In research that may redefine ear buds, earphones, stereo loudspeakers, and
other devices for producing sound, researchers in China are reporting development
of flexible loudspeakers thinner than paper that might be inserted into the
ears with an index finger or attached to clothing, walls, or windows. Their
report on what may be the world's thinnest loudspeakers, made from transparent
carbon nanotube films, is scheduled for the December 10 issue of ACS'
Nano Letters, a monthly journal.
 | | Carbon nanotube thin film loudspeakers. (a) The CNT thin film was pulled out from a superaligned CNT array grown on a 4 in. silicon wafer and put on two electrodes of a frame to make a loudspeaker. (b) SEM image of the CNT thin film showing that the CNTs are aligned in the drawing direction. (c) A4 paper size CNT thin film loudspeaker. (d) The cylindrical cage shape CNT thin film loudspeaker can emit sounds to all directions, diameter 9 cm, height 8.5 cm. Copyright © 2008 American Chemical Society |
Kaili Jiang, Shoushan Fan, and colleagues note that most of today's loudspeakers
are relatively bulky, complex, and inflexible, consisting of a permanent magnet
fixed to a voice coil and a cone. To meet the growing demand for smaller speakers
for portable digital consumer electronics devices, manufacturers need new technology,
they say.
The scientists describe the development of super-thin carbon nanotube (CNT)
films — 1/1,000th the width of a single human hair — that are capable
of transmitting music and other sounds. In laboratory tests, the researchers
mounted a thin CNT film onto two electrodes to form a simple loudspeaker. The
speaker produced sound with the same excellent quality as conventional loudspeakers,
but without magnets and moving components, the researchers say. They also demonstrated
that the flexible film could be used just as effectively to play music from
an iPod and while pasted to a flexible, waving flag.
“These CNT thin film loudspeakers are transparent, flexible, and stretchable,
which can be tailored into many shapes and mounted on a variety of insulating
surfaces, such as room walls, ceilings, pillars, windows , flags, and clothes
without limitations. Furthermore, CNT thin films can also be made into small
area devices, such as earphones and buzzers. There is no doubt that more and
more applications will be developed as time goes on. This technique might open
new applications of and approaches to manufacturing loudspeakers and other acoustic
devices.”
Posted November 14th, 2008
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