A novel microreactor with 3D rotating flow to boost fluid reaction and mixing of viscous fluids

Based on a concept encompassing splitting and recombination (SAR) and chaotic advection, an efficient microreactor, called a SAR μ-reactor, has been designed to mix fluids at Reynolds numbers from 0.01 to 100 and to be suitable for mixing fluids with viscosity over a wide range (μ = 0.000855–0.186 kg m⁻¹ s⁻¹). This SAR μ-reactor was compared, numerically and experimentally, with a slanted-groove micromixer (SGM) for reaction or mixing of fluids. Results of simulations characterized the designed structure with inducing a 3D rotating flow involving a strong lateral component to stretch intensely the contact interface in the SAR μ-reactor. Chemical colorimetry of two kinds – involving reactions of phenolphthalein with sodium hydroxide and of ascorbic acid with diiodine – revealed that the SAR μ-reactor provided a smaller mixing length, reaction length and period than the SGM; the mixing performance of the SAR μ-reactor was much better than that of the SGM. We assessed the mixing behavior of fluorescent proteins (C-phycocyanin and R-phycoerythrin) in viscous fluids with a confocal microscope. Experimental results and simulations showed that the effect of fluid viscosity on the mixing efficiency of the SAR μ-reactor is less than for the SGM; the SAR mechanism effectively augmented the contact interface even though the intrinsic diffusivity of fluids was diminished.