Mixing impeller blade with pressure relief geometry

Abstract

An impeller includes a flat blade region that further includes a generally rectangular cross-section with front and back faces, sidewalls, and a blade tip at a distal end of the impeller. A transition region extends proximally from the flat blade region towards a tapered region, the tapered region extends proximally from the transition region and distally towards a drive region, and the drive region extends to a proximal end of the impeller.

Description

MIXING IMPELLER BLADE WITH PRESSURE RELIEF GEOMETRYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of US Provisional Patent Application Serial No. 63 / 746,572, filed on January' 17, 2025, entitled “MIXING IMPELLER BLADE WITH PRESSURE RELIEF GEOMETRY,” the entire contents of which is hereby incorporated by reference herein.TECHNICAL FIELD

[0002] The present disclosure relates to fluid mixing devices and methods, specifically to impeller designs used in mixing fluids within reaction vessels for laboratory' applications.BACKGROUND

[0003] In many laboratory applications, particularly those involving biochemical assays or chemical reactions, it is important to ensure consistent and efficient mixing of small fluid volumes. Traditional mixing methods used in reaction vessels for low-volume fluid mixing face challenges, particularly in ensuring homogeneity of the fluid without introducing air bubbles or carrying out excess liquid during impeller extraction. Such issues can compromise the precision of analytical results, as air bubbles can interfere with optical or photometric measurements, while fluid carry out may alter the reaction volume.

[0004] Traditionally, various mixing methods such as magnetic stirrers, shakers, and impellers are used to agitate fluids within reaction vessels. Impellers are commonly used for their ability’ to provide controlled and efficient mixing, especially in larger volumes. However, when dealing with low-volume reaction vessels, conventional impeller designs often face challenges. Issues such as air bubble entrainment, fluid carryout upon impeller extraction, and sensitivity to precise alignment within the vessel can compromise the quality of mixing. Air bubbles can interfere with analytical measurements, while fluid carryout can alter the intended reaction volume, affecting the accuracy of experimental results. Moreover, the need for precise impeller alignment increases the complexity and potential for errors in laboratory' performance.

[0005] There is thus a need for improved impeller designs that can provide efficient, homogeneous mixing in low-volume reaction vessels while minimizing air bubble formation and fluid carryout. Such designs should also reduce sensitivity to alignment variations and be compatible with a range of operating conditions, including different rotational speeds and vessel sizes. Enhancing impeller performance in these areas would significantly benefit laboratory practices by improving the reliability and accuracy of fluid mixing processes.SUMMARY

[0006] Embodiments of the present invention address and overcome one or more of the above shortcomings and drawbacks.

[0007] In an exemplary embodiment, an impeller includes a flat blade region that further includes a generally rectangular cross-section with front and back faces, sidewalls, and a blade tip at a distal end of the impeller. A transition region extends proximally from the flat blade region towards a tapered region, the tapered region extends proximally from the transition region and distally towards a drive region, and the drive region extends to a proximal end of the impeller.

[0008] In another exemplary embodiment, at a proximal end of the flat blade region and as the transition region extends proximally, the sidewalls curve inward toward a central longitudinal axis of the impeller and the front and back faces of the flat blade region curve outward away from the central longitudinal axis of the impeller.

[0009] In another exemplary embodiment, the inward curvature of the sidewalls occurs more distally than the outward curvature of the front and back faces.

[0010] In another exemplary embodiment, the flat blade region is laterally wider from sidewall to sidewall than thick from front face to back face.

[0011] In another exemplary embodiment, the flat blade region is longer from the blade tip to a proximal end than it is laterally wide from sidewall to sidewall.

[0012] In another exemplary embodiment, the front and back faces of the flat blade region curve into the sidewalls at a radius.

[0013] In another exemplary embodiment, the blade tip of the flat blade region is rounded and merges with the sidewalls and front and back faces.

[0014] In another exemplary embodiment, the tapered region comprises a first section, a second section, and a third section.

[0015] In another exemplary embodiment, the first section of the tapered region has a cylindrical profile.

[0016] In another exemplary embodiment, the first section of the tapered region has a diameter smaller than a lateral width of the flat blade region from sidewall to sidewall.

[0017] In another exemplary embodiment, the second section of the tapered region has a conical taper that increases in diameter proximally.

[0018] In another exemplary embodiment, the third section of the tapered region has a conical taper that increases in diameter proximally.

[0019] In another exemplary embodiment, the third section of the tapered region has a conical taper that increases in diameter proximally at an angle greater than the conical taper of the second section.

[0020] In another exemplar ' embodiment, the impeller comprises an enlarged region between the tapered region and the drive region.

[0021] In another exemplary embodiment, the tapered region transitions into the enlarged region at a chamfered radius.

[0022] In another exemplary embodiment, the drive region is cylindrical.

[0023] In another exemplary embodiment, the drive region comprises a partially hollow interior.

[0024] In another exemplary embodiment, the hollow interior of the drive region comprises a hexagonal cross-section profile.

[0025] In another exemplary embodiment, all external surfaces of the impeller have a surface roughness average of 0.4 micrometers or less.

[0026] In another exemplary embodiment, the flat blade region has a surface roughness average of 0.04 micrometers or less.

[0027] In another exemplary embodiment, the impeller comprises stainless steel.

[0028] In another exemplary7embodiment, the impeller comprises 316 stainless steel.

[0029] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Additional features and advantages of the disclosed technology will be made apparent from the following detailed description of illustrative embodiments that proceeds with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The foregoing and other aspects of the present invention are best understood from the following detailed description when read in connection with the accompanying drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments that are presently preferred, it being understood, however, that the invention is not limited to the specific instrumentalities disclosed. Included in the drawings are the following Figures:

[0031] FIG. 1 depicts a perspective view of the impeller, showing the cylindrical drive region at the top, the tapered transition region, and the flat blade region extending longitudinally, according to an embodiment of the present disclosure.

[0032] FIG. 2A depicts a detailed perspective view of the flat blade region of the impeller, according to an embodiment of the present disclosure.

