Method for Making Electrically Conductive Three-Dimensional Structures

Abstract

Methods are provided for fabricating three-dimensional electrically conductive structures. Three-dimensional electrically conductive microstructures are also provided. The method may include providing a mold having at least one microdepression which defines a three-dimensional structure; filling the microdepression of the mold with at least one substrate material; molding the at least one substrate material to form a substrate; and depositing and patterning of at least one electrically conductive layer either during the molding process or subsequent to the molding process to form an electrically conductive structure. In one embodiment, the three-dimensional electrically conductive microstructure comprises an electrically functional microneedle array comprising two or more microneedles, each including a high aspect ratio, polymeric three dimensional substrate structure which is at least substantially coated by an electrically conductive layer.

1 . A method for fabricating a three-dimensional, electrically conductive structure comprising: 
 providing a mold having at least one microdepression which defines a three-dimensional structure;    depositing and patterning at least one electrically conductive layer within the microdepression of the mold;    filling the microdepression of the mold with at least one substrate material;    molding the at least one substrate material to form a substrate on top of the at least one electrically conductive layer; and    transferring the at least one electrically conductive layer to the substrate, thereby forming an electrically conductive structure.    
     
     
         2 . The method of  claim 1 , further comprising removing the electrically conductive structure from the mold.  
     
     
         3 . The method of  claim 1 , further comprising electroplating onto the electrically conductive layer.  
     
     
         4 . The method of  claim 1 , wherein the mold comprises a photoresist.  
     
     
         5 . The method of  claim 1 , wherein the substrate material is substantially non-electrically conductive.  
     
     
         6 . The method of  claim 1 , wherein the substrate material comprises a polymer.  
     
     
         7 . The method of  claim 1 , wherein the electrically conductive layer comprises nickel, iron, gold, titanium, copper, platinum, palladium, a stainless steel, or an alloy thereof.  
     
     
         8 . The method of  claim 1 , wherein the patterning comprises removing selectively the electrically conductive layer from protruding and/or recessed surfaces of the mold.  
     
     
         9 . The method of  claim 1 , wherein the at least one microdepression defines a high-aspect ratio three-dimensional structure.  
     
     
         10 . A method for fabricating a three-dimensional, electrically conductive structure comprising: 
 providing a mold having at least one microdepression which defines a three-dimensional structure;    filling the microdepression of the mold with at least one substrate material;    molding the substrate material to form a substrate structure; and    depositing at least one electrically conductive layer onto the substrate structure by directional deposition to form an electrically conductive structure.    
     
     
         11 . The method of  claim 10 , further comprising patterning the electrically conductive layer.  
     
     
         12 . The method of  claim 10 , further comprising electroplating onto the electrically conductive layer.  
     
     
         13 . The method of  claim 10 , wherein the mold comprises a photoresist.  
     
     
         14 . The method of  claim 10 , wherein the substrate comprises a polymer.  
     
     
         15 . The method of  claim 10 , wherein the electrically conductive layer comprises nickel, iron, gold, titanium, copper, platinum, palladium, a stainless steel, or an alloy thereof.  
     
     
         16 . The method of  claim 10 , wherein the patterning comprises removing selectively the electrically conductive layer from protruding and/or recessed surfaces of the mold.  
     
     
         17 . The method of  claim 10 , wherein the at least one microdepression defines a high-aspect ratio three-dimensional structure.  
     
     
         18 . A method for fabricating a three-dimensional, electrically conductive structure comprising: 
 providing a mold having at least one microdepression which defines a three-dimensional structure;    filling the microdepression of the mold with at least one substrate material;    molding the substrate material to form a substrate structure;    depositing a conductive seed layer onto the substrate structure;    patterning the conductive seed layer using a laser ablation or other selective ablation technique; and    electroplating an electrically conductive layer onto the patterned seed layer to form an electrically conductive structure.    
     
     
         19 . The method of  claim 18 , wherein the mold comprises a photoresist.  
     
     
         20 . The method of  claim 18 , wherein the molding comprises a solvent casting or melt casting technique.  
     
     
         21 . The method of  claim 18 , wherein the substrate material comprises a polymer.  
     
     
         22 . The method of  claim 18 , wherein the conductive seed layer comprises an alloy of titanium and copper.  
     
