Bouncing off biology: legless robots leap 10ft in the air

Lead coauthor of the paper and a postdoctoral researcher in the School of Chemical and Biomolecular Engineering (ChBE), Sunny Kumar commented: “Nematodes are amazing creatures with bodies thinner than a human hair. They don’t have legs but can jump up to 20 times their body length. That’s like me laying down and somehow leaping onto a three-story building.”

What are nematodes, and why do they jump?

Nematodes, also known as roundworms or eelworms, are one of the most abundant creatures on Earth. While most feed on microorganisms in the soil and water, many species are parasitic, living in plants, animals, and humans.

The way some of these parasitic nematodes latch onto a new host is by bending their form and then, like a spring uncoiling, rapidly jumping.

Looking into this novel way of moving is Victor Ortega-Jimenez, a lead author and former research scientist at Georgia Tech and now a faculty member at the University of California, Berkeley, who, using high speed cameras, watched as these creatures bent their bodies based on the direction they wishes to travel.

The mechanics behind the leap

Ortega-Jimenez spent more than a year refining a method to reliably trigger and capture the nematode jumps on film. What he discovered was that the nematodes used a form of movement based on energy storage through body kinking.

To jump backwards, nematodes raise their head and bend the middle of their body into a tight kink – similar to a person crouched before a backflip. This bent shape stores energy, which is rapidly released, launching the worm end over end in reverse.

To jump forwards, the worm directs its head straight while arching the rear part of its body upwards. This stance is more like someone preparing for a standing long jump. Rather than moving horizontally, however, the worm catapults upwards with remarkable height. Kumar commented that “Changing their centre of mass allows these creatures to control which way they jump. We’re not aware of any other organism at this tiny scale that can effectively leap in both directions at the same height.”

Ishant Tiwari, ChBE Postdoctoral Fellow and lead coauthor of the study, added: “Kinks are typically dealbreakers. Kinked blood vessels can lead to strokes. Kinked straws are worthless. Kinked hoses cut off water. But a kinked nematode stores energy that is used to propel itself in the air.”

Turning biology into engineering

The device is a soft robot that is able to mimic the required movement. It is made with a silicone rod embedded with a carbon-fibre spine – a structure that allows the robot to quickly store and release energy, within a tenth of a millisecond, repeatedly.

But what’s it all about? Why look into these different modes of moving? Well, the findings suggest that engineers could build simple elastic systems from carbon fibre or similar materials that could be tailored to move across numerous environments where traditional devices, such as those with wheels or legs, may struggle. Meaning these robots could be deployed in search and rescue missions, where the ability to traverse unpredictable terrain and obstacles is paramount.

“Our lab continues to find interesting ways that creatures use their unique bodies to do interesting things, then build robots to mimic them,” said Kumar.

Image credit: Candler Hobbs, Courtesy of Georgia Tech