Preparation method of warp-knitted fabric-based artificial heart valve composite material with hexagonal structure

Abstract

The invention discloses a preparation method of a warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure, and belongs to the technical field of cardiovascular medical instruments, and the preparation method comprises the following steps: constructing a stable mechanical skeleton through a warp-knitted fabric base material with a hexagonal structure, and co-dissolving a high-modulus polymer and a low-modulus polymer in an organic solvent to form a polymer blended solution; directional volatilization and phase separation of a solvent are induced by utilizing temperature gradient, so that high-modulus polymers are enriched towards the fabric side, low-modulus polymers are diffused towards the surface, and a gradient transition layer without an obvious interface is formed; and removing the residual solvent through vacuum drying. The warp-knitted base material with a hexagonal structure and a high-modulus and low-modulus blended polymer system are adopted, and the synergistic effect of temperature gradient induced polymer blended phase separation is combined, so that the pain points of unbalanced mechanics and biocompatibility and unstable structure of a traditional material are solved, and the composite material has the advantages of structural strength, elastic adaptability and biological safety, and can be applied to the field of medical materials. The method is suitable for preparing the artificial heart valve leaflet for transcatheter implantation or surgical replacement.

Description

Technical Field

[0001] This invention relates to the field of cardiovascular medical device technology, and in particular to a method for preparing a warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure. Background Technology

[0002] Artificial heart valves are core medical devices for treating congenital or acquired valvular heart diseases, and their performance directly determines the patient's postoperative quality of life and survival. Currently, the artificial heart valves used clinically mainly include bioprosthetic valves, mechanical valves, and polymer valves.

[0003] Bioprosthetic valves are mostly made from natural tissues such as bovine pericardium and porcine aortic valves through chemical fixation. While they possess good hemodynamic performance and biocompatibility, and patients do not require lifelong anticoagulation after surgery, they are prone to calcification and decay. Clinical data shows that the 5-year calcification and decay rate of bioprosthetic valves can reach 20%, and their average lifespan is usually less than 10 years, making them unsuitable for young patients or those requiring long-term implantation. Mechanical valves typically use metallic materials such as titanium alloys and cobalt-chromium alloys as the matrix, combined with sealing structures such as polytetrafluoroethylene (PTFE). While they have excellent mechanical stability and an extremely long lifespan, their blood compatibility is poor, requiring implanted patients to receive lifelong anticoagulation therapy. This results in an annual bleeding risk of no less than 3%, which can lead to life-threatening complications such as intracranial hemorrhage in severe cases. Polymer valves and fabric-based polymer valves, as emerging technologies, aim to balance mechanical performance and biocompatibility. The former often uses homogeneous polymer materials such as PTFE, but suffers from low tear strength (≤50MPa) and a low crack propagation threshold (≤5J / m). 2 The problem is that the former is prone to failure due to fatigue under long-term repeated impact of blood flow; although the latter introduces woven fabric as a reinforcing skeleton, the traditional warp and weft weaving structure has yarn slippage defects, stress is easily concentrated at the yarn intersection point, and there is a lack of microstructure design to inhibit crack propagation, making it difficult to meet the comprehensive requirements of high strength, high elasticity and high cycle fatigue resistance at the same time.

[0004] Therefore, there is an urgent need to develop a new type of artificial heart valve material that can combine high strength, high fatigue resistance, and good biocompatibility. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a method for preparing a warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure.

[0006] The technical solution adopted in this invention is: a method for preparing a warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure, comprising the following steps:

[0007] S1. A warp-knitted fabric substrate with a hexagonal structure is fixed in a mold; a high-modulus polymer and a low-modulus polymer are dissolved together in an organic solvent to prepare a polymer blend solution; wherein the Young's modulus of the high-modulus polymer is higher than that of the low-modulus polymer;

[0008] S2. Introduce the polymer blend solution into the mold and cover it with the warp-knitted fabric substrate; control the temperature at the bottom of the mold to be maintained at 35-50℃ and the temperature at the top to be maintained at 20-30℃, allow the solvent to evaporate for 15-40 hours, induce phase separation between the high-modulus polymer and the low-modulus polymer and form a gradient distribution to obtain the composite material preform.

[0009] S3. The composite material blank is subjected to vacuum drying treatment to obtain the warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure.

[0010] In a preferred embodiment of the present invention, in step S1, the width and length of each hexagonal unit of the warp-knitted fabric substrate are both 100-900 μm, the thickness is 50-250 μm, and the basis weight is 40-120 g / m². 2 .

[0011] In a preferred embodiment of the present invention, in step S1, the knitting fibers used in the warp-knitted fabric substrate include one or more of polyester, nylon, acrylic, spandex, polypropylene, polyethylene yarn, carbon fiber, aramid fiber, polyimide fiber, or polybenzimidazole fiber.

