Magnetics Business & Technology - May/June 2020 - 18

RESEARCH & DEVELOPMENT

Technique Uses Magnets and Light to Control, Reconfigure Soft Robots

Using soft robots made of a polymer embedded with magnetic
iron particles, researchers from North Carolina State University
and Elon University have developed a technique that allows
them to remotely control the movement of soft robots, lock them
into position for as long as needed and later reconfigure the robots into new shapes. The technique relies on light and magnetic
fields.
"We're particularly excited about the reconfigurability," says
Joe Tracy, a professor of materials science and engineering at
NC State and corresponding author of a paper on the work. "By
engineering the properties of the material, we can control the
soft robot's movement remotely; we can get it to hold a given
shape; we can then return the robot to its original shape or
further modify its movement; and we can do this repeatedly. All
of those things are valuable, in terms of this technology's utility in
biomedical or aerospace applications."
For this work, the researchers used soft robots made of a polymer embedded with magnetic iron microparticles. Under normal
conditions, the material is relatively stiff and holds its shape.
However, researchers can heat up the material using light from
a light-emitting diode (LED), which makes the polymer pliable.
Once pliable, researchers demonstrated that they could control
the shape of the robot remotely by applying a magnetic field.
After forming the desired shape, researchers could remove the
LED light, allowing the robot to resume its original stiffness - effectively locking the shape in place.
By applying the light a second time and removing the magnetic
field, the researchers could get the soft robots to return to their
original shapes. Or they could apply the light again and manipulate the magnetic field to move the robots or get them to assume
new shapes.
In experimental testing, the researchers demonstrated that the
soft robots could be used to form "grabbers" for lifting and transporting objects. The soft robots could also be used as cantilevers
or folded into "flowers" with petals that bend in different directions.

Magnetics Business & Technology * May/June 2020

Rotation of a "flower" with six petals is shown in the photo above.
Turning on the LED in sync with the rotation of every second
petal beneath the magnet causes lifting of alternating petals,
which remain lifted.
"We are not limited to binary configurations, such as a grabber
being either open or closed," says Jessica Liu, first author of the
paper and a Ph.D. student at NC State. "We can control the light
to ensure that a robot will hold its shape at any point."
In addition, the researchers developed a computational model
that can be used to streamline the soft robot design process.
The model allows them to fine-tune a robot's shape, polymer
thickness, the abundance of iron microparticles in the polymer,
and the size and direction of the required magnetic field before
constructing a prototype to accomplish a specific task.
In cantilevers and flowers, multiple cycles of locking and unlocking were demonstrated. Scrolls show that the permanent
shape of the film can be programmed, and they can be frozen in
intermediate configurations. Bistable snappers can be magnetically and optically actuated, as well as biased, by controlling the
permanent shape. Grabbers can pick up and release objects
repeatedly. Simulations of combined photothermal heating and
magnetic actuation are useful for guiding the design of new
devices.
"Next steps include optimizing the polymer for different applications," Tracy says. "For example, engineering polymers that
respond at different temperatures in order to meet the needs of
specific applications."
The paper, "Photothermally and Magnetically Controlled Reconfiguration of Polymer Composites for Soft Robotics," appears in
the journal Science Advances. The paper was co-authored by
Jonathan Gillen, a former undergraduate at NC State; Sumeet
Mishra, a former Ph.D. student at NC State; and Benjamin Evans, an associate professor of physics at Elon University.
For more info, see https://news.ncsu.edu/2019/08/magnets-lightsoft-robots/ and www.advances.sciencemag.org.

www.MagneticsMag.com

https://news.ncsu.edu/2019/08/magnets-light-soft-robots/ https://news.ncsu.edu/2019/08/magnets-light-soft-robots/ https://advances.sciencemag.org/ http://www.MagneticsMag.com

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