Belcher’s process matches DNA sequences with elements on the periodic table to create a sped-up form of unnatural selection. Coding the DNA one way might cause a virus to latch on to iron phosphate, but, if the code is tweaked, the virus might prefer cobalt oxide. The technique could be extended to any element on the periodic table, it’s just a matter of finding the DNA sequence that matches it. In this sense, what Belcher is doing is not so far from the selective breeding done by dog fanciers to create pooches with desirable aesthetic qualities that would be unlikely to ever show up in nature. But instead of breeding poodles, Belcher is breeding battery-building viruses.
Belcher has used her viral assembly technique to build electrodes and implement them in a range of different battery types. The cell she demoed for Obama was a standard lithium-ion coin cell like you might find in a watch and was used to power a small LED. But for the most part, Belcher has used electrodes with more exotic chemistries like lithium-air and sodium-ion batteries. The reason, she says, is that she didn’t see much sense in trying to compete with the well-established lithium-ion producers. “We aren’t trying to compete with current technology,” Belcher says. “We look at the question, ‘Can biology be used to solve some problems that haven’t been solved so far?’”
One promising application is to use the viruses to create highly ordered electrode structures to shorten the path of an ion as it moves through the electrode. This would increase the battery’s charge and discharge rate, which is “one of the ‘holy grails’ of energy storage,” says Paul Braun, director of the Materials Research Laboratory at the University of Illinois. In principle, he says, viral assembly can be used to significantly improve the structure of battery electrodes and boost their charging rates.
So far Belcher’s virally-assembled electrodes have had an essentially random structure, but she and her colleagues are working on coaxing the viruses into more ordered arrangements. Nevertheless, her virus-powered batteries performed as well or better than those with electrodes made with traditional manufacturing techniques, including improved energy capacity, cycle life, and charging rates. But Belcher says the biggest benefit of viral assembly is that it is eco-friendly. Traditional electrode manufacturing techniques require working with toxic chemicals and high temperatures. All Belcher needs are the electrode materials, room temperature water, and some genetically-engineered viruses.
“Something my lab is completely focused on now is trying to get the cleanest technology,” Belcher says. This includes taking into consideration things like where the mined material for electrodes is sourced, and the waste products produced by manufacturing the electrodes.
Belcher hasn’t brought the technology to market yet, but says she and her colleagues have several papers under review that show how the technology can be commercialized for energy and other applications. (She declined to get into the specifics.)
When Belcher first suggested that these DNA-driven assembly lines might be harnessed to build useful things for humans, she encountered a lot of skepticism from her colleagues. “People told me I was crazy,” she says. The idea no longer seems so far-fetched, but taking the process out of the lab and into the real world has proven challenging. “Traditional battery manufacturing uses inexpensive materials and processes, but engineering viruses for performance and solving scalability issues will require years of research and associated costs,” says Bogdan Dragnea, a professor of chemistry at the Indiana University Bloomington. “We have only recently started to understand the potential virus-based materials hold from a physical properties perspective.”
Belcher has already co-founded two companies based on her work with viral assembly. Cambrios Technologies, founded in 2004, uses a manufacturing process inspired by viruses to build the electronics for touch screens. Her second company, Siluria Technologies, uses viruses in a process that converts carbon dioxide to ethylene, a gas widely used in manufacturing. At one point, Belcher was also using viruses to assemble solar cells, but the technology wasn’t efficient enough to compete with new perovskite solar cells.