Lab-built BeanBot jumps without motors or software

A small shell hits the ground, and what happens next depends less on a command than on the surface beneath it. BeanBot, built by researchers in the Italian Institute of Technology’s Bioinspired Soft Robotics department, can jump, roll, flip, slide and climb slopes without motors, batteries, sensors or onboard computing.

Its engine is a tiny heat-responsive spring made from a shape-memory alloy, a material that changes shape when heated. Magnets hold the spring as it stores energy; once it reaches about 70–80°C, the spring releases that energy suddenly and pushes the bean-shaped shell into the air. The shell then determines the next move rather than following software instructions.

The design has one curved side and two flat sides. The curved side lets BeanBot roll, while the flat sides help it remain stable and can help it climb slopes between 10 and 18 degrees. The shape can also help it turn itself over after landing. In tests of 92 jumps, about 81.5 percent developed into further movements such as rolling, sliding, bouncing or flipping.

The results are small but tangible: BeanBot can jump as high as about 30 centimetres and roll around 80 centimetres. Its shell weighs about 3.8 grams, and the jumping module about 8 grams. The complete system combines a 3D-printed shell, the spring and magnets, with no onboard electronics.

Concretely, BeanBot shows how a robot’s body and surroundings can take over part of the work normally assigned to sensors, computers and software. That could offer a simpler way to produce varied movement in complex environments, but the current machine is slow: activation takes 30 to 180 seconds, and recovery takes 130 to 140 seconds before another cycle. The researchers say future material improvements could reduce those times and lower the temperature needed to trigger a jump.