Hemodialysis machine drainage pipe suspension anti-backflow device and preparation method thereof

Abstract

This invention discloses a suspended anti-backflow device for hemodialysis machine drain tubing and its preparation method, belonging to the field of additive manufacturing technology for vascular filters. The method includes two core steps: suspended gradient flow channel additive configuration and photosensitive resin gradient photocuring integral molding. By constructing a continuous flow channel model with a gradient flow-limiting section and a suspended air gap section, combined with a progressive process of resin degassing pretreatment, layered variable power scanning, water-soluble support layout, post-curing stress elimination, and internal cavity hydrophobic modification, high-precision fabrication of a seamless integrated device is achieved. The flow channel gradient shrinkage ratio is 1:0.62, and the effective height of the suspended air gap is 25mm. The device prepared by this method has no moving valve core or assembly seams, a reverse blocking pressure resistance of 0.15MPa, an inner wall roughness Ra≤0.6μm, and a performance retention rate of over 98% after 1000 sterilization cycles, simultaneously improving the reliability and biosafety of hemodialysis drain anti-backflow.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology for vascular filters, specifically to a device for preventing backflow of fluid from a hemodialysis machine's drain pipe and its preparation method. Background Technology

[0002] During hemodialysis treatment, dialysis waste fluid is continuously discharged through the drainage line. When the downstream drainage line becomes blocked, the fluid level rises, or the negative pressure is abnormal, there is a risk that the waste fluid may flow back into the hemodialysis machine, potentially causing equipment contamination, cross-infection among patients, and other medical safety issues.

[0003] Existing backflow prevention devices mostly adopt a mechanical one-way valve structure, relying on moving parts such as springs and sealing plugs to achieve unidirectional flow. The manufacturing of this type of device depends on traditional injection molding and assembly processes, which have three inherent defects: First, waste liquid residues easily accumulate in the gaps between the moving parts and the valve seat, which cannot be completely removed by conventional disinfection, and microorganisms are prone to grow with long-term use; Second, the assembly of multiple parts has many seams, which are disinfection dead zones, and the bonded parts are prone to aging and failure after repeated disinfection; Third, due to the limitations of the demolding process, it is impossible to manufacture an integrated structure with an internal suspended cavity, making it difficult to realize a valve core-free air gap anti-backflow solution.

[0004] Current applications of 3D printing technology in the field of vascular filters are mostly concentrated on the preparation of implants and customized assistive devices. There is no integrated molding process developed specifically for the scenario of preventing backflow of hemodialysis drainage. When ordinary photopolymerization molding is directly used to prepare suspended inner cavity structures, problems such as deformation of the suspended end face, obvious step effect of the inner wall, and large internal stress leading to dimensional instability after sterilization occur, which cannot meet the precision and durability requirements of vascular filters. Summary of the Invention

[0005] The core technical problem solved by this invention is that existing hemodialysis drainage anti-backflow devices rely on mechanically movable valve cores and assembly processes, which have problems such as many dead corners for fluid accumulation, incomplete disinfection, and easy failure of components; moreover, traditional manufacturing processes cannot achieve high-precision preparation of seamless suspended inner cavity structures, and ordinary additive manufacturing processes cannot meet the dimensional stability and biosafety requirements of vascular filters, resulting in the inability to simultaneously improve the reliability of anti-backflow and biosafety.

[0006] To address the aforementioned technical challenges, this invention employs a dual-core, collaborative manufacturing approach: a suspended gradient flow channel additive configuration step to precisely design the valve-core-free air gap anti-backflow structure, structurally eliminating the risk of moving part failure; and a photosensitive resin gradient curing integral molding step to achieve seamless fabrication of the complex suspended internal cavity, eliminating dead zones for liquid accumulation at seams. These two steps are interdependent and synergistic. The complex internal cavity of the suspended flow channel can only be precisely integrally molded through gradient curing. The layered control capability of gradient curing ensures the dimensional accuracy of the suspended air gap and gradient flow channel, thereby guaranteeing the stability of the anti-backflow performance.

