“This is just damned cool”

That is how Doug at Nanoscale view feels about a recent paper on the ability of carbon nanotubes to amplify sound; he also gives a one paragraph explanation of the physics behind the experiments:

The authors take very thin films of carbon nanotubes and are able to use them as speakers even without making the films vibrate directly. The idea is very simple: convert the acoustic signal into current (just as you would to send it through an ordinary speaker) and run that current through the film. Because of the electrical resistance of the film (low, but nonzero), the film gets hot when the current is at a maximum. Because the film is so impressively low-mass, it has a tiny heat capacity, meaning that small energy inputs result in whopping big temperature changes. The film locally heats the air adjacent to the film surface, launching acoustic waves. Voila. A speaker with no moving parts. This is so simple it may well have real practical implementation. Very clever.

Take a look!

PS: Previously, if I had seen such a news item, my first response would have been “Let us ask this question in BMQ“. Nowadays, I tend to think, “Ha! Might be a nice one to talk about in the class”.


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