Tech Briefs Magazine - March 2021 - 40

Aeronautics

Obstacle-Avoiding Drone Uses Live Moth Antenna
" Smellicopter " uses a live moth antenna to avoid obstacles and seek out smells.
University of Washington, Seattle

ne advantage of drones is that they
can go places where people can't
including areas that might be too dangerous such as unstable structures after a
natural disaster or a region with unexploded devices.
Researchers are interested in developing devices that can navigate these situations by sniffing out chemicals in the air
to locate disaster survivors, gas leaks,
explosives, and more. But most sensors
are not sensitive or fast enough to find
and process specific smells while flying
through the patchy odor plumes these
sources create.
A team has developed Smellicopter, an
autonomous drone that uses a live antenna from a moth to navigate toward smells.
It can also sense and avoid obstacles as it
travels through the air. By using an actual
moth antenna, researchers were able to
get the best of both worlds: the sensitivity
of a biological organism on a robotic platform on which motion can be controlled.
The moth uses its antennae to sense
chemicals in its environment and navigate
toward sources of food or potential mates.
The team used antennae from the Manduca sexta hawkmoth for Smellicopter.
Researchers placed moths in the fridge to
anesthetize them before removing an
antenna. Once separated from the live
moth, the antenna stays biologically and
chemically active for up to four hours.
That time span could be extended by storing antennae in the fridge.
By adding tiny wires into either end of
the antenna, the researchers were able to
connect it to an electrical circuit and
measure the average signal from all of
the cells in the antenna. The team then
compared it to a typical human-made
sensor by placing both at one end of a
wind tunnel and wafting smells that both
sensors would respond to: a floral scent
and ethanol, a type of alcohol. The
antenna reacted more quickly and took
less time to recover between puffs.
To create Smellicopter, the team added
the antenna sensor to an open-source,
handheld, commercially available quadcopter drone platform that allows users
to add special features. The researchers
also added two plastic fins on the back of
the drone to create drag to help it be constantly oriented upwind.

The Smellicopter autonomous drone uses a live antenna from a moth to navigate toward smells.
Shown here is a hawkmoth in front of the Smellicopter. (Mark Stone/University of Washington)

By adding tiny wires into either end of the antenna (the arc being attached here), the researchers
were able to connect it to a circuit and record its responses. (Mark Stone/University of Washington)

Smellicopter doesn't need any help
from the researchers to search for
odors. The team created a " cast and
surge " protocol for the drone that mimics how moths search for smells.
Smellicopter begins its search by moving to the left for a specific distance. If
nothing passes a specific smell threshold, Smellicopter then moves to the
right for the same distance. Once it
detects an odor, it changes its flying pattern to surge toward it.
Another advantage to Smellicopter is
that it doesn't need GPS. Instead, it uses
a camera to survey its surroundings, sim-

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ilar to how insects use their eyes. This
makes Smellicopter well-suited for exploring indoor or underground spaces
like mines or pipes.
During tests in the lab, Smellicopter
was naturally tuned to fly toward smells
that moths find interesting such as floral
scents. But researchers hope that future
work could have the moth antenna sense
other smells such as the exhaling of carbon dioxide from someone trapped
under rubble or the chemical signature
of an unexploded device.
For more information, contact Sarah
McQuate at smcquate@uw.edu; 206-543-2580.
Tech Briefs, March 2021

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Tech Briefs Magazine - March 2021

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