Ultrastretchable and Self-Healing Double-Network Hydrogel for 3D Printing and Strain Sensor

On the basis of the thermoreversible sol-gel transition behavior of K-carrageenan in water, a double-network (DN) hydrogel has been fabricated by combining an ionically cross-linked kappa-carrageenan network with a covalently cross-linked polyacrylamide (PAAm) network. The kappa-carrageenan/PAAm DN hydrogel demonstrated an excellent recoverability and significant self-healing capability (even when notched). More importantly, the warm pregel solution of kappa-carrageenan/AAm can be used as an ink of a three-dimensional (3D) printer to print complex 3D structures with remarkable mechanical strength after UV exposure. Furthermore, the kappa-carrageenan/PAAm DN hydrogel exhibited a great strain sensitivity with a gauge factor of 0.63 at the strain of 1000%, and thus, the hydrogel can be used as sensitive strain sensors for applications in robotics and human motion detection.