[0007] Based on this, through progressive process steps such as resin pretreatment, layered variable power scanning, stress relief, and hydrophobic modification, the problems of molding bubbles, deformation of suspended end faces, dimensional drift after disinfection, and high internal wall residue are gradually solved. Each step is centered on the anti-backflow reliability and biosafety of the lifting device. The technical features are interlinked, ultimately achieving a cumulative improvement in performance.

[0008] The specific technical solution is as follows: This invention provides a method for preparing a suspended anti-backflow device for the drain tube of a hemodialysis machine, comprising an additive configuration step of a suspended gradient flow channel and an integral molding step of photosensitive resin gradient photocuring.

[0009] The additive manufacturing process for the suspended gradient flow channel generates a continuous 3D model of the flow channel, including an inlet connecting section, a gradient flow-limiting section, a suspended air gap section, and an outlet confluence section. The inner diameter of the gradient flow-limiting section gradually narrows along the flow direction of the waste liquid, allowing the waste liquid to accelerate smoothly in a laminar flow state and avoiding turbulent splashing. The suspended air gap section is located between the outlet of the gradient flow-limiting section and the inlet of the outlet confluence section, forming an air-isolated area without physical contact, relying on air to physically block reverse backflow.

[0010] The photosensitive resin gradient curing integrated molding process involves slicing the 3D model into layers of predetermined thickness, then using photosensitive resin as the raw material and curing it layer by layer under ultraviolet light to obtain a seamless, integrated device body. The molding process employs progressive control through pretreatment, layered variable power scanning, precise support, and stress relief to ensure structural accuracy and stability.

[0011] The gradient contraction ratio of the flow channel limits the ratio of the inlet inner diameter to the outlet inner diameter of the gradient flow restrictor to 1:0.62. The effective height of the suspended air gap limits the vertical distance between the outlet end face of the gradient flow restrictor and the inlet end face of the outlet confluence section to 25mm. These two parameters together ensure smooth forward flow of waste liquid and reliable reverse blocking.

[0012] The suspended gradient flow channel additive configuration step is performed according to the following process: The first step is to construct the inlet connection section, set the inner diameter and axial length of the inlet connection section, set a standard Luer tapered joint structure at the outer end of the inlet connection section, and set an annular anti-detachment flange at the root of the joint.

[0013] The second step is to construct a gradient flow restriction section, which is smoothly connected to the inlet connection section. Three-stage inner diameter contraction is set along the flow direction of waste liquid, and the ratio of the axial length of each contraction section to the inner diameter contraction amount of that section is 4:1.

[0014] The third step is to construct a suspended air gap section. An annular exhaust groove is set on the side wall of the suspended air gap section, and the annular exhaust groove is connected to the external atmosphere of the device. An annular anti-climbing wall protrusion is set on the lower inner wall of the suspended air gap section.

[0015] The fourth step is to construct the outlet manifold. The inlet end face of the outlet manifold is located directly below the outlet end face of the gradient flow limiting section. The inner diameter of the outlet manifold gradually increases along the direction of waste liquid flow, and a standard pipeline insertion structure is installed at the outer end.

[0016] The fifth step is to construct an axial spiral guide rib on the inner wall of the gradient flow limiting section, with the guide rib extending along the direction of waste liquid flow.

[0017] Furthermore, the gradient contraction ratio of the flow channel limits the ratio of the inlet inner diameter to the outlet inner diameter of the gradient flow-limiting section to 1:0.62. The effective height of the suspended air gap limits the vertical distance between the outlet end face of the gradient flow-limiting section and the inlet end face of the outlet confluence section to 25 mm. These two parameters together ensure smooth forward flow of waste liquid and reliable reverse blocking.

[0018] Furthermore, the gradient photocuring integral molding step of the photosensitive resin is performed according to the following process: The first step is resin pretreatment. The photosensitive resin is placed in a vacuum degassing device and kept at 35℃ and 0.09MPa for 20 minutes to remove air bubbles from the resin. The photosensitive resin used in this step is a polyurethane acrylate system adapted to 365nm ultraviolet wavelength, which is a common raw material in the field of photopolymer 3D printing.

