An evanescent-field technique for dielectrophoresis studies of colloidal particles

Dielectrophoretic collection rates have been used to measure the dielectric properties of particles. For accurate collection-rate measurements it is i mportant to be able to discriminate between particles collecting on an elec trode and particles that are in the bulk solution. In this paper we demonst rate how evanescent-imaging methods can be used to observe only those parti cles that are in the plane of the electrode array, so that significant impr ovements in the signal-to-noise ratio compared with conventional imaging me thods are achieved.