A microphone made of graphene could capture ultrasonic frequencies

Super-sensitive graphene microphone could be ultrasonic

Researchers have created a microphone made of graphene that is 32 times more sensitive than a conventional nickel-based device. 

Made by a team from the University of Belgrade, Serbia, the condenser-type microphone is based on a vibrating membrane consisting of 60 layers of graphene – a one atom thick layer of carbon.

The team said they had grown the membrane on a nickel foil using chemical vapour deposition, the most common method of graphene manufacturing.

Once the graphene layer was created, the nickel foil was removed and the resulting membrane placed into a shell of a conventional microphone to ensure no other factors influenced the measurement.

"We wanted to show that graphene, although a relatively new material, has potential for real-world applications," said Marko Spasenovic, an author of a paper published in the journal 2D materials. "Given its light weight, high mechanical strength and flexibility, graphene just begs to be used as an acoustic membrane material."

In tests, the microphone displayed sensitivity of up to 15dB higher compared to commercially available devices and was able to capture frequencies of up to 11kHz.

The researchers also simulated a 300-layer thick graphene membrane, which showed potential for performance far into the ultrasonic part of the spectrum.

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

The researchers said the major obstacle for making graphene microphones a reality is the cost of manufacturing large sheets of graphene. However, they said they were hopeful the problem would eventually be solved enabling production of ultra-sensitive graphene microphones at acceptable cost.

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