Band type multicontact electrode and method of making the same

Abstract

A multicontact electrode array suitable for implantation in living tissue includes a distal end having multiple spaced-apart ring or band electrode contacts carried on a flexible tube carrier. Each ring electrode contact is laser welded to a respective wire tip that has a multi-helix orientation on the inside of a separation tube. The center of the multi-helix wire defines a lumen wherein a positioning stylet, or other suitable positioning tool, may be removably inserted when the electrode array is implanted. The method of making the multicontact electrode array includes, as an initial step, winding lead wires around a suitable mandrel so as to form a multi-helix configuration. (Alternatively, the wire may be purchased in a multiwire pre-wound configuration that defines a lumen, in which case the mandrel is slipped inside the lumen.) Then, at a distal end of the electrode, each wire within the multi-helix winding is unwound so as to protrude out from the winding. Next, a non-conductive separation silicone tube which has a longitudinal slit along its length, is placed around the wound wires. Ring contacts are then placed over the silicone tube at a distal end of the electrode array and spaced apart as desired. These ring contacts also have a slit therein through which the protruding wire ends may exit. The silicone tube is used as a spacer to centrally locate the multi-helix wound wires with the ring contacts. A compressive die may be used to hold the pre-assembled ring contact, multi-helix wire, separation tube in their desired positions, and may be used to close the opening or slit of each ring contact through which the wire tips protrude. The wire tips are then individually trimmed to a suitable distance. A laser welding process may then be used to bond each lead wire to a corresponding ring contact. Finally, the preassembled electrode array is placed in a molding die, and a polymer filler is injected into the internal gaps of the electrode array components.

What is claimed is:  
     
         1 . A multicontact electrode array comprising: 
 a plurality of insulated wires, helically wound to define a lumen, each of said wires having a distal end;    a separation tube positioned around the helically wound wires, said separation tube having a longitudinal slit through which the distal end of each wire radially extends;    a plurality of ring contacts positioned around the separation tube at the respective locations where the distal end of each of the plurality of wires extends through the slit of the tube, wherein the distal end of each wire is electrically and mechanically bonded to a respective ring contact; and    a polymer filler that fills the gap created by the longitudinal slit of the tube and all gaps between the electrode array components.    
     
     
         2 . The electrode array of  claim 1  wherein the number of ring contacts comprises at least four.  
     
     
         3 . The electrode array of  claim 1  wherein each of the plurality of ring contacts comprises a split ring having an axial gap, and wherein the distal end of the wire that is bonded to the ring contact passes through the axial gap.  
     
     
         4 . The electrode array of  claim 1  wherein the ring contact is made from a softer material than the wire, and wherein the split ring deforms to conform with the shape of the wire at a point where the distal end of the wire passes through the axial gap when the split ring is compressed.  
     
     
         5 . The electrode array of  claim 1  wherein the distal end of the wire is flush with a surface of the split ring.  
     
     
         6 . The electrode array of  claim 3  wherein the distal end of each wire is electrically and mechanically bonded to the ring contact with a laser weld.  
     
     
         7 . A method of making a multicontact electrode array comprising: 
 a. forming on a mandrel a multiwire helically-wound configuration wherein each wire of the multiwire helically-wound configuration has a distal end that is bent to extend radially outward, and wherein the multiwire helically-wound configuration has an outer diameter;    b. forming a separation tube having an inside diameter that is approximately the same as the outer diameter of the multiwire lead;    c. positioning the separation tube over the helically wound multiwire lead and mandrel, the separation tube having a longitudinal slit at one end thereof through which the pigtail end of each wire extends;    d. placing a plurality of open-ring contacts having an open axial gap snugly over the separation tube, with the pigtail end of each wire extending through the axial gap of a respective open-ring contact;    e. using a compressive die to firmly close the gap between the ring contacts and the pigtail end of each wire;    f. electrically and mechanically bonding the pigtail end of each wire to the open-ring contact;    g. removing the mandrel from the central lumen and replacing it with a molding stylet;    h. placing the pre-assembled electrode array and molding stylet in a molding die;    i. filling all internal gaps formed by the electrode components with a polymer filler material through an access hole in the molding die;    j. curing the polymer filler material;    k. removing the molding stylet to form a central lumen in the electrode array.    
     
     
         8 . The method of  claim 7  wherein electrically and mechanically bonding the pigtail end of each wire to an open-ring contact comprises 
 trimming the pigtail to a desired length, and  
 laser welding the wire to the ring contact.  
 
     
     
         9 . The method of  claim 8  further including positioning the assembled multiwire lead, separation tube, and open ring contacts in a compressive die prior to trimming the pigtail lead to a desired length, and applying a sufficient compressive force to the open-ring contact so as to close the open-ring contact firmly against the pigtail lead passing through the axial gap.  
     
     
         10 . The method of  claim 9  wherein the ring contact is made from a compressible material, and wherein the method further includes closing the open ring contacts with sufficient compressive force so as to compress the ring contact into the body of the separation tube and closing the gap between the ring contact and the lead wires.  
     
     
         11 . The method of  claim 8  further including closing the distal end of the electrode array to form a rounded tip.  
     
     
         12 . The method of  claim 11  wherein closing the distal end of the electrode array comprises applying a liquid polymer to the distal end of the electrode array, and allowing the liquid polymer to cure.  
     
     
         13 . The method of  claim 11  wherein closing the distal end of the electrode array comprises applying a pre-cured plug made from the same material as the filler molding material to the distal end of the electrode array.  
     
     
         14 . The method of  claim 7  wherein forming the multiwire helically wound configuration comprises placing the multiwire helically wound configuration on a mandrel, and unwrapping the distal end of each wire to form a distal protruding tip.  
     
     
         15 . The method of  claim 14  further including unwrapping the distal end of each wire to achieve a desired axial separation or pitch between the distal protruding tips.  
     
     
         16 . The method of  claim 15  further including trimming the distal protruding tips of each wire to a desired length.