[0012] In a preferred embodiment of the present invention, in step S1, the high-modulus polymer is selected from at least one of polycarbonate-polyurethane copolymer, polyester polyurethane, and polystyrene-isobutylene-styrene triblock copolymer; the low-modulus polymer is selected from at least one of polysiloxane-polyurethane copolymer and polyether polyurethane.

[0013] In a preferred embodiment of the present invention, in step S1, the mass ratio of the high-modulus polymer to the low-modulus polymer is 1.5-2:1.

[0014] In a preferred embodiment of the present invention, in step S1, the organic solvent includes one or more of N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

[0015] In a preferred embodiment of the present invention, in step S1, the total polymer mass concentration of the polymer blend solution is 15-30%, and the viscosity is 150-300 mPa·s.

[0016] In a preferred embodiment of the present invention, in step S3, the drying temperature of the vacuum drying process is 40-60℃ and the drying time is 8-40h.

[0017] In a preferred embodiment of the present invention, the thickness of the warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure is 100-400 μm, the fiber volume content of the warp-knitted fabric is 10-60%, and the surface roughness is 0.1-1 μm.

[0018] In a preferred embodiment of the present invention, the composite material is used to prepare artificial heart valve leaflets.

[0019] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0020] (1) This invention uses a warp-knitted fabric with a hexagonal structure as a reinforcing skeleton. Its loop interlocking structure can effectively lock the fibers, fundamentally eliminating the defect of easy yarn slippage in traditional woven fabrics. The hexagonal mesh structure can evenly distribute stress when under stress, avoiding stress concentration at intersections, and significantly improving the overall structural stability and fatigue resistance of the composite material. Compared with ordinary mesh fabrics, the material of this invention has higher tear resistance and crack propagation threshold, which can meet the dynamic mechanical requirements of artificial heart valves to withstand long-term blood flow impact in the body.

[0021] (2) This invention successfully constructs a gradient transition layer with continuously varying modulus from the fabric substrate to the surface of the composite material by blending high- and low-modulus polymers and inducing phase separation using a temperature gradient field. This structure eliminates the obvious interface between different materials, achieves smooth stress transfer, and effectively suppresses fatigue failure caused by interface stress concentration. This gradient structure mimics the mechanical stratification of natural petioles, providing solid mechanical support through the high-modulus region and optimizing elasticity and blood compatibility through the low-modulus surface region, thereby achieving a highly efficient synergy between material mechanical properties and biocompatibility.

[0022] (3) This invention constructs a smooth and dense layer with a surface roughness of 0.1-1 μm on the outer surface of the composite material through a temperature gradient process, which greatly inhibits platelet adhesion and activation. Semi-in vivo blood circulation experiments have verified that no significant thrombus formation occurs on the material surface, demonstrating excellent anticoagulant properties and comprehensive superior blood compatibility. This makes it possible for artificial heart valves made from this material to significantly reduce or even eliminate patients' reliance on lifelong anticoagulation therapy after surgery, providing a clinical solution with both high safety and high quality of life for a wider range of patients. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a structural diagram of the warp-knitted fabric substrate with a hexagonal structure used in this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0027] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0028] Among them, N,N-dimethylacetamide (DMAc, Sinopharm Chemical Reagent Co., Ltd., AR, ≥99.0%), dimethyl sulfoxide (DMSO, Shanghai Aladdin Biochemical Technology Co., Ltd., AR, ≥99.0%), tetrahydrofuran (THF, Sinopharm Chemical Reagent Co., Ltd., AR, ≥99.5%); polycarbonate-polyurethane copolymer (PCU, Lubrizol, USA), polysiloxane-polyurethane copolymer (SiPU, Lubrizol, USA), polyester polyurethane (Lubrizol, USA), polystyrene-isobutylene-styrene triblock copolymer (SIBS, Kuraray, Japan), polyether polyurethane (Lubrizol, USA); ultra-high molecular weight polyethylene (UHMWPE) yarn (Guangdong Weiwoke Weaving Co., Ltd.), carbon fiber (Toray, Japan), aramid fiber (DuPont, USA), polyimide fiber (Evonik, Austria), polybenzimidazole fiber (Celanese, USA), polyester, nylon, acrylic, spandex, and polypropylene were all purchased from INVISTA, USA.

[0029] A method for preparing a warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure includes the following steps:

[0030] S1. A warp-knitted fabric substrate with a hexagonal structure is fixed in a mold; a high-modulus polymer and a low-modulus polymer are dissolved together in an organic solvent to prepare a polymer blend solution; wherein the Young's modulus of the high-modulus polymer is higher than that of the low-modulus polymer;

[0031] S2. Introduce the polymer blend solution into the mold and cover it with the warp-knitted fabric substrate; control the temperature at the bottom of the mold to be maintained at 35-50℃ and the temperature at the top to be maintained at 20-30℃, allow the solvent to evaporate for 15-40 hours, induce phase separation between the high-modulus polymer and the low-modulus polymer and form a gradient distribution to obtain the composite material preform.

[0032] S3. The composite material blank is subjected to vacuum drying treatment to obtain the warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure.

