DE102015209511A1 - A rotor shaft for a cardiac assist system, cardiac assist system and method of manufacturing a rotor shaft for a cardiac assist system - Google Patents

Abstract

The invention relates to a rotor shaft (102) for a cardiac assist system. The rotor shaft (102) comprises at least one bearing section (600, 602) for supporting the rotor shaft (102) in a rotor shaft carrier and at least one structural element (608) arranged in the bearing section (600, 602) for generating a fluid film in a lubrication gap between the bearing section (600, 602) and the rotor shaft carrier when rotating the rotor shaft (102) in a fluid.

Description

State of the art

The invention is based on a device or a method according to the preamble of the independent claims.

Cardiovascular disease remains one of the leading causes of death. Heart failure, in particular, is the most common cause of hospitalization in the elderly today.

The non-drug therapy of end-stage heart failure consists in heart transplantation and alternatively in the implantation of so-called mechanical circulatory support systems, such as a cardiac assist system, English ventricular assist device or VAD for short. By using small axial or radial pumps instead of large pneumatic pumps, the complication rate was lowered and the prognosis significantly improved. Such cardiac assist systems are increasingly being used as a permanent replacement for heart transplantation.

Disclosure of the invention

Against this background, with the approach presented here, a rotor shaft for a cardiac assist system, a cardiac assist system and a method for manufacturing a rotor shaft for a cardiac assist system according to the main claims are presented. The measures listed in the dependent claims advantageous refinements and improvements of the independent claim device are possible.

The approach presented here provides a rotor shaft for a cardiac assist system, the rotor shaft having the following features:
at least one bearing section for supporting the rotor shaft in a rotor shaft carrier; and
at least one arranged in the bearing portion structural element for generating a fluid film in a lubrication gap between the bearing portion and the rotor shaft carrier when rotating the rotor shaft in a fluid.

By way of example, the cardiac assist system may be an intracardiac pump for mechanical cardiac assist, wherein the pump may be implemented as a hydrostatic or hydrodynamic pump. Furthermore, the cardiac assist system may be a pump in which these two physical principles of action are combined. The rotor shaft can be designed, for example, as a displacement component or in the form of a blade or propeller. A bearing section can be understood as meaning a section of a mantle or end face of the rotor shaft. For example, the bearing section may be a shaft journal of the rotor shaft or a section of the lateral surface of the rotor shaft located between two shaft journal. A rotor shaft carrier can be understood as a bearing carrier which can be designed to support the rotor shaft in the axial or radial direction. The rotor shaft carrier may for example be part of a housing or a cage of the cardiac assist system. A structural element can be understood to be a raised area or a depression for profiling a surface of the rotor shaft. A fluid film may be understood to mean a lubricating film. The fluid may be a liquid, in particular blood.

The approach described here is based on the finding that a rotor of a hydrostatic or hydrodynamic cardiac assist pump can be supported by means of a suitable structuring of a surface of the rotor, for instance in the form of microstructured shaft journals, such that the rotor is exclusively after the first implantation of the pump after the surgical implantation operated in the stress regime of fluid friction. By such a hydrodynamic bearing of the rotor can be ensured that a sufficient separating fluid film between one or more shaft journals of the rotor and other components required for the storage of the shaft journals is present. Advantageously, the so-called notching point on the Stribeck curve can thereby be displaced at very low rotational speeds.

Such a rotor offers the advantage of high reliability. Furthermore, zero promotion can be avoided by the rotor and the power consumption of a mechanical drive unit of the cardiac assist pump can be reduced. Minimizing mixed or boundary friction can prevent failures of the pump and associated life-threatening consequences for the patient.

According to one embodiment, the structural element may be a depression. Such a structural element in the form of a depression can be realized very simply and inexpensively.

Furthermore, it is advantageous if a longitudinal axis of the structural element and a longitudinal axis of the rotor shaft are oriented in different directions. As a result, depending on the flow direction, type and strength certain flow effects can be caused that the generation and Maintaining the fluid film in the lubrication gap can favor. For example, it is thereby possible to produce a permanent fluid film even at very low rotational speeds of the rotor shaft.

