Method and apparatus for direct laser cutting of metal stents

Abstract

An improved expandable stent for implantation in a body lumen, such as an artery, and an improved method for making it from a single length of tubing. The stent consists of a plurality of radially expandable cut cylindrical elements generally aligned on a common axis and interconnected by one or more interconnective elements, the elements having a rectangular cross-section from cut-to-cut. The individual radially expandable cylindrical elements are disposed in an undulating pattern. The stent is manufactured by direct laser cutting from a single metal tube using a finely focused laser beam passing through a coaxial gas jet structure to impinge on the working surface of the tube as the linear and rotary velocity of the tube is precisely controlled.

1 . A longitudinal flexible stent for implanting in a body lumen, comprising: 
 a plurality of cut cylindrical elements which are independently expandable in the radial direction and which are interconnected so as to be generally aligned on a common longitudinal axis, each cylindrical element having a rectangular cross-section from one cut edge to another; and    a plurality of connecting elements for interconnecting said cut cylindrical elements, said connecting elements configured to interconnect said cylindrical elements that are adjacent to each other.    
     
     
         2 . The stent of  claim 1 , wherein said plurality of cut cylindrical elements include a plurality of peaks and valleys having a serpentine pattern.  
     
     
         3 . The stent of  claim 2 , wherein said plurality of peaks and valleys include a plurality of U-shaped members, a plurality of Y-shaped members, and a plurality of W-shaped members, some of said U-shaped, Y-shaped, and W-shaped members being interconnected.  
     
     
         4 . The stent of  claim 1 , wherein at least some of said plurality of cut cylindrical elements tip radially outwardly to form outwardly projecting edges upon radial expansion of said stent.  
     
     
         5 . The stent of  claim 1 , wherein said cut cylindrical elements are capable of retaining their expanded condition upon the expansion thereof.  
     
     
         6 . The stent of  claim 1 , wherein said stent is formed of stainless steel.  
     
     
         7 . The stent of  claim 1 , wherein said stent is formed from a single piece of tubing.  
     
     
         8 . A method of making an expandable metal stent, comprising the steps of: 
 supporting a metal tube for controlled linear and rotary motion;    impinging a finely focused laser beam upon the working surface of said metal tube; and    providing a protective mandrel within said tube to protect the tube wall opposite the tube wall being cut from being ablated by said laser beam,    whereby a precise pattern is cut into said tube to form said stent.    
     
     
         9 . A method as set forth in  claim 8 , wherein said metal tube is stainless steel.  
     
     
         10 . A method as set forth in  claim 8 , wherein said protective mandrel is stainless steel.  
     
     
         11 . A method as set forth in  claim 8 , wherein said laser beam is circularly polarized.  
     
     
         12 . A method as set forth in  claim 11 , wherein said circular polarization is accomplished by a quarter wave plate.  
     
     
         13 . A method as set forth in  claim 8 , wherein said laser beam is spatially filtered.  
     
     
         14 . A method as set forth in  claim 8 , wherein the size of the focused laser beam spot and depth of field is controlled by selecting beam diameter.  
     
     
         15 . A method as set forth in  claim 8 , wherein the size of the focused laser beam spot and depth of field is controlled by selecting focal length of the beam focusing lens.  
     
     
         16 . A method as set forth in  claim 8 , wherein said laser beam passes through a coaxial gas jet adjacent said tube.  
     
     
         17 . A method as set forth in  claim 16  wherein the gas is oxygen.  
     
     
         18 . A method as set forth in  claim 8  and further including the steps of: 
 ultrasonically cleaning said stent after it is formed.  
 
     
     
         19 . A method as set forth in either of  claim 1  or  18 , and further including the step of electro-polishing said stent after it is formed.