Soft robot prototypes leap continuously under infrared light

Under an infrared lamp, a teardrop-shaped robot from North Carolina State University twists tighter, snaps against the ground and springs into the air. Then it returns to its original shape and starts again. The soft robot can keep leaping for as long as infrared light remains present, according to the researchers’ proof-of-concept tests.

The mechanism is compact. A ribbon made from liquid crystal elastomer contracts at its surface when exposed to infrared light, while a thin V-shaped aluminum tube prevents the robot from rolling in place. The resulting twist stores elastic energy; once it reaches a critical point, the V snaps downward and launches the teardrop. Because the ribbon restores its original shape after releasing that energy, the cycle resets itself.

Geometry controls the behavior. With the V opened to 120 degrees, the robot crawls forward. At 90 degrees, it jumps forward. At 50 degrees, it leaps vertically. Fangjie Qi, the paper’s first author and a postdoctoral researcher at NC State, says adding a small amount of weight to the rounded end improved the distance and stability of forward motion. Light intensity still sets a boundary: too little fails to trigger the movement, while too much can send the robot in unpredictable directions.

The team tested the robots across slopes, hurdles and surfaces including grass, sand, rocks and mulch. Jie Yin, a professor of mechanical and aerospace engineering at NC State, says the work could eventually be explored for environmental navigation, swarm robotics and unstructured terrain navigation. The paper appears in the Proceedings of the National Academy of Sciences.

So what does it change in practice? For now, it gives soft-robotics researchers a self-resetting locomotion mechanism that can be tuned with one geometric parameter and powered by light. It does not yet deliver an immediate application or a field-ready machine: the evidence is limited to proof-of-concept testing, and the researchers describe potential uses rather than a current deployment.