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.

Latest Developments in Micro Total Analysis Systems

“…The Yang group have fabricated 3D nanostructures using holography for passive micromixing (148). Obstruction pairs in a microfluidic channel have been integrated for chaotic mixing by Kwon and co-workers (149).…”

Micromixing enhancement in a novel passive mixer with symmetrical cylindrical grooves

“…[15] Although the aforementioned examples obtained good mixing effect of fluids, external energy is required in all of them, which may be harmful to biological reagents. Fortunately, this problem can be solved by passive mixers, because passive mixers are designed by channels with different geometry (chaotic method [18][19][20][21][22][23] ) or special types of baffles embedded in the main channel (split-and-rejoin strategy [24][25][26][27][28][29][30][31][32] ) with no other external energy. Chaotic method is widely used for micromixing with special structures modified on the channel wall.…”

“…[22] This method was extended with more detailed investigations on the effects of the parameters of the herringbone recently. [20,21,23] Detailed investigations of an obstruction-pair mixer were presented with numerical and experimental analysis, [18] which is also a variation of staggered herringbone structure. In the other aspect, split-and-join approach is also a commonly used strategy to enhance mixing in passive mixers, in which many types of baffles were embedded into the main channel, such as cylindrical obstructions, [24,25,32] diamond obstructions, [24,26,31] triangle baffles, [24] elliptic-shape barriers, [29] J-shape baffles [30] and other special structures.…”

Mixing enhancement of a passive microfluidic mixer containing triangle baffles

“…Those problems can be solved by passive mixers, which are simple to fabricate and have better compatibility with other fluidic components. Practically, split‐and‐rejoin method and the chaotic approach are two main schemes to achieve effective mixing within a short distance. Bhagat et al fabricated passive mixers with flow break‐up obstructions such as cylindrical, square and triangle obstructions .…”