THE EFFECT OF JOULE HEATING ON THE HEIGHT RISE OF AQUEOUS SOLUTIONS BETWEEN ELECTRODES

Strong electric fields have numerous vital applications in micro-fluidic pumping. For example, strong electric fields can apply a body force to a dielectric liquid, a canonical example of which is liquid rising between two parallel electrodes. However, for solutions with a finite conductivity, a temperature change of the system is an inevitable consequence of Joule heating. In the case of aqueous solutions with even very low conductivity, the temperature rise across 10 microns channel due to Joule heating can easily result in boiling of the aqueous solution with an electric field strength of 1 MV/m. Further, the temperature change will couple through the permittivity of the liquid to impact the height rise which negatively affects the pumping performance. This paper develops a generic heat model for an aqueous solution under the application of an AC electric field and explores how the application of alternating electric fields will impact the height rise of aqueous solutions between two parallel electrodes. It was found that for low concentration/low conductivity solutions, a height penalty of several millimeters is likely to be seen while for high conductivity solutions the liquid is likely to boil before a significant change in height rise is experienced.