Inertial focusing of non-spherical microparticles

In the last decade, inertial microfluidics has attracted significant attention and a wide variety of channel designs that focus, concentrate and separate particles and fluids have been demonstrated. In contrast to conventional microfluidic technologies, where fluid inertia is negligible and flow remains almost within the Stokes flow region with very low Reynolds number (Re < 1), inertial microfluidics works in the intermediate Reynolds number range (~1 < Re < ~100) between Stokes and turbulent regimes. In this intermediate range, both inertia and fluid viscosity are finite and bring about several intriguing effects that form the basis of inertial microfluidics including (i) inertial migration and (ii) secondary flow. Due to the superior features of high-throughput, simplicity, precise manipulation and low cost, inertial microfluidics is a very promising candidate for cellular sample processing, especially for samples with low abundant targets. In this review, we first discuss the fundamental kinematics of particles in microchannels to familiarise readers with the mechanisms and underlying physics in inertial microfluidic systems. We then present a comprehensive review of recent developments and key applications of inertial microfluidic systems according to their microchannel structures. Finally, we discuss the perspective of employing fluid inertia in microfluidics for particle manipulation. Due to the superior benefits of inertial microfluidics, this promising technology will still be an attractive topic in the near future, with more novel designs and further applications in biology, medicine and industry on the horizon. ABSTRACT:In the last decade, inertial microfluidics has attracted significant attention and a wide variety of channel designs that focus, concentrate and separate particles and fluids have been demonstrated. In contrast to conventional microfluidic technologies, where fluid inertia is negligible and flow remains almost within Stokes flow region with very low Reynolds number Re <<1, inertial microfluidics works in the intermediate Reynolds number range (~1 < Re < ~100) between Stokes and turbulent regimes. In this intermediate range, both inertia and fluid viscosity are finite, and bring about several intriguing effects that form the basis of inertial microfluidics including: (i) inertial migration and (ii) secondary flow. Due to the superior features of high-throughput, simplicity, precise manipulation and low cost, inertial microfluidics is a very promising candidate for cellular sample processing, especially for sample with low abundant targets. In this review, we first discuss the fundamental kinematics of particles in microchannels to familiarise readers with mechanisms and underlying physics in inertial microfluidic systems. We then present a comprehensive review of recent developments and key applications of inertial microfluidic systems according to their microchannel structures. Finally, we discuss the perspective of employing fluid inertia in microfluidics for particle manipu...

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“…deformability, shape, size) and the fluid property (e.g. viscoelasticity) may also influence the lateral migration of particles 45,49,110 .…”

Section: Discussionmentioning

confidence: 99%

“…Besides particle deformability, the shape of particles 49 and the properties of medium 50 also impact the inertial migration and equilibrium positions, which will not be discussed here. A summary of particle kinetics in inertial microfluidics is shown in Figure 3.…”

Section: Deformability-induced Lift Forcementioning

confidence: 99%

Fundamentals and applications of inertial microfluidics: a review

et al. 2016

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mentioning

confidence: 99%

“…These forces allow for the precise alignment of particles in a flow at throughputs orders of magnitudes higher than in previous microfluidic technologies. The high throughput nature of inertial focusing has enabled a range of microfluidic technologies for biomedical applications from separation technologies [8][9][10][11][12] , to automated sample preparations 13,14 , to novel cell analysis techniques such as cell deformability cytometry 15 and the isolation of circulating tumor cells from blood 16,17 .It is generally accepted that inertial focusing in straight channels is dependent on two main parameters: Reynolds number, defined as Re C 5 rU Max D h /m, where r is the fluid density, m is the fluid viscosity, U Max > 3/2U Avg is the maximum velocity of the fluid and D h is the hydraulic diameter of the channel defined as D h 5 2hw/(h 1 w) where h and w are the height and width of the channel cross section respectively, and the particle confinement ratio, l 5 a/D h , where a, is the particle size. Prior research has determined a minimum threshold for inertial focusing to occur such that l .…”