[0033] The steps will be described in detail below.

[0034] Step S1 is the pre-preparation stage, which aims to construct a stable hexagonal warp-knitted fabric substrate and a uniform polymer blend solution.

[0035] Specifically, in step S1, conventional synthetic fibers or high-performance, high-strength fibers, whether monofilament or multifilament, are selected and cut into yarn rolls 100-200m in length, ensuring no fiber breakage and a hairiness rate ≤0.5 strands / m. Multifilaments need to be doubling-processed to a fineness of 10-40D. Conventional fibers include one or more of polyester, nylon, acrylic, spandex, or polypropylene, while high-performance, high-strength fibers include one or more of high-strength ultra-high molecular weight polyethylene yarn, carbon fiber, aramid fiber, polyimide fiber, or polybenzimidazole fiber.

[0036] Furthermore, a twisting machine is used to twist the yarn, controlling the twist to be 0-120 twists / 10cm, and the twisting speed is set to 500-800 r / min. For conventional fibers such as polyester, 60-80 twists / 10cm are used to enhance yarn cohesion; for high-performance, high-strength fibers such as ultra-high molecular weight polyethylene, 30-50 twists / 10cm are used to avoid excessive twisting that could lead to fiber strength loss.

[0037] Furthermore, a Raschel warp knitting machine is used, and the process parameters are set according to the target hexagonal unit size. The guide bar swing is 5-15mm, 5-8mm when the unit size is 100-300μm, and 12-15mm when it is 600-900μm; the needle pitch is 0.2-0.5mm, and this parameter must be matched with the fineness of the yarn used to ensure no missed needles during the weaving process and appropriate fabric density; the weaving speed is set to 100-200r / min to ensure the stability of loop formation.

[0038] Furthermore, during the warp knitting process, the front guide bar uses a 1-0 / 1-2 yarn padding pattern to form the transverse edges of the hexagonal units; the rear guide bar uses a 2-3 / 0-1 yarn padding pattern to form the longitudinal edges of the hexagonal units. The two guide bars move in tandem, causing the loops to interlock and form a structurally stable hexagonal mesh, weaving a mesh fabric with the width and length of individual hexagonal units ranging from 100-900 μm.

[0039] Further, the fabric is placed in a heat-setting machine and heat-set at 80-120℃ for 10-20 minutes; then, the fabric is cut into the desired shape using a trimming machine, ultimately obtaining a thickness of 50-250μm and a weight of 40-120g / m². 2 Warp-knitted fabric substrates, such as Figure 1 As shown.

[0040] Specifically, the warp-knitted fabric substrate is placed in anhydrous ethanol and ultrasonically cleaned for 10-15 minutes to remove oil stains and weaving residues from the fabric surface, and then vacuum dried at 50-70°C for 1-3 hours.

[0041] Specifically, the warp-knitted fabric substrate is flattened and fixed in the mold to ensure that the substrate does not shift or wrinkle during the subsequent solution coating process.

[0042] Specifically, the mold is an adaptable structure with a breathable bottom and a semi-sealed top. Its inner wall is smooth and its size matches the warp-knitted fabric substrate. The bottom and top of the mold can be independently temperature controlled to create a stable temperature gradient field. The bottom breathable design accelerates the directional evaporation of solvents, while the top semi-sealed design slows down the surface evaporation rate, providing the necessary environmental conditions for the separation and gradient enrichment of high and low modulus polymer phases.

[0043] Specifically, high and low modulus polymers with a mass ratio controlled at 1.5-2:1 are added to an organic solvent, magnetically stirred until completely dissolved, and allowed to stand for 1-2 hours to remove bubbles, thereby obtaining a polymer blend solution with a polymer mass concentration of 15-30% and a viscosity of 150-300 mPa·s.

[0044] Among them, the high-modulus polymer has a higher Young's modulus than the low-modulus polymer. The high-modulus polymer molecular chain is more rigid and has a higher degree of crystallinity, which can provide mechanical support for the composite material. At least one of polycarbonate-polyurethane copolymer, polyester polyurethane, and polystyrene-isobutylene-styrene triblock copolymer is selected. The low-modulus polymer molecular chain contains flexible segments such as polyether chain and polysiloxane chain, which can optimize the surface elasticity and blood compatibility of the material. At least one of polysiloxane-polyurethane copolymer and polyether polyurethane is selected. The organic solvent includes one or more of N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

[0045] Furthermore, step S2 is the gradient structure forming stage, the key of which is to regulate the solvent evaporation rate through a temperature gradient field, thereby inducing polymer phase separation and gradient enrichment.

[0046] Specifically, the polymer blend solution prepared in step S1 is smoothly introduced into the mold on which the warp-knitted fabric substrate is fixed, ensuring that the solution fully covers the substrate and penetrates into the fiber gaps and mesh.

