David Kirkpatrick

March 7, 2009

Nanotech medical imaging breakthrough

More medical nanotechnology news. Better medical imaging (CTs, MRIs, et.al.) means better diagnosis and treatment.

The release:

UConn chemists find secret to increasing luminescence efficiency of carbon nanotubes

Breakthrough procedure has potential applications in medical imaging, homeland security, biological sensors

STORRS, Conn. – Chemists at the University of Connecticut have found a way to greatly increase the luminescence efficiency of single-walled carbon nanotubes, a discovery that could have significant applications in medical imaging and other areas.

Increasing the luminescence efficiency of carbon nanotubes may someday make it possible for doctors to inject patients with microscopic nanotubes to detect tumors, arterial blockages and other internal problems. Rather than relying on potentially harmful x-rays or the use of radioactive dyes, physicians could simply scan patients with an infrared light that would capture a very sharp resolution of the luminescence of the nanotubes in problem areas.

UConn’s process of increasing the luminescence efficiency of single-walled carbon nanotubes will be featured in Science magazine on Friday, March 6, 2009. The research was performed in the Nanomaterials Optoelectronics Laboratory at the Institute of Materials Science at the University of Connecticut, in Storrs, CT. A patent for the process is pending.

University of Connecticut Chemist Fotios Papadimitrakopoulos describes the discovery as a major breakthrough and one of the most significant discoveries in his 10 years of working with single-walled carbon nanotubes. Assisting Papadimitrakopoulos with the research were Polymer Program graduate student Sang-Yong Ju (now a researcher at Cornell University) and William P. Kopcha, a former Chemistry undergraduate assistant in the College of Liberal Arts and Sciences who is now a first-year graduate student at UConn.

Although carbon is used in many diverse applications, scientists have long been stymied by the element’s limited ability to emit light. The best scientists have been able to do with solution-suspended carbon nanotubes was to raise their luminescence efficiency to about one-half of one percent, which is extremely low compared to other materials, such as quantum dots and quantum rods.

By tightly wrapping a chemical ‘sleeve’ around a single-walled carbon nanotube, Papadimitrakopoulos and his research team were able to reduce exterior defects caused by chemically absorbed oxygen molecules.

This process can best be explained by imagining sliding a small tube into a slightly larger diameter tube, Papadimitrakopoulos says. In order for this to happen, all deposits or protrusions on the smaller tube have to be removed before the tube is allowed to slip into the slightly larger diameter tube. What is most fascinating with carbon nanotubes however, Papadimitrakopoulos says, is the fact that in this case the larger tube is not as rigid as the first tube (i.e. carbon nanotube) but is rather formed by a chemical “sleeve” comprised of a synthetic derivative of flavin (an analog of vitamin B2) that adsorbs and self organizes onto a conformal tube.

Papadimitrakopoulos claims that this process of self-assembly is unique in that it not only forms a new structure but also actively “cleans” the surface of the underlying nanotube. It is that active cleaning of the nanotube surface that allows the nanotube to achieve luminescence efficiency to as high as 20 percent.

 

NOTE: To see a QuickTime animation of how a single-walled carbon nanotube is wrapped with the synthetic flavin derivative to increase its luminescence go to: http://www.ims.uconn.edu/~papadim/research.htm

“The nanotube is the smallest tube on earth and we have found a sleeve to put over it,” Papadimitrakopoulos says. “This is the first time that a nanotube was found to emit with as much as 20 percent luminescence efficiency.”

Papadimitrakopoulos has been working closely with the UConn Center for Science and Technology Commercialization (CSTC) in transferring his advances in research into the realm of patents, licenses and corporate partnerships. The CSTC was created several years ago as a way to help expand Connecticut’s innovation-based economy and to help create new businesses and jobs around new ideas.

This is the second major nanotube discovery at UConn by Papadimitrakopoulos in the past two years. Last year, Papadimitrakopoulos and Sang-Young Ju, along with other UConn researchers, patented a way to isolate certain carbon nanotubes from others by seamlessly wrapping a form of vitamin B2 around the nanotubes. It was out of that research that Papadimitrakopoulos and Sang-Yong Ju began wrapping nanotubes with helical assemblies and probing their luminescence properties.

