- Diatoms, a single-celled marine life form that has
been around at least 100 million years, are being
harnessed by researchers at Oregon State University
to help make progress in one of the newest and most
promising fields of science - nanotechnology.
These ancient, microscopic organisms are found in
the fossil record as far back as the time of the dinosaurs
and, as a major component of phytoplankton, are an
important basis for much ocean life. But they may
also be the key to a more efficient, less costly way
to produce some of the most advanced high tech materials
in the world, scientists say.
Progress in this research is being presented by a
team of researchers at the Micro Nano Breakthrough
Conference in Portland, Ore., sponsored by OSU and
the Pacific Northwest National Laboratory.
The goal, experts say, is to find a better way to
create oxide nanocomposite materials that incorporate
elements such as germanium, a semiconductor material
that has interesting properties that could be of value
in optoelectronics, photonics, thin film displays,
solar cells and a wide range of electronic devices.
The building blocks of these materials are referred
to as nanoparticles because they are extraordinarily
small - clusters of several hundred molecules less
than 100 nanometers in size - compared to a human
hair that is 20,000 nanometers wide.
"Procedures exist to produce germanium nanocomposites,
but they are fairly inefficient, difficult to control
and expensive," said Gregory Rorrer, an associate
professor of chemical engineering at OSU.
Rorrer is an expert in marine biotechnology, so as
an alternative to the "high tech" way of
producing germanium oxides, he turned to one of nature's
most low-tech, but nonetheless intricate creations
- the diatom.
"Diatoms are single-celled algae, and they are
the dominant photosynthetic part of marine phytoplankton,"
Rorrer said. "Of course, as a basis for the marine
food chain, they are extremely important, and they
also have other functions, such as cycling carbon
dioxide from the atmosphere."
But one of their unique capabilities, he said, is
to take silicon from sea water and process it into
intricate microstructures to form a tiny, rigid shell.
The shell is composed of tiny silica nanospheres,
and provides a ready made, natural system to create
organized structures at the nano level.
With the assistance of Alex Chang, an OSU assistant
professor of chemical engineering, and two graduate
students, Clayton Jeffryes and Shu-hong Liu, this
team of OSU chemical engineers have cultured diatoms
in a laboratory environment and "fed" them
germanium. They have successfully incorporated the
germanium into their structure.
"We've succeeded in getting the germanium into
diatoms and we're getting good replication, we expect
very good uniformity in these materials," Chang
said. "We still need to have a better understanding
of the internal structure and how successfully it
is patterning the nanocomposite material we're seeking,
but the results so far are very encouraging."
Rorrer said this is a way to let nature do the engineering.
"With this approach, the living organism does
the work and creates the order we want at the nano
level, as the diatom builds its shell wall,"
"For use as electronic materials, the germanium
oxides need to be in a certain form and order, and
it appears the diatoms may produce that for us."
Instead of using lasers, high temperatures, crystallization
and other advanced technologies, the approach being
developed at OSU operates at room temperature and
in theory could produce nanostructured germanium oxides
in large volumes, inexpensively, through the natural,
environmentally benign process of biomineralization.
Most solid-state electronic devices consist of patterned
arrays of metal or metal-oxide semiconductor materials
based on silicon, germanium and other materials. The
technologies for making those devices on the micron
size scale are well established, but many experts
believe the next major technological breakthroughs
will be created with devices that work at the much
smaller nano scale, which traditionally has required
exotic processing technologies.
Research in nanotechnology and production of the first
products is already a multi-billion dollar industry,
The studies at OSU are being supported by the Nanoscale
Exploratory Research Program of the National Science