GB2568495A

GB2568495A - Methods of coating medical devices

Info

Publication number: GB2568495A
Application number: GB1719029.9A
Authority: GB
Inventors: Van Der Wal Pieter; Hillen Albert; Hegger Koen; Domingus Wessel; Mckee William
Original assignee: Merit Medical Coatings BV
Current assignee: Merit Medical Coatings BV
Priority date: 2017-11-17
Filing date: 2017-11-17
Publication date: 2019-05-22
Anticipated expiration: 2037-11-17
Also published as: GB201719029D0; GB2568495B

Abstract

A medical device 205 is coated 211 with polyether sulphone (PES). This coating 211 is cured in a convection oven having consecutive heating sections at 120-180°C, 270-310°C and 360-540°C. Crosslinked PES 215 is coated 212 with polyamide imide (PAI). This PAI coating 212 is cured in a convection oven and then coated 213 with an outermost layer of polytetrafluoroethylene (PTFE). This PTFE coating 213 is cured using a convection oven and infrared (IR) heaters. The first PES coating 211 is coated with a second PES coating 214 if the first PES coating 211 is found to be free of wrinkles. The 2nd PES coating 214 is similarly cured and evaluated. The coatings 211, 214 and preferably third PES coating 215, PAI coating 212 and PTFE coating 213 are applied by passing the medical device 205 through dies. Preferably all of the coatings are cured using three heating sections at the previously mentioned temperatures or at a higher temperature for the PTFE coating 213, before being inspected for wrinkles. The device 205 is preferably a wire having a diameter = 50-1000µm, which is passed through the ovens at 10-120 metres per minute. The medical device is a guide wire, hypotube, stylet, mandrel, stent, or a device used in interventional cardiology, neurovascular, interventional peripheral or endoscopy interventions.

Description

METHODS OF COATING MEDICAL DEVICES

TECHNICAL FIELD [0001] The present disclosure relates generally to methods of coating medical devices. More specifically, the present disclosure relates to methods of applying multilayer coatings to medical devices.

BRIEF DESCRIPTION OF THE DRAWINGS [0002] The embodiments disclosed herein will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. While various aspects of the embodiments are presented in drawings, the drawings depict only typical embodiments, which will be described with additional specificity and detail through use of the accompanying drawings in which:

[0003] FIG. 1 is a cross-sectional view of a medical device coated in accordance with an embodiment of the present disclosure.

[0004] FIG. 2 is a cross-sectional view of a medical device coated in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION [0005] Elongate medical devices, appliances, or instruments, such as guidewires, hypotubes, stylets, etc., are often inserted into a patient for diagnostic or therapeutic procedures. Such medical devices may include a coating that imparts one or more characteristics or properties to the medical device. For instance, a coating may affect, among other properties or characteristics, the biocompatibility, chemical resistance, elasticity, durability, and/or lubricity of the medical device.

[0006] The present disclosure relates to methods of applying such coatings to medical devices. Methods of applying coatings to medical devices are known in the art. However, a problem that remains unsolved is that the curing step in such processes suffers from a lack of uniformity. A further problem that remains unsolved is that the sintering step in such processes suffers from a lack of uniformity. A further problem that remains is that methods of coating known in the art suffer from wrinkling, which is undesirable.

[0007] The present invention addresses these and other problems.

[0008] In certain embodiments, the present disclosure relates to methods of applying multilayer coatings. In some of such embodiments, the methods include heating one or more coating layers with infrared radiation. In other embodiments, the methods include screening one or more coating dies to reduce wrinkling in one or more of the coating layers. These and other methods are further detailed below.

[0009] The components of the embodiments as generally described and illustrated herein can be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of various embodiments. While various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0010] FIG. 1 depicts a cross-sectional view of a medical device 100 that has been coated in accordance with an embodiment of the present disclosure. As shown therein, the coated medical device 100 comprises a medical device 105 (which can also be referred to as a substrate 105) and a coating 110. The coating 110 further comprises a plurality of coating layers 111, 112, 113.

[0011] In the illustrated embodiment, the medical device or substrate 105 is represented as a wire or guidewire. However, it will be appreciated that various types of medical devices or substrates 105 can be coated in accordance with the methods disclosed herein. Illustrative medical devices or substrates 105 include, but are not limited to, interventional cardiology medical devices, neurovascular medical devices, interventional peripheral medical devices, endoscopy medical devices, wires, guidewires, hypotubes, stylets, mandrels, stents, etc. In certain embodiments, the substrate 105 comprises an elongate medical device.

[0012] In particular embodiments, the substrate 105 comprises a wire, such as a guide-wire. Various sizes of wires can be used. For example, in some embodiments, the diameter of the wire is between about 50 microns and about 1000 microns, such as between about 50 microns and about 150 microns, between about 250 microns and about 800 microns, or between about 330 microns and about 1000 microns.

