Method for producing implantable electrode coatings with a plurality of morphologies
An implantable electrode comprising a substrate supporting microscopic surface structures such as columnar titanium nitride and further having nanoscopic surface structures on titanium nitride deposited on the exposed surface of the microscopic columnar structures is described. This is done through physical vapor deposition (PVD) and is based upon a relatively abrupt change in the surface mobility of the depositing material with a consequential variation in nucleation site density and surface mobility. At low mobility, there are increased nucleation sites and the condensation features are more numerous and finer. As mobility of the deposited species increases, the nucleation sites in the condensate film become fewer with coarser features. Consequently, the change from a relatively coarse microscopic surface structure to a relatively fine nanoscopic surface structure is accomplished by abruptly changing the total gas pressure in the processing chamber within a relatively short period of time of about ten seconds, or less.
1. An implantable electrode, comprising:
a) a substrate selected from the group consisting of tantalum, titanium, zirconium, iridium, platinum, palladium, niobium, and mixtures thereof;
b) microscopic surface structures directly contacting at least a portion of the substrate, wherein the microscopic surface structures are of a first material in the form of columnar structures providing inter-columnar porosity between adjacent columns, and wherein the first material is selected from the group consisting of a nitride of the group consisting of boron, platinum, palladium, iridium, gold, titanium, tantalum, niobium, ruthenium, zirconium, and alloys and mixtures thereof; and
c) secondary nanoscopic surface structures supported directly on the microscopic surface structures, wherein the secondary nanoscopic surface structures comprise a second material selected from the group consisting of a carbide, a nitride, a carbonitrides, and an oxide of the group consisting of carbon, boron, platinum, palladium, iridium, gold, titanium, tantalum, niobium, ruthenium, zirconium, and alloys and mixtures thereof.
2. The implantable electrode of claim 1 wherein the microscopic surface structures range from about 100 nm to about 1000 nm,
3. The implantable electrode of claim 1 wherein the nanoscopic surface structures have features of less than about 50 nm.
4. The implantable electrode of claim 1 wherein the first material of the microscopic surface structures and the second material of the nanoscopic surface structures are of the same material.
5. The implantable electrode of claim 1 wherein the first material of the microscopic surface structures and the second material of the nanoscopic surface structures are of different materials.
6. The implantable of claim 1 wherein the first material of the microscopic surface structures and the second material of the nanoscopic surface structures are selected from the group consisting of iridium nitride, titanium nitride, tantalum nitride, niobium nitride, ruthenium nitride, zirconium nitride, and mixtures thereof.
7. The implantable electrode of claim 1 wherein the microscopic surface structures provide both inter-columnar and intra-columnar porosity.
8. The implantable electrode of claim 1 being configured for delivery of an electrical pulse to body tissue.
9. A cardiac pacing lead assembly, comprising:
a) an implantable electrode, comprising:
i) a substrate selected from the group consisting of tantalum, titanium, zirconium, iridium, platinum, palladium, niobium, and mixtures thereof;
ii) microscopic surface structures directly contacting at least a portion of the substrate and configured for transmission of an electrical pulse to tissue, wherein the microscopic surface structures are of a first material in the form of columnar structures providing inter-columnar porosity between adjacent columns; and
iii) secondary nanoscopic surface structures of a second material supported directly on the microscopic surface structures,
iv) wherein the first material of the microscopic surface structures and the second material of the nanoscopic surface structures are selected from the group consisting of a nitride of the group consisting of boron, platinum, palladium, iridium, gold, titanium, tantalum, niobium, ruthenium, zirconium, and alloys and mixtures thereof; and
b) an electrical conductor electrically connected to the implantable electrode.
10. The cardiac pacing lead assembly of claim 9 wherein the microscopic surface structures range from about 100 nm to about 1000 nm.
11. The cardiac pacing lead assembly of claim 9 wherein the nanoscopic surface structures have features of less than about 50 nm.
12. The cardiac pacing lead assembly of claim 9 wherein the first material of the microscopic surface structures and the second material of the nanoscopic surface structures are selected from the group consisting of iridium nitride, titanium. nitride, tantalum nitride, niobium nitride, ruthenium nitride, zirconium nitride, and mixtures thereof.
13. The cardiac pacing lead assembly of claim. 9 wherein the substrate is of platinum/10% iridium.
14. The cardiac pacing lead assembly of claim 9 wherein the microscopic surface structures provide both inter-columnar and intra-columnar porosity.
15. The cardiac pacing lead assembly of claim 9 wherein the first material of the microscopic surface structures and second material of the nanoscopic surface structures are of the same material.
16. The cardiac pacing lead assembly of claim 9 wherein the first material of the microscopic surface structures and the second material of the nanoscopic surface structures are of different materials.
17. The cardiac pacing lead assembly of claim 9 being configured for delivery of an electrical pulse to body tissue.
18. An implantable electrode, comprising:
a) a substrate selected from the group consisting of tantalum, titanium, zirconium, iridium, platinum, palladium, niobium, and mixtures thereof;
b) microscopic surface structures directly contacting at least a portion of the substrate, wherein the microscopic surface structures comprise columnar titanium nitride; and
c) secondary nanoscopic surface structures supported directly on the titanium nitride microscopic surface structures, wherein the nanoscopic surface structures comprise titanium nitride.
19. The implantable electrode of claim 18 wherein the macroscopic and nanoscopic surface structures consist essentially of titanium nitride having both inter-columnar and intra-columnar porosity.
20. A method for making an implantable electrode, comprising the steps of:
a) selecting a substrate from the group consisting of tantalum, titanium, zirconium, iridium, platinum, palladium, niobium, and mixtures thereof;
b) depositing microscopic surface structures in the form of columnar structures providing inter-columnar porosity between adjacent to columns directly onto the substrate, the microscopic surface structures being of a first material selected from the group consisting of a nitride of the group consisting of boron, platinum, palladium, iridium, gold, titanium, tantalum, niobium, ruthenium, zirconium, and alloys and mixtures thereof; and
c) depositing nanoscopic surface structures directly onto the microscopic surface structures, the nanoscopic surface structures being of a second material selected from the group consisting of a carbide, a nitride, a carbonitrides, and an oxide of the group consisting of carbon, boron, platinum, palladium, iridium, gold, titanium, tantalum, niobium, ruthenium, zirconium, and alloys and mixtures thereof.
21. The method of claim 20 including providing the first material of the microscopic surface structures and the second material of the nanoscopic surface structures being of the same material.
22. The method of claim 20 including providing the first material of the microscopic surface structures and the second material of the nanoscopic surface structures being of different materials.
23. The method of claim 20 including providing the microscopic surface structures ranging from about 100 nm to about 1000 nm and providing the nanoscopic surface structures being less than about 50 nm.
24. The method of claim 20 including selecting the first material of the microscopic surface structures and the second material of the nanoscopic surface structures from the group consisting of iridium nitride, titanium nitride, tantalum nitride, niobium nitride, ruthenium nitride, zirconium nitride, and mixtures thereof.
25. The method of claim 20 including providing the substrate being of platinum/10% iridium.
26. The method of claim 20 including providing the microscopic surface structures having both inter-columnar and intra-columnar porosity.