The more luminescent the nanotube, the brighter it appears under infrared irradiation or by electrical excitation (such as that provided by a light-emitting diode or LED). A number of important applications may be possible as a result of this research, Papadimitrakopoulos says. Carbon nanotube emissions are not only extremely sharp, but they also appear in a spectral region where minimal absorption or scattering takes place by soft tissue. Moreover, carbon nanotubes display superb photo bleaching stability and are ideally suited for near-infrared emitters, making them appropriate for applications in medicine and homeland security as bio-reporting agents and nano-sized beacons. Carbon nanotube luminescence also has important applications in nano-scaled LEDs and photo detectors, which can readily integrate with silicon-based technology. This provides an enormous repertoire for nanotube use in advanced fiber optics components, infrared light modulators, and biological sensors, where multiple applications are possible due to the nanotube’s flavin-based (vitamin B2) helical wrapping.

 

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A complete copy of the research article that will appear in Science magazine on Friday, March 6, will be available after 2 p.m. on Thursday, March 5 at: http://www.sciencemag.org/sciencexpress/recent.dtl

More information about the University of Connecticut’s Nanomaterials Optoelectronics Laboratory can be found at: http://chemistry.uconn.edu/papadim/index.htm
Photo available at: http://dropbox.uconn.edu/dropbox?n=Papadim.zip&p=Wwe748VCBRIWDUDwv

January 16, 2009

The latest in cloaking tech

Haven’t blogged on this subject in a while. It’s always fun to cover, though.

The release:

Next generation cloaking device demonstrated

IMAGE: Pictured is the new cloak with bump, left, and the prototype, right.

Click here for more information. 

DURHAM, N.C. – A device that can bestow invisibility to an object by “cloaking” it from visual light is closer to reality. After being the first to demonstrate the feasibility of such a device by constructing a prototype in 2006, a team of Duke University engineers has produced a new type of cloaking device, which is significantly more sophisticated at cloaking in a broad range of frequencies.

The latest advance was made possible by the development of a new series of complex mathematical commands, known as algorithms, to guide the design and fabrication of exotic composite materials known as metamaterials. These materials can be engineered to have properties not easily found in natural materials, and can be used to form a variety of “cloaking” structures. These structures can guide electromagnetic waves around an object, only to have them emerge on the other side as if they had passed through an empty volume of space.

IMAGE: This is David R. Smith with the new cloak device.

Click here for more information. 

The results of the latest Duke experiments were published Jan. 16 in the journal Science. First authors of the paper were Duke’s Ruopeng Liu, who developed the algorithm, and Chunlin Li. David R. Smith, William Bevan Professor of electrical and computer engineering at Duke, is the senior member of the research team.

Once the algorithm was developed, the latest cloaking device was completed from conception to fabrication in nine days, compared to the four months required to create the original, and more rudimentary, device. This powerful new algorithm will make it possible to custom-design unique metamaterials with specific cloaking characteristics, the researchers said.

“The difference between the original device and the latest model is like night and day,” Smith said. “The new device can cloak a much wider spectrum of waves — nearly limitless — and will scale far more easily to infrared and visible light. The approach we used should help us expand and improve our abilities to cloak different types of waves.”

Cloaking devices bend electromagnetic waves, such as light, in such a way that it appears as if the cloaked object is not there. In the latest laboratory experiments, a beam of microwaves aimed through the cloaking device at a “bump” on a flat mirror surface bounced off the surface at the same angle as if the bump were not present. Additionally, the device prevented the formation of scattered beams that would normally be expected from such a perturbation.

The underlying cloaking phenomenon is similar to the mirages seen ahead at a distance on a road on a hot day.

“You see what looks like water hovering over the road, but it is in reality a reflection from the sky,” Smith explained. “In that example, the mirage you see is cloaking the road below. In effect, we are creating an engineered mirage with this latest cloak design.”

Smith believes that cloaks should find numerous applications as the technology is perfected. By eliminating the effects of obstructions, cloaking devices could improve wireless communications, or acoustic cloaks could serve as protective shields, preventing the penetration of vibrations, sound or seismic waves.

