Design method and stent of inflatable heterogeneous shape memory polymer vascular stent

Abstract

The present invention relates to a design method and stent for an inflatable heterogeneous shape memory polymer vascular stent, comprising selecting a corresponding number of unit cells in the axial and circumferential directions according to requirements, determining the material distribution of two heterogeneous materials and the structural dimensions of the stent; calculating the bending curvature of the hollow slender tube under the action of inflation pressure based on the material distribution and the structural dimensions of the stent; calculating the spatial configuration of the centerline of the hollow slender tube under the action of a concentrated force based on the bending curvature under the action of inflation pressure; and calculating the quantitative relationship between inflation pressure and the deployed diameter of the stent based on the number of unit cells in the axial and circumferential directions and the spatial configuration of the centerline. The technical solution provided by the present invention improves the rationality of the structural design of the shape memory polymer vascular stent. The stent constructed using the method provided by the present application significantly improves the support stiffness and deployment speed during deployment, thereby accelerating the deployment time of the stent and increasing its clinical application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and in particular relates to a design method and a stent of an inflatable heterogeneous shape memory polymer vascular stent. Background Art

[0002] Coronary artery disease is one of the most common and deadly diseases in the world today, claiming millions of lives each year. Coronary artery disease begins with the accumulation of fat, cholesterol, and other substances within the blood vessels. The resulting plaque narrows the arteries, reducing the supply of blood, oxygen, and other nutrients to the heart muscle. In severe cases, it can lead to heart attacks. Vascular stent implantation is currently an effective clinical treatment for coronary artery stenosis. However, the mainstream commercially available stents are made of metal materials such as 316L stainless steel (or platinum or titanium). Metal stents are relatively rigid, and while they provide good radial support, they can easily cause mechanical damage to the vessel wall during implantation, leading to complications such as inflammation and perforation. Furthermore, metal stents are not easily degraded by the intravascular environment, often requiring secondary surgery for removal, which causes additional pain for the patient. Therefore, developing novel vascular stents with excellent biodegradability and mechanical properties compatible with human vascular structures is of great clinical value.

[0003] In the related art, existing shape memory polymer stents can obtain internal environment degradability by selecting biodegradable material components. However, since the shape memory polymer stent is in a high-temperature and low-modulus state when the configuration is self-developed, its radial support force is greatly reduced compared to that of metal stents. When the blood vessels are thicker or the plaques are harder, it is difficult to completely open the blocked blood vessels. In addition, the relatively slow deformation recovery rate of the shape memory polymer material causes the stent to take a long time to deploy, which brings a burden to doctors and patients during the operation. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide a design method and stent of an inflatable heterogeneous shape memory polymer vascular stent to solve the problems of slow deformation and low recovery rate of the shape memory vascular stent in the existing technology, which brings a burden to the surgical process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a design method for an inflatable heterogeneous shape memory polymer vascular stent, comprising:

[0006] The stent is composed of unit cells periodically arranged in the axial and circumferential directions. The unit cells are composed of multiple hollow, slender tubes. After inflation, the multiple hollow, slender tubes are alternately bent in opposite directions to open the unit cells, so that the stent structure is deployed as a whole. The hollow, slender tubes are made of two heterogeneous materials.

[0007] The design method of the inflatable heterogeneous shape memory polymer vascular stent comprises:

[0008] Select the corresponding number of unit cells in the axial and circumferential directions according to the requirements, determine the material distribution of the two heterogeneous materials, and the structural dimensions of the stent;

[0009] Calculating the bending curvature of the hollow elongated tube under the action of inflation pressure according to the material distribution and the structural dimensions of the stent;

[0010] Calculating the spatial configuration of the centerline of the end of the hollow slender tube under the action of concentrated force based on the bending curvature under the action of the inflation pressure;

[0011] The quantitative relationship between the inflation pressure and the deployed diameter of the stent is calculated based on the number of the unit cells in the axial and circumferential directions and the spatial configuration of the centerline.

[0012] Furthermore, the heterogeneous material includes a first heterogeneous material and a second heterogeneous material; wherein, under high temperature conditions, the modulus of the first heterogeneous material is lower than the modulus of the second heterogeneous material, so that the deformation area after inflation is concentrated in the area where the first heterogeneous material is located;

[0013] The region of the first heterogeneous material on the hollow elongated tube is a hoop-shaped region that is uniformly and discretely distributed; wherein the hoop-shaped region includes a plurality of regions.

