Controlled positioning of carbon nanotubes by dielectrophoresis: insights into the solvent and substrate role.

We demonstrate the ability to precisely control the deposition of a defined number of carbon nanotubes (CNTs) from solution onto microfabricated electrodes using dielectrophoresis. The solvation shell around the CNTs, exhibiting a high dielectric constant which is possibly larger than the intrinsic dielectric constant of CNTs, is found to play a crucial role in electrophoretic processes. Substrate resistivity is also very important: The spatial repartition of the electric field between the substrate and the microelectrodes leads to deviations from the precise location of the CNTs. A recipe is given for the dielectrophoresis of CNTs which can be extended to other nanowires or nanotubes.