Preparation process of shape memory alloy skeleton capable of degrading left auricle plugging device

Abstract

The invention belongs to the technical field of preparation of skeletons of left auricle occluders, and particularly relates to a preparation process of a shape memory alloy skeleton of a degradable left auricle occluder. The method comprises the following steps of: firstly, accurately controlling the grain size of an alloy wire through multi-channel micro-scale drawing and annealing treatment for reducing the wire diameter step by step, so as to optimize the degradation rate and the mechanical property of a framework; secondly, the fine alloy wires are woven into a framework of a three-dimensional net structure through a cylindrical multi-axis weaving technology, uniform oxidation treatment is conducted on the surface of the framework through a vacuum plasma oxidation treatment technology, and the uniformity and binding force of a surface modification layer are ensured; by optimizing the preparation process, the biocompatibility, stability and degradation performance of the skeleton are improved, the process can customize skeletons with different degradation rates according to clinical requirements, it is ensured that the plugging device stably plays a role in the body, and the treatment effect and the patient safety are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of left atrial appendage occluder framework preparation, in particular to a shape memory alloy framework preparation process of a degradable left atrial appendage occluder. BACKGROUND

[0002] The left atrial appendage occluder is an interventional medical device for preventing stroke in patients with non-valvular atrial fibrillation. In the atrial fibrillation state, blood flow in the left atrial appendage is slow and easy to form thrombus, and thrombus detachment may cause serious complications such as cerebral embolism. The device is implanted in the left atrial appendage through percutaneous intervention to physically block the blood flow channel between the left atrial appendage and the left atrium, preventing thrombus formation and detachment, thereby reducing the risk of stroke. It is commonly used in atrial fibrillation patients who cannot tolerate anticoagulant drugs for a long time, and has the advantages of minimally invasive, quick postoperative recovery, etc. The framework is the core supporting structure in the left atrial appendage occluder.

[0003] However, in the existing preparation process of the left atrial appendage occluder framework, the grain size and degradation rate are difficult to be cooperatively controlled in the multi-pass micro-scale drawing process of the degradable wire material. Abnormal grain growth or excessive refinement may be caused by uneven drawing deformation or improper annealing parameters, thereby causing fluctuation of the degradation rate and affecting the safety of clinical use. At the same time, it is difficult to ensure the uniformity of the entire surface modification layer and the interface bonding force after the three-dimensional network framework is woven. The traditional surface treatment process is easily affected by the shielding of the complex network structure of the framework, resulting in local missing of the modification layer, uneven thickness or insufficient bonding force, which not only reduces the biocompatibility of the framework, but also may cause the modification layer to fall off, affecting the long-term stability and degradability of the occluder.

[0004] Therefore, the present application provides a shape memory alloy framework preparation process of a degradable left atrial appendage occluder. SUMMARY

[0005] In order to solve the technical problems of the existing preparation process of the left atrial appendage occluder framework mentioned in the background art, that is, the grain size and degradation rate are difficult to be cooperatively controlled in the multi-pass micro-scale drawing of the degradable wire material, and the surface modification treatment after the three-dimensional network framework is woven cannot ensure the uniformity of the entire modification layer and the interface bonding force, the purpose of the present application is to provide a shape memory alloy framework preparation process of a degradable left atrial appendage occluder.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: The shape memory alloy framework preparation process of the degradable left atrial appendage occluder comprises: S1: sequentially performing multi-pass micro-scale drawing with gradually reduced wire diameter on the raw material alloy wire, and immediately performing intermediate annealing treatment after each drawing process is completed to obtain alloy wire with refined grain size; S2: the alloy wire with refined grain size is subjected to final drawing, the drawing process is completed by air cooling, and a micro-alloy wire is obtained; S3: the micro-alloy wire is used to weave a three-dimensional network structure framework by a cylindrical multi-axial weaving process, and the whole framework is formed according to a specified wire arrangement mode and weaving density; S4: the formed three-dimensional network structure framework is placed in a vacuum plasma reaction cavity, oxygen is introduced, and a plasma surface treatment process is implemented to perform oxidation treatment on the framework surface.

