Researchers in Singapore have designed a paper battery that converts urine into electricity. The scientists from Singapore’s Institute of Bioengineering and Nanotechnology built the battery to power tiny biochips that tests bodily fluids for diseases. With their approach, urine is not only tested but also acts as the power source for the testing device. From a press release about the scientific publication in the Journal of Micromechanics and Microengineering:
The battery unit is made from a layer of paper that is steeped in copper chloride (CuCl) and sandwiched between strips of magnesium and copper. This “sandwich” is then held in place by being laminated, which involves passing the battery unit between a pair of transparent plastic films through a heating roller at 120ºC. The final product has dimensions of 60 mm x 30 mm, and a thickness of just 1 mm (a little bit smaller than a credit card)… Using 0.2 ml of urine, they generated a voltage of around 1.5 V with a corresponding maximum power of 1.5 mW…
“Our urine-activated battery would be integrated into biochip systems for healthcare diagnostic applications,” says (lead researcher Ki Bang) Lee. He envisions a world where people will easily be able to monitor their health at home, seeking medical attention only when necessary.
UPDATE: Dan Steingart, a graduate student in UC Berkeley’s Department of Materials Science and Engineering, comments on the research described above:
1. It’s not piss powered. The piss is the electrolyte, allowing ionic conduction (but not electronic conduction) when added. The electronic current must then flow through the device, completing the circuit. The electrochemical reaction at the electrode is a standard redox couple driven not by the piss, but by the potential difference between the Mg and the Cu. It’s more like a piss switch.
2. The tech has been around for a long time. The salt solution activated (key word) cells have been around for a long time and have seen a lot of use in deep sea applications. Why piss is needed is beyond me. Table salt and water would be fine. Remember: piss is poisonous to the body, so it’s not like this would make a very practical implantable device out side the bladder or urethra, never mind that it’s not rechargeable.
UPDATE: Seminal cyberpunk SF author Paul Di Filippo emailed me this bit from his 1990 short story Cockfight, reprinted in his Ribofunk collection:
“The boys…had to take a piss real bad. Side effect of the bloodwash…./Stack called out, “Don’t waste the biomass, boys.”/Tino and Drifter grumbled, but they each opened up a fuel-intake cap, unvelcroed their flies, butted their groins up to the vans, and did their best to top off the tanks.”