[0033] FIG. 2B depicts a detailed perspective view of the flat blade region of the impeller with exemplar}' measurements, according to an embodiment of the present disclosure.

[0034] FIG. 3 A depicts a side view of the impeller, the perspective depicting the flat blade face, according to an embodiment of the present disclosure.

[0035] FIG. 3B depicts a side view of the impeller, the perspective depicting the flat blade face with exemplary measurements, according to an embodiment of the present disclosure.

[0036] FIG. 4A depicts a cross-sectional side view of the impeller, showing the hollow interior and the sidewalls of the flat blade section, according to an embodiment of the present disclosure.

[0037] FIG. 4B depicts a cross-sectional side view of the impeller with exemplary measurements, showing the hollow interior and the sidewalls of the flat blade section, according to an embodiment of the present disclosure.

[0038] FIG. 5A depicts a view from the distal end of the impeller, showing the flat blade section from the axial perspective, according to an embodiment of the present disclosure.

[0039] FIG. 5B depicts a view from the distal end of the impeller with exemplary measurements, showing the flat blade section from the axial perspective, according to an embodiment of the present disclosure.

[0040] FIG. 6A depicts a view from the proximal end of the impeller, showing the internal bore, according to an embodiment of the present disclosure.

[0041] FIG. 6B depicts a view from the proximal end of the impeller with exemplar}' measurements, showing the internal bore, according to an embodiment of the present disclosure.

[0042] FIG. 7 depicts an "off-center" alignment of impellers within reaction vessels during the mixing process, according to an embodiment of the present disclosure. On the left, the present invention impeller is depicted, while on the right, an impeller without taper is shown for comparison.

[0043] FIG. 8 depicts two impellers positioned in narrow reaction vessels during the mixing process, showing a comparison between an impeller with a tapered region (on the left) and an impeller without a tapered region (on the right).

[0044] FIG. 9 depicts two impellers being retracted from a solution, showing a comparison between an impeller with a tapered region (on the left) and an impeller without a tapered region (on the right).DETAILED DESCRIPTION

[0045] The present disclosure pertains to an impeller that incorporates pressure relief geometry to improve the mixing process. The impeller’s geometry is configured to maintain fluid homogeneity over a wide range of operating conditions. The impeller minimizes air bubble formation and reduces liquid carryout when the impeller is removed from a reaction vessel. This design allows for more reliable mixing, even when the impeller is not perfectly centered within the reaction vessel. The ability of this impeller to perform efficient mixing across a range of vessel alignments and rotational speeds offers enhanced performance in fluid mixing and reduces the sensitivity to misalignment, operating solely through rotational motion without the need for translational movement along the X, Y, or Z axes.

[0046] In some embodiments, as depicted in FIG. 1, an impeller 100 comprises three primary’ components to its structure: a flat blade region 200, a tapered region 300, and a drive region 400.

[0047] For clarity, the “distal end” of the impeller refers to the end that includes the blade tip, while the “proximal end” refers to the ends that includes the drive region. As shown in FIGs. 3B and 4B, Datum A corresponds to the central rotational axis of the impeller. Various geometric tolerances, including perpendicularity, flatness, and circular runout, are defined relative to Datum A. Datum B corresponds to planes perpendicular to Datum A, serving as secondary’ references for describing features of the impeller, such as the drive region’s proximal surface.

[0048] The flat blade region 200 comprises a generally rectangular cross-sectional blade extending outward from the central axis of the impeller, where the width of the blade is greater than its thickness. The term “generally rectangular” refers to a cross-section where the front and back faces of the blade are substantially parallel and broader in dimension than the narrower sidewalls. That is, the faces of the blade are wider than the sidewalls between the faces (i.e. the blade has an elongated cross section when viewed in the direction of the axis defined by Datum A). It should be noted that this term is not intended to exclude cross sections where a filet or chamfer exists at two comers of the faces and sidewalls. In some embodiments, a rounded filet is placed at the comers of the parallel faces and the sidewalls of the blade (e.g., FIGs. 5A and 5B). leaving a generally rectangular cross section having rounded comers. Insome embodiments, the filet radius is such that the sidewalls are entirely radiused forming an obround cross section, which may be referred to as generally rectangular with fully radiused sidewalls. It should be appreciated that the degree of fileting at the comers of the generally rectangular blade cross section (and how large a portion of the sidewall is straight / flat) is a design choice that depends on the application. This blade is dimensioned to fit within standard reaction vessels. The longitudinal extension of the flat blade 200 promotes the formation of a vortex during rotation, ensuring uniform mixing of the reaction fluid.

[0049] The tapered region 300 is located proximally to flat blade region 200. The tapered region 300 increases in cross-sectional area as it transitions proximally away from the blade to the drive region 400. This taper minimizes fluid carryout and reduces air bubble formation by causing consistent fluid flow during both mixing and impeller extraction. The taper avoids sharp changes in geometry, which could otherwise induce turbulence, and allows the impeller to maintain a smooth and uninterrupted fluid flow.

[0050] The cylindrical drive region 400 is located proximally to the tapered region 300, at the proximal end of the impeller 100, and connects directly to a rotational drive mechanism.

[0051] In some embodiments, as depicted in FIG. 2A, the impeller 100 comprises a flat blade region 200. This flat blade region 200 has a generally rectangular cross-section, where the width of the blade is greater than its thickness. The rectangular shape maximizes the surface area that interacts with the fluid.

[0052] In some embodiments, the flat blade region 200 is dimensioned to fit within standard reaction vessels and / or vessels, such as a cuvette, used for low-volume fluid applications. Its width may approach, but not exceed, the internal diameter of the reaction vessel, allowing the impeller to mix the fluid effectively without contacting the vessel walls. The thickness of the blade is kept minimal to reduce the drag forces during rotation, yet sufficient to maintain structural integrity at high rotational speeds. In an exemplary embodiment, the cuvette has a cross section of roughly 7mm x 3mm. In an exemplary embodiment, the cuvette has a cross section of 2-8 mm x 2-4 mm. Other cuvette dimensions are of course possible, and impeller dimensions should be selected to fit within the cuvette without impacting the sides during normal operation.

