Enhanced Strength for Double Network Hydrogel Adhesive Through Cohesion‐Adhesion Balance

Hydrogel adhesives exhibit great potential in various biomedical fields such as tissue sealing and soft robotics. However, the high‐water content and defective network structures of these hydrogel adhesives result in low intrinsic mechanical strength, severely impeding their application. In this study, it is reported that the strong hydrogel adhesive strength can be achieved when a balance is established between adhesive forces and cohesive forces. Based on this principle, a new double network (DN) design is created to combine an adhesive polyvinyl alcohol (PVA) as the first network with a flexible sodium alginate (SA) as the second network. A delicate balance is achieved between cohesion and adhesion by adjusting the ratio between the first rigid adhesive network and the second flexible network. As a result, this balanced DN hydrogel adhesive exhibits a strong tissue adhesion strength, approximately three times higher than that in the non‐balance situation. A robust adhesive is achieved through a balance between internal cohesion and interfacial adhesion forces. Utilizing a double network structure and adjusting the ratio between the PVA rigid adhesive network and the SA flexible network, this equilibrium results in strong adhesive strength. This universal design principle offers new possibilities for the advanced hydrogel adhesives.