Peristaltic pump for vacuum generation

Abstract

A peristaltic pump comprises a tube (410) in contact with one or more rollers (420), wherein the tube (410) comprises a flexible material, and wherein walls of the tube in contact with the rollers comprise notches (412). The rollers (420) each consist of a compliant outer layer (422) comprising a flexible material and a rigid inner layer (424), wherein the peristaltic pump is configured for producing a vacuum. Also disclosed is a method of making the tube (410) and rollers (420) of the peristaltic pump.

Description

RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 367,512, filed Jul. 1, 2022, and entitled “Peristaltic Pumps for Vacuum Generation,” which is incorporated herein by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] Pumps and related systems and methods, such as peristaltic pumps for vacuum generation, are generally described.SUMMARY

[0003] This Summary introduces a selection of concepts in simplified form that are described further below in the Detailed Description. This Summary neither identifies key or essential features, nor limits the scope, of the claimed subject matter.

[0004] One aspect of the disclosure herein relates to a peristaltic pump, wherein the peristaltic pump comprises a tube in contact with one or more rollers; wherein the tube comprises a flexible material; and wherein walls of the tube in contact with the rollers comprise notches.

[0005] One aspect of the disclosure herein relates to a peristaltic pump comprising a tube in contact with one or more rollers; wherein the tube comprises a flexible material; and wherein the tube is configured to prevent dead volumes when compressed by the rollers.

[0006] One aspect of the disclosure herein relates to a peristaltic pump, comprising a tube in contact with one or more rollers; wherein the tube comprises a flexible material; and wherein the tube is configured such that the peristaltic pump is capable of maintaining a vacuum when the tube is compressed by the rollers.

[0007] One aspect of the disclosure herein is a peristaltic pump, wherein the peristaltic pump comprises a tube in contact with one or more rollers; wherein the tube comprises a flexible material; wherein walls of the tube in contact with the rollers comprise notches; wherein the rollers each consist of a compliant outer layer comprising the flexible material and a rigid inner layer; and wherein the peristaltic pump is configured for producing a vacuum.

[0008] In one embodiment of the peristaltic pump disclosed herein, walls of the tube have a thickness that varies along the length of the tube.

[0009] In one embodiment of the peristaltic pump disclosed herein, the flexible material of the tube and / or the compliant outer material of the rollers and / or the rigid inner material of the rollers comprise one or more materials suitable for additive manufacturing.

[0010] In one embodiment of the peristaltic pump disclosed herein, the flexible material is Fiberflex 40D or Fiberflex 30D.

[0011] In one embodiment of the peristaltic pump disclosed herein, the rigid inner layer of the rollers comprises rigid polylactic acid-based, acrylonitrile butadiene styrene-based, or nylon-based filaments.

[0012] In one embodiment of the peristaltic pump disclosed herein, the walls of the tube in contact with rollers has two notches on opposite sides of tube, whereby the tube is configured to prevent dead volumes when compressed by the rollers.

[0013] One aspect of the disclosure herein is a method of making the tube and rollers of the peristaltic pump, comprising printing by extrusion transverse sections of a flexible material to produce a flexible tube, wherein walls of part of the tube have a notch; and a compliant outer layer of rollers; and printing by extrusion transverse sections of a rigid material to produce a rigid inner layer of rollers.

[0014] One aspect of the disclosure herein is a method of making the tube and rollers of the peristaltic pump, comprising casting a flexible material to produce a flexible tube, wherein walls of part of the tube have a notch; and a compliant outer layer of rollers; and casting a rigid material to produce a rigid inner layer of rollers.

[0015] In one embodiment, the method further comprises printing a housing, rotor, holder, lid, outer and inner layer of rollers.

[0016] In one embodiment, the method further comprises casting a housing, rotor, holder, lid, outer and inner layer of rollers.

[0017] In one embodiment of the method disclosed herein, the printing is with material comprising rigid polylactic acid-based, acrylonitrile butadiene styrene-based, or nylon-based filaments.

[0018] In one embodiment of the method disclosed herein, the flexible tube is printed vertically with a support truss structure.

[0019] One aspect of the disclosure herein relates to a method of operating a peristaltic pump, comprising compressing a flexible tube by contacting the flexible tube with one or more rollers, such that the internal walls of the tube contact each other to eliminate dead volume, and fluid is transported along the length of the tube.

[0020] One aspect of the disclosure herein relates to a method of operating a peristaltic pump, comprising compressing a flexible tube by contacting the flexible tube with one or more rollers, the flexible tube comprising one or more notches, such that fluid is transported along the length of the tube.

[0021] One aspect of the disclosure herein relates to a method of generating a vacuum using a peristaltic pump, comprising compressing a flexible tube by contacting the flexible tube with one or more rollers such that gas is transported along the length of the tube and a vacuum is generated and maintained.

[0022] In one embodiment of such peristaltic pumps and methods described herein, the flexible tube comprises notches.

[0023] In one embodiment of such peristaltic pumps and methods described herein, the one or more rollers of the peristaltic pump comprise a flexible material. In one embodiment, the flexible tube of the rollers is the same flexible material from which the tube is made.

[0024] In one embodiment of such peristaltic pumps and methods described herein, compressing the flexible tube comprises applying a pressure of less than or equal to 10 MPa. In one embodiment of such peristaltic pumps and methods described herein, compressing the flexible tube comprises applying a pressure of greater than or equal to 0.1 MPa. In one embodiment of such peristaltic pumps and methods described herein, compressing the flexible tube eliminates dead volume.

[0025] In one embodiment of the methods described herein, compressing the tube comprises generating and / or maintaining a vacuum.

[0026] In one embodiment of such peristaltic pumps and methods described herein, the fluid that is moved by the pump comprises gas and / or liquid.

[0027] The following Detailed Description references the accompanying drawings which form a part this application, and which show, by way of illustration, specific example implementations. Other implementations may be made without departing from the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure.

[0029] FIG. 1 is a schematic of a peristaltic pump.

[0030] FIGS. 2A-2B are (a) an image showing the cross-section when a tube with circular cross-section is compressed; and (b) the results of a simulation showing a tube with notches can compress with no dead volume while distributing the stress concentration, in accordance with certain embodiments.

[0031] FIG. 3 is a series of schematic illustrations showing cross-sections of a tube, in accordance with certain embodiments.

[0032] FIG. 4A is a schematic that shows an exploded view of a peristaltic pump, in accordance with some embodiments.

[0033] FIG. 4B is a schematic illustration showing the operation of a peristaltic pump, in accordance with certain embodiments.

[0034] FIG. 4C is a schematic illustration showing how tubes can be connected to a pneumatic pump, where compressing the tubes can prevent bubbles from forming on the other end, while the force required to attain this result is measured, according to some embodiments.

[0035] FIGS. 5A-5B show plots of pressure measured over time while operating a peristaltic pump, in accordance with some embodiments.

[0036] FIGS. 6A-6B are selected views of the printing of a flexible tube, with (a) showing a thin square layer that was added at the top of the tube that was printed vertically and (b) being a print preview from Simplify3D showing the support structures, in accordance with certain embodiments.

[0037] FIGS. 7A-7B show the flexible tube sealing performance, in accordance with certain embodiments, with (a) being a schematic illustration showing how the tubes were connected to a pneumatic pump; compressing the tubes prevented the bubbles from forming on the other end, while the force required to attain this result was measured; and (b) showing force versus displacement data for the three designs considered in Example 1, with the plot showing the required forces to completely compress the tubes (with the design having the largest notch requiring the least amount of force).

[0038] FIGS. 8A-8B show flexible tube fatigue experiments based on Design #2 from Example 1, in accordance with certain embodiments, with (a) showing compression force versus time; the dotted line indicating the trace of the maximum force for each peak; and (b) showing the maximum compression force versus number of cycles; with the plot showing how the max force slowly decreases and plateaus at about 150 N.

[0039] FIGS. 9A-9C are, in accordance with certain embodiments, schematics of a 3D-printed peristaltic vacuum pump and characterization apparatus, with (a) showing an exploded view schematic of the peristaltic vacuum pump developed in Example 1; (b) showing a 3D-printed peristaltic vacuum pump; and (c) showing a schematic of the setup used to characterize the performance of the peristaltic vacuum pump.

[0040] FIG. 10 shows, in accordance with certain embodiments, a plot of base pressure versus pumping period for a 3D-printed peristaltic vacuum pump using an unoptimized testing setup (large leak). FIG. 10 shows that there is a linear dependence between the base pressure and the pumping period.

