Solutal transport in rectangular nanochannels under pressure-driven flow conditions

Abstract

In this article, we investigate the effect of channel sidewalls on the transport of neutral samples through rectangular conduits under pressure-driven flow and small zeta potential conditions. Our analyses show that while these structures can significantly reduce the streaming potential in small aspect ratio rectangular channels, they introduce a very minor variation in the sample velocity with the extent of Debye layer overlap in the system. Moreover, the increase in sample dispersion due to the channel side-regions has been shown to be nearly independent of the Debye layer thickness and very comparable to that reported under simple pressure-driven flow conditions. Interestingly however, a simple one-dimensional (1D) model that decouples band broadening arising due to diffusional limitations across the depth and width of the rectangular conduit has been shown to capture the predicted dependence of the Taylor–Aris dispersion coefficient on the channel aspect ratio under all operating conditions with less than 3% error.