Category Archives: graphene

Psst: secret marriage … Buckyballs and Graphene get together!

A March 1, 2018 news item on Nanowerk announces  a new coupling,

Scientists combined buckyballs, [also known as buckminsterfullerenes, fullerenes, or C60] which resemble tiny soccer balls made from 60 carbon atoms, with graphene, a single layer of carbon, on an underlying surface. Positive and negative charges can transfer between the balls and graphene depending on the nature of the surface as well as the structural order and local orientation of the carbon ball. Scientists can use this architecture to develop tunable junctions for lightweight electronic devices.

The researchers have made this illustration of their work available,

Researchers are developing new, lightweight electronics that rapidly conduct electricity by covering a sheet of carbon (graphene) with buckyballs. Electricity is the flow of electrons. On these lightweight structures, electrons as well as positive holes (missing electrons) transfer between the balls and graphene. The team showed that the crystallinity and orientation of the balls, as well as the underlying layer, affected this charge transfer. The top image shows a calculation of the charge density for a specific orientation of the balls on graphene. The blue represents positive charges, while the red is negative. The bottom image shows that the balls are in a close-packed structure. The bright dots correspond to the projected images of columns of buckyball molecules. Courtesy: US Department of Energy Office of Science

A February 28, 2018 US Department of Energy (DoE) Office of Science news release, which originated the news item, provides more detail,

The Impact

Fast-moving electrons and their counterpart, holes, were preserved in graphene with crystalline buckyball overlayers. Significantly, the carbon ball provides charge transfer to the graphene. Scientists expect the transfer to be highly tunable with external voltages. This marriage has ramifications for smart electronics that run longer and do not break as easily, bringing us closer to sensor-embedded smart clothing and robotic skin.

Summary

Charge transfer at the interface between dissimilar materials is at the heart of almost all electronic technologies such as transistors and photovoltaic devices. In this study, scientists studied charge transfer at the interface region of buckyball molecules deposited on graphene, with and without a supporting substrate, such as hexagonal boron nitride. They employed ab initio density functional theory with van der Waals interactions to model the structure theoretically. Van der Waals interactions are weak connections between neutral molecules. The team used high-resolution transmission electron microscopy and electronic transport measurements to characterize experimentally the properties of the interface. The researchers observed that charge transfer between buckyballs and the graphene was sensitive to the nature of the underlying substrate, in addition, to the crystallinity and local orientation of the buckyballs. These studies open an avenue to devices where buckyball layers on top of graphene can serve as electron acceptors and other buckyball layers as electron donors. Even at room temperature, buckyball molecules were orientationally locked into position. This is in sharp contrast to buckyball molecules in un-doped bulk crystalline configurations, where locking occurs only at low temperature. High electron and hole mobilities are preserved in graphene with crystalline buckyball overlayers. This finding has ramifications for the development of organic high-mobility field-effect devices and other high mobility applications.

Here’s a link to and a citation for the paper,

Molecular Arrangement and Charge Transfer in C60 /Graphene Heterostructures by Claudia Ojeda-Aristizabal, Elton J. G. Santos, Seita Onishi, Aiming Yan, Haider I. Rasool, Salman Kahn, Yinchuan Lv, Drew W. Latzke, Jairo Velasco Jr., Michael F. Crommie, Matthew Sorensen, Kenneth Gotlieb, Chiu-Yun Lin, Kenji Watanabe, Takashi Taniguchi, Alessandra Lanzara, and Alex Zettl. ACS Nano, 2017, 11 (5), pp 4686–4693 DOI: 10.1021/acsnano.7b00551 Publication Date (Web): April 24, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

How does sticky tape make graphene?

As I understand it, Andre Geim one of the two men (the other was Konstantin Novoselov) to first isolate graphene from a block of graphite by using sticky tape is not thrilled that it’s known in some quarters as the graphene sticky tape method. Still, the technique caught the imagination as Steve Connor’s March 18, 2013 article for the Independent made clear.

It seems scientists are still just as fascinated as anyone else as a February 27, 2018 news item for Nanowerk describes,

Scientists at UCL [University College London] have explained for the first time the mystery of why adhesive tape is so useful for graphene production.

The study, published in Advanced Materials (“Graphene–Graphene Interactions: Friction, Superlubricity, and Exfoliation”), used supercomputers to model the process through which graphene sheets are exfoliated from graphite, the material in pencils.

A February 26, 2018 UCL press release, which originated the news item, provides more detail,

There are various methods for exfoliating graphene, including the famous adhesive tape method developed by Nobel Prize winner Andre Geim. However little has been known until now about how the process of exfoliating graphene using sticky tape works.

Academics at UCL are now able to demonstrate how individual flakes of graphite can be exfoliated to make one atom thick layers. They also reveal that the process of peeling a layer of graphene demands 40% less energy than that of another common method called shearing. This is expected to have far reaching impacts for the commercial production of graphene.

“The sticky tape method works rather like peeling egg boxes apart with a vertical motion, it is easier than pulling one horizontally across another when they are neatly stacked,” explained Professor Peter Coveney, Director of the Centre for Computational Science (UCL Chemistry).

“If shearing, then you get held up by this egg carton configuration. But if you peel, you can get them apart much more easily. The polymethyl methacrylate adhesive on traditional sticky tape is ideal for picking up the edge of the graphene sheet so it can be lifted and peeled,” added Professor Coveney.

Graphite occurs naturally, its basic crystalline structure is stacks of flat sheets of strongly bonded carbon atoms in a honeycomb pattern. Graphite’s many layers are bound together by weak interactions and can easily slide large distances over one another with little friction due to their superlubricity.

The scientists at UCL simulated an experiment conducted in 2015 at Lawrence Berkeley Laboratory in Berkeley, California, which used a special microscope with atomic resolution to see how graphene flakes move around on a graphite surface.

The supercomputer’s results matched Berkeley’s observations showing that there is less movement when the graphene atoms neatly line up with the atoms below.

“Despite the vast amount of research carried out on graphene since its discovery, it is clear that until now our understanding of its behaviour on an atomic length scale was very poor,” explains PhD student Robert Sinclair (UCL Chemistry).

“The one reason above all others why the material is difficult to use is because it is hard to make. Even now, a dozen years after its discovery, companies have to apply sticky tape methods to pull it apart, as the Laureates did to uncover it; hardly a hi-tech and industrially simple process to implement. We’re now in a position to assist experimentalists to figure out how to prise it apart, or make it to order. That could have big cost implications for the emerging graphene industry,” said Professor Coveney.

Here’s a link to and a citation for the paper,

Graphene–Graphene Interactions: Friction, Superlubricity, and Exfoliation by Robert C. Sinclair, James L. Suter, and Peter V. Coveney. Advanced Materials DOI: 10.1002/adma.201705791 First published: 13 February 2018

This paper is open access.

