Electrical and media-tight insulation of metal implants by applying a glass layer or a ceramic layer

Abstract

The present invention relates to a method for coating an outer surface (2a) of a housing (2) of a medical device (1), wherein the method comprises the steps of: - providing a housing (2) of a medical device (1), the housing comprising an outer surface (2a), - applying a coating material (3) to at least a portion of said outer surface (2a), - heating the coating material (3) arranged on said outer surface to melt said coating material (3), and - curing the coating material (3) to form a coating (4) of said outer surface (2a), the coating (4) being bonded to the outer surface (2a).

Description

[0001] Electrical and media-tight insulation of metal implants by applying a glass layer or a ceramic layer

[0002] The present invention relates to a method for coating a surface of a housing of a medical device.

[0003] In order to achieve biocompatible outer surfaces of medical devices, particularly implants, coating of outer surfaces with parylene is known in the state of the art.

[0004] However, coating a surface with parylene usually requires a time-consuming batch process including many mandatory upstream and downstream processes. In addition, the equipment for conducting the batch process requires a lot of maintenance.

[0005] Furthermore, coating a surface with silicone is a laborious and rather imprecise manual dipping process. Silicone is not stable over the long term and can wear off over time.

[0006] Based on the above, the problem to be solved by the present invention is to provide a method for coating an outer surface of a housing of a medical device that allows to coat the surface in a more efficient manner. Particularly, it is desirable to achieve a complete or partial electrical and media-tight insulation of metal housings of medical implants.

[0007] This problem is solved by a method having the features of claim 1. Further aspects of the present invention relate to a medical implant coated by the method according to the present invention, a medical device having a coated housing, and a coating device for coating a medical implant. According to claim 1 a method for coating a surface of a housing of a medical device is disclosed, wherein the method comprises the steps of:

[0008] - providing a housing of a medical device, the housing comprising an outer surface,

[0009] - applying a coating material to at least a portion of said outer surface,

[0010] - heating the coating material arranged on said outer surface to melt said coating material, and

[0011] - hardening or curing the coating material to form a coating of said outer surface, the coating being bonded to the surface.

[0012] According to a preferred embodiment of the method, the coating is biocompatible, i.e., it may be in contact with a human without producing an adverse effect.

[0013] Furthermore, according to a preferred embodiment, heating is applied to a spot of the applied coating material, wherein said spot is moved along said outer surface. This movement may be performed by moving a device generating the heat, e.g. a laser, or by moving the housing of the medical device to be coated.

[0014] Preferably, according to an embodiment, said heating is applied to said spot by generating laser light that impinges on said spot. Particularly, laser light may be used, which is absorbable by the coating. In an example, the coating or coating material comprises or is a glass, particularly a glass having a low thermal expansion coefficient, e.g., a borosilicate glass or a quartz glass, or a glass-forming oxide, and said heating is applied by laser light being adsorbable by the glass, e.g., a carbon dioxide laser. Other heating methods are also conceivable.

[0015] According to yet another preferred embodiment of the method, the housing of the medical device encloses an internal space, wherein a cooling material, particularly a gel, is arranged in said internal space to protect components of the medical implant, particularly electronic components, arranged in said internal space from said heating applied to the coating material.

[0016] Furthermore, according to a preferred embodiment, the coating material is formed as a powder, or a paste when the coating material is applied to the at least one portion of said surface. In an embodiment the coating material, particularly in form of a powder, is applied by means of a foil or film, wherein the foil or film carries the coating material, and wherein particularly the foil is arranged such on the housing that the coating material contacts the housing.

[0017] According to a preferred embodiment, the coating is or comprises a glass. Non-limiting suitable glasses include borosilicate glasses (e.g., Bor-Kron-Glas (BK7) or D263 bio, Schott AG, Mainz)), a quartz glasses or non-silicate glasses (e.g., CABAL 12), D 263 bio (Schott Mainz).

