Monday, June 30, 2008

'Nanoglassblowing' seen as boon to study of individual molecules

Schematic of a T-junction nanofluidic device

Caption: Left: Schematic of a T-junction nanofluidic device with a "nanoglassblown" funnel-shaped entrance to a nanochannel. The funnel tapers down to 150 micrometers (about the diameter of a human hair) at the nanochannel entrance. Right: Photomicrograph of the T-junction with the first section of the nanochannel visible at the bottom. The colors are a white light interference pattern caused by the changing depth of the curved glass funnel. Credit: Credit: Elizabeth Strychalski, Cornell University. Usage Restrictions: None.
While the results may not rival the artistry of glassblowers in Europe and Latin America, researchers at the National Institute of Standards and Technology (NIST) and Cornell University have found beauty in a new fabrication technique called "nanoglassblowing" that creates nanoscale (billionth of a meter) fluidic devices used to isolate and study single molecules in solution—including individual DNA strands. The novel method is described in a paper posted online next week in the journal Nanotechnology.*
Traditionally, glass micro- and nanofluidic devices are fabricated by etching tiny channels into a glass wafer with the same lithographic procedures used to manufacture circuit patterns on semiconductor computer chips. The planar (flat-edged) rectangular canals are topped with a glass cover that is annealed (heated until it bonds permanently) into place. About a year ago, the authors of the Nanotechnology paper observed that in some cases, the heat of the annealing furnace caused air trapped in the channel to expand the glass cover into a curved shape, much like glassblowers use heated air to add roundness to their work. The researchers looked for ways to exploit this phenomenon and learned that they could easily control the amount of "blowing out" that occurred over several orders of magnitude.

As a result, the researchers were able to create devices with "funnels" many micrometers wide and about a micrometer deep that tapered down to nanochannels with depths as shallow as 7 nanometers—approximately 1,000 times smaller in diameter than a red blood cell. The nanoglassblown chambers soon showed distinct advantages over their planar predecessors.

"In the past, for example, it was difficult to get single strands of DNA into a nanofluidic device for study because DNA in solution balls up and tends to bounce off the sharp edges of planar channels with depths smaller than the ball," says Cornell's Elizabeth Strychalski. "The gradually dwindling size of the funnel-shaped entrance to our channel stretches the DNA out as it flows in with less resistance, making it easier to assess the properties of the DNA," adds NIST's Samuel Stavis.

Future nanoglassblown devices, the researchers say, could be fabricated to help sort DNA strands of different sizes or as part of a device to identify the base-pair components of single strands. Other potential applications of the technique include the manufacture of optofluidic elements—lenses or waveguides that could change how light is moved around a microchip—and rounded chambers in which single cells could be confined and held for culturing. ###

This work was supported in part by Cornell's Nanobiotechnology Center, part of the National Science Foundation's Science and Technology Center Program. It was performed while Samuel Stavis held a National Research Council Research Associateship Award at NIST.

* E.A. Strychalski, S.M. Stavis and H.G. Craighead. Non-planar nanofluidic devices for single molecule analysis fabricated using nanoglassblowing. Nanotechnology, Posted online the week of June 15, 2008.

Contact: Michael E. Newman michael.newman@nist.gov 301-975-3025 National Institute of Standards and Technology (NIST)

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Sunday, June 29, 2008

Microwave synthesis connects with the (quantum) dots

luminescent, water soluble quantum dots

Caption: Brightly glowing vials of highly luminescent, water soluble quantum dots produced by the new NIST microwave process span a wavelength range from 500 to 600 nm. Credit: NIST. Usage Restrictions: None.
Materials researchers at the National Institute of Standards and Technology (NIST) have developed a simplified, low-cost process for producing high-quality, water-soluble "quantum dots" for biological research. By using a laboratory microwave reactor to promote the synthesis of the widely used nanomaterials, the recently published* NIST process avoids a problematic step in the conventional approach to making quantum dots, resulting in brighter, more stable dots.
Quantum dots are specially engineered nanoscale crystals of semiconductor compounds. The name comes from the fact that their infinitesimal size enables a quantum electronics effect that causes the crystals to fluoresce brilliantly at specific, sharply defined colors. Bright, stable, tiny and tunable across a broad spectrum of colors, quantum dots that are engineered to attach themselves to particular proteins have become a popular research tool in areas such as cancer research for detecting, labeling and tracking specific biomarkers and cells.

Making good quantum dots for biological research is complex. First a semiconductor compound—typically a mixture of cadmium and selenium—must be induced to crystallize into discrete nanocrystals of just the right size. Cadmium is toxic, and the compound also can oxidize easily (ruining the effect), so the nanocrystals must be encapsulated in a protective shell such as zinc sulfide. To make them water soluble for biological applications, a short organic molecule called a "ligand" is attached to the zinc atoms. The organic ligand also serves as a tether to attach additional functional molecules that cause the dot to bind to specific proteins.

The accepted commercial method uses a high-temperature reaction (about 300 degrees Celsius) that must be carefully controlled under an inert gas atmosphere for the crystallization and encapsulation stages. An intermediate ligand material that can tolerate the high temperature is used to promote the crystallization process, but it must be chemically swapped afterwards for a different compound that makes the material water soluble. The ligand exchange step—as well as several variations on the process—is known to significantly alter the luminescence and stability of the resulting quantum dots.

Seeking a better method, NIST researchers turned to microwave-assisted chemistry. Microwaves have been employed in a variety of chemical reactions to reduce the required times and temperatures. Working at temperatures half those of commercial processes, the group developed a relatively simple two-stage process that requires no special atmospheric conditions and directly incorporates the water-soluble ligand into the shell without an exchange step. Using commercially available starting materials, they have synthesized highly uniform and efficient quantum dots for a range of frequencies and shown them to be stable in aqueous solutions for longer than four months. ###

* M.D. Roy, A.A. Herzing, S.H. De Paoli Lacerda and M,L. Becker. Emission-tunable microwave synthesis of highly luminescent water soluble CdSe/ZnS quantum dots. Chemical Communications, 2008, 2106-2108.

Contact: Michael Baum michael.baum@nist.gov 301-975-2763 National Institute of Standards and Technology (NIST)

Saturday, June 28, 2008

Northwestern Chemist Investigates Lost Reds In Homer Painting

Winslow Homer For to Be a Farmer's Boy

Winslow Homer American, 1836-1910 For to Be a Farmer's Boy, 1887 Transparent and opaque watercolor, with rewetting, blotting, and scraping, heightened with gum glaze, over graphite, on thick, rough-textured ivory wove paper (lower edge trimmed) 355 x 509 mm Signed recto, lower right, in black watercolor: "Winslow Homer/1887" [over old signature, blotted out: "Winslow Homer/1887"] Gift of Mrs. George T. Langhorne in memory of Edward Carson Waller, 1963.760
EVANSTON, Ill. --- More than 30 years ago, when Northwestern University chemist Richard Van Duyne developed a powerful new sensing technique, he never thought he would be using it to learn more about treasures in the Art Institute of Chicago’s collection -- including a watercolor recently featured in the museum’s exhibition “Watercolors by Winslow Homer: The Color of Light.”

In Homer’s watercolor “For to be a Farmer’s Boy,” painted in 1887, some of the red and yellow pigments have faded in the sky, leaving that area virtually without color.
Van Duyne, Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, is working with Francesca Casadio, a conservation scientist at the Art Institute, to determine what the original colors were.

To solve this mystery, they are using surface enhanced Raman spectroscopy (SERS), the analytical technique pioneered by Van Duyne in 1977. SERS uses laser light and nanoparticles of precious metals to interact with molecules to show the chemical make-up of a particular dye.

SERS is a variation of Raman spectroscopy, a widely used technique first developed in the 1920s. What sets SERS apart is its ability to analyze extremely minute samples of organic dyes; some samples are so small they cannot be seen by the naked eye.

Organic dyes are natural substances that were used to color artworks created before the introduction of synthetic dyes in the late 1800s and 1900s. That’s a lot of art -- from Egyptian textiles to Renaissance tapestries to Impressionist paintings and beyond.

