Cheap Plastic Used in CDs Could Improve Aircraft, Computer Electronics

If one University of Houston professor has his way, the inexpensive plastic now used to manufacture CDs and DVDs will one day soon be put to use in improving the integrity of electronics in aircraft, computers and iPhones.

Thanks to a pair of grants from the U.S. Air Force, Shay Curran, associate professor of physics at Houston, and his research team have demonstrated ultra-high electrical conductive properties in plastics, called polycarbonates, by mixing them with just the right amount and type of carbon nanotubes.

The findings are chronicled in a paper titled "Electrical Transport Measurements of Highly Conductive Carbon Nanotube/Poly(bisphenol A carbonate) Composite," appearing in a recent issue of the Journal of Applied Physics, the archival publication of the American Institute of Physics.

Curran, who initially began this form of research a decade ago at Trinity College Dublin, started to look at high-conductive plastics in a slightly different manner. Curran's team has come up with a strategy to achieve higher conductivities using carbon nanotubes in plastic hosts than what has been currently achieved. By combining nanotubes with polycarbonates, Curran's group was able to reach a milestone of creating nanocomposites with ultra-high conductive properties.

"While its mechanical and optical properties are very good, polycarbonate is a non-conductive plastic. That means its ability to carry an electrical charge is as good as a tree, which is pretty awful," Curran says. "Imagine that this remarkable plastic can now not only have good optical and mechanical properties, but also good electrical characteristics. By being able to tailor the amount of nanotubes we can add to the composite, we also can change it from the conductivity of silicon to a few orders below that achieved by metals."

Making this very inexpensive plastic highly conductive could benefit electronics in everything from military aircraft to personal computers. Computer failure, for instance, results from the build up of thermal and electrical charges, so developing these polymer nanotube composites into an antistatic coating or to provide a shield against electromagnetic interference would increase the lifespan of computing devices, ranging from PCs to PDAs.

The next step of this research is to develop ink formulations to paint these polycarbonate nanocomposites onto various electrical components. Normally, metal plates are used to dissipate electrical charge, so it's not surprising that the availability of a paintable ink would be particularly appealing to the Air Force for its lightweight properties, resulting in lighter aircraft that guzzle less gas.

Another key component of this latest research is that pristine nanotubes disbursed in this polycarbonate were found to possess an even higher conductivity than acid-treated carbon nanotubes. Traditionally, the tubes are sonicated, or treated with acid, to clean them and remove soot to get a higher conductivity. This, however, damages the tubes and exposes them to defects. Instead, Curran and his group were able to centrifuge, or swirl, them. This takes a little longer, but increases the potential to have higher conductivities. He attributes this to the incredibly clean samples of carbon nanotubes obtained from fellow collaborator David Carroll in the physics department at Wake Forest University.

In addition to Curran and Carroll, the team behind these remarkable findings includes Donald Birx, professor of electrical engineering and vice president for research at UH, two of Curran's former post-doctoral students, Jamal Talla and Donghui Zhang, and a current Curran student, Sampath Dias.

Coincidentally, Curran's former thesis supervisor Werner Blau and his group in the department of physics at Trinity College Dublin have come out with similar findings recently in the journal ACS Nano. Both groups really have been pushing hard in the area of polymer nanotube composites during the course of the last decade. Curran said his group at Houston achieved the highest conductivity levels so far, but also is encouraged by Blau's success and said repeating these types of outcomes will open doors for even higher values.

"While these are phenomenal results, finding these unusual highly conductive properties has not even begun to scratch the surface," Curran says. "There is hard science behind it, so developing it further will require significant investment. And we are very thankful to the Air Force for giving us this auspicious start."

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Scientists Pioneer Method for Making Giant Lunar Telescopes

Scientists working at NASA's Goddard Space Flight Center in Greenbelt, Md., have concocted an
innovative recipe for giant telescope mirrors on the Moon. To make a mirror that dwarfs anything on Earth, just take a little bit of carbon, throw in some epoxy, and add lots of lunar dust.

"We could make huge telescopes on the moon relatively easily, and avoid the large expense of transporting a large mirror from Earth," says Peter Chen of NASA Goddard and the Catholic University of America, which is located in Washington, D.C. "Since most of the materials are already there in the form of dust, you don't have to bring very much stuff with you, and
that saves a ton of money."

Chen and his Goddard colleagues Douglas Rabin, Michael Van Steenberg, and Ron Oliversen are presenting their mirror-making technique in a poster at the 212th meeting of the American Astronomical Society in St. Louis, Mo.

