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302 Cha pte r T e n

in addition to chemical and physical properties. Although Raman
spectroscopy is a known technique in material physics and chemistry,
there is conspicuous margin left for expanding this technique to a
fully nondestructive three-dimensional analysis of the micromechan-
ical characteristics of biomaterials and related devices. In this, we
believe our studies hold some novelty. In addition, the usefulness of
Raman spectroscopy is particularly relevant in the field of biomedical
devices and we sincerely hope that this chapter will help improving
biomaterials and their design in such an important field for human
health and welfare. In this context, we feel that if a rationally con-
ceived biomaterials design as well as an improved quality control
employing a powerful nondestructive tool like Raman spectroscopy
is applied, many of the problems presently affecting the biomaterials
field can be solved. With the aim of seeking the assistance of the inter-
national scientific and orthopaedic communities for more advanced
studies employing Raman spectroscopy in inorganic biomaterials, we
show in this chapter some examples of how Raman techniques may pro-
vide definitive answers to so far unanswered questions in the field of
chemical and structural reliability of this important class of materials.

10.2 Principles of Raman Spectroscopy
Raman spectroscopy is based on the Raman effect, which is the
inelastic scattering of light from a molecule or a crystal, due to the
interaction of the incident radiation with the vibrational energies of
the atoms involved. A Raman spectrum is obtained, which is shifted in
frequency with respect to the incident radiation, and is a characteris-
tic fingerprint of the substance under examination. The Raman spec-
trum conveys information about the chemical and crystallographic
structure, mechanical properties, and crystallographic orientation of
the involved compounds. Raman spectroscopic experiments are use-
ful for substance characterization, orientation measurements, phase
and crystalline fractions in crystals, and residual stress assessment on
a wide range of biomaterials. Moreover, the coupling of a Raman
device with a confocal microscope allows obtaining in-depth-resolved
analyses and information also from thin layers of material, which is
particularly advantageous when bulk samples are not supplied. In
principle, it is possible to separate the energy of an atom (or a group
of atoms) in a crystal into three additive components: (1) rotational
(for molecules), (2) vibrational (referred to vibrations between the
constituent atoms), and (3) electronic (due to the electronic motion
inside atoms). The basis for this separation lies in the fact that the
velocity of electrons is much greater than the vibrational velocity of
nuclei, which is in turn much greater than the velocity of molecular
rotation. If a crystal is analyzed under incident light, a transfer of
energy from the electromagnetic field of light to the atom will occur,
which equals the energy gap between two quantized states.