Monodisperse particle production:: A method to prevent drop coalescence using electrostatic forces

The controlled break-up of a disturbed jet is a well-known technique for monodisperse particle production. For non-Newtonian, especially highly concentrated suspensions, an irregular break-up mechanism results in droplet coalescence and monodispersity is lost. A method to prevent droplet coalescence by charging the droplets with a high voltage electrode (400-1400 V) is presented (pat. pend.). The droplet charging process and the droplet trajectories due to electrostatic repulsion forces have been both investigated theoretically and experimentally with good agreement. The system has been developed for the immobilization of cells in polymer beads of 160-800 mu m in diameter under sterile conditions. Error particles due to droplet coalescence could be suppressed completely. (C) 1999 Elsevier Science B.V. All rights reserved.