Biomedical Engineering Reference
In-Depth Information
8.6
Biocompatibility and Corosion Resistance of
Nickel Titanium SMA
Biocompatibility is deined as the ability to remain biologically
innocuous during the functional period of material inside the host,
connect with more rigorous conditions so as to not cause allergic
reaction, and not release ions into the blood stream. We attempt to
compare the material properties as shown in Fig. 8.27, with known
living tissue characteristics that should be as close as possible for
better mimic natural reaction of living organism.
Figure 8.27 Deformation characteristics comparison of living tissues
and NiTi placed between them [39]. See also Color Insert.
Generally, allergic reactions are a result of the material surface
and inlammatory response of the host, mostly dependent on patient
characteristics such as age, immunological state, and health. The
surface state proile, porosity or rugosity and also toxic effect of
individual elements present in material play an essential role in this
situation.
The pH and temperature value are crucial because they affect
the rate and progress of the corrosion behavior of the material and
can also change the resistivity and solubility of the substance in the
operating solution [46].
Experiments show that Nitinol corrosion resistance is
signiicantly affected by the methods of surface preparation. For
example, mechanical polishing does not give good results compared
with electropolishing as shown in Fig. 8.28. It also decreases nickel
 
Search WWH ::




Custom Search