Capillary force between wetted nanometric contacts

Contextual Informations

We present here an analytical expression and a numerical modelisation of the capillary force between highly curved surfaces covered by wetting liquid films. By extending the exact calculation of Orr et al. (J. Fluid Mech. 1975) for a pendular ring connecting two dry surfaces to the case of perfect wetting, we provide an approximate analytical expression of the capillary force valid for any wetting interface potential. The domain of validity of this expression is assessed and extended by an exact numerical resolution. We show that in the case of attractive liquid-solid van der Waals interactions, the capillary force increases monotonically with decreasing vapor pressure up to several times its saturation value. The accurate description of the capillary force is applicable to the estimation of the adhesion force between wetted nano-particles, as well as to the quantitative interpretation of pull-off forces realized by Atomic Force Microscopy.