Deep eutectic solvent-assisted self-healing and anti-freezing composite hydrogels regulated by sodium phytate for wearable sensors

Stretchable conductive hydrogels with high strain sensitivity have become hot topics in the area of wearable flexible devices. However, practical applications are limited by their weak mechanical properties and high-water content, especially under low temperature conditions. Deep eutectic solvents (DESs) are known as green solvents owing to the great conductivity, stability and biocompatibility. Although some functional gels have been designed assisted by DES, it has remained a significant challenge to construct composite gels containing DES with various properties. Here, we designed self-healing, stretchable and conductive composite hydrogels based on sodium phytate and DES (acrylic acid/choline chloride). The mechanical, self-healing, conductivity properties and transparency of the resulting gels could be adjusted by the content of sodium phytate. A simple device for information encryption display was built by using the transparency change of the gels. Moreover, flexible strain sensor based on gels could detect human movement like finger bending, facial expressions even human pulse after exercise. In addition, the strain sensor could be used at low temperatures of − 20 °C and still possess great sensitivity after self-healing.