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  • richardmitnick 12:00 pm on April 3, 2019 Permalink | Reply
    Tags: "The Robot Makers", , Electronics, ,   

    From Stanford University Engineering: “The Robot Makers” 

    Stanford University Name
    From Stanford University Engineering

    All articles by By Taylor Kubota

    1
    Image courtesy of Frederic Osada and Teddy Seguin/DRASSM
    Oussama Khatib: My group has always been inspired by the human example
    From cooperative robots like Romeo and Juliet to the diving robot OceanOne, Khatib’s lab has brought human-centered artificial intelligence to the fore.
    See the full article here .

    Balance of photo credits L.A. Cicero
    2
    Allison Okamura: I wasn’t one of those kids that always loved robots
    Okamura discusses her first robotics project and the resurgence of creativity in robotics she’s witnessing — and influencing.
    See the full article here .

    3
    David Lentink: We want to fly anywhere, regardless of turbulence
    Lentink is known for his work on aerial vehicles that are inspired by birds, bats and flying insects.
    See the full article here .

    4
    Mark Cutkosky: The work in my lab centers around bio-inspired robots
    Cutkosky describes how his research turned from robots in manufacturing to robots that climb, stick, perch, grasp and push.
    See the full article here .

    5
    Andrew Ng: Deep learning has created a sea change in robotics
    Ng’s early work at Stanford focused on autonomous helicopters; now he’s working on applications for artificial intelligence in health care, education and manufacturing.
    See the full article here .

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    Please help promote STEM in your local schools.

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    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 9:07 am on September 2, 2018 Permalink | Reply
    Tags: , , , David Livoti, Electronics   

    From Brookhaven National Lab: “Meet David Livoti: Radiofrequency Technician in Collider-Accelerator Department” 

    From Brookhaven National Lab

    August 31, 2018
    Rebecca Wilkin
    rebeccalwilkin@gmail.com

    Former intern now employee helps to maintain radiofrequency systems for particle accelerators.

    1
    Former intern David Livoti is now a full-time employee in the radiofrequency (RF) group of the C-AD complex, where he’s part of a team of technicians that maintains RF systems for the Lab’s particle accelerators. No image credit.

    Growing up, David Livoti spent his summers working at libraries and garden centers near his home in Center Moriches. Then, in 2017, he landed his first internship just a few minutes down the road at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, as a participant in the Office of Science’s Science Undergraduate Laboratory Internships (SULI) program. He quickly developed a passion for designing and studying the performance of electronics while building devices to measure snowfall amounts in Brookhaven’s Department of Environmental Science. One year later, Livoti is now helping to maintain acceleration systems for the Lab’s particle accelerators as a radiofrequency technician.

    “I like the atmosphere here at Brookhaven,” said Livoti, who graduated from Farmingdale State College last December with a dual degree in electrical and computer engineering. “I wanted to be in the research and design field, and I figured what better place to start a career than at a national laboratory where the most advanced research and design is done.”

    While interning under the direction of engineer Scott Smith, Livoti and fellow interns developed a machine that monitors snowfall accumulation—an improvement over the standard method of monitoring snowfall. That tedious task required taking manual measurements with a ruler every six hours!

    “The conventional method of measuring snow is archaic,” said Livoti, who completed all of the electronics and programming for the new device.

    The new device, developed in collaboration with the National Weather Service, has an electronic sensor that operates using sound waves, similar to the way sonar devices measure ocean depths. As snow accumulates, the sensor sends out sound waves to measure the change in distance between itself and the high point of accumulated snow piled up on a retractable table below. When the snow builds up to a certain point, the pre-programmed table tilts downward and the snow slides off, allowing the sensor to start measuring again, adding the additional accumulation to the running total.

    “This new, solar-powered device could help scientists determine snowfall rates more accurately, and it eliminates the task of taking manual measurements,” said Smith, who recently submitted the design for a patent. He noted that Livoti played a prominent role in building the device.

    “David has an incredible work ethic—he came to the lab early, stayed here late, and was relentless when it came to figuring out why something wasn’t working,” Smith said. “He’s also easy to get along with, and he has a great personality.”

    Hoping to continue his work with programming and electronics, Livoti applied for a position at the Lab after finishing his last semester of college. Within one month, he was hired as a technician in the radiofrequency (RF) group of the Collider-Accelerator Department (C-AD).

    The 23-year-old now works in the radiofrequency (RF) group of the C-AD complex, where he’s part of a team of technicians that maintains the RF systems. RF systems generate electric fields that control particles circulating in particle accelerators, including the Relativistic Heavy Ion Collider (RHIC)—a DOE Office of Science user facility for nuclear physics research that collides protons and/or heavy ions so scientists can study the building blocks of matter.

