Patent Publication Number: US-2023158290-A1

Title: Blood pump shaft bearing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of prior U.S. application Ser. No. 16/657,246, filed Oct. 18, 2019, which claims priority to Provisional Application No. 62/747,346, filed Oct. 18, 2018, which are herein incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to percutaneous circulatory support devices. More specifically, the disclosure relates to bearings using in percutaneous circulatory support devices. 
     BACKGROUND 
     Percutaneous circulatory support devices such as blood pumps typically provide circulatory support for up to approximately three weeks of continuous use. Wear at bearing surfaces can limit the lifetime of the devices. Additionally, heat generation and mechanical interactions with the blood at the bearing surface can lead to hemolysis, which can further lead to health complications such as anemia, requiring blood transfusions. 
     SUMMARY 
     In an Example 1, a bearing assembly configured to retain an end of a drive shaft of a blood pump, the bearing assembly comprising: a bearing; and a lubricant chamber configured to hold a lubricant. 
     In an Example 2, the bearing assembly of Example 1, wherein the end of the drive shaft is at least partially rounded, and the bearing comprising a concave depression defined in a first side of the bearing, wherein the depression is configured to receive the end of the drive shaft. 
     In an Example 3, the bearing assembly of either of Examples 1 or 2, further comprising a cup washer having a base and peripheral wall extending away from the base, forming a cavity bounded by an inner surface of the peripheral wall and an inner surface of the base, wherein the bearing is configured to be at least partially disposed within the cavity. 
     In an Example 4, the bearing assembly of Example 3, the cup washer further comprising a shaft aperture defined in the base, extending from the outer surface of the base to the inner surface of the base, wherein the shaft aperture is configured to receive a portion of the drive shaft. 
     In an Example 5, the bearing assembly of either of Examples 3 or 4, wherein at least a portion of the lubricant chamber is defined between the inner surface of the peripheral wall of the cup washer, the inner surface of the base of the cup washer, and a first side of the bearing. 
     In an Example 6, the bearing assembly of Example 2, the lubricant chamber comprising at least one channel defined in a second side of the bearing, the at least one channel passing through the depression, wherein the at least one channel is configured to retain lubricant. 
     In an Example 7, a blood pump, comprising: an impeller; a drive shaft coupled to the impeller and configured to rotate with the impeller; a motor configured to drive the impeller; and a bearing assembly disposed adjacent the motor and configured to receive an end of the drive shaft, the bearing assembly comprising a bearing, wherein the end of the drive shaft is at least partially rounded, and the wherein the bearing includes a concave depression defined in a first side of the bearing, wherein the depression is configured to receive the end of the drive shaft. 
     In an Example 8, the blood pump of Example 7, the bearing assembly further comprising a lubricant chamber configured to hold a lubricant. 
     In an Example 9, the blood pump of Example 8, the bearing assembly further comprising a cup washer having a base and peripheral wall extending away from the base, forming a cavity bounded by an inner surface of the peripheral wall and an inner surface of the base, wherein the bearing is configured to be at least partially disposed within the cavity. 
     In an Example 10, the blood pump of Example 9, the cup washer further comprising a shaft aperture defined in the base, extending from the outer surface of the base to the inner surface of the base, wherein the shaft aperture is configured to receive a portion of the drive shaft. 
     In an Example 11, the blood pump of either of Examples 9 or 10, wherein at least a portion of the lubricant chamber is defined between the inner surface of the peripheral wall of the cup washer, the inner surface of the base of the cup washer, and a first side of the bearing. 
     In an Example 12, the blood pump of Example 8, wherein the lubricant chamber is at least partially defined within the bearing. 
     In an Example 13, the blood pump of Example 12, the lubricant chamber comprising at least one channel defined in a second side of the bearing, the at least one channel passing through the depression, wherein the at least one channel is configured to retain lubricant. 
     In an Example 14, the blood pump of Example 13, the at least one channel comprising two channels that intersect one another in the depression. 
     In an Example 15, the blood pump of Example 8, the bearing assembly comprising a cylindrical-shaped bearing at an intersection of the drive shaft and a stationary shaft mounting pin, wherein the drive shaft is configured to rotate with respect to the stationary shaft mounting pin, and wherein the lubricant chamber is defined between an inner surface of the bearing and an outer surface of the stationary shaft mounting pin. 
     In an Example 16, a bearing assembly configured to retain an end of a drive shaft of a blood pump, the bearing assembly comprising: a bearing; and a lubricant chamber configured to hold a lubricant. 
     In an Example 17, the bearing assembly of Example 16, wherein the end of the drive shaft is at least partially rounded, and the bearing comprising a concave depression defined in a first side of the bearing, wherein the depression is configured to receive the end of the drive shaft. 
