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  • richardmitnick 9:44 am on March 29, 2017 Permalink | Reply
    Tags: , , , Nanotechnology, ,   

    From MIT: “Progress toward a Zika vaccine” A lot of Zika News Lately 

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    March 29, 2017
    Anne Trafton

    1
    MIT researchers have devised a new vaccine candidate for the Zika virus. “It functions almost like a synthetic virus, except it’s not pathogenic and it doesn’t spread,” says postdoc Omar Khan. Image: Jose-Luis Olivares/MIT

    Researchers program RNA nanoparticles that could protect against the virus.

    Using a new strategy that can rapidly generate customized RNA vaccines, MIT researchers have devised a new vaccine candidate for the Zika virus.

    The vaccine consists of strands of genetic material known as messenger RNA, which are packaged into a nanoparticle that delivers the RNA into cells. Once inside cells, the RNA is translated into proteins that provoke an immune response from the host, but the RNA does not integrate itself into the host genome, making it potentially safer than a DNA vaccine or vaccinating with the virus itself.

    “It functions almost like a synthetic virus, except it’s not pathogenic and it doesn’t spread,” says Omar Khan, a postdoc at MIT’s Koch Institute for Integrative Cancer Research and an author of the new study. “We can control how long it’s expressed, and it’s RNA so it will never integrate into the host genome.”

    This research also yielded a new benchmark for evaluating the effectiveness of other Zika vaccine candidates, which could help others who are working toward the same goal.

    Jasdave Chahal, a postdoc at MIT’s Whitehead Institute for Biomedical Research, is the first author of the paper, which appears in Scientific Reports. The paper’s senior author is Hidde Ploegh, a former MIT biology professor and Whitehead Institute member who is now a senior investigator in the Program in Cellular and Molecular Medicine at Boston Children’s Hospital.

    Other authors of the paper are Tao Fang and Andrew Woodham, both former Whitehead Institute postdocs in the Ploegh lab; Jingjing Ling, an MIT graduate student; and Daniel Anderson, an associate professor in MIT’s Department of Chemical Engineering and a member of the Koch Institute and MIT’s Institute for Medical Engineering and Science (IMES).

    Programmable vaccines

    The MIT team first reported its new approach to programmable RNA vaccines last year. RNA vaccines are appealing because they induce host cells to produce many copies of the proteins encoded by the RNA. This provokes a stronger immune reaction than if the proteins were administered on their own. However, finding a safe and effective way to deliver these vaccines has proven challenging.

    The researchers devised an approach in which they package RNA sequences into a nanoparticle made from a branched molecule that is based on fractal-patterned dendrimers. This modified-dendrimer-RNA structure can be induced to fold over itself many times, producing a spherical particle about 150 nanometers in diameter. This is similar in size to a typical virus, allowing the particles to enter cells through the same viral entry mechanisms. In their 2016 paper, the researchers used this nanoparticle approach to generate experimental vaccines for Ebola, H1N1 influenza, and the parasite Toxoplasma gondii.

    In the new study, the researchers tackled Zika virus, which emerged as an epidemic centered in Brazil in 2015 and has since spread around the world, causing serious birth defects in babies born to infected mothers. Since the MIT method does not require working with the virus itself, the researchers believe they might be able to explore potential vaccines more rapidly than scientists pursuing a more traditional approach.

    Instead of using viral proteins or weakened forms of the virus as vaccines, which are the most common strategies, the researchers simply programmed their RNA nanoparticles with the sequences that encode Zika virus proteins. Once injected into the body, these molecules replicate themselves inside cells and instruct cells to produce the viral proteins.

    The entire process of designing, producing, and testing the vaccine in mice took less time than it took for the researchers to obtain permission to work with samples of the Zika virus, which they eventually did get.

    “That’s the beauty of it,” Chahal says. “Once we decided to do it, in two weeks we were ready to vaccinate mice. Access to virus itself was not necessary.”

    Measuring response

    When developing a vaccine, researchers usually aim to generate a response from both arms of the immune system — the adaptive arm, mediated by T cells and antibodies, and the innate arm, which is necessary to amplify the adaptive response. To measure whether an experimental vaccine has generated a strong T cell response, researchers can remove T cells from the body and then measure how they respond to fragments of the viral protein.

    Until now, researchers working on Zika vaccines have had to buy libraries of different protein fragments and then test T cells on them, which is an expensive and time-consuming process. Because the MIT researchers could generate so many T cells from their vaccinated mice, they were able to rapidly screen them against this library. They identified a sequence of eight amino acids that the activated T cells in the mouse respond to. Now that this sequence, also called an epitope, is known, other researchers can use it to test their own experimental Zika vaccines in the appropriate mouse models.

