Patent Description:
Blood pumps of different types are known, such as axial blood pumps, centrifugal blood pumps, or mixed-type blood pumps, where the blood flow is caused by both axial and radial forces. Intravascular blood pumps are inserted into a patient's vessel such as the aorta by means of a catheter. A blood pump typically comprises a pump casing having a blood flow inlet and a blood flow outlet. In order to cause a blood flow from the blood flow inlet to the blood flow outlet, an impeller or rotor is rotatably supported with the pump casing about an axis of rotation, with the impeller being provided with on or more impeller blades for conveying blood. A blood pump is described in <CIT>. Pumps are also described in <CIT>, <CIT>, <CIT> entitled "Loading Guide Lumen" and <CIT>.

The motor <NUM> of a blood pump is illustrated in <FIG>. The impeller has a drive unit <NUM> and impeller blades <NUM> are on the distal end <NUM> of the motor <NUM>. The motor <NUM> has a stator <NUM> and a rotor <NUM>. The skilled person is aware that rotary systems typically have a stator (the stationary portion) and a rotor (the rotating portion). <FIG> illustrates the motor of <FIG> in an exploded view with the rotor <NUM> outside the stator <NUM>.

<FIG> is an exploded view of the stator. The stator has a yoke <NUM>, a coil <NUM>, and a coil holding sleeve <NUM>. The yoke <NUM> is typically made of metal, while the coil <NUM> is typically made of copper. The coil holding sleeve <NUM> can be either plastic or ceramic. These components are illustrated in an exploded view in <FIG>. The coil holding sleeve <NUM> in <FIG> is made of ceramic.

<FIG> is a cross section of the stator of <FIG> and also illustrates the yoke <NUM>, the coil <NUM> and the coil holding sleeve <NUM>. The stator is assembled using epoxy adhesive <NUM> to provide a stable and secure assembly. The epoxy <NUM> essentially encapsulates the coil <NUM> such that epoxy <NUM> is at the yoke <NUM>/coil <NUM> interface and the coil <NUM>/sleeve <NUM> interface. <FIG> is a stator <NUM> cross section that illustrates the windings that form the coils <NUM>. The stator has epoxy <NUM> interposed between the metal yoke <NUM> and the coil <NUM> and between the coil <NUM> and the sleeve <NUM>. The sleeve <NUM> illustrated in <FIG> is a plastic sleeve.

One skilled in the art is aware that a variety of epoxy adhesives are suitable for use in a blood pump. <CIT>, which is entitled Thermistor Imbedded [sic] Therapeutic Catheter, describes an intracardiac blood pump that includes an electrically driven motor, a rotor positioned within the blood pump (for example in the cannula), and an electrical line configured to supply current to the motor. In some embodiments the motor is implanted with the rotor. Optionally, the pump is described as powered by an external motor with a drive cable that extends through the catheter and out to a drive unit located external to the patient. US Patent Publication describes a blood pump that has a thermistor with a temperature sensitive head. The temperature sensitive head is described as being embedded in epoxy. <CIT> describes an implantable blood pump with a toroidal chamber coated with epoxy (e.g. Stycast Epoxy <NUM>).

<CIT> discloses an intravascular blood pump with an electric motor <NUM> comprising a stator winding <NUM> which is embedded in a matrix of synthetic resin and a rotor <NUM> surrounded by the stator winding <NUM>, wherein each wire of the stator winding <NUM> is surround by an insulating sheath 33a which is further coated with stoving paint 33b. In the process of manufacturing the stator winding <NUM>, the stoving paint layers of adjacent wires are fused to each other to form a fixed wire structure.

<CIT> discloses an intravascular blood pump with a pumping device comprising an impeller <NUM> and a motor which comprises a rotor and a stator. In a method of manufacturing the blood pump, epoxy is injected into an interspace <NUM> formed between an inner sleeve <NUM> and an outer sleeve <NUM> containing the coil winding <NUM> to encapsulate the coil winding <NUM>.

Reliable and consistent blood pump operation is critical to patient care. Therefore, due to the environment in which the pumps are configured to operate, the performance of certain pump components can degrade over time. Therefore, modifications to blood pumps that mitigate such problems continue to be sought.

The problem above is solved by a blood pump and a method of making the blood pump according to the independent claims. Further embodiments are specified in the dependent claims.

Described herein is a pump motor for a blood pump and a method for making the pump motor. The pump motor has a rotor portion having proximal and distal ends and a stator portion having proximal and distal ends, wherein the proximal portion of the rotor portion is received into a cavity defined by the stator portion at the distal end of the stator portion. The rotor portion has an impeller, wherein the impeller comprises impeller blades and a drive unit. The impeller blades are positioned at the distal end of the rotor portion and not received into the stator. The drive unit is positioned in a portion of the rotor received into the stator portion. The drive unit is coupled to the impeller blades. The stator portion has a yoke, a coil and a coil holding sleeve. The sleeve defines the cavity into which the proximal portion of the rotor is received.