     In an Example 18, the bearing assembly of Example 16, further comprising a cup washer having a base and peripheral wall extending away from the base, forming a cavity bounded by an inner surface of the peripheral wall and an inner surface of the base, wherein the bearing is configured to be at least partially disposed within the cavity. 
     In an Example 19, the bearing assembly of Example 18, the cup washer further comprising a shaft aperture defined in the base, extending from the outer surface of the base to the inner surface of the base, wherein the shaft aperture is configured to receive a portion of the drive shaft. 
     In an Example 20, the bearing assembly of Example 19, wherein at least a portion of the lubricant chamber is defined between the inner surface of the peripheral wall of the cup washer, the inner surface of the base of the cup washer, and a first side of the bearing. 
     In an Example 21, the bearing assembly of Example 16, wherein the lubricant chamber is at least partially defined within the bearing. 
     In an Example 22, the bearing assembly of Example 21, the lubricant chamber comprising at least one channel defined in a second side of the bearing, the at least one channel passing through the depression, wherein the at least one channel is configured to retain lubricant. 
     In an Example 23, a blood pump, comprising: an impeller; a drive shaft coupled to the impeller and configured to rotate with the impeller; a motor configured to drive the impeller; and a bearing assembly disposed adjacent the motor and configured to receive an end of the drive shaft, the bearing assembly comprising a bearing, wherein the end of the drive shaft is at least partially rounded, and the wherein the bearing includes a concave depression defined in a first side of the bearing, wherein the depression is configured to receive the end of the drive shaft. 
     In an Example 24, the blood pump of Example 22, the bearing assembly further comprising a lubricant chamber configured to hold a lubricant. 
     In an Example 25, the blood pump of Example 24, the bearing assembly further comprising a cup washer having a base and peripheral wall extending away from the base, forming a cavity bounded by an inner surface of the peripheral wall and an inner surface of the base, wherein the bearing is configured to be at least partially disposed within the cavity. 
     In an Example 26, the blood pump of Example 24, the cup washer further comprising a shaft aperture defined in the base of the cup washer, extending from the outer surface of the base to the inner surface of the base, wherein the shaft aperture is configured to receive a portion of the drive shaft. 
     In an Example 27, the blood pump of Example 24, wherein at least a portion of the lubricant chamber is defined between the inner surface of the peripheral wall of the cup washer, the inner surface of the base of the cup washer, and a first side of the bearing. 
     In an Example 28, the blood pump of Example 24, wherein the lubricant chamber is at least partially defined within the bearing. 
     In an Example 29, the blood pump of Example 28, the lubricant chamber comprising at least one channel defined in a second side of the bearing, the at least one channel passing through the depression, wherein the at least one channel is configured to retain lubricant. 
     In an Example 30, the blood pump of Example 29, the at least one channel comprising two channels that intersect one another in the depression. 
     In an Example 31, the blood pump of Example 24, the bearing assembly comprising a cylindrical-shaped bearing at an intersection of the drive shaft and a stationary shaft mounting pin, wherein the drive shaft is configured to rotate with respect to the stationary shaft mounting pin, and wherein the lubricant chamber is defined between an inner surface of the bearing and an outer surface of the stationary shaft mounting pin. 
     In an Example 32, the blood pump of Example 23, further comprising another bearing assembly configured to receive another end of the drive shaft. 
     In an Example 33, a blood pump, comprising: an impeller; a drive shaft coupled to the impeller and configured to rotate with the impeller; a motor configured to drive the impeller; and a bearing assembly disposed adjacent the motor and configured to receive an end of the drive shaft, the bearing assembly comprising a bearing and a lubricant chamber configured to hold a lubricant. 
     In an Example 34, the blood pump of Example 33, wherein the end of the drive shaft is at least partially rounded, and the wherein the bearing includes a concave depression defined in a first side of the bearing, wherein the depression is configured to receive the end of the drive shaft. 
     In an Example 35, the blood pump of Example 34, the lubricant chamber comprising at least one channel defined in a second side of the bearing, the at least one channel passing through the depression, wherein the at least one channel is configured to retain lubricant. 
     While multiple embodiments are disclosed, still other embodiments of the presently disclosed subject matter will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the disclosed subject matter. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  depicts a cross-sectional side view of a portion of an illustrative percutaneous mechanical circulatory support device (also referred to herein, interchangeably, as a “blood pump”), in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  1 B  is a close-up view of the first bearing assembly of  FIG.  1 A , in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  2 A  depicts a perspective view of an illustrative percutaneous mechanical circulatory support device, in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  2 B  depicts a cross-sectional side view of the circulatory support device depicted in  FIG.  2 A , in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  2 C  is a close-up view of the first bearing assembly of  FIG.  2 B , in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  3    depicts a cross-sectional side view of an illustrative circulatory support device having an impeller assembly, in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  4    depicts a cross-sectional side view of an illustrative circulatory support device having an impeller assembly, in accordance with embodiments of the subject matter disclosed herein. 
