18 Sep 2014
Originally posted on Great Things from Small Things .. Nanotechnology Innovation:
Published on Sep 16, 2014
Take a look around the headquarters of MC10, a company developing electronics that can bend and flex, leading to applications such as sensors that can conform to clothing and skin. Visit physicsworld.com for more videos, webinars and podcasts.
18 Sep 2014
The very idea of fibers made of carbon nanotubes is neat, but Rice University scientists are making them neat—literally.
Why It Matters: To create strong, conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.
The single-walled carbon nanotubes in new fibers created at Rice line up like a fistful of uncooked spaghetti through a process designed by chemist Angel Martí and his colleagues.
The tricky bit, according to Martí, whose lab reported its results this month in the journal ACS Nano, is keeping the densely packed nanotubes apart before they’re drawn together into a fiber.
Rice University scientists are making carbon nanotube solutions that act as liquid crystals as a precursor to pulling them into strong, conductive fibers. Credit: Martí Group
Left to their own devices, carbon nanotubes form clumps that are perfectly wrong for turning into the kind of strong, conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.
Earlier research at Rice by chemist and chemical engineer Matteo Pasquali, a co-author on the new paper, used an acid dissolution process to keep the nanotubes separated until they could be spun into fibers. Now Martí, Pasquali and their colleagues are producing “neat” fibers with the same mechanical process, but they’re starting with a different kind of feedstock.
“Matteo’s group used chlorosulfonic acid to protonate the surface of the nanotubes,” Martí said. “That would give them a positively charged surface so they would repel each other in solution. The technique we use is exactly the opposite.”
A process revealed last year by Martí and lead authors Chengmin Jiang, a graduate student, and Avishek Saha, a Rice alumnus, starts with negatively charging carbon nanotubes by infusing them with potassium, a metal, and turning them into a kind of salt known as a polyelectrolyte. They then employ cage-like crown ethers to capture the potassium ions that would otherwise dampen the nanotubes’ ability to repel one another.
Put enough nanotubes into such a solution and they’re caught between the repellant forces and an inability to move in a crowded environment, Martí said. They’re forced to align—a defining property of liquid crystals—and this makes them more manageable.
The tubes are ultimately forced together into fibers when they are extruded through the tip of a needle. At that point, the strong van der Waals force takes over and tightly binds the nanotubes together, Martí said.
But to make macroscopic materials, the Martí team needed to pack many more nanotubes into the solution than in previous experiments. “As you start increasing the concentration, the number of nanotubes in the liquid crystalline phase becomes more abundant than those in the isotropic (disordered) phase, and that’s exactly what we needed,” Martí said.
The researchers discovered that 40 milligrams of nanotubes per milliliter gave them a thick gel after mixing at high speed and filtering out whatever large clumps remained. “It’s like a centrifuge together with a rotary drum,” Martí said of the mixing gear. “It produces unconventional forces in the solution.”
Feeding this dense nanotube gel through a narrow needle-like opening produced continuous fiber on the Pasquali lab’s equipment. The strength and stiffness of the neat fibers also approached that of the fibers previously produced with Pasquali’s acid-based process. “We didn’t make any modifications to his system and it worked perfectly,” Martí said.
The hair-width fibers can be woven into thicker cables, and the team is investigating ways to improve their electrical properties through doping the nanotubes with iodide. “The research is basically analogous to what Matteo does,” Martí said. “We used his tools but gave the process a spin with a different preparation, so now we’re the first to make neat fibers of pure carbon nanotube electrolytes. That’s very cool.”
Pasquali said that the spinning system worked with little need for adaptation because the setup is sealed. “The nanotube electrolyte solution could be protected from oxygen and water, which would have caused precipitation of the nanotubes,” he said.
“It turns out that this is not a showstopper, because we want the nanotubes to precipitate and stick to each other as soon as they exit the sealed system through the needle. The process was not hard to control, adapt and scale up once we figured out the basic science.”
Provided by Rice University
18 Sep 2014
Researchers have found a way to boost the energy density of supercapacitors through the use of more sophisticated electrodes. These electrodes are composed of hemp fibers, and they have a high energy storage capacity.
The development breakthrough has been made by a Canadian start-up company, led by Dr. David Mitlin. The idea arose from some applied thinking, when Mitlin’s group decided to see if they could make graphene-like carbons from hemp bast fibers.
From Mitlin’s research, it seems that hemp fibers can hold as much energy and power as graphene, the current favored material for supercapacitors. Supercapacitors are energy storage devices that have huge potential to transform the way future electronics are powered. Unlike batteries, which store energy chemically in the material of their electrodes, a capacitor stores energy physically, on the electrodes’ surfaces.
