Extremely large-stroke hair artificial muscles with fast
recovery prepared by a facile and green method
Artificial muscles with large strokes are of special interest in diverse fields. However, it is difficult for large-diameter muscles to be rapidly cycled. In this study, hair artificial muscles with extremely large tensile stroke and fast recovery were prepared simply by twist insertion, coiling and steaming. The maximum tensile stroke for the hair artificial muscles upon water actuation was as large as 10000% and the large-stroke muscles could recover fast in ethanol. With a diameter of 7 mm and a twist density of 2500 turns m-1, the compacted heterochiral hair artificial muscle could elongate 100 times of its original length in water and returned to its initial length in ethanol within 10 s. In addition, these hair artificial muscles maintained their excellent performance after either 100 water-ethanol stimulation cycles or staying in open air for 5 months. Moreover, the hair artificial muscle was able to contract by 59% when lifting 10 times its own weight, pull a wheel model or climb a long distance under water and work as a smart water-sensitive switch. This work demonstrates a facile and green strategy to prepare advanced natural fiber-based artificial muscles that have promising applications in soft robotics and biomedical engineering.