Patent Publication Number: US-2023158287-A1

Title: Glass impeller for a blood pump

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 17/004,110, filed Aug. 27, 2020, which claims priority to U.S. Provisional Application No. 62/894,010, filed Aug. 30, 2019, which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to percutaneous circulatory support devices. More specifically, the disclosure relates to impellers used 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 and impeller-blade surface can lead to hemolysis, which can further lead to health complications such as anemia, requiring blood transfusions. Additionally, increased friction at the blood-surface interface may require higher motor power to maintain the pump output, which may warrant a bigger motor size. 
     SUMMARY 
     In an Example 1, a blood pump, comprising: an impeller assembly housing; and an impeller assembly disposed within the impeller assembly housing, the impeller assembly comprising an impeller having a main body, at least one impeller blade extending outwardly therefrom, and a skirt disposed around at least a portion of the main body, wherein at least a portion of the at least one impeller blade is disposed between the main body and an inner surface of the skirt. 
     In an Example 2, the blood pump of Example 1, wherein the at least one impeller blade is connected to the skirt. 
     In an Example 3, the blood pump of either of Examples 1 or 2, wherein the impeller is one solid piece. 
     In an Example 4, the blood pump of any of Examples 1-3, wherein the impeller is made of chemically strengthened glass. 
     In an Example 5, the blood pump of any of Examples 1-4, wherein the impeller assembly is configured to rotate within the impeller assembly housing. 
     In an Example 6, the blood pump of Example 5, the skirt comprising an outer surface configured to be disposed adjacent an inner surface of the impeller assembly housing. 
     In an Example 7, the blood pump of any of Examples 1-6, the skirt having a proximal end and a distal end, the distal end having a distal outer edge, wherein the at least one impeller blade includes a leading edge that is at least partially coplanar with at least a portion of the distal outer edge. 
     In an Example 8, the blood pump of Example 7, wherein at least a portion of the leading edge is coplanar with the distal outer edge. 
     In an Example 9, the blood pump of either of Examples 7 or 8, wherein the leading edge extends radially inward from an inner surface of the skirt to an outer surface of the main body. 
     In an Example 10, the blood pump of any of Examples 7-9, wherein a first portion of the leading edge is coplanar with at least a portion of the distal outer edge, and 
     wherein a second portion of the leading edge slopes axially toward the proximal end of the skirt. 
     In an Example 11, the blood pump of Example 10, the main body comprising a distal end that is disposed proximal the distal outer edge. 
     In an Example 12, the blood pump of any of Examples 7-9, wherein the entire leading edge is coplanar with the entire distal outer edge. 
     In an Example 13, the blood pump of any of Examples 1-12, wherein a width of distal end of the skirt is greater than a width of the proximal end of the skirt. 
     In an Example 14, the blood pump of any of Examples 1-13, wherein the impeller assembly is maintained in place using only one bearing assembly, the one bearing assembly being disposed at a proximal end of the impeller assembly. 
     In an Example 15, an impeller fora blood pump, comprising: a main body;
         at least one impeller blade extending outwardly therefrom; and a skirt disposed around at least a portion of the main body, wherein the impeller is made of glass.       

     In an Example 16, a blood pump, comprising: an impeller assembly housing; and an impeller assembly disposed within the impeller assembly housing, the impeller assembly comprising an impeller having a main body, at least one impeller blade extending outwardly therefrom, and a skirt disposed around at least a portion of the main body, wherein at least a portion of the at least one impeller blade is disposed between the main body and an inner surface of the skirt. 
     In an Example 17, the blood pump of Example 16, wherein the at least one impeller blade is connected to the skirt. 
     In an Example 18, the blood pump of Example 16, wherein the impeller is one solid piece. 
     In an Example 19, the blood pump of Example 16, wherein the impeller is made of chemically strengthened glass. 
     In an Example 20, the blood pump of Example 16, wherein the impeller assembly is configured to rotate within the impeller assembly housing. 
     In an Example 21, the blood pump of Example 20, the skirt comprising an outer surface configured to be disposed adjacent an inner surface of the impeller assembly housing. 
     In an Example 22, the blood pump of Example 16, the skirt having a proximal end and a distal end, the distal end having a distal outer edge, wherein the at least one impeller blade includes a leading edge that is at least partially coplanar with at least a portion of the distal outer edge. 
