Self-expanding drug-coated vascular stent
By adopting the design of fishbone-shaped connecting tendons in the self-expanding vascular stent, the problem of stent fracture caused by uneven expansion is solved, and the uniform expansion of the vascular stent and higher adherence are achieved, reducing the risk of surgery.
Patent Information
- Application Number
- CN202110621693.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-06-03
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2041-06-03
AI Technical Summary
The existing self-expanding vascular stents expand unevenly when they are automatically deployed, resulting in uneven support force of the blood vessel wall, which may cause stent breakage and arterial damage, increasing the risk of surgery.
The network tube structure is adopted formed by multiple main tendons and connecting tendons. The main tendons are evenly distributed along the circumference. The connecting tendons extend in the shape of fish bones and are connected at the peaks or valleys of the main tendons to ensure uniform distribution of mechanical support and avoid uneven expansion and bending. .
Through the design of fish bone-like connecting tendons, the expansion force is evenly dispersed, the radial support force is enhanced, the axial flexibility is improved, the vascular stent is prevented from breaking during the expansion process, the risk of surgery is reduced, and the adherence and resilience are improved.
Smart Images
Figure CN115429507B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of medical devices, and in particular to a self-expanding drug-coated vascular stent. Background Art
[0002] Cerebral artery atherosclerotic stenosis is an important cause of ischemic cerebrovascular disease, and the probability of cerebral infarction increases with the degree of stenosis. Currently, many studies have shown that even with drug treatment, the probability of cerebral infarction remains high. Currently, the effective means of treating severe cerebral artery stenosis is to implant stents in the arteries. Commonly used stents include balloon-expandable stents and self-expandable stents.
[0003] The self-expanding vascular stent is made of a thin-walled nickel-titanium superelastic alloy tube through laser precision engraving. It reaches the arterial lesion through a compression-grip delivery catheter. After the fixation is released, it expands automatically to allow blood to flow freely and supports the lesion. However, when the self-expanding stent in the prior art is automatically deployed in the blood vessel, due to the instantaneous non-uniform expansion phenomenon, the expansion degree of the stent end is much greater than that of the middle end, resulting in different expansion degrees at different parts of the stent when the vascular stent is deployed, and the supporting force on the vascular wall is uneven. In severe cases, the bent part of the vascular stent may break, causing serious damage to the artery and leading to surgical failure. Summary of the invention
[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of the prior art self-expanding vascular stent that when it is automatically deployed, the stent expands unevenly at various locations, which may easily cause artery damage, thereby providing a self-expanding drug-coated vascular stent.
[0005] In order to solve the above technical problems, the present invention provides a self-expanding drug-coated vascular stent, which is a mesh tube structure formed by connecting a plurality of main ribs and a plurality of connecting ribs, wherein the plurality of main ribs are evenly distributed along the circumference, and two adjacent main ribs are connected by connecting ribs;
[0006] When the mesh structure is in the expanded state, the main reinforcements extend in a sinusoidal waveform, the connecting reinforcements extend in the same direction as the main reinforcements, the connecting reinforcements are connected to the protruding side of the crest or trough of the main reinforcements, one side of the same connecting reinforcement is connected to the crest of a main reinforcement, and the other side of the connecting reinforcement is connected to the trough of another adjacent main reinforcement;
[0007] When the network tube structure is unfolded and laid flat, a plurality of main reinforcements are parallel to each other, and the connecting reinforcements extend in a fishbone shape along the extension direction of the main reinforcements.
[0008] Optionally, the connecting ribs include a plurality of first ribs and a plurality of second ribs arranged in an alternating manner, the front end of the first rib is connected to an adjacent previous second rib, the rear end of the first rib is connected to a trough of one of the main ribs, the front end of the second rib is connected to an adjacent previous first rib, and the rear end of the second rib is connected to a crest of another main rib.
