Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L29/00—Materials for catheters, medical tubing, cannulae, or endoscopes or for coating catheters
  • A61L29/14—Materials characterised by their function or physical properties, e.g. lubricating compositions
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L29/00—Materials for catheters, medical tubing, cannulae, or endoscopes or for coating catheters
  • A61L29/08—Materials for coatings
  • A61L29/085—Macromolecular materials
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M25/00—Catheters; Hollow probes
  • A61M25/0043—Catheters; Hollow probes characterised by structural features
  • A61M25/005—Catheters; Hollow probes characterised by structural features with embedded materials for reinforcement, e.g. wires, coils, braids
  • A61M25/0052—Localized reinforcement, e.g. where only a specific part of the catheter is reinforced, for rapid exchange guidewire port
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M25/00—Catheters; Hollow probes
  • A61M25/01—Introducing, guiding, advancing, emplacing or holding catheters
  • A61M25/09—Guide wires
  • A61M2025/09058—Basic structures of guide wires
  • A61M2025/09075—Basic structures of guide wires having a core without a coil possibly combined with a sheath
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M25/00—Catheters; Hollow probes
  • A61M25/0043—Catheters; Hollow probes characterised by structural features
  • A61M25/0054—Catheters; Hollow probes characterised by structural features with regions for increasing flexibility
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/131—Glass, ceramic, or sintered, fused, fired, or calcined metal oxide or metal carbide containing [e.g., porcelain, brick, cement, etc.]
  • Y10T428/1317—Multilayer [continuous layer]
  • Y10T428/1321—Polymer or resin containing [i.e., natural or synthetic]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
  • Y10T428/139—Open-ended, self-supporting conduit, cylinder, or tube-type article
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber

Definitions

• the invention pertains generally to medical devices and more specifically to medical devices that include or are formed from a hypotube.
• the invention pertains to medical devices that include a highly flexible coated hypotube.
• a number of medical devices including elongated medical devices such as catheters and guidewires, are known. Such devices can include or be formed from a hypotube. In some cases, a number of slots can be formed in the hypotube to improve the flexibility of the hypotube. The resulting product is sometimes referred to as a micromachined hypotube.
• a hypotube such as a micromachined hypotube may be subjected to one or more coating processes to provide the micromachined hypotube with a hydrophilic coating that lends biocompatibility and lubricity to the hypotube.
• a hydrophilic coating that lends biocompatibility and lubricity to the hypotube.
• a tie layer is oftentimes provided prior to forming the hydrophilic coating.
• a tie layer may negatively impact the flexibility of a micromachined hypotube by, for example, limiting relative movement between adjacent turnings or portions of the hypotube. Therefore, a need remains for improved tie layers that provide sufficient support for an overlaying hydrophilic coating. A need also remains for improved tie layers that do not negatively impact the flexibility of the micromachined hypotube.
• the present invention pertains to micromachined hypotubes that include one or more tie layers appropriate for subsequent application of a hydrophilic coating while retaining the flexibility of the micromachined hypotube.
• an illustrative embodiment of the invention may be found in a medical device that includes a micromachined hypotube having a level of flexibility and a tie layer disposed over the hypotube such that the medical device has a level of flexibility at least substantially equivalent to the level of flexibility of the hypotube.
• a medical device that includes a metallic substrate, an elastomeric tie layer that includes a polysiloxane-containing polyurethane, and a hydrophilic coating disposed on the tie layer.
• a medical device that includes a micromachined hypotube that has an outer surface.
• the outer surface of the hypotube includes a plurality of radially aligned voids and a plurality of surface elements disposed between adjacent voids.
• the medical device also includes a tie layer that is disposed over the micromachined hypotube such that the tie layer contacts at least most of the plurality of surface elements but does not cover at least some of the voids.
• Another illustrative embodiment of the invention may be found in a method of forming a tie layer on a micromachined hypotube that includes a plurality of radially aligned voids and a plurality of surface elements that are disposed between adjacent voids.
