Separation of erythrocytes and latex beads by dielectrophoretic levitation and hyperlayer field-flow fractionation.

A model system consisting of a mixture of latex beads and erythrocytes has been investigated to demonstrate the practical feasibility of particle separation by means of the combined application of negative dielectrophoresis and hyperlayer field-flow fractionation. The dielectrophoretic levitation of latex beads is demonstrated by energizing interdigitated electrodes, of widths and separation ranging from 5 to 40 μm, with AC signals of 0–10 V (rms) in the frequency range 1 kHz–10 MHz. Maximum levitation was attained at 1 MHz, at which frequency levitation is relatively independent of the suspending medium conductivity. Levitation was also independent of particle size, but dependent on particle density and dielectric properties. At 1 MHz the erythrocytes were attracted to the electrodes by positive dielectrophoresis, and so could be separated from the latex beads by fluid flow. The electric field and field gradient above the electrodes were also computer modelled, and this information was used to design the electrode and chamber geometries for optimum DEP-field-flow fractionation.