[0041] FIG. 11 is a plot of pressure versus time for a 3D-printed peristaltic vacuum pump, in accordance with certain embodiments. A 9 Torr base pressure was achieved with a low actuation speed of 12 rpm. The inset shows the data as a semi-log plot, verifying that the pressure plateaus for long times of continuous operation.

[0042] FIG. 12 is a plot of mass flow rate versus pressure characteristic of the 3D-printed peristaltic vacuum pump design reported in Example 1, in accordance with certain embodiments.

[0043] FIGS. 13A-13D are related to pump temperature characterization, in accordance with certain embodiments, with (a) including an image of a 3D-printed peristaltic vacuum pump connected to the characterization apparatus; (b)-(c) showing temperatures measured with an infrared camera at t=100 s and 300 s; and (d) showing the maximum temperature plotted over time.

[0044] FIGS. 14A-14C are related to printing resolution experiments of FiberFlex 40D, in accordance with some embodiments, with (a) showing a schematic of the test structure used; (b) showing a plot of printed height versus CAD height; and (c) showing a plot of printed in-plane length versus corresponding CAD length. In the least-squares fits of (b) and (c) PD is printed dimension and CD is CAD dimension.DETAILED DESCRIPTION

[0045] Pumps and related systems and methods, such as peristaltic pumps for vacuum generation, are generally described.

[0046] Devices for moving fluids are used in a variety of applications. For example, in some cases, liquid may be pumped to condition air (e.g., in heating, ventilation, and air conditioning systems), to move fluids such as natural gas, and / or to treat the liquid for various chemical and / or biomedical applications. Another example of devices that move fluids are vacuum-generating devices (e.g., vacuum pumps), which are useful for numerous new technologies that have been developed over time that utilize vacuum environments. For instance, many analysis or fabrication methods in the nano-scale or lower should be operated in a clean and stable vacuum chamber. The semiconductor industry, in particular, must conduct most experimental steps in vacuum environments to precisely fabricate and analyze their products. Depending on the application, the method may require low-vacuum (between 760 Torr and 1 Torr) or even high vacuum (below 10−5 Torr). The difference between these vacuum ranges is enormous, and they require different steps or methods to achieve the desired vacuum.

[0047] Low-vacuum pumps are essential for applications such as backing up a high-vacuum system or regulating the pressure and flow rate of an environment not far from atmospheric conditions. While fluid-sealed pumps that use grease or mercury can improve pump performance, dry pumps are preferred for applications affected by contamination, e.g., chemical sensing. Examples of dry pumps include diaphragm, piston, and lobe pumps. Some of these pumps have important drawbacks such as complexity in their hardware and minimum pressure attainable. The most commonly used dry pumps for compact systems are diaphragm pumps, which are limited by the compression ratio of the chamber, requiring multiple chambers to reach Torr-level vacuum. Accordingly, in some cases, relatively simple devices (e.g., pumps) that may be miniaturized are needed.

[0048] Peristaltic pumps are generally based on a tube that is continuously squeezed by a set of rotating rollers. A non-limiting example of a peristaltic pump is shown in FIG. 1. Here, tube 110 in compressed by rollers 120 that rotate in direction of arrow 130 to positively displace fluid from the inlet 140 to the outlet 150. Peristaltic pumps are profusely used to move liquids in biomedical applications, but they are not typically used to create and maintain vacuum, perhaps due to the extreme deformation that is required to compress the tubes and the difficulty to manufacture more complex designs through conventional methods. However, peristaltic pumps are attractive to create vacuum as they are not limited by the compression ratio of the chamber. Furthermore, it has been recognized, within the context of the present disclosure, that the recent development of advanced additive manufacturing methods allows for fabricating complex, multi-material designs with more selection of materials. Thus, the present disclosure aims to overcome the limitations of peristaltic vacuum pumps and to develop a method of easily fabricating peristaltic pumps through additive manufacturing. Certain embodiments described herein are related to peristaltic pumps that are configured for moving fluids, for example, liquids and / or gases. In certain cases, the peristaltic pump can be used to create and / or maintain a vacuum (e.g., by moving gas(es)).

[0049] Miniaturizing the peristaltic pump may be desirable, according to some embodiments. It may be desirable to use a miniaturized peristaltic pump, for example, when integrating the peristaltic pump within relatively compact systems and / or when the system is designed to be transportable. In some cases, the volume the peristaltic pump may be less than or equal to 1000 cm3, less than or equal to 900 cm3, less than or equal to 800 cm3, less than or equal to 700 cm3, less than or equal to 600 cm3, less than or equal to 500 cm3, less than or equal to 400 cm3, or less than or equal to 300 cm3 (and / or, in some embodiments, as little as 100 cm3, as little as 50 cm3, or less.) Note that while, in some embodiments, it may be useful to miniaturize the peristaltic pump, in other cases the peristaltic pump may not be miniaturized. According to some embodiments, the volume of the peristaltic pump may be greater than or equal to 300 cm3, greater than or equal to 400 cm3, greater than or equal to 500 cm3, greater than or equal to 600 cm3, greater than or equal to 700 cm3, greater than or equal to 800 cm3, greater than or equal to 900 cm3, greater than or equal to 1000 cm3, greater than or equal to 1250 cm3, greater than or equal to 1500 cm3, greater than or equal to 1750 cm3, greater than or equal to 2000 cm3, greater than or equal to 2500 cm3, or greater than or equal to 3000 cm3. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 300 cm3 and less than or equal to 700 cm3). Other ranges are also possible.

[0050] In some embodiments, manufacturing the peristaltic pump may comprise manufacturing relatively complex parts. According to some embodiments, the relatively complex parts may be miniaturized, adding further difficulty to the manufacturing process. Advantageously, in some embodiments, it may be cheaper and / or easier to additively manufacture some and / or all the parts of the peristaltic pump.

[0051] The main limitation of using peristaltic pumps for vacuum applications probably comes from the severe deformation of the flexible tube. It is believed that every peristaltic pump to date employs tubes of circular cross-section due to the ease of fabrication through extrusion. However, these tubes have dead volume when compressed, which is shown in FIG. 2A. Specifically, FIG. 2A shows a schematic illustration of a conventional tube 210 having a circular cross-section compressed between a first block 212 and second block 214. When compressed, the walls of the circular tube 210 do not sit flush with each other, thereby leaving dead volumes 216 (volumes that remain open after compression such that fluid can be transported from a location upstream of the dead volume, through the dead volume, and to a location downstream of the dead volume). The existence of these dead volumes 216 drastically hinders the ability to produce higher vacuum, since gas can leak back into the vacuum chamber. Completely sealing the circular tube requires a much higher force that also drastically increases stress concentration where the material folds. Such high stress concentration affects the fatigue life, which leads to premature failure that greatly limits practical applications. In addition, it is difficult to maintain the tube in position when the roller rotates with high compression force. In most peristaltic pumps for liquids, an additional part is installed around the inlet and outlet of the tube to prevent the tube from sliding towards the rotating direction of the rotor.

[0052] In order to address these limitations, certain embodiments described herein involve the use of a tube with a special cross-section, one example of which is shown in FIG. 2B. FIG. 2B shows a numerical simulation of a tube 220 comprising two notches 222 between a first block 224 and a second block 226. The two notches 222 were made so that there are no dead volumes when the tube 220 is compressed 228 between the first block 224 and the second block 226. This design requires less force to fully compress than a conventional circular tube, while also distributing the stress concentration, which can improve fatigue life of the tube 220.

[0053] In accordance with certain embodiments, any of a variety of materials can be used in the tube in the peristaltic pump, given the tube is flexible and / or compressible. Non-limiting examples include Tygon® tubing (e.g., R-3603 Laboratory Tubing, R-1000 Ultra-Soft Tubing, Long Flex Life Pump Tubing), polyvinyl chloride, silicone rubber, Fiberflex 40D, and Fiberflex 30D. In some embodiments, the tube comprises a polymer (e.g., an organic polymer). In certain embodiments, the tube comprises an elastomer. According to some embodiments, the tube may comprise a thermoplastic polymer, e.g., a thermoplastic polyurethane and / or a thermoplastic polyester elastomer. In some cases, the tube may comprise a polymer comprising butylene and / or poly(alkylene ether) phthalate. In some cases, it may be particularly advantageous to use materials that are capable of being additively manufactured, e.g., Fiberflex 40D and / or Fiberflex 30D, to fabricate the tube with the notches. In some cases, the one or more rollers of the peristaltic pump may also comprise a flexible material and / or a compliant outer layer. According to some embodiments, the tube and the one or more rollers comprise the same flexible material.

