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  • richardmitnick 6:02 pm on November 21, 2017 Permalink | Reply
    Tags: , , , , , , , Nanotechnology, Plasma-facing material   

    From BNL: “Designing New Metal Alloys Using Engineered Nanostructures” 

    Brookhaven Lab

    Stony Brook University assistant professor Jason Trelewicz brings his research to design and stabilize nanostructures in metals to Brookhaven Lab’s Center for Functional Nanomaterials.

    1
    Materials scientist Jason Trelewicz in an electron microscopy laboratory at Brookhaven’s Center for Functional Nanomaterials, where he characterizes nanoscale structures in metals mixed with other elements.

    Materials science is a field that Jason Trelewicz has been interested in since he was a young child, when his father—an engineer—would bring him to work. In the materials lab at his father’s workplace, Trelewicz would use optical microscopes to zoom in on material surfaces, intrigued by all the distinct features he would see as light interacted with different samples.

    Now, Trelewicz—an assistant professor in the College of Engineering and Applied Sciences’ Department of Materials Science and Chemical Engineering with a joint appointment in the Institute for Advanced Computational Science at Stony Brook University and principal investigator of the Engineered Metallic Nanostructures Laboratory—takes advantage of the much higher magnifications of electron microscopes to see tiny nanostructures in fine detail and learn what happens when they are exposed to heat, radiation, and mechanical forces. In particular, Trelewicz is interested in nanostructured metal alloys (metals mixed with other elements) that incorporate nanometer-sized features into classical materials to enhance their performance. The information collected from electron microscopy studies helps him understand interactions between structural and chemical features at the nanoscale. This understanding can then be employed to tune the properties of materials for use in everything from aerospace and automotive components to consumer electronics and nuclear reactors.

    Since 2012, when he arrived at Stony Brook University, Trelewicz has been using the electron microscopes and the high-performance computing (HPC) cluster at the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory—to perform his research.

    “At the time, I was looking for ways to apply my idea of stabilizing nanostructures in metals to an application-oriented problem,” said Trelewicz. “I’ve long been interested in nuclear energy technologies, initially reading about fusion in grade school. The idea of recreating the processes responsible for the energy we receive from the sun here on earth was captivating, and fueled my interest in nuclear energy throughout my entire academic career. Though we are still very far away from a fusion reactor that generates power, a large international team on a project under construction in France called ITER is working to demonstrate a prolonged fusion reaction at a large scale.”

    Plasma-facing materials for fusion reactors

    Nuclear fusion—the reaction in which atomic nuclei collide—could provide a nearly unlimited supply of safe, clean energy, like that naturally produced by the sun through fusing hydrogen nuclei into helium atoms. Harnessing this carbon-free energy in reactors requires generating and sustaining a plasma, an ionized gas, at the very high temperatures at which fusion occurs (about six times hotter than the sun’s core) while confining it using magnetic fields. Of the many challenges currently facing fusion reactor demonstrations, one of particular interest to Trelewicz is creating viable materials to build a reactor.

    2
    A model of the ITER tokamak, an experimental machine designed to harness the energy of fusion. A powerful magnetic field is used to confine the plasma, which is held in a doughnut-shaped vessel. Credit: ITER Organization.

    “The formidable materials challenges for fusion are where I saw an opportunity for my research—developing materials that can survive inside the fusion reactor, where the plasma will generate high heat fluxes, high thermal stresses, and high particle and neutron fluxes,” said Trelewicz. “The operational conditions in this environment are among the harshest in which one could expect a material to function.”

    A primary candidate for such “plasma-facing material” is tungsten, because of its high melting point—the highest one among metals in pure form—and low sputtering yield (number of atoms ejected by energetic ions from the plasma). However, tungsten’s stability against recrystallization, oxidation resistance, long-term radiation tolerance, and mechanical performance are problematic.

    Trelewicz thinks that designing tungsten alloys with precisely tailored nanostructures could be a way to overcome these problems. In August, he received a $750,000 five-year award from the DOE’s Early Career Research Program to develop stable nanocrystalline tungsten alloys that can withstand the demanding environment of a fusion reactor. His research is combining simulations that model atomic interactions and experiments involving real-time ion irradiation exposure and mechanical testing to understand the fundamental mechanisms responsible for the alloys’ thermal stability, radiation tolerance and mechanical performance. The insights from this research will inform the design of more resilient alloys for fusion applications.

    In addition to the computational resources they use at their home institution, Trelewicz and his lab group are using the HPC cluster at the CFN—and those at other DOE facilities, such as Titan at Oak Ridge Leadership Computing Facility (a DOE Office of Science User Facility at Oak Ridge National Laboratory)—to conduct large-scale atomistic simulations as part of the project.

    ORNL Cray Titan XK7 Supercomputer

    “The length scales of the structures we want to design into our materials are on the order of a few nanometers to 100 nanometers, and a single simulation can involve up to 10 million atoms,” said Trelewicz. “Using HPC clusters, we can build a system atom-by-atom, representative of the structure we would like to explore experimentally, and run simulations to study the response of that system under various external stimuli. For example, we can fire a high-energy atom into the system and watch what happens to the material and how it evolves, hundreds or thousands of times. Once damage has accumulated in the structure, we can simulate thermal and mechanical forces to understand how defect structure impacts other behavior.”

    These simulations inform the structures and chemistries of experimental alloys, which Trelewicz and his students fabricate at Stony Brook University through high-energy milling. To characterize the nanoscale structure and chemical distribution of the engineered alloys, they extensively use the microscopy facilities at the CFN—including scanning electron microscopes, transmission electron microscopes, and scanning transmission electron microscopes. Imaging is conducted at high resolution and often combined with heating within the microscope to examine in real time how the structures evolve with temperature. Experiments are also conducted at other DOE national labs, such as Sandia through collaboration with materials scientist Khalid Hattar of the Ion Beam Laboratory. Here, students in Trelewicz’s research group simultaneously irradiate the engineered alloys with an ion beam and image them with an electron microscope over the course of many days.

    3
    Trelewicz and his students irradiated a nanostructured tungsten-titanium alloy with high-energy gold ions to explore the radiation tolerance of this novel material.

    “Though this damage does not compare to what the material would experience in a reactor, it provides a starting point to evaluate whether or not the engineered material could indeed address some of the limitations of tungsten for fusion applications,” said Trelewicz.

    Electron microscopy at the CFN has played a key role in an exciting discovery that Trelewicz’s students recently made: an unexpected metastable-to-stable phase transition in thin films of nanostructured tungsten. This phase transition drives an abnormal “grain” growth process in which some crystalline nanostructure features grow very dramatically at the expense of others. When the students added chromium and titanium to tungsten, this metastable phase was completely eliminated, in turn enhancing the thermal stability of the material.

    “One of the great aspects of having both experimental and computational components to our research is that when we learn new things from our experiments, we can go back and tailor the simulations to more accurately reflect the actual materials,” said Trelewicz.

    Other projects in Trelewicz’s research group.

    The research with tungsten is only one of many projects ongoing in the Engineered Metallic Nanostructures Laboratory.

