The application of a.c. electric fields to control and manipulate isolated particles in suspension using microelectrode structures is a well-established technique. In particular, the dielectrophoretic manipulation of sub-micron bioparticles such as viruses, cells and DNA is now possible. As the size of the particle is reduced, so the effects of Brownian motion become greater. Therefore, to enable the dielectrophoretic manipulation of sub-micron particles using realistic voltages, the characteristic dimensions of the system must be reduced, to increase the electric field. However, a high strength electric field also produces a force on the suspending electrolyte, setting it into motion. Indeed, this motion may be a far greater limiting factor than Brownian motion.
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