A communication published online in Angewandte Chemie describes what you could call a working nano-motor. Ayusman Sen and his coworkers at Pennsylvania State University have prepared little spheres less than a micrometer across - one side of the sphere is gold and the other side is silica (SiO2). On the silica side they have attached a Ruthenium compound known as a Grubbs Catalyst. The Grubbs Catalyst reacts with alkenes which are the "fuel" for the motor.
|Image via Angewandte Chemie|
When they place their motor-particles in a solution containing norbornene, the catalyst group on the silica side of the particle polymerizes the norbornene, and the amount of unreacted norbornene molecules on the silica side of the particle decreases. This causes a concentration gradient - the concentration of norbornene on the gold side is higher than the concentration of norbornene on the silica side.
It is this difference in concentration of "fuel" molecules that makes the particle move. Osmosis involves solvent molecules moving from a region where concentration is low, to a region where concentration is high. As a result, solvent molecules flow around the "nano-motor" from the silica side (less norbornene - because the Grubbs cayalyst polymerized it) to the gold side (lots of norbornene). And this causes the particle to move in the opposite direction.
Professor Sen anticipates that eventually you could redesign his nano-motor to use a "fuel" like glucose and doctors could use it in the bloodstream to repair damaged tissue. Just like something out of Fantastic Voyage.
Image via Wikipedia
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Original research article: A Polymerization-Powered Motor DOI: 10.1002/anie.201103565