Aortic valve prosthesis additive forming method and system

Abstract

The invention provides an aortic valve prosthesis additive forming method and system, and relates to the technical field of soft material additive manufacturing The method comprises the steps that a plane expansion model is generated according to a three-dimensional model of a to-be-formed prosthetic valve, and a trajectory strategy of additive forming and a tension combination of a tension device are preset; the sacrificial layer film is stretched according to the tension combination of the current printing layer through a tension device and fixed to a base plate, and prosthetic valve patterns are printed on the sacrificial layer film layer by layer through an additive forming device; the tension combination of the tension device is adjusted layer by layer, and the step S2 is repeated until all layers of the prosthetic valve are printed; the printed workpiece and the sacrificial layer film are removed together, the sacrificial layer film is dissolved through a dissolving agent, and a prosthetic valve sample is obtained through separation. The production time of the whole aortic heart valve prosthesis can be shortened, and production and application of personalized aortic heart valves more suitable for specific patients are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing of soft materials, and particularly, to an additive forming method and system for an aortic valve prosthesis. Background Art

[0002] Biological products such as artificial heart valves and artificial blood vessels and their natural prototypes generally have complex shapes, have certain requirements for surface smoothness, need to be made of high-soft-elastic polymer materials, and the finished products need to be sensitive to liquid pressure and have good dynamic response characteristics. Therefore, in the development and process optimization stages of such biological products, a large number of new shape designs and new materials (such as various biological hydrogels) are often required.

[0003] Taking the aortic heart valve as an example. The main body of the aortic heart valve prosthesis consists of valve leaflets and a stent; it is preferable that the valve leaflets mimic the shape of the natural aortic heart valve, and the shape is complex. This is because: the natural aortic heart valve has no specific shape when not under force; when cut from the aortic root and stretched out, it is close to a semi-circular shape; in in-vivo observations, when the valve leaflets are fully closed, its spatial shape is a composite thin-shell structure composed of an abdominal region approximated to a paraboloid and a contact region approximated to a plane. In addition, the natural aortic heart valve has a very small thickness, with an average between 0.3 - 1.2 mm; it is not uniform, showing a thin abdominal region and a thick contact region, gradually thickening from the abdominal region to the contact region, with a striped thickness distribution, and the stripe distribution is close to the shape of the collagen fiber distribution captured in the valve polarized light film. The natural aortic heart valve also has the characteristics that the ventricular side surface is smooth while the aortic side surface is rough, and it is natural to specify the solid ventricular side surface as the reference surface in the design drawings of the product; this characteristic also has a high similarity with the fiber distribution characteristic of the valve.

[0004] Therefore, it is relatively difficult to manufacture a prosthetic valve that meets the extremely small wall thickness and ultra-high elasticity requirements closer to those of natural aortic valves to meet the requirements of deformation and durability and can exhibit a similar complex shape under a liquid pressure of 120 mmHg through direct 3D printing or injection molding methods. Moreover, since the heart valve material is a material with anisotropic biaxial mechanical properties and the shape of the valve is a complex shell, it is difficult to calculate the natural shape when it is not stressed by back-calculating the shape under 120 mmHg. In particular, when the valve drawing is drawn closer to the striped thickness distribution of the natural valve, direct 3D printing often accompanies many defects such as tearing or material fracture, and the difficulty of replacing the injection molding manufacturing with a process optimization mainly based on materials closer to natural valve materials will also increase. In addition, the shape of the natural valve that can be relatively quickly and directly obtained through CT images, autopsy or reverse scanning modeling is often the shape exhibited by the valve under a liquid pressure of 120 mmHg; the thickness data of the natural aortic valve is also the data measured when a certain tensile force is applied to the valve to fully stretch it to be close to a plane; there is a certain difference between the natural valve when it is not stressed and the measurable shape and thickness. It is very difficult to achieve this difference by adjusting 3D printing or injection molding processes. Although dip molding is a technology that can obviously solve this pain point, it cannot achieve the biaxial mechanical property differences caused by fiber distribution of natural valve materials and the non-uniform thickness characteristics of the valve. In particular, in the stage of needing to experiment with a variety of new materials, in order to obtain samples with ideal shapes, many additional process adjustments are often required for the 3D printing platform and injection molding process package (such as release agents, mold shapes, etc.), and even some concessional improvements need to be made to the new materials or the valve shapes designed themselves. The process is cumbersome and time-consuming, and the effect is often unsatisfactory, reducing the efficiency of early prototype manufacturing.

