‘Nanotube’ Sheets Slender but Strong

Researchers have made electrically conductive sheets of carbon atoms one-thousandth the diameter of a human hair, but 50 times stronger than steel by weight.

The sheets could be used to make ultralight race cars whose bodies could also serve as batteries, synthetic muscles with 100 times the strength of natural muscle or half-square-mile sails to power a solar spaceship.

The researchers, writing in the current issue of the journal Science, made the sheets by depositing iron particles on a silicon plate. By heating the plate and exposing it to a carbon-rich gas, they created rows of tiny carbon cylinders called nanotubes.

The nanotubes naturally aligned themselves like trees in a forest, said study author Ray Baughman, director of the NanoTech Institute at the University of Texas at Dallas. The researchers gently pulled on a row of nanotubes with an adhesive strip similar to a Post-It note.

As the first row of nanotubes was pulled by the adhesive, the next row attached itself, drawn by an atomic attraction known as Van der Waals forces.

By pulling row upon row of nanotubes, the team was able to create sheets up to 2 feet wide, 3 feet long and just two-millionths of an inch thick.

Two sheets put together were strong enough to support droplets of water. Multiple layers of the transparent sheet could be strong enough to make heated car windows or bulletproof vests.

A key advantage of carbon nanotubes is that they are highly conductive.

Since the 1990s, scientists have been able to fabricate tiny electrical wires by linking nanotubes with resin or some other polymer. But the wires are inefficient because they lose current at each joint.

The new sheets don’t suffer from that problem since they are made of unbroken nanotube rows. A wire cut from a sheet could operate with a fraction of the power need by the earlier technology.