Quantification of the meniscus effect in adhesion force measurements

Adhesion forces between a gold sphere and flat gold substrate are studied using atomic force microscopy in different environments. The pull-off force measured in a vacuum is found to be a small fraction of that in ambient air or nitrogen atmosphere. Calculations of capillary condensation forces, including the effects of elastic deformation of the contacting bodies and of adsorption layers, reveal that the meniscus force is the dominant source of the observed difference in pull-off forces. The experimental data show that nitrogen purge does not eliminate the meniscus contribution to the pull-off force.