“The ability of the cloak to hide the bump is compelling, and offers a path towards the realization of forms of cloaking abilities approaching the optical,” Liu said. “Though the designs of such metamaterials are extremely complex, especially when traditional approaches are used, we believe that we now have a way to rapidly and efficiently produce such materials.”

With appropriately fine-tuned metamaterials, electromagnetic radiation at frequencies ranging from visible light to radio could be redirected at will for virtually any application, Smith said. This approach could also lead to the development of metamaterials that focus light to provide more powerful lenses.

The newest cloak, which measures 20 inches by 4 inches and less than an inch high, is actually made up of more than 10,000 individual pieces arranged in parallel rows. Of those pieces, more than 6,000 are unique. Each piece is made of the same fiberglass material used in circuit boards and etched with copper.

The algorithm determined the shape and placement of each piece. Without the algorithm, properly designing and aligning the pieces would have been extremely difficult, Smith said.

 

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The research was supported by Raytheon Missile Systems, the Air Force Office of Scientific Research, InnovateHan Technology, the National Science Foundation of China, the National Basic Research Program of China, and National Science Foundation of Jiangsu Province, China.

Others members of the research team were Duke’s Jack Mock, as well as Jessie Y. Chin and Tie Jun Cui from Southeast University, Nanjing, China.

December 19, 2008

Start cowering under your afghans …

Filed under: et.al., Politics, Science, Technology — Tags: , , , , , — David Kirkpatrick @ 12:14 am

… the killer robots are coming.

Well, not yet.

The release:

British scientist warns we must protect the vulnerable from robots

Top robotics expert Professor Noel Sharkey, of the University of Sheffield, has called for international guidelines to be set for the ethical and safe application of robots before it is too late. Professor Sharkey, writing in the prestigious Science journal, believes that as the use of robots increases, decisions about their application will be left to the military, industry and busy parents instead of international legislative bodies.

Robots have been used in laboratories and factories for many years, but their uses are changing fast. Since the turn of the century, sales of professional and personal service robots have risen sharply and are estimated to total 5.5 million in 2008. IFR Statistics estimate 11.5 million in the next two years. The price of robot manufacture is also falling. With robots 80% cheaper in 2006 than they were in 1990, they are set to enter our lives in unprecedented numbers.

Service robots are currently being used in all walks of life, from child-minding robots to robots that care for the elderly. These types of robots can be controlled by a mobile phone or from a PC, allowing input from camera “eyes” and remote talking from caregivers. Sophisticated elder-care robots like the Secom “My Spoon” automatic feeding robot; the Sanyo electric bathtub robot that automatically washes and rinses; and the Mitsubishi Wakamura robot, used for reminding people to take their medicine, are already in widespread use.

Despite this no international legislation or policy guidelines currently exist, except in terms of negligence. This is still to be tested in court for robot surrogates and may be difficult to prove in the home (relative to cases of physical abuse).

Professor Sharkey urges his fellow scientists and engineers working in robotics to be mindful of the unanticipated risks and the ethical problems linked to their work. He believes that robots for care represent just one of many ethically problematic areas that will soon arise from the increase in their use, and that policy guidelines for ethical and safe application need to be set before the guidelines set themselves.

He said: “Research into service robots has demonstrated close bonding and attachment by children, who, in most cases, prefer a robot to a teddy bear. Short-term exposure can provide an enjoyable and entertaining experience that creates interest and curiosity.

“However, because of the physical safety that robot minders provide, children could be left without human contact for many hours a day or perhaps for several days, and the possible psychological impact of the varying degrees of social isolation on development is unknown.

“At the other end of the age spectrum, the relative increase in many countries in the population of the elderly relative to available younger caregivers has spurred the development of elder-care robots. These robots can help the elderly to maintain independence in their own homes, but their presence could lead to the risk of leaving the elderly in the exclusive care of machines without sufficient human contact.”