    “I enjoy maintaining the accelerators when they’re running, because it’s cool to see what the physicists are studying,” Livoti said. “But I also like when the accelerators are shut down, because that’s when the technicians get to experiment.”

    As part of the RF group, Livoti is assisting the lead engineers in maintaining and troubleshooting high power RF amplifiers and cavities that are integral parts of the C-AD complex. In addition, he is learning new technologies and conducting tests on solid-state and vacuum-tube amplifiers, as well as learning to program and use devices that control power supplies and monitor the status of other accelerator subcomponents.

    Livoti plans to continue this research and someday obtain a master’s degree in electrical engineering. When he isn’t busy maintaining and testing RF systems, he spends his time snowboarding and playing softball in the Lab’s league.

    See the full article here .

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    Please help promote STEM in your local schools.

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    BNL Campus

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    BNL NSLS II

    BNL RHIC Campus

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    BNL RHIC PHENIX

    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 3:16 pm on March 8, 2018 Permalink | Reply
    Tags: , Electronics, , Thanks To A New Type Of Inductor, The Last Barrier To Ultra-Miniaturized Electronics Is Broken   

    From Ethan Siegel: “The Last Barrier To Ultra-Miniaturized Electronics Is Broken, Thanks To A New Type Of Inductor” 

    From Ethan Siegel
    Mar 8, 2018

    1
    Artist’s depiction of the intercalated multilayer-graphene inductor (center blue spiral) which relies on kinetic inductance. Background images show its predecessors which rely on magnetic inductance, a vastly inferior and less efficient concept for microelectronics. Peter Allen / UC Santa Barbara.

    In the race for ever-improving technology, there are two related technical capabilities that drive our world forward: speed and size. These are related, as the smaller a device is, the less distance the electrical signal driving your device has to travel. As we’ve been able to cut silicon thinner, print circuit elements smaller, and develop increasingly miniaturized transistors, gains in computing speed-and-power and decreases in device size have gone hand-in-hand. But at the same time these advances have comes in leaps and bounds, one fundamental circuit element — the inductor — has had its design remain exactly the same. Found in everything from televisions to laptops to smartphones to wireless chargers, radios, and transformers, it’s one of the most indispensable electronic components in existence.

    Since their 1831 invention by Michael Faraday, their design has remained basically unchanged. Until last month, that is, when a UC Santa Barbara team led by Kaustav Banerjee [Nature Electronics] demonstrated a fundamentally new type of inductor. Without the limitations of the original inductor design, it should allow a new breakthrough in miniaturization and speed, potentially paving the way for a more connected world.

    2
    One of the earliest applications of Faraday’s law of induction was to note that a coil of wire, which would create a magnetic field inside, could magnetize a material, causing a change in its internal magnetic field. This changing field would then induce a current in the coil on the other side of the magnet, causing the needle (at right) to deflect. Modern inductors still rely on this same principle. Wikimedia Commons user Eviatar Bach.

    The classic way inductors work is one of the simplest designs possible: a simple coil of wire. When you pass a current through a loop or coil of wire, it creates a magnetic field through the center. But according to Faraday’s law of induction, that changing magnetic field then induces a current in the next loop, a current which opposes the one you’re trying to create. If you create a greater coil density, or (even better) put a core of magnetizable material inside the inductor, you can greatly increase the inductance of your device. This results in inductors which are very effective, but also which are required to be physically quite large. Despite all the advances we’ve made, the fundamental limitation of this design style means there’s been a limit to how small an inductor can get.

    3
    Even with all the revolutions the 19th, 20th and 21st centuries have brought along in electronics, the conventional magnetic inductor, in concept, remains virtually unchanged from Faraday’s original designs. Image credit: Shutterstock.

    The applications, however, are tremendous. Along with capacitors and resistors, inductors are one of the three passive elements that are the foundations of all electronics. Create an electric current of the right magnitude and frequency, and you’ll build an induction motor. Pass the magnetic core in-and-out through the coil, and you’ll generate electricity from a mechanical motion. Send both AC and DC currents down your circuit, and the inductor will block AC while allowing DC to pass through. They can separate signals of different frequencies, and when you use a capacitor along with an inductor, you can make a tuned circuit, of paramount importance in television and radio receivers.

    But while resistors have been miniaturized with, for example, the development of the surface mount resistor, and capacitors have given way to supercapacitor materials that approach the theoretical limit, the basic design of inductors has remained the same throughout the centuries. Despite being invented way back in 1831, nothing about their basic design has changed in nearly 200 years. They function on the principle of magnetic inductance, where a current, a coil of wire, and a core of magnetizable material are used in tandem.

