A method for strengthening a vascular stent and a vascular stent

Abstract

The present invention provides a method for strengthening a vascular stent and a vascular stent. The vascular stent includes a body made of a zinc-containing material. Ion irradiation implantation is performed on the zinc material used to make the vascular stent. The specific steps include: obtaining mechanical property indexes of an ideal vascular stent according to clinical medical data, including yield strength, tensile strength, and elongation at break; selecting the type of ion implantation; determining the implantation dose, implantation energy, and implantation temperature of the selected ions by comparing with the mechanical property indexes of the ideal vascular stent, and irradiating and implanting the selected ions into the zinc material. The method for strengthening a vascular stent and the vascular stent provided by the embodiments of the present invention can strengthen the mechanical properties of a zinc-based vascular stent and have sufficient radial support strength for implanting into blood vessels.

Description

Technical Field

[0001] The present invention relates to the field of medical materials, and in particular to a method for strengthening a vascular stent and a vascular stent. Background Art

[0002] As an important method for treating cardiovascular diseases at present, the performance of the stent used greatly affects the treatment effect of the stent surgery. With the research and development of stent technology, after the development of two generations of stent technologies, namely bare metal stents and drug-eluting stents, the current research focus is on bioabsorbable stents. Such stents degrade continuously after being implanted into the human body and are degraded and absorbed by the human body after completing the vascular plastic work, avoiding problems such as chronic inflammation and vascular restenosis caused by the long-term retention of the stent in the human body.

[0003] Currently, two materials, magnesium and zinc, are often used for bioabsorbable vascular stents. Although both materials have been experimentally proven to have good biocompatibility and harmless degradation products, due to the excessive activity of magnesium, the magnesium stent can only maintain the structural integrity in the human body for 3-4 months, which does not meet the requirement of the degradation rate <0.02 mm / yr and the mechanical integrity for about 6 months required for an ideal vascular stent. The chemical activity of zinc is weaker than that of magnesium. Therefore, zinc stents generally have a relatively ideal degradation rate. Animal experiments by Bowen et al. showed that the degradation rate of pure zinc is 20 μm / yr, and the stent can still maintain 70% integrity after 4 months of degradation, and shows an obvious accelerated degradation in the later stage of implantation. This makes pure zinc have a slower degradation rate in the initial stage, so as to maintain the complete structure of the blood vessel in the early stage, and be degraded and metabolized faster after the support task is completed.

[0004] Currently, the main problem of zinc stents is their poor mechanical properties and insufficient radial support strength. Therefore, finding a method that can play a good strengthening role in zinc is crucial for promoting the clinical application of zinc vascular stents. Summary of the Invention

[0005] The embodiment of the present invention provides a method for strengthening a vascular stent, which can strengthen the mechanical properties of a zinc vascular stent and has sufficient radial support strength for implanting into a blood vessel.

[0006] The technical solution provided by the embodiment of the present invention is as follows:

[0007] An embodiment of the present invention provides a method for strengthening a vascular stent. The vascular stent includes a body made of a zinc-containing material. The zinc material used to make the vascular stent is subjected to ion irradiation implantation to introduce at least one of crystal defects such as vacancies and their clusters, interstitial atoms and their clusters, dislocation loops, irradiation black spots, and dislocation lines into the zinc material, thereby hindering the dislocation slip of zinc and improving the strength of the vascular stent. The specific steps include: S10: According to clinical medical data, obtain the mechanical property indexes of an ideal vascular stent, including yield strength, tensile strength, and fracture elongation rate; S20: Select the type of ion implantation; S30: By comparing with the mechanical property indexes of the ideal vascular stent, determine the implantation dose, implantation energy, and implantation temperature of the selected ion, and irradiate and implant the selected ion into the zinc material.

[0008] In some embodiments, the ion irradiation implantation of the zinc material used to make the vascular stent includes: S01: Before making the vascular stent, perform ion implantation on the used zinc material; or, S02: After making the vascular stent, perform ion implantation on the vascular stent body.

[0009] In some embodiments, the method for strengthening the vascular stent further includes: after step S30, S40: Use nanoindentation technology to measure the hardness of the zinc-based vascular stent after ion implantation to ensure compliance with the hardness index among the mechanical property indexes of the rational stent.