 

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In the article Professor Sharkey also writes about the immediate ethical problems linked to military applications of robotics, particularly with regards to the protection of innocents. For the full article visit http://www.sciencemag.org/

December 6, 2008

Super ceramic

Lots of great applications for this material.

The release:

December 05, 2008

Scientists Create Tough Ceramic That Mimics Mother of Pearl

Biomimicry – technological innovation inspired by nature – is one of the hottest ideas in science but has yet to yield many practical advances. Time for a change. Scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have mimicked the structure of mother of pearl to create what may well be the toughest ceramic ever produced.

The roughness of the alumina/PMMA hybrid ceramic controls the strength of the interfaces, which is critical in determining the material’s overall toughness as it affects the sliding process in the polymeric "mortar" layers.

The roughness of the alumina/PMMA hybrid ceramic controls the strength of the interfaces, which is critical in determining the material’s overall toughness as it affects the sliding process in the polymeric “mortar” layers.

Through the controlled freezing of suspensions in water of an aluminum oxide (alumina) and the addition of a well known polymer, polymethylmethacrylate (PMMA), a team of researchers has produced ceramics that are 300 times tougher than their constituent components. The team was led by Robert Ritchie, who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the Materials Science and Engineering Department at the University of California, Berkeley.

“We have emulated nature’s toughening mechanisms to make ice-templated alumina hybrids that are comparable in specific strength and toughness to aluminum alloys,” says Ritchie. “We believe these model materials can be used to identify key microstructural features that should guide the future synthesis of bio-inspired, yet non-biological, light-weight structural materials with unique strength and toughness.”

The results of this research were reported in the December 5, 2008 issue of the journal Science, in a paper entitled:“Tough, bio-inspired hybrid materials.” Co-authoring the paper with Ritchie were Etienne Munch, Max Launey, Daan Hein Alsem, Eduardo Saiz and Antoni Tomsia.

 

Naturally Tough

Mother of pearl, or nacre, the inner lining of the shells of abalone, mussels and certain other mollusks, is renowned for both its iridescent beauty and its amazing toughness. Nacre is 95-percent aragonite, a hard but brittle calcium carbonate mineral, with the rest of it made up of soft organic molecules. Yet nacre can be 3,000 times (in energy terms) more resistant to fracture than aragonite. No human-synthesized composite outperforms its constituent materials by such a wide margin. The problem has been that nacre’s remarkable strength is derived from a structural architecture that varies over lengths of scale ranging from nanometers to micrometers. Human engineering has not been able to replicate these length scale variances.

brick and mortar structure of alumina/PMMA hybrid

In the “brick-and-mortar” phase of the alumina/PMMA hybrid, aragonite “bricks” slide past each other to dissipate strain energy while the polymer “mortar” acts as a lubricant.

Two years ago, however, Berkeley Lab researchers Tomsia and Saiz found a way to improve the strength of bone substitutes through a processing technique that involved the freezing of seawater. This process yielded a ceramic that was four times stronger than artificial bone. When seawater freezes, ice crystals form a scaffolding of thin layers. These layers are pure ice because during their formation impurities, such as salt and microorganisms, are expelled and entrapped in the space between the layers. The resulting architecture roughly resembles that of nacre.

“Since seawater can freeze like a layered material, we allowed nature to guide the process by which we were able to freeze-cast ceramics that mimicked nacre,” said Tomsia when this research was reported.

Engineered to be Tough

In this latest research, Ritchie, working with Tomsia and Saiz, refined the freeze-casting technique and applied it to alumina/PMMA hybrid materials to create large porous ceramic scaffolds that much more closely mirrored the complex hierarchical microstructure of nacre. To do this, they first employed directional freezing to promote the formation of thin layers (lamellae) of ice that served as templates for the creation of the layered alumina scaffolds. After the ice was removed, spaces between the alumina lamellae were filled with polymer.

Robert Ritchie (seated) led a research effort in which the microstructure of mother of pearl was mimicked to create what may well be the toughest ceramic ever produced. Collaborating with Ritchie were (from left) Maximilien Launey, Daan Hein Alsem, Eduardo Saiz and Antoni Tomsia.

