If biological cells dissolved in an aqueous medium are exposed to inhomogeneous electrical fields, an electric dipole moment can be induced and an interaction with the field is induced. Consequently, a force is exerted on the cell, which is called dielectrophoresis (DEP) or dielectrophoretic effect. The majority of biotechnological investigations in this field involve the manipulation of cell currents in microfluidic channels in which DEP is induced by metallic electrodes. The DEP force may be either attractive or repulsive, depending on whether the cell is attracted to or repelled from the electrode with higher field line density.
Dielectrophoresis is a remarkable phenomenon because it allows to separate different cells according to their different polarizabilities - without marking them as shown in the schematic drawing. The technique has therefore already been tested for the sorting of different E. coli strains or on microorganisms with different densities of cell organelles. Within the Joint Lab its use for the optimization of bioprocesses is being tested [Abt et al. 2020].