Microchannel targeted coronary microcatheter and method of use

Abstract

This invention relates to the field of medical device technology, and discloses a microchannel targeted coronary microcatheter and its usage method, comprising a microcatheter body and a visible tip; the body has an inner layer, a braided layer, and an outer layer; the inner layer surface has alternating hydrophilic and hydrophobic strips extending spirally along the axial direction; the gaps in the braided layer are filled with a shear-thickening fluid matrix; the visible tip has a radial gradient modulus; the usage method includes maintaining compliant navigation using the liquid matrix under low pressure; increasing pressure as it approaches the lesion, using the strips to induce a spiral jet to align with the inlet; using negative pressure under high pressure to sharpen the tip and triggering matrix solidification using micro-vibration; and releasing pressure to restore the tip after passing through the lesion. This invention achieves adaptive morphological transformation of the visible tip and automatic alignment and insertion into the microchannel inlet by inducing a high-speed spiral jet through alternating hydrophilic and hydrophobic strips in the inner layer of the catheter, and using the transwall pressure difference generated by the jet to drive the visible tip to contract and sharpen.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically to a microchannel targeted coronary microcatheter and its usage method. Background Technology

[0002] Coronary microcatheters, as important auxiliary devices in percutaneous coronary intervention (PCI), are widely used to treat complex cases such as chronic total occlusion lesions, bifurcation lesions, and severely calcified lesions. Existing microcatheter technologies, based on their function and structural characteristics, mainly include ordinary microcatheters, dilatational microcatheters, dual-lumen microcatheters, and extension microcatheters. These devices assist the operator in opening occluded vessels by providing guidewire support, assisting guidewire shaping, establishing collateral circulation pathways, or performing highly selective angiography. In actual clinical applications, microcatheters typically employ a multi-layered composite structure. By adjusting the hardness distribution of the polymer material or the density of the metal braided layers, a structure is designed with higher proximal hardness to ensure thrust transmission and lower distal hardness to maintain flexibility, thus balancing intravascular permeability and lesion puncture support to a certain extent.

[0003] However, existing microcatheters still suffer from limitations in terms of fixed structural characteristics when dealing with complex chronic total occlusion lesions. Once manufactured, traditional microcatheters have fixed axial stiffness gradients and tip geometry, making dynamic adjustment impossible based on navigation or puncture requirements during surgery. While high catheter flexibility is required for navigation through tortuous vessels, a flexible catheter structure can lead to reduced thrust transmission efficiency and kinking or rebound when the catheter approaches a hard fibrous cap or calcified lesion requiring puncture. Furthermore, the tips of existing microcatheters are typically fixed, blunt, or conical in shape, lacking the ability to adapt using hydrodynamic effects. Locating the microchannel entry point relies primarily on mechanical probes with a guidewire, making automatic alignment with low-resistance areas on the lesion surface difficult, increasing operational uncertainty and the risk of intimal damage.

[0004] In summary, existing microcatheters struggle to simultaneously achieve the flexibility required for low-resistance navigation and the rigidity required for high-intensity puncture on the same instrument, and lack an adaptive mechanism that can utilize fluid energy to assist the catheter in locating and penetrating the lesion's microchannel. Therefore, designing a microcatheter capable of dynamically switching between compliant and rigid states, and possessing fluid-driven automatic alignment and tip sharpening functions, is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a microchannel targeted coronary microcatheter and its usage method, which solves the problems that existing microcatheters cannot balance distal flexibility and puncture support, and lack the ability to utilize fluid energy to assist the catheter in achieving adaptive alignment and sharpening of the lesion microchannel.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] The present invention provides a microchannel targeted coronary microcatheter, comprising a microcatheter body, wherein a visible tip is fixedly connected to the distal end of the microcatheter body;

[0008] The microcatheter body has an inner layer that forms a guide cavity inside, a braided layer on the outside of the inner layer, and an outer layer on the outside of the braided layer.

[0009] The inner surface of the inner layer of the conduit is provided with hydrophilic strips and hydrophobic strips that extend spirally along the axial direction and are arranged alternately. The hydrophilic strips and the hydrophobic strips are configured to induce the fluid to generate a tangential velocity component along the spiral direction when the fluid flow rate in the conduit exceeds the working flow rate threshold.

