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  • richardmitnick 2:45 pm on December 17, 2016 Permalink | Reply
    Tags: , CAGE system, Graphene Studies,   

    From LBNL: “New Graphene-Based System Could Help Us ‘See’ Electrical Signaling in Heart and Nerve Cells” 

    Berkeley Logo

    Berkeley Lab

    December 16, 2016
    Glenn Roberts Jr.
    geroberts@lbl.gov
    510-486-5582

    1
    This photo shows the setup for a system known as CAGE (Critically coupled waveguide-Amplified Graphene Electric field imaging device) that is designed to precisely record the properties of faint electrical signals using an infrared laser and a layer of graphene. The CAGE platform can be used to image the electrical signals of living cells. (Credit: Halleh Balch and Jason Horng/Berkeley Lab and UC Berkeley)

    Scientists have enlisted the exotic properties of graphene, a one-atom-thick layer of carbon, to function like the film of an incredibly sensitive camera system in visually mapping tiny electric fields in a liquid. Researchers hope the new method will allow more extensive and precise imaging of the electrical signaling networks in our hearts and brains.

    The ability to visually depict the strength and motion of very faint electrical fields could also aid in the development of so-called lab-on-a-chip devices that use very small quantities of fluids on a microchip-like platform to diagnose disease or aid in drug development, for example, or that automate a range of other biological and chemical analyses.

    The setup could potentially be adapted for sensing or trapping specific chemicals, too, and for studies of light-based electronics (a field known as optoelectronics).

    A new way to visualize electric fields

    “This was a completely new, innovative idea that graphene could be used as a material to sense electrical fields in a liquid,” said Jason Horng, a co-lead author of a study published Dec. 16 in Nature Communications that details the first demonstration of this graphene-based imaging system. Horng is affiliated with the Kavli Energy NanoSciences Institute, a joint institute at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, and is a postdoctoral researcher at UC Berkeley.

    2
    This chart, produced using imaging data from the CAGE system, maps out a tiny electrical field in a fluid as the field dissipates over time. The strength of the field is color-coded, with yellow showing its peak and dark blue showing the weakest field strength. This chart covers the first 70 milliseconds (thousandths of a second) after the field is generated, and the area covered by the field is represented in microns, or millionths of a meter. (Credit: Halleh Balch and Jason Horng/Berkeley Lab and UC Berkeley)

    The idea sprang from a conversation between Feng Wang, a faculty scientist in Berkeley Lab’s Materials Sciences Division whose research focuses on the control of light-matter interactions at the nanoscale, and Bianxiao Cui, who leads a research team at Stanford University that specializes in the study of nerve-cell signaling. Wang is also a UC Berkeley associate professor of physics, and Cui is an associate professor of chemistry at Stanford University.

    “The basic concept was how graphene could be used as a very general and scalable method for resolving very small changes in the magnitude, position, and timing pattern of a local electric field, such as the electrical impulses produced by a single nerve cell,” said Halleh B. Balch, a co-lead author in the work. Balch is also affiliated with the Kavli Energy NanoSciences Institute and is a physics PhD student at UC Berkeley.

    “One of the outstanding problems in studying a large network of cells is understanding how information propagates between them,” Balch said.

    3
    This animation shows the appearance and dissipation of an electric field recorded using the CAGE system. The strength of the field is color-coded, with yellow showing the strongest peak and dark blue showing the weakest measure. (Credit: Halleh Balch and Jason Horng/Berkeley Lab and UC Berkeley)

    Other techniques have been developed to measure electrical signals from small arrays of cells, though these methods can be difficult to scale up to larger arrays and in some cases cannot trace individual electrical impulses to a specific cell.

    Also, Cui said, “This new method does not perturb cells in any way, which is fundamentally different from existing methods that use either genetic or chemical modifications of the cell membrane.”

    The new platform should more easily permit single-cell measurements of electrical impulses traveling across networks containing 100 or more living cells, researchers said.

    Tapping graphene’s light-absorbing properties

    Graphene, which is composed of a honeycomb arrangement of carbon atoms, is the focus of intense R&D because of its incredible strength, ability to very efficiently conduct electricity, high degree of chemical stability, the speed at which electrons can move across its surface, and other exotic properties. Some of this research is focused on the use of graphene as a component in computer circuits and display screens, in drug delivery systems, and in solar cells and batteries.