[0019] The second step is layered variable power scanning. The 3D model is imported into the slicing software, the layer thickness is set to 0.05mm, and the ultraviolet light scanning path for each layer is generated. Different scanning powers are set for the inner wall layer of the flow channel and the suspended end face layer.

[0020] The third step involves support installation and layer-by-layer curing. A water-soluble support material is used to support the suspended end face of the air gap section. The contact area between the support and the main body is controlled to be within 8% of the suspended end face area. Curing is performed layer by layer according to the planned scanning path and power. The water-soluble support material used in this step is a PVA-based water-soluble photosensitive resin, which can be completely removed by water-based cleaning.

[0021] The fourth step is to remove the support and clean the inner cavity. Take out the molded device body, remove the external support, and put it into an ultrasonic cleaning device. Use isopropanol to ultrasonically clean the inner cavity and the outer surface for 120 seconds.

[0022] The fifth step is to eliminate post-curing stress. After cleaning, the device is placed in a UV curing chamber and post-cured at 40°C for 30 minutes to eliminate the internal stress of the molding.

[0023] Furthermore, the axial spiral guide ribs on the inner wall of the gradient flow limiting section are constructed according to the following parameters: there are 4 guide ribs, which are evenly distributed circumferentially along the inner wall of the gradient flow limiting section; the height of the guide ribs is 0.8 mm, and the ratio of the width to the height of the guide ribs is 1.2:1; the spiral angle of the guide ribs is 15 degrees, and the guide ribs start at the inlet end face of the gradient flow limiting section and end at the outlet end face of the gradient flow limiting section; the edges of the guide ribs adopt a rounded transition with a radius of 0.2 mm.

[0024] Furthermore, the specific parameters for the layered variable power scanning are as follows: the scanning power of the inner wall layer of the flow channel is set to 120mW, and the scanning line spacing is 0.03mm; the scanning power of the suspended end face layer is set to 150mW, and the scanning line spacing is 0.02mm; the scanning power of the main structure layer is set to 100mW, and the scanning line spacing is 0.05mm.

[0025] Furthermore, the specific parameters for post-curing stress relief are as follows: the ultraviolet light wavelength in the curing chamber is 365nm, the irradiation intensity is 15mW / cm², the ambient temperature is constant at 40℃, and the treatment time is 30min.

[0026] Furthermore, after the post-curing stress relief step is completed, an internal cavity hydrophobic modification step is also included. The specific parameters for the internal cavity hydrophobic modification are as follows: a low-temperature plasma treatment device is used to introduce hexamethyldisiloxane working gas into the internal cavity of the device, the working gas pressure is 20 Pa, the discharge power is 100 W, and the treatment time is 90 s.

[0027] Furthermore, after the internal cavity cleaning step is completed, an in-situ airtightness test is also included. The specific parameters for the in-situ airtightness test are as follows: clean compressed air at 0.2 MPa is introduced into the inlet of the device, the entire device is immersed in purified water at 35°C, and kept for 30 seconds. Observe whether any bubbles overflow; if no bubbles overflow, it is considered qualified.

[0028] Furthermore, annular anti-climbing protrusions are provided on the lower inner wall of the suspended air gap section. There are two protrusions, which are equidistantly distributed along the axial direction of the suspended air gap section. The cross-section of the protrusion is a right triangle, with the right-angled side attached to the inner wall of the air gap section and the hypotenuse facing the center of the air gap. The radial height of the protrusion is 1.5 mm and the axial width is 1 mm.

[0029] This invention also provides a device for preventing backflow of the drain pipe of a hemodialysis machine. The device is prepared by the above-mentioned method. The main body of the device is an integrated structure. The internal structure is connected in sequence to an inlet connection section, a gradient flow limiting section, a suspended air gap section, and an outlet confluence section. The inner diameter of the gradient flow limiting section gradually decreases along the direction of waste liquid flow. An air isolation area is formed inside the suspended air gap section. There are no moving valve core components. Beneficial effects:

[0030] The configuration and molding steps work synergistically: the non-contact anti-backflow structure of the suspended gradient flow channel fundamentally eliminates the risk of wear and jamming of the mechanical valve core; the gradient photopolymerization integrated molding process enables seamless fabrication of this complex structure, eliminating dead zones for liquid accumulation at assembly seams. The two are mutually dependent and mutually reinforcing: the suspended inner cavity can only be integrally molded through additive manufacturing, and the high-precision control of gradient photopolymerization ensures stable blocking effect of the suspended air gap, ultimately achieving a simultaneous improvement in anti-backflow reliability and biosafety.