[0010] In some embodiments, the above step S40 includes: S41, according to the indentation size effect, the relationship between the hardness H of the vascular stent and the current indentation depth h is: wherein, H0 is the macroscopic intrinsic hardness of the material, h* is the characteristic depth constant. By the current indentation depth, obtain the hardness of the vascular stent at the current depth to determine whether it meets the hardness index among the mechanical property indexes of the rational stent. S42: According to the relationship between the hardness H of the zinc material and the yield strength σ: H = 3σ, obtain the yield strength of the zinc material after ion implantation to determine whether it meets the yield strength index among the mechanical property indexes of the rational stent.

[0011] In some embodiments, the ion irradiation implantation of the zinc material used to make the vascular stent introduces microscopic defects into the zinc material, thereby hindering the dislocation slip of zinc and improving the strength of the vascular stent, including: calculating the critical shear stress caused by the point defects on the dislocation slip plane according to the point defects that occur when high-energy ions collide with zinc atoms in the lattice positions. Specifically, the Orowan strength model is used to determine the relationship between the strength of the zinc material and the microscopic defects: Where Δτs is the change in critical shear stress caused by the defect on the dislocation slip plane; α is the strength factor, which is related to the defect size, defect type, implantation temperature, and strain rate, and is a constant with a value range of 0-1; μ is the shear modulus of the matrix; b is the magnitude of the Burgers vector of the dislocation; N is the defect number density; d is the defect diameter; by controlling the ion implantation energy, implantation dose, and implantation temperature, the size of the micro-defects in the zinc material is adjusted, so as to adjust the value of the critical shear stress, and further accurately control the strengthening effect on the zinc vascular stent.

[0012] In some embodiments, step S30 specifically includes S31: By comparing with the mechanical property indexes of the ideal vascular stent, it is determined that the implantation dose of the selected ion is above the parts per million (ppm) level, the implantation energy is above megaelectron volts (MeV), and the implantation temperature is room temperature in the range of 15°C to 30°C. The selected ion is irradiated and implanted into the zinc material to ensure that the selected ion is implanted within the expected depth range of the vascular stent, and the expected depth range of the vascular stent is 10 micrometers (μm) to 100 micrometers (μm).

[0013] In some embodiments, it includes: S111: According to clinical medical data, obtain the mechanical property indexes of the ideal vascular stent, including a yield strength greater than 200 megapascals (MPa), a tensile strength of 300 megapascals (MPa), and a fracture elongation of 15-18%; S211: Select carbon ions to implant into the zinc material; S311: According to the data in step S11, it is determined that under the conditions of a room temperature implantation temperature, an implantation energy of 6 MeV, and an implantation dose of 1x1017 ions / cm2 for carbon ions, high-energy irradiation is used to implant carbon ions into the zinc material of the vascular stent.

[0014] In some embodiments, step S20 specifically includes S21: Select at least one of the metal ions potassium, calcium, sodium, magnesium, aluminum, zinc, iron, titanium, vanadium, chromium, manganese, nickel, tin, lead, copper, silver, platinum, gold and implant it into the zinc material; or, S22: Select at least one of the non-metal ions hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, sulfur, chlorine, arsenic, selenium, bromine, tellurium, iodine, astatine, helium, neon, argon, krypton, xenon, radon and implant it into the zinc material.

[0015] In some embodiments, in step S30, the determining the implantation dose, implantation energy, and implantation temperature of the selected ion by comparing with the mechanical property indexes of the ideal vascular stent, and irradiating and implanting the selected ion into the zinc material includes S32: Uniformly irradiating and implanting the selected ion into the zinc material from at least one direction.

[0016] An embodiment of the present invention further provides a vascular stent, including a body made of zinc material, and the zinc material is strengthened by the strengthening method of the vascular stent in any of the above embodiments.

[0017] The beneficial effects brought by the embodiments of the present invention are as follows:

[0018] In the above embodiment, ion irradiation implantation is performed on the zinc material used to make the vascular stent, introducing microscopic defects into the new material, thereby hindering the dislocation slip of zinc and enhancing the strength of the vascular stent. Using zinc material to make the vascular stent not only retains the good biodegradability of the zinc material itself, effectively ensuring that more than 70% of the mechanical integrity of the vascular stent remains in the later stage after the stent is implanted into the blood vessel, but also can enhance the mechanical properties of the vascular stent, thus providing strong support for the radial direction of the implanted blood vessel. Moreover, due to the uniformity of ion implantation, the stent can maintain good mechanical properties in all directions when working in blood vessels with a large curvature, effectively preventing the occurrence of stent fracture accidents.