    4
    This diagram shows the setup for an imaging method that mapped electrical signals using a sheet of graphene and an infrared laser. The laser was fired through a prism (lower left) onto a sheet of graphene. An electrode was used to send tiny electrical signals into a liquid solution (in cylinder atop the graphene), and a camera (lower right) was used to capture images mapping out these electrical signals. (Credit: Halleh Balch and Jason Horng/Berkeley Lab and UC Berkeley)

    n the latest study, researchers first used infrared light produced at Berkeley Lab’s Advanced Light Source [ALS] to understand the effects of an electric field on graphene’s absorption of infrared light.

    LBNL ALS interior
    LBNL ALS interior

    In the experiment, they aimed an infrared laser through a prism to a thin layer called a waveguide. The waveguide was designed to precisely match graphene’s light-absorbing properties so that all of the light was absorbed along the graphene layer in the absence of an electric field.

    Researchers then fired tiny electrical pulses in a liquid solution above the graphene layer that very slightly disrupted the graphene layer’s light absorption, allowing some light to escape in a way that carried a precise signature of the electrical field. Researchers captured a sequence of images of this escaping light in thousandths-of-a-second intervals, and these images provided a direct visualization of the electrical field’s strength and location along the surface of the graphene.

    Millionths-of-a-volt sensitivity

    The new imaging platform—dubbed CAGE for “Critically coupled waveguide-Amplified Graphene Electric field imaging device”—proved sensitive to voltages of a few microvolts (millionths of a volt). This will make it ultrasensitive to the electric fields between cells in networks of heart cells and nerve cells, which can range from tens of microvolts to a few millivolts (thousandths of a volt).

    5
    Another view of the CAGE system, with the graphene sample at lower right. (Credit: Halleh Balch and Jason Horng/Berkeley Lab, UC Berkeley)

    Researchers found that they could pinpoint an electric field’s location along the graphene sheet’s surface down to tens of microns (millionths of a meter), and capture its fading strength in a sequence of time steps separated by as few as five milliseconds, or thousandths of a second.

    In one sequence, researchers detailed the position and dissipation, or fade, of a local electric field generated by a 10-thousandths-of-a-volt pulse over a period of about 240 milliseconds, with sensitivity down to about 100 millionths-of-a-volt.

    Next up: living heart cells

    Balch said that there are already plans to test the platforms with living cells. “We are working with collaborators to test this with real heart cells,” she said. “There are several potential applications for this research in heart health and drug screening.”

    There is also potential to use other atomically thin materials besides graphene in the imaging setup, she said.

    “The kind of elegance behind this system comes from its generality,” Balch said. “It can be sensitive to anything that carries charge.”

    The research team included participants from Berkeley Lab, UC Berkeley, and Stanford University. The work was supported by the U.S. Department of Energy Office of Science, the National Science Foundation, the David and Lucile Packard Foundation, and the Stanford University Bio-X Graduate Fellowship Program.

    The Advanced Light Source is a DOE Office of Science User Facility.

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  • richardmitnick 7:21 am on September 7, 2016 Permalink | Reply
    Tags: , Graphene Studies, ,   

    From Rutgers via New Jersey Business: “Rutgers Engineers Use Microwaves to Produce High-Quality Graphene” 

    Rutgers University
    Rutgers University

    1

    New Jersey Business

    Sep 1, 2016
    Todd B. Bates, Rutgers

    Rutgers experts discover easy way to make graphene for flexible and printable electronics, energy storage, and catalysis.

    `
    No image caption. No image credit.

    Rutgers University engineers have found a simple method for producing high-quality graphene that can be used in next-generation electronic and energy devices: bake the compound in a microwave oven.

    The discovery is documented in a study published online [today] in the journal Science.

    “This is a major advance in the graphene field,” said Manish Chhowalla, professor and associate chair in the Department of Materials Science and Engineering in Rutgers’ School of Engineering. “This simple microwave treatment leads to exceptionally high quality graphene with properties approaching those in pristine graphene.”

    The discovery was made by post-doctoral associates and undergraduate students in the department, said Chhowalla, who is also the director of the Rutgers Institute for Advanced Materials, Devices and Nanotechnology. Having undergraduates as co-authors of a Science paper is rare but he said “the Rutgers Materials Science and Engineering Department and the School of Engineering at Rutgers cultivate a culture of curiosity driven research in students with fresh ideas who are not afraid to try something new.’’

    Graphene – 100 times tougher than steel – conducts electricity better than copper and rapidly dissipates heat, making it useful for many applications. Large-scale production of graphene is necessary for applications such as printable electronics, electrodes for batteries and catalysts for fuel cells.

    Graphene comes from graphite, a carbon-based material used by generations of students and teachers in the form of pencils. Graphite consists of sheets or layers of graphene.