     
         23 . The method of  claim 18 , wherein the electroplated electrically conductive layer comprises a metal selected from the group consisting of nickel, iron, gold, titanium, copper, platinum, palladium, stainless steels, and alloys thereof.  
     
     
         24 . The method of  claim 18 , wherein the electroplated electrically conductive layer comprises nickel.  
     
     
         25 . The method of  claim 18 , wherein the at least one microdepression defines a high-aspect ratio three-dimensional structure.  
     
     
         26 . The method of  claim 1 , wherein the electrically conductive structure has an aspect ratio of greater than about 4:1.  
     
     
         27 . The method of  claim 10 , wherein the electrically conductive structure has an aspect ratio of greater than about 4:1.  
     
     
         28 . The method of  claim 18 , wherein the electrically conductive structure has an aspect ratio of greater than about 4:1.  
     
     
         29 . A three-dimensional, electrically conductive microstructure made by the method of  claim 1 .  
     
     
         30 . A three-dimensional, electrically conductive microstructure made by the method of  claim 10 .  
     
     
         31 . A three-dimensional, electrically conductive microstructure made by the method of  claim 18 .  
     
     
         32 . An electrically functional microneedle array comprising: 
 two or more microneedles extending from a base, wherein each microneedle comprises a high aspect ratio, polymeric three dimensional substrate structure which is coated, at least substantially, by an electrically conductive layer.    
     
     
         33 . The microneedle array of  claim 32 , wherein the two or more microneedles have an aspect ratio of greater than about 4:1.  
     
     
         34 . The microneedle array of  claim 32 , wherein the substrate structure comprises a polymer.  
     
     
         35 . The microneedle array of  claim 34 , wherein the polymer is selected from the group consisting of polymethylmethacrylate, polycarbonate, polystyrene, polyethylene terphthalate, polyethylene, polyvinylchloride, cyclic olefin copolymer, polyurethane, polyamide, polysulfone, polylactide, polyglycolide, poly(lactic-co-glycolic)acid, polyacrylonitrile, copolymers thereof and blends thereof.  
     
     
         36 . The microneedle array of  claim 32 , wherein the conductive layer comprises a metal layer having a thickness of between about 10 and about 50 microns.  
     
     
         37 . The microneedle array of  claim 32 , wherein the microneedles are tapered.  
     
     
         39 . The microneedle array of  claim 32 , further comprising a coating which comprises a biological macromolecule.  
     
     
         40 . The microneedle array of  claim 39 , wherein the biological macromolecule comprises DNA, RNA, a protein, or a peptide.  
     
     
         41 . The microneedle array of  claim 32 , wherein the two or more microneedles are electrically isolated from each other.  
     
     
         42 . The microneedle array of  claim 32 , made by a method comprising: 
 providing a mold having at least one microdepression which defines a high-aspect ratio three-dimensional structure;    depositing and patterning at least one electrically conductive layer within microdepression of the mold;    filling the microdepression of the mold with at least one substrate material;    molding the at least one substrate material to form a substrate on top of the at least one electrically conductive layer; and    transferring the at least one electrically conductive layer to the substrate, thereby forming a high-aspect ratio, electrically conductive structure.    
     
     
         43 . The microneedle array of  claim 32 , made by a method comprising: 
 providing a mold having at least one microdepression which defines a high-aspect ratio three-dimensional structure;    filling the microdepression of the mold with at least one substrate material;    molding the substrate material to form a high-aspect ratio substrate structure; and    depositing at least one electrically conductive layer onto the high-aspect ratio substrate structure by directional deposition to form a high-aspect ratio, electrically conductive structure.    
     
     
         44 . The microneedle array of  claim 32 , made by a method comprising: 
 providing a mold having at least one microdepression which defines a high-aspect ratio three-dimensional structure;    filling the microdepression of the mold with at least one substrate material;    molding the substrate material to form a high-aspect ratio substrate structure;    depositing a conductive seed layer onto the high-aspect ratio substrate structure;    patterning the conductive seed layer using a laser ablation or other selective ablation technique; and    electroplating an electrically conductive layer onto the patterned seed layer to form a high-aspect ratio, electrically conductive structure.