[0007] Further, the alloy wire is made of NiTi alloy as a basic alloy material, and the proportion is 70%; and a degradable magnesium alloy is selected as an additive material, and the total proportion is 30%; The molten NiTi alloy is sprayed into fine particles by an air atomization method, and finally NiTi alloy powder with a particle size of 20 μm to 50 μm is obtained; similarly, the magnesium alloy powder is prepared by the air atomization method, and the powder particle size is consistent with that of the NiTi alloy powder; The prepared NiTi alloy powder and the magnesium alloy powder are mixed in proportions of 70% and 30% respectively to form alloy powder, and a ball milling method is used for auxiliary mixing treatment; Polyvinyl alcohol is selected as a binder, and the specific amount needs to be calculated according to 5% of the total mass of the alloy powder; if the total mass of the alloy powder used in the preparation process is 100g, the required amount of PVA binder is , that is, 5g PVA of binder is required; The dissolution of the polyvinyl alcohol binder needs to be carried out in isopropyl alcohol solvent, and the dosage of the isopropyl alcohol solvent is twice that of the polyvinyl alcohol binder. The isopropyl alcohol solvent is added to the polyvinyl alcohol binder and stirred until the polyvinyl alcohol binder is completely dissolved and a uniform binding slurry is formed, and then the binding slurry is added to the alloy powder and mixed uniformly; The mixed slurry of the alloy powder and the binding slurry is injected into a mold by a metal injection molding process to produce an alloy wire with a diameter of 4 mm .

[0008] Further, a multi-station drawing machine is used to draw the alloy wire, and the alloy wire is sent into a box-type annealing furnace for annealing treatment after each drawing; The multi-station drawing machine has four sets of dies, each corresponding to a different aperture, to gradually reduce the diameter of the alloy wire; the drawing aperture corresponding to die one is 3.0 mm. mm The drawing bore diameter corresponding to die two is 2.0. mm The drawing bore diameter corresponding to die three is 1.5. mm The drawing bore diameter corresponding to die four is 1.0. mm ; One pull is used to pull a diameter of 4 mm The alloy wire is drawn to a diameter of 3.0 mm through the die. mm Alloy wire; secondary drawing is used to draw wires with a diameter of 3.0 mm. mm The alloy wire is drawn to a diameter of 2.0 mm through the second die. mm The alloy wire; three drawing processes are used to draw wires with a diameter of 2.0 mm. mm The alloy wire is drawn to a diameter of 1.5 mm through the die. mm The alloy wire; four drawing processes are used to draw wire with a diameter of 1.5 mm. mm The alloy wire is drawn to a diameter of 1.0 mm through the die. mm Alloy wire.

[0009] Furthermore, the final drawing process is performed using a single-station drawing machine, and the die aperture of the single-station drawing machine is set to 0.5 mm. mm ; The single-station drawing machine has a built-in drawing speed and force control system. Through the equipment's integrated Siemens S7-1500 PLC control system, the control panel is adjusted. During the actual drawing process, the overall drawing speed needs to be controlled within 0.1... mm / s Up to 0.3 mm / s Meanwhile, the pull-out force should be controlled at 200. N Up to 300 N between; The diameter of the drawn alloy wire is 0.5 mm. mm Temperature degradation is achieved through air cooling, utilizing airflow for natural cooling to prevent the generation of thermal stress; the cooling rate needs to be controlled between 0.5°C / s and 1°C / s, while the cooling environment needs to be maintained within the temperature range of 20°C to 25°C.

[0010] Furthermore, the alloy wires are tension calibrated, and a wire tension regulator is used to control the initial tension of each wire at 5. N -8 N At the same time, alcohol is used to wipe the surface of the silk to remove residual oil and impurities; The pre-designed skeleton has a diameter of 15. mm -25mm 20 mm -30 mm The alloy wire is processed by selecting a 16-shaft cylindrical multi-axial braiding machine, and the three-dimensional network structure skeleton braiding process includes initial braiding positioning, distributed braiding and length control ending, and finally the overall forming of the three-dimensional network structure skeleton is completed.

[0011] Further, the three-dimensional network structure skeleton is processed, and the processing steps include preliminary preparation and cavity pretreatment, oxygen input and plasma excitation, oxidation process monitoring and parameter adjustment, post-processing cooling and cavity pressure relief, and oxidation treatment effect verification.

