Three-dimensional thin-film nitinol devices

Abstract

A method of manufacturing three-dimensional thin-film nitinol (NiTi) devices includes: depositing multiple layers of nitinol and sacrificial material on a substrate. A three-dimensional thin-film nitinol device may include a first layer of nitinol and a second layer of nitinol bonded to the first layer at an area masked and not covered by the sacrificial material during deposition of the second layer.

What is claimed is: 
     
         1 . A method comprising:
 deep reactive ion etching a pattern of grooves on a surface of a semiconductor substrate, the grooves corresponding to fenestrations in a desired three-dimensional nitinol structure;   depositing a lift-off layer on the grooved semiconductor substrate surface;   depositing a first NiTi layer over the lift-off layer;   depositing a sacrificial layer to partially cover the first NiTi layer, the sacrificial layer corresponding to a lumen in the desired three-dimensional nitinol structure; and   depositing a second NiTi layer over the sacrificial layer.   
     
     
         2 . The method of  claim 1 , further comprising:
 removing the lift-off layer and the sacrificial layer so that the first and second NiTi layers are separated from the semiconductor substrate and so that the lumen is formed in the resulting three-dimensional nitinol structure.   
     
     
         3 . The method of  claim 1 , wherein depositing the lift-off layer comprises depositing a copper or chromium lift-off layer. 
     
     
         4 . The method of  claim 1 , wherein depositing the sacrificial layer comprises depositing a chromium sacrificial layer. 
     
     
         5 . The method of  claim 1 , wherein depositing the sacrificial layer comprises depositing the sacrificial layer through a first mask, the method further comprising:
 depositing an aluminum bonding layer onto the first NiTi layer through a reverse mask prior to deposition of the second NiTi layer, the reverse mask being approximately a reverse image of the first mask.   
     
     
         6 . The method of  claim 5 , further comprising heating the aluminum bonding layer so that the aluminum bonding layer bonds the first NiTi layer to the second NiTi layer. 
     
     
         7 . The method of  claim 2 , further comprising inserting a mandrel into the lumen of the three-dimensional nitinol structure, and heating the three-dimensional nitinol structure while it is on the mandrel to crystallize the first and second nitinol layers. 
     
     
         8 . The method of  claim 7 , wherein the three-dimensional nitinol structure is a flow diverter stent cover, the method further comprising covering a flow diverter stent with the flow diverter stent cover. 
     
     
         9 . A nitinol stent cover, comprising:
 a first nitinol layer;   an aluminum bonding layer; and   a second nitinol layer, wherein the aluminum bonding layer is configured to bond longitudinal edges of the first nitinol layer to longitudinal edges of the second nitinol layer.   
     
     
         10 . The nitinol stent cover of  claim 9 , wherein the first nitinol layer and the second nitinol layer each includes an array of fenestrations. 
     
     
         11 . The nitinol stent cover of  claim 10 , wherein the fenestrations are diamond-shaped. 
     
     
         12 . The nitinol stent cover of  claim 11 , wherein the first and second nitinol layers form a wire mesh having a width of 5 to 20 microns. 
     
     
         13 . The nitinol stent cover of  claim 11 , wherein each diamond-shaped fenestration has a longitudinal extent of approximately 300 microns and a lateral extent of approximately 150 microns. 
     
     
         14 . The nitinol stent cover of  claim 11  where the percent metal coverage of the nitnol film is ≦15% when covering the fully-expanded stent backbone. 
     
     
         15 . The nitinol stent cover of  claim 11  where the density of fenestrations is between 15 and 25 fenestrations per square millimeter when covering the fully-expanded stent backbone. 
     
     
         16 . The nitinol stent cover of  claim 9 , further comprising a flow diverter stent within a lumen of the nitinol stent cover. 
     
     
         17 . The flow diverter stent of  claim 16  where the percent metal coverage of the total device (i.e. thin film nitinol cover and stent backbone is ≦20%.