For years, Chen had been working with carbon-fiber composite materials to produce high-quality telescope mirrors. But Chen and his colleagues decided to try an experiment. They substituted carbon nanotubes (tiny tubular structures made of pure carbon) for the carbon-fiber composites. When they mixed small amounts of carbon nanotubes and epoxies (glue-like materials) with crushed rock that has the same composition and grain size as lunar dust, they discovered to their surprise that they had created a very strong material with the consistency of concrete. This material can be used instead of glass to make mirrors.

They next applied additional layers of epoxy and spun the material at room temperature. The result was a 12-inch-wide mirror blank with the parabolic shape of a telescope mirror. All of this was achieved with minimal effort and cost.

"After that, all we needed to do was coat the mirror blank with a small amount of aluminum, and voila, we had a highly reflective telescope mirror," says Rabin. "Our method could be scaled-up on the moon, using the ubiquitous lunar dust, to create giant telescope mirrors up to 50 meters in diameter." Such an observatory would dwarf the largest optical telescope in the world right now: the 10.4-meter Gran Telescopio Canarias in the Canary Islands.

The capabilities of a 50-meter telescope on the Moon boggle the imagination, according to NASA. With a stable platform, and no atmosphere to absorb or blur starlight, the monster scope could record the spectra of extra solar terrestrial planets and detect atmospheric biomarkers such as
ozone and methane. Two or more such telescopes spanning the surface of the Moon can work together to take direct images of Earth-like planets around nearby stars and look for brightness variations that come from oceans and continents. Among many other projects, it could make detailed observations of galaxies at various distances, to see how the universe evolved.

"Constructing giant telescopes provides a strong rationale for doing astronomy from the moon," says Chen. "We could also use this on-site composite material to build habitats for the astronauts, and mirrors to collect sunlight for solar-power farms."

Chen notes that his group achieved this breakthrough with only the support of small NASA internal seed funds. The carbon nanotubes were contributed by Dan Powell, lead nanotechnologist for NASA Goddard. Several amateur astronomers made key contributions by advising and making special epoxy formulations, helping with polishing experiments, and vacuum coating the 12-inch mirror.

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Carbon Nanotubes That Look Like Asbestos, Behave Like Asbestos

A major study published today in Nature Nanotechnology suggests some forms of carbon nanotubes -- a poster child for the "nanotechnology revolution" -- could be as harmful as asbestos if inhaled in sufficient quantities.

Carbon nanotubes are atom-thick sheets of graphite formed into cylinders. They may be formed from a single layer of graphite or they may consist of multiple concentric layers of graphite, resulting in multi-walled carbon nanotubes. While the diameter of a nanotube can vary
from a few nanometers up to tens of nanometers, they can be hundreds or even thousands of nanometers long. Carbon nanotubes come in many forms, with different shapes, different atomic arrangements, and varying amounts and types of added chemicals -- all of which affect their properties and might influence their impact on human health and the environment.

The study used established methods to see if specific types of nanotubes have the potential to cause mesothelioma -- a cancer of the lung lining that can take 30 to 40 years to appear following exposure. The results show that long, thin multi-walled carbon nanotubes that look like asbestos fibers, behave like asbestos fibers.

Discovered nearly 20 years ago, carbon nanotubes have been described as the wonder material of the 21st Century. Light as plastic and stronger that steel, they are being developed for use in new drugs, energy-efficient batteries and futuristic electronics. But since their discovery, questions have been raised about whether some of these nanoscale materials may cause
harm and undermine a nascent market for all types of carbon nanotubes, including multi- and single-walled carbon nanotubes. Leading forecasting firms say sales of all nanotubes could reach $2 billion annually within the next four to seven years, according to an article in the U.S. publication Chemical & Engineering News.

"This study is exactly the kind of strategic, highly focused research needed to ensure the safe and responsible development of nanotechnology," says Andrew Maynard, chief science advisor to the Project on Emerging Nanotechnologies and a co-author on the paper. "It looks at a specific nanoscale material expected to have widespread commercial applications and asks specific questions about a specific health hazard. Even though scientists have been raising concerns about the safety of long, thin carbon nanotubes for over a decade, none of the research needs in the current U.S. federal nanotechnology environment, health and safety risk research
strategy address this question."

Widespread exposure to asbestos has been described as the worst occupational health disaster in U.S. history and the cost of asbestos-related disease is expected to exceed $200 billion, according to major U.S. think tank RAND Corporation.

Dr Anthony Seaton, MD, a co-author on the paper and a professor emeritus at the University of Aberdeen in the United Kingdom, says, "The toll of asbestos-related cancer, first noticed in the 1950s and 1960s, is likely to continue for several more decades even though usage reduced rapidly some 25 years ago. While there are reasons to suppose that nanotubes can be used
safely, this will depend on appropriate steps being taken to prevent them from being inhaled in the places they are manufactured, used and ultimately disposed of. Such steps should be based on research into exposure and risk prevention, leading to regulation of their use. Following this study, the results of which were foreseen by the Royal Society in the U.K. in 2004, we
can no longer delay investing in such research."

