Finds its own fuel Bristol robotics laboratory

Lying in a bath in Bristol, UK, is a robotic scavenger, gorging itself on its surroundings. It’s able to get just enough energy to take in another stomach full of food, before ejecting its waste and repeating the process. This is no ordinary robot. It’s a self-sustaining soft robot with a mouth and gut.

Developed by a Bristol-based collaboration, this robot imitates the life of salps – squishy tube-shaped marine organisms. Salps have an opening at each end, one for food to enter and one for waste to leave. They digest any tasty treats that pass through their body, giving them just enough energy to wiggle about. The same is true for the Bristol bot.

By opening its “mouth”, made from a soft polymer membrane, the robot can suck in a belly full of water and biomatter. The artificial gut – a microbial fuel cell (MFC) – is filled with greedy microbes that break down the biomass and convert its chemical energy into electrical energy, which powers the robot. Digested waste matter is then expelled out the rear end, just as more water is sucked in the front for the next feed. With every mouthful, the robot’s reserves are replenished, so in theory it could roam indefinitely.


“Squeezing out enough energy to be self-sustainable is the real breakthrough,” says Fumiya Iida, a robotics researcher from the University of Cambridge.

Leave it alone

The energy that an MFC can get from food like this is currently pretty low. But by using soft materials for the mouth and the gut, the team was able to reduce the robot’s energy consumption. They got more power by putting several MFCs in series, like a battery.

One advantage of a self-sustaining robot is that if you don’t have to charge it, change its batteries, or hook it up to a power source, it won’t need any human interference. This would make it ideal for use in inhospitable environments: leave the robot in a radioactive disaster zone or a lake filled with pollution, then let it to get to work.

At the moment, it is just a proof of concept. The surrounding water is idealised, meaning that the nutrients have been evenly spread and are in an easy-to-digest form, but other researchers have shown that MFCs can work in more testing conditions.

A self-sustaining robot could one day clean up “red tides” like this one in China, as well as collecting rubbish Getty Images News

Now that self-sustainability has been achieved, the team wants to get more power so that the robot can start performing useful tasks.

“In the future, robots like this could be released into the ocean to collect garbage,” says Hemma Philamore, one of the robot’s creators from the University of Bristol. Another application could see the robots feeding in agricultural irrigation systems while monitoring plants or applying chemicals to crops. “What we are developing is a robot that can act naturally, in a natural environment,” says Philamore.

Journal reference: Soft Robotics, DOI: 10.1089/soro.2016.0020