A transparent lacquer containing carbon nanotubes could clear car windscreens or mirrors by acting as a heater. Thicker, opaque versions of the coating could turn entire floors of buildings into radiators, researchers claim.

The lacquer can be sprayed onto any surface and consists of a liquid base containing a mixture of nanotubes that conduct electricity. As the liquid dries, the nanotubes form a conducting network inside the lacquer. Passing a current through this network causes the layer to heat up.

In tests, a coating connected to a 12 volt power supply similar to car battery was able to clear ice from a plastic sheet in about 2 minutes although the test sheet was only the size of a paper back book.

"We can heat up the whole of any surface with a transparent coating," researcher Dominik Nemec told New Scientist: "It could be used to clear windscreens or mirrors of water or ice." Nemec is working on the coating with colleague Ivica Kolaric at the Fraunhofer Technology Development Group in Stuttgart, Germany.

Don't mind the gap

The team hopes the technology will replace the built-in wire filament heaters in car windscreens. As well providing more uniform heat than a filament heater, the nanotube film is more resistant to damage, says Nemec. "If a filament is broken the whole heater won't work," he explains, "this new film can have gaps in – by accident or design – and still work."

Adding more nanotubes to the lacquer increases the heat the material can produce but also makes it opaque. "Anywhere you need heat, you could coat a surface in this material," says Nemec.

He adds that the coating could also be used for under-floor heating. A square metre of film about 0.3 millimetres thick provides around 15 kilowatts of heat – enough to heat a good sized hall.