Electrokinetically-driven plug flow

Fig. 9.7.1 Visualization of (a) pressure-driven Poiseuille flow (parabolic) in a 100 )xm ID fused silica capillary and (b) electrokinetically-driven plug flow in a 75 pm ID capillary. Numbers denote time in milliseconds between micrographs in both sequences. See text for details.

Electrokinetic flow covers in principle the transport of liquids (electroosmosis) and samples (electrophoresis) in respraise to an electric field. Both motions are associated with the electric double layer that is formed spraitaneously at the solid-liquid interface in which there is a net charge density. Compared to the traditional pressure-driven flow, electrokinetic flow is more suited to miniaturization due to its nearly plug-like velocity profile and much lower flow resistance. However, Joule heating is a ubiquitous phenomenon in electrokinetic flow that will affect the transport of both liquids and samples via temperature-sensitive material properties. 

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