UTA researcher to develop nanomaterials to treat antibiotic-resistant infections


A researcher at The University of Texas at Arlington has been awarded a prestigious National Science Foundation Faculty Early Career Development, or CAREER, grant to develop new synthetic antimicrobial nanomaterials to treat antibiotic-resistant infections in hospitals and military facilities.

Bacterial resistance to conventional antibiotics is a major threat to public health, and antibiotic-resistant infections are associated with close to $20 billion in direct medical costs each year, according to the Alliance for the Prudent Use of Antibiotics. Overuse of existing antibiotics has worsened the problem, resulting in an urgent need to develop new types of antimicrobial agents to combat the ever-increasing emergence of multidrug-resistant bacterial infections.

“We are developing synthetic antimicrobial materials that only target toxic bacteria and are biocompatible with healthy mammalian cells,” said He Dong, the UTA associate professor of chemistry and biochemistry and joint associate professor of bioengineering who received the grant. “These new molecules show great promise to treat infections not only on external surfaces or the skin like traditional antimicrobial peptides do, but also internally through oral or intravenous treatments, as they do not attack healthy human cells.”

The earlier discovery of new antimicrobials based on small proteins or peptides had shown tremendous promise, but their widespread use and translation into clinical application was hampered by their toxicity toward a range of healthy human cells.

“Dong and her colleagues have taken this idea one step further by developing synthetic peptides that self-assemble into nanostructured fibers that can punch holes in the bacterial membrane, killing the pathogen,” said Frederick MacDonnell, the chair of UTA’s Department of Chemistry and Biochemistry. “These synthetic self-assembling antimicrobial nanofibers, or SAANs, are the nucleus of a new therapeutic platform that could have a transformative impact on the multi-billion-dollar research industry around conventional antibiotics.”

This new grant builds on work done over the last three years by Dong around nanomaterials that can mimic nature and self-assemble into larger groups of molecules that have antimicrobial effects without hurting other healthy cells. The $456,985 grant is aimed at furthering the understanding of how SAANs are so effective against bacteria without harming healthy mammalian cells.

“The multidisciplinary nature of this research, involving chemistry, microbiology, engineering, nanoscience and pharmaceutical sciences will also provide opportunities to train students at all levels,” Dong added. “We plan to collaborate closely with Dr. Liping Tang in UTA’s bioengineering department to develop intelligent SAANs technologies that will permit highly effective and accurate disease-specific diagnoses and therapies in the future.”

Dong will soon be transferring to UTA’s new 229,000-square-foot Science & Engineering Innovation & Research or SEIR building, a world-class research and teaching facility focused on health science research that is scheduled to open in July 2018. This facility will advance research at UTA by utilizing the modern concept of research lab neighborhoods to drive cross-disciplinary collaboration like Dong’s research. Each of the 12 research lab neighborhoods will accommodate multiple teams in a wide range of fields, including biology, bioengineering, computational research, nursing and kinesiology.

Dong came to UTA from Clarkson University, where she was an assistant professor of chemistry and biomolecular science. She earned her bachelor and master degrees in chemistry from Tsinghua University in Beijing, China, and her doctorate in chemistry from Rice University in Houston. She did her first post-doctoral fellowship in the Department of Surgery at Emory University in Atlanta, and her second in materials science and engineering at the University of California, Berkeley.

“Dr. Dong’s research exemplifies UTA’s interdisciplinary approach to research, especially in the area of health and the human condition, one of four themes of the University’s strategic plan,” added MacDonnell. “This early CAREER grant recognizes the potential of her research focus to make a real impact on the field.”

Lithium-ion battery inventor introduces new technology for fast-charging, noncombustible batteries – Is it “Goodenough?”

goodenough-1-lithiumionbaJohn Goodenough, professor in the Cockrell School of Engineering at The University of Texas at Austin and co-inventor of the lithium-ion battery, in the battery materials lab he oversees. Credit: Cockrell School of Engineering

A team of engineers led by 94-year-old John Goodenough, professor in the Cockrell School of Engineering at The University of Texas at Austin and co-inventor of the lithium-ion battery, has developed the first all-solid-state battery cells that could lead to safer, faster-charging, longer-lasting rechargeable batteries for handheld mobile devices, electric cars and stationary energy storage.

