Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers

Kyoya, Kohei; Matsunaga, Daiki; Imai, Yohsuke; Omori, Toshihiro; Ishikawa, Takuji

doi:10.1103/physreve.92.063027

Cited by 39 publications

(25 citation statements)

References 44 publications

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“…For squirmer pullers polar order can emerge [333], which was also quantified further in [138,[339][340][341]. This is in contrast to hydrodynamic simulations of self-propelled rods, which show local polar order for generic pushers but not for pullers (see the last paragraph of this section).…”

Section: Microswimmers With Hydrodynamic Interactionsmentioning

confidence: 81%

Emergent behavior in active colloids

Zöttl

Stark

2016

J. Phys.: Condens. Matter

500

559

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Active colloids are microscopic particles, which self-propel through viscous fluids by converting energy extracted from their environment into directed motion. We first explain how articial microswimmers move forward by generating near-surface flow fields via self-phoresis or the self-induced Marangoni effect. We then discuss generic features of the dynamics of single active colloids in bulk and in confinement, as well as in the presence of gravity, field gradients, and fluid flow. In the third part, we review the emergent collective behavior of active colloidal suspensions focussing on their structural and dynamic properties. After summarizing experimental observations, we give an overview on the progress in modeling collectively moving active colloids. While active Brownian particles are heavily used to study collective dynamics on large scales, more advanced methods are necessary to explore the importance of hydrodynamic and phoretic particle interactions. Finally, the relevant physical approaches to quantify the emergent collective behavior are presented.

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Section: Microswimmers With Hydrodynamic Interactionsmentioning

confidence: 81%

Emergent behavior in active colloids

Zöttl

Stark

2016

J. Phys.: Condens. Matter

500

559

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“…We believe that particle shape plays an important role in the formation of emerging collective patterns [61], and it deserves a study on its own.…”

Section: Discussionmentioning

confidence: 97%

Morphology of clusters of attractive dry and wet self-propelled spherical particle suspensions

2017

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In order to asses the effect of hydrodynamics in the assembly of active attractive spheres, we simulate a semi-dilute suspension of attractive self-propelled spherical particles in a quasi two dimensional geometry comparing the case with and without hydrodynamics interactions. To start with, independently on the presence of hydrodynamics, we observe that depending on the ratio between attraction and propulsion, particles either coarsen or aggregate forming finite-size clusters. Focusing on the clustering regime, we characterize two different clusters parameters, i.e. their morphology and orientational order, and compare the case when active particles behave either as pushers or pullers (always in the regime where inter-particles attractions competes with self-propulsion). Studying cluster phases for squirmers with respect to those obtained for active Brownian disks (indicated as ABP), we have shown that hydrodynamics alone can sustain a cluster phase of active swimmers (pullers), while ABP form cluster phases due to the competition between attraction and self propulsion. The structural properties of the cluster phases of squirmers and ABP are similar, although squirmers show sensitivity to active stresses. Active Brownian disks resemble weakly pusher squirmer suspensions in terms of cluster size distribution, structure of the radius of gyration on cluster size and degree of cluster polarity.

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“…In our basis, harmonics indexed by l produce bulk flows that decay as r − l , a simplicity that is absent in the bases used by Cichocki [92] and Ichiki [57]. For active colloids, earlier work closest in spirit to ours is that of Ishikawa et al [117][118][119] where axisymmetric slip velocities, truncated to the first two non-trivial modes, are considered. The far-field and near-field hydrodynamic interactions are obtained, respectively, in superposition and lubrication approximations.…”

Section: Discussion and Summarymentioning

confidence: 99%

Generalized Stokes laws for active colloids and their applications

Singh

Adhikari

2018

J. Phys. Commun.

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The force per unit area on the surface of a colloidal particle is a fundamental dynamical quantity in the mechanics and statistical mechanics of colloidal suspensions. Here we compute it in the limit of slow viscous flow for a suspension of N spherical active colloids in which activity is represented by surface slip. Our result is best expressed as a set of linear relations, the 'generalized Stokes laws', between the coefficients of a tensorial spherical harmonic expansion of the force per unit area and the surface slip. The generalized friction tensors in these laws are many-body functions of the colloidal configuration and can be obtained to any desired accuracy by solving a system of linear equations. Quantities derived from the force per unit area-forces, torques and stresslets on the colloids and flow, pressure and entropy production in the fluid-have succinct expressions in terms of the generalized Stokes laws. Most notably, the active forces and torques have a dissipative, long-ranged, many-body character that can cause phase separation, crystallization, synchronization and a variety of other effects observed in active suspensions. We use the results above to derive the Langevin and Smoluchowski equations for Brownian active suspensions, to compute active contributions to the suspension stress and fluid pressure, and to relate the synchrony in a lattice of harmonically trapped active colloids to entropy production. Our results provide the basis for a microscopic theory of active Brownian suspensions that consistently accounts for momentum conservation in the bulk fluid and at fluid-solid boundaries.

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Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers

Cited by 39 publications

References 44 publications

Emergent behavior in active colloids

Emergent behavior in active colloids

Morphology of clusters of attractive dry and wet self-propelled spherical particle suspensions

Generalized Stokes laws for active colloids and their applications

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