[0005] 4D printing is a new technology developed on the basis of 3D printing to overcome the difficulty that 3D-printed soft material parts are difficult to meet the requirements of dynamic structural performance. Compared with direct 3D printing, 4D printing generally requires the printing material to have some programmable characteristics, and the three-dimensional drawing of the part is unfolded into a flat drawing in a certain way, or other surfaces with excellent properties such as some single-curved surfaces. After the part is printed on a plane or near-plane, the printing material refolds under certain stimulation conditions (such as light, magnetism, heat, specific liquid) to restore the flat or near-plane drawing into the originally designed three-dimensional shape. There have been many successful cases of 4D printing in manufacturing soft pliers, self-assembly systems and smart actuators using highly soft elastomer materials typified by hydrogels. Therefore, this application proposes a method and system for additive manufacturing of an aortic valve prosthesis applying the concept of 4D printing forming. Summary of the Invention

[0006] According to the above-mentioned technical problems of biaxial mechanical property difference and non-uniform thickness of the valve in the existing 3D-printed aortic valve prosthesis, an aortic valve prosthesis additive forming method and system are provided. The method mainly prints the aortic valve leaflet drawing within the allowable range of the expansion rate on the substrate stretched and wrapped by the fixture with a specific force, and finally obtains a valve prosthesis leaflet with a thickness characteristic close to the natural valve that can generate a specific three-dimensional shape under a specific liquid pressure.

[0007] The technical means adopted by the present invention are as follows:

[0008] A method for additively molding an aortic valve prosthesis comprises the following steps:

[0009] S1. Generate a planar unfolded model according to the three-dimensional model of the prosthetic valve to be formed, preset the trajectory strategy of the additive forming and the tension combination of the tensioning device, wherein the tension combination includes the magnitude and direction of the tension in the X-axis and Y-axis directions;

[0010] S2, stretching the sacrificial layer film according to the tensile force combination of the current printing layer by a tensioning device and fixing it on the substrate, and printing the prosthetic valve pattern layer by layer on the sacrificial layer film by an additive forming device;

[0011] S3, adjusting the tension combination of the tensioning device layer by layer and repeating step S2 until all layers of the prosthetic valve are printed;

[0012] S4, removing the printed product together with the sacrificial layer film, dissolving the sacrificial layer film with a solvent, and separating to obtain a prosthetic valve sample;

[0013] The setting of the tension combination is based on the stress conditions of the natural valve when it is unfolded and its shape is measured, and the stretching direction of the sacrificial layer film matches the tension direction of the valve leaflets under liquid pressure.

[0014] Furthermore, the material of the sacrificial layer film is water-soluble polyvinyl alcohol or resin, and the additive molding material is a soft elastomer whose elastic modulus matches that of the natural valve material, including PVE polyvinyl chloride ether or hydrogel.

[0015] Furthermore, the additive manufacturing device includes a DIW module, and the DIW module includes at least two material injection tubes, and multi-material synchronous or alternating printing is achieved through laser radar positioning.

[0016] Furthermore, in step S2, the tensioning device drives the roller via a servo motor to apply a tension combination to the sacrificial layer film, and the tension combination is dynamically adjusted according to preset parameters during layer-by-layer printing;

[0017] The substrate and the tensioning device are integrated into a five-axis linkage machine tool. The extrusion needle of the additive manufacturing device performs five-axis movement under the control of a servo motor to synchronously complete material extrusion and trajectory positioning.

[0018] Further, in steps S2 and S3, the position and movement speed of the extrusion needle are monitored in real time, and the extrusion needle is adjusted to ensure the movement regularity and material distribution uniformity in the edge area.

[0019] Meanwhile, the real-time tensile forces of each layer of pattern in the X-axis and Y-axis directions are detected, and the tensile force combination parameters of the next layer are dynamically corrected.

[0020] The present invention also provides an additive manufacturing system for an aortic valve prosthesis, including an additive manufacturing device, a tensioning and fixing device, and a workbench. Among them, a substrate is placed on the workbench, and the additive manufacturing device is located above the substrate. During processing, the sacrificial layer film is stretched and fixed on the substrate by the tensioning device in the set X direction and Y direction with a specific tensile force combination, and the additive manufacturing device is used to layer-by-layer form the prosthesis valve to be formed on the sacrificial layer film.

[0021] Further, the additive manufacturing system is installed on a five-axis linkage machine tool. The tensioning and fixing device is installed on the machine tool workbench, and four servo motors drive rollers to tension and contract the sacrificial layer film.

