A Review of Passive Micromixers with a Comparative Analysis

Abstract

A wide range of existing passive micromixers are reviewed, and quantitative analyses of ten typical passive micromixers were performed to compare their mixing indices, pressure drops, and mixing costs under the same axial length and flow conditions across a wide Reynolds number range of 0.01–120. The tested micromixers were selected from five types of micromixer designs. The analyses of flow and mixing were performed using continuity, Navier-Stokes and convection-diffusion equations. The results of the comparative analysis were presented for three different Reynolds number ranges: low-Re (Re ≤ 1), intermediate-Re (1 < Re ≤ 40), and high-Re (Re > 40) ranges, where the mixing mechanisms are different. The results show a two-dimensional micromixer of Tesla structure is recommended in the intermediate- and high-Re ranges, while two three-dimensional micromixers with two layers are recommended in the low-Re range due to their excellent mixing performance.

Biosensors-on-Chip: An Up-to-Date Review

“…In this manner, by integrating passive or active mixers, the slow mixing challenge can be overcome [ 27 , 52 ]. Passive micromixers are more economical and convenient, as the mixing occurs through molecular diffusion and chaotic advection with no external energy sources [ 52 , 53 ]. Chaotic advection is highly efficient at low Reynold numbers owing to the stream splitting, stretching, folding, or breaking up [ 54 ].…”

“…Chaotic advection is highly efficient at low Reynold numbers owing to the stream splitting, stretching, folding, or breaking up [ 54 ]. Moreover, it is generally achieved through microchannel geometry modifications in order to reduce diffusion length and increase interfacial area [ 27 , 53 ], subsequently causing pressure and velocity variations [ 54 ].…”

Understanding Interdependencies between Mechanical Velocity and Electrical Voltage in Electromagnetic Micromixers

“…Commonly, the mixing efficiency of micromixers is analysed by mixing parameters such as time, length, and the mixing index [ 18 , 19 ], and these parameters depend on the ability of the transducer system (which includes the energy source, transducers, and membrane/transmission materials). To optimise transducer efficiency, there are generally a few approaches.…”

Enhancement of Fluid Mixing with U-Shaped Channels on a Rotating Disc

“…Both active and passive methods have been proposed to enhance mixing at microscale. An extensive review on the recent development of various types and designs of active and passive mixing methods can be found in the articles of Nguyen and Wu [ 12 ], Chang and Yang [ 13 ] and Ward and Fang [ 14 ], and very recently in Raza et al [ 15 ]. The passive method appears to be more appealing than the active one in the applications to chemical and biochemical analyses.…”

“…In any case, the complex channel structure tends to raise flow resistance, which leads to increasing the residence time of mixing fluids at the cost of pressure loss. A recent comparative analysis of five types of passive micromixers by Raza et al [ 15 ] shows that a 2D micromixer with split-and-recombination (SAR) Tesla structure outperforms other 2D serpentine and SAR mixers in the intermediate and high Reynolds number ranges (1 < Re ≤ 40 and 40 < Re ≤ 120, respectively). Nevertheless, a 2D micromixer with Tesla structure, which utilizes the Coanda effect to generate the transverse dispersion resulting in strong cross-channel convection of the mixing, still suffers high pressure drop [ 15 , 23 , 24 ].…”