Biomimetic Design of Hydration‐Responsive Silk Fibers and their Role in Actuators and Self‐Modulated Textiles.

Hydration‐induced shape‐morphing behavior has been discovered in many natural fiber‐based materials, yet this smart behavior in regenerated fibers from biopolymers lacks investigation. Here, hierarchically structured silk fibers are developed with anisotropic long‐range molecular organization and water‐responsive effects resembling natural spider silk. The regenerated silk fibers exhibit the water‐triggered shape‐memory effect and a water‐driven cyclic response. The reversible hydrogen bonds and transformation in the metastable secondary structure from α‐helices/random coils to β‐sheets are explored as the mechanisms responsible for the water‐responsiveness. The silk fibers obtained possess a tensile strength higher than 104 MPa at a fracture strain of ≈100%, showing noticeable toughness. The water‐responsive silk fibers exhibit a shape recovery rate of ∼83% and generate a maximum actuation stress of up to 18 MPa during the water‐driven cyclic contraction that outperforms most traditional natural textile fibers. The regenerated silk fibers show potential for use in water‐driven actuators, artificial muscle, and smart fabrics based on the integration of suitable mechanical properties and water responsiveness. [ABSTRACT FROM AUTHOR]