Micro catheter

Abstract

The invention relates to the technical field of medical instruments, and discloses a micro catheter. Wherein the microcatheter is sequentially provided with a lining tube and a high polymer material layer from inside to outside in the radial direction, a variable-diameter section is arranged at the far end of the microcatheter, a small-diameter section is arranged on one side of the far end of the variable-diameter section, and a large-diameter section is arranged on one side of the near end of the variable-diameter section; the high polymer material layer comprises a first hardness area, a second hardness area and a third hardness area which are sequentially arranged from the far end to the near end, the first hardness area is located on a part of the small-diameter section, the second hardness area is located on the other part of the small-diameter section, the variable-diameter section and a part of the large-diameter section, and the third hardness area is located on the other part of the large-diameter section; the hardness of the first hardness area is smaller than that of the second hardness area, the hardness of the second hardness area is smaller than that of the third hardness area, and smooth transition of different hardness materials of the large-diameter section and the small-diameter section of the microcatheter is achieved; the flexural rigidity of the reducing section is reduced, so that the change value of the flexural rigidity is reduced, the stress concentration is reduced, and the reliability of the microcatheter is improved.

Description

A microcatheter Technical Field

[0001] This invention relates to the field of medical device technology, and more particularly to a microcatheter. Background Technology

[0002] With the increasing complexity of minimally invasive surgeries such as neurointerventions and peripheral vascular interventions, the performance requirements for microcatheters have reached unprecedented levels. During the procedure, the microcatheter needs to navigate through tortuous and narrow vascular pathways to reach the target location. This process requires the microcatheter to possess excellent distal compliance to navigate sharp bends, proximal support to provide sufficient pushing force, and precise torsional control for directional adjustments. To meet the needs of interventional treatment for deeper and more tortuous lesions, the market demand for microcatheters with thinner outer diameters has become increasingly urgent, as this can significantly improve their permeability and delivery rate.

[0003] Adjustable bendable microcatheters allow operators to controllably bend the distal end of the catheter using a handle. This significantly enhances the selectivity and positioning capabilities of the catheter in complex vascular branches, making it a key tool in challenging interventional procedures. However, this functionality relies on sophisticated mechanical structures (such as draw-wire mechanisms and laser-engraved tubing) and complex multi-layered composite material structures. Repeated bending operations essentially subject the distal catheter structure to cyclical mechanical loading, easily leading to material fatigue and cumulative structural damage. This has become an inherent bottleneck restricting its performance and reliability.

[0004] Therefore, there is an urgent need for a microcatheter to solve the aforementioned problems. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a microcatheter that solves the problem of weak fatigue resistance at the distal end of an adjustable bendable microcatheter after repeated bending.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a microcatheter, wherein the microcatheter is provided with an inner liner and a polymer material layer sequentially from the inside to the outside in a radial direction; a variable diameter section is provided at the distal end of the microcatheter; a small diameter section is provided on one side of the distal end of the variable diameter section; a large diameter section is provided on one side of the proximal end of the variable diameter section; the polymer material layer includes a first hardness region, a second hardness region, and a third hardness region sequentially arranged from the distal end to the proximal end; the first hardness region is located in a portion of the small diameter section; the second hardness region is located in another portion of the small diameter section, the variable diameter section, and a portion of the large diameter section; and the third hardness region is located in another portion of the large diameter section; the hardness of the first hardness region is less than the hardness of the second hardness region, and the hardness of the second hardness region is less than the hardness of the third hardness region.

[0007] As a preferred technical solution for microcatheters, the hardness range of the first hardness zone is 25D-35D; the hardness range of the second hardness zone is 35D-55D; and the hardness range of the third hardness zone is 55D-95D.

[0008] As a preferred technical solution for a microcatheter, the connection position between the first hardness zone and the second hardness zone is located within a range of 2mm-5mm on the distal side of the variable diameter section; the connection position between the second hardness zone and the third hardness zone is located within a range of more than 150mm on the proximal side of the variable diameter section.

[0009] As a preferred technical solution for microcatheters, a braided layer is provided within the polymer material layer. The braided layer includes a first braided area, a first gradient area, and a second braided area arranged sequentially from the distal end to the proximal end. The first braided area is located in the small diameter segment and the variable diameter segment, while the first gradient area and the second braided area are located in the large diameter segment. The braiding density of the first braided area is greater than that of the second braided area, and the braiding density of the first braided area and the braiding density of the second braided area gradually transition through the first gradient area.