    But there is another approach, in theory, that inductors can take. There’s also a phenomenon known as kinetic inductance, where instead of a changing magnetic field inducing an opposing current as in magnetic inductance, it’s the inertia of the particles that carry the electric current themselves — such as electrons — that oppose a change in their motion.

    4
    As current flows uniformly through a conductor, it obeys Newton’s law of an object (the individual charges) remaining in uniform motion unless acted upon by an outside force. But even if they are acted on by an outside force, their inertia resists that change: the concept behind kinetic inductance. Wikimedia Commons users lx0 / Menner

    If you envision an electric current as a series of charge carriers (like electrons) all moving steadily, in a row, and at a constant speed, you can imagine what it would take to change that current: an additional force of some type. Each of those particles would need a force to act on them, causing them to accelerate or decelerate. The same principle that creates Newton’s most famous law of motion, F = ma, tells us that if we want to change the motions of these charged particles, we need to exert a force on them. In this equation, it’s their masses, or the m in the equation, that resists that change in motion. That’s where kinetic inductance comes from. Functionally, it’s indistinguishable from magnetic inductance, it’s just that kinetic inductance has only ever been practically large under extreme conditions: either in superconductors or in extremely high-frequency circuits.

    5
    An on-chip metal inductor, center, still relies on the Faraday-inspired concept of magnetic inductance. There are limits to its efficiency and how well it can be miniaturized, and in the smallest electronics, these inductors can take up a full 50% of the total surface area available for electronic components.
    H. Wang et al., Journal of Semiconductors, 38, 11 (2017).

    In conventional metallic conductors, kinetic inductance is negligible, and so it’s never been applied in conventional circuits before. But if it could be applied, it would be a revolutionary advance for miniaturization, since unlike magnetic inductance, its value doesn’t depend on the inductor’s surface area. With that fundamental limitation removed, it could be possible to create a kinetic inductor that’s far smaller than any magnetic inductor we’ve ever made. And if we can engineer that advance, perhaps we can take the next great leap forward in miniaturization.

    6
    On-chip metal inductors revolutionized radio frequency electronics two decades ago, but there are inherent limitations to their scalability. With the breakthroughs inherent to replacing magnetic inductance with kinetic inductance, it may be possible to engineer another, greater revolution still. Image credit: Shutterstock.

    That’s where the work of Banerjee’s Nanoelectronics Research Lab and their collaborators comes in. By exploiting the phenomenon of kinetic inductance, they were able to, for the first time, demonstrate the effectiveness a fundamentally different kind of inductor that didn’t rely on Faraday’s magnetic inductance. Instead of using conventional metal inductors, they used graphene — carbon bonded together into an ultra-hard, highly-conductive configuration that also has a large kinetic inductance — to make the highest inductance-density material ever created. In a paper last month published in Nature Electronics [link is above], the group demonstrated that if you inserted bromine atoms between various layers of graphene, in a process known as intercalation, you could finally create a material where the kinetic inductance exceeded the theoretical limit of a traditional Faraday inductor.

    7
    The novel graphene design for the kinetic inductor (right) has finally surpassed traditional inductors in terms of inductance density, as the central panel (in blue and red, respectively) demonstrates. J. Kang et al., Nature Electronics 1, 46-51 (2018).

    Already achieving 50% greater inductance for its size, in a scalable way that should allow material scientists to miniaturize this type of device even further. If you can make the intercalation process more efficient, which is exactly what the team is now working on, you should be able to increase the inductance density even further. According to Banerjee,

    “We essentially engineered a new nanomaterial to bring forward the previously ‘hidden physics’ of kinetic inductance at room temperature and in a range of operating frequencies targeted for next-generation wireless communications.”

    With connected devices and the Internet of Things poised to become a multi-trillion dollar enterprise by the mid-2020s, this new type of inductor could be exactly the kind of revolution the burgeoning industry has been hoping for. Next-generation communications, energy storage, and sensing technologies could be smaller, lighter, and faster than ever. And thanks to this great leap in nanomaterials, we might finally be able to go beyond the technology that Faraday brought to our world nearly 200 years ago.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

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

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

    Stanford University Name
    Stanford University

    March 28, 2017
    Ula Chrobak

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

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

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

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

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

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

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

    Scorching heat

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

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

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

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

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

    Radiation damage

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

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

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

    Hot electronics at home

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

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

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

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

    Media Contacts

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

    See the full article here .

