Time-dependent Dynamic Receding Contact Angles Studied during the Flow of Dilute Aqueous Surfactant Solutions through Fluorinated Microtubes

Anyfantakis, Manos; Fell, Daniela; Butt, Hans‐Jürgen; Auernhammer, Guenter K.

doi:10.1246/cl.2012.1232

Cited by 3 publications

(4 citation statements)

References 16 publications

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“…It is found that Marangoni stresses increase the rate at which the dynamic contact angle in our geometry increases with Dynamic wetting failure in surfactant solutions 305 contact-line speed, consistent with experimental observations of the behaviour of receding contact angles in surfactant solutions (Fell et al 2011Anyfantakis et al 2012). The hydrodynamic model shows that 2D steady wetting fails at a critical substrate speed corresponding to a critical capillary number Ca crit .…”

Section: Resultssupporting

confidence: 90%

“…Figure 7 at which θ M increases with Ca. This is consistent with experimental observations of receding contact angles that decrease more quickly with contact-line speed when surfactant is present (Fell et al 2011Anyfantakis et al 2012). Figure 7(b,c) shows that interface deformation primarily occurs near the dynamic contact line as the interface elongates, which confirms the formation of a thin-film wedge in the receding phase (Kistler 1993;Marchand et al 2012).…”

Section: Influence Of Surfactants On Wetting Failuresupporting

confidence: 87%

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Dynamic wetting failure in surfactant solutions

et al. 2016

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The influence of insoluble surfactants on dynamic wetting failure during displacement of Newtonian fluids in a rectangular channel is studied in this work. A hydrodynamic model for steady Stokes flows of dilute surfactant solutions is developed and evaluated using three approaches: (i) a one-dimensional (1D) lubrication-type approach, (ii) a novel hybrid of a 1D description of the receding phase and a 2D description of the advancing phase, and (iii) an asymptotic theory of Cox (J. Fluid Mech., vol. 168, 1986b, pp. 195-220). Steady-state solution families in the form of macroscopic contact angles as a function of the capillary number are determined and limit points are identified. When air is the receding fluid, Marangoni stresses are found to increase the receding-phase pressure gradients near the contact line by thinning the air film without significantly changing the capillary-pressure gradients there. As a consequence, the limit points shift to lower capillary numbers and the onset of wetting failure is promoted. The model predictions are then used to interpret decades-old experimental observations concerning the influence of surfactants on air entrainment (Burley & Kennedy, Chem. Engng Sci., vol. 31, 1976, pp. 901-911). In addition to being a computationally efficient alternative for the rectangular geometries considered here, the hybrid modelling approach developed in this paper could also be applied to more complicated geometries where a thin air layer is present near a contact line.

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Section: Resultssupporting

confidence: 90%

Section: Influence Of Surfactants On Wetting Failuresupporting

confidence: 87%

Dynamic wetting failure in surfactant solutions

et al. 2016

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“…2B). 61 A glass beaker containing milli-Q water was placed on a translation stage. The beaker was connected to a capillary (inner diameter 855 mm) through a tubing system and a metering valve.…”

Section: Microtubing Setupmentioning

confidence: 99%

“…This procedure was found to provide clean surfaces, an essential requirement for reproducible results. 61…”

Section: Microtubing Setupmentioning

confidence: 99%

Influence of surfactants in forced dynamic dewetting

et al. 2016

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In this work we show that the forced dynamic dewetting of surfactant solutions depends sensitively on the surfactant concentration. To measure this effect, a hydrophobic rotating cylinder was horizontally half immersed in aqueous surfactant solutions. Dynamic contact angles were measured optically by extrapolating the contour of the meniscus to the contact line. Anionic (sodium 1-decanesulfonate, S-1DeS), cationic (cetyl trimethylammonium bromide, CTAB) and nonionic surfactants (CE, CE and CE) with critical micelle concentrations (CMCs) spanning four orders of magnitude were used. The receding contact angle in water decreased with increasing velocity. This decrease was strongly enhanced when adding surfactant, even at surfactant concentrations of 10% of the critical micelle concentration. Plots of the receding contact angle-versus-velocity almost superimpose when being plotted at the same relative concentration (concentration/CMC). Thus the rescaled concentration is the dominating property for dynamic dewetting. The charge of the surfactants did not play a role, thus excluding electrostatic effects. The change in contact angle can be interpreted by local surface tension gradients, i.e. Marangoni stresses, close to the three-phase contact line. The decrease of dynamic contact angles with velocity follows two regimes. Despite the existence of Marangoni stresses close to the contact line, for a dewetting velocity above 1-10 mm s the hydrodynamic theory is able to describe the experimental results for all surfactant concentrations. At slower velocities an additional steep decrease of the contact angle with velocity was observed. Particle tracking velocimetry showed that the flow profiles do not differ with and without surfactant on a scales >100 μm.

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Forced dynamic dewetting of structured surfaces: Influence of surfactants

Henrich¹,

Linke²,

Sauer³

et al. 2019

Phys. Rev. Fluids

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We analyse the dewetting of printing plates for gravure printing with well-defined gravure cells. The printing plates were mounted on a rotating horizontal cylinder that is half immersed in an aqueous solution of the anionic surfactant sodium 1-decanesulfonate. The gravure plates and the presence of surfactants serve as one example of a real-world dewetting situation. When rotating the cylinder, a liquid meniscus was partially drawn out of the liquid forming a dynamic contact angle at the contact line. The dynamic contact angle is decreased on a structured surface as compared to a smooth one. This is due to contact line pinning at the borders of the gravure cells. Additionally, surfactants tend to decrease the dynamic receding contact angle. We consider the interplay between these two effects. We compare the height differences of the meniscus on the structured and unstructured area as function of dewetting speeds. The height difference increases with increasing dewetting speed. With increasing size of the gravure cells this height difference and the induced changes in the dynamic contact angle increased. By adding surfactant, the height difference and the changes in the contact angle for the same surface decreased. We further note that although the liquid dewets the printing plates some liquid is always left in the gravure cell. At high enough surfactant concentrations or high enough dewetting speed, the dynamic contact angles in the structured surface approach those in flat surfaces. We conclude that surfactant reduces the influence of surface structure on dynamic dewetting.

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Time-dependent Dynamic Receding Contact Angles Studied during the Flow of Dilute Aqueous Surfactant Solutions through Fluorinated Microtubes

Cited by 3 publications

References 16 publications

Dynamic wetting failure in surfactant solutions

Dynamic wetting failure in surfactant solutions

Influence of surfactants in forced dynamic dewetting

Forced dynamic dewetting of structured surfaces: Influence of surfactants

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