The wetting problem of fluids on solid surfaces: Dynamics of lines and contact angle hysteresis

Superhydrophobicity is directly related to the wettability of the surfaces. Cassie-Baxter state relating to geometrical configuration of solid surfaces is vital to achieving the Superhydrophobicity and to achieve Cassie-Baxter state the following two criteria need to be met: 1) Contact line forces overcome body forces of unsupported droplet weight and 2) The microstructures are tall enough to prevent the liquid that bridges microstructures from touching the base of the microstructures [1]. In this paper we discuss different measurements used to characterise/determine the superhydrophobic surfaces.Keywords: Wettability, contact angle, contact angle hysteresis, contact time, surface roughness, drag reduction measurements, morphology, surface friction, Reynolds number

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Tensiometric studies on wetting. I. Some effects of surface roughness (theoretical)

Canadian Journal of Chemistry ◽

10.1139/v81-290 ◽

1981 ◽

Vol 59 (13) ◽

pp. 1954-1961 ◽

Cited By ~ 23

Author(s):

Erdal Bayramli ◽

Theodore G. M. van de Ven ◽

Stanley G. Mason

Keyword(s):

Surface Roughness ◽

Contact Angle ◽

Contact Angle Hysteresis ◽

Solid Surfaces ◽

Surface Slopes ◽

Receding Contact ◽

Receding Contact Angle ◽

Wetting Hysteresis ◽

Non Equilibrium ◽

Roughness Size

The effect of roughness on the wettability of an axisymmetric cylinder is investigated theoretically by making use of equilibrium meniscus shapes on solid surfaces analogously to previous studies for drops on horizontal surfaces. Employing circumferential sinusoidal and saw-toothed grooved structure, and using mechanistic arguments, one can explain wetting hysteresis, the formation of composite surfaces, and the presence of non-equilibrium jumps during contact line motion.On unidirectionally random surfaces the maximum surface slopes mainly determine the value of the advancing, and the minimum slopes of the receding contact angle. These effects of surface slopes diminish with decreasing roughness size. Diminishing roughness size also gives rise to numerous small non-equilibrium jumps imposed upon larger jumps during wetting. The contact angle hysteresis is found to show a nearly linear relationship with the spread in the distribution of solid surface slopes.

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Contact angle hysteresis on rough solid surfaces

Heat Transfer-Asian Research ◽

10.1002/htj.20013 ◽

2004 ◽

Vol 33 (4) ◽

pp. 201-210 ◽

Cited By ~ 16

Author(s):

X.D. Wang ◽

X.F. Peng ◽

J.F. Lu ◽

T. Liu ◽

B.X. Wang

Keyword(s):

Contact Angle ◽

Contact Angle Hysteresis ◽

Solid Surfaces

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The wetting problem of fluids on solid surfaces. Part 2: the contact angle hysteresis

Continuum Mechanics and Thermodynamics ◽

10.1007/s00161-003-0137-1 ◽

2003 ◽

Vol 15 (6) ◽

pp. 597-611 ◽

Cited By ~ 7

Author(s):

Henri Gouin

Keyword(s):

Contact Angle ◽

Contact Angle Hysteresis ◽

Solid Surfaces

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Contact Angle Hysteresis – Advantages and Disadvantages: A Critical Review

Reviews of Adhesion and Adhesives ◽

10.7569/raa.2020.097302 ◽

2020 ◽

Vol 8 (1) ◽

pp. 47-67

Author(s):

Andrew Terhemen Tyowua ◽

Stephen Gbaoron Yiase

Keyword(s):

Contact Angle ◽

Contact Angle Hysteresis ◽

Theoretical Models ◽

Contact Angles ◽

Solid Surfaces ◽

Advantages And Disadvantages ◽

Volatile Liquid ◽

Receding Contact ◽

Rain Drops ◽

The Difference

The existence of contact angle hysteresis – the difference between the values of the advancing and receding contact angles – is evident in nature (e.g. sticking of rain drops to car windscreens and window panes) and many industrial processes (e.g. surface coating, spraying, and dyeing of fabrics). This phenomenon is often viewed as a nuisance, but it is advantageous in many processes including dip and spin coating, spraying, and painting. With the early theoretical framework of Thomas Young, Robert Wenzel, and A. B. D. Cassie and S. Baxter, describing the wettability of solid surfaces and by extension contact angle, contact angle hysteresis has been deeply investigated. We review here the various ways of measuring contact angle and, consequently, contact angle hysteresis as well as related theoretical models. The successes and limitations of these models are highlighted. We conclude with the advantages and disadvantages of contact angle hysteresis whose presence in many processes is often considered as a nuisance, especially when "coffee stain" forms from the evaporation of a volatile liquid drop containing nonvolatile components.

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Motion of Newtonian drops deposited on liquid-impregnated surfaces induced by vertical vibrations

Journal of Fluid Mechanics ◽

10.1017/jfm.2019.600 ◽

2019 ◽

Vol 876 ◽

Cited By ~ 8

Author(s):

Paolo Sartori ◽

Elia Guglielmin ◽

Davide Ferraro ◽

Daniele Filippi ◽

Annamaria Zaltron ◽

...

Keyword(s):

Phase Diagram ◽

Contact Angle ◽

Fast Rate ◽

Contact Angle Hysteresis ◽

Solid Surfaces ◽

Distilled Water ◽

Liquid Drops ◽

Dynamical Phase ◽

Viscous Drops ◽

Vertical Vibrations

We have studied the motion of drops on inclined liquid-impregnated surfaces (LISs) subject to vertical vibrations. The liquid drops comprise distilled water and different aqueous solutions of glycerol of increasing viscosity. The use of weak pinning LISs strongly affects the dynamical phase diagram. First of all, there is no trace of the dominant static region at low oscillating amplitudes reported for oscillating solid surfaces characterized by contact angle hysteresis. On the contrary, at sufficiently low oscillating amplitudes, the drops always move downwards with a velocity that depends only on the drop viscosity. Further increasing the oscillating amplitude may drive the drop upwards against gravity, as reported for dry surfaces. The use of more viscous drops widens this climbing region. Arguably, the main novelty of this work concerns the observation of two distinct descending regimes where the downhill speed differs by a factor of five or more. Fast-rate videos show that the evolution of the drop profile is diverse in the two regimes, likely because the vertical oscillations reduce the effect of the oil meniscus surrounding the drop at high accelerations.

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