| GM viruses build a better battery|
|A tiny virus has been trained to build a more efficient and powerful lithium battery, say US researchers.|
Researchers at the Massachusetts Institute of Technology (MIT) modified two genes in a virus called M13, which caused it to build a shell made out of a compound called iron phosphate. These shells attached to a carbon nanotube to create a powerful and tiny electrode.
The virus boosted battery could provide more power for MP3 players or cellular telephones, and are far more environmentally friendly than current battery technologies, says MIT materials scientist Angela Belcher, who led the research, which appears today in the journal Science.
"It has some of the same capacity and energy power performance as the best commercially available state-of-the-art batteries," says Belcher.
"We could run an iPod on it for about three times as long as current iPod batteries. If we really scale it, it would be used in a car," she says.
But Belcher admits that such scaling is some time away.
She says the technology is inherently green because it involves a live virus.
"We are having organisms make the materials for us," says Belcher. "We are confined to temperatures and solvents - water - that organisms can live in. It's a clean technology. We can't do anything that kills our organisms."
The viruses used in the battery are a common bacteriophage, which infect bacteria, but are harmless to humans
Current lithium batteries are powerful and light, but they do not release their electrons very quickly.
Belcher's team genetically engineered the viruses to grow shells of amorphous iron phosphate.
The material is generally not a good conductor, but makes a useful battery material when patterned at the nanoscale - a microscopic molecular scale.
The virus-made material increases the cathode's conductivity inside the battery, making it more powerful without adding too much weight.
"My students hate it when I say we sit back and let them (the viruses) do the work. We put a lot of work in too," says Belcher.
"But once you have the right genetic sequence and have the right proteins then you just put them in solution with water and ions and they template the battery in the same way an abalone templates a shell. They build little shells around themselves."
The team is already working on a second-generation battery using materials with higher voltage and electrical capacity, such as manganese phosphate and nickel phosphate, says Belcher.