Placing a sheet of atom-thin graphene into a feedback circuit causes spontaneous self-oscillation that can be tuned to create frequency-modulated (FM) signals. Changyao Chen, Sunwoo Lee, Columbia University

The world’s smallest FM radio transmitter was created using the strongest and thinnest material known to man.

A team of engineers from Columbia Engineering created the nano-mechanical system using graphene, a form of carbon that has properties similar to silicon commonly used to make software chips. The study, published in Nature Nanotechnology, describes how the tiny transmitter may have broader applications in wireless electronic devices like cell phones and tablets.

"This work is significant in that it demonstrates an application of graphene that cannot be achieved using conventional materials," Mechanical Engineering Professor James Hone said in a statement. "And it's an important first step in advancing wireless signal processing and designing ultrathin, efficient cell phones. Our devices are much smaller than any other sources of radio signals, and can be put on the same chip that's used for data processing."

Graphene is a sheet of carbon atoms bonded together in a thin film that is only one atom thick. Discovered by a team from the University of Manchester in 2004, the material is extracted from graphite and possesses tremendous mechanical strength.

The team used graphene’s mechanical “stretchability” to create a voltage-controlled oscillator (VCO) – an electronic component that can generate an FM signal. The VCO was used to send and receive audio signals of 100 megahertz, which falls in the middle of the FM bandwidth. The team used pure tones and more-complex music signals to tune the VCO’s output. The team found that both kinds of signals could be “faithfully reproduced” by an ordinary radio receiver.

"This device is by far the smallest system that can create such FM signals," Hone said.

While the graphene FM transmitter is a feat of modern engineering, the nano-sized device cannot be used to replace conventional radios. Rather, it may be used in cell phones.

"Due to the continuous shrinking of electrical circuits known as 'Moore's Law', today's cell phones have more computing power than systems that used to occupy entire rooms,” said electrical engineering professor Kenneth Shepard. “However, some types of devices, particularly those involved in creating and processing radio-frequency signals, are much harder to miniaturize.”

The FM transmitter’s small size allows for easy integration with all kinds of electronics, and graphene’s mechanical strength allows the device to have a wide range. But more research needs to be done to take advantage of these features.

"There is a long way to go toward actual applications in this area," Hone said, "but this work is an important first step. We are excited to have demonstrated successfully how this wonder material can be used to achieve a practical technological advancement -- something particularly rewarding to us as engineers."