Ricerc@Sapienza

A well-known limitation of hydrodynamic chromatography arises from the synergistic interaction
between transverse diffusion and streamwise convection, which enhances axial dispersion through
the Taylor-Aris mechanism. We show that a periodic sequence of slip/no-slip conditions at the channel
walls (e.g., representing wall indentations hosting stable air pockets) can significantly reduce axial
dispersion, thus enhancing separation performance. The theoretical/numerical analysis is based on a
generalization of Brenner’s macrotransport approach to solute transport, here modified to account for
the finite-size of the suspended particles. The most effective dispersion-taming outcome is observed
when the alternating sequence of slip/no-slip conditions yields non-vanishing cross-sectional flow
components. The combination of these components with the hindering interaction between the chan-
nel boundaries and the finite-sized particles gives rise to a non-trivial solution of Brenner’s problem
on the unit periodic cell, where the cross-sectional particle number density departs from the spa-
tially homogeneous condition. In turn, this effect impacts upon the solution of the so-called b-field
defining the large-scale dispersion tensor, with an overall decremental effect on the axial disper-
sion coefficient and on the Height Equivalent of a Theoretical Plate. Published by AIP Publishing.
https://doi.org/10.1063/1.5022257