Idiot’s guide to carbon nanotubes

If you have just been reading the piece (New way to test a chilli’s piquancy), I know what is on your mind. You are wondering what on earth a carbon nanotube is.

Let me explain. Carbon nanotubes are variations on the buckyball. Oh, come on! You must have heard of buckyballs — spherical carbon molecules with a structure resembling the geodesic domes invented by Buckminster “Bucky” Fuller, the American architect, engineer, poet and philosopher. Hence their name — and their other name, fullerenes.

The bog standard buckyball has 60 carbon atoms arranged in a pattern resembling one of those footballs made up from five- and six-sided panels. Now imagine this: take half a buckyball and join it to a cylinder made of yet more carbon atoms to form a shape like a test tube.

That is the most common form of single-walled carbon nanotube molecule, although some have buckycap hemispheres at both ends and some have none. Unlike a test tube, however, they can have a length-to-diameter ratio of more than 1,000,000:1.

In other words, although only about a nanometre in diameter (yes, that’s where the name comes from), they can be several millimetres long.

Carbon nanotubes exhibit great tensile strength and flexibility, have unique electrical properties and are efficient conductors of heat. Those with practical applications tend to be of the multi-walled variety. These are either concentric tubes (the “Russian doll” model) or sheets of carbon atoms rolled up like a scroll (the “parchment” model).

Scientists are excited about carbon nanotubes because their unusual properties can be harnessed in many ways. However, their use in healthcare applications may be limited because of research suggesting carcinogenicity and other toxic effects.