Interfacing With The Peripheral Nervous System (PNS) Using Targeted Fascicular Interface Device

Abstract

A stealthy conductor that may be placed inside a fascicle in the peripheral nervous system (PNS) is described. The conductor is placed using a targeted-fascicle or targeted-axon approach to improve specificity and signal to noise ratio (SNR). The conductor is part of a targeted fascicular interface device and is placed using an insertion tool in a manner that reduces nerve damage as compared to conventional systems. The conductor is so small (e.g., <10 μm diameter) and so flexible (e.g., approximates flexibility of surrounding neuronal material) that biological reactions (e.g., recruitment of macrophages, edema) to the presence of the conductor may be reduced. The targeted fascicular interface device has an insulated portion and a non-insulated portion that may act as an electrode. The insulated portion may include materials that promote healing at the entry/exit site and that adhere to the perineurium.

What is claimed is: 
     
         1 . A device for interfacing with a selected axon inside a single fascicle in a nerve in the peripheral nervous system (PNS) via a single hole in the epineurium of the nerve and a single hole in the perineurium of the fascicle, comprising:
 a biocompatible conductor capable of receiving an electrical signal from the axon or providing an electrical stimulation to the axon while positioned within a threshold distance of the axon, where the conductor has a diameter of less than 11 μm, and where the conductor has a flexural rigidity measure of less than 1.5×10 −15  Pa*m 2 , and   an insulator that covers at least a portion of the conductor,
 where the insulator comprises a material that promotes healing at the single hole in the perineurium, and where the insulator comprises a material that adheres to the perineurium. 
   
     
     
         2 . The device of  claim 1 , the conductor being one or more conduction wires including platinum wires, or carbon nanotubes. 
     
     
         3 . The device of  claim 1 , the insulator being coated with titanium, and comprising Teflon, parylene-C, Silicone, siloxanes, or Polydimethylsiloxane. 
     
     
         4 . The device of  claim 1 , the insulator being amorphous carbon with a purity of at least 99%. 
     
     
         5 . The device of  claim 1 , comprising an amplifier electrically connected to the conductor. 
     
     
         6 . The device of  claim 5 , where the combination of the conductor and the amplifier provide a signal with a signal to noise ratio (SNR) of less than 2 μV RMS. 
     
     
         7 . The device of  claim 5 , where the combination of the conductor and the amplifier have an input impedance greater than 20MΩ, provide a signal with a bandwidth of 800 Hz to 6 kHz, provide a signal with a dynamic voltage range of 0-1 mV, and provide a signal with an amplitude of 0-1 mA. 
     
     
         8 . The device of  claim 1 , where the threshold distance is 100 μm. 
     
     
         9 . An assembly for use in surgically implanting a device for interfacing with an axon inside a single fascicle in a nerve in the peripheral nervous system (PNS) via a hole in the epineurium of the nerve and a hole in the perineurium of the fascicle, the assembly comprising:
 an insertion tool shaped and sized to create the hole in the perineurium and to place the device inside the fascicle through the hole in the perineurium, and   the device;   where the tip of the insertion tool that creates the hole in the perineurium is less than 5 μm in diameter, where the insertion tool has a stiffness of at least 200 GPa, and where the insertion tool is shaped and sized to penetrate the perineurium surrounding the axon with an applied force less than that required by a 35 gauge needle;   and   where the device comprises:
 a biocompatible conductor capable of receiving an electrical signal from the axon or providing an electrical stimulation to the axon while positioned longitudinally within a threshold distance of the axon for at least a run length, where the conductor has a diameter of less than 11 μm, and 
 an insulator that covers at least a portion of the conductor, where the insulator comprises a material that adheres to the perineurium. 
   
     
     
         10 . The assembly of  claim 9 , where a portion of the device is wound at least two complete turns around the insertion tool prior to insertion. 
     
     
         11 . The assembly of  claim 9 , where a portion of the device is affixed to the insertion tool prior to insertion. 
     
     
         12 . The assembly of  claim 11 , where the portion of the device is affixed to the insertion tool by a biodegradable or dissolvable substance. 
     