    The easiest way to make large quantities of graphene is to exfoliate graphite into individual graphene sheets by using chemicals. The downside of this approach is that side reactions occur with oxygen – forming graphene oxide that is electrically non-conducting, which makes it less useful for products.

    Removing oxygen from graphene oxide to obtain high-quality graphene has been a major challenge over the past two decades for the scientific community working on graphene. Oxygen distorts the pristine atomic structure of graphene and degrades its properties.

    Chhowalla and his group members found that baking the exfoliated graphene oxide for just one second in a 1,000-watt microwave oven, like those used in households across America, can eliminate virtually all of the oxygen from graphene oxide.

    The Rutgers engineers’ research was funded by the National Science Foundation, Rutgers Energy Institute, U.S. Department of Education and Rutgers Aresty Research Assistant Program.

    The study’s lead authors are Damien Voiry, a former Rutgers post-doctoral associate in Chhowalla’s Nano-materials & Devices Group who is now at the University of Montpellier in France, and Jieun Yang, a post-doctoral associate in Chhowalla’s group. Other authors include Jacob Kupferberg, who will be a Rutgers senior this fall; graduate student Raymond Fullon; Calvin Lee, who graduated in 2015; Hu Young Jeong and Hyeon Suk Shin from the Ulsan National Institute of Science and Technology in South Korea; and Chhowalla.

    See the full article here. .

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  • richardmitnick 10:57 am on August 5, 2016 Permalink | Reply
    Tags: , Graphene Studies, , Pseudospin, Spinning electrons could lead to new electronics   

    From phys.org: “Spinning electrons could lead to new electronics” 

    physdotorg
    phys.org

    August 5, 2016
    No writer credit found

    1
    Credit: University of Manchester

    Among the unusual properties of graphene, one of the most exciting and least understood is the additional degree of freedom experienced by electrons.

    It is called the pseudospin and it determines the probability to find electrons on neighbouring carbon atoms. The possibility to control this degree of freedom would allow for new types of experiments, but potentially also enable to use it for electronic applications.

    Now, writing in Science, Manchester physicists demonstrate how electrons with well-controlled pseudospin can be injected into graphene. The scientists used two layers of graphene, rotated by a small angle with respect to each other and separated by a thin layer of boron nitride, another two-dimensional material and an excellent insulator.

    Applying strong magnetic field parallel to the graphene layers, the pseudospin state of the tunnelling electrons can be chosen.

    Graphene was first isolated from graphite in at The University of Manchester in 2004. Its range of superlative properties, including fantastic strength, conductivity, flexibility and transparency, has paved the way for applications ranging from water filtration to bendable smartphones; from rust-proof coatings to anti-cancer drug delivery systems.

    Combining graphene with other materials, which individually have excellent characteristics complimentary to the extraordinary properties of graphene, has resulted in exciting scientific developments and could produce applications as yet beyond our imagination.

    Sir Kostya Novoselov, who along with colleague Sir Andre Geim was awarded the Nobel prize for Physics for their ground-breaking experiments on graphene, believes the findings could have a significant impact.

    He said: “Our experiments offer an unprecedented control over the quantum state of the electrons in graphene”.

    Co-author Professor Vladimir Fal’ko added: “We hope that the opportunity to control the pseudospin and chirality of electrons in graphene will expand the range of quantum phenomena studied in this remarkable material”.

    One of the lead authors, Dr Artem Mishchenko, is very optimistic. He said: “Who knows, maybe one day we will see chirotronics, alongside with spintronics, valleytronics and electronics”.

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 7:31 am on July 15, 2016 Permalink | Reply
    Tags: , , Graphene Studies   

    From EPFL: “Graphene could revolutionize the internet of things” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne EPFL

    08.07.16
    Laure-Anne Pessina

    1
    © Thinkstock

    Wireless communications come in many forms – such as mobile phones using 4G or 5G connectivity, GPS devices, and computers connected via Bluetooth to portable sensors – and operate in different frequency bands. To work across multiple platforms, connected objects have to be compatible with a whole range of frequencies without being weighed down by excessive hardware.

    Most portable, wireless systems currently come equipped with reconfigurable circuits that can adjust the antenna to transmit and receive data in the various frequency bands. The only problem is that the technologies currently available like MEMS and MOS, using silicon or metal, do not work well at high frequencies. And that’s where data can travel much faster.

    EPFL researchers have come up with a tunable graphene-based solution that enables circuits to operate at both low and high frequencies with unprecedented efficiency. Their work has been published in Nanoletters.

