Manipulation of carbon nanotubes using AC dielectrophoresis

Single-wall carbon nanotubes (SWNTs) suspended in isopropyl alcohol are placed between two cross-structured electrodes using an ac dielectrophoresis technique. The SWNTs are found to attach to the electrodes along the direction of the ac external electric field. The SWNTs predominately bridge the shortest gap between the two electrodes and the spatial distribution of the tubes becomes wider for a long manipulation time (say, greater than 300 s). The observed phenomenon is analyzed in terms of the dielectrophoresis-induced torque and force on the SWNTs. Our simulation shows that the time for rotating SWNTs to the direction of the electric field is much smaller than that for translating SWNTs. We also found that metallic SWNTs are forced along the gradient direction of spacial distribution of the electric field strength while semiconducting SWNTs are forced in the opposite direction.