20 Scientific American, September 2019
RICHA BATRA, JANE NISSELSON AND KYLE PARSONSColumbia EngineeringADVANCES
TECHRobot Herd
Simple automatons expand and contract to move as one
Scientists have created a robot consisting
of multiple units that can operate as a clus-
ter, responding to stimuli and acting on
their environment without the need for any
centralized control—much like living cells.
Each of the circular units, or “particles,”
measures up to 23.5 centimeters in diame-
ter. The particles are loosely joined together
with magnets and can move only by ex pand -
ing or contracting. But despite their individu-
al simplicity, as a group they are capable of
more sophisticated behavior, such as moving
toward a light source. The weakly linked
mass is more resilient than many other
robotic systems because it has no single
point of failure and can keep working even
if some individuals become disabled, the
researchers reported in March in Nature.
The scientists say miniaturized versions
of the particles could be used in search and
rescue operations—for example, spreading
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Tiny units could also deliver drugs to hard-
to-reach parts of the human body or boost
research by modeling the cellular action
involved in organ formation.
The prototype particles are equipped
with light sensors and simple electronics
that make them expand or contract in
accordance with an algorithm. Each particle
measures the intensity of nearby light and
broadcasts that reading to its neighbors. By
comparing how much light it detects rela-tive to the others, each unit decides when
to start a cycle of expansion and contrac-
tion—causing them all to move as a group.
The researchers created clusters of up
to 24 particles and showed they could shuf-
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comparable to the way living cells aggre-
gate and migrate for wound healing and
other functions. “In our system, each parti-
cle is very simple, and there is no central
control over the cluster,” says Daniela Rus,
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cial Intelligence Laborator y at the Massa-
chusetts Institute of Technology and one
of the team leaders. The units “work togeth-
er without relying on any particular individ-
uals.” (Rus ser ves on 2_w²í_Ĉ¬wÞ_C²Ûs
board of advisers.)
The robot can also skirt obstacles and
push objects around. And in simulations
with up to 100,000 units, even if 20 percent
stopped functioning the cluster could still
travel at about half of its top speed.
“This kind of technology is expected to
be applied to tasks such as searching, col-
lecting and transmitting information and
transporting [objects] as a swarm,” says
Hajime Asama, a professor of engineering
at the University of Tokyo, who was not
involved in the study. “But there are still
many problems to be solved before reaching
actual applications, including the ability to
adapt to changes in tasks, the environment
and the robot’s own state.” — 4¬·Þ²ĀC¥