A team of researchers at UC Berkeley have invented a radio made of a single carbon nanotube. The device is just a few billionths of a meter in size - so small that it could fit inside a living cell, or float along in your bloodstream. According to physicist and project lead Alex Zettl, who helped researcher Kenneth Jensen come up with the idea for the radio:
A single carbon nanotube molecule serves simultaneously as all essential components of a radio — antenna, tunable band-pass filter, amplifier, and demodulator. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation (FM and AM), we were able to demonstrate successful music and voice reception.
Zettl and his colleagues imagine that there will be many applications for the radio. It could be used in medical devices that swim through your body, responding to radio commands. Or it could be put inside tiny wireless devices. It could even be put inside a human ear, an idea which inevitably leads to visions of a dark future where people are implanted with radios and telephones that they can't ever turn off.
So how does it work? Essentially, the nano radio is a very tiny vacuum tube. According to a release about the invention:
The carbon nanotube radio consists of an individual carbon nanotube mounted to an electrode in close proximity to a counter-electrode, with a DC voltage source, such as from a battery or a solar cell array, connected to the electrodes for power. The applied DC bias creates a negative electrical charge on the tip of the nanotube, sensitizing it to oscillating electric fields. Both the electrodes and nanotube are contained in vacuum, in a geometrical configuration similar to that of a conventional vacuum tube.
Incoming radio waves cause the tube to vibrate. The tube itself can be "tuned" to respond to vibrations that match certain frequencies, or "channels" on the radio dial.
Of course, Zettl, Jensen and their lab buddies tested the nano radio by broadcasting the Beach Boys song "Good Vibrations." Says Zettle proudly, "The nanotube radio faithfully reproduced the audio signal, and the song was easily recognisable by ear." Image courtesy of Los Alamos National Lab. [Eurekalert]