[0010] The braided layer is made of metal wires, and the gaps between the metal wires are filled and encapsulated with a shear-thickening fluid matrix. The shear-thickening fluid matrix is ​​configured to be in a liquid sol state at low shear rates and to restrict the relative sliding between the metal wires by phase change solidification at high shear rates induced by high-frequency micro-vibrations generated by fluid flow in the guide cavity.

[0011] The visible head end is made of a polymer material with a radial gradient modulus. The visible head end includes an inner wall layer and an outer wall layer. The elastic modulus of the inner wall layer is less than that of the outer wall layer. The inner wall layer is configured to contract towards the central axis to form a tapered sharpening structure when the fluid flow rate in the guide cavity increases, causing the static pressure in the cavity to decrease.

[0012] Preferably, the angle between the helix of the hydrophilic strip and the hydrophobic strip and the central axis of the conduit is between 15 degrees and 45 degrees, and the width of a single strip in the hydrophilic strip and the hydrophobic strip is between 10 micrometers and 100 micrometers.

[0013] Preferably, the surface material of the hydrophilic strip has a contact angle between 0 and 30 degrees, and the surface material of the hydrophobic strip has a contact angle between 120 and 180 degrees.

[0014] Preferably, the shear-thickening fluid matrix is ​​a nano-silica suspension dispersed in polyethylene glycol; the shear-thickening fluid matrix has thixotropic properties and is configured to recover from the solidified state to the liquid sol state after the high-frequency micro-vibration is removed.

[0015] Preferably, the visual head end has an initial relaxed state and an activated sharpening state;

[0016] In the initial relaxed state, the visible tip maintains its original inner diameter, which is greater than or equal to the inner diameter of the lumen at the microcatheter body;

[0017] In the activated sharpening state, the visible head end is in a radially contracted state driven by the transwall pressure difference and is configured to recover to the initial relaxed state by utilizing the viscoelasticity of the material after the fluid pressure is removed.

[0018] Preferably, the microcatheter body includes a torsion control section, a flexural resistance section, and a coaxial section in sequence from near to far along the axial direction, and the material hardness of the outer layer of the catheter corresponding to the torsion control section, the flexural resistance section, and the coaxial section decreases in sequence; the outer surface of the outer layer of the catheter is coated with a hydrophilic coating.

[0019] Preferably, the inner layer of the catheter is made of polytetrafluoroethylene or high-density polyethylene; the metal wire is stainless steel wire or nickel-titanium alloy wire; the outer layer of the catheter is made of polyether block polyamide or nylon; the visible tip is made of thermoplastic polyurethane or polyether block polyamide, and is internally doped with a developer selected from platinum-iridium alloy powder or tungsten powder.

[0020] This invention also provides a method for using a microchannel targeted coronary microcatheter, employing the following technical solution:

[0021] A method for using a microchannel targeted coronary microcatheter includes the following steps:

[0022] S100. Push the microchannel-targeted coronary microcatheter along the guidewire to the proximal end of the coronary lesion. During the pushing process, keep the fluid injection pressure in the lumen below the working pressure threshold required to generate eddy currents, so that the inner layer of the catheter maintains laminar flow characteristics and the shear-thickening fluid matrix located in the braided layer is in a liquid sol state.

[0023] S200. When approaching the occluded lesion and the guidewire cannot pass through, the fluid injection pressure in the lumen is increased to above the working pressure threshold. The hydrophilic and hydrophobic stripes on the inner surface of the catheter are used to induce the fluid to generate a high-speed spiral jet, forming a vortex nucleus at the outlet of the visible tip, and the vortex nucleus is used to align with the microchannel inlet.

[0024] S300. While maintaining the fluid injection pressure above the working pressure threshold, the negative pressure generated by the high-speed spiral jet drives the visible head end to contract toward the central axis to form a conical sharpening shape. At the same time, the high-frequency micro-vibration induced by the high-speed spiral jet triggers the shear thickening fluid matrix in the braided layer to undergo phase change solidification.

[0025] S400. While maintaining the fluid injection pressure above the working pressure threshold, apply axial thrust and use the visible tip in the conical sharpening shape and the braided layer in the solidified state to penetrate the lesion.

