Numerical investigation of axial dispersion reduction in chromatography using AC-electroosmotic flow in tapered geometries: concept and numerical investigation

Axial dispersion is a major limitation in chromatographic systems, reducing resolution and separation efficiency. While electroosmotic flow (EOF) has been used to control dispersion in pressure-driven systems, most studies conducted so far have focused on channels with rectangular geometries. In this work, we investigate the impact of tapered microchannel designs combined with alternating current to actively induce lateral electroosmotic (AC-EOF) vortex flows that enhance mixing and reduce axial dispersion. Using macrotransport theory and numerical simulations, we demonstrate that trapezoidal geometries with top–bottom electrode configurations generate lateral flow patterns that significantly alter solute transport. These vortices enhance transverse mixing, counteracting the dispersion typically caused by geometrical asymmetry or retention. Importantly, the proposed design can in future be easily implemented using polymeric microfluidic chips, which can makes the approach not only cost-effective, but also practically feasible. We propose a device design strategy that can be readily fabricated and scaled, thereby highlighting a realistic and robust solution for dispersion management. This approach is strongly influenced by taper angle, aspect ratio, and applied voltage, with optimal configurations leading to marked improvements in transport uniformity. This study advances the understanding of AC-EOF in non-rectangular channels and paves the way to the use of low-cost polymeric devices as a scalable platform for improving chromatographic performance.