Because red dyes are easily damaged by light and fluoresce when probed with conventional Raman spectroscopy but not by SERS, Van Duyne and Casadio have been focusing on organic red dyes in particular, working to identify those used in Homer’s painting as well as in a variety of textiles, such as a 16th century carpet from Istanbul and a rare textile fragment from Peru, dated from 800 to 1350 A.D.

“Our research provides an entirely new window onto the analysis of artworks,” said Van Duyne. “There’s a broad range of physical science methods used in the conservation business. The trick is you can’t harm the work -- the method has to be non-destructive or minimally destructive. Conservators do a lot of work with X-ray photography and infrared photography, but those techniques don’t tell you what elements are present. The Raman technique tells you about what molecules are there.”

In preparing for the Art Institute’s major Homer exhibition, conservators discovered, using X-ray fluorescence spectrometry and visual examination through a microscope, that the painting’s white skies were originally painted in unstable red and orange dyes that have almost completely faded.

In discerning the painting’s original colors, Van Duyne’s team must figure out a reliable way of preparing microscopic watercolor samples for SERS analysis. In the end, Art Institute conservators won’t repaint the original skies but, in conjunction with the Homer exhibition, they created a digital image that offers viewers an idea of the artist’s intentions. (View the digital simulation of “For to be a Farmer’s Boy” at artic.edu/collections/exhibitions/homer/.)

Van Duyne says that conservation scientists are unlocking the secrets of dye and pigment analysis, and that in the future such analysis will help conservators determine forgery, authenticity, exact provenance and best restoration methods. “If we have a better idea about which materials are used in paintings, for instance, we’ll have a better idea of how to restore them. Just identifying what’s involved is a very important step."

The work, which also has involved a number of Northwestern students, is part of a long-term collaboration between Northwestern and the Art Institute that focuses on scientific research in the field of art conservation.

This story was adapted from the article “Conserving Masterpieces: Today’s Chemists Penetrate Mysteries of Yesterday’s Art” by Lisa Stein that appeared in the fall/winter 2007-08 issue of CrossCurrents, a publication of the Weinberg College of Arts and Sciences.

Contact: Megan Fellman fellman@northwestern.edu 847-491-3115 Northwestern University

Friday, June 27, 2008

Livermore researchers use carbon nanotubes for molecular transport

FAST FLOW THROUGH CARBON NANOTUBES

The depiction of the water flow through a regular "rough" pipe. The molecules near the wall stick to it and move much slower than the molecules in the middle of the pipe.

They do not stick to the surface of the nanotube because that surface is very slippery. The water molecules travel in chains because they interact with each other strongly via hydrogen bonds. These two effects (the slippery nanotube surface and formation of water molecule chains inside the nanotube) combine to produce this phenomenon of ultra-fast flow through carbon nanotubes.
LIVERMORE, Calif. – Molecular transport across cellular membranes is essential to many of life’s processes, for example electrical signaling in nerves, muscles and synapses.

In biological systems, the membranes often contain a slippery inner surface with selective filter regions made up of specialized protein channels of sub-nanometer size. These pores regulate cellular traffic, allowing some of the smallest molecules in the world to traverse the membrane extremely quickly, while at the same time rejecting other small molecules and ions.
Researchers at Lawrence Livermore National Laboratory are mimicking that process with manmade carbon nanotube membranes, which have pores that are 100,000 times smaller than a human hair, and were able to determine the rejection mechanism within the pores.

“Hydrophobic, narrow diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robust platform,” said Olgica Bakajin, who led the LLNL team whose study appeared in the June 6 online edition of the journal Proceedings of the National Academy of Sciences.

In the initial discovery, reported in the May 19, 2006 issue of the journal Science, the LLNL team found that water molecules in a carbon nanotube move fast and do not stick to the nanotube’s super smooth surface, much like water moves through biological channels. The water molecules travel in chains – because they interact with each other strongly via hydrogen bonds.

“You can visualize it as mini-freight trains of chain-bonded water molecules flying at high speed through a narrow nanotube tunnel,” said Hyung Gyu Park, an LLNL postdoctoral researcher and a team member.

One of the most promising applications for carbon nanotube membranes is sea water desalination. These membranes will some day be able to replace conventional membranes and greatly reduce energy use for desalination.

In the recent study, the researchers wanted to find out if the membranes with 1.6 nanometer (nm) pores reject ions that make up common salts. In fact, the pores did reject the ions and the team was able to understand the rejection mechanism.

“Our study showed that pores with a diameter of 1.6nm on the average, the salts get rejected due to the charge at the ends of the carbon nanotubes,” said Francesco Fornasiero, an LLNL postdoctoral researcher, team member and the study’s first author

Fast flow through carbon nanotube pores makes nanotube membranes more permeable than other membranes with the same pore sizes. Yet, just like conventional membranes, nanotube membranes exclude ions and other particles due to a combination of small pore size and pore charge effects.

“While carbon nanotube membranes can achieve similar rejection as membranes with similarly sized pores, they will provide considerably higher permeability, which makes them potentially much more efficient than the current generation of membranes,” said Aleksandr Noy, a senior member of the LLNL team.

Researchers will be able to build better membranes when they can independently change pore diameter, charge and material that fills gaps between carbon nanotubes.

Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.

Contact: Anne Stark stark8@llnl.gov 925-422-9799 DOE/Lawrence Livermore National Laboratory

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Thursday, June 26, 2008

Gene silencer and quantum dots reduce protein production to a whisper

Quantum dots, suspended in liquid

Caption: Each of these jars contains the same substance. The difference is the size of the particles. Quantum dots, suspended in liquid, absorb white light and then reemit it in a specific color that depends on the particle's size. Each quantum dot is about one ten-millionth of an inch in diameter and is composed of a few hundred atoms of material. Credit: Xiaohu Gao, University of Washington. Usage Restrictions: None.
More than 15 years ago scientists discovered a way to stop a particular gene in its tracks. The Nobel Prize-winning finding holds tantalizing promise for medical science, but so far it has been difficult to apply the technique, known as RNA interference, in living cells.

Now scientists at the University of Washington in Seattle and Emory University in Atlanta have succeeded in using nanotechnology known as quantum dots to address this problem.
Their technique is 10 to 20 times more effective than existing methods for injecting the gene-silencing tools, known as siRNA, into cells.

"We believe this is going to make a very important impact to the field of siRNA delivery," said Xiaohu Gao, a UW assistant professor of bioengineering and co-author of a study published online this week in the Journal of the American Chemical Society.
quantum dot-siRNA complex

Caption: A fluorescent image of the cell taken 15 minutes after introducing the quantum dot-siRNA complex. At this early stage the particles are in the cell membrane. Credit: University of Washington. Usage Restrictions: None.
"This work helps to overcome the longstanding barrier in the siRNA field: How to achieve high silencing efficiency with low toxicity," said co-author Shuming Nie, a professor in the Wallace H. Coulter Department of Biomedical Engineering, jointly affiliated with the Georgia Institute of Technology and Emory University.

Other co-authors are Maksym Yezhelyev and Ruth O'Regan at Emory and Lifeng Qi at the UW.
Short pieces of RNA, the working copy of DNA, can disable production of a protein by silencing, or deactivating, a stretch of genetic code. Research laboratories regularly use the technique to figure out what a particular gene does. In the body, RNA interference could be used to treat conditions ranging from breast cancer to deteriorating eyesight.
quantum dot-siRNA complex

Caption: A fluorescent image of the cell taken four hours into the same experiment. At this time the quantum dot-siRNA complex is distributed throughout the cellular fluid. The dark region in the middle of the cell is the nucleus. Credit: University of Washington. Usage Restrictions: None.
The recent experiments used quantum dots, fluorescent balls of semiconductor material just six nanometers across (lining up 9,000 dots end to end would equal the width of a human hair). Quantum dots' unique optical properties cause them to emit light of different colors depending on their size. The dots are being developed for cellular imaging, solar cells and light-emitting diodes.