[0019] In a further embodiment of the present invention, at room temperature, C+ with an implantation energy of 6 MeV and an implantation dose of 1x10 17 ions / cm 2 is irradiated and implanted into the zinc vascular stent. Through the study and simulation of the indentation size effect, it is determined that the intrinsic hardness of the zinc vascular stent can be increased by 15%, and the yield strength can be increased by 28 Mpa. Description of the Drawings

[0020] The drawings incorporated herein and constituting a part of the specification illustrate embodiments of the present invention and, together with the specification, are further used to explain the principles of the present invention and enable those skilled in the relevant art to implement and use the present invention.

[0021] Figure 1-8 It is a flowchart of the strengthening method of the vascular stent provided by the embodiment of the present invention;

[0022] Figure 9 It is a schematic diagram showing the distribution of C+ concentration (at.%) and irradiation damage amount (dpa) of SRIM-2008 simulated carbon-implanted pure zinc with depth;

[0023] Figure 10 a is a schematic diagram showing the change of nano-indentation hardness of the test sample with depth after ion implantation;

[0024] Figure 10 b is a schematic diagram showing the change of nano-indentation hardness of the test sample with depth without ion implantation;

[0025] Figure 11 It is a schematic diagram showing the change of average hardness with depth before and after ion implantation;

[0026] Figure 12 Schematic diagram of the H2-1 / h relationship before and after ion implantation of zinc material.

[0027] Figure 13 Schematic diagram of the average grain size of the second phase in different zinc alloys in the prior art;

[0028] Figure 14 Schematic diagram of the influence of different hot working processes on the mechanical properties of zinc in the prior art.

[0029] As shown in the figure, in order to clearly implement the structure of the embodiments of the present invention, specific structures and devices are marked in the figure, but this is only for schematic needs and is not intended to limit the present invention to this specific structure, device and environment. According to specific needs, those of ordinary skill in the art can adjust or modify these devices and environments, and the adjustments or modifications still fall within the scope of the appended claims. Detailed implementation manners

[0030] In the related art, the two main strengthening methods for zinc vascular stents are: alloying and hot working. Currently, in combination Figure 13 , the commonly used alloying elements for alloying include Al, Mg, Cu, Ag, Li, Mn, etc. The main strengthening principles are solid solution strengthening and dispersion strengthening. Solid solution strengthening refers to when a part of the alloying element dissolves in the zinc matrix, due to the difference between the alloy atom size and the zinc atom size, the lattice near the alloy atom is distorted, which hinders the dislocation slip and ultimately leads to an increase in the strength of the zinc alloy. This strengthening principle is mainly reflected in zinc-copper alloys. Since the solubility of copper in zinc is relatively large, when the added copper content is low, copper can completely dissolve in the zinc matrix to form a copper-zinc alloy without generating a second phase. At this time, mainly the mechanism of solid solution strengthening is at work. Dispersion strengthening refers to the strengthening effect of the material obtained by mixing multi-phase structures. In zinc-magnesium alloys and most other zinc alloys, the main strengthening mechanism is dispersion strengthening. Taking the zinc-magnesium alloy as an example, after adding a certain amount of magnesium element to zinc, the Mg2Zn11 phase will be generated in the matrix. Mg2Zn11 belongs to intermetallic compounds, which have the characteristics of high hardness and high strength, and can strongly pin the dislocations moving in the matrix, thereby increasing the strength of zinc. Although alloying can significantly improve the strength of zinc, there is a problem of a significant decrease in ductility. This is because the generation of the second phase hinders the dislocation slip and increases the strength while also reducing the ductility of zinc. As listed in Table 1 below for some of the second phases generated in different zinc alloys,

[0031]

[0032] Table 1

[0033] According to the experimental research by Mostaed et al., the grain size of the Mg2Zn11 phase in the zinc-magnesium alloy can reach several micrometers or even more than ten micrometers, while the thickness of a general zinc vascular stent is only about 100 micrometers. This makes the size of the hard phase contained in the zinc-magnesium alloy too large after being fabricated into a stent, which will lead to a further decline in the ductility of the stent and there is a risk of microcracks occurring near the hard phase. Besides magnesium, other types of zinc alloys also face the same problem due to the generation of hard phases.

[0034] Hot working mainly involves hot rolling and hot extrusion processes. By performing hot working processes such as hot rolling or hot extrusion on the zinc ingots obtained by casting, the grain size inside the ingots can be significantly refined, thereby enhancing the strength of zinc. Fine grain strengthening is a commonly used strengthening method for polycrystalline materials, which improves the strength of metals and alloys by refining the grain size. When the grain size inside the material is finer, the number of grain boundaries inside the material is more, the resistance to dislocation movement is greater, and the strength of the polycrystal is higher.