• a source of liquid polymer is provided, and a roller is contacted with the liquid polymer.
• the micromachined hypotube is then contacted with the roller bearing the liquid polymer to form the tie layer.
• the resulting tie layer is in contact with at least some of the plurality of surface elements but does not cover at least some of the plurality of voids.
• Figure 1 is a perspective view of a micromachined hypotube in accordance with an embodiment of the invention
• Figure 2 is a view of the micromachined hypotube of Figure 1, including a continuous tie layer applied to an exterior surface of the hypotube in accordance with an embodiment of the invention
• Figure 3 is an axial cross-section taken along line 3-3 of Figure 2;
• Figure 4 is a view of a portion of a guidewire bearing the micromachined hypotube of Figure 2;
• Figure 5 is a view of a portion of a catheter including the micromachined hypotube of Figure 2, seen with an optional inner liner;
• Figure 6 is an axial cross-section taken along line 6-6 of Figure 5;
• Figure 7 is a diagrammatic view of a coating apparatus in accordance with an embodiment of the invention.
• Figure 8 is a perspective view of a micromachined hypotube coated using the coating apparatus of Figure 7;
• Figure 9 is an axial cross-section taken along line 9-9 of Figure 8.
• Figure 10 is a view of a portion of a guidewire bearing the coated micromachined hypotube of Figure 8;
• Figure 11 is a view of a portion of a catheter including the coated micromachined hypotube of Figure 8, seen with an optional inner liner;
• Figure 12 is an axial cross-section taken along line 12-12 of Figure 11.
• the invention pertains generally to medical devices that include a hypotube such as a micromachined hypotube.
• a hypotube such as a micromachined hypotube.
• Such medical devices may include guidewires and microcatheters.
• the hypotube 10 includes an elongate body 12 having a plurality of slots 14 cut into the elongate body 12.
• the slots 14 may be radially oriented.
• adjacent slots 14 define voids on either side of a surface element 16.
• the slots 14 may be formed in any suitable manner.
• the slots 14 are formed via laser cutting.
• the slots 14 may be formed by saw cutting, abrasion, or any other known cutting or grinding mechanism.
• the slots 14 can be dimensioned and located to provide a desired level of flexibility.
• the slots 14 may be equally spaced from a distal portion 18 to a proximal portion 20.
• the slots 14 may be, for example, more closely spaced together near the distal portion 18 for additional flexibility and more spaced apart near the proximal portion 20 for additional strength.
• the slots 14 may have a width that is in the range of about 0.0005 inches to about 0.020 inches.
• Each slot 14 may extend about ten percent, about twenty percent, about thirty percent, about forty percent, about fifty percent, about sixty percent, about seventy percent, about eighty percent, about ninety percent or more about the circumference of the elongate body 12.
• the hypotube 10 may have any suitable dimensions, depending on an ultimate use thereof. In some cases, the hypotube 10 can have an overall length that is in the range of about 30 centimeters to about 300 centimeters.
• the hypotube 10 may have an outer diameter that is in the range of about 0.008 inches to about 0.156 inches, a wall thickness that is in the range of about 0.001 inches to about 0.02 inches, and a resulting inner diameter that is in the range of about 0.006 inches to about 0.0116 inches.
• the elongate body 12 may be formed of any suitable metallic, polymeric or composite material. In some embodiments, part or all of the elongate body 12 can be formed of a metal or a metal alloy. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316L stainless steel; alloys including nickel-titanium alloy such as linear elastic or superelastic (i.e.
• pseudoelastic nitinol
• nickel-chromium alloy nickel-chromium-iron alloy
• cobalt alloy tungsten or tungsten alloys
• MP35-N having a composition of about 35% Ni, 35% Co, 20% Cr, 9.75% Mo, a maximum 1% Fe, a maximum 1% Ti, a maximum 0.25% C, a maximum 0.15% Mn, and a maximum 0.15% Si
• hastelloy monel 400; inconel 825; or the like; or other suitable material.
• the particular material used can be chosen in part based on the desired characteristics of the elongate body 12, for example flexability, pushability, torqueability, and the like.
