Lateral capillary forces measured by torsion microbalance.

The forces of capillary interaction between two thin cylindrical rods or two spherical particles placed at a liquid/air interface and immersed partially in the liquid are measured by a sensitive torsion microbalance. Cylindrical rods of radii 50, 165, and 365 mm are used. The spheres have radius 600 mm; they are modeling the lateral interaction between colloidal particles trapped in a thin liquid film. The measured forces range in magnitude between 1024 and 1029 N depending on the particle size and the interparticle distance. The experimental data agree well with the theory of capillary immersion forces.