Coupling atomization, emulsification, and polymerization steps for creating gel microspheres

Calibrated gel microspheres are used in several life-science applications, from embolization to DNA barcoding and drug delivery. Along with selecting or designing specific materials that depend on the application, various processes have been developed to produce such hydrogel particles. Here, we report a high throughput strategy that is based on the controlled fragmentation of an aqueous jet in air that results in droplets of monomer solution, their entry and collection in an oil bath, followed by polymerization of the emulsion droplets which thus turn into gel beads. Each step of the process is detailed and the operating conditions are optimized to obtain homogeneous polyacrylamide gel microspheres. The impact area of the stream of droplets at the free surface, that can be tuned with the help of an electric field, plays a major role in minimizing coalescence of droplets as well as mass transport between the dispersed phase and the continuous phase which is correlated to the sedimentation flow features of the dilute emulsion.