Researchers Take on the Task of Developing New Manufacturing Techniques for 2D Materials
From industrial production to making graphene products in your own home, 2D manufacturing is improving
Sorting out all the wonderful properties and capabilities of graphene and other two-dimensional (2D) materials is always exciting, filled with seemingly endless possibilities. But then you have to try and manufacture the graphene itself and then use that graphene to make a device and at which point the fun seems to come to an end.
The engineering grind of producing graphene of a particular quality and at particular price point is a challenge that is only matched or exceeded by then trying to make a device from it that does what it’s supposed to do and does so cost effectively.
This past quarter there have been some significant research achievements in both producing 2D materials more efficiently and cheaply as well as making new and improved devices.
Produce Graphene-based Electronics From Home
Photo: Graphene 3D Lab
You may not have to wait for a factory to produce devices out of graphene; you may be able to do it from your own home thanks to a new company that is offering a 3D printing solution using graphene.
The start-up Graphene 3D Lab, Inc., based in Calverton, NY is now selling a graphene-based conductive polymer filament for use in 3-D printing to fabricate electronic devices that can be used either by industry or the hobbyist.
The company claims that its graphene-based filament is the most electrically conductive material on the market right now and offers the best option for 3-D printing of electronics.
In terms of volume resistivity, the top of the market offers around 15 Ohms-centimeter (Ohms-cm), according to Elena Polyakova, co-CEO of the company, whereas Graphene 3D Lab’s product—dubbed Black Magic 3D—has a measured volume resistivity of 0.6 Ohms-cm—25 times better than the current state-of the-art.
New Twist to CVD Processes Could Make Graphene 100 Times Cheaper to Produce
Along the lines of the more industrial scales of graphene production, researchers at the University of Glasgow in Scotland claim to have added a new twist to chemical vapor deposition (CVD) production of graphene that could lead to producing large-area graphene 100 times more cheaply than previous methods.
CVD processes involve introducing gaseous reactants into a furnace to form a film on a metal substrate that’s usually made of copper. What the Scotland-based researchers have done is to use the smooth surface of copper foils typically used as the negative electrodes in the lithium-ion batteries.
Image: University of Glasgow
“The commercially-available copper we used in our process retails for around one dollar per square meter, compared to around $115 for a similar amount of the copper currently used in graphene production,” said Ravinder Dahiyam who led the research, in a press release.
The problem has been that the more expensive form of copper required additional processing before it could be used, which tacked on even more cost.
“Our process produces high-quality graphene at low cost,” says Dahiyam. This breakthrough, he adds, takes us, “one step closer to creating affordable new electronic devices with a wide range of applications, from the smart cities of the future to mobile healthcare.”
In the research paper published in the journal Scientific Reports, the large-area graphene produced from the new method is suggested for use over large flexible substrates such as soft plastic and paper.
Dahiyam’s own personal interest in the graphene would be for synthetic skin for prosthetics.
Much of my own research is in the field of synthetic skin,” said Dahiyam. “Graphene could help provide an ultraflexible, conductive surface which could provide people with prosthetics capable of providing sensation in a way that is impossible for even the most advanced prosthetics today.”
Graphene Gets More Attractive With a Few Wrinkles
One of the most aggressively pursued aims in graphene manufacturing is to create wrinkle-free single-crystal monolayer graphene on a silicon wafer, such as the work Samsung’s Advanced Institute of Technology has been conducting.
Now researchers at the RIKEN research institute in Japan have turned that quest on its ear by suggesting that it is in fact the wrinkles that makes graphene attractive.
The Japanese researchers reported in the journal Nature Communications that wrinkles in graphene create unique electronic qualities, specifically a one-dimensional electron confinement. This restriction of electron movement results in a junction-like structure that changes from a zero-gap conductor to a semiconductor and back to zero-gap conductor.
The other finding in the research was that it was possible to manipulate the wrinkles to change graphene’s band gap mechanically rather than chemically.
