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Optimization of Electroosmotic Microchannel Geometries Motivation Recent studies have shown the potential benefits of miniaturizing capillary electrophoresis on microfabricated chips. Among these benefits are reduced reagent use and shorter analysis times. However, since separation efficiency increases with the length of the separation channel, it is desirable to use longer microchannels within a small area, thus requiring turns in the microchannel. Project Description Researchers at Oak Ridge National Labs have shown that constant radius turns increase dispersion and therefore cancel the added benefit of the extra channel length that a serpentine channel permits. In collaboration with researchers at Agilent Laboratories, we have attempted to design a turn geometry that does not introduce additional dispersion. To predict the performance of the new corner geometries, we have used simulation tools (MEMCAD, Microcosm Inc.). The figure below shows images from a simulation that demonstrates the effect of constant radius, 90 degree turn on an initially Gaussian sample. The simulations are compared to data collected in the laboratory using bleached fluorescence imaging.
Figure 1. Simulation (top) and bleached fluorescence imaging (bottom) showing the dispersion of an initially Gaussian analyte band traveling through a constant radius turn. New corner designs have been successful in decreasing the amount of dispersion caused by the corner. The figure below shows images from a simulation that demonstrates the effect of compensating, 90 degree turn on an initially Gaussian sample. The simulations are compared to data collected in the laboratory using caged fluorescence imaging.
Figure 2. Simulation (top) and bleached fluorescence imaging (bottom) showing the dispersion of an initially Gaussian analyte band traveling through a compensating turn. (Mouseover figure to begin movie) Figure 3. Simulation (left) and caged fluorescence imaging (right) showing the dispersion of an initially Gaussian analyte band traveling through a 180 degree radius turn. The two bands at the end of the movie is an artifact of the caged-fluorescence dye which elecrophoretically separated during this experiment. References
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