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Growing hairy materials at the microscale
Scientists at the DOE’s Argonne National
Laboratory, Ill., attacked a tangled problem
by developing a new technique to grow tiny
“hairy” materials that assemble themselves at
the microscale. Epoxy is the key ingredient
and it is added to a mixture of hardener and
solvent inside an electric cell. An alternating
current is run through the cell while long,
twisting fibers spring up—similar to the way
Chia Pets grow.
“The process is very simple, the materi-
als are inexpensive and available, and they
can grow on almost every surface we’ve
tried,” explains physicist Igor Aronson. By
tweaking the process, many different shapes
can be grown—short forests of dense straight
hairs, long branching strands, or “mush-
rooms” with tiny pearls at the tips. Although
the structures can be permanent, the process is also instantly reversible.
Gummy material prevents fires in lithium batteries
Researchers fromWashington State University, Pullman, developed a chewing gum-like
battery material that could dramatically improve the safety of lithium ion batteries. The
biggest risk comes from the battery’s electrolyte, which is made from either a liquid or gel.
These acidic liquid solutions can leak, potentially causing fires or chemical burns.
Professor Katie Zhong’s research group developed a gum-like lithium battery elec-
trolyte, which conducts electricity as well as liquid versions, but does not create a fire haz-
ard. The material—a liquid-solid hybrid—contains liquid electrolyte material that hangs on
solid particles of wax or a similar material. Current can easily travel through the liquid
parts of the electrolyte while solid particles provide protection. If the material gets too hot,
the solid melts and stops conduction, preventing fire hazards. The electrolyte material is
flexible and lightweight, and can be stretched, smashed, and twisted. For more information:
Katie Zhong, 509/335-7658, , .
Flat-pack lens boosts solar power
Researchers at the State Key Laboratory of Precision Measuring Technology & Instru-
ments, Tianjin University, China, are able to craft the surface structures on a Fresnel lens
with an array of microscopic cones (rather than concentric ridges), bringing incident light
to a point at a more precise depth on the photoactive layer in solar panels.
Initial tests with their precision-machined Fresnel solar collector showed a peak power
four times higher than standard panels at low resistance. The difference in power falls off
quickly as the device’s resistance rises, which it
does as it gets hotter under sunlight and as a
byproduct of generating electricity. Nevertheless,
the differential would be enough to boost its elec-
trical output, substantially offsetting the addi-
tional cost of the Fresnel collector so that the
overall cost of solar panels might be reduced. This
simple addition to older, less efficient solar panels
might also make them viable for places and appli-
cations where modern devices of higher intrinsic
efficiency are not commercially tenable.
ADVANCED MATERIALS & PROCESSES • APRIL 2014 14
ENERGY TRENDS
briefs
The DOE recently announced that
the U.S. solar industry is more than
60% of the way to achieving cost-
competitive, utility-scale solar
photovoltaic (PV) electricity—only
three years into the Department’s
decade-long SunShot Initiative. To
facilitate further progress, $25
million in funding will help
strengthen U.S. solar
manufacturing for PV and
concentrating solar power
technologies and maintain a strong
domestic solar industry—
supporting the broader Clean
Energy Manufacturing Initiative.
Plastic shopping bags, an
abundant source of litter on land
and at sea, can be converted into
diesel, natural gas, and other
useful petroleum products,
according to researchers at the
Illinois Sustainable Technology
Center at the University of
Illinois, Champaign. The
conversion produces significantly
more energy than it requires and
results in transportation fuels—
diesel, for example—that can be
blended with existing ultra-low-
sulfur diesels and biodiesels. Other
products, such as natural gas,
naphtha (a solvent), gasoline,
waxes, and lubricating oils such as
engine oil and hydraulic oil also
can be obtained from shopping
bags. .
Used plastic shopping bags can
be converted into petroleum
products that serve a multitude
of purposes. Courtesy of Julie
McMahon.
These tiny “mushrooms” could be useful in
new energy technologies. The scale bar
shows 20 µm, about the size of a single
bacterium. Courtesy of Alexey Snezhko and
Igor Aronson/Argonne National Laboratory.
Researchers at the Helmholtz Center Berlin
(HZB), Germany, demonstrated that tiny voids
within the silicon network are partly respon-
sible for reducing solar cell efficiency by
roughly 10 to 15% as soon as use begins.
Defects in amorphous silicon come in two
types: Those that are uniformly distributed
and those that are concentrated in clusters
on internal surfaces of small voids—known
as microvoids—which form within the ma-
terial during solar cell manufacturing.