     
         13 . The assembly of  claim 12 , the biodegradable or dissolvable substance being sucrose. 
     
     
         14 . The assembly of  claim 9 , the insertion tool comprising a body having a channel configured to receive at least a portion of the device. 
     
     
         15 . The assembly of  claim 14 , where a portion of the device is affixed in the channel. 
     
     
         16 . The assembly of  claim 9 , where the insertion tool is a tungsten needle. 
     
     
         17 . The assembly of  claim 9 , where the insertion tool is shaped and sized to make the single hole in the epineurium less than 25 μm in diameter and to make the single hole in the perineurium less than 20 μm in diameter. 
     
     
         18 . The assembly of  claim 9 , where the conductor is one or more platinum wires, or one or more carbon nanotubes, and where the insulator is coated with titanium, and where the insulator comprises Teflon, parylene-C, Silicone, or amorphous carbon with a purity of at least ninety nine percent. 
     
     
         19 . A surgical technique for implanting a device for interfacing with an axon inside a single fascicle in a nerve in the peripheral nervous system (PNS) via a single hole in the epineurium of the nerve and a single hole in the perineurium of the fascicle, the surgical technique comprising:
 applying a first substance to at least partially dissolve the epineurium to at least partially expose the perineurium;   puncturing the perineurium with an insertion tool to produce the single hole in the perineurium;   positioning the device through the single hole in the epineurium and the single hole in the perineurium using the insertion tool so that a conducting portion of the device is located longitudinally in the fascicle and so that an insulating portion of the device is in contact with an edge of the single hole in the perineurium;   removing the insertion tool through the single hole in the perineurium and the single hole in the epineurium;   applying a second substance to the single hole in the perineurium to promote healing of the perineurium and to fix the device in place with respect to the fascicle, and   applying a third substance to the single hole in the epineurium to promote healing of the epineurium and to fix the device in place with respect to the nerve.   
     
     
         20 . The surgical technique of  claim 19 , where the device comprises:
 a biocompatible conductor capable of receiving an electrical signal from the axon or providing an electrical stimulation to the axon while positioned longitudinally within a threshold distance of the axon for at least a run length, where the conductor has a diameter of less than 11 μm, and where the conductor has a flexural rigidity of less than 1.5×10 −15  Pa·m 2 , and   an insulator that covers at least a portion of the conductor, where the insulator comprises a material that adheres to the perineurium.   
     
     
         21 . The surgical technique of  claim 20 , where the insertion tool is shaped and sized to create the single hole in the perineurium and to deliver the device to the inside of the fascicle through the single hole in the perineurium,
 where the tip of the insertion tool that creates the single hole in the perineurium is less than 5 μm in diameter, and   where the insertion tool is shaped and sized to penetrate the perineurium surrounding the axon with an applied force of similar or less to that produced by a needle used for microsurgery   
     
     
         22 . The surgical technique of  claim 19 , the first substance being collagenase. 
     
     
         23 . The surgical technique of  claim 22 , the second substance being a fibrin sealant. 
     
     
         24 . The surgical technique of  claim 23 , the third substance being a fibroblast growth factor. 
     
     
         25 . The surgical technique of  claim 20 , where the device is placed within a threshold distance of a targeted axon for a run length. 
     
     
         26 . The surgical technique of  claim 25 , the threshold distance being 200 μm. 
     
     
         27 . The surgical technique of  claim 25 , the run length being 5 mm. 
     
     
         28 . The surgical technique of  claim 19 , comprising:
 testing the position of the device with respect to a desired axon by stimulation or recording, and   repositioning the device until a desired positioning with respect to the desired axon is achieved.   
     
     
         29 . The surgical technique of  claim 19 , comprising mechanically attaching a portion of the device to the insertion tool before inserting the device into the fascicle. 
     
     
         30 . The surgical technique of  claim 29 , comprising detaching the device from the insertion tool before removing the insertion tool. 
     
     
         31 . The surgical technique of  claim 19 , comprising chemically attaching a portion of the device to the insertion tool before inserting the device into the fascicle. 
     
     
         32 . The surgical technique of  claim 31 , comprising waiting for the device to become unattached from the insertion tool before removing the insertion tool.