This invention relates to a method and device for separating charged particles according to their diffusivities in a separation medium by means of a spatially and temporally varying
electric potential. The method is particularly suited to
sizing and separating
DNA fragments, to generating
DNA fragment length polymorphism patterns, and to sequencing
DNA through the separation of
DNA sequencing reaction products. The method takes
advantage of the transport of charged particles subject to an
electric potential that is cycled between an off-state (in which the potential is flat) and one or more on-states, in which the potential is preferably spatially periodic with a plurality of eccentrically shaped stationary potential wells. The potential wells are at constant spatial positions in the on-state. Differences in liquid-phase diffusivities lead to
charged particle separation. A preferred embodiment of the device is microfabricated. A separation medium fills physically defined separation lanes in the device. Electrodes deposited substantially transverse to the lanes create the required electric potentials. Advantageously, injection ports allow sample loading, and special gating electrodes focus the sample prior to separation. The effects of thermal gradients are minimized by placing the device in contact with a
thermal control module, preferably a plurality of Peltier-effect
heat transfer devices. The small size of a microfabricated device permits rapid separation in a plurality of separation lanes.