Wrinkled double network hydrogel: Via simple stretch-recovery

The wrinkled structures in biological tissues play a key role in nutrition transportation and organ protection and cannot be easily achieved in synthetic hydrogels using universal and convenient strategies. Wrinkles are highly desirable for the nascent applications of hydrogels in biomaterials and artificial organs. Here, we propose a strategy for inducing different viscoelastic behaviours inside a double network hydrogel to achieve regular wrinkles that are formed by the mass redistribution. The wrinkles can be designed on multiple dimensions and can be well reserved in repeated tensile loadings. These wrinkled hydrogels exhibit unusual characteristics, such as the anisotropy of mechanics and J type tensile curves. This strategy is particularly valuable for biomaterials and artificial organs and may become a universal method for designing the surface morphology of soft materials in large-scale preparation.