Robugs: Smart Dust Has Legs
by David Pescovitz
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Professor Kris Pister is currently on industrial leave from the University, working at his start-up company Dust Inc.
Peg Skorpinski photo
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"For fourteen
years, I've had this dream of making silicon walk," says UC
Berkeley professor Kristofer Pister of the Department of Electrical
Engineering and Computer Sciences.
It's a startling idea: Swarms of ant-size robots burrowing through
the rubble of a building after an earthquake searching for survivors
or crawling onto the hull of a spacecraft to repair damage in-flight.
But perhaps the most amazing thing about Pister's dream is that
it's not as far off as one might think. Already Pister and his graduate
students have built simple solar-powered microrobots just 8.5 millimeters
long and less than 4 millimeters wide.
"It only has two legs and its tail is too heavy, so it can't
quite walk," Pister says. "But it does push-ups."
Still, the solar-powered bug demonstrates that tiny autonomous robots
can be fabricated using the same technology used to manufacture
integrated circuits. The current microrobot prototypes were built
in three separate pieces in UC Berkeley's state-of-the-art Microfabrication
Laboratory. The first component is a digital logic chip that controls
the walking motion of the two legs. The second includes the near-microscopic
solar cells, designed by Pister's former graduate student Seth Hollar.
Those two components are then combined with the legs, motors and
frame of the robot. Eventually, all three steps could be combined
into a single process, enabling the microrobots to be cranked out
in bulk at costs of perhaps less than $1 each.
Graduate student Sarah Bergbreiter examines a microrobot using a high-powered magnifying glass.
David Pescovitz photo
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Key to the microrobot's
locomotion is the novel MEMS (micro-electromechanical systems) the
researchers developed during the last several years. Aptly-named
"inchworm" motors work by repeatedly engaging a shuttle
that pulls the leg forward a minuscule amount, releases it, and
then engages it again to move it a bit more. Similar to the way
a person climbs a ladder, the repetition of small steps will provide
the legs with enough force and displacement (distance of travel)
to carry the microrobot along.
"Traditionally with MEMS, you get either high force or large
displacements," says lead graduate student Sarah Bergbreiter.
"With the inchworm motors, you have both."
Right now, the microrobot is crippled by a clutch that slips when
the leg pushes against the ground. The problem, Bergbreiter says,
should be solvable with minor adjustments to the design of the device
before the next batch of microrobots is fabricated.
A
scanning electron microscope (SEM) image of the microrobot's
legs. (Click on image to download 58KB
size.)
Photo courtesy the researchers
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The microrobot
research preceded Pister's Smart Dust motes, tiny wireless transceivers
outfitted with sensors for myriad applications. A key component
in the efforts of the Center for Information Technology Research
in the Interest of Society (CITRIS), Smart Dust has a multitude
applications— from diagnosing a building's structural integrity
to measuring light and temperature for energy use monitoring. Outfitted
with their own TinyOS operating system, the motes self-organize
into ad hoc wireless networks and pass their data from one to another
bucket-brigade style until the information reaches a central computer
for processing. Now, Pister and Bergbreiter, with private sector
collaborator Anita Flynn of MicroPropulsion Corporation are finally
able to realize the full potential of the Smart Dust platform.
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A
full view of the two-legged microrobot. Image courtesy
the researchers.
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"MEMS technology
has shrunk so much that we can start to make microrobots which are
essentially smart dust with legs," Bergbreiter says.
The Smart Dust-style sensors and on-board computer processing
are what will provide the microrobots with their autonomy, Bergrbreiter
says. While each robot will control its own activity, the power
will come from deploying them in swarms. For instance, much like
ants build a nest, a swarm of microrobots dropped on Mars could
work collaboratively to construct a satellite antenna so they can
transmit their environmental readings to an orbiting spacecraft.
Even more amazing, Bergbreiter says, they could crawl on top of
each other to build a larger silicon structure out of themselves.
"In my opinions, robotics has always meant big lumbering machines,"
Bergbreiter says. "I like the idea of making very simple robots,
but a lot of them. If one component of a big robot fails, the robot
is finished. But if one microrobot dies, the rest of them continue
to function and the task can still be completed."
Silicon
Microrobots
Kristofer
Pister's home page
Smart
Dust
Dust Inc.
MicroPropulsion
Corp.
Center for
Information Technology Research in the Interest of Society (CITRIS)
CITRIS
Video (6:05)
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Updated 8/29/03.
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