- Physical properties: surface topography, roughness, adhesion forces, elasticity, surface charge, surface composition
- Lateral resolution from micrometers to fractions of Ångströms
- Images collected in situ, in solution or gas
- Mass change with picogram resolution
The sample, mounted on a piezoelectric scanner, moves with subnanometre resolution. A sharp tip, mounted on a cantilever, feels the forces between itself and the sample. Deflections in the cantilever are monitored with a laser and a position sensitive detector to make maps of physical and chemical properties.
T. Hassenkam, A. Johnsson, K. Bechgaard and S. L. S. Stipp, Tracking single coccolith dissolution with picogram resolution and implications for CO2 sequestration and ocean acidification, Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 8571–8576
Atomic force spectroscopy (AFS) or Chemical force mapping (CFM)
- Adhesion force and elasticity maps with nanometre lateral resolution
- Unraveling of single molecules, proteins
- Properties of interfaces
A set of force-distance curves is collected as the tip is rastered over the sample. This probing of the surface forces is carried out in liquid. We often collect 10,000 curves over areas of 5 μm x 5 μm, to produce maps of 100 x 100 pixel information.
The reaction of the tip with the surface provides spectra and maps of how the adhesion forces are distributed over the mapped area. By functionalising the AFM tip, we can give it a specific character that can then be used to probe surface properties, such as hydrophobicity, negative or positive charge, elasticity and so on, allowing us to can make maps of surface forces and chemical properties of the sample.
Hassenkam, T., L. L. Skovbjerg, and S. L. S. Stipp, (2009) Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution, Proc. Natl. Acad. Sci. U. S. A., 106, 6071–6076