Experimental Robot Glides Silently Underwater Like an Eel

an electric eel/ Photo By Vladimir Wrangel via Shutterstock

 

Researchers from the University of California have created a robot that can move silently underwater, similar to an eel, and is a major breakthrough in underwater exploration, according to Ioana Patringenaru, writing for the UC San Diego News Center.


The newly-developed robot does not use an electric motor to power itself but relies on artificial muscles filled with water to move underwater. It is also entirely transparent and is connected to an electronics board that remains above water. Being transparent makes the robot very useful in underwater exploration because it can use passive camouflage and blend with the underwater surroundings with being painted.

Powered by Salt Water

The robot employs soft artificial muscles to swim noiselessly like an eel underwater and relies on the salt water where it swims to generate the electrical forces needed to make it move forward. It has cables that apply a voltage to the surrounding salt water and the water inside the artificial muscles. Negative charges are then created in the water in the vicinity of the robot and positive charges inside the robot. The electrical charges induce the artificial muscles to bend and make the robot move like an eel underwater. The charges are in the robot’s immediate surface but generate a negligible current that does not pose a threat to nearby marine life. The conductive chambers of the robot’s artificial muscles are filled with fluorescent dyes that can be used as a signaling system in the future.

The robot was able to achieve undulatory swimming with a maximum forward swimming speed of 1.9 millimeters per second and a Froude efficiency of 52 percent. It had an average transmittance of 94 percent across the visible spectrum, similar to that of a leptocephalus.  

The biggest innovation that they were able to achieve was to use the environment as part of their research, according to Michael T. Tolley, the study’s corresponding author. Tolley added that a lot more needs to be done to realize an untethered robotic eel but they have proven that it can be done. It may be the softest robot built for use in underwater exploration, Tolley claimed.  Improving the robot’s reliability and geometry remain the researchers’ top priority. The robot will also be equipped with ballast and weights so that it can dive deeper. The researchers are currently using magnets as improvised ballast weights. Researchers also plan to give the robotic eel a head, which will house a variety of sensors. But for now, the robot is just a proof-of-concept to illustrate a method of underwater propulsion.

The robot was tested at the Birch Aquarium at the Scripps Institution of Oceanography at UC San Diego and at Tolley’s laboratory.

Underwater Exploration Without the Noise

Robots used in underwater exploration are usually powered by propellers or jets that create a lot of noise, scaring away fish. They are also made of rigid materials that may damage the surrounding areas if the robots would bump into these. On the other hand, the new robot has a soft structure that lessens the risk of damage to the underwater environment. The artificial muscles also allow the robot to swim without making any noise. It answers the need to monitor underwater life without having to disturb, disrupt or damage the marine ecosystem. The researchers pointed out that most scientific underwater vessels are closely related to submarines. Their rigid structures and electric motors ensure that they can be heard from afar. The researchers claim the robot is a big step forward to a future when soft robots will swim alongside fish and invertebrates without harming them.

 

ocean floor/ Photo By Vlad61 via Shutterstock

 

Marine exploration is a flourishing area for robotics with applications such as environmental monitoring, extreme-weather mapping, and tidal studies. Tidal studies can be used in monitoring the movement of plastic waste and the surveillance and repair of remote installations.

But studying the marine environment brings with it its own set of challenges such as protecting the marine life from underwater exploration vehicles. The research done by the University of California scientists is remarkable because it made creative use of innovative power sources and materials. It proves that dielectric elastomer actuators can be a potential technology for various nascent applications -- robotics, artificial muscles, and microfluidics -- because of their large actuation strains, rapid response rate, low cost and noise, high energy density, and high efficiency when compared with traditional actuators.

Such physical characteristics make DEAs perfect for the actuation of soft submersible devices, but their application has been restricted by the lack of suitable and compliant electrode materials, the need to insulate the actuator electrodes from the surrounding fluid, and the use of rigid frames to restrain the dielectric layers.

Results of the research were published in the Science Robotics journal. Funding for the research was given by the Office of Naval Research and the National Science Foundation.