This paper describes one of the first applications of quantum dots to drug delivery.
Each quantum dot was surrounded by a proton sponge that carried a positive charge. Without any quantum dots attached, the siRNA's negative charge would prevent it from penetrating a cell's wall. With the quantum-dot chaperone, the more weakly charged siRNA complex crosses the cellular wall, escapes from the endosome (a fatty bubble that surrounds incoming material) and accumulates in the cellular fluid, where it can do its work disrupting protein manufacture.

Key to the newly published approach is that researchers can adjust the chemical makeup of the quantum dot's proton-sponge coating, allowing the scientists to precisely control how tightly the dots attach to the siRNA.

Quantum dots were dramatically better than existing techniques at stopping gene activity. In experiments, a cell's production of a test protein dropped to 2 percent when siRNA was delivered with quantum dots. By contrast, the test protein was produced at 13 percent to 51 percent of normal levels when the siRNA was delivered with one of three commercial reagents, or reaction-causing substances, now commonly used in laboratories.

Central to the finding is that fluorescent quantum dots allow scientists to watch the siRNA's movements. Previous siRNA trackers gave off light for less than a minute, while quantum dots, developed for imaging, emit light for hours at a time. In the experiments the authors were able to watch the process for many hours to track the gene-silencer's path.

The new approach is also five to 10 times less toxic to the cell than existing chemicals, meaning the quantum dot chaperones are less likely to harm cells. The ideal delivery vehicle would have no effect; the only biological change would be siRNA blocking cells' production of an unwanted protein.

The exact reason that the quantum dots were more effective than previous techniques is, however, still a mystery.

"We believe the improvement is caused by the endosome escape, and the ability of the quantum dots to separate from the siRNA," Gao said.

Quantum dots are not yet approved for use in humans. The authors are now transferring their techniques to particles of iron oxide, several types of which have been approved by the Food and Drug Administration for use in humans. They are also working to target cancer cells by attaching to specific markers on the cells' surface. "Looking forward, this work will have important implications in in-vivo siRNA therapeutics, which will require the use of nontoxic iron oxide and biodegradable polymeric carriers rather than quantum dots," Nie said. ###

The research was funded by grants from the National Institutes of Health, the National Science Foundation and the Georgia Cancer Coalition.

For more information, contact Gao at (206) 543-6562 or xgao@u.washington.edu and Nie at (404) 712-8595, (404) 727-0391 or snie@emory.edu.

RELATED:

Contact: Hannah Hickey hickeyh@u.washington.edu 206-543-2580 University of Washington

Wednesday, June 25, 2008

Stripes key to nanoparticle drug delivery

striped nanoparticles

MIT researchers have created 'striped' nanoparticles capable of entering a cell without rupturing it. In the background of this cartoon are cells that have taken up nanoparticles carrying fluorescent imaging agents Image courtesy / Francesco Stellacci, Darrell Irvine and colleagues, MIT
Work could also explain biological mystery

CAMBRIDGE, Mass.--In work that could at the same time impact the delivery of drugs and explain a biological mystery, MIT engineers have created the first synthetic nanoparticles that can penetrate a cell without poking a hole in its protective membrane and killing it.

The key to their approach? Stripes.

The team found that gold nanoparticles coated with alternating bands of two different kinds of molecules can quickly pass into cells without harming them, while those randomly coated with the same materials cannot. The research was reported in a recent advance online publication of Nature Materials.
"We've created the first fully synthetic material that can pass through a cell membrane without rupturing it, and we've found that order on the nanometer scale is necessary to provide this property," said Francesco Stellacci, an associate professor in the Department of Materials Science and Engineering and co-leader of the work with Darrell Irvine, the Eugene Bell Career Development Associate Professor of Tissue Engineering.

In addition to the practical applications of such nanoparticles for drug delivery and more-the MIT team used them to deliver fluorescent imaging agents to cells-the tiny spheres could help explain how some biological materials such as peptides are able to enter cells.

"No one understands how these biologically derived cell-penetrating materials work," said Irvine. "So we could use the new particles to learn more about their biological counterparts. Could they be analogues of the biological system?"

When a cell membrane recognizes a foreign object such as a nanoparticle, it normally wraps around or "eats" it, encasing the object in a smaller bubble inside the cell that can eventually be excreted. Any drugs or other agents attached to the nanoparticle therefore never reach the main fluid section of the cell, or cytosol, where they could have an effect.

Such nanoparticles can also be "chaperoned" by biological molecules into the cytosol, but this too has drawbacks. Chaperones can work in some cells but not others, and carry one cargo but not another.

Hence the importance of the MIT work in developing nanoparticles that can directly penetrate the cell membrane, deliver their cargo to the cytosol, and do so without killing the cell.

Irvine compares the feat to a phenomenon kids can discover. "If you have a soap film and you poke it with a bubble wand, you'll pop it," he said. "But if you coat the bubble wand with soap before poking the film, it will pass through the film without popping it because it's coated with the same material." Stellacci notes that the coated nanoparticles have properties similar to the cell membrane-not identical-but the analogy is still apt.

Stellacci first reported the creation of the striped nanoparticles in a 2004 Nature Materials paper. At the time, "we noticed that they interacted with proteins in an interesting way," he said. "Could they also have interesting interactions with cells?" Four years later, he and his colleagues report a resounding "yes." ###

Stellacci and Irvine's coauthors are Ayush Verma, Oktay Uzun, Ying Hu and Suelin Chen of the Department of Materials Science and Engineering (MSE); Yuhua Hu of the Department of Chemical Engineering; Hee-Sun Han of the Department of Chemistry, and Nicky Watson of the Department of Biology.

Irvine has appointments in the Department of Biological Engineering and MSE, and is a member of the David H. Koch Institute for Integrative Cancer Research at MIT. He was recently named a Howard Hughes Medical Institute investigator.

The research was funded in part by the NSF, the NIH and the Packard Foundation.

Written by Elizabeth Thomson, MIT News Office

A version of this article appeared in MIT Tech Talk on June 11, 2008 (download PDF).

Contact: Elizabeth Thomson thomson@mit.edu 617-258-5402 Massachusetts Institute of Technology

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Tuesday, June 24, 2008

Microspheres to carry hydrogen, deliver drugs, filter gases and detect nuclear development

A Microballoon and its Contents

Caption: SRNL researchers removed the top of a glass microsphere to show how palladium has easily passed through the sphere's pores and assembled itself into a new nanostructure. Credit: Savannah River National Lab, American Ceramic Society. Usage Restrictions: None.
Savannah River researchers unveil permeable, pourable glass 'microballoons'

WESTERVILLE, OH – What looks like a fertilized egg, flows like water, gets stuffed with catalysts and exotic nanostructures and may have the potential of making the current retail gasoline infrastructure compatible with hydrogen-based vehicles of the future – not to mention also contributing to arenas such as nuclear proliferation and global warming?
The answer is contained in the June issue of The Bulletin, the monthly magazine of The American Ceramic Society, which carries the first news of a never-before-seen class of materials and technology developed by scientists at the Savannah River National Laboratory. (The full article can be downloaded in PDF format at ceramics.org/.)
hollow glass microspheres

Caption: Unique nanostructures have been grown on both the interior and exterior of the hollow glass microspheres. Credit: Savannah River National Lab, American Ceramic Society. Usage Restrictions: None.
This unique material, dubbed Porous Wall-Hollow Glass Microspheres (PW-HGM), consists of porous glass 'microballoons' that are smaller than the diameter of a human hair. The key characteristic of these 2-100 micron spheres is an interconnected porosity in their thin outer walls that can be produced and varied on a scale of 100 to 3,000 Angstroms.

SRNL Researchers G.G. Wicks, L.K. Heung, and R.F. Schumacher have been able to use these open channels to fill the microballons with gas absorbents and other materials.
Hydrogen or other reactive gases can then enter the microspheres through the pores, creating a relatively safe, contained, solid-state storage system.

Photographs of these glass-absorbent composites also reveal that the wall porosity generates entirely new nano-structures.

