Droplet Motion Induced by Diffusion of Soluble Surfactant to the External Medium: Experiment

Experimental examinations were performed for the motion of liquid droplets suspended under the condition of neutral buoyancy (Plateau technique) in the second liquid in the presence of surfactant transfer from droplets to the surrounding liquid or surfactant transfer to the droplet from the external medium. It was shown that, at a certain initial surfactant concentration, spontaneous droplet motion arises, which has the oscillation character. When the initial concentration exceeds a certain critical value, almost steady-state translational droplet motion occurs in addition to oscillation displacements. In the case of surfactant transfer from the surrounding liquid to the droplet, only oscillation displacements of a droplet with larger amplitude take place.