Immiscible surfactant droplets on thin liquid films: Spreading dynamics, subphase expulsion and oscillatory instabilities

Sinz, Dkn David; Hanyak, M Myroslava; Darhuber, Anton A.

doi:10.1016/j.jcis.2011.08.055

Cited by 16 publications

(13 citation statements)

References 53 publications

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“…Hence, after each surface contamination by the CTAB-containing DCM film, these three mechanisms altogether allow the system to gradually meet conditions making a new pulsation able to start. Although qualitative, this description provides the overall explanation for the observed pulsating behaviour which, compared to the scarce examples present in the literature 19 , 39 , 40 , appears to be unique, given the amplitude, regularity, and symmetry of the repeated pulsations.…”

Section: Resultsmentioning

confidence: 71%

Marangoni-driven flower-like patterning of an evaporating drop spreading on a liquid substrate

et al. 2018

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Drop motility at liquid surfaces is attracting growing interest because of its potential applications in microfluidics and artificial cell design. Here we report the unique highly ordered pattern that sets in when a millimeter-size drop of dichloromethane spreads on an aqueous substrate under the influence of surface tension, both phases containing a surfactant. Evaporation induces a Marangoni flow that forces the development of a marked rim at the periphery of the spreading film. At some point this rim breaks up, giving rise to a ring of droplets, which modifies the aqueous phase properties in such a way that the film recoils. The process repeats itself, yielding regular large-amplitude pulsations. Wrinkles form at the film surface due to an evaporative instability. During the dewetting stage, they emit equally spaced radial strings of droplets which, combined with those previously expelled from the rim, make the top view of the system resemble a flower.

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Section: Resultsmentioning

confidence: 71%

Marangoni-driven flower-like patterning of an evaporating drop spreading on a liquid substrate

et al. 2018

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“…31 In all cases, the spreading was observed to be faster on films of larger thickness. [36][37][38] In this paper, we experimentally determine the scaling law for the Marangoni spreading due to a continuous flux of miscible liquid (isopropyl alcohol (IPA)-water mixture) on a water film. It is found that for all conditions, r ∼ t 1/2 , while accurate control over the liquid composition and deposition allows us to quantify how the prefactor of this law depends on the experimental parameters.…”

Section: Introductionmentioning

confidence: 99%

Marangoni spreading due to a localized alcohol supply on a thin water film

2015

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Bringing two miscible fluids into contact naturally generates strong gradients in surface tension. Here, we investigate such a Marangoni-driven flow by continuously supplying isopropyl alcohol (IPA) on a film of water, using micron-sized droplets of IPA-water mixtures. These droplets create a localized depression in surface tension that leads to the opening of a circular, thin region in the water film. At the edge of the thin region, there is a growing rim that collects the water of the film, reminiscent of Marangoni spreading due to locally deposited surfactants. In contrast to the surfactant case, the driving by IPA-water drops gives rise to a dynamics of the thin zone that is independent of the initial layer thickness. The radius grows as r ∼ t 1/2 , which can be explained from a balance between Marangoni and viscous stresses. We derive a scaling law that accurately predicts the influence of the IPA flux as well as the thickness of the thin film at the interior of the spreading front. C 2015 AIP Publishing LLC. [http://dx.

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“…The same scaling with h 0 had been observed for the case of insoluble surfactants. 5,18,19 Fig. 6(a) shows the spreading exponent a for the case of solution deposition, as a function of the surfactant concentration in the deposited droplet.…”

Section: Resultsmentioning

confidence: 99%

“…3,7,8,[15][16][17]19,20,25,26,33,34,36,45,46,48,51,53 It was observed that film thinning occurred in the vicinity of the deposited surfactant as well as film thickening and the formation of a rim near the surfactant leading edge. The rim position x rim (t) follows a power law behavior x rim z t a , where a is the so-called spreading exponent.…”

Section: Soluble Surfactant I Introductionmentioning

confidence: 99%

“…The spreading of insoluble surfactants at the air-liquid interface of thin liquid films has been extensively studied. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] It was observed that film thinning occurred in the vicinity of the deposited surfactant as well as film thickening and the formation of a rim near the surfactant leading edge. The rim position x rim (t) follows a power law behavior x rim $ t a , where a is the so-called spreading exponent.…”

Section: Introductionmentioning

confidence: 99%

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Soluble surfactant spreading on spatially confined thin liquid films

2012

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We studied the spreading of soluble surfactants on spatially confined thin liquid films by means of comprehensive experiments and numerical simulations. We determined the time evolution of the liquid film thickness both from interference microscopy measurements and finite element calculations. A characteristic rim develops ahead of the spreading surfactant front. Within certain time intervals, the rim position can be well represented by a power-law relation x rim $ t a . The corresponding spreading exponent a depends on the method of surfactant deposition and the numerical values deduced from experiments and simulations quantitatively agree. Depth-resolved simulations that account for domain deformability using the Arbitrary Lagrangian-Eulerian method show that shear-induced concentration non-uniformities across the rim film thickness tend to reduce the rim height. Fingering instabilities that are frequently observed in experiments were qualitatively reproduced in the simulations.

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Immiscible surfactant droplets on thin liquid films: Spreading dynamics, subphase expulsion and oscillatory instabilities

Cited by 16 publications

References 53 publications

Marangoni-driven flower-like patterning of an evaporating drop spreading on a liquid substrate

Marangoni-driven flower-like patterning of an evaporating drop spreading on a liquid substrate

Marangoni spreading due to a localized alcohol supply on a thin water film

Soluble surfactant spreading on spatially confined thin liquid films

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