Carbon nanotube sheets for the use as artificial muscles

Low voltage artificial muscles are of great importance for an enormous variety of industrial applications. In 1999 a new material, carbon nanotube sheets also called bucky paper, was described with suitable electromechanical properties. We developed an experimental set-up which allows, for the first time, the analysis of actuation forces vertical to the sheet plane. Single walled carbon nanotubes (SWNT) from arc discharge or HiPco process as well as multi walled carbon nanotubes (MWNT) were used as received or after further purification steps to produce carbon nanotube sheets by the filtration technique. The fastest actuation time of three seconds could be, up to now, obtained with the HiPco-material, which is free of amorphous carbon particles. Several parameters influence the electromechanical properties like the sheet thickness, the used electrolyte, the applied voltage and so on. But also the nanotube material itself and the procedure for the bucky paper production must be considered intensively to avoid large differences between different batches and to produce indiscriminate and reproducible carbon nanotube sheets. We characterized the material, among others, by TGA, SEM/EDX, and BET analysis. (C) 2004 Elsevier Ltd. All rights reserved.