[0054] In some cases, the material of the tube may have a relatively low compression set, such that the material may be compressed without its shape deforming. The compression set of an article generally refers to the amount of permanent (plastic) deformation that occurs when the article is compressed to a given deformation, for a given amount of time, at a given temperature. Compression set of an article can be measured, for example using ASTM D395. According to some embodiments, the material of the tube may have a compression set less than or equal to 10%, less than or equal to 5%, less than or equal to 1%, or less (e.g., as little as 0.1%, as little as 0.01%, or less). In some embodiments, the tube has a compression set value in one of the ranges above determined using a constant force measurement (e.g., ASTM D395 Test Method A). In some embodiments, the tube has a compression set value in one of the ranges above determined using a constant displacement measurement (e.g., ASTM D395 Test Method B).

[0055] In some embodiments, the peristaltic pump is capable of producing a vacuum (e.g., when the tube is compressed by the rollers, as described in more detail below). In some cases, producing a vacuum may comprise generating a vacuum (e.g., from ambient pressure) and / or maintaining a vacuum. In some cases, the notches on the tube allow for the use of a relatively large tube for generating and / or maintaining vacuums since they minimize and / or eliminate the dead volume of the tube. A larger tube may be useful for generating and / or maintaining lower pressure vacuums, in some cases. According to some embodiments, a larger tube may allow for the quicker generation of vacuums than when using a relatively smaller tube. In some cases, the inner diameter of the tube may be greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 4.8 mm, greater than or equal to 5 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, greater than or equal to 9 mm, greater than or equal to 9.7 mm, greater than or equal to 9.8 mm, greater than or equal to 1.5 cm, greater than or equal to 2 cm, greater than or equal to 3 cm, greater than or equal to 5 cm, or greater than or equal to 8 cm. In accordance with some embodiments, using a tube with a relatively small inner diameter may facilitate miniaturizing the peristaltic pump. In some embodiments, the inner diameter of the tube may be less than or equal to 10 cm, less than or equal to 8 cm, less than or equal to 5 cm, less than or equal to 3 cm, less than or equal to 2 cm, less than or equal to 1 cm, less than or equal to 9.8 mm, less than or equal to 9.5 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 5 mm, less than or equal to 4.8 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2 mm, or less than or equal to 1 mm. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 0.5 mm and less than or equal to 10 cm, greater than or equal to 4 mm and less than or equal to 10 cm, greater than or equal to 4.8 mm and less than or equal to 10 cm, greater than or equal to 7 mm and less than or equal to 10 cm, or greater than or equal to 9.5 mm and less than or equal to 10 cm). Other ranges are also possible.

[0056] According to some embodiments, the thickness of the walls of the tube may be relatively thin so that the tube may be compressed using a relatively small force. In some embodiments, the thickness of the walls of the tube may be greater than or equal to 0.2 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, or greater than or equal to 3 mm. In some cases, the thickness of the tube may be less than or equal to 5 mm, less than or equal to 3 mm, less than or equal to 2 mm, less than or equal to 1.5 mm, less than or equal to 1 mm, or less than or equal to 0.5 mm. Combinations of the foregoing ranges are possible. In some cases, the thickness of the walls of the tube may vary along the length of the tube. As a non-limiting example, a first portion of the tube may have walls with a thickness of 2 mm, whereas a second portion of the tube may have walls with a thickness of 5 mm. Other changes in thickness of the tube walls along the length of the tube are possible.

[0057] In accordance with some embodiments, the tube may be repetitively compressed without failing. Failing, in some embodiments, may refer to the tube cracking, fraying, and / or deforming such that it can no longer be used to generate and / or maintain a vacuum when used, for example, within a peristaltic pump. In some cases, the tube may be subjected to greater than or equal to 100,000 compression cycles, greater than or equal to 500,000 compression cycles, greater than or equal to 1,000,000 compression cycles, greater than or equal to 2,000,000 compression cycles, greater than or equal to 5,000,000 compression cycles, or greater than or equal to 10,000,000 compression cycles (and / or up to 20,000,000 compression cycles, up to 100,000,000 compression cycles, up to 1,000,000,000 compression cycles, or more) without failure. A “compression cycle” refers to a cycle of compressing a tube that is initially in an unstressed state to an extent that the tube is internally sealed with no dead volumes, followed by release of the compression such that the tube returns to an unstressed state.

[0058] In some embodiments, the tube comprises one or more notches, which may aid in eliminating dead volume upon compression of the tube. Consider the non-limiting embodiments shown in FIG. 3, which shows a cross-sectional view of a tube having radius 310 where there are no notches, a thickness of 320, and a radius 330 where the notch is present. Three exemplary, magnified cases 342, 344, and 346 of portion 340 of the tube are illustrated, specifically, wherein there is no notch 342 and two cases with a smaller notch 344 and a larger notch 346.

[0059] In some cases, a relatively large portion of the tube has a cross-section comprising one or more notches, such as the notches shown in FIG. 3. According to some embodiments, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 99%, or 100% of the length of the tube has a cross-section comprising one or more notches (such as the notches shown in FIG. 3). In some cases, a relatively large portion of the tube that contacts the roller(s) during operation of the peristaltic pump has a cross-section comprising one or more notches. According to some embodiments, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 99%, or 100% of the length of the tube that contacts the roller(s) during operation of the peristaltic pump has a cross-section comprising one or more notches (such as the notches shown in FIG. 3).

[0060] In accordance with some embodiments, a first portion of the tube may have a cross-section comprising a notch (e.g., such as the notches shown in FIG. 3), wherein at least a second portion of the tube may have a different cross-section. In some such cases, the cross-sectional shape of the second portion may differ from the cross-sectional shape of the first portion. In other such cases, the size (e.g., the cross-sectional area) of the second portion may differ from the size of the first portion. One example of this is shown in FIG. 6A, in which tube 600 comprises region 630, which has a larger cross-sectional dimension than region 640. The presence of region 630 can prevent the tube from being dragged along the direction of the spinning rotor in certain embodiments. In some embodiments, the region of the tube with the larger maximum cross-sectional dimension (e.g., region 630 in FIG. 6A) has a maximum cross-sectional dimension that is at least 5%, at least 10%, at least 20%, or at least 50% larger than the maximum cross-sectional dimension of the region with the smaller maximum cross-sectional dimension (e.g., region 640 in FIG. 6A). In some such embodiments, both the size and the shape of the cross-section of the first portion of the tube differ from the size and shape of the cross-section of the second portion of the tube. According to some embodiments, there may be a third portion, a fourth portion, a fifth portion, and so forth, of the tube that may be the same and / or have a different size and / or shape from the other portions of the tube.

[0061] In some cases, the notches extend into the tube a relatively large amount. For example, in some embodiments, the notch(es) may extend through at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70% of the thickness of the tube. In FIG. 3, for example, the notch in design 344 extends through about 40% of the thickness of the tube.

[0062] In some embodiments, two surface portions of the notch can define a relatively large angle. For example, in some embodiments, two surface portions of the notch can define an angle of at least 15°, at least 20°, at least 25°, at least 30°, at least 35°, at least 40°, at least 45°, at least 50°, at least 55°, at least 60°, at least 65°, at least 70°, at least 75°, at least 80°, at least 85°, at least 90°, or more (and / or, in some embodiments, an angle of up to 60°, up to 75°, up to 90°, up to 100°, up to 110°, up to 120°, up to 130°, up to 140°, up to 150°, or more). In FIG. 3, for example, the notch in design 344 has two surface portions that define an angle of about 90°.

[0063] In some embodiments, the shape of the notches may vary. According to some cases, the notches may be triangular, as shown in the non-limiting embodiment of FIG. 3. In some embodiments, the shape of the notches may be semi-circular, square, rectangular, or any other regular or irregular shape. In certain embodiments, it can be advantageous to use a notch (or notches) that have at least one acute angle. The notches can be located on the inner surface of the tube, as illustrated in the non-limiting example of FIG. 4A. In some embodiments, the tube has two notches, such as in the embodiment shown in FIG. 4A. It can be advantageous to use two notches across each section of the tube, in some embodiments, to simplify fabrication of the tube. In other embodiments, more notches can be used (e.g., at least 3 notches, at least 4 notches, at least 6 notches, at least 8 notches, or more). Having multiple notches (e.g., 4 notches, 6 notches, or other amounts of notches as disclosure herein), in accordance with some embodiments, may allow a pressure to be applied from various directions relative to the tube to compress the tube such that there is no dead volume.

[0064] In some cases, it may be advantageous to have two notches on opposite surfaces such that a straight line may pass through the first notch, the center of the tube, and the second notch, as shown with dashed line 414 in FIG. 4A. In some cases, the two notches on opposite sides of the tube may be arranged such that the tube is configured to prevent dead volumes when compressed by rollers. For example, in some embodiments, when a force is applied orthogonally (e.g., by rollers) to the dashed line 414, the tube may be compressed such that there is no dead volume.

