Carbon nanotube yarns: sensors, actuators, and current carriers

Abstract

Carbon nanotubes (CNTs) have attracted extensive attention in the past few years because of their appealing mechanical and electronic properties. Yarns made through spinning multi-walled carbon nanotubes (MWNTs) have been reported. Here we report the application of these yarns as electrochemical actuators, force sensors and microwires. When extra charge is stored in the yarns, 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 yarns 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 yarns offer a conductivity of ∼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 yarns have a density (0.8 g/cm 3 ) that is an order of magnitude lower than metallic wires. The MWNT yarns 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.