Carbon nanotube yarns: Sensors, actuators and current carriers

Carbon nanotubes (CNTs) have attracted extensive attention in the past few years because of their appealing mechanical and electronic properties. Yams made through spinning multi-walled carbon nanotubes (MWNTs) have been reported. Here we report the application of these yams as electrochemical actuators, force sensors and microwires. When extra charge is stored in the yams, change in length. This actuation is thought to be because of electrostatic as well as quantum chemical effects in the nanotube backbones. We report strains up to 0.7 %. At the same time, the charged yams can respond to a change in the applied tension by generating a current or a potential difference that is related to the applied tension force. As current carriers, the yams offer a conductivity of similar to 300 S/cm, which increases linearly with temperature. We report a current capacity of more than 10(8) A/m(2), which is comparable to those of macroscopic metal wires. However, these nanotube yams have a density (0.8 g/cm(3)) that is an order of magnitude lower than metallic wires. The MWNT yams are mechanically strong with tensile strengths reaching 700 MPa. These properties together make them a candidate material for use in many applications including sensors, actuators and light-weight current carriers.