An Integrated Asymmetric Wet Adhesive Hydrogel with Gradient Charge Distribution Induced by Electrostatic Field

Adhesive hydrogels have been applied in biomedical field as an alternative to surgical sutures. However, there still exist rigorous challenges in rough underwater adhesion and asymmetric adhesion of hydrogels, especially applied in wound healing and organ repair in vivo. Herein, a strategy is proposed to prepare integrated hydrogels with asymmetric underwater adhesion capability by forming the asymmetric electrical interface under an electrostatic field. The synergistic effects between catechol and amine and complex coacervation are used to improve the underwater adhesion of hydrogel. Furthermore, by applying an electrostatic field, the cations and anions in solution of monomers are separated to form asymmetric adhesion interfaces. The hydrogel exhibits obvious asymmetric underwater adhesion ability on porcine skin with a strong adhesive strength of 97 kPa on cation side and 25 kPa on the anion side. Animal experiment outcomes reveal that only one side of the asymmetric hydrogel could adhere firmly to the rat liver and the rabbit stomach, while the other side could not effectively prevent postoperative tissue adhesion. The asymmetric distribution of adhesive molecules induced by electrostatic fields will provide a new alternative for designing and adjusting asymmetric adhesives after surgery. The asymmetric wet adhesive hydrogel with gradient charge distribution is prepared by using a new process of hydrogels prepared by electrostatic field. Catechol‐cation enrichment provides strong underwater adhesion at the bottom of the hydrogel, while the other side can effectively prevent unnecessary adhesion after surgery.