Electric field, separations based dielectrophoresis

Herbert A. Pohl/ Ph.D./ (deceased), Profe.s.sor of Physics, Oklahoma State University. (Separation Proce.s.se.s Based Primarily on Action in an Electric Field Dielectrophoresis)... 

Another electrokinetic effect is based on polarization of particles within an oscillating electrical field or field gradient (dielectrophoresis), as depicted in Fig. 13c. Dielectrophoresis is applied in many fields, e.g. for the controlled separation and trapping of submicron bioparticles [245], for the fusion and transport of cells [246], or the separation of metallic from semiconducting carbon nanotubes [13, 247-249]. Other applications are cell sorting [250, 251] and apoptosis of cells [252, 253]. 

The approaches are principally based on the subtle difference between various properties such as density, chemical reactivity, dielectric constant, etc., of M- and S-CNTs. Moreover, the growth parameters also affect the fractional amounts of M- and S-CNTs in a mixture. Li et al. have observed that CNTs synthesized by PECVD at 600°C are preferably S-CNTs (90%), while those produced by HiPco and Laser ablation consist of 61 and 70% M-CNTs, respectively [187]. The first successful approach for M/S CNT separation is alternating current dielectrophoresis [188]. It uses the different dielectric constants of M- and S-CNTs. In an electric field gradient, metallic CNTs are attracted towards the electrode, while the semiconducting CNTs remain in the solution. Song et al. have reported a separation method based on the observation that metallic CNTs are burned faster compared to... 

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