One of the more exotic possibilities is creating fibers from viruses that Belcher has genetically engineered to bind to and organize inorganic materials. She has already shown that the viruses can be used to make high-energy-density battery electrodes and fibers. The machine could combine battery electrodes with a polymer separator and electrolyte to form a complete battery. A similar approach could be used with photovoltaic materials. (Indeed, photovoltaic fibers made by other means have been demonstrated in the past.)
Among the cross-sectional patterns possible with the machine (and illustrated by the slide show accompanying this article) are some that look like sliced pies or concentric rings, and others that are much more complex. Once made, the fibers can be modified by dissolving certain polymers, leaving behind fibers with increased surface area. In one example, called "islands in the sea," a fiber thinner than a human hair is divided into dozens of nanoscale fibers. The machine can also produce fibers with cross sections that, instead of being circular, could have the shape of a cross or a three-lobed structure.
"Pretty much any cross section can be made," Fossey says. Indeed, what's lacking now is not the capabilities of the machine, he says, but enough researchers with ideas for how to use it.