Scientists at Cornell University in Ithaca, New York, have created small robots that can build copies of themselves.

Each robot consists of several 10cm cubes which have identical machinery, electromagnets to attach and detach to each other and a computer programme for replication. The robots can bend and pick up and stack the cubes.

"Although the machines we have created are still simple compared with biological self-reproduction, they demonstrate that mechanical self-reproduction is possible and not unique to biology," Hod Lipson said in a report in the science journal Nature on Wednesday.

He and his team believe the design principle could be used to make long-term, self-repairing robots that could mend themselves and be used in hazardous situations and on space flights.

Copying robots 

The experimental robots, which do not do anything else except make copies of themselves, are powered through contacts on the surface of the table and transfer data through their faces.

They self-replicate by using additional modules placed in special "feeding locations".

The machines duplicate themselves by bending over and putting their top cube on the table. Then they bend again, pick up another cube, put it on top of the first and repeat the entire process. As the new robot begins to take shape it helps to build itself.

"The four-module robot was able to construct a replica in 2.5 minutes by lifting and assembling cubes from the feeding locations," said Lipson.