Hollow microcatheters and their preparation methods

Abstract

This invention relates to the field of medical catheter technology, specifically to hollow microcatheters and their preparation methods. It includes a catheter body, an outer layer disposed outside the catheter body, and an inner layer disposed within the catheter body. The catheter body comprises multiple rigid tube segments, which are arranged closely along an axis, with an adjustable angle between adjacent segments. In this invention, each rigid tube segment can move independently, allowing it to adapt to the shape of the balloon's inner wall, thus conforming to the balloon's bending performance and achieving a bending angle compatible with the balloon without lifting it. Furthermore, because each rigid tube segment moves independently, it does not affect other rigid tube segments. This allows each rigid tube segment to adapt to the angle of its respective curved cavity, thereby solving the problem of insufficient adaptability of microcatheters.

Description

Technical Field

[0001] This invention relates to the field of medical catheter technology, and more specifically, to hollow microcatheters and their preparation methods. Background Technology

[0002] The hospital's microcatheter is an extremely sophisticated interventional medical device that plays a crucial role in cardiovascular, neurovascular, peripheral vascular, and tumor interventional surgeries.

[0003] In the prior art, MicroPort Neuroscience Medical Technology (Shanghai) Co., Ltd. has disclosed the following patents:

[0004] Chinese Patent Publication No. CN212016424U discloses a medical balloon, balloon catheter, and medical device, which solves the problem of poor compliance of medical balloons with blood vessels when reaching lesion locations through curved blood vessels. Specifically, it discloses a balloon body and a recess formed on the outer surface of the balloon body. The recess improves the bending performance of the medical balloon, thereby enhancing its bending ability to better adapt to the shape of blood vessels.

[0005] As can be seen from a medical balloon, balloon catheter and medical device, a linear medical balloon is inserted into a blood vessel through a catheter, and the medical balloon inflates when it reaches the lesion site.

[0006] The company also disclosed a catheter and delivery device, with the publication number CN209679245U, specifically disclosing a catheter that includes an inner layer, a middle layer, and an outer layer in the radial direction from the inside to the outside. The middle layer includes a base layer, which includes liquid crystal polymer filaments. Although this material has both high tensile strength and bending performance, it is still insufficient compared to improving the bending performance of medical balloons through recesses. This causes the catheter to "lift" the balloon wall when facing sharp turns (e.g., acute angle bends) that exceed the design value, causing the balloon wall to form local "wrinkles" or "bulges". This prevents the balloon from sliding smoothly along the catheter, thus directly affecting the operation performance of the device and requiring the physician to apply more force to push the balloon forward.

[0007] The more critical hidden danger is that it significantly increases the risk of damage to the balloon itself and blood vessels. Summary of the Invention

[0008] The purpose of this invention is to provide a hollow microcatheter and its preparation method to solve the problem that the bending performance of the catheter cannot be adapted to the balloon, which increases the difficulty of operation.

[0009] To achieve the above objectives, one objective of the present invention is to provide a hollow microcatheter, comprising a catheter body, an outer layer disposed outside the catheter body, and an inner layer disposed within the catheter body, wherein the catheter body comprises at least:

[0010] Multiple rigid pipe sections are arranged closely together along an axis, and there is a movable angle between two adjacent rigid pipe sections.

[0011] An elastic body disposed between two adjacent rigid pipe sections is used to limit the size of the angle of movement;

[0012] A first hardness value and a second hardness value, wherein the first hardness value is less than the second hardness value;

[0013] The hardness value of the rigid pipe section is located between the first hardness value and the second hardness value.

[0014] In the above scheme, the hardness value of the rigid tube segment was adjusted to be between the first hardness value and the second hardness value. The first hardness value is the hardness of the inner layer of the medical catheter (<20D), and the second hardness value is the hardness of the middle layer of the medical catheter (40D-60D). In this way, the rigid tube segment itself has the ability to resist flattening / kinking, and there is no need to set the middle layer (metal / non-metal wire braid / spiral layer). When the rigid tube segment is not constrained by the middle layer, it can move more flexibly, and the bending performance of the entire microcatheter will not be reduced due to the middle layer.