Wicks, Heung and Schumacher have shown that the PW-HGM's permeable walls can be used for non-composite purposes, too. For example, the porosity can be altered and controlled in various ways that allow the spheres to filter mixed gas streams within a system.
representation of microsphere wall porosity

Caption: Schematic representation of microsphere wall porosity. Credit: Savannah River National Lab, American Ceramics Society. Usage Restrictions: None.
Another feature of the microballoons is that their mechanical properties can be altered so they can be made to flow like a liquid. This suggests that an existing infrastructure that currently transports, stores and distributes liquids such as the existing gasoline distribution and retail network can be used. This property and their relative strength also make the PW-HGMs suitable for reuse and recycling.
The SRNL team is involved in more than a half dozen programs and collaborations involving the PW-HGMs in areas such as hydrogen storage in vehicles (Toyota), gas purification and separations, and even very diverse applications including abatement of global warming effects, improving lead-acid battery performance and nuclear non-proliferation. Applications such as the development of new drug delivery systems and MRI contrast agents are also blossoming in the medical field (Medical College of Georgia). ###

Founded in 1898, The American Ceramics Society is the professional membership organization for international ceramics and materials scientists, engineers, researchers, manufacturers, plant personnel, educators, students. Drawing members from 60 countries, ACerS serves the informational, educational, and professional needs of its 6,000 members and provides them with access to periodicals and books, meetings and expositions, and online technical information. Besides The Bulletin, ACerS publishes the peer-reviewed Journal of the American Ceramic Society and the International Journal of Applied Ceramic Technology, two of the most cited ceramic publications in the world.

Contact: Peter Wray pwray@ceramics.org 614-794-5853 The American Ceramics Society

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Monday, June 23, 2008

GE Energy to market SNS-developed detector electronics system

Neutron science research at Oak Ridge National LaboratoryOAK RIDGE, Tenn., June 3, 2008 -- GE Energy, manufacturer of Reuter Stokes radiation detection equipment, has signed a technology transfer agreement to market the electronics and software associated with the SNS 8Pack neutron detector system, an award-winning design for a system of sensitive neutron detectors developed at Oak Ridge National Laboratory.
The SNS 8Pack is a compact neutron detection system that was developed for the Department of Energy's Spallation Neutron Source, a record-setting neutron science facility located at ORNL. The SNS electronics can determine both the time and position of the neutron captured, enabling very accurate neutron time-of-flight measurements. It has large-area detector coverage, extremely low power requirements and digital communication capability.

"It is exciting that, even as the SNS ramps up to its full power of 1.4 megawatts, technologies from its development are already finding their way to the marketplace," said ORNL Director Thom Mason.

"Combining GE's expertise in designing detectors for neutron scattering instruments with the high-speed electronics and software developed by SNS is a natural fit," said Leo VanderSchuur, Product Line General Manager for GE Energy's Reuter Stokes Measurement Solutions. "This state-of-the-art design will benefit the neutron scattering community with high-speed performance and advanced time-of-flight capabilities."

SNS engineers developed the electronics and software for the integrated detector system to accommodate the very large detector areas and high rates required by the SNS. Interest in the product for commercial applications has ranged from other neutron science facilities to security applications, such as monitoring land, air and sea shipping.

"The system is modular so that very large detector arrays can be built. You can have greater than 50 square meters of detector coverage," said Ron Cooper, a member of the SNS development team. "It has high rate capability, good position resolution, and features modern, distributed personal-computer-based electronics."

Another attractive feature is its very lower power requirement. "The SNS 8Pack requires very little power to operate; less than 10 watts. In fact, it can be powered by a small solar panel," said Cooper, of ORNL's Neutron Facilities Development Division. ###

The 8Pack technology development was funded by the DOE Office of Science's Basic Energy Science program. Developed by Cooper, Richard Riedel of ORNL's Neutron Scattering Science Division and Lloyd Clonts of ORNL's Measurement Science and Systems Engineering Division, the solar power version called Pharos won an R&D 100 award in 2007 as one of the year's top technologies as determined by R&D Magazine.

ORNL is managed by UT-Battelle for the Department of Energy.

GE Energy (www.ge.com/energy) is one of the world's leading suppliers of power generation and energy delivery technologies, with 2007 revenue of $22 billion. Based in Atlanta, Ga., GE Energy works in all areas of the energy industry including coal, oil, natural gas and nuclear energy; renewable resources such as water, wind, solar and biogas; and other alternative fuels.

NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at www.ornl.gov/news.

Contact: Bill Cabage cabagewh@ornl.gov 865-574-4399 DOE/Oak Ridge National Laboratory

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Sunday, June 22, 2008

Microrobotic Ballet VIDEO



Microrobotic Ballet, Tiny robots dance on a stage one millimeter square.
Duke computer science professor and colleagues' creations dance on something smaller than a pin's head

Microscopic robots crafted to maneuver separately without any obvious guidance are now assembling into self-organized structures after years of continuing research led by a Duke University computer scientist.


"It's marvelous to be able to do assembly and control at this fine a resolution with such very, very tiny things," said Bruce Donald, a Duke professor of computer science and biochemistry.

Each microrobot is shaped something like a spatula but with dimensions measuring just microns, or millionths of a meter. They are almost 100 times smaller than any previous robotic designs of their kind and weigh even less, Donald added.

Formally known as microelectromechanical system (MEMS) microrobots, the devices are of suitable scale for Lilliputian tasks such as moving around the interiors of laboratories-on-a-chip.

In videos produced by the team, two microrobots can be seen pirouetting to the music of a Strauss waltz on a dance floor just 1 millimeter across. In another sequence, the devices pivot in a precise fashion whenever their boom-like steering arms are drawn down to the surface by an electric charge. This response resembles the way dirt bikers turn by extending a boot heel.

New research summaries describe the group’s latest accomplishment: getting five of the devices to group-maneuver in cooperation under the same control system.

“Our work constitutes the first implementation of an untethered, multi-microrobotic system,” Donald's team writes in a report to be presented on June 1-2, 2008 during the Hilton Head Workshop on Solid State Sensors, Actuators and Microsystems in South Carolina.

More comprehensive details on how the scientists achieve this “microassembly” will be published later in their report for the Journal of Microelectromechanical Systems.

The research was funded by the National Institutes of Health and the Department of Homeland Security, and also included Donald’s graduate student Igor Paprotny and Dartmouth College engineering professor Christopher Levey.

Donald has been working on various versions of the MEMS microrobots since 1992, initially at Cornell and then at Stanford and Dartmouth before coming to Duke. The first versions were arrays of microorganism-mimicking ciliary arms that could “move objects such as microchips on top of them in the same way that a singer in a rock band will crowd surf,” he said. “We made 15,000 silicon cilia in a square inch.”

A February 2006 report in the Journal of Microelectromechanical Systems by Donald, Paprotny, Levey and others detailed the basics of the current design: devices about 60 microns wide, 250 microns long and 10 microns high that each run off power scavenged from an electrified surface.

Propelling themselves across such surfaces in an inchworm-like fashion impelled by a “scratch-drive” motion actuator, the microrobots advance in steps only 10 to 20 billionths of a meter each, but repeated as often as 20,000 times a second.

The microrobots can be so small because they are not encumbered by leash-like tethers attached to an external control system. Built with microchip fabrication techniques, they are each designed to respond differently to the same single “global control signal” as voltages charge and discharge on their working parts.

This global control is akin to ways proteins in cells respond to chemical signals, said Donald, who also uses computer algorithms to study processes in biochemistry and biology.

In their new reports, the team shows that five of the microrobots can be made to advance, turn and circle together in pre-planned ways when each is built with slightly different dimensions and stiffness.

Following a choreography mapped out with the aid of mathematics, the microdevices ultimately assemble into group micro-huddles that could set the stage for something more elaborate.

“Initially, we wanted to build something like a car that could drive around at the microscopic scale," Donald said. “Now what we’ve been able to do is create the first microscopic traffic jam.”

He said it took him and various colleagues from 1997 to 2002 to create a microrobot that can operate without a tether, three more years to make the devices steer under global control, and another three to independently maneuver more than one at a time.

