A new jellyfish-mimicking robot runs on hydrogen to fuel its artificial muscles as it propels itself through water.
Although the current version requires tanks of hydrogen and oxygen to provide the fuel, the researchers hope the robot, called "Robojelly," may one day be able to fuel itself by gathering hydrogen and oxygen from its surroundings or a regenerating source, allowing it to run indefinitely.
Here's how it works: The hydrogen and oxygen fuel meet in channels running over a platinum catalyst. When they react, the reaction produces heat, which drives the robot's artificial muscles.
Carbon nanotubes conduct the heat to a specialized material that bends when heated, contracting the outer umbrella of the jellyfish and creating the squirting motion that propels the jellyfish.
Then the material, called a "shape memory alloy" returns to its original shape, ready to contract again when a new burst of heat arrives.
Jellyfish are good organisms to model a robot on because "the swimming mechanism is very simple and the structure is very simple to mimic," explained lead author Yonas Tadesse, who carried out the work while at Virginia Tech., but who is now at the University of Texas at Dallas.
The simplicity is part of the attraction, but there are other advantages to deploying a robotic jellyfish instead of robots based on other sea denizens: "There are fewer predators for jellyfish," Tadesse said.
The robot replicates a moon jellyfish, Aurelia aurita, and is just over 6 inches across. The team reports the findings today in the journal Smart Materials and Structures.
The robots could be used for ocean monitoring, including to track a pollution spill or for civilian or military surveillance, Tadesse said. The work is sponsored by the Navy.
Although the components have each been reported before, "It is probably one of the first and best demonstrations of a combination of nanotechology, hydrogen-fuel technology and soft robotics," said Xin Chen of Boston University who was not a part of the study.
For now, fuel-based versions have been tested using only one of the jelly's segments at a time. In the future, the team plans to control each segment of the robot separately but simultaneously, allowing more precise and complicated control and steering of the robot.
Watch a video of the robot below.