March 21, 2012
Robotic Jellyfish Fuses Hi-Tech Materials With Nature’s Elegant Design
In an article published Wednesday, a team of Navy-sponsored researchers outlined an in-the-works project for a robotic jellyfish that is able to propel itself through water by harnessing the latent power of the ocean.
Humorously dubbed 'Robojelly', scientists say that the plans for the mechanical Cnidarian were hatched with a very serious purpose in mind: Researchers say they hope the experimental gizmo will eventually be used to assist emergency teams in dangerous underwater rescue operations — like the recent Costa Concordia disaster that claimed the lives of at least 25 people when the cruise liner ran aground off the coast of Italy in January.
Particularly ingenious is the means the scientists have devised for powering the device. Drawing on and modifying existing hydrogen-power technology, Robojelly would derive its fuel from sea water, giving it access to an essentially unlimited power source.
“To our knowledge this is the first successful powering of an underwater robot using external hydrogen as a fuel source,” wrote lead author Yonas Tadesse, a mechanical engineer at Virginia Tech.
REPRODUCING NATURE´S MECHANICS
Equally impressive is how Tadesse´s team plans make the robot swim.
And if mimicry really is the highest form of flattery, then Mother Nature ought to be blushing.
Though still in the early phases of development, the scientist´s model draws on the elegant simplicity of the mechanism used by real jellyfish to propel themselves through the water.
One of the world´s most ancient and primitive life forms, jellyfish are equipped with simple rows of circular muscle that line the inside of their mushroom-shaped cap. When these muscles relax, the cap becomes engorged with water and puffs out, giving the creature its characteristic bell-shaped form.
When the circular muscles contract, the water held in the cap is forcefully ejected, propelling the gelatinous invertebrate through the water in rhythmic bursts.
In an attempt to replicate this movement, the researchers are making use of a material known to engineers as shape-metal alloy. As the name indicates, the material is an amalgam of metals that is able to resume its original shape after being deformed or scrunched up.
Essentially, it´s as malleable as tin-foil and resilient as rubber.
The researchers say the body of the robot consists of eight segments of this shape-metal alloy arranged in a form similar to the jellyfish´s bell-like cap.
In order to mimic the contraction and relaxation of natural muscles, the researchers coated each of these eight segments with a layer of platinum black powder. With electrical help from additional “straws” of pure carbon, the platinum coating catalyzes a chemical reaction with oxygen and hydrogen molecules in the sea water, releasing heat that is then transferred to Robojelly´s artificial muscles.
When the heat reaches the rings of shape-metal alloy, it causes them to temporarily change their shape, or ℠contract´. They are then immediately cooled off by the surrounding water and resume their original shape, ready to start the process again.
While the basic mechanism for allowing the robot to glide through water has already been worked out, the researchers say that they still have a bit of tinkering to do to figure out how to coordinate and control Robojelly´s movements.
In their current model, the eight segments that make up the bell-shaped cap all contract and relax simultaneously. In order to guide its movements, however, the team says it will have to work out a mechanism for controlling the contraction of each individual segment separately.
Funding for the project came from the US Office of Naval Research, which supports independent private research that is considered potentially beneficial to the US Navy and Marine Corps.
The team´s report was published Wednesday in the journal Smart Materials and Structures, a of publication of Britain´s Institute of Physics.