[0065] The thickness of a conventional tube may be relatively uniform around the entire circumference of the tube. In some cases, however, when the tube comprises notches, the thickness of the tube may not be relatively uniform around the entire circumference of the tube, and may be relatively thinner at the notches than at other portions of the tube circumference. For example, in some cases, the thickness of the tube may be at least 10% smaller, at least 20% smaller, at least 30% smaller, at least 40% smaller, at least 50% smaller, at least 60% smaller, at least 70% smaller, or smaller (e.g., up to 80% smaller, up to 90% smaller, up to 95% smaller, or smaller) at the notch(es) than at other portions of the tube.

[0066] According to some embodiments, the notches may allow for the tube to be compressed such that there is no dead volume using a relatively small force when compared to the force required to compress a conventional tube. In some embodiments, as shown by the non-limiting example of FIG. 4C, the minimum force to compress a tube such that there is no dead volume may be measured by applying a force 472 to the tube 474 while simultaneously flowing air through the tube from a pneumatic valve 476 into a liquid 478 (e.g., water), where air flow is indicated by bubbles 480 being generated in the liquid. When no bubbles 480 are observed in the liquid 478, the air flow is 0, which indicates that the tube 474 is fully compressed with no dead volume. In some embodiments, the tube can be fully compressed, such that there is no dead volume, using a force of less than or equal to 800 N, less than or equal to 600 N, less than or equal to 500 N, less than or equal to 400 N, less than or equal to 350 N, less than or equal to 300 N, less than or equal to 250 N, less than or equal to 200 N, less than or equal to 150 N, or less than or equal to 100 N (and / or as little as 50 N, at little as 10 N, as little as 1 N, or less).

[0067] Similarly, according to some embodiments, the notches may allow the tube to be compressed such that there is no dead volume using a relatively small pressure when compared to the pressure required to compress a conventional tube. The pressure may be calculated by dividing the force used to compress the tube by the surface area over which the force is applied to compress the tube. In some embodiments, the tube can be fully compressed, such that there is no dead volume, using a pressure of less than or equal to 10 MPa, less than or equal to 8 MPa, less than or equal to 6 MPa, less than or equal to 3 MPa, less than or equal to 1 MPa (and / or, in some embodiments, greater than or equal to 0.1 Mpa, greater than or equal to 0.2 MPa, greater than or equal to 0.5 MPa, or greater than or equal to 1 MPa). In some embodiments, applying a pressure of 1.4 MPa results in zero dead volume in the tube.

[0068] In some embodiments, the peristaltic pump comprises a tube in contact with one or more rollers, wherein the tube comprises a flexible material, and wherein the walls of the tube in contact with the rollers comprises notches. One example of such a pump is shown in FIGS. 4A-4B. FIG. 4A shows an exploded-view schematic of the overall peristaltic pump, according to certain embodiments. FIG. 4B shows a font view of the assembled pump from FIG. 4A. In FIG. 4A, tube 410 has a cross-section (upper left inset) comprising notches 412. In some embodiments, the tube 410 and the outer layers 422 of the rollers 420 are 3-D printed through a flexible material (e.g., Fiberflex 40D), while the inner layer 424 of the roller 420, the housing 430, the rotor 440, the holder 450, and the lid 460 are 3-D printed through rigid (e.g., polylactic acid, PLA) filaments. In accordance with certain embodiments, the diameter of the tube can easily change along the length since the component is fabricated through additive manufacturing. In some embodiments, a section with a wider outer diameter fixes the tube in place, while the inner diameter of the inlet can be designed to fit any tube connectors. In certain embodiments, the outer layer of the roller is printed with flexible material to fully seal the tube along its length. In accordance with certain embodiments, the flexible tube and / or the outer layer of the roller can be fabricated using materials with Shore hardness less than or equal to 60 D, less than or equal to 40 D, less than or equal to 20 D, less than or equal to 10 D, less than or equal to 50 A, less than or equal to 30 A, or less than or equal to 10 A. In some embodiments, small gaps exist between the rollers and the rotor so that the rollers can freely rotate. These small gaps, combined with any errors from print resolution, can result in uneven compression throughout the length of the tube. Using a flexible roller solves this problem, in accordance with certain embodiments, as the material is compliant (e.g., flexible) and can deform to fully compress the tube at multiple points even when the rotating axis is slightly off-center. Accordingly, in some cases, the flexible roller sleeve of each roller may apply a relatively uniform force and / or pressure along the tube when the rotor rotates each roller along the length of the tube. In some cases, the roller(s) may comprise a rigid inner layer and a compliant outer layer. According to some embodiments, the roller(s) may consist of a rigid inner layer and a compliant outer layer. In some such cases, the compliant outer layer comprises a flexible material, as disclosed elsewhere herein. In some cases, the material (e.g., flexible material and / or rigid material) of the tube and / or the rollers may be suitable for additive manufacturing. Non-limiting examples of rigid materials include polylactic acid-based, acrylonitrile-butadiene styrene-based, and nylon-based filaments. In some such cases, the rigid materials may be used during additive manufacturing to form the peristaltic pump of the present disclosure.

[0069] FIG. 5A shows the performance of one embodiment of the pump by plotting the pressure of the chamber being pumped by the peristaltic pump as a function of time. The motor was powered with about 8 W, and the speed of the rotor was only 22 rpm. The pump operated successfully, and the pressure plateaued at 12 Torr, showing that the pump can generate and maintain a vacuum in a relatively energy efficient manner (e.g., at a relatively low power consumption). A small leak from the tube connection was present, and the method has the potential to perform even further with a complete seal. That is, in some cases, a lower vacuum may be generated and / or maintained. According to some such embodiments, more precisely fabricated tube may be used to eliminate the leak from the tube. Additionally, in some such cases, a larger force may be applied to the tube by the roller.

[0070] FIG. 5B shows the performance of another pump which achieved a drop in pressure from 760 Torr to 9 Torr after 50 minutes of actuation. The motor was powered with about 10 W, and the speed of the rotor was only 12 rpm. The pump operated successfully, and the pressure plateaued at 9 Torr, showing that this pump could also generate and maintain a vacuum in a relatively energy efficient manner (e.g., at a relatively low power consumption).

[0071] In some embodiments, the use of a tube comprising notches that eliminate the dead volume of the tube when compressed can allow for the generation of a vacuum when rotating the rotor of the peristaltic pump. According to some embodiments, the peristaltic pump may be able to generate and / or maintain the vacuum from ambient pressures (e.g., atmospheric pressure, 760 Torr). In some cases, the vacuum generated and / or maintained by the peristaltic pump can result in a gauge pressure of less than or equal to 50 Torr, less than or equal to 20 Torr, less than or equal to 10 Torr, less than or equal to 8 Torr, less than or equal to 5 Torr, less than or equal to 3 Torr, less than or equal to 2 Torr, less than or equal to 1 Torr, less than or equal to 0.8 Torr, less than or equal to 0.5 Torr, less than or equal to 0.3 Torr, less than or equal to 0.2 Torr, less than or equal to 0.1 Torr, less than or equal to 0.08 Torr, less than or equal to 0.05 Torr, less than or equal to 0.03 Torr, or less than or equal to 0.02 Torr. According to some embodiments, the vacuum generated and / or maintained by the peristaltic pump may result in a gauge pressure of greater than or equal to 0.01 Torr, greater than or equal to 0.02 Torr, greater than or equal to 0.03 Torr, greater than or equal to 0.05 Torr, greater than or equal to 0.08 Torr, greater than or equal to 0.1 Torr, greater than or equal to 0.2 Torr, greater than or equal to 0.3 Torr, greater than or equal to 0.5 Torr, greater than or equal to 0.8 Torr, greater than or equal to 1 Torr, greater than or equal to 2 Torr, greater than or equal to 3 Torr, greater than or equal to 5 Torr, greater than or equal to 8 Torr, greater than or equal to 10 Torr, or greater than or equal to 20 Torr. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 10 Torr and less than or equal to 20 Torr). Other ranges are also possible.

