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  • richardmitnick 11:05 am on May 16, 2019 Permalink | Reply
    Tags: , Nanotechnology, Phonon lasers, , The optical tweezer   

    From The Conversation: “Laser of sound promises to measure extremely tiny phenomena” 

    Conversation
    From The Conversation

    May 16, 2019
    Mishkat Bhattacharya
    Associate Professor of Physics and Astronomy, Rochester Institute of Technology

    Nick Vamivakas
    Associate Professor of Quantum Optics & Quantum Physics, University of Rochester

    1
    The crests (bright) and troughs (dark) of waves spread out after they were produced. The picture applies to both light and sound waves. Titima Ongkantong

    Most people are familiar with optical lasers through their experience with laser pointers. But what about a laser made from sound waves?

    What makes optical laser light different from a light bulb or the sun is that all the light waves emerging from it are moving in the same direction and are pretty much in perfect step with each other. This is why the beam coming out of the laser pointer does not spread out in all directions.

    In contrast, rays from the sun and light from a light bulb go in every direction. This is a good thing because otherwise it would be difficult to illuminate a room; or worse still, the Earth might not receive any sunlight. But keeping the light waves in step – physicists call it coherence – is what makes a laser special. Sound is also made of waves.

    Recently there has been considerable scientific interest in creating phonon lasers in which the oscillations of light waves are replaced by the vibrations of a tiny solid particle. By generating sound waves that are perfectly synchronized, we figured out how to make a phonon laser – or a “laser for sound.”

    In work we recently published in the journal Nature Photonics, we have constructed our phonon laser using the oscillations of a particle – about a hundred nanometers in diameter – levitated using an optical tweezer.

    2
    A red laser beam from a high-power lab laser. Doug McLean/Shutterstock.com

    Waves in sync

    An optical tweezer is simply a laser beam which goes through a lens and traps a nanoparticle in midair, like the tractor beam in “Star Wars.” The nanoparticle does not stay still. It swings back and forth like a pendulum, along the direction of the trapping beam.

    Since the nanoparticle is not clamped to a mechanical support or tethered to a substrate, it is very well isolated from its surrounding environment. This enables physicists like us to use it for sensing weak electric, magnetic and gravitational forces whose effects would be otherwise obscured.

    To improve the sensing capability, we slow or “cool” the nanoparticle motion. This is done by measuring the position of the particle as it changes with time. We then feed that information back into a computer that controls the power in the trapping beam. Varying the trapping power allows us to constrain the particle so that it slows down. This setup has been used by several groups around the world in applications that have nothing to do with sound lasers. We then took a crucial step that makes our device unique and is essential for building a phonon laser.

    This involved modulating the trapping beam to make the nanoparticle oscillate faster, yielding laser-like behavior: The mechanical vibrations of the nanoparticle produced synchronized sound waves, or a phonon laser.

    The phonon laser is a series of synchronized sound waves. A detector can monitor the phonon laser and identify changes in the pattern of these sound waves that reveal the presence of a gravitational or magnetic force.

    It might appear that the particle becomes less sensitive because it is oscillating faster, but the effect of having all the oscillations in sync actually overcomes that effect and makes it a more sensitive instrument.

    3
    An artist’s depiction of optical tweezers (pink) holding the nanoparticle in midair, while allowing it to move back and forth and create sound waves. A. Nick Vamivakas and Michael Osadciw, University of Rochester illustration, CC BY-SA

    Possible applications

    It is clear that optical lasers are very useful. They carry information over optical fiber cables, read bar codes in supermarkets and run the atomic clocks which are essential for GPS.

    We originally developed the phonon laser as a tool for detecting weak electric, magnetic and gravitational fields, which affect the sound waves in a way we can detect. But we hope that others will find new uses for this technology in communication and sensing, such as the mass of very small molecules.

    On the fundamental side, our work leverages current interest in testing quantum physics theories about the behavior of collections of billion atoms – roughly the number contained in our nanoparticle. Lasers are also the starting point for creating exotic quantum states like the famous Schrodinger cat state, which allows an object to be in two places at the same time. Of course the most exciting uses of the optical tweezer phonon laser may well be ones we cannot currently foresee.

    See the full article here .

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    The Conversation launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 11:10 am on May 13, 2019 Permalink | Reply
    Tags: "Better Microring Sensors for Optical Applications", , , Microring sensors, Nanotechnology, ,   

    From Michigan Technical University: “Better Microring Sensors for Optical Applications” 

    Michigan Tech bloc

    From Michigan Technical University

    May 10, 2019
    Kelley Christensen

    1
    An exceptional surface-based sensor. The microring resonator is coupled to a waveguide with an end mirror that partially reflects light, which in turn enhances the sensitivity. Image Credit: Ramy El-Ganainy and Qi Zhong

    Tweaking the design of microring sensors enhances their sensitivity without adding more implementation complexity.

    Optical sensing is one of the most important applications of light science. It plays crucial roles in astronomy, environmental science, industry and medical diagnoses.

    Despite the variety of schemes used for optical sensing, they all share the same principle: The quantity to be measured must leave a “fingerprint” on the optical response of the system. The fingerprint can be its transmission, reflection or absorption. The stronger these effects are, the stronger the response of the system.

    While this works well at the macroscopic level, measuring tiny, microscopic quantities that induce weak response is a challenging task. Researchers have developed techniques to overcome this difficulty and improve the sensitivity of their devices. Some of these techniques, which rely on complex quantum optics concepts and implementations, have indeed proved useful, such as in sensing gravitational waves in the LIGO project.


    Others, which are based on trapping light in tiny boxes called optical resonators, have succeeded in detecting micro-particles and relatively large biological components.

    Nonetheless, the ability to detect small nano-particles and eventually single molecules remains a challenge. Current attempts focus on a special type of light trapping devices called microring or microtoroid resonators — these enhance the interaction between light and the molecule to be detected. The sensitivity of these devices, however, is limited by their fundamental physics.

    In their article “Sensing with Exceptional Surfaces in Order to Combine Sensitivity with Robustness” published in Physical Review Letters, physicists and engineers from Michigan Technological University, Pennsylvania State University and the University of Central Florida propose a new type of sensor. They are based on the new notion of exceptional surfaces: surfaces that consist of exceptional points.

    Exceptional Points for Exceptionally Sensitive Detection

    In order to understand the meaning of exceptional points, consider an imaginary violin with only two strings. In general, such a violin can produce just two different tones — a situation that corresponds to a conventional optical resonator. If the vibration of one string can alter the vibration of the other string in a way that the sound and the elastic oscillations create only one tone and one collective string motion, the system has an exceptional point.

    A physical system that exhibits an exceptional point is very fragile. In other words, any small perturbation will dramatically alter its behavior. The feature makes the system highly sensitive to tiny signals.

    “Despite this promise, the same enhanced sensitivity of exceptional point-based sensors is also their Achilles heel: These devices are very sensitive to unavoidable fabrication errors and undesired environmental variations,” said Ramy El-Ganainy, associate professor of physics, adding that the sensitivity necessitated clever tuning tricks in previous experimental demonstrations.

    “Our current proposal alleviates most of these problems by introducing a new system that has the same enhanced sensitivity reported in previous work, while at the same time robust against the majority of the uncontrivable experimental uncertainty,” said Qi Zhong, lead author on the paper and a graduate student who is currently working towards his doctorate degree at Michigan Tech.

    Though the design of microring sensors continues to be refined, researchers are hopeful that by improving the devices, seemingly tiny optical observations will have large effects.

    See the full article here .

