Tech Briefs Magazine - October 2021 - 38

Power & Energy
The team found that thinner lithium
strips are adept at creating a good SEI,
while the thicker strips have a higher
chance of contributing to harmful SEI;
the researchers use the terms " wet SEI "
and " dry SEI. " The wet version retains
contact between the liquid electrolyte and
the anode, making important electrochemical
reactions possible.
But in the dry version, the liquid electrolyte
doesn't reach all of the lithium.
Simply, because the lithium strips are thicker,
the electrolyte needs to flow into deeper
pockets of the lithium and as it does so, it
leaves other portions of the lithium dry.
This stops important reactions from occurring,
effectively smothering necessary electrochemical
reactions, and contributes
directly to the early death of the battery.
For more information, contact Tom Rickey
at tom.rickey@pnnl.gov; 509-375-3732.
System Harvests Energy from Radio Waves to Power
Wearable Devices
The electricity can be used to power wireless devices or to charge energy storage devices
such as batteries and supercapacitors.
The Pennsylvania State University, University Park
rom microwave ovens to Wi-Fi connections,
the radio waves that permeate
the environment are not just signals
of energy consumed but are also sources
of energy themselves. Researchers have
F
developed a way to harvest energy from
radio waves to power wearable devices.
Current energy sources for wearable
health-monitoring devices have their
place in powering sensor devices but
each has its setbacks. Solar power, for
example, can only harvest energy when
exposed to the Sun. A self-powered triboelectric
device can only harvest energy
when the body is in motion.
The researchers developed a stretchable
wideband dipole antenna system
capable of wirelessly transmitting data
that is collected from health-monitoring
sensors. The system consists of two
stretchable metal antennas integrated
onto conductive graphene material with
a metal coating. The wideband design
of the system allows it to retain its frequency
functions even when stretched,
bent, and twisted. This system is then
connected to a stretchable rectifying circuit,
creating a rectified antenna, or
" rectenna, " capable of converting energy
from electromagnetic waves into
electricity. This electricity can be used
to power wireless devices or to charge
energy storage devices such as batteries
and supercapacitors.
The stretchable antenna and rectenna system harvests energy from radio waves in the ambient
environment to power wearable devices. (Image: Larry Cheng)
38
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ToC
The rectenna can convert radio, or
electromagnetic, waves from the ambient
environment into energy to power the
sensing modules on the device that track
temperature, hydration, and pulse oxygen
level. Compared to other sources,
less energy is produced but the system
can generate power continuously. Com -
bining the technology with a wireless
transmissible data device will provide a
critical component that will work with
the team's existing sensor modules.
Next steps will be exploring miniaturized
versions of the circuits and working
on developing the stretchability of
the rectifier. The technology can be
easily extended or adapted for other
applications.
For more information, contact Megan
Lak a tos at mkl5024@psu.edu; 814-865-5544.
Tech Briefs, October 2021

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Tech Briefs Magazine - October 2021

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