Scientists have developed a circuit that derives power from freestanding sheets of graphene. Photo by University of Arkansas
Oct. 2 (UPI) -- Scientists have developed a new graphene-based circuit capable of producing clean, limitless power. Researchers suggest the energy-harvesting circuit -- described Friday in the journal Physical Review E -- could be used to power small, low-voltage devices and sensors.
The circuit's ability confirms the theory -- developed by the study's authors, a group of physicists at the University of Arkansas -- that micron-sized sheets of freestanding graphene naturally move in a way conducive to energy harvesting.
The breakthrough also contradicts the assertion by Richard Feynman that so-called Brownian motion, the thermal motion of atoms, cannot perform work. But lab tests showed the Brownian motion of atoms in freestanding sheets of graphene can generate an alternating current.
Famously, physicist Léon Brillouin proved that a single diode, a one-way electrical gate, added to a circuit was not sufficient to turn Brownian motion into energy. The team of physicists at the University of Arkansas developed their novel circuit using two diodes.
Positioned in opposition, the two diodes allow current to flow in both directions, turning the alternating current into a pulsing direct current. The pulsing direct current, taking separate paths back-and-forth through the circuit, performs work on a load resistor.
"We also found that the on-off, switch-like behavior of the diodes actually amplifies the power delivered, rather than reducing it, as previously thought," lead researcher Paul Thibado, professor of physics at Arkansas, said in a news release. "The rate of change in resistance provided by the diodes adds an extra factor to the power."
According to the researchers, the thermal movement in the graphene and circuit is inherent in the material, not the result of temperature differences between the two components -- no heat flows between the graphene and circuit.
"This means that the second law of thermodynamics is not violated, nor is there any need to argue that 'Maxwell's Demon' is separating hot and cold electrons," Thibado said.
Tests also showed that the graphene's Brownian motion yielded low-frequency currents -- good news for the technology's application, as most electronics are more efficient at lower frequencies.
"People may think that current flowing in a resistor causes it to heat up, but the Brownian current does not. In fact, if no current was flowing, the resistor would cool down," Thibado said. "What we did was reroute the current in the circuit and transform it into something useful."
