Summary: Roboticists have developed an eel-like robot that uses artificial muscles to help propel itself through water.
Source: UCSD.
An innovative, eel-like robot developed by engineers and marine biologists at the University of California can swim silently in salt water without an electric motor. Instead, the robot uses artificial muscles filled with water to propel itself. The foot-long robot, which is connected to an electronics board that remains on the surface, is also virtually transparent.
The team, which includes researchers from UC San Diego and UC Berkeley, details their work in the April 25 issue of Science Robotics. Researchers say the bot is an important step toward a future when soft robots can swim in the ocean alongside fish and invertebrates without disturbing or harming them. Today, most underwater vehicles designed to observe marine life are rigid and submarine-like and powered by electric motors with noisy propellers.
“Instead of propellers, our robot uses soft artificial muscles to move like an eel underwater without making any sound,” said Caleb Christianson, a Ph.D. student at the Jacobs School of Engineering at UC San Diego.
One key innovation was using the salt water in which the robot swims to help generate the electrical forces that propel it. The bot is equipped with cables that apply voltage to both the salt water surrounding it and to pouches of water inside of its artificial muscles. The robot’s electronics then deliver negative charges in the water just outside of the robot and positive charges inside of the robot that activate the muscles. The electrical charges cause the muscles to bend, generating the robot’s undulating swimming motion. The charges are located just outside the robot’s surface and carry very little current so they are safe for nearby marine life.
“Our biggest breakthrough was the idea of using the environment as part of our design,” said Michael T. Tolley, the paper’s corresponding author and a professor of mechanical engineering at the Jacobs School at UC San Diego. “There will be more steps to creating an efficient, practical, untethered eel robot, but at this point we have proven that it is possible.”
Previously, other research groups had developed robots with similar technology. But to power these robots, engineers were using materials that need to be held in constant tension inside semi-rigid frames. The Science Robotics study shows that the frames are not necessary.
Image: The conductive chambers inside the robot’s artificial muscles can be loaded with fluorescent dye (as shown in the video accompanying the study and this release). In the future, the fluorescence could be used as a kind of signaling system. Credit: UCSD.
“This is in a way the softest robot to be developed for underwater exploration,” Tolley said.
The robot was tested inside salt-water tanks filled with jelly fish, coral and fish at the Birch Aquarium at the Scripps Institution of Oceanography at UC San Diego and in Tolley’s lab.
The conductive chambers inside the robot’s artificial muscles can be loaded with fluorescent dye (as shown in the video accompanying the study and this release). In the future, the fluorescence could be used as a kind of signaling system.
Next steps also include improving the robot’s reliability and its geometry. Researchers need to improve ballast, equipping the robot with weights so that it can dive deeper. For now, engineers have improvised ballast weights with a range of objects, such as magnets. In future work, researchers envision building a head for their eel robot to house a suite of sensors.
Funding: The research was supported with a grant from the Office of Naval Research. Christianson is supported by a National Science Foundation Graduate Research Fellowship.
Translucent soft robots driven by frameless fluid electrode dielectric elastomer actuators
Caleb Christianson, Department of Nanoengineering, UC San Diego; Nathaniel N. Goldberg, Department of Mechanical Engineering, UC Berkeley; Professor Dimitri D. Deheyn, Scripps Institution of Oceanography, UC San Diego; Professors Shengqiang Cai and Michael T. Tolley, Department of Mechanical and Aerospace Engineering, UC San Diego.
Source: Ioana Patringenaru – UCSD
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com images are credited to UCSD.
Video Source: Video credited to JacobsSchoolNews.
Original Research: Abstract for “Translucent soft robots driven by frameless fluid electrode dielectric elastomer actuators” by Caleb Christianson, Nathaniel N. Goldberg, Dimitri D. Deheyn, Shengqiang Cai and Michael T. Tolley in Science Robotics. Published April 25 2018.
doi:10.1126/scirobotics.aat1893
[cbtabs][cbtab title=”MLA”]UCSD “Transparent Eel-Like Soft Robot Can Swim Silently Underwater.” NeuroscienceNews. NeuroscienceNews, 25 April 2018.
<https://neurosciencenews.com/eel-robot-swimming-8880/>.[/cbtab][cbtab title=”APA”]UCSD (2018, April 25). Transparent Eel-Like Soft Robot Can Swim Silently Underwater. NeuroscienceNews. Retrieved April 25, 2018 from https://neurosciencenews.com/eel-robot-swimming-8880/[/cbtab][cbtab title=”Chicago”]UCSD “Transparent Eel-Like Soft Robot Can Swim Silently Underwater.” https://neurosciencenews.com/eel-robot-swimming-8880/ (accessed April 25, 2018).[/cbtab][/cbtabs]
Abstract
Translucent soft robots driven by frameless fluid electrode dielectric elastomer actuators
Dielectric elastomer actuators (DEAs) are a promising enabling technology for a wide range of emerging applications, including robotics, artificial muscles, and microfluidics. This is due to their large actuation strains, rapid response rate, low cost and low noise, high energy density, and high efficiency when compared with alternative actuators. These properties make DEAs ideal for the actuation of soft submersible devices, although their use has been limited because of three main challenges: (i) developing suitable, compliant electrode materials; (ii) the need to effectively insulate the actuator electrodes from the surrounding fluid; and (iii) the rigid frames typically required to prestrain the dielectric layers. We explored the use of a frameless, submersible DEA design that uses an internal chamber filled with liquid as one of the electrodes and the surrounding environmental liquid as the second electrode, thus simplifying the implementation of soft, actuated submersible devices. We demonstrated the feasibility of this approach with a prototype swimming robot composed of transparent bimorph actuator segments and inspired by transparent eel larvae, leptocephali. This design achieved undulatory swimming with a maximum forward swimming speed of 1.9 millimeters per second and a Froude efficiency of 52%. We also demonstrated the capability for camouflage and display through the body of the robot, which has an average transmittance of 94% across the visible spectrum, similar to a leptocephalus. These results suggest a potential for DEAs with fluid electrodes to serve as artificial muscles for quiet, translucent, swimming soft robots for applications including surveillance and the unobtrusive study of marine life.