[0015] Furthermore, each rigid tube segment can move independently. At this time, the rigid tube segment can move according to the shape of the inner wall of the balloon, thereby adapting to the bending performance of the balloon and achieving a bending angle that matches the balloon without pushing the balloon up. Moreover, since each rigid tube segment moves independently, it will not affect other rigid tube segments. In this way, each rigid tube segment adapts to the angle of the bending cavity it is in.

[0016] Furthermore, the outer layer strengthens the integrity of the catheter body, which consists of multiple rigid tube segments, and the thrust efficiency is not significantly affected. Moreover, the connection of the elastic body increases the resistance between the rigid tube segments, preventing them from moving freely and ensuring that the catheter body has sufficient thrust efficiency. In addition, the ease of movement of the rigid tube segments of different catheter bodies can be adjusted according to actual needs.

[0017] The rigid pipe section includes an intermediate rigid pipe section and an end rigid pipe section, wherein the end rigid pipe sections are disposed at both ends of the conduit body;

[0018] The cross-section of the intermediate rigid pipe section is an isosceles trapezoid, and the two hypotenuses of the isosceles trapezoid form the two inclined surfaces of the intermediate rigid pipe section.

[0019] The cross-section of the end rigid pipe section is a right trapezoid, and the hypotenuse of the right trapezoid forms the inclined surface of the end rigid pipe section;

[0020] Among them, the concave part of the catheter body is formed by the connection of two adjacent inclined surfaces;

[0021] The elastic body is a ring structure or is formed by at least two independent elastic parts to enclose the outer side of the depression to form a hollow cavity.

[0022] On the one hand, the indentation increases the space and freedom of movement between rigid tube segments, thus accommodating smaller bending angles. On the other hand, the hollow chamber formed under the elastomeric enclosure allows for relative angular displacement between rigid tube segments when the catheter body is subjected to stress due to balloon or vascular bending. In this situation, the enclosed hollow chamber acts as a buffer space. The air within the chamber provides a compliant cushioning effect, absorbing some of the impact force and transferring concentrated stress more evenly to the surrounding elastomeric body and adjacent rigid tube segments, effectively preventing wear or plastic creep (permanent deformation) caused by excessive stress concentration at the contact points of the rigid tube segments.

[0023] The first improvement method is as follows: the rigid pipe section is set in two parts, and the head of one end of the middle rigid pipe section is provided with a groove, while the head of the other end is provided with a protrusion; the end rigid pipe section is selected to be provided with a groove or a protrusion according to the adaptability of the head of the middle rigid pipe section on its side.

[0024] The protrusion engages with the groove;

[0025] The elastomer includes a bent arm and ram's horn portions disposed at both ends of the bent arm. The ends of the ram's horn portions are provided with connectors, which are hook-shaped structures.

[0026] The upper bottom of the cross-section of the end rigid pipe section forms the horizontal plane of the end rigid pipe section. On the horizontal plane of the middle rigid pipe section, two annular hook grooves with opposite orientations and dovetails facing the inclined plane of the middle rigid pipe section are formed around its surface.

[0027] On the horizontal surface of the end rigid pipe section, an annular hook groove with a dovetail facing the inclined surface of the end rigid pipe section is formed around its surface;

[0028] The hook-shaped structure is connected to the hook groove.

[0029] Preferably, the hardness value of the rigid pipe section is 30D-45D.

[0030] The second improvement method: the rigid pipe section is integrally formed;

[0031] On the inclined surface, an annular straight slot is formed around its surface;

[0032] The elastomer includes a bent arm and ram's horn portions disposed at both ends of the bent arm. The ends of the ram's horn portions are provided with connectors. The connectors are teardrop-shaped structures and are connected to the straight slot.

[0033] Preferably, the hardness value of the rigid pipe section is 30D-40D.

[0034] By setting the hardness value of the integrally formed rigid pipe section to 30D-40D (30D-45D in the first improvement method), a geometrically weak area is formed by pre-setting a deep recess at the inclined connection. By utilizing the elastic deformation potential of the low-hardness material, a large-angle bending is allowed at the deepest point. Ultimately, without additional mechanical joints, the integral rigid pipe section can move flexibly at the deepest point of the recess.