[0009] Optionally, the second branch bar is connected to the first node of the first branch bar, the first branch bar is connected to the second node of the second branch bar, the distance from the end of the first branch bar connected to the main bar to the first node is smaller than the distance from the end of the first branch bar connected to the second branch bar to the first node, and the distance from the end of the second branch bar connected to the main bar to the second node is smaller than the distance from the end of the second branch bar connected to the first branch bar to the second node.
[0010] Optionally, the cross-sectional width of the first rib at the end of the first rib and the first node is greater than the cross-sectional width of the first rib at any position between the first node and the end of the first rib; the cross-sectional width of the second rib at the end of the second rib and the second node is greater than the cross-sectional width of the second rib at any position between the second node and the end of the second rib.
[0011] Optionally, the cross-sectional width of the first rib at the first node and the end of the first rib is 30-60 microns, and the cross-sectional width of the first rib at a position between the first node and the end of the first rib is 20-50 microns.
[0012] Optionally, when the mesh tube structure is in an expanded state, the crests of the main reinforcement are aligned with the crests of adjacent main reinforcements, the crests of the main reinforcements are all connected to one of the connecting reinforcements, and the troughs on the same main reinforcement are all connected to another connecting reinforcement.
[0013] Optionally, at least one end of the network tube structure is provided with an embedding portion for mounting a developing component.
[0014] Optionally, at least one end of the mesh tube structure is provided with a developing component to indicate the position of the mesh tube structure in the human body.
[0015] Optionally, the cross-sectional width of the main reinforcement at the connection points of the connecting reinforcements on the main reinforcement is greater than the cross-sectional width of the main reinforcement between the connection points of the connecting reinforcements on the main reinforcement.
[0016] Optionally, the cross-sectional width of the main ribs at the connection points of the connecting ribs on the main ribs is 30-60 microns, and the cross-sectional width of the main ribs between the connection points of the connecting ribs on the main ribs is 20-50 microns.
[0017] The technical solution of the present invention has the following advantages:
[0018] 1. The self-expanding drug-coated vascular stent provided by the present invention is a mesh tube structure formed by connecting a plurality of main ribs and a plurality of connecting ribs, wherein the plurality of main ribs are evenly distributed along the circumference, and two adjacent main ribs are connected by connecting ribs; when the mesh tube structure is in an expanded state, the main ribs extend in a sinusoidal waveform, the connecting ribs extend in the same direction as the main ribs, the connecting ribs are connected to the side of the main ribs where the crest or trough protrudes, one side of the same connecting rib is connected to the crest of a main rib, and the other side of the connecting rib is connected to the trough of another adjacent main rib; when the mesh tube structure is in an expanded and flattened state, the plurality of main ribs are parallel to each other, and the connecting ribs extend in a fishbone shape along the extension direction of the main ribs. By setting the connecting ribs into a fishbone structure and connecting adjacent main ribs with the fishbone-shaped connecting ribs, when the vascular stent enters the human body and automatically expands and unfolds, the fishbone-shaped connecting ribs disperse the force of expansion to the main ribs, which can enhance the radial support force of the connecting ribs. At the same time, in the extension direction of the main ribs, different branch ribs of the connecting ribs exert force on the main ribs, making the axial flexibility of the vascular stent better, which can effectively alleviate the instantaneous non-uniform expansion phenomenon of the vascular stent during the expansion process, making the expansion process of the vascular stent more uniform and smooth, and effectively overcoming the uneven expansion of the vascular stent, preventing the bending part of the vascular stent from breaking during the expansion process, ensuring that the vascular stent will not cause damage to the artery, thereby reducing the risk of vascular stent implantation surgery. By allowing the vascular stent to expand evenly, it is ensured that the outer wall of the vascular stent is flush after the expansion, and the wall adhesion of the vascular stent is improved, which can effectively prevent the blood vessel from shrinking and narrowing again due to insufficient support force of the vascular stent after the blood vessel is expanded. At the same time, by using fishbone-shaped connecting ribs to support the main ribs, the circumferential support force of the stent is increased, the flexibility of the stent is increased, and the vascular stent is placed in the human body more smoothly.
