Imaging of electroosmotic flow in plastic microchannels

We have characterized electroosmotic now in plastic microchannels using video imaging: of caged fluorescent dye after it has been uncaged with a laser pulse. We studied now in microchannels composed of a single material, poly(methyl methacrylate) (acrylic) or poly-(dimethylsiloxane) (PDMS), as well as in hybrid microchannels composed of both materials. Plastic microchannels used in this study were fabricated by imprinting or molding using a micromachined silicon template as the stamping tool. We examined the dispersion of the uncaged dye in the plastic microchannels and compared it with results obtained in a fused-silica capillary. For PDMS microchannels, it was possible to achieve dispersion similar to that found in fused silica. For the acrylic and hybrid microchannels, we found increased dispersion due to the nonuniformity of surface charge density at the walls of the channels. In all cases, however, electroosmotic now resulted in significantly less sample dispersion than pressure-driven flow at a similar velocity.