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  • richardmitnick 7:51 am on February 22, 2017 Permalink | Reply
    Tags: , Nanotechnology, New nanoscale antenna array, Terahertz detectors, , Useful for biological sensing and medical imaging chemical identification and material characterization   

    From UCLA: “UCLA engineers develop high-performance terahertz detectors” 

    UCLA bloc

    UCLA

    February 21, 2017
    Matthew Chin

    1
    UCLA electrical engineering graduate student Nezih Tolga Yardimci. Art Montes De Oca/UCLA Engineering

    Researchers from the UCLA Henry Samueli School of Engineering and Applied Science have developed a new antenna array that greatly expands the operation bandwidth and level of sensitivity for imaging and sensing systems that use terahertz frequencies.

    Terahertz frequencies are an underused part of the electromagnetic spectrum that lies between the infrared and microwave bands. The unique features of this part of the spectrum could be useful for biological sensing and medical imaging, chemical identification and material characterization.

    “For example, a terahertz-based imaging system could allow doctors to see how wounds are healing underneath bandages,” said Mona Jarrahi, associate professor of electrical engineering in the UCLA Henry Samueli School of Engineering and Applied Science and the principal investigator of the research. The study was published in Scientific Reports, an open-access journal from Nature.

    However terahertz technology is not yet mature. One component researchers are aiming to make more efficient is a terahertz detector, which receives the terahertz signals, much like photodetectors in a camera that sense light to produce an image.

    By operating across a broader bandwidth, the new nanoscale antenna array developed by Jarrahi and Nezih Tolga Yardimci, a UCLA graduate student in electrical engineering, can extract more information about material characteristics. The device’s higher signal-to-noise ratios mean it can find faint target signals. For example, the new terahertz detector can be tuned to detect certain chemicals even when target molecules are present in miniscule amounts. It can also be used to image both the surface of the skin, and deeper tissue layers.

    The unique nanoscale geometry of the antenna array addresses the bandwidth and sensitivity problems of previously used terahertz detectors, the researchers said.

    “Up close, it looks like a row of small grates,” Yardimci said. “We specifically designed the dimensions of the nanoantenna elements and their spacing such that an incoming terahertz beam is focused into nanoscale dimensions, where it efficiently interacts with a stream of optical pump photons to produce an electrical signal proportional to the terahertz beam intensity.”

    Jarrahi said: “The broad operation bandwidth and high sensitivity of this new type of terahertz detector extends the scope and potential uses of terahertz waves for many imaging and sensing applications.”

    The research was supported by financial support from Moore Inventor Fellowship and the Presidential Early Career Award for Scientists and Engineers.

    See the full article here .

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    UC LA Campus

    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 1:35 pm on February 18, 2017 Permalink | Reply
    Tags: , Breakthrough in understanding heat transport with a chain of gold atoms, Nanotechnology, , Wiedemann-Franz law   

    From phys.org: “Breakthrough in understanding heat transport with a chain of gold atoms” 

    physdotorg
    phys.org

    February 17, 2017

    1
    Artists’ view of the quantized thermal conductance of an atomically thin gold contact. Credit: Enrique Sahagun

    The precise control of electron transport in microelectronics makes complex logic circuits possible that are in daily use in smartphones and laptops. Heat transport is of similar fundamental importance and its control is for instance necessary to efficiently cool the ever smaller chips. An international team including theoretical physicists from Konstanz, Junior Professor Fabian Pauly and Professor Peter Nielaba and their staff, has achieved a real breakthrough in better understanding heat transport at the nanoscale. The team used a system that experimentalists in nanoscience can nowadays realize quite routinely and keeps serving as the “fruit fly” for breakthrough discoveries: a chain of gold atoms. They used it to demonstrate the quantization of the electronic part of the thermal conductance. The study also shows that the Wiedemann-Franz law, a relation from classical physics, remains valid down to the atomic level. The results were published in the scientific journal Science on 16 February 2017.

    To begin with, the test object is a microscopic gold wire. This wire is pulled until its cross section is only one atom wide and a chain of gold atoms forms, before it finally breaks. The physicists send electric current through this atomic chain, that is through the thinnest wire conceivable. With the help of different theoretical models the researchers can predict the conductance value of the electric transport, and also confirm it by experiment. This electric conductance value indicates how much charge current flows when an electrical voltage is applied. The thermal conductance, that indicates the amount of heat flow for a difference in temperature, could not yet be measured for such atomic wires.

    Now the question was whether the Wiedemann-Franz law, that states that the electric conductance and the thermal conductance are proportional to each other, remains valid also at the atomic scale. Generally, electrons as well as atomic oscillations (also called vibrations or phonons) contribute to heat transport. Quantum mechanics has to be used, at the atomic level, to describe both the electron and the phonon transport. The Wiedemann-Franz law, however, only describes the relation between macroscopic electronic properties. Therefore, initially the researchers had to find out how high the contribution of the phonons is to the thermal conductance.

