Light-powered soft robots can keep jumping forever
North Carolina State University researchers have built soft robots that leap, crawl and reset themselves continuously under infrared light.
Researchers at North Carolina State University have built soft robots that can keep jumping as long as they remain under infrared light. The tiny teardrop-shaped machines store energy by twisting themselves, launch into the air and then reset during flight — no motors, batteries or pit crew required.
What’s actually going on: each robot is made from a liquid crystal elastomer ribbon shaped like a teardrop, paired with a thin V-shaped aluminium tube. Infrared light makes the ribbon’s surface contract. The V-shaped tail stops the robot from simply rolling, forcing the ribbon to twist and store elastic energy until it reaches a critical point.
At that point, the tail snaps against the ground and launches the robot. Once airborne, the ring untwists back towards its original shape, allowing the cycle to repeat under constant illumination. The researchers describe this as a self-resetting mechanism for autonomous, continuous leaping.
Small changes to the tail geometry control the movement. A 120-degree V angle produces crawling, 90 degrees creates forward jumping and 50 degrees produces vertical leaps. Adding a little weight to the rounded end changes the centre of mass and can improve forward distance and stability.
The team reports vertical jumps exceeding 80 body heights and directional leaps longer than three body lengths. In proof-of-concept tests, the robots crossed slopes, hurdles, grass, sand, rocks, mulch, water surfaces and water–land interfaces. Infrared intensity also mattered: too little light failed to trigger the behaviour, while too much made movement erratic.
Why you should care: soft robots are attractive for environments where rigid machines struggle, but continuous movement usually requires batteries, motors or complicated mechanisms. This design turns light into stored mechanical energy and uses its own shape to reset for the next jump. That could eventually help with environmental navigation, swarm robotics and unstructured terrain — although the researchers stress that there are no immediate applications yet.
The study was published in PNAS under the title “A Self-Resetting Soft Ring for Autonomous, Continuous Leaping in Unstructured Environments”. The authors are Fangjie Qi, Caizhi Zhou, Haitao Qing, Haoze Sun, Yaoye Hong and Jie Yin.
Our opinion
A robot that jumps forever sounds like the opening scene of a tiny machine uprising, but the engineering is wonderfully grounded. The clever part is not simply making something leap; it is making the same motion reset the robot automatically. It is still a laboratory demonstration, yet a light-powered machine that can negotiate grass, rocks and water is precisely the sort of odd little breakthrough that may become useful once someone works out how to make a swarm behave itself.