[0014] Furthermore, determining the material distribution of the two heterogeneous materials and the structural dimensions of the stent includes:

[0015] Calculating the structural dimensions of the hollow elongated tube according to its radius and wall thickness; the structural dimensions are the ratio of the wall thickness to the radius;

[0016] The ratio of the hoop-shaped area is calculated according to the width and interval of the hoop-shaped area, and the winding angle is obtained; the material distribution includes the winding angle and the ratio of the hoop-shaped area.

[0017] Furthermore, the hoop-shaped region where the first heterogeneous material is located and the adjacent region where the second heterogeneous material is located are used as the first region, and the remaining region where the second heterogeneous material is located is used as the second region; and the bending curvature of the hollow elongated tube under the action of inflation pressure is calculated according to the material distribution and the structural dimensions of the stent, including:

[0018] Obtaining a volume fraction of the second heterogeneous material according to the ratio of the hoop-shaped regions and the number of the hoop-shaped regions;

[0019] Calculating a composite modulus of the first heterogeneous material and the second heterogeneous material according to the volume fraction, the first modulus of the first heterogeneous material, and the second modulus of the second heterogeneous material;

[0020] Determine the position of the neutral layer according to the first modulus, the second modulus, the composite modulus, the radius, the wall thickness and the winding angle;

[0021] Determining a first relationship between the longitudinal elongation ratio and the bending curvature of the first region and a second relationship between the circumferential depth-to-length ratio and the bending curvature according to the radius, thickness, and neutral layer position;

[0022] calculating the deformation energy of the first region based on the first modulus, the second modulus, the volume fraction of the second heterogeneous material, the first relationship, and the second relationship;

[0023] Calculating the bending deformation energy of the large deformation area in the hollow slender tube based on the deformation energy, calculating the bending deformation energy of the small deformation area in the hollow slender tube based on the neutral layer position, radius and wall thickness, and calculating the potential energy corresponding to the inflation pressure load based on the inflation pressure and volume change;

[0024] The total energy of the inflated hollow slender tube is obtained by integrating the bending deformation energy of the large deformation area, the bending deformation energy of the small deformation area and the potential energy corresponding to the inflation pressure load;

[0025] The total energy is solved according to the principle of minimum potential energy to obtain the bending curvature of the hollow slender tube under the action of inflation pressure.

[0026] Furthermore, the spatial configuration of the centerline of the end of the hollow elongated tube under the action of the concentrated force is calculated based on the bending curvature under the action of the inflation pressure, including:

[0027] The hollow elongated tube is assumed to be an elastic rod with an initial curvature; the initial curvature corresponds to the bending curvature under the action of inflation pressure;

[0028] Calculating the plane coordinates of a preset point on the arc length of the center line of the elastic rod based on the equivalent bending stiffness of the elastic rod against deformation and the bending curvature under the action of the inflation pressure;

[0029] The spatial configuration of the center line of the hollow slender tube under the concentrated force at the end is calculated based on the plane coordinates of the preset point of the arc length of the center line of the elastic rod.

[0030] Furthermore, the quantitative relationship between the inflation pressure and the deployed diameter of the stent is calculated based on the number of the unit cells in the axial and circumferential directions and the spatial configuration of the centerline, including:

[0031] The inner radius of the deformed plaque is calculated based on the number of unit cells in the annular direction, the spatial configuration of the centerline, and the expanded diameter of the stent;

[0032] The force exerted by the plaque on the stent is calculated based on the inner radius of the deformed plaque and the shape of the stent in its initial state;

[0033] The load force at the end of the hollow slender rod is calculated based on the inner radius of the deformed plaque, the force exerted by the plaque on the stent, the axial length of the stent in the initial state, and the number of unit cells in the axial direction.

[0034] The quantitative relationship between the inflation pressure and the expanded diameter of the stent is obtained according to the load force at the end of the hollow slender rod.

[0035] Further, determining whether the stent manufactured according to the obtained quantitative relationship between the inflation pressure and the deployed diameter of the stent meets the requirements;

[0036] If not, the number of unit cells in the axial and circumferential directions, the material distribution of the two heterogeneous materials, and the structural dimensions of the stent are adjusted.

[0037] Furthermore, a unit cell of the stent is composed of eight hollow slender tubes, and the eight hollow slender tubes are divided into a pair of four hollow slender tubes.

[0038] The embodiments of the present application provide a designed inflatable heterogeneous shape memory polymer vascular stent, which is manufactured using the design method of the inflatable heterogeneous shape memory polymer vascular stent described in any of the above embodiments.

