Array of Microelectrodes for Interfacing to Neurons within Fascicles

Abstract

Methods and apparatus are disclosed for interfacing with nerve fibers, such as axons. Embodiments provide multiple micro-channels, into which individual fascicles of a nerve may be placed, one fascicle per micro-channel. Each micro-channel has an associated set of micro-wire electrodes that penetrate the fascicle in the micro-channel. The micro-wire electrodes are thinner than prior art photolithographed micro-electrode arrays. Consequently, more micro-wire electrodes may interface with a single fascicle, and each micro-wire electrode interfaces with fewer axons, than in the prior art. Multiple rows of micro-channels may be stacked to construct two-dimensional arrays of micro-channels. These embodiments thereby facilitate finer motor control in prosthetic devices, and more granular sensory feedback from prosthetic devices to central nervous systems, than is achievable in the prior art.

What is claimed is: 
     
         1 . An electrode array, comprising:
 a substrate comprising a bio-compatible dielectric and at least one nerve micro-channel, each nerve micro-channel comprising:
 a trench defined by the substrate, the trench being at most about 2.5 cm wide; 
 a lid associated with the trench, comprising a bio-compatible dielectric and configured to be attachable to the substrate so as to close the trench at least along at least a portion of the trench's length such that, when the lid closes the trench, the substrate and the lid collectively define a respective nerve capture volume within the trench; and 
 at least three micro-wire electrodes, each micro-wire electrode protruding from at least one of the substrate defining the trench and the lid associated with the trench and having a diameter of at most about 25 μm substantially along its protrusion. 
   
     
     
         2 . An electrode array according to  claim 1 , wherein the trench is at most about 5,000 μm wide. 
     
     
         3 . An electrode array according to  claim 1 , wherein the trench is at most about 500 μm wide. 
     
     
         4 . An electrode array according to  claim 1 , wherein the trench is at most about 20 μm wide. 
     
     
         5 . An electrode array according to  claim 1 , wherein the at least one nerve micro-channel comprises a plurality of horizontally distributed nerve micro-channels. 
     
     
         6 . An electrode array according to  claim 1 , wherein the at least one nerve micro-channel comprises a plurality of vertically distributed rows of nerve micro-channels, each row of nerve micro-channels comprising a plurality of horizontally distributed nerve micro-channels. 
     
     
         7 . An electrode array according to  claim 1 , wherein, for each nerve micro-channel, the at least three micro-wire electrodes are arranged in a two-dimensional array having a spacing between adjacent micro-wire electrodes of less than about 100 μm. 
     
     
         8 . An electrode array according to  claim 1 , wherein, for each nerve micro-channel, the at least three micro-wire electrodes are arranged in a two-dimensional array having a spacing between adjacent micro-wire electrodes of less than about 40 μm. 
     
     
         9 . An electrode array according to  claim 1 , wherein, for each nerve micro-channel, the at least three micro-wire electrodes are arranged in a two-dimensional array having a spacing between adjacent micro-wire electrodes of less than about 20 μm. 
     
     
         10 . An electrode array according to  claim 1 , wherein, for each nerve micro-channel, the at least three micro-wire electrodes are arranged along at least one diagonal line, relative to a longitudinal axis of the trench. 
     
     
         11 . An electrode array according to  claim 1 , wherein, for each nerve micro-channel, at least one micro-wire electrode of the at least three micro-wire electrodes protrudes at most about 125 μm and less than about 250 μm, and another at least one micro-wire electrode of the at least three micro-wire electrodes protrudes at least about 275 μm. 
     
     
         12 . An electrode array according to  claim 1 , wherein, for each nerve micro-channel, the at least three micro-wire electrodes comprise a plurality of groups of micro-wire electrodes, each group of micro-wire electrodes:
 comprising at least five micro-wire electrodes; and   being spaced longitudinally along the trench, such that micro-wire electrodes of two adjacent groups of micro-wire electrodes are spaced at most about 125 μm apart.   
     
     
         13 . An electrode array according to  claim 1 , further comprising, for each nerve micro-channel, a substantially planar electrode in at least one of the substrate defining the trench and the lid associated with the trench and electrically exposed to the nerve capture volume within the trench. 
     
     
         14 . An electrode array according to  claim 1 , wherein each micro-wire electrode comprises:
 an electrically conductive core; and   an electrically non-conductive layer surrounding the core substantially along the length of the micro-wire electrode protruding from the at least one of the substrate defining the trench and the lid associated with the trench, and exposing at most about a 10 μm distal end portion of the core.   
     
     
         15 . An electrode array according to  claim 14 , wherein the electrically conductive core comprises metal. 
     
     
         16 . An electrode array according to  claim 14 , wherein the electrically conductive core comprises an electrically conductive polymer. 
     
     
         17 . An array according to  claim 14 , wherein the electrically conductive core comprises a carbon fiber. 
     
     
         18 . An electrode array according to  claim 14 , wherein the electrically non-conductive layer comprises glass. 
     
     
         19 . A method for attaching electrodes to at least a portion of a nerve, the method comprising:
 making a longitudinal incision in an epineurial sheath of the nerve, without laterally bisecting the nerve;   displacing, through the incision, a portion of at least one fascicle from inside the epineurial sheath to outside the epineurial sheath, thereby defining a displaced fascicle;   disposing at least a portion of the displaced fascicle in a trench of a nerve micro-channel;   penetrating the displaced fascicle with micro-wire electrodes of the micro-channel; and   attaching a lid to the micro-channel, thereby enclosing the displaced fascicle in the trench.   
     
     
         20 . A method according to  claim 19 , wherein:
 displacing the portion of the at least one fascicle from inside the epineurial sheath to outside the epineurial sheath comprises displacing a plurality of fascicles from inside the epineurial sheath to outside the epineurial sheath, thereby defining a plurality of displaced fascicles;   disposing the at least the portion of the displaced fascicle in the trench of a nerve micro-channel comprises disposing each fascicle of the plurality of displaced fascicles in a trench of a respective nerve micro-channel of a plurality of micro-channels;   penetrating the displaced fascicle with the micro-wire electrodes of the micro-channel comprises penetrating each fascicle of the plurality of displaced fascicles with respective micro-wire electrodes of the respective micro-channel of the plurality of micro-channels; and   attaching a lid to the micro-channel comprises attaching the lid to the plurality of micro-channels.