How closely can a solid approach an air-water surface without becoming wet?
Through a study of the van der Waals interaction between a solid and an air-water interface, we investigate the practical and fundamental problem of the limiting height at which an object can approach a free surface. A numerical study of the interface shape reveals dependencies governed by two disparate length scales associated with the relative strengths of the van der Waals and bouyancy forces, to surface tension. A study of the limits of solvability of the governing equation has led to the principal result: a closed-form expression for the absolute limiting height to which an object can be lowered to the air-water interface. The formula depends explicitly and only on the Hamaker constant of the van der Waals force and the geometry of the solid.
Cortat
F P A
FP
Department of Science and Technology, Linköping University, Campus Norrköping, S-601 74 Norrköping, Sweden.
Miklavcic
S J
SJ