A self-resetting soft robot can repeatedly jump under infrared light, with simple design changes controlling how and where it moves.
A teardrop-shaped soft robot developed at North Carolina State University can keep jumping for as long as infrared light shines on it, without needing to be reset between leaps. Depending on a simple change to its geometry, the same design can crawl forward, jump ahead, or leap vertically.
The self-resetting movement comes from a mechanism that stores elastic energy through twisting and then releases it all at once. The work demonstrates a new approach to repeated jumping behavior in soft robotics.
“This ‘ring leaper’ design is very simple,” says Jie Yin, corresponding author of a paper on the work and a professor of mechanical and aerospace engineering at NC State. “We use torsion to store elastic energy and then release that energy all at once. And the nature of the design means that it does not need to be reset between jumps. It resets itself.”
Twisting motion powers repeated jumps
The robot consists of a liquid crystal elastomer ribbon formed into a teardrop, with a thin V-shaped aluminum tube attached at one end. Infrared light causes the surface of the ribbon to contract, which makes the ribbon rotate.
Instead of allowing the ribbon to simply roll, the stiff V at one end forces it to twist progressively tighter. Energy builds until the twist reaches a critical point. The stored energy is then released, snapping the V downward against the surface and launching the robot into the air.
Once that energy is released, the teardrop returns to its original shape and begins the process again. As long as the infrared light remains on, the cycle can continue.
Video of the robots. Credit: NCSU
One angle changes how robots move
A small change to the V-shaped end determines what kind of movement the robot produces.
“We found that we can control the nature of the robot’s movement by making minor design changes,” says Fangjie Qi, first author of the paper and a postdoctoral researcher at NC State. “If the V at one end of the teardrop is very wide – an angle of 120 degrees – the robot simply crawls forward. If you reduce the angle to 90 degrees, it jumps forward. And if you reduce the angle further to 50 degrees, the robot leaps vertically. In other words, a single geometric parameter determines whether it crawls, jumps forward, or leaps upward.
The researchers also found that adding a small amount of weight to the rounded end could improve jumping distance.
“We could also improve the robot’s jumping distance by adding a small amount of weight to the rounded end of the teardrop,” says Qi. “This changes the robot’s center of mass and leads to a more powerful and stable forward motion – much like a swimmer leaning forward as they dive off the starting block.”
Infrared light intensity provides another level of control. The light must be strong enough to trigger jumping, but excessive intensity can make the movement unstable.
“It has to be strong enough to induce the jumping behavior, but not too strong – because that can cause the robot to jump erratically and in unpredictable directions,” says Qi.
Soft robots cross difficult terrain
In proof-of-concept tests, the teardrop-shaped robots successfully leaped across slopes and hurdles and moved over surfaces that included grass, sand, rocks, and mulch.
The researchers are not proposing an immediate practical use for the design. Instead, they see the self-resetting mechanism as a foundation for exploring how soft robots might move through more complicated environments.
“There are no immediate applications for this work, but it’s a fundamental advance that is worth exploring for potential use in environmental navigation, swarm robotics, and unstructured terrain navigation,” says Yin.
Reference: “A self-resetting soft ring for autonomous, continuous leaping in unstructured environments” by Fangjie Qi, Caizhi Zhou, Haitao Qing, Haoze Sun, Yaoye Hong and Jie Yin, 27 August 2026, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2607940123
This work was done with support from the National Science Foundation under grants 2329674, 2445551 and 2527304.
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