EPFL's imposter robotic fish infiltrates a school of zebrafish

researchers at EPFL’s robotic systems laboratory (LSRO), headed by professor francesco mondada, have developed a miniature robot that can integrate perfectly into schools of zebrafish. the robot is seven centimeters long – longer than the fish it’s modeled after but with the same shape and proportions. it is equipped with magnets that link it to a tiny engine installed under the aquarium to propel it through the water. the researchers chose zebrafish for their study because it is a robust species whose schools tend to switch direction and move about very quickly.

the researchers wanted to develop a closed-loop system in which the robot is able to not only influence the fish’s behavior, but also adapt its own behavior by learning how to communicate and move like they do

‘we created a kind of ‘secret agent’ that can infiltrate these schools of small fish,’ says EPFL post-doc researcher frank bonnet. there are two aspects to the research program. the first deals with biology, studying the social interactions between individual fish. here the robot helps scientists generate targeted stimuli and test the fish’s response. the second aspect deals with robotics, and this is where the EPFL researchers focused their work.

the robot’s swimming mechanism – initially designed with the help of biologists – gradually improved as the robot spent more time with the fish

the team determined the key criteria that would allow the robot to integrate into schools of zebrafish and subsequently influence their behavior. these included the fish’s physical characteristics, like shape, color, stripes, etc. their behavioral characteristics were also taken into account, such as linear velocity, acceleration speed, the distance between individual fish, the size of the schools, their vibrations and motion, and the rhythm at which they move their tails.

‘the fish accepted the robot into their schools without any problem,’ says bonnet. ‘and the robot was also able to mimic the fish’s behavior, prompting them to change direction or swim from one room to another.