To the general disbelief of experts in the field, a University of Buffalo scientist claimed Thursday to have discovered a material that conducts electricity with “negative resistance” at room temperature.
Such a miraculous material would be a quantum leap better than long-sought room temperature superconductors, which would only carry electricity friction-free, without energy loss. A negative resistance material would actually create electricity.
However, most scientists interviewed said they were highly skeptical of the report by Buffalo’s Deborah Chung. “Negative resistance means you are generating power,” said mechanical engineer Cetin Cetinkaya of Clarkson University in Potsdam, N.Y., who saw Chung demonstrate her experiment at the International Conference on Composites Engineering in Las Vegas, where she presented her findings.
“Physically, that’s not possible,” Cetinkaya said. “I would love to see that. It would mean when you’re working on your laptop, you would be creating energy.”
Cetinkaya and others do believe that Chung may have discovered an “intriguing” new way to change the direction of electric currents, with possibly useful applications. “This is very similar to the transistor concept,” Cetinkaya said.
‘It’s Possible They’ve Made a Little Battery’
Although a news release from the University of Buffalo announced that Chung had discovered a material that “superconducts at room temperature,” she herself stressed that the material was not superconducting--a unique zero-resistance state accompanied by peculiar magnetic effects.
“We are not claiming that we’ve discovered a new superconductor,” she said in an interview. However, she did say that the negative resistance effect could be used in an electric circuit to “negate positive resistance . . . and the totality would be zero.”
Other scientists said this was not possible. “Negative resistance violates the second law of thermodynamics,” said UCLA physicist Steve Kivelson. “It’s impossible.”
Caltech material scientist Brendt Fultz agreed. “It’s hard to believe. I’m sure it’s violating one of the two laws of thermodynamics,” he said. “It’s possible they’ve [inadvertently] made a little battery.” If so, the “negative resistance” effect would be temporary, and not useful in applications, he said. It would certainly not produce zero resistance for any length of time, he added.
Since no peer-reviewed scientific paper was available--only a four-page abstract--scientists could not adequately evaluate Chung’s claims. She is a widely published expert in the field of “smart” materials, which can act as sensitive sensors or electrical components by their very structure, without any added parts like computer chips or electrical leads.
Chung discovered the effect accidentally while testing a material made of bundles of carbon fibers at high pressure. She placed two layers of fibers crosswise to each other, and pressed them together with epoxy. She then attached electrodes to the top and bottom layer, and passed a small current through. At the point where fibers from the two layers met, she says, she measured negative resistance.
Like water running over a waterfall, electric currents normally flow only toward one end of the circuit--that is, “downhill.” (Instead of a difference in height, electric currents are propelled by a difference in voltage.) As water flows down the hill, it encounters resistance from obstacles like rocks. Currents similarly run into resistance from atoms as they flow through wires.
Of course, if the bottom of a waterfall were raised higher than the top, one would expect the water to reverse its flow. The same is true of a reversal of voltage; current flows in the opposite direction.
However, Chung’s measurements show the current switching direction even when the voltage remained unchanged, as if water suddenly started flowing up a waterfall, she said. Although Chung said she was not claiming to have created energy, she did not have a good explanation for the effect.
Current flowing in the wrong direction for any length of time, and without any additional input of energy, probably violates fundamental laws of nature, scientists said.
Chung theorized that some new mechanism was at work that “overshadowed” these laws.
Peers Intrigued by Startling Report
Several scientists at the meeting said they were intrigued by Chung’s findings. “The electrons are flowing in the other direction,” said materials scientist Jason Lo of the Canada Center for Minerals and Energy Technology. “That’s not usual, so something has to be happening at the juncture [of the fibers]. The cause and effect is not known.” If the effect is real, said Lo, then it could be “quite valuable. . . . Whether it is an infinite source of energy, that is not known yet.”
Scientists studying zero-resistance materials have certainly been surprised before. Before 1986, virtually no physicists believed that superconductivity could exist much above absolute zero--minus 450 degrees Fahrenheit. The discovery that year of so-called “high temperature superconductors"--which carry currents friction-free at temperatures hundreds of degrees higher, though still quite cold--set off a frenzy of research into new materials.
Since then, the discovery of room temperature superconductivity has been announced many times, but never confirmed.
Discovery of negative resistance, however, would make the search for room temperature superconductors moot, Kivelson said. Zero resistance at room temperature would be “trivial” next to negative resistance, he said. “Who cares about zero when you can do better than zero?”
Several experts in materials research who read Chung’s abstract declined to comment.