Hydrodynamic attraction and repulsion between asymmetric rotors

Schreiber, Steffen; Fischer, Thomas M.; Zimmermann, Walter

doi:10.1088/1367-2630/12/7/073017

Cited by 5 publications

(5 citation statements)

References 35 publications

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“…The important role of the azimuthal hydrodynamic interactions between colloidal particles driven to rotate in a fluid by an external drive in controlling the dynamical assembly of such artificial microswimmers has been recognized for some time. [2][3][4][5]34 Yet, only recently it has been pointed out that this interaction yields a net finite velocity for the center of mass of two rotors of opposite vorticity, which will therefore behave as a self-propelled pair. 27 Such a ''cooperative self-propulsion'' is a novel effect with potential applications.…”

Section: Discussionmentioning

confidence: 99%

Cooperative self-propulsion of active and passive rotors

Fily

Baskaran

2012

Soft Matter

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Reynolds number passive and active rotors in a fluid, we characterize the hydrodynamic interactions among rotors and the resulting dynamics of a pair of interacting rotors. This allows us to treat in a common framework passive or externally driven rotors, such as magnetic colloids driven by a rotating magnetic field, and active or internally driven rotors, such as sperm cells confined at boundaries. The hydrodynamic interaction of passive rotors is known to contain an azimuthal component ∼ 1/r 2 to dipolar order that can yield the recently discovered "cooperative self-propulsion" of a pair of rotors of opposite vorticity. While this interaction is identically zero for active rotors as a consequence of torque balance, we show that a ∼ 1/r 4 azimuthal component of the interaction arises in active systems to octupolar order. Cooperative self-propulsion, although weaker, can therefore also occur for pairs of active rotors.

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Section: Discussionmentioning

confidence: 99%

Cooperative self-propulsion of active and passive rotors

Fily

Baskaran

2012

Soft Matter

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“…The phenomenon is related to a recent study on the flow induced polymer-polymer attraction [39] mediated through inter-chain HI, where the second polymer causes very similar effects as the boundary in this work. Both are examples of hydrodynamically induced particle-particle attraction, which has recently been found for rotors as well [38].…”

Section: Discussionmentioning

confidence: 72%

“…For several disconnected particles there are a number of other interesting hydrodynamically induced interaction effects even in the bulk and in the absence of fluctuations. Besides the oscillatory dynamics of three sedimenting free particles [37] and of three trapped particles in shear flow [35], one finds also HI induced attraction or repulsion between asymmetric rotors [38], and an attraction between tethered polymers in plug flow [39]. For a diluted suspension of Brownian particles in shear flow an enhanced self-diffusion in shear flows is reported [40], which is explained by a wall-induced migration of free particles [41].…”

Section: Introductionmentioning

confidence: 85%

Wall attraction and repulsion of hydrodynamically interacting particles

Schreiber,

Bammert,

Peyla

et al. 2013

Preprint

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We investigate hydrodynamic interaction effects between colloidal particles in the vicinity of a wall in the low Reynolds-number limit. Hydrodynamically interacting pairs of beads being dragged by a force parallel to a wall, as for instance during sedimentation, are repelled by the boundary. If a pair of beads is trapped by harmonic potentials parallel to the external flow and at the same distance to a wall, then the particle upstream is repelled from the boundary while its neighbor downstream is attracted. The free end of a semiflexible bead-spring polymer-model, which is fixed at one end in a flow near a wall, is bent towards the wall by the same reason. The results obtained for point-like particles are exemplarily confirmed by fluid particle dynamics simulations of beads of finite radii, where the shear induced particle rotations either weaken or enhance the effects obtained for point-like particles.

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“…Spontaneous fusion of two ring-like clusters. Spontaneous pattern formation and pair interaction of rotating particles and vortex arrays, has been aroused a lot of interest in the past few years, in experiments [40][41][42] and in theory [43][44][45][46] revealing the importance of the HI in this type of systems. It has been proved that magnetic rotors at finite Reynolds number exhibit pattern formation and hydrodynamic repulsion while a pair of interacting rotors in the Stokes limit exhibit hydrodynamic attraction.…”

Section: Induced Fission and Fusionmentioning

confidence: 99%

Fission and fusion scenarios for magnetic microswimmer clusters

2016

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Fission and fusion processes of particle clusters occur in many areas of physics and chemistry from subnuclear to astronomic length scales. Here we study fission and fusion of magnetic microswimmer clusters as governed by their hydrodynamic and dipolar interactions. Rich scenarios are found that depend crucially on whether the swimmer is a pusher or a puller. In particular a linear magnetic chain of pullers is stable while a pusher chain shows a cascade of fission (or disassembly) processes as the self-propulsion velocity is increased. Contrarily, magnetic ring clusters show fission for any type of swimmer. Moreover, we find a plethora of possible fusion (or assembly) scenarios if a single swimmer collides with a ringlike cluster and two rings spontaneously collide. Our predictions are obtained by computer simulations and verifiable in experiments on active colloidal Janus particles and magnetotactic bacteria.

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Hydrodynamic attraction and repulsion between asymmetric rotors

Cited by 5 publications

References 35 publications

Cooperative self-propulsion of active and passive rotors

Cooperative self-propulsion of active and passive rotors

Wall attraction and repulsion of hydrodynamically interacting particles

Fission and fusion scenarios for magnetic microswimmer clusters

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