Mitlin’s group discovered that when hemp fibers were heated for 24 hours at a little over 350 degrees Fahrenheit this would exfoliated the material into carbon nanosheets. From the reformed material, the group constructed supercapacitors using the hemp-derived carbons as electrodes and an ionic liquid as the electrolyte. In tests, the devices performed far better than commercial supercapacitors. This was assessed by examining for energy density and across a range of temperatures. The hemp-based devices yielded energy densities as high as 12 Watt-hours per kilogram, which is two to three times higher than currently available commercial systems.
Interviewed by Phys.Org, Mitlin expands on the success so far: “Our device’s electrochemical performance is on par with or better than graphene-based devices. The key advantage is that our electrodes are made from biowaste using a simple process, and therefore, are much cheaper than graphene.”
The parallels with graphene are a reference to the considerable research that has gone into to new variant of carbon. Graphene is a single-layer mesh of carbon atoms. Graphene is considered the new “wonder material,” due its durability and lightness. Graphene can be described as a one-atom thick layer of graphite.
Mitlin’s new research could trigger the electronic industry to move in a new direction. The research group are currently preparing the hemp-based prototype supercapacitor for small-scale manufacturing.
Aircraft designer Titan Aerospace unveiled recently its Solara 50 and 60 unmanned aircrafts, the world’s first atmospheric satellites powered by the sun with a mission range of over 4 million kilometres. According to reports, Solara 50 and 60 can be launched at night using power from internal battery banks. Solara 50 can travel at 104 kilometres an hour (about 64 MPH).
An atmospheric satellite is a drone that can conduct most of the operations of an orbital satellite, but is much cheaper and more versatile.
When the sun rises, the solar panels covering the crafts’ wings and tails, store enough energy to allow them ascend to a position of 20 km above the sea level and to stay aloft continuously for five years, without ever having to land and refuel. The aircrafts will operate in an atmospheric sweet spot known as the tropopause where winds are generally less than 5 knots.
Despite its massive dimensions, Solara 50 only weighs about 160 kg, and can carry a payload of 32 kg. According to reports, differently from satellites, it is possible to get the payload back at the end of its five years endurance.
According to reports, smaller versions of Solara have already flown, and Titan Aerospace is planning to start selling operational systems in less than a year which opens up possibilities like regional internet or a version of Google Maps with real-time images. Among the applications of a Solara aircraft there are disaster recovery, weather monitoring, communications relay, oceanographic research and earth imaging
Scientists using lasers at a Science and Technology Facilities Council (STFC) facility in the UK believe that they are a step closer to finding a replacement for silicon chips that are faster and use less energy than at present. The team has tested the behaviour of bilayer graphene to discover whether or not it could be used as a semiconductor. Their results suggest that it could replace silicon transistors in electronic circuits.
|STFC’s Dr Emma Springate, one of the research team, with the Artemis laser.|
|Graphene is pure carbon in the form of a very thin, almost transparent sheet, one atom thick. It is known as a ‘miracle material’ because of its remarkable strength and efficiency in conducting heat and electricity.|
|In its current form graphene is not suitable for transistors, which are the foundation of all modern electronics. For a transistor to be technologically viable, it must be able to ‘switch off’ so that only a small electric current flows through its gate when in standby state. Graphene does not have a band gap so cannot switch off.|
|The research team, led by Professor Philip Hofmann from Aarhus University in Denmark, used a new material – bilayer graphene – in which two layers of graphene are placed one on top of the other, leaving a small band gap to encourage the transfer of energy between layers (“Ultrafast Dynamics of Massive Dirac Fermions in Bilayer Graphene”).|
|Using Artemis at STFC’s Central Laser Facility, which is based at the Rutherford Appleton Laboratory in Oxfordshire, the researchers fired ultra-short pump laser pulses at the bilayer graphene sample, boosting electrons into the conduction band.|
|A second short, extreme ultraviolet, wavelength pulse then ejected electrons from the sample. These were collected and analysed to provide a snapshot of the energies and movement of the electrons.|
|“We took a series of these measurements, varying the time delay between the infrared laser pump and extreme ultraviolet probe, and sequenced them into a movie,“ said STFC’s Dr Cephise Cacho, one of the research team. “To see how the fast-moving electrons behave, each frame of the movie has to be separated by just a fraction of a billionth of a second.”|
|Professor Hofmann said, “What we’ve shown with this research is that our sample behaves as a semiconductor, and isn’t short-circuited by defects.”|
|There can be imperfections in bilayer graphene as the layers sometimes become misaligned.|
|The results of this research, in which the graphene showed no defects, suggest that further technological effort should be carried out to minimise imperfections. Once this is done, there is a chance that the switch-off performance of bilayer graphene can be boosted enough to challenge silicon-based devices.|
|Graphene transistors could make smaller, faster electronic chips than are achievable with silicon. Eventually more and more transistors could be placed onto a single microchip to produce faster, more powerful processors for use in electronic equipment.|
|Source: Science and Technology Facilities Council|
As computer chips continue to get smaller and more powerful, the field of electronics is approaching some severe limits. “Once a device becomes too small it falls prey to the strange laws of the quantum world,” says University of Saskatchewan researcher Neil Johnson, who is using the Canadian Light Source synchrotron to help develop the next generation of computer materials. Johnson is a member of Canada Research Chair Alexander Moewes’ group of graduate students studying the nature of materials using synchrotron radiation.
