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Now, there is a way to control the outcome, thanks to an international research group led by scientists at the National Institute of Standards and Technology (NIST). The team has developed the first switch that turns on and off this mysterious quantum behavior. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices. To study this quantum property, NIST physicist and fellow Joseph A. Stroscio and his colleagues studied electrons corralled in special orbits within a nanometer-sized region of graphene—an ultrastrong, single layer of tightly packed carbon atoms. The corralled electrons orbit the center of the graphene sample just as electrons orbit the center of an atom. The orbiting electrons ordinarily retain the same exact physical properties after traveling a complete circuit in the graphene. But when an applied magnetic field reaches a critical value, it acts as a switch, altering the shape of the orbits and causing the electrons to possess different physical properties after completing a full circuit. The researchers report their findings in the May 26, 2017, issue of Science. The newly developed quantum switch relies on a geometric property called the Berry phase, named after English physicist Sir Michael Berry who developed the theory of this quantum phenomenon in 1983. The Berry phase is associated with the wave function of a particle, which in quantum theory describes a particle's physical state. The wave function—think of an ocean wave—has both an amplitude (the height of the wave) and a phase—the location of a peak or trough relative to the start of the wave cycle. When an electron makes a complete circuit around a closed loop so that it returns to its initial location, the phase of its wave function may shift instead of returning to its original value. This phase shift, the Berry phase, is a kind of memory of a quantum system's travel and does not depend on time, only on the geometry of the system—the shape of the path. Moreover, the shift has observable consequences in a wide range of quantum systems. Although the Berry phase is a purely quantum phenomenon, it has an analog in non-quantum systems. Consider the motion of a Foucault pendulum, which was used to demonstrate Earth's rotation in the 19th century. The suspended pendulum simply swings back and forth in the same vertical plane, but appears to slowly rotate during each swing—a kind of phase shift—due to the rotation of Earth beneath it. Since the mid-1980s, experiments have shown that several types of quantum systems have a Berry phase associated with them. But until the current study, no one had constructed a switch that could turn the Berry phase on and off at will. The switch developed by the team, controlled by a tiny change in an applied magnetic field, gives electrons a sudden and large increase in energy. Several members of the current research team—based at the Massachusetts Institute of Technology and Harvard University—developed the theory for the Berry phase switch. To study the Berry phase and create the switch, NIST team member Fereshte Ghahari built a high-quality graphene device to study the energy levels and the Berry phase of electrons corralled within the graphene. First, the team confined the electrons to occupy certain orbits and energy levels. To keep the electrons penned in, team member Daniel Walkup created a quantum version of an electric fence by using ionized impurities in the insulating layer beneath the graphene. This enabled a scanning tunneling microscope at NIST's nanotechnology user facility, the Center for Nanoscale Science and Technology, to probe the quantum energy levels and Berry phase of the confined electrons. The team then applied a weak magnetic field directed into the graphene sheet. For electrons moving in the clockwise direction, the magnetic field created tighter, more compact orbits. But for electrons moving in counterclockwise orbits, the magnetic field had the opposite effect, pulling the electrons into wider orbits. At a critical magnetic field strength, the field acted as a Berry phase switch. It twisted the counterclockwise orbits of the electrons, causing the charged particles to execute clockwise pirouettes near the boundary of the electric fence. Ordinarily, these pirouettes would have little consequence. However, says team member Christopher Gutiérrez, "the electrons in graphene possess a special Berry phase, which switches on when these magneticallyinduced pirouettes are triggered." When the Berry phase is switched on, orbiting electrons abruptly jump to a higher energy level. The quantum switch provides a rich scientific tool box that will help scientists exploit ideas for new quantum devices, which have no analog in conventional semiconductor systems, says Stroscio. More information: F. Ghahari, D. Walkup, C. Gutiérrez, J.F. Rodriguez-Nieva, Y. Zhao, J. Wyrick, F.D. Natterer, W.G. Cullen, K. Watanabe, T. Taniguchi, L.S. Levitov, N.B. Zhitenev, J.A. Stroscio. An on/off Berry phase switch in circular graphene resonators. Science. May 26. science.sciencemag.org/cgi/doi/10.1126/science.aal0212


