Abstract

Micromixers are vital components in micro-total analysis systems (μ-TAS) and Lab-on-Chip (LOC) devices, with applications in drug delivery, medical diagnostics, and chemical analyses, amongst others. Traditional macroscale mixing techniques may not be applied at the microscale, where viscous forces become important compared to inertial forces. As such, it remains a challenge to effectively and thoroughly mix liquid species in small characteristic dimensions.
The present work aims to analyze flow phenomena and mass transfer in three novel scaled-up micromixers, which make use of variations in channel geometry to induce mixing. Designs based on multi-lamination inlets, obstruction filled channels, Dean vortex inducing curved channels, and helical flow inducing grooves are investigated. Flow visualization is used as a qualitative tool, providing valuable information regarding flow patterns and mixing. Induced fluorescence is applied to assess whole field concentration distribution, and provide quantitative species distribution data. Complex three dimensional flows are analyzed using numerical simulations, which show good agreement with experimental work.
The mixers are evaluated over Reynolds numbers ranging from 0.5 to 100, corresponding to Péclet numbers ranging from 1.25 × 103 to 1.25 × 105. Results show a decreasing-increasing trend in the degree of mixing with increasing Reynolds number, as the dominant mixing mechanism changes from mass diffusion to mass advection. Up to 90% mixing is reported. To allow for reasonable mixing performance comparison with published work, an equivalent length parameter is proposed. The present devices offer good mixing in shorter lengths over a wide range of Reynolds numbers compared to numerous published devices.