An oxidized alginate linked tough conjoined-network hydrogel with self-healing and conductive properties for strain sensing

In this article, we prepared a conjoined-network hydrogel with acrylamide-modified chitosan, oxidized alginate and polyacrylamide. The oxidized alginate can not only crosslink with chitosan to form a hydrogel network but also link with the polyacrylamide network through Schiff base linkage and hydrogen bonds. These dynamic bonds confer high toughness and self-healing properties to the hydrogel. The hydrogel with 20 wt% acrylamide, 0.1 wt% modified chitosan and 5 wt% oxidized alginate can be stretched to more than 20 times its original length. This self-healed hydrogel has 40% fracture stress and 53% fracture strain of the original hydrogel. The hydrogel possessed ionic conductivity due to the free ions in the modified chitosan and alginate. The conjoined-network hydrogels can be used as strain sensors to detect different motions. The hydrogel also showed high stability and can still be used as a soft sensor after storing for six months. This tough conjoined-network hydrogel with self-healing and conductivity can be applied in different engineering fields.