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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 4:33 pm on March 3, 2016 Permalink | Reply
    Tags: , , Electronics,   

    From Cornell: “Light-up skin stretches boundaries of robotics” 

    Cornell Bloc

    Cornell University

    March 3, 2016
    Tom Fleischman
    cunews@cornell.edu

    Electroluminescent skin Cornell
    The research group of Rob Shepherd, assistant professor of mechanical and aerospace engineering, has developed a highly stretchable electroluminescent skin capable of stretching to nearly six times its original size while still emitting light. The group’s work is documented in a paper published online March 3 in the journal Science. Chris Larson

    A health care robot that displays a patient’s temperature and pulse, and even reacts to a patient’s mood.

    An autonomous vehicle with an information display interface that can be changed based on the passenger’s needs.

    Even in this age of smartphones and other electronics wonders, these ideas sound quite futuristic. But a team of Cornell graduate students – led by Rob Shepherd, assistant professor of mechanical and aerospace engineering – has developed an electroluminescent “skin” that stretches to more than six times its original size while still emitting light. The discovery could lead to significant advances in health care, transportation, electronic communication and other areas.

    “This material can stretch with the body of a soft robot, and that’s what our group does,” Shepherd said, noting that the material has two key properties: “It allows robots to change their color, and it also allows displays to change their shape.”

    This hyper-elastic light-emitting capacitor (HLEC), which can endure more than twice the strain of previously tested stretchable displays, consists of layers of transparent hydrogel electrodes sandwiching a dielectric (insulating) elastomer sheet. The elastomer changes luminance and capacitance (the ability to store an electrical charge) when stretched, rolled and otherwise deformed.

    “We can take these pixels that change color and put them on these robots, and now we have the ability to change their color,” Shepherd said. “Why is that important? For one thing, when robots become more and more a part of our lives, the ability for them to have emotional connection with us will be important. So to be able to change their color in response to mood or the tone of the room we believe is going to be important for human-robot interactions.”

    In addition to its ability to emit light under a strain of greater than 480 percent its original size, the group’s HLEC was shown to be capable of being integrated into a soft robotic system. Three six-layer HLEC panels were bound together to form a crawling soft robot, with the top four layers making up the light-up skin and the bottom two the pneumatic actuators.

    The chambers were alternately inflated and deflated, with the resulting curvature creating an undulating, “walking” motion.

    Shepherd credited a group of four graduate students – Bryan Peele, Chris Larson, Shuo Li and Sanlin Robinson – with coming up with the idea for the material. All but Li were in Shepherd’s Rheology and Processing of Soft Materials class in spring 2014, when the seeds for this discovery were planted.

    “They would say something like, ‘OK, we have a single pixel that can stretch 500 percent in length.’ And so I’d say, ‘That’s cool, but what is the application for it?’” Shepherd said. “And that’s the biggest thing – you can have something cool, but you need to find a reason to use it.”

    In addition to the four graduate students, all members of the Shepherd Group, contributors included Massimo Tottaro, Lucia Beccai and Barbara Mazzolai of the Italian Institute of Technology’s Center for Micro-BioRobotics, a world leader in robotics study. Shepherd met Beccai and Mazzolai at a conference two years ago; this was their first research collaboration.

    The group’s paper, Highly Stretchable Electroluminescent Skin for Optical Signaling and Tactile Sensing, is published in the March 3 online edition of the journal Science.

    Although Shepherd admitted to “not being very fashion-forward,” another application involves wearable electronics. While wearable technology today involves putting hard electronics onto a soft base (think Apple Watch or Fitbit), this discovery paves the way for devices that fully conform to the wearer’s shape.

    “You could have a rubber band that goes around your arm that also displays information,” Larson said. “You could be in a meeting and have a rubber band-like device on your arm and could be checking your email. That’s obviously in the future, but that’s the direction we’re looking in.”

    The Shepherd Group has also developed a lightweight, stretchable material with the consistency of memory foam, with the potential for use in prosthetic body parts, artificial organs and soft robotics.

    The group’s latest work was supported by a grant from the Army Research Office, a 2015 award from the Air Force Office of Scientific Research, and two grants from the National Science Foundation.

    See the full article here .

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    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 6:59 am on May 8, 2015 Permalink | Reply
    Tags: , Electronics, , ,   

    From MIT: “Electrons corralled using new quantum tool” 


    MIT News

    May 7, 2015
    David L. Chandler

    1
    Image: Jon Wyrick/NIST

    “Whispering gallery” effect confines electrons, could provide basis for new electron-optics devices.

    Researchers have succeeded in creating a new “whispering gallery” effect for electrons in a sheet of graphene — making it possible to precisely control a region that reflects electrons within the material. They say the accomplishment could provide a basic building block for new kinds of electronic lenses, as well as quantum-based devices that combine electronics and optics.

    The new system uses a needle-like probe that forms the basis of present-day scanning tunneling microscopes (STM), enabling control of both the location and the size of the reflecting region within graphene — a two-dimensional form of carbon that is just one atom thick.

