In an MIT lab, polyelectrolyte coated with anode nanowires eyes next-generation energy: Battery technology has historically lagged far behind semiconductor technology. While chips double their capacity every 18 months or so, batteries are lucky to double capacities in a decade. But now, say materials scientists at the Massachusetts Institute of Technology, bioengineering has broken the bottleneck. Almost half the materials in today's batteries do not contribute to electricity storage, whereas MIT's bioengineered batteries aim to put more than 90 percent of their materials to work storing energy. To do that, the scientists--professors Angela Belcher, Paula Hammond and Yet-Ming Chiang--employ genetically engineered living viruses to assemble thin-film nanowires as the anodes and cathodes of a flexible "battery wrap." At 100 nanometers thick, the next-generation battery wrap can conform to any shape, they said. The battery wrap invented at MIT is based on a genetically engineered derivative of the M13 bacteriophage--a virus parasite that infects a bacterium and reproduces inside it. By altering the genetic dispositions of this well-understood laboratory virus, which cannot infect humans, the materials scientists have been able to persuade the virus to extract cobalt-oxide and gold ions from solution and assemble them into a monolayer of nanowires functioning as a battery anode atop a polyelectrolyte substrate.