They were able to show up to 15 dB higher sensitivity compared to a commercial microphone at frequencies up to 11 kHz. "We wanted to show that graphene, although a relatively new material, has potential for real world applications," explains Marko Spasenovic, an author of the paper.

The graphene membrane, approximately 60 layers thick, was grown on a nickel foil using chemical vapour deposition to ensure consistent quality across all the samples. The researchers also simulated a 300-layer thick graphene membrane, which shows potential for performance far into the ultrasonic part of the spectrum.

"The microphone performed as well as we hoped it would," Spasenovic added. “A thicker graphene membrane, theoretically, could be stretched further, enabling ultrasonic performance, but sadly we're just not quite there yet experimentally," he noted.

The industry is working hard to improve graphene production. Eventually, this should mean we have better microphones at lower cost, the authors concluded in the journal 2D Materials.