[0031] The gradient flow restriction and air gap structure work synergistically: the gradient flow restriction section allows waste liquid to enter the air gap region smoothly in a laminar flow state, avoiding splashing and wall adhesion; the suspended air gap forms a physical air barrier, and the reverse blocking capability is not affected by the composition of the medium; the anti-climbing wall protrusion further prevents the reverse liquid surface from climbing up the wall. The three structures work together to achieve low forward flow resistance and smooth discharge, and a high reverse blocking threshold with no risk of leakage.

[0032] Synergistic effects of layered variable power scanning and post-curing processes: Layered variable power scanning improves the curing density of the inner wall of the flow channel and the suspended end face, reducing the step effect; post-curing stress elimination eliminates the internal stress of molding, improving dimensional stability after sterilization cycles. The combination of these two processes simultaneously improves the molding accuracy and durability of the device, and the backflow prevention performance does not degrade after long-term use.

[0033] Synergistic effect of inner wall finishing and hydrophobic modification: Layered variable power scanning reduces inner wall roughness and decreases the number of contaminant adhesion sites; plasma hydrophobic modification increases the inner wall contact angle, further reducing waste liquid adhesion. The combination of these two treatments significantly reduces the residue on the inner wall of the device, significantly improves disinfection efficiency, and provides double protection for biosafety. Detailed Implementation

[0034] The technical solution of the present invention will be further explained below through 7 sets of examples and 5 sets of comparative examples, combined with performance test results. Example 1

[0035] This embodiment describes the preparation of a device to prevent backflow of the hemodialysis machine's drain pipe. The steps are as follows: The suspended gradient flow channel additive configuration consists of: an inlet connecting section with an inner diameter of 10 mm and an axial length of 15 mm, featuring a 6% Luer tapered connector at the outer end and an annular anti-detachment flange at the connector root; a gradient flow limiting section with three stages of inner diameter contraction, an inlet inner diameter of 10 mm, an outlet inner diameter of 6.2 mm, a flow channel gradient contraction ratio of 1:0.62, and a ratio of axial length to inner diameter contraction of each stage of contraction of 4:1; a suspended air gap section with an effective height of 25 mm, featuring two annular exhaust grooves on the sidewall, each groove 1 mm wide, and two annular anti-climbing bosses on the lower inner wall, each boss having a radial height of 1.5 mm and an axial width of 1 mm; and an outlet confluence section with an inlet inner diameter of 8 mm, an outlet inner diameter of 12 mm, and an axial length of 18 mm. Four spiral guide ribs are constructed on the inner wall of the gradient flow limiting section, with a rib height of 0.8 mm, a width-to-height ratio of 1.2:1, a spiral angle of 15 degrees, and a rib radius of 0.2 mm.

[0036] Gradient photocuring of photosensitive resin for one-piece molding: (1) Resin pretreatment: The polyurethane acrylate photosensitive resin with a wavelength of 365nm was placed in a vacuum degassing device and kept at a temperature of 35℃ and a negative pressure of 0.09MPa for 20min. (2) Layered variable power scanning: Import the 3D model, with a layer thickness of 0.05mm. The scanning power of the main structure layer is 100mW and the line spacing is 0.05mm. The scanning power of the inner wall of the flow channel layer is 120mW and the line spacing is 0.03mm. The scanning power of the suspended end face layer is 150mW and the line spacing is 0.02mm. (3) Support layout and layer-by-layer curing: PVA-based water-soluble support material is used to support the suspended end face, with the support contact area accounting for 8% of the area of ​​the suspended end face, and the material is cured layer by layer according to the planned path. (4) Support removal and cavity cleaning: After removing the support, ultrasonically clean with isopropanol for 120 seconds; (5) Post-curing stress relief: Place in a UV curing chamber and treat for 30 min at a wavelength of 365 nm, an intensity of 15 mW / cm², and a temperature of 40 °C.