    The new finding is described in a paper appearing in the journal Science, co-authored by MIT professor of physics Leonid Levitov and researchers at the National Institute of Standards and Technology (NIST), the University of Maryland, Imperial College London, and the National Institute for Materials Science (NIMS) in Tsukuba, Japan.

    When the sharp tip of the STM is poised over a sheet of graphene, it produces a circular barrier on the sheet that “acts as a perfect curved mirror” for electrons, Levitov says, reflecting them along the curved surface until they begin to interfere with themselves. This controllable reflectivity and interference is similar, he adds, to so-called “whispering gallery” confinement modes that have been used in optical and acoustic systems — but these have not been tunable or adjustable.

    “In optics, whispering gallery resonators are known and useful,” Levitov says. “They provide high-quality cavities that find applications in sensing, spectroscopy, and communications. But the usual problem in optics is they’re not tunable.” Similarly, previous attempts to create quantum “corrals” for electrons have used atoms precisely positioned on a surface, which cannot be reconfigured easily.

    The confinement in this case is produced by the boundary between two different regions on the graphene surface, corresponding to the “p” and “n” regions in a transistor. In this case, a circular region just beneath the STM tip takes on one polarity, and the surrounding region the opposite polarity, creating a controllable circular junction between the two regions. Electrons inside sheets of graphene behave like particles of light; in this case, the circular junction acts as a curved mirror that can focus and control the electrons.

    It’s too early to predict what specific uses might be found for this phenomenon, Levitov says, but adds, “Any resonator can be used for a variety of things.”

    This electron resonator combines several good features. There’s clearly something special about having tunability and also high quality at the same time.”

    Philip Kim, a professor of physics at Harvard University who was not connected with this research, says it is “a very notable example of demonstrating novel electronic properties of graphene.” He adds, “Electrons in graphene behave like photons confined in a two-dimensional atomic sheet. This work unambiguously demonstrates that electrons confined in the potential created by scanning probe microscope exhibit a wave like resonance behavior, known as whispering gallery mode.”

    Because the new system is based on well-established STM technology, it could be developed relatively quickly into usable devices, Levitov suggests. And conveniently, the STM not only creates the whispering gallery effect, but also provides a means of observing the results, to study the phenomenon. “The tip does double-duty in this case,” he says.

    This could be a step toward the creation of electronic lenses, Levitov says — “a concept that intrigues graphene researchers.” In principle, these could provide a way of observing objects one-thousandth the size of those visible using light waves.

    Electronic lenses would represent a fundamentally different approach from existing electron microscopes, which bombard a surface with high-energy beams of electrons, obliterating any subtle effects within the objects being observed. Electron lenses, by contrast, would be able to observe the ambient low-energy electrons within the object itself.

    An appealing feature of the setup developed in NIST is that the boundary between the two surface regions, which can serve as a lens, is movable, since it is carried along with the STM tip when it is scanning the surface. This could make it possible to study “subtle things about how charge carriers behave at a microscopic level, that you can’t see from the outside,” Levitov says.

    The new work by Levitov and his colleagues provides one piece of such a system — and potentially of other advanced electro-optical systems, he says, such as negative-refraction materials that have been proposed as a kind of “invisibility cloak.” The new whispering-gallery mode for electrons is part of a toolbox that could lead to a whole family of new quantum-based electron-optics devices. It could also be used for high-fidelity sensing, since such resonators “can be used to enhance your sensitivity to very small signals,” Levitov says.

    Harvard’s Kim says that this work “is an important step toward building novel electronic applications, based on the unique relativistic quantum-mechanical behavior of electrons in graphene.”

    The research team also included graduate student Joaquin Rodriguez-Nieva from MIT; Yue Zhao, Jonathan Wyrick, Fabian Natterer, Nikolai Zhitenev, and Joseph Stroscio from NIST; Cyprian Lewandowski from Imperial College London; and Kenji Watanabe and Takashi Taniguchi from NIMS.

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  • richardmitnick 5:08 pm on December 17, 2014 Permalink | Reply
    Tags: , Electronics, , ,   

    From LBL: “Switching to Spintronics” 

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    Berkeley Lab

    December 17, 2014
    Lynn Yarris (510) 486-5375

    In a development that holds promise for future magnetic memory and logic devices, researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Cornell University successfully used an electric field to reverse the magnetization direction in a multiferroic spintronic device at room temperature. This demonstration, which runs counter to conventional scientific wisdom, points a new way towards spintronics. and smaller, faster and cheaper ways of storing and processing data.

    s
    Conceptual illustration of how magnetism is reversed (see compass) by the application of an electric field (blue dots) applied across gold capacitors. Blurring of compass needles under electric field represents two-step process. (Image courtesy of John Heron, Cornell)

    “Our work shows that 180-degree magnetization switching in the multiferroic bismuth ferrite can be achieved at room temperature with an external electric field when the kinetics of the switching involves a two-step process,” says Ramamoorthy Ramesh, Berkeley Lab’s Associate Laboratory Director for Energy Technologies, who led this research. “We exploited this multi-step switching process to demonstrate energy-efficient control of a spintronic device.”