[0047] Furthermore, the mold is placed in a gradient temperature control chamber, maintaining the bottom temperature at 35-50℃ and the top temperature at 20-30℃, thereby constructing a stable longitudinal temperature gradient field. Under the influence of this temperature gradient field, the solvent evaporation rate is fast in the high-temperature zone at the bottom, and high-modulus polymers preferentially precipitate and accumulate on the fabric side; the solvent evaporation is slow in the low-temperature zone at the top, and low-modulus polymers migrate to and accumulate in this region. This process lasts for 15-40 hours, inducing phase separation between high-modulus and low-modulus polymers and forming a gradient distribution from the surface of the warp-knitted fabric substrate to the outer surface of the composite material, thus obtaining the composite preform.

[0048] During the penetration process, polymer molecules form a strong physical bond with the surface of the fabric fibers. Specifically, the fabric fiber surface contains polar groups such as hydroxyl and carboxyl groups, while the polymer molecular chain contains polar structures such as urethane bonds and ether bonds. These polar groups form stable hydrogen bonds through intermolecular forces, achieving tight adhesion between the polymer and the fiber, effectively improving interfacial bonding and preventing interlayer delamination during subsequent use. Once the gaps inside the fabric are saturated, the excess solution spreads under surface tension to form a continuous liquid film. The thickness of the liquid film is controlled by both the solution viscosity and the coating amount to ensure a smooth surface without accumulation.

[0049] Furthermore, step S3 is the vacuum drying and curing stage. The composite material preform obtained after step S2, along with the mold, is placed in a vacuum drying oven with a vacuum degree ≤ -0.08MPa and dried at 40-60℃ for 8-40 hours. The mild vacuum low-temperature conditions can effectively avoid structural defects such as pores and cracks caused by rapid solvent evaporation.

[0050] Further, the dried mold is removed and cooled to room temperature to avoid deformation of the composite material caused by high-temperature demolding. The edges of the composite material are trimmed to remove burrs and excess material, ultimately obtaining a warp-knitted fabric-based artificial heart valve composite material with a thickness of 100-400 μm, a fiber volume content of 10-60%, and a surface roughness (Ra) of 0.1-1 μm.

[0051] Example 1:

[0052] Step S1: Prepare a warp-knitted fabric substrate with a hexagonal structure. Use 25D fineness, 50 twists / 10cm ultra-high molecular weight polyethylene (UHMWPE) yarn as raw material. Weave the fabric using a Raschel warp knitting machine with a loop-interlocking process. Control the loom parameters to ensure that the width and length of each hexagonal unit are 300×300μm, the thickness is 180μm, and the weight is 100g / m². 2 Cut the fabric into 8cm×8cm square pieces and fix them flat in a mold with a breathable bottom and a semi-sealed top. Weigh 18g of polycarbonate-polyurethane copolymer (PCU) and 10g of polysiloxane-polyurethane copolymer (SiPU) at a mass ratio of 1.8:1, and add them together to 80mL of organic solvent prepared by mixing tetrahydrofuran (THF) and N,N-dimethylacetamide (DMAc) at a volume ratio of 7:3. Stir magnetically until completely dissolved, and let stand for 1 hour to remove bubbles, to obtain a homogeneous polymer blend solution with a polymer mass concentration of 20% and a viscosity of 220mPa·s.

[0053] Step S2: Smoothly introduce the polymer blend solution prepared in step S1 along the inner wall of the mold, ensuring that the solution uniformly covers the surface of the warp-knitted fabric substrate and fills the fiber gaps and mesh gaps without generating bubbles; place the mold in a gradient temperature control chamber, set the bottom temperature of the mold to 45℃ and the top temperature to 25℃, and maintain this state to allow the solvent to evaporate for 24 hours; during this process, the temperature gradient induces the solvent to evaporate in a directional manner and drives phase separation, PCU is enriched in the high-temperature zone at the bottom, and SiPU diffuses to the low-temperature zone at the top, thereby forming a gradient structure with a continuous transition from the surface of the substrate to the outer surface of the composite material, and obtaining the composite material preform.

[0054] Step S3: Place the composite material blank obtained in step S2 and the mold together into a vacuum drying oven, set the vacuum degree to -0.09MPa and the drying temperature to 50℃, and dry for 24 hours to completely remove residual solvent and solidify the composite structure, thereby obtaining a warp-knitted fabric-based artificial heart valve composite material.

[0055] Example 2:

[0056] Step S1: Prepare a warp-knitted fabric substrate with a hexagonal structure. Use aramid fiber with a fineness of 20D and a twist of 40 twists / 10cm as raw material. Weave the fabric using a Raschel warp knitting machine with a loop-interlocking process. Control the loom parameters to ensure that the width and length of each hexagonal unit are 400×400μm, the thickness is 150μm, and the weight is 90g / m². 2 Cut the fabric into 8cm×8cm square pieces and fix them flat in a mold with a breathable bottom and a semi-sealed top. Weigh 15g of polyester polyurethane and 10g of polyether polyurethane at a mass ratio of 1.5:1, add them to 60mL of dimethyl sulfoxide (DMSO) organic solvent, stir magnetically until completely dissolved, and let stand for 1 hour to remove bubbles, so as to obtain a homogeneous polymer blend solution with a polymer mass concentration of 25% and a viscosity of 250mPa・s.