News Article | May 25, 2017
Site: www.eurekalert.org

When a ballerina pirouettes, twirling a full revolution, she looks just as she did when she started. But for electrons and other subatomic particles, which follow the rules of quantum theory, that's not necessarily so. When an electron moves around a closed path, ending up where it began, its physical state may or may not be the same as when it left. Now, there is a way to control the outcome, thanks to an international research group led by scientists at the National Institute of Standards and Technology (NIST). The team has developed the first switch that turns on and off this mysterious quantum behavior. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices. To study this quantum property, NIST physicist and fellow Joseph A. Stroscio and his colleagues studied electrons corralled in special orbits within a nanometer-sized region of graphene--an ultrastrong, single layer of tightly packed carbon atoms. The corralled electrons orbit the center of the graphene sample just as electrons orbit the center of an atom. The orbiting electrons ordinarily retain the same exact physical properties after traveling a complete circuit in the graphene. But when an applied magnetic field reaches a critical value, it acts as a switch, altering the shape of the orbits and causing the electrons to possess different physical properties after completing a full circuit. The researchers report their findings in the May 26, 2017, issue of Science. The newly developed quantum switch relies on a geometric property called the Berry phase, named after English physicist Sir Michael Berry who developed the theory of this quantum phenomenon in 1983. The Berry phase is associated with the wave function of a particle, which in quantum theory describes a particle's physical state. The wave function--think of an ocean wave -- has both an amplitude (the height of the wave) and a phase -- the location of a peak or trough relative to the start of the wave cycle. When an electron makes a complete circuit around a closed loop so that it returns to its initial location, the phase of its wave function may shift instead of returning to its original value. This phase shift, the Berry phase, is a kind of memory of a quantum system's travel and does not depend on time, only on the geometry of the system -- the shape of the path. Moreover, the shift has observable consequences in a wide range of quantum systems. Although the Berry phase is a purely quantum phenomenon, it has an analog in non-quantum systems. Consider the motion of a Foucault pendulum, which was used to demonstrate Earth's rotation in the 19th century. The suspended pendulum simply swings back and forth in the same vertical plane, but appears to slowly rotate during each swing--a kind of phase shift--due to the rotation of Earth beneath it. Since the mid-1980s, experiments have shown that several types of quantum systems have a Berry phase associated with them. But until the current study, no one had constructed a switch that could turn the Berry phase on and off at will. The switch developed by the team, controlled by a tiny change in an applied magnetic field, gives electrons a sudden and large increase in energy. Several members of the current research team -- based at the Massachusetts Institute of Technology and Harvard University--developed the theory for the Berry phase switch. To study the Berry phase and create the switch, NIST team member Fereshte Ghahari built a high-quality graphene device to study the energy levels and the Berry phase of electrons corralled within the graphene. First, the team confined the electrons to occupy certain orbits and energy levels. To keep the electrons penned in, team member Daniel Walkup created a quantum version of an electric fence by using ionized impurities in the insulating layer beneath the graphene. This enabled a scanning tunneling microscope at NIST's nanotechnology user facility, the Center for Nanoscale Science and Technology, to probe the quantum energy levels and Berry phase of the confined electrons. The team then applied a weak magnetic field directed into the graphene sheet. For electrons moving in the clockwise direction, the magnetic field created tighter, more compact orbits. But for electrons moving in counterclockwise orbits, the magnetic field had the opposite effect, pulling the electrons into wider orbits. At a critical magnetic field strength, the field acted as a Berry phase switch. It twisted the counterclockwise orbits of the electrons, causing the charged particles to execute clockwise pirouettes near the boundary of the electric fence. Ordinarily, these pirouettes would have little consequence. However, says team member Christopher Gutiérrez, "the electrons in graphene possess a special Berry phase, which switches on when these magneticallyinduced pirouettes are triggered." When the Berry phase is switched on, orbiting electrons abruptly jump to a higher energy level. The quantum switch provides a rich scientific tool box that will help scientists exploit ideas for new quantum devices, which have no analog in conventional semiconductor systems, says Stroscio. Paper: F. Ghahari, D. Walkup, C. Gutiérrez, J.F. Rodriguez-Nieva, Y. Zhao, J. Wyrick, F.D. Natterer, W.G. Cullen, K. Watanabe, T. Taniguchi, L.S. Levitov, N.B. Zhitenev, J.A. Stroscio. An on/off Berry phase switch in circular graphene resonators. Science. May 26.