Goodenough’s latest breakthrough, completed with Cockrell School senior research fellow Maria Helena Braga, is a low-cost all-solid-state that is noncombustible and has a long cycle life (battery life) with a high volumetric and fast rates of charge and discharge. The engineers describe their new technology in a recent paper published in the journal Energy & Environmental Science.

“Cost, safety, energy density, rates of charge and discharge and cycle life are critical for battery-driven cars to be more widely adopted. We believe our discovery solves many of the problems that are inherent in today’s batteries,” Goodenough said.

li_battery_principleThe Basics of the Lithium Ion Battery Principle

Today’s lithium-ion batteries use liquid electrolytes to transport the lithium ions between the anode (the negative side of the battery) and the cathode (the positive side of the battery). If a battery cell is charged too quickly, it can cause dendrites or “metal whiskers” to form and cross through the liquid electrolytes, causing a short circuit that can lead to explosions and fires. Instead of liquid electrolytes, the researchers rely on glass electrolytes that enable the use of an alkali-metal anode without the formation of dendrites.

The researchers demonstrated that their new have at least three times as much energy density as today’s lithium-ion batteries. A battery cell’s energy density gives an electric vehicle its driving range, so a higher energy density means that a car can drive more miles between charges. The UT Austin battery formulation also allows for a greater number of charging and discharging cycles, which equates to longer-lasting batteries, as well as a faster rate of recharge (minutes rather than hours).

The use of an alkali-metal anode (lithium, sodium or potassium)—which isn’t possible with conventional batteries—increases the energy density of a cathode and delivers a long cycle life. In experiments, the researchers’ cells have demonstrated more than 1,200 cycles with low cell resistance.

Additionally, because the solid-glass electrolytes can operate, or have high conductivity, at -20 degrees Celsius, this type of battery in a car could perform well in subzero degree weather. This is the first all-solid-state battery cell that can operate under 60 degree Celsius.

Braga began developing solid-glass electrolytes with colleagues while she was at the University of Porto in Portugal. About two years ago, she began collaborating with Goodenough and researcher Andrew J. Murchison at UT Austin. Braga said that Goodenough brought an understanding of the composition and properties of the solid-glass electrolytes that resulted in a new version of the electrolytes that is now patented through the UT Austin Office of Technology Commercialization.

The engineers’ glass electrolytes allow them to plate and strip alkali metals on both the cathode and the anode side without dendrites, which simplifies battery cell fabrication.

Another advantage is that the battery cells can be made from earth-friendly materials.

“The glass allow for the substitution of low-cost sodium for lithium. Sodium is extracted from seawater that is widely available,” Braga said.

Goodenough and Braga are continuing to advance their battery-related research and are working on several patents. In the short term, they hope to work with battery makers to develop and test their new materials in electric vehicles and energy storage devices.


Explore further: Cathode material with high energy density for all-solid lithium-ion batteries

Provided by University of Texas at Austin

U of Texas: Graphene-based sensor can track vital signs


Researchers at the University of Texas have developed a graphene-based health sensor that attaches to the skin like a temporary tattoo and takes measurements with the same precision as bulky medical equipment. The graphene tattoos are said to be the thinnest epidermal electronics ever made. They can measure electrical signals from the heart, muscles, and brain, as well as skin temperature and hydration.

The research team hopes to integrate these sensors applications like consumer cosmetics, in addition to providing a more convenient replacement for existing medical equipment. The sensor takes advantage of graphene’s mechanical invisibility – when the sensor goes on the skin, it doesn’t just stay flat—it conforms to the microscale ridges and roughness of the epidermis.1-Brain Transparentgraphene1-640x353

The Texas researchers started by growing single-layer graphene on a sheet of copper. The 2D carbon sheet is then coated with a stretchy support polymer, and the copper is etched off. Next, the polymer-graphene sheet is placed on temporary tattoo paper, the graphene is carved to make electrodes with stretchy spiral-shaped connections between them, and the excess graphene is removed. Then the sensor is ready to be applied by placing it on the skin and wetting the back of the paper.

