Conclusion
In this study, tether-free hair
artificial muscles with extremely large tensile stroke and fast recovery
were successfully made through twist insertion, coiling and steaming,
without any chemical crosslinking. Coiling the twisted hair fiber with
large diameters increases the muscles’ tensile stroke, and ethanol
stimulation enables their fast recovery. The tensile stroke upon water
actuation could be as large as 10000%, three times larger than the
largest tensile stroke reported so far20. The fastest
actuated muscle could fully recover in 10 to 20 seconds. Various
applications such as long-distance climbing robots, weight pulling or
lifting, and a smart water-sensitive switch were also demonstrated. This
study provides a facile and green strategy to prepare advanced natural
fiber-based artificial muscles, which have promising applications in
soft robotics and biomedical fields.
Acknowledgement
This work was supported by the
National Natural Science Foundation of China (grant no. 62002079,
62172114, 61772376, 62072129 and 62202112) and the National Key R&D
Program of China (Grant no. 2019YFA0706401). The authors would like to
thank Shiyanjia Lab
(www.shiyanjia.com) for the
support of DSC analysis.