When a sufficiently high voltage is applied to a liquid droplet, the body of the
liquid becomes charged, and electrostatic repulsion counteracts the surface tension
and the droplet is stretched; at a critical point a stream of liquid erupts from
the surface. This point of eruption is known as the Taylor cone. If the molecular
cohesion of the liquid is sufficiently high, stream breakup does not occur (if it
does, droplets are electrosprayed) and a charged liquid jet is formed.
As the jet dries in flight, the mode of current flow changes from ohmic to convective
as the charge migrates to the surface of the fiber. The jet is then elongated by
a whipping process caused by electrostatic repulsion initiated at small bends in
the fiber, until it is finally deposited on the grounded collector. The elongation
and thinning of the fiber resulting from this bending instability leads to the formation
of uniform fibers with nanometer-scale diameters.