In their proof-of-concept work, the researchers used the graphene tattoos to take five kinds of measurements, and compared the data with results from conventional sensors. The graphene electrodes were able to pick up changes in electrical resistance caused by electrical activity in the tissue underneath. When worn on the chest, the graphene sensor detected faint fluctuations that were not visible on an EKG taken by an adjacent, conventional electrode. The sensor readouts for electroencephalography (EEG) and electromyography (EMG, which can be used to register electrical signals from muscles and is being incorporated into next-generation prosthetic arms and legs) were also of good quality. The sensors could also measure skin temperature and hydration, which could be useful for cosmetics companies.

Graphene’s conformity to the skin might be what enables the high-quality measurements. Air gaps between the skin and the relatively large, rigid electrodes used in conventional medical devices degrade these instruments’ signal quality. Newer sensors that stick to the skin and stretch and wrinkle with it have fewer airgaps, but because they’re still a few micrometers thick, and use gold electrodes hundreds of nanometers thick, they can lose contact with the skin when it wrinkles. The graphene in the Texas researchers’ device is 0.3-nm thick. Most of the tattoo’s bulk comes from the 463-nm-thick polymer support.

The next step is to add an antenna to the design so that signals can be transmitted from the device to a phone or computer.

Source:  spectrum.ieee

U of Texas – Arlington – Researchers Devise more Efficient Materials for Solar Fuel Cells

Solar Fuel Cell U of T energy_cycle

University of Texas at Arlington chemists have developed new high-performing materials for cells that harness sunlight to split carbon dioxide and water into usable fuels like methanol and hydrogen gas. These “green fuels” can be used to power cars, home appliances or even to store energy in batteries.

“Technologies that simultaneously permit us to remove greenhouse gases like carbon dioxide while harnessing and storing the energy of sunlight as fuel are at the forefront of current research,” said Krishnan Rajeshwar, UTA distinguished professor of chemistry and biochemistry and co-founder of the University’s Center of Renewable Energy, Science and Technology.

“Our new material could improve the safety, efficiency and cost-effectiveness of solar fuel generation, which is not yet economically viable,” he added.

The new hybrid platform uses ultra-long carbon nanotube networks with a homogeneous coating of copper oxide nanocrystals. It demonstrates both the high electrical conductivity of carbon nanotubes and the photocathode qualities of copper oxide, efficiently converting light into the photocurrents needed for the photoelectrochemical reduction process.

Morteza Khaledi, dean of the UTA College of Science, said Rajeshwar’s work is representative of the University’s commitment to addressing critical issues with global environmental impact under the Strategic Plan 2020.

“Dr. Rajeshwar’s ongoing, global leadership in research focused on solar fuel generation forms part of UTA’s increasing focus on renewable and sustainable energy,” Khaledi said. “Creating inexpensive ways to generate fuel from an unwanted gas like carbon dioxide would be an enormous step forward for us all.”

For the solar fuel cells project, Rajeshwar worked with Csaba Janáky, an assistant chemistry professor at the University of Szeged in Hungary and Janáky’s master’s student Egon Kecsenovity. Janaky served as a UTA Marie Curie Fellow from 2011 to 2013.

The findings are the subject of a Feb. 15 minireview, “Electrodeposition of Inorganic Oxide/Nanocarbon Composites: Opportunities and Challenges,” published in ChemElectroChem Europe and a companion article in the Journal of Materials Chemistry A on “Decoration of ultra long carbon nanotubes with Cu2O nanocrystals: a hybrid platform for photoelectrochemical CO2 reduction.”

“The performance of our hybrid has proved far superior to the properties of the individual materials,” Rajeshwar said. “These new hybrid films demonstrate five-fold higher electrical conductivity compared to their copper oxide counterparts, and generate a three-fold increase in the photocurrents needed for the reduction process.”

The new material also demonstrates much greater stability during long-term photoelectrolysis than pure copper oxide, which corrodes over time, forming metallic copper.

