Paging Doctor Nano Worm

The idea of nano machines that can repair cells, deliver drugs and diagnose medical problems has been a mainstay of SF for decades, the shiny, happy twin of the idea that one day grey goo will surely destroy us all. It's also a concept that's taken one tiny step closer thanks to a team of scientists in Oxford, reports New Scientist .

The scientists have apparently perfected a prototype "walker", a nanonmachine made of two connected feet, in turn built of a short DNA sequence. The walker's DNA "plugs" into a complementary sequence on the DNA of the patient and the impetus for forward motion is provided, cleverly, by the feet "competing" for a foothold. Only one can be connected at a time so as one foot falls, the other is forced to lift, propelling the walker forward. Power is provided by nearby molecules, which release energy when a specific catalyst is present. That catalyst is the walker's feet themselves, triggering a chemical reaction and pushing the walker forward every time a foot lifts.

Even better, the walker is designed so the back foot is the only one that can lift. The walker can put its foot back in the same place and move it forwards but can never take a backward step ensuring it's always attached to its DNA track.

The walker isn't perfect by any means, the biggest problem being that the DNA track can get tangled and stop the walker moving. This means the walker has, so far, only taken a single step but the team hope to move it up to 100 nanometres soon. They've already been able to stop and start the motor by controlling the fuel intake and future plans include allowing multiple walkers to interact and attaching "cargo", allowing it to deliver drugs directly to injured or sick areas.

So who knows? In a few years you may find yourself being treated by two doctors, one you go and see and one you can't see, patiently walking up your DNA strand towards the injured areas of your body. Sort of the ultimate house call...

This article contributed by Alasdair Stuart, of Hub magazine ( ). Find more about the walker at New Scientist .