Tech Briefs Magazine - June 2022 - 28

Electrical/Electronics
Based on this modeling, the team
then built and tested structures in the
lab, using advanced methods for imaging
and quantifying patterns of flow. The
resulting structures can be formed across
a wide variety of sizes and shapes.
To manufacture the devices, the team
drew inspiration from another familiar
novelty: a child's pop-up book. The
team first fabricated precursors to flying
structures in flat, planar geometries.
Then, they bonded these precursors
onto a slightly stretched rubber substrate.
When the stretched substrate is
relaxed, a controlled buckling process
occurs that causes the wings to " pop up "
into precisely defined three-dimensional
forms.
The microfliers comprise two parts: millimeter-sized
electronic functional components
and their wings. As the microflier
falls through the air, its wings interact with
the air to create a slow, stable rotational
motion. The weight of the electronics is
distributed low in the center of the microflier
to prevent it from losing control and
chaotically tumbling to the ground.
In demonstrated examples, the team
included sensors, a power source that
can harvest ambient energy, memory
storage, and an antenna that can wirelessly
transfer data to a smartphone, tablet,
or computer. The team outfitted one
device with all of these elements to detect
particulates in the air. In another example,
they incorporated pH sensors that
could be used to monitor water quality
and photodetectors to measure Sun exposure
at different wavelengths.
Large numbers of devices could be
dropped from a plane or building and
broadly dispersed to monitor environmental
remediation efforts after a chemical
spill or to track levels of air pollution
at various altitudes.
The physically transient electronics systems
use degradable polymers, compostable
conductors, and dissolvable integrated
circuit chips that naturally
vanish into environmentally benign end
products when exposed to water.
For more information, contact Amanda
Morris at amandamo@northwestern.edu;
847-467-6790.
Heat-Management Material Keeps Computers Running Cool
The semiconductor material is integrated into high-power chips to reduce heat on processors
and improve their performance.
University of California, LA
C
omputer processors have shrunk to
nanometer scales over the years, with
billions of transistors sitting on a single
computer chip. While the in creased
number of transistors helps make computers
faster and more powerful, it also
generates more hot spots in a highly condensed
space. Without an efficient way
to dissipate heat during operation, computer
processors slow down and result in
unreliable and inefficient computing. In
addition, the highly concentrated heat
and soaring temperatures on computer
chips require extra energy to prevent
processers from overheating.
An ultrahigh thermal-management material
- defect-free boron arsenide - was
developed that is more effective in drawing
and dissipating heat than other known
metal or semiconductor materials such as
diamond and silicon carbide. The researchers
integrated the material into computer
chips with state-of-the-art, wide-bandgap
transistors of gallium nitride called
high-electron-mobil ity transistors (HEMTs).
When running the processors at near
maximum capacity, chips that used boron
arsenide as a heat spreader showed a
maximum heat increase from room temperatures
to nearly 188 °F. This is significantly
lower than chips using diamond to
spread heat, with temperatures rising to
approximately 278 °F or the ones with silicon
carbide showing a heat increase to
about 332 °F.
28
Electronic chip
Heat spreader
Schematic illustrating thermal management in electronics chip packaging. (Image: the H-Lab)
These results clearly show that boron-arsenide
devices can sustain much
higher operation power than processors
using traditional thermal management
materials. Boron arsenide is ideal
for heat management because it not
only exhibits excellent thermal conductivity
but also displays low heat transport
resistance. When heat crosses a
boundary from one material to another,
there's typically some slowdown to get
into the next material. The boron arsewww.techbriefs.com
nide
material has very low thermal
boundary resistance.
The team has also developed boron
phosphide as another excellent heatspreader
candidate. During their experiments,
the researchers first illustrated
the way to build a semiconductor structure
using boron arsenide and then integrated
the material into a HEMT-chip
design.
For more information, contact Christine
Wei-li Lee at clee@seas.ucla.edu.
Tech Briefs, June 2022
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6/13/22 4:32 PM

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Tech Briefs Magazine - June 2022

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