Scientists at the Max Planck Institute for Intelligent Systems (MPI-IS) have developed a small, efficient, quiet robot like a jellyfish for easy handling.
Oceans, covering most of the earth, suffer from high pollution levels. Robots can clean up waste around coral reefs. But current underwater robots are noisy and bulky with rigid bodies, limiting their ability to navigate complex and irregular environments.
Scientists at the Max Planck Institute for Intelligent Systems (MPI-IS) have developed a versatile, energy-efficient, and almost noiseless robot, reminiscent of a jellyfish, that can fit into the palm of a hand. The team built the robot with electrohydraulic actuators, which act as artificial muscles powered by electricity. Soft and rigid components and air cushions stabilize the robot and make it waterproof, preventing high-voltage contact with the surrounding water. Thin wires connected to a power supply cause the muscles to contract and expand, enabling the robot to swim gracefully and create swirls underneath its body.
The robot, inspired by jellyfish, creates currents around its body and can collect objects and biological samples gently and noiselessly. This makes it useful for cleaning waste and collecting fragile samples without negatively impacting the environment. Jellyfish-Bots trap objects without contact and can work alone or in groups, moving at a fast speed of up to 6.1 cm/s. They also have a low input power of around 100 mW. Jellyfish-Bot is safe for humans and fish even if the insulating polymer is damaged. Its noise is indistinguishable from the background, making it gentle on the environment.
The robot has multiple layers, including stiffening and floating layers and a polymer skin. Its electrically powered artificial muscles, called HASELs, are embedded in the middle of the layers. HASELs are plastic pouches filled with liquid dielectric, partially covered by electrodes. When a high voltage is applied, the electrodes are charged positively, and the surrounding water is charged negatively. HASEL muscles contract and relax like real muscles by pushing oil inside plastic pouches using electrical charges. They can sustain high electrical stresses and are insulated to protect against water. They have never been used before to build an underwater robot. First, the team developed Jellyfish-Bot with one electrode with six fingers or arms and then divided the single electrode into separated groups to actuate them independently.
The team added buoyancy to the top and the battery and microcontroller to the bottom. They tested it in a pond and successfully steered it. However, they couldn’t make it swim in the opposite direction yet. The team is expected to achieve this goal soon.
Reference : Tianlu Wang et al, A versatile jellyfish-like robotic platform for effective underwater propulsion and manipulation, Science Advances (2023). DOI: 10.1126/sciadv.adg0292