Graphene-based microphone mimics bat's ultrasound

A group of researchers with University of California at Berkeley have developed a microphone and a speaker that can pick up and emit ultrasound like bats and dolphins do with their unique communication system.

In achieving the goal, enabling humans to hear and talk through thick objects and underwater, the U.S. team used a material known as graphene, instead of the more traditional ones like paper and plastic.

Bats and dolphins emit sounds at very high frequency and at much longer range than the human ear can detect and can locate objects and communicate using these pulsating sounds.

Dr. Qin Zhou, a postdoctoral student at UC Berkeley's physics department, told Xinhua that the idea had been studied for a long time, but the technology was not available until graphene use was common. Zhou was part of the research team led by the study's senior author Alex Zettl to work on the device.

Zhou explained that "speakers and phones use diaphragms, that vibrate and create or detect sounds when we speak or hear sounds."

Two years ago, he built loudspeakers using a sheet of graphene for the diaphragm, and since has been developing the electronic circuitry to build a microphone with a similar graphene diaphragm. Typically, diaphragms are made of paper or plastic, like those in our phone's speakers, but the team used graphene instead of the traditional materials.

Thanks to graphene's composition, he said, the team was able to make the diaphragm "extremely light and thin," allowing it to vibrate more intensively to receive and detect at much higher fidelity.

The graphene-based membrane picks up the sound by using 99 percent of the device's energy, whereas regular speakers use eight percent.

When used for communications, the possibilities are believed to be endless. "Usually, the sounds the human ear can detect, are not able to go through tunnels, walls, or other geographical barriers, " Zhou said. The ultrasound device easily bypasses those and even goes underwater, using electromagnetic waves, with far more fidelity than current ultrasound or sonar devices.

Zettl, Zhou and other team members, including Zhou's wife, Jinglin Zheng, describe their graphene microphone and ultrasonic radio in a paper appearing online this week in the Proceedings of the National Academy of Sciences. Endite