    “All of our projects fall under the umbrella of developing new metal alloys with enhanced and/or multifunctional properties,” said Trelewicz. “We are looking at different strategies to optimize material performance by collectively tailoring chemistry and microstructure in our materials. Much of the science lies in understanding the nanoscale mechanisms that govern the properties we measure at the macroscale.”

    4
    Jason Trelewicz (left) with Olivia Donaldson, who recently graduated with her PhD from Trelewicz’s group, and Jonathan Gentile, a current doctoral student, in front of the scanning electron microscope/focused-ion beam at Stony Brook University’s Advanced Energy Center. Credit: Stony Brook University.

    Through a National Science Foundation CAREER (Faculty Early Career Development Program) award, Trelewicz and his research group are exploring another class of high-strength alloys—amorphous metals, or “metallic glasses,” which are metals that have a disordered atomic structure akin to glass. Compared to everyday metals, metallic glasses are often inherently higher strength but usually very brittle, and it is difficult to make them in large parts such as bulk sheets. Trelewicz’s team is designing interfaces and engineering them into the metallic glasses—initially iron-based and later zirconium-based ones—to enhance the toughness of the materials, and exploring additive manufacturing processes to enable sheet-metal production. They will use the Nanofabrication Facility at the CFN to fabricate thin films of these interface-engineered metallic glasses for in situ analysis using electron microscopy techniques.

    In a similar project, they are seeking to understand how introducing a crystalline phase into a zirconium-based amorphous alloy to form a metallic glass matrix composite (composed of both amorphous and crystalline phases) augments the deformation process relative to that of regular metallic glasses. Metallic glasses usually fail catastrophically because strain becomes localized into shear bands. Introducing crystalline regions in the metallic glasses could inhibit the process by which strain localizes in the material. They have already demonstrated that the presence of the crystalline phase fundamentally alters the mechanism through which the shear bands form.

    Trelewicz and his group are also exploring the deformation behavior of metallic “nanolaminates” that consist of alternating crystalline and amorphous layers, and are trying to approach the theoretical limit of strength in lightweight aluminum alloys through synergistic chemical doping strategies (adding other elements to a material to change its properties).

    5
    Trelewicz and his students perform large-scale atomistic simulations to explore the segregation of solute species to grain boundaries (GBs)—interfaces between grains—in nanostructured alloys, as shown here for an aluminum-magnesium (Al-Mg) system, and its implications for the governing deformation mechanisms. They are using the insights gained through these simulations to design lightweight alloys with theoretical strengths.

    “We leverage resources of the CFN for every project ongoing in my research group,” said Trelewicz. “We extensively use the electron microscopy facilities to look at material micro- and nanostructure, very often at how interfaces are coupled with compositional inhomogeneities—information that helps us stabilize and design interfacial networks in nanostructured metal alloys. Computational modeling and simulation enabled by the HPC clusters at the CFN informs what we do in our experiments.”

    Beyond his work at CFN, Trelewicz collaborates with his departmental colleagues to characterize materials at the National Synchrotron Light Source II—another DOE Office of Science User Facility at Brookhaven.

    BNL NSLS-II


    BNL NSLS II

    “There are various ways to characterize structural and chemical inhomogeneities,” said Trelewicz. “We look at small amounts of material through the electron microscopes at CFN and on more of a bulk level at NSLS-II through techniques such as x-ray diffraction and the micro/nano probe. We combine this local and global information to thoroughly characterize a material and use this information to optimize its properties.”

    Future of next-generation materials

    When he is not doing research, Trelewicz is typically busy with student outreach. He connects with the technology departments at various schools, providing them with materials engineering design projects. The students not only participate in the engineering aspects of materials design but are also trained on how to use 3D printers and other tools that are critical in today’s society to manufacture products more cost effectively and with better performance.

    Going forward, Trelewicz would like to expand his collaborations at the CFN and help establish his research in metallic nanostructures as a core area supported by CFN and, ultimately, DOE, to achieve unprecedented properties in classical materials.

    “Being able to learn something new every day, using that knowledge to have an impact on society, and seeing my students fill gaps in our current understanding are what make my career as a professor so rewarding,” said Trelewicz. “With the resources of Stony Brook University, nearby CFN, and other DOE labs, I have an amazing platform to make contributions to the field of materials science and metallurgy.”

    Trelewicz holds a bachelor’s degree in engineering science from Stony Brook University and a doctorate in materials science and engineering with a concentration in technology innovation from MIT. Before returning to academia in 2012, Trelewicz spent four years in industry managing technology development and transition of harsh-environment sensors produced by additive manufacturing processes. He is the recipient of a 2017 Department of Energy Early Career Research Award, 2016 National Science Foundation CAREER award, and 2015 Young Leaders Professional Development Award from The Minerals, Metals & Materials Society (TMS), and is an active member of several professional organizations, including TMS, the Materials Research Society, and ASM International (the Materials Information Society).

    See the full article here .

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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 1:26 pm on November 9, 2017 Permalink | Reply
    Tags: , , Nanotechnology, Oil and water do not mix?, , Surfactants   

    From MIT: “A new way to mix oil and water” 

    MIT News
    MIT Widget

    MIT News

    November 8, 2017
    David L. Chandler

    1
    Graduate student Ingrid Guha holds a jar containing a clear liquid that looks like water to the naked eye, but it’s actually an emulsion of oil and water at the nanoscale.
    Image: Melanie Gonick, MIT

    2
    Optical images demonstrate that when water droplets condense on an oil bath, the droplets rapidly coalesce to become larger and larger (top row of images, at 10-minute intervals). Under identical conditions but with a soap-like surfactant added (bottom row), the tiny droplets are much more stable and remain small. Courtesy of the researchers

    Condensation-based method developed at MIT could create stable nanoscale emulsions.

    The reluctance of oil and water to mix together and stay that way is so well-known that it has become a cliché for describing any two things that do not go together well. Now, a new finding from researchers at MIT might turn that expression on its head, providing a way to get the two substances to mix and remain stable for long periods — no shaking required. The process may find applications in pharmaceuticals, cosmetics, and processed foods, among other areas.

    The new process involves cooling a bath of oil containing a small amount of a surfactant (a soap-like substance), and then letting water vapor from the surrounding air condense onto the oil surface. Experiments have shown that this can produce tiny, uniform water droplets on the surface that then sink into the oil, and their size can be controlled by adjusting the proportion of surfactant. The findings, by MIT graduate student Ingrid Guha, former postdoc Sushant Anand, and associate professor Kripa Varanasi, are reported in the journal Nature Communications.

    As anyone who has ever used salad dressing knows, no matter how vigorously the mixture gets shaken, the oil and the vinegar (a water-based solution) will separate within minutes. But for many uses, including new drug-delivery systems and food-processing methods, it’s important to be able to get oil in water (or water in oil) to form tiny droplets — only a few hundred nanometers across, too small to see with the naked eye — and to have them stay tiny rather than coalescing into larger droplets and eventually separating from the other liquid.

    Typically, in industrial processes these emulsions are made by either mechanically shaking the mix or using sound waves to set up intense vibrations within the liquid, a process called sonicating. But both of these processes “require a lot of energy,” Varanasi says, “and the finer the drops, the more energy it takes.” By contrast, “our approach is very energy inexpensive,” he adds.