    Ramesh, who also holds the Purnendu Chatterjee Endowed Chair in Energy Technologies at the University of California (UC) Berkeley, is the senior author of a paper describing this research in Nature. The paper is titled Deterministic switching of ferromagnetism at room temperature using an electric field. John Heron, now with Cornell University, is the lead and corresponding author. (See below for full list of co-authors).

    r
    Ramamoorthy Ramesh is Berkeley Lab’s Associate Laboratory Director for Energy Technologies, a UC Berkeley professor, and a leading authority on multiferroics. (Photo by Roy Kaltschmidt)

    Multiferroics are materials in which unique combinations of electric and magnetic properties can simultaneously coexist. They are viewed as potential cornerstones in future data storage and processing devices because their magnetism can be controlled by an electric field rather than an electric current, a distinct advantage as Heron explains.

    “The electrical currents that today’s memory and logic devices rely on to generate a magnetic field are the primary source of power consumption and heating in these devices,” he says. “This has triggered significant interest in multiferroics for their potential to reduce energy consumption while also adding functionality to devices.”

    Nature, however, has imposed thermodynamic barriers and material symmetry constrains that theorists believed would prevent the reversal of magnetization in a multiferroic by an applied electric field. Earlier work by Ramesh and his group with bismuth ferrite, the only known thermodynamically stable room-temperature multiferroic, in which an electric field was used as on/off switch for magnetism, suggested that the kinetics of the switching process might be a way to overcome these barriers, something not considered in prior theoretical work.

    “Having made devices and done on/off switching with in-plane electric fields in the past, it was a natural extension to study what happens when an out-of-plane electric field is applied,” Ramesh says.

    Ramesh, Heron and their co-authors set up a theoretical study in which an out-of-plane electric field – meaning it ran perpendicular to the orientation of the sample – was applied to bismuth ferrite films. They discovered a two-step switching process that relies on ferroelectric polarization and the rotation of the oxygen octahedral.

    j
    John Heron is the lead author of a Nature paper describing the switching of ferromagnetism at room temperature using an electric field.

    “The two-step switching process is key as it allows the octahedral rotation to couple to the polarization,” Heron says. “The oxygen octahedral rotation is also critical because it is the mechanism responsible for the ferromagnetism in bismuth ferrite. Rotation of the oxygen octahedral also allows us to couple bismuth ferrite to a good ferromagnet such as cobalt-iron for use in a spintronic device.”

    To demonstrate the potential technological applicability of their technique, Ramesh, Heron and their co-authors used heterostructures of bismuth ferrite and cobalt iron to fabricate a spin-valve, a spintronic device consisting of a non-magnetic material sandwiched between two ferromagnets whose electrical resistance can be readily changed. X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) images showed a clear correlation between magnetization switching and the switching from high-to-low electrical resistance in the spin-valve. The XMCD-PEEM measurements were completed at PEEM-3, an aberration corrected photoemission electron microscope at beamline 11.0.1 of Berkeley Lab’s Advanced Light Source.

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    “We also demonstrated that using an out-of-plane electric field to control the spin-valve consumed energy at a rate of about one order of magnitude lower than switching the device using a spin-polarized current,” Ramesh says.

    In addition to Ramesh and Heron, other co-authors of the Nature paper were James Bosse, Qing He, Ya Gao, Morgan Trassin, Linghan Ye, James Clarkson, Chen Wang, Jian Liu, Sayeef Salahuddin, Dan Ralph, Darrell Schlom, Jorge Iniguez and Bryan Huey.

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  • richardmitnick 4:28 pm on November 20, 2014 Permalink | Reply
    Tags: , Electronics, ,   

    From MIT: “Controlling a material with voltage” 


    MIT News

    November 20, 2014
    David L. Chandler | MIT News Office

    Technique could let a small electrical signal change materials’ electrical, thermal, and optical characteristics.

