Upcycling Waste Wool to Sustainable Shape‐Memory Fibers via Molecular Order Reconstruction of Keratin

ABSTRACT Upcycling waste wool into high‐performance actuators remains challenging because keratin's hierarchical architecture is readily disrupted during extraction, and the mechanistic connection between its secondary‐structure transitions and long‐range molecular order is still unclear. Herein, we present a sustainable strategy for fabricating regenerated wool fibers (RWFs) that enable tunable α‐helix‐to‐β‐sheet transitions and exhibit humidity‐triggered shape‐memory behavior. A selective disulfide‐cleavage strategy is introduced to extract intact keratin fibrils from waste fabrics, and long‐range molecular order of keratin is reconstructed through a continuous flow‐induced alignment process, yielding RWFs with hierarchical orientation and native secondary structures. Under tensile strain and hydration, RWFs undergo a reversible α‐helix‐to‐β‐sheet transition, resulting in rapid and repeatable shape recovery and humidity‐triggered actuation. By integrating machine learning with molecular‐dynamics simulations, the molecular pathway comprising helix uncoiling, β‐sheet formation, and hydrogen‐bond rearrangement is systematically elucidated. The resulting fibers can function as programmable humidity‐responsive switches, self‐tightening sutures, and adaptive compression bandages. This work establishes a viable route to hierarchically ordered, shape‐memory biomass fibers with molecular‐level precision, opening avenues for advanced bioengineering and biomedical applications.