High-Stability Wool-Based Single-Helix Artificial Muscles via Dithiol-Mediated Disulfide Rebonding

Compared to the complex and time-consuming preparation of traditional double-helix structures, the single-helix structure is simpler and more scalable, but its reliance on hydrogen bonds makes it prone to shape relaxation and instability. This study utilized the disulfide bond cleavage-repair reaction of DTT to achieve chemical immobilization of single-helix wool artificial muscles, enabling them to maintain high structural stability without external constraints while demonstrating excellent reversible actuation under wet-heat conditions. The prepared R-St-C-O wool yarn exhibited outstanding shape stability, thermal stability, and curl properties. Raman spectroscopy analysis revealed that the relative disulfide bond content (normalized to untreated) increased by approximately 24%, with wool breaking strength improving by 20%. The yarn's humidity sensitivity significantly decreased, with the wicking height reaching 47 mm and the radial volume expansion of fibers achieving 15%. X-ray diffraction and Raman analysis further confirmed the formation of a more organized macromolecular structure after wool reconstruction, characterized by denser disulfide cross-linking networks and the transition from an α-helix to β-sheet. This enabled the single-helix wool artificial muscles to exhibit a sustainable dual-switch actuation mechanism: reversible actuation under heat or water stimulation and programmable permanent shaping under UV and reductant conditions. When applied to smart bionic arms and electrical switches, this artificial muscle demonstrates significant potential in use in bionic actuators and controllers.