**On The Measured Current In Electrospinning**

By P.K.
Bhattacharjee1,T. M.
Schneider2, M. P.
Brenner, G. H. McKinley, G. C. Rutledge

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 *I*_{TOTAL}
~*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 *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.