Electrothermal actuation of the spiral coil from Fig. 3 when restrained to one axis. A brass rod in the center of the coil confines actuation so that the coil must actuate vertically, against gravity, when heated.
Carter S. Haines, Na Li, Geoffrey M. Spinks, Ali E. Aliev, Jiangtao Di, and Ray H. Baughman
PNAS. 2016. 113:11709-11716 DOI: 10.1073/pnas.1605273113