Superfast Active Droplets as Micromotors for Locomotion of Passive Droplets and Intensification of Mixing

Micromotors are fascinating objects that are able to move autonomously and perform various complex tasks related to drug delivery, chemical processes, and environmental remediation. Among the types of micromotors, droplet-based micromotors are characterized by a wide range of functional properties related to the capability of encapsulation and deformation and the possibility of using them as microreactors. Relevant problems of micromotor utilization in the chemical processes include intensification of mixing and locomotion of passive objects. In this paper, the technique for preparation of superfast active droplets, which can be used as micromotors for effective locomotion of passive droplets in the oil-in-water emulsion, is demonstrated. The possibility of passive droplet locomotion in the emulsion is determined by a relation between the diameters of active and passive droplets. If the diameter of active droplets is larger than the diameter of passive droplets, the agglomerates form spontaneously in the emulsion and move in a straight line. In the case of the opposite relation between diameters, the agglomerates consisting of active and passive droplets rotate intensively. This makes it impossible to move the passive droplets to a given distance. Such micromotors can achieve unprecedentedly high velocities of motion and can be used to intensify mixing on the microscales.