Intravascular blood pump with ceramic inner sleeve

Abstract

To provide: an intravascular blood pump providing improved sealing of electric parts of the blood pump against purge fluid while not increasing a diameter of the blood pump; and an individual method of manufacturing such an intravascular blood pump.SOLUTION: An intravascular blood pump P has a pumping device 1, which includes an impeller 6 and an electric motor for driving the impeller 6. A rotor 7 of the electric motor is disposed inside a cavity 22 in the pumping device 1 rotatably about an axis of rotation, and coupled to the impeller 6 so as to be able to cause rotation of the impeller 6. The cavity 22 is formed by an inner sleeve 14 made of a ceramic material. At least a portion of a stator of the electric motor, specifically a coil winding 9, may be arranged on the ceramic inner sleeve 14.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an intravascular blood pump for percutaneous insertion into a patient's blood vessel, and in particular to be advanced into the patient's heart, and respective methods of fabricating the intravascular blood pump. [Background technology]

[0002] Intravascular blood pumps, designed to be inserted percutaneously into a patient's blood vessels, such as the femoral or axillary artery or vein, can be advanced into the patient's heart to serve as left or right ventricular assist devices. Therefore, blood pumps may also be referred to as intracardiac blood pumps. Intravascular blood pumps typically include a catheter and a pumping device attached to the distal end of the catheter. The catheter may include supply line tubing, such as electrical wires and purge tubing. Throughout this disclosure, the term "distal" refers to a direction away from the user and toward the heart, whereas the term "proximal" refers to a direction toward the user.

[0003] The pumping device may include an electric motor and an impeller coupled to the rotor of the electric motor for rotation of the impeller about a rotation axis. During operation of the blood pump, the impeller transports blood from a blood flow inlet to a blood flow outlet of the blood pump, for example, through a flow cannula. The pump speed depends on the size of the pumping device. In particular, the efficiency of the electric motor contained within the pumping device is highly dependent on the limited space. However, due to anatomical limitations for insertion into blood vessels, it is desirable to reduce the size of the pumping device, particularly its diameter.

[0004] In known intravascular blood pumps having a micromotor for driving the blood pump impeller, such as the blood pump disclosed in WO 98 / 44619 A1, the stator of the electric motor, or at least stator parts, are encapsulated in a casting compound, such as a polymer material, e.g., epoxy. According to the method for fabricating the micromotor disclosed in WO 98 / 44619 A1, the stator parts of the motor are placed on a mandrel, which is then inserted into a mold cavity. The casting compound is then injected into the mold cavity, encapsulating the stator parts and forming the housing of the pumping device.

[0005] The inner surface of the molded housing surrounds a cavity in which the rotor of the electric motor, typically a magnet, is located. The rotor typically comes into contact with a purge fluid, such as a glucose solution, supplied to the cavity using purge tubing. The casting material forms a barrier for the purge fluid to avoid corrosion of the stator parts, particularly the coil windings typically provided and configured to generate a magnetic field, such as a rotating magnetic field, that causes the rotor to rotate. However, because the coil windings are placed on a mandrel during injection molding, there may be exposed portions of the coil windings on the inner surface of the housing that defines the cavity. The coil windings may also have relatively large manufacturing tolerances that cannot be compensated for during injection molding. Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an object of the present invention to provide an intravascular blood pump that provides improved sealing of the electrical parts of the blood pump against purge fluid without increasing the diameter of the blood pump, and to provide a respective method for manufacturing such an intravascular blood pump. [Means for solving the problem]

[0007] This object is achieved according to the invention by an intravascular blood pump and a method for producing a blood pump having the features of the independent claims. Preferred embodiments and further developments of the invention are specified in the claims dependent thereon.

[0008] According to one aspect of the present invention, an intravascular blood pump for percutaneous insertion into a patient's blood vessel is provided. The blood pump includes a pumping device including an impeller and an electric motor having a stator and a rotor for driving the impeller. The rotor is disposed within a cavity within the pumping device and is rotatable about an axis of rotation and coupled to the impeller to cause rotation of the impeller. The cavity is defined by an inner sleeve made of a ceramic material, such as zirconia, or more preferably alumina toughened zirconia (ATZ). In particular, a coil winding, which may be part of the stator as described above, is preferably disposed on the inner sleeve.