[0012] Further, the specific steps of the preliminary preparation and cavity pretreatment are that the three-dimensional network structure skeleton is fixed by a high-temperature-resistant quartz support and placed in the center of the vacuum plasma reaction cavity, vacuumized to a specified vacuum degree by a mechanical pump and a molecular pump, and the radio frequency plasma power parameters are initialized and the temperature monitoring is started; The specific steps of the oxygen input and plasma excitation are that high-purity oxygen is inputted and the flow is controlled to stabilize the pressure in the cavity, and then the plasma power is started, the radio frequency power is increased to the target value in a gradient manner, and the oxygen plasma is excited; The specific steps of the oxidation process monitoring and parameter adjustment are that during the set oxidation treatment time, the plasma state is monitored by an optical emission spectrometer, the temperature sensor and the vacuum gauge are fed back, the oxygen flow and the radio frequency power are dynamically adjusted, and the temperature and the pressure are ensured to be stable in a reasonable range; The specific steps of the post-processing cooling and cavity pressure relief are that the plasma power is turned off, the three-dimensional network structure skeleton is gradiently cooled to a specified temperature in an oxygen atmosphere, the reaction cavity is slowly depressurized to atmospheric pressure by inert gas, and finally the three-dimensional network structure skeleton is taken out and the surface is cleaned; The specific steps of the oxidation treatment effect verification are that the SEM, EDS and XPS are used to detect the morphology, element composition and thickness of the oxidation layer on the surface of the skeleton, and the universal material testing machine and the simulated body fluid degradation test are used to verify whether the mechanical properties and degradation characteristics of the skeleton meet the standards.

[0013] Compared with the prior art, the advantages of the present application are that: 1、The present application can precisely control the grain size of the alloy wire by gradually reducing the wire diameter through a multi-pass micro-scale drawing process combined with intermediate annealing treatment, so that the degradation rate of the three-dimensional network structure skeleton can be precisely adjusted, and its mechanical properties can be optimized.

[0014] 2、The vacuum plasma oxidation treatment technology is adopted in the application, an oxidation layer is uniformly formed on the surface of the three-dimensional network framework, the problems of local missing and uneven thickness in the traditional surface treatment process are effectively avoided by accurately controlling the oxygen flow and the plasma power, the biocompatibility of the three-dimensional network structure framework and the in-vivo environment is improved, the bonding force between the modified layer and the three-dimensional network structure framework is strengthened, the surface layer of the three-dimensional network structure framework is prevented from falling off in the long-term use process, and the stability and safety of the left atrial appendage occluder are further enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] mm The skeleton preparation workflow of the present application is shown in the figure. mm The multi-pass micro-scale drawing and intermediate annealing process flow diagram of the present application is shown in the figure. r / min The vacuum plasma surface oxidation treatment process flow diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0018] In order to achieve the above purpose, the present application is realized by the following technical solutions, the present application provides a shape memory alloy skeleton preparation process of a degradable left atrial appendage occluder, as shown in the figure, the process includes: r / min S1: The raw material alloy wire is sequentially subjected to multi-pass micro-scale drawing with gradually reduced wire diameter, and intermediate annealing treatment is immediately performed after each drawing process is completed, to obtain alloy wire with refined grain size.

