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  • richardmitnick 10:47 am on August 15, 2015 Permalink | Reply
    Tags: , Nanotechnology,   

    From Rice U: “Nanotube fibers being tested as a way to restore electrical health to hearts” 

    Rice U bloc

    Rice University

    August 14, 2015
    Mike Williams

    1
    Rice scientist Matteo Pasquali holds a spool of fiber made of pure carbon nanotubes. The fibers are being studied to bridge gaps in the conductivity in damaged heart tissues. Photo by Jeff Fitlow

    Rice University and Texas Heart Institute researchers are studying the use of soft, flexible fibers made of carbon nanotubes to restore electrical conductivity to damaged heart tissue.

    With support from the American Heart Association, these institutions will test the fibers’ ability to bridge electrical gaps in tissue caused by cardiac arrhythmias that affect more than 4 million Americans each year.

    A beating heart is controlled by electrical signals that prompt its tissues to contract and relax. Scars in heart tissue conduct little or no electricity. Soft, highly conductive fibers offer a way to work around those gaps.

    “They’re like extension cords,” said Mehdi Razavi, the director of electrophysiology clinical research at the Texas Heart Institute and the project’s lead investigator. “They allow us to pick up charge from one side of the scar and deliver it to the other side. Essentially, we’re short-circuiting the short circuit.”

    The nanotube fibers developed at Rice by the lab of chemist and chemical engineer Matteo Pasquali are about a quarter of the thickness of a human hair. But even an inch-long piece of the material contains millions of nanotubes, microscopic cylinders of pure carbon discovered in the early 1990s.

    Though the fibers were developed to replace the miles of cables in commercial airplanes to save weight, their potential for medical applications became quickly apparent, Pasquali said.

    “We didn’t design the fiber to be soft, but it turns out to be mechanically very similar to a suture,” he said. “And it has all the electrical function necessary for an application like this.”

    Because the fibers are soft, flexible and extremely tough, they are expected to be far more suitable for biological applications than the metal wires used to deliver power to devices like pacemakers. They have already shown potential for helping people with Parkinson’s disease who require brain implants to treat their neurological condition.

    2
    Rice research scientist Flavia Vitale is developing nanotube fiber applications. She is part of a collaboration with Texas Heart Institute to use the fibers as conductive bridges for damaged heart tissue. Photo by Jeff Fitlow

    “People who progress to heart failure can have the formation of scar tissue over time,” said Mark McCauley, a cardiac electrophysiologist at the Texas Heart Institute. “There are a lot of different ways scarring can affect conduction in the heart. Recently we’ve been most interested in the development of scarring after heart attacks, but we believe this fiber may help us treat all kinds of cardiac arrhythmias and electrical-conduction issues.”

    “Metal wires themselves can cause tissue to scar,” said Flavia Vitale, a research scientist in Pasquali’s lab who is developing nanotube fiber applications. “If you think about inserting a needle into your skin, eventually your skin will react and completely isolate it, because it’s stiff. Scar will form around the needle.

    “But these fibers are unique,” she said. “They’re smaller and more flexible than a human hair and so strong that they can resist flexural fatigue due to the constant beating of the heart.”

    Vitale noted the fibers’ low impedance (its resistance to current) allows electricity to move from tissue to bridge and back with ease, far better than with metal wires.

    The researchers are testing the fibers’ biocompatibility but hope human trials are no more than a few years away.

    Razavi said a safe, effective way to conduct electricity through scarred heart tissue will revolutionize treatment. “Should these more extensive studies confirm our initial findings, a paradigm shift in treatment of sudden cardiac death will be within reach, as for the first time the underlying cause for these events may be corrected on a permanent basis,” he said.

    Pasquali said he is gratified to see a new way in which nanotechnology, for which Rice is renowned, can help save lives. “We’ve been excited from the beginning to learn about each other’s areas and come up with uses for the material,” he said of his friendship – and now collaboration – with Razavi. “We’re determined to find ways to treat rather than manage disease.”

    Pasquali is the A.J. Hartsook Professor of Chemical and Biomolecular Engineering, chair of the Department of Chemistry and a professor of materials science and nanoengineering and of chemistry.

    See the full article here.

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    Rice U campus

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

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

     
  • richardmitnick 10:34 pm on August 12, 2015 Permalink | Reply
    Tags: , Nanotechnology,   

    From Science Times: “Medical Nanotechnology Breakthrought Will Change Mankind Forever” 

    Science Times

    Science Times

    Aug 12, 2015
    Darlene Tverdohleb

    1
    (Photo : Reuters/Jonathan Ernst) U.S. President Barack Obama (R) speaks with Ruchi Pandya from San Jose, California, who was born congenital scoliosis, about her nanotechnology project to test biological samples.

    It has been speculated since long by futurists that nanotechnology will revolutionize virtually every field of our lives, medicine making no exception. Nanotechnology focuses on the engineering of materials and devices at a nanoscale, by using building blocks of atoms and molecules.

    Medical nanotechnology may be able to extend our lives in two ways. It can repair our bodies at the cellular level, reverse aging and providing a certain version of the fountain of youth, and it can help the medical community to eradicate life-threatening diseases such as stroke, heart attack, HIV or cancer.

    By curing life-threatening disease, nanotech can extend the average lifespan far beyond the remarkable achievements of the last century. For instance, the nanotechnology applications in healthcare are likely to minimize the number of deaths from conditions such as heart disease and cancer over the next decade or so. There are already many research programs in place working on these techniques.

    Curing cancer could finally become reality, thanks to medical nanotech. Targeted chemotherapy methods based on nanotech use nanoparticle to deliver chemotherapy drugs.

    A separate nanoparticle is used to guide the drug carrier directly to the cancer tumor. Gold nanorods can also be introduced in circulation through the bloodstream. Once they accumulate at the tumor site, they would concentrate the heat from an infrared light, heating up the tumor to a level where its cells die with minimal damage to the surrounding healthy cells.

    This heat could also be used in order to increase the level of a stress related protein present on the tumor’s surface. Then a drug carrying liposome nanoparticles can be attached to amino acids that bind to this protein. This way, the accumulation of the liposome chemotherapy drug is speeded up by the increased level of protein at the tumor.

    Magnetic nanoparticles attaching to cancer cells present in the bloodstream could also allow the removal of cancer cells before they establish new tumors.

    Individual research programs like those mentioned above are in place at various private companies and universities. Similar research programs are also sustained at the national level. One of them is a group formed at the U.S. National Cancer Institute, called the Alliance for Nanotechnology in Cancer. The NCI group is catalyzing efforts for targeted discovery and development in order to achieve the greatest advances in the near term and beyond. They are also planning to facilitate the process of handing off those advances for commercial development to the private sector. This alliance includes eight Centers of Cancer Nanotechnology Excellence as well as a Nanotechnology Characterization Lab.

    Similar research projects are in place for studying ways of fighting heart disease, another major killer in our time. Several efforts are going on in this area. For example, researchers at the University of Santa Barbara have designed a nanoparticle able to deliver drugs to the wall arteries plaque.

    Extending the average lifespan by repairing cells is another area of interest for medical nanotech. This is perhaps the most exciting application. Our bodies can be repaired at the cellular level by nanorobots. Such technologies are being under development already at various private companies and universities.

    For instance, nanorobots might repair our DNA in our cells when it get damaged by toxins in our bodies or radiation. The Nanomedicine Center for Nucleoprotein Machines is studying protein-based biological machines (nano-robots) able to repair damage in our bodies and assist in DNA replication.

    The Nanofactory Collorabation is an international group focused on developing the techniques for nanoscale precise manufacturing, The ability to work at this scale will allow manufacturing of unique materials and devices that will feature improved and novel properties.

    Recent breakthroughs in medical nanotechnology were announced by various research groups. Among them, it is worth to mention the first self-assembling molecule that open the gate for further manufacturing of state-of-the-art nanomedical devices.

