Truncated versus Extended Microfilms at a Vapor−Liquid Contact Line on a Heated Substrate

Rednikov, Alexei; Colinet, Pierre

doi:10.1021/la102065c

Cited by 32 publications

(29 citation statements)

References 13 publications

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“…The studies encompass different conditions: constant pressure and temperature, elevated pressure, fast compression, still gas atmosphere and turbulent reacting flows, strongly and weakly pinning substrates [1,2]. The experimental, theoretical and computer simulation studies carried out so far [1][2][3][18][19][20][21][22][23][24][25][26][27] have taken into account different physical processes: heat transfer inside droplets, mass diffusion in bi-and multicomponent fluids, droplet interactions in sprays, turbulence, radiation absorption, thermal conductivity of the solid substrate, Marangoni convection inside the droplets.…”

Section: Introductionmentioning

confidence: 99%

Evaporation of Droplets of Surfactant Solutions

Semenov

Trybała

Agogo³

et al. 2013

Langmuir

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The simultaneous spreading and evaporation of droplets of aqueous trisiloxane (superspreader) solutions onto a hydrophobic substrate has been studied both experimentally, using a video-microscopy technique, and theoretically. The experiments have been carried out over a wide range of surfactant concentration, temperature and relative humidity. Similar to pure liquids, four different stages have been observed: the initial one corresponds to spreading till the contact angle, θ, reaches the value of the static advancing contact angle, θad. Duration of this stage is rather short and the evaporation during this stage can be neglected. The evaporation is essential during next three stages.The next stage after the spreading, which is referred to below as the first stage, takes place at constant perimeter and ends when θ reaches the static receding contact angle, θr. During the next, second stage, the perimeter decreases at constant contact angle θ=θr for surfactant concentration above critical wetting concentration (CWC). The static receding contact angle decreases during the second stage for concentrations below CWC because the concentration increases due to the evaporation. During the final stage both the perimeter and the contact angle decrease till the drop disappears. Below we consider only the longest stages one and two.The developed theory predicts universal curves for the contact angle dependency on time during the first stage, and for the droplet perimeter on time during the second stage. A very good agreement between theory and experimental data has been found for the first stage of evaporation, and for the second stage for concentrations above CWC, however, some deviations were found for concentrations below CWC.3

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Section: Introductionmentioning

confidence: 99%

Evaporation of Droplets of Surfactant Solutions

Semenov

Trybała

Agogo³

et al. 2013

Langmuir

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“…Here we consider the contact line motion of a volatile liquid in contact with an atmosphere of its pure vapor, see [20][21][22][23][24] and references therein. We show that the lubrication equation is perfectly regular when evaporation/condensation processes are taken into account.…”

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confidence: 99%

Moving contact line of a volatile fluid

et al. 2013

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Interfacial flows close to a moving contact line are inherently multi-scale. The shape of the interface and the flow at meso-and macroscopic scales inherit an apparent interface slope and a regularization length, both called after Voinov, from the dynamical processes at work at the microscopic level. Here, we solve this inner problem in the case of a volatile fluid at equilibrium with its vapor. The evaporative/condensation flux is then controlled by the dependence of the saturation temperature on interface curvature -the so-called Kelvin effect. We derive the dependencies of the Voinov angle and of the Voinov length as functions of the substrate temperature. The relevance of the predictions for experimental problems is finally discussed.The dynamics of a macroscopic solid plunging in a liquid bath [1,2] or withdrawn from it [3-5] depends sensitively on its wetting properties i.e. on the intermolecular interactions at the nanoscopic scale. The motion of the contact line separating wet from dry regions is therefore an inherently multi-scale problem. Amongst the important consequences of the coupling between inner and outer scales (Fig. 1), the speed at which a contact line can recede over a flat solid surface cannot exceed a critical value, associated to a dynamical wetting transition which leads to the formation of a dewetting ridge [6,7], of a V-shaped dewetting corner [1,[8][9][10] or to the entrainment of films [2, 10, 11] (see [12,13] for detailed reviews). In many applications, such as coating, imbibition of powders, immersion lithography or boiling-free heating, these entrainment phenomena are crucial limiting factors for industrial processes. Fig. 1 shows schematically the structure of the flow close to a moving contact line. Even for an infinitesimal velocity U , there exists a range of mesoscopic scales -roughly six decades -separating the microscopic scale from the macroscopic length L, in which the diverging viscous stress is balanced by a gradient of capillary pressure. This balance can be made quantitative in the lubrication approximation, for which the angles are assumed small, and which gives a third order differential equation for the interface profile h(x):where η is the liquid dynamic viscosity and γ the surface tension; U is positive for an advancing contact line. This equation has an exact solution [14] which reduces to the asymptotic form proposed by Voinov [15] far from the contact line, but for x ≪ L:θ V is by definition the apparent contact angle in the static case (U = 0), which can be different from the Young angle θ Y due to out of equilibrium processes taking place at a microscopic scale. The Voinov length ℓ V is also a quantity defined in the mesoscopic range of scales but inherited from the inner region, where the problem is regularized. The mesoscopic solution (2) must also be matched at the macroscopic scale L to an outer solution where viscosity can usually be neglected. Fig. 1 features the case of a spreading drop or of a growing bubble but the outer matching problem has been s...

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“…However, in the evaporating thin film region, as the film thickness gradually increases and the disjoining pressure effect becomes relatively weaker, the liquid flow from the surroundings was induced by the pressure difference contributed by the disjoining [26] and capillary pressure effects. The test surfaces in this study belong to the partial wetting condition, the non-evaporating film might not exist as shown in Rednikov and Colinet's study [27]. However, the considerations of the evaporating thin film and intrinsic meniscus, in which rapid evaporation occurs, seem to be valuable to explain that the micro-sized roughness on a surface significantly influences the evaporation behaviors near the triple contact lined region.…”

Section: Resultsmentioning

confidence: 90%