[0009] By providing an inner sleeve made of a ceramic material, a fluid-tight enclosure can be created for the cavity in which the rotor is placed. The ceramic material has diffusion resistance to the purge fluid. Therefore, effective corrosion protection of the stator, specifically electrical stator parts such as the coil windings, can be achieved. Because the ceramic sleeve forms the cavity for the rotor, rather than the inner surface of the casting material, corrosion protection does not depend on the injection molding process, and the ceramic material of the inner sleeve forms a safe barrier against the purge fluid.

[0010] In addition to the sealing properties of ceramic materials, ceramic inner sleeves can be manufactured with very small manufacturing tolerances. Therefore, for example, by placing the coil windings on the ceramic sleeve before injection molding, the dimensions of the coil windings, particularly the inner diameter and therefore the outer diameter, can be defined and adjusted very precisely. The ceramic sleeve is substantially rigid and easy to handle, which can improve handling of the coil windings when they are placed on the sleeve. Ceramic materials allow for very small wall thicknesses of the inner sleeve. This is important to avoid increasing the overall diameter of the pumping device and to maintain a small air gap between the stationary coil and the rotating magnet to ensure high motor efficiency and low core temperatures. Additionally, the inner sleeve may be manufactured with a surface finish, particularly on the inner surface of the sleeve, so that even blood can be pumped through the air gap, i.e., the space between the inner sleeve and the rotor, without significant blood damage or clotting. This may be relevant for purgeless pumps.

[0011] In one embodiment, an end piece made of a ceramic material, preferably the same ceramic material from which the inner sleeve is made, is provided and can be attached in a fluid-tight manner to the axial end of the inner sleeve to surround the cavity. The ceramic end piece can be attached to the inner sleeve, for example, by adhesive, or can be integrally formed with the inner sleeve. Preferably, the end piece includes a bearing, such as a journal bearing, that rotatably supports the rotor. For example, the rotor, or a shaft carrying the rotor, can be inserted into a hole in the end piece to form a journal bearing.

[0012] The cavity is preferably in fluid communication with purge tubing of the blood pump, which is configured to supply purge fluid into the cavity. Specifically, the purge tubing can be connected to the end piece described above. More specifically, the purge tubing can be connected to the end piece, such that purge fluid is supplied directly to the bearing formed by the end piece and through the bearing into the cavity. For example, the end piece can include a central hole and a central hollow post aligned with the hole, and the purge tubing can be connected to the hollow post.

[0013] The stator, particularly the coil windings and other electrical parts susceptible to corrosion, is preferably sealed in a fluid-tight manner to the cavity by an inner sleeve. As explained above, the ceramic material effectively prevents the diffusion of the purge fluid, thereby protecting the stator parts.

[0014] In one embodiment, electrical connections for the stator, preferably the coil windings, may be formed at least partially on the inner sleeve, preferably on the end pieces. The ceramic inner sleeve, and possibly the ceramic end pieces, are suitable for carrying the electrical connections because ceramic materials withstand the high temperatures encountered during soldering of electrical connections, such as copper pads that connect to the wires (typically copper wires) of the coil windings. It may be advantageous to place the electrical connections, particularly the copper pads, on the ceramic inner sleeve and / or the ceramic end pieces, particularly when multiple, complexly arranged coil winding terminals are required. The copper pads may be formed by copper coating the ceramic sleeve and / or the ceramic end pieces at the desired locations.

[0015] To be able to control the coil windings to generate a magnetic field, particularly a rotating magnetic field, a relatively large number of electrical connections for the coil windings are required. For example, to control the coil windings in multiple phases, e.g., three phases, to create a rotating magnetic field, six electrical connections are required in a two-layer arrangement of the coil winding wire. More specifically, the coil windings may be divided into multiple angular sections, e.g., three sections of 120 degrees each, that can be continuously controlled to cause rotation of the rotor, which may be a permanent magnet. A more powerful four-layer arrangement would then require 12 electrical connections.

[0016] For example, to achieve three controllable section placement of the coil winding, one could make a complete loop of coil wire and, while winding the wire at 120 degrees and 240 degrees, cut it to create two terminals to close one section and start the next. Thus, in a two-layer coil configuration, this would result in six terminals: one at the beginning (at 0 degrees), two at 120 degrees, two at 240 degrees, and one at the end (at 360 degrees, which is the same as the 0 degree position). It will be understood that as few as two sections of 180 degrees each, or more than three sections, may be provided if desired, so long as they are capable of producing a dynamic magnetic field to cause rotor rotation.

