Sessile-Water-Droplet Contact Angle: the Effect of Adsorption

2010 ◽  
Author(s):  
H. Ghasemi ◽  
C. A. Ward
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Closed System ◽  
Water Droplet ◽  
Line Tension ◽  
Water Droplets ◽  
Three Phase ◽  
To Come ◽  
Predicted Values ◽  
Solid Liquid

A method has been recently proposed for determining the surface tension of solid-vapor interfaces. The proposed method was used in conjunction with Gibbsian thermodynamics to investigate both analytically and experimentally the possible role of line tension in determining the contact angle of sessile-water-droplets. After forming a sessile-water-droplet in a closed system, its contact angle was determined by measuring the curvature of three-phase contact line and the height of the axisymmetric droplet on its centerline. The total number of the moles in the closed system was determined from the minimum in the Helmholtz function. The total number of moles in the system was then changed to a new value and the system allowed to come to equilibrium again. The contact angle in the new equilibrium condition could be measured and predicted by taking the adsorption at the solid-liquid and solid-vapor interfaces into account but with line tension completely neglected. The predicted values of contact angle are in closed agreement with those measured indicating line tension plays no role in determining the contact angle of mm-sized water droplets on a polished Cu surface. The surface tension of the solid-vapor interface was approximately constant and equal to the surface tension of adsorbing fluid; that is, the Young equation could be simplified.

Dependence of the Contact Angle on Adsorption at the Solid-Liquid Interface

2010 ◽  
Author(s):  
C. A. Ward
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Pressure Range ◽  
Line Tension ◽  
Liquid Interface ◽  
Fluid Interfaces ◽  
Phase Line ◽  
Three Phase ◽  
Solid Liquid Interface ◽  
Solid Liquid

A method for determining the surface tension of solid-fluid interfaces has been proposed. For a given temperature and fluid-solid combination, these surface tensions are expressed in terms of material properties that can be determined by measuring the amount of vapor adsorbed on the solid surface as a function of xV, the ratio of the vapor-phase pressure to the saturation-vapor pressure. The thermodynamic concept of pressure is shown to be in conflict with that of continuum mechanics, but is supported experimentally. This approach leads to the prediction that the contact angle, θ, can only exist in a narrow pressure range and that in this pressure range, the solid-vapor surface tension is constant and equal to the surface tension of the liquid-vapor interface, γLV. The surface tension of the solid-liquid interface, γSL, may be expressed in terms of measurable properties, γLV and θ: γSL = γLV(1 − cosθ). The value of θ is predicted to depend on both the pressure in the liquid at the three-phase, line x3L, and the three-phase line curvature, Ccl. We examine these predictions using sessile water droplets on a polished Cu surface, maintained in a closed, constant volume, isothermal container. The value of θ is found to depend on the adsorption at the solid-liquid interface, nSL = nSL(x3L,Ccl). The predicted value of θ is compared with that measured, and found to be in close agreement, but no effect of line tension is found.

Investigation of Pool Boiling Critical Heat Flux Enhancement on a Modified Surface Through the Dynamic Wetting of Water Droplets

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Ho Seon Ahn ◽  
Joonwon Kim ◽  
Moo Hwan Kim
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Contact Angle ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Water Layer ◽  
Contact Angles ◽  
Water Droplets ◽  
Dynamic Wetting ◽  
Modified Surface

Dynamic wetting behaviors of water droplet on the modified surface were investigated experimentally. Dynamic contact angles were measured as a characterization method to explain the extraordinary pool boiling critical heat flux (CHF) enhancement on the zirconium surface by anodic oxidation modification. The sample surface is rectangular zirconium alloy plates (20 × 25 × 0.7 mm), and 12 μl of deionized water droplets were fallen from 40 mm of height over the surface. Dynamic wetting movement of water on the surface showed different characteristics depending on static contact angle (49.3 deg–0 deg) and surface temperature (120 °C–280 °C). Compared with bare surface, wettable and spreading surface had no-receding contact angle jump and seemed stable evaporating meniscus of liquid droplet in dynamic wetting condition on hot surface. This phenomenon could be explained by the interaction between the evaporation recoil and the surface tension forces. The surface tension force increased by micro/nanostructure of the modified zirconium surface suppresses the vapor recoil force by evaporation which makes the water layer unstable on the heated surface. Thus, such increased surface force could sustain the water layer stable in pool boiling CHF condition so that the extraordinary CHF enhancement could be possible.

