Energy-Efficient, Hydrogen-Fueled Robot Can Swim Like a Jellyfish

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Between airborne drones, spycams that can see around walls and a flood of other new surveillance devices, it’s beginning to seem like the only place you can go for real privacy is deep-sea diving. Well, guess again. Researchers at Virginia Tech are working with the U.S. Navy to design Robojelly, a seagoing reconnaissance robot that looks like a jellyfish, “feeds” itself like a jellyfish and propels itself under water by pulsing, just like a jellyfish. As if there aren’t enough jellyfish in the sea already!

Harvesting energy from the environment

Robojelly is still in the initial stages of development so it still has a ways to go, but the finished concept is for a device that can supply its own energy through a reaction between oxygen and hydrogen in seawater, using platinum as a catalyst. The reaction creates enough energy in the form of heat to operate the robot’s propulsion system, without the need for batteries or any external fuel source.

Biomimicry and undersea propulsion

Robojelly’s movements have little of the stiffness usually associated with robotic movement. As described somewhat poetically by Alaska Dispatch reporter Doug O’Harra, “It oozes. It glides. It pulses to a waltz-like beat.”

Somewhat less poetically, the secret behind Robojelly’s natural-looking movement is the result of a type of actuator (an actuator is a motor that operates robotic systems) made from a “smart material” developed at Virginia Tech.

Smart materials are beginning to emerge as players in the world of energy efficient movement. They are capable of changing shape and springing back to their original form, typically when stimulated by a chemical reaction that creates heat.

Virginia Tech’s material is called Bio-Inspired Shape Memory Alloy Composite (BISMAC). According to the project’s research abstract published in the Institute of Physics’ Smart Materials and Structures journal, it consists of:

“…nano-platinum catalyst-coated multi-wall carbon nanotube sheets, wrapped on the surface of nickel–titanium shape memory alloy (SMA). As a mixture of oxygen and hydrogen gases makes contact with the platinum, the resulting exothermic reaction activates the nickel–titanium-based SMA. The sheets serve as a support for the platinum particles and enhance the heat transfer due to the high thermal conductivity between the composite and the SMA.”

This complicated set-up enables Robojelly to mimic the muscular contractions of a real jellyfish, which jet-propels itself by enclosing water within its bell-shaped body, then expelling it with force.

Given the Navy’s history of using dolphins for mine detection, the deployment of robotic jellyfish for military purposes is not all that far fetched. As for peacetime work, Robojelly could find itself detailed for‌

environmental surveillance, monitoring and reporting on the condition of underwater equipment, and search-and-rescue operations.

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