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Nanotubes in particular can behave as excellent conductors, insulators or semiconductors according to how the atoms are specifically arranged. Taking this further, a nanotube filled with a row of spherical buckyballs makes a nanotube peapod, and these seem to have potential for creating more complex computing and control circuits.

Commercial applications are still limited, with research mostly focused on understanding the basic physical properties of these materials and on working out how to achieve pure yields of particular structures rather than a jumble of many different kinds. Numerous potential applications have been explored, though, including nanotube transistors for use in computing circuits, electron emitters for flat-panel displays and microwave sources for telecommunications transmitters.

Most recently, NASA's Ames Laboratory in California announced in April that it had produced hybrid silicon chips which use nanotubes to act as interconnects within the integrated circuit. Laying down power supply and signal paths on a chip is becoming increasingly difficult as dimensions shrink. Normally, a narrow trench has to be etched into the chip substrate and copper or some other metallic conductor deposited into it. The narrower the connection, the less current it can carry without overheating or deteriorating.

NASA's new nanotube connections appear more robust and can provide a significantly higher current density, as much as a million Amps of current per square centimetre of cross-section. This, according to Meyya Meyyappan,

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director of the Center for Nanotechnology at NASA Ames, should allow silicon devices to continue shrinking further. 'While we're working on carbon nanotube-based chips for long-term needs, we're also indirectly helping industry to keep silicon-based computer chips in use for as long as possible,' he said.

Aside from computer electronics, fullerenes are being studied for possible applications in catalysts, pharmaceuticals, sensors, chemically active surface coatings and, because of their high strength-to-weight ratio, for use in everything from industrial composites to car tyres. If only some of those areas become commercially viable, fullerenes will be widespread. Yet little is known about their environmental safety or even simple toxicity. The few small studies that have been done so far reached contradictory conclusions on nanotube toxicity. But even if fullerenes turn out not to be toxic in themselves, there are many other ways in which they might be harmful.

It's already known, for example, that they can cross bacterial cell membranes. Once there, they've entered the food chain on the ground floor and could end up in other species higher up that chain. Fullerenes are generally very stable so they don't biodegrade and aren't even easy to destroy deliberately. Even though they're rather inert themselves, one proposed use of fullerenes is as molecular cages to hold other reactive substances or catalysts, but these might interfere drastically with natural or industrial processes. There are many other possibilities - just like asbestos, they might cause cancer or other diseases simply by virtue of their size and shape. Or they might provide a vehicle for other harmful substances to piggyback on.

Atomic wars

All this is speculation and may be quite unfounded. The problem is that nobody really knows because so little research has been done on the side effects. According to Kathy Jo Wetter of ETC, 'Even though industry is scaling up the manufacture of nanoparticles and carbon nanotubes, there appear to be no government regulations in Europe or North America to ensure the safety of workers or consumers.'