[0022] Further, the additive manufacturing device includes a DIW print head. The DIW print head is installed on the V axis of the machine tool. The DIW print head is driven by a servo motor to drive a screw, and the screw pushes a piston to extrude TPE material to complete layer-by-layer printing.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The present invention can significantly accelerate the update and iteration process of printing materials; the formed parts have better formability and surface morphology, and are more restored; the design idea of the printed valve drawing is beneficial to the design of its special prosthesis stent, which can shorten the production time of an entire adult aortic heart valve prosthesis, and is beneficial to the production and application of personalized aortic heart valves more suitable for specific patients.

[0025] The film required to be covered on the substrate in the present invention can dissolve a specific solvent, which is beneficial to the adhesion-free removal between the workpiece and the substrate, and successfully ensures the forming quality of the workpiece.

[0026] The extrusion unit in the present invention can be composed of a plurality of extrusion modules (Direct Ink Writing, DIW), and the accuracy control of the extrusion needle and the moving unit is realized jointly by a lidar and a servo motor, so as to realize the accuracy of the finished products printed with different experimental materials. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a flowchart of the additive manufacturing forming method of the present invention.

[0029] Figure 2 It is a schematic diagram of the system of the additive manufacturing forming method of the present invention.

[0030] In the figure: 1, workbench; 2, substrate; 3, sacrificial layer thin film; 4, additive forming device; 5, workpiece to be formed; 6, tensioning device. Specific embodiments

[0031] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail the present invention.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] It should be noted that the terms used here are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used here, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprise" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0034] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0035] For the sake of convenience of description, spatial relative terms such as "above", "over", "on the upper surface", "upper", etc. may be used here to describe the spatial positional relationship of a device or feature shown in the figure with other devices or features. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figure for the device. For example, if the device in the figure is inverted, the device described as "above other devices or structures" or "over other devices or structures" will then be positioned "below other devices or structures" or "under other devices or structures". Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations should be made for the spatial relative descriptions used here.

[0036] The present invention provides a method and system for additive manufacturing of an aortic valve prosthesis. The purpose is to stretch the sacrificial layer film 3 in the set X-axis direction and Y-axis direction by a stretching device 6 on a substrate 2 wrapped by a fixture applying a specific force, and then support it by the substrate 2 and tightly wrap it on the surface of the substrate 2. The additive manufacturing device 4 extrudes materials onto the sacrificial layer film 3 according to a specified path in accordance with the drawing. Since the patterns formed by the stretching device 6, the sacrificial layer film 3, the substrate 2, and the extrusion of the additive manufacturing device 4 are relatively stationary, the tensile force on the extruded pattern in the set X-axis and Y-axis directions is equal to the tensile force applied by the stretching device 6 to the sacrificial layer film 3. According to the mechanical properties of the specific sacrificial layer material and the printing material, the combination of the tensile force of the stretching device 6 is adjusted so that the valve drawing can be manufactured under the stress conditions that fully restore the shape of the natural valve when it is unfolded, thereby completing a valve product with better static shape and dynamic performance. The aortic valve leaflet drawing within the allowable range of the printed elongation rate is finally obtained, and a valve prosthesis leaflet with a thickness characteristic similar to that of the natural valve and capable of generating a specific three-dimensional shape under a specific liquid pressure is obtained.

[0037] As a further preference, the material of the sacrificial layer film 3 is PVA or water-soluble resin for additive manufacturing, the printing material is a soft elastomer such as PVE or hydrogel with an elastic modulus close to that of the natural valve material, the additive manufacturing device includes a DIW module, and the additive manufacturing method adopted is Direct Ink Writing (DIW);

[0038] As a further preference, the stretching device includes rollers, clamping jaws, a fixed base, an angle dial, a force sensor, and a servo motor. The combination of the tensile force applied to the sacrificial layer film 3 is accurately controlled by the rollers. The rollers can ensure that the fixture of the stretching device has sufficient contact area with the sacrificial layer film 3 and enable the sacrificial layer film 3 to be fully tensioned and fixed on the substrate 2. The scheme of the stretching device is analogous to the device scheme of a tensile testing machine.

[0039] As a further preference, the DIW module includes two or more material injection tubes, and a lidar to ensure that the device still maintains a certain positioning accuracy when different combinations of material injection tubes are replaced.

