Biology – you, me, and the tree – is all based on chemical energy, yet batteries for our electronic devices have mostly relied on non-lifelike arrangements such as lead-acid and nickel-cadmium hybrids to produce power. But that may soon change. Researchers at the Massachusetts Institute of Technology (M.I.T) report in Science today that they constructed a battery that uses biological matter – namely a virus dubbed M13 – as a key component. The virus essentially acts as a “biological scaffold,” the scientists write, to support elements of a lithium ion-type battery.

Talk of such devices is not new. Three years ago, the same makers of the new battery crafted an anode -- one of the two poles (the other being a cathode) in a battery that have opposite electrical charges -- prompting Scientific American magazine last year to ask “Whatever Happened to Virus-Built Batteries?” Now the researchers have completed the trickier task of constructing a cathode that also incorporates the M13 virus.

Technically a bacteriophage (a virus that preys on bacteria but leaves human cells alone), M13 has a cylindrical body that measures about a micrometer – one millionth of a meter – in length, says study co-author Angela Belcher, professor of materials science and biological engineering at M.I.T.

Researchers had to modify two of M13’s genes before it could be put to use, though. Tweaking one gene that makes proteins in the phage’s coat allowed bits of iron phosphate to tack on and bulge “like tiny fists all along the length of the virus,” Belcher says. The second gene, expressed on one end of the phage’s tubelike body, lets carbon nanotubes attach, forming a network of millions of tiny viruses that conduct electricity.

The researchers succeeded in turning M13 into a battery fabricating toolkit at or below room temperature, Belcher says, noting that current processes require super-hot temps of about 660 degrees Fahrenheit (350 degrees Celsius) to manufacture state-of-the-art, high-powered rechargeable batteries with nanoscale components.  

A virus-battery prototype M.I.T. built exists as a coin cell, similar to the ones found in watches and calculators, and they’ve used it to turn on some small lights in the lab. In terms of energy storage, a third of an ounce (10 grams) of the viral battery material could power an iPod for 40 hours, according to Belcher.

But she believes the technology would be more suited for making big, high performance batteries for hybrid cars and the like rather than to fuel small electronic devices. But she acknowledges it will be a challenge to scale up the technique to build batteries large enough to power big machines. “Cell phones are not too hard size-wise,” says Belcher. “But getting up to kilograms [for car batteries], that’s harder.”

She notes that a viral battery used to power, say, a hybrid car “would not need any more mass than current batteries, and you’d actually get a bit more power.”

In the intervening years between viral anode and cathode construction, Belcher’s team also developed thin micro-batteries incorporating their favorite phage that could someday energize mini devices and even help make power-storing spray paint, along with other futuristic applications. 

Hear a 60-Second Science podcast on this study.

A computer graphic of a carbon nanotube connected to five modified proteins on one end of the M13 phage (yellow), forming one “wire” in a viral cathode. Image Credit: M.I.T.