Our gadgets just keep getting smaller and smaller. Hey, if you reach under your purse, you could hardly tell the difference anymore between your cell phone and your tic tacs.

This week, in Science Out of the Box, let's consider how absurdly small technology can get.

(Soundbite of music)

LYDEN: Researchers at the University of California, Berkeley, have developed a very tiny radio. It's barely a collection of atoms - so small that it would take 10,000 of them to span a diameter of a single human hair.

The Berkeley lab team listened to the Beach Boys on it as they watched their contraption the only way they could - through a high-powered electron microscope.

I spoke with Alex Zettl, who led that team. This microscopic radio is what's called a carbon nanotube - a needle which vibrates at the exact frequency of the station you're trying to listen to.

Professor ALEX ZETTL (Physics, University of California, Berkeley): The entire radio, functionally, operates in a similar way to a conventional radio. It has an antenna. It has a tuner, where you can tune in different stations, an amplifier and what's called the demodulator. All this is built into one molecule, one carbon nanotube. It's basically the size of DNA.

LYDEN: Professor Zettl, could you please explain how you would change the station on this little nanoradio?

Prof. ZETTL: Right. We do this simply by adjusting the voltage that's across this one molecule. It tensions the nanotube much like you would adjust the guitar string on a guitar to change its frequency to tune it in. So we're constantly changing tension to tune in different stations.

LYDEN: Well, I would love to know what it sounds like.

Prof. ZETTL: That sounds great.

(Soundbite of music through nanoradio)

LYDEN: Far be it for me to criticize, is there some interference that I'm hearing there? It sounded like static.

Prof. ZETTL: Actually, the fact that you can hear anything at all is, in my mind, truly amazing. But that's a good point. That static is actually, at the nanoscale, something very important happening. Since our radio is so small, it is sensitive to molecular prodibation(ph). So an atom or molecule of air landing on the radio and jumping off - normally, on a regular radio, you wouldn't even notice that - but at the nanoscale that sounds as a pop. And so the static is atoms and molecules landing on a radio and jumping off.

LYDEN: So I presume that I'm not going to be listening to the Beach Boys or anything else on this for a while, but what do you hope to do with it?

Prof. ZETTL: There are many different applications. This was sponsored by a program here at Berkeley that is to develop small-scale sensors that can monitor air and water quality throughout the country. For that to happen, we needed very low-power small sensors and to transmit and receive data so you could click on the Web and say, well, what's the quality of air like in any place in New York today or Washington or San Francisco. And you'd get a real-time map of that generated by many sensors.

One can think of other applications as well. For example, the size of this radio is now smaller than living cells. It can be integrated inside of cells or one could implant it in other biological structures such as a brain, transmit information to that and have that information be coupled into the biological system so people with brain dysfunctions or hearing loss, vision loss, one can imagine that this could help.

LYDEN: Of course, doesn't that open up ethical questions that those very techniques could also somehow be exploited for tracking people or perhaps implanting one of these devices on them?

Dr. ZETTL: That's true. In case you didn't know it, you've already have a nanoradio on you over the past week and I've been listening to your personal life.

(Soundbite of laughter)

Prof. ZETTL: This is a great concern.

LYDEN: Go ahead.

Prof. ZETTL: And every new technology has pros and cons, and things can be used for ways that weren't intended that can be bad. It's in a sense unethical not to forge ahead to exploring nanotechnology because it has so much potential for helping in medical applications, solving power problems, solving greenhouse effects and so on. We need to forge ahead, but cautiously and correctly.

LYDEN: Well, Professor Zettl, fascinating. Thank you very, very much for being with us.

Prof. ZETTL: Thank you.

LYDEN: Alex Zettl is a professor of physics at the University of California at Berkeley. He and his team of researchers have developed the world's smallest radio, one ten-thousandths the width of a human hair.

Thank you again, Professor Zettl. And I think we'll end this segment with a little Eric Clapton as heard from your nanoradio.

(Soundbite of song, "Layla")

LYDEN: And you can watch a video and hear audio of the nanotube broadcasting the theme from "Star Wars," wow, at npr.org.

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