A microcatheter based on braided layer torque delay compensation and a preparation method thereof

Abstract

This invention discloses a microcatheter based on braided layer torque delay compensation and its fabrication method, belonging to the field of medical device technology. The microcatheter comprises, from the inside out, an inner liner, a braided reinforcement layer, a torque delay compensation spring layer, and an outer cover layer. The core feature is that the spring layer is formed by spirally winding at least one metal wire, with the wire tightly attached to or partially embedded in the mesh of the braided reinforcement layer, thereby creating radial constraint on the braided layer. This structure allows the spring layer to respond instantly as a low-delay torque transmission channel and works synergistically with the braided layer to effectively reduce the relative slippage between the braided wires, significantly reducing the torque transmission delay present in traditional braided layers. The fabrication method includes steps such as inner liner forming, braided layer forming, spring layer lamination, outer cover layer coating, and post-processing. The key is controlling the spring wires to embed into the braided mesh with a specific tension.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically to a microcatheter based on braided layer torque delay compensation and its preparation method. Background Technology

[0002] Microcatheters are key instruments in neurosurgical, cardiac, and peripheral vascular interventional procedures. Their core function is to reach the target lesion through the complex vascular pathways of the human body under image guidance. In this process, microcatheters need to meet a series of seemingly contradictory technical requirements: they must have sufficient pushing force to overcome the friction of the blood vessel wall and have excellent flexibility to safely pass through tortuous blood vessels; their structure must have excellent anti-kink ability to prevent collapse at bends, but most importantly, they must have precise and real-time torsion control response to ensure that the tiny rotational movements applied by the physician at the proximal end of the catheter can be transmitted to the distal tip with almost no delay and no distortion, thereby achieving millimeter-level precise control over the catheter's trajectory.

[0003] To achieve the aforementioned comprehensive performance, existing technologies primarily employ a structural scheme that incorporates a composite metal reinforcement layer within the polymer tubing. Among these, braided reinforcement and spring-loaded reinforcement are two of the most basic and mainstream technical approaches. Braided reinforcement typically consists of multiple stainless steel flat wires interlaced at specific angles (e.g., ±45°) to form a dense mesh layer. Its advantages lie in providing extremely high radial support, tensile strength, and resistance to flattening, forming the cornerstone of catheter delivery and kinking resistance. However, this structure inherently suffers from torque transmission performance issues: when rotation is applied proximally, the braided wires must first overcome mutual friction and undergo minute relative slippage and structural deformation to transmit the torsional force step by step. This process leads to perceptible operational delays and nonlinear responses, a phenomenon known in the industry as "torque delay," which severely impacts the instantaneous and predictable control of the catheter tip direction during delicate operations.

[0004] Another type of spring-reinforced structure consists of one or more metal wires tightly wound in a spiral, resembling a tubular spring. This structure gives the catheter excellent flexibility and resistance to bending fatigue, and its continuous spiral characteristic also allows for a faster initial response to rotational input. However, the axial tensile strength of a simple spring layer is relatively weak, making it prone to "shortening" when pushed through complex paths, and its resistance to kinking is significantly insufficient, making it unsuitable as an independent support structure for microcatheters.

[0005] To balance strength and torsional control, existing technologies often attempt to combine the two structures mentioned above in a simple way, such as by superimposing a spring layer on top of the braided layer. However, this simple physical superposition fails to fundamentally solve the torque delay problem of the braided layer. The lack of mechanical coupling between the outer spring and the inner braided mesh means they often deform independently and may even create new response hysteresis points due to mutual interference. Another approach uses a segmented design with a braided layer at the proximal end and a spring layer at the distal end, but this design can create abrupt changes in mechanical properties at the junction of the two structures, affecting the consistency of push-pull and torsional control. More complex designs attempt to embed additional flat springs specifically for torque transmission within the braided layer, but this significantly increases process complexity and manufacturing costs.