    Medical nanotech is also behind the new non-drug therapy called hyperthermia, which comes with the advantage of being non-toxic and with no harmful side effects. A 3D printer at nano-scale is able to manufacture new cancer drugs just by drag-and-dropping DNA. And the list of examples may continue for long. All these revolutionary medical advances are possible thanks to the emerging field of nanotechnology. They will change our lives forever.

    See the full article here.

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  • richardmitnick 10:27 am on August 4, 2015 Permalink | Reply
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    From U Washington: “UW to invest $37 million in nanofabrication lab critical to researchers, start-ups” 

    U Washington

    University of Washington

    August 3, 2015
    Jennifer Langston

    1
    UW students taking a microfabrication class get hands-on training in cleanroom laboratory techniques at the Washington Nanofabrication Facility.University of Washington

    For start-up companies looking to make chips with nanoscale features for sequencing DNA or wafers for industrial barcode printing, the equipment costs to fabricate those parts could easily devour every last dollar of seed funding.

    The same goes for grant-funded researchers designing quantum information devices or micro-scale sensors to measure cell movement— which is where the Washington Nanofabrication Facility comes in.

    The WNF makes things that aren’t practical, economical or possible to fabricate at commercial foundries — inconceivably tiny parts, chips made from unconventional materials that industrial factories won’t touch, devices that probe the boundaries of our universe. Part of the National Nanotechnology Infrastructure Network, the lab on the University of Washington campus is the largest publicly accessible nanofabrication facility north of Berkeley and west of Minneapolis.

    To serve growing demand for nanofabrication services, the UW Board of Regents has approved spending up to $37 million to renovate the facility, which is housed in Fluke Hall. The overhaul, scheduled to begin in November, will upgrade basic building systems and roughly double the amount of highly-specialized fabrication space that academics and entrepreneurs increasingly rely on to build innovative devices.

    The “fab lab” in Fluke Hall — currently used by 48 UW faculty members and 134 students — has supported $32 million in UW research grant funding this year. A third of its 223 users are with commercial companies, which range from multinational corporations to UW spinouts to minority-owned local start-ups. Regional demand for nanofabrication services is growing rapidly, with WNF revenues nearly tripling in the last four years.

    “The Washington Nanofabrication Facility is vital to my existence,” said Jevne Branden Micheau-Cunningham, who launched a new company called FLEXFORGE six months ago. He’s using WNF equipment and expertise to manufacture nanoscale electronics with applications in the automotive, aerospace and medical devices industries.

    “It allows entrepreneurs such as myself to flesh out ideas and bring products to life — the costs to get up and running on my own would have been prohibitive,” said Micheau-Cunningham. “Nanofabrication is also a pretty specific thing, and they’ve really looked over my shoulder throughout the process.”

    The WNF houses nearly 100 different pieces of equipment that perform everything from electron beam lithography and atomic layer deposition to plasma etching and wafer bonding. User fees paid by academic and non-university clients are invested back into the facility. Applications for the devices those tools enable range from tissue engineering and silicon photonics to semiconductor technologies and basic scientific research.

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    The WNF houses equipment used in nanofabrication, from simple microscopes to this tool that deposits dielectric materials at low temperatures.SPTS Technologies

    “Fabrication is basically a repetitive sequence of steps where we add or subtract material to create the microsystems and devices that people ask for,” said WNF associate director Michael Khbeis. “A lot of companies don’t have fabrication experts, so we also do a lot of design assistance and handholding to take an idea or concept and engineer a process and turn it into a prototype.”

    The UW assumed ownership of the nonprofit nanofabrication facility in 2011, which was formerly run by the Washington Department of Commerce. Through private donations, grants, UW funding and corporate gifts, the lab has invested in excess of $8 million over the last four years to modernize tools and equipment.

    But the infrastructure in Fluke Hall, built in 1988, needs upgrades to meet basic safety and environmental standards and the highly specialized needs of nanofabrication users. The renovation, which will be done in three phases over 14 months to minimize downtime, will allow the lab to better control temperature, humidity and air quality inside the “clean room,” where unwelcome fluctuations can poison an entire production line.

    “One dust speck can damage a device if it’s in the wrong place, so this renovation will make a major difference,” said WNF director Karl Böhringer, a UW professor of electrical engineering and of bioengineering. “The other advantage will be having more space — usage and revenues have increased, and we are bursting at the seams.”

    3
    These flexible microposts are used for rapid blood analysis by Stasys, a biomedical spin-off that developed their technology at the UW and received a microfabrication commercialization grant.University of Washington

    By helping fledgling companies realize prototypes and develop scalable production processes, the WNF plays an important role in the region’s innovation ecosystem. With funding from the Washington Research Foundation, the lab has awarded $140,000 in Microfabrication Commercialization Grants that help bridge the gap from academic or applied research to commercialization of micro-fabricated devices. So far, those grants have supported two UW spin-out companies.

    The nanofabrication lab also offers an undergraduate research program for students who spend up to three years learning how to calibrate and operate the highly sensitive and specialized equipment. This summer’s program will include 20 UW undergrads, up from three in 2011.

    The electronics industry workforce that spurred the development of personal computers and mobile devices is aging and retiring; nationwide there is a shortage of engineers entering the workforce to backfill essential positions and skillsets. By training students in real-world challenges, the WNF’s workforce development mission supports the future success of the U.S. tech industry.

    “When they leave here, they’re highly sought-after in the semiconductor and electronics and aerospace worlds,” Khbeis said. “Every one of our students has multiple offers, and those companies are extremely happy to get them.”

    For more information, contact Khbeis and Böhringer at wnf-info@coral.engr.washington.edu.

    See the full article here.

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

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

     
  • richardmitnick 10:40 am on July 30, 2015 Permalink | Reply
    Tags: , , , , Nanotechnology   

    From MIT: “How to look for a few good catalysts” 


    MIT News

    July 30, 2015
    David L. Chandler

    New research shows non-wetting surfaces promote chemical reaction rates.

    1
    Materials that have good wetting properties, as illustrated on the left, where droplets spread out flat, tend to have hydroxyl groups attached to the surface, which inhibits catalytic activity. Materials that repel water, as shown at right, where droplets form sharp, steep boundaries, are more conducive to catalytic activity, as shown by the reactions among small orange molecules. Illustration: Xiao Renshaw Wang

    Two key physical phenomena take place at the surfaces of materials: catalysis and wetting. A catalyst enhances the rate of chemical reactions; wetting refers to how liquids spread across a surface.

    Now researchers at MIT and other institutions have found that these two processes, which had been considered unrelated, are in fact closely linked. The discovery could make it easier to find new catalysts for particular applications, among other potential benefits.

    “What’s really exciting is that we’ve been able to connect atomic-level interactions of water and oxides on the surface to macroscopic measurements of wetting, whether a surface is hydrophobic or hydrophilic, and connect that directly with catalytic properties,” says Yang Shao-Horn, the W.M. Keck Professor of Energy at MIT and a senior author of a paper describing the findings in the Journal of Physical Chemistry C. The research focused on a class of oxides called perovskites that are of interest for applications such as gas sensing, water purification, batteries, and fuel cells.

    Since determining a surface’s wettability is “trivially easy,” says senior author Kripa Varanasi, an associate professor of mechanical engineering, that determination can now be used to predict a material’s suitability as a catalyst. Since researchers tend to specialize in either wettability or catalysis, this produces a framework for researchers in both fields to work together to advance understanding, says Varanasi, whose research focuses primarily on wettability; Shao-Horn is an expert on catalytic reactions.

    “We show how wetting and catalysis, which are both surface phenomena, are related,” Varanasi says, “and how electronic structure forms a link between both.”