The research involved developing a multi-step electrodeposition process to ensure that a homogeneous coating of copper oxide nanoparticles were deposited on the carbon nanotube networks. By varying the thickness of the carbon nanotube film and the amount of electrodeposited copper oxide, the researchers were able to optimize the efficiency of this new hybrid material.

Rajeshwar also is working with Brian Dennis, a UTA associate professor of mechanical and aerospace engineering, and Norma Tacconi, a research associate professor of chemistry and biochemistry, on a project with NASA to develop improved methods for oxygen recovery and reuse aboard human spacecraft.

The team is designing, building and demonstrating a “microfluidic electrochemical reactor” to recover oxygen from carbon dioxide extracted from cabin air. The prototype will be built over the next months at the Center for Renewable Energy Science and Technology at UTA.

Rajeshwar joined the College of Science in 1983, is a charter member of the UTA Academy of Distinguished Scholars and senior vice president of The Electrochemical Society, an organization representing the nation’s premier researchers who are dedicated the advancing solid state, electrochemical science and technology.

He is an expert in photoelectrochemistry, nanocomposites, electrochemistry and conducting polymers, and has received numerous awards, including the Wilfred T. Doherty Award from the American Chemical Society and the Energy Technology Division Research Award of the Electrochemical Society.

Rajeshwar earned his Ph.D. in chemistry from the Indian Institute of Science in Bangalore, India, and completed his post-doctoral training in Colorado State University.

Story Source:

The above post is reprinted from materials provided byUniversity of Texas at Arlington. Note: Materials may be edited for content and length.

Journal Reference:

  1. E. Kecsenovity, B. Endrődi, Zs. Pápa, K. Hernádi, K. Rajeshwar, C. Janáky. Decoration of ultra-long carbon nanotubes with Cu2O nanocrystals: a hybrid platform for enhanced photoelectrochemical CO2reduction. J. Mater. Chem. A, 2016; 4 (8): 3139 DOI:10.1039/C5TA10457B

Laser Blast Makes Pure (Green) Quantum Dots

Laser PW-2014-12-08-Dume-quantumQuantum dots made of pure selenium can be made by simply firing a laser beam at selenium powder mixed into a glass of water. The easy and inexpensive process was developed by researchers at the University of Texas at San Antonio and Northeastern University in the US, and unlike other techniques, does not involve potentially toxic chemicals. The high-quality nanostructures could be used in two very different applications: as antibacterial agents and as light harvesters in solar cells.

Quantum dots are tiny pieces of semiconductor – such as selenium – that are typically tens of nanometres across. The size of a quantum dot dictates how their charge-carrying electrons and holes interact with light. As a result, they are of great interest to researchers trying to develop photonic technologies and especially solar cells. However, growing quantum dots that are pure and all the same size can be a challenge.A usingsolaren

Green and easy

The researchers, led by Gregory Guisbiers in San Antonio, created their pure selenium quantum dots using a technique called pulsed laser ablation in liquids (PLAL), which involves simply firing a pulsed laser beam at a target – in this case selenium powder in water. “Our method is ‘green’ because it does not involve any dangerous solvents, only water, and there are no toxic adducts or by-products, like those often encountered in many wet chemistry processes,” explains Guisbiers. “It is also cheap and easy because we do not need a vacuum chamber or clean room – everything is done in a beaker of water.” The pure nanoparticles produced are also easy to collect and store because they are directly synthesized in solution, he adds.

This is the first time that selenium quantum dots have been synthesized using PLAL at ultraviolet and visible wavelengths, he says. These wavelengths are particularly interesting because they are better at reducing the size of particles compared with light at near-infrared wavelengths. Guisbiers and colleagues also showed that the crystallinity of the nanoparticles created by this technique depends on their size – that is, the smallest particles are crystalline while the largest ones are amorphous.

Antibacterial and anti-cancer

Selenium nanoparticles have antibacterial and anti-cancer properties, and could be used in medicine because the material is biocompatible and already exists in our bodies. However, nanoparticles need to be free of surface contaminants if they are to be employed in a biomedical setting – something that has proved difficult to achieve in the past.

