Bioinspired fabrication of self-recovery, adhesive, and flexible conductive hydrogel sensor driven by dynamic borate ester bonds and tannic acid-mediated noncovalent network

[Display omitted] •TA-modified BT nanoparticles were used to prepare multifunctional PVA hydrogels.•The hydrogel was constructed by dynamic borate ester bonds and hydrogen bonds.•The flexible conductive hydrogel had good self-healing and adhesive properties.•Various human movements can be monitored quickly and reproducibly by the hydrogel. Conductive polymer hydrogels have received enormous attention because of their promising applications in healthcare monitoring, soft robots, and wearable electronics. Development of hydrogel sensor with strong mechanical properties, excellent sensing capabilities, self-healing and adhesive properties is highly desirable and still remains a critical challenge. Herein, we report a borax crosslinked flexible hydrogel based on polyvinyl alcohol (PVA), sodium alginate (SA), and tannic acid (TA) modify barium titanate (BT) nanoparticles (T@BT) via a facile one-pot method. The crosslinking network was formed by dynamic reversible borate ester bond and TA-enabled interactions including hydrogen bonds and coordination bonds, which endowed the hydrogel with excellent self-healing and mechanical properties. Meanwhile, the combination of functional catechol groups in TA with the significantly improved cohesion of the hydrogel enabled the hydrogel to exhibit strong and residue-free adhesion to a variety of inorganic and organic materials. The adhesion strength to wood was up to 67.5 kPa. Furthermore, the addition of the T@BT not only rendered the hydrogel highly conductive (1.91 S/m) and sensitive for sensing, but also synergistically enhanced the toughness (587.1 KJ/m3) of the hydrogel. This work provides new ideas for the preparation of multifunctional conductive hydrogels.