[0053] The flat blade region extends longitudinally from the proximal end, or transition end 210, which is connected to the tapered region 300, to a blade tip 250. In some embodiments, the flat blade region 200 is longer than it is wide.

[0054] In some embodiments, as depicted in FIG. 2A, the flat blade region 200 comprises a blade tip 250, sidewalls 230. and front and back faces 240 of the blade. At the distal end of the flat blade region 200, the geometry is characterized by a rounded blade tip 250 that integrates the sidewalls 230 and the front and back faces 240 of the blade. The blade’s distal portion exhibits a curve along its perimeter, which rounds into the front and back faces 240, as well as the curved sidewalls 230. In some embodiments, as depicted in FIG. 2A, the blade tip 250 and the sidewalls 230 are flat. In some embodiments the edges of the blade are fdeted to create smooth transitions between faces, the tip, and the sidewalls with a constant or varying radius to minimize turbulence or cavitation created by the edges at high speeds, such as shown in FIG. 2B.

[0055] In some embodiments, as depicted in FIG. 2B, the front and back faces 240 transition into the sidewalls 230 at a radius of about 0.25 mm. In some embodiments, the front and back faces 240 transition into the blade tip 250 at a radius of about 0.25 mm. In some embodiments, as depicted in FIG. 3B, the blade tip 250 comprises a radius of about 0.36 mm.

[0056] The flat blade region’s 200 longitudinal length and the rectangular cross-section contribute to the vortex motion that drives the homogeneous mixing of fluids without requiring any translational motion along the X, Y, or Z axes. Additionally, this geometry helps to minimize the formation of air bubbles during mixing, as the blade's wide face displaces fluid outward effectively. The curved transition from the front and back faces 240 to the sidewalls 230 helps to reduce the likelihood of air becoming trapped along the blade's surfaces during operation.

[0057] In some embodiments, the front and back faces 240 of the blade at this region are flat, extending longitudinally along the blade’s length. In some embodiments, as the blade approaches its blade tip 250. the flat surfaces begin to gently curve inward, forming a smooth rounded termination at the very tip of the blade. In some embodiments as the blade approaches its blade tip 250, the flat surfaces begin to gently curve inward, until they reach a flat blade tip 250. In some embodiments, as depicted in FIG. 2A, this flat blade tip 250 curves up proximally and forms flat side walls 230. The sidewalls 230. which form the narrower dimension of the blade, also curve inw ard toward the front and back faces 240.

[0058] In some embodiments, the transition of the curved sidewalls 230 into the rounded blade tip 250 is smooth and continuous, without sharp edges. The overall geometry of the blade tip 250 is a rounded profile. The transition is gradual, with the front and back faces 240 converging into the curved sidewalls 230 to form a unified rounded end.

[0059] Moving proximally from the rounded blade tip 250, the sidewalls 230 extend vertically along the length of the blade. These sidewalls 230 are thinner in cross-section compared to the width of the front and back faces 240. As the sidewalls 230 extend upward, their curvature / fdeting towards the front and back faces 240 remains consistent, in some embodiments.

[0060] The front and back faces 240 extend longitudinally and form the broader dimension of the flat blade region 200. These faces 240 are flat and parallel to one another, providing a wide surface area. The cross-section of the blade is elongated and close to rectangular (with rounded comers in most embodiments), with the thickness between the faces 240 being smaller than the width between the sidewalls 230. This creates a flatter, broader profile when viewed from the side, as depicted in FIG. 3A, which contrasts with the thinner side view created by the narrow dimension between the sidewalls, as depicted in FIG. 4A. In some embodiments, as depicted in FIG. 5B, the width of the flat blade region is about 2.00 mm.

[0061] As depicted in FIG. 2A, moving proximally from the flat blade region 200 towards the tapered region 300, there is a distinct geometric shift, or a transition region 210. between the flat blade region 200 and the tapered region 300. The sidewalls 230 of the flat blade region 200 start to narrow and taper inward towards the cylindrical axis of the impeller. In some embodiments, such as shown in FIG. 2A, the transition for the sidewalls 230 to the rounded cross section of tapered region 300 occurs more distally compared to the transition for the front and back faces 240. In some embodiments, as depicted in FIG. 4B, the length of the sidewall transition region is about 0.74 mm. As the sidewalls 230 taper, they curve inwards towards the cylindrical axis, gradually reducing the width of the blade’s profile. In contrast to the sidewalls 230, the front and back faces 240 of the blade region 200 taper outward and taper more proximally. As the sidewalls 230 taper inward, the proximal planes of the front and back faces 240 round away from the center line. The front and back faces 240 taper outward at a more proximal point, in a plane perpendicular to the taper of the sidewalls 230. In some embodiments, as depicted in FIG. 3B, the length of the front and back face 240 transition region 210 is about 0.45 mm. Thus, the sidewalls 230 curve inward more distally, while the front and back faces 240 taper outward more proximally.

[0062] In some embodiments, as depicted in FIG. 4B, the flat blade region 200 has a length of about 6.8 mm from the distal end to the proximal end of the transition region 210. In some embodiments, as depicted in FIG. 5B, the flat blade region 200 has a width, from sidewall tosidewall, of about 2 mm. In some embodiments, as depicted in FIG. 5B, the flat blade region 200 has a width, between front and back faces 240, of about 0.8.

[0063] As depicted in FIG. 1, proximal to the transition region 210, the sidewalls 230 and the front and back faces 240 converge into a multi-segmented taper region 300, which comprises three distinct geometric sections, moving proximally from the flat blade region 200. This transition provides a gradual transformation in shape and cross-sectional area between the flat blade region 200 and the cylindrical drive region 400. The first section 310, located proximally to the transition region, is a cylindrical portion. This section does not taper and maintains a consistent circular cross-section. It serves as an intermediary region, connecting the transition region 210 of flat blade region 200 with the subsequent tapering sections. The second section 320 features a slight taper, where the diameter of the impeller 100 begins to gradually widen as it progresses proximally. This section provides a moderate increase in cross-sectional area. The third section 330 exhibits a more pronounced taper, where the diameter increases more significantly. This conical taper leads into an extended region 500 of the impeller and eventually transitions to the drive region 400.

