Thin-film micromesh covers for medical devices and related methods
A thin-film covered stent device may include a thin-film mesh and a stent backbone covered by the thin-film mesh, thereby forming a dual-layer stent structure. The thin-film covered stent device may have smaller pores and a high pore density compared to conventional stents. For example, the thin-film covered stent device may have a slit length of between 50 and 250 micrometers and a pore density of between 134 and 227 pores per mm 2 . The thin-film covered stent device facilitates rapid healing of tissue defects such as those encountered during the endovascular treatment of an aneurysm.
1. A method comprising:
deep reactive ion etching a micropattern of trenches on a surface of a semiconductor substrate, the trenches corresponding to slits in a desired thin-film Nitinol mesh,
wherein the etching of the micropattern of trenches comprises etching the micropattern of trenches such that the thin-film Nitinol mesh, when expanded, has pore densities of between 81 and 1075 pores per mm 2 , and comprises a region of high pore density flanked by regions of low pore density, wherein radiopaque markers delineate transition zones between the regions;
depositing a lift-off layer on the grooved semiconductor substrate surface;
depositing a first Nitinol layer over the lift-off layer;
depositing a sacrificial layer over the first Nitinol layer leaving edges along the longitudinal axis exposed;
depositing a second Nitinol layer over the sacrificial layer;
etching the lift-off layer and the sacrificial layer to form the thin-film Nitinol mesh;
expanding the thin-film Nitinol mesh along the longitudinal axis to open the slits to corresponding pores, each pore having a long axis and a short axis; and
attaching the expanded thin-film Nitinol mesh to a stent backbone such that the long axis of the pores are perpendicular to a longitudinal axis of the stent backbone.
2. The method of claim 1 , wherein the etching of the micropattern of trenches comprises etching the micropattern of trenches such that the thin-film Nitinol mesh, when expanded, has percent metal coverages of between 19 and 66%.
3. The method of claim 1 , wherein the etching of the micropattern of trenches comprises etching the micropattern of trenches corresponding to slit lengths of between 50 and 250 micrometers.
4. The method of claim 1 , wherein the depositing of the first thin-film Nitinol layer and the depositing of the second thin-film Nitinol layer comprise depositing Nitinol to a thickness of between 1 and 50 micrometers.
5. The method of claim 1 , wherein the expanding of the thin-film Nitinol mesh forms the pores having a largest dimension of less than 250 micrometers, and wherein the attaching the expanded thin-film Nitinol mesh to the stent backbone forms a carotid stent configured to be deployed at a carotid artery.
6. The method of claim 1 , further comprising coating the thin-film Nitinol mesh with a drug eluting polymer to reduce a rate of neointimal hyperplasia or increases biocompatibility or hemocompatibility of the thin-film Nitinol mesh.