“The hard thing was designing how multiple microrobots can all work independently, even while they receive the same power and control,” he said.

Donald and other Duke researchers are now thinking of trying to enlist the maneuverable microrobots to insert tiny, billionths-of-a-meter electrodes called nanotubes into neural cells. The research will be supported by the Duke Institute for Brain Sciences.

Contact: Monte Basgall monte.basgall@duke.edu 919-681-8057 Duke University

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Saturday, June 21, 2008

Research measures movement of nanomaterials in simple model food chain

Photomicrograph of ciliate T. pyriformis

Caption: Photomicrograph of ciliate T. pyriformis during cell division with accumulated quantum dots appearing red. Credit: NIST. Usage Restrictions: None.
New research* shows that while engineered nanomaterials can be transferred up the lowest levels of the food chain from single celled organisms to higher multicelled ones, the amount transferred was relatively low and there was no evidence of the nanomaterials concentrating in the higher level organisms. The preliminary results observed by researchers from the National Institute of Standards and Technology (NIST) suggest that the particular nanomaterials studied may not accumulate in invertebrate food chains.
The same properties that make engineered nanoparticles attractive for numerous applications—biological and environmental stability, small size, solubility in aqueous solutions and lack of toxicity to whole organisms—also raise concerns about their long-term impact on the environment. NIST researchers wanted to determine if nanoparticles could be passed up a model food chain and if so, did the transfer lead to a significant amount of bioaccumulation (the increase in concentration of a substance in an organism over time) and biomagnification (the progressive buildup of a substance in a predator organism after ingesting contaminated prey).
Closeup photomicrograph of rotifer B. calyciflorus

Caption: Closeup photomicrograph of rotifer B. calyciflorus (whole organism seen in upper left corner) with quantum dots assimilated from ingested ciliates appearing red. Credit: NIST. Usage Restrictions: None.
In their study, the NIST team investigated the dietary accumulation, elimination and toxicity of two types of fluorescent quantum dots using a simple, laboratory-based food chain with two microscopic aquatic organisms—Tetrahymena pyriformis, a single-celled ciliate protozoan, and the rotifer Brachionus calyciflorus that preys on it. The process of a material crossing different levels of a food chain from prey to predator is called "trophic transfer."
Quantum dots are nanoparticles engineered to fluoresce strongly at specific wavelengths. They are being studied for a variety of uses including easily detectable tags for medical diagnostics and therapies. Their fluorescence was used to detect the presence of quantum dots in the two microorganisms.

The researchers found that both types of quantum dots were taken in readily by T. pyriformis and that they maintained their fluorescence even after the quantum dot-containing ciliates were ingested by the higher trophic level rotifers. This observation helped establish that the quantum dots were transferred across the food chain as intact nanoparticles and that dietary intake is one way that transfer can occur. The researchers noted that, "Some care should be taken, however, when extrapolating our laboratory-derived results to the natural environment."

"Our findings showed that although trophic transfer of quantum dots did take place in this simple food chain, they did not accumulate in the higher of the two organisms," says lead author David Holbrook. "While this suggests that quantum dots may not pose a significant risk of accumulating in aquatic invertebrate food chains in nature, additional research beyond simple laboratory experiments and a more exact means of quantifying transferred nanoparticles in environmental systems are needed to be certain." ###

* R.D. Holbrook, K.E. Murphy, J.B. Morrow and K.D. Cole. Trophic transfer of nanoparticles in a simplified invertebrate food chain. Nature Nanotechnology, June 2008 (advance online publication).

Contact: Michael E. Newman michael.newman@nist.gov 301-975-3025 National Institute of Standards and Technology (NIST)

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Friday, June 20, 2008

MIT develops a 'paper towel' for oil spills VIDEO

video

Video / Courtesy Francesco Stellacci, MIT, and Nature Nanotechnology
A swatch of MIT's new material for absorbing oil and other organic pollutants removes gasoline (dyed blue) from a dish of water.
Nanowire mesh can absorb up to 20 times its weight in oil

CAMBRIDGE, Mass.--A mat of nanowires with the touch and feel of paper could be an important new tool in the cleanup of oil and other organic pollutants, MIT researchers and colleagues report in the May 30 online issue of Nature Nanotechnology.
The scientists say they have created a membrane that can absorb up to 20 times its weight in oil, and can be recycled many times for future use. The oil itself can also be recovered. Some 200,000 tons of oil have already been spilled at sea since the start of the decade.
mesh of nanowires

The mesh of nanowires behind MIT's new material for absorbing oil and other organic pollutants, here shown at increasing magnifications (left to right). Image courtesy / Francesco Stellacci, MIT, and Nature Nanotechnology
“What we found is that we can make 'paper' from an interwoven mesh of nanowires that is able to selectively absorb hydrophobic liquids-oil-like liquids-from water,” said Francesco Stellacci, an associate professor in the Department of Materials Science and Engineering and leader of the work.
In addition to its environmental applications, the nanowire paper could also impact filtering and the purification of water, said Jing Kong, an assistant professor of electrical engineering in the Department of Electrical Engineering and Computer Science and one of Stellacci's colleagues on the work. She noted that it could also be inexpensive to produce because the nanowires of which it is composed can be fabricated in larger quantities than other nanomaterials.
oil-absorbing nanowire mesh

A swatch of MIT's new oil-absorbing nanowire mesh next to a pen for scale. Image courtesy / Courtesy Francesco Stellacci, MIT, and Nature Nanotechnology
Stellacci explained that there are other materials that can absorb oils from water, “but their selectivity is not as high as ours.” In other words, conventional materials still absorb some water, making them less efficient at capturing the contaminant.

The new material appears to be completely impervious to water. “Our material can be left in water a month or two, and when you take it out it's still dry,” Stellacci said. “But at the same time, if that water contains some hydrophobic contaminants, they will get absorbed.”
Made of potassium manganese oxide, the nanowires are stable at high temperatures. As a result, oil within a loaded membrane can be removed by heating above the boiling point of oil. The oil evaporates, and can be condensed back into a liquid. The membrane-and oil-can be used again.
new material for absorbing oil and other organic pollutants

MIT has developed a new material for absorbing oil and other organic pollutants. Here the material is used to remove a layer of gasoline (dyed blue) from a vial of water. Image courtesy / Francesco Stellacci, MIT, and Nature Nanotechnology
Two key properties make the system work. First, the nanowires form a spaghetti-like mat with many tiny pores that make for good capillarity, or the ability to absorb liquids. Second, a water-repelling coating keeps water from penetrating into the membrane. Oil, however, isn't affected, and seeps into the membrane.

The membrane is created by the same general technique as its low-tech cousin, paper. “We make a suspension of nanowires, like a suspension of cellulose [the key component of paper], dry it on a non-sticking plate, and we get pretty much the same results,” Stellacci said.
In a commentary accompanying the Nature Nanotechnology paper, Joerg Lahann of the University of Michigan concluded: “Stellacci and co-workers have provided an example of a nanomaterial that has been rationally designed to address a major environmental challenge.” ###

In addition to Stellacci and Kong (who is also affiliated with MIT's Research Laboratory of Electronics, or RLE), other authors are Jikang Yuan, a postdoctoral associate in MIT's Department of Electrical Engineering and Computer Science (EECS) and RLE; Xiaogang Liu, now at the National University of Singapore; Ozge Akbulut of the Department of Materials Science and Engineering; Junqing Hu of the National Institute for Materials Science in Japan; and Steven L. Suib of the University of Connecticut, Storrs.

This work was primarily funded by the Deshpande Center for Technological Innovation at MIT.

Contact: Elizabeth Thomson thomson@mit.edu 617-258-5402 Massachusetts Institute of Technology

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Thursday, June 19, 2008

Nanoparticles assemble by millions to encase oil drops

Designer 'nanobatons' could be used to trap oil, deliver drugs

HOUSTON -- In a development that could lead to new technologies for cleaning up oil spills and polluted groundwater, scientists at Rice University have shown how tiny, stick-shaped particles of metal and carbon can trap oil droplets in water by spontaneously assembling into bag-like sacs.



