Wearable energy generator powered by pee

What do you get when you take a pair of socks, embed them with miniaturised microbial fuel cells (MFCs) and add some urine? You get fuel for a wireless transmitter!

Researchers from the Bristol BioEnergy Centre at the University of the West of England (UWE Bristol) developed an experiment whereby soft MFCs embedded within a pair of socks were supplied with fresh urine, circulated by the human operator walking. MFCs use bacteria to generate electricity from waste fluids, tapping into the biochemical energy used for microbial growth and converting it directly into electricity.

“Having already powered a mobile phone with MFCs using urine as fuel, we wanted to see if we could replicate this success in wearable technology,” said Professor Ioannis Ieropoulos, the leader of the research. “We also wanted the system to be entirely self-sufficient, running only on human power — using urine as fuel and the action of the foot as the pump.”

Normally, continuous-flow MFCs would rely on a mains-powered pump to circulate the urine over the microbial fuel cells, but this latest experiment relied solely on human activity. The manual pump was based on a simple fish circulatory system and the action of walking caused the urine to pass over the MFCs and generate energy. Soft tubes, placed under the heels, ensured frequent fluid push-pull by walking.

Writing in the journal Bioinspiration and Biomimetics, the researchers recorded how the wearable MFC system was successfully used to power a wireless transmitter, which was able to send a message every 2 min to the PC-controlled receiver module. They also suggest that their study “opens a new avenue for research in the utilisation of waste products for powering portable as well as wearable electronics”.

“For example, recent research shows it should be possible to develop a system based on wearable MFC technology to transmit a person’s coordinates in an emergency situation,” said Professor Ieropoulos. “At the same time this would indicate proof of life, since the device will only work if the operator’s urine fuels the MFCs.”

Image caption: A schematic drawing and image of the developed wearable generator.

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