Tech Briefs Magazine - April 2024 - MD-26

plane. This allowed them to control the
orientation of two types of common liquid
crystals and create patterns with features
the size of a few micrometers, a
fraction of the thickness of a human
hair.
The findings could lead to the creation
of programmable tools that
shapeshift in response to stimuli, like
those needed in soft robots to handle
complex objects and environments or
camera lenses that automatically focus
depending on lighting conditions,
said Serra, who is also an Associate
Professor at the University of Southern
Denmark.
" If I wanted to make an arbitrary
three-dimensional shape, like an arm
or a gripper, I would have to align the
liquid crystals so that when it is subject
to a stimulus, this material restructures
spontaneously into those shapes, "
Serra said. " The missing information
until now was how to control this
three-dimensional axis of the alignment
of liquid crystals, but now we
have a way to make that possible, " he
added.
The team is working to obtain a patent
for their discovery and plan to further
test it with different types of liquid
crystal molecules and solidified polymers
made of these molecules.
For more information, contact
Roberto Molar Candanosa at molarc1@
jh.edu; 443-997-0258.
Tiny, Fully Functional Water-Strider and Mini-Bug Robots
Such miniature robots could someday be used for work in areas such as artificial pollination, search
and rescue, environmental monitoring, or robotic-assisted surgery.
Washington State University, Pullman, WA
T
wo insect-like robots, a mini-bug and a
water strider, developed at Washington
State University, are the smallest, lightest
and fastest fully functional micro-robots.
Such miniature robots could someday
be used for work in areas such as artificial
pollination, search and rescue,
environmental monitoring, micro-fabrication
or robotic-assisted surgery.
Reporting on their work in the proceedings
of the IEEE Robotics and
Automation Society's International
Conference on Intelligent Robots and
Systems, the mini-bug weighs in at
eight milligrams while the water strider
weighs 55 milligrams. Both can move at
about six millimeters a second.
" That is fast compared to other micro-robots
at this scale although it still
lags behind their biological relatives, "
said Conor Trygstad, a Ph.D student in
the School of Mechanical and Materials
Engineering and lead author on the
work. An ant typically weighs up to five
milligrams and can move at almost a
meter per second.
The key to the tiny robots is their tiny
actuators that make the robots move.
Trygstad used a new fabrication technique
to miniaturize the actuator down
to less than a milligram, the smallest
ever known to have been made.
" The actuators are the smallest and fastest
ever developed for micro-robotics, "
said Néstor O. Pérez-Arancibia, Flaherty
Associate Professor in Engineering
at WSU's School of Mechanical and
Materials Engineering who led the project.
26
The actuator uses a material called
a shape memory alloy that is able to
change shapes when it's heated. It is
called 'shape memory' because it remembers
and then returns to its original
shape. Unlike a typical motor that
would move a robot, these alloys don't
have any moving parts or spinning
components.
An advance in actuator design allowed
for the creation of the tiny, fully-functional
WaterStrider and MiniBug robots.
" They're very mechanically sound, "
said Trygstad. " The development of the
very lightweight actuator opens up new
realms in micro-robotics. "
Shape memory alloys are not generally
used for large-scale robotic movement
because they are too slow. In the
case of the WSU robots, however, the actuators
are made of two tiny shape memory
alloy wires that are 1/1000 of an
inch in diameter. With a small amount
of current, the wires can be heated up
and cooled easily, allowing the robots to
flap their fins or move their feet at up to
40 times per second. In preliminary tests,
the actuator was also able to lift more
than 150 times its own weight.
Compared to other technologies used
to make robots move, the SMA technology
also requires only a very small
amount of electricity or heat to make
them move.
" The SMA system requires a lot less
sophisticated systems to power them, "
said Trygstad.
Trygstad, an avid fly fisherman, has
long observed water striders and would
like to further study their movements.
While the WSU water strider robot does
a flat flapping motion to move itself, the
natural insect does a more efficient rowing
motion with its legs, which is one of
the reasons that the real thing can move
much faster.
The researchers would like to copy
another insect and develop a water
strider-type robot that can move across
the top of the water surface as well as
just under it. They are also working to
use tiny batteries or catalytic combustion
to make their robots fully autonomous
and untethered from a power
supply.
The WaterStrider weighs 55 milligrams and can move
at 6 millimeters per second. (Image: Bob Hubner,
WSU Photo Services)
For more information, contact Conor
Trygstad at conor.trygstad@wsu.edu;
425-829-7115.
Motion Design, April 2024

Tech Briefs Magazine - April 2024

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