Atomic force microscopy (AFM)

Principle

Atomic force microscopy (AFM) is a high-resolution surface imaging technique which operates by scanning a sharp probe over the surface of a sample, while measuring the forces experienced by the probe (Binnig G., Quate C.F. and Gerber C., Phys. Rev. Lett., 1986, 56, 930-933). In the most commonly used imaging mode, the probe and sample are brought in contact and the probe is scanned over the surface while the interaction force is kept constant. Alternatively, the deflection of the cantilever can be measured while the probe scans at constant height. This provides an image of the surface topography with (sub)nanometer scale resolution.
A major advantage of the AFM over classical microscopy techniques, is that it can simultaneously provide information on local physical properties, such as mechanical properties and interaction forces. In particular, force-distance curves, made by recording the deflection of the cantilever while the sample is moved up and down, allow one to measure directly surface forces in aqueous environments, such as van der Waals and electrostatic forces, solvation forces, steric forces and intermolecular forces between complementary molecules.