Separation of Polystyrene Microbeads Using Dielectrophoretic/Gravitational Field-Flow-Fractionation

Abstract

The characterization of a dielectrophoretic/gravitational field-flow-fractionation (DEP/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15 microm in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and applied field frequency and voltage. Experimental data were analyzed using a previously reported theoretical model and good agreement between theory and experiment was found. It was shown that separation of PS beads was based on the differences in their effective dielectric properties. Particles possessing different dielectric properties were positioned at different heights in a fluid-flow profile in a thin chamber by the balance of DEP and gravitational forces, transported at different velocities under the influence of the fluid flow, and thereby separated. To explore hydrodynamic (HD) lift effects, velocities of PS beads were determined as a function of fluid flow rate in the separation chamber when no DEP field was applied. In this case, particle equilibrium height positions were governed solely by the balance of HD lift and gravitational forces. It was concluded that under the experimental conditions reported here, the DEP force was the dominant factor in controlling particle equilibrium height and that HD lift force played little role in DEP/G-FFF operation. Finally, the influence of various experimental parameters on separation performance was discussed for the optimization of DEP/G-FFF.

Role of peroxide in AC electrical field exposure effects on Friend murine erythroleukemia cells during dielectrophoretic manipulations

“…In this paper, we studied the effects of such exposure under the conditions most appropriate to DEP manipulations of cells, especially to cell DEP/FFF (field-flow fractionation) [45,46] sorting and DEP trapping [22,23,25]. Our experiments showed that under these conditions cell membrane integrity as revealed by trypan blue dye exclusion test was not compromised, and that cells were not stopped from proliferation.…”

“…Inside a nonuniform standing field like that used in our experiments, the overall field stress also results in a nonzero dielectrophoretic force given by (4) where p(f) is the polarization factor, namely, the ratio of the voltage dropped across the bulk solution to that applied to the electrodes. This dielectrophoretic force can be made suffciently strong to overcome the sedimentation force and cause cell levitation in the sub-MHz frequency range where Re(f CM ) is negative, an effect that is exploited in cell sorters based on DEP/FFF [45,46]. Fig.…”

Dielectrophoretic Segregation of Different Human Cell Types on Microscope Slides

“…Combining Equations 1 and 4, we find that a repulsive DEP force and the sedimentation force will balance when the height of the cell above the electrode plane is given by 10,19,27 h eq = 2πd log…”

Simultaneous separation and concentration of micro- and nano-particles by optically induced electrokinetics

“…Besides, several complex components such as a high numerical aperture lens and extremely precise motion translation stages are required, which may further inhibit the practical application of optical tweezers due to higher system cost. Dielectrophoresis (DEP) is another widely used technology that has been exploited in the past decade to separate polystyrene beads [12], and multiwall CNTs based sensors [13]. This technology provides a parallel and rapid method for micro-/nano-manipulation.…”