    “We can synthetically make these vaccines that are almost like infecting someone with the actual virus, and then generate an immune response and use the data from that response to help other people predict if their vaccines would work, if they bind to the same epitopes,” Khan says. The researchers hope to eventually move their Zika vaccine into tests in humans.

    “The identification and characterization of CD8 T cell epitopes in mice immunized with a Zika RNA vaccine is a very useful reference for all those working in the field of Zika vaccine development,” says Katja Fink, a principal investigator at the A*STAR Singapore Immunology Network. “RNA vaccines have received much attention in the last few years, and while the big breakthrough in humans has not been achieved yet, the technology holds promise to become a flexible platform that could provide rapid solutions for emerging viruses.”

    Fink, who was not involved in the research, added that the “initial data are promising but the Zika RNA vaccine approach described needs further testing to prove efficacy.”

    Another major area of focus for the researchers is cancer vaccines. Many scientists are working on vaccines that could program a patient’s immune system to attack tumor cells, but in order to do that, they need to know what the vaccine should target. The new MIT strategy could allow scientists to quickly generate personalized RNA vaccines based on the genetic sequence of an individual patient’s tumor cells.

    The research was funded by the National Institutes of Health, a Fujifilm/MediVector grant, the Lustgarten Foundation, a Koch Institute and Dana-Farber/Harvard Center Center Bridge Project award, the Department of Defense Office of Congressionally Directed Medical Research’s Joint Warfighter Medical Research Program, and the Cancer Center Support Grant from the National Cancer Institute.

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  • richardmitnick 7:22 am on March 29, 2017 Permalink | Reply
    Tags: , , Nanotechnology, , Stanford Extreme Environment Microsystems Laboratory   

    From Stanford: “New nano devices could withstand extreme environments in space and on earth” 

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    Stanford University

    March 28, 2017
    Ula Chrobak

    1
    Professor Debbie Senesky, left, works with graduate student Caitlin Chapin on electronics that can resist extreme environments. (Image credit: L.A. Cicero)

    Behind its thick swirling clouds, Venus is hiding a hot surface pelted with sulfuric acid rains. At 480 degrees C, the planet’s atmosphere would fry any of today’s electronics, posing a challenge to scientists hoping to study this extreme environment.

    Researchers at the Stanford Extreme Environment Microsystems Laboratory, or the XLab, are on a mission to conquer these conditions. By developing heat-, corrosion- and radiation-resistant electronics, they hope to move research into extreme places in the universe – including here on Earth. And it all starts with tiny, nano-scale slices of material.

    “I think it’s important to understand and gain new insight through probing these unique environments,” said Debbie Senesky, assistant professor of aeronautics and astronautics and principal investigator at the XLab.

    Senesky hopes that by studying Venus we can better understand our own world. While it’s hard to imagine that hot and corrosive Venus ever looked like Earth, scientists think that it used to be much cooler. Billions of years ago, a runaway greenhouse effect may have caused the planet to absorb far more heat than it could reflect, creating today’s scorching conditions. Understanding how Venus got so hot can help us learn about our atmosphere.

    “If we can understand the history of Venus, maybe we can understand and positively impact the future evolution of our own habitat,” said Senesky.

    What’s more, devices that can withstand the rigors of space travel could also monitor equally challenging conditions here on earth, such as in our cars.

    Scorching heat

    One hurdle to studying extreme environments is the heat. Silicon-based semiconductors, which power our smartphones and laptops, stop working at about 300 degrees C. As they heat up, the metal parts begin to melt into neighboring semiconductor and don’t move electricity as efficiently.

    Ateeq Suria, graduate student in mechanical engineering, is one of the people at the XLab working to overcome this temperature barrier. To do that, he hopped into his bunny suit — overall lab apparel that prevents contamination — and made use of ultra-clean work spaces to create an atoms-thick, heat-resistant layer that can coat devices and allow them to work at up to 600 degrees C in air [sorry, no image].

    “The diameter of human hair is about 70 micrometers,” said Suria. “These coatings are about a hundredth of that width.”

    Suria and others at the XLab are working to improve these nano-devices, testing materials at temperatures of up to 900 C degrees. For space electronics, it’s a key step in understanding how they survive for long periods of time. Although a device might not be exposed to such temperature extremes in space, the test conditions rapidly age materials, indicating how long they could last.