News Article | May 25, 2017
Site: www.sciencedaily.com

When a ballerina pirouettes, twirling a full revolution, she looks just as she did when she started. But for electrons and other subatomic particles, which follow the rules of quantum theory, that's not necessarily so. When an electron moves around a closed path, ending up where it began, its physical state may or may not be the same as when it left. Now, there is a way to control the outcome, thanks to an international research group led by scientists at the National Institute of Standards and Technology (NIST). The team has developed the first switch that turns on and off this mysterious quantum behavior. The discovery promises to provide new insight into the fundamentals of quantum theory and may lead to new quantum electronic devices. To study this quantum property, NIST physicist and fellow Joseph A. Stroscio and his colleagues studied electrons corralled in special orbits within a nanometer-sized region of graphene -- an ultrastrong, single layer of tightly packed carbon atoms. The corralled electrons orbit the center of the graphene sample just as electrons orbit the center of an atom. The orbiting electrons ordinarily retain the same exact physical properties after traveling a complete circuit in the graphene. But when an applied magnetic field reaches a critical value, it acts as a switch, altering the shape of the orbits and causing the electrons to possess different physical properties after completing a full circuit. The researchers report their findings in the May 26, 2017, issue of Science. The newly developed quantum switch relies on a geometric property called the Berry phase, named after English physicist Sir Michael Berry who developed the theory of this quantum phenomenon in 1983. The Berry phase is associated with the wave function of a particle, which in quantum theory describes a particle's physical state. The wave function -- think of an ocean wave -- has both an amplitude (the height of the wave) and a phase -- the location of a peak or trough relative to the start of the wave cycle. When an electron makes a complete circuit around a closed loop so that it returns to its initial location, the phase of its wave function may shift instead of returning to its original value. This phase shift, the Berry phase, is a kind of memory of a quantum system's travel and does not depend on time, only on the geometry of the system -- the shape of the path. Moreover, the shift has observable consequences in a wide range of quantum systems. Although the Berry phase is a purely quantum phenomenon, it has an analog in non-quantum systems. Consider the motion of a Foucault pendulum, which was used to demonstrate Earth's rotation in the 19th century. The suspended pendulum simply swings back and forth in the same vertical plane, but appears to slowly rotate during each swing -- a kind of phase shift -- due to the rotation of Earth beneath it. Since the mid-1980s, experiments have shown that several types of quantum systems have a Berry phase associated with them. But until the current study, no one had constructed a switch that could turn the Berry phase on and off at will. The switch developed by the team, controlled by a tiny change in an applied magnetic field, gives electrons a sudden and large increase in energy. Several members of the current research team -- based at the Massachusetts Institute of Technology and Harvard University -- developed the theory for the Berry phase switch. To study the Berry phase and create the switch, NIST team member Fereshte Ghahari built a high-quality graphene device to study the energy levels and the Berry phase of electrons corralled within the graphene. First, the team confined the electrons to occupy certain orbits and energy levels. To keep the electrons penned in, team member Daniel Walkup created a quantum version of an electric fence by using ionized impurities in the insulating layer beneath the graphene. This enabled a scanning tunneling microscope at NIST's nanotechnology user facility, the Center for Nanoscale Science and Technology, to probe the quantum energy levels and Berry phase of the confined electrons. The team then applied a weak magnetic field directed into the graphene sheet. For electrons moving in the clockwise direction, the magnetic field created tighter, more compact orbits. But for electrons moving in counterclockwise orbits, the magnetic field had the opposite effect, pulling the electrons into wider orbits. At a critical magnetic field strength, the field acted as a Berry phase switch. It twisted the counterclockwise orbits of the electrons, causing the charged particles to execute clockwise pirouettes near the boundary of the electric fence. Ordinarily, these pirouettes would have little consequence. However, says team member Christopher Gutiérrez, "the electrons in graphene possess a special Berry phase, which switches on when these magneticallyinduced pirouettes are triggered." When the Berry phase is switched on, orbiting electrons abruptly jump to a higher energy level. The quantum switch provides a rich scientific tool box that will help scientists exploit ideas for new quantum devices, which have no analog in conventional semiconductor systems, says Stroscio.


News Article | December 16, 2016
Site: www.eurekalert.org

Scientists at the National Institute of Standards and Technology (NIST) have developed a new device that measures the motion of super-tiny particles traversing distances almost unimaginably small--shorter than the diameter of a hydrogen atom, or less than one-millionth the width of a human hair. Not only can the handheld device sense the atomic-scale motion of its tiny parts with unprecedented precision, but the researchers have devised a method to mass produce the highly sensitive measuring tool. It's relatively easy to measure small movements of large objects but much more difficult when the moving parts are on the scale of nanometers, or billionths of a meter. The ability to accurately measure tiny displacements of microscopic bodies has applications in sensing trace amounts of hazardous biological or chemical agents, perfecting the movement of miniature robots, accurately deploying airbags and detecting extremely weak sound waves traveling through thin films. NIST physicists Brian Roxworthy and Vladimir Aksyuk describe their work (link is external) in the Dec. 6, 2016, Nature Communications. The researchers measured subatomic-scale motion in a gold nanoparticle. They did this by engineering a small air gap, about 15 nanometers in width, between the gold nanoparticle and a gold sheet. This gap is so small that laser light cannot penetrate it. However, the light energized surface plasmons--the collective, wave-like motion of groups of electrons confined to travel along the boundary between the gold surface and the air. The researchers exploited the light's wavelength, the distance between successive peaks of the light wave. With the right choice of wavelength, or equivalently, its frequency, the laser light causes plasmons of a particular frequency to oscillate back and forth, or resonate, along the gap, like the reverberations of a plucked guitar string. Meanwhile, as the nanoparticle moves, it changes the width of the gap and, like tuning a guitar string, changes the frequency at which the plasmons resonate. The interaction between the laser light and the plasmons is critical for sensing tiny displacements from nanoscale particles, notes Aksyuk. Light can't easily detect the location or motion of an object smaller than the wavelength of the laser, but converting the light to plasmons overcomes this limitation. Because the plasmons are confined to the tiny gap, they are more sensitive than light is for sensing the motion of small objects like the gold nanoparticle. The amount of laser light reflected back from the plasmon device reveals the width of the gap and the motion of the nanoparticle. Suppose, for example, that the gap changes--due to the motion of the nanoparticle--in such a way that the natural frequency, or resonance, of the plasmons more closely matches the frequency of the laser light. In that case, the plasmons are able to absorb more energy from the laser light, and less light is reflected. To use this motion-sensing technique in a practical device, Aksyuk and Roxworthy embedded the gold nanoparticle in a microscopic-scale mechanical structure--a vibrating cantilever, sort of a miniature diving board--that was a few micrometers long, made of silicon nitride. Even when they're not set in motion, such devices never sit perfectly still, but vibrate at high frequency, jostled by the random motion of their molecules at room temperature. Even though the amplitude of the vibration was tiny--moving subatomic distances--it was easy to detect with the new plasmonic technique. Similar, though typically larger, mechanical structures are commonly used for both scientific measurements and practical sensors; for example, detecting motion and orientation in cars and smartphones. The NIST scientists hope their new way of measuring motion at the nanoscale will help to further miniaturize and improve performance of many such micromechanical systems. "This architecture paves the way for advances in nanomechanical sensing," the researchers write. "We can detect tiny motion more locally and precisely with these plasmonic resonators than any other way of doing it," said Aksyuk. The team's fabrication approach allows production of some 25,000 of the devices on a computer chip, with each device tailored to detect motion according to the needs of the manufacturer. Roxworthy and Aksyuk, the two authors of the new paper, work in NIST's Center for Nanoscale Science and Technology (CNST).