[0039] The present invention adopts the above technical solution, and the beneficial effects that can be achieved include:

[0040] The present invention provides a design method and stent for an inflatable heterogeneous shape memory polymer vascular stent. This application fully considers the scenarios encountered by the inflatable heterogeneous shape memory polymer stent during actual application, selects a hollow slender circular tube as the minimum structural unit, constructs an orderly layout with alternating distribution of two materials, establishes a quantitative relationship between inflation pressure, material distribution, and structural dimensions, and constructs a quantitative material layout and structural dimension determination scheme by studying the deformation of the slender tube under inflation load and external concentrated force load, combined with the force analysis of the stent structure during deployment, thereby improving the rationality of the vascular stent structural design. Compared with existing shape memory polymer stents, the stent constructed by the method provided in this application can significantly improve the support stiffness and deployment speed during deployment, and has greater clinical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1Schematic diagram of the steps of the design method of the inflatable heterogeneous shape memory polymer vascular stent of the present invention;

[0043] Figure 2 Schematic diagram of the process of designing the inflatable heterogeneous shape memory polymer vascular stent of the present invention;

[0044] Figure 3 A schematic diagram of the overall appearance of the inflatable vascular stent provided by the present invention;

[0045] Figure 4 Schematic diagram of the heterogeneous slender tube, a component unit of the vascular stent structure provided by the present invention, before and after deformation;

[0046] Figure 5 Schematic diagram of force and deformation analysis during the deployment of the vascular stent of the present invention. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0048] In related technologies, shape memory polymers are a type of intelligent soft material that can return to its initial shape from a temporary shape under environmental stimuli such as temperature or light. Its modulus is very low (~0.5MPa) at high temperatures (above the glass transition temperature), and relatively high (~1GPa) at room temperature (below the glass transition temperature), but lower than the modulus of common metals. Before implantation, shape memory polymer stents are thermally programmed from their initial configuration to a compact configuration. After being implanted in a blocked blood vessel, they are driven by high temperature to spontaneously expand into their initial configuration. Compared with metal stents, this can effectively reduce the probability of vascular damage during implantation. However, the relatively slow deformation recovery rate of shape memory polymer stents results in a longer stent deployment time, which places a burden on doctors and patients during surgery.

[0049] Therefore, how to develop new shape memory polymer stent design schemes to improve the radial support stiffness and deployment speed of the shape memory polymer stent during deployment is the key to determining whether the shape memory polymer stent can replace metal stents and achieve degradable and low-risk implantation.

[0050] The following describes a specific design method and stent of an inflatable heterogeneous shape memory polymer vascular stent provided in the embodiments of the present application in conjunction with the accompanying drawings.

[0051] The stent is composed of unit cells periodically arranged in the axial and circumferential directions, wherein the unit cells are composed of multiple hollow elongated tubes. After inflation, the multiple hollow elongated tubes are alternately bent in opposite directions to open the unit cells, so that the stent structure is unfolded as a whole; wherein the hollow elongated tubes are made of two heterogeneous materials; Figure 1 As shown, the design method of the inflatable heterogeneous shape memory polymer vascular stent provided in the embodiments of the present application includes:

[0052] S101, selecting the corresponding number of unit cells in the axial and circumferential directions according to requirements, determining the material distribution of the two heterogeneous materials, and the structural dimensions of the stent;

[0053] It should be noted that in this application, a hollow slender tube is selected as the minimum structural unit to construct an orderly layout of alternating distribution of two materials, and to establish a quantitative relationship between inflation pressure, material distribution and structural size.

[0054] S102, calculating the bending curvature of the hollow elongated tube under the action of inflation pressure according to the material distribution and the structural dimensions of the stent;

[0055] It is understood that material distribution, also known as material layout, includes the wrap angle, spacing, and width ratio of the hoop-shaped region. Structural dimensions are the ratio of the wall thickness to the radius of the hollow, elongated tube, both of which can be calculated based on the dimensions of the hollow, elongated tube. In this application, the curvature of the hollow, elongated tube under inflation pressure can be understood as the free bending of the hollow, elongated tube solely under inflation pressure, i.e., the free deformation response.

[0056] S103, calculating the spatial configuration of the centerline of the end of the hollow elongated tube under the action of a concentrated force based on the bending curvature under the action of the inflation pressure;

[0057] After obtaining the bending curvature of the hollow slender tube under the action of inflation pressure alone, we then calculate how the centerline changes when the end of the hollow slender tube is subjected to a concentrated force, similar to how the hollow slender tube deforms and bends when it is subjected to plaque accumulation, that is, the load deformation response of the hollow slender tube.

