THE NEXT TIME YOU FLUSH, consider the potential source of energy you’re wasting.

Korean scientist Ki Bang Lee has developed a urine-fueled battery that can power home tests for kidney disease, blood-glucose levels and even some pregnancy abnormalities. The battery (diagrammed above) is the size of a credit card and made of paper soaked in copper chloride (middle layer) sandwiched between strips of magnesium (upper) and copper. It produces a small electric charge when urine reaches the copper (electricity is needed to run biosensors and display test results).

The paper battery could eventually be integrated into any small biochip system that tests urine for disease and could be modified to test saliva or blood samples. Scientists say it could even eventually activate any electric device with low energy consumption, such as MP3 players and cell phones.