Formation of microgel beads by electric dispersion of polymer solutions

Microcapsules are produced by a dropwise addition of one solution into a solidifying bath. By applying an electrostatic potential between the droplet formation device and the collecting solution, it is possible to obtain smaller droplets which are desirable for many applications. Droplet formation may be divided into two phases. Under a certain critical value of the electric potential Uc, liquid exits the nozzle as droplets. The surface tension decreases with increasing electric potential resulting in a reduction of droplet diameter to approximately 200 μm. At higher electric potential, liquid exits the nozzle as a jet which subsequently breaks into droplets, which are smaller than 200 μm. In this case, droplet size is mainly determined by the jet instability (theory of Rayleigh).