    The doctoral researchers Jan Klöckner and Manuel Matt did complementary theoretical calculations, which showed that usually the contribution of phonons to the heat transport in atomically thin gold wires is less than ten percent, and thus is not decisive. At the same time, the simulations confirm the applicability of the Wiedemann-Franz law. Manuel Matt used an efficient, albeit less accurate method that provided statistical results for many gold wire stretching events to calculate the electronic part of the thermal conductance value, while Jan Klöckner applied density functional theory to estimate the electronic and phononic contributions in individual contact geometries. The quantization of the thermal conductance in gold chains, as proven by experiment, ultimately results from the combination of three factors: the quantization of the electrical conductance value in units of the so-called conductance quantum (twice the inverse Klitzing constant 2e2/h), the negligible role of phonons in heat transport and the validity of the Wiedemann-Franz law.

    For quite some time it has been possible to theoretically calculate, with the help of computer models as developed in the teams of Fabian Pauly and Peter Nielaba, how charges and heat flow through nanostructures. A highly precise experimental setup, as created by the experimental colleagues Professor Edgar Meyhofer and Professor Pramod Reddy from the University of Michigan (USA), was required to be able to compare the theoretical predictions with measurements. In previous experiments the signals from the heat flow through single atom contacts were too small. The Michigan group succeeded in improving the experiment: Now the actual signal can be filtered out and measured.

    The results of the research team make it possible to study heat transport not only in atomic gold contacts but many other nanosystems. They offer opportunities to experimentally and theoretically explore numerous fundamental quantum heat transport phenomenona that might help to use energy more efficiently, for example by exploiting thermoelectricity.

    See the full article here .

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    About Phys.org in 100 Words

    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 9:24 am on February 2, 2017 Permalink | Reply
    Tags: Advanced electron microscopy, , , GENFIRE (GENeralized Fourier Iterative Reconstruction), , Mapping out the three-dimensional atomic positions at the grain boundaries for the first time, Nanotechnology, ,   

    From UCLA: “UCLA physicists map the atomic structure of an alloy” 

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    UCLA

    February 01, 2017
    Katherine Kornei

    1
    Identification of the precise 3-D coordinates of iron, shown in red, and platinum atoms in an iron-platinum nanoparticle. Courtesy of Colin Ophus and Florian Nickel

    In the world of the very tiny, perfection is rare: virtually all materials have defects on the atomic level. These imperfections — missing atoms, atoms of one type swapped for another, and misaligned atoms — can uniquely determine a material’s properties and function. Now, UCLA physicists and collaborators have mapped the coordinates of more than 23,000 individual atoms in a tiny iron-platinum nanoparticle to reveal the material’s defects.

    The results demonstrate that the positions of tens of thousands of atoms can be precisely identified and then fed into quantum mechanics calculations to correlate imperfections and defects with material properties at the single-atom level. This research will be published Feb. 2 in the journal Nature.

    Jianwei “John” Miao, a UCLA professor of physics and astronomy and a member of UCLA’s California NanoSystems Institute, led the international team in mapping the atomic-level details of the bimetallic nanoparticle, more than a trillion of which could fit within a grain of sand.

    “No one has seen this kind of three-dimensional structural complexity with such detail before,” said Miao, who is also a deputy director of the Science and Technology Center on Real-Time Functional Imaging. This new National Science Foundation-funded consortium consists of scientists at UCLA and five other colleges and universities who are using high-resolution imaging to address questions in the physical sciences, life sciences and engineering.

    Miao and his team focused on an iron-platinum alloy, a very promising material for next-generation magnetic storage media and permanent magnet applications.

    By taking multiple images of the iron-platinum nanoparticle with an advanced electron microscope at Lawrence Berkeley National Laboratory and using powerful reconstruction algorithms developed at UCLA, the researchers determined the precise three-dimensional arrangement of atoms in the nanoparticle.

    “For the first time, we can see individual atoms and chemical composition in three dimensions. Everything we look at, it’s new,” Miao said.

    The team identified and located more than 6,500 iron and 16,600 platinum atoms and showed how the atoms are arranged in nine grains, each of which contains different ratios of iron and platinum atoms. Miao and his colleagues showed that atoms closer to the interior of the grains are more regularly arranged than those near the surfaces. They also observed that the interfaces between grains, called grain boundaries, are more disordered.

    “Understanding the three-dimensional structures of grain boundaries is a major challenge in materials science because they strongly influence the properties of materials,” Miao said. “Now we are able to address this challenge by precisely mapping out the three-dimensional atomic positions at the grain boundaries for the first time.”

    The researchers then used the three-dimensional coordinates of the atoms as inputs into quantum mechanics calculations to determine the magnetic properties of the iron-platinum nanoparticle. They observed abrupt changes in magnetic properties at the grain boundaries.

    “This work makes significant advances in characterization capabilities and expands our fundamental understanding of structure-property relationships, which is expected to find broad applications in physics, chemistry, materials science, nanoscience and nanotechnology,” Miao said.

    In the future, as the researchers continue to determine the three-dimensional atomic coordinates of more materials, they plan to establish an online databank for the physical sciences, analogous to protein databanks for the biological and life sciences. “Researchers can use this databank to study material properties truly on the single-atom level,” Miao said.

    Miao and his team also look forward to applying their method called GENFIRE (GENeralized Fourier Iterative Reconstruction) to biological and medical applications. “Our three-dimensional reconstruction algorithm might be useful for imaging like CT scans,” Miao said. Compared with conventional reconstruction methods, GENFIRE requires fewer images to compile an accurate three-dimensional structure.

    That means that radiation-sensitive objects can be imaged with lower doses of radiation.

