Chaotic Mixer for Microchannels

TLDR

Mixing in microchannels is challenging because flows are laminar, lacking turbulence-driven homogenization, and molecular diffusion across the channel is slow. The study introduces a passive method to mix steady pressure‑driven flows in microchannels at low Reynolds number. The method employs bas‑relief structures on the channel floor, fabricated with standard planar lithography techniques. With this approach, the required channel length for mixing increases only logarithmically with the Peclet number, and hydrodynamic dispersion is reduced compared to a smooth channel.

Abstract

It is difficult to mix solutions in microchannels. Under typical operating conditions, flows in these channels are laminar—the spontaneous fluctuations of velocity that tend to homogenize fluids in turbulent flows are absent, and molecular diffusion across the channels is slow. We present a passive method for mixing streams of steady pressure-driven flows in microchannels at low Reynolds number. Using this method, the length of the channel required for mixing grows only logarithmically with the Péclet number, and hydrodynamic dispersion along the channel is reduced relative to that in a simple, smooth channel. This method uses bas-relief structures on the floor of the channel that are easily fabricated with commonly used methods of planar lithography.