His work focuses on silicene, a recent and exciting addition to the class of two-dimensional materials. Silicene is made up of an almost flat hexagonal pattern of silicon atoms. Every second atom in each hexagonal ring is slightly lifted, resulting in a buckled sheet that looks the same from the top or the bottom. In 2012, mere months before Johnson began to study silicene, it was discovered and first created by the research group of Prof. Guy Le Lay of Aix-Marseille University, using silver as a base for the thin film.
The Le Lay group is the world-leader in silicene growth, and taught Johnson and his colleagues how to make it at the CLS themselves. “I read the paper when the Le Lay announced they had made silicene, and within three or four months, Alex had arranged for us to travel down to the Advanced Light Source with these people who had made it for the first time,” says Johnson. It was an exciting collaboration for the young physicist. “This paper had already been cited over a hundred times in a matter of months. It was a major paper, and we were going to measure this new material that no one had really started doing experiments on yet.” The most pressing question facing silicene research was its potential as a semiconductor.
Today, most electronics use silicon as a switch, and researchers looking for new materials to manage quantum effects in computing could easily use the 2-D version if it was also semiconducting. Calculations had shown that because of the special buckling of silicene, it would have what’s called a Dirac cone – a special electronic structure that could allow researchers to tune the band gap, or the energy space between electron levels. The band gap is what makes a semiconductor: if the space is too small, the material is simply a conductor. Too large, and there is no conduction at all. Since silicene has only ever been made on a silver base, the materials community also wondered if silicene would maintain its semiconducting properties in this condition. Though its atomic structure is slightly different than freestanding silicene, it was still predicted to have a band gap.
However, silver is a metal, which may make the silicene act as a metal as well. No one really knew how silicene would behave on its silver base. To adapt the Le Lay group’s silicene-growing process to the equipment at the CLS took several days of work. Though their team had succeeded in silicene synthesis at the Advanced Light Source at Berkeley lab, they had no way to keep those samples under vacuum to prevent them from oxygen damage. Thanks to the work of fellow beamteam members Drs. David Muir and Israel Perez, samples grown at the CLS could be produced, transported and measured in a matter of hours without ever leaving a vacuum chamber.
|Johnson grew the silicene sheets at the Resonant Elastic and Inelastic X-ray Scattering (REIXS), beamline, then transferred them in a vacuum to the XAS/XES endstation for analysis. Finally, Johnson could find the answer to the silicene question.|
|“I didn’t really know what to expect until I saw the XAS and XES on the same energy scale, and I thought to myself, that looks like a metal,” says Johnson.|
|And while that result is unfortunate for those searching for a new computing wonder material, it does provide some vital information to that search.|
|“Our result does help to guide the hunt for 2-D silicon in the future, suggesting that metallic substrates should be avoided at all costs,” Johnson explains. “We’re hopeful that we can grow a similar structure on other substrates, ideally ones that leave the semiconducting nature of silicene intact.”|
|That work is already in process, with Johnson and his colleagues planning to explore three other growing bases this summer, along with multilayers and nanoribbons of silicene.|
|Source: Canadian Light Source|
18 Sep 2014
Engineers from the Energy Department’s Idaho National Laboratory and the National Renewable Energy Laboratory identified a new way to launch economically viable hydrogen fueling stations for FCEVs in Honolulu, Hawaii, based on a report titled “Hydrogen Fueling Station in Honolulu, Hawaii.”
While that’s great news for the sunny state, the report’s findings could also have a broad national impact.