[0064] In some embodiments, as depicted in FIG. 3 A, the first section 310 of the tapered region has a smaller diameter compared to the sidewall-to-sidewall width of the flat blade region 200. In some embodiments, as depicted in FIG. 4A, the first sect on 310 of the tapered region has a larger diameter compared to the front-to-back face width of the flat blade region 200. In some embodiments, as depicted in FIG. 3B, the diameter of the first section 310 of the tapered region is about 1.3 mm. In some embodiments, the length of the first section 310 of the tapered region to the more distal portion of the transition region 210 where the front and back faces begin to taper is about 7.24 mm. In some embodiments, as depicted in FIG. 3B, the length from the more proximal end of the first section 310 of the tapered region to the distal end is about 13.3 mm.

[0065] In some embodiments, the second section 320 of the tapered region 300 features a slight taper, where the diameter begins to gradually widen as it progresses proximally. In some embodiments, as depicted in FIG. 3B, the second section 320 of the tapered region grows in diameter from a diameter of about 1.3 mm at its distal end to a diameter of about 2 mm at its proximal end. In some embodiments, the length of the second section 320 of the tapered region is about 10 mm.

[0066] In some embodiments, the third section 330 of the tapered region 300 exhibits a more pronounced taper, where the diameter increases more significantly. This conical taperleads into the extended region 500 of the impeller and facilitates the transition to the larger diameter of the drive region 400. In some embodiments, as depicted in FIG. 3B, there is an initial chamfered taper from the second tapered region 320 to the third tapered region 330 at about a 3.41 mm radius. In some embodiments, as depicted in FIG. 3B, there is about a 6.76 degree taper from the more distal end of the third section 330 of the tapered region 300 to the more proximal end of the third section 330 of the tapered region 300. In some embodiments, the more distal end of the third section 330 of the tapered region 300 is about 2 mm. In some embodiments, the more proximal end of the third section 330 of the tapered region 300 is about 4 mm. In some embodiments, the length of the third section 330 of the tapered region 300 is about 9.5 mm.

[0067] In some embodiments, as depicted in FIG. 3A. the third section 330 comprises a distal cylindrical end that transitions proximally into a tapered end.

[0068] The smaller cross-sectional area at the distal end of the tapered region 300 reduces capillary action between the impeller 100 and the inner surface of the reaction vessel, minimizing fluid carryout during extraction, particularly in low-volume laboratory reactions. The taper provides a continuously narrowing surface that directs fluid back into the vessel, preventing liquid from adhering to the impeller during removal. This helps maintain the accuracy of the fluid volume and reduces turbulence within the vessel. In addition to reducing fluid carryout, the segmented tapered region plays a role in reducing air bubble entrainment. The gradual reduction in cross-sectional area and the elimination of abrupt changes in geometry prevent sudden pressure buildups near the liquid-air interface, reducing the risk of air pocket formation. The segmented tapered region also contributes to the structural integrity of the impeller. By avoiding sharp transitions and using gradual geometric changes between the flat blade region and the cylindrical drive, the transition minimizes stress concentrations. This design helps to ensure that the impeller withstands high rotational speeds while maintaining mechanical stability during mixing operations.

[0069] In some embodiments, as depicted in FIG. 1, just before the drive region 400, there is an enlarged region 500. This enlarged region 500 has a diameter along its length, which is significantly wider than both the distal tapered section 330 and the more proximal drive section 400. In some embodiments, this enlarged region 500 comprises concentric grooves or rings that wrap around its outer circumference, forming several distinct ridges. The enlarged region 500 transitions into the drive region 400 at its proximal end.

[0070] In some embodiments, as depicted in FIG. 3B, the enlarged region comprises a chamfered radius of about 0.2 mm from its widest diameter to a flat portion that transitions to the drive region and / or the third section of the tapered region.

[0071] In some embodiments, as depicted in FIG. 4B, there is a chamfered radius of about 0.4 mm from the third section of the tapered region 330 into the enlarged region 500. In some embodiments, the enlarged region 500 has a diameter of about 7 mm. In some embodiments, the enlarged region is about 1.6 mm long, from its proximal end to its distal end. In some embodiments, there is a chamfered radius from the enlarged region 500 to the drive region 400. In some embodiments, the chamfered radius from the enlarged region 500 to the drive region 400 is a max of 0.1 mm. In some embodiments, the enlarged region 500 transitions to the drive region 400 at about a 90-degree angle.

[0072] In some embodiments, as depicted in FIG. 1, the most proximal section of the impeller comprises a drive region 400 with a hollow interior. In some embodiments, the drive region 400 engages with a drive mechanism.

[0073] In some embodiments, the drive region 400 is positioned at the proximal end of the impeller 100 and serves as the primary interface between the impeller 100 and a rotating drive mechanism. In some embodiments, the drive region 400 comprises a cylindrical cross-section with a hollow interior, designed to engage with the drive mechanism. In some embodiments, as depicted in FIG. 1 and FIG. 6A, the internal surface of the drive region 400 includes a hexagonal internal profile, which can be used to secure a corresponding hexagonal drive shaft. The length of the drive region 400 is sufficient to provide structural integrity and maintain the impeller’s 100 attachment to the drive mechanism during operation. This length is optimized to ensure secure attachment without increasing the overall profile of the impeller 100.

[0074] In some embodiments, as depicted in FIG. 3B. the drive region 400 is about 15 mm in length. The diameter of this drive region 400 is about 4 mm.

[0075] In some embodiments, the drive region 400 comprises an interior that is at least partially hollow. This hollow region 420 is visible in the cross-sectional view depicted in FIG.4B. where the length of the hollow region 420 is indicated as about 5.93 mm. In some embodiments, as depicted in FIG. 6B, the hollow region may be hexagonal in shape. The wall-to-wall length of the hexagon, measured from one flat side to the opposite flat side, is about 2.68 mm.