    The study’s co-authors include Yongsoo Yang, Rui Xu, AJ Pryor, Li Wu and Jihan Zhou, all at UCLA; Mary Scott, Colin Ophus, and Peter Ercius of Lawrence Berkeley National Laboratory; Chien-Chun Chen of the National Sun Yat-sen University; Fan Sun and Hao Zeng of the University at Buffalo; Markus Eisenbach and Paul Kent of Oak Ridge National Laboratory; Wolfgang Theis of the University of Birmingham; and Renat Sabirianov of the University of Nebraska Omaha.

    This work was supported by the U.S. Department of Energy’s Office of Basic Energy Sciences (grants DE-SC0010378, DE-AC02—05CH11231 and DE-AC05-00OR22725) as well as the U.S. National Science Foundation’s Division of Materials Research (grants DMR-1548924 and DMR-1437263).

    See the full article here .

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    UC LA Campus

    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 2:39 pm on January 27, 2017 Permalink | Reply
    Tags: , Carbon nanotube “stitches” strengthen composites, , Nanotechnology   

    From MIT: “Carbon nanotube “stitches” strengthen composites” 

    MIT News
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    August 2, 2016 [Where has this been?]
    Jennifer Chu

    1
    MIT aerospace engineers have found a way to bond composite layers, producing a material that is substantially stronger and more resistant to damage than other advanced composites. The improvement may lead to stronger, lighter airplane parts. Illustration: Christine Daniloff/MIT

    The newest Airbus and Boeing passenger jets flying today are made primarily from advanced composite materials such as carbon fiber reinforced plastic — extremely light, durable materials that reduce the overall weight of the plane by as much as 20 percent compared to aluminum-bodied planes. Such lightweight airframes translate directly to fuel savings, which is a major point in advanced composites’ favor.

    But composite materials are also surprisingly vulnerable: While aluminum can withstand relatively large impacts before cracking, the many layers in composites can break apart due to relatively small impacts — a drawback that is considered the material’s Achilles’ heel.

    Now MIT aerospace engineers have found a way to bond composite layers in such a way that the resulting material is substantially stronger and more resistant to damage than other advanced composites. Their results are published this week in the journal Composites Science and Technology.

    The researchers fastened the layers of composite materials together using carbon nanotubes — atom-thin rolls of carbon that, despite their microscopic stature, are incredibly strong. They embedded tiny “forests” of carbon nanotubes within a glue-like polymer matrix, then pressed the matrix between layers of carbon fiber composites. The nanotubes, resembling tiny, vertically-aligned stitches, worked themselves within the crevices of each composite layer, serving as a scaffold to hold the layers together.

    In experiments to test the material’s strength, the team found that, compared with existing composite materials, the stitched composites were 30 percent stronger, withstanding greater forces before breaking apart.

    Roberto Guzman, who led the work as an MIT postdoc in the Department of Aeronautics and Astronautics (AeroAstro), says the improvement may lead to stronger, lighter airplane parts — particularly those that require nails or bolts, which can crack conventional composites.

    “More work needs to be done, but we are really positive that this will lead to stronger, lighter planes,” says Guzman, who is now a researcher at the IMDEA Materials Institute, in Spain. “That means a lot of fuel saved, which is great for the environment and for our pockets.”

    The study’s co-authors include AeroAstro professor Brian Wardle and researchers from the Swedish aerospace and defense company Saab AB.

    “Size matters”

    Today’s composite materials are composed of layers, or plies, of horizontal carbon fibers, held together by a polymer glue, which Wardle describes as “a very, very weak, problematic area.” Attempts to strengthen this glue region include Z-pinning and 3-D weaving — methods that involve pinning or weaving bundles of carbon fibers through composite layers, similar to pushing nails through plywood, or thread through fabric.

    “A stitch or nail is thousands of times bigger than carbon fibers,” Wardle says. “So when you drive them through the composite, you break thousands of carbon fibers and damage the composite.”

    Carbon nanotubes, by contrast, are about 10 nanometers in diameter — nearly a million times smaller than the carbon fibers.

    “Size matters, because we’re able to put these nanotubes in without disturbing the larger carbon fibers, and that’s what maintains the composite’s strength,” Wardle says. “What helps us enhance strength is that carbon nanotubes have 1,000 times more surface area than carbon fibers, which lets them bond better with the polymer matrix.”

    Stacking up the competition

    Guzman and Wardle came up with a technique to integrate a scaffold of carbon nanotubes within the polymer glue. They first grew a forest of vertically-aligned carbon nanotubes, following a procedure that Wardle’s group previously developed. They then transferred the forest onto a sticky, uncured composite layer and repeated the process to generate a stack of 16 composite plies — a typical composite laminate makeup — with carbon nanotubes glued between each layer.

    To test the material’s strength, the team performed a tension-bearing test — a standard test used to size aerospace parts — where the researchers put a bolt through a hole in the composite, then ripped it out. While existing composites typically break under such tension, the team found the stitched composites were stronger, able to withstand 30 percent more force before cracking.

    The researchers also performed an open-hole compression test, applying force to squeeze the bolt hole shut. In that case, the stitched composite withstood 14 percent more force before breaking, compared to existing composites.

    “The strength enhancements suggest this material will be more resistant to any type of damaging events or features,” Wardle says. “And since the majority of the newest planes are more than 50 percent composite by weight, improving these state-of-the art composites has very positive implications for aircraft structural performance.”

