Biomedical Engineering Reference
In-Depth Information
FIGURE 18.3
(A) HA coating pre-adsorbed with fluorescein isothiocyanate tagged fibronectin (FITC-FN) and
(B) collagen-FN network bundles after 5 min of collagen deposition with insert showing topographical
view of bound FITC-FN
[22]
.
into the Ca(PO
3
)
2
glass melt. The crystallographic
c
-axis of most crystals were oriented in the direc-
tion perpendicular to the surface of Al
2
O
3
plate. The plate was then cut to extract crystal samples
oriented perpendicular and parallel to the plate. The influence of crystal alignment on corrosion
behaviors in simulated body fluid was investigated by measuring and comparing the changes of sur-
face roughness from three-dimensional surface topography which was measured using confocal laser
scanning microscopy. By measuring surface area roughness from the topology measurements, it was
found that crystals aligned parallel to the plate were attacked more strongly than crystals aligned per-
pendicular to the plate. This new information indicates that directionality of these coatings must be
taken into account if these are to be used on implant surfaces.
18.1.3.2 Interferometry
Interferometers are used to measure the interference pattern of a specific light source from the surface
to be profiled. A common interferometer is the white-light scanning interferometer or the coherence
scanning interferometer
[24-29]
. This system is used to capture the intensity of interference patterns
from the surface during scanning in the vertical direction. The surface can then be reconstructed digit-
ally by using the shape of the white-light interferogram, the localized phase of the interferogram, or
a combination of both shape and phase. From recorded peak fringe contrast as a function of wave-
length, an interference function which is dependent on optical path difference can be employed to
map the surface. Captured data are processed in a variety of ways depending on the interferometer
system manufacturer, including being Fourier-transformed into frequency space, subject to cross-
correlation methods, or analysis in the spatial domain.