         FIGS.  5 A and  5 B  are perspective views of an illustrative bearing, in accordance with embodiments of the subject matter disclosed herein. 
     
    
    
     While the disclosed subject matter is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the subject matter disclosed herein to the particular embodiments described. On the contrary, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the subject matter disclosed herein, and as defined by the appended claims. 
     As used herein in association with values (e.g., terms of magnitude, measurement, and/or other degrees of qualitative and/or quantitative observations that are used herein with respect to characteristics (e.g., dimensions, measurements, attributes, components, etc.) and/or ranges thereof, of tangible things (e.g., products, inventory, etc.) and/or intangible things (e.g., data, electronic representations of currency, accounts, information, portions of things (e.g., percentages, fractions), calculations, data models, dynamic system models, algorithms, parameters, etc.), “about” and “approximately” may be used, interchangeably, to refer to a value, configuration, orientation, and/or other characteristic that is equal to (or the same as) the stated value, configuration, orientation, and/or other characteristic or equal to (or the same as) a value, configuration, orientation, and/or other characteristic that is reasonably close to the stated value, configuration, orientation, and/or other characteristic, but that may differ by a reasonably small amount such as will be understood, and readily ascertained, by individuals having ordinary skill in the relevant arts to be attributable to measurement error; differences in measurement and/or manufacturing equipment calibration; human error in reading and/or setting measurements; adjustments made to optimize performance and/or structural parameters in view of other measurements (e.g., measurements associated with other things); particular implementation scenarios; imprecise adjustment and/or manipulation of things, settings, and/or measurements by a person, a computing device, and/or a machine; system tolerances; control loops; machine-learning; foreseeable variations (e.g., statistically insignificant variations, chaotic variations, system and/or model instabilities, etc.); preferences; and/or the like. 
     The terms “up,” “upper,” and “upward,” and variations thereof, are used throughout this disclosure for the sole purpose of clarity of description and are only intended to refer to a relative direction (i.e., a certain direction that is to be distinguished from another direction), and are not meant to be interpreted to mean an absolute direction. Similarly, the terms “down,” “lower,” and “downward,” and variations thereof, are used throughout this disclosure for the sole purpose of clarity of description and are only intended to refer to a relative direction that is at least approximately opposite a direction referred to by one or more of the terms “up,” “upper,” and “upward,” and variations thereof. 
     Although the term “block” may be used herein to connote different elements illustratively employed, the term should not be interpreted as implying any requirement of, or particular order among or between, various blocks disclosed herein. Similarly, although illustrative methods may be represented by one or more drawings (e.g., flow diagrams, communication flows, etc.), the drawings should not be interpreted as implying any requirement of, or particular order among or between, various steps disclosed herein. However, certain embodiments may require certain steps and/or certain orders between certain steps, as may be explicitly described herein and/or as may be understood from the nature of the steps themselves (e.g., the performance of some steps may depend on the outcome of a previous step). Additionally, a “set,” “subset,” or “group” of items (e.g., inputs, algorithms, data values, etc.) may include one or more items, and, similarly, a subset or subgroup of items may include one or more items. A “plurality” means more than one. 
     DETAILED DESCRIPTION 
     Embodiments of the subject matter disclosed herein include bearing designs that may facilitate reducing heat formation by using lubrication, and reducing mechanical blood damage by preventing ingress of blood onto bearing surfaces. Bearing designs that include concave depressions and closed cavities facilitate preventing blood ingress onto bearing surfaces. Lubrication may be used to provide a fluid film at bearing surfaces to minimize wear. According to embodiments, any number of different types of lubricants may be used such as, for example, hydrophobic, water-insoluble lubricants (e.g., perfluoropolyether or poly-alpha-olefins classes of synthetic lubricants) may be used. 
       FIG.  1 A  depicts a cross-sectional side view of a portion of an illustrative percutaneous mechanical circulatory support device  100  (also referred to herein, interchangeably, as a “blood pump”), in accordance with embodiments of the subject matter disclosed herein. As shown in  FIG.  1 A , the circulatory support device  100  includes a motor  102  disposed within a motor housing  104 . The motor  102  is configured to drive an impeller assembly  106  to provide a flow of blood through the device  100 . The impeller assembly  106  is disposed within an impeller assembly housing  108 , which includes a number of outlet apertures  110  defined therein. According to embodiments, the motor housing  104  and the impeller assembly housing  108  may be integrated with one another. In other embodiments, the motor housing  104  and the impeller assembly housing  108  may be separate components configured to be coupled together, either removeably or permanently. 