     In an Example 23, the blood pump of Example 22, wherein at least a portion of the leading edge is coplanar with the distal outer edge. 
     In an Example 24, the blood pump of Example 22, wherein the leading edge extends radially inward from an inner surface of the skirt to an outer surface of the main body. 
     In an Example 25, the blood pump of Example 22, wherein a first portion of the leading edge is coplanar with at least a portion of the distal outer edge, and wherein a second portion of the leading edge slopes axially toward the proximal end of the skirt. 
     In an Example 26, the blood pump of Example 25, the main body comprising a distal end that is disposed proximal the distal outer edge. 
     In an Example 27, the blood pump of Example 22, wherein the entire leading edge is coplanar with the entire distal outer edge. 
     In an Example 28, the blood pump of Example 16, wherein a width of distal end of the skirt is greater than a width of the proximal end of the skirt. 
     In an Example 29, the blood pump of Example 16, wherein the impeller assembly is maintained in place using only one bearing assembly, the one bearing assembly being disposed at a proximal end of the impeller assembly. 
     In an Example 30, an impeller for a blood pump, comprising: a main body;
         at least one impeller blade extending outwardly therefrom; and a skirt disposed around at least a portion of the main body, wherein the impeller is made of glass.       

     In an Example 31, the impeller of Example 30, wherein the at least one impeller blade is connected to the skirt. 
     In an Example 32, the impeller of Example 30, wherein the impeller is one solid piece. 
     In an Example 33, the impeller of Example 30, the skirt having a proximal end and a distal end, the distal end having a distal outer edge, wherein the at least one impeller blade includes a leading edge that is at least partially coplanar with at least a portion of the distal outer edge. 
     In an Example 34, the impeller of Example 30, wherein the impeller assembly is maintained in place using only one bearing assembly, the one bearing assembly being disposed at a proximal end of the impeller assembly. 
     In an Example 35, a blood pump, comprising: an impeller assembly housing; and an impeller assembly disposed within the impeller assembly housing, the impeller assembly comprising an impeller having a main body, at least one impeller blade extending outwardly therefrom, and a skirt disposed around at least a portion of the main body, wherein at least a portion of the at least one impeller blade is disposed between the main body and an inner surface of the skirt, wherein the impeller is made of glass. 
     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    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 prior designs. 
         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 end view of the circulatory support device depicted in  FIG.  2 A , in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  3    is a perspective view of an illustrative impeller, in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  4    is a perspective view of another illustrative impeller, in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  5 A  is a perspective view depicting another illustrative impeller, in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  5 B  is a schematic end view of the impeller depicted in  FIG.  5 A , in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  6 A  is a perspective view depicting another illustrative impeller, in accordance with embodiments of the subject matter disclosed herein. 
         FIG.  6 B  is a partially cut-away perspective view of the impeller depicted in  FIG.  6 A , shown disposed within an impeller assembly housing, 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. 
     DETAILED DESCRIPTION 
       FIG.  1    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 prior designs. As shown in  FIG.  1   , 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. 
     As shown in  FIG.  1   , 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 (not shown) that is part of the motor  102 . In this manner, as a magnetic field is applied to the impeller rotor  116  by the stator in the motor  102 , the rotor  116  rotates, causing the drive shaft  112  and impeller  114  to rotate. 
     As shown, the impeller assembly  106  is maintained in its orientation by the drive shaft  112 , which is retained, at a first end  118 , by a first (proximal) bearing assembly  120  and, at a second end  122 , by a second (distal) bearing assembly  124 . According to embodiments, the first bearing assembly  120  and the second bearing assembly  124  may include different types of bearings. According to embodiments, the first bearing assembly  120  and/or the second bearing assembly  124  may include lubrication, while, in other embodiments, one and/or the other may not include lubrication. As the terms “proximal” and “distal” are used herein, “proximal” refers to the general direction opposite that of insertion—that is, the direction in which one would travel along the device to exit the subject&#39;s body; whereas distal refers to the general direction of implantation—that is, the direction in which one would travel along the device to reach the end of the device that is configured to advance into the subject&#39;s body. 