Wearable technology: two types of sensors one from the University of Glasgow (Scotland) and the other from the University of British Columbia (Canada)

Sometimes it’s good to try and pull things together.

University of Glasgow and monitoring chronic conditions

A February 23, 2018 news item on phys.org describes the latest wearable tech from the University of Glasgow,

A new type of flexible, wearable sensor could help people with chronic conditions like diabetes avoid the discomfort of regular pin-prick blood tests by monitoring the chemical composition of their sweat instead.

In a new paper published in the journal Biosensors and Bioelectronics, a team of scientists from the University of Glasgow’s School of Engineering outline how they have built a stretchable, wireless system which is capable of measuring the pH level of users’ sweat.

A February 22, 2018 University of Glasgow press release, which originated the news item, expands on the theme,

Ravinder Dahiya

 Courtesy: University of Glasgow

 

Sweat, like blood, contains chemicals generated in the human body, including glucose and urea. Monitoring the levels of those chemicals in sweat could help clinicians diagnose and monitor chronic conditions such as diabetes, kidney disease and some types of cancers without invasive tests which require blood to be drawn from patients.

However, non-invasive, wearable systems require consistent contact with skin to offer the highest-quality monitoring. Current systems are made from rigid materials, making it more difficult to ensure consistent contact, and other potential solutions such as adhesives can irritate skin. Wireless systems which use Bluetooth to transmit their information are also often bulky and power-hungry, requiring frequent recharging.

The University of Glasgow team’s new system is built around an inexpensively-produced sensor capable of measuring pH levels which can stretch and flex to better fit the contours of users’ bodies. Made from a graphite-polyurethane composite and measuring around a single square centimetre, it can stretch up to 53% in length without compromising performance. It will also continue to work after being subjected to flexes of 30% up to 500 times, which the researchers say will allow it to be used comfortably on human skin with minimal impact on the performance of the sensor.

The sensor can transmit its data wirelessly, and without external power, to an accompanying smartphone app called ‘SenseAble’, also developed by the team. The transmissions use near-field communication, a data transmission system found in many current smartphones which is used most often for smartphone payments like ApplePay, via a stretchable RFID antenna integrated into the system – another breakthrough innovation from the research team.

The smartphone app allows users to track pH levels in real time and was demonstrated in the lab using a chemical solution created by the researchers which mimics the composition of human sweat.

The research was led by Professor Ravinder Dahiya, head of the University of Glasgow’s School of Engineering’s Bendable Electronics and Sensing Technologies (BEST) group.

Professor Dahiya said: “Human sweat contains much of the same physiological information that blood does, and its use in diagnostic systems has the significant advantage of not needing to break the skin in order to administer tests.

“Now that we’ve demonstrated that our stretchable system can be used to monitor pH levels, we’ve already begun additional research to expand the capabilities of the sensor and make it a more complete diagnostic system. We’re planning to add sensors capable of measuring glucose, ammonia and urea, for example, and ultimately we’d like to see a system ready for market in the next few years.”

The team’s paper, titled ‘Stretchable Wireless System for Sweat pH Monitoring’, is published in Biosensors and Bioelectronics. The research was supported by funding from the European Commission and the Engineering and Physical Sciences Research Council (EPSRC).

Here’s a link to and a citation for the paper,

Stretchable wireless system for sweat pH monitoring by Wenting Dang, Libu Manjakkal, William Taube Navaraj, Leandro Lorenzelli, Vincenzo Vinciguerra. Biosensors and Bioelectronics Volume 107, 1 June 2018, Pages 192–202 [Available online February 2018] https://doi.org/10.1016/j.bios.2018.02.025

This paper is behind a paywall.

University of British Columbia (UBC; Okanagan) and monitor bio-signals

This is a completely other type of wearable tech monitor, from a February 22, 2018 UBC news release (also on EurekAlert) by Patty Wellborn (A link has been removed),

Creating the perfect wearable device to monitor muscle movement, heart rate and other tiny bio-signals without breaking the bank has inspired scientists to look for a simpler and more affordable tool.

Now, a team of researchers at UBC’s Okanagan campus have developed a practical way to monitor and interpret human motion, in what may be the missing piece of the puzzle when it comes to wearable technology.

What started as research to create an ultra-stretchable sensor transformed into a sophisticated inter-disciplinary project resulting in a smart wearable device that is capable of sensing and understanding complex human motion, explains School of Engineering Professor Homayoun Najjaran.

The sensor is made by infusing graphene nano-flakes (GNF) into a rubber-like adhesive pad. Najjaran says they then tested the durability of the tiny sensor by stretching it to see if it can maintain accuracy under strains of up to 350 per cent of its original state. The device went through more than 10,000 cycles of stretching and relaxing while maintaining its electrical stability.

“We tested this sensor vigorously,” says Najjaran. “Not only did it maintain its form but more importantly it retained its sensory functionality. We have further demonstrated the efficacy of GNF-Pad as a haptic technology in real-time applications by precisely replicating the human finger gestures using a three-joint robotic finger.”

The goal was to make something that could stretch, be flexible and a reasonable size, and have the required sensitivity, performance, production cost, and robustness. Unlike an inertial measurement unit—an electronic unit that measures force and movement and is used in most step-based wearable technologies—Najjaran says the sensors need to be sensitive enough to respond to different and complex body motions. That includes infinitesimal movements like a heartbeat or a twitch of a finger, to large muscle movements from walking and running.

School of Engineering Professor and study co-author Mina Hoorfar says their results may help manufacturers create the next level of health monitoring and biomedical devices.

“We have introduced an easy and highly repeatable fabrication method to create a highly sensitive sensor with outstanding mechanical and electrical properties at a very low cost,” says Hoorfar.

To demonstrate its practicality, researchers built three wearable devices including a knee band, a wristband and a glove. The wristband monitored heartbeats by sensing the pulse of the artery. In an entirely different range of motion, the finger and knee bands monitored finger gestures and larger scale muscle movements during walking, running, sitting down and standing up. The results, says Hoorfar, indicate an inexpensive device that has a high-level of sensitivity, selectivity and durability.

Hoorfar and Najjaran are both members of the Okanagan node of UBC’s STITCH (SmarT Innovations for Technology Connected Health) Institute that creates and investigates advanced wearable devices.

The research, partially funded by the Natural Sciences and Engineering Research Council, was recently published in the Journal of Sensors and Actuators A: Physical.

Here’s a link to and a citation for the paper,

Low-cost ultra-stretchable strain sensors for monitoring human motion and bio-signals by Seyed Reza Larimi, Hojatollah Rezaei Nejad, Michael Oyatsi, Allen O’Brien, Mina Hoorfar, Homayoun Najjaran. Sensors and Actuators A: Physical Volume 271, 1 March 2018, Pages 182-191 [Published online February 2018] https://doi.org/10.1016/j.sna.2018.01.028

This paper is behind a paywall.