    Stephen Tsai, emeritus professor of aeronautics and astronautics at Stanford University, says advanced composites are unmatched in their ability to reduce fuel costs, and therefore, airplane emissions.

    “With their intrinsically light weight, there is nothing on the horizon that can compete with composite materials to reduce pollution for commercial and military aircraft,” says Tsai, who did not contribute to the study. But he says the aerospace industry has refrained from wider use of these materials, primarily because of a “lack of confidence in [the materials’] damage tolerance. The work by Professor Wardle addresses directly how damage tolerance can be improved, and thus how higher utilization of the intrinsically unmatched performance of composite materials can be realized.”

    This work was supported by Airbus Group, Boeing, Embraer, Lockheed Martin, Saab AB, Spirit AeroSystems Inc., Textron Systems, ANSYS, Hexcel, and TohoTenax through MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium and, in part, by the U.S. Army.

    See the full article here .

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    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

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  • richardmitnick 9:04 am on January 25, 2017 Permalink | Reply
    Tags: , , How to deliver drugs to brain using ultrasound, , Nanotechnology   

    From Hopkins: “Johns Hopkins researchers figure out how to deliver drugs to brain using ultrasound” 

    Johns Hopkins
    Johns Hopkins University

    1.24.17
    Shawna Williams

    1
    When drug-laden nanoparticles (left) absorb energy from ultrasound waves, their liquid center (green) turns to gas and expands the particles (right), loosening their exterior and releasing the drug (blue). Image credit: Raag Airan

    Biomedical engineers at Johns Hopkins report they have worked out a noninvasive way to release and deliver concentrated amounts of a drug to the brain of rats in a temporary, localized manner using ultrasound. The method “cages” a drug inside tiny, biodegradable “nanoparticles,” then activates its release through precisely targeted sound waves, such as those used to create images of internal organs.

    Because most psychoactive drugs could be delivered this way, as well as many other types of drugs, the researchers say their method has the potential to advance many therapies and research studies inside and outside the brain.

    The researchers say that their method should minimize a drug’s side effects because the drug’s release is concentrated in a small area of the body, so the total amount of drug administered can be much lower. And because the individual components of the technology—including the use of the specific biomaterials, ultrasound, and FDA-approved drugs—have already been tested in people and found to be safe, the researchers believe their method could be brought into clinical use more quickly than usual. They hope to start the regulatory approval process within the next year or two.

    “If further testing of our combination method works in humans, it will not only give us a way to direct medications to specific areas of the brain, but will also let us learn a lot more about the function of each brain area,” said Jordan Green, associate professor of biomedical engineering, who is also a member of JHU’s Kimmel Cancer Center and Institute for NanoBioTechnology.

    Details of the research were published Monday in the journal Nano Letters.

    In their experiments, Green’s group designed nanoparticles with an outer expandable “cage” made of a biodegradable plastic. The center of the cage was filled with the liquid perfluoropentane. When the sound waves of ultrasound—delivered noninvasively across the rats’ scalp and skull—strike perfluoropentane in the center of the nanoparticles, the liquid transforms to a gas, expanding the surrounding cage and letting the drug escape.

    The new research, Green says, was designed to further advance means of getting drugs safely to the brain, a delicate and challenging organ to treat. To protect itself from infectious agents—and from swelling that can be caused by the immune system, for example—the brain is surrounded by a molecular fence, called the blood-brain barrier, which lines the surface of every blood vessel feeding the brain. Only very small drug molecules that dissolve in oil can get through the fence, along with gases. Because of this, most drugs developed for treating brain disorders fit those criteria but are dispersed to all parts of the brain—and the rest of the body, where they may be unneeded and unwanted.

    “When working with a patient who has post-traumatic stress disorder, for example, it would be nice to quiet down the overactive part of the brain—for instance, the amygdala—during talk therapy sessions,” says Raag Airan, assistant professor of radiology at Stanford University Medical Center and co-author of the paper. “Current technologies can at best quiet down half of the brain at a time, so they are too nonspecific to be useful in this setting.”

    See the full article here .

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    The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

     
  • richardmitnick 1:52 pm on January 5, 2017 Permalink | Reply
    Tags: , Nanotechnology, , , Semiconductor discs could boost night vision   

    From physicsworld.com: “Semiconductor discs could boost night vision” 

    physicsworld
    physicsworld.com.com

    1
    Frequency double: Maria del Rocio Camacho-Morales studies the new optical material.

    A new method of fabricating nanoscale optical crystals capable of converting infrared to visible light has been developed by researchers in Australia, China and Italy. The new technique allows the crystals to be placed onto glass and could lead to improvements in holographic imaging – and even the development of improved night-vision goggles.

    Second-harmonic generation, or frequency doubling, is an optical process whereby two photons with the same frequency are combined within a nonlinear material to form a single photon with twice the frequency (and half the wavelength) of the original photons. The process is commonly used by the laser industry, in which green 532 nm laser light is produced from a 1064 nm infrared source. Recent developments in nanotechnology have opened up the potential for efficient frequency doubling using nanoscale crystals – potentially enabling a variety of novel applications.

    Materials with second-order nonlinear susceptibilities – such as gallium arsenide (GaAs) and aluminium gallium arsenide (AlGaAs) – are of particular interest for these applications because their low-order nonlinearity makes them efficient at conversion.

