Tsinghua University (Beijing City, CN) and Hon Hai Precision Industry CO., LTD. (Tu-Cheng City, TW) have developed a carbon nanotube loudspeaker. The sound wave generator includes a carbon nanotube structure. The carbon nanotube structure is capable of converting electrical signals into heat. The heat is transferred to a medium and causes a thermoacoustic effect. The means to fabricate a carbon nanotube loudspeaker are detailed in U.S. Patent Application 20100046784.
The carbon nanotube loudspeaker was invented by Tsinghua University nanotechnologists Kai-Li Jiang, Lin Xiao, Zhuo Chen and Shou-Shan Fan. The carbon nanotube film used in the loudspeaker can be produced by a adopting a "kite-mechanism" and can produce carbon nanotubes with a length of even above 10 centimeters. This is considered by some to be ultra-long carbon nanotubes. However, this method can be used to grow carbon nanotubes of many sizes.
One end (e.g., the root) of the carbon nanotubes is fixed on the growing substrate, and the other end (e.g., the top/free end) of the carbon nanotubes grow continuously. The growing substrate is near an inlet of the introduced carbon source gas, the ultra-long carbon nanotubes float above the insulating substrate with the roots of the ultra-long carbon nanotubes still sticking on the growing substrate, as the carbon source gas is continuously introduced into the chamber. The length of the ultra-long carbon nanotubes depends on the growth conditions.
After growth has been stopped, the ultra-long carbon nanotubes land on the insulating substrate. The carbon nanotubes are then separated from the growing substrate. This can be repeated many times so as to obtain many layers of carbon nanotube films on a single insulating substrate. The layers may have an angle from 0 to less than or equal to 90 degrees between them by changing the orientation of the insulating substrate between growing cycles.
Loudspeakers are apparatus that reproduce sound recorded in different media. The loudspeaker commonly includes an enclosure (i.e., housing, box, or cabinet) and a sound wave generator disposed in the enclosure. The loudspeakers can be divided into passive loudspeakers and active loudspeakers. The active loudspeakers are any loudspeakers that contain their own amplifiers (e.g. those for computers or i-pods), or loudspeakers that divide the frequencies for each sound wave generator before power-amplification, using an active crossover. The passive loudspeakers are loudspeakers without amplifiers.
FIG. 5 shows an SEM image of a carbon nanotube segment produced by pushing down a strip-shaped carbon nanotube array. The material is suitable for use in a carbon nanotube loudspeaker
The carbon nanotube structure may have a substantially planar structure. The thickness of the carbon nanotube structure may range from about 0.5 nanometers to about 1 millimeter. The smaller the specific surface area of the carbon nanotube structure, the greater the heat capacity will be per unit area. The larger the heat capacity per unit area, the smaller the sound pressure level of the acoustic device.