The motor drives gears that that turn a vertical screw. This screw threads in and out of a brass bushing. As the screw threads into the bushing, it pulls the bushing (and whole head assembly) downward. As it unthreads, it pushes the bushing and head upward.
The coarse height of the AFM is adjusted by the three large vertical screws at the edges of the unit (not now shown). But the motorized movement here (of only a few tenths of a millimeter) allows a final automatic approach to the sample that minimizes the chance of damaging the cantilever’s tip.
