Microscopic Radio Sets Miniaturization Record
This image, taken by a transmission electron microscope, shows a single carbon nanotube protruding from an electrode. This nanotube is less than a micron long and only 10 nanometers wide, or 10,000 times thinner than the width of a single human hair. When a radio wave of a specific frequency impinges on the nanotube, it begins to vibrate vigorously. An electric field applied to the nanotube forces electrons to be emitted from its tip.(The waves shown in this image were added for visual effect, and are not part of the original microscope image.
Credit: Zettl Research Group, Lawrence Berkeley National Laboratory and UC Berkeley

Since its advent in the early 20th century, the radio has shrunken dramatically from the clunky wooden "cathedral" design of the 1930s to devices you can slip in your pocket. Future radios could be invisible to the naked eye altogether.

Researchers led by Alex Zetttl at the University of California, Berkeley have crafted a fully working radio from a single carbon nanotube 10,000 times thinner than a human hair. Carbon nanotubes are man-made microscopic mesh rods composed entirely of carbon atoms.

Fixed between two electrodes, the nanotube vibrates and performs the four critical roles required to receive radio waves: antenna, tunable filter, amplifier and demodulator. Power is supplied by streaming electrons from an attached battery.

Its inventors have already used it to broadcast two songs: "Layla" by Derek and the Dominos and "Good Vibrations" by the Beach Boys.

The team beat another group at the University of California, Irvine, who announced last month they had created a demodulator, which converts AM radio signals into electrical signals, out of a carbon nanotube. But that device was only part of what's needed to make a radio.

The Berkeley team says its microscopic radio, detailed in an upcoming issue of the journal Nano Letters, could be used to create radio-controlled devices capable of swimming in the human bloodstream and other novel applications.

The work was funded by the National Science Foundation and the U.S. Department of Energy.

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