Particle manipulation using moving dielectrophoresis

After rigorous development over the years, dielectrophoresis has been established as an effective method to manipulate micron and sub-micron sized particles. In particular, it is a promising technology for lab-on-a-chip or micro total analysis system (TAS) to separate cells for biomedical applications. This technology is based on the knowledge that a particle suspended in a fluid medium experiences a net electrical force, due to a polarization effect, when non-uniform electrical fields are applied across the fluid. By varying the applied electric field frequencies, the magnitude and the direction of the dielectrophoretic forces on the particle can be varied and controlled. When the applied electric field only varies in magnitude over time, the dielectrophoretic force is 1-dimensional. This is commonly referred as conventional dielectrophoresis. When the applied electric field has a varying magnitude and phase, the dielectrophoretic force is 2-dimensional. This is commonly referred as traveling wave dielectrophoresis. While particle separations have been demonstrated with devices based on these two techniques, the separated particles were confined in space. To overcome this issue, fluid flow is generally used to carry the particles. In this investigation, moving dielectrophoresis (mDEP) is introduced for the manipulation and transportation of particles. The moving dielectrophoresis is generated by a series of electrodes which can be individually energized to induce an electric field that moves from one electrode to another. Beside the electric field frequency, the switching speed of the electrode is a second time parameter introduced in moving dielectrophoresis. A major difference of this technique from the traveling wave dielectrophoresis is that the moving speed of the energized electrodes is independent of the electric field frequency. By sequentially energizing the electrodes, a particle can be controlled to move in the same direction. By controlling the electric field frequencies and the energizing of the electrodes, other manipulation techniques like separation, isolation, fractionation and trapping can be achieved. A mathematical model is also presented to provide a theoretical basis for the use of the moving dielectrophoresis.