Temperature-Dependent Wettability of Water on a Nickel Surface at Pressurized Condition: A Molecular Dynamics Study

2019 ◽  
Author(s):  
Dong-Lei Zeng ◽  
Biao Feng ◽  
Jia-Wen Song ◽  
Li-Wu Fan
Keyword(s):  
Contact Angle ◽  
Hydrogen Bonds ◽  
Average Energy ◽  
Contact Angles ◽  
Nickel Surface ◽  
Free Energies ◽  
Water Droplets ◽  
Temperature Dependent ◽  
Interfacial Free Energies ◽  
Solid Liquid

Abstract Temperature-dependent wettability of water droplets on a metal surface in a pressurized environment is of great theoretical and practical significance. In this paper, molecular dynamic simulation is used to study this problem by relating the temperature-dependent apparent contact angles to the changes in solid-liquid and solid-vapor interfacial free energies and hydrogen bonds in the nano-sized water droplets with increasing the temperature. The temperature range of interest is set from 298 K to 538 K in a 20 K interval under a constant pressure of 7 MPa. The results show that the contact angle in general decreases with raising the temperature and decreasing trend can be divided into two sections with different slopes. The contact angle drops slowly when the temperature is below 458 K as a critical point. Beyond this point, the contact angle shows a much steeper decrease. The difference between solid-vapor and solid-liquid interfacial free energies is found to decrease slightly with temperature. Combining with that the surface tension drops with increasing the temperature, a decreasing trend of the contact angle is expected according to the Young’s equation. As the temperature increases, the number and average energy of the hydrogen bonds both decrease, and the hydrogen bonds tend to aggregate at the bottom of the nano-droplets.

Molecular Simulation of the Contact Angle of Water Droplet on a Platinum Surface

2005 ◽  
Author(s):  
Bo Shi ◽  
Shashank Sinha ◽  
Vijay K. Dhir
Keyword(s):  
Contact Angle ◽  
Molecular Simulation ◽  
Simulation Study ◽  
Water Droplet ◽  
Solid Wall ◽  
Contact Angles ◽  
Water Droplets ◽  
Platinum Surface

This paper presents a molecular simulation study of the contact angles of water droplets on a platinum surface for a range of temperatures. SPC/E and Z-P model are used for the water-water and water-platinum potentials, respectively. The results show that the contact angle decreases with the increase of system temperatures and increases when the potential decreases. When the temperature is high enough, the contact angles drop to zero degrees. The results were compared with the argon-virtual solid wall and water-Aluminum results, a similar trend was found.

scholarly journals Water droplet friction and rolling dynamics on superhydrophobic surfaces

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Matilda Backholm ◽  
Daniel Molpeceres ◽  
Maja Vuckovac ◽  
Heikki Nurmi ◽  
Matti J. Hokkanen ◽  
...  
Keyword(s):  
Contact Angle ◽  
Friction Force ◽  
Water Droplet ◽  
Superhydrophobic Surfaces ◽  
Silicon Surfaces ◽  
Force Sensors ◽  
Water Droplets ◽  
Indirect Contact ◽  
Gold Standard Method ◽  
Superhydrophobic Coatings

Abstract Superhydrophobicity is a remarkable surface property found in nature and mimicked in many engineering applications, including anti-wetting, anti-fogging, and anti-fouling coatings. As synthetic superhydrophobic coatings approach the extreme non-wetting limit, quantification of their slipperiness becomes increasingly challenging: although contact angle goniometry remains widely used as the gold standard method, it has proven insufficient. Here, micropipette force sensors are used to directly measure the friction force of water droplets moving on super-slippery superhydrophobic surfaces that cannot be quantified with contact angle goniometry. Superhydrophobic etched silicon surfaces with tunable slipperiness are investigated as model samples. Micropipette force sensors render up to three orders of magnitude better force sensitivity than using the indirect contact angle goniometry approach. We directly measure a friction force as low as 7 ± 4 nN for a millimetric water droplet moving on the most slippery surface. Finally, we combine micropipette force sensors with particle image velocimetry and reveal purely rolling water droplets on superhydrophobic surfaces.

scholarly journals Amphiphobic Nanostructured Coatings for Industrial Applications

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 787 ◽  
Author(s):  
Federico Veronesi ◽  
Giulio Boveri ◽  
Mariarosa Raimondo
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Photoelectron Spectroscopy ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Friction Reduction ◽  
Hybrid Coatings ◽  
Wetting Behavior ◽  
Wide Range ◽  
Solid Liquid

The search for surfaces with non-wetting behavior towards water and low-surface tension liquids affects a wide range of industries. Surface wetting is regulated by morphological and chemical features interacting with liquid phases under different ambient conditions. Most of the approaches to the fabrication of liquid-repellent surfaces are inspired by living organisms and require the fabrication of hierarchically organized structures, coupled with low surface energy chemical composition. This paper deals with the design of amphiphobic metals (AM) and alloys by deposition of nano-oxides suspensions in alcoholic or aqueous media, coupled with perfluorinated compounds and optional infused lubricant liquids resulting in, respectively, solid–liquid–air and solid–liquid–liquid working interfaces. Nanostructured organic/inorganic hybrid coatings with contact angles against water above 170°, contact angle with n-hexadecane (surface tension γ = 27 mN/m at 20 °C) in the 140–150° range and contact angle hysteresis lower than 5° have been produced. A full characterization of surface chemistry has been undertaken by X-ray photoelectron spectroscopy (XPS) analyses, while field-emission scanning electron microscope (FE-SEM) observations allowed the estimation of coatings thicknesses (300–400 nm) and their morphological features. The durability of fabricated amphiphobic surfaces was also assessed with a wide range of tests that showed their remarkable resistance to chemically aggressive environments, mechanical stresses and ultraviolet (UV) radiation. Moreover, this work analyzes the behavior of amphiphobic surfaces in terms of anti-soiling, snow-repellent and friction-reduction properties—all originated from their non-wetting behavior. The achieved results make AM materials viable solutions to be applied in different sectors answering several and pressing technical needs.