Final comments

The term ‘wearable tech’ covers a lot of ground. In addition to sensors, there are materials that harvest energy, detect poisons, etc.  making for a diverse field.

Do you want that coffee with some graphene on toast?

These scientists are excited:

For those who prefer text, here’s the Rice University Feb. 13, 2018 news release (received via email and available online here and on EurekAlert here) Note: Links have been removed),

Rice University scientists who introduced laser-induced graphene (LIG) have enhanced their technique to produce what may become a new class of edible electronics.

The Rice lab of chemist James Tour, which once turned Girl Scout cookies into graphene, is investigating ways to write graphene patterns onto food and other materials to quickly embed conductive identification tags and sensors into the products themselves.

“This is not ink,” Tour said. “This is taking the material itself and converting it into graphene.”

The process is an extension of the Tour lab’s contention that anything with the proper carbon content can be turned into graphene. In recent years, the lab has developed and expanded upon its method to make graphene foam by using a commercial laser to transform the top layer of an inexpensive polymer film.

The foam consists of microscopic, cross-linked flakes of graphene, the two-dimensional form of carbon. LIG can be written into target materials in patterns and used as a supercapacitor, an electrocatalyst for fuel cells, radio-frequency identification (RFID) antennas and biological sensors, among other potential applications.

The new work reported in the American Chemical Society journal ACS Nano demonstrated that laser-induced graphene can be burned into paper, cardboard, cloth, coal and certain foods, even toast.

“Very often, we don’t see the advantage of something until we make it available,” Tour said. “Perhaps all food will have a tiny RFID tag that gives you information about where it’s been, how long it’s been stored, its country and city of origin and the path it took to get to your table.”

He said LIG tags could also be sensors that detect E. coli or other microorganisms on food. “They could light up and give you a signal that you don’t want to eat this,” Tour said. “All that could be placed not on a separate tag on the food, but on the food itself.”

Multiple laser passes with a defocused beam allowed the researchers to write LIG patterns into cloth, paper, potatoes, coconut shells and cork, as well as toast. (The bread is toasted first to “carbonize” the surface.) The process happens in air at ambient temperatures.

“In some cases, multiple lasing creates a two-step reaction,” Tour said. “First, the laser photothermally converts the target surface into amorphous carbon. Then on subsequent passes of the laser, the selective absorption of infrared light turns the amorphous carbon into LIG. We discovered that the wavelength clearly matters.”

The researchers turned to multiple lasing and defocusing when they discovered that simply turning up the laser’s power didn’t make better graphene on a coconut or other organic materials. But adjusting the process allowed them to make a micro supercapacitor in the shape of a Rice “R” on their twice-lased coconut skin.

Defocusing the laser sped the process for many materials as the wider beam allowed each spot on a target to be lased many times in a single raster scan. That also allowed for fine control over the product, Tour said. Defocusing allowed them to turn previously unsuitable polyetherimide into LIG.

“We also found we could take bread or paper or cloth and add fire retardant to them to promote the formation of amorphous carbon,” said Rice graduate student Yieu Chyan, co-lead author of the paper. “Now we’re able to take all these materials and convert them directly in air without requiring a controlled atmosphere box or more complicated methods.”

The common element of all the targeted materials appears to be lignin, Tour said. An earlier study relied on lignin, a complex organic polymer that forms rigid cell walls, as a carbon precursor to burn LIG in oven-dried wood. Cork, coconut shells and potato skins have even higher lignin content, which made it easier to convert them to graphene.

Tour said flexible, wearable electronics may be an early market for the technique. “This has applications to put conductive traces on clothing, whether you want to heat the clothing or add a sensor or conductive pattern,” he said.

Rice alumnus Ruquan Ye is co-lead author of the study. Co-authors are Rice graduate student Yilun Li and postdoctoral fellow Swatantra Pratap Singh and Professor Christopher Arnusch of Ben-Gurion University of the Negev, Israel. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice.

The Air Force Office of Scientific Research supported the research.

Here’s a link to and a citation for the paper,

Laser-Induced Graphene by Multiple Lasing: Toward Electronics on Cloth, Paper, and Food by Yieu Chyan, Ruquan Ye†, Yilun Li, Swatantra Pratap Singh, Christopher J. Arnusch, and James M. Tour. ACS Nano DOI: 10.1021/acsnano.7b08539 Publication Date (Web): February 13, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

h/t Feb. 13, 2018 news item on Nanowerk

An exoskeleton for a cell-sized robot

A January 3, 2018 news item on phys.org announces work on cell-sized robots,

An electricity-conducting, environment-sensing, shape-changing machine the size of a human cell? Is that even possible?

Cornell physicists Paul McEuen and Itai Cohen not only say yes, but they’ve actually built the “muscle” for one.

With postdoctoral researcher Marc Miskin at the helm, the team has made a robot exoskeleton that can rapidly change its shape upon sensing chemical or thermal changes in its environment. And, they claim, these microscale machines – equipped with electronic, photonic and chemical payloads – could become a powerful platform for robotics at the size scale of biological microorganisms.

“You could put the computational power of the spaceship Voyager onto an object the size of a cell,” Cohen said. “Then, where do you go explore?”

“We are trying to build what you might call an ‘exoskeleton’ for electronics,” said McEuen, the John A. Newman Professor of Physical Science and director of the Kavli Institute at Cornell for Nanoscale Science. “Right now, you can make little computer chips that do a lot of information-processing … but they don’t know how to move or cause something to bend.”

Cornell University has produced a video of the researchers discussing their work (about 3 mins. running time)

For those who prefer text or need it to reinforce their understanding, there’s a January 2, 2018 Cornell University news release (also on EurekAlert but dated Jan. 3, 2018) by Tom Fleischman, which originated the news item,

The machines move using a motor called a bimorph. A bimorph is an assembly of two materials – in this case, graphene and glass – that bends when driven by a stimulus like heat, a chemical reaction or an applied voltage. The shape change happens because, in the case of heat, two materials with different thermal responses expand by different amounts over the same temperature change.

As a consequence, the bimorph bends to relieve some of this strain, allowing one layer to stretch out longer than the other. By adding rigid flat panels that cannot be bent by bimorphs, the researchers localize bending to take place only in specific places, creating folds. With this concept, they are able to make a variety of folding structures ranging from tetrahedra (triangular pyramids) to cubes.

In the case of graphene and glass, the bimorphs also fold in response to chemical stimuli by driving large ions into the glass, causing it to expand. Typically this chemical activity only occurs on the very outer edge of glass when submerged in water or some other ionic fluid. Since their bimorph is only a few nanometers thick, the glass is basically all outer edge and very reactive.

“It’s a neat trick,” Miskin said, “because it’s something you can do only with these nanoscale systems.”