     The prior impeller is generally made out of PEEK using conventional machining and subsequent polishing. The impeller needs to be strong, precisely dimensioned and smooth to avoid damage to the blood cells. There are significant limitations regarding the freedom of design because of this manufacturing process. Although 3D printing might give much broader freedom regarding shapes, one has to realize that complex shapes will make polishing more difficult or even impossible. The impeller  114  is furthermore mounted in a metal housing  108 . Studies of the flowlines though the prior pump have revealed that there is quite a bit of shear force between the rotating fluid and the static inner wall of the housing  108 . 
     Furthermore, as described above, the impeller  114  is supported by the two endpoints, allowing it to rotate. The proximal bearing  120  dissipates both axial and radial force, while the distal bearing  124  just holds the impeller  114  in radial position. Having the distal bearing  124  in place requires axial space for mounting and introduces flow resistance. Embodiments of the disclosure include a blood pump having only a proximal bearing (the distal bearing is not included). This may reduce flow resistance and facilitate shortening the overall construction of the blood pump, which may enable the device to better fit within an arching aorta. 
       FIG.  2 A  depicts a cross-sectional side view of a portion of an illustrative percutaneous mechanical circulatory support device  200  (also referred to herein, interchangeably, as a “blood pump”); and  FIG.  2 B  depicts a cross-sectional end 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, a number of various components of the circulatory support device  200  may be the same as, or similar to, corresponding components of the circulatory support device  100  depicted in  FIG.  1   . 
     As shown in  FIG.  2 A , 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 outlet apertures  210  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 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.  2 A , the impeller assembly  206  includes a drive shaft  212  and an impeller  214  coupled thereto, where the drive shaft  212  is configured to rotate with the impeller  214 . As shown, the drive shaft  212  is at least partially disposed within the impeller  214 . In embodiments, the drive shaft  212  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  216  coupled to, and at least partially surrounding, the drive shaft  212 . The impeller rotor  216  may be any type of magnetic rotor capable of being driven by a stator (not shown) that is part of the motor  202 . In this manner, as a magnetic field is applied to the impeller rotor  216  by the stator in the motor  202 , the rotor  216  rotates, causing the drive shaft  212  and impeller  214  to rotate. In embodiments, the impeller assembly  206  may be configured to be directly driven by the motor  202 . That is, for example, instead of having a rotor/stator configuration, the motor  202  may be configured to cause the drive shaft  212  to rotate, which thereby causes the impeller  214  to rotate. 
     As shown, the impeller assembly  206  is maintained in its orientation by the drive shaft  212 , which is retained, at a first end  218 , by a proximal bearing assembly  220 . According to embodiments, the bearing assembly  220  may include lubrication, and may be, or include, any number of different types of bearings. In contrast to prior designs (e.g., as shown in  FIG.  1   ), embodiments of the device  200  disclosed herein may omit a distal bearing assembly that is independent of the impeller assembly  206 . Instead, as shown, the impeller  214  includes a skirt  222  disposed around at least a portion of a main body  224 . One or more impeller blades  226  are connected to the skirt  222  and the main body  224  and are disposed at least partially between the skirt  222  and the main body  224 . According to embodiments, the skirt  222  may include an outer surface that is configured to be disposed adjacent an inner surface  230  of the impeller assembly housing  208  such that the skirt  222  functions as a bearing, maintaining the position of the impeller  214  within the impeller assembly housing  208 . In embodiments, since both surfaces (the blades and surrounding tubing (skirt)) are all rotating at the same speed and in the same direction, there may be much less shear force on the flow, thereby producing less damage to the blood. 
     According to embodiments, the impeller  214  may be made of glass such as, for example, by using selective laser etching to fashion the impeller  214  all in one piece from a glass block. Selective laser-induced etching (SLE) is a two-step process to produce 3D structures in transparent materials (also known as ISLE: In-volume selective laser induced etching—to distinguish our process from laser ablation). In a first step, the transparent fused silica glass is modified internally by laser radiation to increase the chemical etchability locally. To prevent the formation of cracks in the brittle material, short pulse duration (fs-ps) and a small focal volume (a few μm3) may be used. The focus is scanned inside the glass to modify a 3D connected volume with contact to the surface of the workpiece. 
