Simple passive micromixer using recombinant multiple flow streams

Over a wide Reynolds number range (0.1 B Re B 40), the new planar obstacle micromixer has been demonstrated over 85% mixing efficiency covering the mixing improvement in both convection-enhanced (higher Re flow) and diffusion-enhanced (lower Re flow) mechanisms. Mixing behavior between two operation windows was investigated by numerical simulations and experiments. For the adaptive design, numerical simulations and Taguchi method were used to study the effect of four geometrical factors on sensitivity of mixing. The factors are gap ratio (H/W), number of mixing units, baffle width (W b ) and chamber ratio (W m /W). The degree of sensitivity using the Taguchi method can be ranked as: Gap ratio [ Number of mixing units [ Baffle width [ Chamber ratio. Micromixer performance is greatly influenced by the gap ratio and Reynolds number. Beside the wide Reynolds number range, good mixing efficiency can be obtained at short distance of a mixing channel and relatively low-pressure drop. This micromixer had improved both complex fabrication process of multi-layer or 3D micromixers and low mixing efficiency of planar micromixer at Re \ 100. The trend of the verified experimental results is in agreement with the simulate results.

Section: Fabrication and Experimentsmentioning

confidence: 95%

A high-efficiency planar micromixer with convection and diffusion mixing over a wide Reynolds number range

Shih

Chung

2007

“…Obstructive mixers have been demonstrated by many groups Shih and Chung 2008;Bhagat et al 2007a;Shim et al 2007;Bhagat and Papautsky 2008). These mixers are based on placing obstacles in the flow path.…”

Section: Introductionmentioning

confidence: 95%

“…A number of groups have noted the existence of an inflection point in the mixing efficiency as Re is varied (Bhagat et al 2007b;Chung and Shih 2008;Shih and Chung 2008;Bhagat et al 2007a;Shim et al 2007). This is characterised by a decrease in mixing efficiency as Re passes through 1, but an increase in mixing efficiency as Re increases above 5.…”

Section: Introductionmentioning

confidence: 96%

“…Mixing efficiency of 90% was achieved in a distance of 7 mm for an Re of 1. Both Shim et al (2007) and Chung and Shih (2008) incorporated a variation of diamond obstructions into their respective designs. Chung and Shih found that diffusion processes gave way to recirculation effects at higher Re accounting for the increase in mixing efficiency, leading to 99% at Re of 200.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of passive microfluidic mixers incorporating 2D and 3D baffle geometries fabricated using an excimer laser

Conlisk

O’Connor

2012

We present new passive microfluidic mixing structures based on 2D and 3D geometries. The primary mechanism of mixing in these devices is based on chaotic advection. The mixers which incorporate 3D structures introduce transverse flow rotation greatly enhancing performance. Simulations and experimental tests were performed over a Reynolds number (Re) range from 0.1 to 20 and showed good agreement. At an Re of 0.1, 90% mixing was achieved in a path length of 32 and 7 mm, for the 2D and 3D geometrical mixers, respectively. This represents an improvement in performance over a standard T-mixer of 20% for the 2D mixer and 82.5% for the 3D mixer. An inflection point in the mixing efficiency was observed for both mixer types around an Re of 1. The devices were fabricated on a polymethylmethacrylate (PMMA) substrate, using an excimer laser beam incorporating an intelligent pinhole mask. Initially, structures were developed off-line using a laser simulation tool. A design-of-experiments (DOE) approach along with computational fluid dynamic (CFD) analysis was used to optimise mixing element geometry. This precursor to the fabrication step greatly reduces the time between the design stage and device realisation.

“…Many groups involved in fabricating microfluidics and microfluidic mixers use a polymer casting technique (Chung and Shih 2008;Bhagat et al 2007;Shim et al 2007;Shih and Chung 2007;Stroock et al, 2002). A master mould is created by exposing a silicon wafer coated in SU-8 resist through a photomask.…”

Section: Introductionmentioning

confidence: 99%

Application of reconfigurable pinhole mask with excimer laser to fabricate microfluidic components

Conlisk

Favre

Lasser³

et al. 2011

An excimer laser incorporating a reconfigurable intelligent pinhole mask (IPM) is demonstrated for the fabrication of microfluidic geometries on a poly(methyl methacrylate) substrate. Beam reconfiguration techniques are used to overcome some of the drawbacks associated with traditional scanning laser ablation through a static mask. The production of zero lead-in (ZLI) features are described, where the ramp lead-in angle-inherent to scanning laser ablation-is reduced to be in line with the cross-sectional side-wall angle of the microchannel itself. The technique is applied to eliminate under-cutting and ramping at channel junctions-features resulting from scanning ablation through a fixed mask-and produce flat crossing sections, junctions and inlets. The development of a prediction model for microchannel visualisation and refinement prior to the fabrication step is also described. The model includes variables from the IPM, laser, scanning stage and material etch rate allowing quantitative measurement of generated microchannel geometry. One application of the model is the development of microchannel mixing geometry which is analysed using computational fluid dynamic (CFD) techniques. For this purpose, the effect of varying the overall channel geometry on mixing within a microchannel was investigated for flows with low Reynolds numbers. The resulting geometry is found to reduce the distance required for mixing by 50% in comparison to a straight planar channel, thereby enabling smaller device geometries.