Three-dimensional thin-film nitinol devices
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.
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 through a shadow mask to partially cover the first NiTi layer, the sacrificial layer corresponding to a lumen in the desired three-dimensional nitinol structure;
sputter depositing an aluminum bonding layer onto the first NiTi layer through a reverse mask prior to deposition of a second NiTi layer, the reverse mask being approximately a reverse image of the shadow mask; and
depositing the second NiTi layer over the sacrificial layer and the aluminum bonding 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 , further comprising heating the aluminum bonding layer so that the aluminum bonding layer bonds the first NiTi layer to the second NiTi layer.
6. 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.
7. The method of claim 6 , 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.