[0010] As a preferred technical solution for a microcatheter, the distal end of the first gradient zone is located at the proximal end of the diameter-changing section, and the proximal end of the first gradient zone is located within 10mm-20mm of the diameter-changing section on the proximal side.

[0011] As a preferred technical solution for microcatheters, the braiding density of the first braided area ranges from 290 PPI to 350 PPI, and the braiding density of the second braided area ranges from 150 PPI to 250 PPI.

[0012] As a preferred technical solution for a microcatheter, a spring coil layer is disposed within the polymer material layer. The spring coil layer includes a first pitch region, a second gradient region, and a second pitch region arranged sequentially from the distal end to the proximal end. The first pitch region is located in the small diameter segment and part of the variable diameter segment. The second gradient region is located in another part of the variable diameter segment and part of the large diameter segment. The second pitch region is located in another part of the large diameter segment. The pitch of the first pitch region is greater than the pitch of the second pitch region. The pitch of the first pitch region and the pitch of the second pitch region gradually transition through the second gradient region.

[0013] As a preferred technical solution for a microcatheter, the pitch of the first pitch region is 0.1mm-0.3mm, and the pitch of the second pitch region is 0.7mm-1.1mm.

[0014] As a preferred technical solution for a microcatheter, the distal end of the second gradient zone is located within 1.5mm-2mm of the distal end of the variable diameter section near the proximal end, and the proximal end of the second gradient zone is located within 8mm-13mm of the variable diameter section near the proximal end.

[0015] As a preferred technical solution for a microcatheter, it also includes a pull wire, which is threaded through the microcatheter and connected to the distal end of the microcatheter, and the pull wire is a twisted wire.

[0016] The beneficial effects of this invention are as follows: This invention provides a microcatheter comprising a polymer material layer including a first hardness region, a second hardness region, and a third hardness region arranged sequentially from distal to proximal. The hardness of the first hardness region is less than that of the second hardness region, and the hardness of the second hardness region is less than that of the third hardness region. The first hardness region, with the lowest hardness, is located in a portion of the small-diameter section, which facilitates deformation of the small-diameter section, thus improving the passage and selectivity of the distal end of the microcatheter. The second hardness region, with moderate hardness, is located in another portion of the small-diameter section, the variable-diameter section, and a portion of the large-diameter section. On the one hand, it achieves a smooth transition between the different hardness materials in the large-diameter and small-diameter sections of the microcatheter; on the other hand, the variable-diameter section has lower hardness relative to the proximal end of the microcatheter, which reduces the bending stiffness of the variable-diameter section when the outer diameter of the microcatheter changes, thereby reducing the change in bending stiffness, reducing stress concentration, improving the fatigue resistance of the microcatheter, and preventing fatigue fracture or permanent creases. The third hardness region, with the highest hardness, is located in another portion of the large-diameter section, ensuring good pushing performance at the proximal end of the microcatheter. By setting three different hardness regions, stress concentration in the microcatheter is reduced, improving the reliability of the microcatheter in use. Furthermore, in this application, the connection between the first hardness zone and the second hardness zone is located on the small diameter section, and the connection between the second hardness zone and the third hardness zone is located on the large diameter section. Neither the connection between the first hardness zone and the second hardness zone nor the connection between the second hardness zone and the third hardness zone has a starting point or ending point for the variable diameter section, which further smooths the bending stiffness of the microcatheter and improves the reliability of the microcatheter. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0018] Figure 1 is one of the structural cross-sectional views of the microcatheter provided in a specific embodiment of the present invention; Figure 2 is an enlarged view of Figure 1 at point A; Figure 3 is another structural cross-sectional view of the microcatheter provided in a specific embodiment of the present invention; Figure 4 is a third structural cross-sectional view of the microcatheter provided in a specific embodiment of the present invention; Figure 5 is a schematic diagram of the structure of the pull wire provided in a specific embodiment of the present invention; Figure 6 is a schematic diagram of the structure of the laser ablation layer with a grid pattern provided in a specific embodiment of the present invention; Figure 7 is a schematic diagram of the structure of the laser ablation layer with a honeycomb pattern provided in a specific embodiment of the present invention.

