Could blood be used to power batteries ?

Batteries­ are pr­actically essential devices but present
a whole ho­st of problems. Over time they can have trouble
retaining a charge. Some stop working altogether. Others
overheat or leak or even explode. They're also rigid and
sometimes bulky. Then how about, instead of your standard
AA or lithium-ion, a flexible, incredibly thin battery that
could be powered by blood or sweat? Seems like an improvement,
right?

A group of scientists at Rensselaer Polytechnic Institute
claims they've created just such a battery, one that uses the
electrolytes naturally found in bodily fluids. The results of
the research, detailed in the Aug. 13, 2007, issue of the
Proceedings of the National Academy of Sciences, are
generating some excitement as part of a new crop of
"bio-batteries" that run off of bodily fluids or other
organic compounds. (The RPI team claims that theirs could
even run on tears or urine.)

The battery is not only as thin as paper; it essentially is
paper. At least 90 percent of the battery is made from
cellulose, which makes up traditional paper and other paper
products [source: RPI]. Aligned carbon nanotubes make up the
other 10 percent, give the paper its conductive abilities and
also make it black. The nanotubes are imprinted in the very
fabric of the paper, creating what's called a nanocomposite
paper. One of the paper's authors said that the battery
"looks, feels and weighs the same as paper".

Using nanotechnology, the battery's small size, flexibility
and replenishing electrolyte source -- that is, as long as
you eat -- make it ideal for medical applications. When using
the battery away from the human body, scientists soaked the
paper in an ionic fluid (a salt in liquid form), which
provides the electrolytes.

The battery's paper-like construction grants it significant
flexibility. The RPI research team believes that the battery
could, in the future, be printed in long sheets, which could
then be cut into small, custom-shaped batteries. The
nanocomposite paper can have holes poked in it or be cut
into unusual shapes and continue to function. Several sheets
could be lumped together to power medical implants, such as
pacemakers, artificial hearts or advanced prosthetics.
The battery would easily fit under the skin without causing
any discomfort.

Because the ionic liquid used doesn't freeze or evaporate
like water, the battery could be employed at a wide range of
temperatures: from -100 degrees Fahrenheit up to 300 degrees
Fahrenheit. Its temperature resistance and light weight mean
that manufacturers of automobiles and airplanes -- both of
which require light, durable materials -- may come calling.

The researchers behind the battery claim that their device is
unique because it can act "as both a high-energy battery and
a high-power supercapacitor" [source: RPI]. ­Supercapacitors
allow for large, quick bursts of energy, potentially extending
the technology's already wide range of applications.

The battery, which is considered environmentally friendly
because of its lack of chemicals and high cellulose content,
was announced in the summer of 2007, but it may be years
before it's ready to stream off production lines in long
sheets. The RPI research team says that, in the meantime,
they're trying to boost the battery's efficiency and to
figure out the best method for production.

Other Types of Bio-Batteries

It's not just researchers at the Rensselaer Polytechnique
Institute who are working on bio-batteries. Many other
corporations, universities and research foundations are
competing to produce viable batteries that can be powered
off of organic compounds, especially human fluids.
Researchers consider sugar and human blood glucose potentially
valuable sources of power because they occur naturally, are
easily accessible and don't produce harmful emissions.

In 2003, Japanese researchers at Panasonic's Nanotechnology
Research Laboratory announced that they were working on
extracting power from blood glucose. At the time, they were
using enzymes -- a frequent component of bio-batteries due to
their catalytic properties -- to retrieve electrons from
glucose. Two years later, a different Japanese research team,
this one from Tohoku University, announced that they had
succeeded in creating a small "biological fuel cell." Their
cell could be used to power small medical devices, such as an
implant to measure blood sugar levels in diabetics. Future
versions of such technology could, like RPI's nanocomposite
paper, be used to power an artificial heart with the blood
that flows through and around it.

In August 2005, scientists in Singapore developed a battery
that uses human urine as its fuel. Despite its potentially
off-putting power source, the battery has a wide variety of
applications. The researchers said that their device was the
size of a credit card and could form the basis of inexpensive,
disposable disease-testing kits. (Urine is already used to
detect drugs and some diseases.) What makes the device
particularly useful is that it integrated the battery and
testing device into one disposable chip. Imagine a one-time
use home-testing kit for diseases like cancer or hepatitis.
One of the researchers involved in the project said that
the battery could also be adapted to provide a brief charge
to other electronic devices. A lost hiker might use one to
power a cell phone for a short emergency call.

Electronics giant Sony announced in August 2007 that it had
also created a battery that derives energy from sugar. One
demonstration showed the small battery extracting energy from
a glucose solution. In another demonstration, the battery
sipped on a sports drink for power.

If urine-powered or sports drink-sipping batteries were not
strange enough, a South Korean research team may have
produced one of the strangest of all bio-devices in September
2007. These scientists produced "crab-like microrobots"
made out of genuine living tissue. They made the tiny robots
by extracting tissue from neonatal rat hearts and growing it
on miniscule 'E'-shaped skeletons. These heart cells then
"pulsated" for more than 10 days, allowing the robots to move
up to 50 meters [source: Primidi.com]. With the right
refinements, these microrobots could be used to clear away
blockages in arteries.

While many exciting announcements have been made in the field
of bio-batteries, it may be some time before we see them
replacing nickel-cadmium, lithium-ion or the several other
types of traditional batteries. Even so, the small, flexible,
long-lasting and environmentally friendly battery technologies
discussed here show the great possibilities researchers see
in bio-batteries, especially for the field of medicine. With
that in mind, scientists seem to be exploring every possible
option in bio-battery and fuel-cell technology: One research
team even devised a fuel cell that ran off of gin and vodka.