[0019] 2. The self-expanding drug-coated vascular stent provided by the present invention comprises a plurality of first ribs and a plurality of second ribs arranged in an alternating manner, wherein the front end of the first rib is connected to the adjacent previous second rib, the rear end of the first rib is connected to the trough of one of the main ribs, the front end of the second rib is connected to the adjacent previous first rib, and the rear end of the second rib is connected to the crest of another main rib. By connecting the connecting rib to the crest or trough of the main rib, it is ensured that the supporting force of the connecting rib on the main rib is large enough, the axial flexibility of the vascular stent is improved, and the vascular stent itself can effectively overcome the torsional stress, or can quickly return to its original state after being twisted.
[0020] 3. The self-expanding drug-coated vascular stent provided by the present invention has the second rib connected to the first node of the first rib, the first rib connected to the second node of the second rib, the distance from the end of the first rib connected to the main rib to the first node is less than the distance from the end of the first rib connected to the second rib to the first node, and the distance from the end of the second rib connected to the main rib to the second node is less than the distance from the end of the second rib connected to the first rib to the second node. The first node and the second node are both arranged close to the main rib, so that when the vascular stent is in the expanded state, the first node and the second node are staggered between two rows of main ribs, so that the size and shape of the hole surrounded by the first rib, the second rib and the main rib are uniform, ensuring that the stress can be evenly transmitted on the vascular stent after the vascular stent is subjected to force, and avoiding the vascular stent from being fractured due to uneven local force.
[0021] 4. In the self-expanding drug-coated vascular stent provided by the present invention, the cross-sectional width of the first rib at the first rib end and the first node is greater than the cross-sectional width of the first rib at any position between the first node and the first rib end; the cross-sectional width of the second rib at the second rib end and the second node is greater than the cross-sectional width of the second rib at any position between the second node and the second rib end. The first rib and the second rib are configured as variable-section ribs, so that the stress on the first rib and the second rib is dispersed, and stress concentration is avoided at the first node or the second node or the node of the first rib on the main rib, which can effectively improve the radial support force and rebound recovery rate of the stent as a whole.
[0022] 5. The self-expanding drug-coated vascular stent provided by the present invention has an inlay portion at at least one end of the mesh structure for mounting a developing component. By mounting the developing component on the vascular stent, the position of the vascular stent in the human body can be accurately observed during surgery, which facilitates the positioning of the vascular stent. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0024] Figure 1 It is a schematic structural diagram of the self-expanding drug-coated vascular stent in the unfolded and laid-out state provided in an embodiment of the present invention.
[0025] Figure 2 for Figure 1 The schematic diagram of the structure of the connecting ribs of the self-expanding drug-coated vascular stent is shown.
[0026] Figure 3 It is a schematic structural diagram of a folded state of a self-expandable drug-coated vascular stent provided in an embodiment of the present invention.
[0027] Figure 4 for Figure 3 A partial enlarged view of point A in the middle.
[0028] Figure 5 It is a schematic structural diagram of the expanded state of the self-expandable drug-coated vascular stent provided in an embodiment of the present invention.
[0029] Explanation of the reference numerals: 1. main rib; 2. connecting rib; 3. inlaid part. DETAILED DESCRIPTION
[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0033] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0034] like Figures 1 to 5The self-expanding drug-coated vascular stent provided in this embodiment is a mesh tube structure formed by connecting four main ribs 1 and four connecting ribs 2. The four main ribs 1 are evenly distributed along the circumference, and two adjacent main ribs 1 are connected by connecting ribs 2. Thrombotherapy drugs are coated on the surfaces of the main ribs 1 and the connecting ribs 2 to change the surface properties of the inner wall of the blood vessel and reduce the formation of thrombi.