• the elongate body 12 can be formed from a superelastic or linear elastic nickel-titanium alloy, for example, linear elastic or superelastic (i.e. pseudoelastic) nitinol.
• linear elastic or superelastic i.e. pseudoelastic
• nitinol was coined by a group of researchers at the United States Naval Ordinance Laboratory (NOL) who were the first to observe the shape memory behavior of this material.
• NOL United States Naval Ordinance Laboratory
• the word nitinol is an acronym including the chemical symbol for nickel (Ni), the chemical symbol for titanium (Ti), and an acronym identifying the Naval Ordinance Laboratory (NOL).
• linear elastic Within the family of commercially available nitinol alloys, is a category designated "linear elastic” which, although is similar in chemistry to conventional shape memory and superelastic varieties, exhibits distinct and useful mechanical properties.
• the wire By skilled applications of cold work, directional stress, and heat treatment, the wire is fabricated in such a way that it does not display a substantial "superelastic plateau” or “flag region” in its stress/strain curve. Instead, as recoverable strain increases, the stress continues to increase in an essentially linear relationship until plastic deformation begins.
• the linear elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by DSC and DMTA analysis over a large temperature range.
• the mechanical bending properties of such material are therefore generally inert to the effect of temperature over this very broad range of temperature.
• the mechanical properties of the alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature.
• the use of the linear elastic nickel-titanium alloy allows the guidewire to exhibit superior "pushability" around tortuous anatomy.
• the linear elastic nickel-titanium alloy is in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some particular embodiments, the composition is in the range of about 54 to about 57 weight percent nickel.
• a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co. of Kanagawa, Japan.
• Some examples of nickel-titanium alloys include those disclosed in U.S. Patent Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference.
• Figure 2 is a schematic illustration of a coated hypotube 22.
• coated hypotube 22 may represent the hypotube 10 (Figure 1) with a polymer layer disposed over an outer surface of the hypotube 10.
• the polymer layer 24 is best seen in Figure 3, which is an axial cross-section taken along line 3-3 of Figure 2.
• the polymer layer 24 can represent a tie layer that is capable of bonding to the material used to form the hypotube 10.
• the tie layer can be formed from a material that is capable of bonding to nickel/titanium alloys such as the nitinol alloys discussed above.
• the polymer layer 24 may be applied to the hypotube 10 in any suitable manner. In some instances, the polymer layer 24 may be spray coated or dip coated onto the hypotube 10.
• the polymer layer 24 may be at least substantially continuous, i.e. the polymer layer 24 covers at least substantially all of the surface elements 16 (Figure 1) as well as at least substantially all of the slots 14 ( Figure 1). It is contemplated, however, that the polymer layer 24 may also be at least partially discontinuous, i.e. perhaps at least some of the slots 14 remain uncovered.
• the polymer layer 24 may be formed of any suitable polymeric material.
• the polymer layer 24 is formed of a material such as the ELAST-EONTM materials commercially available from AORTECH BIOMATERIALS, of Australia.
• the ELAST-EONTM materials generally are polyurethanes that include a polysiloxane component. While these materials encompass both elastomeric and non-elastomeric polymers, elastomeric polymers are useful in particular embodiments of the present invention. In some instances, useful elastomeric polymers may exhibit an elongation of at least about 500 percent.
• the ELAST-EONTM materials may encompass elastomeric polyurethanes that include significant amounts of a polysiloxane and either a polyether, a polycarbonate, or both a polyether and a polycarbonate. Exemplary materials are described for example in U.S. Patent No. 6,627,724, the contents of which are expressly incorporated by reference herein. These materials may be heat- cured to form the polymer layer 24. In some instances, the polymer layer 24 may have a thickness that is about 4 microns or less,
• Suitable polysiloxanes include those of the formula:
• R 1 , R 2 , R 3 , R 4 , R 5 and R 6 can each independently be hydrocarbon radicals and n is an integer that can range from 1 to 100.
