43 As polymer networks infiltrated with water, hydrogels have been widely used as scaffolds for tissue 44 engineering (1), vehicles for drug delivery (2) and model platforms for biological studies (3). More 45 recently, hydrogels have been explored for applications in devices and machines, inclu...
yet most hydrogels are too fragile to tolerate cyclic mechanical loads. Single-network hydrogels lack a mechanism to prevent crack propagation and facilitate energy dissipation. Therefore, they are intrinsically weak and prone to fracture. On the other hand, double-network hydrogels are famous for the...