Intravascular functional element and method of manufacture
The invention relates to a method of manufacture of an intravascular functional element that can be introduced into a hollow organ and that comprises at least one wire ( 10 ) of an alloy having nickel and titanium as alloying elements, with the following steps: preparation of a metal body of the wire ( 10 ) with a metallic surface, then formation of a first oxide layer on the metallic surface of the metal body, then performance of a heat treatment of the wire ( 10 ) in a nitrogen-containing salt bath for thermal formation of a second mixed oxide layer on the first oxide layer, wherein the total layer thickness is 15 nm to 100 nm and the mixed oxide layer contains TiO 2 and at least one nitride, especially titanium oxynitride and/or titanium nitride.
1. A method of manufacturing an intravascular functional element, the intravascular functional element for introduction into a hollow organ;
the intravascular functional element comprising
a wire comprising an alloy of nickel and titanium as alloying elements; and
a mixed oxide layer formed on the surface of the wire, the mixed oxide layer comprising
a layer thickness from 15 nm to 100 nm,
TiO 2 , and
a nitride, the nitride being a titanium nitride or an titanium oxynitride,
wherein the wire forms a wire structure comprising the wire;
wherein the wire structure comprises a coil for aneurysm treatment or a braid;
wherein the wire structure comprises a contact zone, the contact zone having
a plurality of cross-overs of the wire where the wire crosses-over itself or
a plurality of self-contact points of the wire where the wire contacts itself; and
wherein the mixed oxide layer is homogeneous and has a substantially constant thickness on the wire even at cross-overs or self-contact points;
the method comprising the steps of:
(a) preparing a metal body of the wire;
(b) subsequent to step (a), forming a first oxide layer on the surface of the wire; and
(c) subsequent to step (b), heat treating the wire in a nitrogen-containing salt bath for thermal formation of the mixed oxide layer on the first oxide layer.
2. The method according to claim 1 , wherein the layer thickness is at least 55 nm.
3. The method according to claim 1 , wherein the layer thickness is at most 95 nm.
4. The method according to claim 1 , wherein
a peak of a oxygen concentration in the mixed oxide layer is formed as a plateau.
5. The method according to claim 4 , wherein a ratio of intensities between nitrogen and oxygen comprises a range of 1:2.5 to 1:10 in the plateau, and decreases toward an interior of the wire,
wherein the intensities are determined respectively by Auger electron spectroscopy (AES).
6. The method according to claim 1 , wherein the nitride extends from an exterior surface of the mixed oxide layer to a depth in the wire of ⅔ of the total thickness of the mixed oxide layer.
7. The method according to claim 1 , wherein the mixed oxide layer comprises nickel, the nickel in a region extending from an exterior surface of the mixed oxide layer to a depth of 30% of the total thickness of the mixed oxide layer is at most 6% by weight.
8. The method according to claim 1 , further comprising a step of forming an enrichment of nickel oxide in an inner portion of the mixed oxide layer.
9. The method according to claim 1 , further comprising a step of forming the contact zone of the wire prior to step (c).
10. The method according to claim 9 , wherein the step of forming the contact zone of the wire is performed by braiding the wire.
11. The method according to claim 9 , wherein the step of forming the contact zone of the wire is performed by winding the wire into a coil.
12. The method according to claim 1 , wherein
a contact angle measured with distilled water is smaller than 90° and at least 30°.
13. The method according to claim 1 , wherein
the salt bath comprises an alkali metal-nitrogen salt, a potassium nitrate, a sodium nitrite, or a mixture of potassium nitrate and sodium nitrite.
14. The method according to claim 13 , wherein
the content of potassium nitrate is greater than the content of sodium nitrite.
15. A method according to claim 13 , wherein
the salt bath comprises
30-40 wt % KNO3
25-35 wt % NaNO2
rest usual carbon compounds and impurities,
wherein a content of potassium nitrate is greater than a content of sodium nitrite.
16. The method according to claim 1 , wherein step (c) is performed after performing a step of introducing a functional item, the functional item being a radiologically visible markings, or after performing a step of joining process.
17. The method according to claim 1 , wherein step (a) is performed by electro-polishing the wire.
18. An intravascular functional element for introduction into a hollow organ, the intravascular functional element comprises:
a wire comprising an alloy of nickel and titanium as alloying elements; and
a mixed oxide layer formed on the surface of the wire, the mixed oxide layer comprising
a layer thickness from 15 nm to 100 nm,
TiO 2 , and
a nitride, the nitride being a titanium nitride or an titanium oxynitride;
wherein the wire forms a wire structure comprising the wire;
wherein the wire structure comprises a coil for aneurysm treatment or a braid;
wherein the wire structure comprises a contact zone, the contact zone having
a plurality of cross-overs of the wire where the wire crosses-over itself or
a plurality of self-contact points of the wire where the wire contacts itself; and
wherein the mixed oxide layer is homogeneous and has a substantially constant thickness on the wire even at cross-overs or self-contact points.
19. A functional element according to claim 18 ,
wherein the mixed oxide layer is disposed in the contact zone.
20. A functional element according to claim 18 ,
wherein the layer thickness is from 15 nm to 60 nm or is from 30 nm to 100 nm.
21. A functional element according to claim 18 ,
wherein the wire structure is non-unitary.
22. A functional element according to claim 18 ,
wherein a peak of a concentration of TiO 2 in the mixed oxide layer forms a plateau.
23. A functional element according to claim 22 ,
wherein a ratio of intensities between nitrogen and oxygen comprises a range of 1:2.5 to 1:10 in the plateau, and decreases toward an interior of the wire,
wherein the intensities are determined respectively by Auger electron spectroscopy (AES).
24. A functional element according to claim 18 ,
wherein the nitride extends from an exterior surface of the mixed oxide layer to a depth in the wire of ⅔ of the total thickness of the mixed oxide layer.
25. A functional element according to claim 18 ,
wherein the mixed oxide layer comprises nickel, the nickel in a region extending from an exterior surface of the mixed oxide layer to a depth of 30% of the total thickness of the mixed oxide layer is at most 6% by weight.
26. A functional element according to claim 18 ,
wherein an enrichment of nickel oxide is formed in an inner portion of the mixed oxide layer.
27. An intravascular functional element for introduction into a hollow organ, the intravascular functional element comprises:
a plurality of wires comprising a first wire and a second wire, each wire comprising an alloy of nickel and titanium as alloying elements; and
a mixed oxide layer formed on the surface of each wire, the mixed oxide layer comprising
a layer thickness from 15 nm to 100 nm,
TiO 2 , and
a nitride, the nitride being a titanium nitride or an titanium oxynitride;
wherein the plurality of wires form a non-unitary wire structure;
wherein the wire structure comprises a coil for aneurysm treatment or a braid;
wherein the wire structure comprising comprises a contact zone, the contact zone having
a plurality of wire cross-overs where the first wire crosses-over the second wire or
a plurality of wire self-contact point where the first wire contacts the second wire; and
wherein the mixed oxide layer is homogeneous and has a substantially constant thickness of each wire even at wire cross-overs or wire self-contact points.