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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U N E 2 0 1 5
8 METALS | POLYMERS | CERAMICS
RESONANCE PHENOMENON
HELPS ROBOTIC BIRDS SOAR
Researchers from the Harbin In-
stitute of Technology, China, and the
University of California, Los Angeles
(UCLA), discovered a new resonance
phenomenon in a dielectric elastomer
rotary joint that can make the artificial
joint bend up and down, like a flapping
wing. “The dielectric elastomer is a kind
of electro-active polymer that can de-
form if you apply a voltage on it,” says
Jianwen Zhao, an associate professor
at Harbin. He says that most studies
on dielectric elastomers use a static
or stable voltage to stimulate the joint
motion, which makes the joint bend
at a fixed angle. Zhao and his team are
interested in seeing how the artificial
joint reacts to an alternating or periodi-
cally changing voltage.
“We found that alternating voltag-
es canmake the joint continuously bend
at different angles. When the rotational
inertia of the joint or the applied voltage
is large enough, the joint can deform to
negative angles, in other words, it can
bend beyond 90 to 180 degrees,” says
Zhou. He adds that this new phenome-
nonmakes the dielectric elastomer joint
a good candidate for creating a soft and
lightweight flapping wing for robotic
birds, which would be more efficient
than wings based on electrical motors
due to the higher energy conversion effi-
ciency (60-90%) of the dielectric elasto-
mer. , .
CARBON-FIBER EXOSKELETON
BOOSTS WALKING EFFICIENCY
Research results show that hu-
mans can get better “gas mileage”
while walking using an unpowered
exoskeleton to modify the structure
of their ankles. The device puts an ex-
tra spring in each human step, reduc-
ing metabolic energy consumption by
7% below walking in normal athletic
The Watchman LAA Closure Tech-
nology medical device from Boston
Scientific Corp., Marlborough,
Mass., received approval from
the U.S. FDA, Silver Spring, Md.
It consists of a delivery catheter
plus a device that is permanently
implanted in the left atrial append-
age (LAA) of the heart. The device
prevents LAA blood clots from
entering the bloodstream, which
could potentially cause a stroke. It
is made of a self-expanding Nitinol
frame with an attached woven
plastic cap. .
BRIEFS
Rolls-Royce, London, chose Bristol as the location for a center of ad-
vanced fan system composite technology development, creating a hub of
composite knowledge in the UK. The hub will benefit frommanufacturing
techniques being developed in partnership with the National Composites
Centre (NCC), part of the University of Bristol. The advanced manufac-
turing facility will develop next-generation fan blades and cases made
of carbon-fiber composite materials for future Rolls-Royce aero-engines.
Treadmill results show that exoskeleton devices boost walking efficiency by 7% in
able-bodied adults. Photo courtesy of Marc Hall, NCSU.
The structure of the rotary joint (left) and the system to measure joint rotation
(right). Courtesy of Jianwen Zhao/Harbin Institute of Technology, UCLA.