Patent ID: 7211183

Claim:
A method of fractionation of a mixture of particles which are suspended in an electrolyte solution between a first electrode positioned in a first plane and the surface of a second planar electrode positioned in a second plane different from the first plane, and wherein the surface or the interior of the second electrode either is or can be patterned to modify the electric field extending from the surface into the electrolyte solution, and wherein the particles comprise at least two types of particles distinguished by their respective relaxation frequencies; and generating an electric field between the first and the second electrodes by applying an AC voltage between the two electrodes, said electric field having a frequency that is less than or equal to the relaxation frequency of at least one of said particle types but greater than the relaxation frequencies of at least one other of said particle types, wherein the particles having relaxation frequencies greater than or equal to the frequency of the electric field are separated from other particles.