Tech Briefs Magazine - October 2023 - 30

Electrical/Electronics
taining a similar coefficient of performance
(COP), or the ratio of useful
cooling to energy required, the scientists
reported in Nature Communications.
" This solves two out of the three big
challenges in making thermoelectric
cooling devices, " said Shashank Priya,
Vice President for Research at the University
of Minnesota and a co-author on
the paper. " First, it can provide a high
cooling power density with a high COP.
This means a small amount of electricity
can pump a lot of heat. Second, for a
high-powered laser or applications that
require a lot of localized heat to be removed
from a small area, this can provide
the optimum solution. "
The new device is made from a compound
of half-Heusler alloys, a class of
materials with special properties that
show promise for energy applications
like thermoelectric devices. These materials
offer good strength, thermal stability,
and efficiency.
The researchers used a special annealing
process, which deals with how materials
are heated and cooled, that allowed
them to modify and manipulate the microstructure
of the material to remove
defects. It had not been used previously
to make half-Heusler thermoelectric materials,
the scientists said.
The annealing process also dramatically
grew the grain size of the material,
leading to fewer grain boundaries - areas
in a material where crystallite structures
meet and that reduce electrical or
thermal conductivity.
" In general, half-Heusler material has
very small grain size - nano-sized grain, "
said Wenjie Li, assistant research professor
in the Department of Materials Science
and Engineering at Penn State.
" Through this annealing process we can
control the grain growth from the nanoscale
to the microscale - a difference
of three orders of magnitude. "
Reducing the grain boundaries and
other defects substantially enhanced
carrier mobility of the material, or how
electrons can move through it, yielding
a higher power factor, the scientists
A Thin, Flexible OLED Display
The material can bend in half or stretch to more than twice its original length and has
applications ranging from wearable electronics to health sensors and computer screens.
University of Chicago, IL
I
magine a thin, digital display so flexible
that you can wrap it around your wrist,
fold it in any direction, or even curve it over
your car's steering wheel. Well, imagine no
more - researchers at the Pritzker School
of Molecular Engineering (PME) at the
University of Chicago have designed such a
material; it can even bend in half or stretch
to more than twice its original length -
and still emit a fluorescent pattern.
The material, described in Nature Materials,
has a wide range of applications,
from wearable electronics and health
sensors to foldable computer screens.
" One of the most important components
of nearly every consumer electronic
we use today is a display, and
we've combined knowledge from many
said. The power factor determines the
maximum cooling power density and is
especially important in electronics-cooling
applications.
" For instance, in laser diode cooling,
a significant amount of heat is
generated in a very small area, and it
must be maintained at a specific temperature
for the optimal performance
of the device, " Li said, " That's where
our technology can be applied. This
has a bright future for local high thermal
management. "
In addition to the high-power factor,
the materials produced the highest average
figure of merit, or efficiency, of any
half-Heusler material in the temperature
range of 300 to 873 °K (80 to 1,111 °F).
According to the scientists, the results
show a promising strategy for optimizing
the new half-Heusler materials for
near-room-temperature thermoelectric
applications.
For more information, contact Patricia
Craig at plc103@psu.edu; 814-8634663.
A
material developed by Assistant Professor Sihong Wang and Proffesor Juan de Pablo can stretch more than twice its original length without disrupting
its ability to emit light and display a clear image. (Image: Wang Group)
30
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Tech Briefs, October 2023

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Tech Briefs Magazine - October 2023

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