Heat-Transfer-Enhancement Measurement for Microfabricated Electrostatic Fluid Accelerators

Air cooling, because of its simplicity, remains as the most popular cooling solution for microelectronics in the consumer market. However, the trend of increasing heat generation in microelectronics and the demand for compact devices result in heat fluxes approaching the limit of conventional rotary-fan air-cooling technology. Electrostatic fluid accelerators (EFAs), also known as electrohydrodynamic ionic wind pumps, have the potential of becoming a critical element of electronic thermal-management solutions. In this technique, application of voltage to a sharp electrode ionizes air molecules, which are propelled by the electric field, transferring part of their energy to neutral air molecules, thus creating airflow and cooling effects. The airflow, so-called "corona wind," can be used discretely for hot-spot cooling or integrated into a compact thermal-exchange surface to decrease the fluid boundary layer and increase heat transfer. The EFA investigated in this paper consists of a microfabricated atomic force microscopy (AFM)-cantilever corona electrode and a flat collecting electrode that doubles as the thermal-exchange surface. The fabrication results, as well as electrical and thermal performance characterization of microfabricated EFAs, are presented in this paper. Air-gap separation distances of 2, 3, 4, and 5 mm between the corona electrode and the thermal-exchange surface were examined under constant surface-to-ambient-temperature difference of approximately 38.3 degrees C. [2008-0173] Index Terms-Corona wind, electrohydrodynamic (EHD) ionic wind pump, electrostatic fluid accelerators (EFAs).