A theoretical expression for the dielectrophoretic velocity of oblate spheroidal cells is presented in this paper. The cell velocity has been measured using the Stokes method and a dielectrophoretic V-shaped electrode chamber and calculated as a function of the cell's position. Human red blood cells (RBC) were used to verify the theoretical model. Velocity measurements were performed in the frequency range between 150 kHz and 3 MHz for a suspending medium of conductivity 2 mS . A parameter that includes the dielectrophoretic properties of RBC, the cell dimensions (the length of the long semiaxis and the axial ratio) and electrical properties (the real component of the cell-medium Clausius-Mossotti factor, is defined. The calculated values of are corrected for the polarization effects that take place at the electrode-medium interface. The good agreement between the experimental observations and the theoretical predictions that we found validates the theory. The value of the parameter can be used as a very sensitive tool to detect small differences in size between cells and changes in their shape and electrical properties.

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A chamber and method for the measurement of dielectrophoretic (DEP) force in yeast cells (Saccharomyces cerevisiae) is described. The physical method uses the Stokes drag force and a V-shaped chamber. Velocity measurements were induced over the frequency range of between 50 kHz and 5 MHz for a suspending medium of 2.2 mS/m in conductivity. Average values of DEP force and effective polarizability have been determined from the velocity measurements. Experimental data with single cells confirm the theoretical expression for the axial profile of the electric field. The results show that this method-and-chamber system is an accurate tool for measuring of DEP force over single cells. Population data of 129 cells confirm the theory showing that the DEP velocity distribution density of the population is similar to the cellular "square radius".

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