A SAMPLE OF THE ENERGY-HARVESTING CHIP, STILL UNDER DEVELOPMENT.
University of Arkansas physicists have made progress in their development of circuits capable of capturing graphene’s thermal motion and converting it into an electrical current.
Talking on Short Talks From The Hill last month, Paul Thibado, professor of physics and lead researcher in the discovery, gave the public an update on its research. After spending three years on this project, Thibado’s team has now successfully developed a circuit capable of harvesting energy from graphene. Paul Thibado holding a box with sample energy-harvesting chips. Image used courtesy of the University of Arkansas.
Graphene is a material composed of a single layer of carbon atoms, in which the atoms are arranged in a honeycomb lattice structure.
“You can get graphene from graphite,” Thibado said in the podcast. “So if you take graphite, which is basically coal, and you kind of peel it, it’s very flaky, you thin it down. Eventually, you’ll get down to one atomic plane of graphite and that is graphene.”
Scientists first isolated graphene in 2004, but it was only during Thibado’s research that a single layer of the material was examined as a ‘sheet of atoms’.
“What’s very interesting is we [took] this single layer of graphene and we put it over a picture frame so that it’s freestanding in the middle of the frame, and it has very unique properties because it’s this sheet of atoms that never existed before,” Thibado explained.
Among these properties, the scientists discovered was the material’s capacity for generating energy.
Three Year’s of Research
The paper describing the results of Thibado’s research was first published on 2 October 2020 in the journal Physical Review E.
Titled “Fluctuation-induced current from freestanding graphene,” the researchers described how freestanding graphene rippled and buckled in a way that showed promise for energy harvesting.
From a technical standpoint, the experiments showed that, when examined at room temperature, the thermal motion of graphene did induce an alternating current (AC) in a circuit.
The theory rapidly became controversial at the time of publication, as it contradicted physicist Richard Feynman’s assertion that the thermal motion of atoms (known as Brownian motion) cannot create energy.
Thibado’s research has been developed further, however, and his team has now created the first circuit capable of harvesting energy from an individual sheet of graphene atoms.
Moving Toward Limitless Power Applications
To develop the circuit, the University of Arkansas physicists took advantage of a property called a varying capacitance.
Thibado’s team brought a sharp metal probe close to the graphene surface, and as the graphene surface waved around, it caused the distance between the metal probe in the graphene to also vary.
The scientists then applied a bias voltage between the two, causing the charge on the graphene to increase when closer to the metal probe and decrease when further away from it. This created an alternating current that could potentially power a circuit.
During the Short Talks From The Hill last month, Thibado confirmed his team has now built a circuit by connecting the metal probe to diodes, and through them, isolated the flow of current.
Testing the energy-harvesting chips. Image used courtesy of the University of Arkansas.
According to the researcher, the first experiments were done in an ultra-high vacuum chamber measuring about 10-feet by 10-feet by 10-feet and produced around a microwatt of power.
Moving forward, the team will try to boost the power output to a higher level and hope to eventually integrate the technology into commercial products, like wristwatches.
According to Thibado, the new circuit could actually power up these devices without ever needing replacement.
“It won’t produce a lot of power, but we think that we can have it,” he explained. “It’s kind of like solar power, […] in the sense that you can harvest this energy, and maybe store it and use it later.”