Enhancing Mixing Efficiency of Shear-Thinning Liquids in Split-and-Recombine Microdevices

Efficient mixing of shear-thinning fluids is crucial in many industries, with micromixers playing a key role in improving fluid handling. This study introduces innovative passive micromixer designs aimed at enhancing chaotic advection through secondary flows, especially in curved channels. We examined various split-and-recombine (SAR) microchannels, including a flow-focusing straight type, using numerical simulations across a range of Reynolds numbers with carboxymethyl cellulose solutions of different power-law indices. Performance metrics such as mixing index, pressure drop, and mixing energy cost were evaluated. While SAR configurations induced higher pressure drops, their relatively higher mixing index values resulted in lower mixing energy costs compared to the straight-type channel. Dean flow analysis showed that the splitting and recombining mechanism in SAR configurations generated stronger secondary flows, promoting greater stretching and folding of fluid elements. This significantly enhanced chaotic advection in curved geometries, leading to superior mixing efficiency over the straight-type configuration. These findings offer valuable insights into optimizing micromixer designs, balancing enhanced mixing with energy efficiency for shear-thinning fluids.