Contact angle dependence of solid probe–liquid drop forces in AFM measurements

Abstract

In order to obtain the force between an atomic force microscopy probe particle and a liquid drop, we require the small change δR in the mean radius of curvature of the drop, which is proportional to the small change in liquid pressure inside the drop. These quantities depend on the total force F, the contact angle θ made by the unperturbed drop at the substrate, and the nature of the boundary conditions imposed at the contact line. Chan et al. [J. Colloid Interface Sci. 236 (2001) 141] developed a semi-analytical method for calculating the force in the fixed contact line case, while more recently Attard and Miklavcic [Langmuir 17 (2001) 8217] considered the fixed contact angle condition. Due..