Single Nanotube Becomes World's Smallest Radio

Invisible Pink Unicorn writes "Researchers at the National Science Foundation have utilized a single carbon nanotube to perform all the functions of a standard radio, acting as an antenna, tunable filter, amplifier, and demodulator. They were then able to tune in a radio signal generated in the room and play it back through an attached speaker. The device is functional across a bandwidth widely used for commercial radio. From the NSF: 'The source content for the first laboratory test of the radio was "Layla," by Derek and the Dominos, followed soon after by "Good Vibrations" by the Beach Boys.'"

Journal abstract and Project page

[InvisblePinkUnicorn]

Their project page has videos, simulations, and audio playback samples: NSF Nanotube Radio [berkeley.edu]

Here is their journal abstract [acs.org]:

"We have constructed a fully functional, fully integrated radio receiver from a single carbon nanotube. The nanotube serves simultaneously as all essential components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A direct current voltage source, as supplied by a battery, powers the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, we demonstrate successful music and voice reception."

Going full circle

[sm62704]

In the 19th century they had pocket watches. Then watches got small enough to strap on your wrist. Then we got cell phones, threw away our wristwatches and put the phone in a pocket.

In the 19 century [wikipedia.org] we had vacuum tubes. In the mid 20th century these were replaced by semiconductors, which were smaller and less bulky. Now we're back to tubes again, and the TFA sounds like these are kind of nano vacuum tubes, only without the vacuum.

The nanotube radio is likely like these geek toys [wikipedia.org] nerds have been building since the early 1900s. All you need to build one is a diode, some wire, a piece of wood, and headphones to listen to it with. They used to call these things "catwhisker radios", the "cat whisker" being the diode.

-mcgrew [kuro5hin.org]

Clearly, you're misinformed

[PhysSurfer]

Your tuning fork analogy is valid, but you need to remember that it is a nanometer sized tuning fork that vibrates in response to EM waves, not sound waves, and serves as a field emitter. Good luck doing that with any other material. In addition, they were not using a "specially" tuned receiver to pick up the movement - the movement is detected through the resulting modulation of the Field Emission Current, which is especially sensitive to the location of the end of the nanotube. The only tuning involved is through a DC field that changes the tension on the nanotube, which in turn changes its resonant frequency. This is a good thing, because it means you can change the channel on the resulting radio. It's novel and exciting research because the "tuning fork" is on the nanometer scale. Mounting the nanotube in the TEM and observing its vibration is hardly trivial.

Re:Tubes vs. Transistors

[murderlegendre]

Not to go too far OT with this, but.. there is much more to the "tubes vs. transistors" thing, than the sonic performance of a given tube vs. a given transistor. This is one area where the /. membership is willfully ignorant..

Spend a little time learning about the design differences between complete tube and transistor circuits, and you'll soon discover that tube circuits allow the designer to select passive components which offer greater sonic advantage than the passive components populating a typical transistor circuit. Here are a couple of clues to get you started: high impedances, low current densities.

Even if all tubes sounded exactly the same as all transistors (which they do not, this is objective fact) the tube-based circuits would still offer design advantages.