[0019] The diagram is labeled as follows: 1. Microcatheter; 11. Inner liner; 111. Laser ablation layer; 12. Braided layer; 13. Polymer material layer; 141. Small diameter section; 142. Variable diameter section; 143. Large diameter section; 151. First hardness zone; 152. Second hardness zone; 153. Third hardness zone; 161. First braided zone; 162. First gradient zone; 163. Second braided zone; 171. First pitch zone; 172. Second gradient zone; 173. Second pitch zone; 18. Spring coil layer; 2. Wire. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0024] In this application, the distal end refers to the end of the microcatheter that is furthest from the operator during use, and the proximal end refers to the end of the microcatheter that is closest to the operator during use.

[0025] As shown in Figures 1 and 2, this embodiment provides a microcatheter 1. The microcatheter 1 has an inner liner 11 and a polymer material layer 13 arranged radially from the inside to the outside. A variable diameter section 142 is provided at the distal end of the microcatheter 1. A small diameter section 141 is provided on one side of the distal end of the variable diameter section 142, and a large diameter section 143 is provided on one side of the proximal end of the variable diameter section 142. The polymer material layer 13 includes a first hardness region 151, a second hardness region 152, and a third hardness region 153 arranged sequentially from the distal end to the proximal end. The first hardness region 151 is located in part of the small diameter section 141, the second hardness region 152 is located in another part of the small diameter section 141, the variable diameter section 142, and a part of the large diameter section 143, and the third hardness region 153 is located in another part of the large diameter section 143. The hardness of the first hardness region 151 is less than the hardness of the second hardness region 152, and the hardness of the second hardness region 152 is less than the hardness of the third hardness region 153.

[0026] The polymer material layer 13 includes a first hardness region 151, a second hardness region 152 and a third hardness region 153 arranged sequentially from the distal end to the proximal end. The hardness of the first hardness region 151 is less than the hardness of the second hardness region 152, and the hardness of the second hardness region 152 is less than the hardness of the third hardness region 153. The first hardness zone 151, with the lowest hardness, is located in part of the small-diameter section 141, which facilitates deformation of the small-diameter section 141, thus improving the passage and selectivity of the distal end of the microcatheter 1. The second hardness zone 152, with moderate hardness, is located in another part of the small-diameter section 141, the variable-diameter section 142, and part of the large-diameter section 143. On the one hand, it achieves a smooth transition between the different hardness materials of the large-diameter section 143 and the small-diameter section 141 of the microcatheter 1. On the other hand, the variable-diameter section 142 has lower hardness than the proximal end of the microcatheter 1, which can reduce the bending stiffness of the variable-diameter section 142 when the outer diameter of the microcatheter 1 changes, thereby reducing the change in bending stiffness, reducing stress concentration, improving the fatigue resistance of the microcatheter 1, and thus preventing fatigue fracture or permanent creases in the microcatheter 1. The third hardness zone 153, with the highest hardness, is located in another part of the large-diameter section 143, ensuring that the proximal end of the microcatheter 1 has good pushing performance. By setting three different hardness zones, stress concentration in the microcatheter 1 is reduced, and the reliability of the microcatheter 1 in use is improved. Furthermore, in this application, the connection point between the first hardness region 151 and the second hardness region 152 is located on the small-diameter section 141, and the connection point between the second hardness region 152 and the third hardness region 153 is located on the large-diameter section 143. Neither the connection point between the first hardness region 151 and the second hardness region 152 nor the connection point between the second hardness region 152 and the third hardness region 153 has a starting point or ending point for the variable-diameter section 142, further smoothing the bending stiffness of the microcatheter 1 and improving its reliability. In this embodiment, the microcatheter 1 is constructed by splicing together materials of at least three hardnesses, improving the reliability and service life of the microcatheter 1.