     A controller (not shown) is operably coupled to the motor  102  and is configured to control the motor  102 . The controller may be disposed within the motor housing  104  in embodiments, or, in other embodiments, may be disposed outside the housing  104  (e.g., in a catheter handle, independent housing, etc.). In embodiments, the controller may include multiple components, one or more of which may be disposed within the housing  104 . According to embodiments, the controller may be, include, or be included in one or more Field Programmable Gate Arrays (FPGAs), one or more Programmable Logic Devices (PLDs), one or more Complex PLDs (CPLDs), one or more custom Application Specific Integrated Circuits (ASICs), one or more dedicated processors (e.g., microprocessors), one or more central processing units (CPUs), software, hardware, firmware, or any combination of these and/or other components. Although the controller is referred to herein in the singular, the controller may be implemented in multiple instances, distributed across multiple computing devices, instantiated within multiple virtual machines, and/or the like. 
     As shown in  FIG.  1 A , the impeller assembly  106  includes a drive shaft  112  and an impeller  114  coupled thereto, where the drive shaft  112  is configured to rotate with the impeller  114 . As shown, the drive shaft  112  is at least partially disposed within the impeller  114 . In embodiments, the drive shaft  112  may be made of any number of different rigid materials such as, for example, steel, titanium alloys, cobalt chromium alloys, nitinol, high-strength ceramics, and/or the like. The impeller assembly  106  further includes an impeller rotor  116  coupled to, and at least partially surrounding, the drive shaft  112 . The impeller rotor  116  may be any type of magnetic rotor capable of being driven by a stator  118  that is part of the motor  102 . In this manner, as a magnetic field is applied to the impeller rotor  116  by the stator  118  in the motor  102 , the rotor  116  rotates, causing the drive shaft  112  and impeller  114  to rotate. 
     As shown, the impeller assembly is maintained in its orientation by the drive shaft  112 , which is retained, at a first end  120 , by a first bearing assembly  122  and, at a second end  124 , by a second bearing assembly  126 . According to embodiments, the first bearing assembly  122  and the second bearing assembly  126  may include different types of bearings. According to embodiments, the first bearing assembly  122  and/or the second bearing assembly  126  may include lubrication, while, in other embodiments, one and/or the other may not include lubrication. Various embodiments of bearing technology are described herein with respect to the first and second bearing assemblies  122  and  126 . 
       FIG.  1 B  is a close-up view of the first bearing assembly  122  of  FIG.  1 A , in accordance with embodiments of the subject matter disclosed herein. The second bearing assembly  126  may include, for example, a journal bearing, or any other type of suitable bearing. As shown in  FIG.  1 B , the first bearing assembly  122  includes a bearing  128  having a first side  130 , facing toward the impeller assembly  106 , and an opposite, second side  132 , facing toward the motor  102 . A concave depression  134  is defined in the first side  130  of the bearing  128 . The concave depression  134  is configured to receive the first end  120  of the drive shaft  112 . As shown, the first end  120  of the drive shaft  112  may be at least partially rounded and, in embodiments, may include a curvature corresponding to the curvature of the concave depression  134 . In this manner, the surface area of contact between the drive shaft  112  and the bearing  128  may be as small as possible, reducing the chance that any blood cells will be able to get between the drive shaft  112  and the bearing  128  at their interface. 
     According to embodiments, the first bearing assembly  122  may also include a biasing feature  136  disposed between the second side  132  of the bearing  128  and the motor  102 . The biasing feature  136  may have a compliance configured such that the biasing feature  136  biases the bearing  128  in the direction of the drive shaft  112 , resisting the load generated by the attraction between the impeller rotor  116  and the stator  118 , while allowing enough flexibility to prevent the bearing  128  from being cracked or otherwise broken by the load. The bearing  128  may also, as shown, be retained in place by a bearing support feature  138 , which may be integrated into the motor housing  104 , the impeller assembly housing  108 , or which may be a separate feature coupled to the motor housing  104  and/or the impeller assembly housing  108 . According to embodiments, the bearing support feature  138  may include any number of different types of features configured to maintain the bearing  128  in its position. For example, the bearing support feature  138  may include multiple edges, a notch configured to receive a tab or edge, edges configured to form an interference fit with the periphery of the bearing, and/or the like. 
     The illustrative circulatory support device  100  shown in  FIGS.  1 A and  1 B  is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the present disclosure. The illustrative circulatory support device  100  also should not be interpreted as having any dependency or requirement related to any single component or combination of components illustrated therein. Additionally, various components depicted in  FIGS.  1 A and  1 B  may be, in embodiments, integrated with various ones of the other components depicted therein (and/or components not illustrated), all of which are considered to be within the ambit of the present disclosure. 
