A team of engineering researchers has invented soft robots inspired by jellyfish capable of outswimming their real-life cousins in the sea, according to a new paper published in the journal Advanced Materials Technologies.
Jellyfish-inspired soft robots swim faster
Developed jointly under the purview of researchers at North Carolina State University and Temple University, the soft jellyfish-bots make use of a technique that uses pre-stressed polymers — which strengthen the pseudo-jellyfishes' proverbial hands.
"Our previous work focused on making soft robots that were inspired by cheetahs — and while the robots were very fast, they still had a stiff inner spine," said Jie Yin, assistant professor of aerospace and mechanical engineering at NC State, and corresponding author of the new paper. "We wanted to make a completely soft robot, without an inner spine, that still utilized that concept of switching between two stable states in order to make the soft robot move more powerfully — and more quickly. And one of the animals we were inspired by was the jellyfish."
Together, the researchers invented their new soft robots from two bonded layers of identical elastic polymer. The first layer was pre-stressed (or stretched), while the second wasn't, and contained a channel of air.
"We can make the robot 'flex' by pumping air into the channel layer, and we control the direction of that flex by controlling the relative thickness of the pre-stressed layer," added Yin.
Engineering jellyfish robots
When the pre-stressed layer is combined with a third stress-free layer (called the intermediate), it tries to move in a specific direction. For example, if we take a polymetric strip — pre-stressed by being pulled in two directions — and attach it to the intermediate layer, the result is a bilayer strip with a downward curve (a frown).
If the bilayer strip — which is also called the pre-stressed layer — is thinner than the air channel layer, the "frown" curve will bend up into a smiling curve while air is pumped into the channel layer. But if the pre-stressed layer is thicker than the channel layer, the so-called frown will grow more and more extreme as air moves into the channel layer via a pump.
Smiling or frowning, once the air leaves the channel layer, the material snaps back to a "resting" state of indifference.
The video above shows the jellyfish-bot in action, in addition to a crawling robot with rasping claw — both of which use the pre-stressed technique, according to phys.org.
Jellyfish-bots are fast, but slightly complicated
Jellyfish-bots work much the same way — resembling the way larval insects curl their bodies before jumping forward with released energy.
However, jellyfish-bots are a little more complicated — the pre-stressed disk-like layer is stretched in a whopping four directions. Additionally, the channel layer is different, consisting of an air channel in the shape of a ring. The result is a novel dome that resembles a real-life jellyfish.
When the jellyfish-bot "relaxes," the dome curves up like a little bowl. But when air is pumped back into the channel layer, the dome rapidly curves down, pushing water out and propelling the entire contraption forward in the ocean.
Experimental testing saw the jellyfish-bot make an impressive 53.3 millimeters per second. Relative to an actual jellyfish's average speed of 30 millimeters per second, this is worth a little praise.