Acoustic Streaming-Induced Vortex Chromatography in Micron-Scale Rectangular Open Tubular Channels

The separation resolution in the most advanced pressure-driven separation devices is predominantly limited by the Taylor-Aris dispersion. The induction of lateral flow perpendicular to the axial flow has recently been proposed and validated as a strategy to improve separation resolution by reducing Taylor-Aris dispersion. In the present study, we introduce an acoustic-based lateral flow into a microfluidic channel, which is enabled by matching the applied acoustic wavelength with the channel depth. With this approach, a small micrometer-scale (critical) dimension is foreseen for chromatographic purposes, and a larger dimension is foreseen to attain acoustic resonance. It is experimentally observed (in a 10 μm × 75 μm channel) that the induced acoustic streaming reduces Taylor-Aris dispersion by a factor of 10, hence resulting in a chromatographic system that behaves as if it has a critical dimension of 1 μm. It is also shown numerically that this gain can be further improved and what the impact of inevitable imperfections in the microfabricated chips is. The first example of the implication of the improvement in the chromatographic separation efficiency is shown for a macromolecule separation operated under reverse-phase conditions.