Stephen W. Montgomery

Miniaturization of Electrostatic Fluid Accelerators

Existing thermal-management methods for electronics do not meet the technology needs and remain a major bottleneck in the evolution of computing, sensing, and information technology. The decreasing size of microelectronic components and the resulting increasing thermal output density require novel cooling solutions. 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 order to take full advantage of EFA-based thermal management, it is essential to miniaturize EFA technology. This paper demonstrates the successful operation of a mesoscale microfabricated silicon EFA. Several cantilever structures fabricated in bulk silicon with radii of tip curvature ranging from 0.5 to 25 mum are used as the corona electrode. The device was fabricated using the combination of deep reactive ion etching (DRIE) and reactive ion etch (RIE) microfabrication processes. Forced convection cooling is demonstrated using infrared imaging, showing a 25degC surface temperature reduction over an actively heated substrate. The fabrication and test results of a mesoscale microfabricated EFA are presented in this paper.

Fouling of high density heat sinks - theoretical origins and numerical analysis

Heat sinks and other components must operate in a thermal envelope that calls for continuous operation over long periods of time. Increasing thermal loads are resulting in widespread acceptance of densely packed heat sinks with closely spaced fins. However, the environment surrounding heat sinks and other electronic components is not ideal. Particulate contaminants are present in the ambient supply air in nearly every office, home or other zone of operation. These contaminants are ingested by the cooling systems and subsequently introduced to these heat sinks. Repeated exposure to particulate contamination can lead to the phenomena known as thermal fouling, where contaminant particles adhere themselves to the surface of the heat sink, acting as an insulating layer and thus reducing thermal performance. This analysis seeks to quantify the reduction in performance experienced by a dense pin fin array exposed to a contaminated operating environment. Results of numerical simulations illustrate the potentially drastic effects on fin effectiveness and overall airflow rate in a uniformly coated, fouled array. The fundamental theories of particulate adhesion are discussed and an experimental course of action for verification of the reduction in performance owing to fouling is suggested.