Continuous sheath-free separation of particles by shape in viscoelastic fluids

Lu, Xinglin; Zhu, Lin; Hua, Ri Mao; Xuan, Xiangchun

doi:10.1063/1.4939267

Cited by 61 publications

(62 citation statements)

References 53 publications

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“…Specifically, at the lowest flow rate tested in this work (e.g., 1 μl min −1 ), both the fluid inertia and the Dean flow can be neglected (Re c ∼ OĲ0.01) ≈ 0, De ∼ OĲ0.001) ≈ 0, see the ESI † Table S1 for the detailed values of the calculated dimensionless numbers) and the particle lateral migration is dominated by the fluid elasticity effects (Wi ∼ OĲ0.1), El > 1). 13,16 Instead of single-line focusing, the particles in low-aspect-ratio straight channels would equilibrate at two central symmetric positions which then evolve to become three with an additional one at the channel center at a slightly higher flow rate, as found in previous studies 16,34 and our work (see Fig. The stronger elastic force vector in the vertical direction first moves the particles to the center plane along the channel height.…”

Section: Discussionsupporting

confidence: 68%

Fundamentals of elasto-inertial particle focusing in curved microfluidic channels

et al. 2016

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Elasto-inertial focusing in viscoelastic fluids has attracted increasing interest in recent years due to its potential applications in particle counting and sorting. However, current investigations of the elasto-inertial focusing mechanisms have mainly been focused on simple straight channels with little attention being paid to curved channels. Herein, we experimentally explore the elasto-inertial focusing behaviors of particles in spiral microfluidic channels over a wide range of flow rates, channel aspect ratios and channel radii. As compared with those observed in inertial microfluidics without viscoelasticity, the particle focusing pattern in our spiral elasto-inertial microfluidic system appears in a more interesting manner due to the complex coupling of elasticity, inertia and Dean flow effects. On the basis of the obtained data, the underlying mechanics and force competition behind the focusing behaviors are analyzed. In addition, for the first time, we propose a six-stage process model illustrating the particle focusing process in Dean-coupled elasto-inertial flows with increasing flow rate. It is interesting to find that the Dean drag force makes a significant contribution to particle focusing only at high flow rates and finally shifts the particle focusing positions into the outer channel region. Through carefully balancing the forces acting on particles, single-line 3D focusing can also be achieved at a throughput level of ∼100 μl min(-1), which is much higher than those in most existing studies. We envision that this improved understanding of the particle focusing mechanisms would provide helpful insights into the design and operation of spiral elasto-inertial microfluidic systems.

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Section: Discussionsupporting

confidence: 68%

Fundamentals of elasto-inertial particle focusing in curved microfluidic channels

et al. 2016

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“…This phenomenon indicates the strong shapedependence of the flow-induced elasto-inertial lift, which, through a high-speed imaging of particle motion, is speculated to correlate with the rotational effects of non-spherical particles. Lu et al [130] later found that the differential elasto-inertial focusing, which had been demonstrated to separate particles by size in a sheath-free manner [110], is also capable of separating the spherical and peanut particles in 1000 ppm PEO solution flow at greater than 95% efficiency and purity (Fig. 11b).…”

Section: Separation Based On Other Intrinsic Markersmentioning

confidence: 99%

Particle manipulations in non-Newtonian microfluidics: A review

Liu

et al. 2017

Journal of Colloid and Interface Science

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235

192

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a b s t r a c tMicrofluidic devices have been widely used since 1990s for diverse manipulations of particles (a general term of beads, cells, vesicles, drops, etc.) in a variety of applications. Compared to the active manipulation via an externally imposed force field, the passive manipulation of particles exploits the flow-induced intrinsic lift and/or drag to control particle motion with several advantages. Along this direction, inertial microfluidics has received tremendous interest in the past decade due to its capability to handle a large volume of samples at a high throughput. This inertial lift-based approach in Newtonian fluids, however, becomes ineffective and even fails for small particles and/or at low flow rates. Recent studies have demonstrated the potential of elastic lift in non-Newtonian fluids for manipulating particles with a much smaller size and over a much wider range of flow rates. The aim of this article is to provide an overview of the various passive manipulations, including focusing, separation, washing and stretching, of particles that have thus far been demonstrated in non-Newtonian microfluidics.

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“…For most commonly‐used viscoelastic fluids,

N_{2} false(\overset{γ}{true} false)

is very small and thus can often be neglected under most flow conditions . Therefore, the positive

N_{1} false(\overset{γ}{true} false)

generates an elastic force

F_{E} \sim a_{p}^{3} \nabla N_{1} false(\overset{γ}{true} false) \sim 8 a_{p}^{3} λ Q^{3} / {(h w^{2})}^{3}

(where λ is the relaxation time of viscoelastic fluids) on particles in the direction of decreasing shear rate . When the shear thinning effect is weak, the particles would migrate towards five cross‐sectional positions (four corners and one center) where the shear rates are at the minimum.…”

Section: Methodsmentioning

confidence: 99%

Concentration‐controlled particle focusing in spiral elasto‐inertial microfluidic devices

2017

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Herein, we proposed a strategy for controlling the particle focusing position in Dean-coupled elasto-inertial flows via adjusting the polymer concentration of viscoelastic fluids. The physics behind the control strategy was then explored and discussed. At high polymer concentrations, the flowing particles could be single-line focused exactly at the channel centerline under the dominated elastic force. The center-line focusing in our spiral channel may employed as a potential pretreatment scheme for microflow cytometry detection. With further decreasing polymer concentrations, the particles would shift into the outer channel region under the comparable competition between inertial lift force, elastic force and Dean drag force. Finally, the observed position-shifting was successfully employed for particle concentration at a throughput much higher than most existing elasto-inertial microfluidics.

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Continuous sheath-free separation of particles by shape in viscoelastic fluids

Cited by 61 publications

References 53 publications

Fundamentals of elasto-inertial particle focusing in curved microfluidic channels

Fundamentals of elasto-inertial particle focusing in curved microfluidic channels

Particle manipulations in non-Newtonian microfluidics: A review

Concentration‐controlled particle focusing in spiral elasto‐inertial microfluidic devices

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