The team, which has already tested its nanoparticles on E. coli, is now looking to see if they are efficient at killing other types of bacteria. “We are particularly interested in other bacteria involved in nosocomial diseases, like the methicillin-resistant Staphylococcus aureus,” Guisbiers says. “I’m told that [hospital-acquired infections] cause roughly 100,000 deaths every year in the US alone because bacteria are becoming more and more resistant to existing antibiotics. What’s more, these so-called super-germs are spreading worldwide, making this a major international health concern.”

The researchers will report their work in an upcoming issue of Laser Physics Letters. The team is also planning to incorporate the pure selenium quantum dots that they made into third-generation solar cells. “Indeed, since the element itself is a p-type semiconductor, when combined with an n-type semiconductor, we can build p–n junctions (the building blocks of all modern-day electronics) at the nanoscale,” adds Guisbiers.

University of Texas & German ‘Axitron’ Develop ‘Wafer-Scale’ Graphene: Scalability for the Use in Processors

 UT German Scale Graphene Wafers 300mmwafersA research team from the University of Texas and German nanotechnology company Aixtron have worked out a way to make wafer-scale graphene measuring between 100 and 300mm.

The research offers the prospect of integrating carbon-based graphene, which is just one atom thick, with silicon on a semi-industrial scale. Until now, graphene has proved difficult to manufacture in sufficient area, quantity and reliability for viable use in processors.


 The largest applications of high-performance graphene will likely be realized when combined with ubiquitous Si very large scale integrated (VLSI) technology, affording a new portfolio of “back end of the line” devices including graphene radio frequency transistors, heat and transparent conductors, interconnects, mechanical actuators, sensors, and optical devices. To this end, we investigate the scalable growth of polycrystalline graphene through chemical vapor deposition (CVD) and its integration with Si VLSI technology. The large-area Raman mapping on CVD polycrystalline graphene on 150 and 300 mm wafers reveals over 95% monolayer uniformity with negligible

UT German Scale Graphene Wafers 300mmwafers

About 26 000 graphene field-effect transistors were realized, and statistical evaluation indicates a device yield of ∼74% is achieved, 20% higher than previous reports. About 18% of devices show mobility of over 3000 cm squared per(V s), more than 3 times higher than prior results obtained over the same range from CVD polycrystalline graphene.

The peak mobility observed here is ∼40% higher than the peak mobility values reported for single-crystalline graphene, a major advancement for polycrystalline graphene that can be readily manufactured. Intrinsic graphene features such as soft current saturation and three-region output characteristics at high field have also been observed on wafer-scale CVD graphene on which frequency doubler and amplifiers are demonstrated as well. Our growth and transport results on scalable CVD graphene have enabled 300 mm synthesis instrumentation that is now commercially available.

A research team from the University of Texas and German nanotechnology company Aixtron have worked out a way to make wafer-scale graphene measuring between 100 and 300mm.

The research offers the prospect of integrating carbon-based graphene, which is just one atom thick, with silicon on a semi-industrial scale. Until now, graphene has proved difficult to manufacture in sufficient area, quantity and reliability for viable use in processors.

IBM research scientist Shu-Jen Han led a project that announced the creation of a wafer-scale graphene circuit in January of this year but did not solve the issue of reliable industrial-scale production. The polycrystalline graphene developed by IBM has improved carrier transport characteristics and fewer defects, enabling the team to manufacture 25,000 graphene field-effect transistors from lab-generated graphene film.

ACS Nano – Toward 300 mm Wafer-Scalable High-Performance Polycrystalline Chemical Vapor Deposited Graphene Transistors

8 pages of supplemental information

New Synthetic Molecule from the U of Texas & International Team Gives Hope for Anti-Cancer Drugs that Cause Cancer Cells to “Self-Destruct”