    “The key to overcoming that separation is to have really small, nanoscale droplets,” Guha explains. “When the drops are small, gravity can’t overcome them,” and they can remain suspended indefinitely.

    For the new process, the team set up a reservoir of oil with an added surfactant that can bind to both oil and water molecules. They placed this inside a chamber with very humid air and then cooled the oil. Like a glass of cold water on a hot summer day, the colder surface causes the water vapor to precipitate. The condensing water then forms droplets at the surface that spread through the oil-surfactant mixture, and the sizes of these droplets are quite uniform, the team found. “If you get the chemistry just right, you can get just the right dispersion,” Guha says. By adjusting the proportion of surfactant in the oil, the droplet sizes can be well-controlled.

    In the experiments, the team produced nanoscale emulsions that remained stable over periods of several months, compared to the few minutes that it takes for the same mixture of oil and water to separate without the added surfactant. “The droplets stay so small that they’re hard to see even under a microscope,” Guha says.

    Unlike the shaking or sonicating methods, which take the large, separate masses of oil and water and gradually get them to break down into smaller drops — a “top down” approach — the condensation method starts off right away with the tiny droplets condensing out from the vapor, which the researchers call a bottom-up approach. “By cloaking the freshly condensed nanoscale water droplets with oil, we are taking advantage of the inherent nature of phase-change and spreading phenomena,” Varanasi says.

    “Our bottom-up approach of creating nanoscale emulsions is highly scalable owing to the simplicity of the process,” Anand says. “We have uncovered many new phenomena during this work. We have found how the presence of surfactant can change the oil and water interactions under such conditions, promoting oil spreading on water droplets and stabilizing them at the nanoscale.”

    The team says that the approach should work with a variety of oils and surfactants, and now that the process has been identified, their findings “provide a kind of design guideline for someone to use” for a particular kind of application, Varanasi says.

    “It’s such an important thing,” he says, because “foods and pharmaceuticals always have an expiration date,” and often that has to do with the instability of the emulsions in them. The experiments used a particular surfactant that is widely used, but many other varieties are available, including some that are approved for food-grade products.

    In addition, Guha says, “we envision that you could use multiple liquids and make much more complex emulsions.” And besides being used in food, cosmetics, and drugs, the method could have other applications, such as in the oil and gas industry, where fluids such as the drilling “muds” sent down wells are also emulsions, Varanasi says.

    The work was supported by the MIT Energy Initiative, the National Science Foundation, and a Society in Science fellowship. Anand, the co-author who was a postdoc at MIT, is now an assistant professor at the University of Illinois.

    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 5:05 pm on November 7, 2017 Permalink | Reply
    Tags: , Color me Purple or Red or Green or …, Directional color filter ruled with grooves that are not uniformly spaced, Nanotechnology, ,   

    From NIST: “Color me Purple, or Red, or Green, or … “ 


    NIST

    November 07, 2017

    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    1
    Schematic shows two different ways that white light interacts with a newly developed device, a directional color filter ruled with grooves that are not uniformly spaced. When white light illuminates the patterned side of the compact metal device at three different angles—in this case, 0° degrees, 10° and 20°—the device transmits light at red, green and blue wavelengths, respectively. When white light incident at any angle illuminates the device from the non-patterned side, it separates the light into the same three colors, and sends off each color in different directions corresponding to the same respective angles. Credit: NIST

    Imagine a miniature device that suffuses each room in your house with a different hue of the rainbow—purple for the living room, perhaps, blue for the bedroom, green for the kitchen. A team led by scientists at the National Institute of Standards and Technology (NIST) has, for the first time, developed nanoscale devices that divide incident white light into its component colors based on the direction of illumination, or directs these colors to a predetermined set of output angles.

    Viewed from afar, the device, referred to as a directional color filter, resembles a diffraction grating, a flat metal surface containing parallel grooves or slits that split light into different colors. However, unlike a grating, the nanometer-scale grooves etched into the opaque metal film are not periodic—not equally spaced. They are either a set of grooved lines or concentric circles that vary in spacing, much smaller than the wavelength of visible light. These properties shrink the size of the filter and allow it to perform many more functions than a grating can.

    For instance, the device’s nonuniform, or aperiodic, grid can be tailored to send a particular wavelength of light to any desired location. The filter has several promising applications, including generating closely spaced red, green and blue color pixels for displays, harvesting solar energy, sensing the direction of incoming light and measuring the thickness of ultrathin coatings placed atop the filter.

    In addition to selectively filtering incoming white light based on the location of the source, the filter can also operate in a second way. By measuring the spectrum of colors passing through a filter custom-designed to deflect specific wavelengths of light at specific angles, researchers can pinpoint the location of an unknown source of light striking the device. This could be critical to determine if that source, for instance, is a laser aimed at an aircraft.

    “Our directional filter, with its aperiodic architecture, can function in many ways that are fundamentally not achievable with a device such as a grating, which has a periodic structure,” said NIST physicist Amit Agrawal. “With this custom-designed device, we are able to manipulate multiple wavelengths of light simultaneously.”

    Matthew Davis and Wenqi Zhu of NIST and the University of Maryland, along with Agrawal and NIST physicist Henri Lezec, described their work in the latest edition of Nature Communications. The work was performed in collaboration with Syracuse University and Nanjing University in China.

    The operation of the directional color filter relies on the interaction between the incoming particles of light—photons—and the sea of electrons that floats along the surface of a metal. Photons striking the metal surface create ripples in this electron sea, generating a special type of light wave—plasmons—that has a much smaller wavelength than the original light source.

    The design and operation of aperiodic devices are not as intuitive and straightforward as their periodic counterparts. However, Agrawal and his colleagues have developed a simple model for designing these devices. Lead author Matthew Davis explained, “this model allows us to quickly predict the optical response of these aperiodic designs without relying on time-consuming numerical approximation, thereby greatly decreasing the design time so we can focus on device fabrication and testing.”

    The work described in the new paper was conducted at NIST’s Center for Nanoscale Science and Technology.

    See the full article here.

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    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 4:45 pm on November 7, 2017 Permalink | Reply
    Tags: Nanotechnology, , , , Quantum photonic circuits, Waveguides   

    From NIST: “Hybrid Circuit Combines Single-Photon Generator and Efficient Waveguides on One Chip” 


    NIST

    November 07, 2017

    Ben Stein
    benjamin.stein@nist.gov
    (301) 975-2763

    New architecture could prove essential for high-performance quantum photonic circuits.

    1
    The architecture of this hybrid quantum photonic circuit is among the first to combine on a single chip a reliable generator of individual photons—a quantum dot (red dot), here embedded in gallium arsenide (yellow)—with passive elements such as a low-loss waveguide (purple) that transports the photons. Credit: NIST

    Scientists at the National Institute of Standards and Technology (NIST) and their collaborators have taken a new step forward in the quest to build quantum photonic circuits—chip-based devices that rely on the quantum properties of light to process and communicate information rapidly and securely.

    The quantum circuit architecture devised by the team is among the first to combine two different types of optical devices, made from different materials, on a single chip—a semiconductor source that efficiently generates single particles of light (photons) on demand, and a network of “waveguides” that transports those photons across the circuit with low loss. Maximizing the number of photons, ideally having identical properties, is critical to enabling applications such as secure communication, precision measurement, sensing and computation, with potentially greater performance than that of existing technologies.

