Experimental Study of the Splayed Electrode Design on Performance of a Microfabricated EHD Thin Film Evaporator: Application in High Heat Flux Cooling

This paper presents details of the geometry, fabrication, and pumping performance of an electrohydrodynamically (EHD) driven thin film evaporator with a new electrode design. The operation principle of the device is based on the action of the EHD force on molecules of a dielectric liquid in a highly convergent electric field starting at the end of a pair of electrodes, where the electric field changes from zero to a finite value in between the electrodes. This force drives the liquid into the spacing between the electrodes. Because the electrodes are microfabricated very thinly on a surface, the liquid can be held within microns in thickness over the surface. The new design is a modification of the original device with parallel electrodes. The electrodes in the new design were fabricated in a splayed configuration with the narrow side dipped in the liquid. A relatively large (32 mm × 32 mm) area was covered with the splayed electrodes. The electrodes were fabricated through a lift-off process. It was found that a higher voltage can be sustained between the electrodes prior to breakdown threshold and a pumping head of about three times more than that of the parallel electrode configuration was achieved in the new design.