[0013] The substrate 105 can also be made of various materials. In certain embodiments, for example, the substrate 105 comprises a metallic material. Preferred metallic materials are selected from metallic alloys, stainless steel, nitinol, tungsten, titanium, and copper. For instance, in one embodiment, the substrate 105 comprises a wire that includes stainless steel, nitinol, or copper. In other embodiments, the substrate 105 comprises polymeric or composite materials.

[0014] In some embodiments, the methods disclosed herein include a step of applying a first material onto a surface of the substrate 105 to form a first coating layer 111. In some of such embodiments, the first material can be configured to adhere to or otherwise interact with the surface of the substrate 105. For example, the first material can be configured to adhere to or otherwise interact with a substrate 105 comprising a metallic material, preferably selected from the group consisting of stainless steel, nitinol, tungsten, titanium, and copper. In preferred embodiments, the first material acts as a primer to aid in adhering one or more additional coating layers to the substrate 105, such as the second and/or third coating layers 112, 113 depicted in FIG. 1. In such instances, the first layer 111 can be referred to as a primer layer 111. In further embodiments, a plurality of primer layers 111 can be applied (as is shown in FIG. 2).

[0015] Exemplary materials that can be used in the first layer 111 are preferably selected from the group consisting of polymeric materials, more preferably polyethersulfones and derivatives thereof. In certain preferred embodiments, the first material (e.g., polyethersulfone) is mixed with one or more carriers (e.g., solvents) to form a first mixture that is applied onto the surface of the substrate 105. Preferred carriers are selected from the group consisting of organic solvents. N-methyl pyrrolidone is particularly preferred. One or more colorants (e.g., dyes and/or pigments) can also be used to impart a particular color (e.g., black, green, grey, blue, etc.) to the first coating layer 111. For example, one or more colorants can be mixed with other materials (e.g., polyethersulfone) and applied onto a surface of the substrate 105.

[0016] The first material can be applied onto the substrate 105 in various ways. In one preferred embodiment, the first material is applied using a reel-to-reel coating process (also known as a spool-to-spool coating process). Preferably, the first material can be applied to a substrate 105 as it is being drawn from a “payoff” reel or spool and wound onto a “take-up” reel or spool. Preferably, a first mixture comprising the first material may be applied to the substrate 105 by passing the substrate 105 through one or more vessels that contain the first mixture. As the coated substrate 105 emerges from the vessel, the substrate 105 may pass through a die that meters (or controls) the volume or thickness of material that is applied to the substrate 105.

[0017] The methods disclosed herein further include a step of at least partially curing and/or drying the first coating layer 111. In some preferred embodiments, curing and/or drying the first coating layer 111 comprises heating or otherwise exposing the first coating layer 111 to temperatures that are sufficient to cure and/or dry the first coating layer 111. In one preferred embodiment, the first coating layer 111 is heated to remove (e.g., evaporate) at least a portion of the one or more carriers (e.g., organic solvents) that is mixed with the first material. In some preferred embodiments, the optimal curing temperature for the first coating layer 111 is between about 200 °C and about 260 °C, or between about 210 °C and about 250 °C.

[0018] In certain preferred embodiments, the first coating layer 111 (e.g., a first coating layer 111 comprising polyethersulfone) is heated by passing the substrate 105 through an oven, such as a convection oven. In some preferred embodiments, the oven comprises a multi-zone oven. In particularly preferred embodiments, the oven includes at least three zones. For example, the oven can comprise a first heating zone having a first temperature, a second heating zone having a second temperature that is greater than the first temperature, and a third heating zone having a third temperature that is greater than the second temperature. In one embodiment, the first heating zone is held at a temperature of between about 120 °C and about 180 °C, or between about 140 °C and about 160 °C; the second heating zone is held at a temperature of between about 270 °C and about 310 °C, or between about 280 °C and about 300 °C; and the third heating zone is held at a temperature of between about 360 °C and about 540 °C, between about 360 °C and about 500 °C, or between about 370 °C and about 450 °C.

[0019] In another preferred embodiment, the oven includes six zones. For example, the oven can comprise a first heating zone held at a temperature of between about 120 °C and about 180 °C, or between about 140 °C and about 160 °C; a second heating zone held at a temperature of between about 270 °C and about 310 °C, or between about 280 °C and about 300 °C; and third, fourth, fifth, and sixth heating zones each held at a temperature of between about 360 °C and about 540 °C, between about 360 °C and about 500 °C, or between about 370 °C and about 450 °C. As can be appreciated, heat is transferred to the substrate 105 as it is being drawn or otherwise passed through the various zones of the oven.

