3. Quantum electrodynamic forces

As we saw in the previous paragraph, nanostructures require us to work at largely submicron scales. When two objects come into close proximity, separated by only a distance of between 10 nm and 500 nm, surface interaction forces appear. These may be repulsive or attractive, depending on the origin of the phenomenon concerned. In general, they act simultaneously and can be listed as follows:

• Van der Waals force (1 nm to 100 nm) ;

• Casimir force (50 nm to 1 µm) ;

• Pauli repulsion force (very small action radius – 0.1 nm);

• electrostatic force (when electric potentials are different) ;

• chemical bonding strength (very small radius of action – covalent, hydrogen, ionic, metallic bonding...);

• ...