The bimorph is built using atomic layer deposition – chemically “painting” atomically thin layers of silicon dioxide onto aluminum over a cover slip – then wet-transferring a single atomic layer of graphene on top of the stack. The result is the thinnest bimorph ever made. One of their machines was described as being “three times larger than a red blood cell and three times smaller than a large neuron” when folded. Folding scaffolds of this size have been built before, but this group’s version has one clear advantage.

“Our devices are compatible with semiconductor manufacturing,” Cohen said. “That’s what’s making this compatible with our future vision for robotics at this scale.”

And due to graphene’s relative strength, Miskin said, it can handle the types of loads necessary for electronics applications. “If you want to build this electronics exoskeleton,” he said, “you need it to be able to produce enough force to carry the electronics. Ours does that.”

For now, these tiniest of tiny machines have no commercial application in electronics, biological sensing or anything else. But the research pushes the science of nanoscale robots forward, McEuen said.

“Right now, there are no ‘muscles’ for small-scale machines,” he said, “so we’re building the small-scale muscles.”

Here’s a link to and a citation for the paper,

Graphene-based bimorphs for micron-sized, autonomous origami machines by Marc Z. Miskin, Kyle J. Dorsey, Baris Bircan, Yimo Han, David A. Muller, Paul L. McEuen, and Itai Cohen. PNAS [Proceedings of the National Academy of Sciences] 2018 doi: 10.1073/pnas.1712889115 published ahead of print January 2, 2018

This paper is behind a paywall.

Canada’s ‘Smart Cities’ will need new technology (5G wireless) and, maybe, graphene

I recently published [March 20, 2018] a piece on ‘smart cities’ both an art/science event in Toronto and a Canadian government initiative without mentioning the necessity of new technology to support all of the grand plans. On that note, it seems the Canadian federal government and two provincial (Québec and Ontario) governments are prepared to invest in one of the necessary ‘new’ technologies, 5G wireless. The Canadian Broadcasting Corporation’s (CBC) Shawn Benjamin reports about Canada’s 5G plans in suitably breathless (even in text only) tones of excitement in a March 19, 2018 article,

The federal, Ontario and Quebec governments say they will spend $200 million to help fund research into 5G wireless technology, the next-generation networks with download speeds 100 times faster than current ones can handle.

The so-called “5G corridor,” known as ENCQOR, will see tech companies such as Ericsson, Ciena Canada, Thales Canada, IBM and CGI kick in another $200 million to develop facilities to get the project up and running.

The idea is to set up a network of linked research facilities and laboratories that these companies — and as many as 1,000 more across Canada — will be able to use to test products and services that run on 5G networks.

Benjamin’s description of 5G is focused on what it will make possible in the future,

If you think things are moving too fast, buckle up, because a new 5G cellular network is just around the corner and it promises to transform our lives by connecting nearly everything to a new, much faster, reliable wireless network.

The first networks won’t be operational for at least a few years, but technology and telecom companies around the world are already planning to spend billions to make sure they aren’t left behind, says Lawrence Surtees, a communications analyst with the research firm IDC.

The new 5G is no tentative baby step toward the future. Rather, as Surtees puts it, “the move from 4G to 5G is a quantum leap.”

In a downtown Toronto soundstage, Alan Smithson recently demonstrated a few virtual reality and augmented reality projects that his company MetaVRse is working on.

The potential for VR and AR technology is endless, he said, in large part for its potential to help hurdle some of the walls we are already seeing with current networks.

Virtual Reality technology on the market today is continually increasing things like frame rates and screen resolutions in a constant quest to make their devices even more lifelike.

… They [current 4G networks] can’t handle the load. But 5G can do so easily, Smithson said, so much so that the current era of bulky augmented reality headsets could be replaced buy a pair of normal looking glasses.

In a 5G world, those internet-connected glasses will automatically recognize everyone you meet, and possibly be able to overlay their name in your field of vision, along with a link to their online profile. …

Benjamin also mentions ‘smart cities’,

In a University of Toronto laboratory, Professor Alberto Leon-Garcia researches connected vehicles and smart power grids. “My passion right now is enabling smart cities — making smart cities a reality — and that means having much more immediate and detailed sense of the environment,” he said.

Faster 5G networks will assist his projects in many ways, by giving planners more, instant data on things like traffic patterns, energy consumption, variou carbon footprints and much more.

Leon-Garcia points to a brightly lit map of Toronto [image embedded in Benjamin’s article] in his office, and explains that every dot of light represents a sensor transmitting real time data.

Currently, the network is hooked up to things like city buses, traffic cameras and the city-owned fleet of shared bicycles. He currently has thousands of data points feeding him info on his map, but in a 5G world, the network will support about a million sensors per square kilometre.

Very exciting but where is all this data going? What computers will be processing the information? Where are these sensors located? Benjamin does not venture into those waters nor does The Economist in a February 13, 2018 article about 5G, the Olympic Games in Pyeonchang, South Korea, but the magazine does note another barrier to 5G implementation,

“FASTER, higher, stronger,” goes the Olympic motto. So it is only appropriate that the next generation of wireless technology, “5G” for short, should get its first showcase at the Winter Olympics  under way in Pyeongchang, South Korea. Once fully developed, it is supposed to offer download speeds of at least 20 gigabits per second (4G manages about half that at best) and response times (“latency”) of below 1 millisecond. So the new networks will be able to transfer a high-resolution movie in two seconds and respond to requests in less than a hundredth of the time it takes to blink an eye. But 5G is not just about faster and swifter wireless connections.

The technology is meant to enable all sorts of new services. One such would offer virtual- or augmented-reality experiences. At the Olympics, for example, many contestants are being followed by 360-degree video cameras. At special venues sports fans can don virtual-reality goggles to put themselves right into the action. But 5G is also supposed to become the connective tissue for the internet of things, to link anything from smartphones to wireless sensors and industrial robots to self-driving cars. This will be made possible by a technique called “network slicing”, which allows operators quickly to create bespoke networks that give each set of devices exactly the connectivity they need.

Despite its versatility, it is not clear how quickly 5G will take off. The biggest brake will be economic. [emphasis mine] When the GSMA, an industry group, last year asked 750 telecoms bosses about the most salient impediment to delivering 5G, more than half cited the lack of a clear business case. People may want more bandwidth, but they are not willing to pay for it—an attitude even the lure of the fanciest virtual-reality applications may not change. …

That may not be the only brake, Dexter Johnson in a March 19, 2018 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website), covers some of the others (Note: Links have been removed),

Graphene has been heralded as a “wonder material” for well over a decade now, and 5G has been marketed as the next big thing for at least the past five years. Analysts have suggested that 5G could be the golden ticket to virtual reality and artificial intelligence, and promised that graphene could improve technologies within electronics and optoelectronics.

But proponents of both graphene and 5G have also been accused of stirring up hype. There now seems to be a rising sense within industry circles that these glowing technological prospects will not come anytime soon.

