Jellyfish seem made for their watery world. These gelatinous creatures, with tentacles that dangle from umbrella-shaped bodies, are 95 percent water. But their fragile bodies have made it hard for scientists to safely catch them for study. Until now. A new soft robot that mimics a human hand can gently catch and clasp jellyfish without harm.
“Jellyfish and other gelatinous animals … have a huge amount of potential to teach us things,” notes Nina Sinatra. She and her colleagues designed and built their new robot to make it easier to study those jellies. Sinatra is a mechanical engineer. That’s someone who uses physics and materials science to design gadgets with moving parts. She worked on the project while at Harvard University in Cambridge, Mass.
Her team described its new device August 28 in Science Robotics. Resembling a robotic hand, its six soft fingers can cradle a flopsy and fragile jellyfish.
“If we aren’t able to safely hold and handle these animals without damaging them,” says Hannah Stuart, “then it makes it really hard to study them.” Stuart is a mechanical engineer at the University of California, Berkeley, who did not take part making the robot. The new robot’s fingers are so soft and flexible that they might not be able to hold themselves up when outside of the water, she notes. But, she adds, the dangly strips work well when they are submerged.
The fingers clip onto a 3-D printed “palm.” It looks like a rectangular box. The scientists made the fingers out of layers of soft and rubbery silicone. One surface has a stiffer layer embedded with tiny nanofibers. The scientists made this layer tougher and less bendy.
Inside each finger is a channel through which water can flow. When directed to grab a jelly, the robot uses a pump to fill the channel with water from around the robot. This makes the fingers curl toward the stiffer side and close in around the jelly.
At first, the scientists designed the hand with four fingers, two each on opposite sides of the palm. But jellyfish easily wriggled out. “As we were trying to go in and give them a little soft hug, they would just exit stage left,” Sinatra quips. The scientists solved the problem by adding a finger to the top and bottom of the palm.
“[The fingers] have a gentle grasping force,” Stuart says. “It’s really the first time that somebody has demonstrated this [approach to handling such soft objects].” The amount of force the fingers exert is less than one newton. Stuart likens that force to the weight of an apple in someone’s hand. But to see if the robot can help biologists study jellies in the ocean, the team should test it in the field, she says. That might require attaching the hand to a deep sea submersible. The new robot should survive that. Its materials can withstand the pressure of the deep sea. Sea water won’t corrode them either.
This project aims to help scientists safely gather information on soft critters, Sinatra says. Her team is also thinking up ways to modify the hand so that it collects other information below the waves. The robot might someday include sensors, samplers that can grab a bit of DNA or cameras that take photos. Getting data on the creatures’ features in the ocean might mean scientists won’t even need retrieve the animal to study it.
The robotic hand also demonstrates how robots can take on all sorts of shapes and sizes, Sinatra says. “[A robot] doesn’t necessarily have to be C-3PO from Star Wars or a big assembly-line robot in a car-manufacturing plant,” she says. “Robots can be made of squishy things. They can be made of foam. They can be kind of whatever you imagine them to be.”
3-D printer A means of producing physical items — including toys, foods and even body parts — using a machine that takes instructions from a computer program. That program tells the machine how and where to lay down successive layers of some raw material (the “ink”) to create a three-dimensional object.
biologist A scientist involved in the study of living things.
colleague Someone who works with another; a co-worker or team member.
corrode (adj. corrosive) A chemical process that weakens or destroys normally robust materials, such as metals or rock.
DNA (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
field A term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.
force Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
jellies (in biology) These are gelatinous animals that drift in water (mostly seawater) or brackish (semi-salty) estuaries. For more than 500 million years, they have moved around the oceans by pumping pulses of water through their jelly-like tissue. Their body often has an umbrella-shaped bell. Trailing from around a central mouth may be many tentacles. Although jellies don’t have brains, they do have a nervous system which can sometimes detect light, movement or certain chemicals. Some members of this family, known as cnidarians, are known as jellyfish. In fact, none are true fish but related to hydras and corals.
mechanical engineer Someone trained in a research field that uses physics to study motion and the properties of materials to design, build and/or test devices.
newton A unit of force named for Sir Isaac Newton, a 17th century English physicist and mathematician. One newton is an amount that would give a mass of one kilogram an acceleration of one meter per second per second.
pressure Force applied uniformly over a surface, measured as force per unit of area.
robot A machine that can sense its environment, process information and respond with specific actions. Some robots can act without any human input, while others are guided by a human.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
sensor A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.
silicone Heat-resistant substances that can be used in many different ways, including the rubber-like materials that provide a waterproof seal around windows and in aquariums. Some silicones serve as grease-like lubricants in cars and trucks. Most silicones, a type of molecule known as a polymer, are built around long chains of silicon and oxygen atoms.
submersible A boat or submarine designed to work when it is completely underwater. Such vehicles are usually deployed for exploration or do research.
Journal: N.R. Sinatra et al. Ultragentle manipulation of delicate structures using a soft robotic gripper. Science Robotics. Vol. 4, August 28, 2019, p. eaax5425. doi: 10.1126/scirobotics.aax5425.