The bearing portion may, for example, extend radially around an end portion of the rotor shaft. Alternatively or additionally, the bearing portion may extend along an end face of the rotor shaft. The end portion may be about a shaft journal of the rotor shaft. As a result, a radial or axial bearing of the rotor shaft is made possible.

Depending on the embodiment, the structural element may be configured in the form of circles, ellipses, cups, diamonds, cones, cylinders, wedges, spirals and / or wings. As a result, the structural element can be adapted flexibly to different flow conditions, depending on the design of the cardiac assist system. Thus, the efficiency and reliability of the cardiac assist system can be increased.

It is also advantageous if the structural element is at least two different depths and / or high. For example, the depth of the structural element can be uniformly larger starting from a first edge to a second edge opposite the first edge. Also by this embodiment, the flow-influencing properties of the structural element can be optimized depending on the application.

According to a further embodiment, a bottom surface of the structural element may have the shape of an airfoil profile. Alternatively or additionally, a peripheral edge of the structural element may also have the shape of such an airfoil profile. Under a wing profile can be understood in the broadest sense teardrop-shaped profile, which can in particular the same cross-section of an aircraft wing. A bottom surface can be understood as a ground of the structural element. A peripheral edge can be understood as meaning an edge which delimits an opening of a structural element designed as a depression. By means of such a structural element, a sufficiently thick, constant lubricating film can be produced in the lubricating gap even at relatively low rotational speeds of the rotor shaft.

Depending on the embodiment, the structural element may have a length between 1 nm and 500 μm, a width between 1 nm and 100 μm or a depth between 1 nm and 20 μm. As a result, the structural element can be realized as a microstructure.

It is particularly favorable if the rotor shaft has at least one further structural element arranged in the bearing section for producing the fluid film. This can increase the reliability and efficiency of the cardiac assist system.

It is furthermore advantageous if the rotor shaft has at least one fluid channel for fluidically connecting the structural element and the further structural element. Thereby, a tearing of the fluid film can be prevented.

In this case, the structural element and the further structural element can be oriented in different directions. Also by this embodiment, the hydrodynamic bearing of the rotor shaft can be designed as friction and wear as possible.

The rotor shaft can also have a plurality of structural elements arranged in the bearing section for producing the fluid film. In particular, the structural elements can be arranged along at least one straight line and, additionally or alternatively, at least one curve. As a result, a radiant or wavy, in particular, for example, helical arrangement of the structural elements can be realized.

It is also conceivable that the structural elements extend spirally around a lateral surface of the rotor shaft. Additionally or alternatively, the structural elements may extend spirally along an end face of the rotor shaft, for example around a center of the end face. This allows a particularly low-friction radial or axial bearing of the rotor shaft can be realized.

The approach described here also provides a cardiac assist system with the following features:
a rotor shaft carrier; and
a rotatably mounted in the rotor shaft carrier rotor shaft according to one of the embodiments described herein.

Such a heart support system, such as an axial or radial pump, offers the advantage of a compact design, a particularly high reliability, low wear and thus a long life.

Finally, the approach proposed herein provides a method of manufacturing a rotor shaft for a cardiac assist system, the method comprising the steps of:
Providing the rotor shaft with at least one bearing portion for supporting the rotor shaft in a rotor shaft carrier; and
Forming at least one structural element in the bearing portion, wherein the structural element in such a way is formed that when rotating the rotor shaft in a fluid, a fluid film is generated in a lubrication gap between the bearing portion and the rotor shaft carrier.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also creates a device that is designed to perform the steps of a variant of a method presented here in appropriate facilities to drive or implement. Also by this embodiment of the invention in the form of a device, the object underlying the invention can be solved quickly and efficiently.