• An exemplary polysiloxane is a compound of the above formula in which R 1 , R 2 , R 3 and R 4 are each methyl.
• R 5 and R 6 can each independently be selected from propylene, butylene, pentylene, hexylene, ethoxypropyl, propoxypropyl and butoxypropyl.
• Polysiloxane may be obtained commercially from Shin Etsu or prepared according to known methods.
• Suitable polyethers include those represented by the formula: where m can be an integer of at least 4 and in particular may be 5 to 18, and n can be an integer in the range of 2 to 50.
• suitable polyethers include polyhexamethylene oxide, polyheptamethylene diol, polyoctamethylene oxide and polydecamethylene oxide.
• Suitable polycarbonate macrodiols include poly(alkylene carbonates) such as poly(hexamethylene carbonate) and poly(decamethylene carbonate); polycarbonates prepared by reacting alkylene carbonate with alkanediols for example 1,4-butanediol, 1,10-decandiol, 1,6-hexanediol and/or 2,2-diethyl 1,3-propanediol; and silicon based polycarbonates prepared by reacting alkylene carbonate with 1,3 -bis (4- hydroxybutyl)-l,l,3,3-tetramethyldisiloxane and/or alkanediols.
• alkanediols 1,4-butanediol, 1,10-decandiol, 1,6-hexanediol and/or 2,2-diethyl 1,3-propanediol
• silicon based polycarbonates prepared by reacting alkylene carbonate with
• polyether and polycarbonate may be present as a mixture or a copolymer.
• a suitable copolymer is a copoly(ether carbonate) of the formula:
• Ri and R 2 are each independently be hydrocarbon radicals, and m and n are each integers ranging from 1 to 20.
• these materials may be formed using any suitable technique.
• the polysiloxane, polyether and/or polycarbonate and chain extender are mixed together and then the mixture is reacted with a diisocyanate.
• a diisocyanate may be reached with the polysiloxane and polyether and/or polycarbonate to form a prepolymer that is subsequently reacted with a chain extender.
• diisocyanates examples include 4,4'-methylenediphenyl diisocyanate, methylene bis (cyclohexyl) diisocyanate, p-phenylene diisocyanate, trans-cyclohexane-l,4-diisocyanate or a mixture of the cis and trans isomers, 1,6- hexamethylene diisocyanate, 2,4-toluene diisocyanate or its isomers or mixtures thereof, p-tetramethylxylene diisocyanate and m-tetramethylxylene diisocyanate.
• chain extenders examples include 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonadiol, 1,10-decanediol 1,4-cyclohexane dimethanol, p- xyleneglycol, 1,4-bis (2-hydroxyethoxy) benzene and 1,12-dodecanediol.
• a coated hypotube 22 (Figure 3) may be employed in a variety of medical devices. Exemplary uses of a coated hypotube 22 includes guidewires and catheters such as microcatheters. Figure 4 illustrates an exemplary guidewire while Figures 5 and 6 illustrate an exemplary catheter.
• the guidewire 26 includes a core 28 that narrows down to a tapered portion 30.
• the coated hypotube 22 may be disposed over the tapered portion 30.
• the core 28 may be formed of any suitable material and may be constructed using any known techniques for forming guidewire cores. In some instances, the core 28 can be formed from stainless steel or perhaps a nickel/titanium alloy such as Nitinol (previously discussed).
• the coated hypotube 22 can be secured to the core 28 using any known attachment technique, such as welding.
• welding refers to a process in which two materials such as metal or metal alloys are joined together by heating the two materials sufficiently to at least partially melt adjoining surfaces of each material.
• a variety of heat sources can be used to melt the adjoining materials. Examples of welding processes that can be suitable in some embodiments include LASER welding, resistance welding, TIG welding, microplasma welding, electron beam, and friction or inertia welding.
