Application of droplet charging: Shown is a schematic of High Precision Printing with electrostatically charged and deflected molten metal droplet streams.  Ball Grid Array on the right was "printed" in  0.14 seconds, and the balls were generated from a 100 micron diameter orifice.

Generation of charged droplets from capillary stream break-up.  A capillary stream issues from a nozzle as shown.  A periodic, axisymmetric mechanical disturbance initiates a radial disturbance on the circumference of the stream which will become unstable and grow for disturbances in the Rayleigh regime.  Droplets are charged by encompassing the stream at the point of break-up in a charge electrode.  Charged droplets are deflected when they travel through a deflection field later downstream.  Drops can be charged on a drop-to-drop basis.