[0017] A typical winding pattern results in an even number of winding layers, with the wire starting at 0 degrees at one longitudinal end of the coil winding, being guided toward the opposite longitudinal end at 180 degrees, and returning to the starting point to complete one cycle. To keep the outer diameter of the coil winding as small as possible, subsequent layers may be offset by half the diameter of the coil wire perpendicular to the longitudinal direction of the coil wire in order to nest the subsequent layers between the wire of the underlying layer.

[0018] In particular, providing precise alignment of the coil winding layers without crossovers or gaps is important for the efficiency of the electric motor, on the one hand, and for maintaining the outer diameter within narrow manufacturing tolerances, on the other. Specifically, the wire sections of the coil winding must be precisely aligned side-by-side along their length without defects in the form of straddling. Accurate side-by-side alignment of the wires can further improve the structural stability of the coil winding, since precise alignment allows the wire sections to be properly secured to adjacent wire sections by their insulating coating, which may include a thermosetting varnish, such as baking lacquer, as the outermost layer. Providing a ceramic inner sleeve as a support for the coil winding can help provide improved precise alignment of the coil winding wires, particularly with respect to the above-mentioned aspects.

[0019] As outlined above, the inner sleeve may have a small wall thickness. More specifically, the inner sleeve may have a wall thickness of about 20 μm to about 100 μm, preferably about 40 μm to about 60 μm, and more preferably about 50 μm. The inner sleeve may have a tubular shape. Preferably, the inner sleeve is substantially cylindrical. The inner diameter of the inner sleeve is preferably slightly larger than the outer diameter of the rotor to form a small gap, for example, about 50 μm. A small gap is preferable in terms of optimizing the magnetic flux to optimize the efficiency of the electric motor, as described above. In this regard, it should be understood that another advantage of ceramic materials is that they do not affect the magnetic flux of the electric motor. The inner sleeve may have a length of about 5 mm to about 20 mm, preferably about 8 mm to about 15 mm.

[0020] The intravascular blood pump may further include an outer sleeve that may form at least a portion of the outer surface of the pumping device. At least a portion of the stator may then be disposed in the gap between the outer sleeve and the inner sleeve. The outer sleeve may include a magnetically conductive material, such as a metal or metal alloy, for forming a yoke (back iron) of an electric motor. The stator, or at least stator parts, preferably at least the coil windings, may be fixed to the outside of the inner sleeve, particularly in the gap between the inner sleeve and the outer sleeve, using a casting material, such as a polymer material like epoxy.

[0021] A method for fabricating an intravascular blood pump, particularly an intravascular blood pump as described above, includes providing an inner sleeve made of a ceramic material to form a cavity for receiving the rotor, and placing the coil windings on the inner sleeve. The ceramic sleeve thereby forms a support for the coil windings that can be easily handled as described above. Furthermore, as also described above, the ceramic inner sleeve has very small manufacturing tolerances that allow for very precise calibration of the coil windings. The coil windings may be pre-wound and then placed on the ceramic sleeve, allowing the coil windings to be adjusted to the dimensions of the ceramic sleeve. Alternatively, the coil windings may be wound directly on the ceramic sleeve. In either case, the coil windings are properly centered by the ceramic sleeve.

[0022] As mentioned above, the ceramic inner sleeve can be connected to a ceramic end piece, which can include a bearing. Therefore, the method can further include fluid-tightly attaching an end piece made of a ceramic material to the axial end of the inner sleeve so as to surround the cavity. The end piece can be attached to the inner sleeve by gluing or other adhesive methods. This can be done before placing the coil winding on the inner sleeve and, in some cases, before injection molding the casting material around the inner sleeve.

[0023] The method may further comprise injection-molding the casting material around the inner sleeve to encapsulate at least the coil windings arranged on the inner sleeve. If the pumping device comprises an outer sleeve as described above, the injection molding may be carried out in particular by injecting the casting material into the outer sleeve, more particularly into the gap formed between the inner and outer sleeves. However, it should be understood that the ceramic inner sleeve may be provided independently of the outer sleeve, and the stator parts may be encapsulated by any other injection molding technique, for example by injecting the casting material into a mold, as described, for example, in WO 98 / 44619 A1.

