Abstract
Particles migrate toward the channel center in electrophoretic motion through a rectangular microchannel due to a wall-induced electrical force.
The fundamental study of particle electrophoresis in microchannels is relevant to many applications. It has long been accepted that particles move parallel to the applied electric field in a straight uniform microchannel. This paper presents the first experimental demonstration of lateral particle migration in electrophoresis through a rectangular microchannel. This wall-induced dielectrophoresis-resembled motion is driven by the electrical force arising from the non-uniform electric field around the particle. It decays rapidly when the particle is away from the channel wall, and vanishes in the center of the channel. The observed result is a focused particle stream flowing along the channel centerline. The measured widths of the particle stream at various electric fields agree reasonably with the predictions of an approximate analytical model.