[0035] like Figure 5 As shown, when the mesh tube structure is in the expanded state, the main reinforcement 1 extends in a sinusoidal waveform, the connecting reinforcement 2 extends in the same direction as the main reinforcement 1, the connecting reinforcement 2 is connected to the side of the main reinforcement 1 where the crest or trough is protruding, one side of the same connecting reinforcement 2 is connected to the crest of one main reinforcement 1, and the other side of the connecting reinforcement 2 is connected to the trough of another adjacent main reinforcement 1. When the mesh tube structure is in the expanded state, the crest of the main reinforcement 1 is aligned with the crest of the adjacent main reinforcement 1, the crest of the main reinforcement 1 is connected to one of the connecting reinforcements 2, and the trough on the same main reinforcement 1 is connected to another connecting reinforcement 2.
[0036] like Figure 1 and Figure 2 As shown, when the mesh tube structure is unfolded and laid flat, the four main reinforcements 1 are parallel to each other, and along the extension direction of the main reinforcements 1, the connecting reinforcements 2 extend in a fishbone shape.
[0037] The connecting rib 2 includes a plurality of first ribs and a plurality of second ribs arranged in an alternating manner. The front end of the first rib is connected to the adjacent previous second rib, the rear end of the first rib is connected to the trough of one of the main ribs 1, the front end of the second rib is connected to the adjacent previous first rib, and the rear end of the second rib is connected to the crest of another main rib 1. The second rib is connected to the first node of the first rib, and the first rib is connected to the second node of the second rib. The distance from the end of the first rib connected to the main rib 1 to the first node is smaller than the distance from the end of the first rib connected to the second rib to the first node, and the distance from the end of the second rib connected to the main rib 1 to the second node is smaller than the distance from the end of the second rib connected to the first rib to the second node. The cross-sectional width of the first rib at the end of the first rib and the first node is greater than the cross-sectional width of the first rib at any position between the first node and the end of the first rib; the cross-sectional width of the second rib at the end of the second rib and the second node is greater than the cross-sectional width of the second rib at any position between the second node and the end of the second rib.
[0038] The cross-sectional width of the first rib at the first node and the end of the first rib is 30-60 microns, and the cross-sectional width of the first rib at any position between the first node and the end of the first rib is 20-50 microns. In this embodiment, the cross-sectional width of the first rib at the first node and at both ends of the first rib is 45 microns, and the cross-sectional width of the first rib at the midpoint between the first node and the end of the first rib is 40 microns, and the cross-sectional width of the first rib changes uniformly.
[0039] The second rib has the same structure as the first rib, the cross-sectional width of the second rib at the second node and the second rib end is 30-60 microns, and the cross-sectional width of the second rib at any position between the second node and the second rib end is 20-50 microns. In this embodiment, the cross-sectional width of the second rib at the second node and at both ends of the second rib is 45 microns, and the cross-sectional width of the second rib at the midpoint between the second node and the second rib end is 40 microns, and the cross-sectional width of the second rib changes uniformly.
[0040] The cross-sectional width of the main reinforcement 1 at the connection point of the main reinforcement 1 connecting the reinforcement 2 is greater than the cross-sectional width of the main reinforcement 1 between the connection points of the main reinforcement 1 connecting the reinforcement 2. The cross-sectional width of the main reinforcement 1 at the connection point of the main reinforcement 1 connecting the reinforcement 2 is 30-60 microns, and the cross-sectional width of the main reinforcement 1 between the connection points of the main reinforcement 1 connecting the reinforcement 2 is 20-50 microns. In this embodiment, the cross-sectional width of the main reinforcement 1 at the connection point of the main reinforcement 1 connecting the reinforcement 2 is 45 microns, and the cross-sectional width at the midpoint between the connection points of the main reinforcement 1 connecting the reinforcement 2 is 40 microns, and the cross-sectional width of the main reinforcement 1 changes uniformly.
