Nonflat Equilibrium Liquid Shapes on Flat Surfaces

2 NONFLAT EQUILIBRIUM LIQUID SHAPES ON FLAT SURFACES 

In thin fiat liquid films (oil and aqueous thin films, thin films of aqueous electrolyte and surfactant solutions, and both free films and films on solid substrates), the disjoining pressure acts alone and determines their thickness. However, if the film surface is curved or uneven, both the disjoining and the capillary pressures act together. In the case of partial wetting, their simultaneous action is expected to yield nonfiat equilibrium shapes. For instance, due to the S-shaped disjoining pressure isotherm, microdrops, microdepressions, and equilibrium periodic films could exist on fiat solid substrates. We shall establish a criteria for both existence and stability of such nonfiat equilibrium liquid shapes. On the other hand, we 

The main idea of this section is to show that the simultaneous action of the capillary pressure and S-shaped disjoining pressure isotherm results in the formation of nonflat equilibrium liquid shapes even on smooth homogeneous solid substrates. Again, we should emphasize that the shape is specific for water and aqueous solutions and hence is vitally important for life. However, we are still completely unaware of the way in which it is important. 

Consideration of the equilibrium nonflat liquid layers allows the suggestion of a new scenario of rupture of thick metastable P-films and their transition to absolutely stable a-films (see the following section). 

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