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    Michigan Tech Campus
    Michigan Technological University (http://www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 130 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.
    The College of Sciences and Arts (CSA) fills one of the most important roles on the Michigan Tech campus. We play a part in the education of every student who comes through our doors. We take pride in offering essential foundational courses in the natural sciences and mathematics, as well as the social sciences and humanities—courses that underpin every major on campus. With twelve departments, 28 majors, 30-or-so specializations, and more than 50 minors, CSA has carefully developed programs to suit many interests and skill sets. From sound design and audio technology to actuarial science, applied cognitive science and human factors to rhetoric and technical communication, the college offers many unique programs.

     
  • richardmitnick 11:57 am on May 9, 2019 Permalink | Reply
    Tags: A new genetically engineered shell based on natural structures and the principles of protein evolution., , Bacteria across our planet contain nanometer-sized factories that do many different things., , , , Nanotechnology, Natural protein shells   

    From Michigan State University: “Simpler and smaller: A new synthetic nanofactory inspired by nature” 

    Michigan State Bloc

    From Michigan State University

    May 2, 2019
    Igor Houwat
    MSU-DOE Plant Research Laboratory office
    (517) 353-2223
    houwatig@msu.edu

    1

    Bacteria across our planet contain nanometer-sized factories that do many different things. Some make nutrients, others isolate toxic materials that could harm the bacteria. We have barely scratched the surface of their functional diversity.

    But all share a common exterior, a shell made of protein tiles, that Michigan State University researchers are learning how to manipulate in the lab. This will allow them to build factories of their own design, using the natural building blocks. Indeed, scientists see the structures as a source of new technologies. They are trying to repurpose them to do things they don’t in nature.

    In a new study, the lab of Cheryl Kerfeld reports a new genetically engineered shell, based on natural structures and the principles of protein evolution. The new shell is simpler, made of only a single designed protein. It will be easier to work with and, perhaps, even evolve in the lab. The study is published in ACS Synthetic Biology.

    Natural shells are made of up to three types of proteins. The most abundant is called BMC-H. Six BMC-H proteins come together to form a hexagon shape to tile the wall.

    At some time in evolutionary history, some pairs of BMC-H proteins became joined together, in tandem. Three of these mergers, called BMC-T, join to also form a hexagon shape.

    “The two halves of a BMC-T protein can evolve separately while staying next to each other, because they are fused together,” said Bryan Ferlez, a postdoc in the Kerfeld lab. “This evolution allows for diversity in the structures and functions of BMC-T shell proteins, something that we want to recreate by design in the lab.”

    Taking their cue from this natural evolution of shell proteins, the team created an artificial BMC-T protein, called BMC-H2, by fusing two BMC-H protein sequences together. The new design was successful.

    “To our surprise, BMC-H2 proteins form shells on their own,” said. Sean McGuire a former undergraduate research student and technician in the Kerfeld lab. “They look like wiffle balls, with gaps in the shell,”

    This is because natural shells are icoshedral, meaning that they are made of hexamers and pentamers—think of a soccer ball.

    Next, the team capped the gaps in the wiffle ball shell with BMC-P, the third type of shell protein that forms pentamers.

    “The result is a shell, about 25 nanometers wide, made up of only two protein types: the new BMC-H2 and BMC-P,” Bryan says. “It is around half the size of the structure built with all three protein types.”

    The next goal is to fit it with custom enzymes and fine tune it to enhance the chemical reactions within. The new ‘designer’ shell could have uses in biofuel production, medicine and industrial applications.

    See the full article here .


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    Michigan State Campus

    Michigan State University (MSU) is a public research university located in East Lansing, Michigan, United States. MSU was founded in 1855 and became the nation’s first land-grant institution under the Morrill Act of 1862, serving as a model for future land-grant universities.

    MSU pioneered the studies of packaging, hospitality business, plant biology, supply chain management, and telecommunication. U.S. News & World Report ranks several MSU graduate programs in the nation’s top 10, including industrial and organizational psychology, osteopathic medicine, and veterinary medicine, and identifies its graduate programs in elementary education, secondary education, and nuclear physics as the best in the country. MSU has been labeled one of the “Public Ivies,” a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.

    Following the introduction of the Morrill Act, the college became coeducational and expanded its curriculum beyond agriculture. Today, MSU is the seventh-largest university in the United States (in terms of enrollment), with over 49,000 students and 2,950 faculty members. There are approximately 532,000 living MSU alumni worldwide.

     
  • richardmitnick 9:55 am on April 29, 2019 Permalink | Reply
    Tags: , , , Magnetic microrobot, , , Nanotechnology   

    From MIT News: “Nanoparticles take a fantastic, magnetic voyage” 

    MIT News
    MIT Widget

    From MIT News

    1
    MIT engineers have designed a magnetic microrobot that can help push drug-delivery particles into tumor tissue (left). They also employed swarms of naturally magnetic bacteria to achieve the same effect (right). Image courtesy of the researchers.

    Tiny robots powered by magnetic fields could help drug-delivery nanoparticles reach their targets.

    MIT engineers have designed tiny robots that can help drug-delivery nanoparticles push their way out of the bloodstream and into a tumor or another disease site. Like crafts in Fantastic Voyage — a 1960s science fiction film in which a submarine crew shrinks in size and roams a body to repair damaged cells — the robots swim through the bloodstream, creating a current that drags nanoparticles along with them.

    The magnetic microrobots, inspired by bacterial propulsion, could help to overcome one of the biggest obstacles to delivering drugs with nanoparticles: getting the particles to exit blood vessels and accumulate in the right place.

    “When you put nanomaterials in the bloodstream and target them to diseased tissue, the biggest barrier to that kind of payload getting into the tissue is the lining of the blood vessel,” says Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science, a member of MIT’s Koch Institute for Integrative Cancer Research and its Institute for Medical Engineering and Science, and the senior author of the study.

    “Our idea was to see if you can use magnetism to create fluid forces that push nanoparticles into the tissue,” adds Simone Schuerle, a former MIT postdoc and lead author of the paper, which appears in the April 26 issue of Science Advances.

    In the same study, the researchers also showed that they could achieve a similar effect using swarms of living bacteria that are naturally magnetic. Each of these approaches could be suited for different types of drug delivery, the researchers say.

    Tiny robots

    Schuerle, who is now an assistant professor at the Swiss Federal Institute of Technology (ETH Zürich), first began working on tiny magnetic robots as a graduate student in Brad Nelson’s Multiscale Robotics Lab at ETH Zürich. When she came to Bhatia’s lab as a postdoc in 2014, she began investigating whether this kind of bot could help to make nanoparticle drug delivery more efficient.

    In most cases, researchers target their nanoparticles to disease sites that are surrounded by “leaky” blood vessels, such as tumors. This makes it easier for the particles to get into the tissue, but the delivery process is still not as effective as it needs to be.

    The MIT team decided to explore whether the forces generated by magnetic robots might offer a better way to push the particles out of the bloodstream and into the target site.

    The robots that Schuerle used in this study are 35 hundredths of a millimeter long, similar in size to a single cell, and can be controlled by applying an external magnetic field. This bioinspired robot, which the researchers call an “artificial bacterial flagellum,” consists of a tiny helix that resembles the flagella that many bacteria use to propel themselves. These robots are 3-D-printed with a high-resolution 3-D printer and then coated with nickel, which makes them magnetic.

    To test a single robot’s ability to control nearby nanoparticles, the researchers created a microfluidic system that mimics the blood vessels that surround tumors. The channel in their system, between 50 and 200 microns wide, is lined with a gel that has holes to simulate the broken blood vessels seen near tumors.