[0027] In this embodiment, a braided layer 12 and a spring coil layer 18 are disposed within the polymer material layer 13. The braided layer 12 is located on the radial inner side of the spring coil layer 18. The distal end of the variable diameter section 142 is 10mm-13mm away from the tip of the microcatheter 1. The length of the variable diameter section 142 is 2mm-5mm. Within a range of 0.5-1.5mm from the tip of the microcatheter 1, the spring coil layer 18 and the braided layer 12 are not disposed and are used to install the imaging ring. The outer diameter of the small diameter section 141 can be 0.8mm, and the outer diameter of the large diameter section 143 can be 0.9mm. The outer diameters of the small diameter section 141 and the large diameter section 143 gradually change through the variable diameter section 142.

[0028] In this embodiment, the hardness range of the first hardness zone 151 is 25D-35D, specifically 25D, 27D, 29D, 31D, 33D or 35D, to ensure the passability and selectivity of the distal end of the microcatheter 1; the hardness range of the second hardness zone 152 is 35D-55D, specifically 35D, 40D, 45D or 55D, to ensure that the variable diameter section 142 does not experience fatigue fracture or permanent creases; the hardness range of the third hardness zone 153 is 55D-95D, specifically 55D, 65D, 75D, 85D or 95D, to ensure that the proximal end of the microcatheter 1 has good pushing performance.

[0029] Furthermore, the connection position of the first hardness zone 151 and the second hardness zone 152 is located within a range of 2mm-5mm on the distal side of the diameter-changing section 142; the connection position of the second hardness zone 152 and the third hardness zone 153 is located within a range of more than 150mm on the proximal side of the diameter-changing section 142. While ensuring the performance and reliability of the microcatheter 1, the connection positions of the first hardness zone 151 and the second hardness zone 152 and the second hardness zone 152 and the third hardness zone 153 are both far away from the diameter-changing section 142.

[0030] According to the theory of moment of inertia, the bending stiffness of the small-diameter section 141 is significantly weaker than that of the large-diameter section 143. Since the geometric stiffness of the variable-diameter section 142 increases too rapidly from the distal to the proximal end, this embodiment compensates for this by reducing the reinforcing effect of the braiding. The main function of the braided layer 12 is to greatly improve the torsional load resistance and collapse resistance of the microcatheter 1. Simultaneously, it also has a significant reinforcing effect on bending stiffness, and its reinforcing effect is closely related to the braiding parameters. Further, as shown in Figure 3, the braided layer 12 includes a first braided area 161, a first transition area 162, and a second braided area 163 arranged sequentially from the distal to the proximal end. The first braided area 161 is located in the small-diameter section 141 and the variable-diameter section 142, while the first transition area 162 and the second braided area 163 are located in the large-diameter section 143. The braiding density of the first braided area 161 is greater than that of the second braided area 163, and the braiding density of the first braided area 161 and the second braided area 163 gradually transitions through the first transition area 162. In this embodiment, the weaving density of the first braided area 161 is greater than that of the second braided area 163. The first braided area 161, with its increased weaving density, is used in the small-diameter section 141 to provide sufficient support and torsional resistance for the flexible section, establishing a basic stiffness. After the diameter-changing section 142, a weaving density attenuation zone is formed through the first gradient zone 162. Within this zone, the weaving density is gradually reduced by precisely controlling the braiding machine, providing reverse compensation for the increase in geometric stiffness of the diameter-changing section 142. After the diameter change, the enhancing effect of the braided layer 12 on bending stiffness gradually weakens. This effectively offsets the fourth-power increase in the moment of inertia of the cross-section caused by the increased diameter, ensuring a smooth transition in bending strength in and around the diameter-changing section 142. This prevents or reduces stress concentration at the point of increase during bending due to a sudden increase in bending strength. Finally, a second braided area 163 is provided at the proximal end of the microcatheter 1, employing a lower but constant PPI. At this point, the diameter of the large-diameter section 143 is already very large, and the moment of inertia itself is already very high. There is no need for excessively dense weaving to provide stiffness; overly dense weaving would actually make the microcatheter 1 too rigid. In this embodiment, by varying the weaving density of the braided layer 12, the increase in the geometric stiffness of the variable-diameter section 142 is reduced, thereby improving the smoothness of the bending stiffness of the microcatheter 1 and enhancing its reliability.

