Self-healing dynamics of surfactant coatings on thin viscous films

Strickland, Stephen L.; Hin, Matthew; Sayanagi, M. Richard; Gaebler, Cameron; Daniels, Karen E.; Levy, Rachel

doi:10.1063/1.4872020

Cited by 14 publications

(27 citation statements)

References 36 publications

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“…A key advantage of these techniques is that they are non-invasive. Additionally, this and similar optical techniques (Vogel et al 2001;Fallest et al 2010;Strickland et al 2014;Swanson et al 2014) for measuring Γ depend upon the mean distance between the fluorophores and therefore are not affected by the dynamics of either molecular rearrangement or domain formation/relaxation. The container (black) is connected by low-friction air bushings to an electromagnetic shaker, and filled with a thin layer of water onto which a monolayer of NBD-PC surfactant is deposited.…”

Section: Introductionmentioning

confidence: 98%

Spatiotemporal measurement of surfactant distribution on gravity–capillary waves

2015

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Materials adsorbed onto the surface of a fluid -for instance, crude oil, biogenic slicks or industrial/medical surfactants -will move in response to surface waves. Owing to the difficulty of non-invasive measurement of the spatial distribution of a molecular monolayer, little is known about the dynamics that couple the surface waves and the evolving density field. Here, we report measurements of the spatiotemporal dynamics of the density field of an insoluble surfactant driven by gravity-capillary waves in a shallow cylindrical container. Standing Faraday waves and travelling waves generated by the meniscus are superimposed to create a non-trivial surfactant density field. We measure both the height field of the surface using moiré imaging, and the density field of the surfactant via the fluorescence of NBD-tagged phosphatidylcholine, a lipid. Through phase averaging stroboscopically acquired images of the density field, we determine that the surfactant accumulates on the leading edge of the travelling meniscus waves and in the troughs of the standing Faraday waves. We fit the spatiotemporal variations in the two fields using an ansatz consisting of a superposition of Bessel functions, and report measurements of the wavenumbers and energy damping factors associated with the meniscus and Faraday waves, as well as the spatial and temporal phase shifts between them. While these measurements are largely consistent for both types of waves and both fields, it is notable that the damping factors for height and surfactant in the meniscus waves do not agree. This raises the possibility that there is a contribution from longitudinal waves in addition to the gravity-capillary waves.

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Section: Introductionmentioning

confidence: 98%

Spatiotemporal measurement of surfactant distribution on gravity–capillary waves

2015

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“…For example, they are present in healthy lungs to enable breathing, and are also used in industrial 1 cm 1 cm 1 cm Figure 1. Images of fluorescently-tagged surfactant spreading from experiments [39,38] viewed from above; brighter regions have a larger concentration of surfactant. Left: inward-spreading below Γ c with laser line to show fluid profile with capillary ridges.…”

Section: Introductionmentioning

confidence: 99%

“…The solutions provide predictions of spreading behavior including a spreading timescale as well as fluid and surfactant spatial distribution over time. To test the model, experiments by physicists [16,38] have provided new measurements of the motion of both the surfactant molecules and the underlying fluid, directly testing the validity of the model. While this has led to the identification of some limitations in the model [39], the new data also suggests possible improvements.…”

Section: Introductionmentioning

confidence: 99%

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Simulating surfactant spreading: Influence of a physically motivated equation of state

Sinclair¹,

Levy²,

Daniels³

2017

Eur. J. Appl. Math

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In this paper, we present numerical simulations that demonstrate the effect of the particular choice of the equation of state (EoS) relating the surfactant concentration to the surface tension in surfactant-driven thin liquid films. Previous choices of the model EoS have been an ad-hoc decreasing function. Here, we instead propose an empirically motivated EoS; this provides a route to resolve some discrepancies and raises new issues to be pursued in future experiments. In addition, we test the influence of the choice of initial conditions and values for the non-dimensional groups. We demonstrate that the choice of EoS improves the agreement in surfactant distribution morphology between simulations and experiments, and influences the dynamics of the simulations. Because an empirically motivated EoS has regions with distinct gradients, future mathematical models may be improved by considering more than one timescale. We observe that the non-dimensional number controlling the relative importance of gravitational versus capillary forces has a larger influence on the dynamics than the other non-dimensional groups, but is nonetheless not a likely cause of discrepancy between simulations and experiments. Finally, we observe that the experimental approach using a ring to contain the surfactant could affect the surfactant and fluid dynamics if it disrupts the intended initial surfactant distribution. However, the fluid meniscus itself does not significantly affect the dynamics.

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“…47 The present Ginzburg-Landau theory, however, has some limitations. The theory is general; therefore, it can be applied for various real systems, including surfactant coated free surfaces of liquids appearing in medical sciences.…”

Section: Spinodal Decompositionmentioning

confidence: 98%

Phase field modelling of spinodal decomposition in the oil/water/asphaltene system

Tóth

Kvamme

2015

Phys. Chem. Chem. Phys.

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In this paper the quantitative applicability of van der Sman/van der Graaf type Ginzburg-Landau theories of surfactant assisted phase separation [van der Sman et al., Rheol. Acta, 2006, 46, 3] is studied for real systems displaying high surfactant concentrations at the liquid-liquid interface. The model is applied for the water/heptane/asphaltene system (a model of heavy crude oil), for which recent molecular dynamics (MD) simulations provide microscopic data needed to calibrate the theory. A list of general requirements is set up first, which is then followed by analytical calculations of the equilibrium properties of the system, such as the equilibrium liquid densities, the adsorption isotherm and the interfacial tension. Based on the results of these calculations, the model parameters are then determined numerically, yielding a reasonable reproduction of the MD density profiles. The results of time-dependent simulations addressing the dynamical behaviour of the system will also be presented. It will be shown that the competition between the diffusion and hydrodynamic time scales can lead to the formation of an emulsion. We also address the main difficulties and limitations of the theory regarding quantitative modelling of surfactant assisted liquid phase separation.

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Self-healing dynamics of surfactant coatings on thin viscous films

Cited by 14 publications

References 36 publications

Spatiotemporal measurement of surfactant distribution on gravity–capillary waves

Spatiotemporal measurement of surfactant distribution on gravity–capillary waves

Simulating surfactant spreading: Influence of a physically motivated equation of state

Phase field modelling of spinodal decomposition in the oil/water/asphaltene system

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