Tiny nanotube antennas may yield better signals

In the future, mobile phone calls and television pictures could become a lot clearer thanks to tiny antennas thousands of times smaller than the width of a human hair. At least that's the speculation of a University of Southern California researcher who has been investigating nanotube transistors.

The USC scientist, Bart Kosko, Ph.D., a professor in the school's Electrical Engineering Department, led a study that has demonstrated for the first time that minuscule antennas, in the form of carbon nanotube transistors, can dramatically enhance the processing of electrical signals, a development that could pave the way for improved performance of consumer electronic devices.

The finding adds to a growing number of promising electronic components that are nanotube-based, including logic gates for computers and diodes for light displays.

"No one knows exactly how these little tubes work or even if they will work out in manufacturing, but they are surprisingly good at detecting electrical signals," says Kosko. "Once we figure out all the parameters that are needed to fine tune them, both physically and chemically, we hope to turn these tubes into powerful little antennas."

If all goes well, the tubes could start appearing in consumer products within five to ten years, he predicts.

The finding hinges on a well-known but counterintuitive theory called 'stochastic resonance' that claims noise, or unwanted signals, can actually improve the detection of faint electrical signals. Kosko set out to show that the theory was applicable at the nano scale.

Under controlled laboratory conditions, Kosko's graduate student, Ian Lee, generated a sequence of faint electrical signals ranging from weak to strong. In combination with noise, the faint signals were then exposed to devices with and without carbon nanotubes. The signals were significantly enhanced in the container with the nanotubes compared to those without nanotubes, Kosko says.

Although much testing needs to be conducted before the structures are proven to be of practical use, Kosko sees big potential for the little tubes. He says they show promise for improving 'spread spectrum' technology, a signal processing technique used in many newer phones that allows listeners to switch to different channels for clearer signals and to prevent others from eavesdropping.

Arrays of the tiny tubes could also process image pixel data, leading to improved television images, including flat-panel displays, according to Kosko. The tubes also have the potential to speed up Internet connections, the researcher says.

In a more futuristic application, Kosko believes the tubes have the potential to act as artificial nerve cells, which could help enhance sensation and movement to damaged nerves and limbs. The sensors might even be used as electrical components in artificial limbs, he adds.

By adjusting the shape, length and chemical composition of the nanotubes, as well as the size of the tube array, they can in essence be customised for a wide-variety of electronic needs, Kosko predicts. "There are likely many good applications for the technology that we have not foreseen."