Researchers get the eel robot ready for testing. Source: EPFL A robot eel swimmer has been developed in order to trace the source of pollution in water.

The robot comes equipped with sensors that guide it in water but it can also be moved autonomously. The robot has already shown it can draw maps of the conductivity of water and temperatures in part of Lake Geneva in France.

The robot was developed by École Polytechnique Fédérale De Lausanne (EPFL) and funded in part by the Swiss Nano-Tera program. Called Envirobot, it measures about 1.5 meters and moves like an eel in lakes and streams without stirring mud or disturbing aquatic fauna. The sensors are able to perform measurements at different locations and send the result in real time to a local computer.

The robot was tested regularly in Lake Geneva. Researchers simulated the presence of pollution by locally scattering salt near the shoreline, resulting in changes in water conductivity. The robot then managed to record these variations and provide a map of temperatures in the lake. Researchers say the goal is to get the robot to detect the presence of heavy metals such as mercury or other pollutants.

"The use of a robot-snake has several advantages. It allows real-time measurements to be collected, more quickly than if stationary stations in lakes are deployed,” says Auke Ijspeert, director of the Laboratory of BioRob at EPFL. “And compared to more traditional submarine propeller robots, it can sneak up with less chance of getting stuck in algae or branches. The robot also creates less wake, so disperses less pollution. Envirobot is able to follow a programmed route, but it also has the potential to make its own decisions, and go back on its own to the source of pollution."

How It Works

Envirobot comes equipped with different modules, each equipped with a small electric motor. This allows for curvature of movement. Researchers say the robot can be assembled in different lengths and configurations. This flexibility makes it easier to transport the robot to remote locations and assemble it on site.

Some of the modules include conductivity and temperature sensors. Others include small chambers that fill with water, where miniaturized biological sensors can test for bacteria, small crustaceans or fish cells, and observe their behavioral changes in contact with water.

"For example, we have developed bacteria that emit light in the presence of very low concentrations of mercury, says R. van der Meer, director of the UNIL Basic Microbiology Department. “We detect these changes with luminometers, and then the information is transmitted as electrical signals.”

So far, researchers have tested only the conductivity and temperature sensors in the field. Testing for biological sensors is more difficult since they cannot contaminate the lake as they do test water in the lab. The teams plans to test these sensors by the end of the summer and will carry out tests with salt until the robot can determine the source of the salt diffusion easily. Then they will equip the robot with biological sensors to make measurements of toxic components.