Biomedical Engineering Reference
In-Depth Information
and are closely analogous to IIT measurements in that they generate
“force-distance” curves. The great difference between AFM and IIT,
which enables force spectroscopy with AFM to measure adhesive
interactions, is the stiffness of the probe spring.
A schematic diagram of a typical AFM is shown in Fig. 2-2 . The
microscope consists of a very stiff frame supporting the probe and
surrounding a platform for the test surface. The probe in this case
consists of a cantilever beam that is built in (clamped) at one end to a
displacement actuator controlled by the AFM (and the AFM is thus the
“indenter” environment in this case). Attached to the other end of the
cantilever is the probe tip that interacts with the surface. Such
interactions impose a force on the cantilever through an indentation axis
that passes through the tip but not the actuator and as a consequence
a bending moment is imposed on the cantilever. This moment causes the
Figure 2-2. A schematic diagram of an AFM contact testing apparatus. The cantilever
spring and tip comprise a probe, which together with a sample test surface comprise a
simple mechanical thermodynamic system. The AFM indenter environment imposes and
measures load, displacement, and temperature exterior to the system.
 
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