Computer scientists at Brandeis University say they have taken a significant step toward creating robots that will evolve into ever more sophisticated machines, capable of repairing and modifying their own hardware.

What they have come up with isn't exactly the "2001" film star, Hal, or even R2D2 of "Star Wars." But they have produced software that allows a computer to design structures, such as bridges and cranes, without human intervention.

"It's a kind of science fiction," conceded Jordan Pollack, associate professor of computer science at the university's Volen National Center for Complex Systems in Waltham, Mass. "But it works."

They pulled off their achievement with the help of toys designed for children, the ubiquitous Lego blocks that have spread from the kid's room to prestigious research laboratories around the world. The small plastic blocks, manufactured by international toy giant Lego Group, can be attached to each other in a variety of ways, making it possible to build robotic prototypes in minutes and with minimal cost.

Lego blocks were chosen because they lend themselves to modular construction techniques, according to graduate researcher Pablo Funes, who has done most of the work on the project.

"Legos are modular in the sense that they can be combined in different positions," Funes said. "Any brick can attach to any other brick."

The Brandeis scientists created algorithms, or computer programs, that established the basic physics needed to build strong structures. Then the computer was given a single Lego brick, along with a goal, called a "fitness function"--in this case to design a bridge two meters in length.

That single brick "mutated" into other bricks, and the computer tried many ways to assemble the bricks into a bridge. Each step along the way, it compared the structure with the physics model contained in the software.

"That program basically calculates whether or not the structure will collapse," Pollack said.

A day and a half later, the computer produced a cantilevered design for a bridge.

The scientists then broke out their set of Legos and built a real bridge exactly like the computer had designed.

It not only worked, Pollack said, but it was a good design. In fact, it took humans centuries to develop similar structures--bridges that are based on counterbalances.

The computer also designed a crane, based on an inverted triangle, and a table.