    The architecture, developed by Marcelo Davanco and other NIST researchers along with collaborators from China and the U.K., employs a nanometer-scale semiconductor structure called a quantum dot—made from indium arsenide—to generate individual photons on the same chip as the optical waveguides—made from silicon nitride. Combining these two materials requires special processing techniques. Such hybrid circuit architectures could become building blocks for more complex systems.

    Previously, quantum integrated photonic circuits typically consisted of only passive devices such as waveguides and beam splitters, which let photons through or allowed them to coalesce. The photons themselves still had to be produced outside the chip, and getting them onto the chip resulted in losses, which significantly degraded the performance of the circuit. Circuit architectures that did include quantum light generation on a chip either incorporated sources that only produced photons randomly and at low rates—which limits performance—or had sources in which one photon was not necessarily identical with the next. In addition, the fabrication processes supporting these previous architectures made it difficult to scale up the number, size and complexity of the photonic circuits.

    In contrast, the new architecture and the fabrication processes the team developed should enable researchers to reliably build larger circuits, which could perform more complex computations or simulations and translate into higher measurement precision and detection sensitivity in other applications.

    The quantum dot employed by the team is a well-studied nanometer-scale structure: an island of the semiconductor indium arsenide surrounded by gallium arsenide. The indium arsenide/gallium arsenide nanostructure acts as a quantum system with two energy levels—a ground state (lower energy level) and an excited state (higher energy level). When an electron in the excited state loses energy by dropping down to the ground state, it emits a single photon.

    Unlike most types of two-level emitters that exist in the solid state, these quantum dots have been shown to generate—reliably, on demand, and at large rates—the single photons needed for quantum applications. In addition, researchers have been able to place them inside nanoscale, light-confining spaces that allow a large speedup of the single-photon emission rate, and in principle, could also allow the quantum dot to be excited by a single photon. This enables the quantum dots to directly assist with the processing of information rather than simply produce streams of photons.

    The other part of the team’s hybrid circuit architecture consists of passive waveguides made of silicon nitride, known for their ability to transmit photons across a chip’s surface with very low photon loss. This allows quantum-dot-generated photons to efficiently coalesce with other photons at a beam splitter, or interact with other circuit elements such as modulators and detectors.

    “We’re getting the best of both worlds, with each behaving really well together on a single circuit,” said Davanco. In fact, the hybrid architecture keeps the high performance achieved in devices made exclusively of each of the two materials, with little degradation when they are put together. He and his colleagues described the work (link is external) in a recent issue of Nature Communications.

    To make the hybrid devices, Davanco and his colleagues first bonded two wafers together—one containing the quantum dots, the other containing the silicon nitride waveguide material. They used a variation of a process that had originally been developed for making hybrid photonic lasers, which combined silicon for waveguides and compound semiconductors for classical light emission. Once the bonding was finished, the two materials were then sculpted with nanometer-scale resolution into their final geometries through state-of-the-art semiconductor device patterning and etching techniques.

    Although this wafer bonding technique was developed more than a decade ago by other researchers, the team is the first to apply it towards making integrated quantum photonic devices.

    “Since we have expertise in both fabrication and quantum photonics, it seemed clear that we could borrow and adapt this process to create this new architecture,” notes Davanco.

    This work was performed in part at NIST’s Center for Nanoscale Science and Technology (CNST), a shared-use facility available to researchers from industry, academia and government, and also included researchers from NIST’s Physical Measurement Laboratory.

    Science paper:
    Heterogeneous integration for on-chip quantum photonic circuits with single quantum dot devices. Nature Communications.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NIST Campus, Gaitherberg, MD, USA

    NIST Mission, Vision, Core Competencies, and Core Values

    NIST’s mission

    To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
    NIST’s vision

    NIST will be the world’s leader in creating critical measurement solutions and promoting equitable standards. Our efforts stimulate innovation, foster industrial competitiveness, and improve the quality of life.
    NIST’s core competencies

    Measurement science
    Rigorous traceability
    Development and use of standards

    NIST’s core values

    NIST is an organization with strong values, reflected both in our history and our current work. NIST leadership and staff will uphold these values to ensure a high performing environment that is safe and respectful of all.

    Perseverance: We take the long view, planning the future with scientific knowledge and imagination to ensure continued impact and relevance for our stakeholders.
    Integrity: We are ethical, honest, independent, and provide an objective perspective.
    Inclusivity: We work collaboratively to harness the diversity of people and ideas, both inside and outside of NIST, to attain the best solutions to multidisciplinary challenges.
    Excellence: We apply rigor and critical thinking to achieve world-class results and continuous improvement in everything we do.

     
  • richardmitnick 12:34 pm on November 7, 2017 Permalink | Reply
    Tags: , , Discovering detrimental leaks by developing “smart” paper that can sense the presence of water, Nanotechnology, , Smart paper,   

    From University of Washington: “‘Smart’ paper can conduct electricity, detect water” 

    U Washington

    University of Washington

    November 6, 2017
    Michelle Ma

    1
    Anthony Dichiara, a University of Washington professor in the School of Environmental and Forest Sciences, holds a piece of “smart” paper created in his lab. Mark Stone/University of Washington

    In cities and large-scale manufacturing plants, a water leak in a complicated network of pipes can take tremendous time and effort to detect, as technicians must disassemble many pieces to locate the problem. The American Water Works Association indicates that nearly a quarter-million water line breaks occur each year in the U.S., costing public water utilities about $2.8 billion annually.

    A University of Washington team wants to simplify the process for discovering detrimental leaks by developing “smart” paper that can sense the presence of water. The paper, laced with conductive nanomaterials, can be employed as a switch, turning on or off an LED light or an alarm system indicating the absence or presence of water.

    The researchers described their discovery in a paper appearing in the November issue of the Journal of Materials Chemistry A.

    “Water sensing is very challenging to do due to the polar nature of water, and what is used now is very expensive and not practical to implement,” said lead author Anthony Dichiara, a UW assistant professor of bioresource science and engineering in the School of Environment and Forest Sciences. “That led to the reason to pursue this work.”

    See slide show of images at the full article.

    Along with Dichiara, a team of UW undergraduate students in the Bioresource Science and Engineering program successfully embedded nanomaterials in paper that can conduct electricity and sense the presence of water. Starting with pulp, they manipulated the wood fibers and carefully mixed in nanomaterials using a standard process for papermaking, but never before used to make sensing papers.

    Discovering that the paper could detect the presence of water came by way of a fortuitous accident. Water droplets fell onto the conductive paper the team had created, causing the LED light indicating conductivity to turn off. Though at first they thought they had ruined the paper, the researchers realized they had instead created a paper that was sensitive to water.

    When water hits the paper, its fibrous cells swell to up to three times their original size. That expansion displaces conductive nanomaterials inside the paper, which in turn disrupts the electrical connections and causes the LED indicator light to turn off.

    This process is fully reversible, and as the paper dries, the conductive network re-forms so the paper can be used multiple times.

