Dielectrophoresis of single-walled carbon nanotubes

Abstract

This work was focused on the behavior of single-walled carbon nanotubes under the influence of dielectrophoretic forces. In particular, it aimed at an understanding of the basic processes in dielectrophoretic separation and assembly experiments. By dielectrophoretic deposition onto interdigitated electrode arrays continuous films of carbon nanotubes were produced, in which metallic and semiconducting nanotubes possess a significantly different degree of alignment with respect to the electric field. These findings were explained with an advanced theoretical model for nanotube dielectrophoresis, which takes into account the structural and dielectric anisotropy of single-walled carbon nanotubes. An experiment was designed to measure the degree of alignment of dispersed single-walled carbon nanotubes under variation of the applied electric field, from which-according to the theoretical predictions-the dielectric properties of the nanotubes can be derived. First results revealed a weak dependence of the alignment on the electric field. The possibility of separating metallic and semiconducting single-walled carbon nanotubes by electrodeless dielectrophoresis through nanopores was studied under various experimental conditions. The results suggest that after an optimization of the process parameters, electrodeless dielectrophoresis might be suited for an upscaling of the separation of single-walled carbon nanotubes. Additionally, finite element simulations were carried out to visualize the electric potential and dielectrophoretic force fields in various electrode setups. The results allowed for an interpretation of experimental observations regarding the influence of the sample substrate on the dielectrophoretic deposition of single-walled carbon nanotubes, the self-limiting single-nanotube assembly and the characterization of carbon nanotubes by voltage-contrast scanning tunneling microscopy.