Current-voltage characteristic of electrospray processes in microfluidics.

We use a glass-based microfluidic device to study the electric current behavior of an electrospray process in the presence of a coflowing liquid. The current shows strong voltage dependence and weak flow rate dependence, in stark contrast to classical electrospray. By considering that the current is dominated by convection near the apex of the conical meniscus and driven by tangential electric stresses, we quantitatively capture the voltage and flow rate dependence of the current. Our results elucidate the influence of external field strength and open the way to achieve robust electric control of the current and of the drop size in microfluidics.