It may sound more like science fiction than science fact, but researchers have created bionic jellyfish by embedding microelectronics into these ubiquitous marine invertebrates with hopes to deploy them to monitor and explore the world's oceans.
A small prosthetic enabled the jellyfish to swim three times faster and more efficiently without causing any apparent stress to the animals, which have no brain, central nervous system or pain receptors, the researchers said.
The next steps will be to test ways to control where the jellyfish go and develop tiny sensors that could perform long-term measurements of ocean conditions such as temperature, salinity, acidity, oxygen levels, nutrients and microbial communities. They even envision installing miniscule cameras.
"It's very sci-fi futuristic," said Stanford University bioengineer Nicole Xu, co-author of the research published this week in the journal Science Advances. "We could send these bionic jellyfish to different areas of the ocean to monitor signs of climate change or observe natural phenomena."
An initial goal will be deep dives because measurements at great depths are a major gap in our understanding of the oceans, added California Institute of Technology mechanical engineering professor John Dabiri, the study's other co-author.
"Basically, we'd release the bionic jellyfish at the surface, have it swim down to increasing depths, and see just how far we can get it to go down into the ocean and still make it back to the surface with data," Dabiri added.
The study involved a common type of jellyfish called moon jellyfish, with a diameter of 4-8 inches (10-20 cm).
Jellyfish propel themselves through the water by contracting their muscles to collapse their umbrella-shaped body, and then relaxing. The prosthetic - basically a chip, battery and electrodes that stimulate the muscle - causes the jellyfish to pulse their bodies more frequently, akin to how a pacemaker regulates heart rate. The prosthetic is eight-tenths of an inch (2 cm) in diameter.
Jellyfish are known to secrete mucus when stressed. No such reaction occurred during the research and the animals swam normally after the prosthetic was removed, the researchers said.
"Care is taken not to harm the jellyfish," Dabiri said.
There are many existing technologies to study the ocean near the surface including satellites and robotic sailboats called saildrones, Dabiri said.
But knowledge of the ocean declines at depths greater than about 65 feet (20 meters), where researchers must rely either on instruments deployed from ships - costly to operate - or use smaller underwater vehicles typically limited to day-long operation due to energy-storage limitations, Dabiri added.
"Jellyfish have existed for over 500 million years, and over that time, their body structure has remained largely unchanged, so it's interesting to figure out what makes them so special and how we can learn from them," Xu said.
"Because we use animals with natural swimming motions, the hope is that they won't disturb the environment in the same way that a submarine might, so we can expand the types of environments we can monitor," she added.