Tech Briefs Magazine - July 2021 - 28

Materials & Coatings
High-Performance, Energy-Absorbing Material
The new material could provide efficient and reusable protection from shock, vibration,
and explosion.
University of Birmingham, United Kingdom
P
ressurized insertion of aqueous solutions
into water-repellent nano -
porous materials, such as zeolites and
metal-organic frameworks, could help to
create high-performance, energy-ab -
sorbing systems. Researchers experimented
with hy drothermally stable
zeolitic imidazolate frameworks (ZIFs)
with a hydrophobic cage-like molecular
structure, finding that such systems
are remarkably effective energy ab -
sorbers at realistic, high-rate loading
conditions and this phenomenon is
associated with the water clustering
and mobility in nanocages.
Rubber is widely used for shock absorption
but the new process creates a material
that can absorb more mechanical energy
per gram with very good reusability
due to its unique nanoscale mechanism.
The material has significance for vehicle
crash safety for both occupants and
pedestrians, military armored vehicles
and infrastructures, and as human
body protection. Soldiers and police
could benefit from better body armor
and bomb suits and athletes could have
more effective helmets, knee pads, and
shoe insoles since the material is liquidlike
and flexible to wear.
The reusability of the material, stemming
from the spontaneous liquid extrusion,
also makes the material suitable for
damping purposes, meaning that it
could be used to create vehicles with
lower noise and vibration as well as better
ride comfort. The material could also
be incorporated into machinery to re -
duce harmful vibrations and noise, re -
ducing maintenance costs. It could be
used to reduce vulnerability to earthquakes
for bridges and buildings.
For more information, contact Tony Moran
at t.moran@bham.ac.uk; +44 (0)782 783
2312.
Generation of Polystyrene Latex Spheres with Incorpo -
rated Fluorescent Dyes
Microspheres are used in wind tunnel experiments to monitor airflow, to stain biological
samples, and in time-delayed drug release.
Langley Research Center, Hampton, Virginia
olymeric particles are used extensively
for seeding airflows in wind tunnels,
and biological and histological staining,
among other applications. For wind tunnel
applications, particle image velocimetry
is often used to determine the interaction
of various models and surfaces with
surrounding airflows. Meas urements near
the wall are particularly relevant and
unfortunately, exceptionally challenging
Laser Source
P
due to the large level of background noise
arising from reflection of incident light off
the surface of the model being studied.
Thus, the ability to seed the airflow with a
material that can be used to accurately
portray the airflow properties (i.e., minimal
particle lag) - while enabling nearwall
measurements with improved signalto-noise
ratio - is of high interest to wind
tunnel researchers.
Vortex Core
Flow Direction
Seed
Although polystyrene microspheres
are often the seed material of choice for
subsonic airflow studies, these seed materials
do not provide any benefit for nearwall
measurements compared to other
state-of-the-art seed materials. Con se -
quently, in this innovation, NASA scientists
de veloped a method of generating
dye-doped polystyrene micro spheres
using novel synthetic approaches.
The novel features of this invention
are the utility of specific chemical functionalities,
monomeric species, environmental
additives (buffers), and polyelectrolytes
to promote incorporation of dye
molecules into developing polystyrene
microspheres while enabling control of
the spectral properties of the dye relative
to pH dependence.
Laser airflow shown with microspheres. (Image: NASA)
28
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These particles will have great utility
for wind tunnel measurements near the
wall where the state-of-the-art seed materials
are not able to collect data. Addi -
tionally, the incorporation of these dyes
will offer other avenues of data collection
including temperature and pressure
of the airflows and wind tunnel
regions. Likewise, the ability to selectively
filter the data collected from these
Tech Briefs, July 2021
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Tech Briefs Magazine - July 2021

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