[0019] The alloy wire is selected from mm / s ​The alloy is used as a base alloy material, and the proportion is 70%; meanwhile, a degradable magnesium alloy is selected as an additive material, and the total proportion is 30% to ensure that the alloy wire has degradability, wherein the selected magnesium alloy is AZ31 alloy, and the main components are 90% of magnesium, 3% of aluminum (Al), and 1% of zinc; The melted mm / s alloy is sprayed into fine particles by an air atomization method, and finally mm the alloy powder particle size is controlled to be 20 mm to 50 mm ; similarly, the magnesium alloy powder is also prepared by the air atomization method, and the powder particle size is consistent with that of the mm alloy powder; The prepared mm² alloy powder and the magnesium alloy powder are mixed into alloy powder in proportions of 70% and 30% respectively, and are subjected to auxiliary mixing treatment by a ball milling method, and the ball milling time of the ball mill is set to be 8 to 12 hours; In the metal injection molding process, the addition of the binder is the key to ensuring the uniform molding and good fluidity of the alloy powder, and the polyvinyl alcohol is selected as the binder, and the specific addition amount needs to be calculated according to 5% of the total mass of the alloy powder; This embodiment provides an example: if the total mass of the alloy powder used in the preparation process is 100 g , the required mm addition amount of the binder is , that is, 5g mm of the binder is required; The dissolution of the polyvinyl alcohol binder needs to be carried out in isopropyl alcohol solvent, and the dosage of the isopropyl alcohol solvent is 2 times that of the polyvinyl alcohol binder. The isopropyl alcohol solvent is added to the polyvinyl alcohol binder and stirred until the polyvinyl alcohol binder is completely dissolved and a uniform binding slurry is formed. Then the binding slurry is added to the alloy powder and mixed uniformly to ensure that each powder particle is uniformly coated; The mixed slurry of the alloy powder and the binding slurry is injected into a mold by a metal injection molding process, and the injection temperature of the process is set to be 150°C to 200°C, and finally an alloy wire with a diameter of 4mm is obtained; The 4 sccm mm alloy wire is used as an initial raw material, and an automatic cutting machine is used to cut the alloy wire into 300 nm mm alloy wires for standby; A multi-station drawing machine is used to draw the alloy wire, and after each drawing, the alloy wire is sent into a box-type annealing furnace for annealing treatment, and the specific treatment process is shown in the following table: The multi-station drawing machine is built-in four sets of dies, each die corresponds to a different aperture to gradually reduce the diameter of the alloy wire; the drawing aperture corresponding to die one is 3.0 counts , the drawing aperture corresponding to die two is 2.0 sccm , the drawing aperture corresponding to die three is 1.5 nm , and the drawing aperture corresponding to die four is 1.0 nm ; The first drawing is used to draw the alloy wire with a diameter of 4 Ni to an alloy wire with a diameter of 3.0 Ti through the die one; the second drawing is used to draw the alloy wire with a diameter of 3.0 Mg to an alloy wire with a diameter of 2.0 Ni through the die two; the third drawing is used to draw the alloy wire with a diameter of 2.0 mg / L to an alloy wire with a diameter of 1.5 ​ through the die three; and the fourth drawing is used to draw the alloy wire with a diameter of 1.5 ​ to an alloy wire with a diameter of 1.0 ​ through the die four; The alloy wire after each drawing process is sent into the box-type annealing furnace for treatment to ensure that the grain size is refined and internal stress is eliminated. During annealing, the inside of the box-type annealing furnace is ensured to be inert gas to avoid the surface oxidation of the alloy wire. After annealing, the alloy wire is naturally cooled at room temperature. After cooling, the alloy wire needs to be inspected for quality. If surface defects are found, the polishing machine is used for finishing to ensure that the alloy wire surface is free of burrs and has good smoothness. After the drawing and annealing process, the diameter of the alloy wire is gradually reduced to 1.0 mm, the grain size is refined, and the strength, ductility and shape memory characteristics of the alloy wire are optimized.

[0020] S2: The alloy wire with refined grain size is subjected to final drawing, and air cooling is used to complete the drawing process to obtain a micro-alloy wire.

[0021] The final drawing is carried out using a single-station drawing machine, and the die aperture of the single-station drawing machine is set to 0.5 ​ ; The model of the single-station drawing machine is DREHER T200, which is built-in with a drawing speed and drawing force control system. The Siemens S7-1500 PLC control system of the equipment is used to adjust the equipment control panel. The drawing speed of the whole machine needs to be controlled at 0.1 ​ to 0.3​ between 200 N and 300 N ; The diameter of the drawn alloy wire is 0.5 ​ mm, and temperature degradation is performed by air cooling to naturally cool by air flow to prevent the generation of thermal stress; the rate of the cooling process needs to be controlled between 0.5°C / s and 1°C / s, and the cooling environment needs to be kept in a temperature range of normal temperature 20°C to 25°C.

[0022] S3: Using the micro-alloy wire, a three-dimensional network structure skeleton is woven by a cylindrical multi-axial weaving process, and the overall skeleton is formed according to the specified wire arrangement mode and weaving density.