[0058] S104 , calculating a quantitative relationship between the inflation pressure and the deployed diameter of the stent according to the number of the unit cells in the axial and circumferential directions and the spatial configuration of the centerline.

[0059] In the present application, the quantitative relationship between the inflation pressure and the deployed diameter of the stent is obtained, and the force and deformation of the stent during the deployment process are simplified to the level of the slender tube structure unit.

[0060] The working principle of the design method of inflatable heterogeneous shape memory polymer vascular stent is as follows: Figure 2This application first selects a slender hollow circular tube as the minimum structural unit, constructs an orderly layout with alternating distribution of two materials, establishes a quantitative relationship between inflation pressure and material distribution and structural size, first calculates the free bending of the hollow slender tube under the action of inflation pressure alone, then calculates the bending change of the center line when the end of the hollow slender tube is subjected to concentrated force, and finally calculates the quantitative relationship between the inflation pressure and the deployment diameter of the stent based on the number of unit cells in the axial and circumferential directions and the spatial configuration of the center line. This application not only qualitatively gives the overall appearance scheme of the inflatable vascular stent, but also constructs a quantitative material layout and structural size determination scheme by studying the deformation of the slender tube unit under inflation load and external concentrated force load, combined with the force analysis of the stent structure during deployment, thereby improving the rationality of the vascular stent structure design.

[0061] In some embodiments, the heterogeneous material includes a first heterogeneous material and a second heterogeneous material; wherein, under high temperature conditions, the modulus of the first heterogeneous material is lower than the modulus of the second heterogeneous material, so that the deformation area after inflation is concentrated in the area where the first heterogeneous material is located;

[0062] The region of the first heterogeneous material on the hollow elongated tube is a hoop-shaped region that is uniformly and discretely distributed; wherein the hoop-shaped region includes a plurality of regions.

[0063] As a preferred embodiment, the determining of the material distribution of the two heterogeneous materials and the structural dimensions of the stent includes:

[0064] Calculating the structural dimensions of the hollow elongated tube according to its radius and wall thickness; the structural dimensions are the ratio of the wall thickness to the radius;

[0065] The ratio of the hoop-shaped area is calculated according to the width and interval of the hoop-shaped area, and the winding angle is obtained; the material distribution includes the winding angle and the ratio of the hoop-shaped area.

[0066] Specifically, in this application, for each slender tube unit, the two component materials are marked as the first heterogeneous material M-1 and the second heterogeneous material M-2, respectively. The region where the first heterogeneous material M-1 is located is a series of uniformly discretely distributed hoop-shaped regions with a width of w and an interval of d. At high temperatures, the modulus E1 of the first heterogeneous material M-1 is significantly lower than the modulus E2 of the second heterogeneous material M-2. Therefore, after inflation, the deformation is mainly concentrated in the region where the first heterogeneous material M-1 is distributed, and the hollow slender tube bends as a whole, as shown in FIG. Figure 3 As shown. For radius R, wall thickness t, length L, winding angle φ winding The number of hoop-shaped regions is N, and the ratio of the spacing to the width of the hoop-shaped regions is β = d / w, which is a hollow slender tube.

[0067] In some embodiments, the hoop-shaped region where the first heterogeneous material is located and the adjacent region where the second heterogeneous material is located are defined as the first region, and the remaining region where the second heterogeneous material is located is defined as the second region; and calculating the bending curvature of the hollow elongated tube under inflation pressure based on the material distribution and the structural dimensions of the stent includes:

[0068] Obtaining a volume fraction of the second heterogeneous material according to the ratio of the hoop-shaped regions and the number of the hoop-shaped regions;

[0069] Calculating a composite modulus of the first heterogeneous material and the second heterogeneous material according to the volume fraction, the first modulus of the first heterogeneous material, and the second modulus of the second heterogeneous material;

[0070] Determine the position of the neutral layer according to the first modulus, the second modulus, the composite modulus, the radius, the wall thickness and the winding angle;

[0071] Determining a first relationship between the longitudinal elongation ratio and the bending curvature of the first region and a second relationship between the circumferential depth-to-length ratio and the bending curvature according to the radius, thickness, and neutral layer position;

[0072] calculating the deformation energy of the first region based on the first modulus, the second modulus, the volume fraction of the second heterogeneous material, the first relationship, and the second relationship;

[0073] Calculating the bending deformation energy of the large deformation area in the hollow slender tube based on the deformation energy, calculating the bending deformation energy of the small deformation area in the hollow slender tube based on the neutral layer position, radius and wall thickness, and calculating the potential energy corresponding to the inflation pressure load based on the inflation pressure and volume change;

[0074] The total energy of the inflated hollow slender tube is obtained by integrating the bending deformation energy of the large deformation area, the bending deformation energy of the small deformation area and the potential energy corresponding to the inflation pressure load;

[0075] The total energy is solved according to the principle of minimum potential energy to obtain the bending curvature of the hollow slender tube under the action of inflation pressure.