[0020] In some preferred embodiments, the speed at which the substrate 105 is passed through the oven can be controlled to ensure proper curing and/or drying has occurred. Additionally, the speed at which the substrate 105 is passed through the oven can also be controlled to ensure that the layers and materials are not overheated, as applying too much heat can have a negative impact on the coating layer. In some embodiments, the speed at which the substrate 105 is passed through the oven can be dependent upon the size of the substrate 105 and/or the thickness of the coating layer 111, 112, 113.

[0021] In embodiments where the substrate 105 comprises a wire, the speed at which the substrate 105 is passed through the multi-zone oven can be between about 10 meters/minute and about 120 meters/minute. The speed can also be varied depending on the diameter of the wire. For example, in embodiments where the wire comprises a diameter of between about 50 microns and about 150 microns, the speed can be between about 80 meters/minute and about 120 meters/minute. In embodiments where the wire comprises a diameter of between about 250 microns and about 800 microns, the speed can be between about 50 meters/minute and about 15 meters/minute. And in embodiments where the wire comprises a diameter of between about 330 microns and about 1000 microns, the speed can be between about 50 meters/minute and about 10 meters/minute.

[0022] After at least partially drying and/or curing the first layer 111, a step of applying a second material onto the substrate 105 can be employed to form a second coating layer

112. In certain embodiments, the second layer 112 is disposed on the first layer 111. In other embodiments, one or more additional layers are disposed between the first and second layers 111, 112 (as is shown in FIG. 2 and further detailed below). In some embodiments, the second material is configured to act as a binder. For example, the second material can aid in binding or otherwise adhering a third layer 113 (or topcoat or outer layer) to one or more of the inner coating layers, such as the first layer 111.

[0023] Exemplary materials that can be used in the second layer 112 are preferably selected from the group consisting of polymers and copolymers of amides, imides, and mixtures thereof. More preferably, the second material can include polymers and/or copolymers comprising one or more amides and one or more imides. Aromatic and/or aliphatic amides and/or imides can be used. In one preferred embodiment, a polyamic acid (or a derivative thereof) that is at least partially imidized is used. In another preferred embodiment, the second material comprises a polyamide-imide.

[0024] In certain preferred embodiments, the second material is mixed with one or more carriers to form a second mixture that is applied onto the substrate 105. A preferred carrier is water. One or more surfactants can also be used to stabilize the second material in the one or more carriers. For example, one or more surfactants can be used to help stabilize an emulsion comprising the second material disposed in the one or more carriers.

[0025] Additional materials can also be mixed with the second material, preferably fluoropolymers, more preferably polytetrafluoroethylene. For example, fluoropolymers can be mixed with the second material (e.g., a polyamide-imide or a polymer comprising one or more amides and one or more imides) to aid in adhering the third layer 113 to one or more inner coating layers. Use of a fluoropolymer can be advantageous in many circumstances, including instances in which the third layer 113 (or outer layer) includes one or more fluoropolymer materials. One or more colorants (e.g., dyes and/or pigments) can also be used to impart a particular color (e.g., black, green, grey, blue, etc.) to the second material and/or the second coating layer 112.

[0026] The second material can be applied in a manner that is analogous to the methods described above for applying the first material. For example, a substrate 105 to which a first coating layer 111 has been applied may be drawn through a vessel containing a second mixture to be applied to the substrate 105. Once the second coating layer 112 has been applied to the first coating layer 111, a step of at least partially curing and/or drying the second coating layer 112 can be employed.

[0027] In some preferred embodiments, curing and/or drying the second coating layer 112 comprises heating or otherwise exposing the second coating layer 112 to temperatures that are sufficient to cure and/or dry the second coating layer 112. In some more preferred embodiments, the optimal curing temperature for the second coating layer 112 (e.g., a second coating layer 112 comprising a polyamide-imide or a polymer comprising one or more amides and one or more imides) is between about 220 °C and about 260 °C, or between about 230 °C and about 250 °C.

[0028] In some preferred embodiments, the second coating layer 112 is heated by passing the substrate 105 through an oven, analogous to the ovens described above and used for heating the first coating layer 111. Further, the same oven can be used, and the temperature of the oven, or temperatures of the zones in a multi-zone oven, can remain the same as those used in heating the first coating layer 111. The parameters of the oven can thus remain constant during formation of the first and second layers 111, 112.

[0029] After at least partially drying and/or curing the second layer 112, a step of applying a third material onto the substrate 105 can be employed to form a third coating layer 113. In certain embodiments, the third layer 113 is disposed on the second layer 112. In some of such embodiments, the third material is configured to impart one or more properties or characteristics to the outer surface of the coating 110. For example, in certain preferred embodiments, the third material imparts lubricious and/or non-stick characteristics to the coating 110. As shown in the illustrated embodiment, in some embodiments, the third coating layer 113 is the outermost coating layer, and can also be referred to as a topcoat.