     In a second step, the modified material is selectively removed by wet chemical etching resulting in the development of the 3D product. The selectivity is the ratio of the etching rate of the modified material and the etching rate of the untreated material. The selectivity in fused silica glass is larger than 500:1, resulting in long fine channels with small conicity. Therefore, by the SLE-technique, complex 3D cavities can be produced, like micro fluidic structures and micro structures 3D parts. According to embodiments, advantages of SLE are the large precision (˜1 μm), no debris, true 3D capability and the high processing speed using micro scanners. 
     A prior polishing process for glass materials uses disc or point tools and a polishing liquid, which is applied to the work piece. In that process, large amounts of waste can arise. By means of laser polishing, glass surfaces can be polished without creating waste, independent of the surface form and with the same tool. In addition, the processing time of laser polishing is smaller by a factor of up to 100 times. It can attain a surface roughness of quartz glass down to Root Mean Square roughness (RMS)&lt;5 nm (1×1 mm2 measuring field) and micro roughness down to RMS&lt;0.4 nm (50×70 p m2 measuring field). Applications for laser polishing of glass surfaces are, among others, lighting optics, for which the values currently achieved are sufficient. The process can be applied to nearly all kinds of glass, whereas higher process speeds are reached for low-melting glasses. The very low roughness values compared to the PEEK impeller designs (RMS of roughly 100 nm) results in a much lower friction on the blood, hence a reduction in hemolysis. 
     In embodiments, impellers described herein may be made of chemically strengthened glass. Chemically strengthened glass is a type of glass that has increased strength as a result of a post-production chemical process. Chemically strengthened glass is typically six to eight times the strength of float glass. The glass is chemically strengthened by a surface finishing process. Glass is submersed in a bath containing a potassium salt (typically potassium nitrate) at 300° C. (572° F.). This causes sodium ions in the glass surface to be replaced by potassium ions from the bath solution. These potassium ions are larger than the sodium ions and therefore wedge into the gaps left by the smaller sodium ions when they migrate to the potassium nitrate solution. This replacement of ions causes the surface of the glass to be in a state of compression and the core in compensating tension. The surface compression of chemically strengthened glass may reach up to 690 MPa. 
     The strengthening mechanism depends on the fact that the compressive strength of glass is significantly higher than its tensile strength. With both surfaces of the glass already in compression, it takes a certain amount of bending before one of the surfaces can even go into tension. More bending is required to reach the tensile strength. The other surface simply experiences more and more compressive stress. But since the compressive strength is so much larger, no compressive failure is experienced. There also exists a more advanced two-stage process for making chemically strengthened glass, in which the glass article is first immersed in a sodium nitrate bath at 450° C. (842° F.), which enriches the surface with sodium ions. This leaves more sodium ions on the glass for the immersion in potassium nitrate to replace with potassium ions. In this way, the use of a sodium nitrate bath increases the potential for surface compression in the finished article. Chemical strengthening results in a strengthening similar to toughened glass. However, the process does not use extreme variations of temperature and therefore chemically strengthened glass has little or no bow or warp, optical distortion or strain pattern. This differs from toughened glass, in which slender pieces can be significantly bowed. 
     According to embodiments, by using aspects of the manufacturing process described above to produce blood pump impellers made of glass, the impellers may be designed to have any number of different shapes, optimized for hydrodynamic performance, and/or the like. Examples of some illustrative design concepts are described below with respect to  FIG.  3    and  FIG.  4   . 
     The illustrative circulatory support device  200  shown in  FIGS.  2 A and  2 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  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 and  2 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.  3    is a perspective view of an illustrative impeller  300 , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the impeller  300  may be made from glass such as, for example, by using aspects of a manufacturing processes described herein, and may be, or be similar to, the impeller  214  described. As shown in  FIG.  3   , the impeller  300  includes a main body  302  and a skirt  304  disposed around at least a portion of the main body  302 . A first impeller blade  306  and a second impeller blade  308  extend outwardly from the main body  302 . 
     Embodiments of the impeller may incorporate as shown in  FIG.  3   , at least a portion of each of the two impeller blades  306  and  308  is disposed between the main body  302  and an inner surface  310  of the skirt  304 . Each of the impeller blades  306  and  308  is connected to the skirt  304 . In embodiments, the impeller blades  306  and  308  may be connected to the skirt  304  at various points. The skirt  304  also includes an outer surface  312  configured to be disposed adjacent an inner surface of an impeller assembly housing (not shown). 
