Antimicrobial and anti-freezing conductive hydrogels driven by quaternary ammonium chitosan salt for flexible strain sensors

Conductive hydrogels have great development prospects in the field of flexible strain sensors due to the unique characteristics of sufficient flexibility, comfort and functional diversification. However, long-term direct contact between hydrogel sensors and human skin can cause the phenomenon of bacterial infection, which accelerates the replaceable frequency of hydrogel wearable sensors, hindering the application of hydrogel wearable sensors. Here, the hydrogel with distinguished antibacterial, biocompatibility, frost resistance, water retention and toughness were designed and manufactured by a freeze–thaw method introducing polyvinyl alcohol, quaternary ammonium chitosan salt, polyhexamethylene biguanide hydrochloride, glycerin and lithium chloride. The hydrogel maintains remarkable tensile properties and fatigue resistance in the range from 25 °C to −20 °C, expanding the application of hydrogels as sensors. Meanwhile, the hydrogel was resistant to E. coli and Bacillus subtilis and could be preserved in mice for 14 days. As a result, the hydrogel sensors could be used to detect human movement in real time, such as finger bending, frowning, speaking and other movements. Therefore, the design of the hydrogel provides a simple research idea for implantable sensing devices.