At Mobile World Congress (MWC) in Barcelona last month [February 2018], some misgivings for these long promised technologies may have been put to rest, though, thanks in large part to each other.

In a meeting at MWC with Jari Kinaret, a professor at Chalmers University in Sweden and director of the Graphene Flagship, I took a guided tour around the Pavilion to see some of the technologies poised to have an impact on the development of 5G.

Being invited back to the MWC for three years is a pretty clear indication of how important graphene is to those who are trying to raise the fortunes of 5G. But just how important became more obvious to me in an interview with Frank Koppens, the leader of the quantum nano-optoelectronic group at Institute of Photonic Sciences (ICFO) just outside of Barcelona, last year.

He said: “5G cannot just scale. Some new technology is needed. And that’s why we have several companies in the Graphene Flagship that are putting a lot of pressure on us to address this issue.”

In a collaboration led by CNIT—a consortium of Italian universities and national laboratories focused on communication technologies—researchers from AMO GmbH, Ericsson, Nokia Bell Labs, and Imec have developed graphene-based photodetectors and modulators capable of receiving and transmitting optical data faster than ever before.

The aim of all this speed for transmitting data is to support the ultrafast data streams with extreme bandwidth that will be part of 5G. In fact, at another section during MWC, Ericsson was presenting the switching of a 100 Gigabits per second (Gbps) channel based on the technology.

“The fact that Ericsson is demonstrating another version of this technology demonstrates that from Ericsson’s point of view, this is no longer just research” said Kinaret.

It’s no mystery why the big mobile companies are jumping on this technology. Not only does it provide high-speed data transmission, but it also does it 10 times more efficiently than silicon or doped silicon devices, and will eventually do it more cheaply than those devices, according to Vito Sorianello, senior researcher at CNIT.

Interestingly, Ericsson is one of the tech companies mentioned with regard to Canada’s 5G project, ENCQOR and Sweden’s Chalmers University, as Dexter Johnson notes, is the lead institution for the Graphene Flagship.. One other fact to note, Canada’s resources include graphite mines with ‘premium’ flakes for producing graphene. Canada’s graphite mines are located (as far as I know) in only two Canadian provinces, Ontario and Québec, which also happen to be pitching money into ENCQOR. My March 21, 2018 posting describes the latest entry into the Canadian graphite mining stakes.

As for the questions I posed about processing power, etc. It seems the South Koreans have found answers of some kind but it’s hard to evaluate as I haven’t found any additional information about 5G and its implementation in South Korea. If anyone has answers, please feel free to leave them in the ‘comments’. Thank you.

Graphite ‘gold’ rush?

Someone in Germany (I think) is very excited about graphite, more specifically, there’s excitement around graphite flakes located in the province of Québec, Canada. Although, the person who wrote this news release might have wanted to run a search for ‘graphite’ and ‘gold rush’. The last graphite gold rush seems to have taken place in 2013.

Here’s the March 1, 2018 news release on PR Newswire (Cision), Note: Some links have been removed),

PALM BEACH, Florida, March 1, 2018 /PRNewswire/ —

MarketNewsUpdates.com News Commentary

Much like the gold rush in North America in the 1800s, people are going out in droves searching for a different kind of precious metal, graphite. The thing your third grade pencils were made of is now one of the hottest commodities on the market. This graphite is not being mined by your run-of-the-mill old-timey soot covered prospectors anymore. Big mining companies are all looking for this important resource integral to the production of lithium ion batteries due to the rise in popularity of electric cars. These players include Graphite Energy Corp. (OTC: GRXXF) (CSE: GRE), Teck Resources Limited (NYSE: TECK), Nemaska Lithium (TSX: NMX), Lithium Americas Corp. (TSX: LAC), and Cruz Cobalt Corp. (TSX-V: CUZ) (OTC: BKTPF).

These companies looking to manufacturer their graphite-based products, have seen steady positive growth over the past year. Their development of cutting-edge new products seems to be paying off. But in order to continue innovating, these companies need the graphite to do it. One junior miner looking to capitalize on the growing demand for this commodity is Graphite Energy Corp.

Graphite Energy is a mining company, that is focused on developing graphite resources. Graphite Energy’s state-of-the-art mining technology is friendly to the environment and has indicate graphite carbon (Cg) in the range of 2.20% to 22.30% with average 10.50% Cg from their Lac Aux Bouleaux Graphite Property in Southern Quebec [Canada].

Not Just Any Graphite Will Do

Graphite is one of the most in demand technology metals that is required for a green and sustainable world. Demand is only set to increase as the need for lithium ion batteries grows, fueled by the popularity of electric vehicles. However, not all graphite is created equal. The price of natural graphite has more than doubled since 2013 as companies look to maintain environmental standards which the use of synthetic graphite cannot provide due to its pollutant manufacturing process. Synthetic graphite is also very expensive to produce, deriving from petroleum and costing up to ten times as much as natural graphite. Therefore manufacturers are interested in increasing the proportion of natural graphite in their products in order to lower their costs.

High-grade large flake graphite is the solution to the environmental issues these companies are facing. But there is only so much supply to go around. Recent news by Graphite Energy Corp. on February 26th [2018] showed promising exploratory results. The announcement of the commencement of drilling is a positive step forward to meeting this increased demand.

Everything from batteries to solar panels need to be made with this natural high-grade flake graphite because what is the point of powering your home with the sun or charging your car if the products themselves do more harm than good to the environment when produced. However, supply consistency remains an issue since mines have different raw material impurities which vary from mine to mine. Certain types of battery technology already require graphite to be almost 100% pure. It is very possible that the purity requirements will increase in the future.

Natural graphite is also the basis of graphene, the uses of which seem limited only by scientists’ imaginations, given the host of new applications announced daily. In a recent study by ResearchSEA, a team from the Ocean University of China and Yunnan Normal University developed a highly efficient dye-sensitized solar cell using a graphene layer. This thin layer of graphene will allow solar panels to generate electricity when it rains.

Graphite Energy Is Keeping It Green

Whether it’s the graphite for the solar panels that will power the homes of tomorrow, or the lithium ion batteries that will fuel the latest cars, these advancements need to made in an environmentally conscious way. Mining companies like Graphite Energy Corp. specialize in the production of environmentally friendly graphite. The company will be producing its supply of natural graphite with the lowest environmental footprint possible.

From Saltwater To Clean Water Using Graphite

The world’s freshwater supply is at risk of running out. In order to mitigate this global disaster, worldwide spending on desalination technology was an estimated $16.6 billion in 2016. Due to the recent intense droughts in California, the state has accelerated the construction of desalination plants. However, the operating costs and the impact on the environment due to energy requirements for the process, is hindering any real progress in the space, until now.

Jeffrey Grossman, a professor at MIT’s [Massachusetts Institute of Technology, United States] Department of Materials Science and Engineering (DMSE), has been looking into whether graphite/graphene might reduce the cost of desalination.