     In the illustrated embodiments, the skirt  304  includes a cylinder having a first (proximal) end  314  and a second (distal) end  316 . The inner and outer surfaces  310  and  312  extend between the first and second ends  314  and  316 . In other embodiments, the skirt  304  may be tapered such that a diameter of the skirt at one end is larger than the diameter at the other end. For example, in embodiments, the diameter of the skirt  304  may be greater at or near the distal end  316  than the diameter of the skirt  304  at or near the proximal end  314 . In embodiments, the skirt may be configured, as illustrated, to have a circular radial cross section, while, in other embodiments, the skirt  304  may be configured to have a radial cross section of any number of other shapes, so long as the shape of the skirt does not prevent the skirt from rotating within an impeller housing. 
     Each of the impeller blades  306  and  308  includes a leading edge  318 ,  320 , respectively. The leading edge  318  is the distal-most edge of the impeller blade  306 , and the leading edge  320  is the distal-most edge of the impeller blade  308 . That is, the leading edges  318  and  320  are the edges of the impeller blades  306  and  308 , respectively, that first encounter blood as it flows into the device and across the impeller  300 . As shown in  FIG.  3   , the skirt  304  includes a proximal outer edge  322  at the proximal end of the skirt  304 , and a distal outer edge  324  at the distal end  316  of the skirt  304 . In the illustrated embodiments, the entire leading edge  318  of the first impeller blade  306  and the entire leading edge  320  of the second impeller blade  308  each are coplanar with the entire distal outer edge  324  of the skirt  304 . In embodiments, one or more of the leading edges  318  and  320  may be at least partially coplanar with at least a portion of the distal outer edge  324  of the skirt  304 . 
     That is, for example, any portion or portions of one or more of the leading edges  318  and  320  (and/or leading edges of other blades not depicted) may be coplanar with one or more portions of the distal outer edge  324  of the skirt  304 . Although the distal outer edge  324  of the skirt  304  is illustrated as being entirely within a single plane, embodiments may include a distal outer edge  324  that is curved in any number of configurations such that one or more portions of the outer edge lie in different planes. In other embodiments, one or more of the leading edges  318  and  320  may be connected to the distal outer edge  324 , but not have any portion that is coplanar therewith. According to embodiments, one or more of the impeller blades  306  and  308  may connect to the skirt  304  at the distal outer edge  324  and/or any other location on the skirt  304 . The impeller blades  306  and  308  are each shown as having a width that is greater near the distal end  316  than the width near the proximal end  314 , where the width is the distance between the outer surface  326  of the main body and a trailing edge  328  or  330  of the impeller  306  or  308  respectively, in a direction normal to the outer surface  326 . In embodiments, one or more of the impeller blades  306  and  308  may be configured to have a greater width near the proximal end  314  than near the distal end  316 , in which case, for example, the impeller blades  306  and/or  308  may be connected to the skirt  304  at or near the proximal end  314 . In embodiments, the trailing edge  328  and/or  330  may be integrated with the leading edge  316  and/or  318 , respectively. 
     In embodiments, the leading edge  318  of the impeller  306  extends radially inward from a surface (e.g., the distal outer edge  324 , the inner surface  310 , etc.) of the skirt  304  to an outer surface  326  of the main body  302 . Similarly, the leading edge  320  of the impeller  308  extends radially inward from a surface of the skirt  304  to the outer surface  326  of the main body  302 . In embodiments, the leading edge and/or trailing edge of an impeller may be straight and/or curved. That is, for example, the leading edge and/or trailing edge of an impeller blade may be curved radially and/or axially to provide a hydrodynamic shape. 
     As shown in  FIG.  3   , the main body may include a distal end  332  that protrudes axially in the distal direction beyond a plane of the distal outer edge  324  of the skirt  304 . The distal end  332  may be rounded, flat, and/or the like. The distal end  332  may, in embodiments, be coplanar with a plane of the distal outer edge  324  of the skirt  304 , or, in other embodiments, may be located proximal to one or more planes of the distal outer edge  324 . For example,  FIG.  4    is a perspective view of another illustrative impeller  400 , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the impeller  400  may be made from glass such as, for example, by using aspects of a manufacturing processes described herein, and may include aspects that are the same as, or similar to, corresponding aspects of the impeller  300  depicted in  FIG.  3   . 
