Fancy a world where jellyfish can get around more?
New prosthetic could turn them into assets, researchers say.
By Nick Carne
US engineers have developed a tiny prosthetic they say motivates jellyfish to swim with greater speed and efficiency than they normally do, without causing them any stress.
That might cause you stress, especially if even slow jellyfish give you the heebie-jeebies, but the researchers say there is a positive to all this.
They envision a future in which jellyfish equipped with sensors could be directed to explore and record information about the ocean.
Cosmos has previously written about a soft robot inspired by a larval jellyfish and even electronic skin that takes a lesson from jellyfish, but this new work is about improving the beast, not learning from it.
The researchers, who were led by led by John Dabiri from the California Institute of Technology and Nicole Xu from Stanford University, explain themselves in a paper in the journal Science Advances.
Jellyfish use a pulsing motion to propel themselves forward, swishing their tentacles as they move to capture prey. They typically travel at around two centimetres a second, because there’s no prey-capturing advantage in making more effort.
The prosthetic uses electrical impulses to regulate and speed up the pulsing, in much the same way that a cardiac pacemaker regulates heart rate. About two centimetres in diameter and neutrally buoyant in water, it is attached via a small wooden barb.
When Dabiri, Xu and colleagues used a microelectronic controller pulsing at a frequency three times faster than the jellyfish's usual body pulses (without causing them any distress, they stress), their swimming speed increased to four-to-six centimetres per second.
The electrical jolts also made them swim more efficiently: they achieved three times the speed using just twice as much energy as normal (as measured by the amount of oxygen consumed by the animals while swimming).
In fact, says Xu, the prosthetic-equipped jellyfish were over 1000 times more efficient than swimming robots.
"We've shown that they're capable of moving much faster than they normally do, without an undue cost on their metabolism," she says. "This reveals that jellyfish possess an untapped ability for faster, more efficient swimming. They just don't usually have a reason to do so."
Currently, the prosthetic can direct jellyfish to start swimming and control the pace. The next step, Dabri says, will be to develop a system that guides it in specific directions and allows it to respond to signals from onboard sensors.
If the electronic controls are small enough, they could even be embedded in the jellyfish's tissue, making them permanent but unnoticed prosthetics.
"Only a small fraction of the ocean has been explored, so we want to take advantage of the fact that jellyfish are everywhere already to make a leap from ship-based measurements, which are limited in number due to their high cost," he says.
"If we can find a way to direct these jellyfish and also equip them with sensors to track things like ocean temperature, salinity, oxygen levels, and so on, we could create a truly global ocean network where each of the jellyfish robots costs a few dollars to instrument and feeds themselves energy from prey already in the ocean."
There might even be a role for a cuttlefish wearing 3D glasses.