[0076] In some embodiments, as depicted in FIG. 4A, the distal end of the hollow region 420 comprises a pilot hole for engaging with a rotary broach. In some embodiments, asdepicted in FIG. 6B, the pilot hole for rotary' broach processes comprising a diameter of 2.75 mm.

[0077] In some embodiments, as depicted in FIG. 3B, the proximal end of the drive region 400 chamfers at a radius of about 0.28 mm to a proximal end of the impeller 100.

[0078] In some embodiments, as depicted in FIG. 3B. the impeller is 49.4 mm in length, from the distal end of the blade tip 250 to the proximal end of the drive region 400. In some embodiments, the impeller is 48.4 mm in length, from the proximal end of the blade tip 250 to the proximal end of the drive region 400. In some embodiments, as depicted in FIG. 4B, the impeller is 43.33 mm in length from the distal end of the transition region 210 to the proximal end of the drive region 400.

[0079] The drive region plays a role in the overall balance and stability of the impeller. By maintaining a consistent, circular geometry; the drive region helps distribute forces evenly across the impeller during rotation. This balance prevents wobbling or uneven wear, particularly when the impeller is operating at high rotational speeds. The design also allows for easy maintenance and replacement of the impeller, as the drive interface can be standardized across different mixing systems.

[0080] In some embodiments, the mixing process facilitated by the impeller design is based on rotational motion, allowing for efficient fluid mixing without the need for any translational movement along the X, Y, or Z axes. In some embodiments, the impeller can operate within a rotational speed range between 3,000 and 12,000 revolutions per minute (RPM). This range allows for flexibility in achieving optimal mixing conditions for different fluids, including those with vary ing viscosities and densities.

[0081] As a non-limiting example, a typical mixing cycle using the impeller may last between 500 to 650 milliseconds, providing sufficient time to homogenize the fluid volume within low-volume reaction vessels while minimizing the risk of over-mixing or damage to sensitive biological or chemical samples.

[0082] During the mixing process, the drive region serves as the interface between the impeller and a drive mechanism, maintaining consistent rotational forces. Exemplary drive mechanisms include, but are not limited to, direct drive motors, magnetic couplings, and belt-driven systems.

[0083] The rotational motion of various embodiments of the impeller induces a vortex within the fluid, promoting the homogeneity of the fluid mixture. The smooth, continuous taper minimizes air bubble formation, which is particularly important where air bubbles couldinterfere with optical or photometric measurements or alter reaction volumes. The mixing process parameters, including speed, duration, impeller geometry and rotational motion, ensure that fluid homogeneity is achieved efficiently while preventing common issues such as air bubble entrainment and excess fluid carryout. This allows reliable, repeatable mixing results across a range of conditions.

[0084] The tapered region 300 also enhances mixing efficiency by providing a smooth, uninterrupted flow of fluid around the impeller. The gradual reduction in cross-sectional area along the taper ensures that turbulence and air entrainment is minimized. This transition reduces the chance of fluid stagnation or uneven flow, which could otherwise lead to incomplete mixing or the formation of air bubbles. The taper also allows the impeller to maintain a steady flow of fluid, regardless of the alignment of the reaction vessel or slight misalignments of the impeller itself.

[0085] In contrast to conventional designs that require precise alignment of the impeller within the reaction vessel to achieve optimal mixing, this impeller design exhibits reduced sensitivity to such factors. The structural properties of the flat blade and tapered regions work together to maintain fluid movement, even when the impeller is not perfectly centered within the vessel.

[0086] Fluid carry' out is a common issue in low-volume reaction vessels, where even small amounts of liquid adhering to the impeller during extraction can alter the total fluid volume and impact the accuracy of analytical results. The design of this impeller mitigates this issue. For example, the tapered region reduces fluid carryout by creating a narrowing surface as the impeller is withdrawn from the reaction vessel. This geometry' directs excess fluid back into the vessel rather than allowing it to adhere to the impeller and be carried out upon extraction. The continuous taper prevents abrupt changes in the impeller’s geometry that could cause fluid to be trapped or retained on the surface of the blade. This tapering is especially effective in preventing capillary action at the junction between the impeller and the vessel wall, which could otherwise contribute to unwanted fluid retention. Capillary action from small spaces between the surfaces of the impeller and the walls of the vessel causes fluid adhesion. By using a taper to increase the distances between the shaft of the impeller and the walls, this effect can be reduced, as shown in FIG. 8.

[0087] The tapered region plays a role in limiting w ash w ater retention. As the impeller is removed from the wash basin, the taper directs any residual liquid along its narrowing surface, allowing gravity and cohesion to return the liquid to the basin rather than carrying it to the nextreaction vessel. The tapered transition geometry allows wash water to be 'shed' more efficiently thus reducing water carry over to vessels after cleaning. This feature helps to maintain the purity of the reaction mixture and to ensure that unwanted dilution or contamination does not occur.

[0088] In some embodiments, the impeller is constructed from 316 stainless steel, or other similar materials selected for corrosion resistance, mechanical strength, and compatibility with a variety of chemical and biological environments typically encountered in laboratory applications. The high corrosion resistance of 316 stainless steel makes it particularly well-suited for use in environments where exposure to corrosive agents, such as acidic or basic reagents, is common. Additionally, this material exhibits significant resistance to pitting and crevice corrosion.

[0089] In some embodiments, the hollow region 420 may be comprised of materials other than 316 stainless steel.

[0090] 316 stainless steel is particularly appropriate for use in fluid mixing applications where the impeller may be exposed to harsh chemicals or biological reagents. Its high mechanical strength ensures that the impeller maintains its structural integrity during highspeed operation, where rotational forces can exert significant stress on the component. 316 stainless steel also allows the impeller to withstand elevated temperatures that may be encountered during sterilization procedures, such as autoclaving. Its thermal stability ensures that the impeller does not warp, degrade, or lose its structural properties during repeated heating and cooling cycles.