    The new graphene-based solution, which was developed in the Nanoelectronic Devices Laboratory, is designed to replace tunable capacitors, which can be found in all wireless devices. The new device “tunes” the circuits to different frequencies so that they can operate across a wide range of frequency bands. It also meets other needs that neither MEMS nor MOS capacitors can: good performance at high frequency, miniaturization and the ability to be tuned using low energy.

    The EPFL researchers overcame these obstacles with a graphene-based capacitor that is compatible with traditional circuits. The device consumes very little energy and, above 2.1 GHz, easily outperforms its competitors and has a miniaturized design. “The surface area of a conventional MEMS system would have to be a thousand times greater to get the capacitance value,” said Clara Moldovan.

    2
    © 2016 EPFL

    How does it work?

    The researchers’ breakthrough is based on a clever sandwich structure that takes graphene’s unique characteristics into account. “When graphene was discovered more than 10 years ago, it caused a real stir,” said Moldovan. “It was considered a miracle material: it is a very good electrical and thermal conductor and it is flexible, lightweight, transparent and sturdy. But researchers discovered that it was difficult to integrate into electronic systems because its atomic thickness gives it high effective resistance.”

    The sandwich-shaped structure takes advantage of the fact that a two-dimensional gas of electrons in a quantum well can behave like a quantum capacitance. This is because it follows the Pauli Exclusion Principle, according to which a certain amount of energy is needed to fill a quantum well with electrons. Quantum capacitance can be easily measured in a single-atom layer of graphene, and the key advantage is that it is tunable by varying the charge density in graphene with a very low voltage.

    “It’s by applying voltage that we can ‘tune’ our capacitors to a given frequency, just like tuning a radio to get different stations,” said Moldovan, the lead author of the article.

    Many advantages

    The EPFL researchers’ device, which is only several hundred micrometers (around 0.05 cm) long and wide, can be stiff or flexible, is easily miniaturized, and uses very little energy. Potential applications are numerous. In addition to improving the flow of data between connected devices, it could extend battery life and lead to ever more compact devices. In its flexible state, it could be easily used in sensors placed in clothes or directly on the human body. “Our results confirm that graphene could truly revolutionize the future of wireless communications,” said Moldovan.

    The end technology will be a hybrid in which graphene will be paired with advanced silicon technologies. “Some have claimed that graphene will one day replace silicon technology,” said Adrian Ionescu, the head of the Nanolab. “But in reality, graphene is most effective in the realm of electronics when it is combined with functional silicon blocks.”

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    EPFL is Europe’s most cosmopolitan technical university with students, professors and staff from over 120 nations. A dynamic environment, open to Switzerland and the world, EPFL is centered on its three missions: teaching, research and technology transfer. EPFL works together with an extensive network of partners including other universities and institutes of technology, developing and emerging countries, secondary schools and colleges, industry and economy, political circles and the general public, to bring about real impact for society.

     
  • richardmitnick 4:49 am on July 14, 2016 Permalink | Reply
    Tags: , Graphene Studies, ,   

    From New Scientist: “Graphene sheets open like a flower’s petals when poked” 

    NewScientist

    New Scientist

    13 July 2016
    Conor Gearin

    1
    Graphene holds promise in nanotechnology. Domhnall Malone

    Give graphene a diamond and you’ll get a flower in return. Researchers have found that poking a sheet of atom-thick graphene with a diamond tool causes tiny ribbons to peel away from the surface, like flower petals opening.

    “I don’t think anyone ever expected it,” says Graham Cross at Trinity College Dublin, Ireland, whose team made the discovery. Graphene sheets, which are made of a single layer of carbon atoms, are both superstrong and highly flexible. Other researchers have folded graphene into origami shapes using chemical reactions and tiny tools, but no one knew that a little prompting could cause graphene to tear and fold itself on its own.

    The find was an accident, discovered when the researchers were conducting an experiment to measure the friction of graphene by piercing it. Once their diamond tip punctured the sheet, they found that the energy from ambient heat was enough to cause the ribbons to keep tearing and unfolding into a tapered strip in less than a minute.

    “What for me is extraordinary is that it tears,” says Annalisa Fasolino at Radboud University in Nijmegen, the Netherlands. The atoms in a graphene sheet are bonded tightly, but there is only a weak attraction between sheets when stacked, she says. However, the researchers showed that after a layer started to tear, the weak attraction between the bottom of an unfolding ribbon and the sheet below was enough for the sheet’s internal bonds to keep ripping.