[0037] Air tightness test: Introduce 0.2MPa clean compressed air into the inlet end, immerse in 35℃ purified water for 30s, and if no bubbles overflow, it is a finished product. Example 2

[0038] The preparation process in this embodiment is basically the same as that in Example 1. The difference is that in the layered variable power scanning step, the scanning power of the suspended end face layer is adjusted to 160mW and the scanning line spacing is adjusted to 0.018mm. The other parameters are the same as those in Example 1. Example 3

[0039] The preparation process of this embodiment is basically the same as that of Example 2. The difference is that in the post-curing stress relief step, the treatment temperature is adjusted to 45°C and the treatment time is adjusted to 25 min. The other parameters are the same as those of Example 2. Example 4

[0040] The preparation process of this embodiment is basically the same as that of Example 3. The difference is that after the post-curing stress relief step is completed, an internal cavity hydrophobic modification step is added: a low-temperature plasma treatment device is used to introduce hexamethyldisiloxane working gas into the internal cavity of the device. The working gas pressure is 20Pa, the discharge power is 100W, and the treatment time is 90s. The remaining parameters are the same as those of Example 3. Example 5

[0041] The preparation process in this embodiment is basically the same as that in embodiment 4. The difference is that the effective height of the suspended air gap is adjusted to 22mm in the suspended air gap section configuration, while the other parameters remain the same as in embodiment 4. Example 6

[0042] The preparation process in this embodiment is the same as that in Example 5, except that the gradient shrinkage ratio of the flow channel is adjusted to 1:0.55, that is, the inner diameter of the gradient flow limiting section outlet is 5.5mm. All other structural parameters and process parameters are the same as those in Example 5. Example 7

[0043] The preparation process in this embodiment is the same as that in Example 5, except that the gradient shrinkage ratio of the flow channel is adjusted to 1:0.70, that is, the inner diameter of the gradient flow limiting section outlet is 7.0 mm. All other structural parameters and process parameters are the same as those in Example 5. Comparative Example 1

[0044] The existing spring-loaded one-way valve drain connector is used. The valve body is injection molded from PP material and internally equipped with a silicone sealing plug and a stainless steel return spring. The interface specifications are consistent with those of the embodiment. Comparative Example 2

[0045] The same flow channel structure design as in Example 1 is adopted, and it is formed by ordinary SLA photopolymerization process. It adopts uniform scanning power, without layered variable power control, without post-curing stress relief step, and without hydrophobic modification step. Comparative Example 3

[0046] Using the same preparation process as in Example 5, only the gradient flow limiting section and the spiral guide ridge are removed. The inlet connection section is a straight pipe of equal diameter directly connected to the suspended air gap section. The remaining structural parameters, such as the effective height of the suspended air gap, the anti-climbing boss, and the outlet confluence section, are the same as in Example 5. Comparative Example 4

[0047] The same flow channel structure design as in Example 3 was adopted, the layered variable power scanning process was retained, the post-curing stress relief step was removed, and the rest of the preparation process and parameters were the same as in Example 3. Comparative Example 5

[0048] The same flow channel structure design as in Example 3 was adopted, the post-curing stress relief process was retained, the layered variable power scanning was cancelled, and a uniform scanning power of 100mW and line spacing of 0.05mm were used. The rest of the preparation process and parameters were the same as in Example 3. Comparative Example 6

[0049] Using the same preparation process as in Example 5, the gradient flow limiting section is retained, but the spiral guide rib is removed. That is, the axial spiral guide rib is not set on the inner wall of the gradient flow limiting section. The remaining structural parameters, such as the inlet connecting section, the three-stage inner diameter contraction structure of the gradient flow limiting section, the suspended air gap section, and the outlet confluence section, are the same as in Example 5. Performance testing and results analysis

[0050] Test items and methods Reverse blocking pressure resistance: Apply gradient water pressure to the outlet end of the device and record the critical pressure at which waste liquid begins to backflow into the inlet end.

[0051] Forward flow resistance: The pressure difference between the inlet and outlet of the test device under a flow rate of 500 mL / min.

