By David Cameron
Flying an F-15 can be hazardous during sharp
maneuvering. Blood can instantly pool into the pilot's
abdomen and extremities and cause him or her to pass out.
One possible solution is an "anti-gravitational suit"—or a
g-suit—that squeezes the lower body, forcing blood to flow
back through the torso and up toward the head.
Unfortunately, current g-suits designed using hydraulics and
pneumatics are slow to respond and often limit a craft's
A group at MIT thinks they may have a better way. Led by
mechanical engineer John Madden, a project leader in Ian
Hunter's BioInstrumentation Laboratory, and working in
collaboration with MIT chemist Timothy Swager, the
researchers have developed materials with properties closer
to human muscles than anything yet seen. They believe that
their muscle material will be perfect for an anti-gravitational
suit, as well as for therapeutic and commercial devices.
The team has recently launched a company called
Molecular Mechanisms in Cambridge, MA to develop the
technology. The group expects to produce a variety of
working prototypes within the next six months that may even
lay the foundation for what Swager calls a "superman suit"
for the armed forces. Such a suit could enable soldiers to
run, jump and lift to a nearly superhuman degree. "Imagine,"
he says, "the psychological damage it would wreak on a foe
if we had entire troops able to leap over 20-foot walls?"
The idea of being able to construct an artificial muscular
system has inspired some grand visions—biological robots,
to name one. Researchers have had some success in the
last decade with electroactive polymers, molecules that
absorb a solvent and then expand and contract when an
electric charge is applied. The good news is that these
materials require a very low voltage in order to respond. The
bad news is that these molecules don't have anywhere near
the power or flexibility of natural mammalian muscles. As a
result, researchers need to mechanically influence the
dimensions of movement in these materials.
But now, Madden and his group have taken a different
approach. Working with polypyrrole—the polymer of choice
for most artificial muscle research—Madden and Swager
have engineered molecules that undergo a fundamental
change in their structure when a voltage is applied. The new
molecules go through an accordion-like deformation,
stretching out and becoming highly elongated, then buckling
in. On a larger scale, this movement mimics that way
mammalian muscles work, which is why Madden and his
colleagues are so excited.
The material created from these molecules looks nothing
like human muscle. The thin, black ribbon feels almost like
electrical tape. But, "these materials are 100 times stronger
than mammalian muscle," Madden claims, with guarded
enthusiasm. Guarded, because these results haven't yet
However, Madden and his colleague Patrick Anquetil will be
presenting these results next month at the International
Society for Optical Engineering, and if this evidence holds
up under the scrutiny of peer review, this work will mark a
significant advance in the field. Says Gordon Wallace,
director of the Intelligent Polymer Research Institute in
Australia's Wallongon University, "Madden's and Swager's
ideas are very novel concepts. When you go back to
designing the polymer materials, then you have the potential
to make a major breakthrough."
Applications are countless. According to Yoseph
Bar-Cohen, senior research scientist as NASA and author of
Electroactive Polymer Actuators as Artificial Muscles,
(currently the only published book on the subject), "This is
an exciting field. We can start thinking in terms of copying
nature. Instead of having motors with gears and bearings,
we'll soon be able to take a blob, attach wires, and it will
change shape as desired."
And while the superman suit might be the long-term goal,
more prosaic applications should emerge sooner. Madden's
group has already begun working on a leg sock that will
prevent venous thrombosis—abnormal blood clotting that
can potentially clog arteries—for people who are at risk due
to long periods of immobility. In this device the artificial
muscular system enclosed in the sock would massage the
legs just enough to prevent the blood from pooling. Two
other possible medical applications include a
cardio-wraparound for patients with weakened heart
muscles and an artificial urinary sphincter.
But because these materials could cost as little as one
dollar per kilogram to mass produce, Madden is also looking
at consumer applications like toys (moving action figures)
and cosmetic and toothpaste dispensers. Anything that
requires motion is fair game, and could be on the market in
one to two years.
Man vs. Machine
While there's presently a lot of interest in electroactive
polymers, most research is confined to the university lab.
Aside from Madden's Molecular Mechanisms, the only other
company devoted exclusively to this technology is
Linkoping, Sweden-based Micromuscle, which focuses
primarily on technologies for powering
This field is still in its infancy and has yet to put any of its
claims to the test, but that hasn't curtailed the zeal of its
proponents. Bar-Cohen, for one, has so much faith in the
potential of electroactive polymers that he has made a
public challenge: once his team at NASA has completed
their prototype of an artificial arm, he dares anyone to stop
by and try to arm wrestle it.
If Madden and his group have their way, the volunteer may
show up in a superman suit.
David Cameron is a staff editor for technologyreview.com.
February 15, 2002