Fabrication, morphology and actuation from novel single-wall carbon nanotube/Nafion composites.

Mechanical actuators that simultaneously provide high power densities and large force generation capacities are of great scientific and technological interest. Recently single wall carbon nanotube (SWNT) sheets ("bucky" papers) were shown to possess significant promise as electrochemical actuators. Embedding polyelectrolytes, like Nafion TM, within the nanotube matrix has the potential to address the limitations of SWNT bundling and tube slippage thus increasing force generation. In this paper two types of Nafion/SWNT composite actuators have been investigated depending on the method of fabrication. In the first case, infiltration of Nafion within SWNT sheet matrix was followed by annealing at 150 degreesC to invert Nafion's micellar structure and render it insoluble. This has resulted in a substantially exfoliated layer morphology that causes a reduction in both conductivity and actuation strain (c.a. 0.03%). In the second case, slow casting of a methanolic suspension of Nafion and SWNT soot, followed by annealing at 150 degreesC, resulted in a more homogeneous structure. This composite, upon electrochemical cycling between -1 and +1 V in aqueous electrolytes, exhibited actuation strains (as high as 0.43%). However, these higher strains are accompanied by an order of magnitude reduction in modulus largely due to Nafion swelling.