[0091] In some embodiments, certain surfaces of the impeller are electropolished to achieve a surface roughness average (RA) of 0.04 micrometers or lower in designated areas. In some embodiments, as depicted as Zone A in FIG. 3B, the impeller is electropolished to an RA of 0.04 micrometers or lower from the distal end of the impeller to at least a portion of the third section of the tapered region. In some embodiments, as depicted in FIG. 3B, Zone A is about 26.53 mm in length.

[0092] Electropolishing is an electrochemical process that removes a thin layer of material from the surface of the stainless steel, resulting in an ultra-smooth, corrosion-resistant finish. The primary function of electropolishing in this context is to reduce the surface roughness of the impeller, which significantly minimizes the retention of fluids, particles, and contaminants on the impeller surface.

[0093] Electropolished surfaces exhibit improved cleanliness and sterility, as the smooth finish reduces the likelihood of fluid adherence and microbial attachment, both of which are critical for applications in biochemical assays and sterile environments. The RA of 0.04 micrometers helps to ensure that the surface is sufficiently smooth to prevent the formation of surface imperfections that could trap fluid during operation or create points of corrosion over time.

[0094] This smooth surface finish also plays a role in reducing capillary action between the impeller and the inner walls of the reaction vessel. The reduced surface roughness limits the area available for fluid retention, ensuring that any fluid adhering to the impeller is minimized during the mixing, washing, and extraction phases. By minimizing fluid retention, the electropolished surface also helps to maintain the accuracy of the reaction volume within the vessel, contributing to more consistent and reliable analytical results.

[0095] The impeller design specifies different levels of surface finish depending on the functional requirements of each region. In some embodiments, the flat blade region and the first and second portions of the tapered transition region are electropolished to an RA of 0.04 micrometers or lower. These regions may be in direct contact with the fluid during mixing and, as such, benefit from a smoother surface that reduces fluid retention, prevents contamination, and ensures consistent fluid dynamics during operation.

[0096] In some embodiments, certain surfaces, such as those areas not in direct contact with the fluid, may have a roughness average of up to 0.4 micrometers or lower. While still relatively smooth, these surfaces are not required to be electropolished to the same degree as the fluid-contact regions, as they do not directly influence the mixing efficiency or cleanliness of the impeller.

[0097] The electropolished surfaces and the streamlined geometry of the present impeller, particularly in the tapered transition region, significantly reduce drag forces during rotation. Namely, the geometry of various embodiments reduces fluid flow restriction between impeller and reaction vessel sidewall. This design helps to ensure a smooth flow of fluid throughout the mixing process, providing uniform vortex formation without the turbulence that is often observed in impellers with abrupt transitions in cross-sectional area.

[0098] In some embodiments, the impeller is optimized for vessels containing fluid volumes ranging from 80 to 250 microliters. The dimensions of the flat blade region, tapered transition region, and cylindrical drive region can be adjusted to accommodate larger or smaller vessels.

[0099] For larger reaction vessels, the width and length of the flat blade region can be increased proportionally to ensure sufficient surface area for effective fluid displacement. The larger surface area would promote more robust vortex formation, ensuring homogeneity of the fluid mixture even in volumes exceeding 250 microliters. The length of the tapered transition region can also be adjusted to maintain smooth fluid dynamics, with a longer taper required to support the increased blade size without introducing turbulence.

[0100] Similarly, for smaller reaction vessels, the impeller’s flat blade and cylindrical drive regions can be reduced in size. In these instances, the transition region may be shortened to minimize the impact on fluid flow and ensure that the smaller blade can still generate sufficient vortex motion without causing excessive shear forces on sensitive biological or chemical samples.

[0101] In some embodiments, alternative materials and surface coatings may be used. For example, in scenarios where weight reduction is critical, such as in microfluidic applications or portable laboratory equipment, lightweight materials such as titanium alloys or high-performance polymers (e.g.. PEEK) may be used. Titanium can help maintain the structural integrity of the impeller while reducing the overall mass of the device.

[0102] In certain chemical applications where specific reagents may react with metals, alternative coatings or materials such as polytetrafluoroethylene or other chemically inert coatings can be applied to fluid-contact areas of the impeller. These coatings can enhance the impeller’s resistance to a wider range of chemical reagents, including strong acids, bases, and organic solvents. Additionally, the use of ultra-smooth coatings could further reduce the likelihood of fluid adherence and carryover during the extraction process.

[0103] In applications requiring highly sterile conditions, such as pharmaceutical manufacturing or biochemical assays involving cell cultures, an antimicrobial surface coating could be applied to the impeller. These coatings could help inhibit the growth of microbes on the impeller surface, reducing the risk of contamination between samples or during extended operation in a sterile environment.

[0104] The angle and length of the tapered transition region may be modified based on the specific requirements of the mixing process. In applications where minimizing fluid carryout is important, a longer and more gradual taper could be employed. This would further reduce fluid adherence to the impeller during extraction by allowing the fluid to drain back into the vessel more effectively. In contrast, in applications where rapid mixing is required, the taper angle could be increased slightly to promote faster fluid flow through the transition region,potentially enhancing the speed at which the fluid reaches a homogeneous state. These adjustments could be particularly useful in industrial processes where throughput is a priority, and multiple reaction vessels are processed in quick succession.

[0105] In some embodiments, the impeller is adapted for alternative drive configurations based on the specific requirements of the mixing apparatus. For instance, in specialized laboratory setups where axial movement is incorporated alongside rotational movement, the drive region can be modified to include a keyed or slotted interface, allowing for both rotational and limited translational motion.

[0106] For laboratory7systems utilizing magnetic or non-contact drive mechanisms, the impeller's cylindrical drive region could be adapted with integrated magnetic elements or ferromagnetic coatings, allowing the impeller to be driven magnetically, without the need for a physical connection to a drive shaft. Such a modification is beneficial in systems where sterility' or isolation of the mixing vessel is required, as it eliminates the need for direct contact between the impeller and the drive system.

[0107] In some embodiments, electropolishing can be selectively applied to different regions of the impeller, allowing for varying levels of surface roughness depending on the functional requirements of each section. For example, while the flat blade region may require the lowest surface roughness to minimize fluid adherence, the drive region can tolerate a slightly rougher finish if it enhances the impeller's engagement with the drive mechanism.