[0006] Therefore, there is an urgent need in this field for an innovative microcatheter structure and its fabrication method. This cannot be a simple stacking of two traditional structures, but should achieve a deep synergy and integration of the braided layer and the spring layer in terms of function and mechanics. The ideal solution should retain the high strength and kink resistance of the braided layer while fundamentally compensating for its delayed torque transmission, thereby providing a high-performance microcatheter with near-instantaneous, linear torque response from proximal to distal end to meet the increasingly sophisticated needs of vascular interventional surgery. Summary of the Invention

[0007] To address the technical problems in the prior art, this invention provides a microcatheter based on braided layer torque delay compensation and its preparation method.

[0008] The technical solution of this invention is implemented as follows:

[0009] This invention discloses a microcatheter based on braided layer torque delay compensation, employing an innovative multi-layer composite structure comprising, from the inside out, an inner liner, a braided reinforcement layer, a torque delay compensation spring layer, and an outer cover layer. Its core innovation lies in the specific composite relationship and synergistic mechanism between the braided reinforcement layer and the torque delay compensation spring layer.

[0010] It includes a braided reinforcement layer, a dense tubular network of multiple flat metal filaments woven together at an optimized angle of approximately ±45°. This layer serves as the primary load-bearing structure, providing the catheter with the necessary axial pushing strength, radial crush resistance, and kink resistance.

[0011] It also includes a torque delay compensation spring layer, which is made of at least one metal wire tightly wound with a specific helical pitch.

[0012] As a continuous helical spring structure, the coiled spring layer itself exhibits extremely fast mechanical wave transmission characteristics to torsional input. When rotation is applied to the proximal end, the coiled spring layer can instantly establish a low-delay torque transmission auxiliary channel.

[0013] In this invention, the spring wires embedded in the braided mesh exert radial constraint and support on the braided wires at the initial moment of torsion, effectively reducing the relative sliding space and micro-displacement between the braided wires, which is equivalent to "locking" the braided network. This significantly reduces the static friction force that needs to be overcome within the braided layer to transmit the starting torque, allowing it to enter the cooperative torsion state more quickly.

[0014] The method for preparing the microcatheter of the present invention includes the following steps:

[0015] S1, Inner liner forming, provides polymer material, and prepares a smooth inner liner with a preset inner diameter and wall thickness through an extrusion molding process.

[0016] S2, forming the braided reinforcement layer: fixing the inner lining tube to the rotating mandrel of the braiding machine; driving multiple flat metal wires to cross-weave at a preset braiding angle on the outer surface of the inner lining tube to form a tightly wrapped tubular braided reinforcement layer.

[0017] S3, Torque delay compensation spring layer composite, at least one metal wire is continuously and coaxially wound along its axial direction at a preset helical pitch on the outer surface of the braided reinforcement layer, so that the metal wire is tightly attached to or partially embedded in the mesh structure of the braided reinforcement layer, thereby forming a torque delay compensation spring layer, and obtaining a composite tube blank with a double-layer metal reinforcement structure.

[0018] S4, outer coating: The composite tube blank is used as the core wire and fed into a co-extruder; molten polymer material is extruded and coated on the outer periphery of the composite tube blank; the polymer material penetrates and fills the gap between the spring layer and the braided reinforcement layer under pressure; after cooling and shaping, an outer coating layer is formed that is tightly integrated with the internal reinforcement structure, and a conduit blank is obtained.

[0019] S5, the catheter blank is subjected to one or more operations including heat treatment, dimensional shaping, surface polishing, cutting and assembly of distal imaging marking ring, and finally the microcatheter is obtained.

[0020] Step S2: the braiding reinforcement layer forming step, specifically includes:

[0021] The inner lining tube is fixed to the rotating mandrel of the braiding machine;

[0022] Multiple flat metal wires are driven to cross-weave at a preset weaving angle of 30° to 60° on the outer surface of the inner liner tube to form a tubular braided reinforcement layer.

[0023] During the weaving process, the weaving density is kept uniform by controlling the traction speed of the mandrel and the rotation speed of the weaving machine; and a constant tension control is applied to each of the metal flat wires.

[0024] In step S2, the inner lining tube is preheated before weaving begins, and the weaving process is carried out in multiple temperature zones.