    The researchers envision an application in which a sheet of conductive paper with a battery could be placed around a pipe or under a complex network of intersecting pipes in a manufacturing plant. If a pipe leaks, the paper would sense the presence of water, then send an electrical signal wirelessly to a central control center so a technician could quickly locate and repair the leak.
    example use around a pipe

    The paper could be wrapped around a pipe, as shown in this example, to detect leaks.Mark Stone/University of Washington

    In addition, the paper is so sensitive that it can also detect trace amounts of water in mixtures of various liquids. This ability to distinguish water from other molecules is particularly valuable for the petroleum and biofuel industries, where water is regarded as an impurity.

    “I believe that for large-scale applications, this is definitely doable,” Dichiara said. “The price for nanomaterials is going to drop, and we’re already using an established papermaking process. You just add what we developed in the right place and time in the process.”

    The nanomaterials added to the paper were engineered in such a way that they can be incorporated during conventional papermaking without having to modify the process. These materials are made of extremely conductive carbon. Because carbon is found in all living things, nearly any natural material can be burned to make charcoal, and then carbon atoms can be extracted to synthesize the materials. The team has experimented with making nanomaterials from banana peels, tree bark and even animal feces.

    They also tried making nanomaterials from wood scraps to show that the entire papermaking process can be completed with cheap, natural materials.

    “Now we have a sustainable process where everything is from pulp and paper, and we can make conductive materials from them,” Dichiara said.

    The paper, stiff and smooth in texture, is a rich black color because of the nanomaterials (carbon from charcoal). The 8-inch disks made in the lab are prototypes; the team hopes to test the process on an industrial-sized papermaking machine next, which will require more nanomaterials and paper pulp.

    Other co-authors are Sheila Goodman, a UW graduate student, and Delong He and Jinbo Bai of Universite Paris-Saclay in France. UW undergraduate students Jimeng Cui, Riley Fitzpatrick, Sydney Fry, Demi Lidorikiotis, Anna Song and Zoie Tisler completed additional lab work.

    Funding for this research came from the U.S. Department of Agriculture’s National Institute of Food and Agriculture, McIntire Stennis project, and from the UW School of Environmental and Forest Sciences.

    ###

    For more information, contact Dichiara at abdichia@uw.edu or 206-543-1581.

    Along with Dichiara, a team of UW undergraduate students in the Bioresource Science and Engineering program successfully embedded nanomaterials in paper that can conduct electricity and sense the presence of water. Starting with pulp, they manipulated the wood fibers and carefully mixed in nanomaterials using a standard process for papermaking, but never before used to make sensing papers.

    Discovering that the paper could detect the presence of water came by way of a fortuitous accident. Water droplets fell onto the conductive paper the team had created, causing the LED light indicating conductivity to turn off. Though at first they thought they had ruined the paper, the researchers realized they had instead created a paper that was sensitive to water.

    When water hits the paper, its fibrous cells swell to up to three times their original size. That expansion displaces conductive nanomaterials inside the paper, which in turn disrupts the electrical connections and causes the LED indicator light to turn off.

    This process is fully reversible, and as the paper dries, the conductive network re-forms so the paper can be used multiple times.

    The researchers envision an application in which a sheet of conductive paper with a battery could be placed around a pipe or under a complex network of intersecting pipes in a manufacturing plant. If a pipe leaks, the paper would sense the presence of water, then send an electrical signal wirelessly to a central control center so a technician could quickly locate and repair the leak.

    3
    The paper could be wrapped around a pipe, as shown in this example, to detect leaks.Mark Stone/University of Washington

    They also tried making nanomaterials from wood scraps to show that the entire papermaking process can be completed with cheap, natural materials.

    “Now we have a sustainable process where everything is from pulp and paper, and we can make conductive materials from them,” Dichiara said.

    The paper, stiff and smooth in texture, is a rich black color because of the nanomaterials (carbon from charcoal). The 8-inch disks made in the lab are prototypes; the team hopes to test the process on an industrial-sized papermaking machine next, which will require more nanomaterials and paper pulp.

    Other co-authors are Sheila Goodman, a UW graduate student, and Delong He and Jinbo Bai of Universite Paris-Saclay in France. UW undergraduate students Jimeng Cui, Riley Fitzpatrick, Sydney Fry, Demi Lidorikiotis, Anna Song and Zoie Tisler completed additional lab work.

    Funding for this research came from the U.S. Department of Agriculture’s National Institute of Food and Agriculture, McIntire Stennis project, and from the UW School of Environmental and Forest Sciences.

    See the full article here .

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    The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.

    So what defines us — the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 12:16 pm on November 3, 2017 Permalink | Reply
    Tags: , , Invisible glass, Making Glass Invisible: A Nanoscience-Based Disappearing Act, Nanotechnology, , the scientists used an approach called self-assembly which is the ability of certain materials to spontaneously form ordered arrangements on their own, To texture the glass surfaces at the nanoscale   

    From BNL: “Making Glass Invisible: A Nanoscience-Based Disappearing Act” 

    Brookhaven Lab

    October 31, 2017
    Ariana Tantillo
    atantillo@bnl.gov
    (631) 344-2347

    Peter Genzer
    genzer@bnl.gov
    (631) 344-3174

    By texturing glass surfaces with nanosized features, scientists almost completely eliminated surface reflections—an achievement that could enhance solar cell efficiency, improve consumers’ experience with electronic displays, and support high-power laser applications

    1
    Glass surfaces with etched nanotextures reflect so little light that they become essentially invisible. This effect is seen in the above image, which compares the glare from a conventional piece of glass (right) to that from nanotextured glass (left), which shows no glare at all. No image credit.

    [Sorry, I do not see the difference.]

    If you have ever watched television in anything but total darkness, used a computer while sitting underneath overhead lighting or near a window, or taken a photo outside on a sunny day with your smartphone, you have experienced a major nuisance of modern display screens: glare. Most of today’s electronics devices are equipped with glass or plastic covers for protection against dust, moisture, and other environmental contaminants, but light reflection from these surfaces can make information displayed on the screens difficult to see.

    Now, scientists at the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory—have demonstrated a method for reducing the surface reflections from glass surfaces to nearly zero by etching tiny nanoscale features into them.

    Whenever light encounters an abrupt change in refractive index (how much a ray of light bends as it crosses from one material to another, such as between air and glass), a portion of the light is reflected. The nanoscale features have the effect of making the refractive index change gradually from that of air to that of glass, thereby avoiding reflections. The ultra-transparent nanotextured glass is antireflective over a broad wavelength range (the entire visible and near-infrared spectrum) and across a wide range of viewing angles. Reflections are reduced so much that the glass essentially becomes invisible.

    This “invisible glass” could do more than improve the user experience for consumer electronic displays. It could enhance the energy-conversion efficiency of solar cells by minimizing the amount of sunlight lost to refection. It could also be a promising alternative to the damage-prone antireflective coatings conventionally used in lasers that emit powerful pulses of light, such as those applied to the manufacture of medical devices and aerospace components.

    “We’re excited about the possibilities,” said CFN Director Charles Black, corresponding author on the paper published online on October 30 in Applied Physics Letters. “Not only is the performance of these nanostructured materials extremely high, but we’re also implementing ideas from nanoscience in a manner that we believe is conducive to large-scale manufacturing.”