News Article | October 28, 2016
Site: www.prweb.com

A new multi-university research center led by Worcester Polytechnic Institute (WPI) aims to dramatically reduce energy and water usage while also increasing the economic competitiveness of a broad spectrum of industries by bringing innovations to one of the most energy-intensive aspects of manufacturing: drying. The Center for Advanced Research in Drying (CARD), funded by the National Science Foundation (NSF) through its Industry/University Cooperative Research Centers program (I/UCRC), brings together researchers at WPI and the University of Illinois at Urbana-Champaign. CARD is the second NSF I/UCRC established at WPI. The Center for Resource Recovery and Recycling (CR3), part of the university's Metal Processing Institute, was launched in 2010 with the mission of developing new technologies for maximizing the recovery and recycling of metals used in manufactured products and structures. Drying is important in industries that handle moist, porous materials. Examples include making food snacks, cereal, and pasta; producing paper; and manufacturing powders and other forms of dry bulk chemicals. About 2 percent of the 100 quadrillion BTUs (or quads) of energy used each year in the United States is wasted by industrial drying processes, said CARD's inaugural director Jamal Yagoobi, George I. Alden Professor and head of WPI's Department of Mechanical Engineering. "The goal of CARD is to improve the efficiency of those processes by 10 percent, which would save 0.2 quads of energy each year," Yagoobi said. "Since steam is the prime media used in industrial heating and drying, by making drying more efficient, the center also aims to help reduce annual water usage in the United States by about 10 billion kilograms, or the equivalent of the water in 4,000 Olympic-sized swimming pools. "By achieving transformative breakthroughs in drying technologies, we can have a profound impact on U.S. manufacturing capabilities," Yagoobi added. "In the short term, major innovations in this field, when commercialized, will positively affect production costs, process efficiency, energy sustainability, and product quality. In the long run, the magnitude of these changes could very well foster a new era of U.S. manufacturing competitiveness and job creation." Yagoobi said CARD will conduct industry-sponsored research on drying technologies used, for example, to make food and agricultural products, paper, building materials and other forest products, bulk chemicals, textiles, and pharmaceuticals. Drying accounts for a significant portion of the energy used in each of these industries, he noted. In the paper industry, for example, 30 percent of all energy consumed goes into drying. In addition to improving the efficiency of drying processes and reducing waste, he said a central goal of the center is helping manufacturers produce better products by giving industries more control over the drying processes. The quality of many products is affected by how quickly or evenly drying takes place, he said, or by the methods used to extract moisture. As an NSF I/UCRC, CARD derives the bulk of its funding from its corporate members, each of which pays an annual membership fee of $50,000. The center currently has 12 members and is seeking to expand to 30 members within five years. CARD members suggest topics for research projects, which are then voted on by the entire membership. Current active projects include the development of innovative impinging jets that will enable delicate items to be dried more efficiently without incurring damage; the design of new sensors to measure moisture levels and other material properties to allow for better control of drying; and studies of how product properties are changed during drying processes. The only major research center at an American university focused on industrial drying, CARD has also been named a partner in one of the nine U.S. National Network for Manufacturing Innovation Institutes launched by the Obama Administration. CARD is a member of the Clean Energy Smart Manufacturing Innovation Institute, established in the summer of 2016 in partnership with the U.S. Department of Energy. The institute brings together a consortium of nearly 200 academic, industry, and nonprofit partners to spur advances in smart sensors and digital process controls, innovations that can radically improve the efficiency of U.S. advanced manufacturing. The center is also part of Rapid Advancement in Process Intensification Deployment (RAPID), a coalition organized by the American Institute of Chemical Engineers that is competing to be named the network's next institute. RAPID would focus on the application of process intensification—a fundamental area of knowledge in chemical engineering—to manufacturing processes to lower costs, improve energy- and resource-efficiency, and increase overall productivity. Yagoobi notes that membership in these national initiatives will bring additional significant federal funding to CARD. Yagoobi, whose research on transport phenomena in porous moist materials led to his establishing a drying research center at Texas A&M University when he was a faculty member there, said he first envisioned CARD four years ago. He began discussing the idea with Irfan Ahmad, executive director of the Center for Nanoscale Science and Technology, and Hao Feng, professor of food science and human nutrition, both at the University of Illinois; Feng is now the Illinois site director for CARD. The center obtained an I/UCRC planning grant from the NSF in 2013, which enabled the researchers to begin reaching out to corporate members. CARD recently received a Phase I grant from the NSF, which will bring annual awards of $300,000 to WPI and the University of Illinois. At the end of five years, the center can apply for continuing funding through a Phase II grant. "I want to acknowledge the valuable contribution of my WPI and Illinois colleagues toward creating this new center," Yagoobi said. "Without their valuable contributions, establishing CARD would not have been possible." Research projects undertaken by CARD are carried out by faculty members and graduate students at WPI and the University of Illinois. Yagoobi said he expects that projects carried out at Illinois will focus on issues in food and agriculture as well as sensor development, while WPI researchers will focus on the engineering aspects of drying. While drying will be the primary focus, Yagoobi said the center will also conduct research on heating, cooling, freezing, and frying—all processes that involve heat and mass transfer. Founded in 1865 in Worcester, Mass., WPI is one of the nation’s first engineering and technology universities. Its 14 academic departments offer more than 50 undergraduate and graduate degree programs in science, engineering, technology, business, the social sciences, and the humanities and arts, leading to bachelor’s, master’s and doctoral degrees. WPI's talented faculty work with students on interdisciplinary research that seeks solutions to important and socially relevant problems in fields as diverse as the life sciences and bioengineering, energy, information security, materials processing, and robotics. Students also have the opportunity to make a difference to communities and organizations around the world through the university's innovative Global Projects Program. There are more than 45 WPI project centers throughout the Americas, Africa, Asia-Pacific, and Europe.


