Biocomposite silk fibroin hydrogel with stretchability, conductivity and biocompatibility for wireless strain sensor

As a natural biopolymer material, silk fibroin with unique mechanical properties can be used in the preparation of biocomposite hydrogels for strain sensors. But, the electromechanical properties of biocomposite hydrogel strain sensors are still insufficient, such as the deterioration of electrical signals and low sensitivity, which need to develop a hydrogel with a stable transmission network for electric conduction. Herein, a silk fibroin biocomposite hydrogel is prepared by incorporating tannic acid and MXene nanosheets into a polyacrylamide and silk fibroin double network. The electromechanical properties of hydrogels are improved by optimizing the proportion of material components. As a result, the double network structure and supramolecular interaction enhance the stretchability of hydrogels (692% fracture strain). The hydrogel also exhibits good biocompatibility and conductivity (0.85 S/m), which shows the application prospect in wearable sensors. The wireless strain sensor assembled by this biocomposite hydrogel presents good portability and sensing performance, such as high sensitivity (gauge factor=6.04), wide working range (500% strain), and outstanding stability (1000 cycles at 100% strain). The results indicate that the hydrogel strain sensor can be used to monitor human body movement. The biocomposite hydrogel is expected to be applied in the field of wearable strain sensors, and this study can provide a new way for the design of flexible electronic materials.