[0035] Combined Figure 14 , although hot working can enhance the strength of zinc through the method of fine grain strengthening, the mechanical properties of the processed material will show anisotropy. This is mainly because obvious texture phenomena will occur in the grains of zinc after hot rolling or hot extrusion, and the generation of texture often leads to differences in the mechanical properties of the material in various directions. For vascular stents, the anisotropic mechanical properties will increase the risk of the stent breaking during use. Long Chun et al. found through finite element simulation of the Mises stress distribution of a vascular stent after dilation in the middle coronary artery that due to the uneven stress distribution in the coronary artery wall, the stress states of different parts of the vascular stent vary greatly. The maximum stress in the stent is 533.3 MPa, and the minimum is only 34.93 MPa. This indicates that the stent is not always under a single stable radial pressure during use, and the stress directions and magnitudes of its various parts are not completely consistent, which puts forward an isotropic requirement for the stent material. Li Ning et al. pointed out through simulation of the instantaneous bending stiffness of vascular stents under different bending curvatures that when the stent is in a blood vessel with a larger curvature, its instantaneous bending stiffness has anisotropic characteristics. This shows that when the stent works in a blood vessel with a larger curvature, it must have good mechanical properties in all directions, otherwise there is a high probability of stent fracture accidents.

[0036] In addition, according to the research by Bednarczyk et al., it was also found that hot working has limited grain refinement effect on pure zinc. Since the recrystallization temperature of pure zinc is relatively low (about -12 °C), it is difficult to obtain an ultrafine-grained structure of pure zinc only by hot working at room temperature. Even if pure zinc is processed by equal-channel angular pressing (ECAP) process, the average grain size will reach about 20 microns and it is difficult to further reduce it. At this time, the mechanical properties of pure zinc (yield strength 61 MPa, tensile strength 91 MPa) still cannot meet the performance requirements of an ideal stent.

[0037] In other words, the current research on the strengthening of zinc vascular stents mainly focuses on two aspects: alloying and hot working. Although both of these methods can strengthen zinc to a certain extent, there are still some problems. After alloying, hard phases are generally newly formed in zinc. For example, the Mg2Zn11 phase in zinc-magnesium alloy, the CuZn5 phase in zinc-copper alloy, the MnZn13 phase in zinc-manganese alloy, etc. These hard phases are generally very coarse, and the average grain size ranges from a few microns to dozens of microns. The thickness of the vascular stent is generally only about 100 microns, and these coarse hard phases will cause a significant decrease in the ductility of the vascular stent; although hot working will not produce coarse secondary phases, the mechanical properties of the processed material will show obvious anisotropy. Therefore, in the above technical solutions, there are shortfalls in the research on the strengthening of zinc vascular stents.

[0038] A method for strengthening a vascular stent and a vascular stent provided by the present invention use ion implantation to cause an increase in the hardness and strength of the material. This is because a large number of microdefects will be generated inside the material after irradiation, which hinders the movement of dislocations.

[0039] The following combines the attached Figures 1 to 12 drawings and specific embodiments to describe in detail a method for strengthening a vascular stent and a vascular stent provided by the present invention. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the drawing part is only for more specific description of the embodiments and is not intended to specifically limit the present invention.

[0040] It should be pointed out that in the specification, references to "an embodiment", "embodiment", "exemplary embodiment", "some embodiments", etc. indicate that the described embodiment may include a specific feature, structure, or characteristic, but not necessarily every embodiment includes that specific feature, structure, or characteristic. Additionally, when combining an embodiment to describe a specific feature, structure, or characteristic, implementing such a feature, structure, or characteristic in combination with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the relevant art.

[0041] Generally, terms can be understood at least in part from their use in context. For example, depending at least in part on the context, the term "one or more" as used herein can be used to describe any feature, structure, or property in a singular sense, or can be used to describe a combination of features, structures, or properties in a plural sense. Additionally, the term "based on" can be understood to not necessarily be intended to convey an exclusive set of factors, but rather can alternatively, depending at least in part on the context, allow for the existence of other factors that are not necessarily explicitly described.

[0042] It can be understood that the meanings of "on", "above", and "over" in the present invention should be construed in the broadest manner such that "on" not only means "directly on" something, but also includes the meaning of being "on" something with intervening features or layers therebetween, and "above" or "over" not only means "above" or "over" something, but can also include the meaning of being "above" or "over" something with no intervening features or layers therebetween.

