Measurements of the unsteady flow field around beating cilia

Wei, Da; Dehnavi, Parviz Ghoddoosi; Aubin‐Tam, Marie‐Eve; Tam, Daniel

doi:10.1017/jfm.2021.149

Cited by 21 publications

(16 citation statements)

References 70 publications

(144 reference statements)

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“…If the oscillatory frequency of the control force were to be large, the commonplace assumption of negligible inertial effects may no longer be valid. For such a rapidly oscillating force actuation, one might seek to apply the unsteady Stokes equations and the associated Stokeslet, called the oscillet, which leads to a correction in the far-field (Wei et al 2021). In this work, we have exploited symmetry to improve the computational tractability of the systems that we have considered, a property not present in many-sphere settings or in more-complex geometries.…”

Section: Discussionmentioning

confidence: 99%

The control of particles in the Stokes limit

et al. 2022

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There are numerous ways to control objects in the Stokes regime, with microscale examples ranging from the use of optical tweezers to the application of external magnetic fields. In contrast, there are relatively few explorations of theoretical controllability, which investigate whether or not refined and precise control is indeed possible in a given system. In this work, seeking to highlight the utility and broad applicability of such rigorous analysis, we recount and illustrate key concepts of geometric control theory in the context of multiple particles in Stokesian fluids interacting with each other, such that they may be readily and widely applied in this largely unexplored fluid-dynamical setting. Motivated both by experimental and abstract questions of control, we exemplify these techniques by explicit and detailed application to multiple problems concerning the control of two particles, such as the motion of tracers in flow and the guidance of one sphere by another. Further, we showcase how this analysis of controllability can directly lead to the construction of schemes for control, in addition to facilitating explorations of mechanical efficiency and contributing to our overall understanding of non-local hydrodynamic interactions in the Stokes limit.

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Section: Discussionmentioning

confidence: 99%

The control of particles in the Stokes limit

et al. 2022

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“…Phase dynamics of flagellar beating is extracted from videography (31,39,40). Recordings are masked and thresholded to highlight the flagella (Fig.…”

Section: Experimental Scheme For Selective Loadingmentioning

confidence: 99%

“…First we explore flow synchronization over a broad range of amplitudes and frequencies. θ aflows with frequencies f f ∈ [40,75] Hz and amplitudes U ∈ [390, 2340] µm/s are imposed. The scanned range covers reported intrinsic frequencies of both the cis and trans flagellum (22,24,26,27); while the amplitude reaches the maximum instantaneous speed of a beating flagellum (∼ 2000 µm/s).…”

Section: Asymmetric Susceptibility To Flow Synchronizationmentioning

confidence: 99%

The younger flagellum coordinates the beating in C. reinhardtii

Wang¹,

Quaranta²,

Aubin‐Tam³

et al. 2023

Preprint

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Eukaryotes swim with coordinated flagellar (ciliary) beating and steer by fine-tuning the coordination. The model organism for studying flagellate motility, C. reinhardtii (CR), employs synchronous, breast-stroke-like flagellar beating to swim, and it modulates the beating amplitudes differentially to steer. This strategy hinges on both inherent flagellar asymmetries (e.g. different response to chemical messengers) and such asymmetries being effectively coordinated in the synchronous beating. In CR, the synchrony of beating is known to be supported by a mechanical connection between flagella, however, how flagellar asymmetries persist in the synchrony remains elusive. For example, it has been speculated for decades that one flagellum leads the beating, as its dynamic properties (i.e. frequency, waveform, etc.) appear to be copied by the other one. In this study, we combine experiments, computations, and modeling efforts to elucidate the roles played by each flagellum in synchronous beating. With a non-invasive technique to selectively load each flagellum, we show that the coordinated beating essentially responds to only load exerted on the cis flagellum; and that such asymmetry in response derives from a unilateral coupling between the two flagella. Our results highlight a distinct role for each flagellum in coordination and have implication for biflagellates' tactic behaviors.

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“…In the pursuit of an understanding of active matter collective dynamics, experimental works have systematically examined the fluid flows generated by propulsive appendages [19][20][21], swimming microorganisms [22][23][24][25], the interactions between pairs of cells [9] and active droplets [26], and the role of nearby boundaries [27][28][29]. Colonies of Volvox exhibit striking bound states [30] mediated by gravity and a bounding wall, while cells of Chlamydomonas reflect in non-trivial ways from no-slip surfaces [31].…”

Section: Introductionmentioning

confidence: 99%

Pairwise scattering and bound states of spherical microorganisms

C.¹,

Ishikawa²,

Pedley³

et al. 2021

Preprint

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The dynamic interactions between pairs of swimming microorganisms underpin the collective behaviour of larger suspensions, but accurately calculating pairwise collisions has typically required the use of numerical simulations in which hydrodynamic interactions are fully resolved. In this paper, we utilise analytical expressions for forces and torques acting on two closely separated spherical squirmers -accurate to second order in the ratio of cell-cell spacing to squirmer radius -in order to calculate their scattering dynamics. Attention is limited to squirmers whose orientation vectors lie in the same plane. We characterise the outgoing angles of pairs of bottom-heavy squirmers in terms of their incoming angles, the squirmer parameter β, and the strength of the external gravitational field, discovering transient scattering, stationary bound states, pairwise swimming motion, and circular orbits. These results compare well with full numerical solutions obtained using boundary element methods, highlighting the utility of lubrication theory. We expect these results will be useful for the foundations of mesoscale continuum models for suspensions of spherical microorganisms.

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Measurements of the unsteady flow field around beating cilia

Abstract: Abstract

Cited by 21 publications

References 70 publications

The control of particles in the Stokes limit

The control of particles in the Stokes limit

The younger flagellum coordinates the beating in C. reinhardtii

Pairwise scattering and bound states of spherical microorganisms

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