&Bullet; physics 14, p69

A robotic fish, triggered to swim in the same way as real fish, could help researchers test predictions about these underwater creatures under well-controlled conditions.

J. Sánchez-Rodríguez et al. [1]

Together with the five senses of touch, sight, hearing, smell and taste, fish can perceive body deformations that are related to their position in the water and the speed at which they swim. Researchers believe that this ability, known as proprioception or colloquially as the “sixth sense,” is used by fish to align their fins for optimal swimming. A research team has now demonstrated a robotic fish whose tail movements are controlled by proprioception. They say the robo-fish could be used to study idealized swimming movements that cannot be seen in living things.

The robot, designed and built by Médéric Argentina of the University of Côte d’Azur, France, and his colleagues, resembles a fish skeleton. The head, backbone, scales and tail (the robot has no fins) were 3D printed separately from different elastic materials and then glued together. A servo motor was attached to the tail with two cables that drive the lateral movement of the tail using information gathered from a force sensor on the head of the robot.

J. Sánchez-Rodríguez et al. [1]
Researchers in France are replicating the sense of proprioception in a robotic fish by connecting the action of a motor that drives movements of the robot’s tail to force sensors on its head.

The team observed that this force measurement caused the fish’s body to curl and its tail to move from side to side in a manner similar to that of real fish. This movement only occurs when the robot is submerged and stops when the robot emerges above the waterline. Argentina says that the robot “chooses” when and how to swim: the movement is entirely determined by a feedback loop between the motor and the force sensor and is not programmed into the robot. This ability to determine its own movement makes this design interesting for use in future autonomous vehicles, the team says.

–Katherine Wright

Katherine Wright is assistant editor of physics.


  1. J. Sánchez-Rodríguez et al., “Proprioceptive Mechanism for Bioinspired Fish Swimming”, Phys. Rev. Lett.126, 234501 (2021).

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