Method of making recessed features on inner surface of tubular structure by thermal ablation
The invention relates to methods and apparatus for manufacturing intravascular stents wherein the intravascular stent has its inner surface treated to promote the migration of endothelial cells onto the inner surface of the intravascular stent. In particular, the inner surface of the intravascular stent has at least one groove formed therein.
1. A method of forming at least one recessed feature on an inner surface of a fenestrated stent structure, comprising the steps of:
providing an electrically conductive fenestrated stent structure having a central lumen, an inner concave surface and an outer convex surface;
mounting the fenestrated stent structure in a dielectric holding fixture;
coupling a bearing block assembly to the fenestrated stent structure;
introducing an electrode into the central lumen of the fenestrated stent structure in cooperation with the bearing block assembly, the electrode having a predefined pattern corresponding to a pattern of the at least one recessed feature to be formed on the inner concave surface of the fenestrated stent structure and the electrode being rotatable within the central lumen;
applying electrical current to the electrode and the predefined pattern; and
transferring the electrical current to the inner concave surface of the fenestrated stent structure thereby cutting the at least one recessed feature on the inner concave surface.
2. The method of claim 1 , wherein the step of coupling a bearing block assembly further comprises the step of providing a bearing block assembly having an indexing and current transfer disk provided within a gear drive mechanism.
3. The method of claim 2 , wherein the step of introducing an electrode further comprises the step of providing an electric discharge machining electrode having bearing shafts disposed at each end thereof and coupling the bearing block assembly and disk to a bearing shaft.
4. The method of claim 1 , wherein the predefined pattern in the electrode corresponds to at least one groove to be imparted to the inner concave surface of the fenestrated stent structure.
5. The method of claim 1 , wherein the dielectric holding fixture further comprises a opposing members having a curved stent holding surfaces forming an inner diameter that approximates the outer diameter of the fenestrated stent structure when the opposing members are brought into apposition.
6. The method of claim 5 , wherein the bearing block assembly operably couples to the fenestrated tubular stent structure at a first end thereof and operably engages with the opposing members.
7. The method of claim 6 , wherein the indexing and current transfer disk provided within a gear drive mechanism is operably coupled to the fenestrated tubular stent structure at a second end thereof and to the electrode.
8. The method of claim 7 , wherein the indexing and current transfer disk provided within a gear drive mechanism are external to the fenestrated stent structure.
9. The method of claim 1 , wherein the electrode is operably coupled to an electrode carrier.
10. The method of claim 9 , wherein the electrode carrier is operably coupled to the indexing and current transfer disk provided within the gear drive mechanism and is positionally controlled thereby within the central lumen of the fenestrated stent structure.