    The team at XLab tests materials and nano-devices they create either in-house in high-temperature probe stations or in a Venus simulator at the NASA Glenn Research Center in Cleveland, Ohio. That simulator mimics the pressure, chemistry and temperature of Venus. To mirror the effects of space radiation, they also test materials at Los Alamos National Laboratory and at NASA Ames Research Center.

    Radiation damage

    More than just surviving on Venus, getting there is important, too. Objects in space are pounded by a flurry of gamma and proton radiation that knock atoms around and degrade materials. Preliminary work at the XLab demonstrates that sensors they’ve developed could survive up to 50 years of radiation bombardment while in Earth’s orbit.

    Senesky said that if their fabrication process for nano-scale materials proves effective it could get incorporated into technologies being launched into space.

    “I’m super excited about the possibility of NASA adopting our technology in the design of their probes and landers,” said Senesky.

    Hot electronics at home

    While space is an exciting frontier, Suria said that interest in understanding car engines initially fueled this research. Inside an engine, temperatures reach up to 1000 degrees C, and the outer surface of a piston is 600 degrees C. Current technology to monitor and optimize engine performance can’t handle this heat, introducing error because measuring devices have to be placed far away from the pistons.

    Electronics designed to survive the intense conditions of space could be placed next to the engine’s pistons to directly monitor performance and improve efficiency.

    “You just put the sensor right in the engine and get much better information out,” said Suria.

    Other fiery, high pressure earth-bound environments that would benefit from these robust electronics include oil and gas wellbores, geothermal vents, aircraft engines, gas turbines and hypersonic structures.

    Media Contacts

    Amy Adams, Stanford News Service; (650) 796-3695, amyadams@stanford.edu

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  • richardmitnick 9:48 am on March 20, 2017 Permalink | Reply
    Tags: , , Crystallites, Disorder can be good, , Nanotechnology, Pyrolysis, Vickers hardness test   

    From MIT: “Disorder can be good” 

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    March 17, 2017
    Denis Paiste

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    MIT aerospace researchers have demonstrated that some randomness in the arrangement of carbon atoms makes materials that are lighter and stronger, shown at lower right in illustration, compared to a more densely packed and tightly ordered structure, shown lower left. They formed a type of disordered graphite-like carbon material that is often called glassy carbon by “baking” a phenol-formadehyde hydrocarbon precursor at high temperature in inert gas, a process commonly known as pyrolysis. Illustration: Itai Stein

    Researchers discover that chaos makes carbon materials lighter and stronger.

    In the quest for more efficient vehicles, engineers are using harder and lower-density carbon materials, such as carbon fibers, which can be manufactured sustainably by “baking” naturally occurring soft hydrocarbons in the absence of oxygen. However, the optimal “baking” temperature for these hardened, charcoal-like carbon materials remained a mystery since the 1950s when British scientist Rosalind Franklin, who is perhaps better known for providing critical evidence of DNA’s double helix structure, discovered how the carbon atoms in sugar, coal, and similar hydrocarbons, react to temperatures approaching 3,000 degrees Celsius (5,432 degrees Fahrenheit) in oxygen-free processing. Confusion over whether disorder makes these graphite-like materials stronger, or weaker, prevented identifying the ideal “baking” temperature for more than 40 years.

    Fewer, more chaotically arranged carbon atoms produce higher-strength materials, MIT researchers report in the journal Carbon. They find a tangible link between the random ordering of carbon atoms within a phenol-formaldehyde resin, which was “baked” at high temperatures, and the strength and density of the resulting graphite-like carbon material. Phenol-formaldehyde resin is a hydrocarbon commonly known as “SU-8” in the electronics industry. Additionally, by comparing the performance of the “baked” carbon material, the MIT researchers identified a “sweet spot” manufacturing temperature: 1,000 C (1,832 F).

    “These materials we’re working with, which are commonly found in SU-8 and other hydrocarbons that can be hardened using ultraviolet [UV] light, are really promising for making strong and light lattices of beams and struts on the nanoscale, which only recently became possible due to advances in 3-D printing,” says MIT postdoc Itai Stein SM ’13, PhD ’16. “But up to now, nobody really knew what happens when you’re changing the manufacturing temperature, that is, how the structure affects the properties. There was a lot of work on structure and a lot of work on properties, but there was no connection between the two. … We hope that our study will help to shed some light on the governing physical mechanisms that are at play.”

    Stein, who is the lead author of the paper published in Carbon, led a team under professor of aeronautics and astronautics Brian L. Wardle, consisting of MIT junior Chlöe V. Sackier, alumni Mackenzie E. Devoe ’15 and Hanna M. Vincent ’14, and undergraduate Summer Scholars Alexander J. Constable and Naomi Morales-Medina.

