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Published online: 19 November 2008 | doi:10.1038/nchina.2008.271

Carbon nanotubes: Loud and clear!

Ai Lin Chun

Introduction

© (2008) ACS

Bulky loudspeakers using coils and magnets could soon be a thing of the past. Kaili Jiang, Shoushan Fan at Tsinghua University in Beijing and co-workers¹ have shown that applying sound-frequency electric currents through a very thin film of carbon nanotubes can cause it to emit sounds with a wide frequency range and high sound-pressure level.

The researchers have previously perfected a way to draw out continuous thin films of carbon nanotube measuring tens of nanometres thick from a silicon wafer containing arrays of super-aligned nanotubes. Now, by connecting the ends of these thin films to two electrodes and applying alternating current to them (pictured), the films form a simple loudspeaker that does not have any moving parts or magnets but still functions like one. The films can be stretched without affecting the sound intensity. They are flexible enough to be shaped into a variety of surfaces such as a flag, and can be placed on windows.

It was suggested that the generation of sounds from the thin films is due to 'thermoacoustic effect' — the alternating current heats up the thin film, and the thermal expansion and contraction of the air near the thin film thereby creates the sound. This effect has been known for nearly 200 years and forms the basis of thermoacoustic engines and refrigerators.

These nanotube-based loudspeakers are expected to be made into a variety of stretchable, lightweight, acoustic devices in the near future.

The authors of this work are from:
Department of Physics and Tsinghua–Foxconn Nanotechnology Research Centre, Tsinghua University, Beijing, China; Department of Physics, Beijing Normal University, Beijing, China.

Reference

1. Xiao, L. et al. Flexible, stretchable, transparent carbon nanotube thin film loudspeakers. Nano Lett. doi:10.1021/nl802750z (2008). | Article |