A PAIR of socks fuelled with urine pumped by the wearer's footsteps has powered a wireless transmitter to send a signal to a computer.
Scientists at the Bristol BioEnergy Centre at the University of the West of England embedded the socks with miniaturised microbial fuel cells (MFCs).
The 24 individual soft MFCs inside the socks were supplied with fresh urine and circulated around by the human operator walking.
Normally, such systems would rely on a mains powered pump to circulate the urine over the MFCs but this 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.
In the experiment, published in the journal Bioinspiration and Biomimetics, soft tubes were placed under the heels of the socks to ensure regular fluid push-pull by walking.
This system successfully ran a wireless transmission board, which was able to send the message "First Wearable MFC" every two minutes to the computer-controlled receiver.
Professor Ioannis Ieropoulos, who led the research, said it "opens up possibilities" for using urine to power wearable devices.
"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," he said.
"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.
"This work opens up possibilities of using waste for powering portable and 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.
"At the same time this would indicate proof of life since the device will only work if the operator's urine fuels the MFCs."
MFCs use bacteria to generate electricity from waste fluids - tapping into the biochemical energy used for microbial growth and converting it directly into electricity.
Scientists say this technology can use any form of organic waste and turn it into useful energy without relying on fossil fuels, making it a "valuable" green technology.
Bristol BioEnergy Centre has recently prototype urinal in partnership with Oxfam that uses pee-power technology to light cubicles in refugee camps.