[0035] Furthermore, the design of the outward-facing curved arm opening and the inward-facing ram's horn opening allows the arched curved arm opening to release ample deformation space in the concave area, and the low-hardness material naturally bends smoothly under the support of the arched arm; at the same time, the inward-facing layout of the ram's horn naturally transforms the tensile force into bending stress pointing towards the root of the connector, making the elastomer easy to bend and not easy to crack.

[0036] The second objective of this invention is to provide a method for fabricating any of the hollow microcatheters described above, comprising the following steps:

[0037] The rigid pipe section is inserted into the center body;

[0038] The central body fitted with the rigid pipe section is connected axially, and the connection method adopts a tapered insertion joint combined with UV adhesive curing.

[0039] TPU or silicone rubber is coated onto the outside of a rigid pipe section using a coaxial extruder to form an outer layer.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. In the hollow microcatheter and its preparation method, the hardness value of the rigid tube segment is between the hardness of the inner layer of the medical catheter and the hardness of the intermediate layer of the medical catheter, so that the rigid tube segment itself has the ability to resist flattening / kinking. In this way, the microcatheter does not need to be equipped with metal / non-metal wire braiding / spiral layer, thereby solving the problem of reduced bending performance of the entire microcatheter due to the intermediate layer.

[0042] 2. In this hollow microcatheter and its preparation method, each rigid segment can move independently, allowing the rigid segment to move according to the shape of the balloon's inner wall, thereby adapting to the balloon's bending performance and achieving a bending angle that matches the balloon without pushing it up. Moreover, since each rigid segment moves independently, it will not affect other rigid segments. In this way, each rigid segment adapts to the angle of its own bending cavity, thus solving the problem of insufficient adaptability of the microcatheter.

[0043] 3. In the hollow microcatheter and its preparation method, the elastomer can not only increase the resistance between rigid tube segments, preventing the rigid tube segments from moving freely to ensure that the catheter body has sufficient thrust efficiency, but also seal the outer side of the depression to form a hollow cavity, thereby serving as a buffer space to solve the problem of wear or plastic creep caused by excessive concentration of contact points of rigid tube segments. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the catheter body structure of the present invention;

[0045] Figure 2 This is an exploded view of part of the catheter body of the present invention;

[0046] Figure 3 This is an exploded view of the rigid pipe section and the elastomer according to the first embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram of the intermediate rigid pipe section structure according to the first embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of the intermediate rigid pipe segment structure of two connections in the first embodiment of the present invention;

[0049] Figure 6 This is a schematic diagram of the end rigid pipe section structure according to the first embodiment of the present invention;

[0050] Figure 7 This is a schematic diagram of the connection structure between the end rigid pipe section and the middle rigid pipe section according to the first embodiment of the present invention;

[0051] Figure 8 This is a schematic diagram of the independent elastic part structure according to the fourth embodiment of the present invention;

[0052] Figure 9 This is a schematic diagram of an elastomer structure with hook-shaped ends, according to the first embodiment of the present invention.

[0053] Figure 10 This is a schematic diagram of an elastomer structure with a raindrop-shaped end, according to a second embodiment of the present invention.

[0054] Figure 11 This is one of the structural diagrams illustrating an application scenario of the present invention;

[0055] Figure 12 This is a second schematic diagram of the application scenario structure of the present invention;

[0056] Figure 13 The third schematic diagram of the application scenario structure of the present invention;

[0057] Figure 14 This is a schematic diagram of the inner layer structure of the third embodiment of the present invention;

[0058] Figure 15 This is an exploded view of a portion of the microcatheter structure of the present invention.

