Adsorption at the solid–liquid interface as the source of contact angle dependence on the curvature of the three-phase line

Ward, C. A.; Sefiane, Khellil

doi:10.1016/j.cis.2009.10.004

Cited by 20 publications

(9 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Experimentally, it is found that the contact angle is sensitive to the pressure in the liquid at the three-phase line. , For example, for water and its vapor, held in a borosilicate glass capillary, an increase in the liquid-phase pressure of 234 Pa was observed to increase the contact angle by 79.4°. This observation indicates that the adsorption at the solid−liquid interface cannot be neglected and that the contact angle cannot be viewed as a material property, but must be viewed as a thermodynamic property that depends on pressure. , …”

Section: Introductionmentioning

confidence: 99%

Sessile-Water-Droplet Contact Angle Dependence on Adsorption at the Solid−Liquid Interface

Ghasemi¹,

Ward²

2010

J. Phys. Chem. C

View full text Add to dashboard Cite

We investigate both analytically and experimentally the possible role of line tension in determining the contact angle of sessile water droplets on a polished Cu substrate. In a closed system with constraints that make the Helmholtz function the thermodynamic potential, the curvature of the three-phase line and the height of an axisymmetric droplet on its center line could be measured. The adsorption on each of the surfaces used to construct the experimental chamber was taken into account, and the value of the total number of water moles in the system was determined from the minimum in the Helmholtz function. The number of water moles was then changed to a new value and the system allowed to come to equilibrium again. The contact angle in the second state could be both measured and predicted with the adsorption at the solid−liquid and solid−vapor interfaces fully taken into account but with line tension completely neglected. The predicted values of the contact angle compared closely with those measured, indicating line tension played no role in determining the contact angle of mm-sized water droplets on a polished Cu surface, and that the dependence of the contact angle on the curvature of the three-phase line could be predicted by including adsorption. The contact angle values ranged from 38.3 to 76.5°, indicating that the contact angle cannot be viewed as a material property of a fluid−solid combination, but must be viewed as a thermodynamic property. The surface tension of the solid−vapor interface was approximately constant and equal to the surface tension of the adsorbing fluid; thus, the Young equation could be simplified. The surface tension of the solid−liquid interface was changed by more than a factor of 3.3 in the experiments.

show abstract

Section: Introductionmentioning

confidence: 99%

Sessile-Water-Droplet Contact Angle Dependence on Adsorption at the Solid−Liquid Interface

Ghasemi¹,

Ward²

2010

J. Phys. Chem. C

View full text Add to dashboard Cite

show abstract

“…Additionally, there is an emerging theory based on the Gibbsian thermodynamics of interfaces and a novel adsorption isotherm. This theory can also be used for explanation of the observations, which have so far been interpreted by the existence of line tension. − Hence, out of purely theoretical considerations, we cannot expect to obtain the same contact angle on flat surfaces and spherical objects, although this difference is only significant when the curvature of the three-phase contact line is high. The first experimental issue, which causes problems most frequently, is the difference in microroughnesses of surfaces manufactured by different processes.…”

Section: Resultsmentioning

confidence: 98%

A Novel Centrifugal Method for Wettability Characterization of Granulates

Swenson

Horváth‐Szabó

Abdallah

et al. 2011

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

The minimum force needed for transporting glass microspheres across oil/water (O/W) interfaces was determined experimentally. From this data, the O/W contact angle was calculated with a mathematical model. First, the measured minimum centrifugal force was combined with a simplified model leading to an approximate contact angle. Then the results were refined by a numerical solution of the accurate mathematical model of particle transport through an oil/water interface. The contact angles calculated by the suggested approach were compared with the contact angles measured by goniometry on flat glass surfaces in the presence and absence of sodium dodecyl sulfate (SDS), Triton X-100, and Igepal CO-520 surfactants. The discrepancies were interpreted with the different surface chemistries/morphologies of glass microspheres and slides. The results show potential for this being a rapid screening method for chemical additives aimed at altering the wettability. This approach could be utilized in the oil and gas industry and especially to support enhanced oil recovery (EOR).