    While both effects are important in a variety of industrial processes and have been the subject of much empirical research, “at the molecular level, we understand very little about what’s happening at the interface,” Shao-Horn says. “This is a step forward, providing a molecular-level understanding.”

    “It’s primarily an experimental technique” that made the new understanding possible, explains Kelsey Stoerzinger, an MIT graduate student and the paper’s lead author. While most attempts to study such surface science use instruments requiring a vacuum, this team used a device that could study the reactions in humid air, at room temperature, and with varying degrees of water vapor present. Experiments using this system, called ambient pressure X-ray photoelectron spectroscopy, revealed that the reactivity with water is key to the whole process, she says.

    The water molecules break apart to form hydroxyl groups — an atom of oxygen bound to an atom of hydrogen — bonded to the material’s surface. These reactive compounds, in turn, are responsible for increasing the wetting properties of the surface, while simultaneously inhibiting its ability to catalyze chemical reactions. Therefore, for applications requiring high catalytic activity, the team found, a key requirement is that the surface be hydrophobic, or non-wetting.

    “Ideally, this understanding helps us design new catalysts,” Stoerzinger says. If a given material “has a lower affinity for water, it has a higher affinity for catalytic activity.”

    Shao-Horn notes that this is an initial finding, and that “extension of these trends to broader classes of materials and ranges of hydroxyl affinity requires further investigation.” The team has already begun further exploration of these areas. This research, she says, “opens up the space of materials and surfaces we might think about” for both catalysis and wetting.

    The research team also included graduate student Wesley Hong, visiting scientist Livia Giordano, and postdocs Yueh-Lin Lee and Gisele Azimi at MIT; Ethan Crumlin and Hendrik Bluhm at Lawrence Berkeley National Laboratory; and Michael Biegalski at Oak Ridge National Laboratory. The work was supported by the National Science Foundation and the U.S. Department of Energy.

    See the full article here.

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  • richardmitnick 4:04 pm on July 28, 2015 Permalink | Reply
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    From BNL: “New Computer Model Could Explain how Simple Molecules Took First Step Toward Life” 

    Brookhaven Lab

    July 28, 2015
    Alasdair Wilkins

    Two Brookhaven researchers developed theoretical model to explain the origins of self-replicating molecules

    1
    Brookhaven researchers Sergei Maslov (left) and Alexi Tkachenko developed a theoretical model to explain molecular self-replication.

    Nearly four billion years ago, the earliest precursors of life on Earth emerged. First small, simple molecules, or monomers, banded together to form larger, more complex molecules, or polymers. Then those polymers developed a mechanism that allowed them to self-replicate and pass their structure on to future generations.

    We wouldn’t be here today if molecules had not made that fateful transition to self-replication. Yet despite the fact that biochemists have spent decades searching for the specific chemical process that can explain how simple molecules could make this leap, we still don’t really understand how it happened.

    Now Sergei Maslov, a computational biologist at the U.S. Department of Energy’s Brookhaven National Laboratory and adjunct professor at Stony Brook University, and Alexei Tkachenko, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN), have taken a different, more conceptual approach. They’ve developed a model that explains how monomers could very rapidly make the jump to more complex polymers. And what their model points to could have intriguing implications for CFN’s work in engineering artificial self-assembly at the nanoscale. Their work is published in the July 28, 2015 issue of The Journal of Chemical Physics.

    To understand their work, let’s consider the most famous organic polymer, and the carrier of life’s genetic code: DNA. This polymer is composed of long chains of specific monomers called nucleotides, of which the four kinds are adenine, thymine, guanine, and cytosine (A, T, G, C). In a DNA double helix, each specific nucleotide pairs with another: A with T, and G with C. Because of this complementary pairing, it would be possible to put a complete piece of DNA back together even if just one of the two strands was intact.

    While DNA has become the molecule of choice for encoding biological information, its close cousin RNA likely played this role at the dawn of life. This is known as the RNA world hypothesis, and it’s the scenario that Maslov and Tkachenko considered in their work.

    The single complete RNA strand is called a template strand, and the use of a template to piece together monomer fragments is what is known as template-assisted ligation. This concept is at the crux of their work. They asked whether that piecing together of complementary monomer chains into more complex polymers could occur not as the healing of a broken polymer, but rather as the formation of something new.

    “Suppose we don’t have any polymers at all, and we start with just monomers in a test tube,” explained Tkachenko. “Will that mixture ever find its way to make those polymers? The answer is rather remarkable: Yes, it will! You would think there is some chicken-and-egg problem—that, in order to make polymers, you already need polymers there to provide the template for their formation. Turns out that you don’t really.”

    Instilling memory

    2
    A schematic drawing of template-assisted ligation, shown in this model to give rise to autocatalytic systems. No image credit.

    Maslov and Tkachenko’s model imagines some kind of regular cycle in which conditions change in a predictable fashion—say, the transition between night and day. Imagine a world in which complex polymers break apart during the day, then repair themselves at night. The presence of a template strand means that the polymer reassembles itself precisely as it was the night before. That self-replication process means the polymer can transmit information about itself from one generation to the next. That ability to pass information along is a fundamental property of life.

    “The way our system replicates from one day cycle to the next is that it preserves a memory of what was there,” said Maslov. “It’s relatively easy to make lots of long polymers, but they will have no memory. The template provides the memory. Right now, we are solving the problem of how to get long polymer chains capable of memory transmission from one unit to another to select a small subset of polymers out of an astronomically large number of solutions.”

    According to Maslov and Tkachenko’s model, a molecular system only needs a very tiny percentage of more complex molecules—even just dimers, or pairs of identical molecules joined together—to start merging into the longer chains that will eventually become self-replicating polymers. This neatly sidesteps one of the most vexing puzzles of the origins of life: Self-replicating chains likely need to be very specific sequences of at least 100 paired monomers, yet the odds of 100 such pairs randomly assembling themselves in just the right order is practically zero.

    “If conditions are right, there is what we call a first-order transition, where you go from this soup of completely dispersed monomers to this new solution where you have these long chains appearing,” said Tkachenko. “And we now have this mechanism for the emergence of these polymers that can potentially carry information and transmit it downstream. Once this threshold is passed, we expect monomers to be able to form polymers, taking us from the primordial soup to a primordial soufflé.”

    While the model’s concept of template-assisted ligation does describe how DNA—as well as RNA—repairs itself, Maslov and Tkachenko’s work doesn’t require that either of those was the specific polymer for the origin of life.

    “Our model could also describe a proto-RNA molecule. It could be something completely different,” Maslov said.

    Order from disorder

    The fact that Maslov and Tkachenko’s model doesn’t require the presence of a specific molecule speaks to their more theoretical approach.

    “It’s a different mentality from what a biochemist would do,” said Tkachenko. “A biochemist would be fixated on specific molecules. We, being ignorant physicists, tried to work our way from a general conceptual point of view, as there’s a fundamental problem.”

    That fundamental problem is the second law of thermodynamics, which states that systems tend toward increasing disorder and lack of organization. The formation of long polymer chains from monomers is the precise opposite of that.

    “How do you start with the regular laws of physics and get to these laws of biology which makes things run backward, which make things more complex, rather than less complex?” Tkachenko queried. “That’s exactly the jump that we want to understand.”

    Applications in nanoscience

    The work is an outgrowth of efforts at the Center for Functional Nanomaterials, a DOE Office of Science User Facility, to use DNA and other biomolecules to direct the self-assembly of nanoparticles into large, ordered arrays. While CFN doesn’t typically focus on these kinds of primordial biological questions, Maslov and Tkachenko’s modeling work could help CFN scientists engaged in cutting-edge nanoscience research to engineer even larger and more complex assemblies using nanostructured building blocks.

    “There is a huge interest in making engineered self-assembled structures, so we were essentially thinking about two problems at once,” said Tkachenko. “One is relevant to biologists, and second asks whether we can engineer a nanosystem that will do what our model does.”