[0059] The meanings of the labels in the diagram are as follows:

[0060] 1. Outer layer; 2. Elastomer; 21. Bend; 22. Connector; 23. Horn; 24. Independent elastic part; 3. Inner layer; 4. Rigid pipe section; 41. Inclined surface; 42. Horizontal surface; 43. Connecting groove; 44. Inner surface; 45. Recess; 5. Central body. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] When entering certain tortuous bifurcation lesions, collateral vessels, or dealing with acute-angled paths that may be encountered when treating chronic total occlusion lesions, the catheter is affected by its middle layer (metal wire), causing its own bending performance to be unable to adapt to the balloon.

[0063] Figure 1 This shows a catheter body that can be adapted to the bending performance of a balloon. Figure 2 A portion of the conduit body was revealed through an explosion. The conduit body consists of multiple rigid tube segments 4. Adjacent rigid tube segments 4 are movable, with a certain angle of movement, which ensures both the rigidity of the conduit body and improves its bending performance. Furthermore, adjacent rigid tube segments 4 are connected by an elastic body 2 to limit the maximum angle of movement of the rigid tube segments 4. The greater the limiting capacity, the smaller the angle of movement, the lower the bending performance of the conduit body, and the higher the thrust efficiency, allowing for a smoother transmission of thrust between the two rigid tube segments 4.

[0064] Furthermore, an outer layer 1 is provided outside the catheter body. This outer layer 1 can be made of medical-grade TPU or silicone rubber with high ultimate elasticity and fatigue resistance. The outer layer 1 creates a continuous arc surface on the outer surface of the catheter body and seals the outside of the catheter body, reducing friction. Moreover, under the protection of the outer layer 1, the overall integrity of the catheter body, composed of multiple rigid tubing segments 4, is strengthened, resulting in higher thrust efficiency.

[0065] Furthermore, the inner surface 44 of the rigid pipe section 4 ( Figure 4(As shown in the figure) forms the inner layer 3, which is smooth and facilitates the smooth passage of guide wires or other instruments through the inner cavity of the rigid tube section 4.

[0066] First embodiment, see Figures 3-5 In this embodiment, the rigid pipe segment 4 is a separate unit, and adjacent rigid pipe segments 4 are connected by an elastic body 2. Figure 4 One of the rigid pipe sections 4 is shown, which is placed horizontally, forming a horizontal surface 42 on the outside of the rigid pipe section 4, and one or two inclined surfaces 41.

[0067] Specifically, rigid pipe section 4 is divided into intermediate rigid pipe section and end rigid pipe section.

[0068] Figure 4 The shown intermediate rigid pipe segment has two inclined planes 41. The cross-section A of the intermediate rigid pipe segment is an isosceles trapezoid, with its upper base corresponding to the horizontal plane 42 and its lower base corresponding to the inner surface 44. The two inclined sides correspond to the two inclined planes 41 of the intermediate rigid pipe segment. The intermediate rigid pipe segment mainly increases the length of the conduit body by itself. Figure 5 The diagram shows two connected intermediate rigid tube segments. After the two intermediate rigid tube segments are connected, a recess 45 is formed between the two intersecting inclined surfaces 41, making the two intermediate rigid tube segments easier to move. Furthermore, another intermediate rigid tube segment can be connected to one or both sides of these two intermediate rigid tube segments, and so on, until the desired length is reached.

[0069] Figure 6 The illustrated end rigid pipe section has an inclined surface 41. The cross-section A of the end rigid pipe section is a right trapezoid, with its upper base corresponding to the horizontal plane 42 and its lower base corresponding to the inner surface 44. One inclined side corresponds to an inclined surface 41 of the end rigid pipe section. The end rigid pipe section is located at both ends of the conduit body to avoid having unnecessary inclined surfaces 41 at both ends of the conduit body. Figure 7 The diagram illustrates a rigid end tube segment connected to an intermediate rigid tube segment. After the connection, the unique bevel 41 of the end rigid tube segment connects with one of the bevels 41 of the intermediate rigid tube segment, forming a recess 45 in the catheter body. The presence of the recess 45 facilitates the movement of the intermediate and end rigid tube segments. Typically, a sufficient number of intermediate rigid tube segments are already connected on one side of the initial or final intermediate rigid tube segment; the end rigid tube segment is then connected to the other side of the initial or final intermediate rigid tube segment. This ensures that each bevel 41 on the catheter body has an adjacent bevel 41 forming a recess 45, preventing any bevel 41 from not forming a recess 45.