[0076] Specifically, in this application, the volume fraction of the second heterogeneous material M-2 is calculated as v based on the number of hoop-shaped regions of the hollow elongated tube being N and the ratio of the spacing to the width of the hoop-shaped region being β=d / w. f =[(1-1 / N)β] / [1+(1-1 / N)β], when the number of hoop regions N is large enough and the ratio of the width of the hoop regions β≥1 / N, the volume fraction v f Controlled by the width ratio β of the hoop region; the modulus of the composite of the first heterogeneous material M-1 and the second heterogeneous material M-2

[0077] The purpose of step S102 is to study the free bending deformation behavior of the hollow slender tube under the action of inflation pressure and determine the layout of the heterogeneous material (winding angle φ winding The influence of the ratio of the width of the hoop region (β) and the structural size (t / R) on the bending curvature κ0 of the hollow slender tube as the inflation pressure P changes.

[0078] Specifically, such as Figure 4 As shown, in this application, the hoop-shaped region where the first heterogeneous material M-1 is located and the adjacent second heterogeneous material M-2 region are regarded as a whole as the first region, which undergoes limited deformation, that is, large deformation, and the remaining portion is entirely composed of the second heterogeneous material M-2, which undergoes small deformation as the second region. For the first region, the longitudinal elongation ratio λ L The relationship between the bending curvature κ0 is Hoop elongation ratio λ R The relationship between the bending curvature κ0 and λ is R =1+(κ0R) 2 , where a=R+t / 2;

[0079] The neutral layer position b can be calculated using the first modulus, second modulus, composite modulus, radius, wall thickness, and winding angle in the following way:

[0080]

[0081] In formula (1), α = φ winding / 2;

[0082] The deformation energy of the first region satisfies:

[0083]

[0084] In formula (2), I1 is the first principal invariant of the right Cauchy-Green deformation tensor, I1 = λ L 2 +λ R 2 +1 / (λ L 2 λ R 2 ), I4 satisfies μ a and μ b It can be calculated using the first modulus, the second modulus, and the volume fraction of the second heterogeneous material in the following manner.

[0085]

[0086] It can be understood that the first region is the composite material, where μ a Represents the shear modulus of the isotropic part after the material is composited, μ bIt represents the shear modulus of the anisotropic part after the material is composited.

[0087] The total energy of the hollow slender tube system π total It consists of three parts:

[0088] Π total =Π s +Π b +Π p (4)

[0089] Among them, the bending deformation energy π in the large deformation area of the hollow slender tube is s It can be determined in the following ways

[0090]

[0091] C1(κ0) and C2(κ0) in formula (5) can be expressed as

[0092]

[0093] It is understandable that, for the convenience of representation in this application, C1(κ0) and C2(κ0) are used as intermediate variables for representation, which have no actual physical meaning.

[0094] The bending deformation energy of the small deformation area in the slender tube in formula (4) is The moment of inertia I2 can be determined by the following method

[0095]

[0096] In addition, the potential energy Π corresponding to the inflation pressure load in formula (4) p Determine in the following way:

[0097] Π p =-PΔV=-P[αλ R 2 +(π-α)][1+κ0(λ R -1)R+κ0b]R 2 L+PπR 2 L (8)

[0098] According to the principle of minimum potential energy, the total energy of the hollow slender tube system Π total The minimum value corresponds to the equilibrium state of the system, based on which the distribution of different materials (winding angle φ winding The quantitative relationship between the bending curvature κ0 of the hollow slender tube and the inflation pressure P under the conditions of the ratio of the width of the hoop-shaped area β) and the structural size (t / R) is obtained, and the bending curvature κ0 of the hollow slender tube under the action of the inflation pressure is obtained.

