An efficient micromixer based on multidirectional vortices due to baffles and channel curvature

Abstract

An efficient planar micromixer based on multidirectional vortices in a curved channel with radial baffles is proposed and examined in this work. The curvature of the microchannel and the radial baffles induce vortices in different directions. The multidirectional vortices and the converging-diverging flow caused by the baffles contribute together to the enhancement of mixing. The micromixer is fabricated with polydimethylsiloxane by a single planar microlithography process and the mixing behaviors are observed by a confocal spectral microscope imaging system to validate the simulation obtained by a commercial code. The simulation and experimental results are in reasonable agreement. The concentration distributions and flow patterns obtained reveal the following trends. (i) The mixing efficiency of the basic C-shaped micromixer with the first baffle attached to the internal cylinder and the second attached to the external cylinder is better than that of the C-shaped micromixer with inverted arrangement of baffles. (ii) When the radius of the curved channel and the width of the passage between the baffle and the cylindrical wall are small enough and the Reynolds number (Re) is large enough, an extra separation vortex develops in the downstream of the second baffle. This phenomenon is one of the reasons of trend (i). (iii) A micromixer consisting of a few basic C-shaped micromixers connected by straight channels may generate a high degree of mixing for the case with a large Re.

An effective splitting-and-recombination micromixer with self-rotated contact surface for wide Reynolds number range applications

“…Electronic addresses: rykhit@hit.edu.cn and jhy_hit@hit.edu.cn. In the last decade, for better mixing efficiency, many researchers have made great effort to develop various types of passive micromixers composed of 2-D curved channel with radial baffles, 23 2-D cylindrical grooves adjoining to the main straight channel 24 and 2-D structures based on the concept of the splitting and recombination. [25][26][27][28] These micromixers did exhibit high performance at high flow rates, but at a low level the channel geometries cannot result in obvious vortices or chaotic advection and the contact surface between the streams are usually vertical without rotation and expansion, so these micromixers are not effective at lower Reynolds number unless these micromixers have a longer mixing length.…”

Enhancement of Mixing Performance of Non-Newtonian Fluids using Curving and Grooving of Microchannels

“…In order to validate the numerical results of Newtonian fluids, the mixing index for water flowing in CSC channel without baffles was simulated and compared with previous numerical results (Tsai and Wu 2011). It can be seen in Fig.…”

“…Also, they compared the mixing performance of sinusoidal micromixers with results of square wave and zig-zag wave micromixers and they observed that the sinusoidal micromixer showed better mixing performance than other geometries. Tsai and Wu (2011) investigated several planar curved micromixers with radial baffles, both numerically and experimentally. They observed that the mixing efficiency improved due to the multidirectional vortices.…”

Numerical analysis of a rapid magnetic microfluidic mixer

“…Previous researchers designed 3-D passive micromixers [21][22][23][24] to achieve a chaotic mixing effect. The mixing ratio of the serpentine microchannel is twice that obtained in a conventional straight microchannel.…”