[0041] Both ends of the mesh tube structure are provided with an inlay part 3, one end of the inlay part 3 on the mesh tube structure is arranged on the main rib 1, and the other end is arranged on the connecting rib 2, a developing metal as a developing part is embedded in the inlay part 3, and bosses are arranged on both sides of the inlay part 3 to position the inlay part 3.
[0042] The vascular stent provided in this embodiment is made of nickel-titanium alloy material, which is formed by laser melting of nickel-titanium alloy ultra-thin tube. The cross-sectional thickness of the main rib 1 and the connecting rib 2 are the same. First, draw a picture in the drawing software. When drawing, control the cross-sectional width of the main rib 1 and the connecting rib 2 to be a gradual size. Import the finished drawing into the laser cutting machine, adjust the laser power: 6w, pulse speed: 800fs, and the laser cutting machine can cut according to the configuration of the drawing. After cutting, the vascular stent is in a folded state, such as Figure 3 and Figure 4 shown.
[0043] By setting the connecting ribs 2 into a fishbone structure, the adjacent main ribs 1 are connected by the fishbone-shaped connecting ribs 2. When the vascular stent enters the human body and automatically expands and unfolds, the fishbone-shaped connecting ribs 2 disperse the force of the expansion to the main ribs 1, which can enhance the radial support force of the connecting ribs 2. At the same time, in the extension direction of the main ribs 1, different branch ribs of the connecting ribs 2 exert force on the main ribs 1, so that the axial flexibility of the vascular stent is better, which can effectively alleviate the instantaneous non-uniform expansion phenomenon of the vascular stent during the expansion process, making the expansion process of the vascular stent more uniform and smooth, and can effectively overcome the uneven expansion of the vascular stent, prevent the bending part of the vascular stent from breaking during the expansion process, and ensure that the vascular stent will not cause damage to the artery, thereby reducing the risk of the vascular stent implantation operation. By allowing the vascular stent to expand evenly, it is ensured that the outer wall of the vascular stent is flush after the expansion, and the wall adhesion of the vascular stent is improved, which can effectively prevent the blood vessel from shrinking and narrowing again due to insufficient support force of the vascular stent after the blood vessel is expanded. At the same time, by using fishbone-shaped connecting ribs to support the main ribs, the circumferential support force of the stent is increased, the flexibility of the stent is increased, and the vascular stent is placed in the human body more smoothly.
[0044] As an alternative embodiment, both ends of the mesh tube structure are connected with medical developing metals serving as developing parts. The developing part at one end of the mesh tube structure is arranged on the main rib 1, and the developing part at the other end is arranged on the connecting rib 2. The developing parts can indicate the position of the mesh tube structure in the human body.
[0045] As an alternative embodiment, the cross-sectional width of the first rib at the first node and at both ends of the first rib is 30 microns, and the cross-sectional width of the first rib at the midpoint between the first node and the end of the first rib is 20 microns. The cross-sectional width of the second rib at the second node and at both ends of the second rib is 30 microns, and the cross-sectional width of the second rib at the midpoint between the second node and the end of the second rib is 20 microns. The cross-sectional width of the main rib 1 at the connection point of the connecting rib 2 on the main rib 1 is 30 microns, and the cross-sectional width at the midpoint between the connection points of the connecting rib 2 on the main rib 1 is 20 microns.
[0046] As an alternative embodiment, the cross-sectional width of the first rib at the first node and at both ends of the first rib is 60 microns, and the cross-sectional width of the first rib at the midpoint between the first node and the end of the first rib is 50 microns. The cross-sectional width of the second rib at the second node and at both ends of the second rib is 60 microns, and the cross-sectional width of the second rib at the midpoint between the second node and the end of the second rib is 50 microns. The cross-sectional width of the main rib 1 at the connection point of the connecting rib 2 on the main rib 1 is 60 microns, and the cross-sectional width at the midpoint between the connection points of the connecting rib 2 on the main rib 1 is 50 microns.
[0047] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.