[0072] In some cases, the vacuum generated and / or maintained by the peristaltic pump can result in an absolute pressure of less than or equal to 50 Torr, less than or equal to 20 Torr, less than or equal to 10 Torr, less than or equal to 8 Torr, less than or equal to 5 Torr, less than or equal to 3 Torr, less than or equal to 2 Torr, less than or equal to 1 Torr, less than or equal to 0.8 Torr, less than or equal to 0.5 Torr, less than or equal to 0.3 Torr, less than or equal to 0.2 Torr, less than or equal to 0.1 Torr, less than or equal to 0.08 Torr, less than or equal to 0.05 Torr, less than or equal to 0.03 Torr, or less than or equal to 0.02 Torr. According to some embodiments, the vacuum generated and / or maintained by the peristaltic pump may result in an absolute pressure of greater than or equal to 0.01 Torr, greater than or equal to 0.02 Torr, greater than or equal to 0.03 Torr, greater than or equal to 0.05 Torr, greater than or equal to 0.08 Torr, greater than or equal to 0.1 Torr, greater than or equal to 0.2 Torr, greater than or equal to 0.3 Torr, greater than or equal to 0.5 Torr, greater than or equal to 0.8 Torr, greater than or equal to 1 Torr, greater than or equal to 2 Torr, greater than or equal to 3 Torr, greater than or equal to 5 Torr, greater than or equal to 8 Torr, greater than or equal to 10 Torr, or greater than or equal to 20 Torr. For example, in some embodiments, the peristaltic pump can be connected to a volume (e.g., a volume within a chamber) and the pump can be operated such that the absolute pressure within the volume reaches a value within any of these ranges. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 10 Torr and less than or equal to 20 Torr). Other ranges are also possible.

[0073] According to some embodiments, because the tube comprising notches can be compressed with a relatively low pressure (e.g., there is no dead volume when compressing the tube using relatively low pressures), a vacuum may be generated using a peristaltic pump comprising the tube comprising notches using a relatively low power draw and / or by rotating the rotor at a relatively low rate. In some cases, the power drawn by the peristaltic pump is less than or equal to 200 W, less than or equal to 150 W, less than or equal to 100 W, less than or equal to 50 W, less than or equal to 25 W, less than or equal to 10 W, less than or equal to 8 W, less than or equal to 5 W, less than or equal to 3 W, or less than or equal to 2 W (and / or as little as 1 W, as little as 0.1 W, or less) during operation. In some cases, the peristaltic pump may have a relatively low power draw as described above (e.g., less than or equal to 10 W) when generating and / or maintaining a vacuum. According to some embodiments, a vacuum may be generated by rotating the rotor of the peristaltic pump at a rate of less than or equal to 500 rpm, less than or equal to 400 rpm, less than or equal to 300 rpm, less than or equal to 200 rpm, less than or equal to 150 rpm, less than or equal to 100 rpm, less than or equal to 50 rpm, less than or equal to 25 rpm, less than or equal to 22 rpm, less than or equal to 20 rpm, less than or equal to 15 rpm, or less than or equal to 10 rpm (and / or as little as 10 rpm, as little as 5 rpm, or less). Rotating the rotor at a relatively slow rate may be advantageous because it may generate little to no heat (e.g., due to friction), which may extend the lifetime of the tube relative to when the rotor is rotated at higher rate and the tube is heated to higher temperatures during operation.

[0074] In some embodiments, the maximum temperature of the pump during operation is relatively low. For example, in some embodiments, the maximum temperature of the pump during operation is less than or equal to 100° C. higher than the ambient environment, less than or equal to 95° C. higher than the ambient environment, less than or equal to 90° C. higher than the ambient environment, less than or equal to 85° C. higher than the ambient environment, less than or equal to 80° C. higher than the ambient environment, less than or equal to 75° C. higher than the ambient environment, less than or equal to 70° C. higher than the ambient environment, less than or equal to 65° C. higher than the ambient environment, less than or equal to 60° C. higher than the ambient environment, less than or equal to 55° C. higher than the ambient environment, less than or equal to 50° C. higher than the ambient environment, or less (e.g., as little as 40° C. higher than the ambient environment, as little as 30° C. higher than the ambient environment, as little as 20° C. higher than the ambient environment, or less). In some embodiments, the maximum temperature of the pump during operation in an ambient environment of 25° C. is less than or equal to 100° C., less than or equal to 95° C., less than or equal to 90° C., less than or equal to 85° C., less than or equal to 80° C., less than or equal to 75° C., less than or equal to 70° C., less than or equal to 65° C., less than or equal to 60° C., less than or equal to 55° C., less than or equal to 50° C., or less (e.g., as little as 40° C., as little as 30° C., or less).

[0075] In accordance with certain embodiments, a 3D-printed peristaltic pump that can generate low-vacuum is described. However, the application is not limited to low-vacuum applications, since in order to achieve high-vacuum, the environment must be first pumped down to low-vacuum before operating a stronger pump. In addition to backing up high-vacuum systems, vacuum technology can be used in various fields including degassing of metals, coating through vapor deposition, electrospray, reducing carbon footprint, and material analytics. Moreover, as mentioned elsewhere herein, the peristaltic pump of the present disclosure, in accordance with certain embodiments, may also be used to move liquids. According to some such embodiments, due to no dead space when compressing the tube comprising notches, the peristaltic pump of the present disclosure, in accordance with certain embodiments, may pump liquid more efficiently than pumps using a conventional tube (e.g., without notches).

[0076] In some cases, some and / or all of the parts of the peristaltic pump of the present disclosure may be additively manufactured. Some aspects of the present disclosure are related to methods of making some and / or all of the parts of the peristaltic pump of the present disclosure by additively manufacturing. In some cases, making the tube and / or the rollers of the peristaltic pump may comprise printing by extrusion of transverse sections of a flexible material and printing by extrusion of transverse sections of a rigid material. In some such cases, printing the flexible material may produce a flexible tube wherein the walls of the tube have at least one notch, and a compliant outer layer of the rollers. In some such cases, printing the rigid material may comprise producing a rigid inner layer of the rollers. According to some embodiments, printing may further comprise producing a housing, rotor, holder, and lid of the peristaltic pump using the rigid material. In some embodiments, the flexible tube may be printed vertically with a support truss structure. In another set of embodiments, the components of the peristaltic pump (e.g., the flexible tube, the roller comprising an inner and an outer layer, the housing, the rotor, the holder, and the lid) may be made by casting with a flexible material and / or a rigid material.

[0077] An earlier study on peristaltic pumps is disclosed in H. V. Piltingsrud, J Vac Sci Technol A 1996, 14, 2610-2617, which is incorporated herein by reference. This study disclosed that commercial components were used to assemble a peristaltic pump and utilized a circular tube. The study did not completely compress the tube, and the performance was limited by the dead volume. As an alternative solution, the study increased the speed up to about 900 rpm to reduce the lowest pressure. Although a lowest pressure of 2×10−2 Torr was achieved, the system heated up to over 100° C. due to high friction and required a cooling fan. Compared to this reported study that used about 20 W of power and about 900 rpm, the peristaltic pump of the present disclosure peristaltic pump performed stably with less than 8 W and 22 rpm. With a complete seal of the tube during compression, the lowest pressure can theoretically reach much lower even with slow rotor speeds. The designed cross-section also prevents severe stress concentration, which improves fatigue life.

[0078] When compared to commercial products, the most commonly used dry pumps for compact systems are diaphragm pumps. A flexible layer is deformed back and forth to pump out gas with each cycle. However, the minimum pressure of these pumps is limited by the compression ratio of the chamber, requiring multiple pumps connected in series to reach Torr-level vacuum. A diaphragm pump fabricated through additive manufacturing that was previously developed (which is described in A. P. Taylor and L. F. Velasquez-Garcia, J Microelectromech S 2017, 26, 1316-1326, which is incorporated herein by reference) reached a minimum pressure of about 110 Torr.

[0079] Accordingly, in certain embodiments, the peristaltic pump of the present disclosure comprising a tube comprising notches may generate and / or maintain a vacuum while drawing a relatively low power, in some cases. This is because the tube may have no dead volume when compressed using a relatively low pressure, in accordance with some embodiments. Moreover, in some cases, due to the lack of dead volume and thus no air leakage when compressing the tube, the rotor may be rotated at a relatively low rate which may further enhance the energy efficiency of the peristaltic pump. Furthermore, the foregoing advantages may be incorporated in a miniaturized format, as described elsewhere herein.

[0080] In some cases, the peristaltic pump of the present disclosure may be configured for operation to move fluids, for example, liquids and / or gases. In some cases, operating the peristaltic pump may comprise compressing a flexible tube by contacting the flexible tube with one or more rollers such that the internal walls of the tube contact each other to eliminate dead volume, and fluid may thus be transported along the length of the tube. For example, referring to FIG. 4B, in some embodiments, operating peristaltic pump 490 may comprise compressing flexible tube 410 by contacting flexible tube 410 with rollers 420 such that the internal walls of tube 410 contact each other to eliminate dead volume, and fluid may thus be transported along the length of the tube, for example from inlet 140 to outlet 150. This may be achieved, for example, by rotating a rotor connected to the rollers in the direction of arrow 130.

