We recently learnt of a new technology that could one day give us invisible loudspeakers! Research scientists at the Fraunhofer Institute for Manufacturing, Engineering and Automation (IPA) in Stuttgart have demonstrated prototype loudspeakers made from carbon nanotubes (CNTs). Using thermo-acoustic properties that result in the conductive coating heating up and expanding when a current is passed through it, and cooling down and contracting when that current is removed, the sound is generated by the way this moves the air molecules around the nanotubes.
The CNTs can be assembled into arrays, which are termed ‘forests’, and these currently resemble black velvet. However, because they can be manufactured in extraordinarily thin layers, these might, in future, be thin enough to become transparent, and could then feasibly become available as coatings for wallpaper, monitor screens, or even advertising hoardings (heaven forbid!).
The CNT forests can also be remotely heated using lasers, which makes them capable of wireless operation. An entire room could become your invisible loudspeaker, and might even incorporate noise-cancelling technology so you won’t hear your neighbours — and they won’t hear you. Commercial manufacturing is rumoured to be three years off (so you won’t be seeing reviews of invisible monitors in SOS for a while yet!), but we’ll bring you more news of this exciting new technology as it comes out. Martin Walker
