Super flexible, self-healing, and self-adhesive double network hydrogel reinforced by okara cellulose nanofibrils

Inspired by the mussel, tannic acid (TA) was modified onto the surface of self-made cellulose nanofibrils (CNFs) to prepare TA@CNFs, which was introduced into borax crosslinked polyvinyl alcohol (PVA) to prepare PTC double-network hydrogel with self-healing properties. Through the comparative observation of TEM images and infrared spectra before and after tannic acid modification, the formation of TA@CNFs was proved. The introduction of TA@CNFs greatly increases the fracture stress of PTC hydrogel, which is more than 10 times higher than that of PVA hydrogel without TA@CNFs, and has high fracture strain (1723 %). Moreover, PTC hydrogel has the ability of rapid self-healing, which can heal to the original form within two minutes. In addition, the temperature response ability of PTC hydrogel makes it capable of reshaping. The self-adhesion ability of PTC hydrogel enables it to adhere to the human epidermis to detect motion signals, as sensitive and as stable as a flexible sensor.