Tech Briefs Magazine - June 2021 - MD-20

atop those layers. When a positive voltage
is applied to the actuators, oxygen atoms
are driven into the platinum and swap
places with platinum atoms. This process,
called oxidation, causes the platinum to
expand on one side in the seams between
the inert glass panels, which bends the
structure into its predesignated shape.
The machines can hold that shape even
after the voltage is removed because the
embedded oxygen atoms bunch up to
form a barrier, which prevents them
from diffusing out.
By applying a negative voltage to the
device, the researchers can remove the
oxygen atoms and quickly restore the
platinum to its pristine state. And by
varying the pattern of the glass panels -
and whether the platinum is exposed on
the top or bottom - they can create a
range of origami structures actuated by
mountain and valley folds.
Nanosized robots that fold themselves into 3D configurations could enable locomotion, novel metamaterial
design, and high-fidelity sensors. (Courtesy Cornell University)
Imagine a million fabricated microscopic
robots releasing from a wafer that
fold themselves into shape, crawl free,
and go about their tasks, even assembling
into more complicated structures.
The robots' shape memory actuator can
drive with voltage and hold a bent
shape.
The actuators can bend with a radius
of curvature smaller than a micron -
the highest curvatures of any voltagedriv
en actuator by an order of magnitude.
This flexibility is important be -
cause one of the basic principles of micro -
scopic robot manufacturing is that the
robot size is determined by how small
the various appendages can be made to
fold. The tighter the bends, the smaller
the folds, and the tinier the footprint for
each machine. It's also important that
these bends can be held by the robot,
which minimizes power consumption -
a feature especially advantageous for
microscopic robots and machines.
The devices consist of a nanometerthin
layer of platinum capped with a
titan ium or titanium dioxide film. Several
rigid panels of silicon dioxide glass sit
The tiny layers are about 30 atoms
thick, compared to a sheet of paper that
might be 100,000 atoms thick. The
machines fold themselves within 100 milliseconds.
They can also flatten and re -
fold themselves thousands of times. And
they only need a single volt to be powered
to life.
The team is currently working to integrate
the shape memory actuators with
circuits to make walking robots with foldable
legs as well as sheet-like robots that
move by undulating forward. These innovations
may someday lead to nanorobots
that can clean bacterial infection from
human tissue, micro-factories that can
transform manufacturing, and robotic
surgical instruments that are ten times
smaller than current devices.
For more information, contact Jeff Tyson
at jeff.tyson@cornell.edu; 607-793-5769.
Swimming Living Robots Can Self-Train
Biobots based on muscle cells can swim at unprecedented velocities.
Institute for Bioengineering of Catalonia, Barcelona, Spain
Roboticists aim to mimic what natural
biological entities have achieved -
actions like moving, adapting to the
environment, or sensing. Beyond traditional
rigid robots, the field of soft
robotics has recently emerged using
compliant, flexible materials capable of
adapting to their environment more effi20
Cov
ToC
ciently
than rigid ones. With this goal in
mind, scientists have been working in
the field of biohybrid robots or biobots.
These generally are composed of muscle
tissue, either cardiac or skeletal, and an
artificial scaffold that can achieve crawling,
grasping, or swimming. Unfortu -
nately, current biobots are unable to
emulate the performance of natural en -
tities in terms of mobility and strength.
Researchers have overcome both challenges
by using bioengineering tools.
They applied 3D bioprinting and engineering
design for the development of
biobots at the centimeter range that can
swim and coast like fish with unpreceMotion
Design, June 2021

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Tech Briefs Magazine - June 2021

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