[0052] Inner wall roughness: The Ra value of the inner wall of the flow channel was detected using a contact profilometer.

[0053] Retention rate of pressure resistance after disinfection cycle: After 1000 cycles of ethylene oxide disinfection, the reverse blocking pressure is retested, and the ratio with the initial value is calculated.

[0054] Organic residue per unit area on the inner wall: After passing simulated dialysis waste liquid through, the wall is rinsed according to the standard procedure, and the amount of organic residue per unit area on the inner wall is measured.

[0055] Dimensional change rate after disinfection: The change rate of the suspended air gap height was tested after 1000 disinfection cycles.

[0056] Cytotoxicity level: The MTT assay was used to perform in vitro cytotoxicity tests to determine the toxicity level.

[0057] The performance test results of each embodiment and comparative example are shown in the table below: Reverse blocking withstand voltage MPa 0.15 0.15 0.15 0.15 0.18 0.17 0.15 0.08 0.12 0.11 0.15 0.14 0.15 Forward flow resistance kPa 1.2 1.2 1.2 1.2 1.2 1.8 1.0 2.7 1.3 1.1 1.2 1.2 1.4 Inner wall roughness Ra μm 0.72 0.61 0.60 0.58 0.58 0.58 0.58 1.6 1.1 0.59 0.61 0.95 0.58 Pressure resistance retention rate after 1000 sterilization cycles % 90 91 98 98 98 98 98 62 75 98 82 92 98 Organic residue per unit area on the inner wall μg / cm² 0.8 0.7 0.7 0.38 0.38 0.42 0.51 3.5 1.9 1.6 0.7 0.7 0.45 Dimensional change rate after disinfection % 0.15 0.14 0.08 0.08 0.08 0.08 0.08 0.3 0.25 0.08 0.18 0.09 0.08 Cytotoxicity level class 0 0 0 0 0 0 0 1 0 0 0 0 0 Total axial length of the device mm 78 78 78 78 78 78 78 65 78 78 78 78 78

[0058] (1) Verification of the advantages of the core solution: The reverse blocking pressure resistance, forward flow resistance, inner wall roughness and disinfection durability of Examples 1-5 are significantly better than the traditional mechanical valve of Comparative Example 1, proving that the integrated suspended air gap solution of the present invention comprehensively surpasses the existing mainstream technical solutions in terms of backflow prevention reliability, smooth flow of liquid and biosafety.

[0059] (2) Demonstration of Structural Synergy and Creativity: Comparing Example 5 with Comparative Example 3, it can be seen that after removing the gradient flow limiting section and the spiral guide ridge, the reverse blocking pressure decreased from 0.18 MPa to 0.11 MPa, and the residual organic matter on the inner wall increased from 0.38 μg / cm² to 1.6 μg / cm². This proves that the gradient flow limiting section and the suspended air gap are not simply superimposed, but have a strong synergistic effect—the gradient flow limiting, through steady flow and acceleration, allows the liquid column to fall evenly, reducing splashing and wall adhesion at the source, which is a necessary prerequisite for the miniaturization, high reliability, and low residue of the air gap structure. The combined effect exceeds the conventional expectations of those skilled in the art and is not a simple accumulation of common knowledge.

[0060] (3) Synergistic effect analysis of the spiral guide ridge: Comparing Example 5 and Comparative Example 6, it can be seen that, under the premise of retaining the gradient flow limiting section, only after removing the spiral guide ridge, the reverse blocking pressure decreased from 0.18MPa to 0.15MPa, the residual organic matter on the inner wall increased from 0.38μg / cm² to 0.45μg / cm², and the forward flow resistance increased from 1.2kPa to 1.4kPa. This proves that the spiral guide ridge, by guiding the waste liquid along the spiral path, prolongs the residence time of droplets in the gradient flow limiting section, allowing the liquid flow to decelerate and stabilize more fully before entering the suspended air gap section, thereby reducing splashing and wall adhesion and reducing residue; at the same time, the spiral guide ridge slightly reduces the forward flow resistance. The synergistic cooperation between the spiral guide ridge and the gradient flow limiting section is an important structural feature for improving the reliability of backflow prevention.

