Laplace-Young formula

The surface tension determines capillary effects, wetting phenomena and a shape of liquid drops, in particular, the spherical shape of small radius drops when the gravity is not essential. The corresponding excess pressure in a drop of radius p is Ap = 2a/p (Laplace-Young formula). Small drops of the nematic phase are, strictly speaking, not spherical due to anisotropy of the surface tension but practically they may be considered spherical. The surface tension of both a liquid crystal and a solid substrate determines orientation of the liquid crystal director on the substrate. 

Young-Laplace formula 7 cos 9 = gs — %s- This can be seen by using the relation pts = d /dh to evaluate the integral explicitly, and observing that 7(/io) equals to the gas-solid surface tension 7, while 7(00) = 7 + 7gs is the sum of the gas-liquid and liquid-solid surface tensions. 

The energy of the vapor-solid interface 7 is expressed in the same way, with pt replaced by pv These expressions can be used in the Young-Laplace formula that derives the contact angle 6 from the balance condition for a three-phase contact line ... 

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