[0025] This invention effectively solves the "torque delay" problem inherent in traditional braided reinforced microcatheters. By creatively incorporating a torque delay compensation spring layer, with its wires tightly attached to or partially embedded within the mesh of the braided reinforcement layer, a deeply synergistic composite structure is constructed. This structure provides a dual function during operation: firstly, the spring layer itself, acting as a continuous helical spring structure, provides a low-delay auxiliary path for torque transmission, enabling instantaneous response to rotational input; secondly, the embedded spring wires exert radial constraints on the braided mesh, limiting relative slippage between the braided wires at the initial moment of torsion, significantly reducing initiation friction and allowing the braided layer to quickly participate in the overall torsion. The synergy of these two aspects significantly improves the efficiency of torque transmission from the proximal to the distal end of the catheter, significantly shortens the response delay, and provides physicians with a direct, linear, and highly predictable control feel, greatly enhancing the accuracy and efficiency of superselection and positioning in complex vascular pathways. Attached Figure Description

[0026] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of the microcatheter structure of the present invention.

[0028] Figure 2 This is a schematic diagram of the preparation method of the microcatheter of the present invention.

[0029] In the diagram: 1-Inner liner; 2-Torque delay compensation spring layer; 3-Woven reinforcement layer; 4-Outer cover layer; 5-Development marking ring. Detailed Implementation

[0030] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0031] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0032] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0033] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0034] Example 1, such as Figure 1 As shown, the present invention provides a microcatheter based on braided layer torque delay compensation, comprising a body, which includes, from the inside to the outside, an inner liner, a braided reinforcement layer, a torque delay compensation spring layer, and an outer cover layer.

[0035] The inner liner is made of polytetrafluoroethylene and its function is to provide a smooth internal channel to facilitate the passage of guidewires and other interventional instruments. The inner liner has a preset inner diameter and wall thickness.

[0036] The braided reinforcement layer is composited on the outer surface of the inner lining layer. It consists of a dense tubular network of multiple stainless steel flat wires woven together. During weaving, the metal flat wires are controlled to cross at a weaving angle of approximately 45 degrees, which achieves a good balance between providing excellent anti-kink properties and smooth pushing performance.

[0037] The torque delay compensation spring layer is composited on the outer surface of the braided reinforcement layer. This layer is formed by tightly winding at least one stainless steel wire with a specific helical pitch to create a tubular structure. During winding, the tension of the wire is controlled to ensure it adheres tightly to and partially embeds into the mesh of the braided reinforcement layer, thereby providing effective radial constraint on the braided layer. In this embodiment, the helical winding direction of the spring layer is set to be the same as the extension direction of one set of braided strands in the braided reinforcement layer. This design allows the spring layer to respond quickly and cooperate with the braided layer to transmit torque during torsional input, effectively reducing the transmission delay inherent in traditional braided layers.

[0038] The outer coating layer covers the coiled spring layer. In this embodiment, a polyamide block copolymer is used as the outer coating layer material. To optimize the handling performance of the catheter, the hardness of the outer coating layer gradually decreases from the proximal end to the distal end along the catheter axis. Through a co-extrusion process, the molten polymer material can penetrate into the gap between the coiled spring layer and the braided layer under pressure, and after cooling, the layers are firmly bonded into a whole.

[0039] In addition, a high-density metal imaging marker ring is fitted at the distal end of the microcatheter to clearly locate the catheter tip under X-ray fluoroscopy.

[0040] This embodiment effectively solves the "torque delay" problem existing in traditional braided reinforced microcatheters. By creatively setting a torque delay compensation spring layer and having its metal wires tightly attached to or partially embedded in the mesh of the braided reinforcement layer, a deeply synergistic composite structure is constructed.

[0041] Example 2, as Figure 2 As shown, the preparation method of the microcatheter of the present invention includes the following steps:

[0042] S1, Inner liner forming, provides polymer material, and prepares a smooth inner liner with a preset inner diameter and wall thickness through an extrusion molding process.

[0043] The basic structure of the entire microcatheter is constructed, forming a tubular cavity with a smooth inner wall and precise dimensions, ensuring that subsequent interventional instruments can pass smoothly and serving as a supporting base for subsequent reinforcement layer structures.

