Dirty AFM probes mess with microscopy measurements

Atomic force microscopy (AFM) tips might not be the impartial, inert probes they are hailed as. Tips that aren’t cleaned before use deposit silicon oils – residues from packaging material – onto samples during measurements potentially altering the results, US researchers have found. Scientists use AFM to visualise individual atoms, reaching resolutions 1000 times better than the optical diffraction limit. To do this, an atom-sharp tip attached to the end of a cantilever is scanned over a sample. Forces between the tip and the surface that bend the cantilever are detected and converted into an image.