Biomedical Engineering Reference
In-Depth Information
Strength and ductility of magnesium alloys are signii cantly enhanced
by nanostructuring. h is imparts better formability during stent process-
ing and improves the in situ expandability and the force bearing capability
of the implanted nanostructured magnesium stents. Signii cant increases
in properties of candidate bioabsorbable magnesium alloys have been
reported by Kutniy
et al.
[334] for alloy WE43 and by Pachla
et al.
[296]
for AZ31, AZ61, and AZ91 alloys, as illustrated in Table 1.3. Appropriate
combinations of mechanical properties need to be specii ed and developed
considering overall stent design factors that af ect stent-host interactions.
For example, antimicrobial properties of magnesium [335] and osteocon-
ductive characteristics of nanostructured surfaces need further explora-
tion. h e
in vivo
characteristics of both conventional and nanostructured
variants of magnesium alloys need to be researched to establish the basis
for realizing the potential of magnesium-based stents and other orthope-
dic devices.
1.3
Summary and Conclusions
In this chapter we have sequentially examined nanostructured metals from
the context of the most prominent categories of metals for medical use:
titanium and its alloys, stainless steels, cobalt-chrome alloys, and magne-
sium alloys. In addition, we should mention also recent studies on zirco-
nium and tantalum [336-339], which have excellent potential for medical
applications as well.
h e possibility of widespread medical applications of nanostructured
metals has been under discussion for over a decade [25, 94]. However, only
through implementation of large scale manufacturing of these metals has
this prospect become viable. h e NanoMet facility in Ufa, Russia became
the world's i rst facility to manufacture nanostructured titanium, achiev-
ing full ISO 9000 quality registration in 2011. At the time of writing of this
chapter nanometals manufacturing and projected sales targets for biomed-
ical applications were announced in the USA by Carpenter Technology
Corporation. Meanwhile, the principles of severe plastic deformation to
produce ultrai ne grained metals and allows are being incorporated in
production of metals and metallic components worldwide [340-342]. h e
positive validation of the technology in the initial commercial applications
such as pure metal sputtering targets and some others [341, 342] has reaf-
i rmed the realization of reliable, reproducible manufacturing of nano-
structured metals. h e body of knowledge in the academic literature and
the patent literature on nanostructured metals is sui ciently large so as to
