Electrokinetic Flow Diagnostics

S. Devasenathipathy and J.G. Santiago The advent of microfabricated chemical analysis systems has led to a growing interest in microfabricated fluidic systems with characteristic scales in the range of a micron to a millimeter. A motivation to integrate components in a manner analogous to modern microelectronics is coupled with a potential for achieving massively parallel functions, and the field is rapidly developing. Most microfluidic systems rely on two modes of fluid transport: pressure-driven and electrokinetically-driven flow. An important class of microfluidic systems is systems that aim to perform basic chemical assays and other processing steps on a fluidic chip. Fluid motion in these chemical biochip systems is often achieved using electroosmotic flow; which enjoys several advantages over pressure-driven flows. Chiefly, electroosmotic flow produces a nearly uniform “plug” profile, which results in reduced sample species dispersion as compared to the velocity gradients associated with pressure-driven flows. This important contrast between pressure-driven and electroosmotic flows is demonstrated by the visualization data in Figure 1.