Researchers at the University of the West of England (UWE Bristol) – the same laboratory that recently introduced the prototype urinal that generates electricity via microbial fuel cells – have now created a pee-powered distress radio built into a foldable, portable paper-based microbial fuel cell system .

Using bacteria to produce power from human waste is where microbial fuel cells (MFCs) show great promise in providing electricity to even the most remote, inaccessible places on Earth. However, their uptake and use may be reduced by the expense of their components and the toxicity of their remains once the units have reached the end of their serviceable lives.

The priority for Dr Jonathan Winfield and his team at the UWE Bristol BioEnergy Centre, then, was that MFCs were made much smaller, lighter and cheaper than conventional units, as well as being safely disposable. In this vein, the researchers chose to use recycled, common materials to construct their new prototype device.

Building on aspects of technology already produced at UWE Bristol to power mobile phones, the new prototype device is an origami-inspired, pyramid-style design made from recycled photocopier paper impregnated with three layers of latex external waterproofing. This external layer serves as the cathode, while the internal layer forms the proton exchange membrane and reactor body, and acts as the device's anode.

Coated with dormant biofilms of electricity-generating bacteria that rapidly return to life when doused in urine, the thin film of tiny bio-generators on the surface of the anode are capable of surviving for extended periods of time dried out and in cold storage, making them ideal for use in rarely deployed emergency radio beacons. According to the researchers, these pyramid-shape bioreactors can currently be stored for up to eight weeks before being reactivated with fresh urine.

Working most efficiently with fresh morning urine, but even able to produce power with the likes of cattle pee, the device is claimed capable of creating enough energy to operate a radio transmitter just 35 minutes after activation. With two of these fuel cells connected in series, the device is reported able to transmit radio signals at approximately six-minute intervals for up to 24 hours, which the team believes could potentially make all the difference in a life-threatening situation.

Future advances on the device, say the researchers, could be the development of flat-packed, interlocking stacks able to be easily transported to where they are most needed. Other suggested uses include backup for remote power supplies, temporary electrical supplies in far-off locations, in refugee camps, or – apparently – even in a backyard garden shed.

Given, however, that the performance of these MFCs is barely enough to drive a very low-powered radio transmitter, it is assumed that much greater research and development will be required to achieve such goals.

Regardless, the researchers also claims that, eventually, they would like to be able to power a biodegradable robot with MFCs similar to those that they have recently developed (other areas of UWE Bristol have already constructed a urine-powered heart pump for a robot, for example).

In on-going experiments, the researchers assert that they are able to employ a wide range of material to this end including natural rubber from laboratory gloves and condoms, bioplastics, gelatine and even biological material, such as eggs.

A bit like Doc Brown supplying garbage to his "Mr Fusion" reactor to power his DeLorean time-machine, Dr Winfield believes that a quick rummage around in the trash could also supply sufficient material to construct a large proportion of a MFC.

"This is an exciting study, by a very talented group of engineers who have been redefining the art of microbial fuel cells over the last decade," said Plamen Atanassov, Director of the Center for Micro-Engineered Materials in New Mexico, US. "I keep being fascinated by their inventiveness, fantasy and drive to bring these new energy harvesting devices to practice."

The results of this research have been published in the Journal of Materials Chemistry A

Source: UW Bristol