[0031] In this embodiment, the distal end of the first gradient region 162 is located at the proximal end of the diameter-changing section 142, and the proximal end of the first gradient region 162 is located within a range of 10mm-20mm on the side of the diameter-changing section 142 closest to the proximal end. The braiding density of the first braided region 161 ranges from 290PPI to 350PPI, specifically 290PPI, 310PPI, 330PPI, or 350PPI; the braiding density of the second braided region 163 ranges from 150PPI to 250PPI, specifically 150PPI, 180PPI, 210PPI, 240PPI, or 250PPI. Through the above settings, the reliability of the microcatheter 1 is provided while ensuring the basic performance requirements of the microcatheter 1.

[0032] More preferably, a spring coil layer 18 is disposed within the polymer material layer 13. The spring coil layer 18 is formed by winding elastic coils. The main function of the spring coil layer 18 is to resist collapse, provide excellent radial support, and prevent the microcatheter 1 from being flattened when bent. Adjusting the bending stiffness: the pitch of the spring coil layer 18 is the key to controlling its contribution to bending stiffness. When the coils of the spring coil layer 18 are precisely wound, the coils contact and support each other, resulting in stronger integrity and a greater contribution to bending stiffness, and higher hardness of the microcatheter 1. Conversely, when the coils are loosely wound, the gaps between the coils are large, making it easier for them to deform independently when bent, resulting in a smaller contribution to bending stiffness and lower hardness of the microcatheter 1. To achieve a smooth transition in stiffness from the small-diameter section 141 to the large-diameter section 143 of the microcatheter 1, as shown in Figure 4, the spring coil layer 18 includes a first pitch region 171, a second gradient region 172, and a second pitch region 173 arranged sequentially from the distal to the proximal end. The first pitch region 171 is located in the small-diameter section 141 and part of the variable-diameter section 142. The second gradient region 172 is located in another part of the variable-diameter section 142 and part of the large-diameter section 143. The second pitch region 173 is located in another part of the large-diameter section 143. The pitch of the first pitch region 171 is greater than the pitch of the second pitch region 173. The pitch of the first pitch region 171 and the pitch of the second pitch region 173 gradually transition through the second gradient region 172. The first pitch region 171, located in the small-diameter section 141 and part of the variable-diameter section 142, uses a smaller pitch in the spring coil layer 18 to provide good support and a certain degree of rigidity for the small-diameter section 141. The second gradient region 172 is located between another portion of the variable diameter section 142 and a portion of the large diameter section 143. The second gradient region 172 is designed between the variable diameter section 142 and the large diameter section 143, allowing the pitch to gradually increase. The coil winding becomes increasingly loose, meaning the stiffness provided by the spring layer 18 gradually weakens. This provides reverse compensation for the increase in geometric stiffness of the variable diameter section 142, further reducing the magnitude of the increase in geometric stiffness, thereby dispersing the bending stress, improving fatigue performance, smoothing the bending stiffness of the microconductor 1, and improving the reliability of the microconductor 1. The second pitch region 173 is located in another portion of the large diameter section 143. The large diameter section 143 can use a larger pitch. The larger diameter section 143 itself already provides sufficient stiffness, and the loose winding prevents the proximal end of the microconductor 1 from becoming too rigid.

[0033] In this embodiment, the pitch of the first pitch region 171 is 0.1mm-0.3mm, specifically 0.1mm, 0.15mm, 0.2mm, 0.25mm, or 0.3mm; the pitch of the second pitch region 173 is 0.7mm-1.1mm, specifically 0.7mm, 0.8mm, 0.9mm, 1mm, or 1.1mm. The distal end of the second gradient region 172 is located within 1.5mm-2mm of the distal end of the diameter-changing section 142 near the proximal end, and the proximal end of the second gradient region 172 is located within 8mm-13mm of the diameter-changing section 142 near the proximal end. Through the above configuration, the reliability of the microcatheter 1 is provided while ensuring its basic performance requirements.

[0034] The microcatheter 1 features a multi-parameter synergistic gradual change design for its variable diameter section 142 based on the theory of smooth stiffness transition. In the variable diameter section 142 of the microcatheter 1, the gradual change relationship between the hardness of the polymer material layer 13, the braiding density of the braided layer 12, and the pitch of the spring coil layer 18 is precisely and synergistically controlled to counteract the nonlinear increase in bending stiffness caused by the fourth-order change in outer diameter. This achieves a smooth stiffness transition for the entire variable diameter section 142, effectively suppressing the initiation and propagation of microcracks in the variable diameter section 142, and solving the technical problem of fatigue fracture or permanent creases in this area.