News Article | April 13, 2016
Site: www.cemag.us

What if doctors could deliver anti-cancer drugs directly to tumors without making patients sick? Bringing this dream of targeted drug delivery closer to reality for pharmaceutical manufacturers, researchers at the National Institute of Standards and Technology (NIST) have received a patent for a method to create precisely sized nanometer-scale capsules. The NIST method employs microfluidics to create precise nanoscale spherical capsules. Made of lipids, the kinds of biomolecules that also comprise fats, the spherical capsules are known as liposomes. Essentially, liposomes are simplified artificial versions of cell membranes, the outer coverings of cells. The inside of a liposome could hold drugs, and the outside could be coated with receptors that bind to specific cancer cells. The method can produce liposomes with typical diameters of 100-400 nanometers, or billionths of a meter. This size range is useful for attaching to cells, whose size is typically 1 to 10 micrometers, or millionths of a meter. Typical methods for making liposomes include pushing a lipid solution through a filter, a process that can lead to wide variations in the size of the resulting liposomes. Furthermore, the methods can be wasteful, and can result in large amounts of expensive drugs not being captured inside the liposomes and being discarded. In the NIST technique, lipid material is dissolved in isopropyl alcohol. The resulting lipid-containing solution is then forced into a narrow channel and further constricted when it is squeezed by streams of water coming at it from multiple sides. Lipid molecules are repelled by water, so they clump together and coalesce into spherical liposomes. Adjusting the flow rate of the water can control the size of the liposomes that form. “We have precision control over making liposomes and changing their size by dialing in flow rates,” says Michael Gaitan, who works in NIST’s Physical Measurement Laboratory. Researchers could dissolve drugs or other molecules of interest into the water stream, Gaitan explains. Adjusting the concentrations of these molecules can determine the amount of the drug that ends up in the liposome, down to the single-molecule level. This method, which has received interest in being licensed by companies, originally developed from basic research. Gaitan and collaborator Laurie Locascio were looking for ways to enclose individual molecules of interest in fluid-filled capsules to study their behavior in a liquid environment. Previous methods had anchored individual molecules in glass slides, which are rather unnatural environments, as opposed to the more cell-like environment of a fluid-filled liposome. Once this technique was developed, researchers were able to create a variety of liposomes of many useful sizes, and the potential drug-delivery applications became clear. The researchers were awarded a patent for this work late last year. "This research and the resulting patent also have implications for the on-demand formulation of drugs in a way that’s applicable to personalized or precision medicine," says Laurie Locascio, director of NIST’s Material Measurement Laboratory. “The reason that this patent is so fundamental is that this is a process patent,” which is a more general form of patent, Gaitan explains. The method does not require a specific experimental configuration, but is a general approach that can be realized in many ways, he says. Moving forward, researchers at NIST’s Center for Nanoscale Science and Technology are continuing to develop this technique for more applications by creating capsules made of different types of nanoparticles. Size — and control — most definitely matter in nanotechnology. Being able to create precisely sized nanocontainers can open up many new applications, Gaitan says.


