[LINK] New Graphene Innovation

[Stephen Loosley]

Graphene Innovation That Is Music to Your Ears

Glenn Roberts Jr. March 11, 2020
https://newscenter.lbl.gov/2020/03/11/graphene-innovation-music-to-your-ears


Just over 15 years since a couple of researchers in the U.K. used adhesive tape to isolate single atomic layers of carbon, known as graphene, from a chunk of graphite, their Nobel Prize-winning discovery has fueled a revolution in ultrathin materials R&D.

Now, technology licensed from Berkeley Lab relating to the use of graphene in a sound-producing component known as a transducer, could transform a variety of devices, including speakers, earbuds and headphones, microphones, autonomous vehicle sensors, and ultrasonic and echolocation systems.

“We have been working on graphene-based materials and structures for a number of years now, and this transducer is one of the applications that came out of that,” said Alex Zettl, a senior faculty scientist at Berkeley Lab and a physics professor at UC Berkeley who is a co-inventor of the technology.

The transducer developed through their team’s research uses a small, several-layers-thick graphene film called a membrane that converts electric signals into sound.

“It is kind of like a drumhead, with a circular frame and the membrane stretched over it,” Zettl said.

The graphene membrane measures about a centimeter across. The membrane and supporting frame are sandwiched between silicon-based electrodes that are driven with alternating voltages.

The electric fields cause the graphene membrane to vibrate and create sound in an efficient, controlled way.

This design, known as an electrostatic transducer, requires fewer parts and far less energy than more conventional designs, which can require electrical coils and magnets.

“When we drive it with an electrical audio signal, it acts as a loudspeaker,” Zettl said.

In some popular in-ear headphones, only about 10 percent of electrical energy gets converted to sound while the rest is lost as heat. The graphene transducer, though, converts about 99 percent of the energy into sound, he said.

Also, the graphene transducer is almost distortion-free and has an extremely “flat” response across a very broad range of sound frequencies – even well beyond what the human ear is capable of hearing.

This means that the sound is of equal quality across a wide range of high and low frequencies – “not just in the audio band, but from subsonic all the way to ultrasonic,” Zettl said.  “This is pretty much unprecedented.”

Because of this large bandwidth, the graphene-based transducer could be used for submarine communications, ultrasonic systems for locating survivors in a rubble-strewn environment, and for high-quality imaging of human fetuses in the womb, as examples.

And the same properties that make the graphene transducer work well in speakers can also make for high-quality microphones, Zettl noted.

Ramchandani of GraphAudio said that sample headphones and microphones that the company demoed at the Consumer Electronics Show this year resulted in consumer experiences that he said evoked a “Wow” response.

The company claims the sound quality of its technology is so crystal-clear that it’s possible to pick out an individual instrument’s tones from a symphony orchestra ...

The Berkeley Lab research is supported by the U.S. Department of Energy’s Office of Basic Energy Sciences.