[0035] In existing technologies, microcatheters primarily use wire drawing as the transmission method, subjecting the microcatheters to repeated stretching, bending, and friction against the tube wall within the ultra-fine lumen. However, the selection of wire materials and surface treatment in existing products are inadequate. After tens of minutes of high-intensity operation, these wires are prone to fracture due to metal fatigue, or permanent elongation and relaxation due to creep of the polymer material layer, resulting in sluggish bending response, inaccurate angles, or even complete loss of function.

[0036] Furthermore, as shown in Figure 5, the microcatheter 1 also includes a drawstring 2. The drawstring 2 is threaded through the microcatheter 1 and connected to its distal end. The drawstring 2 is made of a fine filament material with ultra-high strength and fatigue limit. The material of the drawstring 2 is MP35N cobalt-chromium alloy, high molecular weight polyethylene yarn, tungsten wire, or 304V stainless steel. These materials are ultra-high fatigue strength materials, which fundamentally improve the fatigue limit. Among them, the molecular weight of the high molecular weight polyethylene yarn ranges from 3 million to 6 million.

[0037] In this embodiment, the draw wire 2 is a stranded wire, wherein the draw wire 2 uses multi-strand stranded wire instead of monofilament. When the stranded wire is bent, the internal strands have slight displacement, which can better distribute stress and its fatigue resistance is generally better than that of monofilament. Preferably, a 1*7 stranded wire (one core wire, 6 strands) is used.

[0038] More preferably, a passivation film is formed on the surface of the draw wire 2. The surface of the draw wire 2 requires surface treatment, specifically polishing. Polishing can be performed using electrolytic polishing or shot peening, which effectively eliminates surface stress and forms a residual compressive stress layer. This layer can offset some of the working tensile stress, thereby significantly extending fatigue life. In this embodiment, when the material of the draw wire 2 is metal wire, electrolytic polishing, an electrochemical process, selectively dissolves microscopic protrusions on the metal surface, achieving a smoothing effect. This eliminates stress concentration points such as micro-scratches and burrs generated during the wire drawing process, significantly delaying the initiation of fatigue cracks; it also forms a passivation film rich in chromium oxide on the surface, greatly enhancing corrosion resistance; and it obtains an ultra-smooth surface, reducing friction with polymer layers (such as the outer coating) and minimizing wear.

[0039] Preferably, the surface of the pull wire 2 may be coated with a low coefficient of friction and wear-resistant PTFE (Polytetrafluoroethylene) coating to reduce wear fatigue caused by friction with the inner wall of the conduit.

[0040] In some embodiments, the surface of the draw wire 2 is provided with a hardness-enhancing coating. The hardness-enhancing coating can be formed on the surface of the draw wire 2 using a physical vapor deposition process. The hardness-enhancing coating can be a metastable amorphous carbon material (such as diamond-like carbon (DLC)), a nitride (such as titanium nitride (TiN) or chromium nitride (CrN)), or other coatings with extremely low coefficients of friction and high hardness, which can greatly reduce wear.

[0041] In some embodiments, the surface of the pull wire 2 is provided with a hydrophobic coating, which can be a hydrophobic polydimethylsiloxane with low surface tension and excellent lubrication performance, effectively reducing friction between the pull wire 2 and the cavity wall and extending its service life.

[0042] In this embodiment, the forming steps of the wire 2 are as follows: first, the wire 2 is electrolytically polished to form a chromium-rich oxide passivation film; then, a hardness-enhancing coating is formed on the surface of the chromium-rich oxide passivation film using a physical vapor deposition process; finally, silicone oil is impregnated on the surface of the hardness-enhancing coating to form a lubricating protective layer.

[0043] This draw wire 2 utilizes ultra-high fatigue strength materials at the material level to fundamentally improve the fatigue limit. At the structural level, it employs a stranded wire structure, using micro-displacement between strands to disperse stress, replacing the single-wire structure prone to single-point fracture. At the surface level, it comprehensively applies electropolishing to eliminate micro-defects and form a passivation film, and uses physical vapor deposition to form a hardening coating, significantly reducing the surface friction coefficient and wear rate. This draw wire 2 constructs a triple fatigue-resistant optimization system from the inside out—material-structure-surface—synergistically and significantly improving the bending, wear, and corrosion fatigue resistance of the draw wire 2.

