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Carbon nanotubes are the most important corner of the movement toward sustainability that most consumers have never heard of. And the complexity of the shadowy technology is roughly in-line with that of the stories being told about it.
Last month, Honda Research Institute, along with two universities, released new research (link: http://world.honda.com/news/2009/c091001Nano-Technology) that shows a 91 percent success rate in producing conductive tubes, besting the 25 to 50 percent rate researchers had seem previously. Largely lauding it as important, several mainstream media outlets dubbed the research as a “breakthrough” in the field.
But the claims raise eyebrows among some in the industry, who say the publicity amounts to spectacle.
“This particular Honda report is overselling what had been known and researched in the nanotube community for the last five years or so,” said Dr. David Tomanek, professor of physics at Kyung Hee University in South Korea, who specializes in nanostructured materials.
“This does not mean they can't do something important. But it just indicates they may not be aware of successful past ways to enrich or deplete the native 33 percent fraction of conductive nanotubes.”
A nanotechnology researcher who works in development, Sergei Sarichev, had similar sentiments. “An achievement of around 90 percent [fabrication efficiency] is an important cornerstone in the research, but not quite enough, and it seems that a lot is yet to be done,” he said.
Carbon nanotubes, virtually infinitesimal pieces of carbon a tiny fraction as wide as a human hair, have huge theoretical potential. When successfully fabricated, the nanotubes are stronger than steel, conduct electricity and heat with remarkable efficiency, and are as light as cotton, making their theoretical applications quite wide: cheaper solar panels, efficient drug delivery to eradicate debilitating diseases, more-powerful batteries for cars, synthetic human organs derived from the tiniest speck of source material, and other products that seem more fantastic than realistic. Central to these capabilities are the tubes' extraordinary conductive capacities, which don't always pan out in a lab setting, let alone mass production.
Honda's announcement centered on the frequency with which it said engineers created conductive carbon tubes, or ones that achieve a metallic state. Fabricating carbon tubes produces both semi-conducting nanotubes and metallic nanotubes, Sarichev explained, and a higher purity of one or the other allows for better control of their respective properties, one of which is conductivity.
The company said it achieved the high success rate after learning how to control certain variables it had not been able to control before.
“Further research is in progress with the ultimate goal to take complete control over grown nanotube configuration to support their real-world application,” said Dr. Avetik Harutyunyan, the project's leader, in a statement.
For Honda, carbon tubes could potentially produce conductive automobile paints, reduce the fleet's weight-to-strength ratio, and drive new electronic features as well as longer-lasting, smaller automobile fuel cells.
But new research (link: http://www.sciencedaily.com/releases/2009/10/091025162452.htm) from universities and watchdog groups indicates that, like asbestos, inhaling carbon tubes can affect the outer lining of the lungs, though the effects of long-term exposure remain unclear. Industry insiders say this study is one of many they expect to see that examines the industrial safety of carbon-nanotube production and use.
Replicating Mother Nature
Because of their unusual mechanical, physical, and chemical properties, carbon tubes are science's most-recent fascination with nanotechnology, a field that has been around ever since engineers developed stained-glass windows for the interiors of buildings, on which nano-scaled imperfections create unique properties for refracting light. More recently, NASA's so-called “elevator to space” proposal germinated from the theoretical applications of carbon nanotubes.
In brief, nanotechnology aims to replicate the organic processes originated not by man, but by Mother Nature. For living organisms, growth has a way of happening on its own—and, in fact, carbon tubes do exist in nature. Tomanek said researchers found trace amounts of carbon tubes in ice dating back to the Neolithic Stone Age that they pulled from a Greenland ice cap in June of 1988.
“The observation of carbon nanotubes in the ice core sample is particularly significant since it illustrates that they are also created naturally in antiquity,” a report on those findings stated.
“Nanotechnology is both complex and natural. What appears so simple – plant a seed and see it grow to a rose with just sun, water and fertilizer – is so amazing, beautiful, and complex. There is no waste,” Tomanek explained. “We are learning from nature how to use molecular-based recognition to selectively recognize cancer cells and kill only those. We are learning how structures like nanotubes can make nerve cells that have been severed in spinal fracture grow, like a vine on a tree, to save a human. Companies such as Revlon use nanotechnology to improve optical appearance of human skin.”
Nanotechnology's massive complexities cause its relative lack of awareness when compared to other sustainable technologies that are easier to understand, like solar and wind energy, by those free of a lab-coat and lacking a Ph.D.
