Imaging of electroosmotic flow in plastic microchannels

We have characterized electroosmotic now in plastic microchannels using vid eo 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 microchannel s used in this study were fabricated by imprinting or molding using a micro machined silicon template as the stamping tool. We examined the dispersion of the uncaged dye in the plastic microchannels and compared it with result s obtained in a fused-silica capillary. For PDMS microchannels, it was poss ible to achieve dispersion similar to that found in fused silica. For the a crylic and hybrid microchannels, we found increased dispersion due to the n onuniformity of surface charge density at the walls of the channels. In all cases, however, electroosmotic now resulted in significantly less sample d ispersion than pressure-driven flow at a similar velocity.