In the September issue of The Journal of Micromechanics and Microengineering, Ki Bang Lee described how he and his team of researchers created "the first urine-activated paper battery" by soaking a piece of paper in a solution of copper chloride, sandwiching it between strips of magnesium and copper and then laminating the paper battery between two sheets of plastic. In this setup, the magnesium layer serves as the battery's anode (the negatively charged terminal) and the copper chloride as the cathode (the positively charged terminal). An electricity-producing chemical reaction takes place when a drop of urine, which contains many electrically charged atoms, is introduced to the paper through a small opening in the plastic.
The scientists' largest prototype battery generated a maximum of roughly 1.5 volts, the equivalent of an AA battery, and sustained an average of about 1 volt for about 90 minutes. Lee explains that its uses could extend to any device that consumes a small amount of electricity. "For instance," he says, "we could integrate a small disposable cellphone and our battery on a plastic card, for use in an emergency. And we are continuing to develop batteries that could power regular cellphones, MP3 players and laptop computers." While Lee emphasizes that urine is the biofluid of choice (since "everybody produces large amounts of it"), he notes that other bodily fluids - blood, tears, semen and saliva - will work in a pinch.
Source: NY Times