Abstract
In this article, we report the development of a microchip based hydrodynamic chromatographic device that has an integrated pressure-generation unit to drive the mobile phase during the separation process. The pressure-gradient in this system was realized through introduction of a mismatch in electroosmotic flow rate at the junction of two glass channel segments with different depths as has been previously reported by our research group. A fraction of the resulting pressure-driven flow was then guided into an analysis channel to enable the size-based particle separations. The reported device allowed the realization of hydrodynamic chromatography in both micro- and sub-micrometer deep analysis channels as experiments showed the noted approach to yield pressure-driven velocities in our system that were nearly unaffected upon scaling down the depth of the entire fluidic network. Separations with plate numbers in the range of 500-2000 plates/mm were realized in a 3 cm long analysis column for a mixture of 25, 100 and 250 nm diameter polystyrene beads with analysis times as short as 12 s. The noted separation efficiency exceeds those previously reported in the literature for hydrodynamic chromatographic analysis performed on microchips likely due to a faster mass transfer across the channel cross-section as well as narrower band injections in our assays.