“Up until now, efforts to manipulate the electronic properties of graphene have principally been done through chemical means, but the downside of this is that it can lead to degraded electronic properties due to chemical defects,” said Yousoo Kim, who led the RIKEN team, in a press release. “Here we have shown that the electronic properties can be manipulated merely by changing the shape of the carbon structure. It will be exciting to see if this could lead to ways to find new uses for graphene.”
The ability to change graphene, which is a natural conductor, into a semiconductor with a band gap mechanically with needing to chemically dope the material came about serendipitously.
“We were attempting to grow graphene on a single crystalline nickel substrate, but in many cases we ended up creating a compound of nickel and carbon, Ni2C, rather than graphene,” explained Hyunseob Lim, the paper’s lead author, in a press release. “In order to resolve the problem, we tried quickly cooling the sample after the dosing with acetylene, and during that process we accidentally found small nanowrinkles, just five nanometers wide, in the sample.”
A Bit of Hydrogen Makes Defects Into Benefits for Graphene in Li-ion Batteries
Photo: Julie Russell
Various forms of graphene have joined the growing list of nanomaterials that are aimed at replacing graphite in Li-ion batteries so that they will charge faster and last longer on that charge.
Unfortunately, the most obvious obstacle for using graphene in Li-ion batteries has been the additional cost.
Now researchers at Lawrence Livermore National Laboratory (LLNL) have discovered that they can produce at a low temperature a graphene that is full of defects but still makes a highly effective electrode material simply by treating it with hydrogen.
Defects, of course, are not necessarily a good thing. But what the researchers reported in the journal Nature Scientific Reports was that the hydrogen interacts with the defects and opens up the gaps so that lithium ions can more easily penetrate the material, improving the transport of lithium through the device.
“We found a drastically improved rate capacity in graphene nanofoam electrodes after hydrogen treatment,” said LLNL scientist Brandon Wood, one of the co-authors of the paper, in a press release. “By combining the experimental results with detailed simulations, we were able to trace the improvements to subtle interactions between defects and dissociated hydrogen. This results in some small changes to the graphene chemistry and morphology that turn out to have a surprisingly huge effect on performance.”
This discovery could find its way into improving lithium transport in general and improve the storage capacity of other graphene-based anode materials.
“The performance improvement we’ve seen in the electrodes is a breakthrough that has real world applications,” said Jianchao Ye, the lead author of the paper, in the press release.
Avenues Open for Producing Carbyne in the Real World
Illustration: Liam Krauss/LLNL
A couple of years ago, carbyne—a chain of carbon atoms held together by either double or alternating single and triple atomic bonds—was awarded the title of the world’s strongest material. There was just one problem outside of finding in some samples of compressed graphite, it didn’t really exist outside of some computer models.
Now researchers at Lawrence Livermore National Laboratory (LLNL) have continued modeling, but this time for trying to find ways of actually fabricating the material—and they may have found a way to do it.
The LLNL researchers reported in the Journal of Physical Chemistry that it was possible to form carbyne fiber bundles by melting graphite with a laser.
“There’s been a lot of speculation about how to make carbyne and how stable it is,” said Nir Goldman, an LLNL scientist, in the press release. “We showed that laser melting of graphite is one viable avenue for its synthesis.”
The researchers believe that depending on how you cook the graphite, the resulting carbyne could have some interesting applications, such as tunable semiconductors or even hydrogen storage materials.
“Our method shows that carbyne can be formed easily in the laboratory or otherwise,” said Goldman. “The process also could occur in astrophysical bodies or in the interstellar medium, where carbon-containing material can be exposed to relatively high temperatures and carbon can liquefy.”
This method may not represent the first time that a stable carbyne has been synthesized, it does suggest a way forward for possible scale up of that manufacturing. If carbyne can be produced in bulk, it would have a big impact on nanoelectronics where the material could offer a way of adjusting the amount of electrical current traveling through a circuit depending on the users’ needs.