Cutting Edge

Scientists at the Massachusetts Institute of Technology have demonstrated how a genetically modified virus can be used to construct both the cathode and anode of a lithium ion battery.

Virus-built rechargeable batteries would have the same power capacity as the batteries used to power hybrid cars, project leader professor Angela Belcher said in an MIT press statement on Thursday.

Angela Belcher, an MIT professor, holds a display of the battery she helped build via a genetically modified M13 virus. The battery (the silver-colored disc) is being used to power a light-emitting diode.

(Credit: MIT)

In a paper published in the journal Science, the research team explained that it manipulated two genes of the M13 virus to equip the bacteriophage with peptide groups that attract single-walled carbon nanotubes at one end, while the other end of the virus was equipped with peptides that nucleate amorphous iron phosphate.

Combining the nanotubes with the iron phosphate created a highly conductive material that was used in a cathode, said the MIT statement. Battery energy was transferred in "a very short time," as electrons could travel along the carbon nanotube networks and percolate throughout the electrodes.

Three years ago, a research team led by Belcher used a similar virus modification technique to build an anode--the genetically modified virus coated itself with cobalt oxide and gold to assemble a nanowire.

In tests, researchers found that the virus-built battery could be recharged 100 times without losing capacitance. The incorporation of carbon nanotubes increased battery conductivity without adding too much weight, according to the statement.

The team now plans to genetically modify microbes to assemble materials with higher voltage and capacitance, such as manganese phosphate and nickel phosphate. Once this is achieved, the technology could go into commercial production, Belcher said.

These advances feed into wider cross-disciplinary investigations into energy harvesting: the technique of extracting power from the environment. Current research efforts focus on both biological and nonbiological systems. Nonbiological study includes research into mechanical, thermal, and electromagnetic systems. Biological systems such as photosynthesis and metabolic pathways, already closely analyzed for medical and scientific purposes, are also seen as potential sources of energy for electronic systems, with a cross-over field--synthetic biology--using ideas from living systems in designed processes.

Tom Espiner and Rupert Goodwins of ZDNet UK reported from London.

Researchers at the universities of Miami, Tokyo, and Tohoku have discovered a new form of battery.

Charged by the application of a very strong magnetic field, the Magnetic Tunnel Junction (MTJ) contains a set of nano-magnets--zones some 5 nanometers across in a zinc-gallium-arsenic-magnesium matrix--which absorb energy and then release it over time. Although the effect had been predicted, the size and duration of the result was not.

The MJT is the top part of the illustration, and is roughly the same diameter as a human hair. Beneath that is a magnified image of the central part of the device: the white spots are atoms, and the circles contain the nano-magnets that store the power.

(Credit: Phan Nam Hai/University of Miami)

"We had anticipated the effect, but the device produced a voltage over a hundred times too big and for tens of minutes, rather than for milliseconds as we had expected," said one of the researchers, in a story in ScienceDaily. "That this was counterintuitive is what lead to our theoretical understanding of what was really going on."

I've yet to dig through the paper in Nature to find out how far this is from being useful as a power source--as the current device is a few hundred micrometers across, it's not going to be storing megawatts. But it's the sort of thing that could be created in vast arrays, like any semiconductor device, and if they're getting to the bottom of the underlying physics then the same effect could be used in many different configurations.

What may be much more interesting than just power storage is the fact, mentioned almost in passing in the press release, that the current delivered by the MTJ is spin-polarized; the electrons are predominately spinning in one direction.

That's hot news for spintronics, which, together with graphene, has the most exciting potential for fundamentally new computational devices. Spin logic could work much faster at much lower power than even today's finest electronics, because it doesn't rely on currents flowing and the consequent unavoidable loss.

And, as the researchers say, if this discovery leads to new insights into basic magnetic theory, there are almost no limits to how profoundly it could affect modern life. Which is a bit over the top--just not that much.

Rupert Goodwins of ZDNet UK reported from London.