    Substrate mismatch

    To be able to exploit second-harmonic generation in a practical device, these nanostructures must be fabricated on a substrate with a relatively low refractive index (such as glass), so that light may pass through the optical device. This is challenging, however, because the growth of GaAs-based crystals in a thin film – and type III-V semiconductors in general – requires a crystalline substrate.

    “This is why growing a layer of AlGaAs on top of a low-refractive-index substrate, like glass, leads to unmatched lattice parameters, which causes crystalline defects,” explains Dragomir Neshev, a physicist at the Australian National University (ANU). These defects, he adds, result in unwanted changes in the electronic, mechanical, optical and thermal properties of the films.

    Previous attempts to overcome this issue have led to poor results. One approach, for example, relies on placing a buffer layer under the AlGaAs films, which is then oxidized. However, these buffer layers tend to have higher refractive indices than regular glass substrates. Alternatively, AlGaAs films can be transferred to a glass surface prior to the fabrication of the nanostructures. In this case the result is poor-quality nanocrystals.

    Best of both

    The new study was done by Neshev and colleagues at ANU, Nankai University and the University of Brescia, who combined the advantages of the two different approaches to develop a new fabrication method. First, high-quality disc-shaped nanocrystals about 500 nm in diameter are fabricated using electron-beam lithography on a GaAs wafer, with a layer of AlAs acting as a buffer between the two. The buffer is then dissolved, and the discs are coated in a transparent layer of benzocyclobutene. This can then be attached to the glass substrate, and the GaAs wafer peeled off with minimal damage to the nanostructures.

    The development could have various applications. “The nanocrystals are so small they could be fitted as an ultrathin film to normal eye glasses to enable night vision,” says Neshev, explaining that, by combining frequency doubling with other nonlinear interactions, the film might be used to convert invisible, infrared light to the visible spectrum.

    If they could be made, such modified glasses would be an improvement on conventional night-vision binoculars, which tend to be large and cumbersome. To this end, the team is working to scale up the size of the nanocrystal films to cover the area of typical spectacle lenses, and expects to have a prototype device completed within the next five years.

    Security holograms

    Alongside frequency doubling, the team was also able to tune the nanodiscs to control the direction and polarization of the emitted light, which makes the film more efficient. “Next, maybe we can even engineer the light and make complex shapes such as nonlinear holograms for security markers,” says Neshev, adding: “Engineering of the exact polarization of the emission is also important for other applications such as microscopy, which allows light to be focused to a smaller volume.”

    “Vector beams with spatially arranged polarization distributions have attracted great interest for their applications in a variety of technical areas,” says Qiwen Zhan, an engineer at the University of Dayton in Ohio, who was not involved in this study. The novel fabrication technique, he adds, “opens a new avenue for generating vector fields at different frequencies through nonlinear optical processes”.

    With their initial study complete, Neshev and colleagues are now looking to refine their nanoantennas, both to increase the efficiency of the wavelength conversion process but also to extend the effects to other nonlinear interactions such as down-conversion.

    The research is described in the journal Nano Letters.

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  • richardmitnick 10:07 am on January 4, 2017 Permalink | Reply
    Tags: , Bugs, , Nanotechnology, Seeing Nano   

    From Duke: “Seeing Nano” 

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    Duke University

    Jan 1, 2017

    The sewer gnat is a common nuisance around kitchen and bathroom drains that’s no bigger than a pea. But magnified thousands of times, its compound eyes and bushy antennae resemble a first place winner in a Movember mustache contest.

    1
    An image of a sewer gnat’s head taken through a scanning electron microscope. Courtesy of Fred Nijhout.

    Sewer gnats’ larger cousins, horseflies are known for their painful bite. Zoom in and it’s easy to see how they hold onto their furry livestock prey: the tiny hooked hairs on their feet look like Velcro.

    Students in professor Fred Nijhout’s entomology class photograph these and other specimens at more than 300,000 times magnification at Duke’s Shared Materials Instrumentation Facility (SMIF).

    There the insects are dried, coated in gold and palladium, and then bombarded with a beam of electrons from a scanning electron microscope, which can resolve structures tens of thousands of times smaller than the width of a human hair.

    From a ladybug’s leg to a weevil’s suit of armor, the bristly, bumpy, pitted surfaces of insects are surprisingly beautiful when viewed up close.

    “The students have come to treat travels across the surface of an insect as the exploration of a different planet,” Nijhout said.

    2
    The foot of a horsefly is equipped with menacing claws and Velcro-like hairs that help them hang onto fur. Photo by Valerie Tornini.

    4
    The hard outer skeleton of a weevil looks smooth and shiny from afar, but up close it’s covered with scales and bristles. Courtesy of Fred Nijhout.

    You, too, can gaze at alien worlds too small to see with the naked eye. Students and instructors across campus can use the SMIF’s high-powered microscopes and other state of the art research equipment at no charge with support from the Class-Based Explorations Program.

    Biologist Eric Spana’s experimental genetics class uses the microscopes to study fruit flies that carry genetic mutations that alter the shape of their wings.

    Students in professor Hadley Cocks’ mechanical engineering 415L class take lessons from objects that break. A scanning electron micrograph of a cracked cymbal once used by the Duke pep band reveals grooves and ridges consistent with the wear and tear from repeated banging.