    The next step will be to determine whether template-aided ligation can allow polymers to begin undergoing the evolutionary changes that characterize life as we know it. While this first round of research involved relatively modest computational resources, that next phase will require far more involved models and simulations.

    Maslov and Tkachenko’s work has solved the problem of how long polymer chains capable of information transmission from one generation to the next could emerge from the world of simple monomers. Now they are turning their attention to how such a system could naturally narrow itself down from exponentially many polymers to only a select few with desirable sequences.

    “What we needed to show here was that this template-based ligation does result in a set of polymer chains, starting just from monomers,” said Tkachenko. “So the next question we will be asking is whether, because of this template-based merger, we will be able to see specific sequences that will be more ‘fit’ than others. So this work sets the stage for the shift to the Darwinian phase.”

    This work was supported by the DOE Office of Science.

    See the full article here.

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 12:59 pm on July 24, 2015 Permalink | Reply
    Tags: , , Nanotechnology   

    From BNL: “New Technique to Synthesize Nanostructured Nanowires” 

    Brookhaven Lab

    July 20, 2015
    Justin Eure

    Method for growing ‘hybrid’ crystals at the nanoscale incorporates quantum dots into a host nanowire with perfect junctions between the components

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    IBM scientist Frances Ross (left) with Brookhaven Lab scientists Dong Su (center) and Eric Stach in the Center for Functional Nanomaterials.

    A new approach to self-assemble and tailor complex structures at the nanoscale, developed by an international collaboration led by the University of Cambridge and IBM, opens opportunities to tailor properties and functionalities of materials for a wide range of semiconductor device applications.

    The researchers have developed a method for growing combinations of different materials in a needle-shaped crystal called a nanowire. Nanowires are small structures, only a few billionths of a metre in diameter. Semiconductors can be grown into nanowires, and the result is a useful building block for electrical, optical, and energy harvesting devices. The researchers have found out how to grow smaller crystals within the nanowire, forming a structure like a crystal rod with an embedded array of gems. Details of the new method are published in the journal Nature Materials.

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    Electron microscope images showing the formation of a nickel silicide nanoparticle (colored yellow) in a silicon nanowire. Credit: Stephan Hofmann

    “The key to building functional nanoscale devices is to control materials and their interfaces at the atomic level,” said Dr. Stephan Hofmann of the Department of Engineering, one of the paper’s senior authors. “We’ve developed a method of engineering inclusions of different materials so that we can make complex structures in a very precise way.”

    Nanowires are often grown through a process called Vapour-Liquid-Solid (VLS) synthesis, where a tiny catalytic droplet is used to seed and feed the nanowire, so that it self-assembles one atomic layer at a time. VLS allows a high degree of control over the resulting nanowire: composition, diameter, growth direction, branching, kinking and crystal structure can be controlled by tuning the self-assembly conditions. As nanowires become better controlled, new applications become possible.

    The technique that Hofmann and his colleagues from Cambridge and IBM developed can be thought of as an expansion of the concept that underlies conventional VLS growth. The researchers use the catalytic droplet not only to grow the nanowire, but also to form new materials within it. These tiny crystals form in the liquid, but later attach to the nanowire and then become embedded as the nanowire is grown further. This catalyst mediated docking process can ‘self-optimise’ to create highly perfect interfaces for the embedded crystals.

    To unravel the complexities of this process, the research team used two customised electron microscopes, one at IBM’s TJ Watson Research Center and a second at Brookhaven National Laboratory. This allowed them to record high-speed movies of the nanowire growth as it happens atom-by-atom. The researchers found that using the catalyst as a ‘mixing bowl’, with the order and amount of each ingredient programmed into a desired recipe, resulted in complex structures consisting of nanowires with embedded nanoscale crystals, or quantum dots, of controlled size and position.

    “The technique allows two different materials to be incorporated into the same nanowire, even if the lattice structures of the two crystals don’t perfectly match,” said Hofmann. “It’s a flexible platform that can be used for different technologies.”

    Possible applications for this technique range from atomically perfect buried interconnects to single-electron transistors, high-density memories, light emission, semiconductor lasers, and tunnel diodes, along with the capability to engineer three-dimensional device structures.

    “This process has enabled us to understand the behaviour of nanoscale materials in unprecedented detail, and that knowledge can now be applied to other processes,” said Hofmann.

    See the full article here.

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 2:24 pm on July 23, 2015 Permalink | Reply
    Tags: , Nanotechnology,   

    From Nautilus: “The Ambiguous Colors of Nanotechnology” 

    Nautilus

    Nautilus

    July 23, 2015
    By Jeanne Carstensen, photos by Peter Earl McCollough

    Kate Nichols leans her delicate face against the glass of a chemical fume hood in a University of California, Berkeley lab, peering into a beaker filled with a pale yellow liquid—“like a well hydrated person’s pee,” she says, laughing. The yellow brew is a fresh batch of silver nanoparticles. Over the next week, the liquid will turn green, then turquoise, then blue as the particles morph in shape from spheroids to prisms under the influence of time and fluorescent light. Post-docs and grad students elsewhere in the nanotech lab are synthesizing nanoparticles for research on artificial photosynthesis and quantum dot digital displays. But not Nichols. She isn’t a scientist, but an artist, gripped by color.

    About 15 miles away, in her studio in San Francisco’s Mission District, brightly colored pigments sit on a crowded shelf next to the nanopaints she made in the lab: vials of yellowish and brown solutions containing varying sizes and concentrations of silver nanoparticles. On a nearby wall opposite a large oil painting of close-up fish scales hangs a group of small sculptures she calls “Figments.” Each is made of two triangular pieces of glass covered in nanoparticle paint, and joined by a hinge. They look like eerie birds, or perhaps mutant butterflies, brightening or darkening depending on the light around them and the angle of the viewer, so that they seem to weave in and out of perceptual awareness.

    The scene at her studio is in some sense not so different from the lamp-lit workspace of a Renaissance painter experimenting with new colors. “A lot of pigments were discovered by happy accidents,” explains Philip Ball, author of the book Bright Earth: Art and the Invention of Color. “We understand these mechanisms now, but then it was hands-on experimentation. It seems like [Nichols is doing] the same now with these [nanomaterials].” It’s doubtful any Renaissance painters, though, had an apprenticeship quite like this: Nichols, 34, has spent seven years as artist in residence at a world-class nanotech lab, mastering technically challenging synthesis techniques and learning about colloidal chemistry and optical physics. In the process, she has transformed not just her art, but also the way she looks at color itself.

    2
    Morpho Butterfly

    Nichols’ journey from the studio to the lab has been driven by what she describes as an “almost maniacal obsession with mimesis.” As a young figurative painter, she was intrigued by the ability of Northern Renaissance painters to capture the luminosity of human skin. So in 2002 she dropped out of Kenyon College to study 15th-century oil painting and paint-making techniques as an apprentice to artist Will Wilson in San Francisco. She learned to make her own paints by mixing pigments with oils she concocted out of linseed oil, lead oxide, and mastic resin, following centuries-old recipes.

    Around this time, Nichols became fixated on the Morpho butterfly. Entranced with its flickering blue-green iridescence—the hue shifting subtly as the insect flits through the air—she yearned to capture this luminous marvel of nature on her canvas. But how? She remembered what a science professor had explained to her in college: The Morpho’s color is structural. It doesn’t arise from pigmentation, but from the light scattering off nanoscale structures embedded in its wings.

    Pigments absorb particular bandwidths of light depending on their chemical composition; whatever is not absorbed is reflected, and it is this reflected light that determines the color we perceive. Structural color isn’t chemical: Instead, tiny structures, often smaller than a single wavelength of light, redirect and slow light waves down, causing them to interfere with each other in ways that depend on the shape, size, and spacing of the scattering structures, as well as on the angle of the incoming light and the position of the observer. In the case of the Morpho, these structures scatter blue light most strongly; its hue shimmers and shifts to lighter or darker blue as the butterfly moves, producing iridescence. Structural color is also at work in peacock feathers, fish scales, and beetle casings.

