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," 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.
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, experts say. The studies at OSU are being supported by the Nanoscale Exploratory Research Program of the National Science Foundation.
By David Stauth, 541-737-0787
SOURCES: Gregory Rorrer, 541-737-3370
Alex Chang, 541-737-8548