[0018] Furthermore, according to a preferred embodiment of the method, the coating material comprises a glass-forming oxide, preferably selected from the group comprised of: silicon dioxide (SiCh), boron trioxide (B2O3), potassium oxide (K2O), sodium oxide (Na20) aluminum oxide (AI2O3).

[0019] According to a preferred alternative embodiment of the method according to the present invention, the coating is or comprises a ceramic material.

[0020] According to a further preferred embodiment of the method, the coating material comprises at least one of: titanium oxide, zirconium oxide, molybdenum oxide (particularly as an opacifier).

[0021] According to yet another preferred embodiment, the coating material comprises at least one of: cobalt oxide, nickel oxide.

[0022] Preferably, according to an embodiment, the coating material can further contain a ceramic pigment, particularly at least one of: iron oxide, chromium oxide, a spinel.

[0023] According to yet another preferred embodiment, the housing (and particularly said outer surface) is formed out of a material or comprises a material selected from the group comprised of: a biocompatible material, particularly a biocompatible metal or alloy, for example, gold, titanium, a titanium alloy, a steel, particularly stainless steel, or a non- biocompatible material, particularly a non-biocompatible metal or alloy, such as aluminum or an aluminum alloy.

[0024] However, since the coating is preferably biocompatible and forms a hermetical sealing of at least a portion of the outer surface of the housing, said portion(s) of the outer surface of the housing covered by the coating do not need to be biocompatible which advantageously increases the number of materials that can be selected for the housing. Usually, for implantable medical devices, titanium or a titanium alloy is a preferred housing material, but due to the biocompatible coatings also metals such as aluminum may be used to form the housing.

[0025] According to a preferred embodiment, the medical device is an implantable medical device. Particularly, according to a preferred embodiment of the method according to the present invention, the implantable medical device is an active implantable medical device, preferably one of: an implantable cardiac pacemaker, an implantable intracardiac pacemaker (i.e., leadless pacemaker), an implantable cardioverter-defibrillator, a neurostimulator, an implantable monitoring device (e.g., for monitoring the heart of a patient such as a loop recorder).

[0026] According to a preferred embodiment of the method according to the present invention, at least an area of said outer surface of the housing is not covered with the coating material, wherein preferably said area of the surface of the housing forms an electrode. In case the housing material forming the outer surface of the housing is not biocompatible in said area, a biocompatible metallic layer can be provided to form said area / electrode.

[0027] Furthermore, according to an embodiment of the method according to the present invention, upon applying said coating material and / or upon said heating, the area is covered by a holding device that holds the housing during application of said coating and / or during heating of the coating material. According to yet another preferred embodiment of the method, the outer surface comprises multiple areas that are not covered with the coating material, wherein preferably said areas of the outer surface of the housing each form an electrode of the medical device.

[0028] The method according to the present invention is therefore particularly suitable for coating housings of intracardiac (e.g., leadless) pacemakers where the electrode(s) is / are arranged on the housing.

[0029] According to a further aspect of the present invention, a medical device is disclosed that comprises a coating that has been generated by the method according to the present invention.

[0030] According to yet another aspect of the present invention a coating device for coating the surface of a housing of a medical device is disclosed, wherein the coating device comprises a dispensing device for dispensing a coating material onto an outer surface of the housing, a heating device for melting the coating material applied to the outer surface of the housing, and a holding device for holding the housing when the coating material is applied to the housing and / or when the coating material is heated by the heating device.

[0031] Particularly, as described above, the heating device may comprise a laser and a device for moving a spot of the laser light generated by the laser along the outer surface of the housing. Alternatively, the housing may be moved, while heating device remains stationary.

[0032] According to yet another aspect of the present invention, a medical device is disclosed, particularly an implantable medical device, comprising a housing having a metallic outer surface, wherein at least a portion of the outer surface is coated with a biocompatible coating formed out of or comprising at least one of: a glass, a ceramic material.