“A billion people around the world lack regular access to clean water, and that’s expected to more than double in the next 25 years,” Grossman says. “Desalinated water costs five to 10 times more than regular municipal water, yet we’re not investing nearly enough money into research. If we don’t have clean energy we’re in serious trouble, but if we don’t have water we die.”

Grossman’s lab has demonstrated strong results showing that new filters made from graphene could greatly improve the energy efficiency of desalination plants while potentially reducing other costs as well.

Graphite/Graphene producers like Graphite Energy Corp. (OTC: GRXXF) (CSE: GRE) are moving quickly to provide the materials necessary to develop this new generation of desalination plants.

Potential Comparables

Cruz Cobalt Corp. (TSX-V: CUZ) (OTC: BKTPF) Cruz Cobalt Corp. is cobalt mining company involved in the identification, acquisition and exploration of mineral properties. The company’s geographical segments include the United States and Canada. They are focused on acquiring and developing high-grade Cobalt projects in politically stable, environmentally responsible and ethical mining jurisdictions, essential for the rapidly growing rechargeable battery and renewable energy.

Nemaska Lithium (TSE: NMX.TO)

Nemaska Lithium is lithium mining company. The company is a supplier of lithium hydroxide and lithium carbonate to the emerging lithium battery market that is largely driven by electric vehicles. Nemaska mining operations are located in the mining friendly jurisdiction of Quebec, Canada. Nemaska Lithium has received a notice of allowance of a main patent application on its proprietary process to produce lithium hydroxide and lithium carbonate.

Lithium Americas Corp. (TSX: LAC.TO)

Lithium Americas is developing one of North America’s largest lithium deposits in northern Nevada. It operates nearly two lithium projects namely Cauchari-Olaroz project which is located in Argentina, and the Lithium Nevada project located in Nevada. The company manufactures specialty organoclay products, derived from clays, for sale to the oil and gas and other sectors.

Teck Resources Limited (NYSE: TECK)

Teck Resources Limited is a Canadian metals and mining company.Teck’s principal products include coal, copper, zinc, with secondary products including lead, silver, gold, molybdenum, germanium, indium and cadmium. Teck’s diverse resources focuses on providing products that are essential to building a better quality of life for people around the globe.

Graphite Mining Today For A Better Tomorrow

Graphite mining will forever be intertwined with the latest advancements in science and technology. Graphite deserves attention for its various use cases in automotive, energy, aerospace and robotics industries. In order for these and other industries to become sustainable and environmentally friendly, a reliance on graphite is necessary. Therefore, this rapidly growing sector has the potential to fuel investor interest in the mining space throughout 2018. The near limitless uses of graphite has the potential to impact every facet of our lives. Companies like Graphite Energy Corp. (OTC: GRXXF); (CSE: GRE) is at the forefront in this technological revolution.

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Hopefully my insertions of ‘Canada’ and the ‘United States’ help to clarify matters. North America and the United States are not synonyms although they are sometimes used synonymously.

There is another copy of this news release on Wall Street Online (Deutschland), both in English and German.By the way, that was my first clue that there might be some German interest. The second clue was the Graphite Energy Corp. homepage. Unusually for a company with ‘headquarters’ in the Canadian province of British Columbia, there’s an option to read the text in German.

Graphite Energy Corp. seems to be a relatively new player in the ‘rush’ to mine graphite flakes for use in graphene-based applications. One of my first posts about mining for graphite flakes was a July 26, 2011 posting concerning Northern Graphite and their mining operation (Bissett Creek) in Ontario. I don’t write about them often but they are still active if their news releases are to be believed. The latest was issued February 28, 2018 and offers “financial metrics for the Preliminary Economic Assessment (the “PEA”) on the Company’s 100% owned Bissett Creek graphite project.”

The other graphite mining company mentioned here is Lomiko Metals. The latest posting here about Lomiko is a December 23, 2015 piece regarding an analysis and stock price recommendation by a company known as SeeThruEquity. Like Graphite Energy Corp., Lomiko’s mines are located in Québec and their business headquarters in British Columbia. Lomiko has a March 16, 2018 news release announcing its reinstatement for trading on the TSX (Toronto Stock Exchange),

(Vancouver, B.C.) Lomiko Metals Inc. (“Lomiko”) (“Lomiko”) (TSX-V: LMR, OTC: LMRMF, FSE: DH8C) announces it has been successful in its reinstatement application with the TSX Venture Exchange and trading will begin at the opening on Tuesday, March 20, 2018.

Getting back to the flakes, here’s more about Graphite Energy Corp.’s mine (from the About Lac Aux Bouleaux webpage),

Lac Aux Bouleaux

The Lac Aux Bouleaux Property is comprised of 14 mineral claims in one contiguous block totaling 738.12 hectares land on NTS 31J05, near the town of Mont-Laurier in southern Québec. Lac Aux Bouleaux “LAB” is a world class graphite property that borders the only producing graphite in North America [Note: There are three countries in North America, Canada, the United States, and Mexico. Québec is in Canada.]. On the property we have a full production facility already built which includes an open pit mine, processing facility, tailings pond, power and easy access to roads.

High Purity Levels

An important asset of LAB is its metallurgy. The property contains a high proportion of large and jumbo flakes from which a high purity concentrate was proven to be produced across all flakes by a simple flotation process. The concentrate can then be further purified using the province’s green and affordable hydro-electricity to be used in lithium-ion batteries.

The geological work performed in order to verify the existing data consisted of visiting approachable graphite outcrops, historical exploration and development work on the property. Large flake graphite showings located on the property were confirmed with flake size in the range of 0.5 to 2 millimeters, typically present in shear zones at the contact of gneisses and marbles where the graphite content usually ranges from 2% to 20%. The results of the property are outstanding showing to have jumbo flake natural graphite.

An onsite mill structure, a tailing dam facility, and a historical open mining pit is already present and constructed on the property. The property is ready to be put into production based on the existing infrastructure already built. The company would hope to be able to ship by rail its mined graphite directly to Teslas Gigafactory being built in Nevada [United States] which will produce 35GWh of batteries annually by 2020.

Adjacent Properties

The property is located in a very active graphite exploration and production area, adjacent to the south of TIMCAL’s Lac des Iles graphite mine in Quebec which is a world class deposit producing 25,000 tonnes of graphite annually. There are several graphite showings and past producing mines in its vicinity, including a historic deposit located on the property.

The open pit mine in operation since 1989 with an onsite plant ranked 5th in the world production of graphite. The mine is operated by TIMCAL Graphite & Carbon which is a subsidiary of Imerys S.A., a French multinational company. The mine has an average grade of 7.5% Cg (graphite carbon) and has been producing 50 different graphite products for various graphite end users around the globe.

Canadians! We have great flakes!