[0070] See Figure 4 and Figure 6Connecting grooves 43 are provided on the horizontal plane 42 of both the intermediate rigid pipe section and the end rigid pipe section. In this embodiment, the connecting groove 43 is a hook groove, which is dovetail-shaped, and its direction is described by the dovetail. For details, see [link to documentation]. Figure 4 On the horizontal plane 42 of the intermediate rigid pipe section, two annular hook grooves facing opposite directions and with their dovetails facing the inclined plane 41 are formed around its surface. See also Figure 6 On the horizontal plane 42 of the rigid end pipe section, an annular hook groove with a dovetail facing the inclined plane 41 is formed around its surface. Connected to the hook groove is... Figure 9 The elastic body 2 shown has hook-shaped ends and is annular. Therefore, when the annular elastic body 2 is connected to the hook groove, it will close the outer side of the recess 45 to form a hollow cavity, thereby providing a space for the intermediate rigid pipe section or the end rigid pipe section to move. The elastic body 2 includes a bent arm 21, and horn portions 23 are provided at both ends of the bent arm 21. The end of the horn portion 23 is connected to the connector 22. In this embodiment, the connector 22 is a hook-shaped structure. The hook-shaped structure is connected to the hook groove. After connection, the bent arm 21 generates tension to connect two intermediate rigid pipe sections or one intermediate rigid pipe section and one end rigid pipe section.

[0071] Specifically, due to the characteristics of the connection between the hook groove and the hook-shaped structure, the bent arm 21 needs to be unfolded at a certain angle in the early stage (that is, the opening angle of the bent arm 21 is increased) so that the hook-shaped structure can enter the hook groove and engage with it. After engagement, the bent arm 21 restores its initial elastic force, which is converted into tensile force, so that the heads of the two intermediate rigid pipe sections or one intermediate rigid pipe section and one end rigid pipe section are connected.

[0072] Preferably, one end of the intermediate rigid pipe section has a groove, while the other end has a protrusion. The intermediate rigid pipe section is joined by the engagement of the protrusion and the groove. The end rigid pipe section is configured to have either a groove or a protrusion depending on the suitability of the head of the intermediate rigid pipe section on its side. For example, if the head of the intermediate rigid pipe section to be joined is grooved, then an end rigid pipe section with a protrusion should be selected for joining. In other words, if the head of the intermediate rigid pipe section to be joined is protruding, then an end rigid pipe section with a groove should be selected for joining.

[0073] Among them, the head docking method of two intermediate rigid pipe sections or one intermediate rigid pipe section and one end rigid pipe section is not limited to the engagement of the convex head and the groove, but can also be the insertion and mating of the plate and the groove.

[0074] To further clarify, although the catheter body is composed of rigid segment 4, this rigid segment 4 is still flexible, unlike steel or iron structures which are rigid. It can undergo visible or perceptible deformation when squeezed by hand. Specifically, the hardness of the rigid segment 4 is between the hardness of the inner layer of a medical catheter (first hardness value) and the hardness of the intermediate layer (a composite wire made of metal or non-metal wires) (second hardness value), but is closer to the hardness of the intermediate layer. The preferred hardness value (Shore D hardness) of the rigid segment 4 is in the range of 30D to 45D.

[0075] Comparison of medical catheter rigidity:

[0076] Inner lining of the catheter (smooth lumen layer): It is usually very soft to ensure flexibility, with a hardness of <20D.

[0077] Intermediate layer (metal / non-metal wire braid / spiral layer): provides core resistance to flattening / kinking, and its hardness depends on the matrix material; the hardness of the carrier filament alone is very high (>50D), but the overall hardness of the composite matrix (such as TPU covered with nylon / polyester fiber) is usually between 40D and 60D.

[0078] In this embodiment, the rigid tube segment 4 has a significantly higher hardness than the inner layer of the medical catheter, ensuring that it is not easily flattened or deformed; however, it is close to or even slightly lower than the medium-hardness configuration of the catheter middle layer, so as to serve as a joint segment of the catheter body for movement. The rigid tube segment 4 is selected with a hardness range of 30D-45D, thereby ensuring that it has sufficient rigidity to prevent crushing when used as a joint segment, while also being able to move flexibly.