[0033] According to a preferred embodiment of the medical device, the outer surface of the housing comprises one or several areas that is / are not covered with the coating material. According to a further preferred embodiment, the respective area of the outer surface of the housing of the medical device forms an electrode of the medical device.

[0034] The medical device according to the present invention can be further characterized by the features described above in conjunction with the method according to the present invention. Particularly, the medical device can be one of the medical devices described above.

[0035] In the following, embodiments of the present invention as well as further features and advantages of the present invention shall be described with reference to the Figures, wherein

[0036] Fig. 1 shows in conjunction with Figs. 2 to 4 an embodiment of the method according to the present invention, wherein Fig. 1 shows an uncoated medical device (e.g., implant) clamped in a holding device. An area of an outer surface of the housing of the medical device that is not to be coated is masked by means of the holding device,

[0037] Fig. 2 shows application of a coating material (e.g., either in powder form or as a paste) to said outer surface, wherein the masked area is not covered with the raw coating material,

[0038] Fig. 3 shows local heating of the coating material in a scanning fashion (generating a melt) by means of a laser (preferably an ultrashort pulse laser), and

[0039] Fig. 4 shows the medical device coated with an electrically insulating and gas-tight coating. The masked area is not coated and can form an electrode (e.g., in case of a medical device in form of a leadless pacemaker).

[0040] Fig. 1 shows in conjunction with Figs. 2 to 4 an embodiment of the method according to the present invention. According thereto, a medical device 1 comprising a housing 2 is provided, the housing 2 comprising an outer surface 2a. Preferably, as indicated in Fig. 1 the uncoated medical device (e.g., implant) 1 is clamped in a holding device 10. An area 20 of the outer surface 2a of the housing 2 of the medical device

[0041] I that is not to be coated is masked by means of the holding device 10.

[0042] Furthermore, before the raw coating material 3 is applied to the outer surface 2a, the latter may be pretreated (e.g., by cleaning and / or removing of an oxide layer).

[0043] According to Fig. 2, a coating material 3 (e.g. in form of a powder or a paste) is applied to the outer surface 2a of the housing 2 that is fixed by the holding device 10. The area 20 of the outer surface 2a is covered by the holding device 10 and does therefore not receive any coating material 3. Particularly, the coating material 3 may be applied to the outer surface 2a by means of a dispensing device which may comprise a suitable outlet, such as a nozzle, for applying the coating material 3 to the outer surface 2a.

[0044] Thereafter, the coating material 3 applied to the outer surface 2a is preferably heated by means of a heating device that comprises a laser 12 which generates a spot 5 of laser light

[0045] I I on the coating material 3 to locally heat and melt the coating material 3. The heating device is preferably configured to move the spot 5 along the coating material 3 / outer surface 2a, so as to be able to completely melt the coating material 3. It is also conceivable to use multiple lasers.

[0046] Upon hardening curing of the coating material 3 a coating 4 of said outer surface 2a is formed that is bonded to the outer surface 2a (cf. Fig. 4). The uncoated area 20 may form an electrode of the medical device 1. It is also possible to generate multiple uncoated areas, each of which may form an electrode of the medical device 1. Alternatively, the whole outer surface 2a of the medical device 1 can be coated.

[0047] Particularly, the present invention offers the benefit of a local, short, small-area heating of the connecting partners (e.g., metal and glass) so that no heating of the entire medical device / implant 1 is necessary. Optionally, a thermal insulation of the (e.g., metallic) housing 2 from the inside is possible to reduce the heat acting from the outside, e.g. with an aerogel. Apart from heating the medical device’s housing 2 and the (e.g., glass) raw coating material 3 by laser light 11, also other local heating methods may be employed, preferably in combination with heat protection from the inside of the housing 2.

[0048] Advantageously, the present invention particularly achieves a long-term stable, abrasionresistant insulation layer by means of a one-piece-flow process that can be automated.

[0049] According to an example of the present invention, the coating material 3 may comprise 34% borax, 28% feldspar, 5% fluoride, 20% quartz, 6% soda ash, 5% sodium nitrate and 0.5 to 1.5% each of cobalt, manganese and nickel oxide.