    6
    Magnified 3000 times, the surface of this broken cymbal once used by the Duke Pep Band reveals signs of fatigue cracking. Courtesy of Hadley Cocks.

    These students are among more than 200 undergraduates in eight classes who benefitted from the program last year, thanks to a grant from the Donald Alstadt Foundation.

    You don’t have to be a scientist, either. Historians and art conservators have used scanning electron microscopes to study the surfaces of Bronze Age pottery, the composition of ancient paints and even dust from Egyptian mummies and the Shroud of Turin.

    Instructors and undergraduates are invited to find out how they could use the microscopes and other nanotech equipment in the SMIF in their teaching and research. Queries should be directed to Dr. Mark Walters, Director of SMIF, via email at mark.walters@duke.edu.

    See the full article here .

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    Duke Campus

    Younger than most other prestigious U.S. research universities, Duke University consistently ranks among the very best. Duke’s graduate and professional schools — in business, divinity, engineering, the environment, law, medicine, nursing and public policy — are among the leaders in their fields. Duke’s home campus is situated on nearly 9,000 acres in Durham, N.C, a city of more than 200,000 people. Duke also is active internationally through the Duke-NUS Graduate Medical School in Singapore, Duke Kunshan University in China and numerous research and education programs across the globe. More than 75 percent of Duke students pursue service-learning opportunities in Durham and around the world through DukeEngage and other programs that advance the university’s mission of “knowledge in service to society.”

     
  • richardmitnick 3:08 pm on January 3, 2017 Permalink | Reply
    Tags: , , Center for Functional Nanomaterials (CFN), Nanoscale 'Conversations' Create Complex and Multi-Layered Structures, Nanotechnology   

    From BNL: “Nanoscale ‘Conversations’ Create Complex, Multi-Layered Structures” 

    Brookhaven Lab

    December 22, 2016
    Justin Eure

    1
    Study co-authors Pawel Majewski and Kevin Yager preparing nanoscale films of self-assembling materials.

    Building nanomaterials with features spanning just billionths of a meter requires extraordinary precision. Scaling up that construction while increasing complexity presents a significant hurdle to the widespread use of such nano-engineered materials.

    Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have developed a way to efficiently create scalable, multilayer, multi-patterned nanoscale structures with unprecedented complexity.

    The Brookhaven team exploited self-assembly, where materials spontaneous snap together to form the desired structure. But they introduced a significant leap in material intelligence, because each self-assembled layer now guides the configuration of additional layers.

    The results, published in the journal Nature Communications, offer a new paradigm for nanoscale self-assembly, potentially advancing nanotechnology used for medicine, energy generation, and other applications.

    “There’s something amazing and rewarding about creating structures no one has ever seen before,” said study coauthor Kevin Yager, a scientist at Brookhaven Lab’s Center for Functional Nanomaterials (CFN). “We’re calling this responsive layering—like building a tower, but where each brick is intelligent and contains instructions for subsequent bricks.”

    The technique was pioneered entirely at the CFN, a DOE Office of Science User Facility.

    “The trick was chemically ‘sealing’ each layer to make it robust enough that the additional layers don’t disrupt it,” said lead author Atikur Rahman, a Brookhaven Lab postdoc during the study and now an assistant professor at the Indian Institute of Science Education and Research, Pune. “This granted us unprecedented control. We can now stack any sequence of self-organized layers to create increasingly intricate 3D structures.”

    Guiding nanoscale conversations

    2
    The added color in this scanning electron microscope (SEM) image showcases the discrete, self-assembled layers within these novel nanostructures. The pale blue bars are each roughly 4,000 times thinner than a single human hair. No image credit.

    Other nano-fabrication methods—such as lithography—can create precise nano-structures, but the spontaneous ordering of self-assembly makes it faster and easier. Further, responsive layering pushes that efficiency in new directions, enabling, for example, structures with internal channels or pockets that would be exceedingly difficult to make by any other means.

    “Self-assembly is inexpensive and scalable because it’s driven by intrinsic interactions,” said study coauthor and CFN scientist Gregory Doerk. “We avoid the complex tools that are traditionally used to carve precise nano-structures.”

    The CFN collaboration used thin films of block copolymers (BCP)—chains of two distinct molecules linked together. Through well-established techniques, the scientists spread BCP films across a substrate, applied heat, and watched the material self-assemble into a prescribed configuration. Imagine spreading LEGOs over a baking sheet, sticking it in the oven, and then seeing it emerge with each piece elegantly snapped together in perfect order.

    However, these materials are conventionally two-dimensional, and simply stacking them would yield a disordered mess. So the Brookhaven Lab scientists developed a way to have self-assembled layers discretely “talk” to one another.

    The team infused each layer with a vapor of inorganic molecules to seal the structure—a bit like applying nanoscale shellac to preserve a just-assembled puzzle.

    “We tuned the vapor infiltration step so that each layer’s structure exhibits controlled surface contours,” Rahman said. “Subsequent layers then feel and respond to this subtle topography.”

    Coauthor Pawel Majewski added, “Essentially, we open up a ‘conversation’ between layers. The surface patterns drive a kind of topographic crosstalk, and each layer acts as a template for the next one.”

    Exotic configurations

    4
    An aerial view of a complete, self-assembled, multilayer nanostructure. In this instance, parallel bars of block copolymers with varying thickness were criss-crossed. No image credit.