     As shown in  FIG.  4   , the impeller  400  includes a main body  402  and a skirt  404  disposed around at least a portion of the main body  402 . A first impeller blade  406  and a second impeller blade  408  extend outwardly from the main body  402 . 
     Embodiments may include any number of impeller blades such as, for example, one impeller blade, two impeller blades, three impeller blades, four impeller blades, and/or any other number of impeller blades. As shown in  FIG.  4   , at least a portion of each of the two impeller blades  406  and  408  is disposed between the main body  402  and an inner surface  410  of the skirt  404 . Each of the illustrated impeller blades  406  and  408  is connected to the skirt  404  at one or more locations between a proximal end  412  of the skirt  404  and a distal end  414  of the skirt  404 . 
     Each of the impeller blades  406  and  408  includes a leading edge  416 ,  418 , respectively. The leading edge  416  is the distal-most edge of the impeller blade  406 , and the leading edge  418  is the distal-most edge of the impeller blade  408 . That is, the leading edges  416  and  418  are the edges of the impeller blades  406  and  408 , respectively, that first encounter blood as it flows into the device and across the impeller  400 . As shown in  FIG.  4   , the skirt  404  includes a proximal outer edge  420  at the proximal end  412  of the skirt  404 , and a distal outer edge  422  at the distal end  414  of the skirt  404 . In the illustrated embodiments, a portion  424  of the leading edge  416  of the first impeller blade  406  and a portion  426  of the leading edge  418  of the second impeller blade  408  each are coplanar with the distal outer edge  422  of the skirt  404 . 
     As shown in  FIG.  4   , each leading edge  416  and  418  curves in a proximal direction to a distal end  428  of the main body  402 . The distal end  428  is disposed proximal to the distal outer edge  422  of the skirt  404 . The leading edge  416  of the impeller  406  extends radially inward from a surface (e.g., the distal outer edge  422 , the inner surface  410 , etc.) of the skirt  404  to an outer surface  430  of the main body  402 . Similarly, the leading edge  418  of the impeller  408  extends radially inward from a surface of the skirt  404  to the outer surface  430  of the main body  402 . 
     Although the impeller  400  depicted in  FIG.  4    includes two impeller blades, impellers made in accordance with embodiments of the subject matter disclosed herein may have more than two blades. In embodiments, an impeller may have three blades, four blades, five blades, six blades, and/or the like.  FIG.  5 A  is a perspective view depicting another illustrative impeller  500 , having four blades, in accordance with embodiments of the subject matter disclosed herein.  FIG.  5 B  is a schematic end view of the impeller  500  depicted in  FIG.  5 A , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the impeller  500  may be made from glass such as, for example, by using aspects of a manufacturing processes described herein, and may include aspects that are the same as, or similar to, corresponding aspects of the impeller  300  depicted in  FIG.  3    and/or the impeller  400  depicted in  FIG.  4   . 
     As shown in  FIG.  5 A , the impeller  500  includes a main body  502  and a skirt  504  disposed around at least a portion of the main body  502 . A first impeller blade  506 , a second impeller blade  508 , a third impeller blade  510 , and a fourth impeller blade  512  extend outwardly from the main body  502 . As shown in  FIG.  5 A , at least a portion of each of the four impeller blades  506 ,  508 ,  510 , and  512  is disposed between the main body  502  and an inner surface  514  of the skirt  504 . Each of the illustrated impeller blades  506 ,  508 ,  510 , and  512  is connected to the skirt  504 . 
     Each of the impeller blades  506 ,  508 ,  510 , and  512  includes a leading edge  516 ,  518 ,  520 , and  522 , respectively. The leading edges  516 ,  518 ,  520 , and  522  include the distal-most edges of the respective impeller blades  506 ,  508 ,  510 , and  512 . That is, the leading edges  516 ,  518 ,  520 , and  522  are the edges of the impeller blades  506 ,  508 ,  510 , and  512 , respectively, that first encounter blood as it flows into the device and across the impeller  500 . As shown in  FIG.  5 A , the skirt  504  includes a distal outer edge  524  at the distal end  526  of the skirt  504 . In the illustrated embodiments, a portion  528  of the leading edge  516  of the first impeller blade  506  and a portion  530  of the leading edge  518  of the second impeller blade  508  each are coplanar with the distal outer edge  524  of the skirt  504 , while no portion of either of the distal edges  520  or  522  is coplanar with the distal outer edge  524  of the skirt  504 . 