    Nichols often had the radio on while painting in her studio, and in 2007 heard reports about developments in nanotechnology research on NPR. She began to wonder if it would be possible to make nanomaterials in the lab that would allow her to use structural color in her art. Using her oil technique she could already paint a photorealistic depiction of a Morpho butterfly, but she wanted a deeper mimesis: a blue created from the interaction of light with nanostructures akin to those on the butterfly’s wings.

    On a whim, she wrote to Paul Alivisatos, a nanotechnology expert from UC Berkeley. To her surprise, after just one interview he invited her to join his lab as artist in residence. It was “a very easy” decision to take on Nichols, Alivisatos told me. “I think a scientist is on a personal journey that is very similar to what an artist takes. They each have to struggle to find what is truly beautiful. I always respect people who like to take those quests.”

    Still, when Alivisatos first showed her the wet lab and realized she had never even been in a lab before, he “thought she might get cold feet.” The techniques involved in synthesizing nanomaterials “are quite demanding,” said Alivisatos, who is also the Director of Lawrence Berkeley National Lab. “But she’s been remarkably persistent.”

    After joining the lab in late 2008 Nichols spent long days tagging along with “very generous” graduate students and post-docs. One of those was Jill Millstone, now an assistant professor of chemistry at the University of Pittsburgh. Nichols, who was 27 at the time, hadn’t studied any chemistry since high school. But Millstone said she “picked up on all of the nuances very quickly” regarding everything from mathematical calculations to pipette technique. “She embraced the language of science and the spirit of the way we approach problems,” Millstone added. “That made her melt into the fabric of the lab. She didn’t stick out as an artist.” For her part, Nichols says she found the learning process in the lab to be “similar to her experience of being a painter’s apprentice.”

    At the core of her training were nanoparticles, microscopic particles generally measuring between one and 100 nanometers (one-billionth of a meter). To put this infinitesimal realm into perspective, a water molecule measures about 0.3 nanometers; a human hair is approximately 90,000 nanometers wide. Nanoparticles of metals (such as silver or gold) or semiconductors (such as cadmium sulfide or silicon) exhibit different, electrical, physical, and (especially interesting for Nichols) optical properties than they do in bulk. In addition, the way they interact with light can be controlled by changing their size and shape. To make such tiny structures in a controlled and repeatable way takes a combination of theory and technique, physics and chemistry, and meticulous attention to detail. Nichols understood that she had an opportunity to create materials that would serve as “a bridge between the nanoscopic and visible worlds”—but she was starting from zero.

    She began to fill her lab notebooks with chemical equations and extensive notes for synthesizing nanoparticles made from a variety of materials, including silver, gold, and cadmium. Eventually she settled on silver as her primary material because of its safety and the colors it produced. At first she focused on prism-shaped silver nanoparticles, which displayed beautiful blues and greens in the vial. But she was “disappointed that it looked great in the bottle but if I put it on a glass surface it looked like my dirty windshield.” She couldn’t figure out how to get the silver nanoprisms she had made to adhere to glass the way she wanted. And after a year of solid lab work, she didn’t have any art to show for it. “I had to get knocked on my ass,” she said, remembering the many frustrations.

    Finally, in late 2009, she decided to “listen to the particles.” Instead of using them like paint, she suspended them in sealed glass capillaries, which she attached to each other to create sculptures. They looked a little like ethereal organ pipes, or perhaps clusters of icicles, filled with turquoise liquid. Over time, as light caused the prisms to take on a more rounded shape, the particles turned blue.

    The sculptures were a start, but she wasn’t satisfied. She continued to experiment and eventually found a way to create a paint based on another kind of silver nanoparticle, shaped like soccer balls. The key was their compatibility with a medium. Their specific surface chemistry meant she could suspend the pseudo spheres in organic solvents such as hexane, and apply them to glass. “The important step for her was getting to the stage where she could develop the material,” Alivisatos said. “First, she had to make the material and then have a process where she could embed it so it was stable. Just getting all that to work was hard.”

    By late 2010 Nichols was able to consistently make silver nanopaints and start experimenting with them artistically. The Leonardo Museum in Salt Lake City learned about her experimentations through her 2010 TED talk and commissioned her to create a series of art works, which she called Through the Looking Glass. They consist of abstract, ghostly pools of brown, gold, orange, and purple colors on several superimposed pieces of glass, like large lab slides. These colors shift depending on where you stand and on the light falling on them, because the particles in the nanopaint transmit light in the brown-orange range, but scatter blues and purples. They tend to appear only blue and green on glass with a black background, which eliminates transmitted light, an effect she would explore later.

    2
    Look twice: A detail from a 2013 work by Nichols called “Doppelganger,” which uses silver nanoparticles on glass. The image, which evokes the scintillation of fish scales, shifts with the viewer’s position.

    Success for a nanoscale scientist veers toward precision. The goal of synthesis is to create nanoparticles with the narrowest possible size distribution, allowing the most exact expression of a specific color for the highest-performing bio-imaging tool or information display or laser. Today artists can also get very precise. Ultramarine, one of the only materials available for producing blue pigment in the Middle Ages, was made from grinding up lapis lazuli, a precious stone that was only available from what is today Afghanistan. It was rare and extremely expensive. Now a fine artist has many blues to choose from for oil, acrylic, and watercolor. An industrialist in need of a blue for a Frisbee or toothpaste tube can dip into the over 9,000-page Color Index International. As Ball points out, poetic names such as Prussian Blue are in the minority, having been joined by chemically informative names such as C.I. VAT RED 13, a kind of red. “The ambiguities of older terminology are banished, and undoubtedly some of the magic goes with them.” The quantum dot industry also uses a prosaic naming system for the hundreds of colors in its quantum gamut: the letters QD, plus a number denoting its wavelength. QD680, for example, “is not a very beautiful name like ultramarine,” Alivisatos said. “But it does tell you exactly what it is.”

    Nichols, on the other hand, brought her artist’s sensibility to the lab. The more she explored nanocolor, the more she was intrigued not by its precision, but by its ambivalence. The colors she coaxed out of the lab and into her artwork can’t be described with a single number. Her silver nanopaints are a purposefully “dirty” mix of particles of different sizes, varying from about five to 30 nanometers and scattering light over a range of the blue-green spectrum; she controls the distribution with a centrifuge. Some of her paints include gold as well, which adds reds. In a sense, each vial of Nichols’ paint contains a palette of colors, a mix of particles that interact with light in a variety of ways. Nichols likens the distinction between her “dirty” mixes and the formulas used for scientific purposes to the difference between sound reverberating through a wooden piano and a synthesizer. She’s attracted to the former, “the messier signal that comes with things that exist in the physical world.”

    Nichols is, as far as I have been able to determine, the only artist to synthesize her own nanopaint in the lab. But what Nichols calls “nanocraftsmanship” has a long history. Nanoparticles of gold and silver have been used in art for thousands of years in ceramic glazes to lend iridescence and, most famously, in stained glass. The vibrant colors of the windows in medieval churches such as Sainte-Chapelle in Paris that glow in intense hues are created by nanoparticles embedded in the glass—silver particles for yellow and gold for ruby red. The color of the windows changes, as well, with the time of day and angle of light striking the particles.

    The Lycurgus Cup, a glass chalice made by the Romans in the fourth century A.D. that today sits in the British Museum, looks green under reflected daylight, and red when light is transmitted through the cup. By 1990, scientists discovered that Roman craftsmen had embedded colloidal gold and silver nanoparticles into the glass, and that the effect was due to the same phenomenon (called surface plasmon resonance) that Nichols plays with on the Berkeley campus. These early nanocraftsmen arrived at their technologies through experimentation, and could not have known the science behind it.