Robert Ritchie (seated) led a research effort in which the microstructure of mother of pearl was mimicked to create what may well be the toughest ceramic ever produced. Collaborating with Ritchie were (from left) Maximilien Launey, Daan Hein Alsem, Eduardo Saiz and Antoni Tomsia.

“The key to material toughness is the ability to dissipate strain energy,” says Ritchie. “Infiltrating the spaces between the alumina layers with polymer allows the hard alumina layers to slide (by a small amount) over one another when load is applied, thereby dissipating strain energy. The polymer acts as a lubricant, like the oil in an automobile engine.”

In addition to making the lamellar scaffolds, the team was also able to fabricate nacre-like “brick-and-mortar” structures with very high alumina content. They did this by collapsing the scaffolds in a perpendicular direction to the layers then sintering the resulting alumina “bricks” to promote brick densification and the formation of ceramic bridges between individual bricks.

Says Saiz, “Using such techniques, we have made complex hierarchical architectures where we can refine the lamellae thickness, control their macroscopic orientation, manipulate the chemistry and roughness of the inter-lamellae interfaces, and generate a given density of inorganic bridges, all over a range of size-scales.”

Next Step

For ceramic materials that are even tougher in the future, Ritchie says he and his colleagues need to improve the proportion of ceramic to polymer in their composites. The alumina/PMMA hybrid was only 85-percent alumina. They want to boost ceramic content and thin the layers even further. They also want to replace the PMMA with a better polymer and eventually replace the polymer content altogether with metal.

Says Ritchie, “The polymer is only capable of allowing things to slide past one another, not bear any load. Infiltrating the ceramic layers with metals would give us a lubricant that can also bear some of the load. This would improve strength as well as toughness of the composite.”

Such future composite materials would be lightweight and strong as well as tough, he says, and could find important applications in energy and transportation.

This research was supported by DOE’s Office of Science, through the Division of Materials Sciences and Engineering in the Basic Energy Sciences office.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our Website at http://www.lbl.gov/

November 13, 2008

Nanotech improving lasers and solar cells

The release:

New research expected to improve laser devices and make photovoltaics more efficient

University of Chicago research

University of Chicago scientists have induced electrons in the nanocrystals of semiconductors to cool more slowly by forcing them into a smaller volume. This has the potential to improve satellite communications and the generation of solar power.

“Slowing down the cooling of these electrons—in this case, by more than 30 times—could lead to a better infrared laser source,” said Philippe Guyot-Sionnest, Professor of Chemistry and Physics at the University of Chicago. “This, in turn, could be used to increase the bandwidth of communication satellites, allowing for faster connections.”

Guyot-Sionnest is the principal investigator on the research project, which was described in a paper called “Slow Electron Cooling in Colloidal Quantum Dots,” published Nov. 7 in Science.

The slow cooling of electrons in nanocrystals could lead to better, more efficient photovoltaic devices, he added. “This is because proposals to devise ways to extract the excess heat from these electrons as they cool are more likely to be realized—and to work—due to the fact that we now understand better what is going on with these nanocrystals.”

Slower cooling of electrons in nanocrystals was first theorized in 1990, but no one has been able to observe this effect.

Slow electron cooling in nanocrystals occurs because forcing the electrons into a smaller volume leads them to oscillate between their alternate extremes within a very short period of time. (This is analogous to the way shorter strings on musical instruments produce higher pitches.) The electrons in the nanocrystals used in this experiment oscillated so fast that it became difficult for them to drag along the more sluggish vibrations of the nuclei. As a result, the energy stayed with the electrons for a longer period of time.

The slower cooling effect was difficult to induce and observe because several different mechanisms for energy loss interfered with the process. By eliminating these other mechanisms, the researchers were able to induce and observe slower electron cooling in nanocrystals.

 

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Anshu Pandey, a graduate student in Chemistry at the University of Chicago, did the experiments described in the Science paper, which he co-authored.

October 17, 2008

Transformation optics promise big payoff

It’s been quite a while since I’ve blogged on the possibility of a “cloak of invisibility,” so this PhysOrg article caught my eye. It covers a research field known as transformation optics, and the promise there is great. We’re talking the aforementioned cloak, plusultra-powerful microscopes and computers. All this is done by harnessing nanotechnology and “metamaterials.”

