NANOINDENTATION OF SOFT TISSUES AND OTHER BIOLOGICAL MATERIALS - Nanoindentation with Biological Applications - page 289

comparison of quantitative results between studies may not be
meaningful if different experimental techniques are used (such as
different tip sizes and penetration depths), 22 particularly when the
material being tested has a microstructure that varies with depth.
Although functional parameters may be sufficient to answer many
research questions, the fracture toughness study 21 shows that there is a
potential to develop entirely new experimental methods and models that
can take into account the unique properties of a given material and allow
accurate measurement of truly quantitative mechanical properties and
material parameters that may be comparable to bulk values. The
development of new indentation models for soft tissue characterization
should continue to be pursued in the future, rather than relying on
adapting models that were developed for very different materials.
3. Nanoindentation of Other Biological Materials
Cartilage is only one of many biological materials which have been
characterized using nanoindentation. The previous chapters reviewed the
substantial literature on nanoindentation of bones and teeth, which were
the first biological materials to be studied using nanoindentation. In more
recent years, nanoindentation methods have been applied to the study of
a variety of other biological materials, ranging from soft tissues to plants
to acellular natural materials. Studies of articular cartilage were reviewed
above, demonstrating applications ranging from characterizing cartilage
repair tissue to correlating mechanical properties with morphology in
small animal models. The sections below will provide more examples of
nanoindentation studies of soft tissues, plants, and acellular biological
materials to illustrate the wide range of biological, biomedical and
materials design questions that can be addressed through nanomechanical
testing.
3.1 . Soft tissues
Soft tissues represent a class of hydrated biological materials that often
have a complex and hierarchical microstructure. Characterization of soft
tissues at small length scales has applications in basic science and