Prosthetic device enables bionic jellyfish to swim three times faster
From Tony Stark and fanciful fiction to the real-life prostheses under development in labs around the world, bionic body parts have long promised to enhance the physical capabilities of human beings. But have you ever considered what that would look like for jellyfish? Scientists at Caltech and Stanford University have, and are now showing off a tiny prosthetic that gives the marine creatures an ability to swim faster while using less energy, all without causing them any harm.
Since 2013, engineers and robotics researchers at Caltech and Stanford have been investigating the mechanics of jellyfish movement, with hopes of one day recruiting them for use as a type of environmental monitoring device. The thinking is that these hugely abundant blobs of sea jelly can be equipped with sensors to gather information about the ocean, which remains largely unexplored.
"Only five to 10 percent of the volume 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," says Caltech’s John Dabiri, who led the research.
To do that, Dabiri and his team will first need more control over how jellyfish move through the water. The new technology the team has developed is a first and important step towards this objective, speeding up the swimming motion of the jellyfish and learning more about their mechanics at the same time.
The prosthetic device is likened to a pacemaker, which uses electrical pulses to regulate the rhythm of a patient’s heart. But instead of controlling heart rate, the two-centimeter (0.8 in) wide device controls the rate of pulsing motions that jellyfish rely on to propel themselves forward.
Generally speaking, jellyfish move at a rate of around two centimeters per second, carefully controlling the frequency of their body pulses to move at the optimal speed for catching prey. By attaching the prosthetic to the body of jellyfish with a small wooden barb (which is harmless), the team was able to use electrical pulses to up the ante, beating at three times the rate of the animal’s regular body pulses.
This closely correlated with an accelerated speed through the water, with the jellyfish moving at around four to six centimeters per second. Further to this faster movement, the team measured the oxygen intake of the jellyfish while they swam as a way of tracking their energy levels, finding that they used only around twice as much energy despite traveling around three times as fast. Check out the race below.
"We've shown that they're capable of moving much faster than they normally do, without an undue cost on their metabolism," says Stanford graduate student and co-author Nicole Xu. “This reveals that jellyfish possess an untapped ability for faster, more efficient swimming. They just don't usually have a reason to do so."
Through further development of their prosthetics, Xu and Dabiri hope to give them reason to do so. From here, the team hopes to improve the technology so that in addition to controlling the pace of the jellyfish, it can also guide them in different directions and enable them to respond to signals from onboard sensors.
"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,” says Dabiri.
The research was published in the journal Science Advances, while the video below offers an overview of the research.