Nanotube Speakers

What Are Cabron Nanotubes?

Carbon nanotubes (CNTs) consist of carbon with diameters typically measured in nanometers. Carbon nanotubes often refer to single-wall carbon nanotubes (SWCNTs) with diameters in the range of a nanometer. Iijima, Ichihashi, and Bethune et al. discovered them in carbon arc chambers similar to those used to produce fullerenes. Single-wall carbon nanotubes are one of the allotropes of carbon, intermediate between fullerene cages and flat graphene.

Single-Wall Carbon Nanotubes

Although not made this way, single-wall carbon nanotubes are like cutouts from a two-dimensional hexagonal lattice of carbon atoms rolled up along one of the Bravais lattice vectors of the hexagonal lattice to form a hollow cylinder. Consequently, in this construction, periodic boundary conditions are imposed over the length of this roll-up vector to yield a lattice with helical symmetry of seamlessly bonded carbon atoms on the cylinder surface. Carbon nanotubes also often refer to multi-wall carbon nanotubes (MWCNTs) consisting of nested single-wall carbon nanotubes. If not identical, these tubes are very similar to Oberlin, Endo, and Koyama's long, straight, and parallel carbon layers cylindrically rolled around a hollow tube. Engineers sometimes use multi-wall carbon nanotubes to refer to double and triple-wall carbon nanotubes.  

Paper-Thin Nanotube Speakers

In a recent development, researchers in China developed a paper-thin loudspeaker that you can attach to clothing, walls, windows, or even insert into the ear. These paper-thin loudspeakers consisted of transparent carbon nanotube films. Subsequently, their work was published in the ACS journal Nano Letters (Fan et al. 2008). So, Professor Fan and his research group at Tsinghua University, China, developed the smallest loudspeaker in the world using CNT thin films by a simple fabrication process. Today, the loudspeakers available in the market are bulky and complex. By making these loudspeakers thinner and compact, people can suitably use them for new digital electronic devices and various other applications.

Furthermore, engineers already use carbon nanotubes (CNTs) for various applications, including sound and music transmission. Researchers mounted a carbon nanotube film on two electrodes and found that the system works as a loudspeaker. These thin CNT films can generate sound by applying an audio frequency current through them. What's more, this phenomenon is a result of a thermoacoustic effect. Moreover, the ultra-small heat capacity per unit area of CNT thin films can lead to a wide frequency response range and high sound pressure level. Therefore, this CNT thin film can be a practical magnet-free loudspeaker with a very simple structure. The thin CNT film was pulled from a super-aligned CNT array grown on a 4-inch silicon wafer and put on two frame electrodes to make a loudspeaker.  

Source Texts

• Carbon Nanotube