    Former Brookhaven Lab postdocs Andreas Liapis, now a research fellow at Massachusetts General Hospital’s Wellman Center for Photomedicine, and Atikur Rahman, an assistant professor in the Department of Physics at the Indian Institute of Science Education and Research, Pune, are co-authors.

    To texture the glass surfaces at the nanoscale, the scientists used an approach called self-assembly, which is the ability of certain materials to spontaneously form ordered arrangements on their own. In this case, the self-assembly of a block copolymer material provided a template for etching the glass surface into a “forest” of nanoscale cone-shaped structures with sharp tips—a geometry that almost completely eliminates the surface reflections. Block copolymers are industrial polymers (repeating chains of molecules) that are found in many products, including shoe soles, adhesive tapes, and automotive interiors.

    Black and CFN colleagues have previously used a similar nanotexturing technique to impart silicon, glass, and some plastic materials with water-repellent and self-cleaning properties and anti-fogging abilities, and also to make silicon solar cells antireflective. The surface nanotextures mimic those found in nature, such as the tiny light-trapping posts that make moth eyes dark to help the insects avoid detection by predators and the waxy cones that keep cicada wings clean.

    “This simple technique can be used to nanotexture almost any material with precise control over the size and shape of the nanostructures,” said Rahman. “The best thing is that you don’t need a separate coating layer to reduce glare, and the nanotextured surfaces outperform any coating material available today.”

    “We have eliminated reflections from glass windows not by coating the glass with layers of different materials but by changing the geometry of the surface at the nanoscale,” added Liapis. “Because our final structure is composed entirely of glass, it is more durable than conventional antireflective coatings.”

    To quantify the performance of the nanotextured glass surfaces, the scientists measured the amount of light transmitted through and reflected from the surfaces. In good agreement with their own model simulations, the experimental measurements of surfaces with nanotextures of different heights show that taller cones reflect less light. For example, glass surfaces covered with 300-nanometer-tall nanotextures reflect less than 0.2 percent of incoming red-colored light (633-nanometer wavelength). Even at the near-infrared wavelength of 2500 nanometers and viewing angles as high as 70 degrees, the amount of light passing through the nanostructured surfaces remains high—above 95 and 90 percent, respectively.

    In another experiment, they compared the performance of a commercial silicon solar cell without a cover, with a conventional glass cover, and with a nanotextured glass cover. The solar cell with the nanotextured glass cover generated the same amount of electric current as the one without a cover. They also exposed their nanotextured glass to short laser pulses to determine the intensity at which the laser light begins to damage the material. Their measurements reveal the glass can withstand three times more optical energy per unit area than commercially available antireflection coatings that operate over a broad wavelength range.

    “Our role in the CFN is to demonstrate how nanoscience can facilitate the design of new materials with improved properties,” said Black. “This work is a great example of that—we’d love to find a partner to help advance these remarkable materials toward technology.”

    See the full article here .

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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 3:50 pm on October 23, 2017 Permalink | Reply
    Tags: 2-D materials and Si-CMOS and silicon photonics are a natural match, , Material could bring optical communication onto silicon chips, , Molybdenum ditelluride, Nanotechnology, , Researchers describe a light emitter and detector that can be integrated into silicon CMOS chips,   

    From MIT: “Material could bring optical communication onto silicon chips” 

    MIT News

    MIT Widget

    MIT News

    October 23, 2017
    Helen Knight

    1
    Researchers have designed a light-emitter and detector that can be integrated into silicon CMOS chips. This illustration shows a molybdenum ditelluride light source for silicon photonics. Image: Sampson Wilcox

    Ultrathin films of a semiconductor that emits and detects light can be stacked on top of silicon wafers.

    The huge increase in computing performance in recent decades has been achieved by squeezing ever more transistors into a tighter space on microchips.

    However, this downsizing has also meant packing the wiring within microprocessors ever more tightly together, leading to effects such as signal leakage between components, which can slow down communication between different parts of the chip. This delay, known as the “interconnect bottleneck,” is becoming an increasing problem in high-speed computing systems.

    One way to tackle the interconnect bottleneck is to use light rather than wires to communicate between different parts of a microchip. This is no easy task, however, as silicon, the material used to build chips, does not emit light easily, according to Pablo Jarillo-Herrero, an associate professor of physics at MIT.

    Now, in a paper published today in the journal Nature Nanotechnology, researchers describe a light emitter and detector that can be integrated into silicon CMOS chips. The paper’s first author is MIT postdoc Ya-Qing Bie, who is joined by Jarillo-Herrero and an interdisciplinary team including Dirk Englund, an associate professor of electrical engineering and computer science at MIT.

    The device is built from a semiconductor material called molybdenum ditelluride. This ultrathin semiconductor belongs to an emerging group of materials known as two-dimensional transition-metal dichalcogenides.

    Unlike conventional semiconductors, the material can be stacked on top of silicon wafers, Jarillo-Herrero says.

    “Researchers have been trying to find materials that are compatible with silicon, in order to bring optoelectronics and optical communication on-chip, but so far this has proven very difficult,” Jarillo-Herrero says. “For example, gallium arsenide is very good for optics, but it cannot be grown on silicon very easily because the two semiconductors are incompatible.”

    In contrast, the 2-D molybdenum ditelluride can be mechanically attached to any material, Jarillo-Herrero says.

    Another difficulty with integrating other semiconductors with silicon is that the materials typically emit light in the visible range, but light at these wavelengths is simply absorbed by silicon.

    Molybdenum ditelluride emits light in the infrared range, which is not absorbed by silicon, meaning it can be used for on-chip communication.

    To use the material as a light emitter, the researchers first had to convert it into a P-N junction diode, a device in which one side, the P side, is positively charged, while the other, N side, is negatively charged.

    In conventional semiconductors, this is typically done by introducing chemical impurities into the material. With the new class of 2-D materials, however, it can be done by simply applying a voltage across metallic gate electrodes placed side-by-side on top of the material.

    “That is a significant breakthrough, because it means we do not need to introduce chemical impurities into the material [to create the diode]. We can do it electrically,” Jarillo-Herrero says.

    Once the diode is produced, the researchers run a current through the device, causing it to emit light.

    “So by using diodes made of molybdenum ditelluride, we are able to fabricate light-emitting diodes (LEDs) compatible with silicon chips,” Jarillo-Herrero says.

    The device can also be switched to operate as a photodetector, by reversing the polarity of the voltage applied to the device. This causes it to stop conducting electricity until a light shines on it, when the current restarts.

    In this way, the devices are able to both transmit and receive optical signals.

    The device is a proof of concept, and a great deal of work still needs to be done before the technology can be developed into a commercial product, Jarillo-Herrero says.

    This paper fills an important gap in integrated photonics, by realizing a high-performance silicon-CMOS-compatible light source, says Frank Koppens, a professor of quantum nano-optoelectronics at the Institute of Photonic Sciences in Barcelona, Spain, who was not involved in the research.

    “This work shows that 2-D materials and Si-CMOS and silicon photonics are a natural match, and we will surely see many more applications coming out of this [area] in the years to come,” Koppens says.

    The researchers are now investigating other materials that could be used for on-chip optical communication.