[0030] Exemplary materials that can be used in the third layer 113 are preferably selected from polymeric materials, more preferably fluoropolymers. For example, the third layer 113 can comprise a polytetrafluoroethylene (which is especially preferred in this context). The third material (e.g., polytetrafluorethylene) can also be mixed with one or more carriers to form a third mixture that is applied onto the substrate 105. Water is a preferred carrier. Preferably, the third mixture comprises between about 50% and about 70%, by weight, polytetrafluoroethylene. Other mixtures can also be used. The mixtures can also comprise an emulsion of polytetrafluoroethylene colloids or particles dispersed throughout the carrier.

[0031] Additional materials can also be mixed with the third material. For example, one or more colorants (e.g., dyes and/or pigments) can also be used to impart a particular color (e.g., black, green, grey, blue, etc.) to the third material and/or the third coating layer

113.

[0032] The third material can be applied in a manner that is analogous to the methods described above for applying the first and second materials. In one preferred embodiment, a substrate 105 to which a first coating layer 111 and second coating layer

112 have been applied may be drawn through a vessel containing a third mixture to be applied to the substrate 105. Once the third material has been applied to the second coating layer 112, a step of at least partially curing and/or drying the third coating layer

113 can be employed.

[0033] In some preferred embodiments, curing and/or drying the third coating layer 113 comprises heating or otherwise exposing the third coating layer 113 to temperatures that are sufficient to cure and/or dry the third coating layer 113. Preferably, curing the third coating layer 113 comprises heating the third coating layer 113 to evaporate at least a portion of the one or more carriers (e.g., water) mixed with the third material. During the curing process, the colloids or particles of the third material (e.g., polytetrafluoroethylene) can also fuse together to form a solid and/or continuous third layer 113. In preferred embodiments, little to no colloids are visible or otherwise observable (e.g., observable at 50x magnification with an optical microscope) after curing. Preferably, the optimal curing temperature for the third coating layer 113 (e.g., a third coating layer 113 comprising polytetrafluoroethylene) is between about 300 °C and about 540 °C, between about 340 °C and about 540 °C, between about 340 °C and about 500 °C, or between about 340 °C and about 450 °C. In further embodiments, the third coating layer 113 is heated to a temperature of greater than about 400 °C.

[0034] In some preferred embodiments, the third coating layer 113 is heated by passing the substrate 105 through an oven, analogous to the ovens described above and used for heating the first and second coating layers 111, 112. Further, the same oven can be used, and the temperature of the oven, or temperatures of the zones in a multizone oven, can remain the same as those used in heating the first and second coating layers 111, 112. The parameters of the oven can thus remain constant during formation of the first, second, and third coating layers 111, 112, 113.

[0035] The third coating layer 113 can further be subjected to one or more additional processing steps. For example, in some embodiments, the third coating layer 113 is subjected to additional heat treatment using infrared radiation. As previously discussed, the optimal temperature for curing and/or drying the third coating layer 113 is greater than the optimal temperatures used for curing and/or drying the first and second coating layers 111,112. By heating the third coating layer 113 using infrared radiation, the optimal curing and/or drying temperature of the third coating layer 113 can be achieved without changing the temperatures of the oven. Use of infrared radiation can thus be advantageous in many ways. For example, the coating process can be quicker and more efficient when the temperatures of the oven are not changed. Heat transfer using infrared radiation can also lessen the curing and/or drying time of the third coating layer 113.

[0036] In some preferred embodiments, one or more infrared emitters are employed to generate the infrared radiation. In particularly preferred embodiments, two infrared emitters are employed. The infrared emitters can be coupled to and/or disposed adjacent the heating oven such that infrared radiation can be applied to the third coating layer 113 as the substrate 105 passes through or exits the heating oven.

[0037] Various types of infrared emitters can be employed. In certain preferred embodiments, tubular emitters are used. Tubular emitters preferably include an elongated tubular-shaped structure having a lumen extending therethrough. In other preferred embodiments, slotted emitters are used. Slotted emitters preferably include an elongated tubular-shaped structure having a lumen extending therethrough. An elongated slot also extends along the length of the tubular-shaped structure such that the substrate 105 can be passed into the lumen of the emitter. In a preferred embodiment, the length of the emitter is between about 0.5 meter and about 1.5 meters. In another preferred embodiment, the diameter of the tube is between about 10 mm and about 40 mm, between about 10 mm and about 20 mm, between about 20 mm and about 30 mm, or between about 30 mm and about 40 mm. In embodiments where slotted emitters are used, the width of the slot opening is preferably between about 1 mm and about 20 mm, between about 1 mm and about 10 mm, or between about 10 and about 20 mm.