mentioning

confidence: 99%

Particle Focusing in Curved Microfluidic Channels

Martel

Toner

2013

Sci Rep

178

173

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The decoupled effects of Reynolds and Dean numbers are examined in inertial focusing flows. In doing so, a complex set of inertial focusing behavioral regimes is discovered within curved microfluidic channels over a range of channel Reynolds numbers, curvature ratios and particle confinement ratios. These regimes are characterized by particle migration either towards or away from the center of curvature as the channel Reynolds number is increased. The transition between these two regimes is shown to be a set of conditions where single-point equilibrium position focusing of particles of different sizes is achieved. A mechanism describing the observed motion of particles in such flows is hypothesized incorporating the redistribution of the main flow velocities caused by Dean flow and its effect on the balance forces on suspended particles.I nertial focusing is an area of significant interest in the realm of microfluidics because it combines high throughput capability with precision particle positioning and offers theoretical intrigue due to the seemingly endless surprises that accompany experimental results. Inertial focusing occurs under certain conditions as particles flowing through a microchannel migrate across streamlines to equilibrium positions within the flow. This migration is due to inertial effects of the fluid motion around the particle and the interaction of this flow field with the walls of the channel 1-5 . Equilibrium positions arise from a balance between two distinct effects; a shear gradient lift force directed towards the walls of the channel and an opposing wall effect 6,7 . These forces allow for the precise alignment of particles in a flow at throughputs orders of magnitudes higher than in previous microfluidic technologies. The high throughput nature of inertial focusing has enabled a range of microfluidic technologies for biomedical applications from separation technologies [8][9][10][11][12] , to automated sample preparations 13,14 , to novel cell analysis techniques such as cell deformability cytometry 15 and the isolation of circulating tumor cells from blood 16,17 .It is generally accepted that inertial focusing in straight channels is dependent on two main parameters: Reynolds number, defined as Re C 5 rU Max D h /m, where r is the fluid density, m is the fluid viscosity, U Max > 3/2U Avg is the maximum velocity of the fluid and D h is the hydraulic diameter of the channel defined as D h 5 2hw/(h 1 w) where h and w are the height and width of the channel cross section respectively, and the particle confinement ratio, l 5 a/D h , where a, is the particle size. Prior research has determined a minimum threshold for inertial focusing to occur such that l . 0.07 and Re C l 2 , also known as the particle Reynolds number, Re P , is $1 18 . The equilibrium positions can be further controlled using curved channels, where a secondary flow called Dean flow is established at finite Re C . The strength of this secondary flow is characterized by the inertia of the fluid and the curvature of the cha...

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“…High throughput separation of 10 lm microparticles has also been performed using the Dean flow effect within 'U'-and 'S'-shaped channels (Ardabili et al 2010). Most recently, the applicability of the technique for separation of non-spherical microparticles has also been examined (Hur 2011). To date, the Dean flow-based inertial focusing technique has not been reported with particle sizes below 5 lm.…”

Section: Introductionmentioning

confidence: 99%

Dean flow focusing and separation of small microspheres within a narrow size range

Johnston

McDonnell

Tan

et al. 2014

Microfluid Nanofluid

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Rapid, selective particle separation and concentration within the bacterial size range (1-3 lm) in clinical or environmental samples promises significant improvements in detection of pathogenic microorganisms in areas including diagnostics and bio-defence. It has been proposed that microfluidic Dean flow-based separation might offer simple, efficient sample clean-up: separation of larger, bioassay contaminants to prepare bioassay targets including spores, viruses and proteins. However, reports are limited to focusing spherical particles with diameters of 5 lm or above. To evaluate Dean flow separation for (1-3 lm) range samples, we employ a 20 lm width and depth, spiral microchannel. We demonstrate focusing, separation and concentration of particles with closely spaced diameters of 2.1 and 3.2 lm, significantly smaller than previously reported as separated in Dean flow devices. The smallest target, represented by 1.0 lm particles, is not focused due to the high pressures associated with focussing particles of this size; however, it is cleaned of 93 % of 3.2 lm and 87 % of 2.1 lm microparticles. Concentration increases approaching 3.5 times, close to the maximum, were obtained for 3.2 lm particles at a flow rate of 10 ll min -1 . Increasing concentration degraded separation, commencing at significantly lower concentrations than previously predicted, particularly for particles on the limit of being focused. It was demonstrated that flow separation specificity can be fine-tuned by adjustment of output pressure differentials, improving separation of closely spaced particle sizes. We conclude that Dean flow separation techniques can be effectively applied to sample clean-up within this significant microorganism size range.

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Inertial focusing of non-spherical microparticles

Cited by 118 publications

References 19 publications

Fundamentals and applications of inertial microfluidics: a review

Fundamentals and applications of inertial microfluidics: a review

Particle Focusing in Curved Microfluidic Channels

Dean flow focusing and separation of small microspheres within a narrow size range

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