[0057] Step S2: Smoothly introduce the polymer blend solution prepared in step S1 along the inner wall of the mold, ensuring that the solution uniformly covers the surface of the warp-knitted fabric substrate and fills the fiber gaps and mesh gaps without generating bubbles; place the mold in a gradient temperature control chamber, set the bottom temperature of the mold to 40℃ and the top temperature to 22℃, and maintain this state to allow the solvent to evaporate for 30 hours; during this process, the temperature gradient induces the solvent to evaporate in a directional manner and drives phase separation, the polyester polyurethane accumulates in the high-temperature zone at the bottom, and the polyether polyurethane diffuses to the low-temperature zone at the top, thereby forming a gradient structure with a continuous transition from the surface of the substrate to the outer surface of the composite material, and obtaining the composite material preform.

[0058] Step S3: Place the composite material blank obtained in step S2 and the mold together into a vacuum drying oven, set the vacuum degree to -0.08MPa and the drying temperature to 45℃, and dry for 30h to completely remove residual solvent and solidify the composite structure, thereby obtaining the warp-knitted fabric-based artificial heart valve composite material.

[0059] Comparative Example 1:

[0060] Step S1: Prepare a warp-knitted fabric substrate with a hexagonal structure. Use 25D fineness, 50 twists / 10cm ultra-high molecular weight polyethylene (UHMWPE) yarn as raw material. Weave the fabric using a Raschel warp knitting machine with a loop-interlocking process. Control the loom parameters to ensure that the width and length of each hexagonal unit are 300×300μm, the thickness is 180μm, and the weight is 100g / m². 2Cut the fabric into 8cm×8cm square pieces and fix them flat in a mold with a breathable bottom and a semi-sealed top. Weigh 18g of polycarbonate-polyurethane copolymer (PCU) and 10g of polysiloxane-polyurethane copolymer (SiPU) at a mass ratio of 1.8:1, and add them together to 80mL of organic solvent prepared by mixing tetrahydrofuran (THF) and N,N-dimethylacetamide (DMAc) at a volume ratio of 7:3. Stir magnetically until completely dissolved, and let stand for 1 hour to remove bubbles, to obtain a homogeneous polymer blend solution with a polymer mass concentration of 20% and a viscosity of 220mPa·s.

[0061] Step S2: Smoothly introduce the polymer blend solution prepared in step S1 along the inner wall of the mold, ensuring that the solution evenly covers the surface of the warp-knitted fabric substrate and fills the fiber gaps and mesh gaps without generating bubbles; place the mold in a constant temperature chamber and control the overall temperature to be constant at 35℃, allowing the solvent to evaporate for 24 hours to obtain the composite material preform.

[0062] Step S3: Place the composite material blank obtained in step S2 and the mold together into a vacuum drying oven, set the vacuum degree to -0.09MPa and the drying temperature to 50℃, and dry for 24 hours to completely remove residual solvent and solidify the composite structure, thereby obtaining a warp-knitted fabric-based artificial heart valve composite material.

[0063] Comparative Example 2:

[0064] Step S1: Prepare a warp-knitted fabric substrate with a hexagonal structure. Use ultra-high molecular weight polyethylene (UHMWPE) yarn with a fineness of 25D and a twist of 50 twists / 10cm as raw material. Weave the fabric using a Raschel warp knitting machine with a loop-locking process. Control the loom parameters so that the width and length of each hexagonal unit of the fabric are 300×300μm, the thickness is 180μm, and the weight is 100g / m2. Cut the fabric into 8cm×8cm square pieces and fix them flat in a mold with a breathable bottom and a semi-sealed top. Weigh 28g of polycarbonate-polyurethane copolymer (PCU) and add it to 80mL of organic solvent made by mixing tetrahydrofuran (THF) and N,N-dimethylacetamide (DMAc) in a volume ratio of 7:3. Stir magnetically until completely dissolved and let stand for 1h to remove bubbles, to obtain a polymer solution with a total polymer mass concentration of 25% and a viscosity of 230mPa·s.

[0065] Step S2: Slowly introduce the polymer solution prepared in step S1 along the inner wall of the mold to ensure that the solution evenly covers the surface of the warp-knitted fabric substrate and fills the fiber gaps and mesh gaps without generating bubbles; place the mold in a gradient temperature control chamber, set the bottom temperature of the mold to 45°C and the top temperature to 25°C to build a stable temperature gradient field, and maintain this state to allow the solvent to evaporate for 24 hours.

[0066] Step S3: Place the fabric treated in step S2 and the mold together into a vacuum drying oven, set the vacuum degree to -0.09MPa, the drying temperature to 50℃, and the drying time to 24h, remove the residual solvent and solidify the composite structure to obtain the warp-knitted fabric-based artificial heart valve composite material.

