Nanotube sheets pave way for future flat speakers

London, November 1 : A Chinese research team has moved a step closer to realising flat speakers that will be much cheaper than the existing ones, for they have found that sheets made of carbon nanotubes behave like a loudspeaker when zapped with a varying electric current.

Shoushan Fan and his colleagues at Tsinghua University and Beijing Normal University have become the research team to study the acoustic properties of nanotubes.

For their study, the researchers created a think sheet by roughly aligning many 10-nanometer-diameter carbon nanotubes.

Upon sending an audio frequency current through the sheet, the researchers found that it acted as a loudspeaker.

Fan thinks that the nanotube speaker functions as a thermoacoustic device.

He says when an alternating current passes through it, the nanotube sheet alternates between room temperature and 80 degree Celcius, and such rapid temperature oscillations lead to pressure oscillations in the air next to the film.

The researcher says that such thermally induced pressure oscillations are responsible for the sound.

Fan points out that this phenomenon was first observed over a century ago independently by William Henry Preece and Karl Ferdinand Braun, who showed that it was possible to get sound from a thin metal foil by passing an alternating current through it.

That discovery led to the invention of a device called the "thermophone", he says.

He, however, adds that the thermophone produced a very weak sound, whereas the nanotube sheets can be very loud.

Fan says the nanotube loudspeakers have several key advantages over standard speaker systems, for the flexible sheets can be stretched or flexed into complicated shapes and they still produce sound.

According to him, given the transparent nature of the sheets, they could be attached to the front of an LCD screen to replace standard speakers,

He even believes that nanotube sheets could be stitched into clothing to create "singing and speaking jackets".

Cees Dekker, a nanoscience expert at Delft University of Technology in the Netherlands, finds the new study very interesting.

"It's just amazing how widespread the diversity of applications of these nanotubes are," New Scientist magazine quoted him as saying.

A research article on this work has been published in the journal Nano Letters.

ANI