[0023] The 0.5 ​ mm diameter alloy wire is tension calibrated, and the initial tension of each wire is controlled to 5 N -8 N , and the surface of the wire is wiped with alcohol to remove residual oil stains and impurities; The diameter of the preset skeleton design size is 15 ​ -25 ​ , and the length is 20 ​ -30 ​ , a 16-axis cylindrical multi-axial weaving machine with a model of KBW-16Z is selected, and the diameter of the cylindrical weaving core die of the 16-axis cylindrical multi-axial weaving machine and the weaving head speed are adjusted according to the design size of the preset skeleton, the weaving core die is fixed on the rotating main shaft of the weaving machine, and the axis of the core die is coincided with the axis of the main shaft of the weaving machine, and the deviation is not more than 0.1 ​ ; The weaving parameter setting includes the wire arrangement mode and the weaving density control of the alloy wire; The alloy wire adopts a "8+8" double-layer stacking arrangement mode, that is, the first group of 8 micro-alloy wires is uniformly distributed along the circumference of the weaving core die (the included angle between adjacent wires is 45°), as the warp; the second group of 8 micro-alloy wires is staggered with the first group of wires, as the weft, and the two groups of wires are cross-woven at 90° to form a basic network structure unit; The weaving density is set to contain 12-15 weaving nodes per centimeter length (i.e. 12-15 turns per centimeter) according to the mechanical strength and plugging performance requirements of the occluder skeleton, and the main shaft speed of the weaving machine (50 ​ -80 ​ ) and the wire feeding speed (0.8 ​ -1.2 ​) Density control is realized, in which the wire feeding speed is positively correlated with the spindle speed, ensuring that the wire feeding length matches the preset weaving density per revolution of the spindle; The three-dimensional network structure framework weaving process includes initial weaving positioning, distributed weaving, and length control ending; The initial weaving positioning step includes fixing the pretreated 16 fine alloy wires on the 16 wire shafts of the multi-axial weaving machine, respectively, wherein the starting ends of 8 warp wires are fixed on one end of the weaving core mold, and the starting ends of 8 weft wires are cross-bound with the warp wires at the starting end of the core mold to form the weaving starting point. The step-by-step weaving step includes starting the multi-axial weaving machine, rotating the weaving core mold at a constant speed driven by the spindle, and synchronously feeding the 16 wire shafts according to the preset trajectory. Each revolution, the weft wire and the warp wire cross weave once to form a weaving node. During the weaving process, the tension and wire feeding speed of the alloy wire are monitored in real time by the PLC control system. The length control ending step includes automatically reducing the spindle speed and wire feeding speed of the multi-axial weaving machine when the weaving length reaches the preset 20 ​ -30 ​ meters, gradually stopping weaving, and welding and fixing the ends of the wires at both ends of the woven framework (laser welding, welding temperature control at 800°C-900°C, welding point diameter 0.8 ​ -1.0 ​ mm), to prevent the framework from loosening and complete the overall shaping of the three-dimensional network structure framework.

[0024] S4: Place the shaped three-dimensional network structure framework in a vacuum plasma reaction chamber, introduce oxygen, and implement a plasma surface treatment process to oxidize the surface of the framework.

