Gold, http://scholar.google.com.pk/citations?view_op=view_citation&hl=en&user=oysx25AAAAAJ&citation_for_view=oysx25AAAAAJ:d1gkVwhDpl0C

The DNISP probes from Bruker (http://tinyurl.com/k8odaxd) are designed for nano-indentation experiments with an AFM. They are made with a cantilever in stainless steel (and not silicon). They have spring constant values generally above 200 N/m. They are the stiffest AFM probes I know of and will allow you to apply normal loads a few ten of uN easily. As for an applied force of a few mN with such probes, I am not able to do that with my particular system but I guess this will depend whether your AFM set -up allows you to work with a large range of values with respect to the vertical motion of the probe and also making sure that the subsequent important bending of the cantilever does not lead to its plastic deformation.