March 30, 2011 — Catalysts made of carbon nanotubes (CNT) dipped in a polymer solution equal the energy output and otherwise outperform platinum catalysts in fuel cells, a team of Case Western Reserve University engineers has found.

Liming Dai, professor of chemical engineering and the research team leader, with research associates Shuangyin Wang and Dingshan Yu, found that by simply soaking carbon nanotubes in a water solution of the polymer polydiallyldimethylammoniumn chloride for a couple of hours, the polymer coats the nanotube surface and pulls an electron partially from the carbon, creating a net positive charge.

They placed the nanotubes on the cathode of an alkaline fuel cell. There, the charged material acts as a catalyst for the oxygen-reduction reaction that produces electricity while electrochemically combining hydrogen and oxygen.

In testing, the fuel cell produced as much power as an identical cell using a platinum catalyst. But the activated nanotubes last longer and are more stable, the researchers said.

The simple polymer-coating technique on CNTs can knock down one of the major roadblocks to fuel cell use: cost. Platinum, which represents at least a quarter of the cost of fuel cells, currently sells for about $65,000 per kilogram. These researchers say their activated carbon nanotubes cost about $100 per kilogram.

Unlike platinum, the carbon-based catalyst doesn’t lose catalytic activity or efficiency over time; isn’t fouled by carbon monoxide; and is free from the crossover effect with methanol. Methanol, a liquid fuel that’s easier to store and transport than hydrogen, reduces activity of a platinum catalyst when the fuel crosses over from the anode to the cathode in a fuel cell.

The work is published in the online edition of Journal of the American Chemical Society at http://pubs.acs.org/doi/full/10.1021/ja1112904.

The new process builds on the Dai lab’s earlier work using nitrogen-doped carbon nanotubes as a catalyst. In that process, nitrogen, which was chemically bonded to the carbon, pulled electron partially from the carbon to create a charge. Testing showed the doped tubes tripled the energy output of platinum.

Dai, who is a member of the Great Lakes energy Institute, said the new process is far simpler and cheaper than using nitrogen-doped carbon nanotubes and he’s confident his lab will increase the energy output as well. The researchers believe they can boost the power output and maintain the other advantages by matching the best nanotube layout and type of polymer.

Learn more at http://www.case.edu/.

Also read the Energy Storage Trends Blog

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March 28, 2011 — A Harvard bioengineer and an MIT aeronautical engineer have created a new device that can detect single cancer cells in a blood sample, potentially allowing doctors to quickly determine whether cancer has spread from its original site.

These posts, made of carbon nanotubes, can trap cancer cells and other tiny objects as they flow through a microfluidic device. Each post is 30 microns in diameter. Image: Brian Wardle.

The microfluidic device, described in the March 17 online edition of the journal Small, is about the size of a dime, and could also detect viruses such as HIV. It could eventually be developed into low-cost tests for doctors to use in developing countries where expensive diagnostic equipment is hard to come by, says Mehmet Toner, professor of biomedical engineering at Harvard Medical School and a member of the Harvard-MIT Division of Health Sciences and Technology.

This tiny microfluidic device can separate cancer cells from normal blood cells. Image: Brian Wardle.

Toner built an earlier version of the device four years ago. In that original version, blood taken from a patient flows past tens of thousands of tiny silicon posts coated with antibodies that stick to tumor cells. Any cancer cells that touch the posts become trapped. However, some cells might never encounter the posts at all.

Toner thought if the posts were porous instead of solid, cells could flow right through them, making it more likely they would stick. To achieve that, he enlisted the help of Brian Wardle, an MIT associate professor of aeronautics and astronautics, and an expert in designing nano-engineered advanced composite materials to make stronger aircraft parts.

Out of that collaboration came the new microfluidic device, studded with carbon nanotubes (CNTs), that collects cancer cells eight times better than the original version.

When designing advanced materials, Wardle often uses hollow CNT cylinders whose walls are lattices of carbon atoms. Assemblies of the tubes are highly porous: A forest of carbon nanotubes, which contains 10 billion to 100 billion carbon nanotubes per square centimeter, is less than 1% carbon and 99% air. This leaves plenty of space for fluid to flow through.

The MIT/Harvard team placed various geometries of carbon nanotube forest into the microfluidic device. As in the original device, the surface of each CNT can be coated with antibodies specific to cancer cells. However, because the fluid can go through the forest geometries as well as around them, there is much greater opportunity for the target cells or particles to get caught.

The researchers can customize the device by attaching different antibodies to the nanotubes’ surfaces. Changing the spacing between the nanotube geometric features also allows them to capture different-sized objects: tumor cells (about a micron in diameter), viruses (40nm), etc.

Circulating tumor cells (cancer cells that have broken free from the original tumor) are normally very hard to detect, because there are so few of them — usually only several cells per 1ml sample of blood, which can contain tens of billions of normal blood cells. However, detecting these breakaway cells is an important way to determine whether a cancer has metastasized. "Of all deaths from cancer, 90% are not the result of cancer at the primary site. They’re from tumors that spread from the original site," Wardle says.

Toner’s original cancer-cell-detecting device is now being tested in several hospitals and may be commercially available within the next few years. The researchers are now beginning to work on tailoring the device for HIV diagnosis.