[0079] Unlike the first embodiment, in the second embodiment, all rigid pipe sections 4 are integrally formed.

[0080] In addition, two adjacent rigid pipe sections 4 are connected by an elastic body 2.

[0081] Specifically, the rigid pipe section 4 is divided into an intermediate rigid pipe section and an end rigid pipe section. The intermediate rigid pipe section has two inclined planes 41, and its cross-section A is an isosceles trapezoid with its upper base corresponding to the horizontal plane 42 and its lower base corresponding to the inner surface 44. The two inclined sides correspond to the two inclined planes 41 of the intermediate rigid pipe section. The end rigid pipe section has one inclined plane 41, and its cross-section A is a right-angled trapezoid with its upper base corresponding to the horizontal plane 42 and its lower base corresponding to the inner surface 44. One inclined side corresponds to one inclined plane 41 of the end rigid pipe section. The end rigid pipe sections are located at both ends of the conduit body.

[0082] Among them, two adjacent inclined surfaces 41 form a recess 45 in the catheter body.

[0083] Figure 10An elastomer 2 with a raindrop-shaped end is shown, comprising a curved arm 21, with horn-shaped portions 23 at both ends of the curved arm 21. A connector 22 is connected to the end of each horn-shaped portion 23; in this embodiment, the connector 22 has a raindrop-shaped structure. See also... Figure 10 On the inclined surfaces 41 of the intermediate rigid pipe section and the end rigid pipe section, annular connecting grooves 43 are formed around their surfaces. In this embodiment, the connecting groove 43 is a straight slot with its opening tilted upward to accommodate the insertion angle of the raindrop-shaped structure. The raindrop-shaped structure is connected to the straight slot, and the bent arm 21 after connection generates thrust to support the two adjacent inclined surfaces 41.

[0084] In this embodiment, the elastic body 2 is annular. Therefore, the annular elastic body 2 can close the outer side of the recess 45 to form a hollow cavity, thereby providing space for the middle rigid pipe section or the end rigid pipe section to move.

[0085] The principle of the raindrop-shaped structure connecting to the straight slot: In the early stage, the bent arm 21 is compressed at a certain angle (that is, the opening angle of the bent arm 21 is reduced), so that the raindrop-shaped structure can enter the straight slot and engage with it. After engagement, the bent arm 21 restores its initial elastic force, which is converted into thrust to support the two adjacent inclined surfaces 41.

[0086] Furthermore, in this embodiment, the hardness value (Shore D hardness) of the rigid pipe segment 4 is preferably in the range of 30D to 40D. This ensures that the rigid pipe segment 4, when used as a joint segment, has sufficient rigidity to prevent crushing, while also maintaining the necessary moderate flexibility to achieve flexible and controllable bending activities. Specifically, in this embodiment, two adjacent rigid pipe segments 4 move through their connection point. Because the connection point is located at the deepest position of the recess 45, this position is relatively weak. In addition, the flexible nature of the rigid pipe segment 4 allows two adjacent rigid pipe segments 4 to achieve flexible movement.

[0087] Figure 11 An application scenario of the two embodiments described above is shown. The specific principle is as follows: When the catheter body enters the blood vessel, each rigid tube segment 4 adapts to the bending angle of the blood vessel through its own movement; then, the balloon is pushed into the blood vessel along the catheter body; at this time, due to the setting of the outer layer 1, the outer surface between the rigid tube segments 4 that adapt to the bending of the blood vessel can still maintain a smooth transition, so that the balloon can be smoothly pushed to the lesion position in the blood vessel along the catheter body; then, the balloon is inflated, and the rigid tube segments 4 can still move flexibly according to the shape of the inner wall of the balloon, thereby adapting to the bending performance of the balloon, achieving a bending angle that matches the balloon, and will not push the balloon up.