[0024] In a method of fabricating a blood pump using an outer sleeve as a mold during an injection molding process, the ceramic inner sleeve and additional stator components, such as coil windings, can be placed on a mold base, which can be formed as a mandrel. Next, the outer sleeve, which can be considered the outermost part of the stator components, can be placed on the mold base and thereby over the inner sleeve and other stator components, thereby forming at least a portion of the outer surface of the blood pump and forming a gap between the inner and outer sleeves in which the stator components are placed. Next, a casting material, such as a polymer material, particularly a resin such as epoxy, can be injected through the mold base and into the gap to secure the stator components inside the outer sleeve. The mold base can be a disposable part, for example, made of plastic by injection molding.

[0025] This can be particularly advantageous when the outer sleeve includes a magnetically conductive material for forming the yoke (rear iron) of the electric motor. Specifically, the outer sleeve can include or be made of a metal or a metal alloy, such as a ferrite alloy, e.g., an FeCrAl alloy. The outer surface can be coated with a respective oxide. It should be understood that the outer sleeve can include any suitable biocompatible magnetically conductive material. Metallic materials have the additional advantage of increased heat dissipation compared to plastic materials.

[0026] The foregoing summary, as well as the following detailed description of the preferred embodiments, will be better understood when read in conjunction with the appended drawings. For purposes of illustrating the present disclosure, reference is made to the drawings. However, the scope of the present disclosure is not limited to the specific embodiments disclosed in the drawings. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram of an intravascular blood pump inserted into a patient's heart. [Figure 2] FIG. 1 illustrates a cross-sectional view through an intravascular blood pump. [Figure 3] FIG. 10 shows a perspective view of a ceramic inner sleeve. [Figure 4] FIG. 1 shows a perspective view of a ceramic proximal bearing. DETAILED DESCRIPTION OF THE INVENTION

[0028] FIG. 1 illustrates an intravascular blood pump P inserted into a patient's heart H. More specifically, the blood pump P includes a pumping device 1 attached to a catheter 5. The pumping device 1 is inserted into the left ventricle LV of the patient's heart H using the catheter 5 and pumps blood from the left ventricle LV into the aorta AO. The illustrated application is merely exemplary, and the blood pump P of the present invention is not limited to this application. For example, a reverse application for the right ventricle RV may be envisioned. The blood pump P is percutaneously inserted, for example, via a femoral or axillary access, and advanced into the heart H through the aorta AO. The blood pump P is positioned such that the blood flow outlet 2 is located outside the patient's heart H in the aorta AO, while the blood flow inlet 3, which is in fluid communication with a flow cannula 4, is located inside the left ventricle LV. An impeller is provided within the pumping device 1 to generate blood flow from the blood flow inlet 3 to the blood flow outlet 2, and rotation of the impeller is generated by an electric motor located within the pumping device 1, as will be described in more detail below.

[0029] FIG. 2 shows a cross-sectional view through pumping device 1 along central longitudinal axis L, which coincides with the axis of rotation of rotor 7 and impeller 6. More specifically, rotor 7 and impeller 6 are disposed on a common shaft 8 extending along the axis of rotation. The rotor 7 of the electric motor is formed as a permanent magnet and is disposed within cavity 22 of the pump casing. To cause rotation of rotor 7, coil windings 9, which are part of the stator of the electric motor, surround rotor 7 and are controllable to cause rotation of rotor 7. Impeller 6 is coupled to rotor 7 via shaft 8, such that rotation of rotor 7 causes rotation of impeller 6, which draws blood into blood inlet 3, through flow cannula 4, and out blood outlet 2, as indicated by the arrows in FIG. 2.

[0030] The shaft 8 is rotatably supported by distal bearing 12 and proximal bearing 11, both of which may be formed as journal bearings as shown in FIG. 2 . Bearings 11, 12 and shaft 8 may be formed of a ceramic material. However, other types of bearings, such as ball bearings, may also be used to rotatably support shaft 8. The bearings may be axial or radial bearings, or combined axial and radial bearings. A purge fluid is supplied through cavity 22 in which bearings 11, 12 and rotor 8 are disposed using purge tubing 15. Purge tubing 15 extends through catheter 5 and is connected to proximal bearing 11 in a fluid-tight manner. In this way, the purge fluid does not come into contact with the electrical components of the pumping device 1, but only flows through proximal bearing 11, into cavity 22, and through distal bearing 12.