       FIG.  2 A  depicts a perspective view of an illustrative percutaneous mechanical circulatory support device  200 , in accordance with embodiments of the subject matter disclosed herein; and  FIG.  2 B  depicts a cross-sectional side view of the circulatory support device  200  depicted in  FIG.  2 A , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the circulatory support device  200 , and/or any number of various components thereof, may be the same as, or similar to, corresponding components of the circulatory support device  100  depicted in  FIGS.  1 A and  1 B . 
     As shown in  FIGS.  2 A and  2 B , the circulatory support device  200  includes a motor  202  disposed within a motor housing  204 . The motor  202  is configured to drive an impeller assembly  206  to provide a flow of blood through the device  200 . The impeller assembly  206  is disposed within an impeller assembly housing  208 , which includes a number of inlet apertures  210  and a number of outlet apertures  112  defined therein. According to embodiments, the motor housing  204  and the impeller assembly housing  208  may be integrated with one another. In other embodiments, the motor housing  204  and the impeller assembly housing  208  may be separate components configured to be coupled together, either removeably or permanently. A controller (not shown) is operably coupled to the motor  202  and is configured to control the motor  202 . The controller may be disposed within the motor housing  204  in embodiments, or, in other embodiments, may be disposed outside the housing  204  (e.g., in a catheter handle, independent housing, etc.). In embodiments, the controller may include multiple components, one or more of which may be disposed within the housing  204 . According to embodiments, the motor  204  may be, be similar to, include, or be included in the motor  104  depicted in  FIG.  1 A . 
     As shown in  FIG.  2 B , the impeller assembly  206  includes a drive shaft  214  and an impeller  216  coupled thereto, where the drive shaft  214  is configured to rotate with the impeller  216 . As shown, the drive shaft  214  is at least partially disposed within the impeller  216 . In embodiments, the drive shaft  214  may be made of any number of different rigid materials such as, for example, steel, titanium alloys, cobalt chromium alloys, nitinol, high-strength ceramics, and/or the like. The impeller assembly  206  further includes an impeller rotor  218  coupled to, and at least partially surrounding, the drive shaft  214 . The impeller rotor  218  may be any type of magnetic rotor capable of being driven by a stator (not shown, but which may be the same as, or similar to, the stator  118  depicted in  FIGS.  1 A and  1 B ) that is part of the motor  202 . In this manner, as a magnetic field is applied to the impeller rotor  218  by the stator in the motor  202 , the rotor  218  rotates, causing the drive shaft  214  and impeller  216  to rotate. 
     As shown, the impeller assembly is maintained in its orientation by the drive shaft  214 , which is retained, at a first end  220 , by a first bearing assembly  222  and, at a second end  224 , by a second bearing assembly  226 . According to embodiments, the first bearing assembly  222  and the second bearing assembly  226  may include different types of bearings. According to embodiments, the first bearing assembly  222  and/or the second bearing assembly  226  may include a lubricant chamber configured to hold a lubricant, while, in other embodiments, one and/or the other may not include lubrication. Various embodiments of bearing technology are described herein with respect to the first and second bearing assemblies  222  and  226 . 
       FIG.  2 C  is a close-up view of the first bearing assembly  222  of  FIG.  2 B , in accordance with embodiments of the subject matter disclosed herein. The second bearing assembly  226  may include, for example, a journal bearing, or any other type of suitable bearing. As shown in  FIG.  2 C , the first bearing assembly  222  includes a bearing  228  having a first side  230 , facing toward the impeller assembly  206 , and an opposite, second side  232 , facing toward the motor  202 . A concave depression  234  is defined in the first side  230  of the bearing  228 . The concave depression  234  is configured to receive the first end  220  of the drive shaft  214 . As shown, the first end  220  of the drive shaft  214  may be at least partially rounded and, in embodiments, the concave depression  234  may be sized to just fit the first end  22  of the drive shaft  214 . 
     As shown in  FIG.  2 C , the concave depression  234  may include a first portion  236  and a second portion  238 , where the first portion  236  has an at least approximately cylindrical shape and extends into the bearing  228  from the first side  230  of the bearing  228 . The second portion  238  has an at least approximately concave shape. In embodiments, the first portion  236  may be sized to fit a corresponding first portion  240  of the first end  220  of the drive shaft  214 , while the second portion  238  may be sized to fit a corresponding second portion  242  of the first end  220  of the drive shaft  214 . In embodiments, the first portion  240  of the first end  220  of the drive shaft  214  may have an approximately cylindrical shape, and the second portion  242  of the first end  220  of the drive shaft  214  may have an approximately convex shape. In this manner, the first portion  238  of the depression  234  may facilitate maintaining the drive shaft  214  in its orientation. 
