26 October 2015

A robot powered by microbial fuel cells

Row-bot is a robot with a tank full of bacteria, able to swim forever in dirty water

Not so long ago, we talked about an interesting trend – about robots that draw the energy necessary for their movement from the environment. A representative of such robots, Thermobot, whose limbs are made of bimetallic material, is able to walk forever on a hot surface using its thermal energy. And now we will tell you about another interesting implementation of such an idea, about a robot called Row-bot, which has a container with electricity-generating bacteria and which, due to this, can swim forever in dirty water, from where the bacteria get the nutrients they need.

The Row-bot robot is the brainchild of specialists from the Robotics Laboratory of the University of Bristol, UK. The basis of its energy system is the so-called microbiological fuel Cell (Microbial Fuel Cell, MFC). Such fuel cells generate electricity consisting of electrons, which are the product of redox chemical reactions that form the basis of electrogenetic anabolism of some bacterial species.

In simpler terms, bacteria feed on organic materials that are abundant in water, producing free electrons. And as long as there is enough organic matter in the water for the bacteria to be "full, fat and happy", you will have an almost inexhaustible source of energy that can be used for your own purposes, for example, to make a robot move. Modern microbiological fuel cells are quite versatile, they can work in fresh water of rivers and lakes, in seawater, and they demonstrate the greatest efficiency in wastewater, performing a side function of its purification from dirt of organic origin.

But tiny microbes cannot produce a large amount of energy. Therefore, the robot needs a whole colony of such bacteria. In addition, the design of the Row-bot robot, the prototype of which was a water-skimmer beetle, has high efficiency in terms of using energy for its movement. The robot's four limbs have floats that prevent it from drowning and ensure that there is a certain level of water in its microbiological fuel cell. And the robot moves with the help of two "paddles", which are powered by miniature electric drives.

The Row-bot robot also has a "mouth", a valve that lets a portion of fresh water into the fuel cell. In the back of this element there is another valve through which waste water is discharged out, which is practically purified from organic matter. The cycle of operation of the fuel cell, from the start of a portion of fresh water to the release of waste water, takes three minutes. All the energy generated during this cycle, in the amount of 1.8 joules, is stored in an electric capacitor with low leakage currents. And this energy is enough for the robot to make 10 strokes with its oars at a speed of once per second. 1 joule of energy is enough for the robot to cover a distance of 20 centimeters, and the remaining 0.8 Joules can be used to supply energy to sensors or anything else.

As long as the Row-bot robot is on the water, it will have enough energy to perform fully autonomous swimming. And this robot was created in order to test the possibility of integrating microbiological fuel cells with electric drives. Its design can be further improved and optimized, which will allow it to spend less energy on movement, and the serial connection of several fuel cells will allow the robot to receive more energy, which will be enough even to power low-power laser sensors.

Ultimately, according to the researchers, such robots can be used for remote sensing, environmental monitoring and purification of the aquatic environment from pollution. And the possibility of their use in the exploration of other planets is also not excluded.

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