[0099] In some embodiments, the calculating, based on the bending curvature under the inflation pressure, the spatial configuration of the centerline of the end of the hollow elongated tube under the concentrated force, includes:

[0100] The hollow elongated tube is assumed to be an elastic rod with an initial curvature; the initial curvature corresponds to the bending curvature under the action of inflation pressure;

[0101] Calculating the plane coordinates of a preset point on the arc length of the center line of the elastic rod based on the equivalent bending stiffness of the elastic rod against deformation and the bending curvature under the action of the inflation pressure;

[0102] The spatial configuration of the center line of the hollow slender tube under the concentrated force at the end is calculated based on the plane coordinates of the preset point of the arc length of the center line of the elastic rod.

[0103] Specifically, the hollow, slender tube is simplified into a Kirchhoff rod with a certain initial curvature, and the spatial configuration of the rod centerline after the tube end is subjected to a concentrated force load F is obtained. The initial curvature κ0 is determined by the inflation pressure load within the tube, the material layout, and the structural dimensions. This is the bending curvature of the hollow, slender tube under the inflation pressure calculated in step S102. The spatial configuration of the centerline of the hollow, slender tube under the concentrated force at the end is calculated as follows:

[0104]

[0105] In formula (9), A1 represents the equivalent bending stiffness of the Kirchhoff rod against deformation, which can be obtained by dividing the bending moment generated by the inflation pressure P by the bending curvature κ0, that is, A1 = PπR 2 b / κ0; x(s) and y(s) represent the plane coordinates at the arc length s of the rod centerline; the rotation angles at both ends of the rod are constrained to be zero;

[0106] In this application, the angle θ is first calculated using the bending curvature κ0, and then the plane coordinates x(s), y(s) at the preset point of the centerline arc length of the elastic rod are calculated based on the angle θ. end =y(L) is substituted into the calculation to calculate the spatial configuration of the center line of the hollow slender tube when the end is subjected to concentrated force.

[0107] In some embodiments, calculating the quantitative relationship between the inflation pressure and the deployed diameter of the stent based on the number of the unit cells in the axial and circumferential directions and the spatial configuration of the centerline includes:

[0108] The inner radius of the deformed plaque is calculated based on the number of unit cells in the annular direction, the spatial configuration of the centerline, and the expanded diameter of the stent;

[0109] The force exerted by the plaque on the stent is calculated based on the inner radius of the deformed plaque and the shape of the stent in its initial state;

[0110] The load force at the end of the hollow slender rod is calculated based on the inner radius of the deformed plaque, the force exerted by the plaque on the stent, the axial length of the stent in the initial state, and the number of unit cells in the axial direction.

[0111] The quantitative relationship between the inflation pressure and the expanded diameter of the stent is obtained according to the load force at the end of the hollow slender rod.

[0112] Specifically, this application analyzes the stress and deformation of an inflatable vascular stent during deployment, establishing a quantitative relationship between the applied inflation pressure P and the stent's deployed diameter D, given a certain heterogeneous material layout and structural dimensions. Before deployment, the plaque has an inner diameter of 2A (>D) and an outer diameter of 2B. When the inflation pressure increases from zero to a certain level, the stent contacts the plaque and then continues to expand until the target configuration is reached. This is shown in the schematic diagram. Figure 5 The load F acting on the end of the hollow slender tube of the stent initially remains zero. As the stent contacts the plaque and continues to expand, the load F gradually increases, satisfying

[0113]

[0114] Where m and n are the number of axial and circumferential unit cells in the stent structure, respectively; l0 is the axial length of the stent in the initial state; r a is the inner radius of the deformed patch; p stent is the force exerted by the plaque on the stent, which can be obtained by combining the deformation of the plaque with the constitutive equation and can be generally expressed as p stent =f(r a The combined equations (1-10) can be used to obtain the quantitative relationship between the inflation pressure P and the stent deployment diameter D.

[0115] Specifically, in this application, the spatial configuration of the center line under a certain load F′ (the end displacement y end ) and the inflation pressure P (through equations (1)-(9)), and then using y end The inner radius r of the deformed plaque is calculated based on the number n of unit cells in the annular direction and the stent expansion diameter D. a (Equation (10)); Finally, according to the constitutive equation of plaque deformation (p stent =f(r a / A)) Calculate the load force F at the end of the hollow slender rod, and combine the relationship between the action force and the reaction force (F′=F) to obtain the quantitative relationship between the inflation pressure P and the expanded diameter of the stent.

[0116] In some embodiments, after obtaining a quantitative relationship between the inflation pressure P and the stent deployment diameter D, a grayscale digital light processing 3D printing method can be used to manufacture an inflatable heterogeneous shape memory polymer stent.

