Controlled Group Motion of Anisotropic Janus Droplets Prepared by One-Step Vortex Mixing

In living systems, highly efficient biological micromotors are fascinating and crucial to the maintenance and regulation of normal functions. Inspired by this, solid colloid motors with controlled movements were recently developed for diverse applications. However, to meet the requirements of more elaborate functionalities, the development of droplet-based micromotors, which feature with appealing advantages such as deformability, encapsulation capability, and biocompatibility, is demanding. Herein, responsive Janus droplets with intrinsic magnetic anisotropy were fabricated, taking advantage of the traditional one-step vortex mixing that guarantees large-scale production. Furthermore, the size range of the droplets can be easily extended continuously from hundreds of micrometers down to tens of nanometers. What is more appealing, directed in situ group motions that include alignment, rotation, and transfer of the Janus droplets prepared were successfully realized and precisely controlled by using an external magnetic field. These collective motions induced excellent performances in pollutant adsorption and separation, switchable conductivities, and the size grading. Such scalable, simple, and controllable strategy can expand the application of Janus emulsions to complicated fields of microreactors, microsensors, and environmental regulation.