Dielectrophoretic filter for separation and recovery of biological cells in water

Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized particles in nonuniform electric fields. DEP has found many useful technological applications including separation, levitation, and characterization of dielectric particles such as biological cells. In this study, the authors demonstrated continuous separation and recovery of biological cells suspended in water using a DEP filter. The DEP filter consists of an electrode system that is filled up with many glass beads. These glass beads modify the electric field distribution in the electrode system so that strong DEP force is generated on their surfaces. If the DEP force is stronger than drag force exerted by liquid flow in the filter, the suspended particles can be trapped and eliminated from the flowing liquid. The DEP filter can control trapping and releasing process just by changing electrode energizing AC signal and the resultant DEP force. It was experimentally confirmed that the DEP filter could continuously eliminate yeast cells suspended in water. The cell density decreased from 10/sup 6/ to 10/sup 1/ cells/mL in about 1 h. The electrical conductivity of the medium was a crucial parameter that influenced the liquid temperature by Joule heating and DEP force. Furthermore, the selective separation of viable and nonviable yeast cells was demonstrated by utilizing the viability dependency of the DEP force.