Shaijumon Manikoth
Pulickel Ajayan

Pulickel Ajayan
The tiny particles were found to assemble spontaneously by the tens of millions into spherical sacs as large as BB pellets around droplets of oil in water. In addition, the scientists found that ultraviolet light and magnetic fields could be used to flip the nanoparticles, causing the bags to instantly turn inside out and release their cargo -- a feature that could ultimately be handy for delivering drugs.
"The core of the nanotechnology revolution lies in designing inorganic nanoparticles that can self-assemble into larger structures like a 'smart dust' that performs different functions in the world – for example, cleaning up pollution," said lead research Pulickel Ajayan, Rice's Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science. "Our approach brings the concept of self-assembling, functional nanomaterials one step closer to reality."

The research was published online today by the American Chemical Society's journal Nano Letters.
nano oil drops

nano oil drops

In a development that could lead to new technologies for cleaning up oil spills and polluted groundwater, scientists at Rice University have shown how tiny, stick-shaped particles of metal and carbon can trap oil droplets in water by spontaneously assembling into bag-like sacs.
The multisegmented nanowires, akin to "nanoscale batons," were made by connecting two nanomaterials with different properties, much like an eraser is attached to the end of a wooden pencil. In the study, the researchers started with carbon nanotubes -- hollow tubes of pure carbon. Atop the nanotubes, they added short segments of gold. Ajayan said that by adding various other segments -- like sections of nickel or other materials -- the researchers can create truly multifunctional nanostructures.

The tendency of these nanobatons to assemble in water-oil mixtures derives from basic chemistry. The gold end of the wire is water-loving, or hydrophilic, while the carbon end is water-averse, or hydrophobic. The thin, water-tight sacs that surround all living cells are formed by interlocking arrangements of hydrophilic and hydrophobic chemicals, and the sac-like structures created in the study are very similar.
Ajayan, graduate student Fung Suong Ou and postdoctoral researcher Shaijumon Manikoth demonstrated that oil droplets suspended in water became encapsulated because of the structures' tendency to align their carbon ends facing the oil. By reversing the conditions -- suspending water droplets in oil – the team was able to coax the gold ends to face inward and encase the water.

"For oil droplets suspended in water, the spheres give off a light yellow color because of the exposed gold ends," Ou said. "With water droplets, we observe a dark sphere due to the protruding black nanotubes."

The team is next preparing to test whether chemical modifications to the "nanobatons" could result in spheres that can both capture and break down oily chemicals. For example, they hope to attach catalysts to the water-hating ends of the nanowires that will cause compounds like trichloroethene, or TCE, to break into nontoxic constituents. Another option would be to attach drugs whose release can be controlled with an external stimulus.

"The idea is to go beyond just capturing the compound and initiate a process that will make it less toxic," Ajayan said. "We want to build upon the method of self assembly and start adding functionality so these particles can carry out tasks in the real world."

The research was supported by Rice University, Applied Materials Inc. and the New York State Foundation for Science, Technology and Innovation. ###

Contact: Jade Boyd jadeboyd@rice.edu 713-348-6778 Rice University

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Wednesday, June 18, 2008

Engineers whip up the first long-lived nanoscale bubbles

Micrometer Size Bubble

Caption: Micrometer-size bubble covered with approximately 50 nm hexagons, Credit: Courtesy of the Howard Stone Lab/Science Magazine, Usage Restrictions: Copyright Science Magazine.
Discovery could significantly extend the lifetimes of common gas-liquid products

Cambridge, Mass. -- May 29, 2008 -- With the aid of kitchen mixers, engineers at Harvard’s School of Engineering and Applied Sciences (SEAS) have whipped up, for the first time, permanent nanoscale bubbles – bubbles that endure for more than a year – from batches of foam made from a mixture of glucose syrup, sucrose stearate, and water. Their study appears in the May 30 issue of the journal Science.

The research, led by Howard A. Stone, had its origins in a conference talk on foams delivered by Dr. Rodney Bee, a retired Unilever physical chemist, in 2005. Bee, who had been researching ice cream for the food, beverage,
and personal-care product company, was interested in finding ways to extend the life of foams and other gas-infused mixtures like ice cream. He had produced an unusual bubble formation in the course of his research, and he included a photograph of it in the presentation.

Stone, Vicky Joseph Professor of Engineering and Applied Mathematics and associate dean for applied physical sciences and engineering, was in the audience when Bee projected an image of a micrometer-size bubble with a distinctive polygonal geometry. The bubble surface appeared to be faceted with regular pentagonal, hexagonal, and heptagonal domains that intersected to form a soccer ball-like structure. None of the faces spanned more than 50 nanometers.

“Small bubbles on that scale never last because of surface tension – they instantly disappear. What Rodney showed on that screen was extraordinary,” said Stone. “It was impossible; we all thought it was impossible.”

Smaller bubbles have a greater surface tension and a higher gas pressure than larger ones. As a result, larger bubbles usually grow at the expense of smaller ones, which have very short lifetimes.

“I asked him how he created his foams, and he said he used an ordinary kitchen mixer. The next day I went out and bought a kitchen mixer for the lab,” explained Stone.

The experimental study, conducted by SEAS graduate student Emilie Dressaire in collaboration with Unilever colleagues, revealed that when the bubbles were covered with the chosen surfactant mixture, the surfactant molecules crystallized to form nearly impermeable shells over the bubble surfaces.

The resulting shells possessed an elasticity that allowed them to buckle over time into a remarkably regular and stable pattern. Measurements of the microbubbles’ stability extended over more than a year, and the structural integrity of the bubbles held for the entire period.

The authors note that future applications of these microbubbles could significantly extend the lifetimes of common gas-liquid products that experience rapid disintegration, such as aerated personal-care products and contrast agents for ultrasound imaging. ###

Stone’s co-authors are Dressaire and David C. Bell from SEAS and Bee and Alex Lips from Unilever Research and Development. The research was funded by Unilever.

Contact: Michael Patrick Rutter mrutter@seas.harvard.edu 617-496-3815 Harvard University

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Tuesday, June 17, 2008

Sullivan wins NSF Career Award for research on therapeutic drug carriers

Millicent Sullivan

Caption: Millicent Sullivan, assistant professor of chemical engineering at the University of Delaware, has received the National Science Foundation's prestigious Faculty Early Career Development Award for her research to build new and improved materials for delivering healing drugs and gene therapies to diseased and damaged cells in the human body. Credit: Kevin Quinlan/University of Delaware. Usage Restrictions: Photo must include credit to University of Delaware.
Millicent Sullivan was a born engineer. As a youngster, she had a fascination with shapes and loved building things with Tinker Toys.

Today, Sullivan, an assistant professor of chemical engineering at the University of Delaware and Merck Faculty Fellow, is applying her knowledge and talents to an area critical to human health--she's building new materials for delivering healing drugs and gene therapies to diseased and damaged cells in the human body.

Sullivan is UD's latest recipient of the National Science Foundation's prestigious Faculty Early Career Development Award.
The highly competitive award is bestowed on those scientists and engineers deemed most likely to become the academic leaders of the 21st century.

The five-year, $489,798 grant will support Sullivan's research to determine how cells interact with potential drug carriers and how the resulting structural changes of the carrier affect its ability to efficiently deliver its payload.

"It's an honor. I was thrilled to hear the news," Sullivan said. "The National Science Foundation has always been a respected funding organization. Colleagues in my field do the reviews for the proposals, so that is very gratifying."

"The College of Engineering has some of the best young engineering faculty in the country, and Prof. Sullivan is a perfect example," Michael Chajes, dean of engineering, said. "Her work in the area of new materials for delivering drugs and gene therapies to human cells is groundbreaking research. This award will enable her to take important steps towards moving the research closer to implementation. I look forward to watching Millie's career continue to blossom," Chajes noted.

Sullivan wants to harness the cell's biological environment to "productively evolve" new drug or gene packaging materials as they make the rough-and-tumble journey from a blood vessel, through the connective tissue, through the cell membrane, and finally into the nucleus or other organelle within a target cell where the package will open up to deliver its contents.