    Using external magnets, the researchers applied magnetic fields to the robot, which makes the helix rotate and swim through the channel. Because fluid flows through the channel in the opposite direction, the robot remains stationary and creates a convection current, which pushes 200-nanometer polystyrene particles into the model tissue. These particles penetrated twice as far into the tissue as nanoparticles delivered without the aid of the magnetic robot.

    This type of system could potentially be incorporated into stents, which are stationary and would be easy to target with an externally applied magnetic field. Such an approach could be useful for delivering drugs to help reduce inflammation at the site of the stent, Bhatia says.

    Bacterial swarms

    The researchers also developed a variant of this approach that relies on swarms of naturally magnetotactic bacteria instead of microrobots. Bhatia has previously developed bacteria that can be used to deliver cancer-fighting drugs and to diagnose cancer, exploiting bacteria’s natural tendency to accumulate at disease sites.

    For this study, the researchers used a type of bacteria called Magnetospirillum magneticum, which naturally produces chains of iron oxide. These magnetic particles, known as magnetosomes, help bacteria orient themselves and find their preferred environments.

    The researchers discovered that when they put these bacteria into the microfluidic system and applied rotating magnetic fields in certain orientations, the bacteria began to rotate in synchrony and move in the same direction, pulling along any nanoparticles that were nearby. In this case, the researchers found that nanoparticles were pushed into the model tissue three times faster than when the nanoparticles were delivered without any magnetic assistance.

    This bacterial approach could be better suited for drug delivery in situations such as a tumor, where the swarm, controlled externally without the need for visual feedback, could generate fluidic forces in vessels throughout the tumor.

    The particles that the researchers used in this study are big enough to carry large payloads, including the components required for the CRISPR genome-editing system, Bhatia says. She now plans to collaborate with Schuerle to further develop both of these magnetic approaches for testing in animal models.

    The research was funded by the Swiss National Science Foundation, the Branco Weiss Fellowship, the National Institutes of Health, the National Science Foundation, and the Howard Hughes Medical Institute.

    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 2:29 pm on April 26, 2019 Permalink | Reply
    Tags: "New Lens System for Brighter Sharper Diffraction Images", "The team used a photocathode gun that generates the electrons through a process called photoemission”, , “We made the sample by depositing the gold atoms on a several nanometer thick carbon film using a technique called thermal evaporation”, , Brookhaven’s Accelerator Test Facility, , Electron beam-related research techniques, , Nanotechnology, , The researchers used two groups of four quadrupole magnets to tune the electron beam., Ultra-fast electron diffraction imaging   

    From Brookhaven National Lab: “New Lens System for Brighter, Sharper Diffraction Images” 

    From Brookhaven National Lab

    April 25, 2019

    Cara Laasch
    laasch@bnl.gov
    (631) 344-8458

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

    Researchers from Brookhaven Lab designed, implemented, and applied a new and improved focusing system for electron diffraction measurements.

    1
    Mikhail Fedurin, Timur Shaftan, Victor Smalyuk, Xi Yang, Junjie Li, Lewis Doom, Lihua Yu, and Yimei Zhu are the Brookhaven team of scientists that realized and demonstrated the new lens system for as ultra-fast electron diffraction imaging.

    To design and improve energy storage materials, smart devices, and many more technologies, researchers need to understand their hidden structure and chemistry. Advanced research techniques, such as ultra-fast electron diffraction imaging can reveal that information. Now, a group of researchers from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have developed a new and improved version of electron diffraction at Brookhaven’s Accelerator Test Facility (ATF)—a DOE Office of Science User Facility that offers advanced and unique experimental instrumentation for studying particle acceleration to researchers from all around the world. The researchers published their findings in Scientific Reports, an open-access journal by Nature Research.

    Advancing a research technique such as ultra-fast electron diffraction will help future generations of materials scientists to investigate materials and chemical reactions with new precision. Many interesting changes in materials happen extremely quickly and in small spaces, so improved research techniques are necessary to study them for future applications. This new and improved version of electron diffraction offers a stepping stone for improving various electron beam-related research techniques and existing instrumentation.

    “We implemented our new focusing system for electron beams and demonstrated that we can improve the resolution significantly when compared to the conventional solenoid technique,” said Xi Yang, author of the study and an accelerator physicist at the National Synchrotron Light Source II (NSLS-II) [see below], a DOE Office of Science User Facility at Brookhaven Lab. “The resolution mainly depends on the properties of light – or in our case – of the electron beam. This is universal for all imaging techniques, including light microscopy and x-ray imaging. However, it is much more challenging to focus the charged electrons to a near-parallel pencil-like beam at the sample than it would be with light, because electrons are negatively charged and therefore repulse one another. This is called the space charge effect. By using our new setup, we were able to overcome the space charge effect and obtain diffraction data that is three times brighter and two times sharper; it’s a major leap in resolution.”

    2
    The colorful images are four different electron diffraction measurements at ATF. The left column shows diffraction patterns of the sample using the newly developed quadrupoles, while the right column shows diffraction patterns without the new lens system. In the left column the rings of the pattern are sharper, rounder and turn red, which means that the overall resolution of the measurement is higher.

    Every electron diffraction setup uses an electron beam that is focused on the sample so that the electrons bounce off the atoms in the sample and travel further to the detector behind the sample. The electrons create a so-called diffraction pattern, which can be translated into the structural makeup of the materials at the nanoscale. The advantage of using electrons to image this inner structure of materials is that the so called diffraction limit of electrons is very low, which means scientists can resolve smaller details in the structure compared to other diffraction methods.

    A diverse team of researchers was needed to improve such a complex research method. The Brookhaven Lab team consisted of electron beam experts from the NSLS-II, electron accelerator experts from ATF, and materials science experts from the condensed matter physics & materials science (CMPMS) department.

    “This advance would not have been possible without the combination of all our expertise across Brookhaven Lab. At NSLS-II, we have expertise on how to handle the electron beam. The ATF group brought the expertise and capabilities of the electron gun and laser technologies – both of which were needed to create the electron beam in the first place. And the CMPMS group has the sample expertise and, of course, drives the application needs. This is a unique synergy and, together, we were able to show how the resolution of the technique can be improved drastically,” said Li Hua Yu, NSLS-II senior accelerator physicist and co-author of the study.

    To achieve its improved resolution, the team developed a different method of focusing the electron beam. Instead of using a conventional approach that involves solenoid magnets, the researchers used two groups of four quadrupole magnets to tune the electron beam. Compared to solenoid magnets, which act as just one lens to shape the beam, the quadrupole magnets work like a specialized lens system for the electrons, and they gave the scientists far more flexibility to tune and shape the beam according to the needs of their experiment.

    “Our lens system can provide a wide range of tunability of the beam. We can optimize the most important parameters such as beam size, or charge density, and beam divergence based on the experimental conditions, and therefore provide the best beam quality for the scientific needs,” said Yang.

    The team can even adjust the parameters on-the-fly with online optimization tools and correct any nonuniformities of the beam shape; however, to make this measurement possible, the team needed the excellent electron beam that ATF provides. ATF has an electron gun that generates an extremely bright and ultrashort electron beam, which offers the best conditions for electron diffraction.

    “The team used a photocathode gun that generates the electrons through a process called photoemission,” said Mikhail Fedurin, an accelerator physicist at ATF. “We shoot an ultrashort laser pulse into a copper cathode, and when the pulse hits the cathode a cloud of electrons forms over the copper. We pull the electrons away using an electric field and then accelerate them. The amount of electrons in one of these pulses and our capability to accelerate them to specific energies make our system attractive for material science research – particularly for ultrafast electron diffraction.”

