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By virtue of their chemical makeup, plastics have no business conducting electricity. But in the 1970s, scientists discovered that impurities added to certain polymers made it possible for them to carry small electrical currents. Now, researchers at Lucent Technologies' Bell Labs have gone a step further. By "tricking" a common polymer, they've found a way to make plastic conduct electricity with no resistance at very low temperatures.
The Bell Labs development caps 20 years of research aimed at creating the first organic superconductor. "A new window into nature has opened up," asserts Ananth Dodabalapur, a device physicist at Bell Labs and member of the research team.
The polymer, called polythiophene, is used in making inexpensive optical devices such as display panels and "smart" pixels. But its potential as a superconductor may be far greater. The research, which was reported on Mar. 8 in the journal Nature, may be a harbinger of other superconducting polymers that could be used to create superfast "quantum" computers and other superconducting electronic devices.
USING THEIR "NOODLES." Indeed, the first electrically conductive plastics became a scientific sensation when they were created in the late '70s by Alan J. Heeger, now at the University of California at Santa Barbara, Alan G. MacDiarmid of the University of Pennsylvania, and Hideki Shirakawa of the University of Tsukuba in Japan. The trio's discovery, which won the 2000 Nobel Prize in chemistry, spawned a new generation of inexpensive, flexible plastics electronics.
Yet, subsequent efforts to create superconducting polymers met with defeat, even though physicists were convinced such mediums were theoretically possible. The tangled stands of polymers were simply too unruly to allow the free passage of electrons.
The researchers in Murray Hill, N.J., took a different tack. While Heeger and his colleagues imparted conductivity to polymers by adding metallic impurities, such as iodine, the Bell Labs group positioned a thin, purple film of polythiophene between conductive layers of aluminum oxide and gold. The polymer strands in the film line up like dried noodles in a box, the orderly crystalline structure common to most superconductors.
COOL IT. Instead of replying on impurities, charges injected into the film through its metallic layers create an electrical field -- known as a field-effect transistor -- which strips electrons away from the polymer. The result: a superconducting plastic film.
Like most superconductors, this one works in severe cold, conducting electrons without resistance at a chilling minus-455 degrees Fahrenheit. But, just as researchers working on a group of so-called high-temperature superconductors have proved, the Bell Labs group is confident that its discovery will spawn a generation of new electronic polymers that can function even in warmer environments. "With the method we used, many organic materials may potentially be made superconducting," says Bell Labs chemist Zhenan Bao.
"This stunning and beautiful work opens new vistas for coming studies," observes Olle Inganas, a expert on organic materials from Linkoping University in Sweden. Who knows? We may one day have supercomputers based on superconducting plastics.
By Alan Hall in New York Edited by Douglas Harbrecht
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Copyright 2001, Bloomberg L.P.
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