[0081] As described elsewhere herein, compressing the flexible tube and eliminating dead volume may comprise applying a relatively low pressure to the tube (e.g., any of the pressures mentioned above or elsewhere herein). According to some embodiments, operating the peristaltic pump may further comprise generating and / or maintaining a vacuum.

[0082] The literature listed in the Detailed Description is incorporated by reference herein.

[0083] U.S. Provisional Patent Application No. 63 / 367,512, filed Jul. 1, 2022, and entitled “Peristaltic Pumps for Vacuum Generation” is incorporated herein by reference in its entirety for all purposes.

[0084] The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention.Example 1

[0085] This example describes non-limiting embodiments of peristaltic pumps, as well as methods for making the pumps.

[0086] Exemplary devices were made via material extrusion-one of the few additively manufacturing techniques that are capable of monolithically printing objects made of multiple materials, including flexible filaments. A modified MakerGear M3-ID (MakerGear LLC, Beachwood, OH USA) was used to print the devices using 0.5 mm nozzles. Simplify3D (Simplify3D, Cincinnati, OH USA) was used to slice the CAD files and to finely tune the printing profiles of the materials. The devices comprised rigid components and flexible components. The rigid components of the pumps were made in polylactic acid (PLA). Although the popular NinjaFlex® thermoplastic polyurethane (TPU) filament (NinjaTek®, Manheim, PA USA) was first used for making the flexible parts of the peristaltic pumps, the soft material was easily caught between the extruding gears and failed to perform consistently. Furthermore, a single defect in the tube resulted in a leak that drastically affected the pump's performance. After some exploration, the TPU material FiberFlex 40D (Fiberlogy, Brzezie, Poland)—a relatively new flexible printable material, was chosen to print the flexible parts, as it printed more consistently than the NinjaTek®, even though the hardness of the two materials was similar. According to the material safety data sheet (MSDS) from the manufacturer (fiberlogy.com), FiberFlex 40D is composed of 96% thermoplastic copolyester elastomer and 4% additives. Based on the technical data sheet (TDS) from the manufacturer, FiberFlex 40D has excellent chemical compatibility to substances such as oil, butane, ethyl alcohol, freon, gasoline, glycerin, isopropyl alcohol, and sea water, whereas FiberFlex 40D is soluble in substances such as chlorobenzene, ethylene chloride, nitric acid, and 50% sulfuric acid.

[0087] Printing completely airtight layers in the flexible tube is important to attain working vacuum pumps. In some such cases, it may be advantageous to over-extrude the flexible material to fabricate a flexible and air-tight structure. Consequently, an extrusion multiplier of 1.2, and an extrusion width of 0.4 mm were selected through trial and error. However, these conditions only worked for printing airtight tubes with a small (e.g., a few millimeters) radius; the over-extrusion and overlapping printing path were generally not suitable for printing wide layers in the plane parallel to the printer bed. After tuning the print conditions for FiberFlex 40D, a print resolution study was conducted to confirm that the printing conditions were capable of precisely creating the structures defined by the CAD files.

[0088] The cross-section of the flexible tube was designed to overcome the limitation faced by traditional peristaltic pumps when used to create and maintain vacuum. The starting tube design had an outer diameter of 9 mm with 1 mm wall thickness (FIG. 3). The design included two symmetric notches to prevent dead volumes from forming when the tube was compressed and to reduce stress concentration in the material. The notches could be defined by a triangle with vertical side equal to 5 millimeters and horizontal side 330, as shown in FIG. 3. The horizontal side 330 was set at 3.5 mm (no notch, 342, Design #1), 3.9 mm (344, Design #2), and 4.1 mm (346, Design #3). In Designs #1 and #2, the notches were defined by continuous traces, while in Design #3 the notch was formed by two traces that coalesce.

[0089] The flexible tubes were printed vertically for at least two reasons. First, printing the tubes without any overhangs made it possible to attain cleaner prints without any supports inside the tube. Second, printing individual layers perpendicular to the tube length axis resulted in a more durable structure during compression because the weakest bond in structures printed via material extrusion is between separate layers. Consequently, compressing tubes that are printed horizontally would apply a tension force that separates the layers. However, vertically printing long, slender, thin-walled tubes imposed technical difficulties, as the tube bent and swayed while the nozzle applied force in the shear direction, and the effect worsened the taller the tube was. To prevent the long tubes from bending during the print, a thin square layer 610 was modelled at the top of the tube 600, as shown in FIG. 6A. As shown in FIG. 6B, the slicer software auto-generated support 620 for the thin square around tube 600, which prevented the tube at the center from swaying back and forth during manufacturing. The same FiberFlex 40D material was used to print the support structure. Through trial and error, a horizontal offset between the supports and the central tube was set at 0.27 mm. The resulting thin support was close enough to the tube to prevent it from bending, but also far enough to prevent the support from bonding to the tube. After the print, the flexible support structure was peeled off by hand (the support structure did not touch the inside of the tube, which is one of the surfaces that may affect the seal).

[0090] Even though the shore hardness of NinjaFlex (85A) and FiberFlex 40D (40 D) are similar, FiberFlex 40D requires more stress to deform. However, FiberFlex 40D was selected as the flexible material because it was much easier to print with large extrusion multipliers.

[0091] The printing process of FiberFlex 40D that yielded working actuators was characterized. The results showed that there was linearity and correspondence between the CAD dimensions and the corresponding 3D-printed dimensions. Prototypes of the different tube actuator designs were 3D-printed and characterized, evidencing that Design #3 outperforms the other designs. In addition, a fatigue test evidenced that the actuators 3D-printed in FiberFlex 40D can be used for >100,000 cycles. Prototypes of the complete pump were 3D-printed, assembled, and characterized, showing linearity between base pressure and pumping period, while attaining pressures as low as 9 Torr and flow rates as large as 10 sccm.

[0092] The correspondence between CAD dimensions and 3D-printed FiberFlex 40D dimensions was characterized to ensure that the over-extruding conditions did not affect the printing accuracy. A test structure was designed and printed to compare the dimensions of the original design and the printed objects. The step-like structure is shown in FIG. 14A, where the first step is a single layer high (100 μm). Each step increased in height, while the width of the steps decreased by 5 mm. The height of the first 4 steps (i.e., between 100 μm and 500 μm) was measured with a laser scanning confocal microscope with nanometer level resolution (Keyence VK-X, Keyence, Itasca, IL USA), while the rest were measured with an optical microscope with micrometer level resolution (Aven 26700-207, Aven, Inc., Ann Arbor, MI USA). Each data point was the average of 40 measurements; the standard deviation in the vertical measurements was 20 μm, while the standard deviation in the in-plane measurements was 17 μm. There was linearity and correspondence between the CAD heights and 3D-printed heights (FIG. 14B). There was negligible difference in the printed dimensions in the in-plane directions; therefore, the results are combined in the same data plot (FIG. 14C). Similarly, there was linearity and correspondence between the CAD in-plane dimensions and the corresponding 3D-printed in-plane dimensions. The results show the additive manufacturing method performs with consistent resolution and linearity even under extreme printing conditions (e.g., large over-extrusion).

[0093] Compression tests were conducted to characterize the force required to form a complete seal in each of the three flexible tube designs (FIG. 3). As noted previously, the three designs explored in this example (i.e., from FIG. 3, element 330=3.5 mm, element 330=3.9 mm, and element 330=4.1 mm) were denoted as Design #1, Design #2, and Design #3, respectively. In each test, one end of the tube was connected to a pneumatic pump, while the other end was submerged in a container filled with water. In this configuration, air was transported through the tube and bubbles were released in the water reservoir (FIG. 7A). The tubes were then compressed using the compression fixture of a commercial materials testing system (PASCO, Roseville, CA USA) until the bubbles were no longer observed, indicating a complete seal. FIG. 7B shows the results of the compression tests, where each design was tested 3 times. The numbers on the right are the average of the final forces for the 3 designs. Design #1, i.e., the design without notches, required the most amount of force (411 N). Compared to the notched designs, the experiments show that additional force was required to completely collapse the Design #1 tube, and that increasing the size of the notch reduced the required force, down to a minimum average compression force of 201 N in the case of Design #3. These results indicate that the notches played a role while compressing the tubes. Although Design #3 required the least amount of force, the large notch altered the print pattern. Instead of having a continuous path on both the outer and inner layers like in Designs #1 and #2, the large notch forced two different extrusion paths to meet at the center of the notch (FIG. 3, elements 344 and 346). Multiple printing attempts showed that this bonding of discontinuous paths risked a higher chance of defects for the gas to leak. As a result, Designs #1 and #2 were down selected and further studied.