U of T Cancer Molecule id36877Researchers from The University of Texas at Austin and five other institutions have created a molecule that can cause cancer cells to self-destruct by ferrying sodium and chloride ions into the cancer cells.
These synthetic ion transporters, described this week in the journal Nature Chemistry (“Synthetic ion transporters can induce apoptosis by facilitating chloride anion transport into cells”), confirm a two-decades-old hypothesis that could point the way to new anticancer drugs while also benefitting patients with cystic fibrosis.
Synthetic Ion Transporters
Synthetic ion transporters can induce apoptosis by facilitating chloride anion transport into cells.
Synthetic ion transporters have been created before, but this is the first time researchers have shown them working in a real biological system where transported ions demonstrably cause cells to self-destruct.
Cells in the human body work hard to maintain a stable concentration of ions inside their cell membranes. Disruption of this delicate balance can trigger cells to go through apoptosis, known as programmed cell death, a mechanism the body uses to rid itself of damaged or dangerous cells.
One way of destroying cancer cells would be to trigger this innate self-destruct sequence by skewing the ion balance in cells. Unfortunately, when a cell becomes cancerous, it changes the way it transports ions across its cell membrane in a way that blocks apoptosis.
Almost two decades ago, a natural substance called prodigiosin was discovered that acted as a natural ion transporter and has an anticancer effect.
Since then, it has been a “chemist’s dream,” said Jonathan Sessler, professor in The University of Texas at Austin’s College of Natural Sciences and co-author of the study, to find “synthetic transporters that might be able to do exactly the same job, but better, and also work for treating diseases such as cystic fibrosis where chloride channels don’t work.”
Sessler and his collaborators, led by professors Injae Shin of Yonsei University and Philip A. Gale of the University of Southampton and King Abdulaziz University, were able to bring this dream to fruition.
The University of Texas members of the team created a synthetic ion transporter that binds to chloride ions. The molecule works by essentially surrounding the chloride ion in an organic blanket, allowing the ion to dissolve in the cell’s membrane, which is composed largely of lipids, or fats. The researchers found that the transporter tends to use the sodium channels that naturally occur in the cell’s membrane, bringing sodium ions along for the ride.
Gale and his team found that the ion transporters were effective in a model system using artificial lipid membranes.
Shin and his working group were then able to show that these molecules promote cell death in cultured human cancer cells. One of the key findings was that the cancer cell’s ion concentrations changed before apoptosis was triggered, rather than as a side effect of the cell’s death.
“We have thus closed the loop and shown that this mechanism of chloride influx into the cell by a synthetic transporter does indeed trigger apoptosis,” said Sessler. “This is exciting because it points the way towards a new approach to anticancer drug development.”
Sessler noted that right now, their synthetic molecule triggers programmed cell death in both cancerous and healthy cells. To be useful in treating cancer, a version of a chloride anion transporter will have to be developed that binds only to cancerous cells. This could be done by linking the transporter in question to a site-directing molecule, such as the texaphyrin molecules that Sessler’s lab has previously synthesized.
The results were a culmination of many years of work across three continents and six universities.
“We have demonstrated that this mechanism is viable, that this idea that’s been around for over two decades is scientifically valid, and that’s exciting,” said Sessler. “We were able to show sodium is really going in, chloride is really going in. There is now, I think, very little ambiguity as to the validity of this two-decades-old hypothesis.”
The next step for the researchers will be to take the synthetic ion transporters and test them in animal models.
Source: University of Texas at Austin

Printing Ultrafast Graphene Chips for Flexible Electronics

Futurists are always talking about how flexible electronics will change our lives in amazing ways, but we’ve yet to see anything mind-blowing come to market. A team of scientists from the University of Texas in Austin, however, think they’ve found the key to changing that: ultrafast graphene transistors printed on flexible plastic.

Graphene is amazing. Or at least, it could be. Made from a layer of carbon one-atom thick, it’s the strongest material in the world, it’s… Read…

   9 Incredible Uses for Graphene

Graphene is amazing stuff for a lot different reasons. One reason is that it’s the perfect material for chip-making, and conventional graphene chips have broken several electronic speed records. In the past, however, attempts to put graphene transistors on flexible materials have caused that speed to take a dive. Not with this new method.

