Researchers have recently created rechargeable batteries consisting of genetically-engineered viruses which automatically coat themselves with a metallic layer. This was done by introducing DNA to the M13 virus, which usually infects bacteria, causing it to produce specific molecules on its surface which attract cobalt ions and gold. The result was the formation of an anode, or negative terminal of a battery. Next, a cathode, or the positive terminal, was produced by inserting another additional gene which caused the virus to attract iron and phosphate ions to its surface.Lithium ion batteries work by passing lithium ions from the anode to the cathode inside the battery, and this drives electrons through the external circuit. Therefore, for a lithium ion battery to work effectively, it must be able to conduct both lithium ions and electrons. Researchers found that the virus which they currently had could conduct lithium ions well, but not electrons. To overcome this problem, they added yet another gene to the virus which caused it to produce a protein at its tip which would attach to a carbon nanotube (shown above). The network of carbon nanotubes coupled with the viruses worked effectively as an electron conductor.
The viral battery which was finally produced had a capacity and power performance which matched conventional lithium ion batteries available on the market. In addition to that, the process of manufacturing the battery from viruses could be conducted at room temperature using only water as a solvent. In contrast, the manufacture of conventional batteries requires the use of high temperatures and aggressive solvents. Yet another advantage of the virus-based battery is that it does not leave behind toxic chemicals when it degrades, making it a potential candidate for green batteries of the future. The battery could possibly be used in hybrid vehicles or in portable electronic equipment.
However, materials engineer Angela Belcher, one of the researchers behind this technology, cautions that the newly-designed battery is not yet commercially viable. Her team is currently looking into materials which produce greater voltages and have larger energy storage capacities.
Xiang Wen Lee
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References:
Cahoon, L 2009, Bugs Build Batteries, viewed 16 April 2009, <http://sciencenow.sciencemag.org/cgi/content/full/2009/403/1>
Hutson, S 2006, Battery electrodes self-assembled by viruses, viewed 16 April 2009, <http://www.newscientist.com/article/dn8961-battery-electrodes-selfassembled-by-viruses.html>
Zandonella, C 2009, Batteries grown from 'armour-plated' viruses, viewed 16 April 2009, <http://www.newscientist.com/article/mg20227035.400-batteries-grown-from-armourplated-viruses.html>
