The fabrication of micro- and nano- scale deterministic and stochastic pillar arrays for planar separations

Planar chromatography, unlike high performance liquid chromatography (HPLC), has not experienced a significant evolution in stationary phase media since the development of the technique. This has lead HPLC to become a much more popular and robust analytical method. Main factors that contribute to improved performance of chromatographic systems include a reduction in particle size, homogeneity of the stationary phase, and an increase in velocity of the mobile phase. In general, a reduction in particle size should lead to an improvement in the performance of all chromatography systems. However, the main obstacle of improving the performance of planar chromatography systems is that a reduction in particle size leads to a reduction in the capillary flow that governs solvent velocity. This decrease in solvent velocity leads to band broadening resulting in poor efficiency and resolution which are critical performance parameters for chromatographic systems.

The research presented herein investigates the scaling down of dimensions to the micro- and nano-scale for pillar arrays in order to investigate the effect on plate height and chromatographic efficiency of these capillary action driven micro- and nano-fluidic systems. Sample application is a critical parameter that effects band broadening in UTLC systems. By taking advantage of the superhydrophobic nature of these arrays the development of a spotting method that demonstrates the ability to create reproducible sample spots that are less than 200 microns (micro- scale arrays) and 400nm (nano- scale arrays) within these arrays are highlighted in this dissertation.

We have demonstrated the fabrication of deterministic micro-scale arrays that exhibit plate heights as low as 2µm as well as deterministic and stochastic nanothin-layer chromatographic platforms. Most significantly these systems resulted in bands that were highly efficient, with plate heights in the nm range. This resulted in significant separations of analytical laser test dyes, environmentally significant NBD-derivatized amines, and, biologically relevant chemotherapy drugs (Adriamycin and Daunorubicin).