TIP SURFACE CAPILLARY INTERACTIONS

The capillary adhesion force between the tip of a particle and a flat surface is calculated by numerical solution of the equations which are developed as well as by an approximate analytical equation which is suggested. Results are presented for spherical, paraboloidal, and conical tips. They are compared with the classical approximate equation for the capillary adhesion force between a sphere and a flat surface, which predicts that the force is independent of the position of the liquid-fluid interface. The present analysis shows that the situations for which the classical equation can be used are rather limited. For quantitative analysis of experimental data, such as the measurement of thin film profiles using atomic force microscopy, accurate knowledge of the geometry of the tip of the particle and numerical solution of the equations are usually required.