[0043] In addition, spatial relative terms such as "under", "below", "lower", "above", "upper", etc. can be used herein for convenience of description to describe the relationship of one element or feature to another or other elements or features, as shown in the drawings. The spatial relative terms are intended to cover different orientations in the use or operation of the device in addition to the orientation depicted in the drawings. The device can be oriented in other ways, and the spatial relative descriptive terms used herein can be similarly interpreted accordingly.

[0044] Combined Figure 1 As shown in the figure, an embodiment of the present invention provides a method for strengthening a vascular stent. The vascular stent includes a body made of a zinc-containing material. It is characterized in that ion irradiation implantation is performed on the zinc material for making the vascular stent, introducing microdefects into the zinc material, thereby hindering the dislocation slip of zinc and improving the strength of the vascular stent. The specific steps include:

[0045] S10: According to clinical medical data, obtain the mechanical property indexes of an ideal vascular stent, including yield strength, tensile strength, and elongation at break;

[0046] S20: Select the type of ion implantation;

[0047] S30: By comparing with the mechanical property indexes of the ideal vascular stent, determine the implantation dose, implantation energy, and implantation temperature of the selected ion, and irradiate and implant the selected ion into the zinc material.

[0048] In the embodiment of the present invention, ion irradiation implantation is performed on the zinc material used to make the vascular stent, introducing microscopic defects into the new material, thereby hindering the dislocation slip of zinc and improving the strength of the vascular stent. Using zinc material to make the vascular stent not only retains the good biodegradability of the zinc material itself, effectively ensuring that more than 70% of the mechanical integrity of the vascular stent remains in the later stage after the stent is implanted into the blood vessel, but also can enhance the mechanical properties of the vascular stent, thus providing strong support for the radial direction of the implanted blood vessel. Moreover, due to the uniformity of ion implantation, the stent can maintain good mechanical properties in all directions when working in blood vessels with a large curvature, effectively preventing the occurrence of stent fracture accidents.

[0049] In the above step S10, the performance indicators of an ideal vascular stent are listed in Table 2:

[0050]

[0051]

[0052] Table 2

[0053] Optionally, in combination with Figure 2 , ion irradiation implantation on the zinc material used to make the vascular stent includes:

[0054] S01: Before making the vascular stent, perform ion implantation on the used zinc material; or,

[0055] S02: After making the vascular stent, perform ion implantation on the vascular stent body.

[0056] In the above embodiment, there are two technical solutions. One is to perform ion implantation on the used zinc material before making the vascular stent. In this way, the strength of the zinc material can be improved, and after the strengthened zinc material is made into a vascular stent, the vascular stent also has high mechanical properties to adapt to the radial force faced after being implanted into the blood vessel. The other is to directly perform ion implantation on the finished vascular stent. After ion implantation, the vascular stent obtains high mechanical properties to adapt to the radial force faced after being implanted into the blood vessel.

[0057] Optionally, in combination with Figure 3 , after step S30,

[0058] S40: Use nanoindentation technology to measure the hardness of the zinc-based vascular stent after ion implantation to ensure that it meets the hardness index in the mechanical property indicators of the rational stent.

[0059] In the above embodiments, since a large number of crystal defects are generated in the vascular stent after ion implantation, including vacancies and their clusters, interstitial atoms and their clusters, dislocation loops, irradiation black spots, and dislocation lines, the hardness and strength of the material will both increase. In order to accurately measure the change in hardness of the sample before and after implantation, nanoindentation technology is used to measure the hardness of the implanted zinc, so as to ensure that the hardness index in the mechanical performance index of the rational stent is achieved after ion implantation.

[0060] Optionally, step S40 includes:

[0061] S41: According to the indentation size effect, the relationship between the hardness H of the vascular stent and the current indentation depth h is: where H0 is the macroscopic intrinsic hardness of the material, h* is the characteristic depth constant, and the hardness of the vascular stent at the current depth is obtained through the current indentation depth to determine whether it meets the hardness index in the mechanical performance index of the rational stent.

[0062] In the above embodiments, it can be seen from the formula that H 2 has a linear relationship with 1 / h. Therefore, after processing the data in Figure 10 , the data points in Figure 11 can be obtained, and the comparison value of the intrinsic hardness of Zn before and after ion implantation is calculated by linear fitting, so as to ensure that the hardness index in the mechanical performance index of the rational stent is achieved after ion implantation.