The yoke, coil and sleeve have interior and exterior surfaces, wherein epoxy is introduced between the yoke and the coil and the coil and the sleeve, thereby substantially embedding the coil in epoxy, wherein at least one of the interior surface of the yoke, the exterior surface of the coil, the interior surface of the coil or the exterior surface of the sleeve are treated with a primer prior to the introduction of epoxy therebetween.

The pump motor is made by assembling a pump motor from a rotor portion with proximal and distal ends and a stator portion having proximal and distal ends. The proximal portion of the rotor portion is received into a cavity defined by the stator portion. The rotor portion has an impeller, wherein the impeller has impeller blades and a drive unit. The impeller blades are positioned at the distal end of the rotor portion and are not received into the stator. The drive unit is positioned in a portion of the rotor received into the stator portion. The drive unit is coupled to the impeller blades. The stator portion has a yoke, a coil and a coil holding sleeve, the sleeve defining the cavity into which the proximal portion of the rotor is received.

The yoke, coil and sleeve have interior and exterior surfaces. According to the method, least one of the interior surface of the yoke, the exterior surface of the coil, the interior surface of the coil or the exterior surface of the sleeve are treated with a primer. After the one or more surfaces are treated, epoxy is introduced between the yoke and the coil and the coil and the sleeve, thereby substantially embedding the coil in epoxy.

Blood pumps are deployed in patients that require critical and life-saving care. Consequently, it is important to remediate any aspect of the device that might adversely affect pump operation. Leakage Current (LC) is one such failure mode.

One cause of leakage current is the moisture ingress into the pump stator/rotor assembly. Moisture ingress can occur at the interface between the epoxy and sleeve (such moisture ingress illustrated in <FIG>) and between the epoxy and the yoke (such moisture ingress illustrated in <FIG>). As noted above, the stator of such blood pumps have a coil <NUM> that is essentially embedded in epoxy. The epoxy encapsulates the coil and fills the cavity to form the stator body.

Suitable epoxies for assembling the stator described herein are well known to those skilled in the art and not described in detail herein. Examples of suitable epoxies are an amine base two-part epoxy such as Delo-Duopox, which is obtained from DELO Industrial Adhesives and EPO-TEK® <NUM> from Epoxy Technology, Inc. of Billerica, MA. Suitable epoxies for use in blood pumps are well known to those skilled in the art and are not described in detail herein.

<FIG> illustrates moisture ingression evidence on a coil <NUM>, the moisture ingression from the distal end <NUM> (<FIG>) of the stator <NUM>. The moisture is indicated by the shaded areas <NUM>. <FIG> illustrates evidence of moisture ingression <NUM> on the epoxy <NUM> adjacent the yoke <NUM>, a portion of which is removed to reveal that the epoxy had not adhered well thereto.

Therefore, due to the environment in which the pumps are configured to operate, the performance of certain pump components can degrade over time. Pumps that mitigate such problems are described herein. The method and device described herein increases the bonding strength between the yoke and the epoxy by improving the wettability of the substrate surface (i.e. the surface to which the epoxy is intended to adhere) by the uncured epoxy. The increased bonding strength prevents moisture ingress. Moisture ingress indicates poor adhesion between the sleeve (either ceramic or plastic) and the epoxy. Bonding to ceramic sleeves (e.g. alumina toughened zirconia (ATZ)) in particular is difficult due to the topology of ceramic surfaces.

In the assembly of the blood pump, the epoxy is applied in multiple locations. The epoxy encapsulates the coils to isolate and insulate the coils from the components adjacent to the coils that could otherwise contact the coils. The epoxy also fills the spaces/voids between the sleeve, the coil and the yoke, thereby providing structural strength to the assembled blood pump and avoiding/preventing/mitigating micromovement of the assembled blood that might otherwise occur as the external environment of the pump changes. The epoxy also facilitates the heat transfer from the coils to outside the pump.

However, the gaps between the sleeve, coils and the yoke into which the epoxy is introduced are very small. Such gaps are typically about one micron. As a result, it is important to have a reliably good and consistent surface wettability of the pump component (e.g. coil, sleeve, yoke, etc.) to the uncured epoxy. When the epoxy is injected into the cavities or gaps, a higher wettability surface causes the epoxy to spread evenly and completely fill the small gaps between the pump components. The improved surface wettability for the uncured epoxy results in a higher bonding strength of the epoxy to the adjacent component and excellent encapsulation of components such as the coil. On the contrary, if the substrate (i.e. the component surface) wettability is low or the surface is not otherwise compatible with the uncured epoxy, the uncured epoxy flows away from the substrate surface. As a result of low or poor surface wettability, a low bonding strength between the epoxy and the substrate, or gaps between the substrate and the epoxy, or both, will occur.