    The focusing system together with the ATF electron beam is very sensitive, so the researchers can measure the influences of Earth’ magnetic field on the electron beam.

    “In general, electrons are always influenced by magnetic fields—this is how we steer them in particle accelerators in the first place; however, the effect of Earth’s magnetic field is not negligible for the low-energy beam we used in this experiment,” said Victor Smalyuk, NSLS-II accelerator physics group leader and co-author of the study. “The beam deviated from the desired trajectory, which created difficulties during the initial starting phase, so we had to correct for this effect.”

    Beyond the high brightness of the electron beam and the high precision of the focusing system, the team also needed the right sample to make these measurements. The CMPMS group provided the team with a polycrystalline gold film to fully explore the newly designed lens system and to put it to the test.

    “We made the sample by depositing the gold atoms on a several nanometer thick carbon film using a technique called thermal evaporation,” said Junjie Li, a physicist in the CMPMS department. “We evaporated gold particles so that they condense on the carbon film and form tiny, isolated nanoparticles that slowly merge together and form the polycrystalline film.”

    This film was essential for the measurements because it has randomly oriented crystals that merge together. Therefore, the inner structure of the sample is not uniform, but consists of many differently oriented areas, which means that the diffraction pattern mainly depends on the electron beam qualities. This gives the scientists the best ground to really test their lens system, to tune the beam, and to see the impact of their tuning directly in the quality of the diffraction measurement.

    “We initially set out to improve electron diffraction for scientific studies of materials, but we also found that this technique can help us characterize our electron beam. In fact, diffraction is very sensitive to the electron beam parameters, so we can use the diffraction pattern of a known sample to measure our beam parameters precisely and directly, which is usually not that easy,” said Yang.

    The team intends to pursue further improvements, and they already have plans to develop another setup for ultra-fast electron microscopy to directly visualize a biological sample.

    “We hope to achieve ultrafast single-shot electron beam imaging at some point and maybe even make molecular movies, which isn’t possible with our current electron beam imaging setup,” said Yang.

    This research was supported by Laboratory Directed Research and Development funding and by DOE’s Office of Science through its support of the ATF.

    See the full article here .


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    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 2:03 pm on April 26, 2019 Permalink | Reply
    Tags: "Building a Printing Press for New Quantum Materials", “We realized that building a robot that can enable the design synthesis and testing of quantum materials is extremely well-matched to the skills and expertise of scientists at the CFN.”, , CFN-Center for Functional Nanomaterials, Exotic electronic magnetic and optical properties emerge at such small (quantum) size scales., , Nanotechnology, Once high-quality 2-D flakes from different crystals have been located and their properties characterized they can be assembled in the desired order to create the layered structures., Quantum Material Press or QPress, Structures obtained by stacking single atomic layers (“flakes”) peeled from different parent bulk crystals are of interest   

    From Brookhaven National Lab: “Building a Printing Press for New Quantum Materials” 

    From Brookhaven National Lab

    April 22, 2019
    Ariana Tantillo
    atantillo@bnl.gov

    Scientists at Brookhaven Lab’s Center for Functional Nanomaterials are developing an automated system to synthesize entirely new materials made from stacked atomically thin two-dimensional sheets and to characterize their exotic quantum properties.

    BNL Center for Functional Nanomaterials

    1
    Scientists at Brookhaven Lab’s Center for Functional Nanomaterials are building a robotic system to enable the design, synthesis, and testing of quantum materials, which exhibit unique properties. From left to right: Gregory Doerk, Jerzy Sadowski, Kevin Yager, Young Jae Shin, and Aaron Stein.

    Checking out a stack of books from the library is as simple as searching the library’s catalog and using unique call numbers to pull each book from their shelf locations. Using a similar principle, scientists at the Center for Functional Nanomaterials (CFN)—a U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory—are teaming with Harvard University and the Massachusetts Institute of Technology (MIT) to create a first-of-its-kind automated system to catalog atomically thin two-dimensional (2-D) materials and stack them into layered structures. Called the Quantum Material Press, or QPress, this system will accelerate the discovery of next-generation materials for the emerging field of quantum information science (QIS).

    Structures obtained by stacking single atomic layers (“flakes”) peeled from different parent bulk crystals are of interest because of the exotic electronic, magnetic, and optical properties that emerge at such small (quantum) size scales. However, flake exfoliation is currently a manual process that yields a variety of flake sizes, shapes, orientations, and number of layers. Scientists use optical microscopes at high magnification to manually hunt through thousands of flakes to find the desired ones, and this search can sometimes take days or even a week, and is prone to human error.

    Once high-quality 2-D flakes from different crystals have been located and their properties characterized, they can be assembled in the desired order to create the layered structures. Stacking is very time-intensive, often taking longer than a month to assemble a single layered structure. To determine whether the generated structures are optimal for QIS applications—ranging from computing and encryption to sensing and communications—scientists then need to characterize the structures’ properties.

    “In talking to our university collaborators at Harvard and MIT who synthesize and study these layered heterostructures, we learned that while bits of automation exist—such as software to locate the flakes and joysticks to manipulate the flakes—there is no fully automated solution,” said CFN Director Charles Black, the administrative lead on the QPress project.

    The idea for the QPress was conceived in early 2018 by Professor Amir Yacoby of the Department of Physics at Harvard. The concept was then refined through a collaboration between Yacoby; Black and Kevin Yager, leader of the CFN Electronic Nanomaterials Group; Philip Kim, also of Harvard’s Department of Physics; and Pablo Jarillo-Herrero and Joseph Checkelsky, both of the Department of Physics at MIT.

    According to Black, the unique CFN role was clear: “We realized that building a robot that can enable the design, synthesis, and testing of quantum materials is extremely well-matched to the skills and expertise of scientists at the CFN. As a user facility, CFN is meant to be a resource for the scientific community, and QIS is one of our growth areas for which we’re expanding our capabilities, scientific programs, and staff.”

    Graphene sparks 2-D materials research

    The interest in 2-D materials dates back to 2004, when scientists at the University of Manchester isolated the world’s first 2-D material, graphene—a single layer of carbon atoms. They used a surprisingly basic technique in which they placed a piece of graphite (the core material of pencils) on Scotch tape, repeatedly folding the tape in half and peeling it apart to extract ever-thinner flakes. Then, they rubbed the tape on a flat surface to transfer the flakes. Under an optical microscope, the one-atom-thick flakes can be located by their reflectivity, appearing as very faint spots. Recognized with a Nobel Prize in 2010, the discovery of graphene and its unusual properties—including its remarkable mechanical strength and electrical and thermal conductivity—has prompted scientists to explore other 2-D materials.

    Many labs continue to use this laborious approach to make and find 2-D flakes. While the approach has enabled scientists to perform various measurements on graphene, hundreds of other crystals—including magnets, superconductors, and semiconductors—can be exfoliated in the same way as graphite. Moreover, different 2-D flakes can be stacked to build materials that have never existed before. Scientists have very recently discovered that the properties of these stacked structures depend not only on the order of the layers but also on the relative angle between the atoms in the layers. For example, a material can be tuned from a metallic to an insulating state simply by controlling this angle. Given the wide variety of samples that scientists would like to explore and the error-prone and time-consuming nature of manual synthesis methods, automated approaches are greatly needed.

    “Ultimately, we would like to develop a robot that delivers a stacked structure based on the 2-D flake sequences and crystal orientations that scientists select through a web interface to the machine,” said Black. “If successful, the QPress would enable scientists to spend their time and energy studying materials, rather than making them.”

