Mechanochemistry:: targeted delivery of single molecules

The use of scanning probe microscopy-based techniques to manipulate single molecules(1) and deliver them in a precisely controlled manner to a specific target represents a significant nanotechnological challenge(2,3). The ultimate physical limit in the design and fabrication of organic surfaces can be reached using this approach. Here we show that the atomic force microscope (AFM), which has been used extensively to investigate the stretching of individual molecules(4-12), can deliver and immobilize single molecules, one at a time, on a surface. Reactive polymer molecules, attached at one end to an AFM tip, are brought into contact with a modified silicon substrate to which they become linked by a chemical reaction. When the AFM tip is pulled away from the surface, the resulting mechanical force causes the weakest bond - the one between the tip and polymer - to break. This process transfers the polymer molecule to the substrate where it can be modified by further chemical reactions.