Static micromixers based on large-scale industrial mixer geometry

Abstract

Mixing liquids at the micro-scale is difficult because the low Reynolds numbers in microchannels and in microreactors prohibit the use of conventional mixing techniques based on mechanical actuators and induce turbulence. Static mixers can be used to solve this mixing problem. This paper presents micromixers with geometries very close to conventional large-scale static mixers used in the chemical and food-processing industry. Two kinds of geometries have been studied. The first type is composed of a series of stationary rigid elements that form intersecting channels to split, rearrange and combine component streams. The second type is composed of a series of short helix elements arranged in pairs, each pair comprised of a right-handed and left-handed element arranged alternately in a pipe. Micromixers of both types have been designed by CAD and manufactured with the integral microstereolithography process, a new microfabrication technique that allows the manufacturing of complex three-dimensional objects in polymers. The realized mixers have been tested experimentally. Numerical simulations of these micromixers using the computational fluid dynamics (CFD) program FLUENT are used to evaluate the mixing efficiency. With a low pressure drop and good mixing efficiency these truly three-dimensional micromixers can be used for mixing of reactants or liquids containing cells in many microTAS applications.

Influence of hydrodynamics on liquid mixing during Taylor flow in a microchannel

“…Moreover, increasing of the interfacial area of fluids and introducing advection were also proved to be another two effective methods for the improvement of the mixing in micromixers. 19 Based on these principles, a considerable variety of micromixers have been designed, such as interdigital micromixer, 20 split-and-recombine micromixer, 21 micromixer based on the collision of micro segments, 22 static micromixer, 23 multifunctional micromixer which made used of alternating current electroosmotic flow and asymmetric microelectrodes, 24 etc. However, these micromixers are difficult to manufacture due to the complexity of their structure, and their practical application usually was scarce.…”

Multivortex micromixing

“…A further adaptation of Dean effects are so-called ''twisted pipe'' designs (constructed by joining a series of planar curved segments such that each subsequent segment is oriented at a nonzero pitch angle relative to the previous one) where the inherent symmetry of the secondary flow streamlines is disrupted yielding chaotic particle trajectories (27). Variations of helical and twisted pipe arrangements have been investigated to enhance mixing in microfluidic systems; however, the corresponding nonplanar flow geometries often require multilevel or specialized fabrication processes that can introduce added complexity (17,19,28,29). Conversely, the design of planar curved microchannels capable of sustaining transverse circulation over a sufficient downstream distance to compensate for the incompatibility between flow and diffusion timescales also has proven challenging (30)(31)(32)(33)(34)(35)(36)(37).…”

The Effect of Inertia on the Flow and Mixing Characteristics of a Chaotic Serpentine Mixer

“…The typical diffusion time scale t d is represented by t d ∼ l 2 /D, where l is the characteristic length and D the coefficient of molecular diffusion. To overcome such difficulties, chaotic advection [7][8][9][10], which has been successfully applied to the development of macroscale mixers working in the laminar flow regime, were also adopted in micromixers [11][12][13][14]. It is now well known that, by incorporating chaotic advection, one can achieve enhanced mixing, even in the creeping flow regime (with negligible inertia), which is also the case in microscale flows.…”