    As often occurs in fundamental research, this crosstalk was an unexpected phenomenon.

    “We were amazed when we first saw templated ordering from one layer to the next, Rahman said. “We knew immediately that we had to exhaustively test all the possible combinations of film layers and explore the technique’s potential.”

    The collaboration demonstrated the formation of a broad range of nano-structures—including many configurations never before observed. Some contained hollow chambers, round pegs, rods, and winding shapes.

    “This was really a Herculean effort on the part of Atikur,” Yager said. “The multi-layer samples covered a staggering range of combinations.”

    Mapping never-before-seen structures

    5
    This image shows the range of multilayer morphologies achieved through this new technique. The first column shows a cross section of the novel 3D nanostructures as captured by scanning electron microscopy (SEM). The computer renderings in the second column highlight the integrity and diversity of each distinct layer, while the overhead SEM view of the third column reveals the complex patterns achieved through the “intelligent” layering. No image credit.

    See the full article here .

    Please help promote STEM in your local schools.

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 3:21 pm on December 26, 2016 Permalink | Reply
    Tags: , , Nanotechnology, , Researchers Use World's Smallest Diamonds to Make Wires Three Atoms Wide,   

    From SLAC: “Researchers Use World’s Smallest Diamonds to Make Wires Three Atoms Wide” 


    SLAC Lab

    December 26, 2016

    LEGO-style Building Method Has Potential for Making One-Dimensional Materials with Extraordinary Properties

    1
    Fuzzy white clusters of nanowires on a lab bench, with a penny for scale. Assembled with the help of diamondoids, the microscopic nanowires can be seen with the naked eye because the strong mutual attraction between their diamondoid shells makes them clump together, in this case by the millions. At top right, an image made with a scanning electron microscope shows nanowire clusters magnified 10,000 times. (SEM image by Hao Yan/SIMES; photo by SLAC National Accelerator Laboratory)

    Scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have discovered a way to use diamondoids – the smallest possible bits of diamond – to assemble atoms into the thinnest possible electrical wires, just three atoms wide.

    By grabbing various types of atoms and putting them together LEGO-style, the new technique could potentially be used to build tiny wires for a wide range of applications, including fabrics that generate electricity, optoelectronic devices that employ both electricity and light, and superconducting materials that conduct electricity without any loss. The scientists reported their results today in Nature Materials.

    “What we have shown here is that we can make tiny, conductive wires of the smallest possible size that essentially assemble themselves,” said Hao Yan, a Stanford postdoctoral researcher and lead author of the paper. “The process is a simple, one-pot synthesis. You dump the ingredients together and you can get results in half an hour. It’s almost as if the diamondoids know where they want to go.”

    2
    This animation shows molecular building blocks joining the tip of a growing nanowire. Each block consists of a diamondoid – the smallest possible bit of diamond – attached to sulfur and copper atoms (yellow and brown spheres). Like LEGO blocks, they only fit together in certain ways that are determined by their size and shape. The copper and sulfur atoms form a conductive wire in the middle, and the diamondoids form an insulating outer shell. (SLAC National Accelerator Laboratory)

    The Smaller the Better

    3

    Illustration of a cluster of nanowires assembled by diamondoids
    An illustration shows a hexagonal cluster of seven nanowires assembled by diamondoids. Each wire has an electrically conductive core made of copper and sulfur atoms (brown and yellow spheres) surrounded by an insulating diamondoid shell. The natural attraction between diamondoids drives the assembly process. (H. Yan et al., Nature Materials)

    Although there are other ways to get materials to self-assemble, this is the first one shown to make a nanowire with a solid, crystalline core that has good electronic properties, said study co-author Nicholas Melosh, an associate professor at SLAC and Stanford and investigator with SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC.

    The needle-like wires have a semiconducting core – a combination of copper and sulfur known as a chalcogenide – surrounded by the attached diamondoids, which form an insulating shell.

    Their minuscule size is important, Melosh said, because a material that exists in just one or two dimensions – as atomic-scale dots, wires or sheets – can have very different, extraordinary properties compared to the same material made in bulk. The new method allows researchers to assemble those materials with atom-by-atom precision and control.

    The diamondoids they used as assembly tools are tiny, interlocking cages of carbon and hydrogen. Found naturally in petroleum fluids, they are extracted and separated by size and geometry in a SLAC laboratory. Over the past decade, a SIMES research program led by Melosh and SLAC/Stanford Professor Zhi-Xun Shen has found a number of potential uses for the little diamonds, including improving electron microscope images and making tiny electronic gadgets.

    4
    Stanford graduate student Fei Hua Li, left, and postdoctoral researcher Hao Yan in one of the SIMES labs where diamondoids – the tiniest bits of diamond – were used to assemble the thinnest possible nanowires. (SLAC National Accelerator Laboratory)

    Constructive Attraction

    5
    Ball-and-stick models of diamondoid atomic structures in the SIMES lab at SLAC. SIMES researchers used the smallest possible diamondoid – adamantane, a tiny cage made of 10 carbon atoms – to assemble the smallest possible nanowires, with conductive cores just three atoms wide. (SLAC National Accelerator Laboratory)

    For this study, the research team took advantage of the fact that diamondoids are strongly attracted to each other, through what are known as van der Waals forces. (This attraction is what makes the microscopic diamondoids clump together into sugar-like crystals, which is the only reason you can see them with the naked eye.)