[0038] In preferred embodiments, the maximum power of the infrared emitters is between about 1500 Watts and about 2050 Watts, or between about 2000 Watts and about 2020 Watts, although infrared emitters having other power outputs can also be used. The power can also be variable and/or adjustable to achieve a desired power output.

[0039] In some preferred embodiments, the infrared emitters are configured to heat the coated substrate 105 to temperatures sufficient for sintering of polytetrafluoroethylene without causing substantial degradation of the coating. In particularly preferred embodiments, the infrared emitters are configured to heat the coated substrate 105 to temperatures of between about 300 °C and about 500 °C, between about 340 °C and about 500 °C, or between about 340 °C and about 450 °C.

[0040] FIG. 2 depicts an embodiment of a coated medical device 200 that resembles the coated medical device 100 described above in certain respects. Accordingly, like features are designated with like reference numerals, with the leading digits incremented to “2.” For example, the embodiment depicted in FIG. 2 includes a substrate 205 that may, in some respects, resemble the substrate 105 of FIG. 1. Relevant disclosure set forth above regarding similarly identified features thus may not be repeated hereafter. Moreover, specific features of medical devices and related components shown in FIG. 1 may not be shown or identified by a reference numeral in the drawings or specifically discussed in the written description that follows. However, such features may clearly be the same, or substantially the same, as features depicted in other embodiments and/or described with respect to such embodiments. Accordingly, the relevant descriptions of such features apply equally to the features of the medical device 200 and related components depicted in FIG. 2. Any suitable combination of the features, and variations of the same, described with respect to the medical device 100 and related components illustrated in FIG. 1 can be employed with the medical device 200 and related components of FIG. 2, and vice versa.

[0041] FIG. 2 depicts a cross-sectional view of a medical device 200 that has been coated in accordance with another embodiment of the present disclosure. As shown therein, the coated medical device 200 comprises a medical device or substrate 205 and a coating 210. The coating 210 further comprises a plurality of coating layers 211,212, 213, 214, 215.

[0042] As can be appreciated and is exemplified by FIG. 2, the disclosed methods can also be used to apply coatings having more than three layers. For example, the disclosed methods can be employed to apply coatings comprising four, five, six or more layers. In the illustrated embodiment, for example, the coating 220 comprises a five-layer coating. The additional layers can comprise various materials, such as the materials described above, and can be included to impart additional characteristics and properties to the coating 210. For example, in the illustrated embodiment, the fourth and fifth layers 214, 215 can comprise polyethersulfone and can be substantially the same as the first layer 211. Other arrangements, and/or layers can also be employed.

[0043] Further, as shown in FIGS. 1 and 2, it will be appreciated that the coatings can comprise a series of concentric rings or layers around the substrate 205. However, the methods are not limited to such coatings 210. Rather, in other embodiments, the coating 210 can cover just one surface, two surfaces, or three surfaces of the substrate 205 as desired.

[0044] In another aspect, the present disclosure also relates to methods of applying a multilayer coating that comprises screening one or more components of the coating system. For example, the present disclosure relates to screening tubular wire coating dies that are employed in the coating process to meter (or otherwise control) the amount or thickness of material that has been disposed on the substrate. Die screening can be employed to reduce the wrinkling in one or more layers of the coating.

[0045] In one embodiment, a method for screening dies of a five-layer coating is contemplated. The method preferably comprises a step of applying material onto a surface of the substrate (e.g., a wire). Any of the above-identified substrates can be used. In some preferred embodiments, the substrate comprises a wire having a diameter that is between about 50 microns and about 1000 microns, such as between about 50 microns and about 150 microns, between about 250 microns and about 800 microns, or between about 330 and about 1000 microns.

[0046] Any of the above-identified materials can also be applied to the substrate to form the various coating layers. The materials can also be applied to form one or more coating layers using the above-identified reel-to-reel coating process. In one preferred embodiment, a material can be applied to the substrate as it is being drawn from a “payoff” reel or spool and wound onto a “take-up” reel or spool. For instance, a first mixture comprising a material may be applied to the substrate by passing the substrate through one or more vessels that contain the first mixture. As the coated substrate emerges from the vessel, the substrate may pass through a first die that meters (or controls) the volume or thickness of material that is applied to the substrate.

[0047] The coating layer is then heated by passing the substrate through an oven, such as a convection oven. In some preferred embodiments, the oven comprises a multizone oven. In particularly preferred embodiments, the oven includes at least four heating zones. For example, the oven can comprise a first heating zone held at a temperature of between about 130 °C and about 170 °C; a second heating zone held at a temperature of between about 270 °C and about 310 °C; a third heating zone held at a temperature of between about 400 °C and about 440 °C; and a fourth heating zone held at a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C.

