Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Germs add ripples to make 'groovy' graphene

12.07.2016

New nanomaterial conducts differently at right angles

Graphene, a two-dimensional wonder-material composed of a single layer of carbon atoms linked in a hexagonal chicken-wire pattern, has attracted intense interest for its phenomenal ability to conduct electricity. Now University of Illinois at Chicago researchers have used rod-shaped bacteria - precisely aligned in an electric field, then vacuum-shrunk under a graphene sheet - to introduce nanoscale ripples in the material, causing it to conduct electrons differently in perpendicular directions.


This is an atomic force microscopy image of a graphene sheet draped over a Bacillus bacterium (left). The bacterium is about 1 micron or 1/25,000 of an inch wide. After applying vacuum and heat treatment, regular wrinkles form in the graphene (right, at twice the magnification).

Credit: UNIVERSITY OF ILLINOIS AT CHICAGO/Vikas Berry

The resulting material, sort of a graphene nano-corduroy, can be applied to a silicon chip and may add to graphene's almost limitless potential in electronics and nanotechnology. The finding is reported in the journal ACS Nano.

"The current across the graphene wrinkles is less than the current along them," says Vikas Berry, associate professor and interim head of chemical engineering at UIC, who led the research.

The key to formation of these wrinkles, he said, is graphene's extreme flexibility at the nanometer scale, which allows formation of carbon nanotubes.

"The wrinkle opens a 'V' in the electron cloud around each carbon atom," Berry said, creating a dipole moment, which can open an electronic band gap that flat graphene does not have.

Other researchers have created wrinkles in graphene by stretching the sheet and letting it snap back. But such wrinkles are not confined in microscale and cannot be directed towards a location on a micro-device, Berry said.

He and his colleagues came up with a unique way to introduce circumscribed, guided, and regular graphene ripples using bacillus bacteria, by using the graphene itself as a check-valve to alter the volume of the cells.

The researchers placed the bacteria in an electric field, causing them to line up like strings of hot dogs in repeating rows. Then they applied a sheet of graphene over the top.

"Under vacuum, the graphene lifts, and lets water out," Berry said. But under pressure, graphene sits back down on the substrate and prevents water from re-entering the bacteria, he said.

"It's a nanoscopic valve that actuates unidirectional fluid flow in a microorganism," Berry said. "Futuristically, this valve operation could be applied to microfluidic devices where we want flow in one direction but not the other."

After the bacteria have been vacuum-shrunk, the graphene reconforms, but with wrinkles. After heat treatment, the resulting permanent ripples atop the bacteria are all aligned longitudinally, with a height of 7 to 10 nanometers, and a wavelength of about 32 nm.

The wrinkles were observed by field emission scanning electron microscopy, which must be done under high vacuum, and by atomic force microscopy at atmospheric pressure.

"The [ripple] wavelength is proportional to the thickness of the material, and graphene is the thinnest material in the world," Berry said. "We envision that with graphene one could make the smallest wavelength wrinkles in the world - about 2 nanometers."

The next goal, he said, will be to create processes to further refine the ripples and vary their amplitude, wavelength and longitudinal length.

To measure the effect of the ripples' orientation on the carrier transport, graduate student Shikai Deng, the lead author of the paper, fabricated a plus-shaped device with bacteria aligned parallel to one pair of electrodes and perpendicular to another pair. He found the rippled graphene's conduction barrier was greater in the transverse direction than in the longitudinal direction.

The introduction of oriented ripples to graphene represents an entirely new material, Berry said.

"Along with carbon nanotubes, graphene and fullerene, this is a new carbon allotrope - a half carbon nanotube linked to graphene," he said. "The structure is different, and the fundamental electronic properties are new."

###

The research was funded by the National Science Foundation and UIC.

In addition to Berry and Deng, co-authors on the ACS Nano study are Sanjay Behura of the UIC department of chemical engineering; Enlai Gao, Yanlei Wang and Zhiping Xu of Tsinghua University in Beijing; Soumyo Sen and Petr Král of the UIC department of chemistry; and T. S. Sreeprasad of Clemson University.

Media Contact

Bill Burton
burton@uic.edu
312-996-2269

 @uicnews

http://www.uic.edu 

Bill Burton | EurekAlert!

Further reports about: bacteria carbon nanotubes electric field graphene nanometers wavelength wrinkles

More articles from Materials Sciences:

nachricht The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>