    Nanoscale control

    By changing the initial width of the tear, the researchers could control the length of the resulting ribbons, which tended to grow five times their initial width.

    “We’ve done crumpling, wrinkling and tearing of thin sheets, even one-atom-thin sheets like graphene, but not with such exquisite control,” says Scott Bunch at Boston University.

    2
    Graphene can be torn with a diamond tip, causing it to then self-fold – a property that could be useful in electronics. James Annett

    Graphene’s peculiar self-folding ability could be a big help in making better electronics, says Cross. By setting off ribbon formation in careful patterns, the sheets could be folded to make tiny sensors and even transistors. Such devices could allow for nanoscale electronics and fast-processing computers. “It would take a bit of work to do that, but it might be able to,” he says.

    Engineers could also prepare the sheets to tear at specific temperatures, says Cross. This could help in the food industry – for example, a graphene-based sensor on packaging could break a circuit if an item’s temperature rose above a safe level.

    Itai Cohen at Cornell University in Ithaca, New York, does not think graphene will replace silicon in electronic chips, but says graphene sheets could be used to manufacture very small robots. “Folding atomically thin sheets like graphene is a way of packing many, many features into a small 3D volume,” he says.

    Journal reference: Nature, DOI: 10:1038/nature18304

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  • richardmitnick 12:53 pm on May 16, 2016 Permalink | Reply
    Tags: , Graphene Studies, The quest to harvest light for electronics,   

    From U Washington: “UW researchers unleash graphene ‘tiger’ for more efficient optoelectronics” 

    U Washington

    University of Washington

    May 13, 2016
    James Urton

    1
    Image of one of the graphene-based devices Xu and colleagues worked with.Lei Wang

    In the quest to harvest light for electronics, the focal point is the moment when photons — light particles — encounter electrons, those negatively-charged subatomic particles that form the basis of our modern electronic lives. If conditions are right when electrons and photons meet, an exchange of energy can occur. Maximizing that transfer of energy is the key to making efficient light-captured energetics possible.

    “This is the ideal, but finding high efficiency is very difficult,” said University of Washington physics doctoral student Sanfeng Wu. “Researchers have been looking for materials that will let them do this — one way is to make each absorbed photon transfer all of its energy to many electrons, instead of just one electron in traditional devices.”

    In traditional light-harvesting methods, energy from one photon only excites one electron or none depending on the absorber’s energy gap, transferring just a small portion of light energy into electricity. The remaining energy is lost as heat. But in a paper* released May 13 in Science Advances, Wu, UW associate professor Xiaodong Xu and colleagues at four other institutions describe one promising approach to coax photons into stimulating multiple electrons. Their method exploits some surprising quantum-level interactions to give one photon multiple potential electron partners. Wu and Xu, who has appointments in the UW’s Department of Materials Science & Engineering and the Department of Physics, made this surprising discovery using graphene.

    “Graphene is a substance with many exciting properties,” said Wu, the paper’s lead author. “For our purposes, it shows a very efficient interaction with light.”

    Graphene is a two-dimensional hexagonal lattice of carbon atoms bonded to one another, and electrons are able to move easily within graphene. The researchers took a single layer of graphene — just one sheet of carbon atoms thick — and sandwiched it between two thin layers of a material called boron-nitride.

    “Boron-nitride has a lattice structure that is very similar to graphene, but has very different chemical properties,” said Wu. “Electrons do not flow easily within boron-nitride; it essentially acts as an insulator.”

    Xu and Wu discovered that when the graphene layer’s lattice is aligned with the layers of boron-nitride, a type of “superlattice” is created with properties allowing efficient optoelectronics that researchers had sought. These properties rely on quantum mechanics, the occasionally baffling rules that govern interactions between all known particles of matter. Wu and Xu detected unique quantum regions within the superlattice known as Van Hove singularities.

    2
    The Moiré superlattice they created by aligning graphene and boron-nitride. Sanfeng Wu

    “These are regions of huge electron density of states, and they were not accessed in either the graphene or boron-nitride alone,” said Wu. “We only created these high electron density regions in an accessible way when both layers were aligned together.”

    When Xu and Wu directed energetic photons toward the superlattice, they discovered that those Van Hove singularities were sites where one energized photon could transfer its energy to multiple electrons that are subsequently collected by electrodes— not just one electron or none with the remaining energy lost as heat. By a conservative estimate, Xu and Wu report that within this superlattice one photon could “kick” as many as five electrons to flow as current.

