Graphene is a material with a host of potential applications, including in flexible light sources, solar panels that could be integrated into windows, and membranes to desalinate and purify water. But all these possible uses face the same big hurdle: the need for a scalable and cost-effective method for continuous manufacturing of graphene films.
That could finally change with a new process described this week in the journal Scientific Reports by researchers at MIT and the University of Michigan. MIT mechanical engineering Associate Professor A. John Hart, the paper’s senior author, says the new roll-to-roll manufacturing process described by his team addresses the fact that for many proposed applications of graphene and other 2-D materials to be practical, “you’re going to need to make acres of it, repeatedly and in a cost-effective manner.”
Making such quantities of graphene would represent a big leap from present approaches, where researchers struggle to produce small quantities of graphene — often pulling these sheets from a lump of graphite using adhesive tape, or producing a film the size of a postage stamp using a laboratory furnace. But the new method promises to enable continuous production, using a thin metal foil as a substrate, in an industrial process where the material would be deposited onto the foil as it smoothly moves from one spool to another. The resulting sheets would be limited in size only by the width of the rolls of foil and the size of the chamber where the deposition would take place.
Because a continuous process eliminates the need to stop and start to load and unload materials from a fixed vacuum chamber, as in today’s processing methods, it could lead to significant scale-up of production. That could finally unleash applications for graphene, which has unique electronic and optical properties and is one of the strongest materials known.
The new process is an adaptation of a chemical vapor deposition method already used at MIT and elsewhere to make graphene — using a small vacuum chamber into which a vapor containing carbon reacts on a horizontal substrate, such as a copper foil. The new system uses a similar vapor chemistry, but the chamber is in the form of two concentric tubes, one inside the other, and the substrate is a thin ribbon of copper that slides smoothly over the inner tube.
Gases flow into the tubes and are released through precisely placed holes, allowing for the substrate to be exposed to two mixtures of gases sequentially. The first region is called an annealing region, used to prepare the surface of the substrate; the second region is the growth zone, where the graphene is formed on the ribbon. The chamber is heated to approximately 1,000 degrees Celsius to perform the reaction.
The researchers have designed and built a lab-scale version of the system, and found that when the ribbon is moved through at a rate of 25 millimeters (1 inch) per minute, a very uniform, high-quality single layer of graphene is created. When rolled 20 times faster, it still produces a coating, but the graphene is of lower quality, with more defects.
Some potential applications, such as filtration membranes, may require very high-quality graphene, but other applications, such as thin-film heaters may work well enough with lower-quality sheets, says Hart, who is the Mitsui Career Development Associate Professor in Contemporary Technology at MIT.
So far, the new system produces graphene that is “not quite [equal to] the best that can be done by batch processing,” Hart says — but “to our knowledge, it’s still at least as good” as what’s been produced by other continuous processes. Further work on details such as pretreatment of the substrate to remove unwanted surface defects could lead to improvements in the quality of the resulting graphene sheets, he says.
The team is studying these details, Hart adds, and learning about tradeoffs that can inform the selection of process conditions for specific applications, such as between higher production rate and graphene quality. Then, he says, “The next step is to understand how to push the limits, to get it 10 times faster or more.”
Hart says that while this study focuses on graphene, the machine could be adapted to continuously manufacture other two-dimensional materials, or even to growing arrays of carbon nanotubes, which his group is also studying.
“This is high-quality research that represents significant progress on the path to scalable production methods for large-area graphene,” says Charlie Johnson, a professor of physics and astronomy at the University of Pennsylvania who was not involved in this work. “I think that the concentric tube approach is very creative. It has the potential to lead to significantly lower production costs for graphene, if it can be scaled to larger copper-foil widths.”
The research team also included Erik Polsen and Daniel McNerny of the University of Michigan and postdocs Viswanath Balakrishnan and Sebastian Pattinson of MIT. The work was supported by the National Science Foundation and the Air Force Office of Scientific Research.
University of Manchester scientists have used graphene to target and neutralise cancer stem cells while not harming other cells. Continue reading
UK researchers have taken a step forward in making flexible displays, debuting a warping screen that uses graphene as its electronic material.
Like many of the screens that we view today, the new Cambridge invention uses an electrophoretic display that rearranges particles suspended in a solution by means of an electric field. However, in contrast to most displays the screen is made of flexible plastic and its pixel electronics, also known as backplane, replace the traditional metal electrode with one built from graphene.
According to Cambridge researchers, “Graphene is more flexible than conventional ceramic alternatives like indium-tin oxide (ITO) and more transparent than metal films.” What’s more the 2-dimensional carbon material is also processed and printed very easily making the display simple to produce.
Currently, the Cambridge consortium’s display is only capable of a 150 pixel per inch resolution, however, that may change in short order. Researchers believe they can build a flexible OLED or LCD screen that can project a full color HD image. Looking further into the future the UK team also believes that using graphene-based backplanes might allow them to embed sensors in the displays, making them more capable of interacting with their viewers.
“We are happy to see our collaboration with Plastic Logic resulting in the first graphene-based electrophoretic display exploiting graphene in its pixels’ electronics,” said Professor Andrea Ferrari, Director of the Cambridge Graphene Centre. “This is a significant step forward to enable fully wearable and flexible devices.”
While graphene’s potential has been known since it was first discovered, industries have been slow to leverage its unique abilities. This Cambridge display should do wonders for the development of process engineering for graphene and in the end it might just dazzle us with beautiful, flexible moving images.