Bulletproof graphene

A December 18, 2017 news item on Nanowerk announces research that demonstrates graphene can be harder than diamonds (Note: A link has been removed),

Imagine a material as flexible and lightweight as foil that becomes stiff and hard enough to stop a bullet on impact. In a newly published paper in Nature Nanotechnology (“Ultrahard carbon film from epitaxial two-layer graphene”), researchers across The City University of New York (CUNY) describe a process for creating diamene: flexible, layered sheets of graphene that temporarily become harder than diamond and impenetrable upon impact.

Scientists at the Advanced Science Research Center (ASRC) at the Graduate Center, CUNY, worked to theorize and test how two layers of graphene — each one-atom thick — could be made to transform into a diamond-like material upon impact at room temperature. The team also found the moment of conversion resulted in a sudden reduction of electric current, suggesting diamene could have interesting electronic and spintronic properties. The new findings will likely have applications in developing wear-resistant protective coatings and ultra-light bullet-proof films.

A December 18, 2017 CUNY news release, which originated the news item, provides a little more detail,

“This is the thinnest film with the stiffness and hardness of diamond ever created,” said Elisa Riedo, professor of physics at the ASRC and the project’s lead researcher. “Previously, when we tested graphite or a single atomic layer of graphene, we would apply pressure and feel a very soft film. But when the graphite film was exactly two-layers thick, all of a sudden we realized that the material under pressure was becoming extremely hard and as stiff, or stiffer, than bulk diamond.”

Angelo Bongiorno, associate professor of chemistry at CUNY College of Staten Island and part of the research team, developed the theory for creating diamene. He and his colleagues used atomistic computer simulations to model potential outcomes when pressurizing two honeycomb layers of graphene aligned in different configurations. Riedo and other team members then used an atomic force microscope to apply localized pressure to two-layer graphene on silicon carbide substrates and found perfect agreement with the calculations. Experiments and theory both show that this graphite-diamond transition does not occur for more than two layers or for a single graphene layer.

“Graphite and diamonds are both made entirely of carbon, but the atoms are arranged differently in each material, giving them distinct properties such as hardness, flexibility and electrical conduction,” Bongiorno said. “Our new technique allows us to manipulate graphite so that it can take on the beneficial properties of a diamond under specific conditions.”

The research team’s successful work opens up possibilities for investigating graphite-to-diamond phase transition in two-dimensional materials, according to the paper. Future research could explore methods for stabilizing the transition and allow for further applications for the resulting materials.

There’s an artist’s representation of a bullet’s impact on graphene,

By applying pressure at the nanoscale with an indenter to two layers of graphene, each one-atom thick, CUNY researchers transformed the honeycombed graphene into a diamond-like material at room temperature. Photo credit: Ella Maru Studio Courtesy: CUNY

Here’s a link to and a citation for the paper,

Ultrahard carbon film from epitaxial two-layer graphene by Yang Gao, Tengfei Cao, Filippo Cellini, Claire Berger, Walter A. de Heer, Erio Tosatti, Elisa Riedo, & Angelo Bongiorno. Nature Nanotechnology (2017) doi:10.1038/s41565-017-0023-9 Published online: 18 December 2017

This paper is behind a paywall.

Manipulating graphene’s conductivity with honey

Honey can be used for many things, to heal wounds, for advice (You catch more flies with honey), to clean your hair (see suggestion no. 19 here) and, even, scientific inspiration according to a Sept. 22, 2017 news item on phys.org,

Dr. Richard Ordonez, a nanomaterials scientist at the Space and Naval Warfare Systems Center Pacific (SSC Pacific), was having stomach pains last year. So begins the story of the accidental discovery that honey—yes, the bee byproduct—is an effective, non-toxic substitute for the manipulation of the current and voltage characteristics of graphene.

The news item was originated by a Sept. 22, 2017 article by Katherine Connor (who works for  the US Space and Naval warfare Center) and placed in cemag.us,

Ordonez’ lab mate and friend Cody Hayashi gave him some store-bought honey as a Christmas gift and anti-inflammatory for his stomach, and Ordonez kept it near his work station for daily use. One day in the lab, the duo was investigating various dielectric materials they could use to fabricate a graphene transistor. First, the team tried to utilize water as a top-gate dielectric to manipulate graphene’s electrical conductivity. This approach was unsuccessful, so they proceeded with various compositions of sugar and deionized water, another electrolyte, which still resulted in negligible performance. That’s when the honey caught Ordonez’ eye, and an accidental scientific breakthrough was realized.

The finding is detailed in a paper in Nature Scientific Reports, in which the team describes how honey produces a nanometer-sized electric double layer at the interface with graphene that can be used to gate the ambipolar transport of graphene.

“As a top-gate dielectric, water is much too conductive, so we moved to sugar and de-ionized water to control the ionic composition in hopes we could reduce conductivity,” Ordonez explains. “However, sugar water didn’t work for us either because, as a gate-dielectric, there was still too much leakage current. Out of frustration, literally inches away from me was the honey Cody had bought, so we decided to drop-cast the honey on graphene to act as top-gate dielectric — I thought maybe the honey would mimic dielectric gels I read about in literature. To our surprise — everyone said it’s not going to work — we tried and it did.”

Image of the liquid-metal graphene field-effect transistor (LM-GFET) and representation of charge distribution in electrolytic gate dielectrics comprised of honey. Image: Space and Naval Warfare Systems Center

 

Ordonez, Hayashi, and a team of researchers from SSC Pacific, in collaboration with the University of Hawai′i at Mānoa, have been developing novel graphene devices as part of a Navy Innovative Science and Engineering (NISE)-funded effort to imbue the Navy with inexpensive, lightweight, flexible graphene-based devices that can be used as next-generation sensors and wearable devices.

“Traditionally, electrolytic gate transistors are made with ionic gel materials,” Hayashi says. “But you must be proficient with the processes to synthesize them, and it can take several months to figure out the correct recipe that is required for these gels to function in the environment. Some of the liquids are toxic, so experimentation must be conducted in an atmospheric-controlled environment. Honey is completely different — it performs similarly to these much more sophisticated materials, but is safe, inexpensive, and easier to use. The honey was an intermediate step towards using ionic gels, and possibly a replacement for certain applications.”

Ordonez and Hayashi envision the honey-based version of graphene products being used for rapid prototyping of devices, since the devices can be created quickly and easily redesigned based on results. Instead of having to spend months developing the materials before even beginning to incorporate it into devices, using honey allows the team to get initial tests underway without waiting for costly fabrication equipment.

Ordonez also sees a use for such products in science, technology, engineering, and math (STEM) outreach efforts, since the honey is non-toxic and could be used to teach students about graphene.

This latest innovation and publication was a follow-on from the group’s discovery last year that liquid metals can be used in place of rigid electrodes such as gold and silver to electrically contact graphene. This, coupled with research on graphene and multi-spectral detection, earned them the Federal Laboratory Consortium Far West Regional Award in the category of Outstanding Technology Development.

