Researchers at Northwestern University have created "legged metamachines" — modular robots assembled from autonomous, Lego-like segments that can reconfigure themselves, survive serious damage, and adapt their movement on the fly.

The study, published March 6 in the Proceedings of the National Academy of Sciences, was led by Sam Kriegman at Northwestern's Center for Robotics and Biosystems.

How It Works

Each module is a self-contained robot: half a meter long, with its own motor, battery, and computer. Alone, a module can roll, twist, and hop. Connected in groups, they communicate and produce entirely new locomotion styles — bounding like lizards, undulating like seals, springing like kangaroos.

The key innovation: the body designs were not created by human engineers. The team fed an AI evolutionary algorithm a set of building blocks and a single goal — move efficiently. Over thousands of simulated generations, weak configurations were discarded and strong ones refined. The results look nothing like any existing robot.

Indestructible by Design

In outdoor tests, the machines crossed gravel, mud, grass, and tree roots without stopping. When a module detaches, the remaining structure adapts its gait and continues. The detached module keeps moving independently and can rejoin the group.

"They can survive being chopped in half or cut up into many pieces," Kriegman said.

The team claims these are the first robots to step outdoors after evolving entirely inside a computer simulation — a meaningful milestone for evolutionary robotics.

Current limitations: no outward-facing sensors, no obstacle awareness, slow movement. But the researchers' goal isn't a finished product — it's a new design philosophy where robots are evolved for their environment rather than engineered for it.