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These brief summaries of MIT research are drawn
from several sources and are issued throughout the year. More
information on any of these stories can be obtained by
contacting
the MIT News Office. In some
cases, photos may be available for news organizations.
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Microscopic Patterns. The microscopic 3-D stripes of material that Assistant Professor Paula Hammond is depositing on thin gold wafers represent a new technique for creating patterns -- and structures -- on surfaces. The technique, which Hammond pioneered some two years ago, involves "printing" a pattern onto a surface, then taking advantage of a material's electrical properties to build up layers of that material over the pattern. Because the technique is relatively easy and inexpensive it could become an alternative to conventional patterning procedures such as the photolithography used in the manufacture of computer chips. One potential application: printing electronic circuitry on treated paper or plastic surfaces. "This would be much harder to do with photolithography and would also be more expensive," Hammond explained. In the December 18 issue of the journal Advanced Materials, Hammond and a colleague, both of the Department of Chemical Engineering, report new advances in the work. These include the automation of the process and the ability to create more complex patterns using changes in processing conditions. The work is funded by the Office of Naval Research and the MIT Center for Materials Science and Engineering.
Refueling Nuclear Plants. Today the typical US nuclear power plant spends almost two out of every 18 months shut down for refueling. As plant owners face new competition for customers, they are looking for ways to reduce costs. Refueling less often is one option. To that end MIT Energy Laboratory researchers have designed reactor cores and operating procedures that would enable power plants to run for up to about four years before refueling. Because of the extra cost of the necessary enriched fuel, adopting such a four-year cycle under today's economic conditions would be cost-effective at plants that have relatively long downtimes for refueling and forced shutdowns but not at plants that operate more efficiently. A three-year operating cycle requiring less highly enriched fuel would bring savings at many more plants. And if technology now being developed reduces the cost of enriched uranium, the economics of the extended cycles would improve significantly. The MIT team also identified strategies that plant operators can use to reduce forced shutdowns and to perform more maintenance procedures while their plants are on-line. The team is led by Professor Neil Todreas of the departments of nuclear engineering and mechanical engineering. The research was funded by the DOE's Idaho National Engineering and Environmental Laboratory University Research Consortium.
Mag-Lev for Chips. MIT technology could double the speed of etching still-finer integrated circuits onto the silicon wafers that will become computer chips. Semiconductor equipment typically uses air bearing stages that move silicon wafers through the integrated circuit production process. Now Associate Professor David Trumper of the Department of Mechanical Engineering has developed a promising technology for replacing these air bearing stages with a much faster and more precise magnetic bearing stage. Unlike the slower air bearing stages that require separate components for vertical and horizontal movement of the silicon wafer, Trumper's magnetic version handles both vertical and horizontal positioning of silicon wafers. It does so by using a magnetic field to levitate and move the wafer with nanometer resolution while requiring no mechanical contact between the stage and any part of the photolithography machine. This means that the stage produces no friction or wear on the mechanisms. "The dominant advantage, however, is that you can position the wafer in multiple degrees of freedom with only a single moving part," said Trumper. The work is sponsored by Ultratech/Integrated Solutions and by the NSF.
Measuring Matter. The MIT Bates Linear Accelerator Center in Middleton, MA, has achieved a major milestone en route to a new frontier in measuring the most basic elements of matter. Using its stored beam capability, it has created a continuous intense electron beam with a current that is 1,000 times greater than what is normally available. Electron beams are injected from the accelerator and stored in the South Hall Ring. These intense beams provide a stream of electrons that can be used with internal targets to produce physics events that can be studied more completely and accurately than with a traditional setup. Physicists from 70 research institutions worldwide conduct research at the Bates center, the physics research lab that the MIT Laboratory for Nuclear Science operates for the US Department of Energy as a national user facility. The electron beam work was supported by the DOE.
The Perfect Mirror. MIT researchers report an advance in an age-old device -- the mirror. They expect that their new approach to making a mirror will take much of the scientific community by surprise. "We've discovered an important aspect of (dielectric) mirrors that was apparently overlooked," said Yoel Fink, a graduate student at the MIT Plasma Science and Fusion Center (PSFC) and an author of a recent Science article on the work with others from MIT's materials science and engineering department, PSFC, and physics department. Among the potential uses for the researchers' device, which they've dubbed the "perfect mirror," is trapping light for longer than ever before possible. This would open up a myriad of technological and research possibilities. The researchers report that their "perfect mirror" combines the best characteristics of two existing kinds of mirrors -- metallic and dielectric. It can reflect light from all angles and polarizations, just like metallic mirrors, but also can be as low-loss as dielectric mirrors. In addition, it can be "tuned" to reflect certain wavelength ranges and transmit the rest of the spectrum. This work is funded in part by the Defense Advanced Research Agency through the U.S. Army Research Office and by the Air Force Office of Scientific Research.