Setting laser power for laser machining stents from polymer tubing

Abstract

Laser machining polymer tubing sections to form stents such that the quality and dimensions of stents from the different tubing sections are sensitive to the laser power is disclosed. The average power of the laser machining is the same for each tubing section which yields stents with different quality and strut widths.

What is claimed is: 
     
         1 . A method of fabricating a plurality of stents, comprising:
 providing a plurality of polymer tubing sections that are each formed separately by the same type of processing steps for use in forming stents of the same design,   wherein each of the tubing sections are made of the same polymer and have the same wall thickness,   selecting an average laser power level for use in forming stents from each of the tubing sections with laser machining; and   laser machining stent patterns into the tubing sections to form a plurality of stents using the selected laser power level,   wherein the stent patterns comprise a plurality of struts,   wherein the quality and dimensions of stents obtained from the laser machining of the different tubing sections are sensitive to the laser power such that laser machining with the selected power level that is the same for the different tubing sections yields stents with different quality and strut widths,   wherein the sensitivity is due to variations in morphology between the different tubing sections arising from slight differences in conditions of the processing steps.   
     
     
         2 . The method of  claim 1 , wherein each tubing section is made of the same material and has the same wall thickness and outer diameter. 
     
     
         3 . The method of  claim 1 , wherein a pulse width, repetition rate, and fluence are the same in the laser machining of each of the tubing sections. 
     
     
         4 . The method of  claim 1 , wherein the processing steps comprise tubing extrusion and radial expansion of the extruded tubes, the method further comprising extruding a plurality of tubing sections and radially expanding the extruded tubing sections to form the plurality of tubing sections. 
     
     
         5 . The method of  claim 1 , wherein the laser is a femtosecond laser with a pulse width between 95-120 fs. 
     
     
         6 . The method of  claim 1 , wherein the tubing sections are made of PLLA. 
     
     
         7 . The method of  claim 1 , wherein the stents formed using the determined laser power levels are free of defects including flash, glitter, and melted portions. 
     
     
         8 . The method of  claim 1 , wherein the laser machining parameters include a pulse width of 95-120 fs, a repetition rate is 2.5-5 kHz, a power level of 0.2-0.3 mW, and a fluence of 5-15 J/cm2. 
     
     
         9 . A method of fabricating a plurality of stents, comprising:
 laser machining a plurality of polymer tubing sections to form stents comprising a plurality of struts,   wherein an average power of the laser machining is the same for each tubing section,   wherein the tubing sections are each formed separately by the same type of processing steps for use in forming stents of the same design,   wherein each of the tubing sections are made of the same polymer and have the same wall thickness,   wherein the quality and dimensions of stents from the different tubing sections are sensitive to the laser power such that laser machining the different tubing sections with the same power yields stents with different quality and strut widths,   wherein the sensitivity is due to variations in morphology between the different tubing sections arising from slight differences in conditions of the processing steps.   
     
     
         10 . The method of  claim 9 , wherein each tubing section is made of the same semicrystalline polymer material and each tubing section has the same wall thickness and outer diameter. 
     
     
         11 . The method of  claim 9 , wherein the adjusted power for each tubing section is different from the adjusted power for other tubing sections. 
     
     
         12 . The method of  claim 9 , wherein at least one processing parameter of the processing steps of each tubing section differ and the morphology of the processed tubing sections depends on the at least one parameter. 
     
     
         13 . The method of  claim 12 , wherein the processing steps comprise tubing extrusion and radial expansion of the extruded tubes, the method further comprising extruding a plurality of tubing sections and radially expanding the extruded tubing sections to form the plurality of tubing sections. 
     
     
         14 . The method of  claim 12 , wherein laser machining is performed with a laser having a pulse width of 80-120 fs. 
     
     
         15 . The method of  claim 12 , wherein laser machining is performed with a laser having a pulse width of 10-15 ps.