    A modular approach

    In September 2018, further development of the QPress was awarded funding by the DOE, with a two-part approach. One award was for QPress hardware development at Brookhaven, led by Black; Yager; CFN scientists Gregory Doerk, Aaron Stein, and Jerzy Sadowski; and CFN scientific associate Young Jae Shin. The other award was for a coordinated research project led by Yacoby, Kim, Jarillo-Herrero, and Checkelsky. The Harvard and MIT physicists will use the QPress to study exotic forms of superconductivity—the ability of certain materials to conduct electricity without energy loss at very low temperatures—that exist at the interface between a superconductor and magnet. Some scientists believe that such exotic states of matter are key to advancing quantum computing, which is expected to surpass the capabilities of even today’s most powerful supercomputing.

    3
    A photo of the prototype exfoliator. The robotic system transfers peeled 2-D flakes from the parent crystal to a substrate. The exfoliator allows scientists to control stamping pressure, pressing time, number of repeated presses, angle of pressing, and lateral force applied during transfer, for improved repeatability.

    A fully integrated automated machine consisting of an exfoliator, a cataloger, a library, a stacker, and a characterizer is expected in three years. However, these modules will come online in stages to enable the use of QPress early on.

    The team has already made some progress. They built a prototype exfoliator that mimics the action of a human peeling flakes from a graphite crystal. The exfoliator presses a polymer stamp into a bulk parent crystal and transfers the exfoliated flakes by pressing them onto a substrate. In their first set of experiments, the team investigated how changing various parameters—stamping pressure, pressing time, number of repeated presses, angle of pressing, and lateral force applied during transfer—impact the process.

    “One of the advantages of using a robot is that, unlike a human, it reproduces the same motions every time, and we can optimize these motions to generate lots of very thin large flakes,” explained Yager. “Thus, the exfoliator will improve both the quality and quantity of 2-D flakes peeled from parent crystals by refining the speed, precision, and repeatability of the process.”

    In collaboration with Stony Brook University assistant professor Minh Hoai Nguyen of the Department of Computer Science and PhD student Boyu Wang of the Computer Vision Lab, the scientists are also building a flake cataloger. Through image-analysis software, the cataloger scans a substrate and records the locations of exfoliated flakes and their properties.

    “The flakes that scientists are interested in are thin and thus faint, so manual visual inspection is a laborious and error-prone process,” said Nguyen. “We are using state-of-the-art computer vision and deep learning techniques to develop software that can automate this process with higher accuracy.”

    4
    A schematic showing the workflow for cataloging flake locations and properties. Image grids of exfoliated samples are automatically analyzed, with each flake tracked individually so that scientists can locate any desired flake on a sample.

    “Our collaborators have said that a system capable of mapping their sample of flakes and showing them where the “good” flakes are located—as determined by parameters they define—would be immensely helpful for them,” said Yager. “We now have this capability and would like to put it to use.”

    Eventually, the team plans to store a large set of different catalogued flakes on shelves, similar to books in a library. Scientists could then access this materials library to select the flakes they want to use, and the QPress would retrieve them.

    According to Black, the biggest challenge will be the construction of the stacker—the module that retrieves samples from the library, “drives” to the locations where the selected flakes reside, and picks the flakes up and places them in a repetitive process to build stacks according to the assembly instructions that scientists program into the machine. Ultimately, the scientists would like the stacker to assemble the layered structures not only faster but also more accurately than manual methods.

    5
    The QPress will have five modules when completed: an exfoliator, a cataloger, a materials library, a stacker, and a characterizer/fabricator.

    The final module of the robot will be a material characterizer, which will provide real-time feedback throughout the entire synthesis process. For example, the characterizer will identify the crystal structure and orientation of exfoliated flakes and layered structures through low-energy electron diffraction (LEED)—a technique in which a beam of low-energy electrons is directed toward the surface of a sample to produce a diffraction pattern characteristic of the surface geometry.

    “There are many steps to delivering a fully automated solution,” said Black. “We intend to implement QPress capabilities as they become available to maximize benefit to the QIS community.”

    See the full article here .


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    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 5:30 pm on April 18, 2019 Permalink | Reply
    Tags: , Handedness, , , Nanotechnology, Skyrmions – quasiparticles akin to tiny magnetic swirls,   

    From Lawrence Berkeley National Lab: “Electric Skyrmions Charge Ahead for Next-Generation Data Storage” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    April 18, 2019
    Theresa Duque
    tnduque@lbl.gov
    (510) 495-2418

    Berkeley Lab-led research team makes a chiral skyrmion crystal with electric properties; puts new spin on future information storage applications.


    VIDEO: Simulation of a single polar skyrmion. Red arrows signify that this is a left-handed skyrmion. The other arrows represent the angular distribution of the dipoles. (Credit: Xiaoxing Cheng, Pennsylvania State University; C.T. Nelson, Oak Ridge National Laboratory; and Ramamoorthy Ramesh, Berkeley Lab)

    When you toss a ball, what hand do you use? Left-handed people naturally throw with their left hand, and right-handed people with their right. This natural preference for one side versus the other is called handedness, and can be seen almost everywhere – from a glucose molecule whose atomic structure leans left, to a dog who shakes “hands” only with her right.

    Handedness can be exhibited in chirality – where two objects, like a pair of gloves, can be mirror images of each other but cannot be superimposed on one another. Now a team of researchers led by Berkeley Lab has observed chirality for the first time in polar skyrmions – quasiparticles akin to tiny magnetic swirls – in a material with reversible electrical properties. The combination of polar skyrmions and these electrical properties could one day lead to applications such as more powerful data storage devices that continue to hold information – even after a device has been powered off. Their findings were reported this week in the journal Nature.

    “What we discovered is just mind-boggling,” said Ramamoorthy Ramesh, who holds appointments as a faculty senior scientist in Berkeley Lab’s Materials Sciences Division and as the Purnendu Chatterjee Endowed Chair in Energy Technologies in Materials Science and Engineering and Physics at UC Berkeley. “We hadn’t planned on making skyrmions. So for us to end up making a chiral skyrmion is exciting.”

    1

    When the team of researchers – co-led by Ramesh and Lane Martin, a staff scientist in Berkeley Lab’s Materials Sciences Division and a professor in Materials Science and Engineering at UC Berkeley – began this study in 2016, they had set out to find ways to control how heat moves through materials. So they fabricated a special crystal structure called a superlattice from alternating layers of lead titanate (an electrically polar material, whereby one end is positively charged and the opposite end is negatively charged) and strontium titanate (an insulator, or a material that doesn’t conduct electric current).

    But once they took STEM (scanning transmission electron microscopy) measurements of the lead titanate/strontium titanate superlattice at the Molecular Foundry, a U.S. DOE Office of Science User Facility at Berkeley Lab that specializes in nanoscale science, they saw something strange that had nothing to do with heat: Bubble-like formations had cropped up all across the device.

    Bubbles, bubbles everywhere

    So what were these “bubbles,” and how did they get there?

    Those bubbles, it turns out, were polar skyrmions – or textures made up of opposite electric charges known as dipoles. Researchers had always assumed that skyrmions would only appear in magnetic materials, where special interactions between magnetic spins of charged electrons stabilize the twisting chiral patterns of skyrmions. So when the Berkeley Lab-led team of researchers discovered skyrmions in an electric material, they were astounded.

