The Mutual Interactions of Carbon Nanotubes During Dielectrophoresis

Dielectrophoresis (DEP) has been widely used for the deposition of various types of nanomaterials including carbon nanotubes (CNTs). Here, we report the results of experiments that show that the interactions between deposited and suspended nanotubes during the deposition process can considerably affect the dynamics and the final results of the deposition. Semiperiodic stripes of nanotubes bridging two electrodes are formed from solutions containing no surfactant. The periodicity of the patterns depends on the geometry of the electrodes. Finite-element method simulations are used to explain the mechanisms underlying the observed experimental outcomes. The pattern formation is shown to be related to the mutual effects of CNTs on each other. The reason lies in the changes in the electric field as a result of deposition of CNTs. These changes directly alter the DEP force field and, therefore, the way the CNTs are guided. The extent of effectiveness of the electrothermal force, which turns out to be substantial for some solutions, is also investigated, and it is shown that although in some situations the heat generated by the current passing through the nanotubes considerably increases this force, the DEP force remains dominant when a surfactant-free solution is used.