[0048] In other preferred embodiments, the oven includes at least six heating zones. For example, the oven can comprise a first heating zone held at a temperature of between about 130 °C and about 170 °C; a second heating zone held at a temperature of between about 270 °C and about 310 °C; a third heating zone held at a temperature of between about 400 °C and about 440 °C; a fourth heating zone held at a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C; a fifth heating zone held at a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C; and a sixth heating zone held at a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C.

[0049] The speed at which the substrate is passed through the oven can also vary, as described above in relation to FIG. 1. For example, in certain preferred embodiments, the speed at which the substrate is passed through the oven is between about 10 meters/minute and about 120 meters/minute.

[0050] After the substrate has been passed through the oven, the coating layer is evaluated to determine whether wrinkles are present in the coating layer. In a preferred embodiment, the coating layer is evaluated with an optical microscope. Preferably, the coating layer is evaluated with an optical microscope at 50x magnification, or at least 50x magnification, although other magnifications can also be used. Wrinkles can be observed as flaws in the coating layer, or areas where the coating layer does not form a substantially smooth, continuous outer surface. If one or more wrinkles are identified, the first die is replaced with a second die, and the step of applying the material onto the substrate is repeated until a suitable die is identified. In particularly preferred embodiments, at least one of the reduction angle (e.g., greater or lesser angles) and the land length (e.g., longer or shorter lengths) is varied between the dies. In other preferred embodiments, the reduction angle and land length of the dies are substantially the same. Further, in some embodiments, the bore diameter of the dies can remain substantially the same (regardless of whether the reduction angle and/or land length are varied), such that the thickness of the coating layer can remain substantially the same as the dies are screened. If no wrinkles are observed, a second material is applied onto the first layer to form a second layer. The above-identified coating, curing, and evaluation steps are then repeated until five layers are disposed on the medical device.

[0051] An illustrative method of applying a multilayer coating comprises the following steps:

(i) applying a first material onto a first surface of a medical device to form a first coating layer;

(ii) passing the medical device through a first die to meter the amount of the first material that is disposed on the medical device;

(iii) curing the first coating layer, wherein curing the first coating layer comprises heating the first coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between about 130 °C and about 170 °C; a second heating zone having a temperature of between about 270 °C and about 310 °C; a third heating zone having a temperature of between about 400 °C and about 440 °C; and a fourth heating zone having a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C;

(iv) evaluating the first coating layer and determining whether the first coating layer includes one or more wrinkles on the surface of the first coating layer, wherein if one or more wrinkles are identified on the first coating layer, the method comprises replacing the first die with another die and repeating steps (i), (ii), and (iii), wherein if no wrinkles are identified on the first coating layer, the method comprises proceeding to step (v);

(v) applying a second material onto the medical device to form a second coating layer;

(vi) passing the medical device through a second die to meter the amount of the second material that is disposed on the medical device;

(vii) curing the second coating layer, wherein curing the second coating layer comprises heating the second coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between about 130 °C and about 170 °C; a second heating zone having a temperature of between about 270 °C and about 310 °C; a third heating zone having a temperature of between about 400 °C and about 440 °C; and a fourth heating zone having a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C; and (viii) evaluating the second coating layer and determining whether the second coating layer includes one or more wrinkles on the surface of the second coating layer, wherein if one or more wrinkles are identified on the second coating layer, the method comprises replacing the second die with another die and repeating steps (v), (vi), and (vii).

[0052] If no wrinkles are identified on the second coating layer, the method can comprise proceeding to step (ix):

(ix) applying a third material onto the medical device to form a third coating layer;

(x) passing the medical device through a third die to meter the amount of the third material that is disposed on the medical device;

(xi) curing the third coating layer, wherein curing the third coating layer comprises heating the third coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between about 130 °C and about 170 °C; a second heating zone having a temperature of between about 270 °C and about 310 °C; a third heating zone having a temperature of between about 400 °C and about 440 °C; and a fourth heating zone having a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C; and (xii) evaluating the third coating layer and determining whether the third coating layer includes one or more wrinkles on the surface of the third coating layer, wherein if one or more wrinkles are identified on the third coating layer, the method comprises replacing the third die with another die and repeating steps (ix), (x), and (xi).

[0053] If no wrinkles are identified on the third coating layer, the method can comprise proceeding to step (xiii):

(xiii) applying a fourth material onto the medical device to form a fourth coating layer;

(xiv) passing the medical device through a fourth die to meter the amount of the fourth material that is disposed on the medical device;

(xv) curing the fourth coating layer, wherein curing the fourth coating layer comprises heating the fourth coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between about 130 °C and about 170 °C; a second heating zone having a temperature of between about 270 °C and about 310 °C; a third heating zone having a temperature of between about 400 °C and about 440 °C; and a fourth heating zone having a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C; and (xvi) evaluating the fourth coating layer and determining whether the fourth coating layer includes one or more wrinkles on the surface of the fourth coating layer, wherein if one or more wrinkles are identified on the fourth coating layer, the method comprises replacing the fourth die with another die and repeating steps (xiii), (xiv), and (xv).

