EVENTS, ADVANCES, AND NEWS
■ BY JEFF ECKERT
RADIO PLAYS CLAPTON
PHOTO COURTES Y OF ZE TTL RESEARCH GROUP, LAWRENCE
BERKELEY NATIONAL LABORATORY, AND UNIVERSI T Y OF
CALIFORNIA AT BERKELEY.
■ Transmission electron microscope
image showing a carbon nanotube
radio protruding from an electrode
(“waves” added for effect).
professor of physics, and his team
successfully transmitted such works as
“Layla” (Derek & the Dominos), “Good
Vibrations” (Beach Boys), and “Largo”
(from the Handel opera “Xerxes”) across
To see and hear for yourself, drop
into the Zettl group page at socrates.
io.html. According to the prof, the
nanoradio may prove useful in a
variety of applications “from cell phones
to microscopic devices that sense the
environment and relay information via
radio signals ... The nanotube radio may
lead to radical new applications, such
as radio-controlled devices small enough
to exist in a human’s bloodstream.”
If you think your iPod nano is compact, consider a radio recently developed at the University of California,
Berkeley ( www.berkeley.edu). Said to
be the smallest radio ever built, the
nanoradio, which presently operates
as a receiver but could work as a
transmitter as well, is a single carbon
nanotube that operates as a combined
antenna, tuner, amplifier, and AM/FM
demodulator. (A nanotube, by the way,
is a rolled sheet of interlocked carbon
atoms that form a tube that is extremely strong and also exhibits some
peculiar electronic properties. This one
is about 10 nm in diameter and less
than 1 m long, making it about
1/10,000 as thick as a human hair.)
The operation is fairly straightforward. When radio waves strike the
nanotube, it begins to vibrate. You
then apply an electric field, which
forces electrons to be emitted from its
tip. This current is used to detect the
vibrations and thus turn the radio
waves back into sound.
In one of the early experiments,
team leader Alex Zettl, UC Berkeley
10 January 2008
The UC Berkeley device described
above is powered by a battery, but
PHOTO COURTESY OF UNIVERSI T Y OF ILLINOIS.
perhaps its developers should take
note of the nanogenerator recently
revealed by researchers at the
University of Illinois (www.uillinois.
edu). Because even the smallest
batteries are impractically large for
driving micro and nanoscale devices,
Prof. Min-Feng Yu has been working
on ways of harvesting power from
nanoscale mechanical energy.
Toward that end, he and some
grad students have created a
nanowire that generates a voltage
when mechanically deformed. The
nanowire is a single crystal of barium
titanate (a piezoelectric material used
in ceramic capacitors, microphones,
and other transducers), approximately
280 nm in diameter and 15 m long.
The wire was placed across a 3 m
gap on a test rig and exposed to
induced mechanical vibrations. The
result was an electrical energy output
of 0.3 attojoules (less than a qunitil-lionth of a joule) per vibrational
cycle, which is very interesting.
However, just for perspective, to run a 100W lightbulb for
an hour, you would need about
3. 6 x 1023 of them, so we’re not
talking hydroelectric dams here.
But with further development,
something useful may emerge.
On a more immediately practical level is a breakthrough
in fuel cell technology at the
University of Houston (www.uh.
edu). One of the biggest hurdles
in building economical fuel
cells to drive electric cars of the
■ Top: Schematic setup for piezoelectric charge detection from
barium-titanate nanowire. Bottom:
Scanning electron microscope
image of the wire.