New Invention Converts
Urine to Power
By Sun News Publishing
Monday, August 22, 2005
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Before you next flush the toilet, consider this: Scientists
in Singapore have developed a battery powered by urine.
Researchers at the Institute of Bioengineering and Nanotechnology
created the credit card-size battery as a disposable power
source for medical test kits.
Scientists have been scrambling to create smaller, more efficient
and less expensive “biochips” to test for diseases
such as diabetes. Until now, however, similarly small batteries
to power the devices remained elusive.
Diagnostic test kits commonly analyse the chemical composition
of a person’s urine to detect a malady. Ki Bang Lee
and his colleagues realised that the substance being tested
– urine – could also power the test.
“In order to address this problem, we have designed
a disposable battery on a chip, which is activated by biofluids
such as urine,” Lee wrote in an e-mail to National Geographic
News.
The research team describes the battery in the current issue
of the Journal of Micromechanics and Microengineering.
Daniel Kammen, director of the Renewable and Appropriate Energy
Laboratory at the University of California, Berkeley, said
the technology is a welcome innovation in a time of rising
energy prices.
“All jokes (about) urine aside, what is needed are low-cost
batteries. …” he said. “The other neat thing
about this is the fact that it’s basically a biodegradable
battery.”
Urine Power
To make the battery, Lee and his colleagues soaked a piece
of paper in a solution of copper chloride and sandwiched it
between strips of magnesium and copper. This sandwich was
then laminated between two sheets of transparent plastic.
When a drop of urine is added to the paper through a slit
in the plastic, a chemical reaction takes place that produces
electricity, Lee said.
The prototype battery produced about 1.5 volts, the same as
a standard AA battery and runs for about 90 minutes. Researchers
said the power, voltage and lifetime of the battery can be
improved by adjusting the geometry and materials used.
Urine contains many ions, (electrically charged atoms) which
allows the electricity-producing chemical reaction to take
place in the urine battery, said UC Berkeley’s Kammen.
Other bodily fluids, such as tears, blood and semen, would
work easily as well to activate the battery.
“Little bags of urine may generate chuckles,”
Kammen said. “But really urine is just a nice example
(of) a whole variety of compounds that do this stuff.”
Even children’s lunch-box fruit-juice packets are sufficient,
he added.
Alternative Energy
While medical devices inspired the urine battery, it can activate
any electric device with low power consumption, according
to Lee, the battery’s co-inventor.
“For example, we can integrate a small cell phone and
our battery on a plastic card. This can be activated by body
fluids, such as saliva, during an emergency,” he said.
According to Kammen the technology could even be applied to
laptop computers, mp3 players, televisions and cars. Body-fluid-powered
batteries “can do all kinds of things. The issue is
how they scale up” to produce more power, he said.
One approach is to simply build larger batteries. Another
method is to link lots of little battery cells side by side,
which is how the batteries in laptop computers work, Kammen
explained.
Kammen, who advocates government funding for alternative energy
research, says the wide number of applications for cheap and
efficient biofluid-powered batteries illustrates the value
of research. “Investigation leads to innovation,”
he said.
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