World’s Smallest Radio Is Way Thinner Than a Human Hair

Scientists made a single carbon nanotube radio that is one ten-thousandth the diameter of a human hair


Is that iPod Nano starting to feel a little bulky? No worries. Scientists have now created a radio made from a single carbon nanotube—a rolled up sheet of carbon atoms—that’s one ten-thousandth the diameter of a human hair. Two of the devices could fit into a common cold virus. The single tube performs all the necessary radio functions, and it’s tunable to your favorite FM station—if you have access to an electron microscope and some very teensy scissors.

"It's ridiculously simple. That’s the beauty of it," said Alex Zettl, the UC Berkeley physicist who led the group that invented the receiver.

Practically speaking, the tiny device could have applications far beyond novelty, from radio-controlled devices that could flow in the human bloodstream to highly efficient, miniscule, cell phones. A nanoradio receiver potentially allows the radio control of almost anything, from a single receiver in a living cell to a vast array embedded in an airplane wing.

But for the most part, the microscopic radio is an experiment in the properties of materials only a few molecules big—at the nanoscale. Carbon, for example, behaves differently as a nanotube than it does as a pencil lead. Nanomaterials may conduct heat or electricity better, and they may be stronger or have different magnetic properties than they do in the macroscale—the dimension in which human beings typically interact with their surroundings.

A second challenge in nanotechnology is developing ways to manufacture the tiny machines in large quantities.

"A key issue is how to integrate individual molecular-scale components into a system that maintains the nanometer scale," said Zettl. "The nanoradio achieves this by having one molecular structure, the nanotube, simultaneously perform all critical functions." Indeed, a single nanotube does the jobs of four components of a normal radio: antenna, tuner, amplifier and demodulator.

Also, the nanoradio picks up signals in a radically new way—by physically vibrating thousands to millions of times per second in sync with the radio wave. A normal radio antenna picks up the signals electronically rather than mechanically.

You don’t need an electron microscope to operate the radio either, said Zettl. Using a slightly different configuration, he says, "we successfully transmitted and received signals across the length of our laboratory, a distance of several meters."

The very first song to be played on a nanoradio? The 1970 rock classic "Layla," featuring Eric Clapton in Derek and the Dominos. The nanoradio was developed at the National Science Foundation's (NSF) Center of Integrated Nanomechanical Systems. It was reported Oct. 31, 2007, in the online edition of the journal NANO Letters. The Department of Energy also supported the project.

—Leslie Fink, NSF

This report is provided by the National Science Foundation, an independent federal agency that supports fundamental research and education across all fields of science and engineering, in partnership with U.S. News and World Report.