A chaotic micromixer using obstruction-pairs

Abstract

A micromixer is one of the most important components for a chemical and/or diagnostic analysis in microfluidic devices such as a micro-total-analysis-system and a lab-on-a-chip. In this paper, a novel chaotic micromixer is developed in a simple design by introducing obstruction-pairs on the bottom of a microchannel. An obstruction-pair, which is composed of two hexahedron blocks arranged in an asymmetric manner, can induce a rotational flow along the down-channel direction due to the anisotropy of flow resistance. By utilizing this characteristic of the obstruction-pair, four mixing units are designed in such a way that three obstruction-pairs induce three rotational flows which result in a down-welling and a hyperbolic point in the channel cross-section. There can be a variety of micromixer geometries by arranging the mixing units in various sequences along the microchannel, and their mixing performances will differ from each other due to different flow characteristics. In this regard, numerical investigations are carried out to predict and characterize the mixing performances of various micromixers. Also experimental verifications are carried out by a flow visualization technique using phenolphthalein and sodium hydroxide solutions in a polydimethylsiloxane-based micromixer.