[0088] Figure 12 and Figure 13This illustrates another application scenario of the two embodiments described above. The specific principle is as follows: when faced with an acute bending angle of 65°, the conduit body can move through multiple rigid pipe sections 4. Each rigid pipe section 4 only needs to rotate 1° along the bending direction based on the previous rigid pipe section 4.

[0089] In fact, with the same bending distance and bending angle, the more rigid pipe sections 4 there are, the smaller the angle at which each rigid pipe section 4 rotates along the bending direction based on the previous rigid pipe section 4. Therefore, the length of each rigid pipe section 4 is smaller, and the processing accuracy is higher.

[0090] Based on the above embodiments, the third embodiment adjusts the inner layer 3. In the horizontally placed conduit body, the inner surface 44 of each rigid tube segment 4 is a complete arc surface. In this state, see [reference needed]. Figure 14 As shown, in this embodiment, a coating is provided on the inner surface 44 of the rigid tube section 4 to form the inner layer 3. The coating is a hydrophilic polymer coating, including polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), etc. After contact with water, it quickly absorbs water and expands to form a hydrogel layer, which reduces the friction coefficient of the inner wall of the catheter from 0.3+ when dry to below 0.05, significantly reducing the pushing resistance when the guidewire passes through.

[0091] Based on the above embodiments, the fourth embodiment adjusts the elastomer 2, see [link to previous embodiment]. Figure 8 In this embodiment, the elastic body 2 is formed by at least two independent elastic parts 24 forming a ring structure. In this embodiment, it is preferred to use twenty independent elastic parts 24 to form the elastic body 2, so that the connector 22 of a single independent elastic part 24 can be more easily connected to the hook groove or straight slot.

[0092] A preparation method is provided, the purpose of which is to fabricate the microcatheter in the first embodiment, see [link to documentation]. Figure 15 The specific steps are as follows:

[0093] Select the center body 5 with a target length of 135cm to 150cm;

[0094] Insert one end of the rigid pipe section into the head end of the central body 5 and fit it with the head end limiting piece;

[0095] Insert the intermediate rigid pipe sections into the central body 5 in sequence;

[0096] Insert the other end rigid pipe section into the tail end of the central body 5, and insert the tail end limiting piece into the central body 5 to limit the intermediate rigid pipe section between the head end limiting piece and the tail end limiting piece, as well as the end rigid pipe section.

[0097] Install the elastomer 2 into the connecting groove 43 in sequence;

[0098] The above steps are used to prepare and install multiple intermediate rigid pipe sections, end rigid pipe sections, and the central body 5 of the elastic body 2;

[0099] The central body 5, consisting of the installed intermediate rigid pipe section, end rigid pipe section, and elastomer 2, is connected axially using a tapered insertion method with medical-grade UV adhesive for curing. Specifically, tapered mating surfaces (0.5–1 mm in length) are machined at the beginning and end of adjacent central bodies 5, low-viscosity UV adhesive is applied, and curing is allowed. The mating accuracy requires a coaxial deviation of ≤0.05 mm to prevent subsequent extrusion of the core.

[0100] Continuous extrusion coating molding is performed by using a coaxial extruder to coat the corresponding material onto the rigid pipe section 4 to form the outer layer 1. Specific parameters are shown in the table below:

[0101] parameter TPU silicone rubber Extrusion temperature 180~200℃ 120~140℃ Die diameter Outer diameter of the catheter × 1.3 times Outer diameter of catheter × 1.5 times Traction speed 0.8~1.2m / min 0.5~0.8m / min Vacuum sizing negative pressure -0.06MPa -0.04MPa

[0102] The outer diameter of the component is detected in real time using a LaserScan sensor, and then the position of the extruder die is adjusted accordingly (accuracy ±0.01mm) to ensure that the elastomer 2 is filled with air bubbles.

[0103] Finally, the microcatheter is cut out according to the docking position of the central body 5.

[0104] In addition, a hydrophilic polymer coating can also be provided on the surface of the outer layer 1.

[0105] The above steps can also be used for the microcatheter in the second embodiment, but it is only necessary to directly sleeve the integrally connected rigid tube segment 4 outside the central body 5.