The engineers assessed the technical and economic feasibility of developing a vacant, undeveloped General Services Administration-owned property into an income-producing site equipped with a hydrogen fueling station and a covered 175-stall parking structure with roof-top solar panels. According to the analysis, the solar energy system could generate about 700 kilowatts of power per day that would be used to produce hydrogen from water, through a process called electrolysis.
The use of hydrogen fuel cells in passenger vehicles improves energy efficiency when compared to standard internal combustion engines that power most vehicles on the roads today. With only water coming out of the tailpipe, FCEVs are both more efficient and environmentally friendly.
The challenge lies in producing the hydrogen. Fueling infrastructure is a major barrier to wide-scale adoption, so innovative ways of building cost-effective hydrogen fueling stations are essential to the technology’s widespread adoption in the United States.
The feasibility study was conducted jointly between the Office of Energy Efficiency and Renewable Energy’s (EERE’s) Federal Energy Management Program and Fuel Cell Technologies Office and the General Services Administration. The report concludes that the proposed station will enable the third-party owner to combine income streams by selling excess solar power back to the grid, leasing the covered parking spaces, and selling hydrogen—at competitive prices—to fuel the FCEVs. These FCEVs could include cars, transit buses, and even shuttle buses.
The multi-purpose station detailed in the report would provide a flagship installation in a highly visible site in downtown Honolulu. This station will also demonstrate that producing affordable, renewable hydrogen that benefits the environment and the community is feasible using technologies available today.
Solid objects that are invisible to the naked eye, powering devices with your own sweat, reversible adhesion that will enable devices to be attached to anything, anywhere – these were some of the ideas discussed by University of Auckland senior lecturer, Dr Michelle Dickinson, in her hour-long session on nanotechnology at Microsoft’s TechEd 2014.
“The marketplace today is selling a lot of old stuff, and we are buying it because that is the only thing around. There is so much more that we can do with nanotechnology that is possible, but does not make marketing sense to display or sell,” said Dickinson during her speech.
Standing in front of a packed Skycity Theatre audience in Auckland, Dickinson explained nanotechnology to be work on elements at a tiny scale. She demonstrated some of the things that are enabled by nanotechnology today, while tracing her own history and drive in forming NZ’s only nanomechanical laboratory.
“Today, we can make metamaterial that makes light go around devices rather than be reflected by them. We can cloak devices like that. We have nanofluids that will prove to be the next big cooling technology in most smart devices. I talked about the water cooling in the Surface Pro 3 yesterday in my keynote. Pfft! Nanofluids will be the way of the future,” she said.
Device coatings, superhydrophobicity, which makes surfaces highly difficult to get damp, reversible adhesion and bio-batteries are all possible today, according to Dickinson.
“I worked on reversible adhesion by watching geckos and imitating the nano hairs that they have on their limbs. These nano hairs enable devices to be attached to any number of surfaces and you can take them off again. Think about that. You don’t need tape anymore. You can attach whatever device you want to anything you want.
“Bio-batteries are also possible. Much like temporary tattoos attach to your skin, your sweat can be used to power devices. Imagine what that can mean for the likes of pacemakers. They can be powered with your body for as long as you need,” said Dickinson.
Speaking about nanotechnology for the future, Dickinson talked about some of the work that she is currently doing in her lab in NZ.
“I am currently studying how brain cells go astray and stop communicating. This is what happens in the case of diseases like Alzheimers. Nanotechnology will be able to help. I am also engaged in looking to areas where nanotechnology can become hunters. Nano particles can be constructed and injected into the body, after which they find and bond only with cancer cells. Once they have done so, light can be shone through to heat these nano particles, and in heating they will kill the cells they are attached to. This affects only the cancer cells. What does that mean? I don’t see chemotherapy as an option for long,” she said.
For all its capabilities though, nanotechnology is not yet at a stage where there are little animated robots with arms and legs walking around.
“Will nanobots take over the world one day? Yes. But they don’t exist today. All we have currently are inanimate nanotechnology,” said Dickinson.
Her highly interactive session was part of the second day of Microsoft’s TechEd 2014 taking place in Auckland this year. The four-day event will bring together around 2000 IT developers, tinkerers, vendors and partners to discuss the latest developments in Microsoft and its technologies.
- TechEd 2014: Microsoft kicks off annual event with three keynotes
- TechEd 2014: Building and managing a global engineering team made simple
12 Sep 2014
Researchers at Chalmers University of Technology are first to show the use of sound to communicate with an artificial atom. They can thereby demonstrate phenomena from quantum physics with sound taking on the role of light. The results will be published in the journal Science.
