It’s tough for marine biologists to study deep sea creatures in their natural habitat.
Jellyfish and squid that live a mile or two underwater dwell beyond the range of scuba-diving scientists, who must rely on submarines to explore the near complete darkness at those depths. Once in a while, detritus samplers and other collection tools attached to submersibles can capture the diaphanous animals. But the delicate creatures are at risk of getting stuck in the sampler or destroyed on their way to a lab on dry land.
That’s why David Gruber, a marine biologist at the City University of New York, and a team of engineers are developing soft robots capable of gently grasping live jellyfish and studying them without harming the specimens.
“I always felt that it was a little strange for me as a marine biologist to have to kill the animals that I love and study,” Dr. Gruber said. “I wanted tools that were more gentle, that were able to grasp jellyfish but not hurt them, and that would allow me to swab the creatures and do different things.”
To create a robot strong enough to work in the deep sea, yet gentle enough to handle gelatinous jellyfish that are about 95 percent water, the scientists came up with a six-fingered gripper that could open and close around the animals. They described their design in the journal Science Robotics on Wednesday.
Each of the six noodle-like fingers is composed of thin strips of silicone with a hollow channel inside. The inside edges of the fingers have a stiffer nanofiber coating that controls how they curve. They are attached to a 3D-printed rectangular palm in such a way that they can be removed individually and replaced if they start to become arthritic.
A switch at the back of the gripper fills the channels inside the silicone fingers with water, forcing them to curl shut in the direction of the nanofiber coating. This helps maintain an ultragentle grip; the fingers exert less than one-tenth of the pressure that a human eyelid exerts on the eye.
“When the fingers close, they’re almost cradling the animal, giving it a nice, gentle hug,” said Nina Sinatra, a mechanical engineer and a former graduate student at the Wyss Institute for Biologically Inspired Engineering at Harvard, who helped design the robot.
The robotic gripper is just one in a set of tools the researchers are working on to improve the study of soft-bodied marine organisms. Last year, they revealed another variation of a robot that folds like origami to hold jellyfish for observation without harming them.
But the researchers found that some jellyfish showed signs of stress if the origami robot’s folds didn’t align properly. So the team decided to make a tool that would be less heavy-handed.
First, they needed to find the best angle and speed at which their robot’s fingers would close while underwater. Then they tested the gripper at the New England Aquarium. The device successfully nabbed an assortment of organisms about the size of a golf ball: swimming moon jellies, jelly blubbers and spotted jellies.
The jellyfish were unable to break free until the robot’s fingers unfurled. And they didn’t show any signs of stress or other adverse effects after being released.
The robotic gripper can open and close about 100 times before it starts to show signs of wear. That’s enough to sample plenty of deep sea creatures on a research mission, but scientists hope to continue to refine the tool’s robustness and capabilities, Dr. Gruber said.
Adding cameras and sensors to the gripper could help make it a portable underwater laboratory. Scientists could steer it toward deep sea jellyfish of interest using a joystick, grab a specimen to study, scan its body, swab for DNA and record physiological responses before letting the creature go.
“It’s important to be gentle as we explore new frontiers,” Dr. Gruber said. “If we can be gentle with animals that are almost 95 percent water, we can learn so much about these deep sea creatures.”