  Electrospun polymer jets are imaged for the first time at an ultra-high rate
of 10,000 frames per second, investigating the process dynamics, and the
instability propagation velocity and displacement in space. The polymer
concentration, applied voltage bias and needle-collector distance are
systematically varied, and their influence on the instability propagation
velocity and on the jet angular fluctuations analyzed. This allows us to unveil
the instability formation and cycling behavior, and its exponential growth at
the onset, exhibiting radial growth rates of the order of 10^3 s^-1. Allowing
the conformation and evolution of polymeric solutions to be studied in depth,
high-speed imaging at sub-ms scale shows a significant potential for improving
the fundamental knowledge of electrified jets, leading to obtain finely
controllable bending and solution stretching in electrospinning, and
consequently better designed nanofibers morphologies and structures.
