Graphene is frankly just showing off at this point. Not content with breezing in and smashing records in solar efficiency, kicking the butt of lithium-ion batteries, being the strongest known material in the Universe, being 1,000 times more light-sensitive than any known camera sensor and a thousand other achievements, now this smug supermaterial is having a crack at audio. How's it going? Well, with basically zero acoustic development, a graphene loudspeaker is already boasting a better frequency response curve than a set of Sennheiser MX-400s.
Speakers are basically membranes that are moved back and forth to produce pressure waves in the air that we perceive as sound. To do that, you need a membrane to vibrate, some sort of driver to vibrate it, and some sort of spring effect to bring the membrane back to its starting position at rest.
The heavier the membrane, the more momentum it has on the move, and the more energy needs to go into moving it or changing its direction. Graphene, as we are all constantly reminded, is ridiculously light, stronger than anything else, and can be made extremely thin. Oh, and it conducts electricity, of course. So a team of scientists at UC Berkeley rigged up a graphene diaphragm between two silicon electrodes and ran some acoustic tests to see how it performed as a 7 mm diameter earbud-sized speaker.
How did it go? Well, it's graphene, so you can probably guess. Compared against a Sennheiser MX-400 earbud off the shelf, here's the frequency response charts (noting that a flat line is the ideal shape):
The jury-rigged graphene earbud is very close to the Sennheiser through the low and midrange frequencies, and significantly flatter in the high frequency range above 5 kHz. That's without any acoustic development at all – and still the researchers reported "the fidelity is qualitatively excellent when listening to music."
What's more, it uses very little energy due to the extremely light membrane, and researchers noted, "The configuration described in this letter could also serve as a microphone. The microphone should also have excellent response characteristics due to the graphene's ultra-low mass and the excellent coupling to ambient air."
Now, the Sennheiser MX-400's are a ten-dollar set of earbuds, not some audiophile headset. But it's a ten dollar earbud that's taken a long time to develop, versus what may be the very first graphene speaker ever assembled.
Will it ever hit the market? Well, that's a different matter. But if and when mass production for this stuff becomes cheap and easy, pretty much every sector in engineering and technology will be set to take a giant leap forward.
Source: Arxiv (PDF)