Single-walled carbon nanotubes (SWCNTs) have attracted significant attention as building blocks for future nanoscale electronics due to their small size and unique electronic properties [1-4]. However, current SWCNT production techniques generate a mixture of two types of nanotubes with divergent electrical behaviors due to structural variations [2, 5]. Some of the nanotubes act as metallic materials while others display semiconducting properties. This random mixture has prevented the realization of functional carbon nanotube-based nanoelectronics [3, 6-7].

Here, a method of purifying a continuous flow of semiconducting nanotubes from an initially random mixture of both metallic and semiconducting SWCNTs in suspension is presented. This purification uses AC dielectrophoresis (DEP), and takes advantage of the large difference of the relative dielectric constants between metallic and semiconducting SWCNTs. Because of a difference in magnitude and opposite directions of a dielectrophoretic force imposed on the random SWCNT solution, metallic SWCNTs deposit onto the electrodes while semiconducting SWCNTs remain in suspension [3]. This work presents a significant advancement in nanotube purification in a facile and scalable manner, and can therefore significantly increase the feasibility of manufacturing reliable semiconducting SWCNT-based nanoelectronic devices. A detailed discussion of these techniques will be presented, along with the fabrication of a dielectrophoretic force-utilized microfluidic lab-on-a-chip device that can accomplish purification of semiconducting nanoparticles at industrially relevant processing rates. The effectiveness of the device is characterized using ultraviolet-visible (UV-Vis) spectroscopy analysis on separated samples.

References:

[1] P. Avouris, Physics World 20, 40-45 (March 2007).

[2] P. Avouris and J. Appenzeller, The Industrial Physicist, June/July 2004, American Institute of Physics.

[3] R. Krupke et al., Science 301, 344-347 (2003).

[4] N. Peng et al., J. Appl. Phys. 100, 024309 (2006).

[5] M. S. Dresselhaus, G. Dresselhaus, and M. Pimenta, Euro. Phys. J. D 9, 69-75 (1999).

[6] R. Krupke et al., Nano Lett. 3, 1019-1023 (2003).

[7] T. Tanaka et al., Appl. Phys. Expr. 1, 114001 (2008).

Rustin Golnabi

Johns Hopkins University

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