    3
    Simulation of the cross-section in the middle of the polar-skyrmion bubble. (Credit: Berkeley Lab)

    Through the researchers’ collaboration with theorists Javier Junquera of the University of Cantabria in Spain, and Jorge Íñiguez of the Luxembourg Institute of Science and Technology, they discovered that these textures had a unique feature called a “Bloch component” that determined the direction of its spin, which Ramesh compares to the fastening of a belt – where if you’re left-handed, the belt goes from left to right. “And it turned out that this Bloch component – the skyrmion’s equatorial belt, so to speak – is the key to its chirality or handedness,” he said.

    While using sophisticated STEM at Berkeley Lab’s Molecular Foundry and at the Cornell Center for Materials Research, where David Muller of Cornell University took atomic snapshots of skyrmions’ chirality at room temperature in real time, the researchers discovered that the forces placed on the polar lead titanate layer by the nonpolar strontium titanate layer generated the polar skyrmion “bubbles” in the lead titanate.

    “Materials are like people,” said Ramesh. “When people get stressed, they respond in unpredictable ways. And that’s what materials do too: In this case, by surrounding lead titanate by strontium titanate, lead titanate starts to go crazy – and one way that it goes crazy is to create polar textures like skyrmions.”

    Through the researchers’ collaboration with theorists Javier Junquera of the University of Cantabria in Spain, and Jorge Íñiguez of the Luxembourg Institute of Science and Technology, they discovered that these textures had a unique feature called a “Bloch component” that determined the direction of its spin, which Ramesh compares to the fastening of a belt – where if you’re left-handed, the belt goes from left to right. “And it turned out that this Bloch component – the skyrmion’s equatorial belt, so to speak – is the key to its chirality or handedness,” he said.

    While using sophisticated STEM at Berkeley Lab’s Molecular Foundry and at the Cornell Center for Materials Research, where David Muller of Cornell University took atomic snapshots of skyrmions’ chirality at room temperature in real time, the researchers discovered that the forces placed on the polar lead titanate layer by the nonpolar strontium titanate layer generated the polar skyrmion “bubbles” in the lead titanate.

    Custom-designed scanning transmission electron microscope at Cornell University by David Muller/Cornell University

    LBNL THEMIS scannng transmission electronic micsoscope

    “Materials are like people,” said Ramesh. “When people get stressed, they respond in unpredictable ways. And that’s what materials do too: In this case, by surrounding lead titanate by strontium titanate, lead titanate starts to go crazy – and one way that it goes crazy is to create polar textures like skyrmions.”

    Shining a light on crystal chirality

    To confirm their observations, senior staff scientist Elke Arenholz and staff scientist Padraic Shafer at Berkeley Lab’s Advanced Light Source (ALS), along with Margaret McCarter, a physics Ph.D. student from the Ramesh Lab at UC Berkeley, probed the chirality by using a spectroscopic technique known as RSXD-CD (resonant soft X-ray diffraction circular dichroism), one of the highly optimized tools available to the scientific community at the ALS, a U.S. DOE Office of Science User Facility that specializes in lower energy, “soft” X-ray light for studying the properties of materials.

    LBNL ALS

    3
    Simulations of skyrmion bubbles and elongated skyrmions for the lead titanate/strontium titanate superlattice. (Credit: Berkeley Lab)

    Light waves can be “circularly polarized” to also have handedness, so the researchers theorized that if polar skyrmions have handedness, a left-handed skyrmion, for example, should interact more strongly with left-handed, circularly polarized light – an effect known as circular dichroism.

    When McCarter and Shafer tested the samples at the ALS, they successfully uncovered another piece to the chiral skyrmion puzzle – they found that incoming circularly polarized X-rays, like a screw whose threads rotate either clockwise or counterclockwise, interact with skyrmions whose dipoles rotate in the same direction, even at room temperature. In other words, they found evidence of circular dichroism – where there is only a strong interaction between X-rays and polar skyrmions with the same handedness.

    “The theoretical simulations and microscopy both revealed the presence of a Bloch component, but to confirm the chiral nature of these skyrmions, the last piece of the puzzle was really the circular dichroism measurements,” McCarter said. “It is amazing to observe this effect in materials that typically don’t have handedness. We are excited to explore the implications of this chirality in a ferroelectric and how it can be controlled in a way that could be useful for storing data.”

    Now that the researchers have made a single electric skyrmion and confirmed its chirality, they plan to make an array of dozens of electric skyrmions – each one with a diameter of just 8 nm (for comparison, the Ebola virus is about 50 nm wide) – with the same handedness. “In terms of applications, this is exciting because now we have chirality – switching a skyrmion on or off, or between left-handed and right-handed – on top of still being able to use the charge for storing data,” Ramesh said.

    The researchers next plan to study the effects of applying an electric field on the polar skyrmions. “Now that we know that polar/electric skyrmions are chiral, we want to see if we can electrically manipulate them. If I apply an electric field, can I turn each one like a turnstile? Can I move each one, one at a time, like a checker on a checkerboard? If we can somehow move them, write them, and erase them for data storage, then that would be an amazing new technology,” Ramesh said.

    Also contributing to the study were researchers from Pennsylvania State University, Cornell University, and Oak Ridge National Laboratory.

    The work was supported by the DOE Office of Science with additional funding provided by the Gordon and Betty Moore Foundation’s EPiQS Initiative, the National Science Foundation, the Luxembourg National Research Fund, and the Spanish Ministry of Economy and Competitiveness.

    See the full article here .

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    Bringing Science Solutions to the World

    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

    A U.S. Department of Energy National Laboratory Operated by the University of California.

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    • Arushi 6:58 am on April 19, 2019 Permalink | Reply

      Your blog seems pretty informative. Instead of just NASA can you write about the discoveries of other organizations as well so that the science lovers can get every aspect of physics in your blog? BTW love your blog💝

      Like

      • richardmitnick 3:31 pm on April 19, 2019 Permalink | Reply

        I cover much more than NASA. I cover universities and science institutions all over the world. There is a concentration on Astronomy and Physics, but I also cover volcanology, earthquake science, ASD, HPC, . What you need to do is read the blog or access the Facebook Fan page, http://facebook.com/sciencesprings which is a pretty rich experience if you do not want to bother seeing the blog posts in full.

        Like

        • Arushi 5:15 pm on April 19, 2019 Permalink

          Okay buddy. I’m not much into science but I surely do find physics and astronomy pretty interesting. I’ll check out your Facebook page for sure.

          Like

        • richardmitnick 7:20 pm on April 21, 2019 Permalink

          Thanks.

          Like

  • richardmitnick 9:24 am on April 13, 2019 Permalink | Reply
    Tags: A new photonic switch built with more than 50000 microscopic “light switches”, , Each switch directs one of 240 tiny beams of light to either make a right turn when the switch is on or to pass straight through when the switch is off, , Nanotechnology, Photolithography, Server networks could be connected by optical fibers with photonic switches acting as the traffic cops Wu said, This could one day revolutionize how information travels through data centers and high-performance supercomputers that are used for artificial intelligence and other data-intensive applications.,   

    From insideHPC: “Berkeley Engineers build World’s Fastest Optical Switch Arrays” 

    From insideHPC

    April 12, 2019

    Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers faster and more efficiently than ever.

    1
    The photonic switch is built with more than 50,000 microscopic “light switches” etched into a silicon wafer. (Younghee Lee graphic)

    This optical “traffic cop” could one day revolutionize how information travels through data centers and high-performance supercomputers that are used for artificial intelligence and other data-intensive applications.