[0040] Example 1:

[0041] As Figure 1-2 shown, the present invention provides a method for additive manufacturing of an aortic valve prosthesis, including the following steps:

[0042] S1. Based on the three-dimensional model of the biological product to be formed, such as a prosthetic valve, and the planar unfolded model to be printed, preset the trajectory strategy, trajectory, and tensile force combination of the stretching device 6 (including the magnitude of the tensile force and the preset X and Y directions, preferably XY being a set of orthogonal directions);

[0043] S2. The stretching device 6 stretches the sacrificial layer film 3 according to the set tensile force combination of this printing layer so that it covers the substrate 2, and the additive manufacturing device 4 completes the pattern of this layer on the sacrificial layer film 3 supported by the substrate 2 according to the preset additive manufacturing trajectory;

[0044] S3. Repeat the process of S2. The stretching device 6 can reapply and adjust layer by layer according to the set historical tensile force combination until the manufacturing of the workpiece is completed;

[0045] S4. Remove the sacrificial layer film 3 together with the printed workpiece from the substrate 2 and put it into the sacrificial layer solvent to complete the separation of the workpiece and the sacrificial layer to obtain the workpiece sample.

[0046] Furthermore, the position and moving speed of the extrusion needle in the additive manufacturing device should be monitored in real time by lidar to ensure the regularity of the movement of the extrusion needle in the edge area of the workpiece and the uniform distribution of the extruded material; the tensile force received by each layer of the pattern in the specified XY direction should be detected to appropriately adjust the tensile force combination applied to the sacrificial layer film 3 in the next layer. Because the trajectory strategy of additive manufacturing and the tensile force combination of the stretching device are preset, before printing each layer, the tensile force combination of the stretching device needs to be adjusted to the preset value, and then the printing of this layer can be started.

[0047] The present invention also provides an additive manufacturing system for an aortic valve prosthesis, including an additive manufacturing device 4, a stretching device 6, and a workbench 1; wherein, the additive manufacturing device 4 is located above the workbench 1, and a substrate 2 is placed on the workbench 1; during processing, the sacrificial layer film 3 is stretched and fixed on the substrate 2 by the stretching device 6 in the set X and Y directions with a specific tensile force combination, and the additive manufacturing device 4 forms the prosthesis valve to be formed layer by layer or by other forming strategies on the sacrificial layer film 3.

[0048] Preferably, the sacrificial layer material is selected as water-soluble resin or PVA for 3D printing, usually a prefabricated film, and the thickness adopted is determined by the historical tensile force combination, printing material, and workpiece weight in the specific printing task. The additive manufacturing material is selected as 0-degree TPE.

[0049] Furthermore, the system is installed on a five-axis linkage machine tool to cooperate for additive manufacturing. Among them, the tensioning device 6 is installed on the machine tool table 1, and four servo motors drive the rollers to perform programmable tensioning and contraction on the sacrificial layer film 3. The DIW print head is installed on the V-axis of the machine tool and performs five-axis movement under the command of the G code generated by the 3D printing slicing software. The print head is driven by a servo motor to drive a screw, and the screw pushes a piston to extrude the TPE material to complete layer-by-layer printing. After printing is completed, the sacrificial layer is dissolved in water, and the desired product can be obtained after the tension disappears.

[0050] Specifically, the additive forming device 4 selects the DIW method and supports the simultaneous installation of multiple extrusion needles. Different needles can be individually controlled by the lifting device and the moving device respectively, or they can move in parallel. That is, different needles can define the world coordinate system with their respective initial positions of the needles, and are driven by the same motor and the same set of trajectory commands to perform the same path actions in their respective world coordinate systems in parallel. Obviously, the multi-needle solution can achieve: 1. Achieve certain designed optoelectromagnetic force performance by making material gradients; 2. Construct some special lattice structures, such as the fiber distribution of natural valve leaflets, by adjusting the thickness of the needle orifice and the combination of base materials; 3. Improve the efficiency of some experimental productions, such as when screening new materials for prosthetic valves, multi-nozzle printing allows tasks such as completing experiments on printing samples of multiple materials in one printing task. The sacrificial layer material can also be used as a kind of printing material to complete the printing tasks of some more complex biological products (such as artificial blood vessels): for example, the sacrificial material can be printed between patterns as a support material to play a role in support or reference positioning to complete the printing tasks of some high-complexity drawings. The device can correct the shaping and positioning accuracy of the extrusion needle through lidar to ensure the movement stability of the device in the edge area of the printed pattern, so as to ensure the forming quality of the product;

[0051] The above additive manufacturing method and system are particularly suitable for the rapid prototyping of biological products with high softness and high elasticity, such as:

[0052] Using the above method, the three-dimensional figure of the fully closed heart valve obtained by perfusion with a 120 mmHg rubber solution used in reverse scanning or autopsy is unfolded into a plane within the error dissolution range; according to the axial and radial tensions received by the natural valve under the fully closed condition, the area of the valve, etc., set the tension combination of the rollers of the tensioning device and select the appropriate thickness of the sacrificial layer film 3. The shape of the heart valve printed by this method is more accurate and the dynamic response performance is better. Similarly, this method can be applied to any biological product (such as venous vascular products) that has a specific excellent shape that is convenient for measurement or manufacturing only under certain stress conditions.

