ABSTRACT
The principal methods for so-called bulk dielectrophoretic separation employ conventional dielectrophoresis to achieve these goals; another uses a different electrokinetic phenomenon, called traveling-wave dielectrophoresis. The simplest method of separation is to select a field frequency and suspending medium such that one type of particle experiences positive dielectrophoresis, and the other negative dielectrophoresis as with previous examples involving latex beads, and viruses. A second method of fractionation employing dielectrophoresis is its use in field-flow fractionation. This technique has been used since the 1960s for separating macromolecules and colloids up to about the micrometer scale. The concept of the dielectrophoretic thermal ratchet — using dielectrophoresis as a means of rectifying Brownian motion to move particles around an electrode array — was first described by A. Ajdari and J. Prost who considered the forces acting on a particle in suspension and subject to Brownian motion.
