Helical flows and chaotic mixing in curved micro channels

Jiang, Fengjian; Drese, Klaus; Hardt, Steffen; Küpper, M.; Schönfeld, Friedhelm

doi:10.1002/aic.10188

Cited by 316 publications

(224 citation statements)

References 25 publications

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“…Since its first demonstration, 11 the secondary flow inside a curved channel [12][13][14][15][16][17][18] has received much attention because it is found in many areas from heat exchangers to human arterial systems. 19,20 All previous experimental works were done with large pipes and utilized laser Doppler anemometry 21,22 or tracers, 11,19,20,23,24 like dye, hydrogen bubble, or powder, to explore the secondary flow.…”

Section: Introductionmentioning

confidence: 99%

Optical sectioning for microfluidics: secondary flow and mixing in a meandering microchannel

2008

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Secondary flow plays a critical function in a microchannel, such as a micromixer, because it can enhance heat and mass transfer. However, there is no experimental method to visualize the secondary flow and the associated mixing pattern in a microchannel because of difficulties in high-resolution, non-invasive, cross-sectional imaging. Here, we simultaneously imaged and quantified the secondary flow and pattern of two-liquid mixing inside a meandering square microchannel with spectral-domain Doppler optical coherence tomography. We observed an increase in the efficiency of two-liquid mixing when air was injected to produce a bubble-train flow and identified the three-dimensional enhancement mechanism behind the complex mixing phenomena. An alternating pair of counterrotating and toroidal vortices cooperated to enhance two-liquid mixing.

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Section: Introductionmentioning

confidence: 99%

Optical sectioning for microfluidics: secondary flow and mixing in a meandering microchannel

2008

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“…The twisted microchannels generate curvature induced secondary flows for mixing (Liu et al 2002;Austinand Seader. 1973;Jiang et al 2004Sudarsan and Ugaz 2005Howell et al 2004). All these configurations aim for simple yet efficient mixing in the shortest microchannel distance possible.…”

Section: Introductionmentioning

confidence: 99%

A microgrooved membrane based gas–liquid contactor

Jani

Weßling

Lammertink

2012

Microfluid Nanofluid

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This research presents an approach for applying microgrooved membranes for improved gas-liquid contacting. The study involves analysis of the performance of the microdevice by quantifying the flux enhancement for different membrane configurations. Two kinds of configurations, continuous and non-continuous grooves, were investigated. The microgrooves provide shear-free gasliquid interfaces, which result in local slip velocity at the gas-liquid interface. Exploiting this physical phenomenon, it is possible to reduce mass transport limitations in gasliquid contacting. An experimental study using grooved membranes suggests enhancement in flux up to 20-30 %. The flux enhancement at higher liquid flow rates is observed due to a partial shear-free gas-liquid interface. The performance of the membrane devices decreased with wetted microgrooves due to the mass transport limitations. The flow visualization experiments reveal wetting of the microgrooves at higher liquid flow rates. According to the numerical and experimental study, we have shown that microgrooved membranes can be employed to improve gas-liquid contacting processes.

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confidence: 99%

“…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).In this work, we show how these limitations can be overcome so that transverse Dean flows can be readily harnessed at the microscale to enable efficient micromixing in topologically simple and easily fabricated planar smooth-walled 2D microchannels. Two unique micromixer designs are described as follows: (i) a planar split-and-recombine (P-SAR) arrangement capable of generating multiple alternating lamellae of individual fluid species, and (ii) an asymmetric serpentine micromixer (ASM) configuration coupling vertical transverse Dean flow effects with the action of expansion vortices in the horizontal plane.…”

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confidence: 99%

Multivortex micromixing

Sudarsan

Ugaz

2006

Proc. Natl. Acad. Sci. U.S.A.

290

221

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The ability to mix liquids in microchannel networks is fundamentally important in the design of nearly every miniaturized chemical and biochemical analysis system. Here, we show that enhanced micromixing can be achieved in topologically simple and easily fabricated planar 2D microchannels by simply introducing curvature and changes in width in a prescribed manner. This goal is accomplished by harnessing a synergistic combination of (i) Dean vortices that arise in the vertical plane of curved channels as a consequence of an interplay between inertial, centrifugal, and viscous effects, and (ii) expansion vortices that arise in the horizontal plane due to an abrupt increase in a conduit's cross-sectional area. We characterize these effects by using confocal microscopy of aqueous fluorescent dye streams and by observing binding interactions between an intercalating dye and double-stranded DNA. These mixing approaches are versatile and scalable and can be straightforwardly integrated as generic components in a variety of lab-on-a-chip systems.Dean flow ͉ expansion vortex ͉ microfluidics ͉ lab on a chip A lthough microf luidic mixing is a key process in a host of miniaturized analysis systems (1-7), it continues to pose challenges owing to constraints associated with operating in an unfavorable laminar f low regime dominated by molecular diffusion and characterized by a combination of low Reynolds numbers (Re ϭ Vd͞v Ͻ Ͻ 100, where V is the f low velocity, d is a length scale associated with the channel diameter, and v is the f luid kinematic viscosity) and high Péclet numbers (Pe ϭ Vd͞D Ͼ 100, where D is the molecular diffusivity). The relatively large discrepancy between convective and diffusive timescales implies that in a straight smooth-walled microchannel, the downstream distances over which liquids must travel to become fully intermixed (⌬y m ϳ Vd 2 ͞D ϭ Pe ϫ d) can be on the order of several centimeters. These mixing lengths are generally prohibitively long and often negate many of the benefits of miniaturization.A wide variety of micromixing approaches have been explored (8, 9), most of which can be broadly classified as either ''active'' (involving input of external energy) or ''passive'' (harnessing the inherent hydrodynamic structure of specific flow fields to mix fluids in the absence of external forces). Passive designs are often desirable in applications involving sensitive species (e.g., biological samples) because they do not impose strong mechanical, electrical, or thermal agitation. Examples of passive micromixing approaches that have been widely investigated include the following: (i) ''split-and-recombine'' strategies where the streams to be mixed are divided or split into multiple channels and redirected along trajectories that allow them to be subsequently reassembled as alternating lamellae yielding exponential reductions in interspecies diffusion length and time scales (4, 10-12); and (ii) ''chaotic'' strategies where transverse flows are passively generated that continuously expand interfacial...

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Helical flows and chaotic mixing in curved micro channels

Abstract: The mixing due to helical flows in curved micro channels is investigated. A new chaotic

Cited by 316 publications

References 25 publications

Optical sectioning for microfluidics: secondary flow and mixing in a meandering microchannel

Optical sectioning for microfluidics: secondary flow and mixing in a meandering microchannel

A microgrooved membrane based gas–liquid contactor

Multivortex micromixing

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