A team of researchers from the University of Arkansas has successfully developed a circuit that can capture the thermal motion of graphene and convert it into an electrical current. The physicists say that an energy-harvesting circuit based on graphene could be incorporated into a chip to provide clean, limitless, low-voltage power for small devices and sensors.
The breakthrough is an offshoot of research conducted three years ago at the University of Arkansas that discovered that freestanding graphene, which is a single layer of carbon atoms, ripples, and buckles in a way that holds potential energy harvesting capability. The idea was controversial because it does refute a well-known assertation from physicist Richard Feynman about the thermal motion of atoms, known as Brownian motion, cannot do work.
However, the University researchers found at room temperature thermal motion of graphene does induce an alternating current in a circuit. The achievement was previously thought to be impossible. Researchers also discovered their design increased the amount of power delivered. Researchers say they found the on-off, switch-like behavior of the diodes amplifies the power delivered rather than reducing it as previously believed.
Scientists on the project were able to use a relatively new field of physics to prove diodes increase the circuit’s power. That emerging field is called stochastic thermodynamics. Researchers say that the graphene and the circuit share a symbiotic relationship. While the thermal environment is performing work on the load resistor, the graphene and circuit are at the same temperature, and heat doesn’t flow between the two. That is an important discovery because a temperature difference between the two would contradict the second law of thermodynamics.
Other discoveries included that the relatively slow motion of graphene induces a current in the circuit at low frequencies, which is important from a technological perspective. It’s important because electronics function more efficiently at lower frequencies. The next objective is to determine if the DC current can be stored in a capacitor for later use. Miniaturization is also planned.