On the Measured Current in Electrospinning

The origin and scaling of the current measured during steady electrospinning of polymer solutions in organic solvents is considered. It is demonstrated that, for a specified electric field strength, E, flow rate, Q, and conductivity, K, the total measured current scales as ITOTAL ~EQ 0.5 K 0.4 , for a wide variety of polymer solutions with different electrical conductivities. The exponent of the conductivity dependence differs from the theoretically expected value by 20%. It is also shown that ITOTAL 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.