Unipolar stroke, electroosmotic pump carbon nanotube yarn muscles
Hetao Chu, Xinghao Hu, Zhong Wang, Jiuke Mu, Na Li, Xiaoshuang Zhou, Shaoli Fang, Carter S. Haines, Jong Woo Park, Si Qin, Ningyi Yuan, Jiang Xu, Sameh Tawfick, Hyungjun Kim, Patrick Conlin, Maenghyo Cho, Kyeongjae Cho, Jiyoung Oh, Steven O. Nielsen, Kevin Alberto, Joselito M. Razal, Javad Foroughi, Geoffrey M. Spinks, Seon Jeong Kim, Jianning Ding, Jinsong Leng, Ray H. Baughman
Abstract
Success in making artificial muscles that are faster and more powerful and that provide larger strokes would expand their applications. Electrochemical carbon nanotube yarn muscles are of special interest because of their relatively high energy conversion efficiencies. However, they are bipolar, meaning that they do not monotonically expand or contract over the available potential range. This limits muscle stroke and work capacity. Here, we describe unipolar stroke carbon nanotube yarn muscles in which muscle stroke changes between extreme potentials are additive and muscle stroke substantially increases with increasing potential scan rate. The normal decrease in stroke with increasing scan rate is overwhelmed by a notable increase in effective ion size. Enhanced muscle strokes, contractile work-per-cycle, contractile power densities, and energy conversion efficiencies are obtained for unipolar muscles.