[0117] In some embodiments, determining whether the stent manufactured according to the obtained quantitative relationship between the inflation pressure and the deployed diameter of the stent meets the requirements;

[0118] If not, the number of unit cells in the axial and circumferential directions, the material distribution of the two heterogeneous materials, and the structural dimensions of the stent are adjusted.

[0119] It should be noted that the judgment is made based on the actual situation. If it is not satisfied, it is necessary to change the parameters such as the number of unit cells in the axial and circumferential directions, the material distribution of the two heterogeneous materials, and the structural dimensions of the bracket, and process again.

[0120] The technical solution provided in the present application firstly selects, according to requirements, the number of unit cells in the axial and circumferential directions composed of eight hollow slender tube structural units, the ratio and winding angle of the distribution pattern of the two heterogeneous materials in the slender tube, and structural dimension parameters such as the wall thickness and radius of the slender tube; secondly, a mapping relationship between the free bending deformation curvature of the slender tube and the inflation pressure is established according to the given material distribution and structural dimensions, and the position of the center line of the slender tube when a concentrated force load is applied to the end is obtained; finally, according to periodicity and symmetry, the force and deformation of the stent during the deployment process are simplified to the slender tube structural unit level, and by substituting the displacement and pressure relationship of the slender tube end and performing corresponding conversion, a quantitative relationship between the inflation pressure and the deployment diameter of the inflatable vascular stent is finally established.

[0121] An embodiment of the present application provides an inflatable heterogeneous shape memory polymer vascular stent, which is manufactured using the design method of the inflatable heterogeneous shape memory polymer vascular stent provided by any of the above embodiments.

[0122] In summary, the present invention provides a design method and stent for an inflatable heterogeneous shape memory polymer vascular stent. The technical solution provided by the present invention compensates for and improves the limitations of traditional shape memory polymer vascular stent design methods. It provides a new solution for designing a shape memory polymer vascular stent with high radial support stiffness and a relatively fast deployment speed. On the one hand, it qualitatively provides an overall external design scheme for the inflatable vascular stent. On the other hand, by studying the deformation of slender tubular units under inflation loads and external concentrated force loads, combined with the force analysis of the stent structure during deployment, a quantitative material layout and structural dimension determination scheme is constructed, thereby improving the rationality of the vascular stent structure design. The present invention fully considers the scenarios faced by inflatable heterogeneous shape memory polymer stents during actual application, selects slender hollow circular tubes as the minimum structural unit, constructs an orderly layout with alternating dual materials, and establishes a quantitative relationship between inflation pressure, material distribution, and structural dimensions. Compared with existing shape memory polymer stents, the stent structure under this design scheme can significantly improve its support stiffness and deployment speed during deployment, and has greater clinical application value.

[0123] It can be understood that the method embodiment provided above corresponds to the bracket embodiment above, and the corresponding specific contents can be referenced to each other and will not be repeated here.

[0124] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage and optical storage, etc.) that contain computer-usable program code.

[0125] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A block or multiple blocks specifying a function.

[0126] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction method, which is implemented in the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0127] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0128] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A design method for an inflatable heterogeneous shape memory polymer vascular stent, characterized in that: The stent is composed of unit cells periodically arranged in the axial and circumferential directions. The unit cells are composed of multiple hollow, slender tubes. After inflation, the multiple hollow, slender tubes are alternately bent in opposite directions to open the unit cells, so that the stent structure is deployed as a whole. The hollow, slender tubes are made of two heterogeneous materials. The design method of the inflatable heterogeneous shape memory polymer vascular stent comprises: Select the corresponding number of unit cells in the axial and circumferential directions according to the requirements, determine the material distribution of the two heterogeneous materials, and the structural dimensions of the stent; Calculating the bending curvature of the hollow elongated tube under the action of inflation pressure according to the material distribution and the structural dimensions of the stent; Calculating the spatial configuration of the centerline of the end of the hollow slender tube under the action of concentrated force based on the bending curvature under the action of the inflation pressure; The quantitative relationship between the inflation pressure and the deployed diameter of the stent is calculated based on the number of the unit cells in the axial and circumferential directions and the spatial configuration of the centerline.

2. The method according to claim 1, characterized in that The heterogeneous material includes a first heterogeneous material and a second heterogeneous material; wherein, under high temperature conditions, the modulus of the first heterogeneous material is lower than the modulus of the second heterogeneous material, so that the deformation area after inflation is concentrated in the area where the first heterogeneous material is located; The region of the first heterogeneous material on the hollow elongated tube is a hoop-shaped region that is uniformly and discretely distributed; wherein the hoop-shaped region includes a plurality of regions.

