Fast-response, agile and functional soft actuators based on highly-oriented carbon nanotube thin films

Highly-oriented carbon nanotube (CNT) film, which is made from super-aligned CNT array, is an even, tough and soft material. This CNT film has strong anisotropy in electrical and mechanical properties. The electrical conductivity and Young's modulus of the CNT film (2.8 10⁴ S m^-1, 3000 MPa) along the CNT aligned direction are one magnitude larger than those (2.3 10³ S m^-1, 200 MPa) along the vertical direction. In virtue of easy preparation and good processability, it is competent as high-performance flexible electrodes for soft actuators, advanced film capacitors and batteries. Here, we use this highly-oriented CNT film as a heating electrode to make fast-response soft actuators. The actuator has a thin bilayer composite structure and is driven by current heating. It takes a typical miniaturized actuator only 0.9 s to perform fast and large-angle deformations (270 bending, curvature 4.8 cm^-1), and its bending speed can reach 300 s^-1 by low power driving (2.4 W). Based on this CNT film, graphical designs and fine processing were carried out to make patterned electrodes and functional actuators, such as cross-shaped and hand-shaped ones. Notably, a well-designed gripper-like actuator can even deftly grab and manipulate some tiny things, e.g. a grain of rice. Moreover, the anisotropic properties of the CNT film also effectively influence and regulate the deformation forms of the actuators. In virtue of good and unique performances in electrical, mechanical and thermal aspects, the high-oriented CNT film would have promising application prospects in various emerging soft devices.