Apparatus and methods for bidirectional hyperelastic stent covers
An apparatus and method for a micro-patterned thin film Nitinol (TFN) that is used as a cover for an expandable stent structure, and has elongation/expansion properties that are configured to match the elongation/expansion properties of the expandable stent structure is presented.
1. A thin-film cover for a vascular implant, comprising:
a thin-film sheet comprising a plurality of pores having a size and shape defined by adjacent struts;
wherein the adjacent struts comprise contiguous undulating, alternating struts within a plane of the thin-film sheet, the adjacent struts defining individual pores having a height and a width;
the thin-film sheet configured to be formed into a tubular cover disposed radially adjacent the vascular implant;
the vascular implant comprising a tubular structure having a central axis and a first compressed configuration and a second expanded configuration that is radially outward along the central axis from the first compressed configuration;
the thin-film sheet configured to radially expand along with the vascular implant from the compressed configuration to the expanded configuration;
wherein the thin-film sheet is configured to shorten in the axial direction along the central axis upon expansion from the compressed configuration to the expanded configuration;
wherein the shape and size of the pores of the thin-film sheet are configured such that the thin-film sheet shortens in the axial direction a pre-determined distance;
said predetermined distance corresponding to axial shortening of the vascular implant;
wherein the individual pores are diamond-shaped;
wherein the undulating struts are curved such that each said pore has a mid-curve point; and
wherein an approximately 400% radial stretching of a pore at the mid-curve point results in an approximately 41% axial shortening of the pore.
2. A cover as recited in claim 1 , wherein the axial shortening of the thin-film sheet and vascular implant is a function of deformation resulting from the expansion from the compressed configuration to the expanded configuration.
3. A cover as recited in claim 2 , wherein the vascular implant comprises an expandable stent.
4. A cover as recited in claim 1 , wherein the axial width of the pores is several times larger than the radial height of the pores.
5. A cover as recited in claim 2 , wherein the axial shortening of the thin-film sheet matches the axial shortening of the vascular implant.
6. A cover as recited in claim 2 , wherein the thin-film sheet comprises nitinol.
7. A cover as recited in claim 2 , wherein the thin-film sheet has a thickness of approximately 0.005 mm.
8. A cover as recited in claim 2 , wherein the adjacent struts have an in-plane width of approximately 0.005 mm.
9. A thin-film cover for a vascular implant, comprising:
a thin-film sheet comprising a plurality of pores having a size and shape defined by adjacent struts;
the thin-film sheet configured to be formed into a tubular cover disposed radially adjacent the vascular implant;
the vascular implant comprising a tubular structure having a central axis and a first compressed configuration and a second expanded configuration that is radially outward along the central axis from the first compressed configuration;
the thin-film sheet configured to radially expand along with the vascular implant from the compressed configuration to the expanded configuration;
wherein the thin-film sheet is configured to shorten in the axial direction along the central axis upon expansion from the compressed configuration to the expanded configuration;
wherein the shape and size of the pores of the thin-film sheet are configured such that the thin-film sheet shortens in the axial direction a pre-determined distance;
said predetermined distance corresponding to axial shortening of the vascular implant;
wherein the axial shortening of the thin-film sheet and vascular implant is a function of deformation resulting from the expansion from the compressed configuration to the expanded configuration;
wherein the adjacent struts comprise undulating, alternating struts configured to define individual pores having a height and a width;
wherein the width of the pores is several times larger than the height of the pores;
wherein the individual pores are diamond-shaped;
wherein the undulating struts are curved such that each said pore has a mid-curve point; and
wherein an approximately 400% radial stretching of a pore at the mid-curve point results in an approximately 41% axial shortening of the pore.