Novel Actuating System Based on a Composite of Single-Walled Carbon Nanotubes and an Ionomeric Polymer

We report the fabrication and characterization of a novel composite material based on single walled carbon nanotubes (SWNT)s and the ionomeric polymer Nafion. SWNTs were airbrushed from a chloroform suspension onto both sides of a Nafion membrane (180 μm) and the electromechanical properties of the composite material were explored. The outer layers of carbon nanotubes acted as electrodes in order to pass electrical current through the system while the mechanical response was monitored. Under this design, the mechanical response could be characterized, with respect to the electrical signal, as a function of: voltage, waveform (AC vs. DC), and frequency (AC). Data was also compiled to gauge the effect of size and thickness of each individual layer of the system. The reference samples (graphite-Nafion and sputtered goldNafion) did not exhibit mechanical actuation at the same conditions. An analytical model for current decay was considered that is in agreement with the experimental data. Bi-exponential decay with a long time component was found for bias, which is above the actuating threshold. That was explained in terms of increasing of the water dielectric constant and polymer-SWNT interface area. The possible mechanisms of the actuation in this novel composite are discussed.