In 2012, researchers from the University of Florida reported a record efficiency of 8.6 percent for a prototype solar cell consisting of a wafer of silicon coated with a layer of graphene doped with trifluoromethanesulfonyl-amide (TFSA). Now another team is claiming a new record efficiency of 15.6 percent for a graphene-based solar cell by ditching the silicon all together. Continue reading
Workers stand near pressure vessels at Britain’s first-ever mainland desalination plant, known as the Thames Gateway Water Treatment.
The latest technology for removing salt from seawater, developed by Lockheed Martin, will be a game-changer for the industry, according to Ray O. Johnson, senior vice president and chief technology officer of the jet and weapons manufacturer.
Desalination technology is used in regions of the world, particularly developing countries, where fresh water is not available. Water from oceans or rivers is diverted into treatment plants where the salt is removed and clean drinking water is produced through a process called reverse osmosis.
Imagine a tank with seawater on one side and pure water on the other, separated by a filter with billions of tiny holes. Lots of pressure on the salty side pushes water through faster than the salt, so fresh water comes out the other end.
The problem is that current filters use plastic polymers that use an immense amount of energy (800 to 1,000 pounds per square inch of pressure) to push water through.
Lockheed has developed a special material that doesn’t need as much energy to drag water through the filter.
Graphene is a substance made of pure carbon. Carbon atoms are arranged in a regular hexagonal or honeycomb pattern in a one-atom thick sheet.
This special material is a film of a special structure of carbon, a honeycomb lattice called graphene.
“Graphene is pure carbon that is made in a hot oven on top of a copper sheet
in a vacuum,” John Stetson, the chief technologist at Lockheed for this initiative explained to Business Insider. “Methane gas is put into the vacuum and the methane changes
into a single film of carbon atoms all linked together tightly like chickenwire (at the atomic level) 1,000 times stronger than steel and tolerant of temperature, pressure and pH.”
The sheet is dotted with holes that are one nanometer or less. These holes between carbon atoms trap the salt and other impurities.
Graphene researchers won the Nobel Prize in Physics in 2010 for developing the wonder-material.
In addition, the film is super thin — just a single atom thick — so that the water simply “pops through the very, very small holes that we make in the graphene and leaves the salt behind,” said Stetson.
Lockheed anticipates that their filters will be able to provide clean drinking water “at a fraction of the cost of industry-standard reverse osmosis systems,” their press release says. Water-poor regions of the world will be the first to benefit.
The perforated graphene is aptly called Perforene. Lockheed has the U.S. Patent on this technology and is currently pumping out “pretty big quantities of it” at Lockheed’s advanced technology center in Palo Alto, California, according to Stetson.
The Perforene has a smoky grey-color film that is translucent, even though its carbon, because it is so thin. It’s also about 1,000 times stronger than steel, but still has a permeability that is about 100 times greater than the best competitive membrane out in the market, said Stetson.
Perforene isn’t a game-changer, yet. Lockheed is still in the prototype stage. One challenge is figuring out how to scale up production. Graphene is cheap but it’s very delicate because of its thinness, also making it difficult to transfer.
Stetson says Lockheed is targeting to have a prototype to test in a reverse osmosis plant by 2014 or 2015, where they would simply be able to “plug in” the Perforene to replace the existing filter.
The great news is that this technology is not just limited to desalination plants. It can potentially be used for pharmaceutical filtration, dialysis, and gas separation, to a name a few other uses.
The possibilities are endless.
Graphene – which has a similar molecular structure to the graphite commonly found in pencils – was discovered in 2004. The material is two-dimensional, one atom thick, has superconducting properties, and is 200 times stronger than steel.
Bold claims for new battery technology have been around since the invention of the lead-acid battery more than 150 years ago.
But researchers at Manchester University in the UK say their latest discovery involving the new wonder material graphene could be the most revolutionary advance in battery technology yet.
According to a study published in the journal Nature, graphene membranes could be used to sieve hydrogen gas from the atmosphere — a development that could pave the way for electric generators powered by air.
“It looks extremely simple and equally promising,” said Dr Sheng Hu, a post-doctoral researcher in the project. “Because graphene can be produced these days in square metre sheets, we hope that it will find its way to commercial fuel cells sooner rather than later.”
At the heart of the technology is the remarkable physical properties of graphene — a substance with the same atomic structure as the lead found in the humble household pencil.
Isolated in 2004 by a team from Manchester University headed by Andrew Geim and Kostya Novoselov — both of whom won the Nobel Prize for Physics for their discovery in 2010 — graphene is already well known as a technological game-changer.
The first two-dimensional crystal known to science, graphene is the thinnest, lightest and strongest object ever obtained. It is harder than diamond and 200 times stronger than steel.
Flexible, transparent and able to conduct electricity even better than copper, the ground-breaking substance is set to revolutionize everything from smartphones and wearable technology to green technology and medicine.
Renowned for its barrier qualities, graphene is just one atom thick – more than a million times thinner than a human hair.
The latest discovery makes graphene attractive for possible uses in proton-conducting membranes which are at the core of modern fuel-cell technology.
Fuel cells work by using oxygen and hydrogen as a fuel, converting the chemical energy produced by its input directly into electricity. However, current membranes that separate the protons necessary for this process are relatively inefficient, allowing contamination in the fuel crossover.
Using graphene membranes could boost their efficiency and durability.
The team found the protons passed through the ultra-thin crystals with relative ease, especially at raised temperatures and with the use of a platinum-based catalyst coated on the membrane film.