On the measured current in electrospinning

The origin and scaling of the current measured during steady electrospinning of polymer solutions in organic solvents are considered. For a specified electric field strength E, flow rate Q, and conductivity K, the total measured current is shown empirically to scale as I(total)similar to EQ(0.5)K(0.4), for a wide variety of polymer solutions with different electrical conductivities. It is also shown that I(total) is composed of two distinct components: one that varies linearly with E, and another that is independent of E, but varies with the conductivity K of the fluid and the flow rate Q. The experimental evidence suggests that the latter component arises due to a secondary electrospray emanating from the surface of the jet. The consequence of this secondary electrospray mechanism on the final fiber size achieved during the electrospinning process is also discussed.