Fully autonomous robots that collect human urine to power themselves could be a step closer, according to researchers in Bristol.

The engineers from the Bristol Robotics Laboratory (BRL) have created a pump based on a human heart that can deliver urine to the fuel cells of the waste-powered “EcoBot”, without the risk of mechanical failures and blockages experienced by current technology.

This could enable the robots to operate without human intervention because they it would allow them to collect their own fuel and use it to generate electricity, the researchers claim.

‘We speculate that in the future, urine-powered EcoBots could perform environmental monitoring tasks such as measuring temperature, humidity and air quality,’ said lead researcher Peter Walters of the University of the West of England (UWE), which runs the BRL with Bristol University.

‘In the city environment, they could re-charge using urine from urinals in public lavatories. In rural environments, liquid waste effluent could be collected from farms.’

The robots could even be deployed to monitor areas where there are high levels of pollutants or dangerous predators without putting humans in harm’s way, the researchers claim.

Previous EcoBots have used conventional motor pumps to deliver liquid feedstock to the fuel cells, which use microbes to break down the urine and generate electricity in the process.

The new device, which has an internal volume of 24.5ml, instead copies the human heart by compressing the pump’s body and forcing the liquid out using artificial muscles made from shape memory alloys – materials that can be deformed and then easily returned to their original shape using heat.

‘The artificial heartbeat is mechanically simpler than a conventional electric motor-driven pump by virtue of the fact that it employs artificial muscle fibres to create the pumping action, rather than an electric motor, which is by comparison a more complex mechanical assembly,’ said Walters.

Passing an electric current through the artificial muscles causes them to heat up and compress a soft region in the centre of the pump, ejecting the fluid through an outlet and pumping it to a height sufficient to deliver it to an EcoBot’s fuel cells.

Removing the current allows the muscles to cool and return to their original shape, causing the pump to relax and drawing in more fluid from a reservoir ready for the next cycle.

The researchers showed a stack of 24 microbial fuel cells fed on urine could power the pump via a capacitor. They now plan on improving the pump’s efficiency so it can be integrated into the next generation of EcoBots.

The research is published in the Institute of Physics Publishing’s journal Bioinspiration and Biomimetics.

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