Abstract
Dielectrophoresis is the motion of matter as induced by its polarization in an inhomogeneous electric field. The motion is (usually) into regions of highest field strength and is most evident with neutral matter. The direction of the motion is independent of the sign of the field. Dielectrophoresis is to be distinguished from electrophoresis which is is motion of charged matter induced by an electric field. The direction of the motion here is dependent on the sign of the field. The theoretical problems discussed here are (a) the behavior of real matter (as opposed to ideal dielectrics) in nonuniform field and (b) field configurations for maximum selectivity by dielectrophoresis.