ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869
II. Forces Acting on Droplet Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 870
III. Experimental Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 872
A. Droplet Formation Using Electrostatic Field . . . . . . . . . . . . . . . . . . . . . . . . 872
B. Image Analysis of Droplet Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873
C. Determination of Microbead Size Distribution by Laser Light Scattering . . . 874
D. Extrusion of Animal Cell Suspensions Using Electrostatic
Droplet Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
IV. Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
A. Parameters Affecting Microbead Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
B. Effects of Electrode Geometry on Microbead Size . . . . . . . . . . . . . . . . . . . 875
C. Mechanisms of Droplet Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 877
D. Microbead Size Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 879
E. Forces Acting on Droplet Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880
F. Effects of Electrostatic Droplet Generation on Cell Viability . . . . . . . . . . . . 883
V. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884
Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885
Electrostatic atomization and electrostatically assisted atomization have been employed in a variety
of areas, including paint spraying [1], electrostatic printing [2], and cell immobilization [3].
The basic concept behind these applications involves electrostatic forces, which work to disrupt
the liquid surface to form a charged stream of fine droplets. The effect of electrostatic forces
on mechanically atomized liquid droplets was first studied in detail by Lord Rayleigh [4,5], who
investigated hydrodynamic stability of a jet of liquid with and without applied electric field.
