The prototype soft robot has acquired a "lateral line" - a sensitive organ, thanks to which it can monitor the pressure and speed of water.
Fish are the dominant animals in the aquatic environment, adapted to it by hundreds of millions of years of evolution. Therefore, robotics who create floating systems for working in water often look to the structure and behavior of fish for inspiration. Not so long ago, the tactics of swimming in a flock, borrowed from them, proved to be successful. And the team of Ardian Jusufi from the Max Planck Institute for Intelligent Systems decided to use another feature of fish - the presence of a lateral line.
This sensitive organ helps them perceive the flow, pressure and vibration of the surrounding water in order to orient themselves and more accurately control their movements. In an article published in the journal Advanced Intelligent Systems, Yusufi and his co-authors presented a soft robot that is equipped with a "sideline" of sensors. This allows him to swim against the current of water and precisely maintain the required speed to, for example, stay in place in the middle of a fast stream.
The robot bends to fill and deflate tiny silicone chambers located on either side of its body. Filling with air, the chambers unbend their half of the robot, while the chambers on the opposite half collapse, allowing the body to make floating movements. The "lateral line" is not as developed as in fish: on each side of the robot there is a thinnest microchannel made of the same silicone, filled with a liquid gallium-indium alloy (eGaIn).
When the body is bent, the channel located on the opposite side is stretched, which increases its electrical resistance. Accurate measurements allow the system to register the moment at which the resistance reaches a certain value: that is, the bend reaches a certain angle. These figures are compared with the pressure that was required to create in the silicone chambers for such a bend.
Hydrodynamic calculations make it possible to turn such data into indicators of pressure and flow rate. Therefore, the scientists supplemented the robot with an intelligent control system that was able to use the sideline readings to follow the movement of water in the experimental pool. Demonstrating its capabilities, the robot was able to maintain such a swimming speed at which it remained in place regardless of changes in the current.