[0044] In existing technologies, the polymer material layer is typically made of polar materials such as polyamide, polyurethane, or Pebax (polyether block amide), with PTFE, a material with an extremely low coefficient of friction, used as the inner liner. However, PTFE has extremely low surface energy and is a non-polar material, making it difficult to bond with the outer polymer layer of the catheter. During repeated twisting and bending throughout the body, the interlayer interface is subjected to enormous shear stress. The connection between the inner liner and the polymer material layer is usually achieved through adhesive bonding or mechanical compression. Under conditions of repeated bending at the distal end, stress concentration occurs at the connection point, and existing technologies are prone to risks of adhesive layer cracking and inner liner detachment, causing the inner lumen to collapse and preventing the passage of compatible guidewires or infusion devices / drugs, leading to serious clinical consequences.

[0045] To address the aforementioned issues, as shown in Figures 1, 6, and 7, in this embodiment, a laser ablation layer 111 is provided on the surface of the inner liner tube 11. The laser ablation layer 111 is honeycomb-shaped or grid-shaped. The laser ablation layer 111 increases the bonding area between the inner liner tube 11 and the polymer material layer 13, thereby improving their connection strength. The laser ablation layer 111 uses a laser ablation process to roughen the outer surface of the inner liner tube 11. A 193nm excimer laser is used to scan the surface of the inner liner tube 11, precisely ablating nanometer-scale (10~50nm) grooves, pits, or holes. The laser ablation layer 111 is honeycomb-shaped or grid-shaped. This process offers extremely high controllability and allows for the design of specific ablation patterns.

[0046] More preferably, the inner liner tube 11 is subjected to low-temperature plasma treatment. The inner liner tube 11 is placed in a vacuum chamber, and a reactive gas (such as O2 or N2) is introduced, and high pressure is applied to generate plasma. The active particles (free radicals, ions) in the plasma break the CF and CC bonds on the PTFE surface and react with the introduced gas to introduce oxygen- and nitrogen-containing polar groups (such as -COOH, -C=O, -NH2), which greatly improves the surface properties. The inner liner tube 11 obtained by laser ablation is subjected to low-temperature plasma treatment on the surface of the inner liner tube 11 using O2, N2 or a mixture thereof (the recommended volume ratio of O2:N2 = 1:3 to 1:1). Within a 12-hour time window, the inner liner tube 11 is combined with the polymer material layer 13 through co-extrusion or rheological process to form the tube preform of the microcatheter 1.

[0047] To address the difficulty in bonding the polymer material layer 13 to the inner liner tube 11, this embodiment provides a composite treatment process of "physical roughening-chemical activation-aging window". Laser ablation (physical activation) is combined with a low-temperature plasma treatment process using a specific ratio of O2 and N2 mixed gas (chemical activation), and the co-extrusion aging window after treatment is strictly limited. The laser ablation process uses a specific wavelength laser to create nanoscale microstructures on the surface of the inner liner tube 11, significantly increasing the bonding area. The low-temperature plasma treatment process uses an optimized ratio of O2 and N2 mixed gas to efficiently introduce nitrogen- and oxygen-containing polar groups onto the roughened surface, forming strong hydrogen bonds with the amide groups of the inner liner tube 11. Co-extrusion is completed within 12 hours after activation to ensure maximum bonding before the surface active groups decay. This composite process completely solves the industry-wide problem of delamination between the polymer material layer 13 and the inner liner tube 11 in ultrafine conduits due to repeated bending.

[0048] It is important to note that the microcatheter 1 used in the above parameters is an ultra-fine catheter with a distal outer diameter not exceeding 2.4F. Due to the miniaturization of the structure, the filament 2 is thinner, the distal structure is more fragile, the interlayer bonding area is smaller, and the material tolerance requirements are more stringent, resulting in extremely limited tolerance for fatigue resistance design. A design that performs reasonably well at a conventional size often experiences a precipitous drop in fatigue life when scaled down to an ultra-fine size. The validated and specific optimal parameter range provided in this embodiment is designed and validated specifically for fatigue resistance at ultra-fine scales, rather than a simple scaling up, ensuring reliability and durability at extreme sizes. In accelerated fatigue tests simulating clinical use, the performance degradation rate is far lower than that of existing mainstream products, providing reliable assurance for complex surgeries.

