An original method for measuring liquid surface tension from capillary bridges between two equal-sized spherical particles

This paper presents an original approach for measuring the surface tension of a liquid from capillary bridges between monodisperse spherical particles. This method is based on an exact analytical solution of Young-Laplace equation for a capillary doublet between two spherical particles coupled with capillary force measurement. The capillary forces between two equal-sized spherical particles are measured by a micro-balance, while the geometries of the capillary bridge are recorded using a high resolution camera. From the obtained images of capillary bridges, the meridional profiles of capillary bridges are determined by a high-resolution image processing technique and correlated to the measured capillary forces. The accuracy and effectiveness of the proposed approach have been demonstrated by measuring the surface tensions of silicone oil, castor oil and impure water. The developed capillary bridge method, only requiring a small volume of liquid, can be applied to all liquids with high accuracy.