    Most telecommunication systems, for example, operate using light with a wavelength of 1.3 or 1.5 micrometers, Jarillo-Herrero says.

    However, molybdenum ditelluride emits light at 1.1 micrometers. This makes it suitable for use in the silicon chips found in computers, but unsuitable for telecommunications systems.

    “It would be highly desirable if we could develop a similar material, which could emit and detect light at 1.3 or 1.5 micrometers in wavelength, where telecommunication through optical fiber operates,” he says.

    To this end, the researchers are exploring another ultrathin material called black phosphorus, which can be tuned to emit light at different wavelengths by altering the number of layers used. They hope to develop devices with the necessary number of layers to allow them to emit light at the two wavelengths while remaining compatible with silicon.

    “The hope is that if we are able to communicate on-chip via optical signals instead of electronic signals, we will be able to do so more quickly, and while consuming less power,” Jarillo-Herrero says.

    The research was supported by Center for Excitonics, an EFRC funded by the U.S. Department of Energy.

    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 8:13 am on October 23, 2017 Permalink | Reply
    Tags: Antennas, , “Specific radiation efficiency”, , Nanotechnology, Nanotube fiber antennas as capable as copper, ,   

    From Rice: “Nanotube fiber antennas as capable as copper” 

    Rice U bloc

    Rice University

    October 23, 2017
    Mike Williams

    1
    Rice University graduate student Amram Bengio sets up a nanotube fiber antenna for testing. Scientists at Rice and the National Institute of Standards and Technology have determined that nanotube fibers made at Rice can be as good as copper antennas but 20 times lighter. Photo by Jeff Fitlow

    Rice researchers show their flexible fibers work well but weigh much less

    Fibers made of carbon nanotubes configured as wireless antennas can be as good as copper antennas but 20 times lighter, according to Rice University researchers. The antennas may offer practical advantages for aerospace applications and wearable electronics where weight and flexibility are factors.

    The research appears in Applied Physics Letters.

    The discovery offers more potential applications for the strong, lightweight nanotube fibers developed by the Rice lab of chemist and chemical engineer Matteo Pasquali. The lab introduced the first practical method for making high-conductivity carbon nanotube fibers in 2013 and has since tested them for use as brain implants and in heart surgeries, among other applications.

    The research could help engineers who seek to streamline materials for airplanes and spacecraft where weight equals cost. Increased interest in wearables like wrist-worn health monitors and clothing with embedded electronics could benefit from strong, flexible and conductive fiber antennas that send and receive signals, Pasquali said.

    The Rice team and colleagues at the National Institute of Standards and Technology (NIST) developed a metric they called “specific radiation efficiency” to judge how well nanotube fibers radiated signals at the common wireless communication frequencies of 1 and 2.4 gigahertz and compared their results with standard copper antennas. They made thread comprising from eight to 128 fibers that are about as thin as a human hair and cut to the same length to test on a custom rig that made straightforward comparisons with copper practical.

    “Antennas typically have a specific shape, and you have to design them very carefully,” said Rice graduate student Amram Bengio, the paper’s lead author. “Once they’re in that shape, you want them to stay that way. So one of the first experimental challenges was getting our flexible material to stay put.”

    2
    Bengio prepares a sample nanotube fiber antenna for evaluation. The fibers had to be isolated in Styrofoam mounts to assure accurate comparisons with each other and with copper. Photo by Jeff Fitlow

    Contrary to earlier results by other labs (which used different carbon nanotube fiber sources), the Rice researchers found the fiber antennas matched copper for radiation efficiency at the same frequencies and diameters. Their results support theories that predicted the performance of nanotube antennas would scale with the density and conductivity of the fiber.

    “Not only did we find that we got the same performance as copper for the same diameter and cross-sectional area, but once we took the weight into account, we found we’re basically doing this for 1/20th the weight of copper wire,” Bengio said.

    “Applications for this material are a big selling point, but from a scientific perspective, at these frequencies carbon nanotube macro-materials behave like a typical conductor,” he said. Even fibers considered “moderately conductive” showed superior performance, he said.

    Although manufacturers could simply use thinner copper wires instead of the 30-gauge wires they currently use, those wires would be very fragile and difficult to handle, Pasquali said.

    “Amram showed that if you do three things right — make the right fibers, fabricate the antenna correctly and design the antenna according to telecommunication protocols — then you get antennas that work fine,” he said. “As you go to very thin antennas at high frequencies, you get less of a disadvantage compared with copper because copper becomes difficult to handle at thin gauges, whereas nanotubes, with their textile-like behavior, hold up pretty well.”

    Co-authors of the paper are, from Rice, graduate students Lauren Taylor and Peiyu Chen, alumnus Dmitri Tsentalovich and Aydin Babakhani, an associate professor of electrical and computer engineering, and, from NIST in Boulder, Colo., postdoctoral researcher Damir Senic, research engineer Christopher Holloway, physicist Christian Long, research scientists David Novotny and James Booth and physicist Nathan Orloff. Pasquali is a professor of chemical and biomolecular engineering, of materials science and nanoengineering and of chemistry.

    The U.S. Air Force supported the research.

    See the full article here .

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    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 1:34 pm on October 19, 2017 Permalink | Reply
    Tags: , , , LTEM-Laser terahertz emission microscopy, Nanotechnology, , This new technique enables measurements down to a resolution of 20 nanometers   

    From Brown: “Terahertz spectroscopy goes nano” 

    Brown University

    [THIS POST ID DEDICATED TO E.B.M. WHO MAY ACTUALLY GET TO USE THIS NEW MICROSCOPY]

    Brown University

    1
    Going nano
    Researchers have improved the resolution of terahertz spectroscopy by 1,000 times, making the technique useful at the nanoscale.
    Mittleman Lab / Brown University

    Brown University researchers have demonstrated a way to bring a powerful form of spectroscopy — a technique used to study a wide variety of materials — into the nano-world.

    Laser terahertz emission microscopy (LTEM) is a burgeoning means of characterizing the performance of solar cells, integrated circuits and other systems and materials. Laser pulses illuminating a sample material cause the emission of terahertz radiation, which carries important information about the sample’s electrical properties.

    “This is a well-known tool for studying essentially any material that absorbs light, but it’s never been possible to use it at the nanoscale,” said Daniel Mittleman, a professor in Brown’s School of Engineering and corresponding author of a paper describing the work. “Our work has improved the resolution of the technique so it can be used to characterize individual nanostructures.”

    Typically, LTEM measurements are performed with resolution of a few tens of microns, but this new technique enables measurements down to a resolution of 20 nanometers, roughly 1,000 times the resolution previously possible using traditional LTEM techniques.

    The research, published in the journal ACS Photonics, was led by Pernille Klarskov, a postdoctoral researcher in Mittleman’s lab, with Hyewon Kim and Vicki Colvin from Brown’s Department of Chemistry.

    For their research, the team adapted for terahertz radiation a technique already used to improve the resolution of infrared microscopes. The technique uses a metal pin, tapered down to a sharpened tip only a few tens of nanometers across, that hovers just above a sample to be imaged. When the sample is illuminated, a tiny portion of the light is captured directly beneath the tip, which enables imaging resolution roughly equal to the size of the tip. By moving the tip around, it’s possible to create ultra-high resolution images of an entire sample.

