Bionic jellyfish could be the next deep-ocean explorers
Scientists say they swim faster and longer than the real thing.
In the world of deep-sea creatures, jellyfish are pretty innocuous. These blobs of sea-goo don't have any brains or pain receptors, they don't move particularly fast and they're not likely to harm you -- unless you get too close to their stingers, of course. Despite their lack of ferocity (or perhaps because of it) a team of scientists from Stanford and Caltech have zeroed in on these creatures at possible candidates for deep-sea exploration. But to unlock their hidden potential, the jellyfish needed a bit of an upgrade. That's why they created a bionic jellyfish.
The study, published Wednesday in the journal Science Advances, looked at how cheap electronic devices could be implanted in these jellyfish to learn more about their biological processes while simultaneously improving their overall performance. To do this the team implanted microelectronic controllers capable of emitting electronic pulses into the bell-shaped heads of six jellyfish and secured them in place using small, wooden pins. Jellyfish naturally use a pulsing motion to propel themselves forward through water, typically at a speed of about two centimeters (less than an inch) per second, but the implanted microcontroller allowed scientists to speed-up this process by sending pulse signals to the jellyfish at three times their normal rate.
While there's no shortage of bio-inspired robot creatures in the world today (including bees, dogs and even other fish,) these biohybrid jellyfish differ because instead of mimicking nature, they enhance it.
And while it might sound ethically problematic to create so-called biohybrid jellyfish, the researchers write in the study that the jellyfish used in the trials completely returned to normal following the experiment, bar some cosmetic denting at the implantation point.
The scientists observed that these pulses drove the jellyfish to swim more than double their original speeds, reaching speeds of four to six centimeters (between 1.5 and 2.3 inches) per second. Even more, by measuring the amount of oxygen the jellyfish used, the team also observed that these bionic jellyfish were swimming 1,000 times more efficiently than their slower counterparts. All the while the team monitored the jellyfish's level of discomfort by looking for a type of mucus jellyfish secrete when stressed, but found that the jellyfish appeared mostly unperturbed by the implant as well as their increased swimming speed.
Stanford graduate researcher and first author on the study, Nicole Xu, said in a statement that the jellyfish's comfort with this new speed suggests that they were probably capable of swimming that fast all along, but simply hadn't bothered before.
"We've shown that they're capable of moving much faster than they normally do, without an undue cost on their metabolism," Xu 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."
Because of these jellyfish's unlocked potential, as well as their inherent ability to live in a variety of sea depths and salinities, the researchers write that they would be good candidates for human-aided exploration of watery unknowns in the deep sea. The study's co-author and Centennial Professor of Aeronautics and Mechanical Engineering at Caltech, John Dabiri, tells Inverse that this would be an advantage to other purely bioinspired robots because it helps researchers accomplish the elegance of a biological system with the mechanics of robotic ones.
"Biological systems can directly use chemical energy from prey to power the actuators (i.e. muscles), whereas in our engineering mimics, we’ll often need to use a battery to power a motor, which in turn moves gears/pulleys/etc., and then finally we can achieve body motions that resemble the biological systems. It’s often the case in mechanical systems that we can achieve either large forces or large motions, but not both. Biological systems can do both."
Dabiri also says that these biohybrid jellyfish have an advantage in being able to self-heal as well.
But before these jellyfish begin exploring sunken pirate ships and deep-sea vents, there are some technical improvements that still need to be made. Namely, while this study demonstrated that microcontrollers are capable are driving jellyfish movement without disturbing the jellyfish, the team wasn't able to control where the jellyfish swam or to see what it encountered along the way.
Dabiri said in a statement that future research should be done to develop even smaller sensors that can be permanently implanted into the jellyfish's tissue to direct their movement.
"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," Dabiri 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."
But while Dabiri tells Inverse that a similar approach could be used on land and air animals as well, their pain receptors would make it much more challenging to do ethically.
"[T]he same principles can be applied ethically in other animal systems, then it’s conceivable that robots on land and in the air could also be achieved using a similar approach. But, given that most other animals do have pain receptors, many have a central nervous system, etc., it could be ethically fraught to go down that path in those cases."
Abstract: Artificial control of animal locomotion has the potential to simultaneously address longstanding challenges to actuation, control, and power requirements in soft robotics. Robotic manipulation of locomotion can also address previously inaccessible questions about organismal biology otherwise limited to observations of naturally occurring behaviors. Here, we present a biohybrid robot that uses onboard microelectronics to induce swimming in live jellyfish. Measurements demonstrate that propulsion can be substantially enhanced by driving body contractions at an optimal frequency range faster than natural behavior. Swimming speed can be enhanced nearly threefold, with only a twofold increase in metabolic expenditure of the animal and 10 mW of external power input to the microelectronics. Thus, this biohybrid robot uses 10 to 1000 times less external power per mass than other aquatic robots reported in literature. This capability can expand the performance envelope of biohybrid robots relative to natural animals for applications such as ocean monitoring.
- This article has been updated to include comments from the researchers