    With the discovery of collecting multiple electrons upon the absorption of one photon, researchers may be able to create highly efficient devices that could harvest light with a large energy profit. Future work would need to uncover how to organize the excited electrons into electrical current for optimizing the energy-converting efficiency and remove some of the more cumbersome properties of their superlattice, such as the need for a magnetic field. But they believe this efficient process between photons and electrons represents major progress.

    “Graphene is a tiger with great potential for optoelectronics, but locked in a cage,” said Wu. “The singularities in this superlattice are a key to unlocking that cage and releasing graphene’s potential for light harvesting application.”

    Co-authors were Lei Wang, Xian Zhang, Cory Dean and James Hone at Columbia University; You Lai and Zhiqiang Li at the National High Magnetic Field Laboratory in Florida; Wen-Yu Shan and Di Xiao at Carnegie Mellon University; former UW graduate student Grant Aivazian; and Takashi Taniguchi and Kenji Watanabe at the National Institute for Materials Science in Japan. The work at the UW was funded by the National Science Foundation and the U.S. Air Force Office of Scientific Research. Xu acknowledges the support from the Boeing Distinguished Professorship and Washington’s state-funded Clean Energy Institute.

    *Science paper:
    Multiple hot-carrier collection in photo-excited graphene Moiré superlattices

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  • richardmitnick 12:50 pm on April 6, 2016 Permalink | Reply
    Tags: , , Graphene Studies   

    From EPFL: “A graphene chip filters light to boost communications” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne EPFL

    1

    06.04.16
    Hillary Sanctuary

    A microchip that filters out unwanted radiation with the help of graphene has been developed by scientists from the EPFL and tested by researchers of the University of Geneva (UNIGE). The invention could be used in future devices to transmit wireless data ten times faster.

    EPFL and UNIGE scientists have developed a microchip using graphene that could help wireless telecommunications share data at a rate that is ten times faster than currently possible. The results are published today in Nature Communications.

    “Our graphene based microchip is an essential building block for faster wireless telecommunications in frequency bands that current mobile devices cannot access,” says EPFL scientist Michele Tamagnone.

    Graphene acts like polarized sunglasses

    Their microchip works by protecting sources of wireless data — which are essentially sources of invisible radiation — from unwanted radiation, ensuring that the data remain intact by reducing source corruption.

    They discovered that graphene can filter out radiation in much the same way as polarized glasses. The vibration of radiation has an orientation. Like polarized glasses, their graphene-based microchip makes sure that radiation that only vibrates a certain way gets through. In this way, graphene is both transparent and opaque to radiation, depending on the orientation of vibration and signal direction. The EPFL scientists and their colleagues from Geneva used this property to create a device known as an optical isolator.

    2

    Faster Uploads in the Terahertz Bandwidth

    Moreover, their microchip works in a frequency band that is currently empty, called the terahertz gap.

    Wireless devices work today by transmitting data in the gigahertz range or at optical frequencies. This is imposed by technological constraints, leaving the potential of the terahertz band currently unexploited for data transmission.

    But if wireless devices could use this terahertz bandwidth, your future mobile phone could potentially send or receive data tens of times faster than now, meaning better sound quality, better image quality and faster uploads.

    The graphene-based microchip brings this terahertz technology a step closer to reality. This discovery addresses an important challenge that was so far unsolved due to lacking technologies, confirming once more the extraordinary physical properties of graphene.

    This joint project between EPFL and the University of Geneva was funded by the European Graphene Flagship project and by the Swiss National Science Foundation.

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  • richardmitnick 11:17 am on September 24, 2015 Permalink | Reply
    Tags: , Graphene Studies,   

    From Michigan: “Layered graphene beats the heat” 

    U Michigan bloc

    University of Michigan

    9/24/2015
    Kate McAlpine

    1

    An international team of researchers, led by faculty at the University of Michigan, have found that a layered form of graphene can expel heat efficiently, which is an important feature for its potential applications in building small and powerful electronics.

    2
    Graphene is an atomic-scale honeycomb lattice made of carbon atoms.

    “As you make devices smaller and smaller, you increase the amount of heat generated in a limited space, so you need to find ways to extract the heat,” said Momchil Mihnev, a doctoral student in electrical engineering and computer science at the University of Michigan and first author on the paper in Nature Communications.

    Graphene, a one-atom-thick sheet of carbon, has been hailed as the future of electronics because of its outstanding electrical conductivity. But a number of challenges stand between its promise and its adoption in commercial devices.