    “Our investigations into this carbon material as a matrix for nanocomposites kept leading to more questions making this topic increasingly interesting in and of itself. Through a series of contributions, notably from MIT undergraduate researchers and Summer Scholars, a sustained investigation of several years resulted, allowing some paradoxical results in the extant literature to be resolved,” Wardle says.

    By “baking” the resin at high temperature in inert gas, a process commonly known as pyrolysis, the researchers formed a type of disordered graphite-like carbon material that is often called glassy carbon. Stein and Wardle showed that when it is processed at temperatures higher than 1,000 C, the material becomes more ordered but weaker. They estimated the strength of their glassy carbon by applying a local force and measuring their material’s ability to resist deformation. This type of measurement, which is known to engineers as the Vickers hardness test, is a highly versatile technique that can be used to study a wide variety of materials, such as metals, glasses, and plastics, and enabled the researchers to compare their findings to many well-known engineering materials that include diamond, carbon fiber composites, and metal carbides.

    The carbon atoms within the MIT researchers’ material were more chaotically organized than is typical for graphite, and this was because phenol-formaldehyde with which they started is a complicated mix of carbon-rich compounds. “Because the hydrocarbon was disordered to begin with, a lot of the disorder remains in your crystallites, at least at this temperature,” Stein explains. In fact, the presence of more complex carbon compounds in the material strengthens it by leading to three-dimensional connections that are hard to break. “Basically you get pinned at the crystallite interface, and that leads to enhanced performance,” he says.

    These high-temperature baked materials have only one carbon atom in their structure for every three in a diamond structure. “When you’re using these materials to make nanolattices, you can make the overall lattice even less dense. Future studies should be able to show how to make lighter and cheaper materials,” Stein suggests. Hydrocarbons similar to the phenol-formaldehyde studied here can also be sourced in an environmentally friendly way, he says.

    “Up until now there wasn’t really consensus about whether having a low density was good or bad, and we’re showing in this work, that having a low density is actually good,” Stein says. That’s because low density in these crystallites means more molecular connections in three dimensions, which helps the material resist shearing, or sliding apart. Because of its low density, this material compares favorably to diamond and boron nitrides for aerospace uses. “Essentially, you can use a lot more of this material and still end up saving weight overall,” Stein says.

    “This study represents sound materials science — connecting all three facets of synthesis, structure, and property — toward elucidating poorly understood scaling laws for mechanical performance of pyrolytic carbon,” says Eric Meshot, a staff scientist at Lawrence Livermore National Laboratory, who was not involved in this research. “It is remarkable that by employing routinely available characterization tools, the researchers pieced together both the molecular and nanoscale structural pictures and deciphered this counterintuitive result that more graphitization does not necessarily equal a harder material. It is an intriguing concept in and of itself that a little structural disorder can enhance the hardness.”

    “Their structural characterization proves how and why they achieve high hardness at relatively low synthesis temperatures,” Meshot adds. “This could be impactful for industries seeking to scale up production of these types of materials since heating is a seriously costly step.” The study also points to new directions for making low-density composite structures with truly transformative properties, he suggests. “For example, by incorporating the starting SU-8 resin in, on, or around other structures (such as nanotubes as the authors suggest), can we synthesize materials that are even harder or more resistant to sheer? Or composites that possibly embed additional functionality, such as sensing?” Meshot asks.

    The new research has particular relevance now because a group of German researchers showed last year in a Nature Materials paper how these materials can form highly structured nanolattices that are strong, lightweight, and are outperformed only by diamond. Those researchers processed their material at 900 C, Stein notes. “You can do a lot more optimization, knowing what the scaling is of the mechanical properties with the structure, then you can go ahead and tune the structure accordingly, and that’s where we believe there is broad implication for our work in this study,” he says.

    This work was partly supported by MIT’s Nano-Engineered Composite aerospace STructures (NECST) Consortium members Airbus Group, Boeing, Embraer, Lockheed Martin, Saab AB, ANSYS, Hexcel, and TohoTenax. Stein was supported, in part, by a National Defense Science and Engineering Graduate Fellowship.

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  • richardmitnick 8:48 am on March 20, 2017 Permalink | Reply
    Tags: Anderson limit, , How small can superconductors be?, Nanotechnology, P.W. Anderson, Parity effect, , , Richardson-Gaudin models   

    From phys.org: “How small can superconductors be?” 

