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First-ever underwater robot modeled after Alaska moon jelly

Doug O'Harra
YouTube screengrab

It oozes. It glides. It pulses to a waltz-like beat.

Even better, it will never forces its human friends to dollop on meat tenderizer as an antidote to its vicious stings.

It’s the Robojelly 2.0 -- the high-tech, hydrogen-fueled mechanical jellyfish first produced and now refined by a team of U.S. scientists and engineers at Virginia Tech.

Ocean-loving Alaskans have long been familiar with the many varieties of jellies that bloom offshore by uncounted billions to silently waggle through summer waters. While eerily beautiful when seen afloat in the sea, jellies snarled in nets or caught on fishing lines can also deliver a painful sting.

An old-time Alaskan remedy? Meat tenderizer. (Baking soda also can work.)

This video of the Robojelly at play does suggest the pulsing motions of the common Alaskan moon jelly, minus the stingers.

This underwater robot “not only exhibits characteristics ideal to use in underwater search and rescue operations, but could, theoretically at least, never run out of energy thanks to it being fuelled by hydrogen,” the creators explained in this story about the contraption.

"To our knowledge, this is the first successful powering of an underwater robot using external hydrogen as a fuel source," lead author Yonas Tadesse, an assistant professor of mechanical engineering at Virginia Tech, said here.

The Robojelly can mimic the natural movements of a jellyfish because chemical reactions between the water and the materials on its surface cause the object to pulse and contract. The team describes how this works it in a paper published this week in the journal Smart Materials and Structure.

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“At Robojelly's heart is a commercially available nickel-titanium shape-memory alloy (SMA) – a deformable material that returns to its original shape when heated,” explains this story. “The SMA is wrapped in a sheet of carbon nanotubes that itself is coated in titanium particles, which catalyse the reaction between hydrogen and oxygen. The heat produced as a result of this oxidation then allows the SMA to revert to its original shape.”

Originally designed in cooperation with the Office of Naval Research in 2009, Robojelly was upgraded over the past year. The goal is to create a robot that monitor oceanography or fish while moving through the real ocean just like an actual jellyvish, explained VirginiaTech mechanical engineer Alex Villanueva, one of the five authors on the new paper, while presenting last fall at a conference of the American Physical Society.

"Its geometry is copied almost exactly from a moon jellyfish (Aurelia aurita)," he said here. “The robot is built out of silicone and uses shape memory alloy (SMA) actuators to swim.”

Here’s a moon jellyfish primer. Read much more about Robojelly’s function and future plans here.