Cross-stream migration of asymmetric particles driven by oscillating shear

Laumann, Matthias; Bauknecht, Paul; Gekle, Stephan; Kienle, Diego; Zimmermann, Walter

doi:10.1209/0295-5075/117/44001

Cited by 11 publications

(11 citation statements)

References 52 publications

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“…Such parity breaking mechanisms may be also accompanied by a viscosity contrast [30] or chirality [31]. Recently was found, that CSM takes place also for asymmetric soft particles in time-dependent linear shear flow [32] and that soft particles are actuated even in a homogeneous but time-dependent flow by taking particle inertia into account [33]. downward in a gravitational field migrate away from the tube center and for an upward flow to the tube center, as experimentally observed [34].…”

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confidence: 78%

Migration reversal of soft particles in vertical flows

Förtsch¹,

Laumann²,

Kienle³

et al. 2017

EPL

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-Non-neutrally buoyant soft particles in vertical microflows are investigated. We find, soft particles lighter than the liquid migrate to off-center streamlines in a downward Poiseuille flow (buoyancy-force antiparallel to flow). In contrast, heavy soft particles migrate to the center of the downward (and vanishing) Poiseuille flow. A reversal of the flow direction causes in both cases a reversal of the migration direction, i. e. heavier (lighter) particles migrate away from (to) the center of a parabolic flow profile. Non-neutrally buoyant particles migrate also in a linear shear flow across the parallel streamlines: heavy (light) particles migrate along (antiparallel to) the local shear gradient. This surprising, flow-dependent migration is characterized by simulations and analytical calculations for small particle deformations, confirming our plausible explanation of the effect. This density dependent migration reversal may be useful for separating particles.Introduction. -Microfluidics is a rapidly evolving cross-disciplinary field, ranging from basic physics to a great variety of applications in life science and technology [1][2][3][4][5][6][7][8][9]. The blooming subfield of the dynamics of neutrally buoyant soft particles in suspension and their crossstreamline migration (CSM) in rectilinear shear flows, plays a central role for cell and DNA sorting, blood flow, polymer processing and so on [6,[10][11][12][13]. In contrast, little is known about the dynamics of non-neutrally buoyant soft particles in rectilinear flows, but we show in this work for such particles a novel migration reversal.Segre and Silberberg reported in 1961 about CSM of neutrally buoyant rigid particles at finite Reynolds numbers in flows through pipes [14]. When particles and channels approach the micrometer scale, fluid inertia does not matter and particles follow the Stokesian dynamics. In this limit CSM occurs only for soft particles but in curvilinear [15][16][17] as well as in rectilinear flows [18][19][20], whereby in rectilinear flows, the flows fore-aft symmetry is broken, requiring intra-particle hydrodynamic interaction [18,19]. Such symmetry breaking occurs also near boundaries via wall-induced lift forces [20][21][22][23][24] or by space-dependent shear rates, so that dumbbells [18,19], droplets [25,26], vesicles and capsules [27][28][29] exhibit CSM even in unbounded flow. Such parity breaking mechanisms may be also accompanied by a viscosity contrast [30] or chirality [31]. Recently was found, that CSM takes place also for asymmetric soft particles in time-dependent linear

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confidence: 78%

Migration reversal of soft particles in vertical flows

Förtsch¹,

Laumann²,

Kienle³

et al. 2017

EPL

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“…Moreover, we suppose that the mutual interactions between the membrane particles are pairwise additive and described by forces that depend only on the difference of coordinates of each two neighboring particles. Representing the membrane as a collection of spherical beads arranged on vertices has extensively been employed as a coarse-grained model for cell membranes, see, for instance [42][43][44][45][46][47][48].…”

Section: System Setupmentioning

confidence: 99%

Theory of active particle penetration through a planar elastic membrane

et al. 2019

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With the rapid advent of biomedical and biotechnological innovations, a deep understanding of the nature of interaction between nanomaterials and cell membranes, tissues, and organs, has become increasingly important. Active penetration of nanoparticles through cell membranes is a fascinating phenomenon that may have important implications in various biomedical and clinical applications. Using a fully analytical theory supplemented by particle-based computer simulations, the penetration process of an active particle through a planar two-dimensional elastic membrane is studied. The membrane is modeled as a selfassembled sheet of particles, uniformly arranged on a square lattice. A coarse-grained model is introduced to describe the mutual interactions between the membrane particles. The active penetrating particle is assumed to interact sterically with the membrane particles. State diagrams are presented to fully characterize the system behavior as functions of the relevant control parameters governing the transition between different dynamical states. Three distinct scenarios are identified. These compromise trapping of the active particle, penetration through the membrane with subsequent self-healing, in addition to penetration with permanent disruption of the membrane. The latter scenario may be accompanied by a partial fragmentation of the membrane into bunches of isolated or clustered particles and creation of a hole of a size exceeding the interaction range of the membrane components. It is further demonstrated that the capability of penetration is strongly influenced by the size of the approaching particle relative to that of the membrane particles. Accordingly, active particles with larger size are more likely to remain trapped at the membrane for the same propulsion speed. Such behavior is in line with experimental observations. Our analytical theory is based on a combination of a perturbative expansion technique and a discrete-tocontinuum formulation. It well describes the system behavior in the small-deformation regime. Particularly, the theory allows to determine the membrane displacement of the particles in the trapping state. Our approach might be helpful for the prediction of the transition threshold between the trapping and penetration in real-space experiments involving motile swimming bacteria or artificial active particles.

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“…Surprisingly, CSM of soft particles can be also reversed by gravitational effects [35]. Recently, migration was also found for nonsymmetric soft particles in time-periodic linear shear flows [36] and even in timeperiodic homogeneous plug flows when particle inertia is considered [37].…”

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confidence: 91%

Emerging Attractor in Wavy Poiseuille Flows Triggers Sorting of Biological Cells

et al. 2019

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Microflows constitute an important instrument to control particle dynamics. A prominent example is the sorting of biological cells, which relies on the ability of deformable cells to move transversely to flow lines. A classic result is that soft microparticles migrate in flows through straight microchannels to an attractor at their center. Here, we show that flows through wavy channels fundamentally change the overall picture. They lead to the emergence of a second, coexisting attractor for soft particles. Its emergence and off-center location depends on the boundary modulation and the particle properties. The related cross-stream migration of soft particles is explained by analytical considerations, Stokesian dynamics simulations in unbounded flows, and Lattice-Boltzmann simulations in bounded flows. The novel off-center attractor can be used, for instance, in diagnostics, for separating cells of different size and elasticity, which is often an indicator of their health status.

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Cross-stream migration of asymmetric particles driven by oscillating shear

Cited by 11 publications

References 52 publications

Migration reversal of soft particles in vertical flows

Migration reversal of soft particles in vertical flows

Theory of active particle penetration through a planar elastic membrane

Emerging Attractor in Wavy Poiseuille Flows Triggers Sorting of Biological Cells

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