Development of small-volume, microfluidic chaotic mixers for future application in two-dimensional liquid chromatography

Abstract

We report a microfluidic chaotic micromixer with staggered herringbone grooves having a geometry optimized for fast mobile-phase modification at the interface of a two-dimensional liquid chromatography system. The volume of the 300 μm mixers is 1.6 microliters and they provide mixing within 26 s at a flow rate of 4 μL min⁻¹ and 0.09 s at a flow rate of 1000 μL min⁻¹. Complete mixing is achieved within a distance of 3 cm along the 5 cm-long microchannel over the whole range of flow rates. The mixers can be used to mix aqueous phosphate-buffered saline solutions with methanol or acetonitrile at different ratios (1 : 2, 1 : 5 and 1 : 10). We also describe in detail an improved fabrication protocol for these mixers using a two-step soft photolithographic procedure. Mixers are made by replication in poly(dimethylsiloxane).