In the present case, a device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The device may have an interface, which may be formed in hardware and / or software. In the case of a hardware-based embodiment, the interfaces can be part of a so-called system ASIC, for example, which contains a wide variety of functions of the device. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

Also of advantage is a computer program product or computer program with program code which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the embodiments described above is used, especially when the program product or program is executed on a computer or a device.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. It shows:

1 a schematic representation of a cardiac assist system according to an embodiment;

2 a schematic representation of a cardiac assist system according to an embodiment;

3 a diagram showing a Stribeck curve;

4 a schematic representation of a lubricating gap with thick lubricating film;

5 a schematic representation of a lubricating gap with thin lubricating film;

6 a schematic representation of a rotor shaft according to an embodiment;

7 a schematic representation of a rotor shaft with three bearing sections according to an embodiment;

8th a schematic representation of a rotor shaft with two bearing sections according to an embodiment;

9 a schematic representation of a rotor shaft with two bearing sections according to an embodiment;

10 a schematic representation of a rotor shaft with two bearing sections according to an embodiment;

11 a schematic representation of possible forms of a structural element according to an embodiment;

12 a schematic representation of two structural elements with airfoil according to an embodiment;

13 a schematic representation of two structural elements with airfoil according to an embodiment;

14 a schematic representation of a cylindrical structural element according to an embodiment;

15 a schematic representation of a tapered cylindrical structural element according to an embodiment;

16 a schematic representation of a frusto-conical structural element according to an embodiment;

17 a schematic representation of a rotor shaft with a channel-like connection according to an embodiment;

18 a schematic representation of an end face of a rotor shaft according to an embodiment;

19 a schematic representation of an end face of a rotor shaft according to an embodiment;

20 a schematic representation of an end face of a rotor shaft according to an embodiment;

21 a schematic representation of an end face of a rotor shaft according to an embodiment;

22 a schematic representation of an end face of a rotor shaft according to an embodiment; and

23 a flowchart of a method for producing a rotor shaft according to an embodiment.

In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similar acting, with a repeated description of these elements is omitted.

1 shows a schematic representation of a cardiac assist system 100 according to an embodiment. The cardiac support system 100 , here on a hydrostatic VAD pump principle based screw pump, has a running and a drive spindle as rotor shafts 102 on. The rotor shafts 102 are in two rotor shaft carriers 104 rotatably mounted such that the rotor shafts 102 and the rotor shaft carrier 104 even at low speeds of the rotor shafts 102 separated by a constant lubricating film. This makes it possible the cardiac assist system 100 to operate in the stress regime of fluid friction.

2 shows a schematic representation of a cardiac assist system 100 according to an embodiment. In contrast to 1 is the cardiac support system 100 according to 2 realized as an on a hydrodynamic VAD pump principle based axial flow pump. The cardiac support system 100 comprises a fixed, acting as a front bearing support flow straightener 200 and the rotor shaft 102 in accordance with this embodiment in the flow straightener 200 as well as in one of the flow straightener 200 opposite end of the cardiac assistance system 100 located and acting as a rear bearing support diffuser 202 is rotatably mounted. The rotor shaft 102 has a precursor or an impeller 204 on. One inside a motor stator 206 rotatable portion of the impeller 204 has a plurality of magnets 208 on, depending on the blades of the impeller 204 are attached. A sense of blood flow through the cardiac support system 100 is marked with two arrows.

3 shows a diagram illustrating a Stribeck curve 300 , The Stribeck curve 300 represents a dependent of a speed v curve of a friction coefficient f, wherein the velocity v is plotted on an abscissa and the friction coefficient f on an ordinate. Here, a solid line represents a total friction, a dotted line a boundary friction, and a dashed line a fluid friction. The friction coefficient f drops steeply from an initial friction coefficient f ₀ to a point A. Point A corresponds to a speed at which a thin lubricating film forms in a lubricating gap between two bodies. Starting from the point A, the friction coefficient f increases with increasing speed with a relatively small pitch. A point D on the Stribeck curve 300 marks a speed at which a thick lubricating film forms in the lubrication gap. A section of the Stribeck curve bounded by the point A and a notch point C between the points A, D 300 represents a zone in which there is a mild mixed friction between the two bodies. The notch point C marks a transition from the mixed friction zone to the fluid friction zone.