[0067] Comparative Example 3:

[0068] Step S1: Select plain weave polyester fiber fabric as the weaving material, with a thickness of 180μm and a weight of 100g / m². 2 Cut the fabric into 8cm×8cm square pieces and fix them flat in a mold with a breathable bottom and a semi-sealed top. Weigh 18g of polycarbonate-polyurethane copolymer (PCU) and 10g of polysiloxane-polyurethane copolymer (SiPU) at a mass ratio of 1.8:1, and add them together to 80mL of organic solvent prepared by mixing tetrahydrofuran (THF) and N,N-dimethylacetamide (DMAc) at a volume ratio of 7:3. Stir magnetically until completely dissolved, and let stand for 1 hour to remove bubbles, to obtain a homogeneous polymer blend solution with a total polymer mass concentration of 20% and a viscosity of 220mPa·s.

[0069] Step S2: Smoothly introduce the polymer blend solution prepared in step S1 along the inner wall of the mold, ensuring that the solution uniformly covers the surface of the plain weave fabric substrate and fills the fiber gaps and mesh gaps without generating bubbles; place the mold in a gradient temperature control chamber, set the bottom temperature of the mold to 45℃ and the top temperature to 25℃, construct a stable temperature gradient field, maintain this state to allow the solvent to evaporate for 24 hours, and obtain the composite material preform.

[0070] Step S3: Place the composite material blank obtained in step S2 and the mold together into a vacuum drying oven, set the vacuum degree to -0.09MPa and the drying temperature to 50℃, and dry for 24 hours to completely remove residual solvent and solidify the composite structure, thereby obtaining a warp-knitted fabric-based artificial heart valve composite material.

[0071] Experimental Example 1:

[0072] The relevant properties of the fabric-based artificial heart valve composite materials prepared in Examples 1-2 and Comparative Examples 1-3 were tested.

[0073] The thickness of the composite material samples was measured using a digital thickness gauge; the surface roughness of the composite material was calculated using atomic force microscopy (AFM) combined with scanning electron microscopy (SEM) for verification.

[0074] The fiber volume content was calculated using the composite material density method. The composite material sample was dried in a vacuum drying oven at 40℃ for 24 hours, cooled to room temperature, and weighed. The total mass of the sample, m1 (g), was recorded. The length, width, and thickness were measured five times at different locations on the sample, and the average value was used to calculate the total sample volume, V1 (cm²). 3 The fiber density ρ2 (g / cm³) of the warp-knitted fabric substrate is known. 3 For example, the density of ultra-high molecular weight polyethylene fiber is 0.93 g / cm³. 3 Aramid fiber content is 1.44 g / cm³. 3 By substrate basis weight G (g / m 2 ) and area S (cm) 2 Calculate the mass m2 (g) of the fibers in the sample, and convert the fiber volume V2 (cm²) according to the density formula. 3 Then calculate the fiber volume content V. f (%), taken as the average of 3 parallel samples. Specifically,

[0075] ;

[0076] ;

[0077] .

[0078] A universal testing machine was used to record the maximum tear force and calculate the tear strength, taking the average of three parallel samples. A notched trapezoidal tear specimen was used; by measuring the force-displacement curve during the tearing process, the energy required for crack propagation per unit area, i.e., the crack propagation threshold, was calculated, taking the average of three parallel samples. For fatigue performance testing, composite material samples were sewn onto a valve stent and placed in physiological saline at 37°C. Fatigue testing was conducted using a durability fatigue testing instrument. During the test, every 5 million cycles, the opening and closing state of the valve leaflets, whether the edges were detached, and whether cracks appeared on the surface were observed using a high-speed camera. After accumulating 100 million cycles, the test was stopped, the valve leaflets were removed, and the surface morphology was observed under an optical microscope. The presence of deformation, tearing, crack propagation, and other phenomena was recorded. The fatigue performance of the composite material was evaluated based on the observation results during the cyclic process.

[0079] For the anticoagulation test, the composite material was cut into 2cm×1cm pieces, sterilized with ethylene oxide, and fixed to the inner wall of a sterile catheter. One end of the catheter was led out from the rabbit's carotid artery and the other end was introduced into the jugular vein to form a semi-in vivo blood circulation test. After 60 minutes of circulation, the coagulation status on the surface of the composite material was observed.

[0080] The test results are shown in Table 1.

[0081] Experimental Example 2:

[0082] To verify whether the warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure prepared in this invention will separate, debond, or peel off from the gradient polymer layer under complex conditions such as simulated in vivo dynamic mechanical impact, body fluid immersion aging, and long-term cyclic loading, the composite material prepared in Example 1 was selected for interfacial peel strength test, tensile shear strength test, dynamic fatigue cycle test, and interfacial performance test after simulated body fluid aging.

