In this case, the sample will not survive the intrusion of contact-mode scanning and dynamic force microscopy is required. However, this is also a disadvantage because layers of semi-mobile fluid between the tip and sample degrade resolution. We are primarily concerned with imaging in biological buffers, and this raises the further important question of the nature of the tip-sample interaction in the presence of a fluid. Rapid motion of the molecules in this layer average out any fluid structure, so the layer is not visualized during imaging, but it does affect the overall interaction between tip and sample. We will show that it is possible for the tip to sense a surface many nm from it.
Resolution is reduced substantially when the tip is far from the surface.