Scientists have created microscopic robots out of DNA molecules that can walk, turn and even create tiny products of their own on a nano-scale assembly line.

The ground-breaking devices outlined in the journal Nature, could one day lead to armies of surgeon robots that could clean human arteries or build computer components.

In one of the projects a team from New York's Columbia University created a spider bot just four nanometres across. This is about 100,000 times smaller than the diameter of a human hair.