Strengthening Constitutive Motifs in Isotropic Fibrous Hydrogel for Exceptional Damage Resistance.

Super damage resistance requires high fracture energy in all directions, therefore, although fibrous hydrogels have demonstrated impressive reinforcing effects, their anisotropic nature usually prevents them from performing well. In this work, we propose a strategy to resolve this dilemma by strengthening constitutive motifs in isotropic fibrous hydrogel through nonsolvent quenching followed by salting-out. This strategy generates isotropic nanofiber networks and subsequently reinforces those fibers via densification and crystallization, yielding dense and crystalline isotropic nanofiber (DCIF) networks that can efficiently transfer and dissipate stress to delay crack extension in all directions. Along any three orthogonal directions, the resultant DCIF network hydrogel demonstrates almost identically high strength of 20.15 ± 1.96 MPa, toughness of 126.48 ± 5.30 MJ/m3 and fracture energy of 242.01 ± 2.03 kJ/m2, achieving exceptional damage resistance in classical puncture and impact modes. This work provides a principle and methodology to fabricate and isotropically reinforce nanofiber hydrogels, thereby extending their applicability to versatile scenarios requiring isotropically mechanical superiority.