Fluctuation theory of hydration forces: The dramatic effects of inhomogeneous boundary conditions

An expression for the indirect interaction of surfaces through a liquid is derived that accounts for inhomogeneity of the boundary conditions, which mimics the regular, irregular, or stochastic nature of liquid structure perturbation along the surfaces. This leads to a new picture of hydration forces, which gives an explanation of their main observable features: the dependence of the decay length on the nature of the surfaces and its variation range, and the effect of surface ordering on the magnitude of the force.