On the use of hypodermic needles in electrospray

Abstract

We present an experimental analysis of electrospray where the standard feeding capillary was re- placed with a hypodermic needle. Both the current intensity and the jet diameter were measured for a variety of leaky-dielectric liquids. The results obtained with a feeding capillary and a hypodermic needle of similar dimen- sions were compared. An increase of the liquid conductivity was measured by assuming that the electric current obeys the same scaling law in both configurations. That increase was likely due to the electrochemical reaction taking place in the needle tip.