Abstract-
Electrokinesis (EK) and dielectrophoresis (DEP) are
electrostatic transport mechanisms of considerable practical importance in
microfluidics. In general microsystems, these mechanisms are difficult to
model, requiring the coupled solution of the Poisson-Boltzmann, Stokes (or
Navier-Stokes), and unsteady species-transport equations, in addition to models
of interfacial charges, electrochemical reactions, and material properties in
high-electric fields. This kind of complexity has limited rational approaches
to microfluidic design.
We have developed theoretical and methodological tools and tricks that rigorously skirt this general complexity including the theory of ideal electrokinesis and linear dielectrophoresis and the "faceted" and "corduroy" design methodologies. Together these tools support rational design of broad classes of microfluidic systems.
The concept, usage, and experimental validation of each of these tools is described along with rationally designed particle concentrators and spectrometers for sorting, collecting, and immobilizing cells, bacteria, and spores. These novel designs have no direct macroscopic analog; they provide new capabilities to clinical and biological researchers. Implemented in a system with other microfluidic devices, these devices support automated sample preparation and provide additional selectivity and background rejection.
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| Instantaneous separation of live (green) and dead (orange) E. coli bacteria in a water steam by a competition between electrokinesis and dielectrophoresis. The circles are glass posts on 200 micron centers. Rationally designed microsystems of this type provide new research tools to biologists and new capabilities to miniature sensor systems. |
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