Adherent metal oxide coating forming a high surface area electrode
An implantable electrode having a strong, adherent surface coating of iridium oxide or titanium nitride on a platinum surface, where the platinum surface has a surface area of at least five times that of a smooth shiny platinum surface of the same geometry. The iridium oxide coating may be formed on platinum by a physical deposition process, such as sputtering. A gradient coating of iridium oxide ranging in composition from pure platinum to pure iridium oxide is produced by sputtering.
1. A dual coated high surface area implantable metal electrode comprising:
a smooth metal substrate, suitable for implantation in an eye, having a first surface area and having a geometric shape;
an electrically conductive coating comprised of fractal platinum and not platinum black or shiny platinum, deposited on said smooth metal substrate, suitable for implantation in an eye, having a second surface area,
said electrically conductive coating having said second surface area greater than five times said first surface area of said smooth metal substrate; and
a further protective fractal coating deposited on said electrically conductive coating, suitable for implantation in an eye.
2. The implantable electrode of claim 1 , wherein said implantable metal electrode has a charge storage capacity that is greater than 35 mC/cm 2 .
3. The implantable electrode of claim 1 , wherein said further protective fractal coating is comprised of titanium nitride.
4. The implantable electrode of claim 3 , wherein said titanium nitride is a sputtered coating.
5. The implantable electrode of claim 1 , wherein said implantable metal electrode is suitable for a visual prosthesis.
6. The implantable electrode of claim 5 , wherein said visual prosthesis is a retinal electrode array.
7. The implantable electrode of claim 1 , wherein said surface coating is biocompatible.
8. The implantable electrode of claim 1 , wherein said further protective fractal coating has a third surface area of between 5 and 500 times said the corresponding first surface area of said smooth metal substrate.
9. The implantable electrode of claim 1 , wherein said further protective fractal coating has a thickness of at least 1 micrometer.
10. The implantable electrode of claim 1 , wherein said further protective fractal coating is comprised of iridium oxide.