"It's a challenge to achieve because in protecting the DNA or drug, you generally make it less accessible to its target," Sullivan said. "We need to design packaging materials that protect their cargo, but that also promote the release and functionality of the payload once it reaches its target site," she noted. "What elements within the cell would allow this unpackaging? That is what we want to find out."

Currently, Sullivan is working to design synthetic DNA delivery materials that mimic elements of the architecture and function of histones in chromosomal DNA packaging. Histones are positively charged protein complexes that function as "spools" around which chromosomal DNA is wrapped. They display a series of peptide "tails" with specific sequences that act like switches, and can activate or suppress the transcription process by which DNA is unraveled and read.

Sullivan is creating gold nanoparticles functionalized with histone tail sequences strongly associated with transcriptional activity. When used for packaging therapeutic DNA, these materials will protect and direct their payloads during extra- and intracellular transport. Once they are exposed to the specific chemical cues within the cell's nucleus, the materials are pre-programmed to "trigger," resulting in the partial release and activation of the cargo DNA.

Confocal fluorescence microscopy and cryo-transmission electron microscopy will be used to investigate what happens to the materials once they are introduced to cells, and to determine if they do, indeed, "loosen up" and affect DNA transcription, Sullivan said.

The educational component to the research project is designed to expose students to engineering before they reach college.

As part of the UD College of Engineering's Research Experiences for Teachers program, Sullivan is ready to pilot teacher internships aimed at developing course modules in bioengineering for the high-school curriculum.

Two high-school teachers--including one science teacher and one math teacher--and an in-service teacher in mathematics education will spend six weeks doing research in Sullivan's lab this summer. Their work will include both an experimental component and a modeling component to give each teacher a lead role in his or her area of expertise.

Additionally, teaching assistantships will be offered to high-school students who will work alongside the teachers in the lab and do the full experiments. The students will be co-mentored by UD undergraduate and graduate students.

"Bioengineering and biomaterials research have the potential to lead to dramatic improvements in human health," Sullivan said. "I'm excited about doing the science, and about bringing engineering into the high school classroom."

Sullivan received her bachelor's degree from Princeton University and her doctorate from Carnegie Mellon University, both in chemical engineering. She conducted postdoctoral research in tissue engineering and matrix biology in the Hope Heart Program at the Benaroya Research Institute in Seattle. ###

Contact: Tracey Bryant tbryant@udel.edu 302-831-8185 University of Delaware

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Monday, June 16, 2008

Carbon nanoribbons could make smaller, speedier computer chips

graphene nanoribbon field-effect transistor with palladium contacts

A schematic of graphene nanoribbon field-effect transistor with palladium contacts (S,D) on a 10 nm thick insulating silicon dioxide surface (purple). Beneath the Si02 layer is a highly conductive silicon layer (G).
Stanford chemists have developed a new way to make transistors out of carbon nanoribbons. The devices could someday be integrated into high-performance computer chips to increase their speed and generate less heat, which can damage today's silicon-based chips when transistors are packed together tightly.

For the first time, a research team led by Hongjie Dai, the J. G. Jackson and C. J. Wood Professor of Chemistry, has made transistors called "field-effect transistors"
—a critical component of computer chips—with graphene that can operate at room temperature. Graphene is a form of carbon derived from graphite. Other graphene transistors, made with wider nanoribbons or thin films, require much lower temperatures.

"For graphene transistors, previous demonstrations of field-effect transistors were all done at liquid helium temperature, which is 4 Kelvin [-452 Fahrenheit]," said Dai, the lead investigator. His group's work is described in a paper published online in the May 23 issue of the journal Physical Review Letters.

The Dai group succeeded in making graphene nanoribbons less than 10 nanometers wide, which allows them to operate at higher temperatures. "People had not been able to make graphene nanoribbons narrow enough to allow the transistors to work at higher temperatures until now," Dai said. Using a chemical process developed by his group and described in a paper in the Feb. 29 issue of Science, the researchers have made nanoribbons, strips of carbon 50,000-times thinner than a human hair, that are smoother and narrower than nanoribbons made through other techniques.

Field-effect transistors are the key elements of computer chips, acting as data carriers from one place to another. They are composed of a semiconductor channel sandwiched between two metal electrodes. In the presence of an electric field, a charged metal plate can draw positive and negative charges in and out of the semiconductor. This allows the electric current to either pass through or be blocked, which in turn controls how the devices can be switched on and off, thereby regulating the flow of data.

Researchers predict that silicon chips will reach their maximum shrinking point within the next decade. This has prompted a search for materials to replace silicon as transistors continue to shrink in accordance with Moore's Law, which predicts that the number of transistors on a chip will double every two years. Graphene is one of the materials being considered.

David Goldhaber-Gordon, an assistant professor of physics at Stanford, proposed that graphene could supplement but not replace silicon, helping meet the demand for ever-smaller transistors for faster processing. "People need to realize this is not a promise; this is exploration, and we'll have a high payoff if this is successful," he said.

Dai said graphene could be a useful material for future electronics but does not think it will replace silicon anytime soon. "I would rather say this is motivation at the moment rather than proven fact," he said.

Although researchers, including those in his own group, have shown that carbon nanotubes outperform silicon in speed by a factor of two, the problem is that not all of the tubes, which can have 1-nanometer diameters, are semiconducting, Dai said. "Depending on their structure, some carbon nanotubes are born metallic, and some are born semiconducting," he said. "Metallic nanotubes can never switch off and act like electrical shorts for the device, which is a problem."

On the other hand, Dai's team demonstrated that all of their narrow graphene nanoribbons made from their novel chemical technique are semiconductors. "This is why structure at the atomic scale—in this case, width and edges—matters," he said.

Contact: Louis Bergeron louisb3@stanford.edu 650-725-1944 Stanford University

BY MASSIE SANTOS BALLON Massie Santos Ballon is a science-writing intern at the Stanford News Service

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Sunday, June 15, 2008

Fabrics made of functional nanofibers that would decompose toxic industrial chemicals into harmless byproducts.

Nylon nanofibers coated with metal nanoparticles

Nylon nanofibers coated with metal nanoparticles. These functional nanofibers have potential applications as active air filtration media as well as flexible antibacterial surfaces such as wipes, carpets and upholstery.
Cornell fiber scientist Juan Hinestroza is working with the U.S. government to create fabrics made of functional nanofibers that would decompose toxic industrial chemicals into harmless byproducts.

Potential applications include safety gear for U.S. soldiers and filtration systems for buildings and vehicles.

Hinestroza, assistant professor of fiber science in the College of Human Ecology, is a member of two teams that secured more than $2.2 million from the U.S. Department of Defense;
about $875,000 will go directly to Hinestoza's work. Both grants are multi-university collaborative efforts funded through the U.S. Defense Threat Reduction Agency.

"These nanostructures could be used in creating advanced air filtration and personal protection systems against airborne chemical threats and can find many applications in buildings, airplanes as well as personal respirators," Hinestroza said.

The first project, in collaboration with North Carolina State University, is aimed at understanding how very small electrical charges present in fibers and nanofibers can help in capturing nanoparticles, bacteria and viruses.

"Understanding how these charges are injected into the fibers and how they are dissipated under different environmental conditions can open an avenue to significant improvements in air filtration technology," Hinestroza said.

The position and distribution of the electrical charges on the nanofibers will be fed into computerized fluid dynamics algorithms developed by Andrey Kutznetsov of NC State to predict the trajectory of the nanoparticles challenging the filter. Hinestroza and NC State's Warren Jasper pioneered work in this area a couple of years ago.

The second project, in collaboration with the University of California-Los Angeles (UCLA), will study the incorporation of a new type of molecules -- called metal organic polyhedra and metal organic frameworks -- onto polymeric nanofibers to trap dangerous gases as toxic industrial chemicals and chemical warfare agents, then decompose them into substances that are less harmful to humans and capture them for further decontamination. The synthesis of these molecules was pioneered by Omar Yaghi of UCLA.

