Flocking ferromagnetic colloids

Kaiser, Andreas; Snezhko, Alexey; Aranson, Igor S.

doi:10.1126/sciadv.1601469

Cited by 172 publications

(199 citation statements)

References 43 publications

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“…Here it has been shown, both, experimentally and in simulations, that these particles can exhibit swarming or vortex patterns when energized by a vertical alternating field. 15 Owing to the interplay between self-propulsion and dipolar interactions, these vortices persist even on a flat surface. 16 In nature, magnetotactic bacteria are known to sense the earth's magnetic field and move along or against the field direction.…”

Section: Introductionmentioning

confidence: 99%

Dynamical self-assembly of dipolar active Brownian particles in two dimensions

2020

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Section: Introductionmentioning

confidence: 99%

Dynamical self-assembly of dipolar active Brownian particles in two dimensions

2020

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“…Finally, the surface divergence of v 0 k is obtained from the spherical harmonic decomposition of the surface concentration on that particle, Eq. (32). For particles of uniform mobility M k , we finally obtain…”

Section: Initialization From the Phoretic Slip Distribution (P = 0)mentioning

confidence: 99%

Modeling chemo-hydrodynamic interactions of phoretic particles: A unified framework

Varma

Michelin

2019

Phys. Rev. Fluids

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Phoretic particles exploit local self-generated physico-chemical gradients to achieve self-propulsion at the micron scale. The collective dynamics of a large number of such particles is currently the focus of intense research efforts, both from a physical perspective to understand the precise mechanisms of the interactions and their respective roles, as well as from an experimental point of view to explain the observations of complex dynamics as well as formation of coherent large-scale structures. However, an exact modelling of such multi-particle problems is difficult and most efforts so far rely on the superposition of far-field approximations for each particle's signature, which are only valid asymptotically in the dilute suspension limit. A systematic and unified analytical framework based on the classical Method of Reflections (MoR) is developed here for both Laplace and Stokes' problems to obtain the higher-order interactions and the resulting velocities of multiple phoretic particles, up to any order of accuracy in the radius-to-distance ratio ε of the particles. Beyond simple pairwise chemical or hydrodynamic interactions, this model allows us to account for the generic chemo-hydrodynamic couplings as well as N -particle interactions (N ≥ 3). The ε 5 -accurate interaction velocities are then explicitly obtained and the resulting implementation of this MoR model is discussed and validated quantitatively against exact solutions of a few canonical problems.

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“…The formation of particle swarms from ensembles of artificial prototypes driven by an external field has been recently reported by different research groups who use electric [24,25], optic [26] or magnetic fields [27,28]. In most of the cases, the driven particles are dispersed in an isotropic fluid such as water, and are propelled through lithographic structures or assembled along a circular confinement.…”

Section: Introductionmentioning

confidence: 98%

Assembly and transport of nematic colloidal swarms above photo-patterned defects and surfaces

et al. 2018

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We investigate the dynamic assembly and swarm translocation of anisometric colloidal particles dispersed in a nematic liquid crystal and driven above a photosensitive surface. We use liquid crystalenabled electrophoresis to propel these particles via an alternating electric field perpendicular to the sample cell. By manipulating the anchoring conditions on one surface of the experimental cell, we obtain a spatially extended spiral pattern of the liquid crystal orientation that induces the dynamic assembly of a rotating colloidal mill. This structure can be transported by translocating the topological defect above the photosensitive surface. We complement our findings with a theoretical model that captures the basic physics of the process, by formulating an analytic equation for the director field above the surface. Our reconfigurable nematic assemblies may be used as a test bed for complex swarming behaviour in biological and artificial microscale systems.

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Flocking ferromagnetic colloids

Abstract: Energized by a vertical alternating magnetic field, colloidal particles roll and flock together.

Cited by 172 publications

References 43 publications

Dynamical self-assembly of dipolar active Brownian particles in two dimensions

Dynamical self-assembly of dipolar active Brownian particles in two dimensions

Modeling chemo-hydrodynamic interactions of phoretic particles: A unified framework

Assembly and transport of nematic colloidal swarms above photo-patterned defects and surfaces

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