Effect of soluble surfactants on the kinetics of thinning of liquid bridges during drops formation and on size of satellite droplets

The results of an experimental study on thinning and breakage of liquid bridges during detachment of a drop from the tip of a capillary are presented for a series of surfactant solutions (including cationic, anionic and non-ionic surfactants) over a broad range of molecular masses, values of critical micelle concentration and concentrations. The used experimental protocol revealed that the kinetics of the bridge thinning depends much more on the dynamics of adsorption at the surface of the drop before it destabilises, rather than on the depletion of surfactant from the surface of the thinning bridge due to its stretching as the instability develops. The kinetics of the bridge thinning and the size of satellite droplets formed after the bridge breakage depend considerably on the surfactant concentration and the value of critical micelle concentration. It is proposed that the dynamic surface tension on the time scale of the drop formation can be used as an effective surface tension for the description of the bridge kinetics over the broad range of experimental conditions used.