    Nichols also includes photography and Victorian mirror making, which involves a silver-based recipe “strikingly similar to my nanoparticle synthesis,” in the lineage of nanocraftsmanship. The silver particles in these processes aren’t as small as those in her nanopaints, but they have a similar ambivalent, multifaceted relationship with light.

    As artists begin to intentionally explore the artistic possibilities for using synthesized nanoparticles in their art, exciting new questions about color and how we perceive it will arise. “I think there’s no doubt that the number of different colors that can be purposefully made is much larger,” Alivisatos said. But what artists will do with this expanded palette is still an open question. “We’ve only begun to explore the ways these effects could be used artistically to communicate with color,” said Ball, “and to do everything that artists do to make us think about the visual world around us.”

    Sculptor Anish Kapoor hasn’t ventured into the lab like Nichols but he has recently added a “super black” commercial nanopaint to his palette. Made by Surrey NanoSystems out of vertically aligned carbon nanotubes that trap over 99 percent of incoming light, “Vantablack” has applications such as camouflaging military aircraft. Kapoor has compared looking at the nanopaint to staring into a black hole. He told the BBC that a space painted with the substance is “so dark that as you walk in you lose all sense of where you are, what you are, and especially all sense of time.”

    Nichols’ emphasis on the ambivalent qualities of metal silver nanoparticles could tickle the senses in other ways. Scott Taylor, who is a chief operating officer at Maxis, a division of Electronic Arts, and thinks about perception for his work on the SimCity videogame series, was so attracted to the dynamic nature of her art that he has bought several pieces, including one of the “Figments” series. He said he loves that how it looks depends on “whether I see it out of my peripheral vision or straight on, how the light hits it, what I am thinking at the moment.”

    Nichols’ investigations into structural color have the power to inspire the same sense of wonder that her inspiration, the Morpho butterfly, often does. Her pieces at The Leonardo Museum were very layered, said Jann Haworth, the creative director. “First people saw the beauty, but then they went deeper, into the science of how something in nature could create such magic. It’s like a quest. You understand, then you don’t. It’s almost mystical.”

    The nanopaints Nichols has developed so far are only a nano-sized sampling of the artistic possibilities in this new color realm. “If we’re seeing new visual effects who knows how we will respond to them,” Ball said. “We don’t know how that’s going to be perceived.”

    3
    A new perspective: A portrait of Kate Nichols in her studio.Peter Earl McCullough

    Back in her studio, Nichols is working with some nanoparticle paint on a piece of glass. It’s hard to believe that the yellowish liquid she pours out was made in Alivisato’s nanotechnology lab. It looks like a thin stain or maybe a kind of finger paint—and she treats it as such, letting it flow onto the glass and then manipulating it with broken pieces of glass, and her gloved hand. When she feels the piece is done, she’ll cover it with another piece of glass. She has learned to sense how the pieces will look after the solvent dries and under different light conditions. But she’s often surprised, “and that is what’s delightful and maddening about working with this material,” she laughs.

    I ask her about some dark glass pieces on the wall. Unlike the clear pieces she showed at The Leonardo, these have a black backing to block transmitted light. They look a little like ghostly black-and-white negatives with flickers of blues and greens in different streaks and patches, depending on how you look at it. As I always do when I observe her nano art, I walk around, exploring how it changes. Then I lean in close. “What color is this anyway?”

    She points out a “blue like a gaslight, something more like the silver of silverware, and a green quality but still in blues.” But, she adds, “the question is insufficient.” After working with nanoparticles that look “yellow here and blue there, that change right in front of my eyes,” she thinks about a material’s “particular relationship with light” instead of its color. There is no simple answer to my question. In the last several years, she has brought this sensibility into all of her artwork. Whether painting in traditional oils, making mirrored surfaces, or working with her nanopaint, Nichols crafts “surfaces to catch, scatter, bend, and transmit light in ways that allow us to experience light’s ambivalent nature,” as she described in her 2012 TEDx talk.

    As I continue to circle around the dark glass piece in the afternoon light of the studio, I see new forms and colors that I hadn’t noticed before. Like a Morpho butterfly, the piece is alive with light. It makes me think of all the marvelous things that happen when the sun’s rays fall to Earth.

    See the full article here.

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 8:26 am on May 15, 2015 Permalink | Reply
    Tags: , , , , Nanotechnology   

    From BNL: “Intense Lasers Cook Up Complex, Self-Assembled Nanomaterials” 

    Brookhaven Lab

    May 13, 2015
    Justin Eure

    New technique developed at Brookhaven Lab makes self-assembly 1,000 times faster and could be used for industrial-scale solar panels and electronics

    1
    Brookhaven Lab scientist Kevin Yager (left) and postdoctoral researcher Pawel Majewski with the new Laser Zone Annealing instrument at the Center for Functional Nanomaterials.

    Nanoscale materials feature extraordinary, billionth-of-a-meter qualities that transform everything from energy generation to data storage. But while a nanostructured solar cell may be fantastically efficient, that precision is notoriously difficult to achieve on industrial scales. The solution may be self-assembly, or training molecules to stitch themselves together into high-performing configurations.

    Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have developed a laser-based technique to execute nanoscale self-assembly with unprecedented ease and efficiency.

    “We design materials that build themselves,” said Kevin Yager, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN). “Under the right conditions, molecules will naturally snap into a perfect configuration. The challenge is giving these nanomaterials the kick they need: the hotter they are, the faster they move around and settle into the desired formation. We used lasers to crank up the heat.”

    Yager and Brookhaven Lab postdoctoral researcher Pawel Majewski built a one-of-a-kind machine that sweeps a focused laser-line across a sample to generate intense and instantaneous spikes in temperature. This new technique, called Laser Zone Annealing (LZA), drives self-assembly at rates more than 1,000 times faster than traditional industrial ovens. The results are described in the journal ACS Nano.

    “We created extremely uniform self-assembled structures in less than a second,” Majewski said. “Beyond the extraordinary speed, our laser also reduced the defects and degradations present in oven-heated materials. That combination makes LZA perfect for carrying small-scale laboratory breakthroughs into industry.”

    The scientists prepared the materials and built the LZA instrument at the CFN. They then analyzed samples using advanced electron microscopy at CFN and x-ray scattering at Brookhaven’s now-retired National Synchrotron Light Source (NSLS)—both DOE Office of Science User Facilities.

    “It was enormously gratifying to see that our predictions were accurate—the enormous thermal gradients led to a correspondingly enormous acceleration!” Yager said.

    2
    Illustration of the Lazer Zone Annealing instrument showing the precise laser (green) striking the un-assembled polymer (purple). The extreme thermal gradients produced by the laser sweeping across the sample cause rapid and pristine self-assembly.

    Ovens versus lasers

    Imagine preparing a complex cake, but instead of baking it in the oven, a barrage of lasers heats it to perfection in an instant. Beyond that, the right cooking conditions will make the ingredients mix themselves into a picture-perfect dish. This nanoscale recipe achieves something equally extraordinary and much more impactful.

    The researchers focused on so-called block copolymers, molecules containing two linked blocks with different chemical structures and properties. These blocks tend to repel each other, which can drive the spontaneous formation of complex and rigid nanoscale structures.

    “The price of their excellent mechanical properties is the slow kinetics of their self-assembly,” Majewski said. “They need energy and time to explore possibilities until they find the right configuration.”

    In traditional block copolymer self-assembly, materials are heated in a vacuum-sealed oven. The sample is typically “baked” for a period of 24 hours or longer to provide enough kinetic energy for the molecules to snap into place—much too long for commercial viability. The long exposure to high heat also causes inevitable thermal degradation, leaving cracks and imperfections throughout the sample.