[0031] To provide a safety barrier to protect the electrical components, particularly the coil windings 9, from corrosion and short circuits caused by the purge fluid, the cavity 22 for the rotor 7 may be formed by an inner sleeve 14 made of a ceramic material. The ceramic inner sleeve 14 is attached to the proximal bearing 11 in a fluid-tight manner and is resistant to the diffusion of the purge fluid. The ceramic inner sleeve 14 is also so well defined with a smooth inner surface that, in other configurations of the blood pump, some blood may be allowed to enter the pump instead of the purge fluid without causing clotting or blood breakdown. Further corrosion protection is established by a casting compound 18 that secures the stator components of the pumping device 1 and fills the gap 19 between the inner sleeve 14 and the outer sleeve 13. Specifically, the coil windings 9 are encapsulated within the casting compound 18. The casting compound 18 also provides additional fixation for the electrical connections 16 (i.e., PCB) to the motor cable 10 and purge tubing 15. Casting material 18 may be a polymeric material such as a resin, preferably a two-part epoxy, and more preferably a two-part epoxy with a thermally conductive and electrically insulating filler.

[0032] The outer sleeve 13 defines the outer surface and external dimensions of the pumping device 1. The outer sleeve 13, which surrounds the aforementioned components, particularly the stator components secured by the casting compound 18, thus forms the casing of the pumping device 1. It should be understood that the outer sleeve 13 also forms the magnetically active stator components. The outer sleeve 13 is made of a biocompatible, magnetically conductive material, such as a suitable metal alloy, and serves as a yoke for the magnetic flux of the electric motor. The metallic outer sleeve 13 also allows for good dissipation of heat generated by the operation of the electric motor. The outer surface of the outer sleeve 13 may include a groove 21 for receiving a wire carrying a sensor 20. A hub 17 is attached to the distal end of the outer sleeve 13 and forms a mounting area for the flow cannula 4. The hub 17 is preferably made of the same material as the outer sleeve 13 and houses the distal bearing 12 and impeller 6. A blood flow outlet 2 is formed within the hub 17, allowing heat transfer from the distal bearing 12.

[0033] The outer sleeve 13 may have a length of about 7 mm to about 30 mm, preferably about 10 mm to about 20 mm, and more preferably about 10 mm to about 15 mm. The outer sleeve 13 may have an outer dimension of 18F (French) or less (an outer diameter of 6 mm or less). Despite its small size, a pumping speed of up to 5.5 liters / minute can be achieved.

[0034] FIG. 3 shows the ceramic inner sleeve 14 included in the intravascular blood pump P described above, which surrounds the cavity 22 for the rotor 7. The sleeve 14 has a cylindrical shape and a wall thickness of about 20 μm to about 100 μm, preferably about 50 μm. The ceramic material may be alumina-toughened zirconia (ATZ). Electrical connections for the coil windings 9, particularly copper pads 23 for soldering the electrical connections, may be provided directly on the ceramic sleeve 14, for example, by copper coating the respective locations on the sleeve 14. The ceramic material can withstand high temperatures during soldering and is therefore suitable for forming supports for the copper pads 23, i.e., PCBs. The sleeve 14 may carry three copper pads 23 regularly spaced circumferentially on its surface.

[0035] When the coil windings are applied in a two-layer configuration, there are at least six terminals on the coil winding 9 to enable continuous control of the coil winding 9 to generate a rotating magnetic field. In a four-layer configuration of the coil windings, twelve terminals must be connected. Therefore, additional electrical connections 24, 25 can be placed on the ceramic end piece 11, including the proximal bearing, as shown in FIG. 4. The end piece 11 can be made of the same ceramic material as the inner sleeve 14 and can be attached to the inner sleeve 14 with an adhesive. The central bore of the end piece 11 is sized and shaped to rotatably receive the shaft 8 of the rotor 7. A central hollow stem 26 protruding from the end piece 11 in alignment with the central bore provides an attachment area for the purge tubing 15. In this way, purge fluid can be supplied directly to the bearing and further into the inner sleeve 14.

[0036] In a method for fabricating an intravascular blood pump, end piece 11 can be attached to inner sleeve 14 to form a fluid-tight enclosure for rotor 7. Coil winding 9, which can be pre-wound, can be placed on inner sleeve 14, allowing for precise adjustment of the dimensions of coil winding 9. Therefore, ceramic inner sleeve 14 not only provides a hermetic barrier for purge fluid and electrical insulation, but also helps improve the efficiency of the electric motor by optimizing the placement of coil winding 9. Terminals of coil winding 9 are soldered to copper pads 23, 24, 25, and coil winding 9 mounted on inner sleeve 14 is encapsulated in casting compound 18 during further processing, such as an injection molding process.