The low bonding strength or the gaps between the epoxy and the substrate allow paths to form at the interface between the cured epoxy and the surface of the adjacent pump component through which moisture can travel. Also, gaps function as a heat insulator, which adversely affects the efficiency of heat transfer from the coils to the pump exterior. As a result, the amount of heat dissipated from the coil can be dramatically reduced.

Disclosed herein is an apparatus and method that describes a simple substrate surface treatment that will improve surface-wettability of the substrate to which the epoxy will adhere, improving both the bonding strength of the epoxy to the substrate and the extent of the bonding between the epoxy and the substrate surface. Referring to <FIG>, the wettability of a primer-treated ceramic surface <NUM> (i.e. the sleeve) and a non-treated ceramic surface <NUM> is illustrated. Referring to surface <NUM>, the isolated shaded regions <NUM> (i.e. the beaded regions) indicate that the fluid <NUM> applied to the substrate surface <NUM> was not compatible with the substrate surface <NUM>. Consequently, the fluid <NUM> forms on the surface <NUM> as liquid beads leaving a substantial area of the substrate surface <NUM> uncovered by the liquid. On the other end, the surface <NUM> is more substantially covered by the liquid <NUM>, indicating that surface <NUM> is more compatible with the liquid. The liquid <NUM> is more uniformly spread around the surface <NUM> and, as a consequence of the increased substrate surface wetting, there will be increased bonding strength between the substrate surface and the cured epoxy. <FIG> illustrates that the primer-treated surface described herein enhances the quality of the bond between the epoxy and the substrate.

The primers described herein not only improve wettability of the substrate to the uncured epoxy, but also modify the substrate surfaces that are otherwise hydrophilic and make those surfaces hydrophobic. The resulting hydrophobic surfaces resist moisture ingress into any remaining gaps between the epoxy and the substrate.

The method and device described herein deploys a primer onto the epoxy (or the surface to which the epoxy will adhere). The primer improves adhesion of the bonding surface to the epoxy. The positive effect of applying primer to enhance the adhesion to a substrate material is illustrated in <FIG> illustrates a stator <NUM> in which a portion of the yoke <NUM> is separated from the stator <NUM>. The stator <NUM> in <FIG> had epoxy <NUM> treated with a silane solution. Silane solutions are known primers that function at the interface between the uncured epoxy and act as an adhesion promoter. The silane primer is chosen by matching its organic functionality to the polymer to optimize bonding. The selection of a silane primer that will render the substrate surface hydrophobic and enhance surface wettability/bonding with the epoxy is described in A Guide to Silane Solutions ©<NUM> Dow Coming Corporation. Silane coupling agents contain two types of reactivity, inorganic and organic, in the same molecule. Silane have the general chemical formula (RO)<NUM>SiCH<NUM>CH<NUM>CH<NUM>-X wherein RO is a hydrolysable group such as methoxy, ethoxy, or acetoxy and X in an organofunctional group such as amino, methacryloxy, epoxy, etc. One skilled in the art can select a suitable silane primer for use with the present invention. The alkoxy groups hydrolyze and the resulting hydroxyl groups bond to the hydroxyl groups on the inorganic substrate surfaces (e.g., the metal, metal oxide and ceramic surfaces described herein. The epoxy adheres strongly to the primed surface of the yoke <NUM> such that the epoxy and even a portion of the coil <NUM> is torn away with the portion of the yoke <NUM> separated from the stator <NUM>. The surface treatment is performed prior to the stator being injection molded. Basically, here is a brief flow: <NUM>). the coil is attached to the sleeve; <NUM>). wires and cables are soldered to a printed circuit board (PCB) which is then adhered to the ceramic sleeve; <NUM>). the yoke inner diameter (ID) is treated with primer (<FIG>); <NUM>). the sleeve/coil outer diameter (OD) is then treated with primer (<FIG>); <NUM>). the yoke is installed over the sleeve/coil subassembly; and <NUM>). epoxy is injected into the assembly.