“Humans like to judge the value [of a technology] by the size – big windmills, big power plants, big solar cell batteries,” Tomanek explained. “I believe the potential of nanotechnology is bigger than that of biotechnology, and is still not recognized by many.”
Nanotechnologies like carbon tubes, he added, don't feature mechanical parts that can break and need replacements. It's most accurate to say they're not made, but rather grown organically.
A Backlash, Small but Visible
The hardest material known to humanity is elemental carbon, in its diamond form. Because of the quantum nature of atomic bonding, the carbon-carbon bonds in carbon nanotubes have the additional properties of being incredibly flexible and conductive, which is what makes carbon the ideal source element for nanotechnology.
For a small but visible group of skeptics and critics, this branch of science ought not go much further.
“There is a high level of enthusiasm for the potential benefits of nanotechnology and little concern about its possible dangers,” writes Silvana Fiorito of Italy's Consiglio Nazionale delle Ricerche (National Research Council) in the preface to his 2008 book “Carbon Nanotubes: Angels or Demons?”
These possible dangers Fiorito refers to reflect the reservations of a comparatively small group of accomplished scientists hellbent on showing nanotech's threatening extremes. In fact, the MIT-educated scientist responsible for popularizing nanotechnology in the 1970s and then leading its pool of skeptics years later, Eric Drexler, was characterized in a 2004 Wired article (link: http://www.wired.com/wired/archive/12.10/drexler.html) as a current “industry outcast” because big business now has strong incentives to market nanotechnology in commercial products.
Drexler co-founded The Foresight Institute (link: http://www.foresight.org), a nonprofit organization that has used an ominous mission statement, “Preparing for Nanotechnology.” It aims to discover and promote the upsides, and help avoid the dangers, of nanotechnology, artificial intelligence, biotechnology, and similar life-changing developments.
A similar think tank, The Center for Responsible Nanotechnology (link: http://CRNano.org), lists numerous risks that advancing nanotechnology research could create. These risks range from reasonable concerns like economic disruption brought on by a glut of cheap products to important cautions such as heightened risks for terrorism and an unstable arms race to scenarios from the realms of science fiction such as self-replicating nanomachines that behave independent of human instruction.
Chris Phoenix, director of research at CRN, elaborated. “From a physics point of view, nanoscale structures have new properties, but they're not spooky-new, just cool-new,” he said. “Most of today's nanotech is nanotech simply because it's small and useful. It usually turns out to provide incremental improvements on things we can already do. Stronger materials, new classes of industrial chemicals, some new medical technologies, better computers, better surface treatments, et cetera.”
He said he would not label carbon nanotubes in electronics as a particularly risky technology.
On the other hand, he said, “molecular manufacturing is about what happens when we start building not just structures, but machines, and machines that can make machines. Small things work faster, molecules are highly precise, and direct engineering at the level of molecules will open up vast new realms of manufacturing.” Molecular manufacturing, he said, meets some of the qualifications of being “spooky-new.”
Phoenix said nanotechnologies like carbon tubes would be analogous to the introduction of plastics if molecular manufacturing were analogous to the continued growth of digital computing. “Sure, we use lots of plastics today, but we got along okay with wood and ceramics and metal. [But] you can do things with computers that just can't be done any other way.”
Current and potential applications of carbon nanotubes:
(Source: Dr. David Tomanek, professor of physics at Kyung Hee University)
- 100 percent of the Japanese-made lithium-ion batteries contain carbon nanotubes, amounting to an annual use of 200 tons of the technology.
- Composites, such as the new London Tube for the Olympics, which will have wagons constructed of CNT-based composites produced by air and rail manufacturer Bombardier.
- Electromagnetic shielding for use in in fabrics, sheet metal, plasma, and other substances.
- Flat-panel displays, such as those used on televisions and computer screens, with the potential to be paper-thin.
- Super-capacitors that could replace batteries as a source of energy for all sorts of devices and products.
- Components for smaller fuel cells for automobiles and other power-hungry devices.
- Improving bio-compatibility of implants, such as hip replacements, as scaffolding for bone growth.
- Super-strong UV-resistant fabrics similar to Kevlar for military and law-enforcement uses, with prototypes and weaving machines existing today.
- Potential for medication delivery via cell-like devices injected into a patient's bloodstream and hydrogen storage for industrial applications.
- And, yes, NASA's space elevator is far down the list of potential carbon nanotube applications.
 Andrew Graham (bio) is a writer and media contact in New York. He is on Twitter and writes a blog about global affairs.
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