[0037] Alternatively, the coil winding 9 may be wound directly onto the inner sleeve 14 and the interconnections of the coil winding 9 and copper pads 23, and if applicable, the copper pads 24, 25 may be performed automatically during the winding process. Thus, a secondary soldering step and specific sequencing of the terminal wires of the coil winding 9 (e.g., by terminal wire length or color) may be avoided.

Claims

1. 1. An intravascular blood pump (P) for percutaneous insertion into a patient's blood vessel, comprising: a pumping device (1) including an impeller (6) and an electric motor for driving said impeller (6), said electric motor including a stator and a rotor (7), said rotor (7) being arranged inside a cavity (22) in said pumping device (1), being rotatable about an axis of rotation and being coupled to said impeller (6) so as to cause rotation of said impeller (6), said cavity (22) being formed by an inner sleeve (14) made of ceramic material.

2. 2. The blood pump according to claim 1, wherein the stator includes a coil winding (9) arranged on the inner sleeve (14) and configured to generate a magnetic field, preferably a rotating magnetic field, for causing rotation of the rotor (7).

3. 3. The blood pump according to claim 1 or 2, further comprising an end piece (11) made of ceramic material and attached in a fluid-tight manner to the axial end of the inner sleeve (14) so ​​as to surround the cavity (22).

4. 4. A blood pump according to claim 3, characterized in that the end piece (11) comprises a bearing for rotatably supporting the rotor (7), said bearing being preferably a journal bearing.

5. 5. The blood pump of claim 1, wherein the cavity (22) is in fluid communication with a purge tubing (15) of the blood pump configured to supply a purge fluid into the cavity (22).

6. 6. A blood pump according to any one of claims 1 to 5, characterized in that the stator is sealed in a fluid-tight manner to the cavity (22) by the inner sleeve (14).

7. 7. A blood pump according to claim 1, wherein the stator, preferably the electrical connections (23, 24, 25) of the coil winding (9), are formed at least partially on the inner sleeve (14).

8. 8. A blood pump according to any one of claims 1 to 7, characterized in that the inner sleeve (14) has a wall thickness of about 40 μm to about 60 μm, preferably about 50 μm.

9. 9. A blood pump according to any one of claims 1 to 8, characterized in that the inner sleeve (14) is substantially cylindrical.

10. 10. The blood pump according to claim 1, wherein the stator, preferably at least the coil winding (9), is fixed to the outside of the inner sleeve (14) using a casting compound (18), the casting compound (18) preferably comprising a polymer material, preferably a resin, more preferably an epoxy.

11. 11. A blood pump according to any one of claims 1 to 10, further comprising an outer sleeve (13) forming at least a part of the outer surface of the pumping device (1), wherein at least a part of the stator is arranged in a gap (19) between the outer sleeve (13) and the inner sleeve (14).

12. 12. The blood pump according to claim 11, wherein the outer sleeve (13) comprises a magnetically conductive material for forming a yoke of the electric motor, the outer sleeve (13) preferably comprising a metal or a metal alloy.

13. A method for producing an intravascular blood pump, in particular an intravascular blood pump according to any one of claims 1 to 12, said blood pump comprising a pumping device (1) including an impeller (6) and an electric motor for driving said impeller (6), said electric motor including a stator and a rotor (7), said rotor (7) being rotatable about a rotation axis and coupled to said impeller (6) so as to cause rotation of said impeller (6), said method comprising: - providing an inner sleeve (14) made of ceramic material to form a cavity (22) for receiving said rotor (7); - arranging on said inner sleeve (14) a coil winding (9) for generating a magnetic field, preferably a rotating magnetic field, for causing rotation of said rotor (7).

14. 14. The method according to claim 13, further comprising the step of mounting an end piece (11) made of ceramic material in a fluid-tight manner on the axial end of the inner sleeve (14) so ​​as to surround the cavity (22), the end piece (11) preferably comprising a bearing for rotatably supporting the rotor (7), the bearing preferably being a journal bearing.

15. 15. The method according to claim 13 or 14, further comprising the step of injection molding a casting material (18) around the inner sleeve (14) so ​​as to encapsulate at least the coil windings (9) disposed on the inner sleeve (14).

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