[0025] The treatment steps include preliminary preparation and cavity pretreatment, oxygen introduction and plasma excitation, oxidation process monitoring and parameter adjustment, post-treatment cooling and cavity pressure relief, and oxidation treatment effect verification. The specific treatment steps of the preliminary preparation and cavity pretreatment are: Use a high-temperature-resistant quartz support to fix the shaped three-dimensional network structure framework, ensure that the framework is suspended and does not rigidly contact the support (avoid local shielding affecting surface treatment uniformity), the contact points between the support and the framework are only the welding points at both ends of the framework, and the contact area is controlled within 0.5 ​ mm, slowly place the fixed framework in the center of the vacuum plasma reaction chamber, ensure that the framework axis deviates from the reaction chamber axis by no more than 1 ​ mm, and avoid treatment differences caused by uneven plasma distribution; After the chamber door is closed, a mechanical vacuum pump is first started to perform a preliminary vacuuming, to reduce the pressure in the chamber to below 10 Pa, and then a molecular vacuum pump is switched in, to continue vacuuming until the vacuum degree in the chamber reaches Pa to Pa, which process needs to be maintained for 30 minutes, to completely remove residual air (especially nitrogen, carbon dioxide and other impurity gases) in the chamber, to prevent the impurities from reacting with the surface of the skeleton; A plasma power supply (a radio frequency plasma power supply, model PX-600) is turned on, and initial parameters are set through a matched PLC control system (Allen-Bradley Micro850 series), including pre-adjusting the radio frequency power to 100 W, fixing the electrode spacing to 150 ​ (mm, matched with the inner diameter of the reaction chamber), and turning on a chamber temperature monitoring sensor (accuracy ±1℃), to record the temperature of the skeleton surface in real time during the processing; The specific steps of the oxygen input and plasma excitation are as follows: High-purity oxygen with a purity of ≥99.999% is selected, and the oxygen input rate is controlled through a precision mass flow controller (model D07-19B), at an initial stage, the oxygen is slowly input into the chamber at a flow rate of 5 ​ (sccm, standard cubic centimeter per minute), and the pressure in the chamber is monitored in real time through a vacuum gauge, when the pressure is stabilized at 10 Pa to 20 Pa, the flow rate is maintained for 3 minutes, to ensure that the oxygen uniformly fills the reaction chamber.

[0026] Plasma ignition and power gradient increase: the plasma power supply ignition program is started, the oxygen flow rate is kept unchanged, the radio frequency power is gradually increased from 100 W to 300 W to 350 W at a gradient of 20 W / minute, to avoid local overheating of the skeleton caused by sudden power rise (the surface temperature needs to be controlled below 200℃, which is adjusted in real time through the temperature sensor), after the power is stabilized, the plasma discharge state is maintained, at this time, the oxygen is ionized to form oxygen plasma (the main active species are O⁺, O2⁺ and oxygen free radicals) under the action of the radio frequency electric field, to start the oxidation treatment of the skeleton surface; The specific steps of the oxidation treatment process monitoring and parameter adjustment are as follows: The total length of the plasma surface oxidation treatment is set to 40 minutes to 60 minutes, and the characteristic spectrum line (oxygen atomic spectrum line with a wavelength of 777.2 ​ ) of the oxygen plasma is monitored in real time through an optical emission spectrometer (OES) in the chamber during the processing, to ensure that the spectrum line intensity is stabilized at 5000-6000 ​ , if the intensity fluctuation exceeds ±5%, the oxygen flow rate (±1 ​ ) or the radio frequency power (±10 W) is adjusted to correct it, to ensure the continuous and stable oxidation reaction; During the processing, if the temperature sensor detects that the surface temperature of the skeleton exceeds 200°C, immediately reduce the radio frequency power (each time by 15W) and extend the power adjustment interval to 5 minutes until the temperature falls back to the interval of 180°C-200°C; if the cavity pressure is lower than 8Pa due to air leakage and other factors, the plasma discharge needs to be paused, and after re-vacuuming to the target vacuum degree, the aeration and discharge are continued to avoid affecting the quality of the oxidation layer; The specific steps of the post-processing cooling and cavity pressure relief are as follows: After reaching the set processing time, first, the plasma power is turned off, the oxygen flow rate is kept unchanged, and the skeleton is naturally cooled in the oxygen atmosphere, with the cooling rate controlled at 1°C / min to 2°C / min. When the cavity temperature drops below 50°C, the oxygen valve is closed, and the aeration is stopped. The reaction cavity pressure relief program is started, and inert gas (argon, purity ≥99.99%) is slowly supplied into the cavity, with the supply rate controlled at 10Pa / min until the cavity pressure is balanced with the atmospheric pressure (the pressure relief process needs to last for 20 minutes to avoid the skeleton surface oxidation layer falling off due to sudden pressure rise). The door is opened, the processed three-dimensional network structure skeleton is taken out, and the surface of the skeleton is gently wiped with a dust-free cloth dipped in anhydrous ethanol to remove possible oxidation debris, thus completing the entire plasma surface oxidation processing procedure. The specific steps of the oxidation processing effect verification are as follows: The surface morphology of the skeleton is observed by a scanning electron microscope (SEM, model Zeiss Sigma 300), and the surface element composition is analyzed by an energy dispersive spectrometer (EDS) to confirm that the oxygen element content is ≥15%. At the same time, the oxidation layer thickness is measured by X-ray photoelectron spectroscopy (XPS), and the oxidation layer thickness is required to be controlled at 50 ​ to 100 ​ nm, which ensures that the biocompatibility of the skeleton is improved without affecting the shape memory performance and the degradation rate; Randomly select 3 processed skeleton samples, test their compression strength and elastic recovery rate by a universal material testing machine (model Instron 5969), and require that the compression strength is ≥300MPa and the elastic recovery rate is ≥95% (when the compression deformation is 20%); place the samples in a simulated body fluid (SBF solution, pH=7.4, temperature 37°C) for degradation test, and detect the ion concentration in the solution every week to ensure that the degradation rate meets the clinical requirements (completely degrades within 6 to 12 months) and that no toxic ions are excessively released (the ion concentration is ≤0.1 ​ , ​ , ​ ). ​ ​