The forces acting on the rotor shaft during the fluid delivery, which may be designed as impeller in a hydrostatic pump and a hydrodynamic pump impeller in blade or propeller shape and depending on the embodiment may have additional components for flow guidance, are by one or more bearings in received radial or axial rotor shaft direction.

As with the Stribeck curve 300 In particular, fluid energy machines undergo a start-up from standstill, ie, when the initial speed of the rotor shaft is zero, physically the zone or the load regime of the boundary friction with a very high solids friction ratio first. In this zone, fluid energy machines are usually not operated because of the wear occurring and because of the required due to the high friction coefficient drive torque.

The boundary friction is followed by the stress regime of mixed friction, which is characterized by solid friction and an increasing proportion of fluid friction.

From a load state that is specific and discrete for the tribological system of the fluid energy machine, the fluid energy machine can then be operated by increasing the rotor shaft speed after the release point C in a load regime characterized exclusively by fluid friction.

In this stress regime, the relatively moving components of the tribological system are separated from each other by a fluid film acting as a lubricating film in a lubrication gap that the components no longer have solid state contact with each other.

4 shows a schematic representation of a lubricating gap 400 with thick lubricating film between two bodies 402 , Here are the two bodies 402 completely through the lubrication gap 400 located lubricant film separated from each other. With the two bodies 402 For example, it is a bearing portion of a rotor shaft and a portion of a rotor shaft carrier, as described above with reference to 1 and 2 are described.

5 shows a schematic representation of a lubricating gap 400 with a thin film of lubricant between two bodies 402 , In contrast to 4 have the two bodies 402 in 5 in places contact each other. A fluid pressure p in the area of the contact surfaces or bottlenecks between the two bodies 402 is marked with three vertically hatched curves.

6 shows a schematic representation of a rotor shaft 102 according to an embodiment. At the rotor shaft 102 For example, it is one based on the 1 and 2 described rotor shaft. According to this embodiment, the rotor shaft comprises 102 a first bearing section located on a first shaft journal 600 and a second bearing portion located on a second shaft journal opposite the first shaft journal 602 , also called storage areas. Here is the first storage section 600 in a first shaft bearing 604 and the second storage section 602 in a second shaft bearing 606 rotatably mounted. The two shaft bearings 604 . 606 are, for example, parts of a rotor shaft carrier, as previously described with reference to 1 and 2 is described.

The two bearing sections 600 . 602 each have a plurality of structural elements 608 which serve to create a fluid film within the lubricating gap 400 between the rotor shaft 102 and the two bearing sections 600 . 602 to produce, provided the rotor shaft 102 in a fluid flow, such as a bloodstream, about its longitudinal axis 612 is turned.

By way of example, those in the first bearing section 600 located structural elements 608 in 6 essentially parallel to the longitudinal axis 612 aligned while in the second bearing section 602 located structural elements 608 at an angle of about 45 degrees to the longitudinal axis 612 are aligned.

According to one embodiment, the two bearing sections 600 . 602 realized as microstructured storage areas.

7 shows a schematic representation of a rotor shaft 102 with three storage sections 600 . 602 . 700 according to an embodiment. At the rotor shaft 102 For example, it is a preceding by means of 1 to 6 described rotor shaft. By way of example, the rotor shaft comprises 102 according to 7 next to the first storage section 600 and the second storage section 602 one between the two bearing sections 600 . 602 arranged third storage section 700 , The three storage sections 600 . 602 . 700 are each with a structural element 608 and two further structural elements 706 realized. Here are the two other structural elements 706 each laterally offset to the structural element 608 arranged. In the third storage section 700 are the structural elements 608 . 706 alternately oriented in a different direction.

As in 7 to recognize, are the structural elements 608 . 706 in the first storage section 600 parallel to the longitudinal axis 612 , in the second storage section 602 transverse to the longitudinal axis 612 and in the third storage section 700 at an angle of plus / minus 45 ° to the longitudinal axis 612 arranged.

