Figure 1 - Molecule by molecule delivery process.

a, Reactive polymer molecules, attached at one end to an AFM tip, are brought into contact with a substrate to which they can become linked by a chemical reaction. When the tip is pulled away from the surface, the resulting mechanical force causes the weakest bond — the one between the tip and polymer — to break. b, During the tip–sample contact, a chemical reaction occurs between the activated esters of a poly-N-succinimidyl acrylate chain grafted to the tip and the amino groups of the substrate to form an amide bond, which covalently links the chain to the substrate.