[extropy-chat] Virus-Assembled Batteries

[Jeff Davis]

Too good to pass up.

Best, Jeff Davis

   "Everything's hard till you know how to do it."
                           Ray Charles

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http://www.technologyreview.com/BizTech/wtr_16673,296,p1.html

Friday, April 07, 2006

Virus-Assembled Batteries
A biological template ramps up electrode performance
and scales down size.

By Kevin Bullis

More than half the weight and size of today's
batteries comes from supporting materials that
contribute nothing to storing energy. Now researchers
have demonstrated that genetically engineered viruses
can assemble active battery materials into a compact,
regular structure, to make an ultra-thin, transparent
battery electrode that stores nearly three times as
much energy as those in today's lithium-ion batteries.
It is the first step toward high-capacity,
self-assembling batteries. 


Applications could include high-energy batteries
laminated invisibly to flat screens in cell phones and
laptops or conformed to fit hearing aids. The same
assembly technique could also lead to more effective
catalysts and solar panels, according to the MIT
researchers who developed the technology, by making it
possible to finely control the positions of inorganic
materials. 


"Most of it was done through genetic manipulation --
giving an organism that wouldn't normally make battery
electrodes the information to make a battery
electrode, and to assemble it into a device," says
Angela Belcher, a researcher on the project and an MIT
professor of materials science and engineering and
biological engineering. "My dream is to have a DNA
sequence that codes for the synthesis of materials,
and then out of a beaker to pull out a device. And I
think this is a big step along that path." 


The researchers, in work reported online this week in
Science, used M13 viruses to make the positive
electrode of a lithium-ion battery, which they tested
with a conventional negative electrode. The virus is
made of proteins, most of which coil to form a long,
thin cylinder. By adding sequences of nucleotides to
the virus' DNA, the researchers directed these
proteins to form with an additional amino acid that
binds to cobalt ions. The viruses with these new
proteins then coat themselves with cobalt ions in a
solution, which eventually leads, after reactions with
water, to cobalt oxide, an advanced battery material
with much higher storage capacity than the
carbon-based materials now used in lithium-ion
batteries. 


To make an electrode, the researchers first dip a
polymer electrolyte into a solution of engineered
viruses. The viruses assemble into a uniform coating
on the electrolyte. This coated electrolyte is then
dipped into a solution containing battery materials.
The viruses arrange these materials into an ordered
crystal structure good for high-density batteries. 


[Click here for an illustration of the battery-forming
process.] 


These electrodes proved to have twice the capacity of
carbon-based ones. To improve this further, the
researchers again turned to genetic engineering. While
keeping the genetic code for the cobalt assembly, they
added an additional strand of DNA that produces virus
proteins that bind to gold. The viruses then assembled
as nanowires composed of both cobalt oxide and gold
particles -- and the resulting electrodes stored 30
percent more energy. 







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