[0108] The impeller described herein can be customized and adapted to meet the specific requirements of various laboratory and industrial applications. Whether through adjustments to the dimensions of the flat blade and tapered transition regions, the use of alternative materials or surface coatings, or the incorporation of modified drive configurations, the impeller can be tailored to enhance its performance across a wide range of fluid mixing scenarios. The design's flexibility allows it to be optimized for specific vessel sizes, chemical environments, and operational conditions.Exemplary Embodiments

[0109] The following non-limiting examples demonstrate the improved functionality of the disclosed impeller design, particularly with respect to fluid dynamics, air entrainment prevention, capillary action mitigation, and fluid cany' out reduction. These examples are illustrated in FIGs. 7-9.

[0110] FIG. 7 depicts the effect of the improved impeller geometry on fluid flow during mixing, particularly in cases of slight misalignment relative to the reaction vessel centerline.Misalignment, or “off-center’" alignment, can exacerbate meniscus displacement, air entrainment, and bubble formation, all of which interfere with analytical processes such as photometric reads.[OHl] In FIG. 7, two impellers are depicted. On the left, the impeller geometry of the present disclosure (labeled “A”) includes a tapered region. This taper facilitates fluid flow around the impeller shaft, maintaining a smooth, uniform meniscus without air entrainment or bubble formation. On the right, a comparative impeller lacking the taper feature (labeled “B”) disrupts the meniscus. Pressure builds up around the impeller shaft, displacing the meniscus and causing air entrainment and bubble formation, which can adversely impact analytical accuracy.

[0112] The improved geometry of the present disclosure significantly reduces sensitivity to misalignment, allowing consistent performance across varying positions within the vessel.

[0113] FIG. 8 depicts the effect of the impeller geometry' on capillary action between the impeller shaft and the reaction vessel wall, a common source of fluid carryout during impeller extraction.

[0114] In FIG. 8, two impellers are shown. On the left, the impeller of the present disclosure (labeled “A”) comprises a reduced drive shaft - or tapered region - diameter, which mitigates capillary' action. This prevents fluid from adhering to the impeller shaft and being carrier out of the vessel during removal. On the right, a comparative impeller with a larger, untampered drive shaft diameter (labeled “B”) allows fluid adherence via capillary action. This fluid retention can lead to volume loss, impacting analytical precision.

[0115] The reduced diameter and tapered geometry' ensure minimal fluid carryout, preserving reaction integrity.

[0116] FIG. 9 depicts the improved impeller geometry during retraction from a wash basin, highlighting the reduction in residual wash fluid retention.

[0117] In FIG. 9, two impellers are shown retracting from a wash vessel. On the left, the impeller of the present disclosure (labeled “A”) demonstrates improved dry ing characteristics facilitated by the tapered geometry’. Residual wash fluid is directed back into the wash basin, minimizing carry over into subsequent reaction vessels. On the right, a comparative impeller with an untapered geometry (labeled “B”) exhibits greater fluid retention, increasing the risk of contamination or dilution in subsequent processes.

[0118] The tapered design optimizes fluid drainage during removal, enhancing the purity and accuracy of downstream processes.

[0119] These exemplary' embodiments demonstrate the ability of the disclosed impeller geometry to 1) mitigate air entrainment and bubble formation during mixing, even with slight misalignment (FIG. 7); 2) reduce fluid carryout during extraction by preventing capillary action (FIG. 8); and 3) minimize wash fluid retention during impeller retraction (FIG. 9).

[0120] These features collectively contribute to the impeller's superior performance across various mixing, extraction, and washing scenarios, ensuring accurate and consistent analytical results.

[0121] The elements of the figures are not exclusive. Other embodiments may be derived in accordance with the principles of the invention to accomplish the same objectives. Although this invention has been described with reference to particular embodiments, it is to be understood that the embodiments and variations shown and described herein are for illustration purposes only. Modifications to the cunent design may be implemented by those skilled in the art, without departing from the scope of the invention.

[0122] While various illustrative embodiments incorporating the principles of the present teachings have been disclosed, the present teachings are not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the present teachings and use its general principles. Further, this application is intended to cover such departures from the present disclosure that are within known or customary' practice in the art to which these teachings pertain.

[0123] In the above detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the present disclosure are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subj ect matter presented herein. It will be readily understood that various features of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety' of different configurations, all of which are explicitly contemplated herein.

[0124] The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various features. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to thoseskilled in the art from the foregoing descriptions. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0125] With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for sake of clarity.

[0126] It will be understood by those within the art that, in general, terms used herein are generally intended as “open’' terms (for example, the term “including"’ should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term "‘includes” should be interpreted as “includes but is not limited to,” et cetera). While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of’ or “consist of’ the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups.

[0127] As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Nothing in this disclosure is to be construed as an admission that the embodiments described in this disclosure are not entitled to antedate such disclosure by virtue of prior invention.

[0128] In addition, even if a specific number is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (for example, the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, et cetera). In those instances where a convention analogous to “at least one of A. B, or C, et cetera” is used, in general such a construction isintended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B. or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, et cetera). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, sample embodiments, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "‘A or B” will be understood to include the possibilities of "‘A” or “B” or “A and B.”

[0129] Various of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, each of which is also intended to be encompassed.NON-LIMITING ILLUSTRATIVE EMBODIMENTS

[0130] The following is a list of non-limiting illustrative embodiments disclosed herein:

[0131] Illustrative embodiment 1. An impeller comprising: a flat blade region comprising a generally rectangular cross-section with front and back faces, sidewalls, and a blade tip at a distal end of the impeller; a transition region extending proximally from the flat blade region towards a tapered region, wherein the tapered region extends proximally from the transition region and distally towards a drive region, and wherein the drive region extends to a proximal end of the impeller.

[0132] Illustrative embodiment 2. The impeller of illustrative embodiment 1, wherein, at a proximal end of the flat blade region and as the transition region extends proximally, the sidewalls curve inward toward a central longitudinal axis of the impeller and the front and back faces of the flat blade region curve outward away from the central longitudinal axis of the impeller.

