Deep sea pioneers: Caltech’s jellyfish biohybrid robots to unveil ocean secrets

Their study, published in the journal Bioinspiration & Biomimetics in February, details how transforming jellyfish into biohybrid robots can enable the collection of crucial data from the ocean.

These jellyfish are equipped with electronics that enhance their swimming capabilities and a prosthetic “hat” that improves their streamlined movement while carrying small payloads.

Consequently, these innovative data-gathering devices can measure temperature, salinity, and oxygen levels, providing valuable insights into the effects of climate change on these factors.

Pioneering the project

Simon Anuszczyk, MSc, a graduate student at Caltech Graduate Aerospace Labs and lead author of the study, explains how jellyfish are ideal for muscle stimulation experiments due to their lack of pain receptors. “Jellyfish are the most efficient metazoan in terms of cost of transport,” Anuszczyk told IE in an interview. “Previous work has tried to replicate this efficiency using robotics, so why not use the animals themselves as biohybrid robots.”

Conducted in the lab of John Dabiri, PhD, a Centennial Professor of Aeronautics and Mechanical Engineering at Caltech, the research builds upon his earlier work on augmenting jellyfish. “It’s well known that the ocean is critical for determining our present and future climate on land, and yet, we still know surprisingly little about the ocean, especially away from the surface,” Daibir explains. “Our goal is to finally move that needle by taking an unconventional approach inspired by one of the few animals that already successfully explores the entire ocean.”

Anuszczyk, who has worked on the project for two years, explains the team’s goal to capitalize on jellyfish efficiency to enable more thorough and cost-effective ocean exploration. “Jellyfish live throughout the ocean at different temperatures, salinities, and depths as deep as the Mariana Trench,” he adds.

“Jellyfish are the original ocean explorers, reaching its deepest corners and thriving just as well in tropical or polar waters,” explains Dabiri. “Since they don’t have a brain or the ability to sense pain, we’ve been able to collaborate with bioethicists to develop this biohybrid robotic application in a way that’s ethically principled.”

Insights into the research

In earlier experiments, the team attached electronic pacemakers to jellyfish to regulate their swimming speed. They found that increasing the jellyfish’s speed beyond their usual leisurely pace greatly enhanced their energy efficiency.

Building on this, they have now added a “forebody,” resembling a hat, to the top of the jellyfish’s bell. These attachments streamline the jellyfish’s movement and provide additional space for sensors and other electronic devices.

“We designed the biohybrid robotic system to be cheap and easy to implement. We use microelectronics to stimulate the jellyfish. The hats allow us to include sensors to learn more about the ocean,” says Anuszczyk. “The system uses a combination of off-the-shelf electronics and 3D-printed waterproof housings to control the jellyfish.”

The graduate student explains that after building the electronics, they inserted electrodes into the jellyfish’s muscle tissue to control their contractions. “After removing the electronics, the jellyfish quickly heal, generally in around 24 hours, and are able to return to normal behavior,” he reveals. We use fully grown jellyfish from a local aquarium and care for them in facilities on campus.”

Testing the waters

To evaluate the jellyfish’s swimming abilities, the researchers constructed a towering vertical aquarium spanning three stories inside Caltech’s Guggenheim Laboratory. The tank is tall, rather than wide, to help them collect data on oceanic conditions far below the surface.

“This work found that the biohybrid jellyfish can swim almost 4.5 times faster than natural jellyfish while carrying a payload larger than themselves:, says Anuszczyk. “This could allow us to explore the ocean with a number of scientific sensors onboard the jellyfish biohybrid robots.”

“In the ocean, the round trip from the surface down to several thousand meters will take a few days for the jellyfish, so we wanted to develop a facility to study that process in the lab”, Dabiri explains. “Our vertical tank lets the animals swim against a flowing vertical current, like a treadmill for swimmers. We expect the unique scale of the facility – probably the first vertical water treadmill of its kind – to be useful for a variety of other basic and applied research questions.”

A major obstacle in current ocean exploration is the significant expense, which can soar up to USD 50,000 per day for a research vessel. However, according to Anuszczyk, these jellyfish can be equipped for approximately USD 20 each, potentially enabling the deployment of swarms of robots to conduct more comprehensive ocean exploration in the future.

“We are particularly interested in using these biohybrid jellyfish robots for deep sea exploration in the Mariana Trench where engineering even conventional robots can be challenging due to the crushing pressures,” Anuszczyk says. “Jellyfish are 95 percent water and can adapt to high pressures meaning that only the sensor package would need to be hardened to protect the sensors while the locomotion would be provided by the animal.”

Additionally, the jellyfish power their own locomotion through feeding, requiring only enough battery power for the sensors in general.

Challenges and future plans

Eager to uncover the insights gained from exploring the ocean’s depths for the first time, Anuszczyk highlighted the challenges of working with animals and emphasizes the need for proper care.

“It turns out waterproofing electronics and 3D printed parts is incredibly challenging, especially in seawater,” he adds. “Figuring out a system that kept the electronics protected and interfaced well with the animal required lots of prototyping and iteration to get everything to fit.”

With a keen focus on reducing ocean pollution and minimizing additional waste, the team is now actively investigating the potential of biodegradable electronics for future applications. “At this point, we plan to retrieve the animals after their exploration missions so that we can download the data, remove the electronics, and release the jellyfish back into the ocean,” Anuszczyk adds.

The team is now advancing their research on multiple fronts, including exploring long-term stimulation to understand how the animals behave and feed during exploration missions. “We are also interested in improving our systems to withstand the high pressures they might experience at the bottom of the ocean,” highlights Anuszczyk.

“We have collaborated with bioethicists to study these experiments and follow all protocols for ethical research on these animals,” he concludes. The most important point I want to stress is that there is so much to explore in the ocean and we hope that these biohybrid robots will be able to contribute to our understanding of how climate change impacts the ocean.”