Surface viscosity and Marangoni stresses at surfactant laden interfaces

Elfring, Gwynn J.; Leal, L. Gary; Squires, Todd M.

doi:10.1017/jfm.2016.96

Cited by 68 publications

(57 citation statements)

References 34 publications

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“…Since emphasis is put on the dilute regime, the reference Gibbs elasticity is set by the equilibrium value E 0 = Γ 0 k B T . Following [26], we define the dimensionless surface compressibility as the ratio of viscous over surface tension gradient forces…”

Section: General Considerationsmentioning

confidence: 99%

Hydrodynamic response of a surfactant-laden interface to a radial flow

et al. 2019

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We study the features of a radial Stokes flow due to a submerged jet directed toward a liquid-air interface. The presence of surface-active impurities confers to the interface an in-plane elasticity that resists the incident flow. Both analytical and numerical calculations show that a minute amount of surfactants is enough to profoundly alter the morphology of the flow. The hydrodynamic response of the interface is affected as well, shifting from slip to no-slip boundary condition as the surface compressibility decreases. We argue that the competition between the divergent outward flow and the elastic response of the interface may actually be used as a practical way to detect and quantify a small amount of impurities. arXiv:1909.13540v1 [cond-mat.soft]

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Section: General Considerationsmentioning

confidence: 99%

Hydrodynamic response of a surfactant-laden interface to a radial flow

et al. 2019

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“…The denominator η (s)γ s is the magnitude of the surface stresses of rheological origin, here taken for a shear flow at a shear rateγ s . Three non-dimensional groups will appear in the stress boundary condition for a planar interface undergoing a complex surface deformation, either Bo s , Bo d number and M a, or the combination Bo s , Θ, M a [35,47,49]. When the interface is curved, effects of capillarity (captured by a Capillary number) and bending will additionally contribute.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Interfacial rheology of model particles at liquid interfaces and its relation to (bicontinuous) Pickering emulsions

Thijssen

Vermant

2017

J. Phys.: Condens. Matter

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Interface-dominated materials are commonly encountered in both science and technology, and typical examples include foams and emulsions. Conventionally stabilised by surfactants, emulsions can also be stabilised by micron-sized particles. These so-called Pickering-Ramsden (PR) emulsions have received substantial interest, as they are model arrested systems, rather ubiquitous in industry and promising templates for advanced materials. The mechanical properties of the particle-laden liquid-liquid interface, probed via interfacial rheology, have been shown to play an important role in the formation and stability of PR emulsions. However, the morphological processes which control the formation of emulsions and foams in mixing devices, such as deformation, break-up, and coalescence, are complex and diverse, making it difficult to identify the precise role of the interfacial rheological properties. Interestingly, the role of interfacial rheology in the stability of bicontinuous PR emulsions (bijels) has been virtually unexplored, even though the phase separation process which leads to the formation of these systems is relatively simple and the interfacial deformation processes can be better conceptualised. Hence, the aims of this topical review are twofold. First, we review the existing literature on the interfacial rheology of particle-laden liquid interfaces in rheometrical flows, focussing mainly on model latex suspensions consisting of polystyrene particles carrying sulfate groups, which have been most extensively studied to date. The goal of this part of the review is to identify the generic features of the rheology of such systems. Secondly, we will discuss the relevance of these results to the formation and stability of PR emulsions and bijels.

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“…We neglected surfactant compressibility but could incorporate it explicitly by tracking the surfactant concentration field in a mass conservation equation. This could be further generalized by accounting for the kinetics of adsorption and desorption of species to and from the bulk, in the case of soluble surfactants [43] and nanoparticles [44][45][46]. Surface dilatational viscosities, which would generally also be -dependent, may also play a significant role in flows with a compressional contribution.…”

Section: Implications and Conclusionmentioning

confidence: 99%