Despite all the hubbub about carbon nanotubes as possible building blocks of superstrong materials or as components of supersmall electronics, few practical applications have yet come to fruition. Integrating nanotubes into functioning electronic devices has proved especially difficult, but researchers have now built a carbon-nanotube component into a simple radio receiver.
“We’re showing a system that works that has a nanotube as one of the key components,” says Peter Burke of the University of California, Irvine.
Burke and graduate student Chris Rutherglen placed a nanotube—1 nanometer in diameter and 50 micrometers long—on the surface of a silicon chip. They then attached metal contacts to each end of the nanotube so that they could connect it to an electronic circuit that could receive signals from a standard radio antenna.
To test the system, the researchers broadcast music at a frequency of 1 gigahertz (GHz). They used amplitude modulation (AM), in which the rapidly varying intensity of the radio waves carries the desired broadcast signal. The nanotube device demodulated the received radio transmission, producing an output voltage that could be fed into an amplifier. The receiver picked up the radio waves up to a meter away from the transmitter, the researchers report online and in an upcoming issue of Nano Letters.
The system is rudimentary, with a limited range and no advantage in sound quality. “This was proof of concept to show that it can be done,” Burke says.
He and Rutherglen see their work as a milestone in moving nanotubes from scientific curiosity to technological workhorse. With further refinement, their device could lead to components for a variety of nanoscale wireless systems, including radio, television, or cell phone technology, they say. The next step will be to build more-complicated components, such as a nanotube amplifier, Burke adds.
“This work really demonstrates in a compelling way the ability of carbon nanotubes to operate at high frequencies in electronic systems and do useful things in realistic devices,” says John Rogers of the University of Illinois at Urbana-Champaign. He cautions, however, that making integrated circuits will be more challenging than building the single component was.
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Burke’s group is trying to make nanoscale manufacturing less costly, but he says that that expense remains the greatest obstacle to wide commercialization of nanotube devices.
A nanotube radio could serve as a catalyst to help boost the material beyond the laboratory and lead to a range of technological applications, just as the transistor radio sparked the development of other transistor-based devices, Rogers says. “It’s a long, hard path going from science-based work that has dominated nanotube research [and] moving it towards a real technology. This is an important step,” he adds.