show abstract

“…In the current model of surfactant transport [106], adsorption on the water-air interface is accounted for, while recent investigations show that neglecting adsorption on the solid-air interface [109,110] and solid-water interface [111] is not always valid when the surface is hydrophobic.…”

Section: Future Directionsmentioning

confidence: 99%

“…Simultaneously, an essential change in the curvature of the contact line takes place. In the meantime, a recent investigation [111] has shown that the contact angle depends on the curvature of the three-phase line. This occurs not because of line tension but because of the adsorption at the solid-liquid interface [111].…”

Section: Future Directionsmentioning

confidence: 99%

“…In the meantime, a recent investigation [111] has shown that the contact angle depends on the curvature of the three-phase line. This occurs not because of line tension but because of the adsorption at the solid-liquid interface [111]. This regularity may play a role regarding surfactant influence on rivulet flow in narrow tubes because of surfactant adsorption on the solid-liquid interface.…”

Section: Future Directionsmentioning

confidence: 99%

See 1 more Smart Citation

Surfactant influence on rivulet droplet flow in minitubes and capillaries and its downstream evolution

Labib

Dukhin

Murawski

et al. 2011

Advances in Colloid and Interface Science

View full text Add to dashboard Cite

During our investigations of two-phase flow in long hydrophobic minitubes and capillaries, we have observed transformation of the main rivulet into different new hydrodynamic modes with the use of different kinds of surfactants. The destabilization of rivulet flow at air velocities <80 m/sec occurs primarily due to the strong branching off of sub-rivulets from the main rivulet during the downstream flow in the tube. The addition of some surfactants of not-so-high surface activity was found to increase the frequency of sub-rivulet formation and to suppress the Rayleigh and sinuous instabilities of the formed sub-rivulets. Such instabilities result in subsequent fragmentation of the sub-rivulets and in the formation of linear or sinuous arrays of sub-rivulet fragments (SRFs), which later transform into random arrays of SRFs. In the downstream flow, SRFs further transform into large sliding cornered droplets and linear droplet arrays (LDAs), a phenomenon which agrees with recent theories. At higher surface activity, suppression of the Rayleigh instability of sub-rivulets with surfactants becomes significant, which prevents sub-rivulet fragmentation, and only the rivulet and sub-rivulets can be visualized in the tube. At the highest surface activity, the bottom rivulet transforms rapidly into an annular liquid film. The surfactant influence on the behavior of the rivulets in minitubes is incomparably stronger than the classic example of the known surfactant stabilizing influence on a free jet. The evolution of a rivulet in the downstream flow inside a long minitube includes the following sequence of hydrodynamic modes/patterns: i) single rivulet; ii) rivulet and sub-rivulets; and iii) rivulet, sub-rivulets, sub-rivulet fragments, cornered droplets, linear droplet arrays, linear arrays of sub-rivulet fragments and annular film. The formation of these many different hydrodynamic patterns downstream is in drastic contrast with the known characteristics of two-phase flow, which demonstrates one mode for the entire tube length. Recent achievements in fluid mechanics regarding the stability of sliding thin films and in wetting dynamics have allowed us to interpret many of our findings. However, the most important phenomenon of the surfactant influence on sub-rivulet formation remains poorly understood. To achieve further progress in this new area, an interdisciplinary approach based on the use of methods of two-phase flow, wetting dynamics and interfacial rheology will be necessary.

show abstract

Adsorption at the solid–liquid interface as the source of contact angle dependence on the curvature of the three-phase line

Cited by 20 publications

References 29 publications

Sessile-Water-Droplet Contact Angle Dependence on Adsorption at the Solid−Liquid Interface

Sessile-Water-Droplet Contact Angle Dependence on Adsorption at the Solid−Liquid Interface

A Novel Centrifugal Method for Wettability Characterization of Granulates

Surfactant influence on rivulet droplet flow in minitubes and capillaries and its downstream evolution

Contact Info

Product

Resources

About