    The LZA process, however, offers sharp spikes of heat to rapidly excite the polymers without the sustained energy that damages the material.

    “Within milliseconds, the entire sample is beautifully aligned,” Yager said. “As the laser sweeps across the material, the localized thermal spikes actually remove defects in the nanostructured film. LZA isn’t just faster, it produces superior results.”

    LZA generates temperatures greater than 500 degrees Celsius, but the thermal gradients—temperature variations tied to direction and location in a material—can reach more than 4,000 degrees per millimeter. While scientists know that higher temperatures can accelerate self-assembly, this is the first proof of dramatic enhancement by extreme gradients.

    Built from scratch

    “Years ago, we observed a subtle hint that thermal gradients could improve self-assembly,” Yager said. “I became obsessed with the idea of creating more and more extreme gradients, which ultimately led to building this laser setup, and pioneering a new technique.”

    The researchers needed a high concentration of technical expertise and world-class facilities to move the LZA from proposal to execution.

    “Only at the CFN could we develop this technique so quickly,” Majewski said. “We could do rapid instrument prototyping and sample preparation with the on-site clean room, machine shop, and polymer processing lab. We then combined CFN electron microscopy with x-ray studies at NSLS for an unbeatable evaluation of the LZA in action.”

    Added Yager, “The ability to make new samples at the CFN and then walk across the street to characterize them in seconds at NSLS was key to this discovery. The synergy between these two facilities is what allowed us to rapidly iterate to an optimized design.”

    The scientists also developed a new microscale surface thermometry technique called melt-mark analysis to track the exact heat generated by the laser pulses and tune the instrument accordingly.

    “We burned a few films initially before we learned the right operating conditions,” Majewski said. “It was really exciting to see the first samples being rastered by the laser and then using NSLS to discover exactly what happened.”

    Future of the technique

    The LZA is the first machine of its kind in the world, but it signals a dramatic step forward in scaling up meticulously designed nanotechnology. The laser can even be used to “draw” structures across the surface, meaning the nanostructures can assemble in well-defined patterns. This unparalleled synthesis control opens the door to complex applications, including electronics.

    “There’s really no limit to the size of a sample this technique could handle,” Yager said. “In fact, you could run it in a roll-to-roll mode—one of the leading manufacturing technologies.”

    The scientists plan to further develop the new technique to create multi-layer structures that could have immediate impacts on anti-reflective coatings, improved solar cells, and advanced electronics.

    This research and operations at CFN and NSLS were funded by the DOE Office of Science.

    See the full article here.

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 7:56 am on May 14, 2015 Permalink | Reply
    Tags: , , , , , Nanotechnology,   

    From MIT: “Researchers build new fermion microscope” 


    MIT News

    May 13, 2015
    Jennifer Chu

    1
    Graduate student Lawrence Cheuk adjusts the optics setup for laser cooling of sodium atoms. Photo: Jose-Luis Olivares/MIT

    2
    Laser beams are precisely aligned before being sent into the vacuum chamber. Photo: Jose-Luis Olivares/MIT

    3
    Sodium atoms diffuse out of an oven to form an atomic beam, which is then slowed and trapped using laser light. Photo: Jose-Luis Olivares/MIT

    4
    A Quantum gas microscope for fermionic atoms. The atoms, potassium-40, are cooled during imaging by laser light, allowing thousands of photons to be collected by the microscope. Credit: Lawrence Cheuk/MIT

    5
    The Fermi gas microscope group: (from left) graduate students Katherine Lawrence and Melih Okan, postdoc Thomas Lompe, graduate student Matt Nichols, Professor Martin Zwierlein, and graduate student Lawrence Cheuk. Photo: Jose-Luis Olivares/MIT

    Instrument freezes and images 1,000 individual fermionic atoms at once.

    Fermions are the building blocks of matter, interacting in a multitude of permutations to give rise to the elements of the periodic table. Without fermions, the physical world would not exist.

    Examples of fermions are electrons, protons, neutrons, quarks, and atoms consisting of an odd number of these elementary particles. Because of their fermionic nature, electrons and nuclear matter are difficult to understand theoretically, so researchers are trying to use ultracold gases of fermionic atoms as stand-ins for other fermions.

    But atoms are extremely sensitive to light: When a single photon hits an atom, it can knock the particle out of place — an effect that has made imaging individual fermionic atoms devilishly hard.

    Now a team of MIT physicists has built a microscope that is able to see up to 1,000 individual fermionic atoms. The researchers devised a laser-based technique to trap and freeze fermions in place, and image the particles simultaneously.

    The new imaging technique uses two laser beams trained on a cloud of fermionic atoms in an optical lattice. The two beams, each of a different wavelength, cool the cloud, causing individual fermions to drop down an energy level, eventually bringing them to their lowest energy states — cool and stable enough to stay in place. At the same time, each fermion releases light, which is captured by the microscope and used to image the fermion’s exact position in the lattice — to an accuracy better than the wavelength of light.

    With the new technique, the researchers are able to cool and image over 95 percent of the fermionic atoms making up a cloud of potassium gas. Martin Zwierlein, a professor of physics at MIT, says an intriguing result from the technique appears to be that it can keep fermions cold even after imaging.

    “That means I know where they are, and I can maybe move them around with a little tweezer to any location, and arrange them in any pattern I’d like,” Zwierlein says.

    Zwierlein and his colleagues, including first author and graduate student Lawrence Cheuk, have published their results today in the journal Physical Review Letters.

    Seeing fermions from bosons

    For the past two decades, experimental physicists have studied ultracold atomic gases of the two classes of particles: fermions and bosons — particles such as photons that, unlike fermions, can occupy the same quantum state in limitless numbers. In 2009, physicist Marcus Greiner at Harvard University devised a microscope that successfully imaged individual bosons in a tightly spaced optical lattice. This milestone was followed, in 2010, by a second boson microscope, developed by Immanuel Bloch’s group at the Max Planck Institute of Quantum Optics.

    These microscopes revealed, in unprecedented detail, the behavior of bosons under strong interactions. However, no one had yet developed a comparable microscope for fermionic atoms.

    “We wanted to do what these groups had done for bosons, but for fermions,” Zwierlein says. “And it turned out it was much harder for fermions, because the atoms we use are not so easily cooled. So we had to find a new way to cool them while looking at them.”

    Techniques to cool atoms ever closer to absolute zero have been devised in recent decades. Carl Wieman, Eric Cornell, and MIT’s Wolfgang Ketterle were able to achieve Bose-Einstein condensation in 1995, a milestone for which they were awarded the 2001 Nobel Prize in physics. Other techniques include a process using lasers to cool atoms from 300 degrees Celsius to a few ten-thousandths of a degree above absolute zero.

    A clever cooling technique

    And yet, to see individual fermionic atoms, the particles need to be cooled further still. To do this, Zwierlein’s group created an optical lattice using laser beams, forming a structure resembling an egg carton, each well of which could potentially trap a single fermion. Through various stages of laser cooling, magnetic trapping, and further evaporative cooling of the gas, the atoms were prepared at temperatures just above absolute zero — cold enough for individual fermions to settle onto the underlying optical lattice. The team placed the lattice a mere 7 microns from an imaging lens, through which they hoped to see individual fermions.

    However, seeing fermions requires shining light on them, causing a photon to essentially knock a fermionic atom out of its well, and potentially out of the system entirely.

    “We needed a clever technique to keep the atoms cool while looking at them,” Zwierlein says.

    His team decided to use a two-laser approach to further cool the atoms; the technique manipulates an atom’s particular energy level, or vibrational energy. Each atom occupies a certain energy state — the higher that state, the more active the particle is. The team shone two laser beams of differing frequencies at the lattice. The difference in frequencies corresponded to the energy between a fermion’s energy levels. As a result, when both beams were directed at a fermion, the particle would absorb the smaller frequency, and emit a photon from the larger-frequency beam, in turn dropping one energy level to a cooler, more inert state. The lens above the lattice collects the emitted photon, recording its precise position, and that of the fermion.

