ABSTRACT
Soft and biological matter is governed by three fundamental
interactions. Two of them are long-ranged, namely the van der
Waals and electrostatic forces. For large separations, these two
contributions can be treated in a continuum formulation in
terms of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [1].
In this approximation, the interacting particles or molecules and
the intervening water are treated as continuum media with
homogeneous properties (such as dielectric constant and surface
charge density). The third important and very strong repulsive
fundamental force is the hydration interaction. It results from the
removal of water molecules from hydrophilic groups and is not well
captured by continuum approximations. The hydration repulsion
was experimentally quantified in 1970s in diffraction experiments
of membrane multilayers [2, 3] and by surface force apparatus
measurements of pairs of membranes [4].