[0063] Optionally, step S40 further includes:

[0064] S42: According to the relationship between the hardness H and the yield strength σ of the zinc material: H = 3σ, the yield strength of the zinc material after ion implantation is obtained to determine whether it meets the yield strength index in the mechanical performance index of the rational stent.

[0065] In the above embodiments, after ion implantation, the zinc has obvious hardening, and the specific hardening degree can be obtained by referring to the data in Figures 10 to 11 . Then, according to the relationship between the material hardness and the yield strength, the comparison value of the yield strength of the sample before and after ion implantation can be determined, so as to further determine that the yield strength index in the mechanical performance index of the rational stent is achieved after ion implantation.

[0066] Optionally, ion irradiation implantation is performed on the zinc material used to make the vascular stent to introduce microdefects into the zinc material, thereby hindering the dislocation slip of zinc and enhancing the strength of the vascular stent, including: calculating the critical shear stress caused by the point defects on the dislocation slip plane according to the point defects that occur when high-energy ions collide with zinc atoms in the lattice positions, and specifically using the Orowan strength model to determine the relationship between the strength of the zinc material and the microdefects: where Δτs is the change in the critical shear stress caused by the defects on the dislocation slip plane; α is the strength factor, which is related to the defect size, defect type, implantation temperature, and strain rate, and is a constant with a value range of 0-1; μ is the shear modulus of the matrix; b is the magnitude of the Burgers vector of the dislocation; N is the defect number density; d is the defect diameter;

[0067] By controlling the ion implantation energy, implantation dose, and implantation temperature, the size of the microdefects in the zinc material is adjusted, thereby adjusting the value of the critical shear stress, and further accurately controlling the strengthening effect on the zinc vascular stent.

[0068] In the above embodiments, combined with Figure 9 , the key to using ion implantation to improve the mechanical properties of the zinc vascular stent lies in selecting appropriate implanted ions and implantation + dose. During the process of zinc being implanted with ions, the high-energy implanted ions will collide with zinc atoms in the lattice positions and cause a large number of point defects inside the material, such as vacancies and interstitial atoms. According to the research of Eldrup, as the implantation dose increases, the density of vacancies and interstitial atoms inside the material will increase. As the number and size of the generated defects increase, this will further strengthen the hindering effect of these microdefects on dislocation slip, thereby improving the mechanical properties of zinc. Moreover, through the Orowan strength model, the relationship between the strength of the zinc material and the microdefects can be further determined. In other words, the strengthening degree of zinc can be controlled by the energy, dose, and temperature of ion implantation, so as to accurately control the strengthening effect of the zinc vascular stent material.

[0069] Optionally, combined with Figure 4 , step S30 specifically includes:

[0070] S31: By comparing with the mechanical property indexes of the ideal vascular stent, it is determined that the implantation dose of the selected ions is above the parts per million (ppm) level, the implantation energy is above the megaelectron volt (Mev) level, and the implantation temperature is room temperature in the range of 15°C to 30°C. The selected ions are irradiated and implanted into the zinc material to ensure that the selected ions are implanted within the expected depth range of the vascular stent.

[0071] In the above embodiments, the thickness of the vascular stent is usually about 100 micrometers. The depth of conventional low-energy ion implantation is limited, only within a few micrometers, which can only achieve the purpose of surface modification and cannot increase the overall strength and hardness of the stent. In this embodiment, a high-energy ion accelerator with a megaelectron volt (MeV) energy is used to introduce interstitial atoms, their clusters and dislocation loops within a depth range of dozens of micrometers or even hundreds of micrometers inside the stent material, thereby improving the tensile strength and yield strength and increasing the hardness of the vascular stent material.

[0072] Optionally, in step S31, the expected depth range of the vascular stent is 10 micrometers (μm) to 100 micrometers (μm).

[0073] In the above embodiments, within a depth range of dozens of micrometers or even hundreds of micrometers inside the stent material, interstitial atoms, their clusters and dislocation loops are introduced, thereby improving the tensile strength and yield strength and increasing the hardness of the vascular stent material.

[0074] Optionally, in combination with Figure 5 , including:

[0075] S111: According to clinical medical data, obtain the mechanical property indexes of an ideal vascular stent, including a yield strength greater than 200 megapascals (MPa), a tensile strength of 300 megapascals (MPa), and a fracture elongation of 15 - 18%;

[0076] S211: Select carbon ion implantation into zinc material:

[0077] S311: According to the data in step S11, determine that carbon ions are implanted into the zinc material of the vascular stent by high-energy irradiation under the conditions of a room temperature implantation temperature, an implantation energy of 6 MeV, and an implantation dose of 1x10 17 ions / cm 2 ².