[0083] For the interfacial peel strength test, the dried sample was cut into lengths and widths of 150mm × 25mm, along the warp knitting direction of the fabric, and a 10mm initial tear was made at one end to separate only the fabric and polymer layer without damaging the fabric itself. The two ends of the cut sample were clamped in the upper and lower clamps of a universal testing machine with a clamping distance of 100mm. The tensile speed was set to 50mm / min for a 180° peel test. The maximum peel force and force-displacement curve were recorded in real time, the interfacial peel strength was calculated, and the average value of 3 parallel samples was taken.

[0084] For dynamic fatigue cyclic testing, after accumulating 200 million cycles, the test was stopped, the valve leaflets were removed, and the surface morphology was observed under an optical microscope. The presence of deformation, tearing, crack propagation, and other phenomena was recorded. The dynamic fatigue resistance of the composite material was evaluated by combining the observation results during the cyclic process.

[0085] For the tensile shear strength test, the sample is clamped in the fixture of the universal testing machine, ensuring that the force direction of the fixture is perpendicular to the fabric-polymer interface and there are no wrinkles or uneven local forces. Shear force is applied until the interface separates or breaks, the maximum shear force is recorded, the tensile shear strength is calculated, and the average value of 3 parallel samples is taken.

[0086] For the interface performance test after aging in simulated body fluid, the samples were sterilized with ethylene oxide and immersed in a constant temperature simulated body fluid chamber at 37℃ for 180 days. During this period, the simulated body fluid was changed once a week to maintain a stable pH value of 7.4±0.1. After aging, the samples were taken out, rinsed and dried, and the interface peel strength and tensile shear strength tests were repeated. The performance data and retention rate after aging were recorded. After dynamic fatigue cycle test and aging in simulated body fluid, the samples were taken and the microstructure was characterized by scanning electron microscopy (SEM) to observe whether the polymer still filled the pores of the fabric fibers, whether there were gaps or separation traces at the interface, and the adhesion state between the fibers and the polymer.

[0087]

[0088] Based on the performance test results shown in Table 1, both Examples 1 and 2 used a hexagonal warp-knitted substrate, temperature gradient-induced polymer blend phase separation, and a high / low modulus blend polymer system. The surface roughness was 0.2 μm and 0.3 μm, respectively, the tear strength was 38 MPa and 36 MPa, respectively, and the crack propagation threshold was >80 J / m. 2 This invention achieves both "non-deformable" fatigue resistance and "non-thrombotic" anticoagulant effects. Scanning electron microscopy (SEM) observation of the composite material cross-section revealed no clear delamination lines, pores, or gaps; instead, it exhibited a continuous, transitional microstructure with no discrete interfaces between polymers. Therefore, the gradient process of this invention can construct a dense, smooth, low-modulus polymer surface, achieving excellent anticoagulant properties.

[0089] The composite material prepared in Example 1 underwent interfacial peel strength testing, tensile shear strength testing, dynamic fatigue cycle testing, and interfacial performance testing after simulated body fluid aging. The results showed an average peel strength of 6.2 N / mm, an average tensile shear strength of 9.5 MPa, and after 180 days of simulated body fluid aging, the peel strength retention rate was 89%, and the shear strength retention rate was 91%. After 200 million cycles of dynamic fatigue, no interfacial warping, cracking, or separation of the valve leaflets was observed. High-speed camera recordings showed stable leaflet opening and closing states without abnormal deformation. SEM observation indicated that after fatigue cycles and body fluid aging, the polymer remained completely filled in the fiber pores of the hexagonal warp-knitted fabric, maintaining a complete mechanical interlocking structure with no gaps, voids, or debonding marks at the interface, and the polymer adhered tightly to the fiber surface. Therefore, the composite material prepared in Example 1, through hydrogen bonding between the polymer and fabric fibers and its three-dimensional mechanical interlocking structure, exhibits stable interfacial bonding and high mechanical property retention, meeting the requirements for long-term implantation of artificial heart valves.

[0090] Comparative Example 1, after solvent evaporation at a constant temperature of 35℃, achieved a surface roughness of 0.8μm, a tear strength of 28MPa, localized thrombosis and deformation, and a crack propagation threshold of 65J / m. 2 The main reason is that the phase separation and migration of the polymer in Comparative Example 1 are random and non-directional, failing to form a continuous modulus gradient from the fabric interface to the surface. This results in a significantly weak interface in the composite material, uneven component distribution, and ineffective stress dispersion, leading to a sharp decline in fatigue resistance. Therefore, programmed temperature gradient control is an indispensable key step in achieving high-performance gradient structures and thus obtaining exceptional durability.

[0091] Comparative Example 2, using only a single PCU polymer, exhibited "cracking" with a surface roughness of 0.6 μm and a tear strength of 32 MPa, lower than Example 1. A single homogeneous material cannot achieve a biomimetic stress dispersion mechanism. Although PCU itself has high strength, its homogeneous structure is prone to fatigue cracking and rapid propagation under cyclic loading. In contrast, the gradient structure of Example 1 achieved an organic combination of soft and hard regions; the low-modulus region buffered and dispersed stress, while the high-modulus region provided support. Therefore, using a combination of high / low modulus polymers is necessary and cannot be replaced by a single polymer.

