Hydration-responsive keratin fibers with ultra-high shape recovery via reversible protein conformational change and Au enhancement

Fabricating shape-memory materials from natural macromolecules has gained popularity to facilitate the development of bio-friendly smart materials and devices. However, current biobased shape-memory materials have shortcomings, including insufficient mechanical properties and low shape recovery rate in their real applications. Herein, this work aims to develop hierarchically structured keratin-based fibers with high strength and shape-memory properties in response to hydration. The gold nanoparticle is adopted for enhancement in the keratin system, and a well-aligned anisotropic structure with α-helix to the fiber axis is established in the regenerated keratin fibers by wet spinning. The strong crosslinking effect from AuS bonding endows the keratin fibers with outstanding shape-memory performance, exhibiting a shape fixity of ~92 % and a near-full shape recovery rate of ~96 %. In this system, the transition between α and β conformation under external force and water stimulation is assigned as the fundamental mechanism in response to hydration. In hydration and dehydration, the hydrogen bonds act as ‘switches’ that enable deformation, while the strong AuS bonds are ‘net points’ to maintain the original and temporary shapes. This strategy can promote metal nanomaterial anchoring as a methodology for fabricating shape-memory protein-based fibers with excellent mechanical properties and shape-memory performance.