• LASER welding equipment that may be suitable in some embodiments is commercially available from Unitek Miyachi of Monrovia, California and Rofin-Sinar Incorporated of National, Michigan. Resistance welding equipment that may be useful in some embodiments is commercially available from Palomar Products Incorporated of Carlsbad, California and Polaris Electronics of Olathe, Kansas. TIG welding equipment that may be useful in some embodiments is commercially available from Weldlogic Incorporated of Newbury Park, California. Microplasma welding equipment that may be useful in some embodiments is commercially available from Process Welding Systems Incorporated of Smyrna, Tennessee.
• the guidewire 26 may receive an optional hydrophilic coating 32.
• the hydrophilic coating 32 may include or be formed from a polymer that attracts or binds water molecules when the polymer is placed in contact with an aqueous system. Examples of aqueous systems that can provide water molecules that can bind to a hydrophilic polymer include blood and other bodily fluids. When a hydrophilic polymer comes into contact with such a system, water molecules can bind to the polymer via mechanisms such as hydrogen bonding between the water molecules and substituents or functional groups present within or on the polymer. In some instances, a hydrophilic polymer can bind at least 2 times its own weight in water and in particular instances some hydrophilic polymers can bind up to about 20 times their own weight in water.
• hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof, may be used.
• the more distal portion of the guidewire is coated with a hydrophilic polymer as discussed above, and the more proximal portions is coated with a fluoropolymer, such as polytetrafluroethylene (PTFE).
• PTFE polytetrafluroethylene
• the hydrophilic coating 32 can be formed from a hydrophilic material such as HYDROP ASSTM or HYDROLENETM. These materials are commercially available from Boston Scientific Corporation and Surmodics.
• the hydrophilic coating 32 may only cover the coated hypotube 22, as the tie layer 24 may in some instances provide a superior base for the hydrophilic coating 32.
• the hydrophilic coating 32 may extend proximally onto at least a portion of the core 28.
• the guidewire 26 may include additional structure and elements commonly incorporated into guidewires. Examples of such elements include one or more polymeric layers, one or more coils or springs, an atraumatic tip, and the like.
• the coated hypotube 22 may also be used in medical devices such as catheters.
• Figure 5 a portion of a catheter 34 is illustrated.
• Figure 6 is an axial cross-section taken along line 6-6 of Figure 5.
• the catheter 34 can be seen to include the coated hypotube 22 bearing the tie layer 24, as previously discussed.
• the catheter 34 may optionally include an inner polymeric layer 36.
• the inner polymeric layer 36 may be included to provide a smooth, low-resistance lumen suitable for passing a guidewire or other medical device.
• the inner polymeric layer 36 may, if present, be formed of any suitable polymeric material.
• suitable materials include polyether block amide, polybutylene terephthalate/polybutylene oxide copolymers sold under the Hytrel® and Araitel® trademarks, Nylon 11, Nylon 12, polyurethane, polyethylene terephthalate, polyvinyl chloride, polyethylene naphthalene dicarboxylate, olef ⁇ n/ionomer copolymers, polybutylene terephthalate, polyethylene naphthalate, ethylene terephthalate, butylene terephthalate, ethylene naphthalate copolymers, polyamide/polyether/polyester, polyamides, aromatic polyamides, polyurethanes, aromatic polyisocyanates, polyamide/polyether, and polyester/polyether block copolymers, among others.
• inner polymeric layer 36 may be desirable for inner polymeric layer 36, if present, to be formed of a material having a low coefficient of friction. Suitable materials include fiuoropolymers such as polytetrafluoroethylene (PTFE), better known by its tradename of TEFLON ® .
• PTFE polytetrafluoroethylene
• Figure 7 diagrammatically illustrates a method of coating a medical device.
• a coating apparatus 38 that includes a bath 40 containing a liquid polymer material.
• a transfer roller 42 is in at least partial contact with the polymer within the bath 40, and thereby bears at least some polymer on an outer surface of the transfer roller 42.
• the transfer roller 42 is also in contact with a medical device 44.
• the transfer roller 42 is rotated in a first direction while the medical device 44 is rotated in a second, opposite, direction.
• the transfer roller 42 rotates in a clock-wise direction while the medical device 44 rotates in a counterclockwise-direction, although these directions may of course be reversed.