Indeed, the chips from Texas clock in at a record-breaking 25-gigahertz. The MIT Technology Review explains the manufacturing process:

To make the transistors, the researchers first fabricate all the non-graphene-containing structures—the electrodes and gates that will be used to switch the transistors on and off—on sheets of plastic. Separately, they grow large sheets of graphene on metal, then peel it off and transfer it to complete the devices. …

The graphene transistors are not only speedy but robust. The devices still work after being soaked in water, and they’re flexible enough to be folded up.

And things are only getting better. Earlier this week we learned about a cutting edge technique for making graphene chips developed by a team of researchers from the University of California.

All we need now is a company to take the plunge and start bringing some of this next level technology to market. And you thought Liquidmetal was cool !!     [Technology Review]


Scientists Just Figured Out How to Make Lightning-Fast Graphene CPUs

Graphene has the power to change computing forever by making the fastest transistors ever. In theory. We just haven’t figured out how yet. Sound familiar? Fortunately, scientists have just taken a big step closer to making graphene transistors work for real.

Graphene transistors aren’t just fast; they’re lightning fast. The speediest one to date clocked in at some 427 GHz. That’s orders of magnitude more than what you can tease out of today’s processors.  The problem with graphene transistors, though, is that they aren’t particularly good at turning off. They don’t turn off at all actually, which makes it hard to use them as switches.


Interface Properties of Graphene Paves Way for New Applications

201306047919620Researchers from North Carolina State University and the University of Texas have revealed more about graphene’s mechanical properties and demonstrated a technique to improve the stretchability of graphene – developments that should help engineers and designers come up with new technologies that make use of the material.

Graphene is a promising material that is used in technologies such as transparent, flexible electrodes and nanocomposites. And while engineers think graphene holds promise for additional applications, they must first have a better understanding of its mechanical properties, including how it works with other materials.

“This research tells us how strong the interface is between graphene and a stretchable substrate,” says Dr. Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and co-author of a paper on the work. “Industry can use that to design new flexible or stretchable electronics and nanocomposites. For example, it tells us how much we can deform the material before the interface between graphene and other materials fails. Our research has also demonstrated a useful approach for making graphene-based, stretchable devices by ‘buckling’ the graphene.”

The researchers looked at how a graphene monolayer – a layer of graphene only one atom thick – interfaces with an elastic substrate. Specifically, they wanted to know how strong the bond is between the two materials because that tells engineers how much strain can be transferred from the substrate to the graphene, which determines how far the graphene can be stretched.

The researchers applied a monolayer of graphene to a polymer substrate, and then stretched the substrate. They used a spectroscopy technique to monitor the strain at various points in the graphene. Strain is a measure of how far a material has stretched.

Initially, the graphene stretched with substrate. However, while the substrate continued to stretch, the graphene eventually began to stretch more slowly and slide on the surface instead. Typically, the edges of the monolayer began to slide first, with the center of the monolayer stretching further than the edges.

“This tells us a lot about the interface properties of the graphene and substrate,” Zhu says. “For the substrate used in this study, polyethylene terephthalate, the edges of the graphene monolayer began sliding after being stretched 0.3 percent of its initial length. But the center continued stretching until the monolayer had been stretched by 1.2 to 1.6 percent.”

The researchers also found that the graphene monolayer buckled when the elastic substrate was returned to its original length. This created ridges in the graphene that made it more stretchable because the material could stretch out and back, like the bellows of an accordion. The technique for creating the buckled material is similar to one developed by Zhu’s lab for creating elastic conductors out of carbon nanotubes.

The paper, “Interfacial Sliding and Buckling of Monolayer Graphene on a Stretchable Substrate,” was published online Aug. 1 in Advanced Functional Materials. Lead author of the paper is Dr. Tao Jiang, a postdoctoral researcher at NC State. The paper was co-authored by Dr. Rui Huang of the University of Texas. The research was funded by the National Science Foundation (NSF) and the NSF’s ASSIST Engineering Research Center at NC State.


Note to Editors: The study abstract follows.

“Interfacial Sliding and Buckling of Monolayer Graphene on a Stretchable Substrate”

Authors: Tao Jiang and Yong Zhu, North Carolina State University; Rui Huang, University of Texas at Austin

Published: Aug. 1 2013, Advanced Functional Materials