     Additionally, the concave geometry of the depression, in conjunction with the rounded end of the drive shaft, creates a relatively large bearing surface, thereby distributing axial load over more area. The diameter of the end of the drive shaft (and, thus, of the concave depression) may be configured to facilitate desired performance characteristics. For example, increasing these diameters may lead to higher velocity of rotation, while reducing axial stresses, thereby reducing friction. According to embodiments, the dimensions of the various aspects of the bearing assembly may be selected based on implementation, performance, materials, and/or the like. 
     According to embodiments, the first bearing assembly  222  may also include a biasing feature (not shown) disposed between the second side  232  of the bearing  228  and the motor  202 . The biasing feature may have a compliance configured such that the biasing feature biases the bearing  228  in the direction of the drive shaft  214 , resisting the load generated by the attraction between the impeller rotor  218  and the stator, while allowing enough flexibility to prevent the bearing  228  from being cracked or otherwise broken by the load. The bearing  228  may also, as shown, be retained in place by a bearing support feature  244 , which may be integrated into the motor housing  204 , the impeller assembly housing  208 , or which may be a separate feature coupled to the motor housing  204  and/or the impeller assembly housing  208 . According to embodiments, the bearing support feature  244  may include any number of different types of features configured to maintain the bearing  228  in its position. For example, the bearing support feature  244  may include multiple edges, a notch configured to receive a tab or edge, edges configured to form an interference fit with the periphery of the bearing, and/or the like. 
     As shown, the bearing assembly  222  may also include a cup washer  246  having a base  248  and a peripheral wall  250  extending away from the base  248  towards the motor  202 , forming a cavity  252  bounded by an inner surface  254  of the base  248  and an inner surface  256  of the peripheral wall  250 . The peripheral wall  250  may be oriented approximately orthogonal to the base  248 . A shaft aperture  258  may be defined through the base  248 , extending from an outer surface  260  of the base  248  to the inner surface  254  of the base  248 , and may be configured to receive a portion of the drive shaft  214 . As shown, the bearing  228  is configured to be at least partially disposed within the cavity  252 . 
     Additionally, a lubricant may be disposed within the cavity to facilitate preservation of the bearing  228  and its interface with the drive shaft  214 . That is, for example, at least a portion of a lubricant chamber may be defined between the inner surface  254  of the base  248  of the cup washer  246 , the inner surface  256  of the peripheral wall  250  of the cup washer  246 , and the first side  230  of the bearing  228 . Additionally or alternatively, a portion of a lubricant chamber may be defined within the bearing (e.g., within the bearing  228 ). The lubricant may be any type of hydrophobic lubricant suitable for use in a blood pump. For example, in embodiments, but without intending to limit the disclosure, the lubricant may be a modified silicone lubricant such as, for example, a modified Polydimethylsiloxane (PDMS). In other embodiments, the lubricant may be an oil-based lubricant, a synthetic oil, a carbon-based lubricant, and/or the like. 
     The illustrative circulatory support device  200  shown in  FIGS.  2 A- 2 C  is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the present disclosure. The illustrative circulatory support device  200  also should not be interpreted as having any dependency or requirement related to any single component or combination of components illustrated therein. Additionally, various components depicted in  FIGS.  2 A- 2 C  may be, in embodiments, integrated with various ones of the other components depicted therein (and/or components not illustrated), all of which are considered to be within the ambit of the present disclosure. 
       FIG.  3    depicts a cross-sectional side view of an illustrative circulatory support device  300  having an impeller assembly  301 , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the circulatory support device  300 , and/or any number of various components thereof, may be the same as, or similar to, corresponding components of the circulatory support device  100  depicted in  FIGS.  1 A and  1 B , and/or the circulatory support device  200  depicted in  FIGS.  2 A- 2 C . 
     As shown in  FIG.  3   , the impeller assembly  301  is disposed within an impeller assembly housing  302 , which includes a number of outlet apertures  304  defined therein. The impeller assembly  301  includes a drive shaft  306  and an impeller  308  coupled thereto, where the drive shaft  306  is configured to rotate with the impeller  308 . As shown, the drive shaft  306  is at least partially disposed within the impeller  308 . In embodiments, the drive shaft  306  may be made of any number of different rigid materials such as, for example, steel, titanium alloys, cobalt chromium alloys, nitinol, high-strength ceramics, and/or the like. The impeller assembly  308  further includes an impeller rotor  310  coupled to, and at least partially surrounding, the drive shaft  306 . The impeller rotor  310  may be any type of magnetic rotor capable of being driven by a stator (not shown, but which may be the same as, or similar to, the stator  118  depicted in  FIGS.  1 A and  1 B ) that is part of the motor. In this manner, as a magnetic field is applied to the impeller rotor  310  by the stator in the motor, the rotor  310  rotates, causing the drive shaft  306  and impeller  308  to rotate. 
