Geometric effects of collocated monolithic support structures on separation performance in microfabricated systems

Twenty microfabricated COMOSS columns with varying dimensions were investigated in this work. Columns with different channel depth (1.6–10 μm) and width (2–4 μm) were studied; the size of collocated particles was also varied, including diamonds (5×5–11×11 μm) and their elongated and extended versions: hexagonal structures allowing greater distances between mixing nodes. Comparisons were made by plotting plate height-voltage curves for each type of column geometry using rhodamine 110, fluorescein, or small peptides as standard compounds. It was demonstrated that the efficiency of separation strongly depends on the geometry of resulting channels. An increase of distance between channel intersections (or decrease of trans-channel coupling frequency) was shown to unavoidably lead to a considerable decrease in efficiency of the microfabricated column. It was also found that low aspect ratio structures produced from positive photoresist masters were more efficient than their high aspect ratio equivalents. The highest efficiency of 620000 plates per meter was obtained with 10 μm deep channels and particles of 5.2×5.2 μm (diamonds).