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The earliest study on the relationship between contact angle and surface tensions for sessile droplets on flat surfaces was reported by Thomas Young in 1805. [2] A century later Gibbs [3] proposed a modification to Young's equation to account for the volumetric dependence of the contact angle.
In physics, the Young–Laplace equation (/ l ə ˈ p l ɑː s /) is an algebraic equation that describes the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of surface tension or wall tension, although use of the latter is only applicable if assuming that the wall is very thin.
Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. [4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to ...
Here the key difference to notice is that there is no surface tension between the solid and the vapor for the second surface tension component. This is because of the assumption that the surface of air that is exposed is under the droplet and is the only other substrate in the system. Subsequently, the equation is then expressed as (1 – f ...
One should bear in mind that the surface tension in the numerator can be much smaller in the presence of surfactants or contaminants. The same calculation can be done for small oil droplets in water, where even in the presence of surfactants and a fairly low interfacial tension γ {\displaystyle \gamma } = 5–10 mN/m, the pressure inside 100 ...
Young's equation describes the contact angle of a liquid drop on a plane solid surface as a function of the surface free energy, the interfacial free energy and the surface tension of the liquid. Young's equation was developed further some 60 years later by Dupré to account for thermodynamic effects, and this is known as the Young–Dupré ...
The Young–Dupré equation (Thomas Young 1805, Lewis Dupré 1855) dictates that neither γ SG nor γ SL can be larger than the sum of the other two surface energies. The consequence of this restriction is the prediction of complete wetting when γ SG > γ SL + γ LG and zero wetting when γ SL > γ SG + γ LG .
Surface tension – Tendency of a liquid surface to shrink to reduce surface area; Tribology – Science and engineering of interacting surfaces in relative motion; Unilateral contact – Mechanical constraint which prevents penetration between two bodies; Wetting – Ability of a liquid to maintain contact with a solid surface