[0133] Illustrative embodiment 3. The impeller of illustrative embodiment 2, wherein the inward curvature of the sidewalls occurs more distally than the outward curvature of the front and back faces.

[0134] Illustrative embodiment 4. The impeller of illustrative embodiment 1, wherein the flat blade region is laterally wider from sidewall to sidewall than it is thick from front face to back face.

[0135] Illustrative embodiment 5. The impeller of illustrative embodiment 1, wherein the flat blade region is longer from the blade tip to a proximal end than it is laterally wide from sidewall to sidewall.

[0136] Illustrative embodiment 6. The impeller of illustrative embodiment 1, wherein the front and back faces of the flat blade region curve into the sidewalls at a radius.

[0137] Illustrative embodiment 7. The impeller of illustrative embodiment 1, wherein the blade tip of the flat blade region is rounded and merges with the sidewalls and front and back faces.

[0138] Illustrative embodiment 8. The impeller of illustrative embodiment 1, wherein the tapered region comprises a first section, a second section, and a third section.

[0139] Illustrative embodiment 9. The impeller of illustrative embodiment 8, wherein the first section of the tapered region has a cylindrical profile.

[0140] Illustrative embodiment 10. The impeller of illustrative embodiment 9, wherein the first section of the tapered region has a diameter smaller than a lateral width of the flat blade region from sidewall to sidewall.

[0141] Illustrative embodiment 11. The impeller of illustrative embodiment 8, wherein the second section of the tapered region has a conical taper that increases in diameter proximally.

[0142] Illustrative embodiment 12. The impeller of illustrative embodiment 8, wherein the third section of the tapered region has a conical taper that increases in diameter proximally.

[0143] Illustrative embodiment 13. The impeller of illustrative embodiment 11, wherein the third section of the tapered region has a conical taper that increases in diameter proximally at an angle greater than the conical taper of the second section.

[0144] Illustrative embodiment 14. The impeller of illustrative embodiment 1 , wherein the impeller comprises an enlarged region between the tapered region and the drive region.

[0145] Illustrative embodiment 15. The impeller of illustrative embodiment 14, wherein the tapered region transitions into the enlarged region at a chamfered radius.

[0146] Illustrative embodiment 16. The impeller of illustrative embodiment 1 , wherein the drive region is cylindrical.

[0147] Illustrative embodiment 17. The impeller of illustrative embodiment 1 , wherein the drive region comprises a partially hollow interior.

[0148] Illustrative embodiment 18. The impeller of illustrative embodiment 17, wherein the hollow interior of the drive region comprises a hexagonal cross-section profile.

[0149] Illustrative embodiment 19. The impeller of illustrative embodiment 1, wherein all external surfaces of the impeller have a surface roughness average of 0.4 micrometers or less.

[0150] Illustrative embodiment 20. The impeller of illustrative embodiment 19, wherein the flat blade region has a surface roughness average of 0.04 micrometers or less.

[0151] Illustrative embodiment 21. The impeller of illustrative embodiment 1 , wherein the impeller comprises stainless steel.

[0152] Illustrative embodiment 22. The impeller of illustrative embodiment 21, wherein the impeller comprises 316 stainless steel.

Claims

CLAIMSWe claim:

1. An impeller comprising:a flat blade region comprising a generally rectangular cross-section with front and back faces, sidewalls, and a blade tip at a distal end of the impeller;a transition region extending proximally from the flat blade region towards a tapered region, whereinthe tapered region extends proximally from the transition region and distally towards a drive region, and whereinthe drive region extends to a proximal end of the impeller.

2. The impeller of claim 1, wherein, at a proximal end of the flat blade region and as the transition region extends proximally, the sidewalls curve inward toward a central longitudinal axis of the impeller and the front and back faces of the flat blade region curve outward away from the central longitudinal axis of the impeller.

3. The impeller of claim 2, wherein the inward curvature of the sidewalls occurs more distally than the outward curvature of the front and back faces.

4. The impeller of claim 1, wherein the flat blade region is laterally wider from sidewall to sidewall than it is thick from front face to back face.

5. The impeller of claim 1, wherein the flat blade region is longer from the blade tip to a proximal end than it is laterally wide from sidewall to sidewall.

6. The impeller of claim 1, wherein the front and back faces of the flat blade region curve into the sidewalls at a radius.

7. The impeller of claim 1, wherein the blade tip of the flat blade region is rounded and merges with the sidewalls and front and back faces.

8. The impeller of claim 1, wherein the tapered region comprises a first section, a second section, and a third section.

9. The impeller of claim 8, wherein the first section of the tapered region has a cylindrical profile.

10. The impeller of claim 9, wherein the first section of the tapered region has a diameter smaller than a lateral width of the flat blade region from sidewall to sidewall.

11. The impeller of claim 8, wherein the second section of the tapered region has a conical taper that increases in diameter proximally.

12. The impeller of claim 8, wherein the third section of the tapered region has a conical taper that increases in diameter proximally.

13. The impeller of claim 11, wherein the third section of the tapered region has a conical taper that increases in diameter proximally at an angle greater than the conical taper of the second section.

14. The impeller of claim 1, wherein the impeller comprises an enlarged region between the tapered region and the drive region.

15. The impeller of claim 14. wherein the tapered region transitions into the enlarged region at a chamfered radius.

16. The impeller of claim 1, wherein the drive region is cylindrical.

17. The impeller of claim 1, wherein the drive region comprises a partially hollow interior.

18. The impeller of claim 17, wherein the hollow interior of the drive region comprises a hexagonal cross-section profile.

19. The impeller of claim 1, wherein all external surfaces of the impeller have a surface roughness average of 0.4 micrometers or less.

20. The impeller of claim 19. wherein the flat blade region has a surface roughness average of 0.04 micrometers or less.

21. The impeller of claim 1, wherein the impeller comprises stainless steel.

22. The impeller of claim 21, wherein the impeller comprises 316 stainless steel.

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