Drop motion with surfactant transfer in an inhomogeneous medium

Rednikov, Alexei; Ryazantsev, Yuri S.; Velárde, Manuel G.

doi:10.1016/0017-9310(94)90036-1

Cited by 15 publications

(21 citation statements)

References 5 publications

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“…Both the ‘global’ linearisation and the ‘local’ weakly nonlinear analysis require the use of matched asymptotic expansions in the spirit of classical forced-convection problems (Acrivos & Taylor 1962). Our approach resembles previous theoretical studies of weakly forced active droplets (Rednikov, Ryazantsev & Velárde 1994 a , b , c , d ; Rednikov et al. 1995; Velarde, Rednikov & Ryazantsev 1996), whose mathematical description is partially similar to that of a spherical solid particle with a uniform chemical activity.…”

Section: Introductionmentioning

confidence: 69%

Isotropically active colloids under uniform force fields: from forced to spontaneous motion

2021

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Section: Introductionmentioning

confidence: 69%

Isotropically active colloids under uniform force fields: from forced to spontaneous motion

2021

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“…-Dirichlet boundary condition at the interface The implementation of a Dirichlet boundary condition, is carried out by means of an extrapolated "ghost" bulk concentration field inside the droplet, to be used for the calculation of the explicit advective term (u · ∇c) n in Eq. (31). The adopted procedure is inspired by the one used in [63] for the treatment of the temperature field.…”

Section: Bulk Concentration Field Cmentioning

confidence: 99%

“…II C 2). In particular, we test the numerical solver (31) for the diffusion of the bulk concentration, described in Eq. We found a very good agreement between analytical and numerical results (see Fig.…”

Section: Bulk Diffusionmentioning

confidence: 99%

“…The majority of this works assumes a prescribed fluid flow at the surface, instead of deriving it. However, for self-propelled droplets driven by gradients of mass concentration or temperature [27,28] or by Belousov-Zhabotinsky (BZ) reactions [19], as well as for emulsion droplets [29,30] of the kind described in [21], analytical solutions of the flow profiles are available for simplified cases, and the stability analysis of their motion has been addressed [31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulation of artificial microswimmers driven by Marangoni flow

Stricker

2017

Journal of Computational Physics

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In the present paper the behavior of a single artificial microswimmer is addressed, namely an active droplet moving by Marangoni flow. We provide a numerical treatment for the main factors playing a role in real systems, such as advection, diffusion and the presence of chemical species with different behaviors. The flow field inside and outside the droplet is modeled to account for the two-way coupling between the surrounding fluid and the motion of the swimmer. Mass diffusion is also taken into account. In particular, we consider two concentration fields: the surfactant concentration in the bulk, i.e. in the liquid surrounding the droplet, and the surfactant concentration on the surface. The latter is related to the local surface tension, through an equation of state (Langmuir equation). We examine different interaction mechanisms between the bulk and the surface concentration fields, namely the case of insoluble surfactants attached to the surface (no exchange between the bulk and the surface) and soluble surfactants with adsorption/desorption at the surface. We also consider the case where the bulk concentration field is in equilibrium with the content of the droplet. The numerical results are validated through comparison with analytical calculations. We show that our model can reproduce the typical pusher/puller behavior presented by squirmers. It is also able to capture the self-propulsion mechanism of droplets driven by Belousov-Zhabotinsky (BZ) reactions, as well as a typical chemotactic behavior

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“…Spontaneous fluctuations in the solute density field can yield transient anomalous diffusion of the colloid and enhanced diffusion [5][6][7]. Spontaneous symmetry breaking can also arise from the nonlinear coupling between the solute density and the flows at the surface of the colloid [8][9][10][11] -an effect which was evidenced experimentally with large water droplets in an oil-surfactant medium [12][13][14][15][16]. Alternatively, models where the number of solute particles is conserved were considered.…”

mentioning

confidence: 99%

Spontaneous propulsion of an isotropic colloid in a phase-separating environment

Decayeux,

Dahirel,

Jardat

et al. 2021

Preprint

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The motion of active colloids is generally achieved through their anisotropy, as exemplified by Janus colloids. Recently, there was a growing interest in the propulsion of isotropic colloids, which requires some local symmetry breaking. Although several mechanisms for such propulsion were proposed, little is known about the role played by the interactions within the environment of the colloid, which can have a dramatic effect on its propulsion. Here, we propose a minimal model of an isotropic colloid in a bath of solute particles that interact with each other. These interactions lead to a spontaneous phase transition close to the colloid, to directed motion of the colloid over very long timescales and to significantly enhanced diffusion, in spite of the crowding induced by solute particles. We determine the range of parameters where this effect is observable in the model, and we propose an effective Langevin equation that accounts for it and allows one to determine the different contributions at stake in self-propulsion and enhanced diffusion.

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Drop motion with surfactant transfer in an inhomogeneous medium

Cited by 15 publications

References 5 publications

Isotropically active colloids under uniform force fields: from forced to spontaneous motion

Isotropically active colloids under uniform force fields: from forced to spontaneous motion

Numerical simulation of artificial microswimmers driven by Marangoni flow

Spontaneous propulsion of an isotropic colloid in a phase-separating environment

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