Claims
1. A self-expanding drug-coated vascular stent, characterized in that: A mesh tube structure formed by connecting a plurality of main ribs (1) and a plurality of connecting ribs (2), wherein the plurality of main ribs (1) are evenly distributed along the circumferential direction, and two adjacent main ribs (1) are connected by the connecting ribs (2); When the mesh tube structure is in an expanded state, the main reinforcements (1) extend in a sinusoidal waveform, the connecting reinforcements (2) extend in the same direction as the main reinforcements (1), the connecting reinforcements (2) are connected to the side of the main reinforcements (1) where the crests or troughs protrude, one side of the same connecting reinforcement (2) is connected to the crest of one main reinforcement (1), and the other side of the connecting reinforcement (2) is connected to the trough of another adjacent main reinforcement (1); When the network tube structure is in an unfolded and flattened state, the plurality of main ribs (1) are parallel to each other, and along the extension direction of the main ribs (1), the connecting ribs (2) extend in a fishbone shape; The connecting rib (2) comprises a plurality of first ribs and a plurality of second ribs arranged in a staggered manner, wherein the front end of the first rib is connected to the adjacent previous second rib, the rear end of the first rib is connected to the trough of one of the main ribs (1), the front end of the second rib is connected to the adjacent previous first rib, the rear end of the second rib is connected to the crest of another main rib (1), the second rib is connected to the first node of the first rib, and the first rib is connected to the second node of the second rib.
2. The self-expandable drug-coated vascular stent according to claim 1, characterized in that: The distance from one end of the first branch bar connected to the main bar (1) to the first node is shorter than the distance from one end of the first branch bar connected to the second branch bar to the first node, and the distance from one end of the second branch bar connected to the main bar (1) to the second node is shorter than the distance from one end of the second branch bar connected to the first branch bar to the second node.
3. The self-expanding drug-coated vascular stent according to claim 2, characterized in that: The cross-sectional width of the first rib at the end of the first rib and the first node is greater than the cross-sectional width of the first rib at any position between the first node and the end of the first rib; the cross-sectional width of the second rib at the end of the second rib and the second node is greater than the cross-sectional width of the second rib at any position between the second node and the end of the second rib.
4. The self-expanding drug-coated vascular stent according to claim 3, characterized in that: The cross-sectional width of the first rib at the first node and the end of the first rib is 30-60 microns, and the cross-sectional width of the first rib at the position between the first node and the end of the first rib is 20-50 microns.
5. The self-expandable drug-coated vascular stent according to any one of claims 1 to 4, characterized in that: When the mesh tube structure is in an expanded state, the crests of the main reinforcement (1) are aligned with the crests of the adjacent main reinforcement (1), the crests of the main reinforcement (1) are all connected to one of the connecting reinforcements (2), and the troughs on the same main reinforcement (1) are all connected to another connecting reinforcement (2).
6. The self-expandable drug-coated vascular stent according to any one of claims 1 to 4, characterized in that: At least one end of the network tube structure is provided with an embedding portion (3) for mounting a developing component.
7. The self-expandable drug-coated vascular stent according to any one of claims 1 to 4, characterized in that: At least one end of the net tube structure is provided with a developing component to indicate the position of the net tube structure in the human body.
8. The self-expandable drug-coated vascular stent according to any one of claims 1 to 4, characterized in that: The cross-sectional width of the main reinforcement (1) at the connection point of the connecting reinforcement (2) on the main reinforcement (1) is greater than the cross-sectional width of the main reinforcement (1) between the connection points of the connecting reinforcement (2) on the main reinforcement (1).
9. The self-expandable drug-coated vascular stent according to any one of claims 1 to 4, characterized in that: The cross-sectional width of the main rib (1) at the connection point of the connecting rib (2) on the main rib (1) is 30-60 microns, and the cross-sectional width of the main rib (1) between the connection points of the connecting rib (2) on the main rib (1) is 20-50 microns.