A Bionic Jellyfish Swims With Manic Speed (for a Jellyfish)

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No disrespect, but roboticists have got nothing on the animal kingdom. Birds cut through the air with ease, while our drones plummet out of the sky. Humans balance elegantly on two legs, while humanoid robots fall on their faces. It takes roboticists a whole lot of work to even begin to approach the wonders of evolution.

But maybe if you can’t beat ‘em, hack ‘em. Writing today in the journal Science Advances, researchers from Caltech and Stanford described how they’ve equipped jellyfish with microchips and electrodes to turbocharge their swimming pace, from a leisurely 2 centimeters per second to a less leisurely 6. It’s a first step toward bionic jellyfish, which scientists might use as a sort of floating sensor network to sample water quality in the oceans. And, more generally, it’s a move toward giving animals powers that evolution hasn’t invented since life’s been on Earth.

Energy remains a major challenge in robotics: It takes a lot of power to run a robot’s sensors and get its limbs or propellers to move. That means bulky batteries, which add weight. And in turn, weight means it takes more power to get the thing moving. Animals, on the other hand, are inherently energy efficient—natural selection favors individuals that have surplus energy to mate and pass their genes down to the next generation.

Jellyfish happen to be not only extremely efficient swimmers, but are also devoid of a brain and pain receptors, making them ideal subjects for this research. “That’s important because it allows us to manipulate their swimming in ways that might be ethically questionable in other organisms,” says mechanical engineer John Dabiri of Stanford University and Caltech, coauthor on the paper. But might the jellies be stressed? Unlikely, since jellyfish should secrete a mucus in response to stress, and these test subjects did no such thing. “In addition, it’s reversible, so we can take out our device and the animals return to their normal functioning,” Dabiri says.

A bionic jellyfish can swim three times faster than a regular jelly.
Video: Caltech

The researchers’ setup is fairly straightforward: A microchip controls a pair of electrodes inserted into the layer of muscle that powers the jellyfish’s bell. (The probes are made of wood, which sticks well in the tissue thanks to the material’s microscopic barbs.) These electrodes are analogous to the jellyfish’s own eight pacemakers, or bundles of neurons, positioned around the bell to coordinate movement.

Interestingly, while the human-made pacemaker makes the jellyfish swim three times as fast, the animals only used twice as much energy to do it. So if they’re capable of moving faster, and are more efficient that way, why don’t jellyfish just swim that fast naturally? Because that hypnotic pulsing of their bell does more than propel the animal: Dabiri’s previous research has found that a jellyfish’s methodical movements create vortices that suck in prey. Muck with a jellyfish’s speed, and you might muck with its ability to eat.

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