Parylene-based microelectrode array implant for spinal cord stimulation

Abstract

An implantable electrode array assembly configured to apply electrical stimulation to the spinal cord. A substantially electrically nonconductive layer of the device has a first portion positionable alongside the spinal cord that includes a plurality of first openings. The layer has a second portion that includes a plurality of second openings. Electrodes and traces are positioned inside a peripheral portion of a body portion of the device and alongside the layer. At least one of the first openings is adjacent each of the electrodes to provide a pathway through which the electrode may provide electrical stimulation to the spinal cord. At least one of the second openings is adjacent each of the traces to provide a pathway through which the trace may receive electrical stimulation. At least one trace is connected to each electrode and configured to conduct electrical stimulation received by the trace(s) to the electrode.

The invention claimed is: 
     
         1 . A method of constructing an implantable electrode array assembly, the method comprising:
 forming a patterned layer of electrically conductive material defining a plurality of electrodes and a plurality of traces, at least one trace being connected to each of the plurality of electrodes;   forming a first layer of a substantially electrically nonconductive material, the first layer being adjacent the patterned layer;   forming a plurality of first openings in the first layer, the first openings providing access to the plurality of electrodes through the first layer, a different grid defining portion of the first openings being adjacent each of the electrodes, each grid defining portion exposing a plurality of contacts of the electrode to which the grid defining portion is adjacent; and   forming a plurality of second openings in the first layer, the second openings providing access to the plurality of traces through the first layer.   
     
     
         2 . The method of  claim 1 , further comprising:
 positioning a sacrificial layer on a substrate;   forming a second layer of a substantially electrically nonconductive material on the sacrificial layer; the patterned layer being positioned on the second layer; and   removing the sacrificial layer to thereby release the second layer from the substrate.   
     
     
         3 . The method of  claim 2 , further comprising:
 forming a frame layer on the substrate, the frame layer being underneath the second layer, the frame layer at least partially defining a frame around the patterned layer.   
     
     
         4 . The method of  claim 2 , wherein the first and second layers are each formed from at least one of parylene-A, parylene-C, parylene-AM, parylene-F, paryleneN, and parylene-D. 
     
     
         5 . The method of  claim 2 , wherein the first and second layers are formed from the same material. 
     
     
         6 . The method of  claim 2 , wherein the patterned layer is formed on the second layer using a metal deposition technology. 
     
     
         7 . The method of  claim 6 , wherein the metal deposition technology is e-beam evaporation. 
     
     
         8 . The method of  claim 2 , wherein the sacrificial layer comprises a photoresist material. 
     
     
         9 . The method of  claim 2 , wherein the substrate is a silicon wafer. 
     
     
         10 . The method of  claim 2 , further comprising:
 applying a coating to at least a portion of the second layer and at least a portion of the first layer.   
     
     
         11 . The method of  claim 1 , wherein the plurality of first openings are etched in the first layer. 
     
     
         12 . The method of  claim 1 , wherein the plurality of second openings are etched in the first layer. 
     
     
         13 . A system comprising:
 a stimulation generator configured to generate electrical stimulation;   an implantable electrode array assembly having a proximal end portion connectable to at least one vertebrae and a distal end portion positionable along the spinal cord, the proximal end portion having a plurality of electrical connections to a plurality of electrodes positioned on the distal end portion;   a baseplate configured to be connected to the at least one vertebrae and to connect the assembly to the at least one vertebrae; and   a plurality of wires connected to the baseplate and the stimulation generator, the plurality of wires being configured to conduct electrical stimulation generated by the stimulation generator to the baseplate, the baseplate being configured to conduct the electrical stimulation to the plurality of electrical connections of the proximal end portion of the assembly.   
     
     
         14 . The system of  claim 13 , further comprising:
 an overhanging portion connected to the baseplate and positioned to overhang at least a portion of the proximal portion of the assembly to help protect the assembly from external moving tissue.   
     
     
         15 . An implantable device comprising:
 a plurality of grid structures positioned inside a substantially electrically nonconductive first layer having:
 a first portion positionable alongside a spinal cord comprising a first plurality of openings and 
 a second portion comprising a second plurality of openings with a different one of the grid structures being adjacent to each of a plurality of electrodes and comprising a plurality of cells, 
   wherein for each of the plurality of electrodes, each of the at least one of the first plurality of openings adjacent the electrode being positioned inside a different one of the cells of the grid structure adjacent the electrode.   
     
     
         16 . The device of  claim 15 , wherein the first portion of the first layer is positionable against a dura of the spinal cord. 
     
     
         17 . The device of  claim 16 , wherein and the plurality of electrodes are configured to provide electrical stimulation to the dura. 
     
     
         18 . The device of  claim 15 , further comprising a second layer, wherein the plurality of electrodes are positioned between the first and second layers. 
     
     
         19 . The device of  claim 15 , wherein the first layer is each constructed from at least one of parylene-A, parylene-C, parylene-AM, parylene-F, parylene-N, and parylene-D. 
     
     
         20 . The device of  claim 18 , wherein the second layer is each constructed from at least one of parylene-A, parylene-C, parylene-AM, parylene-F, parylene-N, and parylene-D.