Isodielectric separation and analysis of cells.

Measuring the electrical properties of a cell provides a fast and accessible means of identifying or characterizing cells whose biological state differs from the population as a whole. This chapter describes a microfluidic method for characterizing the electrical properties of cells based upon their convergence to equilibrium in an electrical conductivity gradient. The method, called isodielectric separation, uses the dielectrophoretic force induced on polarizable objects in spatially nonuniform electric fields to deflect cells to the point in the conductivity gradient where their polarization charge vanishes. This equilibrium position encodes the cell's electrical properties and can be used to identify cells that are electrically distinct from a background population, to determine the extent of this difference, and to physically isolate them for further study.