[0078] In the above embodiments, at room temperature, after C+ with an implantation energy of 6 MeV and an implantation dose of 1x10¹⁷ ions / cm² is irradiated and implanted into a zinc-based vascular stent, through the study and simulation of the indentation size effect, it is determined that the intrinsic hardness of the zinc-based vascular stent can be increased by 15% and the yield strength can be increased by 28 MPa.

[0079] Optionally, in combination with Figure 6 , step S20 specifically includes:

[0080] S21: Select at least one of the metal ions potassium, calcium, sodium, magnesium, aluminum, zinc, iron, titanium, vanadium, chromium, manganese, nickel, tin, lead, copper, silver, platinum, and gold for implantation into the zinc material.

[0081] In the above embodiments, metal ions are selected to be implanted into the zinc material to improve the mechanical properties of the zinc material. Among them, except for the metal ions listed above, they will not be listed one by one. However, the embodiments of the present invention include any metal ions suitable for implantation into the zinc material, which are not limited herein.

[0082] Optionally, in combination with Figure 7 , step S20 specifically includes:

[0083] S22: Select at least one ion from non-metal ions hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, sulfur, chlorine, arsenic, selenium, bromine, tellurium, iodine, astatine, helium, neon, argon, krypton, xenon, and radon and implant it into the zinc material.

[0084] In the above embodiments, non-metal ions are selected to be implanted into the zinc material to improve the mechanical properties of the zinc material. Among them, except for the non-metal ions listed above, they will not be listed one by one. However, the embodiments of the present invention include any non-metal ions suitable for implantation into the zinc material, which are not limited herein.

[0085] Optionally, in combination with Figure 8 , in step S30, by comparing with the mechanical property indexes of the ideal vascular stent, determine the implantation dose, implantation energy, and implantation temperature of the selected ions, and irradiate and implant the selected ions into the zinc material, including:

[0086] S32: Inject the selected ions into the zinc material from at least one direction.

[0087] In the above embodiments, injecting into the zinc material from at least one direction includes the front, back, left, right, or multiple measurable directions, so as to ensure that the zinc stent has good mechanical properties in all directions, avoid the risk of fracture of the stent during use caused by the anisotropic mechanical properties of the vascular stent, and ensure that when the stent is in a blood vessel with a large curvature, the anisotropic characteristics of its instantaneous bending stiffness are not obvious.

[0088] The embodiments of the present invention also provide a vascular stent, including a body made of zinc material, and the zinc material is strengthened by the strengthening method of the vascular stent in any of the above embodiments.

[0089] The vascular stent strengthened by the strengthening method of the vascular stent in any of the above embodiments not only retains the good biodegradability of the zinc material itself, effectively ensures that the vascular stent has a mechanical integrity of more than 70% in the later stage of stent implantation into the blood vessel, but also can strengthen the mechanical properties of the vascular stent, thereby providing strong support for the radial direction of the implanted blood vessel. Moreover, due to the uniformity of ion implantation, the stent can maintain good mechanical properties in all directions when working in a blood vessel with a large curvature, and can effectively prevent the occurrence of stent fracture accidents.

[0090] This invention covers any alternatives, modifications, equivalent methods and solutions made within the spirit and scope of this invention. For the purpose of enabling the public to have a thorough understanding of this invention, specific details are elaborated in the following preferred embodiments of this invention. However, those skilled in the art can also fully understand this invention without the description of these details. The above description is only the preferred implementation mode of this invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements can be made without departing from the principle of this invention, and these improvements and refinements should also be regarded as the protection scope of this invention.