For the structural elements 608 . 706 For example, each is a microstructure, where in 7 a possible angular arrangement of these microstructures is shown.

8th shows a schematic representation of a previously with reference to FIG 1 to 7 described rotor shaft 102 with two bearing sections 600 . 602 according to an embodiment. Shown is a spiral arrangement of the structural elements 608 , Here are the structural elements 608 in spiral bands 800 radially around a surface, here a lateral surface, of the rotor shaft 102 arranged. The distance between the individual bands 800 may be constant or variable depending on the embodiment. By way of example, the bands 800 in the storage section 600 a variable distance and in the second bearing section 602 a constant distance from each other.

9 shows a schematic representation of a rotor shaft 102 with two bearing sections 600 . 602 according to an embodiment. The rotor shaft 102 essentially corresponds to the basis of 8th described rotor shaft, with the difference that the structural elements 608 in the first storage section 600 in the x and y directions offset from one another. Here are the structural elements 608 in staggered lines and relative to each other at a defined angle between 0 and 90 degrees on the surface of the rotor shaft 102 arranged.

10 shows a schematic representation of a previously with reference to FIG 1 to 9 described rotor shaft 102 with two bearing sections 600 . 602 according to an embodiment. Shown is a possible surface coverage of the surface of the rotor shaft 102 through the structural elements 608 , An area coverage, for example, is between 5 and 95 percent of a total surface area of the rotor shaft 102 , By way of example, the first bearing section 600 a small area coverage and the second storage section 602 a high surface coverage.

11 shows a schematic representation of possible forms of a structural element 608 according to an embodiment. Shown are possible geometric shapes of the structural element 608 in the plan view, about one above with reference to the 1 to 10 described structural element. Depending on the embodiment, the structural element 608 Seen from left to right, be realized as ellipse, cup, circle, lozenge or wedge.

12 shows a schematic representation of two structural elements 608 with airfoil profile according to one embodiment. In contrast to the preceding with reference to the 1 to 11 have the structural elements described in 12 Structural elements shown in plan view 608 a wing shape on the surface. For example, the airfoil may be substantially parallel or transverse to the longitudinal axis 612 be aligned.

13 shows a schematic representation of two structural elements 608 with airfoil profile according to one embodiment. In contrast to 12 have the structural elements 608 according to 13 the wing shape each on a floor surface 1300 on, also called base or ground. In this case, the surface of the structural elements 608 ie an in 13 with a dashed line marked circumferential edge 1302 , For example, the shape of an ellipse. Depending on the embodiment, the surface may also have other shapes, such as one of the forms as described above with reference to FIG 11 are described.

14 shows a schematic representation of a cylindrical structural element 608 according to an embodiment. The structural element 608 , the part of a preceding on the basis of 1 to 13 described rotor shaft, has over the entire circumference of a constant depth A.

15 shows a schematic representation of a tapered cylindrical structural element 608 according to an embodiment. Depending on the embodiment, the structural element 608 be realized with or without depth increase. In 15 indicates the footprint of the structural element 608 a depth increase going from an edge C to an opposite edge D. Accordingly, the base of the structural element 608 in contrast to 14 beveled.

16 shows a schematic representation of a frusto-conical structural element 608 according to an embodiment. Unlike the 14 and 15 has the structural element 608 according to 16 a cone-shaped geometry. Depending on the embodiment, the structural element 608 be configured in a variety of conical shapes.

17 shows a schematic representation of a rotor shaft 102 with a channel-like connection 1700 according to an embodiment. At the rotor shaft 102 For example, it is a preceding by means of 1 to 16 described rotor shaft. The channel-like connection 1700 is according to this embodiment as a structural element 608 and the further structural element 706 formed fluidly interconnecting connecting channel. Exemplary are the two structural elements 608 . 706 in 17 realized with a trapezoidal base, wherein the connecting channel 1700 for example, each is arranged on a longer of the two parallel sides of the base surfaces.

