Streaming Dielectrophoresis

Cummings EB (2003) Streaming dielectrophoresis for continuous-flow microfluidic devices. IEEE Eng Med Biol Mag 22 75-84... 

An alternative method is electrokinetic focusing, which uses a direct current electric field (at high voltages of 1 kV) to focus particles and Uquids into a narrow stream. Typically, the sample fluid stream is driven along the central channel of a cross-shaped channel. As the sample enters the intersection, three fluid streams meet and the sample stream is focused into narrow stream. Dielectrophoresis (DEP) can also be used for sample focusing. DEP is the movement of polarized particles in a nonuniform electric field. This phenomenon is explained further in the next section. The main advantage of this... 

Direct current dielectrophoresis (DC-DEP) Electrodeless dielectrophoresis Insulating post dielectrophoresis Insulator-based dielectrophoresis (iDEP) Streaming dielectrophoresis Trapping dielectrophoresis... 

An example of a practical dielec trofilter which uses both of the features described, namely, sharp electrodes and dielectric field-warping filler materials, is that described in Fig. 22-34 [H. I. Hall and R. F. Brown, Lubric. Eng., 22, 488 (1966)]) It is intended for use with hydrauhc fluids, fuel oils, lubricating oils, transformer oils, lubricants, and various refineiy streams. Performance data are cited in Fig. 22-35. It must be remarked that in the opinion of Hall and Brown the action of the dielec trofilter was electrostatic and due to free charge on the particles dispersed in the hquids. It is the present authors opinion, however, that both elec trophoresis and dielectrophoresis are operative here but that the dominant mechanism is that of DEP, in wdiich neutral particles are polarized and attracted to the regions of highest field intensity. 

Curvature-Induced Dielectrophoresis, Fig. 1 Mechanism of curvature-induced dielectrophoresis (C-iDEP) in a microchannel turn of angle, 0, where the dielectro-phoretic particle motion, Udep. competes with the elec-trokinetic particle motion, Uek, leading to a cross-stream particle deflection. The background color represent the contour of electric field, E (short arrows indicate the direction) (The figure is adapted from Ref. [2] with permission)... 

Figure 7.3.5. Schematic diagram of continuous dielectrophoresis using a "stream-centered" introduction of the sample cell suspension. (After Pohl (1977).)...

Cells undergoing positive dielectrophoresis move in the radial direction of the merging of the curved rear electrode and the flat front electrode, whereas cells experiencing negative dielectrophoresis move in the opposite direction. Meanwhile, the bulk carrier flow perpendicular to this electrical force carries the cells forward toward the carrier exit. The cells or particles unaffected by the nonuniform electrical field continue to move along the line of original introduction. Thus different cells trace out different trajectories and therefore can be withdrawn at different locations from the stream near the liquid outlet. 

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