Conflicts of interest

None.

Author contributions

The fabrication and characterization of the hair artificial muscles were carried out by Qian-Ru Xiao. The project was designed and performed by Si Sun, Xiao-Li Qiang and Xiao-Long Shi. The schematic illustrations for hair artificial muscles were prepared by Peng Xu. Qian-Ru Xiao and Si Sun prepared the manuscript. Xiao-Li Qiang and Xiao-Long Shi revised the manuscript. All authors commented on the manuscript.