This project will also look into the potential toxicity of these nanofiber-nanoparticle systems to humans in collaboration with Andre Nel from UCLA Medical School.

Hinestroza's research group specializes in understanding and manipulating nanoscale phenomena in fiber and polymer science. Related Information: Hinestroza Research Group

By Sheri Hall assistant communications director for the College of Human Ecology. Contact: Blaine Friedlander bpf2@cornell.edu 607-254-8093. Cornell University Communications

Cornell Chronicle: Susan Lang (607) 255-3613 ssl4@cornell.edu, Media Contact: Press Relations Office (607) 255-6074 pressoffice@cornell.edu

Saturday, June 14, 2008

Super-hard nanocrystalline iron that can take the heat

Dr. Carl C. Koch, an NC State professor of materials science engineering

Carl Koch Professor, Associate Department Head carl_koch@ncsu.edu

Carl Koch was a research group leader with the Metals and Ceramics Division of Oak Ridge National Laboratory before he joined the NCSU faculty in 1983.

Koch's research in recent years has focused on the synthesis, characterization and properties of metastable materials. Metastable materials with unique structures or microstructures that we have studied include metallic glasses, intermetallic compounds, nanocrystalline materials and polymer alloys. The chief nonequilibrium processing methods used to prepare metastable materials are rapid solidification from the liquid phase (at about 106 oC/s) and mechanical attrition of powders in high-energy ball mills.

Koch was the first researcher to demonstrate that amorphous alloys metallic glasses could be made by ball milling certain elemental powder mixtures by the technique known as mechanical alloying. Recent research has turned to nanocrystalline materials prepared by either mechanical attrition or controlled crystallization of amorphous precursors formed by rapid solidification. His group's interest in these materials is due to their special mechanical and soft magnetic properties.

Researchers at North Carolina State University have created a substance far stronger and harder than conventional iron, and which retains these properties under extremely high temperatures – opening the door to a wide variety of potential applications, such as engine components that are exposed to high stress and high temperatures.

Iron that is made up of nanoscale crystals is far stronger and harder than its traditional counterpart, but the benefits of this “nano-iron” have been limited by the fact that its nanocrystalline structure breaks down at relatively modest temperatures. But the NC State researchers have developed an iron-zirconium alloy that retains its nanocrystalline structures at temperatures above 1,300 degrees Celsius – approaching the melting point of iron.

Kris Darling, a Ph.D. student at NC State who led the project to develop the material, explains that the alloy’s ability to retain its nanocrystalline structure under high temperatures will allow for the material to be developed in bulk, because conventional methods of materials manufacture rely on heat and pressure.

In addition, Darling says the ability to work with the material at high temperatures will make it easier to form the alloy into useful shapes – for use as tools or in structural applications, such as engine parts.

The new alloy is also economically viable, since “it costs virtually the same amount to produce the alloy” as it does to create nano-iron, Darling says.

Dr. Carl C. Koch, an NC State professor of materials science engineering who worked on the project, explains that the alloy essentially consists of 1 percent zirconium and 99 percent iron. The zirconium allows the alloy to retain its nanocrystalline structure under high temperatures. ###

The research will appear in the journal Scripta Materialia. Kris Darling is the lead author on the paper, “Grain-size Stabilization in Nanocrystalline FeZr Alloys,” but co-authors include Koch, fellow NC State materials science professor Dr. Ronald O. Scattergood, NC State doctoral student Jonathan E. Semones, and NC State undergraduates Ryan N. Chan and Patrick Z. Wong.

Note to editors: The paper’s abstract follows.

“Grain-size Stabilization in Nanocrystalline FeZr Alloy”
Authors: Kris A. Darling,* Ryan N. Chan, Patrick Z. Wong, Jonathan E. Semones, Ronald O. Scattergood and Carl C. Koch, North Carolina State University
Accepted for publication: May 7, 2008, in Scripta Materialia

Abstract: Nanocrystalline Fe–Zr alloys with a nominal grain size of 10 nm were synthesized by mechanical alloying. The grain size in pure Fe was >200 nm after annealing for 1 h at T/TM = 0.5. Additions of 1 at .% Zr stabilized the grain size at 50 nm up to T/TM = 0.92. Particle pinning, solute drag and reduction in grain-boundary energy have been proposed as stabilization mechanisms. The stabilization in Fe–Zr alloys is attributed to a reduction in grain-boundary energy due to Zr segregation.
Contact: Matt Shipman matt_shipman@ncsu.edu 919-515-6386 North Carolina State University

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Friday, June 13, 2008

New unifying theory of lasers advanced by physicists

Artist's Rendering of a Random Laser

Caption: An artist's rendering of a random laser that is pumped with incoherent light from the top and emits coherent light in random directions. Credit: (Courtesy of Robert Tandy & Science Magazine) Usage Restrictions: with credit given
New Haven, Conn. — Researchers at Yale and the Institute of Quantum Electronics at ETH Zurich have formulated a theory that, allows scientists to better understand and predict the properties of both conventional and non-conventional lasers, according to a recent article in Science.

“The lasers that most people are familiar with emit a narrow beam of light in a fixed direction that has a well-defined wavelength and a predictable power output — like those in laser pointers, bar-code readers, surgical instruments and CD players,” said senior author A. Douglas Stone, the Carl A. Morse Professor of Applied Physics at Yale.

In these conventional lasers, the light is trapped and amplified between parallel mirrors or interfaces and bounces back and forth along one dimension.
Scientists can determine what the light output will be based on the “leakiness” of the mirrors, which is usually quite small.

But, a new breed of lasers — diffusive random lasers (DRLs) — made possible by modern nanofabrication capabilities, consist of a simple aggregate of nanoparticles and have no mirrors to trap light. These lasers were pioneered by Hui Cao, now a professor of applied physics at Yale, and have been proposed for applications in environmental lighting (“laser paint”), medical imaging and displays. Until now, there has been no simple way for scientists to predict the wavelengths and intensities of the light emitted by DRLs.

Although, superficially, conventional lasers and DRLs appear to operate very differently, experimental results indicated many basic similarities, and scientists have searched for a unifying description that would apply to all lasers.

The properties of a laser are determined by measuring the lasing modes, including the pattern of light intensity within the laser, and the wavelengths of light it puts out. With conventional lasers, these modes can easily be obtained through simulations.

“For random lasers, time-dependent simulations are difficult to do, hard to interpret, and don't answer the question: ‘What is the nature of the lasing modes in a random laser,’” according to Stone. “Researchers really wanted a description similar to that for conventional lasers, but no one knew how to develop such a description.”

To create their unifying theory, the researchers derived a wholly new set of non-linear equations that fit both conventional and non-conventional lasers — such as the DRL or other nanostructured lasers. Based on these equations Stone, his former PhD student Hakan Tureci, now at ETH Zurich, and two other members of Stone’s research group, Li Ge and Stefan Rotter, created a detailed computer code that can predict all the important properties of any kind of laser from simple inputs.

“The state of laser theory after forty years was an embarrassment; it was essentially qualitative, but not predictive or quantitative,” says Stone. “We went back to the basics — and we think we have now solved that problem.”

A “Perspective” review of the theory in the same issue of Science noted, “By developing a new theory in which the main properties of a laser can be physically understood . . . they have provided a substantially broader perspective of laser physics that unifies the physical description of many possible laser structures.”

“Ultimately, we hope that our code can be used as a design tool for new classes of micro- and nano-lasers with important applications” says Stone, who also believes that eventually their theory will become part of the answer to the question: “How does a laser work"” ###

This research was funded by the National Science Foundation, the Max Kade and W. M. Keck foundations, and by the Aspen Center for Physics. Citation: Science 320: 643-646. (May 2, 2008) [DOI: 10.1126/science.1155311]. Perspective review: Science 320: 623. (May 2, 2008) [DOI: 10.1126/science.1157494]

Further supporting material is available online at www.sciencemag.org/

Contact: Janet Rettig Emanuel janet.emanuel@yale.edu 203-432-2157 Yale University

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