Bacteria Used to Create Semiconducting Nanotubes

Nanodevices produced by bacteria? Chips made from microbes? If the work in progress at the University of California, Riverside and Gwangju Institute of Science and Technology in Korea bears fruit, "bugs in a jar" could be creating the building blocks for micrcochips and other devices that could use nanotubes as parts of their structures.

In the early edition of the Proceedings of the National Academy of Sciences, the two teams revealed that they have successfully coaxed Shewanella bacterium into secreting polysacarides that appear to produce the template for arsenic sulfide nanotube semi-conductors. If successful in steering the growth to nanotubes made of other materials, a potential revolution in the manufacturing process for everything from solar panels to hydrogen cells is in the works.

By turning to biotechnology for this process, many of the hazards and pollution in the production of a wide variety of products would be eliminated. Everything from computers to plastics rely on harsh and dangerous chemicals, which eventually end up in the environment.

The discovery came while the team in Korea, Hor-Gil Hur and Ji-Hoon Lee, observed a strange behavior going on while using the Shewanella to remove arsenic from a contaminated surface. Shewanella is known and used for arsenic remediation, by secreting a polysaccharide that absorbs the arsenic. The strange behavior was sent to the Riverside lab to find out what was going on and characterize the behavior of the strange material The U.S. team was surprised to find the nanotubes that had been created.

The arsenic-sulfide nanotubes made by the bacteria react to light, and conduct both light and electricity. If successful in developing the process, biomanufacturing of nanowires and photoactive microchips are on the horizon.

How the polysaccharides react with the arsenic remains a mystery and subject to further research and development. Myung and his team have begun a search for similar activity, or another organism, that will create similar structures of cadmium sulfide and other semi-conducting materials, which would bea much more practical and useful semi-conductor than its cousin arsenic sulfide.

Work was partially funded by The Center for Nanoscale Innovation for Defense (CNID). The CNID was established in 2002 by the U.S. government as a scientific research center at the University of California, Los Angeles, with facilities in Riverside and Santa Barbara.

Co-authors of the research are: Nosang V. Myung, associate professor of chemical and environmental engineering in the Bourns College of Engineering, and his postdoctoral researcher Bongyoung Yoo; Min-Gyu Kim, Pohang Accelerator Laboratory, Pohang, Korea; Jongsun Maeng and Takhee Lee, GIST; Alice C. Dohnalkova and James K. Fredrickson, Pacific Northwest National Laboratory, Richland, Wash.; and Michael J. Sadowsky, University of Minnesota.