Removal of an island from a laser cut article

Abstract

Methods and apparatuses for use in such methods for removing islands from laser cut articles. Methods include using a chemical etching solution to remove material in the strut-island gap. Optionally, heat and/or agitation can be applied during the etching process to increase the chemical activity of the chemical etching solution and/or to vibrate the islands out of position.

What is claimed is: 
     
         1 . A method for removing an island from a laser cut article, comprising:
 providing a refractory metal workpiece having an outer surface and an inner surface;   laser cutting the refractory metal workpiece substantially continuously along a laser cut line that extends from the outer surface to the inner surface to produce an article that includes a plurality of laser cuts and one or more islands remaining between the laser cuts; and   chemically treating the article to remove the one or more islands therefrom so as to form an implantable device.   
     
     
         2 . The method of  claim 1 , wherein the laser cutting is performed in a single pass. 
     
     
         3 . The method of  claim 1 , wherein the one or more islands are affixed to the article by one or more of slag, remelt, laser ablated material, oxide-oxide bonding, or geometric constraints. 
     
     
         4 . The method of  claim 1 , wherein the refractory metal workpiece is made from a material selected from the group consisting of tantalum, niobium, tungsten, and alloys thereof. 
     
     
         5 . The method of  claim 1 , wherein the implantable device is an implantable refractory metal stent. 
     
     
         6 . The method of  claim 1 , the chemically treating further comprising disposing the article in a chemical etching solution that includes hydrofluoric acid (HF) and nitric acid (HNO 3 ). 
     
     
         7 . The method of  claim 6 , further comprising disposing the article in the chemical etching solution for a period of time in a range from about 10 minutes to about 60 minutes. 
     
     
         8 . The method of  claim 6 , further comprising:
 sonicating in the chemical etching solution using an ultrasonic cleaning apparatus while the article is disposed in the chemical etching solution; and   heating the article in the chemical etching solution to a temperature in a range from about 40° C. to about 70° C. while the article is disposed in the chemical etching solution.   
     
     
         9 . The method of  claim 1 , the chemically treating further comprising etching the article in a chemical etching solution including at least one mineral acid. 
     
     
         10 . The method of  claim 9 , the at least one mineral acid including hydrofluoric acid (HF). 
     
     
         11 . The method of  claim 9 , the at least one mineral acid including hydrofluoric acid (HF) and nitric acid (HNO 3 ). 
     
     
         12 . The method  claim 11 , the chemical etching solution including about 1% HF by volume to about 10% HF by volume, about 10% HNO 3  by volume to about 50% HNO 3  by volume, and water. 
     
     
         13 . The method  claim 11 , the chemical etching solution including about 1% HF by volume to about 5% HF by volume, about 20% HNO 3  by volume to about 45% HNO 3  by volume, and water. 
     
     
         14 . The method  claim 11 , the chemical etching solution including about 1% HF by volume to about 3% HF by volume, about 25% HNO 3  by volume to about 35% HNO 3  by volume, and water. 
     
     
         15 . The method  claim 11 , wherein the chemical etching solution further includes urea. 
     
     
         16 . The method  claim 11 , the chemical etching solution including about 2% HF by volume to about 4% HF by volume, about 25% HNO 3  by volume to about 35% HNO 3  by volume, about 0.9 weight % (“wt %”) to about 1.3 wt % urea, and water. 
     
     
         17 . A method for removing an island from a refractory metal article, the method comprising:
 providing a refractory metal workpiece having an outer surface and an inner surface;   laser cutting the refractory metal workpiece substantially continuously along a laser cut line that extends from the outer surface to the inner surface in a single pass to produce a laser cut refractory metal article that includes a plurality of laser cuts and one or more islands remaining between the laser cuts; and   treating the laser cut refractory metal article to remove the one or more islands therefrom, the treating comprising:
 disposing the laser cut refractory metal article in a chemical etching solution that includes hydrofluoric acid (HF) and nitric acid (HNO 3 ) for a period of time sufficient to remove the one or more islands therefrom so as to form an implantable device. 
   
