, adhesion, anti-freezing properties, and sensitivity

In recent years, achieving satisfactory mechanical and electrical properties in hydrogels at low temperatures has proven challenging. Herein, we developed an superior ionic conductive hydrogel by a simplified one-pot method. The as-prepared Li+/AgNPs@polyacrylamide-co-polyacrylic acid (Li+/AgNPs@PAM/PAAc) double-network hydrogel exhibited remarkable stretchability of up to 1250 % at room temperature and revealed a robust adhesion on different materials, especially up to 44.2 kPa on aluminum. Furthermore, the hydrogel demonstrated high sensitivity with a gage factor (GF) of 3.20 at a strain of 200 %, and performed reliably at low temperature, with a GF of 1.42 at a strain of 100 % at - 40 °C, suggesting the maintenance of excellent mechanical and electrical properties at low temperature. These remarkable advantages highlighted the significantly enhanced performance of the ionic conductive hydrogel for applications in flexible wearable sensing devices, in the areas of intelligent speech, motion recognition, as well as electrophysiological signal monitoring.