Researchers, led by Kenneth Donaldson at the University of Edinburgh in the United Kingdom, examined the potential for long and short carbon nanotubes, long and short asbestos fibers, and carbon black to cause pathological responses known to be precursors of mesothelioma. Material was injected into the abdominal cavity of mice -- a sensitive predictor of long fiber response in the lung lining.

"The results were clear," says Donaldson. "Long, thin carbon nanotubes showed the same effects as long, thin asbestos fibers."

Asbestos fibers are harmful because they are thin enough to penetrate deep into the lungs, but sufficiently long to confound the lungs' built-in clearance mechanisms for getting rid of particles.

Donaldson stresses there are still pieces of the puzzle to fill in. "We still don't know whether carbon nanotubes will become airborne and be inhaled, or whether, if they do reach the lungs, they can work their way to the sensitive outer lining. But if they do get there in sufficient
quantity, there is a chance that some people will develop cancer -- perhaps decades after breathing the stuff," says Donaldson.

There is a silver lining to this research. According to Donaldson, "Short or curly carbon nanotubes did not behave like asbestos, and by knowing the possible dangers of long, thin carbon nanotubes, we can work to control them. It's a good news story, not a bad one. It shows that carbon nanotubes and their products could be made to be safe."

But Donaldson adds that the present study only tested for fiber-like behavior and did not exonerate carbon nanotubes from damaging the lungs in other ways. "More research is still needed if we are to understand how to use these materials as safely as possible," he notes.

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Future Of Computing -- Carbon Nanotubes, Superconductors to Replace Silicon Chip

The silicon chip, which has supplied several decades’ worth of remarkable increases in computing power and speed, looks unlikely to be capable of sustaining this pace for more than another decade – in fact, in a plenary talk at the the Institute of Physics’ Condensed Matter and Materials Physics conference, Suman Datta of Pennsylvania State University, gives the conventional silicon chip no longer than four years left to run.

As silicon computer circuitry gets ever smaller in the quest to pack more components into smaller areas on a chip, eventually the miniaturized electronic devices are undermined by fundamental physical limits. They start to become leaky, making them incapable of holding onto digital information. So if the steady increases in computing capability that we have come to take for granted are to continue, some new technology will have to take over from silicon.

Replacing the chip with carbon nanotubes

At the conference, researchers at Leeds University in the UK will report an important step towards one prospective replacement. Carbon nanotubes, discovered in 1991, are tubes of pure carbon just a few nanometres wide – about the width of a typical protein molecule, and tens of thousands of times thinner than a human hair. Because they conduct electricity, they have been proposed as ready-made molecular-scale wires for making electronic circuitry.

Some nanotubes behave as semiconductors, like silicon; others carry electric currents like metal wires. Already, fundamental elements of computer circuits such as transistors have been made from individual carbon nanotubes.

But the problem is arranging nanotubes into circuit patterns. One particular difficulty is that they are typically made as mixtures of metallic and semiconducting tubes, whereas just one type or the other is needed for a specific component. These electrical properties depend on the precise arrangement of carbon atoms in the nanotube, but that’s hard to determine for single tubes.

Bryan Hickey and his coworkers at Leeds have now developed a technique that will reveal an individual nanotube’s structure (and thus its electrical properties), and then allow it to be placed in a position on a surface with an accuracy of about 100 nanometres, a fraction of the width of a human blood cell. The nanotubes are grown on a perforated ceramic grid, and tubes lying across the holes are examined in an electron microscope to deduce their atomic structures. Then the researchers use two needle-fine tips like tweezers to pick up a single tube under the microscope and put back down on another surface.

Chris Allen, one of the Leeds teams, says, “With this technique we can make carbon nanotube devices of a complexity that is not achievable by most other means.”

Boosting computer power with superconductors

Two further talks at the meeting will describe an even more dramatic way to overcome the limitations of silicon computers. Hans Mooij of the Delft University of Technology in the Netherlands and Raymond Simmons of the National Institute of Standards and Technology in Boulder, Colorado, USA, will claim that superconductors – materials that conduct electricity with zero electrical resistance – can harness the power of quantum physics to boost computer power tremendously.

So-called quantum computers have become one of the hottest items in physics over the past decade. They attempt to improve on the power of silicon not by making components smaller but by exploiting the counterintuitive principles of quantum mechanics, the theory generally used to understand how objects behave at the scale of atoms and subatomic particles.

