JUNE 2004
Electrically activated plastic
muscles will let robots
smile, arm-wrestle, and
maybe even fly like bugs
BY YOSEPH BAR-COHEN
I ISSUED A CHALLENGE a few
years ago to my fellow researchers:
build a robot using muscles of electri-
cally activated polymers that could
arm-wrestle a human. I was trying to
jump-start research in the field of elec-
troactive polymers, or artificial mus-
cles, and given the state of the art at
the time, I didn't really expect to see
the challenge fulfilled for a couple of
decades.
I was wrong. A little over a year
ago, researchers from SRI
International, a research institute in
Menlo Park, Calif., told me that their
technology could be capable of meet-
ing the challenge. Since then,
Environmental Robots Inc. and the
Swiss Federal Laboratories for
Materials Testing and Research
informed me that they would be ready
to compete less than a year from now!
I couldn't be more delightedeven if
it means that my obligations as an
impresario are a lot closer than I'd
envisioned.
The arm-wrestling match, when it
does come off, will be a watershed on
more than one count. Today's
machinesfrom assembly-line robots
to electric toothbrushesmove thanks
to rotary power, often cleverly translat-
ed by gears, pulleys, hydraulic tubes,
and other intervening parts. Yet such
watchmaker's cleverness has its limits,
and over the centuries, engineers have
imagined countless wonderful
machines that sadly could not see the
light of day. Now, at last, a streamlined
solution is at hand: artificial muscles.
Artificial muscles are plastics that
change shape and size under electrical
stimulation. Because they are plas-
ticsthat is, polymersthey are light
and can be cheap, pliable, quiet, and
shatterproof. Also, they can be
designed for particular properties,
filled with sensors and other compo-
nents, shaped for specific actuators,
and manufactured on scales both
macro and micro. Unlike most active
materials, such as semiconductors and
shape-memory alloys, however, these
electroactive polymers work acco