Stream of urine

Mini battery designed for diagnostic biochips

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Physicists in Singapore have discovered a whole new source of energy: urine. They developed a tiny battery that generates electricity when wet with urine. It is to be used in medical disposable test strips, for example for diabetes.

Scientists worldwide are looking for ever smaller, mass-producible biochips for rapid tests that can detect disease and deliver immediate results. Especially popular as a test object is the urine, as its composition can give important clues to possible diseases. But so far, modern biochip testing has lacked a source of energy that is small and just as cheap to manufacture as the biochips themselves.

Ki Bang Lee, head of a research group at the Institute of Bio- and Nanotechnology in Singapore, has now teamed up with his co-workers to develop a paper-based battery with exactly the features you're looking for: it's small, cheap and uses just the substance which should be tested as an energy source. In principle, it consists of a paper layer soaked with copper chloride, which is stretched between two strips of magnesium and copper. This "sandwich" is coated from the outside as protection with a transparent plastic film.

In experiments, the researchers wetted the battery with 0.2 milliliters of urine and there was a current of voltage of 1.5 volts and a power of 1.5 milliWatt - sufficient for a bioassay. If you change the geometry and materials, you can also change and increase the performance, according to Lee.

"Our urine-activated battery can be integrated into biochip systems for medical diagnostics, " explains the scientist who published his findings in the journal Journal of Micromechanics and Microengineering. "These fully integrated biochip systems have great market potential." According to the researcher, in the future people will monitor their health primarily with such single-use systems of various kinds. display

(Institute of Physics, 15.08.2005 - NPO)