3. The method according to claim 2, characterized in that Determining the material distribution of the two heterogeneous materials and the structural dimensions of the stent includes: Calculating the structural dimensions of the hollow elongated tube according to its radius and wall thickness; the structural dimensions are the ratio of the wall thickness to the radius; The ratio of the hoop-shaped area is calculated according to the width and interval of the hoop-shaped area, and the winding angle is obtained; the material distribution includes the winding angle and the ratio of the hoop-shaped area.

4. The method according to claim 3, characterized in that The hoop-shaped region where the first heterogeneous material is located and the adjacent region where the second heterogeneous material is located are defined as the first region, and the remaining region where the second heterogeneous material is located is defined as the second region; The calculating the bending curvature of the hollow elongated tube under the action of inflation pressure according to the material distribution and the structural dimensions of the stent includes: Obtaining a volume fraction of the second heterogeneous material according to the ratio of the hoop-shaped regions and the number of the hoop-shaped regions; Calculating a composite modulus of the first heterogeneous material and the second heterogeneous material according to the volume fraction, the first modulus of the first heterogeneous material, and the second modulus of the second heterogeneous material; Determine the position of the neutral layer according to the first modulus, the second modulus, the composite modulus, the radius, the wall thickness and the winding angle; Determining a first relationship between the longitudinal elongation ratio and the bending curvature of the first region and a second relationship between the circumferential depth-to-length ratio and the bending curvature according to the radius, thickness, and neutral layer position; calculating the deformation energy of the first region based on the first modulus, the second modulus, the volume fraction of the second heterogeneous material, the first relationship, and the second relationship; Calculating the bending deformation energy of the large deformation area in the hollow slender tube based on the deformation energy, calculating the bending deformation energy of the small deformation area in the hollow slender tube based on the neutral layer position, radius and wall thickness, and calculating the potential energy corresponding to the inflation pressure load based on the inflation pressure and volume change; The total energy of the inflated hollow slender tube is obtained by integrating the bending deformation energy of the large deformation area, the bending deformation energy of the small deformation area and the potential energy corresponding to the inflation pressure load; The total energy is solved according to the principle of minimum potential energy to obtain the bending curvature of the hollow slender tube under the action of inflation pressure.

5. The method according to claim 1, wherein The calculating, based on the bending curvature under the inflation pressure, the spatial configuration of the centerline of the end of the hollow elongated tube under the concentrated force, includes: The hollow elongated tube is assumed to be an elastic rod with an initial curvature; the initial curvature corresponds to the bending curvature under the action of inflation pressure; Calculating the plane coordinates of a preset point on the arc length of the center line of the elastic rod based on the equivalent bending stiffness of the elastic rod against deformation and the bending curvature under the action of the inflation pressure; The spatial configuration of the center line of the hollow slender tube under the concentrated force at the end is calculated based on the plane coordinates of the preset point of the arc length of the center line of the elastic rod.

6. The method according to claim 1, characterized in that Calculating the quantitative relationship between the inflation pressure and the deployed diameter of the stent based on the number of the unit cells in the axial and circumferential directions and the spatial configuration of the centerline includes: The inner radius of the deformed plaque is calculated based on the number of unit cells in the annular direction, the spatial configuration of the centerline, and the expanded diameter of the stent; The force exerted by the plaque on the stent is calculated based on the inner radius of the deformed plaque and the shape of the stent in its initial state; The load force at the end of the hollow slender rod is calculated based on the inner radius of the deformed plaque, the force exerted by the plaque on the stent, the axial length of the stent in the initial state, and the number of unit cells in the axial direction. The quantitative relationship between the inflation pressure and the expanded diameter of the stent is obtained according to the load force at the end of the hollow slender rod.

7. The method according to claim 1, characterized in that Inflatable heterogeneous shape memory polymer blood vessels were fabricated using grayscale digital light processing 3D printing.

8. The method according to claim 7, characterized in that Determining whether the stent manufactured according to the obtained quantitative relationship between the inflation pressure and the deployed diameter of the stent meets the requirements; If not, the number of unit cells in the axial and circumferential directions, the material distribution of the two heterogeneous materials, and the structural dimensions of the stent are adjusted.

9. The method according to claim 1, characterized in that The unit cell of the stent is composed of eight hollow slender tubes, and the eight hollow slender tubes are divided into a pair of four hollow slender tubes.

10. An inflatable heterogeneous shape memory polymer vascular stent, characterized in that: The inflatable heterogeneous shape memory polymer vascular stent is manufactured using the design method according to any one of claims 1 to 9.

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