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" [source: RPI].
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.