SCI/TECH/Experimental research
Small world: diatoms/nanotech

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 (OSU) 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.

The goal is to find a better way to create oxide nanocomposite materials that incorporate elements such as germanium, a semiconductor material that could be of value in optoelectronics, photonics, thin film displays, solar cells and a wide range of electronic devices.

Gregory Rorrer is the lead investigator on the project. Rorrer's lab will develop the biological process technology needed to coax the marine diatoms into making nanoscale semiconductor materials based on silicon, germanium, and titanium.

"This research is significant because a biological process is being used to make nanoscale inorganic materials that may possess novel optical and electronic properties with many high-tech applications," Rorrer said. "Procedures exist to produce germanium nanocomposites, but they are fairly inefficient, difficult to control and expensive.”

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, a 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," Rorrer said. "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.

The OSU researchers have just received part of a $1.3 million, four-year grant from the National Science Foundation to continue the research, and further evaluate the use of diatoms in nanotech.

Get more info: Contact the OSU, (541) 867-0220

Find more sci/tech news in the August 2004 issue of "Arte Six".