    The photonic switch is built with more than 50,000 microscopic “light switches,” each of which directs one of 240 tiny beams of light to either make a right turn when the switch is on, or to pass straight through when the switch is off. The 240-by-240 array of switches is etched into a silicon wafer and covers an area only slightly larger than a postage stamp.

    “For the first time in a silicon switch, we are approaching the large switches that people can only build using bulk optics,” said Ming Wu, professor of electrical engineering and computer sciences at UC Berkeley and senior author of the paper, which appeared online April 11 in the journal Optica. “Our switches are not only large, but they are 10,000 times faster, so we can switch data networks in interesting ways that not many people have thought about.”

    Currently, the only photonic switches that can control hundreds of light beams at once are built with mirrors or lenses that must be physically turned to switch the direction of light. Each turn takes about one-tenth of a second to complete, which is eons compared to electronic data transfer rates. The new photonic switch is built using tiny integrated silicon structures that can switch on and off in a fraction of a microsecond, approaching the speed necessary for use in high-speed data networks.

    Traffic cops on the information highway

    Data centers — where our photos, videos and documents saved in the cloud are stored — are composed of hundreds of thousands of servers that are constantly sending information back and forth. Electrical switches act as traffic cops, making sure that information sent from one server reaches the target server and doesn’t get lost along the way.

    But as data transfer rates continue to grow, we are reaching the limits of what electrical switches can handle, Wu said.

    “Electrical switches generate so much heat, so even though we could cram more transistors onto a switch, the heat they generate is starting to pose certain limits,” he said. “Industry expects to continue the trend for maybe two more generations and, after that, something more fundamental has to change. Some people are thinking optics can help.”

    Server networks could instead be connected by optical fibers, with photonic switches acting as the traffic cops, Wu said. Photonic switches require very little power and don’t generate any heat, so they don’t face the same limitations as electrical switches. However, current photonic switches cannot accommodate as many connections and also are plagued by signal loss — essentially “dimming” the light as it passes through the switch — which makes it hard to read the encoded data once it reaches its destination.

    In the new photonic switch, beams of light travel through a crisscrossing array of nanometer-thin channels until they reach these individual light switches, each of which is built like a microscopic freeway overpass. When the switch is off, the light travels straight through the channel. Applying a voltage turns the switch on, lowering a ramp that directs the light into a higher channel, which turns it 90 degrees. Another ramp lowers the light back into a perpendicular channel.

    “It’s literally like a freeway ramp,” Wu said. “All of the light goes up, makes a 90-degree turn and then goes back down. And this is a very efficient process, more efficient than what everybody else is doing on silicon photonics. It is this mechanism that allows us to make lower-loss switches.”

    The team uses a technique called photolithography to etch the switching structures into silicon wafers. The researchers can currently make structures in a 240-by-240 array — 240 light inputs and 240 light outputs — with limited light loss, making it the largest silicon-based switch ever reported. They are working on perfecting their manufacturing technique to create even bigger switches.

    “Larger switches that use bulk optics are commercially available, but they are very slow, so they are usable in a network that you don’t change too frequently,” Wu said. “Now, computers work very fast, so if you want to keep up with the computer speed, you need much faster switch response. Our switch is the same size, but much faster, so it will enable new functions in data center networks.”

    Co-lead authors on the paper are Tae Joon Seok of the Gwangju Institute of Science and Technology and Kyungmok Kwon, a postdoctoral researcher and Bakar Innovation Fellow at UC Berkeley. Other co-authors are Johannes Henriksson and Jianheng Luo of UC Berkeley.

    See the full article here .

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    Founded on December 28, 2006, insideHPC is a blog that distills news and events in the world of HPC and presents them in bite-sized nuggets of helpfulness as a resource for supercomputing professionals. As one reader said, we’re sifting through all the news so you don’t have to!

    If you would like to contact me with suggestions, comments, corrections, errors or new company announcements, please send me an email at rich@insidehpc.com. Or you can send me mail at:

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  • richardmitnick 9:18 am on April 12, 2019 Permalink | Reply
    Tags: "The Golden Path Toward New Two-Dimensional Semiconductors", 2D gold quantum dots can be used for electronics with a bandgap that is tunable atom-by-atom., , “This is a dream nanotechnology”, , , Nanotechnology, Scanning electron microscopes, The atomic skiing and stopping is related to the so-called energy selective deposition., The search for new materials for future electronics and quantum computing has led researchers down many paths.   

    From Michigan Technical University: “The Golden Path Toward New Two-Dimensional Semiconductors” 

    Michigan Tech bloc

    From Michigan Technical University

    April 10, 2019
    Allison Mills

    1
    Two-dimensional (2D) semiconductors are promising for quantum computing and future electronics. Now, researchers can convert metallic gold into semiconductor and customize the material atom-by-atom on boron nitride nanotubes. Credit: Bill Tembreull/Michigan Tech

    Two-dimensional (2D) semiconductors are promising for quantum computing and future electronics. Now, researchers can convert metallic gold into a semiconductor and customize the material atom-by-atom on boron nitride nanotubes.

    Gold is a conductive material already widely used as interconnects in electronic devices. As electronics have gotten smaller and more powerful, the semiconducting materials involved have also shrunk. However, computers have gotten about as small as they can with existing designs — to break the barrier, researchers dive into the physics underlying quantum computing and the unusual behaviors of gold in quantum mechanics.

    Researchers can convert gold into semiconducting quantum dots made of a single layer of atoms. Their energy gap, or bandgap, is formed by the quantum confinement — a quantum effect when materials behave like atoms as their sizes get so small approaching the molecular scale. These 2D gold quantum dots can be used for electronics with a bandgap that is tunable atom-by-atom.

    Making the dots with monolayer of atoms is tricky and the bigger challenge is customizing their properties. When laid out on boron nitride nanotubes, researchers from Michigan Technological University have found that they can get gold quantum dots to do the near-impossible. The mechanisms behind getting gold dots to clump atom-by-atom is the focus of their new paper, recently published in ACS Nano.

    Energy Selective Deposition

    Yoke Khin Yap, professor of physics at Michigan Tech, led the study. He explains that the behavior his team observed — atomic-level manipulation of gold quantum dots — can be seen with a scanning transmission electron microscope (STEM).

    2
    The Electron Optics Facility (EOF) includes three scanning electron microscopes (SEM), a high-resolution transmission electron microscope (TEM), an atomic resolution scanning transmission electron microscope (S-TEM), and a focused ion beam milling system (FIB)

    The STEM’s high-powered beam of electrons enables researchers like Yap to watch atomic movement in real-time and the view reveals how gold atoms interact with the surface of boron nitride nanotubes. Basically, the gold atoms glide along the surface of the nanotubes and, they stabilize in a hover just above the hexagon honeycomb of the boron nitride nanotubes.

    The atomic skiing and stopping is related to the so-called energy selective deposition. In the lab, the team takes an array of boron nitride nanotubes and runs a gold-laden mist past it; the gold atoms in the mist either stick as multilayered nanoparticles or bounce off the nanotube, but some of the more energetic ones glide along the circumference of the nanotube and stabilize, then start to clump into monolayers of gold quantum dots. The team shows that gold preferentially deposits behind other gold particles that have stabilized.

    “The surface of boron nitride nanotubes are atomically smooth, there are no defects on the surface, it’s a neatly arranged honeycomb,” Yap said, adding that the nanotubes are chemically inert and there is no physical bond between the nanotubes and gold atoms. “It’s much like skiing: You can’t ski on a bumpy and sticky hill with no snow, ideal conditions make it much better. The smooth surface of the nanotubes is like fresh powder.”