[0027] ​​The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0028] Finally, the above merely provides the preferred embodiments of the present application, but is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder, characterized in that, Comprise: S1: The raw material alloy wire is sequentially subjected to multi-pass micro-scale drawing with gradually reduced wire diameter, and intermediate annealing is performed immediately after each drawing process is completed, to obtain alloy wire with refined grain size; S2: The alloy wire with refined grain size is subjected to final drawing, and air cooling is adopted to complete the drawing process, to obtain micro-alloy wire; S3: The micro-alloy wire is used to weave a three-dimensional network structure framework through cylindrical multi-axis weaving process, and the framework is formed as a whole according to the specified wire arrangement mode and weaving density; S4: The formed three-dimensional network structure framework is placed in a vacuum plasma reaction chamber, oxygen is introduced, and a plasma surface treatment process is performed to oxidize the surface of the framework.

2. The process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder according to claim 1, characterized in that, The alloy wire is selected NiTi The alloy is selected as a base alloy material, and the proportion is 70%; meanwhile, the degradable material magnesium alloy is selected as an additive material, and the total proportion is 30%. The molten NiTi alloy is sprayed into fine particles by a gas atomization method, and finally NiTi alloy powder is controlled to have a particle size of 20 μm to 50 μm μm; similarly, the magnesium alloy powder is also prepared by the gas atomization method, and the powder has the same particle size as the NiTi alloy powder. The prepared alloy powder and the magnesium alloy powder are sequentially mixed in a ratio of 70% and 30% into an alloy powder, and auxiliary mixing treatment is performed by using a ball milling method. NiTi The alloy powder and the magnesium alloy powder are sequentially mixed in a ratio of 70% and 30% into an alloy powder, and auxiliary mixing treatment is performed by using a ball milling method. The polyvinyl alcohol is selected as the binder, and the specific addition amount is calculated according to 5% of the total mass of the alloy powder. If the total mass of the alloy powder used in the preparation process is 100 g, the addition amount of the required PVA binder is that is, 5 g PVA binder; The dissolution of the polyvinyl alcohol binder needs to be carried out in isopropyl alcohol solvent, the dosage of the isopropyl alcohol solvent is 2 times that of the polyvinyl alcohol binder, the isopropyl alcohol solvent is added to the polyvinyl alcohol binder and stirred until the polyvinyl alcohol binder is completely dissolved and a uniform adhesive slurry is formed, and then the adhesive slurry is added to the alloy powder and mixed uniformly; The mixed slurry of the alloy powder and the bonding slurry is injected into a mold through a metal injection molding process to produce an alloy wire having a diameter of 4 mm mm.

3. The process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder according to claim 1, characterized in that, The alloy wire is subjected to drawing treatment using a multi-station drawing machine, and the alloy wire is sent into a box-type annealing furnace for annealing treatment after each drawing; The multi-station drawing machine is built-in four sets of molds, each mold corresponds to different aperture, to gradually reduce the diameter of the alloy wire; the drawing aperture corresponding to the mold one is 3.0 mm , the drawing aperture corresponding to the mold two is 2.0 mm , the drawing aperture corresponding to the mold three is 1.5 mm , the drawing aperture corresponding to the mold four is 1.0 mm ; a first drawing pass to draw an alloy wire having a diameter of 4 mm mm through the die to an alloy wire having a diameter of 3.0 mm mm; a second drawing pass to draw an alloy wire having a diameter of 3.0 mm mm through the die to an alloy wire having a diameter of 2.0 mm mm; a third drawing pass to draw an alloy wire having a diameter of 2.0 mm mm through the die to an alloy wire having a diameter of 1.5 mm mm; a fourth drawing pass to draw an alloy wire having a diameter of 1.5 mm mm through the die to an alloy wire having a diameter of 1.0 mm mm.

