RoboJelly diagram
A computer-aided model of Robojelly shows the vehicle’s two bell-like structures.

Undersea Vehicle Powered by Hydrogen and Oxygen

Researchers at The University of Texas at Dallas and Virginia Tech have created an undersea vehicle inspired by the common jellyfish that runs on renewable energy and could be used in ocean rescue and surveillance missions. In a study published this week in Smart Materials and Structures, scientists created a robotic jellyfish, dubbed Robojelly, that feeds off hydrogen and oxygen gases found in water. “We’ve created an underwater robot that doesn’t need batteries or electricity,” said Dr. Yonas Tadesse, assistant professor of mechanical engineering at UT Dallas and lead author of the study. “The only waste released as it travels is more water.”

Engineers and scientists have increasingly turned to nature for inspiration when creating new technologies. The simple yet powerful movement of the moon jellyfish made it an appealing animal to simulate. The Robojelly consists of two bell-like structures made of silicone that fold like an umbrella. Connecting the umbrella are muscles that contract to move. In this study, researchers upgraded the original, battery-powered Robojelly to be self-powered. They did that through a combination of high-tech materials, including artificial muscles that contract when heated. These muscles are made of a nickel-titanium alloy wrapped in carbon nanotubes, coated with platinum and housed in a pipe. As the mixture of hydrogen and oxygen encounters the platinum, heat and water vapor are created. That heat causes a contraction that moves the muscles of the device, pumping out the water and starting the cycle again. “It could stay underwater and refuel itself while it is performing surveillance,” Tadesse said. In addition to military surveillance, Tadesse said, the device could be used to detect pollutants in water. Tadesse said the next step would be refining the legs of the devices to move independently, allowing the Robojelly to travel in more than one direction.

{Dr. Ray Baughman, the Robert A. Welch Distinguished Chair in Chemistry and director of the Alan G. MacDiarmid NanoTech Institute at UT Dallas, was an author of the study. The research was a collaboration between researchers at the University of Texas at Dallas and Virginia Polytechnic Institute and State University, Virginia Tech, including Dr. Shashank Priya, the study’s senior author. The study was funded by the Office of Naval Research.}

The Robojelly, shown here out of water, has an outer structure made out of silicone.

When the Earth is uninhabited, this robotic jellyfish will still be roaming the seas
by Esther Inglis-Arkell  /  March 21, 2012

Virginia Tech and the University of Texas at Dallas have claimed their place as the leading purveyor of robot-based nautical doom with robojelly, a robot that simulates the look and the move of a cnidarian. Anyone who has seen jellies knows that they move with a repetitive contraction of their bells, or their transparent outer shells. This movement requires two motions: a contraction and a snap back to the original position. For this carbon nanotubule jellyfish, the engineers used a commercially available, shape memory, titanium-and-nickel alloy to mimic the snap back. The contraction was harder to engineer. The Robojelly needed muscles, so researchers used platinum-covered carbon nanotubes to cover the shape memory sheets. When hydrogen and oxygen gases in the water made contact with the platinum — which is in the form of black powder — they create a reaction that gives off heat. This causes the nickel-titanium alloy to contract. And since hydrogen and oxygen are in seawater, these jellies could roam the oceans indefinitely, with possible future tinkering.

The deformation of the bell, powered by this reaction, was found to be a modest 13.5%. An electro-robojelly can manage 29% and a biological one can get an impressive 42%, but neither of the latter can power themselves until judgment day.

Yonas Tadesse
email : yonas.tadesse [at] utdallas [dot] edu


“Artificial muscles powered by a renewable energy source are desired for joint articulation in bio-inspired autonomous systems. In this study, a robotic underwater vehicle, inspired by jellyfish, was designed to be actuated by a chemical fuel source. The fuel-powered muscles presented in this work comprise nano-platinum catalyst-coated multi-wall carbon nanotube (MWCNT) sheets, wrapped on the surface of nickel–titanium (NiTi) 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 (NiTi)-based SMA. The MWCNT 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. A hydrogen and oxygen fuel source could potentially provide higher power density than electrical sources. Several vehicle designs were considered and a peripheral SMA configuration under the robotic bell was chosen as the best arrangement. Constitutive equations combined with thermodynamic modeling were developed to understand the influence of system parameters that affect the overall actuation behavior of the fuel-powered SMA. The model is based on the changes in entropy of the hydrogen and oxygen fuel on the composite actuator within a channel. The specific heat capacity is the dominant factor controlling the width of the strain for various pulse widths of fuel delivery. Both theoretical and experimental strains for different diameter (100 and 150 µm) SMA/MWCNT/Pt fuel-powered muscles with dead weight attached at the end exhibited the highest magnitude under 450 ms of fuel delivery within 1.6 mm diameter conduit size. Fuel-powered bell deformation of 13.5% was found to be comparable to that of electrically powered (29%) and natural jellyfish (42%).”


Japanese researcher draws inspiration from slime mold cognition
by Christopher Mims  / 03/09/2012

A new blob-like robot described in the journal Advanced Robotics uses springs, feet, “protoplasm” and a distributed nervous system to move in a manner inspired by the slime mold Physarum polycepharumWatch it ooze across a flat surface, The Blob style:

Skip to 1:00 if you just want to be creeped out by its life-like quivering. (And if anyone can explain why, aside from wanting to kill its creepiness, the researcher stabs it with a pen-knife at 1:40, let me know in the comments.) Researcher Takuya Umedachi of Hiroshima University has been perfecting his blob-bot for years, starting with early prototypes that used springs but lacked an air-filled bladder.

This model didn’t work nearly as well, demonstrating, I guess, the need for a fluid or air-filled sack when you’re going to project your soft-bodied self in a new direction. (Hydraulic pressure is, after all, how our tongues work.) Umedachi modeled his latest version on the “true” slime mold, which has been shown to achieve a “human-like” decision-making capacity through properties emerging from the interactions of its individual spores. Slime molds appear to have general computational abilities, and you’ve probably heard that they can solve mazes. Here’s what they look like in the wild.

Yellow slime mold (detail) by frankenstoen

Yellow slime mold by frankenstoen

Soft-bodied robots can do things their rigid, insectoid brethren can’t, like worm their way into tight spots and bounce back in the face of physical insult. Umedachi’s goal isn’t simply to create a new kind of locomotion, however. He’s exploring the way in which robots that lack a centralized command center — i.e. a brain — can accomplish things anyway. Slime molds are a perfect model for this sort of thing, because they don’t even have the primitive neural nets that characterize the coordinated swimming and feeding actions in jellyfish.

From the abstract:

A fully decentralized control using coupled oscillators with a completely local sensory feedback mechanism is realized by exploiting the global physical interaction between the body parts stemming from the fluid circuit. The experimental results show that this robot exhibits adaptive locomotion without relying on any hierarchical structure. The results obtained are expected to shed new light on the design scheme for autonomous decentralized control systems.

Simulations indicate that the robot should be highly adaptable to deformation — i.e., squeezing through tight spaces.

For a full account of the ways that Umedachi plans to reproduce the world’s most primitive form of cognition in robots, here’s a 2011 talk on the subject by the professor himself.