    They started with the smallest possible diamondoids – single cages that contain just 10 carbon atoms – and attached a sulfur atom to each. Floating in a solution, each sulfur atom bonded with a single copper ion. This created the basic nanowire building block.

    The building blocks then drifted toward each other, drawn by the van der Waals attraction between the diamondoids, and attached to the growing tip of the nanowire.

    “Much like LEGO blocks, they only fit together in certain ways that are determined by their size and shape,” said Stanford graduate student Fei Hua Li, who played a critical role in synthesizing the tiny wires and figuring out how they grew. “The copper and sulfur atoms of each building block wound up in the middle, forming the conductive core of the wire, and the bulkier diamondoids wound up on the outside, forming the insulating shell.”

    A Versatile Toolkit for Creating Novel Materials

    The team has already used diamondoids to make one-dimensional nanowires based on cadmium, zinc, iron and silver, including some that grew long enough to see without a microscope, and they have experimented with carrying out the reactions in different solvents and with other types of rigid, cage-like molecules, such as carboranes.

    The cadmium-based wires are similar to materials used in optoelectronics, such as light-emitting diodes (LEDs), and the zinc-based ones are like those used in solar applications and in piezoelectric energy generators, which convert motion into electricity.

    “You can imagine weaving those into fabrics to generate energy,” Melosh said. “This method gives us a versatile toolkit where we can tinker with a number of ingredients and experimental conditions to create new materials with finely tuned electronic properties and interesting physics.”

    Theorists led by SIMES Director Thomas Devereaux modeled and predicted the electronic properties of the nanowires, which were examined with X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource, a DOE Office of Science User Facility, to determine their structure and other characteristics.

    The team also included researchers from the Stanford Department of Materials Science and Engineering, Lawrence Berkeley National Laboratory, the National Autonomous University of Mexico (UNAM) and Justus-Liebig University in Germany. Parts of the research were carried out at Berkeley Lab’s Advanced Light Source (ALS)

    LBNL ALS interior
    LBNL ALS

    and National Energy Research Scientific Computing Center (NERSC),

    NERSC CRAY Cori supercomputer
    NERSC

    both DOE Office of Science User Facilities. The work was funded by the DOE Office of Science and the German Research Foundation.

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 2:42 pm on December 26, 2016 Permalink | Reply
    Tags: , , , Nanodisc technology, Nanotechnology,   

    From U Michigan via phys.org: “Nanodiscs deliver personalized cancer therapy to immune system” 

    U Michigan bloc

    University of Michigan

    phys.org

    phys.org

    December 26, 2016
    Researchers at the University of Michigan have had initial success in mice using nanodiscs to deliver a customized therapeutic vaccine for the treatment of colon and melanoma cancer tumors.

    “We are basically educating the immune system with these nanodiscs so that immune cells can attack cancer cells in a personalized manner,” said James Moon, the John Gideon Searle assistant professor of pharmaceutical sciences and biomedical engineering.

    Personalized immunotherapy is a fast-growing field of research in the fight against cancer.

    The therapeutic cancer vaccine employs nanodiscs loaded with tumor neoantigens, which are unique mutations found in tumor cells. By generating T-cells that recognize these specific neoantigens, the technology targets cancer mutations and fights to eliminate cancer cells and prevent tumor growth.

    Unlike preventive vaccinations, therapeutic cancer vaccines of this type are meant to kill established cancer cells.

    “The idea is that these vaccine nanodiscs will trigger the immune system to fight the existing cancer cells in a personalized manner,” Moon said.

    The nanodisc technology was tested in mice with established melanoma and colon cancer tumors. After the vaccination, twenty-seven percent of T-cells in the blood of the mice in the study targeted the tumors.

    When combined with immune checkpoint inhibitors, an existing technology that amplifies T-cell tumor-fighting responses, the nanodisc technology killed tumors within 10 days of treatment in the majority of the mice. After waiting 70 days, researchers then injected the same mice with the same tumor cells, and the tumors were rejected by the immune system and did not grow.

    “This suggests the immune system ‘remembered’ the cancer cells for long-term immunity,” said Rui Kuai, U-M doctoral student in pharmaceutical sciences and lead author of the study.

    “The holy grail in cancer immunotherapy is to eradicate tumors and prevent future recurrence without systemic toxicity, and our studies have produced very promising results in mice,” Moon said.

    The technology is made of extremely small, synthetic high density lipoproteins measuring roughly 10 nanometers. By comparison, a human hair is 80,000 to 100,000 nanometers wide.

    “It’s a powerful vaccine technology that efficiently delivers vaccine components to the right cells in the right tissues. Better delivery translates to better T-cell responses and better efficacy,” said study co-senior author Anna Schwendeman, U-M assistant professor of pharmacy.

    The next step is to test the nanodisc technology in a larger group of larger animals, Moon said.

    EVOQ Therapeutics, a new U-M spinoff biotech company, has been founded to translate these results to the clinic. Lukasz Ochyl, a doctoral student in pharmaceutical sciences, is also a co-author.

    The study, Designer vaccine nanodiscs for personalized cancer immunotherapy, is scheduled for advance online publication Dec. 26 on the Nature Materials website.

    See the full article here .

    Please help promote STEM in your local schools.

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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.

     
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