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    phys.org

    March 20, 2017
    Lisa Zyga

    1
    Topographic image of a lead nanocrystal used in the study. Scale bar: 10 nm. Credit: Vlaic et al. Nature Communications

    For the first time, physicists have experimentally validated a 1959 conjecture that places limits on how small superconductors can be. Understanding superconductivity (or the lack thereof) on the nanoscale is expected to be important for designing future quantum computers, among other applications.

    In 1959, physicist P.W. Anderson conjectured that superconductivity can exist only in objects that are large enough to meet certain criteria. Namely, the object’s superconducting gap energy must be larger than its electronic energy level spacing—and this spacing increases as size decreases. The cutoff point (where the two values are equal) corresponds to a volume of about 100 nm3. Until now it has not been possible to experimentally test the Anderson limit due to the challenges in observing superconducting effects at this scale.

    In the new study published in Nature Communications, Sergio Vlaic and coauthors at the University Paris Sciences et Lettres and French National Centre for Scientific Research (CNRS) designed a nanosystem that allowed them to experimentally investigate the Anderson limit for the first time.

    The Anderson limit arises because, at very small scales, the mechanisms underlying superconductivity essentially stop working. In general, superconductivity occurs when electrons bind together to form Cooper pairs. Cooper pairs have a slightly lower energy than individual electrons, and this difference in energy is the superconducting gap energy. The Cooper pairs’ lower energy inhibits electron collisions that normally create resistance. If the superconducting gap energy gets too small and vanishes—which can occur, for example, when the temperature increases—then the electron collisions resume and the object stops being a superconductor.

    The Anderson limit shows that small size is another way that an object may stop being a superconductor. However, unlike the effects of increasing the temperature, this is not because smaller objects have a smaller superconducting gap energy. Instead, it arises because smaller crystals have fewer electrons, and therefore fewer electron energy levels, than larger crystals do. Since the total possible electron energy of an element stays the same, regardless of size, smaller crystals have larger spacings between their electron energy levels than larger crystals do.

    According to Anderson, this large electronic energy level spacing should pose a problem, and he expected superconductivity to disappear when the spacing becomes larger than the superconducting gap energy. The reason for this, generally speaking, is that one consequence of increased spacing is a decrease in potential energy, which interferes with the competition between kinetic and potential energy that is necessary for superconductivity to occur.

    To investigate what happens to the superconductivity of objects around the Anderson limit, the scientists in the new study prepared large quantities of isolated lead nanocrystals ranging in volume from 20 to 800 nm3.

    Although they could not directly measure the superconductivity of such tiny objects, the researchers could measure something called the parity effect, which results from superconductivity. When an electron is added to a superconductor, the additional energy is partly affected by whether there is an even or odd number of electrons (the parity), which is due to the electrons forming Cooper pairs. If the electrons don’t form Cooper pairs, there is no parity effect, indicating no superconductivity.

    Although the parity effect has previously been observed in large superconductors, this study is the first time that it has been observed in small nanocrystals approaching the Anderson limit. In accordance with Anderson’s predictions from more than 50 years ago, the researchers observed the parity effect for larger nanocrystals, but not for the smallest nanocrystals below approximately 100 nm3.

    The results not only validate the Anderson conjecture, but also extend to a more general area, the Richardson-Gaudin models. These models are equivalent to the conventional theory of superconductivity, the Bardeen Cooper Schrieffer theory, for very small objects.

    “Our experimental demonstration of the Anderson conjecture is also a demonstration of the validity of the Richardson-Gaudin models,” coauthor Hervé Aubin at the University Paris Sciences et Lettres and CNRS told Phys.org. “The Richardson-Gaudin models are an important piece of theoretical works because they can be solved exactly and apply to a wide range of systems; not only to superconducting nanocrystals but also to atomic nuclei and cold fermionic atomic gas, where protons and neutrons, which are fermions like electrons, can also form Cooper pairs.”

    On the more practical side, the researchers expect the results to have applications in future quantum computers.

    “One of the most interesting applications of superconducting islands is their use as Cooper pair boxes employed in quantum bits, the elemental unit of a hypothetical quantum computer,” Aubin said. “So far, Cooper pair boxes used in qubits are much larger than the Anderson limit. Upon reducing the size of the Cooper pair box, quantum computer engineers will eventually have to cope with superconductivity at the Anderson limit.”

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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 7:51 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” 

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    February 21, 2017
    Matthew Chin

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    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.

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    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” 

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    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.

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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 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” 

    UCLA bloc

    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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    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
    MIT News
    MIT Widget

    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.

    See the full article here .

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    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
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