     As shown, the impeller assembly  301  is maintained in its orientation by the drive shaft  306 , which is retained, at a first end  312 , by a first bearing assembly  314  and, at a second end (not shown), by a second bearing assembly (not shown). According to embodiments, the first bearing assembly  314  and the second bearing assembly may include different types of bearings. According to embodiments, the first bearing assembly  314  and/or the second bearing assembly may include a lubricant chamber configured to hold a lubricant. The first bearing assembly  314  includes a bearing  316  having a first side  318 , facing toward the impeller assembly  301 , and an opposite, second side  320 , facing toward the motor. A concave depression  322  is defined in the first side  318  of the bearing  316 . The concave depression  322  is configured to receive the first end  312  of the drive shaft  306  and may, in embodiments, be configured in a manner similar to the concave depression  134  depicted in  FIG.  1 B  and/or the concave depression  234  depicted in  FIG.  2 C . As shown, the first end  312  of the drive shaft  214  may configured similar to the first end  120  of the drive shaft  112  depicted in  FIGS.  1 A and  1 B  and/or the first end  220  of the drive shaft  214  depicted in  FIGS.  2 B- 2 C . According to embodiments, the first bearing assembly  314  may also include a biasing feature (not shown) disposed between the second side  320  of the bearing  316  and the motor. 
     As shown, the bearing assembly  314  may also include a cup washer  324  or other similar basin-like structure, having a base  326  and a peripheral wall  328  extending away from the base  326  toward the impeller assembly  301 , forming a cavity  330  bounded by an inner surface  332  of the base  326  and an inner surface  334  of the peripheral wall  328 . As shown, the bearing  316  is configured to be at least partially disposed within the cavity  330 . A cover  336  may be disposed adjacent to the first side  318  of the bearing  316 , and include a shaft aperture  338  configured to receive a portion of the drive shaft  306 . In embodiments, for example, the cover  336  may be a layer of graphite, a polymer, and/or the like. 
     As is further shown in  FIG.  3   , the bearing assembly  314  includes a lubricant chamber configured to retain a lubricant. The lubricant chamber may include at least one channel  340  defined in the second side  320  of the bearing  316 . In embodiments, the channel or channels pass through the depression  322 . According to embodiments, the bearing  316  may include two or more channels  340  defined therein. As can be seen from  FIG.  3   , at least a portion of the inner surface  332  of the base  326  may form a boundary of the lubricant chamber. 
     The illustrative circulatory support device  300  shown in  FIG.  3    is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the present disclosure. The illustrative circulatory support device  300  also should not be interpreted as having any dependency or requirement related to any single component or combination of components illustrated therein. Additionally, various components depicted in  FIG.  3    may be, in embodiments, integrated with various ones of the other components depicted therein (and/or components not illustrated), all of which are considered to be within the ambit of the present disclosure. 
       FIG.  4    depicts a cross-sectional side view of an illustrative circulatory support device  400  having an impeller assembly  402 , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the circulatory support device  400 , and/or any number of various components thereof, may be the same as, or similar to, corresponding components of the circulatory support device  100  depicted in  FIGS.  1 A and  1 B , the circulatory support device  200  depicted in  FIGS.  2 A- 2 C , and/or the circulatory support device  300  depicted in  FIG.  3   . In embodiments, the portion of the circulatory support device  400  depicted in  FIG.  4    is the portion of an impeller assembly associated with an end opposite the end adjacent the motor. That is, for example, the bearing assembly  404  depicted in  FIG.  4    may be, be similar to, and/or otherwise correspond to the bearing assembly  126  depicted in  FIG.  1 A  and/or the bearing assembly  226  depicted in  FIG.  2 B . In embodiments, implementations of the bearing assembly  404  may be used, alternatively or additionally, as the bearing assembly  122  depicted in  FIGS.  1 A and  1 B , the bearing assembly  222  depicted in  FIGS.  2 B and  2 C , the bearing assembly  314  depicted in  FIG.  3   , and/or the like. 
     As shown in  FIG.  4   , the impeller assembly  402  is disposed within an impeller assembly housing  406 , which includes a number of apertures (not shown) defined therein. The impeller assembly  402  includes a drive shaft  408  and an impeller  410  coupled thereto, where the drive shaft  408  is configured to rotate with the impeller  410 . As shown, the drive shaft  408  is at least partially disposed within the impeller  410 . In embodiments, the drive shaft  408  may be made of any number of different rigid materials such as, for example, steel, titanium alloys, cobalt chromium alloys, nitinol, high-strength ceramics, and/or the like. 