    One difficulty is simply producing the stuff. Arguably, the most reliable method is baking silicon carbide, a compound of silicon and carbon atoms, so that the silicon evaporates out, leaving behind a layered graphene structure. This type of graphene is most promising for electronic devices.

    But unlike heat in a 3D chunk of silicon, heat building up in the electrons of graphene was not expected to travel well between layers, since graphene layers tend not to interact with each other very strongly. Meanwhile, the chunk of silicon can conduct heat in any direction.

    Now, researchers led by Theodore Norris, the Gérard A. Mourou Collegiate Professor of Electrical Engineering and Computer Science, have shown the electrons can transmit heat efficiently between layers, enabling it to rapidly dissipate out of the 3D graphene. Mihnev explained that although the electrons in different layers can’t mechanically run into one another, they can interact through their electrical charges.

    The negative charges repel one another, giving the electrons an effective size that extends between the layers. When electrons collide in this way, the hotter of the two transfers energy to the colder. The heat is channeled into the graphene layers closest to the silicon carbide base because these layers had borrowed extra electrons from the silicon carbide. From there, the heat moves into the silicon carbide.

    “The reliability and performance of future graphene-based devices will depend critically on the availability of efficient mechanisms for the dissipation of excess generated heat,” Mihnev said.

    Norris’s team studied graphene samples produced by the group of Walter de Heer, a Regent Professor and professor of physics at the Georgia Institute of Technology in Atlanta. They shot a short and intense burst of laser light into the sample, causing the electrons to heat up to about 5,000°F. Then, they used a weak pulse of radiation that falls between far infrared and microwave on the electromagnetic spectrum to check the temperature of the electrons in the graphene.

    John Tolsma, co-first-author with Mihnev and a doctoral student in physics, and Allan MacDonald, the Sid W. Richardson Foundation Regents Chair Professor of Physics, both at The University of Texas at Austin, worked out a detailed new theory to explain the effect.

    “We believe that this cooling mechanism is not limited to multilayer graphene samples but is likely to be important in many other new, layered nanomaterials under active development by the scientific community,” said Norris.

    The paper on this work is called Electronic cooling via interlayer Coulomb coupling in multilayer epitaxial graphene. The study was supported in part by the National Science Foundation, the Welch foundation and the Department of Energy.

    See the full article here .

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    U MIchigan Campus

    The University of Michigan (U-M, UM, UMich, or U of M), frequently referred to simply as Michigan, is a public research university located in Ann Arbor, Michigan, United States. Originally, founded in 1817 in Detroit as the Catholepistemiad, or University of Michigania, 20 years before the Michigan Territory officially became a state, the University of Michigan is the state’s oldest university. The university moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet (781 acres or 3.16 km²), and has two satellite campuses located in Flint and Dearborn. The University was one of the founding members of the Association of American Universities.

    Considered one of the foremost research universities in the United States,[7] the university has very high research activity and its comprehensive graduate program offers doctoral degrees in the humanities, social sciences, and STEM fields (Science, Technology, Engineering and Mathematics) as well as professional degrees in business, medicine, law, pharmacy, nursing, social work and dentistry. Michigan’s body of living alumni (as of 2012) comprises more than 500,000. Besides academic life, Michigan’s athletic teams compete in Division I of the NCAA and are collectively known as the Wolverines. They are members of the Big Ten Conference.

     
  • richardmitnick 1:30 pm on September 13, 2015 Permalink | Reply
    Tags: , Graphene Studies, ,   

    From UBC: “First superconducting graphene created by UBC researchers” 

    U British Columbia bloc

    University of British Columbia

    September 8, 2015
    No Writer Credit

    1
    Researchers add lithium to graphene to create superconductivity. Credit: Andrea Damascelli.

    Graphene, the ultra-thin, ultra-strong material made from a single layer of carbon atoms, just got a little more extreme. UBC physicists have been able to create the first ever superconducting graphene sample by coating it with lithium atoms.

    Although superconductivity has already been observed in intercalated bulk graphite—three-dimensional crystals layered with alkali metal atoms, based on the graphite used in pencils—inducing superconductivity in single-layer graphene has until now eluded scientists.

    2
    Andrea Damascelli

    “This first experimental realization of superconductivity in graphene promises to usher us in a new era of graphene electronics and nanoscale quantum devices,” says Andrea Damascelli, director of UBC’s Quantum Matter Institute and leading scientist of the Proceedings of the National Academy of Sciences study outlining the discovery.

    Graphene, roughly 200 times stronger than steel by weight, is a single layer of carbon atoms arranged in a honeycomb pattern. Along with studying its extreme physical properties, scientists eventually hope to make very fast transistors, semiconductors, sensors and transparent electrodes using graphene.