[0106] It should be noted that, see Figure 14 As shown, since the elastomer 2 in the second embodiment is housed in the recess 45, the microcatheter obtained in the second embodiment has a smaller radius than the microcatheter in the first embodiment, while keeping the rigid tube segment 4 the same.

[0107] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hollow microcatheter, comprising a catheter body, an outer layer (1) disposed outside the catheter body, and an inner layer (3) disposed within the catheter body, characterized in that, The catheter body includes at least: Multiple rigid pipe sections (4) are arranged closely together along an axis, and there is a movable angle between two adjacent rigid pipe sections (4); An elastic body (2) is disposed between two adjacent rigid pipe sections (4) to limit the size of the angle of movement; A first hardness value and a second hardness value, wherein the first hardness value is less than the second hardness value; Among them, the hardness value of the rigid pipe section (4) is between the first hardness value and the second hardness value; Among them, two adjacent rigid pipe sections (4) are connected by setting an elastic body (2); The first hardness value is less than 20D; The second hardness value is greater than 50D or 40D-60D; The rigid pipe section (4) includes an intermediate rigid pipe section and an end rigid pipe section, wherein the end rigid pipe section is disposed at both ends of the conduit body; The cross-section of the intermediate rigid pipe section is an isosceles trapezoid, and the two hypotenuses of the isosceles trapezoid form the two inclined surfaces (41) of the intermediate rigid pipe section. The cross-section of the end rigid pipe section is a right trapezoid, and the hypotenuse of the right trapezoid forms the inclined surface (41) of the end rigid pipe section. Among them, two adjacent inclined surfaces (41) are connected to form a depression (45) in the catheter body. The elastic body (2) is a ring structure or is formed by at least two independent elastic parts (24) to close the outer side of the recess (45) to form a hollow cavity.

2. The hollow microcatheter according to claim 1, characterized in that, The rigid pipe section (4) can be either split into separate parts or integrally formed.

3. The hollow microcatheter according to claim 1, characterized in that, The rigid pipe section (4) is set in two parts. One end of the middle rigid pipe section has a groove and the other end has a protrusion. The end rigid pipe section is set with either a groove or a protrusion depending on the adaptability of the head of the middle rigid pipe section on its side. The protrusion engages with the groove; The elastomer (2) includes a bent arm (21) and ram's horn portions (23) disposed at both ends of the bent arm (21). The ends of the ram's horn portions (23) are provided with connectors (22), which are hook-shaped structures. The upper bottom of the cross section of the end rigid pipe section forms the horizontal plane (42) of the end rigid pipe section. On the horizontal plane (42) of the middle rigid pipe section, two annular hook grooves with opposite orientations and dovetails facing the inclined plane (41) of the middle rigid pipe section are opened around its surface. On the horizontal plane (42) of the end rigid pipe section, an annular hook groove with a dovetail facing the inclined plane (41) of the end rigid pipe section is provided around its surface; The hook-shaped structure is connected to the hook groove.

4. The hollow microcatheter according to claim 3, characterized in that, The hardness value of the rigid pipe section (4) is 30D-45D.

5. The hollow microcatheter according to claim 1, characterized in that, The rigid pipe section (4) is integrally formed; On the inclined surface (41), an annular straight slot is provided around its surface; The elastomer (2) includes a bent arm (21) and ram's horn portions (23) disposed at both ends of the bent arm (21). The ram's horn portions (23) are provided with connectors (22) at their ends. The connectors (22) are raindrop-shaped structures and are connected to the straight slot.

6. The hollow microcatheter according to claim 5, characterized in that, The hardness value of the rigid pipe section (4) is 30D-40D.

7. A preparation method, characterized in that, The steps for fabricating the hollow microcatheter of claim 1 include: The rigid pipe section (4) is inserted into the outside of the central body (5); The central body (5) fitted with the rigid pipe section (4) is connected axially, and the connection method adopts a tapered insertion joint combined with UV adhesive curing. TPU or silicone rubber is coated onto the rigid pipe section (4) using a coaxial extruder to form an outer layer (1).

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