Contact mode is the most basic mode in AFM operation. The key feature of Contact mode is that the probe remains in a fixed physical contact and force as it sweeps across the sample surface. In contact mode, a soft spring constant AFM probe is typically chosen to keep the force low, and the deflection signal high during scanning. The length of the cantilever is usually in the range of tens of um to hundreds of um, but it is even common to find 400-500um.

Generally speaking, between two probes with the same spring constant, the shorter one will provide higher deflection sensitivity; and therefore, greater resolution and control of force.