[0050] According to another example, the coating material 3 can comprise 23 % borax, 52 % feldspar, 5 % fluoride, 5 % quartz, 5 % soda ash, 2.5 % sodium nitrate, 0.5 to 1.5 % each of cobalt, manganese and nickel oxide and 6.5 % cryolite. Furthermore, 6 to 10% opacifiers (e.g., tin oxide, titanium silicates) and color oxides can be added to this mixture.

[0051] The above substances are preferably finely ground and melted. The melt is poured into water, quenched, and the resulting granular glassy frit is finely ground again. During grinding, 30% to 40% water, clay and quartz powder are added. Depending on the type of enamel, the aforementioned opacifiers and color oxides may also be added. The resulting enamel slip preferably rests for a few days for better mixing before it can be used as coating material and applied to the outer surface.

Claims

Claims1. A method for coating an outer surface (2a) of a housing (2) of a medical device (1), wherein the method comprises the steps of:- providing a housing (2) of a medical device (1), the housing (2a) comprising an outer surface (2a),- applying a coating material (3) to at least a portion of said outer surface (2a),- heating the coating material (3) arranged on said outer surface (2a) to melt said coating material (3), and- hardening the coating material (3) to form a coating (4) of said outer surface (2a), the coating (4) being bonded to the outer surface (2a).

2. The method according to claim 1 , wherein heating is applied to a spot (5) of the coating material (3), wherein said spot (5) is moved along said outer surface (2a).

3. The method according to claim 2, wherein heating is applied to said spot (5) by generating laser light (11) that impinges on said spot (5).

4. The method according to one of the preceding claims, wherein the housing (2) encloses an internal space, wherein a cooling material, particularly a gel, is arranged in said internal space to protect components of the medical device (1), which components are arranged in said internal space of the housing (2), from said heating applied to the coating material (3).

5. The method according to one of the preceding claims, wherein the coating material (3) is formed as a powder or a paste when the coating material (3) is applied to the at least one portion of the outer surface (2a), or the coating material is applied with a foil carrying the coating material.

6. The method according to one of the preceding claims, wherein the coating (4) is or comprises a ceramic material7. The method according to one of the claims 1 to 5, wherein the coating (4) is or comprises a glass, particularly a borosilicate glass, a quartz glass, or a non-silicate glass.

8. The method according to claim 7, wherein the coating material (3) comprises a glassforming oxide selected from the group comprised of: silicon dioxide (SiCh), boron trioxide (B2O3), potassium oxide (K2O), sodium oxide (Na2O) aluminum oxide (AI2O3).

9. The method according to one of the claims 7 to 8, wherein the coating material (3) comprises at least one of: titanium oxide, zirconium oxide, molybdenum oxide.

10. The method according to one of the claims 7 to 9, wherein the coating material (3) comprises at least one of: cobalt oxide, nickel oxide11. The method according to one of the preceding claims, wherein the housing (2) is formed out of a material or comprises a material selected from the group comprised of: a biocompatible material, particularly a biocompatible metal or alloy, such as gold, titanium, a titanium alloy, a steel, particularly stainless steel, or a non-biocompatible material, particularly a non-biocompatible metal or alloy such as aluminum or an aluminum alloy.

12. The method according to one of the preceding claims, wherein the medical device (1) is an implantable medical device.

13. A medical device (1), particularly an implantable medical device (1), comprising a housing (2) having a metallic outer surface (2a), wherein at least a portion of the outer surface (2a) is coated with a biocompatible coating (4) formed out of or comprising one of: a glass, a ceramic material.

14. The medical device according to claim 13, wherein the outer surface (2a) comprises one or several areas (20) that is / are not covered with the coating material (3).

15. The medical device according to claim 14, wherein the respective area (20) of the outer surface (2a) of the housing (2) forms an electrode of the medical device (1).

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