Using snail teeth to improve solar cells and batteries
phys.org |
An assistant professor at the University of California,
Riverside's Bourns College of Engineering is using the teeth of a marine snail
found off the coast of California to create less costly and more efficient
nanoscale materials to improve solar cells and lithium-ion batteries. The most
recent findings by David Kisailus, an assistant professor of chemical and
environmental engineering, details how the teeth of chiton grow. The paper was
published Jan. 16 in the journal Advanced Functional Materials. It
was co-authored by several of his current and former students and scientists at
Harvard University in Cambridge Mass., Chapman University in Orange, Calif. and
Brookhaven National Laboratory in Upton, NY.
The
paper is focused on the gumboot chiton, the largest type of chiton, which can
be up to a foot-long. They are found along the shores of the Pacific Ocean from
central California to Alaska. They have a leathery upper skin, which is usually
reddish-brown and occasionally orange, leading some to give it the nickname
"wandering meatloaf."
Over
time, chitons have evolved to eat algae growing on and within rocks using a
specialized rasping organ called a radula, a conveyer belt-like structure in
the mouth that contains 70 to 80 parallel rows of teeth. During the feeding
process, the first few rows of the teeth are used to grind rock to get to the
algae. They become worn, but new teeth are continuously produced and enter the
"wear zone" at the same rate as teeth are shed.
Kisailus,
who uses nature as inspiration to design next generation engineering products
and materials, started studying chitons five years ago because he was
interested in abrasion and impact-resistant materials. He has previously
determined that the chiton teeth contain the hardest biomineral known on Earth,
magnetite, which is the key mineral that not only makes the tooth hard, but
also magnetic.
In the
just-published paper, "Phase transformations and structural developments
in the radular teeth of Cryptochiton stelleri," Kisailus set out to
determine how the hard and magnetic outer region of the tooth forms.
His
work revealed this occurs in three steps. Initially, hydrated iron oxide
(ferrihydrite) crystals nucleate on a fiber-like chitinous (complex sugar)
organic template. These nanocrystalline ferrihydrite particles convert to a
magnetic iron oxide (magnetite) through a solid-state transformation. Finally,
the magnetite particles grow along these organic fibers, yielding parallel rods
within the mature teeth that make them so hard and tough.
"Incredibly,
all of this occurs at room temperature and under environmentally benign
conditions," Kisailus said. "This makes it appealing to utilize
similar strategies to make nanomaterials in a cost-effective manner."
Kisailus
is using the lessons learned from this biomineralization pathway as inspiration
in his lab to guide the growth of minerals used in solar cells and lithium-ion
batteries. By controlling the crystal size, shape and orientation of
engineering nanomaterials, he believes he can build materials that will allow
the solar cells and lithium-ion batteries to operate more efficiently. In other
words, the solar cells will be able to capture a greater percentage of sunlight
and convert it to electricity more efficiently and the lithium-ion batteries
could need significantly less time to recharge.
Using
the chiton teeth model has another advantage: engineering nanocrystals can be
grown at significantly lower temperatures, which means significantly lower
production costs.
While
Kisailus is focused on solar cells and lithium-ion batteries, the same
techniques could be used to develop everything from materials for car and
airplane frames to abrasion resistant clothing. In addition, understanding the
formation and properties of the chiton teeth could help to create better design
parameters for better oil drills and dental drill bits.
Co-authors
of the Advanced Functional Materials paper were: Qianqian Wang, Michiko Nemoto,
Dongsheng Li, Garrett W. Milliron, Brian Weden, Leslie R. Wood, all of whom are
current or former undergraduate and graduate students at UC Riverside; James C.
Weaver, a former post-doc of Kisailus, now at Harvard University; John
Stegemeier and Christopher S. Kim, of Chapman University; and Elaine DiMasi, of
Brookhaven National Laboratory.
Source: University
of California - Riverside
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