[0061] (4) Demonstration of the synergistic inventiveness of the process: Comparative examples 3, 4, and 5 show that when using layered variable power scanning alone, the pressure resistance retention rate after sterilization is only 82%, and the dimensional change rate is 0.18%; when using post-curing stress relief alone, the inner wall roughness Ra reaches 0.95 μm, and the reverse pressure resistance is only 0.14 MPa; when the two are used in combination, the pressure resistance retention rate increases to 98%, and the inner wall Ra decreases to 0.60 μm, with the performance improvement far exceeding the linear superposition of the effects of the single process. This proves that there is a synergistic effect between layered variable power scanning and post-curing stress relief, and it is not a simple combination of two known processes.

[0062] (5) Demonstration of the non-obviousness of parameter optimization: Comparison of Examples 5, 6, and 7 shows that when the gradient shrinkage ratio deviates from 1:0.62, either the forward flow resistance increases significantly (reaching 1.8 kPa at 1:0.55), or the reverse blocking ability decreases and the residue increases (reaching 0.51 μg / cm² at 1:0.70). 1:0.62 is the optimal value that balances the three core performance aspects of forward flow resistance, reverse pressure resistance, and inner wall residue. This parameter selection needs to be verified through extensive fluid simulation and molding experiments, and is not an obvious result that can be obtained by those skilled in the art through conventional experiments.

[0063] (6) Verification of progressive process gain: The single-variable progressive data from Example 1 to Example 5 clearly show that each additional process / structural feature generates a clear gain in the corresponding performance index, and the final comprehensive performance far exceeds the cumulative effect of single feature improvement, proving that the technical solution of the present invention is an interconnected organic whole with significant systematic improvement value.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Conventional adjustments to specific parameters made by those skilled in the art without departing from the principles of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a device to prevent backflow of fluid from a suspended drain pipe of a hemodialysis machine, characterized in that, This includes the additive manufacturing process of suspended gradient flow channels and the integral molding process of photosensitive resin gradient photocuring: The additive manufacturing process for the suspended gradient flow channel generates a continuous 3D model of the flow channel, including an inlet connecting section, a gradient flow limiting section, a suspended air gap section, and an outlet confluence section. The inner diameter of the gradient flow limiting section gradually narrows along the flow direction of the waste liquid, and the ratio of the inlet inner diameter to the outlet inner diameter is the flow channel gradient contraction ratio. The suspended air gap section is located between the outlet of the gradient flow limiting section and the inlet of the outlet confluence section, forming an air isolation area without physical contact. The vertical distance between the outlet end face of the gradient flow limiting section and the inlet end face of the outlet confluence section is the effective height of the suspended air gap. The photosensitive resin gradient light curing integrated molding process involves slicing the three-dimensional model into slices according to a set layer thickness, and then using photosensitive resin as raw material to cure it layer by layer with ultraviolet light to obtain an integrated device body without splicing gaps. The specific process of the suspended gradient flow channel additive configuration step is as follows: The first step is to construct the inlet connection section, set the inner diameter and axial length of the inlet connection section, set a standard Luer tapered joint structure at the outer end of the inlet connection section, and set an annular anti-detachment flange at the root of the joint; The second step is to construct a gradient flow restriction section, which is smoothly connected to the inlet connection section. Three-stage inner diameter contraction is set along the waste liquid flow direction, and the ratio of the axial length of each contraction section to the inner diameter contraction amount of that section is 4:

1. The third step is to construct a suspended air gap section. An annular exhaust groove is set on the side wall of the suspended air gap section. The annular exhaust groove is connected to the external atmosphere of the device. An annular anti-climbing wall protrusion is set on the lower inner wall of the suspended air gap section. The fourth step is to construct the outlet manifold. The inlet end face of the outlet manifold is located directly below the outlet end face of the gradient flow limiting section. The inner diameter of the outlet manifold gradually increases along the direction of waste liquid flow, and a standard pipe insertion structure is set at the outer end. The fifth step is to construct an axial spiral guide rib on the inner wall of the gradient flow limiting section, with the guide rib extending along the direction of waste liquid flow.

