The Power of Pee

Photo: A flask with urine in the bathroom

Scientists in research groups around the world are trying to design ever smaller “biochips” that can test for a variety of diseases at once, give instant results, and, crucially, can be mass produced cheaply. But until now, no one has been able to solve the problem of finding a power source as small and as cheap to fabricate as the detection technology itself.

Led by Dr Ki Bang Lee, a research team at Singapore’s Institute of Bioengineering and Nanotechnology (IBN) have developed a paper battery that is small, cheap to fabricate, and which uses the fluid being tested (urine) as the power source for the device doing the testing. The chemical composition of urine is widely used as a way of testing for tell-tale signs of various diseases and also as an indicator of a person’s general state of health. The concentration of glucose in urine is a useful diagnostic tool for diabetics.

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).

Lee used 0.2 ml of urine which generated a voltage of around 1.5 V with a corresponding maximum power of 1.5 mW. The researchers also found that the battery performances (such as voltage, power or duration) may be designed or adjusted by changing the geometry or materials used.; Source: Institute of Physics