SSC Pacific is the naval research and development lab responsible for ensuring Information Warfare superiority for warfighters, including the areas of cyber, command and control, intelligence, surveillance and reconnaissance, and space systems.

Here’s a link to and a citation for the paper,

Rapid Fabrication of Graphene Field-Effect Transistors with Liquid-metal Interconnects and Electrolytic Gate Dielectric Made of Honey by Richard C. Ordonez, Cody K. Hayashi, Carlos M. Torres, Jordan L. Melcher, Nackieb Kamin, Godwin Severa, & David Garmire. Scientific Reports 7, Article number: 10171 (2017) doi:10.1038/s41598-017-10043-4 Published online: 31 August 2017

This paper is open access.

Liquid circuitry, shape-shifting fluids and more

I’d have to see it to believe it but researchers at the US Dept. of Energy (DOE) Lawrence Berkeley National Laboratory (LBNL) have developed a new kind of ‘bijel’ which would allow for some pretty nifty robotics. From a Sept. 25, 2017 news item on ScienceDaily,

A new two-dimensional film, made of polymers and nanoparticles and developed by researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), can direct two different non-mixing liquids into a variety of exotic architectures. This finding could lead to soft robotics, liquid circuitry, shape-shifting fluids, and a host of new materials that use soft, rather than solid, substances.

The study, reported today in the journal Nature Nanotechnology, presents the newest entry in a class of substances known as bicontinuous jammed emulsion gels, or bijels, which hold promise as a malleable liquid that can support catalytic reactions, electrical conductivity, and energy conversion.

A Sept. 25, 2017 LBNL news release (also on EurekAlert), which originated the news item, expands on the theme,

Bijels are typically made of immiscible, or non-mixing, liquids. People who shake their bottle of vinaigrette before pouring the dressing on their salad are familiar with such liquids. As soon as the shaking stops, the liquids start to separate again, with the lower density liquid – often oil – rising to the top.

Trapping, or jamming, particles where these immiscible liquids meet can prevent the liquids from completely separating, stabilizing the substance into a bijel. What makes bijels remarkable is that, rather than just making the spherical droplets that we normally see when we try to mix oil and water, the particles at the interface shape the liquids into complex networks of interconnected fluid channels.

Bijels are notoriously difficult to make, however, involving exact temperatures at precisely timed stages. In addition, the liquid channels are normally more than 5 micrometers across, making them too large to be useful in energy conversion and catalysis.

“Bijels have long been of interest as next-generation materials for energy applications and chemical synthesis,” said study lead author Caili Huang. “The problem has been making enough of them, and with features of the right size. In this work, we crack that problem.”

Huang started the work as a graduate student with Thomas Russell, the study’s principal investigator, at Berkeley Lab’s Materials Sciences Division, and he continued the project as a postdoctoral researcher at DOE’s Oak Ridge National Laboratory.

Creating a new bijel recipe

The method described in this new study simplifies the bijel process by first using specially coated particles about 10-20 nanometers in diameter. The smaller-sized particles line the liquid interfaces much more quickly than the ones used in traditional bijels, making the smaller channels that are highly valued for applications.

Illustration shows key stages of bijel formation. Clockwise from top left, two non-mixing liquids are shown. Ligands (shown in yellow) with amine groups are dispersed throughout the oil or solvent, and nanoparticles coated with carboxylic acids (shown as blue dots) are scattered in the water. With vigorous shaking, the nanoparticles and ligands form a “supersoap” that gets trapped at the interface of the two liquids. The bottom panel is a magnified view of the jammed nanoparticle supersoap. (Credit: Caili Huang/ORNL)

“We’ve basically taken liquids like oil and water and given them a structure, and it’s a structure that can be changed,” said Russell, a visiting faculty scientist at Berkeley Lab. “If the nanoparticles are responsive to electrical, magnetic, or mechanical stimuli, the bijels can become reconfigurable and re-shaped on demand by an external field.”

The researchers were able to prepare new bijels from a variety of common organic, water-insoluble solvents, such as toluene, that had ligands dissolved in it, and deionized water, which contained the nanoparticles. To ensure thorough mixing of the liquids, they subjected the emulsion to a vortex spinning at 3,200 revolutions per minute.

“This extreme shaking creates a whole bunch of new places where these particles and polymers can meet each other,” said study co-author Joe Forth, a postdoctoral fellow at Berkeley Lab’s Materials Sciences Division. “You’re synthesizing a lot of this material, which is in effect a thin, 2-D coating of the liquid surfaces in the system.”

The liquids remained a bijel even after one week, a sign of the system’s stability.

Russell, who is also a professor of polymer science and engineering at the University of Massachusetts-Amherst, added that these shape-shifting characteristics would be valuable in microreactors, microfluidic devices, and soft actuators.

Nanoparticle supersoap

Nanoparticles had not been seriously considered in bijels before because their small size made them hard to trap in the liquid interface. To resolve that problem, the researchers coated nano-sized particles with carboxylic acids and put them in water. They then took polymers with an added amine group – a derivative of ammonia – and dissolved them in the toluene.

At left is a vial of bijel stabilized with nanoparticle surfactants. On the right is the same vial after a week of inversion, showing that the nanoparticle kept the liquids from moving. (Credit: Caili Huang/ORNL)

This configuration took advantage of the amine group’s affinity to water, a characteristic that is comparable to surfactants, like soap. Their nanoparticle “supersoap” was designed so that the nanoparticles join ligands, forming an octopus-like shape with a polar head and nonpolar legs that get jammed at the interface, the researchers said.

“Bijels are really a new material, and also excitingly weird in that they are kinetically arrested in these unusual configurations,” said study co-author Brett Helms, a staff scientist at Berkeley Lab’s Molecular Foundry. “The discovery that you can make these bijels with simple ingredients is a surprise. We all have access to oils and water and nanocrystals, allowing broad tunability in bijel properties. This platform also allows us to experiment with new ways to control their shape and function since they are both responsive and reconfigurable.”

The nanoparticles were made of silica, but the researchers noted that in previous studies they used graphene and carbon nanotubes to form nanoparticle surfactants.

“The key is that the nanoparticles can be made of many materials,” said Russell.  “The most important thing is what’s on the surface.”

This is an animation of the bijel

3-D rendering of the nanoparticle bijel taken by confocal microscope. (Credit: Caili Huang/ORNL [Oak Ridge National Laboratory] and Joe Forth/Berkeley Lab)

Here’s a link to and a citation for the paper,

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants by Caili Huang, Joe Forth, Weiyu Wang, Kunlun Hong, Gregory S. Smith, Brett A. Helms & Thomas P. Russell. Nature Nanotechnology (2017) doi:10.1038/nnano.2017.182 25 September 2017

This paper is behind a paywall.