[0053] The above system is particularly suitable for printing biological products using materials such as hydrogels containing living cells, can controllably provide certain mechanical stress for cells and hydrogels during the manufacturing process, and shorten the experimental cycle; moreover, this system can complete certain printing tasks aimed at applying composite materials.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for additive manufacturing of an aortic valve prosthesis, characterized in that: The following steps are involved: S1. Generate a planar unfolded model according to the three-dimensional model of the prosthetic valve to be formed, preset the trajectory strategy of the additive forming and the tension combination of the tensioning device, wherein the tension combination includes the magnitude and direction of the tension in the X-axis and Y-axis directions; S2, stretching the sacrificial layer film according to the tensile force combination of the current printing layer by a tensioning device and fixing it on the substrate, and printing the prosthetic valve pattern layer by layer on the sacrificial layer film by an additive forming device; S3, adjusting the tension combination of the tensioning device layer by layer and repeating step S2 until all layers of the prosthetic valve are printed; S4, removing the printed product together with the sacrificial layer film, dissolving the sacrificial layer film with a solvent, and separating to obtain a prosthetic valve sample; The setting of the tension combination is based on the stress conditions of the natural valve when it is unfolded and its shape is measured, and the stretching direction of the sacrificial layer film matches the tension direction of the valve leaflets under liquid pressure.

2. The method for additive manufacturing of an aortic valve prosthesis according to claim 1, characterized in that: The material of the sacrificial layer film is water-soluble polyvinyl alcohol or resin, and the additive molding material is a soft elastomer whose elastic modulus matches that of the natural valve material, including PVE polyvinyl chloride ether or hydrogel.

3. The method for additive manufacturing of an aortic valve prosthesis according to claim 1, characterized in that: The additive manufacturing device includes a DIW module, and the DIW module includes at least two material injection tubes, which realize multi-material synchronous or alternating printing with controllable accuracy and speed through laser radar positioning.

4. The method for additive manufacturing of an aortic valve prosthesis according to claim 1, characterized in that: In step S2, the tensioning device drives the roller via a servo motor to apply a tension combination to the sacrificial layer film, and the tension combination is dynamically adjusted according to preset parameters during layer-by-layer printing; The substrate and the tensioning device are integrated into a five-axis linkage machine tool, and the extrusion needle of the additive forming device performs five-axis motion under the control of a servo motor to synchronously complete material extrusion and trajectory positioning.

5. The method for additive manufacturing of an aortic valve prosthesis according to claim 1, characterized in that: In steps S2 and S3, the position and movement speed of the extrusion needle are monitored in real time, and the extrusion needle is adjusted to ensure the regularity of movement and uniformity of material distribution in the edge area; At the same time, the real-time tension of each layer of pattern in the X-axis and Y-axis directions is detected, and the tension combination parameters of the next layer are dynamically corrected.

6. An aortic valve prosthesis additive manufacturing system, implemented based on the aortic valve prosthesis additive manufacturing method according to any one of claims 1 to 5, characterized in that: The invention comprises an additive forming device, a tensioning device and a workbench; wherein a substrate is placed on the workbench, and the additive forming device is located above the substrate; during processing, the sacrificial layer film is stretched and fixed on the substrate by the tensioning device in the set X direction and Y direction with a specific tension combination, and the additive forming device forms the prosthetic valve to be formed layer by layer on the sacrificial layer film.

7. The aortic valve prosthesis additive manufacturing system according to claim 6, characterized in that: The additive forming system is installed on a five-axis linkage machine tool; wherein the tensioning and fixing device is installed on a machine tool workbench, and four servo motors drive rollers to tension and shrink the sacrificial layer film.

8. The aortic valve prosthesis additive manufacturing system according to claim 7, characterized in that: The additive manufacturing device includes a DIW print head, which is installed on the V-axis of the machine tool. The DIW print head is driven by a servo motor to drive a screw, and the screw pushes a piston to extrude the TPE material to complete layer-by-layer printing.

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