These bionic jellyfish could use newfound speed to patrol the ocean

To anyone who has received an agonising sting while enjoying a relaxing swim, it sounds like it could be a terrible idea – giving jellyfish prosthetics to make them faster. They could be an important solution to a big problem however, according to their creators.

Researchers at Caltech and Stanford University in California developed the tiny prosthetics, which enable the creatures to swim faster and more efficiently than they normally do without causing stress. Bionic jellyfish could one day be directed to explore and record information in oceans around the world, a currently difficult and expensive task.

Jellyfish use a pulsing motion to propel themselves forward, ‘swishing’ their tentacles as they move to capture prey. The new prosthetic uses electrical impulses to regulate and speed up that pulsing, similar to the way a cardiac pacemaker regulates heart rate. The device, which is neutrally buoyant in water, is about 2cm in diameter and is attached to the body with a small wooden barb.

Typically, the animals swim at about 2cm/s. They are capable of moving more quickly, but that does not help them catch prey. The microelectronic controller pulses three times faster than the usual body pulses. The creatures’ pulsing sped up correspondingly, increasing speed to 4-6cm/s.

The electrical jolts also made them swim more efficiently. Although the jellyfish swam three-times faster, they used just twice as much energy to do so, as measured by the amount of oxygen consumed. The prosthetic-equipped jellyfish were over 1,000 times more efficient than swimming robots, said lead researcher Nicole Xu from Stanford.

The jellyfish were closely monitored to make sure that they were not harmed. They do not have a brain or pain receptors, but they have been found to secrete mucus when stressed. No such secretion was observed and they reportedly went back to swimming normally once the prosthetic was removed.

The bionic animals could have an important application, said Caltech's John Dabiri, who led the research with Xu.

“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,” said Dabiri.

“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.”

The prosthetics can currently direct jellyfish to start swimming and control the pace. The researchers said the next step will be developing a system that guides them in specific directions and allows them to respond to signals from onboard sensors. Dabiri hopes to develop even smaller electronic controls that could be completely embedded in the jellyfish's tissue, making them permanent but ‘unnoticed’ prosthetics.

The research was published in Science Advances.

Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.

Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.