[0054] If no wrinkles are identified on the fourth coating layer, the method can comprise proceeding to step (xvii):

(xvii) applying a fifth material onto the medical device to form a fifth coating layer;

(xviii) passing the medical device through a fifth die to meter the amount of the fifth material that is disposed on the medical device;

(xix) curing the fifth coating layer, wherein curing the fifth coating layer comprises heating the fifth coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between about 130 °C and about 170 °C; a second heating zone having a temperature of between about 270 °C and about 310 °C; a third heating zone having a temperature of between about 400 °C and about 440 °C; and a fourth heating zone having a temperature of between about 360 °C and about 540 °C, between about 450 °C and about 540 °C, or between about 510 °C and about 530 °C; and (xx) evaluating the fifth coating layer and determining whether the fifth coating layer includes one or more wrinkles on the surface of the fifth coating layer, wherein if one or more wrinkles are identified on the fifth coating layer, the method comprises replacing the fifth die with another die and repeating steps (xvii), (xviii), and (xix).

[0055] Examples:

[0056] The following examples are illustrative and not intended to be limiting in any way.

[0057] Example 1:

[0058] Three wire samples were coated in accordance with the embodiments disclosed herein. The first wire had a diameter of about 234 microns, the second wire had a diameter of about 287 microns, and the third wire had a diameter of about 492 microns. Each wire was coated with three layers of polyethersulfone using a reel-to-reel coating process. Each wire was then coated with a layer comprising a polyamide-imide, followed by an outer coating layer of polytetrafluoroethylene, each of which was also applied using a reel-to-reel coating process.

[0059] Each of the layers was cured by passing the wires through a multi-zone oven having six zones. The first heating zone had a temperature of about 150 °C, the second heating zone had a temperature of about 290 °C, and the third, fourth, fifth, and sixth heating zones each had a temperature of about 400 °C.

[0060] Additionally, the outer coating layer was further cured by heating the coating layer with two slotted infrared transmitters placed outside the multi-zone oven. Each infrared transmitter had a maximum power output of 2010 Watts, was set at 40% power, and was configured to heat the outer coating layer to a temperature of between about 300 °C and 500 °C. The coatings performed well, and little to no flaking was observed when the wire samples were coiled and/or straightened (indicating greater bonding and/or adhesion of the coating).

[0061] Example 2:

[0062] A wire sample was coated in accordance with the embodiments disclosed herein. The wire was coated with three layers of polyethersulfone using a reel-to-reel coating process. The wire was then coated with a layer comprising a polyamide-imide, followed by an outer coating layer of polytetrafluoroethylene, each of which was also applied using a reel-to-reel coating process.

[0063] Each of the layers was cured by passing the wire through a multi-zone oven having six zones. The first heating zone had a temperature of about 150 °C, the second heating zone had a temperature of about 290 °C, and the third, fourth, fifth, and sixth heating zones each had a temperature of about 420 °C. Additionally, the outer coating layer was further cured by heating the coating layer with two slotted infrared transmitters placed outside the multi-zone oven. Each infrared transmitter had a maximum power output of 2010 Watts, was set at 40% power, and was configured to heat the outer coating layer to a temperature of between about 300 °C and 500 °C.

[0064] The coated wire was compared to a wire coated using a traditional coating process that employs increased oven temperatures instead of infrared heating. The comparison showed that the wire cured using infrared radiation exhibited better and more uniform sintering than the comparison wire. This was observed by a more uniform appearance and a more vibrant color, signs of improved curing of the binder and outer layers. There was also little to no observable colloidal texture in the outer coating layer, thereby indicating sufficient sintering.

Claims

1. A method of applying a multilayer coating to a medical device, comprising:

applying a first material onto a first surface of a medical device to form a first coating layer, wherein the first material comprises a polyethersulfone;

curing the first coating layer, wherein curing the first coating layer comprises heating the first coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between 120 °C and 180 °C; a second heating zone having a temperature of between 270 °C and 310 °C; and a third heating zone having a temperature of between 360 °C and 540 °C;

applying a second material to form a second coating layer, wherein the second material comprises a polyamide-imide;

curing the second coating layer, wherein curing the second coating layer comprises heating the second coating layer with the convection oven;

applying a third material to form a third coating layer, wherein the third coating layer is the outermost coating layer, and wherein the third material comprises polytetrafluoroethylene; and curing the third coating layer, wherein curing the third coating layer comprises heating the third coating layer with the convection oven, and wherein curing the third coating layer further comprises heating the third coating layer with infrared radiation.

