Characterization of Biomaterials 227
at this critical length scale. It has been used to study the hierarchical structure of a
biological material such as a bone. In particular it plays a crucial role in studying
the lowest hierarchical level, within the nanometer scale, where the distribution
of organic ﬁbers (collagen) and crystalline mineral nano-particles has a major
inﬂuence for mechanical optimization of bone.
10.3 SURFACE ANALYSIS METHODS
The surface structure characterization of a biomaterial presents different analyt-
ical challenges since the composition and spacial arrangement of the molecular
segments on the surface may not be representative of the bulk structure. In
addition, the surface is the interface where the biomaterial meets and interacts
with the molecular constituents of the biological host setting (e.g., bone, soft tissue,
blood, cells, body ﬂuids). These interactions can modify the material and result in
macroscopic events in the biological media which ultimately determine whether
or not an MEMS device will have successful performance in the host biological
environment. Therefore, surface characterization will be discussed in more detail
in this chapter.
The properties that are of interest in the characterization of biomaterial sur-
faces include the chemical structure, the hydrophilicity or hydrophobicity, the
presence of ionic groups, the morphology and topography.
Varying degrees of
information about these properties can be obtained using different analysis meth-
ods including microscopic, spectroscopic and thermodynamic and other methods.
We aim to provide an overview on some of the speciﬁc techniques frequently used
in the characterization of biomaterial surfaces. In addition, discussions and refer-
ences are made to emerging methods such as rapid Raman spectroscopy, optical
coherence tomography (OCT), and multi-photon excitation microscopy that have
recently come to the forefront of biomedical research and possess great potentials
for studying the interactions of biomaterials with real biological environment
10.3.1 Microscopic Methods
Microscopy techniques often used in biomaterial analysis include scanning elec-
tron microscopy (SEM), transmission electron spectroscopy (TEM), scanning tun-
neling microscopy (STM) and atomic force microscopy (AFM).
ments in light microscopy include confocal laser scanning microscopy (CLSM) and
optical near-ﬁeld microscopy.
10.3.1.1 Electron Microscopy
An electron microscope is a type of microscope that uses electrons to illuminate
a specimen in a vacuum environment and create an enlarged image. Electron
microscopes have much greater resolving power than light microscopes. Electron
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