A new palm-sized robot uses snapping elastic rods to move across land and water, mimicking the mechanics of a frog.

Researchers have developed a small, frog-like robot that utilizes a snapping motion to navigate diverse terrains and water. Detailed in a study published September 18 in Science Advances, the robot uses twisted elastic rods to store and release energy, allowing it to move without requiring high-output motors. The prototype, which weighs approximately 3.4 ounces, can hop across surfaces including wood, glass, leather, sand, and grass, and can swim when equipped with paddle attachments.

Mechanical design and propulsion

The robot's movement is driven by the rapid release of tension from bent elastic rods. By programming the rods to snap from one shape to another, the mechanism generates a strong push that propels the robot forward. The team used computer modeling and robotic arm experiments to determine that a helix-like shape provided the optimal energy release. To operate, a motor twists the rods until they reach a snapping point, then unwinds them to repeat the cycle. This design allows the robot to move at a speed of approximately three body lengths per second.

Potential applications and scalability

The researchers suggest that this mechanism could improve robots that operate in cluttered environments or require efficient movement with limited power. Because the design rules are based on the rod's shape and movement, the team believes the technology is scalable, potentially allowing for the creation of robots only a few millimeters in size. In testing, the robot demonstrated the ability to climb and descend steps. By utilizing only one of the two snapping rods, the robot can turn, allowing it to be steered through obstacle courses via remote control.