Watch: These robots can keep jumping forever

Researchers at North Carolina State University have developed soft robots that can jump repeatedly as long as they are exposed to infrared light. The unique design of these teardrop-shaped robots allows them to continuously jump without needing to reset between jumps. The secret lies in the way they store and release elastic energy using torsion.

The robots are composed of a liquid crystal elastomer ribbon, shaped like a teardrop, with a thin aluminum tube forming a V at one end. When infrared light is applied, the surface of the ribbon contracts, causing the robot to twist and store energy. The stiff V prevents the ribbon from rolling, leading to a twisting action that stores energy until the twist reaches a critical point. At this point, the robot releases the stored energy, causing the V to snap downward and propel the robot into the air.

By adjusting the angle of the V, the researchers can control the robot's movement. A wider angle results in a crawling motion, while a narrower angle causes the robot to leap vertically. The angle can even be fine-tuned to achieve forward jumps.

The jumping distance can also be improved by adding a small weight to the rounded end of the teardrop, altering the center of mass and resulting in a more powerful and stable forward motion. The intensity of the infrared light also plays a role, as it needs to be strong enough to induce jumping behavior but not so strong that it causes erratic and unpredictable jumping.

In tests, the robots demonstrated their ability to leap across various surfaces, including slopes, hurdles, grass, sand, rocks, and mulch. While there are no immediate applications for this technology, it represents a fundamental advance in soft robotics that could be useful for environmental navigation, swarm robotics, and unstructured terrain navigation in the future.