Cochlear electrode array

Abstract

A cochlear lead includes a plurality of electrode assemblies partially embedded in a flexible body configured to stimulate an auditory nerve from within a cochlea. Each of the electrode assemblies includes a flexible electrically conductive material forming a plurality of support structures and an electrode pad attached a support structure, the electrode pad having a surface that is configured to be exposed to cochlear tissue and fluids and has a charge transfer to the cochlear tissue and fluids that is higher than the flexible electrically conductive material.

1 . A method of forming a charge transferring surface, the method comprising:
 partially encapsulating an electrode in a flexible body; and   subsequently electrochemically activating a first exposed portion of the electrode to form an iridium oxide surface, the iridium oxide surface having a greater charge transfer density than an unactivated exposed portion of the electrode.   
     
     
         2 . The method of  claim 1  wherein the first exposed portion of the electrode is in a recess and the iridium oxide surface does not extend beyond the recess. 
     
     
         3 . The method of  claim 1 , further comprising a second exposed portion of the electrode in electrical contact with the first exposed portion of the electrode, wherein the second exposed portion of the electrode does not form an iridium oxide surface when exposed to the same electrochemical activation as the first exposed portion. 
     
     
         4 . The method of  claim 3 , wherein the first exposed portion of the electrode is part of an electrode pad comprising iridium and the second exposed portion of the electrode is part of a winged tab. 
     
     
         5 . The method of  claim 3 , wherein the second exposed portion of the electrode is composed of platinum. 
     
     
         6 . The method of  claim 3 , wherein the first exposed portion is a bottom surface of a recess, the second exposed portion is a side of the recess, and the iridium oxide surface does not extend beyond the recess. 
     
     
         7 . The method of  claim 3 , wherein a connection between the first exposed portion and the second exposed portion of the electrode is free of activated iridium oxide. 
     
     
         8 . A method for controlling element separation in a physical array, the method comprising:
 fixing multiple tethered electrode array elements to a temporary substrate with predetermined separations between the multiple tethered electrode array elements;   removing tethers of the multiple tethered electrode array elements to form multiple untethered electrode array elements;   forming a flexible body that connects the multiple untethered electrode array elements at the predetermined separations; and   separating the temporary substrate from the multiple untethered electrode array elements.   
     
     
         9 . The method of  claim 8 , wherein separating the temporary substrate from the multiple untethered electrode array elements comprises dissolving a portion the temporary substrate. 
     
     
         10 . A method for forming an electrode in a cochlear electrode array, comprising:
 forming a first foil of electrically conductive material into a set of winged tabs;   forming a second foil into a set of electrode pads;   fixing a sacrificial substrate to one of: a winged tab and an electrode pad;   attaching the set of winged tabs and the set of electrode pads together; and   electrically connecting a selected wire to each of the winged tabs.   
     
     
         11 . The method of  claim 10 , further comprising:
 bending a wing of each winged tab to constrain additional wires passing over the winged tab to form a wire bundle;   removing the sacrificial substrate to form an electrode assembly; and   partially encapsulating the electrode assembly in a flexible polymer body.   
     
     
         12 . The method of  claim 10 , in which forming the first and second foil comprises short pulse laser machining 
     
     
         13 . The method of  claim 10 , in which forming the first foil comprises forming a tethered set of winged tabs and forming a second foil comprises forming a tethered set of electrode pads. 
     
     
         14 . The method of  claim 13 , further comprising cutting tethers of the tethered set of winged tabs after attaching the winged tabs and the electrode pads together. 
     
     
         15 . The method of  claim 10 , in which the sacrificial substrate comprises an iron strip. 
     
     
         16 . The method of  claim 10 , further comprising electrochemically activating an iridium material by subjecting a surface of the iridium material to a number of electrochemical cycles in a water-based electrolyte such that the surface of the iridium material develops an activated iridium oxide layer which has electrical charge transfer which is superior to the electrically conductive material which makes up the set of winged tabs. 
     
     
         17 . The method of  claim 10 , in which the electrode pad is first attached to the sacrificial substrate and then attaching the winged tab and the electrode pad together. 
     
     
         18 . The method of  claim 10 , further comprising:
 forming an aperture in the winged tab;   attaching the winged tab to the sacrificial substrate; and   attaching the electrode pad over the aperture in the winged tab.   
     
     
         19 . The method of  claim 10 , in which the electrode pad and winged tab are attached using a resistance weld. 
     
     
         20 . The method of  claim 10 , in which the electrode pads comprise a surface modified to be exposed to cochlear tissue and fluid, the surface having a charge transfer to the cochlear tissue and fluid that is higher than that of an unmodified substrate material.