[0049] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A microcatheter, wherein an inner liner (11) and a polymer material layer (13) are sequentially disposed radially from the inside to the outside, characterized in that, The distal end of the microcatheter is provided with a variable diameter section (142), a small diameter section (141) is provided on one side of the distal end of the variable diameter section (142), and a large diameter section (143) is provided on one side of the proximal end of the variable diameter section (142). The polymer material layer (13) includes a first hardness region (151), a second hardness region (152), and a third hardness region (153) arranged sequentially from the distal end to the proximal end. The first hardness region (151) is located in part of the small diameter section (141), the second hardness region (152) is located in another part of the small diameter section (141), the variable diameter section (142), and a part of the large diameter section (143), and the third hardness region (153) is located in another part of the large diameter section (143). The hardness of the first hardness region (151) is less than the hardness of the second hardness region (152), and the hardness of the second hardness region (152) is less than the hardness of the third hardness region (153).

2. The microcatheter according to claim 1, characterized in that, The hardness range of the first hardness zone (151) is 25D-35D; the hardness range of the second hardness zone (152) is 35D-55D; and the hardness range of the third hardness zone (153) is 55D-95D.

3. The microcatheter according to claim 1, characterized in that, The connection position of the first hardness zone (151) and the second hardness zone (152) is located within 2mm-5mm of the distal end of the variable diameter section (142); the connection position of the second hardness zone (152) and the third hardness zone (153) is located within 150mm of the proximal end of the variable diameter section (142).

4. The microcatheter according to claim 1, characterized in that, The polymer material layer (13) is provided with a braided layer (12). The braided layer (12) includes a first braided area (161), a first gradient area (162), and a second braided area (163) arranged sequentially from the distal end to the proximal end. The first braided area (161) is located in the small diameter section (141) and the variable diameter section (142). The first gradient area (162) and the second braided area (163) are located in the large diameter section (143). The braiding density of the first braided area (161) is greater than the braiding density of the second braided area (163). The braiding density of the first braided area (161) and the braiding density of the second braided area (163) are gradually transitioned through the first gradient area (162).

5. The microcatheter according to claim 4, characterized in that, The distal end of the first gradient region (162) is located at the proximal end of the variable diameter section (142), and the proximal end of the first gradient region (162) is located within 10mm-20mm of the variable diameter section (142) on the proximal side.

6. The microcatheter according to claim 4, characterized in that, The weaving density of the first weaving area (161) ranges from 290 PPI to 350 PPI, and the weaving density of the second weaving area (163) ranges from 150 PPI to 250 PPI.

7. The microcatheter according to claim 1, characterized in that, A spring coil layer (18) is provided within the polymer material layer (13). The spring coil layer (18) includes a first pitch region (171), a second gradient region (172), and a second pitch region (173) arranged sequentially from the distal end to the proximal end. The first pitch region (171) is located in the small diameter segment (141) and part of the variable diameter segment (142). The second gradient region (172) is located in another part of the variable diameter segment (142) and part of the large diameter segment (143). The second pitch region (173) is located in another part of the large diameter segment (143). The pitch of the first pitch region (171) is greater than the pitch of the second pitch region (173). The pitch of the first pitch region (171) and the pitch of the second pitch region (173) gradually transition through the second gradient region (172).

8. The microcatheter according to claim 7, characterized in that, The pitch of the first pitch region (171) is 0.1mm-0.3mm, and the pitch of the second pitch region (173) is 0.7mm-1.1mm.

9. The microcatheter according to claim 7, characterized in that, The distal end of the second gradient region (172) is located within 1.5mm-2mm of the distal end of the variable diameter section (142) near the proximal end, and the proximal end of the second gradient region (172) is located within 8mm-13mm of the variable diameter section (142) near the proximal end.

10. The microcatheter according to any one of claims 1-9, characterized in that, It also includes a pull wire (2), which is inserted through the microcatheter and connected to the distal end of the microcatheter. The pull wire (2) is a twisted wire.

Images