The interaction between atoms and light is well known and has been studied extensively in the field of quantum optics. However, to achieve the same kind of interaction with sound waves has been a more challenging undertaking. The Chalmers researchers have now succeeded in making acoustic waves couple to an artificial atom. The study was done in collaboration between experimental and theoretical physicists.
“We have opened a new door into the quantum world by talking and listening to atoms”, says Per Delsing, head of the experimental research group. “Our long term goal is to harness quantum physics so that we can benefit from its laws, for example in extremely fast computers. We do this by making electrical circuits which obey quantum laws, that we can control and study.”
An artificial atom is an example of such a quantum electrical circuit. Just like a regular atom, it can be charged up with energy which it subsequently emits in the form of a particle. This is usually a particle of light, but the atom in the Chalmers experiment is instead designed to both emit and absorb energy in the form of sound.
“According to the theory, the sound from the atom is divided into quantum particles”, says Martin Gustafsson, the article’s first author. “Such a particle is the weakest sound that can be detected.”
Since sound moves much slower than light, the acoustic atom opens entire new possibilities for taking control over quantum phenomena.
“Due to the slow speed of sound, we will have time to control the quantum particles while they travel” says Martin Gustafsson. “This is difficult to achieve with light, which moves 100,000 times more quickly.”
The low speed of sound also implies that it has a short wavelength compared to light. An atom that interacts with light waves is always much smaller than the wavelength. However, compared to the wavelength of sound, the atom can be much larger, which means that its properties can be better controlled. For example, one can design the atom to couple only to certain acoustic frequencies or make the interaction with the sound extremely strong.
The frequency used in the experiment is 4.8 gigahertz, close to the microwave frequencies common in modern wireless networks. In musical terms, this corresponds approximately to a D28, about 20 octaves above the highest note on a grand piano.
At such high frequencies, the wavelength of the sound becomes short enough that it can be guided along the surface of a microchip. On the same chip, the researchers have placed an artificial atom, which is 0.01 millimeters long and made of a superconducting material.
12 Sep 2014
The surface of graphene, a one atom thick sheet of carbon, can be randomly decorated with oxygen to create graphene oxide; a form of graphene that could have a significant impact on the chemical, pharmaceutical and electronic industries. Applied as paint, it could provide an ultra-strong, non-corrosive coating for a wide range of industrial applications.
Graphene oxide solutions can be used to paint various surfaces ranging from glass to metals to even conventional bricks. After a simple chemical treatment, the resulting coatings behave like graphite in terms of chemical and thermal stability but become mechanically nearly as tough as graphene, the strongest material known to man.
The team led by Dr Rahul Nair and Nobel laureate Sir Andre Geim demonstrated previously that multilayer films made from graphene oxide are vacuum tight under dry conditions but, if expose to water or its vapour, act as molecular sieves allowing passage of small molecules below a certain size. Those findings could have huge implications for water purification.
Credit: AlexanderAlUS/Wikipedia/CC BY-SA 3.0
This contrasting property is due to the structure of graphene oxide films that consist of millions of small flakes stacked randomly on top of each other but leave nano-sized capillaries between them. Water molecules like to be inside these nanocapillaries and can drag small atoms and molecules along.
In an article published in Nature Communications this week, the University of Manchester team shows that it is possible to tightly close those nanocapillaries using simple chemical treatments, which makes graphene films even stronger mechanically as well as completely impermeable to everything: gases, liquids or strong chemicals. For example, the researchers demonstrate that glassware or copper plates covered with graphene paint can be used as containers for strongly corrosive acids.
The exceptional barrier properties of graphene paint have already attracted interest from many companies who now collaborate with The University of Manchester on development of new protective and anticorrosion coatings.
Dr Nair said “Graphene paint has a good chance to become a truly revolutionary product for industries that deal with any kind of protection either from air, weather elements or corrosive chemicals. Those include, for example, medical, electronics and nuclear industry or even shipbuilding, to name but the few.”
Dr Yang Su, the first author in this work added: “Graphene paint can be applied to practically any material, independently of whether it’s plastic, metal or even sand. For example, plastic films coated with graphene could be of interest for medical packaging to improve shelf life because they are less permeable to air and water vapour than conventional coatings. In addition, thin layers of graphene paint are optically transparent.”
More information: ‘Impermeable barrier films and protective coatings based on reduced graphene oxide” by Y. Su, V.G. Kravets, S.L. Wong, J. Waters, A.K. Geim & R.R. Nair, Nature Communications, 2014.