Preparation and characterization of the tensile hair artificial muscles

For preparation of the tensile hair artificial muscles, the obtained twist-stable double-plied hair fibers were wrapped around cylindrical mandrels of different diameters tightly in clockwise and counterclockwise directions respectively with both ends tethered. After steaming for 30 min, the coiled hair muscles were untied from the mandrel and relaxed in the open air. The fully relaxed hair muscles were observed with a macro lens and imageJ was used to measure the coil pitch. Differential scanning caborimetry spectra (DSC) for pristine hair fibers, hair fibers heated for 30 min, and hair fibers steamed for 30 min were obtained on a TA differential scanning caborimetry (USA, Q2000).