Chromatographic explanation for the side-wall induced band broadening in pressure-driven and shear-driven flows through channels with a high aspect-ratio rectangular cross-section

Based on a simple, chromatography-based analogy, a quantitatively exact explanation for the strong additional band broadening induced by the presence of the side-walls in flow channels with a large aspect-ratio rectangular cross-section is given and validated for two different flow types: pressure-driven and shear-driven flow.