4. The process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder according to claim 1, characterized in that, The final drawing uses a single-station drawing machine for drawing treatment, and the die hole diameter of the single-station drawing machine is set to 0.5 mm ; The single-station drawing machine is internally provided with a drawing speed and drawing force control system. Through a Siemens S7-1500 PLC control system provided by the equipment, the equipment control panel is adjusted. In the actual drawing process, the drawing speed of the whole machine needs to be controlled between 0.1 mm / s and 0.3 mm / s , and at the same time, the drawing force needs to be controlled between 200 N and 300 N . The diameter of the drawn alloy wire is 0.5 mm and temperature degradation is performed by air cooling to utilize air flow for natural cooling to prevent the generation of thermal stress; the rate of the cooling process needs to be controlled between 0.5°C / s to 1°C / s while the cooling environment needs to be kept in the temperature interval of normal temperature 20°C to 25°C.

5. The process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder according to claim 1, characterized in that, The alloy wires were tension calibrated and the initial tension of each wire was controlled at 5 N -8 N At the same time, the surface of the wire was wiped with alcohol to remove residual oil and impurities. The diameter of the preset skeleton design size is 15 mm -25 mm The length of the preset skeleton design size is 20 mm -30 mm, The alloy wire is woven by selecting a 16-axis cylindrical multi-axial weaving machine. The three-dimensional mesh structure skeleton weaving process includes initial weaving positioning, distributed weaving, and length control ending, and finally completes the overall forming of the three-dimensional mesh structure skeleton.

6. The process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder according to claim 5, characterized in that, The three-dimensional network structure framework is treated, and the treatment steps include preliminary preparation and cavity pretreatment, oxygen introduction and plasma excitation, oxidation process monitoring and parameter adjustment, post-treatment cooling and cavity pressure relief, and oxidation treatment effect verification.

7. The process for preparing a shape memory alloy skeleton of a degradable left atrial appendage occluder according to claim 6, characterized in that, The specific steps of the preliminary preparation and cavity pretreatment are as follows: the three-dimensional network structure framework is fixed by a high-temperature resistant quartz support and placed in the center of the vacuum plasma reaction chamber, vacuum is pumped to a specified vacuum degree by a mechanical pump and a molecular pump, and the parameters of the radio frequency plasma power supply are initialized and the temperature monitoring is started; The specific steps of the oxygen introduction and plasma excitation are as follows: high-purity oxygen is introduced and the flow rate is controlled to stabilize the pressure in the cavity, and then the plasma power supply is started, the radio frequency power is increased to the target value in a gradient manner, and oxygen plasma is formed by exciting oxygen; The specific steps of the oxidation process monitoring and parameter adjustment are as follows: during the set oxidation treatment time, the plasma state is monitored by an optical emission spectrometer, and the oxygen flow rate and the radio frequency power are dynamically adjusted based on the feedback of the temperature sensor and the vacuum gauge, to ensure that the temperature and the pressure are stable in a reasonable range; The specific steps of the post-treatment cooling and cavity pressure relief are as follows: the plasma power supply is turned off, the three-dimensional network structure framework is gradient-cooled to a specified temperature in the oxygen atmosphere, the reaction chamber is slowly depressurized to atmospheric pressure with inert gas, and finally the three-dimensional network structure framework is taken out and the surface is cleaned. The specific step of verifying the effect of the oxidation treatment is to detect the morphology, element composition and thickness of the oxidation layer on the surface of the skeleton by SEM, EDS and XPS, and to verify whether the mechanical properties and degradation characteristics of the skeleton meet the standards by means of a universal material testing machine and a simulated body fluid degradation test.

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