The Atomic Force Microscope (AFM) is a scanning-probe microscope that measures various material properties by bringing a small tip mounted on a cantilever very close to a surface. The AFM has two modes of operation; the first is known as “contact mode,” and involves physically dragging the tip across the sample. The deflection of the cantilever and tip is measured by a laser beam, and the information is compiled into a topographic map. The second mode of operation brings the tip extremely close to the surface without touching it, and a feedback loop adjusts the height of the cantilever so that the force is kept constant. This also produces a topographic map of the surface. The second mode of operation is used by DPN technology, as the molecules are deposited on the surface from the coated probe tip via a water meniscus (the AFM tip does not touch the sample).

Image modeled after the diagram at: Basselt, David. How AFM Works, <http://stm2.nrl.navy.mil/how-afm/how-afm.html#General%20concept>.