Biomedical Engineering Reference
In-Depth Information
clinical studies. Understanding the structure-property relationships in soft
tissues at small length scales can help researchers understand the
behavior of the tissue at the macroscale, and can also aid in the
development of improved tissue replacements with appropriate
mechanical behavior. In addition, nanoindentation studies of soft tissues
can aid in understanding disease processes and repair mechanisms in
tissues.
As was demonstrated in the review of cartilage indentation studies,
applications of nanoindentation to cartilage characterization have
focused on correlating local mechanical properties in small tissue
samples with tissue morphology
20
and investigating tissue damage
21
and
repair processes.
18,19
In contrast, nanoindentation studies in arteries have
focused on gaining understanding of disease processes rather than repair
processes. Several studies have looked at the influence of mineralization
in human atherosclerotic plaques on the mechanical behavior of the
tissue,
23-25
with the goal of generating input parameters for computational
models of diseased arteries. Healthy arteries have also been characterized
using both elastic
25
and viscoelastic
26
analyses to serve as a baseline for
comparison of diseased artery properties.
Other soft tissue studies have included quasi-static and dynamic
mechanical analysis of the 20-40 micrometer thick stratum corneum
layer of skin,
27
the characterization of viscoelastic properties of
demineralized dentin,
28
and the indentation of live fruit fly larvae at
various developmental stages to investigate the role of the developmental
stage on cuticle stiffness.
29
All the soft tissue studies required
maintenance of tissue hydration during testing, and many highlighted
other challenges in sample preparation, tip selection, and data acquisition
and analysis that had to be overcome in applying nanoindentation to the
study of soft tissues. The challenges associated with soft tissue testing
will be discussed in more detail in Section 4.
3.2
. Plants
Characterization of wood, bamboo and the waxy layers on pitcher
plants have also been the subject of many nanoindentation studies.
Wood, like many tissues, is a material with a complex hierarchical
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