A Photoactuator Based on Stiffness-Variable Carbon Nanotube Nanocomposite Yarn.

Actuators based on carbon nanotube (CNT) yarn have attracted extensive attention due to their great properties and potential applications such as artificial muscles, sensors, intelligent robots, and so on. However, the CNT yarn actuators with one-dimensional structure were often only used to drive through electrochemical, thermal, or electrical stimulation, which limits the applications of CNT yarn actuators. In addition, the slow response speed, low output stress, uncontrollable driving deformation, and self-recovery without an external stimulus are also great challenges. Here, we propose a photoactuator with large output stress, fast response speed, large and reversible driving deformation, and good reusability based on stiffness-variable CNT nanocomposite yarn (CNT-NCY). Such a CNT-NCY photoactuator can achieve torsional and contractive actuation under irradiation of near-infrared (NIR) light; it is important that the actuation is reversible and controllable. The maximum rotation rate of the CNT-NCY photoactuator during the torsional actuation is about 45 rpm, and the contractive deformation can reach more than 9%. This CNT-NCY photoactuator can create more than 12 MPa output stress, which is 40 times higher than that of the human skeletal muscle. The driving mechanism of this CNT-NCY photoactuator has been analyzed, and its potential application has also been demonstrated.