Objects governed by quantum theory can be in several different states at once, like a light switch being simultaneously ‘on’ and ‘off’. These ‘superposition’ states don’t correspond to anything familiar from our everyday world, but countless experiments have proved that they can exist so long as the quantum objects are not disturbed by, for example, making a measurement on them.
In a quantum computer, the equivalent of ‘bits’ that hold binary information as 1’s and 0’s in today’s computers will be quantum bits or qubits, which can also exist as superpositions of 1’s and 0’s. This massively increases the amount of information that can be encoded in a quantum computer’s memory. The catch is that superpositions are extremely delicate and hard to maintain, especially in memories containing large numbers of qubits that interact with one another.

Various candidates for making qubits are being explored, such as magnetically trapped atoms or nanometre-scale blobs of semiconductors. But it has long been recognized that loops of superconducting material can also be placed in quantum superposition states, and thus act as qubits. Here the quantum states may correspond to an electric current circulating round the ring in one direction or the other. (In superconductors this circulation can continue more or less indefinitely without petering out, because there is no electrical resistance.)

At the conference, Simmonds will describe the first demonstration of information being transmitted between two such superconducting qubits. This shows that elements of this kind can act as a quantum-computing memory and a “bus” for qubits to communicate with one another, an essential requirement of any working computer.

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Researchers Develop Darkest Manmade Material

Researchers at Rensselaer Polytechnic Institute and Rice University have created the darkest material ever made by man.

The material, a thin coating comprised of low-density arrays of loosely vertically aligned carbon nanotubes, absorbs more than 99.9 percent of light and one day could be used to boost the effectiveness and efficiency of solar energy conversion, infrared sensors, and other devices. The researchers who developed the material have applied for a Guinness World Record for their efforts.

“It is a fascinating technology, and this discovery will allow us to increase the absorption efficiency of light as well as the overall radiation-to-electricity efficiency of solar energy conservation,” says Shawn-Yu Lin, professor of physics at Rensselaer and a member of the university’s Future Chips Constellation, who led the research project. “The key to this discovery was finding how to create a long, extremely porous vertically-aligned carbon nanotube array with certain surface randomness, therefore minimizing reflection and maximizing absorption simultaneously.”

The research results were published in the journal Nano Letters.

All materials, from paper to water, air, or plastic, reflect some amount of light. Scientists have long envisioned an ideal black material that absorbs all the colors of light while reflecting no light. So far they have been unsuccessful in engineering a material with a total reflectance of zero.

The total reflectance of conventional black paint, for example, is between 5 and 10 percent. The darkest manmade material, prior to the discovery by Lin’s group, boasted a total reflectance of 0.16 percent to 0.18 percent.

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Big Screen TVs, Flexible Electronics, Surfboards Made From Same New Material

There is nothing new about combining two materials to make a composite material with more desirable properties than the originals. Fibreglass has been a mainstay of the marine industry for decades and the construction industry is built on reinforced concrete. Now carbon nanotubes (CNT) are getting in on the act with nanotechnologists working out how to grow nanotube reinforcements for polymers in an ideal manner.

Researchers from Trinity College have developed a scalable inexpensive technique to grow grid patterns of nanotube arrays. To maximize the effect of CNT reinforcement on a polymer thin film, while minimizing nanotube content, a controllable way of varying the volume fraction of CNTs within the composite is needed. In order to do this, the inter-grid spacing can be tailored as required giving a simple method of controlling the volume fraction of nanotubes grown on substrates.

The research work by Werner Blau, Emer Lahiff, Andrew Minett and Kentaro Nakajima is expected to lead to incorporation of CNTs in polymer matrices within flat panel displays, sensors, flexible electronic devices and actuators.

The study has been published in a special edition of the open access journal, AZoJono.

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World's Smallest Radio: Nano-Sized Detector Turns Radio Waves Into Music

Researchers in California report development of the world’s first working radio system that receives radio waves wirelessly and converts them to sound signals through a nano-sized detector made of carbon nanotubes. The “carbon nanotube radio” device is thousands of times smaller than the diameter of a human hair. The development marks an important step in the evolution of nano-electronics and could lead to the production of the world’s smallest radio, the scientists say. Their findings appeared online today and are scheduled for publication in the Nov. 14 print edition of ACS’ Nano Letters, a monthly journal.

Peter Burke and Chris Rutherglen developed a carbon nanotube “demodulator” that is capable of translating AM radio waves into sound. In a laboratory demonstration, the researchers incorporated the detector into a complete radio system and used it to successfully transmit classical music wirelessly from an iPod to a speaker several feet away from the music player.

Although other researchers have developed nano-sized radio wave detectors in the past, the current study marks the first time that a nano-sized detector has been demonstrated in an actual working radio system, the scientists say. The study demonstrates the feasibility of making other radio components at the nanoscale in the future and may eventually lead to a “truly integrated nanoscale wireless communications system,” they say. Such a device could have numerous industrial, commercial, medical and other applications.

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