     
     
         18 . The method of  claim 17 , the treating further comprising:
 heating the laser cut refractory metal article in the chemical etching solution to a temperature in a range from about 40° C. to about 70° C.; and   sonicating the laser cut refractory metal article in the chemical etching solution using an ultrasonic apparatus.   
     
     
         19 . The method of  claim 18 , further comprising treating the laser cut refractory metal article for a period of time in a range from about 10 minutes to about 60 minutes. 
     
     
         20 . The method  claim 17 , wherein the chemical etching solution includes about 1% HF by volume to about 10% HF by volume, about 10% HNO 3  by volume to about 50% HNO 3  by volume, and water. 
     
     
         21 . The method of  claim 17 , wherein the refractory metal workpiece is made from a material selected from the group consisting of tantalum, niobium, tungsten, and alloys thereof. 
     
     
         22 . The method of  claim 17 , wherein the refractory metal workpiece is made from a tantalum alloy, comprising:
 about 75 to about 90 weight percent tantalum;   about 8 to about 12 weight percent niobium;   about 2 to about 10 weight percent tungsten.   
     
     
         23 . The method of  claim 22 , wherein the refractory metal workpiece further comprises at least one of zirconium or molybdenum. 
     
     
         24 . A method for removing an island from an implantable article, the method comprising:
 providing a tubular a tantalum alloy workpiece having an outer surface and an inner surface;   laser cutting the tubular a tantalum alloy workpiece substantially continuously along a patterned laser cut line that extends from the outer surface to the inner surface to produce a laser cut stent that includes a patterned plurality of laser cut struts and one or more islands remaining between the laser cut struts, wherein the laser cut struts have a cross-sectional dimension of about 40 μm to about 120 μm; and   treating the laser cut stent to remove the one or more islands therefrom, the treating comprising:
 disposing the laser cut stent in a chemical etching solution that includes hydrofluoric acid (HF) and nitric acid (HNO 3 ); 
 heating the laser cut stent in the chemical etching solution to a temperature in a range from about 40° C. to about 70° C.; 
 sonicating the laser cut stent in the chemical etching solution using an ultrasonic apparatus; and 
   treating the laser cut stent in the chemical etching solution under heating and sonication for a period of time sufficient to remove the one or more islands therefrom so as to form an implantable stent.   
     
     
         25 . The method of  claim 24 , wherein the laser cutting is performed in a single pass using a picosecond laser apparatus. 
     
     
         26 . The method of  claim 24 , wherein the tubular tantalum alloy workpiece includes tantalum and one or more of niobium, tungsten, zirconium and molybdenum. 
     
     
         27 . The method of  claim 24 , wherein the laser cut struts of the laser cut stent have a cross-sectional dimension of about 45 μm to about 80 μm. 
     
     
         28 . The method of  claim 24 , wherein the laser cut struts of the laser cut stent have a cross-sectional dimension of about 50 μm to about 80 μm. 
     
     
         29 . A method of manufacturing an implantable article, comprising
 providing a first refractory metal workpiece having an outer surface and an inner surface, the first refractory metal workpiece being made from a material selected from the group consisting of tantalum, niobium, tungsten, zirconium, molybdenum, and alloys thereof;   laser cutting the first refractory metal workpiece in a single pass using a picosecond laser apparatus substantially continuously along a patterned laser cut line that extends from the outer surface to the inner surface to form a laser cut stent that includes a patterned plurality of laser cut struts and one or more islands remaining between the laser cut struts, wherein the laser cut struts have a cross-sectional dimension of about 40 μm to about 120 μm;   treating the laser cut stent for a period of time sufficient to remove the one or more islands therefrom, the treating comprising:
 disposing the laser cut stent in a chemical etching solution that includes hydrofluoric acid (HF) and nitric acid (HNO 3 ); 
 heating the laser cut stent in the chemical etching solution to a temperature in a range from about 40° C. to about 70° C.; 
 sonicating the laser cut stent in the chemical etching solution using an ultrasonic apparatus; 
 wherein the treating does not include use of a mask capable of defining a plurality of struts and a plurality of islands remaining between the struts; 
   electropolishing the laser cut metal stent in an electropolishing solution; and   heat treating the laser cut refractory metal stent so as to form an implantable stent.