Controlled production of size-tunable Janus droplets for submicron particle synthesis using an electrospray microfluidic chip

Size-tunable Janus droplets of two miscible liquids were produced and further employed for synthesizing Janus particles with submicron size. An electrospray microfluidic chip was fabricated to form the Janus droplets from two-phase laminar flow, and to quickly regulate the droplet size by an electric field. With the aid of a direct-current electric field, we could obtain Janus droplets with various diameters in the range from 135 mm down to 3 mm. This regulation method was adaptive to the droplets made up of both aqueous solutions and organic polymers. The mechanism for the dependency of drop size on the high voltage was discussed comprehensively. Finally, submicron Janus particles were synthesized taking the minimized Janus droplets as templates.