Capillary force on colloidal particles in a freely suspended liquid thin film

The dynamic behavior of micron-sized polystyrene latex particles confined i n a free-standing liquid film is experimentally studied. When the thickness of the film is less than the particle diameter and varies depending on pos ition, the particles are accelerated toward the thicker region. Using a sim ple geometrical model and hydrodynamic theory, we calculate the capillary f orce on the particle. The drag coefficient of the particle is found to depe nd on the thickness of the film from the value of near zero to the Stokes' drag coefficient.