Retinal prosthesis with a new configuration
Polymer materials are useful as electrode array bodies for neural stimulation. They are particularly useful for retinal stimulation to create artificial vision, cochlear stimulation to create artificial hearing, and cortical stimulation, and many related purposes. The pressure applied against the retina, or other neural tissue, by an electrode array is critical. Too little pressure causes increased electrical resistance, along with electric field dispersion. Too much pressure may block blood flow. Common flexible circuit fabrication techniques generally require that a flexible circuit electrode array be made flat. Since neural tissue is almost never flat, a flat array will necessarily apply uneven pressure. Further, the edges of a flexible circuit polymer array may be sharp and cut the delicate neural tissue. By applying the right amount of heat to a completed array, a curve can be induced. With a thermoplastic polymer it may be further advantageous to repeatedly heat the flexible circuit in multiple molds, each with a decreasing radius. Further, it is advantageous to add material along the edges. It is further advantageous to provide a fold or twist in the flexible circuit array. Additional material may be added inside and outside the fold to promote a good seal with tissue.
1. A method of making a flexible circuit electrode array comprising:
depositing a flexible polymer base layer;
depositing metal on said flexible polymer base layer;
patterning said metal to form metal traces;
depositing a flexible polymer top layer on said flexible polymer base layer and said metal traces including openings for electrodes, thus forming an electrode array portion and a cable portion;
embedding said electrode array portion in an oval shaped body having a contracted radius at its edges comprising a soft polymer, said soft polymer being softer than said polymer base layer; and
forming a window in said soft polymer, thus exposing said electrodes.
2. The method according to claim 1 , further comprising heating said flexible circuit electrode array in a mold.
3. The method according to claim 2 , wherein the heating comprises heating the flexible circuit electrode array in the mold to form a spherical curvature in the flexible circuit electrode array.
4. The method according to claim 1 , wherein said step of depositing said flexible polymer base layer and said flexible polymer top layer is depositing polyimide.
5. The method according to claim 1 , wherein said step of depositing said flexible polymer base layer and said flexible polymer top layer is depositing silicone.
6. The method according to claim 1 , wherein said step of depositing said flexible polymer base layer and said flexible polymer top layer is depositing fluoro-polymer.
7. The method according to claim 1 , further comprising forming a twist in said cable portion of said flexible circuit electrode array.
8. The method according to claim 1 , wherein said openings in the flexible polymer top layer are smaller than associated metal traces.
9. The method according to claim 1 , further comprising forming in bend in said polymer base layer, said metal traces, and said polymer top layer where said polymer base layer, said metal traces, and said polymer top layer exit said oval shaped body.
10. The method according to claim 1 , wherein the step of embedding said electrode array portion in a oval shaped body is embedding said electrode array in a body having a hardness of 50 or less on the Shore A scale.