5. Sensors using atomic force or molecular attraction

5.1 Principle

Atoms undergo forces of attraction or repulsion at a distance, depending on the pair of chemical elements present. The law of variation as a function of distance d is 1/d ² , since it is mainly electrostatic forces that come into play. This effect is used to measure surface profile or shape. When heterogeneity is present, the force exerted on the tip is not only orthogonal to the surface, but the blade supporting the tip undergoes torsion, which can also be measured.

The sensor uses a tip placed at the end of a cantilever blade, and a non-contact optical displacement measurement system measures the deflection of the blade with a resolution of 0.01 nm (figure