• the transfer roller 42 and the medical device 44 may both rotate in the same direction, or perhaps the transfer roller 42 can rotate while the medical device 44 is held stationary.
• the coating apparatus 38 may be used to apply a tie layer made from silane (SiH 4 ), polyacrylic acid (PAA), or paralene.
• a tie layer made from silane (SiH 4 ), polyacrylic acid (PAA), or paralene.
• Paralene is available in several different monomers, each of which are shown below:
• a suitable material for forming the tie layer is poly(styrene- b-isobutylene-b-styrene), or SIBS.
• SIBS poly(styrene- b-isobutylene-b-styrene), or SIBS.
• This material is commercially available from Boston Scientific Corporation under the tradename TRANSLUTETM. This is a hydrophobic elastomeric tri-block copolymer that is based upon l,3-di(2-methoxy-2- propyl)-5-tert-butylbenzene).
• SIBS has a number-average molecular weight of about 80,000 to 130,000 grams per mole.
• an advantage of using the coating apparatus 38 is that in some cases, a medical device such as a micromachined hypotube 10 ( Figure 1) or a medical device including a micromachined hypotube 10 may be coated in such a way as to not cover or plug the radially aligned voids 14 ( Figure 1) present within the micromachined hypotube 10.
• the coating apparatus 38 may provide a discontinuous polymeric layer that covers at least some of the surface elements 16 ( Figure 1) but leaves at least some of the radially aligned voids 14 devoid of covering.
• Figure 8 is a perspective view of a portion of a coated hypotube 46. It can be seen that although the hypotube 46 has been coated, it retains at least some of the radially aligned voids 48 separated by surface elements 50 that have been coated. In some cases, virtually all of the radially aligned voids 48 remain devoid of coating while in other embodiments, a certain percentage of the radially aligned voids 48 may be allowed to be at least partially covered.
• Figure 9 is an axial cross-section taken along the 9-9 line of Figure 8.
• Figure 9 clearly illustrates how a coating 52 covers at least some of the surface elements 50 while leaving at least some of the radially aligned voids 48 devoid of covering.
• the coating 52 covers all or virtually all of the surface elements 50 while leaving all or virtually all of the radially aligned voids 48 free of covering.
• a coating hypotube 46 may be employed in a variety of medical devices. Exemplary uses of a coated hypotube 46 includes guidewires and catheters such as microcatheters. Figure 10 illustrates an exemplary guidewire while Figures 11 and 12 illustrate an exemplary catheter.
• the guidewire 54 includes a core 28 that narrows down to a tapered portion 30.
• the coated hypotube 46 may be disposed over the tapered portion 30.
• the core 28 may be formed of any suitable material and may be constructed using any known techniques for forming guidewire cores. In some instances, the core 28 can be formed from stainless steel or perhaps a nickel/titanium alloy such as Nitinol (previously discussed).
• the coated hypotube 46 can be secured to the core 28 using any known attachment technique, such as those discussed with respect to Figure 4.
• the guidewire 54 may include additional structure and elements commonly incorporated into guidewires. Examples of such elements include one or more polymeric layers, one or more coils or springs, an atraumatic tip, and the like.
• the guidewire 54 may optionally include a hydrophilic coating over part or all of the guidewire 54, as discussed previously with respect to Figure 4.
• the coated hypotube 46 may also be used in medical devices such as catheters.
• Figure 11 a portion of a catheter 56 is illustrated.
• Figure 12 is an axial cross-section taken along line 12-12 of Figure 11.
• the catheter 56 can be seen to include the coated hypotube 46 bearing the coating 52, as previously discussed. It can be seen that the coating 52 covers at least some of the surface elements 50 while leaving at least some of the radially aligned voids 48 uncovered.
• the catheter 56 may optionally include an inner polymeric layer 36.
• the inner polymeric layer 36 may be included to provide a smooth, low-resistance lumen suitable for passing a guidewire or other medical device and may be formed of any suitable material as discussed with respect to Figure 6.

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