[Paleopsych] Nanotech Gadgets to Be Built by Algae?
shovland at mindspring.com
Wed Mar 30 12:08:02 UTC 2005
for National Geographic News <http://news.nationalgeographic.com>
March 29, 2005
Ancient, single-celled organisms that are lowly anchors in the marine food
chain may soon be integral players in the lofty realm of nanotechnology,
the science of the very small.
Nanotech materials and devices measure less than a hundred nanometers, a
unit of measurement that is one billionth of a meter. By contrast, a human
hair is about 20,000 nanometers thick.
According to scientists and market analysts, the world is on the cusp of a
nanotechnology revolution: The teeny, tiny materials and devices are
beginning to show up everywhere from clothing and sporting goods to
computer electronics and medical equipment.
But a limitation to the pending revolution is the high expense and
inefficiency of making materials and devices at the nanoscale, according to
Gregory Rorrer, a chemical engineer at Oregon State University in
Rorrer believes a solution to the problem may lie in diatoms, single-celled
marine life-forms that have been around since the age of the dinosaurs.
The algae are well known for their crucial role at the base of the marine
food pyramid and for ridding the greenhouse gas carbon dioxide from the
atmosphere. In addition, diatoms have a unique ability to pull silica from
seawater and mill it into intricately-structured, rigid shells, Rorrer
The organisms create their shells by employing special proteins and
subcellular organs to first assemble silica nanoparticles, which are
composed of just a few hundred atoms. The proteins and subcellular organs
then orchestrate the assembly of those nanoparticles into shells, Rorrer
"You've two levels of structure-these nanoparticles and then, what's way
more interesting, is you can take these particles, and each one is like a
little brick, and they are assembled into ornate microstructures," the
chemical engineer said.
Last July Rorrer's lab at Oregon State University was awarded a four-year,
1.3-million-dollar (U.S.) grant from the National Science Foundation to
develop a process that harnesses diatom shell-construction to create
nanostructured materials. (The foundation also funds National Geographic
News's Pulse of the Planet news series, of which this story is a part.)
Products may include flexible computer screens, cheap and efficient solar
cells, filtration devices, and drug delivery vehicles that can target, for
example, a single cancer cell.
Rorrer's lab aims to incorporate elements such as silicon, germanium,
titanium, and gallium into the diatoms' silica shells. At the nanoscale,
these elements follow the laws of quantum mechanics instead of Newtonian
physics, giving them unique and commercially desirable properties.
(Newtonian physics denotes well-known forces like gravity, while quantum
mechanics describes laws of physics that apply at very small scales, such
as those found in atoms.)
At the nanoscale, for example, the metal germanium glows blue when energy
is applied to it. This has a host of applications in electronic and medical
imaging technologies, Rorrer said.
The process to incorporate germanium nanoparticles in silica is "doable but
difficult with existing technology," the scientist said.
The conventional process involves vaporizing a germanium crystal in a
vacuum with a high-energy laser beam and coaxing the vaporized atoms to
glom onto a silica surface.
"That has to be done at a high temperature [and] at a high vacuum and
[with] all the equipment associated with the control of that," Rorrer said.
"We do essentially the same thing by growing living organisms in a vat."
The trick for Rorrer and his Oregon State University colleague, Chih-hung
Chang, is to add just enough dissolved metal to the vat to allow the
diatoms to absorb it without dying.
To date "the concept for germanium incorporation has been proven," Chang
said. "We will work on incorporating other metals very soon."
Another advantage to using diatoms, Rorrer said, is that when the algae
divide, they make a perfect copy of themselves, meaning "we can make a
gazillion of these, and they are all the same."
In addition to the ability of the diatoms to absorb these metals and create
nanostructured materials, each diatom species makes shells with unique
designs. And there are tens of thousands of diatom species.
Which means there are "tens of thousands of micro-templates," Rorrer said.
"Some have holes, some ribs, some oval, some square-and all the
microfabrication has been done by the organisms. We just put additional
material on it."
In the future, the researchers hope they can use these diatoms to make
intricate designs at the microscale that are currently not possible with
To find the appropriate template, all a researcher would need is a
searchable database of natural diatom designs. Genetic engineering may also
one day make it possible to control diatom design.
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