Biomedical Engineering Reference
In-Depth Information
TABLE 21.11. Material Combinations Tested in Accelerated Durability Tester
Sewing ring
material
Valve model
Cage material
Disc material
Control (TTK - Chitra)
Haynes - 25
UHMWPE
Polyester
Ti + DLC/UHMWPE
Cp Ti + DLC coating
UHMWPE
Polyester
Ti/UHMWPE + DLC
Cp Ti
UHMWPE + DLC
coating
Polyester
Ti + DLC/
UHMWPE + DLC
Cp Ti + DLC Coating
UHMWPE + DLC
coating
Polyester
Ti + TiN/UHMWPE
Ti 6Al 4V + TiN coating
UHMWPE
Polyester
Figure 21.8.
Accelerated Durability Results—The volume of material loss during the opera-
tion of the valve under accelerated cycling conditions is plotted against the number of cycles.
The typical volume loss over 380 million cycles (equivalent to ten years life in the patient) is less
than fi ve microlitres. This very small wear rate is essential to ensure that the valves last the life
span of the patient. Additionally the complications related to wear debris are minimal in such
material combinations. (All valves size #27 mm tissue annulus diameter).
21.8 BIOLOGICAL CHARACTERIZATION
The DLC/TiN-coated materials with their bare metal counterpart as controls
were evaluated for their cytocompatibility, hemocompatibility, and tissue com-
patibility. The biological characterization of the coated surfaces was carried out
based on the International standard ISO 10993. Subsequently, two series of large
animal experiments were carried out to assess the
in vivo
hemocompatibility of
DLC and suitability of use of TiN coating on artifi cial heart valve cages.
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