Read the Small abstract and access the article here: http://onlinelibrary.wiley.com/doi/10.1002/smll.201002076/abstract

Courtesy of Anne Trafton, MIT News Office

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March 24, 2011 – Marketwire — Vendum Batteries (OTCBB: VNDB), a US-based battery technology development company, joined the Nano Knowledge Transfer Network (NanoKTN), a Government agency leading and supporting the commercialization of nanotechnologies in the UK.

NanoKTN is about networking, establishing industry collaborations, partner brokering and accessing R&D and commercialization grant schemes from £5,000 to £250,000 ($7,500 to $390,000). Vendum expects to successfully obtain grants and begin further research and development to further improve its battery technology and immediately commence with pre-production prototypes. Through NanoKTN and working closely with universities, start-up companies like Vendum can build strong supply chains.

Fraser Cottington, CEO of Vendum batteries, believes involvement with NanoKTN is a vital component to linking with the academic community in a meaningful and focused way and allows the company to spread the investment risk, by working with in partnership to achieve common goals, in high-tech battery technology and design.

The NanoKTN aims to simplify the nanotechnology innovation landscape by providing a clear and focused vehicle for the rapid transfer of high-quality information on technologies, markets, funding and partnering opportunities. Objectives include: Improved industrial performance through adoption of nanotechnology; Drive knowledge transfer between companies and the research base; Facilitate interactions through networking and event organization; Provide thought leadership and industry input into UK policy and strategy.

Vendum Batteries has a pending patent on a non-toxic, carbon-based light-weight battery. The paper-thin battery contains none of the toxic elements used in conventional batteries and its carbon nanotube and cellulose-based technology makes it entirely biodegradable. For more information please visit www.vendumbatteries.com

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March 23, 2011 — Researchers at Rice University have created a synthetic material that gets stronger from repeated stress, much like the body strengthens bones and muscles after repeated workouts.

Work by the Rice lab of Pulickel Ajayan, professor in mechanical engineering and materials science and of chemistry, shows the potential of stiffening polymer-based nanocomposites with carbon nanotube (CNT) fillers. The team reported its discovery this month in the journal ACS Nano (see the abstract at http://pubs.acs.org/doi/abs/10.1021/nn103104g).

The complex, dynamic interface between nanostructures and polymers in carefully engineered nanocomposite materials enable this self-enhancing quality. Brent Carey, a graduate student in Ajayan’s lab, found the interesting property while testing the high-cycle fatigue properties of a composite he made by infiltrating a forest of vertically aligned, multiwalled nanotubes (MWCNTs) with polydimethylsiloxane (PDMS), an inert, rubbery polymer. Repeatedly loading the material didn’t seem to damage it at all; the stress made it stiffer.

Carey, whose research is sponsored by a NASA fellowship, used dynamic mechanical analysis (DMA) to test their material. He found that after 3.5 million compressions (five per second) over about a week’s time, the stiffness of the composite had increased by 12% and showed the potential for even further improvement.

"It took a bit of tweaking to get the instrument to do this," Carey said. "DMA generally assumes that your material isn’t changing in any permanent way. In the early tests, the software kept telling me, ‘I’ve damaged the sample!’ as the stiffness increased. I also had to trick it with an unsolvable program loop to achieve the high number of cycles."

Materials scientists know that metals can strain-harden during repeated deformation, a result of the creation and jamming of defects — known as dislocations — in their crystalline lattice. Polymers, which are made of long, repeating chains of atoms, don’t behave the same way.

The team is not sure precisely why their synthetic material behaves as it does. "We were able to rule out further cross-linking in the polymer as an explanation," Carey said. "The data shows that there’s very little chemical interaction, if any, between the polymer and the nanotubes, and it seems that this fluid interface is evolving during stressing."

"The use of nanomaterials as a filler increases this interfacial area tremendously for the same amount of filler material added," Ajayan said. "Hence, the resulting interfacial effects are amplified as compared with conventional composites.

Simply compressing the material didn’t change its properties; only dynamic stress — deforming it again and again — made it stiffer.

Carey drew an analogy between their material and bones. "As long as you’re regularly stressing a bone in the body, it will remain strong," he said. "For example, the bones in the racket arm of a tennis player are denser. Essentially, this is an adaptive effect our body uses to withstand the loads applied to it.

"Our material is similar in the sense that a static load on our composite doesn’t cause a change. You have to dynamically stress it in order to improve it."

Cartilage may be a better comparison — and possibly even a future candidate for nanocomposite replacement. "We can envision this response being attractive for developing artificial cartilage that can respond to the forces being applied to it but remains pliable in areas that are not being stressed," Carey said. Read more about nanotech in medical sciences here.

Both researchers noted this is the kind of basic research that asks more questions than it answers. While they can easily measure the material’s bulk properties, it’s an entirely different story to understand how the polymer and nanotubes interact at the nanoscale.

"People have been trying to address the question of how the polymer layer around a nanoparticle behaves," Ajayan said. "It’s a very complicated problem. But fundamentally, it’s important if you’re an engineer of nanocomposites.

"From that perspective, I think this is a beautiful result. It tells us that it’s feasible to engineer interfaces that make the material do unconventional things."

Co-authors of the paper are former Rice postdoctoral researcher Lijie Ci; Prabir Patra, assistant professor of mechanical engineering at the University of Bridgeport; and Glaura Goulart Silva, associate professor at the Federal University of Minas Gerais, Brazil.

Rice University and the NASA Graduate Student Researchers Program funded the research.

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