Biocompatible and 3D-printable conductive hydrogels driven by sodium carboxymethyl cellulose for wearable strain sensors

Multifunctional hydrogels with high electrical conductivity and mechanical flexibility are widely used as flexible strain sensors in different fields such as artificial intelligence, electronics and flexible sensing. However, when the temperature drops below the freezing point, the solidification of water leads to solidify or even failure of the hydrogel, severely limiting the application in low temperature environments. Thus, the hydrogel was prepared by a freeze-thaw method using polyvinyl alcohol, polyvinylpyrolidone, sodium chloride, glycerol and sodium carboxymethyl cellulose. The hydrogel exhibited excellent electrical conductivity and mechanical property in −40 °C–20 °C. Simultaneously, the hydrogel sensor possessed prominent sensitivity and cyclic stability to accurately monitor human motion in real time, including large-scale human motion such as wrist, elbow, and knee flexion movements as well as subtle human motion. There were no adverse reactions after the hydrogel into mice during14 days, indicating good biocompatibility of the hydrogel. Furthermore, the hydrogel could be printed in different shapes by 3D printing. The investigation provides a new route for the development of multi-functional hydrogel wearable sensors.