Carbon Nanotube Yarn Actuators: An Electrochemical Impedance Model

Abstract

Twist-spun yarns made of carbon nanotubes have been shown to work as electrochemical actuators and force sensors. Deep understanding of yarn electrochemical behavior has so far not been possible, in part because of complicated yarn geometry. The electrochemical response of these yarns at different bias potentials was studied using Electrochemical Impedance Spectroscopy and compared with theoretical results for a cylindrical porous electrode. In the evaluated model, distributed capacitors and resistors are used to represent charge storage, electrolyte resistance and parasitic reactions. Resulting predictions are compared with experimental results and the capacitance per unit surface area of the MWNT bundles in the yarn is estimated. The model provides a foundation that can be elaborated upon for engineering applications.