Generalized Young Equation for Cylindrical Droplets within a Homogeneous and Smooth Regular Triangular Prism Filled with Gas in Three Convex Corners

2016 ◽  
Vol 6 (1) ◽  
pp. 14
Author(s):  
Long Zhou ◽  
Guang-Hua Sun ◽  
Ai-Jun Hu ◽  
Xiao-Song Wang
Keyword(s):  
Line Tension ◽  
Phase System ◽  
Triangular Prism ◽  
Gas Phases ◽  
Three Phase ◽  
Dividing Surface ◽  
Solid Liquid ◽  
Wetting Behaviors ◽  
Young Equation ◽  
Dividing Line

<p class="1Body">Based on the approaches of Gibbs’s dividing surface and Rusanov’s dividing line, the wetting behaviors of cylindrical droplets that at equilibrium are sitting inside a homogeneous and smooth regular triangular prism filled with gas in three convex corners are studied. For the three-phase system, which is composed of solid, liquid and gas phases, a generalized Young equation for cylindrical drops in a homogeneous and smooth regular triangular prism imbued with gas within three apex corners has been successfully derived including the effects of the line tension.</p>

Évaluation du pouvoir adhérant du Lactobacillus helveticus au polystyrène expansé

1992 ◽  
Vol 38 (7) ◽  
pp. 672-675 ◽  
Author(s):  
Nathalie Dion ◽  
Jacques Goulet ◽  
Patrick Boyaval
Keyword(s):  
Surface Tension ◽  
Liquid System ◽  
Contact Angles ◽  
Expanded Polystyrene ◽  
Lactobacillus Helveticus ◽  
Bacterial Cells ◽  
Three Phase ◽  
Thermodynamic Conditions ◽  
Polystyrene Support ◽  
Solid Liquid

We measured the surface tension of a three-phase (solid–solid–liquid) system consisting of the bacterium Lactobacillus helveticus in a culture medium containing an expanded polystyrene support, to determine the adherence capacity of the bacteria to the support. The surface tension of the expanded polystyrene and the L. helveticus cells was evaluated by measuring contact angles. The Wilhelmy's microslide method was used to measure the surface tension of the liquid phase. The values obtained showed that the adherence capacity of the L. helveticus cells to expanded polystyrene pellets was not facilitated under the experimental thermodynamic conditions. The pellet surfaces and adhering bacterial cells were examined with a scanning electron microscope. The pellets exhibited several grooves in which microbial cells preferentially accumulated. Key words: Lactobacillus helveticus, adherence, surface tension, expanded polystyrene. [Translated by the journal]

THE MODIFIED YOUNG'S EQUATION FOR THE CONTACT ANGLE OF A SMALL SESSILE DROP FROM AN INTERFACE DISPLACEMENT MODEL

1999 ◽  
Vol 13 (27) ◽  
pp. 3255-3259 ◽  
Author(s):  
HARVEY DOBBS
Keyword(s):  
Contact Angle ◽  
Sessile Drop ◽  
Unit Length ◽  
Excess Free Energy ◽  
Line Tension ◽  
Rigid Substrate ◽  
Three Phase ◽  
Interface Displacement ◽  
Displacement Model ◽  
Young's Equation

We derive the modified Young's equation for the contact angle of a fluid droplet on a rigid substrate using an interface displacement model and identify the line tension with the excess free energy per unit length calculated previously for a straight three-phase contact line.

scholarly journals Collembola cuticles and the three-phase line tension

2017 ◽  
Vol 8 ◽  
pp. 1714-1722 ◽  
Author(s):  
Håkon Gundersen ◽  
Hans Petter Leinaas ◽  
Christian Thaulow
Keyword(s):  
Contact Angle ◽  
Surface Structure ◽  
Large Change ◽  
Line Tension ◽  
Contact Angles ◽  
Surface Structures ◽  
Exposed Surface ◽  
Phase Line ◽  
Three Phase ◽  
Cuticular Surface

The cuticles of most springtails (Collembola) are superhydrophobic, but the mechanism has not been described in detail. Previous studies have suggested that overhanging surface structures play an important role, but such structures are not a universal trait among springtails with superhydrophobic cuticles. A novel wetting experiment with a fluorescent dye revealed the extent of wetting on exposed surface structures. Using simple wetting models to describe the composite wetting of the cuticular surface structures results in underestimating the contact angles of water. Including the three-phase line tension allows for a prediction of contact angles in the observed range. The discrepancy between the contact angle predicted by simple models and those observed is especially large in the springtail Cryptopygus clavatus which changes, seasonally, from superhydrophobic to wetting without a large change in surface structure; C. clavatus does not have overhanging surface structures. This large change in observed contact angles can be explained with a modest change of the three-phase line tension.

Sign in / Sign up

Export Citation Format

Share Document