    Zwierlein says such high-resolution imaging of more than 1,000 fermionic atoms simultaneously would enhance our understanding of the behavior of other fermions in nature — particularly the behavior of electrons. This knowledge may one day advance our understanding of high-temperature superconductors, which enable lossless energy transport, as well as quantum systems such as solid-state systems or nuclear matter.

    “The Fermi gas microscope, together with the ability to position atoms at will, might be an important step toward the realization of a quantum computer based on fermions,” Zwierlein says. “One would thus harness the power of the very same intricate quantum rules that so far hamper our understanding of electronic systems.”

    Zwierlein says it is a good time for Fermi gas microscopists: Around the same time his group first reported its results, teams from Harvard and the University of Strathclyde in Glasgow also reported imaging individual fermionic atoms in optical lattices, indicating a promising future for such microscopes.

    Zoran Hadzibabic, a professor of physics at Trinity College, says the group’s microscope is able to detect individual atoms “with almost perfect fidelity.”

    “They detect them reliably, and do so without affecting their positions — that’s all you want,” says Hadzibabic, who did not contribute to the research. “So far they demonstrated the technique, but we know from the experience with bosons that that’s the hardest step, and I expect the scientific results to start pouring out.”

    This research was funded in part by the National Science Foundation, the Air Force Office of Scientific Research, the Office of Naval Research, the Army Research Office, and the David and Lucile Packard Foundation.

    See the full article here.

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  • richardmitnick 7:16 am on May 8, 2015 Permalink | Reply
    Tags: , , , , Nanotechnology   

    From MIT: “Plugging up leaky graphene” 


    MIT News

    May 8, 2015
    Jennifer Chu

    1
    In a two-step process, engineers have successfully sealed leaks in graphene. First, the team fabricated graphene on a copper surface (top left) — a process that can create intrinsic defects in graphene, shown as cracks on the surface. After lifting the graphene and depositing it on a porous surface (top right), the transfer creates further holes and tears. In a first step (bottom left), the team used atomic layer deposition to deposit hafnium (in gray) to seal intrinsic cracks, then plugged the remaining holes (bottom left) with nylon (in red), via interfacial polymerization.
    Courtesy of the researchers.

    For faster, longer-lasting water filters, some scientists are looking to graphene —thin, strong sheets of carbon — to serve as ultrathin membranes, filtering out contaminants to quickly purify high volumes of water.

    Graphene’s unique properties make it a potentially ideal membrane for water filtration or desalination. But there’s been one main drawback to its wider use: Making membranes in one-atom-thick layers of graphene is a meticulous process that can tear the thin material — creating defects through which contaminants can leak.

    Now engineers at MIT, Oak Ridge National Laboratory, and King Fahd University of Petroleum and Minerals (KFUPM) have devised a process to repair these leaks, filling cracks and plugging holes using a combination of chemical deposition and polymerization techniques. The team then used a process it developed previously to create tiny, uniform pores in the material, small enough to allow only water to pass through.

    Combining these two techniques, the researchers were able to engineer a relatively large defect-free graphene membrane — about the size of a penny. The membrane’s size is significant: To be exploited as a filtration membrane, graphene would have to be manufactured at a scale of centimeters, or larger.

    In experiments, the researchers pumped water through a graphene membrane treated with both defect-sealing and pore-producing processes, and found that water flowed through at rates comparable to current desalination membranes. The graphene was able to filter out most large-molecule contaminants, such as magnesium sulfate and dextran.

    Rohit Karnik, an associate professor of mechanical engineering at MIT, says the group’s results, published in the journal Nano Letters, represent the first success in plugging graphene’s leaks.

    “We’ve been able to seal defects, at least on the lab scale, to realize molecular filtration across a macroscopic area of graphene, which has not been possible before,” Karnik says. “If we have better process control, maybe in the future we don’t even need defect sealing. But I think it’s very unlikely that we’ll ever have perfect graphene — there will always be some need to control leakages. These two [techniques] are examples which enable filtration.”

    Sean O’Hern, a former graduate research assistant at MIT, is the paper’s first author. Other contributors include MIT graduate student Doojoon Jang, former graduate student Suman Bose, and Professor Jing Kong.

    A delicate transfer

    “The current types of membranes that can produce freshwater from saltwater are fairly thick, on the order of 200 nanometers,” O’Hern says. “The benefit of a graphene membrane is, instead of being hundreds of nanometers thick, we’re on the order of three angstroms — 600 times thinner than existing membranes. This enables you to have a higher flow rate over the same area.”

    O’Hern and Karnik have been investigating graphene’s potential as a filtration membrane for the past several years. In 2009, the group began fabricating membranes from graphene grown on copper — a metal that supports the growth of graphene across relatively large areas. However, copper is impermeable, requiring the group to transfer the graphene to a porous substrate following fabrication.

    However, O’Hern noticed that this transfer process would create tears in graphene. What’s more, he observed intrinsic defects created during the growth process, resulting perhaps from impurities in the original material.

    Plugging graphene’s leaks

    To plug graphene’s leaks, the team came up with a technique to first tackle the smaller intrinsic defects, then the larger transfer-induced defects. For the intrinsic defects, the researchers used a process called “atomic layer deposition,” placing the graphene membrane in a vacuum chamber, then pulsing in a hafnium-containing chemical that does not normally interact with graphene. However, if the chemical comes in contact with a small opening in graphene, it will tend to stick to that opening, attracted by the area’s higher surface energy.

    The team applied several rounds of atomic layer deposition, finding that the deposited hafnium oxide successfully filled in graphene’s nanometer-scale intrinsic defects. However, O’Hern realized that using the same process to fill in much larger holes and tears — on the order of hundreds of nanometers — would require too much time.

    Instead, he and his colleagues came up with a second technique to fill in larger defects, using a process called “interfacial polymerization” that is often employed in membrane synthesis. After they filled in graphene’s intrinsic defects, the researchers submerged the membrane at the interface of two solutions: a water bath and an organic solvent that, like oil, does not mix with water.

    In the two solutions, the researchers dissolved two different molecules that can react to form nylon. Once O’Hern placed the graphene membrane at the interface of the two solutions, he observed that nylon plugs formed only in tears and holes — regions where the two molecules could come in contact because of tears in the otherwise impermeable graphene — effectively sealing the remaining defects.

    Using a technique they developed last year, the researchers then etched tiny, uniform holes in graphene — small enough to let water molecules through, but not larger contaminants. In experiments, the group tested the membrane with water containing several different molecules, including salt, and found that the membrane rejected up to 90 percent of larger molecules. However, it let salt through at a faster rate than water.

    The preliminary tests suggest that graphene may be a viable alternative to existing filtration membranes, although Karnik says techniques to seal its defects and control its permeability will need further improvements.

    “Water desalination and nanofiltration are big applications where, if things work out and this technology withstands the different demands of real-world tests, it would have a large impact,” Karnik says. “But one could also imagine applications for fine chemical- or biological-sample processing, where these membranes could be useful. And this is the first report of a centimeter-scale graphene membrane that does any kind of molecular filtration. That’s exciting.”

    De-en Jiang, an assistant professor of chemistry at the University of California at Riverside, sees the defect-sealing technique as “a great advance toward making graphene filtration a reality.”

    “The two-step technique is very smart: sealing the defects while preserving the desired pores for filtration,” says Jiang, who did not contribute to the research. “This would make the scale-up much easier. One can produce a large graphene membrane first, not worrying about the defects, which can be sealed later.”

    This research was supported in part by the Center for Clean Water and Clean Energy at MIT and KFUPM, the U.S. Department of Energy, and the National Science Foundation.

    See the full article here.

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