[0094] A fatigue test on a Design #2 tube was conducted to evaluate the long-term performance of the flexible material. The notched tube was subjected to cyclic compression for 100,000 cycles, using an actuation period similar to that used in the pump characterization. The initial results are shown in FIG. 8A. The individual peaks evidence that, for each cycle, the force increased slowly during the initial stage of the compression. This slow increase in force was due to the geometrical deformation of the tube structure. After a certain point, the slope of the measured force increased drastically, indicating that the flexible material was compressed. These peaks were repeated consistently, and the trace of the peak values is shown with a dotted line. FIG. 8B shows the long-term trace of the peaks for 100,000 cycles. The maximum value of the peaks decreased slowly, eventually plateauing at about 150 N, suggesting that FiberFlex 40D could be utilized to make components that require cyclic deformations without fatigue failure.

[0095] The peristaltic vacuum pump that was developed was composed of a flexible tube that is sequentially squeezed by a set of rollers against a housing (FIG. 4). The rigid parts of the pump (housing, holder, rotor, roller cores, lid) were printed in PLA, while the flexible components of the pump (tube, roller shells) were printed in FiberFlex 40D. The vertically printed flexible tube were bent and installed inside the PLA housing. The cross-sectional design of the tube changed along the length of the tube to perform different functions. The inlet of the tube was a standard circular tube, so it could be connected to conventional vacuum fittings. A small section of the tube was printed with thicker walls, so that the protrusion was affixed to a feature in the housing to prevent the tube from being pulled into the housing when the rollers were active. The portion of the tube that was squeezed by the rollers was printed with the notched design of Design #2. Printing a tube with variable cross-section that served multiple purposes was another benefit of fabricating the component via additive manufacturing. The assembly between holder and rotor, as well as lid and housing, were designed to “snap in” to fix the components firmly together. Other rotating components were designed to have just enough gap between connections to rotate freely. The pump mechanism had five rollers connected to a rotor that was powered by a DC 12 V 20 rpm gear motor (Greartisan, Shenzhen, China) as shown in FIG. 9. The external shell of the rollers was flexible to accommodate for a varying gap between the housing and the rotor, providing even compression throughout the length of the tube. The shell of the rollers was flexible enough to deform and provide even compression, but stiff enough to seal the tube; specifically, by trial and error, an infill of 35% was selected to serve these purposes. In addition, an infill pattern of honeycomb structures was used to provide an isotropic stiffness. The core of the rollers was printed with PLA, so that they could slide smoothly around the rotors. Given that the pump was made of only two materials, it was possible to print the entire device in a single print with a material extrusion printer with two nozzles. Moreover, the rollers could be monolithically 3D-printed. The 3D-printed peristaltic vacuum pump is shown in FIG. 9B. The curvature of the housing that bends the tube determined how small the pump could be 3D-printed. The reported pump is about the smallest possible working pump, as a smaller pump would require a smaller curvature radius, which would result in delamination between the printed layers.

[0096] An illustrative schematic of the setup to characterize the peristaltic vacuum pump design is shown in FIG. 9C. The motor of the pump was powered with a 12 V DC bias voltage while drawing 0.85 A of current (10 W), resulting in about 12 rpm of rotor actuation. This actuation speed was only about 1.3% of the actuation speed used in other peristaltic pumps (e.g., 900 rpm). In the peristaltic pump of this example, the high degree of sealing allowed for a relatively high vacuum to be generated using a relatively low actuation speed of about 12 rpm. The peristaltic vacuum pump was connected to a Pirani gauge (Kurt J. Lesker, Jefferson Hills, PA USA) and a mass flow controller 825 (Edwards Vacuum, Burgess Hill, UK). First, the pump inlet pressure over time was measured while the mass flow controller was turned off; the pump eventually reached its base pressure. Once the pump reached its base pressure, the flow rate was slowly increased using the mass flow controller to determine the flow rate-versus-pressure characteristic of the pump design (this is analogous to the current-versus-voltage characteristic of electrical components). An infrared camera B20 (HIKMICRO, Zhejiang, China) was used to measure the temperature of the pump throughout the test.

[0097] Increasing the angular speed of the pump proportionally increased its flow rate (each pumping cycle moved the same volume, and how often the volume was moved determined the flow rate); this was confirmed by pumping water and measuring its volume. Actuating the pumps at 12 V successfully created and maintained vacuum and no degradation was observed in the pumps for being actuated at such bias voltage. Using a 12 V bias voltage, a proof-of-concept, novel 3-D printed peristaltic pump that could attain and maintain a lower pressure than mainstream diaphragm pumps using a relatively slow actuation was successfully demonstrated.

[0098] Base pressure vs. period of actuation data were obtained using an unoptimized experimental setup while applying between 6 V and 10 V to the motor (FIG. 10). Varying the bias voltage made it possible to indirectly vary the angular speed of the motor. The data showed there was a linear dependence between the base pressure attained by the pump and the period of the pumping cycle.

[0099] A typical pressure versus time characteristic is shown in FIG. 11. The pressure dropped from 760 Torr to 9 Torr after 50 minutes of actuation. The base pressure was about two orders of magnitude smaller than the base pressure attained if the peristaltic vacuum pump had constant, circular cross-section (about 650 Torr), or than the base pressure a 3D-printed, miniature positive displacement pumps reported by A. P. Taylor, J. Phys. D. Appl. Phys. 2020, 53, 355002 (about 540 Torr). Furthermore, the additively manufactured, single-stage pump of the present disclosure was able to achieve Torr-level vacuum, i.e., an order of magnitude lower pressure than the state-of-the-art, miniaturized (3D-printed or not) diaphragm pumps (about 100 Torr base pressure) as reported by A. P. Tayler et al, J. Microelectromech. S. 2017, 26, 1316-1326. At least three of these pumps in series as reported by Taylor, 2017 would be required to attain better vacuum than the base pressure attained using the peristaltic vacuum pump of the present disclosure. From the data, the leak rate of the 3D-printed peristaltic vacuum pump was estimated at about 4 mm3 / s. The pressure-versus-time curve of a positive displacement pump follows an exponential decay expressed asP⁡(t)=Pb+(Pa⁢t⁢m-Pb)⁢e(-SVS)⁢twhere Pb is the base pressure, Patm is the atmospheric pressure, S is effective pumping speed, VS is the volume being pumped (the meshed volume in FIG. 9C), and t is time. The measured pumping speed was about 340 mm3 / s with the volume of gas pumped down in the setup about 56,000 mm3. The estimated S / VS is about 0.006, which was consistent with the value from the least-squares curve fit. While the measured base pressure was about 9 Torr, the value from the curve was 13.4 Torr. Adding the two terms Pb and (Patm−Pb) from the least-squares fitted curve results in about 760 Torr, which was consistent with the atmospheric pressure. Overall, the base pressure of 9 Torr was a shown using the compact, single-state pump device, which was fabricated via additive manufacturing.The mass flow rate versus pressure of the 3D-printed peristaltic vacuum pump design is shown in FIG. 12. The flow rate was controlled by the mass flow controller, and the pressure was measured until it stabilized. The test was repeated 5 times to calculate the average and standard deviation. For a given pump, the flow rate range was directly controlled by the speed of the motor. For the motor model used in the present example, the minimum flow rate was about 0 sccm and the maximum flow rate is about 10 sccm (FIG. 12).

[0101] The temperature of the pumps was measured with an infrared cameras (FIG. 13B-13C). The temperature at the surface of the rollers started to increase, reaching 41° C. after 100 seconds (FIG. 13B). After 300 seconds, the motor also started to heat up, hence considerable heating was observed from the portion of the motor that was embedded inside the PLA housing (FIG. 13C). Nevertheless, the highest temperature was still measured on the surface of the rollers. The maximum, steady-state temperature is 50° C., which was reached after 500 seconds of actuation (FIG. 13D). The maximum temperature plateaued and remained at about 50° C. for the remainder of the test. While this temperature was half of the temperature as reported by Piltingsrud, further reducing the temperature could help attain faster actuation speeds to potentially reach lower base pressures and larger flow rates. The peristaltic pump of the present disclosure, in some cases, may be able rotate the rotor at a lower rate to attain vacuums, and thus operate at lower temperatures, because the tube comprising notches has no dead volume when compressed. Also, operating the pump at lower temperatures could prolong the fatigue life of the flexible material even further. In some cases, cooling the pump (e.g., by using a fan, flowing a cooling liquid inside the housing) may reduce the temperature of the pump. In some cases, applying grease between the tube, the housing, and the rollers may reduce friction and thus may also cool the pump, relative to when there is no grease applied.