    Klarskov was able to show that the same technique could be used to increase the resolution of terahertz emission as well. For their study, she and her colleagues were able to image an individual gold nanorod with 20-nanometer resolution using terahertz emission.

    The researchers believe their new technique could be broadly useful in characterizing the electrical properties of materials in unprecedented detail.

    “Terahertz emission has been used to study lots of different materials — semiconductors, superconductors, wide-band-gap insulators, integrated circuits and others,” Mittleman said. “Being able to do this down to the level of individual nanostructures is a big deal.”

    One example of a research area that could benefit from the technique, Mittleman says, is the characterization of perovskite solar cells, an emerging solar technology studied extensively by Mittleman’s colleagues at Brown.

    “One of the issues with perovskites is that they’re made of multi-crystalline grains, and the grain boundaries are what limits the transport of charge across a cell,” Mittleman said. “With the resolution we can achieve, we can map out each grain to see if different arrangements or orientations have an influence on charge mobility, which could help in optimizing the cells.”

    That’s one example of where this could be useful, Mittleman said, but it’s certainly not limited to that.

    “This could have fairly broad applications,” he noted.

    The research was supported by the National Science Foundation, the Danish Council for Independent Research and by Honeywell Federal Manufacturing & Technologies.

    See the full article here .

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    Welcome to Brown

    Brown U Robinson Hall
    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

     
  • richardmitnick 8:05 pm on October 15, 2017 Permalink | Reply
    Tags: , , , , , Nanotechnology, Nanotechnology is a multidisciplinary field where chemistry medicine and engineering all intersect, , , Spherical nucleic acid (SNA) technology, Studying and manipulating molecules and materials with dimensions on the 1 to 100 nanometer length scale (1 nm = one billionth of a meter)   

    From Northwestern University- “Titans of nanotechnology: The next big thing is very small” 

    Northwestern U bloc
    Northwestern University

    October 09, 2017

    1
    Teri Odom and Chad Mirkin of the International Institute for Nanotechnology.

    World-renowned nanoscientists and chemists Chad Mirkin, the Director of the International Institute for Nanotechnology (IIN) at Northwestern University, and Teri Odom, the IIN’s Associate Director, sit down to discuss the golden age of miniaturization and how the “science of small things” is fostering major advances.

    The IIN, founded in 2000, is making major strides in nanotechnology and thriving in a big way. Nanoscience and technology — a field focused on studying and manipulating molecules and materials with dimensions on the 1 to 100 nanometer length scale (1 nm = one billionth of a meter) — was anticipated in 1959 by physicist Richard Feynman and made possible with the advent of the electron and scanning tunneling microscopes in the 1980s. It is engaging scientists from all over the world across many disciplines. They are using such tools to explore, and ultimately solve, some of the world’s most pressing issues in medicine, engineering, energy, and defense.

    We [interviewer is not named] sit in on a conversation between Mirkin and Odom to see where this exciting field is headed.

    Q: Your team discovered spherical nucleic acid (SNA) technology, where tiny particles can be decorated with short snippets of DNA or RNA. With the creation of SNAs, you’ve basically taken known molecules, reorganized them at the nanoscale into ball-like forms, and changed their properties. What is the potential of such a discovery, and what exciting breakthroughs are on the near horizon?

    Mirkin: Two really promising areas in which we are applying SNA technology are biomedicine and gene regulation — the idea that one can create ways of using DNA- and RNA-based SNAs as potent new drugs. For example, we can put SNAs into commercially available creams, like Aquaphor®, and apply them topically to treat diseases of the skin. There are more than 200 skin diseases with a known genetic basis, making the DNA- and RNA-based SNAs a general strategy for treating skin diseases. Conventional DNA and RNA constructs based on linear nucleic acids cannot be delivered in this way – they do not penetrate the skin. But, SNAs can because of their unique architecture that changes the way they interact with biological structures and in particular, receptors on skin cells that recognize them, but not linear DNA or RNA. SNAs can also be used to treat diseases of the bladder, colon, lung, and eye — organs and tissues that also are hard to treat using traditional means.

    Q: Nanotechnology is a multidisciplinary field where chemistry, medicine and engineering all intersect to create innovative solutions for a whole range of issues. One area is photonics, where advances at the nanoscale are changing how we communicate. How?

    Odom: We’re trying to reduce the size of lasers, which are typically macroscopic devices, down to the nanometer scale. The ability to design nanomaterials that can control the production and guiding of light — which is composed of individual particles called photons — can transform a range of different technologies. For example, communication based on photons (like in optical fibers) vs. electrons (like in copper wires) is faster and much more efficient. Applications that exploit light can readily be transformed by nanotechnology.

    Q: Nanotechnology has revolutionized the basic sciences, fast-tracking their translational impact. For example, your colleague Samuel Stupp, director of the Simpson Querrey Institute for BioNanotechnology at Northwestern, is on the verge of conducting clinical trials in spinal regeneration through “soft” nanotechnology breakthroughs. Has nanotechnology also revolutionized the traditional scientific method, too?

    Mirkin: The desire to come up with a solution to a given problem often leads scientists to develop new capabilities. That’s the thrilling thing about science in general, but about nanotechnology in particular: we often have goals, which are driven by engineering needs, but along the way we discover fundamentally interesting principles that we didn’t anticipate and that inform our view of the world around us. These discoveries take us down new paths — ones that might be even more interesting than the original ones we were on. This is the nature and importance of basic science research.

    Odom: Nano provides the fundamentals. But then, we adapt, based on these unanticipated properties, while still keeping our long-range goals in mind. That’s pretty neat. You can adjust in ways that keep discovery and creativity at the forefront. Without that, we all would be bored.

    Q: Nobel Prize winner Sir Fraser Stoddart, John Rogers, William Dichtel, Milan Mrksich and the aforementioned Stupp are just a few of the many big names in the Northwestern nanotechnology community. What is Northwestern doing right and what’s the global impact?

    Mirkin: These are heavy hitters, people who can go anywhere in the world, but they chose to come to Northwestern because they recognized that this is a very special time in our history. We are on an incredible trajectory here, and they want to be a part of it.

    Odom: We have a holistic way of training new faculty and graduate students because we want them to have a complete picture of everything that’s going on here. This is how we do science at Northwestern, and we really apply it to nanotechnology. Part of our success as a chemistry department has come from our ability to make things, to measure them, and to model them — I like to think of this integration as the “3Ms” principle. Our achievements in nanotechnology have been built on these three synergistic areas of expertise.

    Mirkin: It really starts with world-class talent, and then collaboration. You can collaborate all you want, but if you don’t have world-class talent, it doesn’t matter. Since we’re going all-in on the medical side, in 15 years I went from having zero collaborations with the medical school, to now having 17. There is a natural interaction here between clinicians, scientists, and engineers that make everyone’s work so much stronger. Within the next five years, I anticipate that there will be cancer treatments based upon nanotechnology that greatly improve outcomes and, in some subsets of diseases, actually leads to cures.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Northwestern South Campus
    South Campus

    On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

    Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

    In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
    Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

    Northwestern is recognized nationally and internationally for its educational programs.

     
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