[0044] S2, Braided Reinforcement Layer Forming: The inner liner tube is fixed to the rotating mandrel of the braiding machine; multiple metal flat wires are driven to cross-braid at a preset braiding angle on the outer surface of the inner liner tube, forming a tightly wrapped tubular braided reinforcement layer. This constructs the main load-bearing structure outside the inner liner tube. Through the cross-braiding of the metal flat wires, the catheter is endowed with the necessary axial pushing strength, radial crush resistance, and kink resistance, providing core mechanical support for the catheter.

[0045] S3, Torque Delay Compensation Spring Layer Composite: On the outer surface of the braided reinforcement layer, at least one metal wire is continuously and coaxially wound along its axial direction at a preset helical pitch, so that the metal wire is tightly attached to or partially embedded in the mesh structure of the braided reinforcement layer, thereby forming a torque delay compensation spring layer, resulting in a composite tube blank with a double-layer metal reinforcement structure. A compensation structure that works in conjunction with the braided layer can be constructed. Through the embedding and composite of the spring wire, radial constraint is formed on the braided mesh to reduce slippage between braided wires during torsion, thereby compensating for the torque transmission delay of traditional braided layers and improving torque control response.

[0046] S4, Outer Coating: The composite tube blank, used as the core wire, is fed into a co-extruder. Molten polymer material is extruded and coated around the outer periphery of the composite tube blank. Under pressure, the polymer material penetrates and fills the gaps between the coiled spring layer and the braided reinforcement layer. After cooling and shaping, an outer coating layer tightly integrated with the internal reinforcement structure is formed, resulting in the catheter blank. This integrates and encapsulates the internal multi-layered structure. The coating and penetration of the molten polymer material solidifies the inner liner, braided layer, and coiled spring layer into a unified whole, providing a smooth, biocompatible surface, protecting the internal metal layer, and optimizing the overall hardness and flexibility of the catheter through material selection and gradient design.

[0047] S5, the catheter blank is subjected to one or more operations including heat treatment, dimensional shaping, surface polishing, cutting, and assembly of distal imaging marker rings to finally obtain the microcatheter. This completes the final shaping and functionalization of the catheter. This step aims to eliminate processing stress, refine the catheter size and tip shape, improve surface finish, and assemble imaging-friendly components for easy positioning under imaging, thereby ensuring that the product meets the final clinical use requirements and quality standards.

[0048] Step S2: the braiding reinforcement layer forming step, specifically includes:

[0049] The inner lining tube is fixed to the rotating mandrel of the braiding machine;

[0050] Multiple flat metal wires are driven to cross-weave at a preset weaving angle of 30° to 60° on the outer surface of the inner liner tube to form a tubular braided reinforcement layer.

[0051] During the weaving process, the weaving density is kept uniform by controlling the traction speed of the mandrel and the rotation speed of the weaving machine; and a constant tension is applied to each of the metal flat wires. Controlling the mandrel traction speed and the weaving machine rotation speed ensures that the weaving density is uniform along the length of the guide tube. Applying constant tension to each metal flat wire ensures a tight weave structure without loose strands, thereby achieving stable and predictable mechanical properties.

[0052] In step S2, the inner lining tube is preheated before weaving begins, and the weaving process is carried out in multiple temperature zones. Preheating the inner lining tube aims to soften its surface and promote the adhesion and fixation of the metal flat wires upon initial contact.

[0053] In step S3, the torque delay compensation spring layer composite step specifically includes continuously and coaxially winding at least one metal wire along its axial direction with a preset helical pitch on the outer surface of the braided reinforcement layer.

[0054] By controlling the winding tension, the metal wire is tightly attached to and partially embedded in the mesh structure of the braided reinforcement layer, thereby forming a torque delay compensation spring layer to obtain a composite tube blank. Controlling the winding tension aims to ensure that the metal wire is tightly adhered to and effectively embedded in the braided layer mesh, achieving the desired mechanical interlocking effect.

[0055] In step S3, the spiral direction of the winding is the same as the extension direction of some of the braided strands in the braided reinforcement layer; or the spiral direction of the winding is opposite to the extension direction of some of the braided strands in the braided reinforcement layer. Controlling the winding spiral direction (in the same direction or opposite to the braided strands) aims to specifically adjust the torsional stiffness and hand feel characteristics of the conduit.

