INTRODUCING DIELECTROPHORESIS AS A NEW FORCE-FIELD FOR FIELD-FLOW FRACTIONATION

We present the principle of cell characterization and separation by di electrophoretic field-flow fractionation and show preliminary experime ntal results. The operational device takes the form of a thin chamber in which the bottom wall supports an array of microelectrodes. By appl ying appropriate AC voltage signals to these electrodes, dielectrophor etic forces are generated to levitate cells suspended in the chamber a nd to affect their equilibrium heights, A laminar Row profile is estab lished in the chamber so that fluid flows faster with increasing dista nce from the chamber walls. A cell carried in the flow stream will att ain an equilibrium height, and a corresponding velocity, based on the balance of dielectrophoretic, gravitational, and hydrodynamic lift for ces it experiences. We describe a theoretical model for this system an d show that the cell velocity is a function of the mean fluid velocity , the voltage and frequency of the signals applied to the electrodes, and, most significantly, the cell dielectric properties. The validity of the model is demonstrated with human leukemia (HL-60) cells subject ed to a parallel electrode array, and application of the device to sep arating HL-60 cells from peripheral blood mononuclear cells is shown.