Medical device including a solderable linear elastic nickel-titanium distal end section and methods of preparation therefor

Abstract

Shapeable guide wire devices and methods for their manufacture. Guide wire devices include an elongate shaft member having a shapeable distal end section that is formed from a linear pseudoelastic nickel-titanium (Ni—Ti) alloy that has linear pseudoelastic behavior without a phase transformation or onset of stress-induced martensite. Linear pseudoelastic Ni—Ti alloy, which is distinct from non-linear pseudoelastic (i.e., superelastic) Ni—Ti alloy, is highly durable, corrosion resistant, and has high stiffness. The shapeable distal end section is shapeable by a user to facilitate guiding the guide wire through tortuous anatomy. In addition, linear pseudoelastic Ni—Ti alloy is more durable tip material than other shapeable tip materials such as stainless steel.

What is claimed is: 
     
         1 . A method for fabricating a medical device, the method comprising:
 fabricating an elongate shaft member that includes a distal end section, wherein the distal end section is formed of a distal nickel-titanium alloy member having a first cross-sectional dimension;   applying a first layer of solder material to at least a portion of the distal end section;   following applying the soldering material, cold working at least a portion of the distal end section having the solder material applied thereto, wherein the cold working yields a distal practitioner-shapeable end section in which the nickel-titanium alloy in this cold worked region has linear pseudoelastic deformation behavior without a phase transformation or onset of stress-induced martensite; and   soldering the distal shapeable section and a helical coil section disposed about the distal practitioner-shapeable section to an atraumatic cap without substantial loss of the linear pseudoelasticity of the distal practitioner-shapeable section;   wherein the distal practitioner-shapeable end section has a yield stress from about 100 ksi to about 300 ksi.   
     
     
         2 . The method of  claim 1 , wherein the cold working includes at least one of high force flattening, stamping, rolling, or calendaring. 
     
     
         3 . The method of  claim 1 , wherein the distal practitioner-shapeable section exhibits 20% to 90% cold work. 
     
     
         4 . The method of  claim 1 , wherein the distal practitioner-shapeable section comprises a cold-worked microstructure that includes 40% to 50% cold work. 
     
     
         5 . The method of  claim 1 , further comprising applying a second coating of solder to at least a portion of the distal end section, over the first layer of solder material, the second coating of solder being a separately applied coating relative to the atraumatic cap. 
     
     
         6 . The method of  claim 1 , wherein the cold-worked distal practitioner-shapeable end section is in a martensitic phase. 
     
     
         7 . The method of  claim 1 , wherein the martensitic phase is substantially preserved in forming the soldered joint. 
     
     
         8 . The method of  claim 1 , wherein the martensitic phase is stabilized by the cold working. 
     
     
         9 . The method of  claim 1 , wherein the elongate shaft member comprises stainless steel, a superelastic nickel-titanium alloy, or a combination thereof. 
     
     
         10 . The method of  claim 1 , wherein the distal practitioner-shapeable end section has a yield stress in a range from about 150 ksi to about 225 ksi. 
     
     
         11 . The method of  claim 1 , wherein the distal practitioner-shapeable end section has a yield stress in a range from about 150 ksi to about 200 ksi. 
     
     
         12 . The method of  claim 1 , the medical device further comprising a distal portion between a proximal end section and the distal end section, wherein the distal portion between the proximal end section and the distal end section comprises a superelastic nickel-titanium alloy, and the distal end section is linear pseudoelastic. 
     
     
         13 . The method of  claim 1 , wherein a core of the distal end section surrounded by the solder material consists of the linear pseudoelastic nickel titanium alloy. 
     
     
         14 . A method for fabricating a medical device having a shapeable distal end section, the method comprising:
 providing an elongate shaft member that includes a distal end section, wherein the distal end section is formed of a nickel-titanium alloy member;   grinding at least a portion of the distal end section to a first cross-sectional dimension;   cold working a first time at least a distal portion of the distal end section;   ultrasonically cleaning at least the distal end section;   dipping at least a portion of the distal end section into a bath of a molten solder material, wherein the bath of molten solder material includes an upper layer of a molten metal hydroxide and a lower layer of the molten solder material;   following dipping at least a portion of the distal end section into a bath of molten solder material, cold working a second time at least a distal portion of the distal end section having the solder material applied thereto, wherein the cold working yields a distal practitioner-shapeable end section in which the nickel-titanium alloy in this cold worked region has linear pseudoelastic deformation behavior such that it is selectively shapeable;   ultrasonically cleaning at least the distal end section;   disposing a helical coil section about the distal practitioner-shapeable section; and   soldering the distal practitioner-shapeable section and the helical coil section to an atraumatic cap without substantial loss of the linear pseudoelasticity of the nickel-titanium alloy in the distal practitioner-shapeable section;   wherein the distal practitioner-shapeable end section has a yield stress from about 100 ksi to about 300 ksi.   
     
     
         15 . The method of  claim 14 , further comprising that after dipping at least a portion of the distal end section into a bath of molten solder material, dipping a second time at least a portion of the distal end section into a bath of molten solder material and thereby having a thicker coating of solder, the second coating of solder being a separately applied coating relative to the atraumatic cap. 
     
     
         16 . The method of  claim 14 , wherein the upper layer of molten metal hydroxide comprises molten potassium hydroxide, molten sodium hydroxide, or combinations thereof. 
     
     
         17 . The method of  claim 14 , wherein dipping at least a portion of the distal end section into a bath comprises dipping at least a portion of the distal end section in the molten solder material at a temperature in a range of about 150° C. to about 350° C. 
     
     
         18 . The method of  claim 14 , wherein dipping at least a portion of the distal end section into a bath comprises dipping at least a portion of the distal end section in the molten solder material at a temperature in a range of about 280° C. to about 300° C. 
     
     
         19 . The method of  claim 14 , wherein the atraumatic cap comprises a cap of solder, wherein the solder comprises a eutectic alloy. 
     
     
         20 . The method of  claim 14 , wherein the helical coil section is secured to the distal portion at a proximal location and at an intermediate location.