2. The preparation method according to claim 1, characterized in that, The parameters of the axial spiral guide ribs on the inner wall of the gradient flow limiting section are as follows: there are 4 guide ribs, which are evenly distributed along the circumference of the inner wall of the gradient flow limiting section; the height of the guide ribs is 0.8 mm, and the ratio of the width to the height of the guide ribs is 1.2:1; the spiral angle of the guide ribs is 15 degrees, and the guide ribs start at the inlet end face of the gradient flow limiting section and end at the outlet end face of the gradient flow limiting section; the edges of the guide ribs adopt a rounded transition with a radius of 0.2 mm.

3. The preparation method according to claim 1, characterized in that, The gradient contraction ratio of the flow channel is the ratio of the inlet inner diameter to the outlet inner diameter of the gradient flow-limiting section, which is 1:0.

62.

4. The preparation method according to claim 1, characterized in that, The effective height of the suspended air gap is 25mm, which is the vertical distance between the outlet end face of the gradient flow limiting section and the inlet end face of the outlet confluence section.

5. The preparation method according to claim 1, characterized in that, The specific process of gradient photocuring integral molding of photosensitive resin is as follows: The first step is resin pretreatment. The photosensitive resin is placed in a vacuum degassing device and kept at a temperature of 35℃ and a negative pressure of 0.09MPa for 20 minutes to remove air bubbles inside the resin. The second step is layered variable power scanning. The 3D model is imported into the slicing software, the layer thickness is set to 0.05mm, and the ultraviolet light scanning path for each layer is generated. Different scanning powers are set for the inner wall layer of the flow channel and the suspended end face layer. The third step is to support the air gap section and solidify it layer by layer. Water-soluble support material is used to support the suspended end face of the air gap section. The contact area between the support and the body is controlled within 8% of the area of ​​the suspended end face. The support is solidified and formed layer by layer according to the planned scanning path and power. The fourth step is to remove the support and clean the inner cavity. Take out the molded device body, remove the external support, put it into an ultrasonic cleaning device, and use isopropanol to ultrasonically clean the inner cavity and the outer surface for 120 seconds. The fifth step is to eliminate post-curing stress. After cleaning, the device is placed in a UV curing chamber and post-cured at 40°C for 30 minutes to eliminate the internal stress of the molding.

6. The preparation method according to claim 5, characterized in that, The specific parameters for layered variable power scanning are as follows: the scanning power of the inner wall layer of the flow channel is set to 120mW and the scanning line spacing is 0.03mm; the scanning power of the suspended end face layer is set to 150mW and the scanning line spacing is 0.02mm; and the scanning power of the main structure layer is set to 100mW and the scanning line spacing is 0.05mm.

7. The preparation method according to claim 5, characterized in that, The specific parameters for post-curing stress relief are as follows: the ultraviolet light wavelength in the curing chamber is 365nm, the irradiation intensity is 15mW / cm², the ambient temperature is constant at 40℃, and the treatment time is 30min.

8. The preparation method according to claim 5, characterized in that, After the post-curing stress relief step is completed, the inner cavity hydrophobic modification step is also included. The specific parameters for the inner cavity hydrophobic modification are as follows: a low-temperature plasma treatment device is used to introduce hexamethyldisiloxane working gas into the inner cavity of the device. The working gas pressure is 20Pa, the discharge power is 100W, and the treatment time is 90s.

9. The preparation method according to claim 5, characterized in that, After the internal cavity cleaning step is completed, the airtightness in situ test step is also included. The specific parameters for the airtightness in situ test are as follows: 0.2 MPa of clean compressed air is introduced into the inlet of the device, the entire device is immersed in purified water at 35°C and kept for 30 seconds. If no bubbles overflow, it is considered qualified.

10. A device for preventing backflow of fluid from a hemodialysis machine drain pipe, manufactured using the preparation method described in any one of claims 1 to 9, characterized in that, The device body is an integrated structure, with the inlet connection section, gradient flow limiting section, suspended air gap section and outlet confluence section connected in sequence inside. The inner diameter of the gradient flow limiting section gradually decreases along the direction of waste liquid flow, and an air isolation area is formed inside the suspended air gap section. There are no moving valve core components inside the device.