CAP Enterprises

"We can make them in larger diameters," Belcher said, "but they are all 880 nanometers in length," which matches the length of the individual virus particles. And, "once we've altered the genes of the virus to grow the electrode material, we can easily clone millions of identical copies of the virus to use in assembling our batteries. For the metal oxide we chose cobalt oxide because it has very good specific capacity, which will produce batteries with high energy density,"

More bang for the buck is what this all measures up to. Just to give you an idea of the microscopicity of this itty bitty battery, a nanometer is one billionth of a meter (500 times smaller than the tip of your pen). And for you engineers, the anode and electrolyte elements for this battery are a done deal. The cathode has given them some difficulty but there are a few working prototypes in the lab, as we speak.

"The nanoscale materials we've made supply two to three times the electrical energy for their mass or volume, compared to previous materials," the team reported.

These futuristic batteries are so tweaky that they could be interwoven into fabric for military applications (the ultimate in warfighting battle armor). "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, explaining that much of this is still in the works, but that it is conceivably possible, in the very near future, that people's clothing, cars, aircraft skins, etc. may be interwoven with finely spun power filaments for every application imaginable.

The size and weight of standard batteries powerful enough to propel electric cars has always been an engineering constraint in design.

The positively-charged anode is created by genetically altering the virus so that it draws to itself the materials it needs to become "the positive terminal" of the battery. "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. Basically, the microbes collect exotic materials, primarily cobalt oxide and gold. And because these viruses are negatively charged, they can be sandwiched in between oppositely charged polymers to form thin, flexible sheets or spun from liquid crystal like a spiderweb to series or parallel strings of tiny power producing networks.

"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."

This research was funded by the Army Research Office Institute of Collaborative Biotechnologies, the Institute of Soldier Nanotechnologies and the David and Lucille Packard Foundation.