[0056] In step S3, the winding step and the braiding step in step S2 are performed continuously on the same equipment without changing the mandrel supporting the inner liner tube. The requirement that the winding and braiding steps be performed continuously on the same equipment without changing the mandrel aims to ensure precise alignment and structural consistency of the composite position of the braided layer and the spring layer, avoiding structural damage or performance fluctuations caused by intermediate transfer.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a microcatheter, comprising the following steps: S1, Inner liner forming, providing polymer material, and preparing a smooth inner liner with a preset inner diameter and wall thickness through an extrusion molding process; S2, forming the braided reinforcement layer: the inner lining tube is fixed on the rotating mandrel of the braiding machine, and multiple metal flat wires are driven to cross-weave at a preset braiding angle on the outer surface of the inner lining tube to form a tightly wrapped tubular braided reinforcement layer. S3, Torque delay compensation spring layer composite, at least one metal wire is continuously and coaxially wound along its axial direction at a preset helical pitch on the outer surface of the braided reinforcement layer. By controlling the winding tension, the metal wire is tightly attached and partially embedded in the mesh structure of the braided reinforcement layer to form a torque delay compensation spring layer, thereby obtaining a composite tube blank with a double-layer metal reinforcement structure. S4, outer coating: The composite tube blank is used as the core wire and fed into a co-extruder. Molten polymer material is extruded and coated on the outer periphery of the composite tube blank. Under pressure, the polymer material penetrates and fills the gap between the spring layer and the braided reinforcement layer. After cooling and shaping, an outer coating layer that is tightly integrated with the internal reinforcement structure is formed, and a conduit blank is obtained. S5, perform one or more operations on the catheter blank including heat treatment, dimensional shaping, surface polishing, cutting and assembly of distal imaging marking ring, and finally obtain the microcatheter; In step S2: The inner lining tube is fixed to the rotating mandrel of the braiding machine; Multiple flat metal wires are driven to cross-weave at a preset weaving angle of 30° to 60° on the outer surface of the inner liner tube to form a tubular braided reinforcement layer. in, During the weaving process, the weaving density is kept uniform by controlling the traction speed of the mandrel and the rotation speed of the weaving machine; and a constant tension control is applied to each of the metal flat wires. Furthermore, the inner lining tube is preheated before weaving begins, and the weaving process is carried out in multiple temperature zones; In step S3, the spiral direction of the winding is the same as the extension direction of some of the braided strands in the braided reinforcement layer; or the spiral direction of the winding is opposite to the extension direction of some of the braided strands in the braided reinforcement layer. In step S3, the winding step and the weaving step in step S2 are performed continuously on the same equipment, and the mandrel carrying the inner liner tube is not changed during the process.

2. A microcatheter based on braided layer torque delay compensation obtained by the preparation method as described in claim 1, comprising an inner liner layer, a braided reinforcement layer, a torque delay compensation spring layer, and an outer cover layer sequentially composited from the inside to the outside; The braided reinforcement layer is a tubular network formed by multiple cross-woven flat metal wires; The torque delay compensation spring layer is a tubular structure formed by spirally winding at least one metal wire. The metal wire is tightly attached to and partially embedded in the mesh of the braided reinforcement layer under the control of the winding tension, so that the spring layer can form a radial constraint on the braided reinforcement layer to cooperate in transmitting torque and reduce transmission delay during torsional input. The material of the outer cladding layer at least partially penetrates and fills the gap between the coiled spring layer and the braided reinforcement layer to bond and solidify the inner lining layer, the braided reinforcement layer, the coiled spring layer and the outer cladding layer into a single unit.

3. The microcatheter according to claim 2, characterized in that, The metal flat wires of the braided reinforcement layer are cross-woven at a braiding angle of 30° to 60°.

4. The microcatheter according to claim 2, characterized in that, The spiral winding direction of the torque delay compensation spring layer is the same as or opposite to the extension direction of some of the braided strands in the braided reinforcement layer.

5. The microcatheter according to claim 2, characterized in that, The outer coating is made of polyamide block copolymer or polyurethane, and its hardness gradually decreases from the proximal end to the distal end along the axial direction of the microcatheter.

6. The microcatheter according to claim 2, characterized in that, It also includes a radiopaque ring disposed at the distal end of the microcatheter.

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