A decade after Belcher demoed her battery at the White House, her viral assembly process has rapidly advanced . She’s made viruses that can work with over 150 different materials and demonstrated that her technique can be used to manufacture other materials like solar cells. Belcher’s dream of zipping around in a “virus-powered car” still hasn’t come true, but after years of work she and her colleagues at MIT are on the cusp of taking the technology out of the lab and into the real world.As nature’s microscopic zombies, viruses straddle the divide between the living and the dead. They are packed full of DNA, a hallmark of all living things, but they can’t reproduce without a host, which disqualifies them from some definitions of life. Yet as Belcher demonstrated, these qualities could be adopted for nanoengineering to produce batteries that have improved energy density, lifetime, and charging rates that can be produced in an eco-friendly way.
Their reliance on toxic, flammable materials means the smallest defect can result in exploding gadgets .A team of researchers led by physicists at the Johns Hopkins Applied Physics Laboratory believed a safer battery was possible, and for the past five years they have been developing a lithium-ion battery that’s seemingly immune to failure.
“There has been growing interest in the battery field to explore materials in nanostructure form for battery electrodes,” says Konstantinos Gerasopoulos, a senior research scientist who works on advanced batteries at Johns Hopkins Applied Physics Laboratory. “There are several ways that nanomaterials can be made with conventional chemistry techniques. The benefit of using biological materials, such as viruses, is that they already exist in this ‘nano’ form, so they are essentially a natural template or scaffold for the synthesis of battery materials.”
Nature has found plenty of ways to build useful structures out of inorganic materials without the help of viruses. Belcher’s favorite example is the abalone shell, which is highly structured at the nanoscale, lightweight, and sturdy. Over the process of tens of millions of years, the abalone evolved so that its DNA produces proteins that extract calcium molecules from the mineral-rich aquatic environment and deposit it in ordered layers on its body. The abalone never got around to building batteries, but Belcher realized this same fundamental process could be implemented in viruses to build useful materials for humans.
Audi has voluntarily recalled some of its first electric vehicles, over battery issues that could cause fires, though none have yet been reported. The E-tron system monitors the battery for moisture, and Audi says a yellow battery warning light should appear if the vehicle’s sensors find something has gone wrong inside.
“We’ve been engineering biology to control nanomaterials that are not normally grown biologically,” Belcher says. “We’ve expanded biology’s toolkit to work with new materials.”
Belcher’s virus of choice is the M13 bacteriophage, a cigar-shaped virus that replicates in bacteria. Although it's not the only virus that can be used for nanoengineering, Belcher says it works well because its genetic material is easy to manipulate. To conscript the virus for electrode production, Belcher exposes it to the material she wants it to manipulate. Natural or engineered mutations in the DNA of some of the viruses will cause them to latch on to the material. Belcher then extracts these viruses and uses them to infect a bacterium, which results in millions of identical copies of the virus. This process is repeated over and over, and with each iteration the virus becomes a more finely-tuned battery architect.
Belcher’s genetically engineered viruses can’t tell a battery anode from a cathode, but they don’t need to. Their DNA is only programmed to do a simple task, but, when millions of viruses perform the same task together, they produce a usable material. For example, the genetically-modified virus might be engineered to express a protein on its surface that attracts cobalt oxide particles to cover its body. Additional proteins on the surface of the virus attract more and more cobalt oxide particles. This essentially forms a cobalt oxide nanowire made of linked viruses that can be used in a battery electrode.