    Dream Nanotechnology

    The search for new materials for future electronics and quantum computing has led researchers down many paths. Yap hopes that by demonstrating the effectiveness of gold, other researchers will be inspired to pay attention to other metal monolayers at the molecular-scale.

    “This is a dream nanotechnology,” Yap said. “It is a molecular-scale technology tunable by atom with an ideal bandgap in the visible light spectra. There is a lot of promise in electronic and optical devices.”

    The team’s next steps include further characterization and incorporating device fabrication to demonstrate all-metal electronics. Potentially, monolayers of metal atoms could make up the entirety of future electronics, which will save a lot of manufacturing energy and materials.

    This work was performed in collaboration Ravindra Pandey, professor of physics at Michigan tech, whose team contributed the theoretical model, and Juan-Carlos Idrobo, scientist at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory.

    See the full article here .

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    Michigan Tech Campus
    Michigan Technological University (http://www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 130 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.
    The College of Sciences and Arts (CSA) fills one of the most important roles on the Michigan Tech campus. We play a part in the education of every student who comes through our doors. We take pride in offering essential foundational courses in the natural sciences and mathematics, as well as the social sciences and humanities—courses that underpin every major on campus. With twelve departments, 28 majors, 30-or-so specializations, and more than 50 minors, CSA has carefully developed programs to suit many interests and skill sets. From sound design and audio technology to actuarial science, applied cognitive science and human factors to rhetoric and technical communication, the college offers many unique programs.

     
  • richardmitnick 3:54 pm on April 2, 2019 Permalink | Reply
    Tags: "Researchers tune material’s color and thermal properties separately", , , , Nanotechnology, Polymers could be designed to reflect or trap heat regardless of hue   

    From MIT News: “Researchers tune material’s color and thermal properties separately” 

    MIT News
    MIT Widget

    From MIT News

    April 2, 2019
    Jennifer Chu

    1
    The visual and thermal properties of polyethylene can be tweaked to produce colorful films with a wide range of heat-radiating capabilities. Image: Felice Frankel

    Polymers could be designed to reflect or trap heat, regardless of hue.

    The color of a material can often tell you something about how it handles heat. Think of wearing a black shirt on a sweltering summer’s day — the darker the pigment, the warmer you’re likely to feel. Likewise, the more transparent a glass window, the more heat it can let through. A material’s responses to visible and infrared radiation are often naturally linked.

    Now MIT engineers have made samples of strong, tissue-like polymer material, the color and heat properties of which they can tailor independently of the other. For instance, they have fabricated samples of very thin black film designed to reflect heat and stay cool. They’ve also made films exhibiting a rainbow of other colors, each made to reflect or absorb infrared radiation regardless of the way they respond to visible light.

    The researchers can specifically tune the color and heat properties of this new material to fit the requirements for a host of wide-ranging applications, including colorful, heat-reflecting building facades, windows, and roofs; light-absorbing, heat-dissipating covers for solar panels; and lightweight fabric for clothing, outerwear, tents, and backpacks — all designed to either trap or reflect heat, depending on the environments in which they would be used.

    “With this material, everything could look more colorful, because then you wouldn’t be concerned with what color does to the thermal balance of, say, a building, or a window, or your clothing,” says Svetlana Boriskina, a research scientist in MIT’s Department of Mechanical Engineering.

    Boriskina is author of a study that appears today in the journal Optical Materials Express, outlining the new material-engineering technique. Her MIT co-authors are Luis Marcelo Lozano, Seongdon Hong, Yi Huang, Hadi Zandavi, Yoichiro Tsurimaki, Jiawei Zhou, Yanfei Xu, and Gang Chen, the Carl Richard Soderberg Professor of Power Engineering, along with Yassine Ait El Aoud and Richard Osgood III, both of the Combat Capabilities Development Command Soldier Center, in Natick, Massachusetts.

    Polymer conductors

    For this work, Boriskina was inspired by the vibrant colors in stained-glass windows, which for centuries have been made by adding particles of metals and other natural pigments to glass.

    “However, despite providing excellent visual transparency, glass has many limitations as a material,” Boriskina notes. “It is bulky, inflexible, fragile, does not spread heat well, and is obviously not suitable for wearable applications.”

    She says that while it’s relatively simple to tailor the color of glass, the material’s response to heat is difficult to tune. For instance, glass panels reflect room-temperature heat and trap it inside the room. Furthermore, if colored glass is exposed to incoming sunlight from a particular direction, the heat from the sun can create a hotspot, which is difficult to dissipate in glass. If a material like glass can’t conduct or dissipate heat well, that heat could damage the material.

    The same can be said for most plastics, which can be engineered in any color but for the most part are thermal absorbers and insulators, concentrating and trapping heat rather than reflecting it away.

    For the past several years, Chen’s lab has been looking into ways to manipulate flexible, lightweight polymer materials to conduct, rather than insulate, heat, mostly for applications in electronics. In previous work, the researchers found that by carefully stretching polymers like polyethylene, they could change the material’s internal structure in a way that also changed its heat-conducting properties.

    Boriskina thought this technique might be useful not just for fabricating polymer-based electronics, but also in architecture and apparel. She adapted this polymer-fabrication technique, adding a twist of color.

    “It’s very hard to develop a new material with all these different properties in it,” she says. “Usually if you tune one property, the other gets destroyed. Here, we started with one property that was discovered in this group, and then we added a new property creatively. All together it works as a multifunctional material.”

    Hotspots stretched away

    To fabricate the colorful films, the team started with a mixture of polyethylene powder and a chemical solvent, to which they added certain nanoparticles to give the film a desired color. For instance, to make black film, they added particles of silicon; other red, blue, green, and yellow films were made with the addition of various commercial dyes.

    The team then attached each nanoparticle-embedded film onto a roll-to-roll apparatus, which they heated up to soften the film, making it more pliable as the researchers carefully stretched the material.

    As they stretched each film, they found, unsurprisingly, that the material became more transparent. They also observed that polyethylene’s microscopic structure changed as it stretched. Where normally the material’s polymer chains resemble a disorganized tangle, similar to cooked spaghetti, when stretched these chains straighten out, forming parallel fibers.

    When the researchers placed each sample under a solar simulator — a lamp that mimics the visible and thermal radiation of the sun — they found the more stretched out a film, the more heat it was able to dissipate. The long, parallel polymer chains essentially provided a direct route along which heat could travel. Along these chains, heat, in the form of phonons, could then shoot away from its source, in a “ballistic” fashion, avoiding the formation of hotspots.

    The researchers also found that the less they stretched the material, the more insulating it was, trapping heat, and forming hotspots within polymer tangles.

    By controlling the degree to which the material is stretched, Boriskina could control polyethylene’s heat-conducting properties, regardless of the material’s color. She also carefully chose the nanoparticles, not just by their visual color, but also by their interactions with invisible radiative heat. She says researchers can potentially use this technique to produce thin, flexible, colorful polymer films, that can conduct or insulate heat, depending on the application.

    Going forward, she plans to launch a website that offers algorithms to calculate a material’s color and thermal properties, based on its dimensions and internal structure.

    In addition to films, her group is now working on fabricating nanoparticle-embedded polyethylene thread, which can be stitched together to form lightweight apparel, designed to be either insulating, or cooling.

    “This is in film factor now, but we’re working it into fibers and fabrics,” Boriskina says. “Polyethylene is produced by the billions of tons and could be recycled, too. I don’t see any significant impediments to large-scale production.”

    This research was supported, in part, by the Combat Capabilities Development Command Soldier Center.

    See the full article here .


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