Assuring that biomaterials exhibit
their functionality and significantly
increasing the power generation
capacity |
| . |
. |
The critical issues for achieving the world's highest
power output were how efficiently glucose
and oxygen could be broken down by
enzymes at the electrodes and how much electrical
energy could be extracted. Here we present
the main points of this research and development
effort.
■ Main Research and Development
Points (See the figure above)
(1) Electric generation performance
improved by high-density immobilization
technologies for enzymes
and electron transport mediators
At the anode, the enzymes and electron transport
mediator must be immobilized at high
density on the electrode in a state where their
activities are maintained. In this work, we
used two polymers as the material that plays
the role of a glue that holds these materials in
place. This immobilization method holds the
enzymes and electron transport mediator fixed
in place at high density by using the electrostatic
interactions of two polymers that have
opposite ionic polarities. By optimizing the
ionic balance and by developing a process for creating an immobilizing film on electrodes,
we have achieved high efficiency in breaking
down glucose and extracting electrons.
(2) Electrical performance improved by
electrolytes optimized for Sony's
unique bio battery structure
Under normal physiological condition, the
concentration of sodium phosphate buffer is typically
around 0.1 M. In contrast, however, the
concentration Sony uses for this newly-developed
bio battery electrolyte is the unusually high
concentration of around 1 M. This is based on
the discovery that such high buffer concentration
levels are effective for maintaining the activity
of the enzymes when immobilized on the
electrodes through electrostatic interactions. Thus
Sony has succeeded in significantly improving
the electrical generation characteristics.
(3) Electrical performance improved by
Sony-developed cathode structure
that efficiently acquires oxygen
To make the enzymes which reduce oxygen work
efficiently while taking up oxygen efficiently
at the cathode, it is necessary to maintain the
moisture content on the cathode electrode at an
appropriate level. In this work, we employed
porous carbon and cellophane as the separator.
By optimizing the structures and fabrication
processes for these materials, Sony was able
to maintain optimal humidity at the cathode with
high reaction efficiency.
(4) Prototype of a bio battery that
achieves both high power output
and compactness
Sony has made a prototype bio battery with high
power output and a compact size using the
technologies described above. This bio battery
is a passive type battery that operates simply
by pouring a glucose solution into a reservoir
that contacts the anode with no stirring required.
Furthermore, oxygen is supplied at the cathode
by natural diffusion. A single unit of this
bio battery, a cube 39 mm on a side, achieves
the world's highest power output, 50 mW.
(See the photograph on the first page of this article.)
●●●
Sony plans to continue working for improvements
in electric performance and durability
with further development of enzyme immobilization
methods and electrode materials.
Through research and development on a wide
range of elemental technologies, Sony plans to
make this bio battery into a commercial product
in the future. |
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Structure of the Newly Developed Bio Battery
 In moving towards practical implementation, we must extract
the potential of the sophisticated systems in living organisms. |
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See
all articles with figures and tables.  |
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Vol.51 |
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