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Sticky Tech: Robots That Mimic Remoras Could Expand Ocean Exploration

Scientists studied how remoras hitch rides on sharks, rays and other animals to develop a device that does the same and that potentially could be used to study marine life and further the reach of underwater autonomous vehicles.

Written by Matthew O. Berger Published on Read time Approx. 3 minutes
Remoras hitching a ride with a devil ray in the Atlantic Ocean.Reinhard Dirscherl/ullstein bild via Getty Images

Li Wen first noticed remoras in 2012.

A postdoc at Harvard University at the time, he was working on 3D printing of synthetic shark skin. “I tried to find a nice image of a real shark online, then I noticed that there is always a parasitic fish attached to the shark,” said Wen, now a professor of bio-robotics at Beihang University in Beijing.

“We were pretty amazed by the morphological structure of the remora’s adhesive disc,” he said. “However, there was no systematic research” about the disc or how to use it to inspire technology for human use.

Jason Nadler had a similar thought a couple years earlier.

Nadler, a professor in materials science and engineering at Georgia Tech, had started looking into the unique capabilities of remoras, also known as suckerfish. Remoras use a disc-shaped sucker-like organ to attach to sharks, whales and other marine species, feeding on parasites, dead skin and food scraps and gaining protection against predators while they hitch a ride.

Figuring out how their adhesive disc works and what makes it so good at attaching and at resisting being knocked off by the shearing force of water could lead to innovations in adhesive technology that could be applied to deep ocean research, ship repair, moving cargo, underwater vehicles, bandages, biological research and reconnaissance. It’s one front in the expanding field of biomimicry, in which solutions to human problems are found by studying – and copying – natural phenomena.

When Nadler started looking into how to mimic remoras’ discs, he came across only one paper addressing the issue, he said.

“Why hasn’t anybody looked at this?” he wondered. Marine biologists, for instance, tag whales and other marine mammals with satellite transmitters to track their movements and study their behavior. “Why not look at what the animals that actually attach to them do?”

Nadler detailed the structure and properties of the remora’s adhesive system in 2012 study. He noted that geckos, tree frogs and insects had all been used as models for adhesives, but “the remora has been overlooked until now.”

His idea was to use detailed knowledge of the remora disc to engineer an adhesive that would be reversible and not damage the surface it sticks to.

Wen and a team of researchers this year developed a prototype of such an artificial remora-like adhesive. By 3D printing the main disc structure, laser-machining carbon-fiber spines and attaching them to flexible flaps, or lamellae, the researchers developed a prototype that remains adhered to the surface when pulled and twisted, according to a paper published last month in the journal Science Robotics.

Side-by-side comparison of a remora’s dorsal fin and a bioinspired composite robot. (Carla Schaffer/AAAS)

The artificial remora disc sucks onto a surface with its flexible out-turned lip to resist being pulled off and its carbon-fiber spines and flexible lamellae press against the surface to resist drag and shearing. In laboratory experiments, the device was firmly attached within four seconds on average, the researchers said.

The scientists then created an underwater robot that incorporates the prototype so it can adhere to smooth, rough and soft surfaces – and shark skin.

“Our next step is towards a reliable robotic device that can achieve reversible attachment and detachment underwater,” Wen said.

Biologists have expressed interest in using this “bio-robotic remora disc as a tag to monitor large marine animals’ behaviors,” according to Wen, who added it could also be used to grip large, relatively flat objects underwater.

While it’s not currently known when the technology will be ready for commercialization, the applications for that latter function could include the repair of ships, tunnels and bridges, where tools, lights or sensors need to be attached underwater, said study coauthor Yufeng Chen, postdoctoral fellow in materials Science and mechanical Engineering in the Wyss Institute at Harvard.

Close-up view of the artificial disc structure. (Wang et al, Science Robotics)

He also envisions remora-inspired adhesive technology being used in nonaquatic industrial settings and to enable autonomous underwater vehicles (UAVs) to travel further and cover more of the ocean by hitchhiking on large vessels – like real remoras. “This design has the potential to greatly extend the range and endurance of ocean exploration UAVs,” Chen said.

But the technology could also diverge further from its remora origins.

“I’m a big fan of not necessarily staying loyal to the entire system,” said Nadler, who wasn’t involved in the prototype project. He said some of the aspects of a remora’s adhesive disc could be extracted for new uses or end up not having “any real resemblance to the biological source. There’s no reason it needs to look anything like a remora’s pad.”

And then there’s the fact that just because remoras are great at adhering to surfaces, it doesn’t mean they can’t be better at it – or that humans can’t engineer something far superior.

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