    A new way of switching the magnetic properties of a material using just a small applied voltage, developed by researchers at MIT and collaborators elsewhere, could signal the beginning of a new family of materials with a variety of switchable properties, the researchers say.

    temp
    This diagram shows the principle behind using voltage to change material properties. In this sandwich of materials, applying a voltage results in movement of ions — electrically charged atoms — from the middle, functional layer of material into the target layer. This modifies some of the properties — magnetic, thermal, or optical — of the target material, and the changes remain after the voltage is removed. Diagram courtesy of the researchers; edited by Jose-Luis Olivares/MIT

    The technique could ultimately be used to control properties other than magnetism, including reflectivity or thermal conductivity, they say. The first application of the new finding is likely to be a new kind of memory chip that requires no power to maintain data once it’s written, drastically lowering its overall power needs. This could be especially useful for mobile devices, where battery life is often a major limitation.

    The findings were published this week in the journal Nature Materials by MIT doctoral student Uwe Bauer, associate professor Geoffrey Beach, and six other co-authors.

    Beach, the Class of ’58 Associate Professor of Materials Science and Engineering, says the work is the culmination of Bauer’s PhD thesis research on voltage-programmable materials. The work could lead to a new kind of nonvolatile, ultralow-power memory chips, Beach says.

    The concept of using an electrical signal to control a magnetic memory element is the subject of much research by chip manufacturers, Beach says. But the MIT-based team has made important strides in making the technique practical, he says.

    The structure of these devices is similar to that of a capacitor, Beach explains, with two thin layers of conductive material separated by an insulating layer. The insulating layer is so thin that under certain conditions, electrons can tunnel right through it.

    But unlike in a capacitor, the conductive layers in these low-power chips are magnetized. In the new device, one conductive layer has fixed magnetization, but the other can be toggled between two magnetic orientations by applying a voltage to it. When the magnetic orientations are aligned, it is easier for electrons to tunnel from one layer to the other; when they have opposite orientations, the device is more insulating. These states can be used to represent “zero” and “one.”

    The work at MIT shows that it takes just a small voltage to flip the state of the device — which then retains its new state even after power is switched off. Conventional memory devices require a continuous source of power to maintain their state.

    The MIT team was able to design a system in which voltage changes the magnetic properties 100 times more powerfully than other groups have been able to achieve; this strong change in magnetism makes possible the long-term stability of the new memory cells.

    They achieved this by using an insulating layer made of an oxide material in which the applied voltage can rearrange the locations of the oxygen ions. They showed that the properties of the magnetic layer could be changed dramatically by moving the oxygen ions back and forth near the interface.

    The team is now working to ramp up the speed at which these changes can be made to the memory elements. They have already reached rates of a megahertz (millions of times per second) in switching, but a fully competitive memory module will require further increase on the order of a hundredfold to a thousandfold, they say.

    The team also found that the magnetic properties could be changed using a pulse of laser light that heats the oxide layer, helping the oxygen ions to move more easily. The laser beam used to alter the state of the material can scan across its surface, making changes as it goes.

    The same techniques could be used to alter other properties of materials, Beach explains, such as reflectivity or thermal conductivity. Such properties can ordinarily be changed only through mechanical or chemical processing. “All these properties could come under electrical control, to be switched on and off, and even ‘written’ using a beam of light,” Beach says. This ability to make such changes on the fly essentially produces “an Etch-a-Sketch for material properties,” he says.The new findings “started as a fluke,” Beach says: Bauer was experimenting with the layered material, expecting to see standard temporary capacitive effects from an applied voltage. “But he turned off the voltage and it stayed that way,” with a reversed magnetic state, Beach says, leading to further investigation.

    “I think this will have broad applications,” Beach says, adding that it uses methods and materials that are already standard in microchip manufacturing.

    In addition to Bauer and Beach, the team included Lide Yao and Sebastiaan van Dijken of Aalto University in Finland and, at MIT, graduate students Aik Jun Tan, Parnika Agrawal, and Satoru Emori and professor of ceramics and electronic materials Harry Tuller. The work was supported by the National Science Foundation and Samsung.

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  • richardmitnick 1:09 pm on November 10, 2014 Permalink | Reply
    Tags: , , Electronics,   

    From Caltech: “Heat Transfer Sets the Noise Floor for Ultrasensitive Electronics” 

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    Caltech

    11/10/2014
    Ker Than

    A team of engineers and scientists has identified a source of electronic noise that could affect the functioning of instruments operating at very low temperatures, such as devices used in radio telescopes and advanced physics experiments.

    The findings, detailed in the November 10 issue of the journal Nature Materials, could have implications for the future design of transistors and other electronic components.

