Aug. 9, 2007 -- Two hundred years ago, as fans of Master and Commander know, the power of a warship was reflected in the size of its guns and the weight of it broadside. Today, one of the most important criteria is the sophistication of its electronics. Modern warships are packed with powerful radar, sonar, communications, navigation, and weapons systems that depend on sophisticated integrated circuits and advanced processors. The U.S. Navy now plans to rely completely on electronic systems in its next generation of destroyers, substituting electricity to power the tasks currently assigned to gas turbines, pressurized air, steam, and other means of propulsion.
There is, however, one hitch that could keep these all-electric vessels in dry dock. Electronic devices produce heat — and the inexorable progress of Moore’s law means that as components are more densely packed with ever smaller transistors, the amount of heat they produce grows exponentially as does the difficulty of dissipating it. The resulting high temperatures degrade device performance and shorten device life.
The Office of Naval Research has awarded Professor Pam Norris and her team of multiuniversity, multidisciplinary investigators a coveted Multidisciplinary University Research Initiative (MURI) award to solve this problem. Norris and her colleagues will receive up to $7.5 million over five years to fund their research. There were scores of preliminary proposals for each of the 36 MURI awards funded in 2007 — and Norris’s grant was one of three won by the School of Engineering and Applied Science at U.Va.
“We’re breaking new ground,” Norris says. “Our task is to explore new ways to cool entire ship-wide systems that are unprecedented in their size and complexity, yet composed of millions of individual elements whose features can be measured in microns. A further requirement is that these solutions, on the macro and micro scale, have to be integrated.” These new approaches will require fundamental advances in the thermal regulation of electronic systems.
Norris’s team of experts comes from Arizona State, the University of California at Berkeley, the University of Illinois, and Rensselaer Polytechnic Institute. Their expertise covers such fields as interfacial heat transfer (between solid surfaces), multiphase heat transfer (the boiling and condensing associated with refrigeration system), surface chemistry, microfabrication, and control systems. “The distinguishing characteristic of the MURI is that it is designed to bring together collaborators from a variety of fields,” Norris says. To date there has been little cross-fertilization among people with these skills, but that’s exactly what’s required to solve this problem.”
Norris’ MURI, entitled System-Level Approach for Multi-phase, Nanotechnology-Enhanced Cooling of High-Power Microelectronic Systems, is organized to attack the problem from three perspectives. Norris is the principal investigator as well as the leader of the first thrust, which is focusing on the interface between chips and the substrates on which they rest. These elements are composed of different materials with different thermal properties, a circumstance that produces resistance at the points where they come in contact, generating additional heat. The goal of the first thrust is to understand the origins of this resistance and to develop new interface materials to decrease it.
The second thrust will approach the problem of thermal resistance at the circuit level. Currently, most electronic circuits are air cooled. The MURI researchers will investigate the potential of integrating a liquid-cooling system composed of a network of microchannels. They will examine the flow and cooling levels of different liquids through micro-devices. This will help them develop modifications to material surface chemistry and structure, understand ideal microchannel configurations, and enhance the phase change heat transfer to improve efficiency.
As part of the third thrust, Norris and her colleagues will explore the control and design issues involved in optimizing thermal management for all the electronics aboard ship. “Up until now, there has been relatively little work done on applying modern control theory to heat transfer, especially for a system of this size,” Norris says.
Norris is optimistic about the team’s prospects, not only because of the reputations of her fellow investigators, but because of their ability to work closely and productively together. “Three of us were students in Chang-Lin Tien’s lab at Berkeley and we learned a lot about collaboration there,” she says. Tien served as chancellor at the University of California at Berkeley for almost a decade and was a pioneer in the field of microscale heat transfer. “We all have taken from Tien the culture of supportiveness that made his lab so extraordinary,” Norris says. “We are looking to build on his insights through our work on the MURI grant.”
Written by Charlie Feigenoff