Researchers recently succeeded in building a molecular motor that "walks" in a single direction instead of wandering about randomly. This feat was already a breakthrough because it was difficult to coordinate the movement of the motor's two "legs" so that they moved in a synchronized way without the legs coming off a predefined track.

Now, Andrew Turberfield's team at Oxford has gone a step further by designing a nanorobot, or nanobot, that can be made to move in any direction along the track, as well as backwards and forwards. In contrast to previous bipedal motors, the new device only has one leg (made of synthetic DNA) anchored to a nanoscale track made of a double-stranded DNA backbone. The robot walks by taking tiny steps that involve its leg tethering and untethering to the DNA backbone and the machine is powered by different "fuel" DNA strands that push it along.

The track and robot are designed to self-assemble, explains team member Richard Muscat, and sections of each DNA strand are designed to bind together, or "hybridize", to form a double helix so the components of the system stick together in the way designed.

The fuel strands are used to pick up the molecular robot from one location and then move it to another position on the track – in steps of six nanometres at a time. Each track location has a unique "address" and the fuel is able to select which address the robot is sent to.

"Using this system, it is possible to navigate track structures such as branched junctions where the robot has the option of two available routes and is directed down one of them," Muscat told nanotechweb.org. "Previous research showed that it was possible to autonomously move a molecular machine along an unbranched track where the only option was to go forwards."

Spurred on by these new results, the team would now like to move the motor over longer tracks. "Using concepts and mechanisms developed in this research, we would also like to coordinate assembly of a chemical product, where a nanorobot moves between locations and picks up ingredients in a reaction," added Muscat. "This would be a nanoscale production line."

The results were described in Nano Letters.