Depending on the embodiment, microstructures may be used as structural elements 608 through a channel structure, for example, the in 17 shown connection channel 1700 comprises, in any desired and at any location above the depth of the structure, interconnected for fluid transport.

18 shows a schematic representation of an end face 1800 a rotor shaft described above 102 according to an embodiment. The structural elements 608 are spirally around one on the longitudinal axis according to this embodiment 612 lying midpoint of the end face 1800 , also called front side arranged. In the 16 spiral shape shown in plan view the structural elements 608 in the form of microstructures is indicated by a solid line. Along this continuous line can be a variety of structural elements 608 be strung together. For example, the structural elements 608 Axial bearings in spiral bands axially on the face 1800 arranged.

19 shows a schematic representation of an end face 1800 a rotor shaft 102 according to an embodiment. In contrast to 18 are the structural elements 608 according to 19 arranged centrally along a plurality of straight lines, which according to this embodiment in the center of the end face 1800 cut, so that a centric beam arrangement of the structural elements 608 results. By way of example, the structural elements extend 608 in 19 over two opposing circular sectors of the face 1800 ,

20 shows a schematic representation of an end face 1800 a rotor shaft 102 according to an embodiment. In contrast to 19 are the structural elements 608 here arranged eccentrically jet-shaped along several straight lines. Depending on the embodiment, the straight lines may be arranged parallel to one another or in one or more points outside the center of the end face 1800 to cut.

21 shows a schematic representation of an end face 1800 a rotor shaft 120 according to an embodiment. Unlike the one based on 20 described end face are the structural elements 608 arranged eccentrically along two straight and curved sections of existing lines. By way of example, the structural elements extend 608 here over three of four equal circular sectors of the face 1800 ,

Depending on the embodiment, the structural elements 608 centered in the form of microstructures in thrust bearings and arranged eccentrically jet-shaped along a straight line or a curve of any length or along a combination of lines and curves on the surface.

22 shows a schematic representation of an end face 1800 a rotor shaft 102 according to an embodiment. Shown is a partial area coverage of the face 1800 with microstructures as structural elements 608 for thrust bearings in plan view. In this case, the structural elements extend 608 partially over certain areas of the face 1800 ,

The embodiments described above apply to both radial and axial rotor shaft bearings. Here, the structural elements in the form of microstructures, in particular in the form of depressions, alternatively or additionally also in the form of elevations, in any desired manner, in particular at an angle between 0 and 90 degrees, arranged to the longitudinal axis of the rotor shaft. Furthermore, the base of the microstructures can be realized from any combination of different surface profiles. For example, the microstructure may have an area whose size and shape change from the surface to the structural ground. The depth and shape of the microstructures may be combined in any manner, and in particular the microstructures may be combined in contiguous bands of increasing or decreasing depth or shape or at a local maximum depth.

A respective length of the microstructures is, for example, between 1 nm and 500 μm.

A respective width of the microstructures is, for example, between 1 nm and 100 μm.

A respective depth of the microstructures is, for example, between 1 nm and 20 μm.

23 shows a flowchart of a method 2300 for producing a rotor shaft according to an embodiment. The procedure 2300 For example, in connection with a preceding on the basis of 1 to 22 described rotor shaft are performed. The procedure 2300 includes a step 2310 in which the rotor shaft is provided. In this case, the rotor shaft has at least one bearing section for supporting the rotor shaft in a rotor shaft carrier, also referred to above as a shaft bearing. In a further process step 2320 is in the region of the bearing section, which corresponds for example to a shaft journal of the rotor shaft, at least one structural element formed such that when rotating the rotor shaft in a fluid, in particular in blood, a sufficiently thick fluid film is produced as a lubricating film in a lubrication gap between the bearing portion and the rotor shaft carrier ,

According to one embodiment, the macroscopically manufactured surface of the rotor shaft in step 2320 executed on one or more bearing sections with microstructures as structural elements in such a way that thereby a separating fluid film can be generated even at very small rotor shaft speeds.

