Single Nanotube Makes World's Smallest Radio

UC Berkeley News ^ | 31 October 2007 | Robert Sanders, Media Relations

[PeaceBeWithYou]

BERKELEY – Physicists at the University of California, Berkeley, have built the smallest radio yet - a single carbon nanotube one ten-thousandth the diameter of a human hair that requires only a battery and earphones to tune in to your favorite station.

The scientists successfully received their first FM broadcast last year - Derek & The Dominos' "Layla" and the Beach Boys' "Good Vibrations" transmitted from across the room. In homage to last year's 100th anniversary of the first voice and music radio transmission, they also transmitted and successfully tuned in to the first music piece broadcast in 1906, the "Largo" from George Frederic Handel's opera "Xerxes."

Nanotube radio on video
The nanotube radio seen under a high-resolution transmission electron microscope, which allows researchers to observe the radio in action as it tunes in Derek & The Dominos playing Eric Clapton's "Layla." When not tuned in, the nanotube does not vibrate. As the researchers tune it to the proper frequency, however, the nanotube vibates at radio frequencies, which blurs its image. The nanotube is about 700 nanometers long and 10 nanometers in diameter — one ten-thousandth the width of a human hair. (Zettl Research Group/LBNL & UC Berkeley)

Watch video (6.6Mb Quicktime file)

"We were just in ecstasy when this worked," said team leader Alex Zettl, UC Berkeley professor of physics. "It was fantastic."

The nanoradio, which is currently configured as a receiver but could also work as a transmitter, is 100 billion times smaller than the first commercial radios, and could be used in any number of applications - from cell phones to microscopic devices that sense the environment and relay information via radio signals, Zettl said. Because it is extremely energy efficient, it would integrate well with microelectronic circuits.

"The nanotube radio may lead to radical new applications, such as radio-controlled devices small enough to exist in a human's bloodstream," the authors wrote in a paper published online today (Wednesday, Oct. 31) by the journal Nano Letters. The paper will appear in the print edition of Nano Letters later in November.

Authors of the nanoradio paper are Zettl, graduate student Kenneth Jensen, and their colleagues in UC Berkeley's Center of Integrated Nanomechanical Systems (COINS) and in the Materials Sciences Division at Lawrence Berkeley National Laboratory (LBNL). COINS is a Nanoscale Science and Engineering Research Center supported by the National Science Foundation (NSF).

Nanotubes are rolled-up sheets of interlocked carbon atoms that form a tube so strong that some scientists have suggested using a nanotube wire to tether satellites in a fixed position above Earth. The nanotubes also exhibit unusual electronic properties because of their size, which, for the nanotubes used in the radio receiver, are about 10 nanometers in diameter and several hundred nanometers long. A nanometer is one billionth of a meter; a human hair is about 50,000-100,000 nanometers in diameter.

In the nanoradio, a single carbon nanotube works as an all-in-one antenna, tuner, amplifier and demodulator for both AM and FM. These are separate components in a standard radio. A demodulator removes the AM or FM carrier frequency, which is in the kiloHertz and megaHertz range, respectively, to retrieve the lower frequency broadcast information.

The nanoradio detects radio signals in a radically new way - it vibrates thousands to millions of times per second in tune with the radio wave. This makes it a true nanoelectromechanical device, dubbed NEMS, that integrates the mechanical and electrical properties of nanoscale materials.

In a normal radio, ambient radio waves from different transmitting stations generate small currents at different frequencies in the antenna, while a tuner selects one of these frequencies to amplify. In the nanoradio, the nanotube, as the antenna, detects radio waves mechanically by vibrating at radio frequencies. The nanotube is placed in a vacuum and hooked to a battery, which covers its tip with negatively charged electrons, and the electric field of the radio wave pushes and pulls the tip thousands to millions of times per second.

While large objects, like a stiff wire or a wooden ruler pinned at one end, vibrate at low frequencies - between tens and hundreds of times per second - the tiny nanotubes vibrate at high frequencies ranging from kiloHertz (thousands of times per second) to hundreds of megaHertz (100 million times per second). Thus, a single nanotube naturally selects only one frequency.

Although it might seem that the vibrating nanotube yields a "one station" radio, the tension on the nanotube also influences its natural vibration frequency, just as the tension on a guitar string fine tunes its pitch. As a result, the physicists can tune in a desired frequency or station by "pulling" on the free tip of the nanotube with a positively charged electrode. This electrode also turns the nanotube into an amplifier. The voltage is high enough to pull electrons off the tip of the nanotube and, because the nanotube is simultaneously vibrating, the electron current from the tip is an amplified version of the incoming radio signal. This is similar to the field-emission amplification of old vacuum tube amplifiers used in early radios and televisions, Zettl said. The amplified output of this simple nanotube device is enough to drive a very sensitive earphone.

Finally, the field-emission and vibration together also demodulate the signal.

"I hate to sound like I'm selling a Ginsu knife - But wait, there's more! It also slices and dices! - but this one nanotube does everything; it performs all radio functions simultaneously and extremely efficiently," Zettl said. "It's ridiculously simple - that's the beauty of it."