    The electronic noise the team identified is related to the temperature of the electrons in a given device, which in turn is governed by heat transfer due to packets of vibrational energy, called phonons, that are present in all crystals. “A phonon is similar to a photon, which is a discrete packet of light,” says Austin Minnich, an assistant professor of mechanical engineering and applied physics in Caltech’s Division of Engineering and Applied Science and corresponding author of the new paper. “In many crystals, from ordinary table salt to the indium phosphide crystals used to make transistors, heat is carried mostly by phonons.”

    ph
    Cross-sectional image of ultra-low noise InP transistor. Electrons, accelerated in the high mobility channel under the 100-nanometer gate, collide and dissipate heat that fundamentally limits the noise performance of the transistor.
    Credit: Illustration courtesy of Lisa Kinnerud and Moa Carlsson, Krantz NanoArt/Chalmers University

    Phonons are important for electronics because they help carry away the thermal energy that is injected into devices in the form of electrons. How swiftly and efficiently phonons ferry away heat is partly dependent on the temperature at which the device is operated: at high temperatures, phonons collide with one another and with imperfections in the crystal in a phenomenon called scattering, and this creates phonon traffic jams that result in a temperature rise.

    One way that engineers have traditionally reduced phonon scattering is to use high-quality materials that contain as few defects as possible. “The fewer defects you have, the fewer ‘road blocks’ there are for the moving phonons,” Minnich says.

    A more common solution, however, is to operate electronics in extremely cold conditions because scattering drops off dramatically when the temperature dips below about 50 kelvins, or about –370 degrees Fahrenheit. “As a result, the main strategy for reducing noise is to operate the devices at colder and colder temperatures,” Minnich says.

    But the new findings by Minnich’s team suggest that while this strategy is effective, another phonon transfer mechanism comes into play at extremely low temperatures and severely restricts the heat transfer away from a device.

    Using a combination of computer simulations and real-world experiments, Minnich and his team showed that at around 20 kelvins, or –424 degrees Fahrenheit, the high-energy phonons that are most efficient at transporting heat away quickly are unlikely to be present in a crystal. “At 20 kelvins, many phonon modes become deactivated, and the crystal has only low-energy phonons that don’t have enough energy to carry away the heat,” Minnich says. “As a result, the transistor heats up until the temperature has increased enough that high-energy phonons become available again.”

    As an analogy, Minnich says to imagine an object that is heated until it is white hot. “When something is white hot, the full spectrum of photons, from red to blue, contribute to the heat transfer, and we know from everyday experience that something white hot is extremely hot,” he says. “When something is not as hot it glows red, and in this case heat is only carried by red photons with low energy. The physics for phonons is exactly the same—even the equations are the same.”

    The electronic noise that the team identified has been known about for many years, but until now it was not thought to play an important role at low temperatures. That discovery happened because of a chance encounter between Minnich and Joel Schleeh, a postdoctoral scholar from Chalmers University of Technology in Sweden and first author of the new study, who was at Caltech visiting the lab of Sander Weinreb, a senior faculty associate in electrical engineering.

    Schleeh had noticed that the noise he was measuring in an amplifier was higher than what theory predicted. Schleeh mentioned the problem to Weinreb, and Weinreb recommended he connect with Minnich, whose lab studies heat transfer by phonons. “At another university, I don’t think I would have had this chance,” Minnich says. “Neither of us would have had the chance to interact like we did here. Caltech is a small campus, so when you talk to someone, almost by definition they’re outside of your field.”

    The pair’s findings could have implications for numerous fields of science that rely on superchilled instruments to make sensitive measurements. “In radio astronomy, you’re trying to detect very weak electromagnetic waves from space, so you need the lowest noise possible,” Minnich says.

    Electronic noise poses a similar problem for quantum-physics experiments. “Here at Caltech, we have physicists trying to observe certain quantum-physics effects. The signal that they’re looking for is very tiny, and it’s essential to use the lowest-noise electronics possible,” Minnich says.

    The news is not all gloomy, however, because the team’s findings also suggest that it may be possible to develop engineering strategies to make phonon heat transfer more efficient at low temperatures. For example, one possibility might be to change the design of transistors so that phonon generation takes place over a broader volume. “If you can make the phonon generation more spread out, then in principle you could reduce the temperature rise that occurs,” Minnich says.

    “We don’t know what the precise strategy will be yet, but now we know the direction we should be going. That’s an improvement.”

    In addition to Minnich and Schleeh, the other coauthors of the paper, Phonon blackbody radiation limit for heat dissipation in electronics, are Javier Mateos and Ignacio Iñiguez-de-la-Torre of the Universidad de Salamanca in Salamanca, Spain; Niklas Wadefalk of the Low Noise Factory AB in Mölndal, Sweden; and Per A. Nilsson and Jan Grahn of Chalmers University of Technology. Minnich’s work on the project at Caltech was funded by a Caltech start-up fund and by the National Science Foundation.

    See the full article here.

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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