The new microwave imaging approach trumps X-ray and electron-based methods that can damage delicate samples and muddy results. And it spares expensive equipment from being exposed to liquids, while eliminating the need to harden probes against corrosive, toxic, or other harmful environments. Writing in the journal ACS Nano, the collaborators—from the Center for Nanoscale Science and Technology at the National Institute of Standards and Technology (NIST) and the Department of Energy's Oak Ridge National Laboratory (ORNL)—describe their new approach to imaging reactive and biological samples at nanoscale levels under realistic conditions. The key element is a window, an ultrathin membrane that separates the needle-like probe of an atomic force microscope (AFM) from the underlying sample, held in tiny containers that maintain a consistent liquid or gas environment. The addition transforms near-field microwave imaging into a versatile tool, extending its use beyond semiconductor technology, where it is used to study solid structures, to a new realm of liquids and gases. "The ultrathin, microwave-transparent membrane allows the sample to be examined in much the same way that Earth's radar was used to reveal images of the surface of Venus through its opaque atmosphere," explained NIST physicist Andrei Kolmakov. "We generate microwaves at the apex—or very end—of the probe tip," Kolmakov said. "The microwaves penetrate through the membrane a few hundred nanometers deep into the liquid up to the object of interest. As the tip scans the sample from across the membrane, we record the reflected microwaves to generate the image." Microwaves are much larger than the nanoscale objects they are used to "seeing." But when emitted from only a minuscule distance away, near-field microwaves reflected from a sample yield a surprisingly detailed image. In their proof-of-concept experiments, the NIST-ORNL team used their hybrid microscope to get a nanoscale view of the early stages of a silver electroplating process. Microwave images captured the electrochemical formation of branching metal clusters, or dendrites, on electrodes. Features nearly as small as 100 nanometers (billionths of a meter) could be discerned. As important, the low-energy microwaves were too feeble to sever chemical bonds, heat, or interfere in other ways with the process they were being used to capture in images. In contrast, a scanning electron microscope that was used to record the same electroplating process at comparable levels of resolution yielded images showing delamination and other destructive effects of the electron beam. The team reports similar success in using their AFM-microwave set-up to record images of yeast cells dispersed in water or glycerol. Levels of spatial resolution were comparable to those achieved with a scanning electron microscope, but again, were free of the damage caused by the electron beam. In their experiments, the team used membranes—made either of silicon dioxide or silicon nitride—that ranged in thickness from 8 nanometers to 50 nanometers. They found, however, that the thinner the membrane the better the resolution—down to tens of nanometers—and the greater the probing depth—up to hundreds of nanometers. "These numbers can be improved further with tuning and development of better electronics," Kolmakov said. In addition to studying processes in reactive, toxic, or radioactive environments, the researchers suggest that their microwave-imaging approach might be integrated into "lab-on-a-chip" fluidic devices, where it can be used to sample liquids and gases. Explore further: New imaging method lets scientists 'see' cell molecules more clearly More information: Alexander Tselev et al. Seeing through Walls at the Nanoscale: Microwave Microscopy of Enclosed Objects and Processes in Liquids, ACS Nano (2016). DOI: 10.1021/acsnano.5b07919


Home > Press > New microwave imaging approach opens a nanoscale view on processes in liquids: Technique can explore technologically and medically important processes that occur at boundaries between liquids and solids, such as in batteries or along cell membranes Abstract: U.S. government nanotechnology researchers have demonstrated a new window to view what are now mostly clandestine operations occurring in soggy, inhospitable realms of the nanoworld--technologically and medically important processes that occur at boundaries between liquids and solids, such as in batteries or along cell membranes. The new microwave imaging approach trumps X-ray and electron-based methods that can damage delicate samples and muddy results. And it spares expensive equipment from being exposed to liquids, while eliminating the need to harden probes against corrosive, toxic, or other harmful environments. Writing in the journal ACS Nano, the collaborators--from the Center for Nanoscale Science and Technology at the National Institute of Standards and Technology (NIST) and the Department of Energy's Oak Ridge National Laboratory (ORNL)--describe their new approach to imaging reactive and biological samples at nanoscale levels under realistic conditions. The key element is a window, an ultrathin membrane that separates the needle-like probe of an atomic force microscope (AFM) from the underlying sample, held in tiny containers that maintain a consistent liquid or gas environment. The addition transforms near-field microwave imaging into a versatile tool, extending its use beyond semiconductor technology, where it is used to study solid structures, to a new realm of liquids and gases. "The ultrathin, microwave-transparent membrane allows the sample to be examined in much the same way that Earth's radar was used to reveal images of the surface of Venus through its opaque atmosphere," explained NIST physicist Andrei Kolmakov. "We generate microwaves at the apex--or very end--of the probe tip," Kolmakov said. "The microwaves penetrate through the membrane a few hundred nanometers deep into the liquid up to the object of interest. As the tip scans the sample from across the membrane, we record the reflected microwaves to generate the image." Microwaves are much larger than the nanoscale objects they are used to "seeing." But when emitted from only a minuscule distance away, near-field microwaves reflected from a sample yield a surprisingly detailed image. In their proof-of-concept experiments, the NIST-ORNL team used their hybrid microscope to get a nanoscale view of the early stages of a silver electroplating process. Microwave images captured the electrochemical formation of branching metal clusters, or dendrites, on electrodes. Features nearly as small as 100 nanometers (billionths of a meter) could be discerned. As important, the low-energy microwaves were too feeble to sever chemical bonds, heat, or interfere in other ways with the process they were being used to capture in images. In contrast, a scanning electron microscope that was used to record the same electroplating process at comparable levels of resolution yielded images showing delamination and other destructive effects of the electron beam. The team reports similar success in using their AFM-microwave set-up to record images of yeast cells dispersed in water or glycerol. Levels of spatial resolution were comparable to those achieved with a scanning electron microscope, but again, were free of the damage caused by the electron beam. In their experiments, the team used membranes--made either of silicon dioxide or silicon nitride--that ranged in thickness from 8 nanometers to 50 nanometers. They found, however, that the thinner the membrane the better the resolution--down to tens of nanometers--and the greater the probing depth--up to hundreds of nanometers. "These numbers can be improved further with tuning and development of better electronics," Kolmakov said. In addition to studying processes in reactive, toxic, or radioactive environments, the researchers suggest that their microwave-imaging approach might be integrated into "lab-on-a-chip" fluidic devices, where it can be used to sample liquids and gases. ### The research was performed at NIST's Center for Nanoscale Science and Technology and at the Center for Nanophase Materials Sciences, a Department of Energy Office of Science User Facility. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | April 19, 2016
Site: www.nanotech-now.com