[0092] Comparative Example 3 used a traditional plain weave woven fabric as the reinforcing skeleton. The test results showed severe "fragmentation," with a surface roughness of 0.9 μm, a tear strength of only 25 MPa, and a crack propagation threshold of only 54 J / m. 2 The main reason is that the structural stability of plain weave fabrics is far inferior to that of hexagonal warp-knitted structures. Under dynamic loads, the yarns of plain weave fabrics are prone to slippage, leading to instability of the reinforcing skeleton itself, which in turn causes early damage to the upper polymer layer. In contrast, hexagonal warp-knitted fabrics, with their extremely high in-plane stability and isotropy, provide a robust support platform for the gradient polymer layer, which helps to achieve long-term durability.

[0093] In this invention, a warp-knitted fabric with a hexagonal structure is selected as the reinforcing skeleton. Its structure resembles a highly stable honeycomb, providing an excellent initial mechanical basis for the material. High-modulus and low-modulus polymers are co-dissolved to form a homogeneous blend solution. A temperature gradient is used to induce phase separation in the polymer blend. The solution undergoes controlled solvent evaporation in a temperature gradient field, guiding high-modulus polymer molecules to accumulate and solidify towards the higher-temperature fabric side, while simultaneously driving low-modulus polymer molecules to migrate towards the lower-temperature air side. This invention constructs a gradient transition layer with continuously varying chemical composition and mechanical modulus from the fabric interface to the outer surface of the material, mimicking the gradual transition of natural heart valve leaflets from a soft ventricular layer to a tough fibrous layer. When the valve leaflets bend under the impact of blood flow, the gradient structure enables smooth stress transfer and efficient dispersion, eliminating the interfacial stress concentration phenomenon caused by abrupt modulus changes in traditional composite materials, thus improving fatigue resistance. Simultaneously, during the enrichment of low-modulus polymers on the surface, precise process control naturally forms a smooth, dense, defect-free surface, providing a physical basis for excellent anticoagulant properties.

[0094] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure, characterized in that, Includes the following steps: S1. A warp-knitted fabric substrate with a hexagonal structure is fixed in a mold; a high-modulus polymer and a low-modulus polymer are dissolved together in an organic solvent to prepare a polymer blend solution; wherein the Young's modulus of the high-modulus polymer is higher than that of the low-modulus polymer; S2. Introduce the polymer blend solution into the mold and cover it with the warp-knitted fabric substrate; control the temperature at the bottom of the mold to be maintained at 35-50℃ and the temperature at the top to be maintained at 20-30℃, allow the solvent to evaporate for 15-40 hours, induce phase separation between the high-modulus polymer and the low-modulus polymer and form a gradient distribution to obtain the composite material preform. S3. The composite material blank is subjected to vacuum drying treatment to obtain the warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure.

2. The preparation method according to claim 1, characterized in that: In step S1, the width and length of each hexagonal unit of the warp-knitted fabric substrate are both 100-900 μm, the thickness is 50-250 μm, and the basis weight is 40-120 g / m². 2 .

3. The preparation method according to claim 1, characterized in that: In step S1, the knitting fibers used in the warp-knitted fabric substrate include one or more of polyester, nylon, acrylic, spandex, polypropylene, polyethylene yarn, carbon fiber, aramid fiber, polyimide fiber, or polybenzimidazole fiber.

4. The preparation method according to claim 1, characterized in that: In step S1, the high modulus polymer is selected from at least one of polycarbonate-polyurethane copolymer, polyester polyurethane, and polystyrene-isobutylene-styrene triblock copolymer; The low-modulus polymer is selected from at least one of polysiloxane-polyurethane copolymer and polyether polyurethane.

5. The preparation method according to claim 1, characterized in that: In step S1, the mass ratio of the high-modulus polymer to the low-modulus polymer is 1.5-2:

1.

6. The preparation method according to claim 1, characterized in that: In step S1, the organic solvent includes one or more of N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

7. The preparation method according to claim 1, characterized in that: In step S1, the polymer blend solution has a polymer mass concentration of 15-30% and a viscosity of 150-300 mPa·s.

8. The preparation method according to claim 1, characterized in that: In step S3, the drying temperature of the vacuum drying process is 40-60℃, and the drying time is 8-40h.

9. A warp-knitted fabric-based artificial heart valve composite material with a hexagonal structure, prepared by the method according to any one of claims 1-8, characterized in that: The thickness of the warp-knitted fabric-based artificial heart valve composite material is 100-400 μm, the fiber volume content of the warp-knitted fabric is 10-60%, and the surface roughness is 0.1-1 μm.

10. The artificial heart valve composite material with a hexagonal structure based on warp-knitted fabric according to claim 9, characterized in that: The composite material is used to prepare artificial heart valve leaflets.

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