The cost of swimming in generalized Newtonian fluids: experiments with<i>C. elegans</i>

Gagnon, David A.; Arratia, Paulo E.

doi:10.1017/jfm.2016.420

Cited by 29 publications

(47 citation statements)

References 45 publications

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“…The efficiency of swimming in shear-thinning fluids, however, remains largely unexplored despite its biological relevance. thinning fluid [8,11,30]. Information on how shearthinning rheology alters the useful power output (DU ) is still required to quantify their swimming efficiency.…”

Section: Introductionmentioning

confidence: 99%

Swimming efficiency in a shear-thinning fluid

2017

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Micro-organisms expend energy moving through complex media. While propulsion speed is an important property of locomotion, efficiency is another factor that may determine the swimming gait adopted by a micro-organism in order to locomote in an energetically favorable manner. The efficiency of swimming in a Newtonian fluid is well characterized for different biological and artificial swimmers. However, these swimmers often encounter biological fluids displaying shear-thinning viscosities. Little is known about how this nonlinear rheology influences the efficiency of locomotion. Does the shear-thinning rheology render swimming more efficient or less? How does the swimming efficiency depend on the propulsion mechanism of a swimmer and rheological properties of the surrounding shear-thinning fluid? In this work, we address these fundamental questions on the efficiency of locomotion in a shear-thinning fluid by considering the squirmer model as a general locomotion model to represent different types of swimmers. Our analysis reveals how the choice of surface velocity distribution on a squirmer may reduce or enhance the swimming efficiency. We determine optimal shear rates at which the swimming efficiency can be substantially enhanced compared with the Newtonian case. The nontrivial variations of swimming efficiency prompt questions on how micro-organisms may tune their swimming gaits to exploit the shear-thinning rheology. The findings also provide insights into how artificial swimmers should be designed to move through complex media efficiently.

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Section: Introductionmentioning

confidence: 99%

Swimming efficiency in a shear-thinning fluid

2017

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“…2b,c) fig. 1b and (b) the effective viscosity fields associated with these shear rates in 300 ppm Xanthum gum solution [40], showing striking differences.…”

Section: B Nematode Worm Modelling 2d Vs 3dmentioning

confidence: 97%

“…and the 2D shear rateγ = [2w 2 z + (w y + v z ) 2 + 2v 2 y ] 1/2 , whereupon substitution of the flow velocity derivatives reveals the somewhat surprising result that the first-order shear rateγ is independent of position s, (c) Effective viscosity relative to µ 0 as a function of distance away from the sheet/filament for models approximating a nematode swimming in 300 ppm Xanthum gum solution [40], with λ = 1.2 s, n = 0.7, and beat frequency f = 2 Hz, so that Cu = 4πλ ≈ 15.…”

Section: A Small-amplitude Modellingmentioning

confidence: 99%

“…The difference between the 2D and 3D swimmers is dramatic; at the surface of the cylinder, the viscosity is approximately 5 times less viscous than the sheet, and the fluid returns to 90% of the zero shear rate viscosity at a distance of 1.2 for the cylinder compared to 2.8 for the sheet. As Gagnon and Arratia [40] note, power expenditure in a shear-thinning fluid is approximately proportional to the fluid viscosity, and as both Li and Ardekani [23] and Gómez et al [36] note, swimming may be enhanced, for fixed kinematics, via pseudo-wall effects of being in a channel of thinned fluid, so that calculations of power expenditure and swimming enhancement are likely to be inaccurate if 2D modelling is employed.…”

Section: A Small-amplitude Modellingmentioning

confidence: 99%

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Fake μs : A cautionary tail of shear-thinning locomotion

Montenegro‐Johnson

2017

Phys. Rev. Fluids

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Propulsion through fluids is a key component in the life cycle of many microbes, be it in development, infection, or simply finding nutrients. In systems of biomedical relevence, this propulsion is often through polymer suspensions that endow the fluid with complex non-Newtonian properties, such as shear-thinning and viscoelastic behaviour. Due to the complexity of 3D non-Newtonian modelling, 2D undulatory propulsion has recently been extensively-studied as a means of garnering physical intuition for these systems. However, while streamlines, swimming speeds, and swimmer trajectories are strikingly similar in 2D and 3D Newtonian calculations, behaviour in non-Newtonian fluids depends upon flow derivatives, such as the shear rate, which are radically different. Taking shear-thinning as an example rheology, prevalent in biological fluids such as physiological mucus, this communication demonstrates how failing to account for this difference can misguide our understanding of 3D non-Newtonian swimming.

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“…For the fixed kinematics of the organism, this result suggests that viscoelasticity reduces the propulsion speed of a small-amplitude sheet compared to its Newtonian value, reaching for large Deborah numbers the limit βU BN . These conclusions were extended to other swimmers [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] or fluids with different rheological properties [53][54][55][56][57][58], and were used as a motivation for experimental studies [59][60][61][62][63][64][65][66][67].…”

Section: Introductionmentioning

confidence: 99%

The mechanism of propulsion of a model microswimmer in a viscoelastic fluid next to a solid boundary

Ives

Morozov

2017

Physics of Fluids

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In this paper we study swimming of a model organism, the so-called Taylor's swimming sheet, in a viscoelastic fluid close to a solid boundary. This situation comprises natural habitats of many swimming microorganisms, and while previous investigations have considered the effects of both swimming next to a boundary and swimming in a viscoelastic fluid, seldom have both effects been considered simultaneously. We re-visit the small wave amplitude result obtained by Elfring and Lauga (Gwynn J. Elfring and Eric Lauga, in Saverio E. Spagnolie, editor, Complex Fluids in Biological Systems, Springer New York, New York, NY, 2015), and give a mechanistic explanation to the decoupling of the effects of viscoelasticity, which tend to slow the sheet, and the presence of the boundary, which tends to speed up the sheet. We also develop a numerical spectral method capable of finding the swimming speed of a waving sheet with an arbitrary amplitude and waveform.We use it to show that the decoupling mentioned above does not hold at finite wave amplitudes and that for some parameters the presence of a boundary can cause the viscoelastic effects to increase the swimming speed of microorganisms.

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The cost of swimming in generalized Newtonian fluids: experiments withC. elegans

Cited by 29 publications

References 45 publications

Swimming efficiency in a shear-thinning fluid

Swimming efficiency in a shear-thinning fluid

Fake μs : A cautionary tail of shear-thinning locomotion

The mechanism of propulsion of a model microswimmer in a viscoelastic fluid next to a solid boundary

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