Abstract: Converting a single photon from one color, or frequency, to another is an essential tool in quantum communication, which harnesses the subtle correlations between the subatomic properties of photons (particles of light) to securely store and transmit information. Scientists at the National Institute of Standards and Technology (NIST) have now developed a miniaturized version of a frequency converter, using technology similar to that used to make computer chips. The tiny device, which promises to help improve the security and increase the distance over which next-generation quantum communication systems operate, can be tailored for a wide variety of uses, enables easy integration with other information-processing elements and can be mass produced. The new nanoscale optical frequency converter efficiently converts photons from one frequency to the other while consuming only a small amount of power and adding a very low level of noise, namely background light not associated with the incoming signal. Frequency converters are essential for addressing two problems. The frequencies at which quantum systems optimally generate and store information are typically much higher than the frequencies required to transmit that information over kilometer-scale distances in optical fibers. Converting the photons between these frequencies requires a shift of hundreds of terahertz (one terahertz is a trillion wave cycles per second). A much smaller, but still critical, frequency mismatch arises when two quantum systems that are intended to be identical have small variations in shape and composition. These variations cause the systems to generate photons that differ slightly in frequency instead of being exact replicas, which the quantum communication network may require. The new photon frequency converter, an example of nanophotonic engineering, addresses both issues, Qing Li, Marcelo Davanço and Kartik Srinivasan write in Nature Photonics. The key component of the chip-integrated device is a tiny ring-shaped resonator, about 80 micrometers in diameter (slightly less than the width of a human hair) and a few tenths of a micrometer in thickness. The shape and dimensions of the ring, which is made of silicon nitride, are chosen to enhance the inherent properties of the material in converting light from one frequency to another. The ring resonator is driven by two pump lasers, each operating at a separate frequency. In a scheme known as four-wave-mixing Bragg scattering, a photon entering the ring is shifted in frequency by an amount equal to the difference in frequencies of the two pump lasers. Like cycling around a racetrack, incoming light circulates around the resonator hundreds of times before exiting, greatly enhancing the device's ability to shift the photon's frequency at low power and with low background noise. Rather than using a few watts of power, as typical in previous experiments, the system consumes only about a hundredth of that amount. Importantly, the added amount of noise is low enough for future experiments using single-photon sources. While other technologies have been applied to frequency conversion, "nanophotonics has the benefit of potentially enabling the devices to be much smaller, easier to customize, lower power, and compatible with batch fabrication technology," said Srinivasan. "Our work is a first demonstration of a nanophotonic technology suitable for this demanding task of quantum frequency conversion." ### This work was performed by researchers at NIST's Center for Nanoscale Science and Technology. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | March 22, 2016
Site: www.nanotech-now.com

