Abstract
One of the main issues with the use of nickel titanium alloy (NiTi) implants in cardiovascular implants (stents) is that these devices must be of very high quality in order to avoid subsequent operations due to failing stents. For small stents with diameters below ca. 2 mm, however, stent characterization is not straightforward. One of the main problems is that there are virtually no methods to characterize the interior of the NiTi tubes used for fabrication of these tiny stents. The current paper reports on a robust hybrid actuator for the characterization of NiTi tubes prior to stent fabrication. The method is based on a polymer/hydrogel/magnetic nanoparticle hybrid material and allows for the determination of the inner diameter at virtually all places in the raw NiTi tubes. Knowledge of the inner structure of the raw NiTi tubes is crucial to avoid regions that are not hollow or regions that are likely to fail due to defects inside the raw tube. The actuator enables close contact of a magnetic polymer film with the inner NiTi tube surface. The magnetic signal can be detected from outside and be used for a direct mapping of the tube interior. As a result, it is possible to detect critical regions prior to expensive and slow stent fabrication processes.
Highlights
Nickel titanium alloys (NiTi, nitinol) are advanced materials used in medical devices.Superelasticity, shape memory, biocompatibility, MRI compatibility, and non-ferromagnetic properties are some of the characteristics that make this alloy popular in medical industry, it is much more expensive than, for example, titanium or steel [1,2,3,4]
The current paper describes an approach to characterize the inner surface of nickel titanium alloy (NiTi) tubes, in particular tubes with diameters below ca. 2 mm
Films 3 and 4 can be detached from the casting substrate, but film 4 is too thick for the intended use inside the NiTi tubes because defects on the order of ca. 5 m should be detected, which can presumably not be seen anymore with a much thicker film such as film 4
Summary
Nickel titanium alloys (NiTi, nitinol) are advanced materials used in medical devices. For the stents to function properly in the body, the starting materials (the NiTi tubes) need to (i) be hollow along the entire length of the final stent, (ii) have the same inner tube diameter throughout the whole tube to avoid pressure buildup once implanted, and (iii) be defect-free to avoid mechanical failure in the body after implantation. Bad areas with lower diameter (1), solid areas (2), and the roughness of the inner surface (3) can be detected on the “magnetic map” of the interior and the respective parts of the tube will be discarded
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