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

Claims (15)

Rotor shaft ( 102 ) for a cardiac assistive system ( 100 ), wherein the rotor shaft ( 102 ) has the following features: at least one bearing section ( 600 . 602 ; 700 ) for supporting the rotor shaft ( 102 ) in a rotor shaft carrier ( 104 ); and at least one in the storage section ( 600 . 602 ; 700 ) arranged structural element ( 608 ) for producing a fluid film in a lubrication gap ( 400 ) between the storage section ( 600 . 602 ; 700 ) and the rotor shaft carrier ( 104 ) when rotating the rotor shaft ( 102 ) in a fluid. Rotor shaft ( 102 ) according to claim 1, characterized in that the structural element ( 608 ) is formed by a depression or has a depression. Rotor shaft ( 102 ) according to one of the preceding claims, characterized in that a longitudinal axis of the structural element ( 608 ) and a longitudinal axis ( 612 ) of the rotor shaft ( 102 ) are oriented in different directions. Rotor shaft ( 102 ) according to one of the preceding claims, characterized in that the bearing section ( 600 . 602 ) radially about an end portion of the rotor shaft ( 102 ) and / or along an end face of the rotor shaft ( 102 ). Rotor shaft ( 102 ) according to one of the preceding claims, characterized in that the structural element ( 608 ) Is designed circular, elliptical, suppository, diamond, conical, cylindrical, wedge, spiral and / or wing-shaped. Rotor shaft ( 102 ) according to one of the preceding claims, characterized in that the structural element ( 608 ) is at least two different depths and / or high. Rotor shaft ( 102 ) according to one of the preceding claims, characterized in that a bottom surface ( 1300 ) and / or a peripheral edge ( 1302 ) of the structural element ( 608 ) has the shape of a wing profile. Rotor shaft ( 102 ) according to one of the preceding claims, characterized in that the structural element ( 608 ) has a length between 1 nm and 500 microns and / or a width between 1 nm and 100 microns and / or a depth between 1 nm and 20 microns. Rotor shaft ( 102 ) according to one of the preceding claims, characterized by at least one in the storage section ( 600 . 602 ; 700 ) arranged further structural element ( 706 ) for producing the fluid film. Rotor shaft ( 102 ) according to claim 9, characterized by at least one fluid channel ( 1700 ) for fluidically connecting the structural element ( 608 ) and the further structural element ( 706 ). Rotor shaft ( 102 ) according to claim 9 or 10, characterized in that the structural element ( 608 ) and the further structural element ( 706 ) are oriented in different directions. Rotor shaft ( 102 ) according to one of the preceding claims, characterized by a plurality of in the storage section ( 600 . 602 ; 700 ) arranged structural elements ( 608 ) for producing the fluid film, in particular wherein the structural elements ( 608 ) are strung together along at least one straight line and / or at least one curve. Rotor shaft ( 102 ) according to claim 12, characterized in that the structural elements ( 608 ) spirally around a lateral surface of the rotor shaft ( 102 ) and / or spirally along an end face ( 1800 ) of the rotor shaft ( 102 ). Cardiac assistance system ( 100 ) having the following features: a rotor shaft carrier ( 104 ); and one rotatable in the rotor shaft carrier ( 104 ) mounted rotor shaft ( 102 ) according to one of claims 1 to 13. Procedure ( 2300 ) for producing a rotor shaft ( 102 ) for a cardiac assistive system ( 100 ), the process ( 2300 ) comprises the following steps: providing ( 2310 ) of the rotor shaft ( 102 ) with at least one storage section ( 600 . 602 ; 700 ) for supporting the rotor shaft ( 102 ) in a rotor shaft carrier ( 104 ); and shaping ( 2320 ) at least one structural element ( 608 ) in the storage section ( 600 . 602 ; 700 ), wherein the structural element ( 608 ) is formed such that when rotating the rotor shaft ( 102 ) in a fluid a fluid film in a lubrication gap ( 400 ) between the storage section ( 600 . 602 ; 700 ) and the rotor shaft carrier ( 104 ) is produced.

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