From the second link:

The field, which applies mathematical principles similar to those in Einstein’s theory of general relativity, will be described in an article to be published Friday (Oct. 17) in the journal Science. The article will appear in the magazine’s Perspectives section and was written by Vladimir Shalaev, Purdue’s Robert and Anne Burnett Professor of Electrical and Computer Engineering.

The list of possible breakthroughs includes a cloak of invisibility; computers and consumer electronics that use light instead of electronic signals to process information; a “planar hyperlens” that could make optical microscopes 10 times more powerful and able to see objects as small as DNA; advanced sensors; and more efficient solar collectors.

“Transformation optics is a new way of manipulating and controlling light at all distances, from the macro- to the nanoscale, and it represents a new paradigm for the science of light,” Shalaev said. “Although there were early works that helped to develop the basis for transformation optics, the field was only recently established thanks in part to papers by Sir John Pendry at the Imperial College, London, and Ulf Leonhardt at the University of St. Andrews in Scotland and their co-workers.”

September 7, 2008

Nanoclusters of gold are valued catalysts

From the press release:

Electron micrographs showing inactive (left) and active (right) catalysts consisting of gold particles absorbed on iron oxide. The red circles indicate the presence of individual gold atoms. The yellow circles...
Electron micrographs showing inactive (left) and active (right) catalysts consisting of gold particles absorbed on iron oxide. The red circles indicate the presence of individual gold atoms. The yellow circles show the location of subnanometer gold clusters that can effectively catalyze the conversion of carbon monoxide to carbon dioxide. One nanometer is about half the size of a DNA molecule. (Color added for clarity)Credit: Lehigh University Center for Advanced Materials and Nanotechnology

NIST and partners identify tiny gold clusters as top-notch catalysts

For most of us, gold is only valuable if we possess it in large-sized pieces. However, the “bigger is better” rule isn’t the case for those interested in exploiting gold’s exceptional ability to catalyze a wide variety of chemical reactions, including the oxidation of poisonous carbon monoxide (CO) into harmless carbon dioxide at room temperatures. That process, if industrialized, could potentially improve the effectiveness of catalytic converters that clean automobile exhaust and breathing devices that protect miners and firefighters. For this purpose, nanoclusters—gold atoms bound together in crystals smaller than a strand of DNA—are the size most treasured.

Using a pair of scanning transmission electron microscopy (STEM) instruments for which spherical aberration (a system fault yielding blurry images) is corrected, researchers at the National Institute of Standards and Technology (NIST), Lehigh University (Bethlehem, Pa.) and Cardiff University (Cardiff, Wales, United Kingdom) for the first time achieved state-of-the-art resolution of the active gold nanocrystals absorbed onto iron oxide surfaces. In fact, the resolution was sensitive enough to even visualize individual gold atoms.

The work is reported in the Sept. 5, 2008, issue of Science.

Surface science studies have suggested that there is a critical size range at which gold nanocrystals supported by iron oxide become highly active as catalysts for CO oxidation. However, the theory is based on research using idealized catalyst models made of gold absorbed on titanium oxide. The NIST/Lehigh/Cardiff aberration-corrected STEM imaging technique allows the researchers to study the real iron oxide catalyst systems as synthesized, identify all of the gold structures present in each sample, and then characterize which cluster sizes are most active in CO conversion.

The research team discovered that size matters a lot—samples ranged from those with little or no catalytic activity (less than 1 percent CO conversion) to others with nearly 100 percent efficiency. Their results revealed that the most active gold nanoclusters for CO conversion are bilayers approximately 0.5-0.8 nanometer in diameter (40 times smaller than the common cold virus) and containing about 10 gold atoms. This finding is consistent with the previous surface science studies done on the gold-titanium oxide models.

 

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A.A. Herzing, C.J. Kiely, A.F. Carley, P. Landon and G.J. Hutchings. Identification of active gold nanoclusters on iron oxide supports for CO oxidation. Science, Vol. 321, Issue 5894, Sept. 5, 2008.