Abstract: When lots of energy hits an atom, it can knock off electrons, making the atom extremely chemically reactive and initiating further destruction. That's why radiation is so dangerous. It's also why high-resolution imaging techniques that use energetic electron beams and X-rays can alter, even obliterate, the samples they explore. For example, monitoring battery dynamics using electron microscopy can introduce artifacts that interfere with electrochemical processes. Another case in point: Employing X-ray spectroscopy to see inside a living cell annihilates that cell. Now, researchers at the Department of Energy's Oak Ridge National Laboratory and the National Institute of Standards and Technology have demonstrated a nondestructive way to observe nanoscale objects and processes in conditions simulating their normal operating environments. They start with an "environmental chamber" to encapsulate a sample in a liquid. The chamber has a window made of an ultrathin membrane (8 to 50 billionths of a meter, or nanometers, thick). The tip of a scanning probe microscope moves across the membrane, injecting microwaves into the chamber. The device records where the microwave signal was transmitted versus impeded and creates a high-resolution map of the sample. Because the injected microwaves are 100 million times weaker than those of a home microwave oven, and they oscillate in opposite directions several billions of times each second so potentially destructive chemical reactions cannot proceed, the ORNL-NIST technique produces only negligible heat and does not destroy the sample. The scientists report their novel approach of combining ultrathin membranes with microwaves and a scanning probe--called scanning microwave impedance microscopy, or sMIM--in the journal ACS Nano. "Our imaging is nondestructive and free from the damage frequently caused to samples, such a living cells or electrochemical processes, by imaging with X-ray or electron beams," said first author Alexander Tselev. With colleagues Anton Ievlev and Sergei Kalinin at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility at ORNL, he performed high-resolution microwave imaging and analysis. "Its spatial resolution is better than what is achievable with optical microscopes for similar in-liquid samples. The paradigm can become instrumental for gaining important insights into electrochemical phenomena, living objects and other nanoscale systems existing in fluids." For example, microwave microscopy may provide a noninvasive way to explore important surface phenomena occurring on the scale of billionths of a meter, such as the formation of a thin coating that protects and stabilizes a new battery's electrode but cannibalizes its electrolyte to make the coating. Microwave microscopy, which allows scientists to watch processes as they're happening without stopping them cold, makes it possible to characterize ongoing chemical reactions at different stages. "At NIST, we developed environmental chambers with ultra-thin membranes to perform electron microscopy and other analytical techniques in liquids," said senior author Andrei Kolmakov. He and colleague Jeyavel Velmurugan at NIST's Center for Nanoscale Science and Technology made chambers to enclose objects and processes in liquid environments and performed preliminary characterizations to identify biologically interesting cells. "Conversations between the ORNL and NIST scientists resulted in the idea to try nondestructive microwaves so the environmental chambers could be used for broader studies. There are very few groups in the world that can image with high resolution using microwaves, and CNMS is among them. The design of the experiment and the adjustment of the technology for imaging required ORNL expertise." The ORNL and NIST researchers combined existing technologies in new ways and came up with a unique approach that may prove useful in medical diagnostics, forensics and materials research. "For the first time, we are able to image through a very thin membrane," Tselev said. "Microwaves and scanning probe microscopy allowed that." The right tool for the job To image highly ordered materials, such as crystals, researchers can employ techniques such as neutron scattering and X-ray diffraction. To image less ordered materials, such as living cell membranes, or processes, such as ongoing chemical reactions, the ORNL-NIST team collaborated closely to innovate the right tool for the job. Once the scientists had combined the environmental chamber with a scanning microwave capability, they investigated a model system to see if their new technique would work and to set a baseline for future experiments. They used the sMIM system to map polystyrene particles self-assembling into densely packed structures in a liquid. With that proof-of-principle achieved, they then asked if their system could discriminate between silver, which is an electrical conductor, and silver oxide, an insulator, during electroplating (an electrically induced reaction to deposit silver onto a surface). Optical microscopy and scanning electron microscopy are not good at distinguishing silver from silver oxide. Microwave microscopy, in contrast, unambiguously distinguished insulators from conductors. Next, the researchers needed to know that observation with sMIM would not introduce artifacts, such as silver precipitation, that scanning electron microscopy may cause--a problem that is not trivial. "One paper lists 79 chemical reactions induced by electrons in water," Tselev noted. Generally, scanning electron microscopy will not allow scientists to follow silver precipitation to form growing dendrites because that technique is destructive. "Dendrites behave very badly under an electron beam," Tselev said. With sMIM, electrochemical artifacts and process stoppage did not occur. "Whereas sMIM is not the only nondestructive technique, in many cases it may be the only one which can be used." Next the researchers imaged living cells. Because healthy and sick cells differ in properties such as the ability to store electrical energy, intracellular mapping could provide a basis for diagnosis. "Tomographic imaging--resolution across the depths--is possible with microwaves as well," Tselev said. "If you have microwaves, you can go variably in depth and get a lot of information about the living biological cell membrane itself--shape and properties that depend very much on the chemical composition and water content, which in turn depend on whether the cell is healthy or not." The researchers were able to detect properties distinguishing healthy from sick cells. In the current experiments, the system allowed observation close to surfaces. "That doesn't mean we'll not be able to see deeper if we redesign the experiment," Tselev said. "Microwaves can penetrate very deeply. The depth is basically limited by the contact size between the probe and the environmental cell membrane." Next the researchers will try to improve the sensitivity and spatial resolution of their system. Because thinning the walls of the environmental chamber would improve the resolution, the researchers will try making the walls with graphene or hexagonal boron nitride, both of which are only one atom thick. They will also use different probes and image-processing algorithms to improve resolution at different depths. The title of the paper is "Seeing Through Walls at the Nanoscale: Microwave Microscopy of Enclosed Objects and Processes in Liquids." The researchers conducted experiments at the CNMS, a DOE Office of Science User Facility at ORNL, and the Center for Nanoscale Science and Technology at NIST. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

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