Locomotion inside a surfactant-laden drop at low surface Péclet numbers

Shaik, Vaseem A.; Vasani, Vishwa; Ardekani, Arezoo M.

doi:10.1017/jfm.2018.491

Cited by 20 publications

(27 citation statements)

References 52 publications

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“…Also as (h 2 cosh (2h) − 2h sinh (2h) + h 2 + cosh (2h) − 1) > 0 and (h sinh (2h) − cosh (2h) + 1) > 0, we see that the surfactant redistribution always increases the swimming velocity at small P e s . This is in contrast with the observation that the surfactant redistribution can increase or even decrease the velocity of a swimming microorganism inside a surfactant laden drop at small P e s [20]. These different influences of the surfactant on the swimming velocity, reported in Ref.…”

Section: Limiting Casescontrasting

confidence: 78%

“…These different influences of the surfactant on the swimming velocity, reported in Ref. [20] and this work, might be due to different shapes of the swimmer and the interface used in these two works.…”

Section: Limiting Casesmentioning

confidence: 56%

“…This is nonintuitive as a surfactant laden drop usually has characteristics that are intermediate between a rigid sphere and a clean drop. Analogous to the interface deformations, finite inertia of the fluid or the organism and the non-Newtonian rheology of the fluid, the surfactant redistribution can enable a time-reversible swimming microorganism near an interface to achieve a net motion [20].…”

Section: Introductionmentioning

confidence: 99%

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Swimming sheet near a plane surfactant-laden interface

Shaik

Ardekani

2019

Phys. Rev. E

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In this work we analyze the velocity of a swimming sheet near a plane surfactant laden interface by assuming the Reynolds number and the sheet's deformation to be small. We observe a nonmonotonic dependence of sheet's velocity on the Marangoni number (M a) and the surface Péclet number (P e s ). For a sheet passing only transverse waves, the swimming velocity increases with an increase in M a for any fixed P e s while at large M a it increases and at small M a it initially increases and then decreases with an increase in P e s . This dependence of the swimming velocity on M a and P e s is altered if the sheet is passing longitudinal waves in addition to the transverse waves along its surface. * ardekani@purdue.edu

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Section: Limiting Casescontrasting

confidence: 78%

Section: Limiting Casesmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

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Swimming sheet near a plane surfactant-laden interface

Shaik

Ardekani

2019

Phys. Rev. E

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“…In addition, a combination of multipole expansion and Faxén's theorem has been used by Zia and collaborators [41,42], providing the elements of the grand mobility tensor of finitesized particles moving inside a rigid spherical cavity. Additional works addressed the low-Reynolds-number locomotion inside a viscous drop [43][44][45], or the dynamics of a particleencapsulating droplet in flow [46,47]. arXiv:1802.00353v2 [physics.flu-dyn] 14 Aug 2018 Despite enormous studies on particle motion inside a rigid cavity or a viscous drop, to the best of our knowledge, no works have been yet conducted to investigate particle motion inside a deformable elastic cavity.…”

Section: Introductionmentioning

confidence: 99%

Creeping motion of a solid particle inside a spherical elastic cavity

2018

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On the basis of the linear hydrodynamic equations, we present an analytical theory for the low-Reynolds-number motion of a solid particle moving inside a larger spherical elastic cavity which can be seen as a model system for a fluid vesicle. In the particular situation where the particle is concentric with the cavity, we use the stream function technique to find exact analytical solutions of the fluid motion equations on both sides of the elastic cavity. In this particular situation, we find that the solution of the hydrodynamic equations is solely determined by membrane shear properties and that bending does not play a role. For an arbitrary position of the solid particle within the spherical cavity, we employ the image solution technique to compute the axisymmetric flow field induced by a point force (Stokeslet). We then obtain analytical expressions of the leading-order mobility function describing the fluid-mediated hydrodynamic interactions between the particle and the confining elastic cavity. In the quasi-steady limit of vanishing frequency, we find that the particle self-mobility function is higher than that predicted inside a rigid no-slip cavity. Considering the cavity motion, we find that the pair-mobility function is determined only by membrane shear properties. Our analytical predictions are supplemented and validated by fully resolved boundary integral simulations where a very good agreement is obtained over the whole range of applied forcing frequencies.

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“…It has been demonstrated that a swimming organism reorients itself and gets scattered from the obstacle or gets trapped or captured by it if the size of the obstacle is large enough and the settling/rising speed of the microorganism is small enough. Near a viscous drop, the surfactant increases the trapping capability [120] and can even break the kinematic reversibility associated with the inertialess realm of swimming microorganisms [123]. In contrast to that, the presence of a surfactant near a planar interface was found not to change the reorientation dynamics [74] but to change the swimming speed [124] in addition to the circling direction [74].…”

Section: Introductionmentioning

confidence: 82%

Towards an analytical description of active microswimmers in clean and in surfactant-covered drops

et al. 2020

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Abstract. Geometric confinements are frequently encountered in the biological world and strongly affect the stability, topology, and transport properties of active suspensions in viscous flow. Based on a far-field analytical model, the low-Reynolds-number locomotion of a self-propelled microswimmer moving inside a clean viscous drop or a drop covered with a homogeneously distributed surfactant, is theoretically examined. The interfacial viscous stresses induced by the surfactant are described by the well-established Boussinesq-Scriven constitutive rheological model. Moreover, the active agent is represented by a force dipole and the resulting fluid-mediated hydrodynamic couplings between the swimmer and the confining drop are investigated. We find that the presence of the surfactant significantly alters the dynamics of the encapsulated swimmer by enhancing its reorientation. Exact solutions for the velocity images for the Stokeslet and dipolar flow singularities inside the drop are introduced and expressed in terms of infinite series of harmonic components. Our results offer useful insights into guiding principles for the control of confined active matter systems and support the objective of utilizing synthetic microswimmers to drive drops for targeted drug delivery applications. Graphical abstract

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Locomotion inside a surfactant-laden drop at low surface Péclet numbers

Cited by 20 publications

References 52 publications

Swimming sheet near a plane surfactant-laden interface

Swimming sheet near a plane surfactant-laden interface

Creeping motion of a solid particle inside a spherical elastic cavity

Towards an analytical description of active microswimmers in clean and in surfactant-covered drops

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