Ultratough Zwitterionic Hydrogel Achieved by Micellar and Dynamic Bonding for Self-Adhesive Strain Sensor

Zwitterionic hydrogels usually display poor mechanical properties due to their strong hydrophilicity, which severely limited their further applications. Herein, an ultratough zwitterionic hydrogel was developed by introducing vinyl-modified micelles as the cross-linker. The synergetic effect of the micellar deformation, dynamic hydrogen bonding, and electrostatic interactions between the polymer chains lead to a pronounced improvement in the hydrogel mechanical property, with tensile strength up to 2.72 MPa and elongation up to 2125%. Unlike those with fillers, this hydrogel is transparent and conductive, attributed to the effective ion channels induced by its inner zwitterionic groups, which is favorable for visualization. It also showed a renewable strong adhesion to various materials after drying from a wetted state, and no visible residue was left after its detachment. A cell viability assay upon the normal 293FT cells proved its excellent biocompatibility. With all these virtues, this hydrogel was used as a self-adhesive strain sensor, which showed excellent performances in real-time monitoring of the bending angle and frequency of body movements.