Zettl's team assembles the nanoradios very simply, too. From nanotubes copiously produced in a carbon arc, they glue several to a fixed electrode. In a vacuum, they bring the electrode within a few microns of a second electrode, close enough for electrons to jump to it from the closest nanotube and create an electrical circuit. To achieve the desired length of the active nanotube, the team first runs a large current through the nanotube to the second electrode, which makes carbon atoms jump off the tip of the nanotube, trimming it down to size for operation within a particular frequency band. Connect a battery and earphones, and voila!

Reception by the initial radios is scratchy, which Zettl attributes in part to insufficient vacuum. In future nanoradios, a better vacuum can be obtained by insuring a cleaner environment, or perhaps by encasing the single nanotube inside a second, larger non-conducting nanotube, thereby retaining the nanoscale.

Zettl won't only be tuning in to oldies stations with his nanoradio. Because the radio static is actually the sound of atoms jumping on and off the tip of the nanotube, he hopes to use the nanoradio to sense the identity of atoms or even measure their masses, which is done today by cumbersome large mass spectrometers.

Coauthors with Jensen and Zettl are UC Berkeley post-doctoral fellow Jeff Weldon and physics graduate student Henry Garcia. The work was supported by NSF and the U.S. Department of Energy.

Further information:

More information and audio from Alex Zettl's lab

Lawrence Berkeley National Laboratory press release

National Science Foundation press release

[Son Of The Godfather]

I have a question for Mr. Jensen. What's the frequency, Kenneth?

Very nice!

[LibWhacker]

Fantastic! Drop a couple of hundred trillion of these radio-bots with GPS functionality integrated into them over Western Pakistan, and there won't be a nook or a cranny or a cave bin Laden and his killers could hide in.

These things would be like motes of dust. They'd get into everything but not be noticeable. Always listening, they could relay everything they heard back to us.

It wouldn't even matter if the signal strength was extremely weak, they'd just relay the information to the bot "standing" next to them, and that bot would in turn relay the info to the bot next to it, and so on and so on, all the way back to the Pentagon. There wouldn't be a cave deep enough bin Laden could hide in, not successfully anyway.

I've said this before, but I just hope to high heaven we have a decades-old Manhattan Project for nanotechnology going full-bore right now. The gravity of the military implications are way too serious to ignore. And whomever masters the technology first rules the world. IMHO

[Leftism is Mentally Deranged]

If transmitters and receivers can be this small, this opens up many possibilities for sending information without wires. Sounds like a real breakthrough.

[skinkinthegrass]

Hey, if it can receive Rush and be implanted into a liberal’s ear I can see all sorts of possibilities.

...in $hrillary/Bubba's ears....their heads would pop/imploded.

[LibWhacker]

The gravity of the military implications are way too serious to ignore.

[PeaceBeWithYou]

ping.

[Calvin Locke]

Battery? Hah! I got a crystal earphone, and a diode. Just show me a ground, and I'm all set.

And if I'm in the mood, an old razor blade, ...

[Tallguy]

These things would be like motes of dust. They'd get into everything but not be noticeable. Always listening, they could relay everything they heard back to us.

There's the little issue of power comsumption & transmitting range to consider. I have not idea if these would be practical at short ranges much less over the distance necessary for satellite-relayed communication. Like the way you think though!

[PeaceBeWithYou]

This could prolly be self powered if a second nanotube(or an array of them) were tuned to a natural frequency, say something in the microwave band.

[3Lean]

But when will someone build a violin on this size so we can all play it for the latest “victim” the Democrats trot out...

[Calvin Locke]

That would work. A lot more convenient than say, trying to light a neon bulb from a long wire antenna and AM radio waves.

I wonder what Tesla would come up with if he had the knowledge?

[Kevmo]

bmflr

[LibWhacker]

It's fascinating thinking about it, isn't it? It seems to me, the cost of raw materials is going to be just about zero, since a trillion of them are only going to weigh about a pound.

As I see it, the real trick would be mass-producing them in great enough numbers and cheaply enough so that you could essentially carpet a theatre of operations with them.

Regarding range... We already know a lot about networks and this would be a network of listening devices. So they wouldn't need much range, just enough to get the signal to the nearest companion bot in the network.

The article mentioned they were extremely efficient in the consumption of power, so if they only last a few days or a week, and they're cheap enough, you just keep reseeding the countryside with them until you've found all your targets and destroyed them.

Never heard of nanobatteries, though, lol. So perhaps it's all still just a lot of pie in the sky.

[Republicus2001]

There is a woman on my block that claims to hear human voices emanating from her radio. Imagine that!

[primatreat]

Gotta be careful cleaning out the ear wax.... My wife wears 2 and this will be wonderful.. Diabetes...... ugggggg

[Son Of The Godfather]

As I see it, the real trick would be mass-producing them in great enough numbers and cheaply enough so that you could essentially carpet a theatre of operations with them.

Use self-replicating nanites/nanobots to construct them... Of course, then the real trick would be making sure we could turn 'em off!

[lesser_satan]

It is pretty incredible. There’s a nanotech ETF available (ticker PXN) if you’re looking for an easy way to invest in it.

[HeartlandOfAmerica]

Hmm, I wonder if there is potential for people like me - who have a hearing loss?

I hear little voices in my head...

Don't want to hear the voices any more? or just want to hear different ones? :)

[perfect stranger]

another ping.

[Erasmus]

Don't want to hear the voices any more? or just want to hear different ones? :)

I think Marvy just wants to hear them louder.

<}B^)