Methods of making flexible electrodes
The novel flexible electrodes disclosed herein utilize the low bending stiffness of electrospun nanofiber mats to achieve the material properties required for surgical implantation and sustained bidirectional communication with peripheral nerves without compromising electronic functionality. According to certain embodiments disclosed herein, implantable neural electrode probes are provided which comprise a polymeric substrate having proximal and distal ends, an electrode interface at the proximal end of the substrate; at least one neural contact at the distal end of the substrate; and electrically conductive traces formed on the fibrous substrate providing electrical communication between the at least one neural contact and the electrode interface, wherein the substrate comprises a nonwoven mass of polymeric nanofibers.
1. A method of making a flexible electrode comprising the steps of:
(a) electrospinning a nanofiber mat comprised of a nonwoven mass of polymeric nanofibers;
(b) depositing a conductive component on or within the nanofiber mat; and
(c) photolithographically forming electrical traces on or within the nanofiber mat.
2. The method according to claim 1 , which further comprises the step of:
(d) coating the nanofiber mat and electrical traces with a silicone layer; and thereafter
(e) etching regions of the silicone layer to form contact points.
3. The method according to claim 2 , which further comprises the step of:
(f) forming a final shape of the electrode.
4. The method according to claim 1 , wherein step (b) comprises applying a photoresist material onto the nanofiber mat and etching conductive channel patterns.
5. The method according to claim 4 , wherein step (b) comprises incorporating an electrically conductive material in the channel patterns.
6. The method according to claim 1 , wherein between steps (a) and (b) there is practiced a step of:
(a1) depositing a photoresist onto the nanofiber mat and allowing the photoresist to fill a lower region of the nanofiber mat and thereby coat the polymeric nanofibers therein and establish a top surface region of the nanofiber mat comprised of polymeric nanofibers uncoated by the photoresist.
7. The method according to claim 6 , wherein step (b) comprises:
(b1) depositing a conductive metal layer onto the top surface region of the nanofiber mat to provide a layer of conductive metal-coated polymeric nanofibers in at least a portion of the top surface region thereof.
8. The method according to claim 7 , wherein step (c) comprises:
(c1) photolithographically forming electrical traces of the conductive metal-coated polymeric nanofibers in the top surface region of the nanofiber mat.
9. The method according to claim 8 , which further comprises the steps of:
(d) applying silicone onto the nanofiber mat to form a silicone layer over the electrical traces; and thereafter
(e) etching regions of the silicone layer to form contact points of the electrical traces.
10. The method according to claim 9 , which further comprises the step of:
(f) forming a final shape of the electrode.
11. The method according to claim 8 , which further comprises the step of:
(d) applying silicone onto the nanofiber mat to form a silicon-filled nanofiber mat and a silicone layer over the electrical traces.
12. The method according to claim 11 , wherein the silicone layer has a thickness of about 5 μm.
13. The method according to claim 11 , which further comprises the step of:
(f) etching regions of the silicone layer to form contact points of the electrical traces.
14. The method according to claim 6 , wherein step (a) comprises providing a silicon wafer, and electrospinning the nanofiber mat onto the silicon wafer.
15. The method according to claim 1 , wherein the nanofiber mat fibrous substrate exhibits an elastic modulus of between about 50 MPa to about 5 GPa.
16. The method according to claim 15 , wherein the polymeric nanofibers comprise an insulating coating.
17. The method according to claim 15 , wherein the nanofiber mat substrate comprises a nanofiber layer which includes the polymeric nanofibers and an insulation layer.
18. The method according to claim 17 , wherein the insulation layer comprises a p-xylyene polymer or polydimethysiloxane.
19. The method according to claim 1 , wherein the polymeric nanofibers are formed of a plastic material selected from the group consisting of nylon, polycaprolactone, cellulose acetate, poly(methyl-methacrylate, ethylene vinyl alcohol and polyimide.
20. The method according to claim 1 , wherein the polymeric nanofibers are formed of nylon-6 and/or nylon-6,12.