Biomedical Engineering Reference
In-Depth Information
(a)
(b)
Open
Closed
in film nitinol
Outer teflon tube
Inner teflon scaffold
FIGURE 9.72
Closed (a) and open (b) positions of a TiNi thin film heart valve. (From Stepan et al.,
J. Biomech. Eng. ASME Trans.
,
127, 915-918, 2005, with permission to use from ASME.)
deposition and fabrication of a TiNi leaflet, the leaflet was wrapped around the anchoring
bar, made of TiNi wire, and fixed in place by the insertion of the smaller tube into the infe-
rior portion of the large tube. Figure 9.72 shows the closed and open positions of the heart
valve (Mohanchandra and Carman, 2009).
Fabrication of Superelastic Thin Film Tubes
Figure 9.73 shows a schematic of the deposition system used to fabricate Ti-Ni microtubes
(Buenconsejo et al., 2008). A rotating jig is placed inside a sputter-deposition chamber and
a Cu wire is fixed such that its length is parallel to the surface of the alloy target. The rota-
tion of the wire is controlled by a motor. Cu wire was rotated at constant rotation speeds
during the deposition process. The composition of the alloy target is Ti-50 at.% Ni and
pure Ti chips were placed on the surface to control the composition. The composition of
deposited Ti-Ni was determined by electron probe microanalysis to be Ti-52 at.% Ni. After
deposition, the Cu wire was completely dissolved in a Nitric acid solution thus producing
a tube hole. The microtubes were sealed in an Ar-filled quartz tube and then crystallized
Rotating jig
Sputter-deposition chamber
Motor
Cu wire
Ti-Ni alloy target
FIGURE 9.73
A schematic of rotating jig placed inside sputter-deposition chamber. (From Buenconsejo et al.,
Acta Mater.
, 56,
2063-2072, 2008, with permission from Elsevier.)
