A two-sphere model for bacteria swimming near solid surfaces

Dunstan, Jocelyn; Miño, Gastón Leonardo; Clément, Éric; Soto, Rodrigo

doi:10.1063/1.3676245

Cited by 41 publications

(41 citation statements)

References 27 publications

(47 reference statements)

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“…This can be seen by modeling a flagellar swimmer modeled as an asymmetric rigid dumbbell with Stokeslets of different hydrodynamic radii located at the head and tail respectively (Appendix A). 39 We obtain for such…”

Section: Resultsmentioning

confidence: 99%

Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

McDonnell

Gopesh

et al. 2015

Soft Matter

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Suspensions of motile cells are model systems for understanding the unique mechanical properties of living materials which often consist of ensembles of self-propelled particles. We present here a quantitative comparison of theory against experiment for the rheology of such suspensions. The influence of motility on viscosities of cell suspensions is studied using a novel acousticallydriven microfluidic capillary-breakup extensional rheometer. Motility increases the extensional viscosity of suspensions of algal pullers, but decreases it in the case of bacterial or sperm pushers. A recent model [Saintillan, Phys. Rev. E, 2010, 81, 56307] for dilute active suspensions is extended to obtain predictions for higher concentrations, after independently obtaining parameters such as swimming speeds and diffusivities. We show that details of body and flagellar shape can significantly determine macroscale rheological behaviour.

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Section: Resultsmentioning

confidence: 99%

Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

McDonnell

Gopesh

et al. 2015

Soft Matter

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“…(28) for values of the Péclet number for which the effects of persistence are conspicuous, P e = 1000 and infinity. In the long time regime the effective diffusion coefficient diminishes as P e is increased, bounded from below by D B + D A /3 [see (49)]. …”

Section: Resultsmentioning

confidence: 99%

“…In the short-time regime the msd is linear in t with a diffusion coefficient that depends only P e and not on chirality as is apparent in the figure. At long times, in the diffusive regime, the effective diffusion coefficient diminishes as chirality is increased, bounded from below by D B + D A /3 [see (49)]. …”

Section: Resultsmentioning

confidence: 99%

“…The processes that lead to chiral motion of active articles may be diverse [46][47][48][49], the simplest situation in two dimensions corresponds to a geometric effect, that is to say, to the misaligning of the direction of the propelling force and the orientation of the particle axis [50,51]. A simple effective-force model, that leads to circular patterns of motion, is the inclusion of an effective constant "torque" in the Langevin equations that drive the orientation of the self-propulsive force [52].…”

Section: Introductionmentioning

confidence: 99%

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Diffusion of active chiral particles

Sevilla

2016

Phys. Rev. E

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The diffusion of chiral active Brownian particles in three-dimensional space is studied analytically, by consideration of the corresponding Fokker-Planck equation for the probability density of finding a particle at position x and moving along the directionv at time t, and numerically, by the use of Langevin dynamics simulations. The analysis is focused on the marginal probability density of finding a particle at a given location and at a given time (independently of its direction of motion), which is found from an infinite hierarchy of differential-recurrence relations for the coefficients that appear in the multipole expansion of the probability distribution which contains the whole kinematic information. This approach allows the explicit calculation of the time dependence of the mean squared displacement and the time dependence of the kurtosis of the marginal probability distribution, quantities from which the effective diffusion coefficient and the "shape" of the positions distribution are examined. Oscillations between two characteristic values were found in the time evolution of the kurtosis, namely, between the value that corresponds to a Gaussian and the one that corresponds to a distribution of spherical shell shape. In the case of an ensemble of particles, each one rotating around an uniformly-distributed random axis, it is found evidence of the so called effect "anomalous, yet Brownian, diffusion", for which particles follow a non-Gaussian distribution for the positions yet the mean squared displacement is a linear function of time.PACS numbers: 02.50.-r 05.40.-a 05.10.Gg

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“…Several models have been introduced to describe the swimming along surfaces (see Ref. [15] and references therein). Interestingly, the direct observation of the cell-wall attraction (see Fig.…”

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confidence: 99%

Geometrical guidance and trapping transition of human sperm cells

et al. 2014

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The guidance of human sperm cells under confinement in quasi 2D microchambers is investigated using a purely physical method to control their distribution. Transport property measurements and simulations are performed with dilute sperm populations, for which effects of geometrical guidance and concentration are studied in detail. In particular, a trapping transition at convex angular wall features is identified and analyzed. We also show that highly efficient microratchets can be fabricated by using curved asymmetric obstacles to take advantage of the spermatozoa specific swimming strategy.PACS numbers: 87.17. Jj, 87.18.Hf, 87.17.Aa, 87.17.Rt Understanding sperm dynamics under confining microgeometries is a general problem and a major challenge both from the basic biophysics and the complex fluids points of view. It is also crucial for microfluidics and biomedical control applications. Our knowledge of the swimming cell motilities in unbounded media cannot be directly extrapolated to their behavior in complex environments such as those found in the oviduct or in the labon-a-chip microfluidic devices used to control and analyze small samples or for in-vitro reproduction procedures. In these cases, the characteristic length scales are of the same order as the cell size, i.e. a few micrometers. Under these circumstances, confined self-propelled microorganisms undergo substantial changes in their locomotion habits, adapting their dynamics to intricate porous media or to solid surfaces vicinity [1], reducing their speed close to boundaries [2] or adjusting their morphology and motility in very narrow channels [3].It has been shown that microswimmers with very different propulsion systems are similarly attracted to the walls and to swim parallel to the surface [2,[4][5][6][7][8][9][10][11]. It is believed that this attractive force has hydrodynamic origin although other possible mechanisms have been proposed [12][13][14]. Several models have been introduced to describe the swimming along surfaces (see Ref.[15] and references therein). Interestingly, the direct observation of the cell-wall attraction (see Fig. 1) have led to the design of ratchet devices that guide and sort self-propelled cells using asymmetric obstacles [16,17]. In particular, different microfluidic devices have been created to either increase sperm cell quality or enhance their concentration [18][19][20]. The creation of inhomogeneous distributions of swimmer populations via asymmetric obstacles has been shown to be particularly efficient for run-and-tumble bacteria [16,[21][22][23]. Alternative ways of achieving nonuniform distributions have also been obtained combining symmetric funnels and flux [24]. Nowadays, numerous theoretical treatments are available to account for the effects of asymmetric obstacles on active particles distributions [25][26][27][28]. Tumbles, rotational diffusion and collisions are efficient mechanisms for separating the cells from the surface, thus permitting bacteria to be reinserted into the bulk of the confining micro...

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A two-sphere model for bacteria swimming near solid surfaces

Cited by 41 publications

References 27 publications

Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

Diffusion of active chiral particles

Geometrical guidance and trapping transition of human sperm cells

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