Biomimetic hierarchical fibrous hydrogels with high alignment and flaw insensitivity

Natural structural materials often feature intricate hierarchical architectures across various scales, from nanometers to hundreds of microns, resulting in exceptional strength, toughness, and flaw insensitivity. However, achieving similar microstructures in engineering materials remains a formidable challenge. In this study, we combine the wet rotary jet spinning (WRJS) system with a salting-out process to fabricate highly anisotropic fibrous poly(vinyl alcohol) (PVA) hydrogels with controlled crystallinity and interfacial adhesion between fibers. We engineered hydrogels to emulate the mechanical characteristics of structural materials in nature. The resulting materials demonstrate excellent anisotropic alignment at both the molecular and fiber scales. By controlling adhesion between fibers, we obtain a compact material that is more ductile than both of the individual fibers of which it is composed and isotropic bulk PVA. Overall, these fibrous hydrogels exhibit mechanical properties comparable to various natural tissues, offering significant potential for applications in soft devices and tissue engineering.