    “This is an amazing material,’” says Bart Ludbrook, first author on the PNAS paper and a former PhD researcher in Damascelli’s group at UBC. “Decorating monolayer graphene with a layer of lithium atoms enhances the graphene’s electron–phonon coupling to the point where superconductivity can be stabilized.”

    Given the massive scientific and technological interest, the ability to induce superconductivity in single-layer graphene promises to have significant cross-disciplinary impacts. According to financial reports, the global market for graphene reached $9 million in 2014 with most sales in the semiconductor, electronics, battery, energy, and composites industries.

    The researchers, which include colleagues at the Max Planck Institute for Solid State Research through the joint Max-Planck-UBC Centre for Quantum Materials, prepared the lithium-decorated graphene in ultra-high vacuum conditions and at ultra-low temperatures (-267 degrees Celsius or 5 Kelvin), to achieve this breakthrough.

    UBC’s Quantum Matter Institute

    UBC’s Quantum Matter Institute (QMI) is internationally recognized for its research and discoveries in quantum structures, quantum materials, and applications towards quantum devices. A recent $66.5-million investment from the Canada First Research Excellence Fund will broaden the scope of QMI’s research and support the discovery of practical applications for computing, electronics, medicine and sustainable energy technologies.

    Study: Evidence for superconductivity in Li-decorated monolayer graphene in Proceedings of the National Academy of Sciences. Tracking number: 2015-10435R

    See the full article here .

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    U British Columbia Campus

    The University of British Columbia is a global centre for research and teaching, consistently ranked among the 40 best universities in the world. Since 1915, UBC’s West Coast spirit has embraced innovation and challenged the status quo. Its entrepreneurial perspective encourages students, staff and faculty to challenge convention, lead discovery and explore new ways of learning. At UBC, bold thinking is given a place to develop into ideas that can change the world.

     
    • flowerpoet 3:47 pm on September 13, 2015 Permalink | Reply

      an amazing breakthrough with ever-increasing possibilities…thanks for sharing this info

      Like

  • richardmitnick 11:01 am on August 13, 2015 Permalink | Reply
    Tags: , Graphene Studies,   

    From MIT Tech Review: “How to Make Graphene Using Supersonic Buckyballs” 

    MIT Technology Review
    M.I.T Technology Review

    August 13, 2015
    By C60 Supersonic Molecular Beam Epitaxy

    1

    Graphene is one of the wonder materials of our age. It is some 200 times stronger than steel, it is an extraordinary conductor of heat and electricity and it is almost transparent. And yet making graphene is still tricky, particularly when it needs to sit on a substrate for applications such as electronics.

    Today, Simone Taioli at the Trento Institute for Fundamental Physics and Applications in Italy and a few pals say they’ve worked out how to do it starting with the famous football-shaped molecule buckminsterfullerene.

    Their idea is remarkably simple: bombard the substrate with buckyballs travelling at supersonic speeds. That’s fast enough to crack them open when they hit and the resulting unzipped cages then bond together to form a graphene film.

    Researchers have long thought of using buckyballs as a precursor for graphene. But the only way to get them to unzip and bind together is to heat them to temperatures in excess of around 600 °C.

    That’s not particularly effective because those high temperatures can change the properties of the substrate, in particular the amount of carbon it adsorbs. That results in irregular films with serious defects.

    The new technique gets around these problems. The team accelerates the buckyballs by releasing them into a helium or hydrogen gas which they allow to expand at supersonic speeds, carrying the carbon balls with it. That gives the buckyballs energies of around 40 keV without changing their internal dynamics (unlike ordinary heating which dramatically increases the molecular vibrations).

    These guys then aim the buckyballs at a copper sheet and watch them smash into it like flies onto a windscreen. The result is a fairly even coating of graphene-like material in a single layer.

    This material has its own idiosyncrasies. For a start, it is not made of regular hexagons, like perfect graphene. Instead it also contains pentagons which come from the original buckyball structures. That’s potentially useful because the pentagons could introduce a band gap into the material, something materials scientists have longed hoped to create in graphene.

    Although just a proof of principle at this stage, the technique looks interesting not least because it produces relatively high quality films and could also be applied to a wide range of other materials such as metals, semiconductors and insulators. And that could pave the way for a new generation of electronic devices.

    Interesting stuff!

    See the full article here.

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    The mission of MIT Technology Review is to equip its audiences with the intelligence to understand a world shaped by technology.

     
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