INDENTATION AND ADHESION AT SMALL LENGTH SCALES - Nanoindentation with Biological Applications - page 22

CHAPTER 2
INDENTATION AND ADHESION AT SMALL LENGTH SCALES
Robert F. Cook
Ceramics Division, National Institute of Standards and Technology
E-mail: [e-mail]
Indentation and adhesion are considered in the context of the two
experimental methods predominantly used to measure contact behavior
at small length scales, instrumented indentation testing and atomic
force microscopy. The typical loads and displacements applied and
sensed by each measurement technique, both within the (probe +
surface) contact system and exterior to it, are considered in turn. The
loads and displacements are placed in the context of the atomic-scale
parameters quantifying material indentation and adhesion behaviors,
atomic bond stiffness and rupture force, respectively. The central role
played by the probe stiffness in determining whether a contact is likely
to be more indentation- or adhesion-like—or something in between—is
highlighted, with an emphasis on quasi-static contact. Dynamic
behavior is also considered, along with the likelihood of measurable
adhesion effects appearing in typical indentation measurements of
biological materials using atomic force microscopes.
1. Introduction
Adhesion and indentation are obviously intimately connected: If two
bodies are brought into close enough contact such that the forces
between their surfaces can interact to form a single connected entity—
adhesion—then it is entirely possible, if not probable, that one body
might deform the other locally at the contact—indentation.
Two extremes of behavior might be imagined. If the forces between
the surfaces of the two bodies are negligible and the forces exerted in
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