The influence of flow intensity and field frequency on continuous-flow dielectrophoretic trapping

• Trapping percentage is obtained for frequencies ranging from 1 kHz to 1 MHz.
• At low frequencies alternating-current-electro-osmosis lowers trapping percentages.
• Background flow may alter the effective cross-over frequency of particles/cells.
• Apparent shift in crossover frequency results in premature onset of zero-trapping.

We examine the combined influence of the intensity of pressure driven background flow and the frequency of the applied field on the continuous-flow dielectrophoretic trapping behavior of micro-particles within a micro-channel. Using an embedded interdigitated electrode array, we find that the measured trapping percentage over a continuous frequency range exhibits several curious effects which are strongly dependent on the flow intensity, including an apparent shift of the cross-over frequency and low-frequency dispersion. A numerical and theoretical model accounting for the combined effects of pressure-driven flow, dielectrophoresis and alternating-current electro-osmosis on the equation of motion for the particle is used to qualitatively describe the main experimental results.

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