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Robotic jellyfish for U.S. Navy powers itself with seawater

Researchers are working on a robot that looks and moves like a jellyfish and powers itself with the help of high-tech materials and seawater. Surveillance and environmental monitoring are possible uses.

A moon jellyfish and, inset, a version of the Robojelly.
Wikimedia Commons/Alex Villanueva

Imagine a military surveillance robot that looks and moves like a jellyfish and can ply the seas indefinitely by powering itself with ocean water.

A team of researchers at Virginia Tech, the University of Texas at Dallas, and several other schools are working to develop just such a device.

In a paper published yesterday in the journal Smart Materials and Structures, team members outlined their recent progress on the "Robojelly" project, which is being funded by the U.S. Navy's Office of Naval Research.

Made of a combination of silicone and various high-tech materials, the Robojelly uses oxygen and hydrogen gases in seawater to trigger a chemical reaction that causes its artificial muscles to contract. The muscular motion copies that of the moon jellyfish, which allows water into its "bell" and then closes the bell to push the water out and create a jet that moves the creature along.

The Robojelly's artificial muscles rely on shape-memory alloy, an alloy that remembers its original shape and returns to it after being deformed.

The Robojelly's bell is made of silicone that contains ribs of springy steel. And the steel, in turn, is attached to a structure made of platinum-coated nanotubes and the shape-memory alloy, made of nickel-titanium. A valve opens, allowing seawater--and the oxygen and hydrogen gases it contains -- to come into contact with the nanotube-alloy structure. The platinum reacts, generating heat that activates the shape-memory alloy and causes it to deform, pull on the steel, and close the bell. When the nanotube-alloy structure cools, the alloy returns to its shape, releasing its pull on the steel and allowing the bell to reopen--and the process to repeat.

The researchers say the process produces no waste other than water vapor, making it environmentally friendly. And they say their next step is to control different parts of the robot's bell separately, to allow for directional movement.

When and if the device is perfected, possible uses include surveillance and environmental monitoring. Team member Alex Villanueva has written that groups of robots could "communicate with each other and make decisions as a network."

The video below shows the robot in action.