A team of University of Arkansas physicists has successfully developed a circuit capable of capturing graphene’s thermal motion and converting it into an electrical current.
“An energy-harvesting circuit based on graphene could be incorporated into a chip to provide clean, limitless, low-voltage power for small devices or sensors,” said Paul Thibado, professor of physics and lead researcher in the discovery.
The findings, published in the journal Physical Review E, are proof of a theory the physicists developed at the U of A three years ago that freestanding graphene — a single layer of carbon atoms — ripples and buckles in a way that holds promise for energy harvesting.
The idea of harvesting energy from graphene is controversial because it refutes physicist Richard Feynman’s well-known assertion that the thermal motion of atoms, known as Brownian motion, cannot do work. Thibado’s team found that at room temperature the thermal motion of graphene does in fact induce an alternating current (AC) in a circuit, an achievement thought to be impossible.
In the 1950s, physicist Léon Brillouin published a landmark paper refuting the idea that adding a single diode, a one-way electrical gate, to a circuit is the solution to harvesting energy from Brownian motion. Knowing this, Thibado’s group built their circuit with two diodes for converting AC into a direct current (DC). With the diodes in opposition allowing the current to flow both ways, they provide separate paths through the circuit, producing a pulsing DC current that performs work on a load resistor.
Additionally, they discovered that their design increased the amount of power delivered. “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,” said Thibado. “The rate of change in resistance provided by the diodes adds an extra factor to the power.”
The team used a relatively new field of physics to prove the diodes increased the circuit’s power. “In proving this power enhancement, we drew from the emergent field of stochastic thermodynamics and extended the nearly century-old, celebrated theory of Nyquist,” said coauthor Pradeep Kumar, associate professor of physics and coauthor.
According to Kumar, the graphene and circuit share a symbiotic relationship. Though the thermal environment is performing work on the load resistor, the graphene and circuit are at the same temperature and heat does not flow between the two.
That’s an important distinction, said Thibado, because a temperature difference between the graphene and circuit, in a circuit producing power, would contradict the second law of thermodynamics. “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.
The team also discovered that the relatively slow motion of graphene induces current in the circuit at low frequencies, which is important from a technological perspective because electronics function more efficiently 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 explained. “What we did was reroute the current in the circuit and transform it into something useful.”
The team’s next objective is to determine if the DC current can be stored in a capacitor for later use, a goal that requires miniaturizing the circuit and patterning it on a silicon wafer, or chip. If millions of these tiny circuits could be built on a 1-millimeter by 1-millimeter chip, they could serve as a low-power battery replacement.
The University of Arkansas holds several patents pending in the U.S. and international markets on the technology and has licensed it for commercial applications through the university’s Technology Ventures division. Researchers Surendra Singh, University Professor of physics; ; Hugh Churchill, associate professor of physics; and Jeff Dix, assistant professor of engineering, contributed to the work, which was funded by the Chancellor’s Commercialization Fund supported by the Walton Family Charitable Support Foundation.
This red light means 'go' for medical discoveries – Phys.org
With a little tweak of the color palette, University of Virginia School of Medicine researchers have made it easier for scientists to understand biological processes, track happenings inside individual cells, unravel the mysteries of disease and develop new treatments.
UVA’s Hui-wang Ai, Ph.D., and Shen Zhang, Ph.D., have developed a simple and effective improvement to fluorescent ‘biosensors’ widely used in scientific and medical research. The biosensors detect specific targets inside cells and sets them aglow, so that scientists can monitor and quantify biological events they otherwise could not.
Most fluorescent protein biosensors give a green or yellow glow, but Ai and Zhang have discovered a way to shift the green to red. This comes with big benefits, including making it easier for scientists to monitor multiple targets at a time and to peer more deeply into tissues.
“This innovative method can convert not only existing biosensors, but also any green biosensors developed in the future,” Ai said. “Multicolor and/or multiplexed imaging with fluorescent biosensors cells will thus become widely accessible.”
Lighting the Way
While there are existing red biosensors, they are typically outperformed by their green counterparts. So scientists have been eager to find ways to shift the green color into red, retaining the benefits of the green sensors while adding new ones, such as reducing the visual confusion that can be caused by the natural fluorescence of tissues and cells.
Ai and Zhang found a solution partly by a stroke of luck—or “serendipity,” as they describe it in a new scientific paper. In the course of their regular lab work, they found that adding a particular amino acid, 3-aminotyrosine, to the green biosensor made it turn red. This is simple to do and quite effective, they report. The red version preserved the brightness, dynamic range and responsiveness of the green sensor, while offering the additional benefits of a red one.
“We modified a panel of green biosensors for metal ions, neurotransmitters and cell metabolites,” Zhang said. “Spontaneous and efficient green-to-red conversion was observed for all tested biosensors, and little optimization on individual sensors was needed.”
The researchers tested their improved biosensor on cells that make insulin in the pancreas. They were able to monitor the effect of high levels of glucose on the cells, gaining new insights and giving the researchers new directions to explore.
They hope their quick-and-easy sensor upgrade will offer similar benefits to many other scientists and lines of scientific research.
“It will have lots of applications,” Ai said, “such as acceleration of our understanding of how pancreas controls insulin secretion or how neuronal activity patterns in the brain correlate with complex behavior.”
Shen Zhang et al, A general strategy to red-shift green fluorescent protein-based biosensors, Nature Chemical Biology (2020). DOI: 10.1038/s41589-020-0641-7
University of Virginia
This red light means ‘go’ for medical discoveries (2020, October 20)
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Asteroid On Track To Buzz Earth The Day Before The Presidential Election – HuffPost
An asteroid hurtling close to Earth is on course to buzz the globe the day before the U.S. presidential election.
According to calculations by the National Aeronautics and Space Administration, the refrigerator-sized space boulder has only a minuscule chance (.41%) of entering Earth’s atmosphere and is likely to be a relatively comfortable — but very close in space terms — 4,776 kilometers (about 3,000 miles) from the center of the Earth when it makes its flyby.
“So if the world ends in 2020, it won’t be the fault of the universe,” astrophysicist Neil deGrasse Tyson said on Instagram Monday:
Asteroid 2018VP1 is hurtling through space at some 25,000 miles per hour. It was discovered two years ago when it was some 280,000 miles away.
If the asteroid entered the Earth’s atmosphere, it would quickly disintegrate because of its small size, per NASA Asteroid Watch. And if that happens, its fiery fall would provide a great light show potentially visible from Earth.
Starlink's BITS licence approved, still needs spectrum to operate in Canada – Cartt.ca
Service launch not coming soon… GATINEAU — The CRTC has approved an application by Elon Musk’s Space Exploration Technologies (SpaceX) for a Basic International Telecommunications Services (BITS) licence to provide telecom services via SpaceX’s Starlink low-Earth-orbit (LEO) satellite constellation. The Commission said in a letter dated October 15 and addressed to SpaceX’s chief financial officer, Bret Johnsen, it received 2,585 interventions regarding the licence application, and after considering the submitted comments, it is approving the application and issuing a BITS licence to SpaceX. Getting a BITS licence is not exactly the highest hurdle there is to clear (most are approved…
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This red light means 'go' for medical discoveries – Phys.org
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