Dynamics of a chiral swimmer sedimenting on a flat plate

Fadda, Federico; Molina, John J.; Yamamoto, Ryōichi

doi:10.1103/physreve.101.052608

Cited by 38 publications

(26 citation statements)

References 68 publications

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“…At low flow velocities, our simulations show significant wall accumulation of the squirmers independent of their active stress but with a stress-specific preferred alignment, as is well established [5,19,50,61,[64][65][66][67][68]. Increasing flow leads to swimmer depletion at walls and at high shear rates additionally to depletion in the channel center, in agreement with previous observations in simulations, theory, and experiments [14,69,70].…”

Section: Introductionsupporting

confidence: 91%

Rheotaxis of spheroidal squirmers in microchannel flow: Interplay of shape, hydrodynamics, active stress, and thermal fluctuations

Annepu

Gompper

et al. 2020

Phys. Rev. Research

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Microswimmers exposed to microchannel flows exhibit an intriguing coupling between propulsion, shape, hydrodynamics, and flow which gives rise to distinct swimming behaviors. We employ a generic coarse-grained model of prolate spheroidal microswimmers, denoted as squirmers, exposed to channel flow to shed light onto their transport properties. The embedding fluid is implemented by the multiparticle collision dynamics approach (MPC), a particle-based mesoscale simulation method, which includes thermal fluctuations. Specifically, the influence of swimmer shape-spherical vs spheroidal-, active stress-pusher, ciliate, puller-, and thermal fluctuations on their rheotactic behavior is analyzed. The microswimmers accumulate at the confining walls at very low flow rates. With increasing flow strength, squirmers are depleted from the walls, and at high flow rates are also depleted from the channel center. The squirmers show pronounced cross-channel swimming between the confining walls with mixed oscillating and rotational motions due to thermal fluctuations. This strongly affects their rheotactic behavior. In particular, spherical pullers and ciliates swim upstream, whereas spherical pushers essentially swim downstream. The anisotropic shape of spheroidal squirmers enhances wall and center depletion and the alignment of the propulsion direction parallel to the flow, which leads to preferred downstream swimming for all active stresses. This emphasizes the importance of swimmer shape and hydrodynamic wall interactions on the transport properties of a microswimmer such as Volvox and Opalina, for example.

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Section: Introductionsupporting

confidence: 91%

Rheotaxis of spheroidal squirmers in microchannel flow: Interplay of shape, hydrodynamics, active stress, and thermal fluctuations

Annepu

Gompper

et al. 2020

Phys. Rev. Research

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“…Additionally, we consider the modes B 2 and C 2 , which we express in terms of the squirmer parameter β = B 2 /B 1 and chirality parameter χ = C 2 /B 1 , see for example Ref. [63]. The parameter β switches between neutral squirmers (β = 0), pullers (β > 0) and pushers (β < 0).…”

Section: Squirmer Modelmentioning

confidence: 99%

“…Furthermore, the rotlet dipole field is an important aspect of many swimming organisms, for example, of bacteria with counter-rotating flagella and cell body. It has been studied in some previous works [63,65].…”

Section: Flow and Vorticity Fieldsmentioning

confidence: 99%

Gyrotactic cluster formation of bottom-heavy squirmers

Rühle¹,

Zantop²,

Stark³

2022

Preprint

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Squirmers that are bottom-heavy experience a torque that aligns them along the vertical so that they swim upwards. In a suspension of many squirmers, they also interact hydrodynamically via flow fields that are initiated by their swimming motion and by gravity. Swimming under the combined action of flow field vorticity and gravitational torque is called gyrotaxis. Using the method of multi-particle collision dynamics, we perform hydrodynamic simulations of a many-squirmer system floating above the bottom surface. Due to gyrotaxis they exhibit pronounced cluster formation with increasing gravitational torque. The clusters are more volatile at low values but compactify to smaller clusters at larger torques. The mean distance between clusters is mainly controlled by the gravitational torque and not the global density. Furthermore, we observe that neutral squirmers form clusters more easily, whereas pullers require larger gravitational torques due to their additional force-dipole flow fields. We do not observe clustering for pusher squirmers. Adding a rotlet dipole to the squirmer flow field induces swirling clusters. At high gravitational strengths, the hydrodynamic interactions with the no-slip boundary create an additional vertical alignment for neutral squirmers, which also supports cluster formation.

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“…Given the quickly increasing complexity of the resulting flows and the myriad possibilities of surface patterns, it is clear that adopting a more analytical approach to understanding the design space of boundary-driven flows is required. For this we turn to solutions of the squirmer model on a sphere [42][43][44][45][46]. Initially adopted to study the external flow fields of microswimmers, we invert the problem and study instead the flow structure within the sphere [47], subject to the condition that flows normal to the surface vanish on the boundary.…”

Section: The Interior Squirmer Modelmentioning

confidence: 99%

Engineering reconfigurable flow patterns via surface-driven light-controlled active matter

Gong¹,

Mathijssen²,

Bryant³

et al. 2020

Preprint

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Surface-driven flows are ubiquitous in nature, from subcellular cytoplasmic streaming to organscale ciliary arrays. Here, we model how confined geometries can be used to engineer complex hydrodynamic patterns driven by activity prescribed solely on the boundary. Specifically, we simulate light-controlled surface-driven active matter, probing the emergent properties of a suspension of active colloids that can bind and unbind pre-patterned surfaces of a closed microchamber, together creating an active carpet. The attached colloids generate large scale flows that in turn can advect detached particles towards the walls. Switching the particle velocities with light, we program the active suspension and demonstrate a rich design space of flow patterns characterised by topological defects. We derive the possible mode structures and use this theory to optimise different microfluidic functions including hydrodynamic compartmentalisation and chaotic mixing. Our results pave the way towards designing and controlling surface-driven active fluids.

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Dynamics of a chiral swimmer sedimenting on a flat plate

Cited by 38 publications

References 68 publications

Rheotaxis of spheroidal squirmers in microchannel flow: Interplay of shape, hydrodynamics, active stress, and thermal fluctuations

Rheotaxis of spheroidal squirmers in microchannel flow: Interplay of shape, hydrodynamics, active stress, and thermal fluctuations

Gyrotactic cluster formation of bottom-heavy squirmers

Engineering reconfigurable flow patterns via surface-driven light-controlled active matter

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