     The impeller assembly  402  is maintained in its orientation by the drive shaft  408 , which is retained, at a first end (not shown), by a first bearing assembly (not shown) and, at a second end  412 , by the bearing assembly. According to embodiments, the first bearing assembly and the second bearing assembly  404  may include different types of bearings. According to embodiments, the first bearing assembly and/or the second bearing assembly  404  may include a lubricant chamber configured to hold a lubricant. The bearing assembly  404  includes a cylindrical-shaped bearing  414  disposed in the end  412  of the drive shaft  408 . The bearing  414  includes a first inside surface  416  facing away from the impeller and a second inside surface  418  extending away from the first inside surface. According to embodiments, the second inside surface  418  may be oriented approximately orthogonal to the first inside surface  416 . 
     As shown in  FIG.  4   , cylindrical-shaped bearing is disposed at an intersection of the drive shaft  408  and a stationary shaft mounting pin  420 . The shaft mounting pin may be made of any number of different materials. For example, in some embodiments, the shaft mounting pin  420  may be made of the same material as the drive shaft  408 . The shaft mounting pin  420  may be coupled to a pin support  422 . The drive shaft  408  is configured to rotate with respect to the stationary shaft mounting pin  420 . To facilitate reduction of friction and preservation of the bearing assembly  404 , the bearing assembly  404  may include a lubricant chamber  424 . The lubricant chamber  424  may be defined between the first inner surface  416  of the bearing  414  and an outer surface  426  of the stationary shaft mounting pin  420 . The lubricant chamber  424  may be further bounded by at least a portion of the second inner surface  418  of the bearing  414 . 
     The illustrative circulatory support device  400  shown in  FIG.  4    is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the present disclosure. The illustrative circulatory support device  400  also should not be interpreted as having any dependency or requirement related to any single component or combination of components illustrated therein. Additionally, various components depicted in  FIG.  4    may be, in embodiments, integrated with various ones of the other components depicted therein (and/or components not illustrated), all of which are considered to be within the ambit of the present disclosure. 
     As indicated above, a portion of a lubricant chamber may be defined within a bearing.  FIGS.  5 A and  5 B  are perspective views of an illustrative bearing  500 , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the bearing  500  may be, or be similar to, the bearing  122  depicted in  FIGS.  1 A and  1 B , the bearing  222  depicted in  FIGS.  2 A- 2 C , the bearing  322  depicted in  FIG.  3   , and/or the like. In embodiments, the bearing  500  includes a first side  502 , configured to face toward an impeller assembly, and an opposite, second side  504 , configured to face toward a motor. A concave depression  506  is defined in the first side  502  of the bearing  500 . The concave depression  506  is configured to receive an end of a drive shaft. As discussed herein, the end of the drive shaft may be at least partially rounded and, in embodiments, the concave depression  506  may be sized to just fit the end of the drive shaft. 
     As shown, the concave depression  500  may include a first portion  508  and a second portion  510 , where the first portion  508  has an at least approximately cylindrical shape and extends into the bearing  500  from the first side  502  of the bearing  500 . The second portion  510  has an at least approximately concave shape. In embodiments, the first portion  508  may be sized to fit a corresponding first portion of the end of the drive shaft, while the second portion  510  may be sized to fit a corresponding second portion of the end of the drive shaft. In embodiments, the first portion of the end of the drive shaft may have an approximately cylindrical shape, and the second portion of the end of the drive shaft may have an approximately convex shape. In this manner, the first portion  508  of the depression  506  may facilitate maintaining the drive shaft in its orientation. 
     As is further shown, two channels  512  are defined in the second side  504  of the bearing  500 . According to embodiments, the bearing  500  may include any number of channels (e.g., 1, 2, 3, 4, 5, etc.) having any number of different depths, widths, and/or the like. In embodiments, for example, the channels do not extend through the outside surface  514  of the periphery wall  516 . In embodiments, the bearing  500  may include multiple channels of varying size. For example, the bearing  500  may include microchannels (e.g., channels that are substantially narrower and shallower than the channels  512  such as, for example, by at least a factor of 5) defined in an upper surface  518  of the concave depression. According to embodiments, using bearings with channels defined therein for lubricant chambers may facilitate using thinner bearings, thereby enabling the rotor of the impeller assembly to be closer to the stator of the motor, which may enable increased torque and efficiency. 
     The bearing  500  shown in  FIGS.  5 A and  5 B  is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the present disclosure. The illustrative bearing  500  also should not be interpreted as having any dependency or requirement related to any single component or combination of components illustrated therein. Additionally, various components depicted in  FIGS.  5 A and  5 B  may be, in embodiments, integrated with various ones of the other components depicted therein (and/or components not illustrated), all of which are considered to be within the ambit of the present disclosure. 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present disclosure. For example, while the embodiments described above refer to particular features, the scope of this disclosure also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present disclosure is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.