(Photo Courtesy of Belcher Laboratory/MIT)
CAMBRIDGE, Mass. — In a surprise power development that could have implications for electronics, cars and even the military, researchers at MIT have created the world's first batteries constructed at the nano-scale by microscopic viruses.
A much buzzed-about paper published in the Proceedings of the National Academy of Sciences earlier this month details the team's success in creating two of the three parts of a working battery—the positively charged anode and the electrolyte. But team leader Angela Belcher told PM yesterday that the team has been working seriously on cathode technology for the past year, creating several complete prototypes.
"We haven't published those yet, actually. We're just getting ready to write them up and send them off," says Belcher, who won a MacArthur "genius" grant from the for her work in 2004, and a Breakthrough Award from PM in 2006. "The cathode material has been a little more difficult, but we have several different candidates, and we have made full, working batteries."
Instead of physically arranging the component parts, researchers genetically engineer viruses to attract individual molecules of materials they're interested in, like cobalt oxide, from a solution, autonomously forming wires 17,000 times thinner than a sheet of paper that pack themselves together to form electrodes smaller than a human cell.
"Once you do the genetic engineering with the viruses themselves, you pour in the solution and they grow the right combination of these materials on them," Belcher says.
The team is working on three main architectures: Film-like structures—as small as a human cell—could form a clear film to power lab-on-a-chip applications, laminate into smart-cards, or even interface with implanted medical devices. Mesh-like architectures—billions of tiny nano-components all interfaced together—might one day replace conventional batteries in larger applications like laptops and cars. And fiber-like configurations—spun from liquid crystal like a spider's silk—might one day be woven into textiles, providing a wearable power-source for the military. "We definitely don't have full batteries on those [fiber architectures]. We've only worked on single electrodes so far, but the idea is to try to make these fiber batteries that could be integrated into textiles and woven into lots of different shapes," Belcher says.
The M13 viruses used by the team can't reproduce by themselves, and are only capable of infecting bacteria. At just 880 nanometers long—500 times smaller than a grain of salt—the bugs allow researchers to work at room temperatures and pressures with molecular precision, using and wasting fewer hazardous materials. Now that they've demonstrated that the construction of such tiny electronic components is possible, the challenge facing researchers is how to make them practical.
"What we're working on is not thinking about a particular device application, but trying to improve the quality of the anode and cathode materials—using biology just to make a higher quality material for energy density," Belcher says. "We haven't ruled out cars. That's a lot of amplification. But right now the thing is trying to make the best material possible, and if we get a really great material, then we have to think about how do you scale it." — Chris Ladd