     As shown in  FIGS.  5 A and  5 B , the impeller blades  506 ,  508 ,  510 , and  512  may be configured such that the blades include more than one set of blades, in which the blades of each set are axially symmetric with each other, similarly shaped, and/or the like. For example, as shown, the impeller  500  may include a first set of impeller blades that includes the first blade  506  and the third blade  510 , and a second set of impeller blades that includes the second blade  508  and the fourth blade  512 . As shown, the first blade  506  is axially symmetric to the third blade  510 , and the second blade  508  is axially symmetric to the fourth blade  512 , but none of the blades of the first set are axially symmetric to any of the blades in the second set. That is, each leading edge  516  and  518  of the first set of impeller blades curves in an axially symmetric direction to the other. Similarly, each leading edge  520  and  522  of the second set of impeller blades curves in an axially symmetric direction to the other. In embodiments, sets of blades may include two blades, three blades, four blades, and/or the like, and an impeller may include any number of distinct sets of impeller blades. 
     Although each of the impellers  300 ,  400 , and  500  depicted in  FIGS.  3 ,  4   , and  5 A- 5 B, respectively, includes a main body through which a central axis (not shown) of the impeller passes, implementation of the manufacturing processes disclosed herein enable creation of impellers having bodies of other configurations. For example, in embodiments, the main body may include a number of different portions or legs, only some of which intersect the central axis. In other embodiments, none of the legs intersect the central axis. An example of such an embodiment is depicted in  FIGS.  6 A and  6 B . 
       FIG.  6 A  is a perspective view depicting another illustrative impeller  600 , in accordance with embodiments of the subject matter disclosed herein.  FIG.  6 B  is a partially cut-away perspective view of the impeller  600  depicted in  FIG.  6 A , shown disposed within an impeller assembly housing  602 , in accordance with embodiments of the subject matter disclosed herein. According to embodiments, the impeller  600  may be made from glass such as, for example, by using aspects of a manufacturing processes described herein, and may include aspects that are the same as, or similar to, corresponding aspects of the impeller  300  depicted in  FIG.  3   , the impeller  400  depicted in  FIG.  4   , and/or the impeller  500  depicted in  FIGS.  5 A and  5 B . 
     As shown in  FIG.  6 A , the impeller  600  includes a main body  604  extending between a base portion  606  and a skirt  608 . The skirt  608  is disposed around at least one impeller blade  610 . As shown in  FIG.  6 A , the main body  604  includes three individual legs  612 ,  614 , and  616 , extending independently from the base portion  606  to the skirt  608 , leaving a central space around the central axis  618  open. In embodiments, the base portion  606  may be a housing containing a rotor (magnet), and may include, as shown, a curved distal surface  620  to facilitate blood flow radially away from the central axis  618 . Although  FIG.  6 A  shows one blade  610  extending across the skirt perimeter, it will be understood that multiple blades may be positioned axially with respect to one another. Additionally, as shown in  FIG.  6 A , each of the three legs  612 ,  614 , and  616  is slightly curved inwards, though other designs may be implemented in accordance with embodiments of the subject matter disclosed herein. Further, as shown in  FIG.  6 B , the flow outlets  622  of the impeller assembly housing  602  may be positioned such that there is space between the legs  612 ,  614 , and  616  and the outlets  622 . 
     The illustrative circulatory support devices  300  shown in  FIG.  3 ,  400    shown in  FIG.  4 ,  500    shown in  FIGS.  5 A and  5 B, and  600    shown in  FIGS.  6 A and  6 B  are not intended to suggest any limitation as to the scope of use or functionality of embodiments of the present disclosure. The illustrative circulatory support devices  300 ,  400 ,  500 , and  600  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.  3 ,  4 ,  5 A,  5 B,  6 A, and  6 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.