The stator <NUM> in <FIG> and <FIG> did not have primer applied to the interior surface of the yoke <NUM>. This is apparent since the portion of the yoke <NUM> that is separated from the stator <NUM> has no epoxy <NUM> thereon. This illustrates that there was little to no bonding of the epoxy <NUM> to the yoke <NUM> in the stator <NUM> illustrated in <FIG>. <FIG> also illustrates a stator <NUM> in which the epoxy <NUM> did not adhere to the portion of the yoke <NUM> removed from the stator. As stated above, the shaded epoxy region <NUM> indicates moisture ingress, demonstrating that, due to the poor adhesion between the epoxy <NUM> and the yoke <NUM>, moisture was able to migrate into the interface between the yoke <NUM> and the epoxy <NUM>. Contrast the stator in <FIG> with that in <FIG>, where the bonding surface was treated as described herein. The yoke <NUM> was significantly damaged when a portion of the yoke <NUM> was separated from the stator <NUM>.

The primer also improves the bond between the sleeve <NUM> and the epoxy <NUM>. Just as the epoxy <NUM> remains adhered to the portion of the yoke <NUM> separated from the stator <NUM>, at least a portion of the epoxy will remain adhered to the sleeve <NUM> during a tear down process in which the sleeve (or a portion thereof) is separated from the stator <NUM>.

Described herein is a motor for a blood pump in which one or more operating surfaces of the blood pump stator are surface treated to mitigate the problems with moisture that can lead to an increase in leakage current of the motor. 7A highlights the interface <NUM> between the yoke <NUM> and the coil/sleeve <NUM>/<NUM>. Referring to <FIG>, the stator <NUM> has a silane treated surface on the interior of the yoke <NUM>, the exterior of the coil <NUM> and exterior of the sleeve <NUM>. The silane treated surface is <NUM> in <FIG>. In the cross section of <FIG> the coil is not visible because it is embedded in the epoxy <NUM>.

In one embodiment a silane primer is provided to improve the bonding between the epoxy and the yoke and or the sleeve. Application of silane primer eliminated the leakage current by improving the adhesion between ceramic sleeve and the epoxy (e.g., EPO-TEK® <NUM> (ES2019-<NUM> rA).

<FIG> illustrates that pumps in which the primer was applied to the surface of at least some of the pump components prior to the introduction of epoxy had consistently lower leakage current. Pumps that were assembled without the application of the primer prior to epoxy injection had a range of leakage current results. Therefore, the application of the primer to the surface of the pump components provides the assembled pumps with reliable and acceptable performance regarding leakage current.

As noted above, wetting of the bonding surfaces as well as chemical bond formation with the bonding surface provides better adhesion between two different surfaces (e.g. the epoxy and the yoke surface or the sleeve surface.

As noted above, the primers described herein are silane-based primers. Such primers improve the wetting of epoxies such as EPO-TEK® <NUM> on the surface of the ceramic sleeve or the metal yoke for better adhesion. As noted above, the silane forms a chemical bond with the substrate surface and with the epoxy that improves the adhesion strength between the epoxy and the substrate (e.g. the metal yoke/ceramic sleeve of the pump). Silane based primers that act as coupling agent between the relevant pump component and the adjacent epoxy that are both hydrophobic and organophilic are contemplated as suitable herein.

In this specification, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of.

Claim 1:
A blood pump, comprising:
a pump motor (<NUM>) comprising a rotor portion (<NUM>) having proximal and distal ends and a stator portion (<NUM>) having proximal and distal ends, wherein the proximal portion of the rotor portion (<NUM>) is received into a cavity defined by the stator portion (<NUM>);
the rotor portion (<NUM>) comprising an impeller, wherein the impeller comprises impeller blades (<NUM>) and a drive unit (<NUM>), the impeller blades (<NUM>) positioned at the distal end of the rotor portion (<NUM>) and not received into the stator (<NUM>) and the drive unit (<NUM>) positioned in a portion of the rotor (<NUM>) received into the stator portion (<NUM>), wherein the drive unit (<NUM>) is coupled to the impeller blades (<NUM>);
the stator portion (<NUM>) comprising a yoke (<NUM>), a coil (<NUM>) and a coil holding sleeve (<NUM>), the sleeve (<NUM>) defining the cavity into which the proximal portion of the rotor (<NUM>) is received;
wherein the yoke (<NUM>), coil (<NUM>) and sleeve (<NUM>) have interior and exterior surfaces, wherein epoxy (<NUM>) is introduced between the yoke (<NUM>) and the coil (<NUM>) and the coil (<NUM>) and the sleeve (<NUM>), thereby substantially embedding the coil (<NUM>) in epoxy (<NUM>),
characterized in that at least one of the interior surface of the yoke (<NUM>), the exterior surface of the coil (<NUM>), the interior surface of the coil (<NUM>) or the exterior surface of the sleeve (<NUM>) are treated with a primer prior to the introduction of epoxy (<NUM>) therebetween.