Claims

1. A method for strengthening a vascular stent, the vascular stent comprising a body made of a zinc-containing material, characterized in that, Ion irradiation implantation is carried out on the zinc material used to make the vascular stent, introducing at least one kind of crystal defect such as vacancies and their clusters, interstitial atoms and their clusters, dislocation loops, irradiation black spots, and dislocation lines into the zinc material, so as to hinder the dislocation slip of zinc and improve the strength of the vascular stent. The specific steps include: S10: According to clinical medical data, obtain the mechanical property indexes of an ideal vascular stent, including yield strength, tensile strength, and elongation at break; S20: Select the type of ion implantation; S30: By comparing with the mechanical property indexes of the ideal vascular stent, determine the implantation dose, implantation energy, and implantation temperature of the selected ion, and irradiate and implant the selected ion into the zinc material; It also includes: after step S30, S40: Use nanoindentation technology to measure the hardness of the zinc-made vascular stent after ion implantation to ensure that it meets the hardness index among the mechanical property indexes of the ideal vascular stent; Step S40 includes: S41: According to the indentation size effect, the relationship between the hardness H of the vascular stent and the current indentation depth h is as follows: where H 0 is the macroscopic intrinsic hardness of the material, and h * is the characteristic depth constant. By the current indentation depth, the hardness of the vascular stent at the current depth is obtained to determine whether it meets the hardness index in the mechanical property index of the ideal vascular stent. S42: According to the relationship between the hardness H and yield strength σ of the zinc material: H = 3σ, obtain the yield strength of the zinc material after ion implantation to judge whether it meets the yield strength index among the mechanical property indexes of the ideal vascular stent.

2. The method for strengthening a vascular stent according to claim 1, wherein, The ion irradiation implantation on the zinc material used to make the vascular stent includes: S01: Before making the vascular stent, perform ion implantation on the used zinc material; or, S02: After making the vascular stent, perform ion implantation on the vascular stent body.

3. The method for strengthening a vascular stent according to claim 1, wherein The ion irradiation implantation on the zinc material used to make the vascular stent introduces microdefects into the zinc material, thus hindering the dislocation slip of zinc and improving the strength of the vascular stent, including: Based on the point defects that occur due to the mutual collision of high-energy ions with zinc atoms in lattice positions, calculate the critical shear stress caused by the point defects on the dislocation slip plane. Specifically, the Orowan strength model is used to determine the relationship between the strength of the zinc material and the microdefects: where Δτ s is the change in the critical shear stress caused by the defects on the dislocation slip plane; α is the strength factor, which is related to the defect size, defect type, injection temperature, and strain rate, and is a constant with a value range of 0 - 1; μ is the shear modulus of the matrix; b is the magnitude of the Burgers vector of the dislocation; N is the defect number density; d is the defect diameter; By controlling the ion implantation energy, implantation dose, and implantation temperature, adjust the size of the microdefects in the zinc material, thereby adjusting the critical shear stress value, and further accurately controlling the strengthening effect on the zinc-made vascular stent.

4. The method for strengthening a vascular stent according to claim 1, characterized in that, Step S30 specifically includes: S31: By comparing with the mechanical property indexes of the ideal vascular stent, determine that the implantation dose of the selected ion is above the parts per million level, the implantation energy is above the megaelectron volt level, and the implantation temperature is room temperature in the range of 15°C to 30°C, and irradiate and implant the selected ion into the zinc material to ensure that the selected ion is implanted within the expected depth range of the vascular stent, where the expected depth range of the vascular stent is 10 microns to 100 microns.

5. The method for strengthening a vascular stent according to claim 4, wherein, It includes: S111: According to clinical medical data, obtain the mechanical property indexes of an ideal vascular stent, including a yield strength greater than 200 MPa, a tensile strength greater than 300 MPa, and an elongation at break of 15 - 18%; S211: Select carbon ion implantation into the zinc material: S311: Determine, based on the data in step S11, that carbon ions are implanted into the zinc material of the vascular stent by means of high-energy irradiation under the conditions of an implantation temperature of room temperature, an implantation energy of 6 MeV, and an implantation dose of 1x10 17 ions / cm 2 .

6. The method for strengthening a vascular stent according to claim 1, characterized in that, Step S20 specifically includes: S21: Select at least one ion of metal ions such as potassium, calcium, sodium, magnesium, aluminum, zinc, iron, titanium, vanadium, chromium, manganese, nickel, tin, lead, copper, silver, platinum, and gold and implant it into the zinc material; or, S22: Select at least one ion of non-metal ions such as hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, sulfur, chlorine, arsenic, selenium, bromine, tellurium, iodine, astatine, helium, neon, argon, krypton, xenon, and radon and implant it into the zinc material.

7. The method for strengthening a vascular stent according to claim 1, wherein, In the step S30, by comparing with the mechanical property indexes of the ideal vascular stent to determine the implantation dose, implantation energy, and implantation temperature of the selected ions, and irradiating and implanting the selected ions into the zinc material, it includes: S32: Irradiating and implanting the selected ions into the zinc material from at least one direction.

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