[0102] The foregoing is a proof-of-concept demonstration of a novel design, made by 3D printing, of a peristaltic pump that can attain, with slow actuation, lower pressure than the most used dry mechanical pumps, i.e., diaphragm pumps. The proposed approach to attain this result entailed using a tube comprising notches. The investigation was conducted on tube geometries close to the limit of what can be made (e.g., the cross-section of the tube may be made of only a few loops of material, as thicker walls make the tube stiffer), also making the cross-section of the tube as small as possible (e.g., to make a miniaturized pump). From experimental observations, it was determined that modifying the inner surface of the tube allowed the tube to fully collapse, and the simplest means to accomplish that was to introduce straight notches on the sides. The tested design considered the angle of the notch and how the loops of material surrounded the notch (continuous loops vs. loops that end at the ends), yielding Design #3 as the best of the 3 tested designs. Other design adjustments, e.g., angle of the notch, notch shape (e.g., a convex curve that effectively creates a zero-degree notch at the ends) are also contemplated herein and may result in smaller leak rates and higher vacuum.

[0103] The pump implemented a novel actuator design with a notched cross-section that required less than half the force to fully seal (e.g., relative to a conventional tube comprising a round cross-section), making it possible to create and maintain low vacuum at low actuation speed. The devices were made via material extrusion: the rigid parts of the pump were made in PLA, while the compliant parts of the pump were made in FiberFlex 40D.Characterization of printed FiberFlex 40D demonstrated infinite (e.g., little-to no fatigue after greater than or equal to 105 cycles) fatigue life. The mechanical behavior of 3D-printed FiberFlex 40D was hyperelastic. Experimental characterization of pump prototypes demonstrated the devices attain an order of magnitude lower base pressure than a state-of-the-art, miniaturized diaphragm vacuum pump. Due to the slow actuation speed, the rise in temperature was much lower than reported by Piltingsrud. In some cases, increasing the actuation speed (e.g., rotation rate of the rotor) may result in even lower base pressures if the pump is forced air-cooled and / or lubricated.

[0104] It should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific implementations described above. The specific implementations described above are disclosed as examples only.

Claims

1. A peristaltic pump, wherein the peristaltic pump comprises a tube in contact with one or more rollers; wherein the tube comprises a flexible material; and wherein walls of the tube in contact with the rollers comprise notches.

2. The peristaltic pump of claim 1, wherein:the rollers each consist of a compliant outer layer comprising a flexible material, such as the flexible material of the tube, and a rigid inner layer; andthe peristaltic pump is configured for producing a vacuum.

3. A peristaltic pump, comprising:a tube in contact with one or more rollers;wherein the tube comprises a flexible material; andwherein the tube is configured to prevent dead volumes when compressed by the rollers.

4. A peristaltic pump, comprising:a tube in contact with one or more rollers;wherein the tube comprises a flexible material; andwherein the tube is configured such that the peristaltic pump is capable of maintaining a vacuum when the tube is compressed by the rollers.

5. The peristaltic pump of any one of claims 1-4, wherein an inner diameter of the tube is greater than 4.8 mm.

6. The peristaltic pump of any one of claims 1-5, wherein a cross section of the tube varies along the length of the tube.

7. The peristaltic pump of any one of claims 1-6, wherein the tube has a compression set of less than or equal to 10%.

8. The peristaltic pump of any one of claims 1-7, wherein the pump is additively manufactured.

9. The peristaltic pump of any one of claims 1-8, wherein a volume of the pump is less than or equal to 700 cm3.

10. The peristaltic pump of any one of claims 1-9, wherein a power draw of the pump is less than or equal to 10 W when generating a vacuum.

11. The peristaltic pump of any one of claims 1-10, wherein a power draw of the pump is less than or equal to 10 W when maintaining a vacuum.

12. The peristaltic pump of any one of claims 1-11, wherein an inner diameter of the tube is greater than 0.5 mm and less than or equal to 10 cm.

13. The peristaltic pump of any one of claims 1-12, wherein an inner diameter of the tube is greater than or equal to 7 mm and less than or equal to 10 cm.

14. The peristaltic pump of any one of claims 1-13, wherein an inner diameter of the tube is greater than or equal to 9.5 mm and less than or equal to 10 cm.

15. The peristaltic pump of any one of claims 1-14, wherein the one or more rollers comprise a compliant outer layer.

16. The peristaltic pump of any one of claims 1-15, wherein applying a pressure of 1.4 MPa results in zero dead volume in the tube.

17. The peristaltic pump of any one of claims 1-16, wherein the peristaltic pump is configured for producing a vacuum.

18. The peristaltic pump of any one of claims 1-17, wherein the rollers each consist of a compliant outer layer comprising the flexible material and a rigid inner layer.

19. The peristaltic pump of any one of claims 1-18, wherein a first cross-sectional size and / or shape of a first portion of the tube is different from a second cross-sectional size and / or shape of a second portion of the tube.

20. The peristaltic pump of any one of claims 1-19, wherein walls of the tube have a thickness that varies along the length of the tube.

21. The peristaltic pump of any one of claims 1-20, wherein the flexible material of the tube and / or the compliant outer material of the rollers and / or the rigid inner material of the rollers comprise one or more materials suitable for additive manufacturing.

22. The peristaltic pump of any one of claims 1-21, wherein the flexible material is Fiberflex 40D or Fiberflex 30D.

23. The peristaltic pump of any one of claims 1-22, wherein the flexible material comprises a polymer comprising butylene and / or poly(alkylene ether) phthalate24. The peristaltic pump of any one of claims 1-23, wherein the rigid inner layer comprises rigid polylactic acid-based, acrylonitrile butadiene styrene-based, or nylon-based filaments.

25. The peristaltic pump of any one of claims 1-24, wherein the walls of the tube in contact with rollers has two notches on opposite sides of tube, whereby the tube is configured to prevent dead volumes when compressed by the rollers.

26. The peristaltic pump of any one of claims 1-25, wherein the tube is configured to prevent dead volumes when compressed by the rollers.

27. The peristaltic pump of any one of claims 1-26, wherein the peristaltic pump is configured for moving fluids.

28. The peristaltic pump of any one of claims 1-27, wherein the fluids comprise liquids and / or gases.

29. A method of making the tube and rollers of the peristaltic pump of any one of claims 1-28, comprising printing by extrusion transverse sections of a flexible material to produce:a) a flexible tube, wherein walls of part of the tube have a notch; andb) a compliant outer layer of rollers; andprinting by extrusion transverse sections of a rigid material to produce a rigid inner layer of rollers.

30. The method of claim 29, further comprising printing a housing, rotor, holder, lid, outer and inner layer of rollers.

31. The method of any one of claims 29-30, wherein the printing is with material comprising rigid polylactic acid-based, acrylonitrile butadiene styrene-based, or nylon-based filaments.

32. The method of any one of claims 29-31, wherein the flexible tube is printed vertically with a support truss structure.

33. A method of making the tube and rollers of the peristaltic pump of any one of claims 1-28, comprising casting a flexible material to produce:a) a flexible tube, wherein walls of part of the tube have a notch; andb) a compliant outer layer of rollers; andcasting a rigid material to produce a rigid inner layer of rollers.

34. The method of claim 33, further comprising casting a housing, rotor, holder, lid, outer and inner layer of rollers.

35. A method of operating a peristaltic pump, comprising:compressing a flexible tube by contacting the flexible tube with one or more rollers, such that the internal walls of the tube contact each other to eliminate dead volume, and fluid is transported along the length of the tube.

36. A method of operating a peristaltic pump, comprising:compressing a flexible tube by contacting the flexible tube with one or more rollers, the flexible tube comprising one or more notches, such that fluid is transported along the length of the tube.

37. A method of generating a vacuum using a peristaltic pump, comprising:compressing a flexible tube by contacting the flexible tube with one or more rollers such that gas is transported along the length of the tube and a vacuum is generated and maintained.

38. The method of any one of claims 35-37, wherein the flexible tube comprises notches.

39. The method of any one of claims 35-38, wherein the one or more rollers comprise a flexible material.

40. The method of claim 39, wherein the flexible tube comprises the flexible material.

41. The method of any one of claims 35-40, wherein compressing the flexible tube comprises applying a pressure of less than or equal to 10 MPa.

42. The method of claim 41, wherein compressing the flexible tube comprises applying a pressure of greater than or equal to 0.1 MPa.

43. The method of any one of claims 35-42, wherein compressing the flexible tube eliminates dead volume.

44. The method of any one of claims 35-43, further comprising generating and / or maintaining a vacuum.

45. The method of any one of claims 35-44, wherein the fluid comprises gas and / or liquid.

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