2. The method of claim 1, wherein the medical device comprises a wire having a diameter of between 50 microns and 1000 microns.

3. The method of any one of the preceding claims, wherein heating the third coating layer with infrared radiation comprises heating the third coating layer with at least two infrared emitters.

4. The method of any one of the preceding claims, wherein curing the first coating layer comprises passing the medical device through the oven at a speed of between 10 meters/minute and 120 meters/minute.

5. The method of any one of the preceding claims, further comprising applying a fourth coating layer and applying a fifth coating layer, wherein the fourth and fifth coating layers are disposed between the first coating layer and the second coating layer.

6. The method of any one of the preceding claims, wherein the convection oven further comprises a fourth heating zone having a temperature of between 360 °C and 540 °C; a fifth heating zone having a temperature of between 360 °C and 540 °C; and a sixth heating zone having a temperature of between 360 °C and 540 °C.

7. The method of any one of the preceding claims, wherein the temperatures of the convection oven are the same when curing the first coating layer, curing the second coating layer, and curing the third coating layer.

8. The method of any one of the preceding claims, wherein heating the third coating layer with infrared radiation comprises heating the third coating layer to a temperature that is sufficient to sinter polytetrafluoroethylene.

9. The method of any one of the preceding claims, wherein the curing temperature of the third coating layer is higher than the curing temperatures of the first and second coating layers.

10. A method of applying a multilayer coating to a medical device, comprising:

(i) applying a first material onto a first surface of a medical device to form a first coating layer, wherein the first material comprises a polyethersulfone;

(iii) curing the first coating layer, wherein curing the first coating layer comprises heating the first coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between 120 °C and 180 °C; a second heating zone having a temperature of between 270 °C and 310 °C; and a third heating zone having a temperature of between 360 °C and 540 °C;

(v) applying a second material onto the medical device to form a second coating layer, wherein the second material comprises a polyethersulfone;

(vii) curing the second coating layer, wherein curing the second coating layer comprises heating the second coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between 120 °C and 180 °C; a second heating zone having a temperature of between 270 °C and 310 °C; and a third heating zone having a temperature of between 360 °C and 540 °C; and (viii) evaluating the second coating layer and determining whether the second coating layer includes one or more wrinkles on the surface of the second coating layer, wherein if one or more wrinkles are identified on the second coating layer, the method comprises replacing the second die with another die and repeating steps (v), (vi), and (vii).

11. The method of claim 10, wherein if no wrinkles are identified on the second coating layer, the method comprises proceeding to step (ix):

(ix) applying a third material onto the medical device to form a third coating layer, wherein the third material comprises a polyethersulfone;

(xi) curing the third coating layer, wherein curing the third coating layer comprises heating the third coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between 120 °C and 180 °C; a second heating zone having a temperature of between 270 °C and 310 °C; and a third heating zone having a temperature of between 360 °C and 540 °C;

(xii) evaluating the third coating layer and determining whether the third coating layer includes one or more wrinkles on the surface of the third coating layer, wherein if one or more wrinkles are identified on the third coating layer, the method comprises replacing the third die with another die and repeating steps (ix), (x), and (xi).

12. The method of claim 11, wherein if no wrinkles are identified on the third coating layer, the method comprises proceeding to step (xiii):

(xv) curing the fourth coating layer, wherein curing the fourth coating layer comprises heating the fourth coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between 120 °C and 180 °C; a second heating zone having a temperature of between 270 °C and 310 °C; and a third heating zone having a temperature of between 360 °C and 540 °C;

(xvi) evaluating the fourth coating layer and determining whether the fourth coating layer includes one or more wrinkles on the surface of the fourth coating layer, wherein if one or more wrinkles are identified on the fourth coating layer, the method comprises replacing the fourth die with another die and repeating steps (xiii), (xiv), and (xv).

13. The method of claim 12, wherein the fourth material comprises a polyamideimide.

14. The method of claim 12, wherein if no wrinkles are identified on the fourth coating layer, the method comprises proceeding to step (xvii):

(xix) curing the fifth coating layer, wherein curing the fifth coating layer comprises heating the fifth coating layer with a convection oven, wherein the convection oven comprises a first heating zone having a temperature between 120 °C and 180 °C; a second heating zone having a temperature of between 270 °C and 310 °C; and a third heating zone having a temperature of between 360 °C and 540 °C; and (xx) evaluating the fifth coating layer and determining whether the fifth coating layer includes one or more wrinkles on the surface of the fifth coating layer, wherein if one or more wrinkles are identified on the fifth coating layer, the method comprises replacing the fifth die with another die and repeating steps (xvii), (xviii), and (xix).

15. The method of claim 14, wherein the fifth material comprises polytetrafluoroethylene.