Conventional speakers drive sound vibrations by pumping the air. But two groups have now shown graphene can achieve the same thing using heat - much as lightning generates thunder by dramatically heating the air. The trick with graphene is that it is so thin, it takes almost no current to heat it, but equally it cools in an instant. Pumping audio-frequency currents through a sheet of graphene – going well into the ultrasound – generates sound waves without the need for any moving parts. In theory this makes devices simpler and cheaper and opens up the possibility of new applications.
The University of Texas's Ji Won Suk, who has been developing the so-called "thermophones" says "it might be fun to have a smartphone with a transparent speaker over the whole screen".
But like just about every facet of graphene, whether this neat idea ever makes it to the market will depend on many factors.
Reading the technical papers exploring its potential, you are immediately struck by the caution expressed by the scientists doing the studies. The stumbling blocks are many. And the electronics industry is ruthlessly Darwinian. We have our mobile phones because the mobile industry and the silicon industry can turn out precision-engineered components by the bucket load, and any competing technology has to be robust in the fabrication plant and in the product. And it has to be cheap. Graphene is still yet to be tested in this environment.
Nor is graphene the only new material on the block; nanowires and plastic electronics are among the competition being explored.
But, whatever the current issues with graphene, it has to be remembered that the first attempts to make electronic components out of silicon five decades back were a complete flop. History now shows that was only a temporary setback. The ability to do so much with a single material is what made silicon (through the notion of the integrated circuit) such a success in the end.
And progress with graphene has been unexpectedly rapid – the successes of the Samsung roll-to-roll production and the IBM circuit took those in the business by surprise. More surprises are surely around the corner. As Nokia researchers have cautiously said “graphene holds tremendous promise”.
Whether it will deliver on these promises, only time will tell.
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