Imagine a credit card-sized, urine-powered paper battery that could make healthcare tests cheaper and even charge mobile phones!
Current biochips need an external reader such as a laser scanner or an external source of power , such as conventional batteries, to perform diagnostic tests.
The technology developed by Ki Bang Lee at the Institute of Bioengineering and Nanotechnology in Singapore, however, houses both the sensors and the battery on one plastic chip, reports New Scientist.
Testing urine can reveal the identity of illnesses, and the new paper battery could allow the sample being tested to also power the diagnostic device, Lee says. It could be a useful power source for cheap healthcare test kits for diseases like diabetes, and could be used in emergency situations to power a cell phone.
"Our battery can be easily integrated into such devices, supplying electricity on contact with biofluids such as urine or blood."
The battery is made of a layer of filter paper steeped in copper chloride, sandwiched between strips of magnesium and copper. This "sandwich" is then laminated in plastic to hold the whole package together.
The resulting battery is just 1 millimetre thick and 60 by 30 mm across - slightly smaller than a credit card.
To activate the battery, a drop of urine is added and soaks through the sandwiched filter paper. The chemicals dissolve and react to produce electricity. The magnesium layer acts as the anode, losing its electrons. And the copper chloride acts as the cathode, mopping up the electrons.
The urine-powered battery was able to generate a voltage of about 1.5 volts - with a corresponding power of 1.5 micro-watts - using just 0.2 millilitres of urine.
And if a second droplet of urine was added 15 hours after the battery was first activated, the replenished urine could generate still more electricity.
The battery is currently suited for use with disposable devices - it is not yet ready to power laptops or iPods.
"But if, for example, we place a small cellular phone or transmitter on a plastic card, the chip will work as a disposable biofluid-activated means of communication in an emergency," he said.
Lee believes the system could be used in home-based health test kits. "The long-term goal is for people to be able to buy disposable biochips for a disease test from any pharmacy," he says.