[0026] S500. After confirming that the fluid has passed through the lesion, the fluid injection pressure is removed, the visible tip is restored to its original diameter, and the shear-thickening fluid matrix is ​​restored to the liquid sol state.

[0027] By employing the above technical solution, this invention utilizes a fluid dynamics-based adaptive adjustment mechanism, enabling the catheter to switch between a compliant navigation state and a rigid puncture state according to changes in injection pressure. Under low pressure, the shear-thickening fluid matrix is ​​in a liquid state, ensuring the catheter's passability and flexibility in tortuous blood vessels; under high pressure, the physical effects induced by fluid energy simultaneously achieve three functions: automatic alignment, tip sharpening, and catheter body hardening. This design effectively solves the technical challenge of traditional microcatheters in balancing distal compliance and puncture support, achieving precise identification and expansion of microchannels for chronically totally occluded lesions using fluid energy.

[0028] Furthermore, in step S200, the high-speed helical jet is formed by the tangential velocity component generated when the fluid flows through the hydrophilic and hydrophobic strips; in step S300, the contraction of the visible head end is driven by the transwall pressure difference formed by the decrease in internal static pressure caused by the high-speed helical jet.

[0029] By employing the above technical solution, the flow field is controlled by the surface wettability differences of micro- and nanostructures, generating a stable helical jet without the need for complex mechanical steering mechanisms. Based on fluid dynamics principles, the vortex core with central negative pressure tends to deflect towards the microchannel inlet where flow resistance is minimal, thus achieving adaptive alignment of the lesion inlet and reducing the difficulty for the surgeon in locating the microchannel.

[0030] Simultaneously, the high flow rate is converted into a transwall pressure differential using Bernoulli's principle. Combined with a gradient design of the modulus of the inner and outer wall layers at the visible tip, this ensures that the tip automatically contracts into a conical structure when the injection pressure increases. This dynamically sharpened shape facilitates catheter insertion into narrow microchannel inlets, reducing damage to surrounding normal vascular tissue. Furthermore, this deformation is entirely controlled by the fluid state, exhibiting rapid response characteristics.

[0031] Furthermore, in step S300, the phase change solidification of the shear-thickening fluid matrix is ​​triggered by the high-frequency micro-vibration induced by the high-speed helical jet on the inner wall of the conduit; in step S500, as the fluid injection pressure is removed, the visible tip recovers using the viscoelastic memory properties of the material.

[0032] By employing the above technical solution, the phase change characteristics of the shear-thickening material are stimulated using the fluid-structure interaction effect. High-frequency micro-vibrations of the pipe wall provide the matrix with the required high shear rate at the microscopic level, causing it to transition from a liquid to a solidified state. This restricts the relative slippage of the metal braided layer, improving the axial thrust transmission efficiency and flexural strength of the conduit.

[0033] This hardening mechanism is triggered only when puncture is required, avoiding the risk of vascular perforation that may occur with conventional rigid-tipped catheters during navigation. At the same time, the automatic recovery mechanism after depressurization ensures the reversibility and reusability of the catheter function. The visible tip returns to its original large-diameter state, facilitating the free exchange of guidewires or the injection of contrast agents in subsequent surgical steps. The reduced rigidity of the catheter body also facilitates the safe withdrawal of the catheter.

[0034] This invention provides a microchannel targeted coronary artery microcatheter and its usage method. It has the following beneficial effects:

[0035] 1. This invention provides hydrophilic and hydrophobic strips that extend axially and alternately on the inner surface of the inner layer of the catheter. When the fluid velocity in the cavity exceeds the working velocity threshold, the fluid is induced to generate a tangential velocity component along the spiral direction, forming a high-speed spiral jet. The increased jet velocity causes a decrease in the static pressure in the cavity, which in turn drives the inner wall layer with a lower modulus to contract towards the central axis. This achieves an adaptive morphological transformation of the visible tip from an initial relaxed state to a tapered and sharpened structure, facilitating the automatic alignment and insertion of the microcatheter into the microchannel using fluid energy.

[0036] 2. This invention fills and encapsulates a shear-thickening fluid matrix within the gaps between the metal wires in the braided layer. The high-frequency micro-vibration induced by the fluid flow within the guide cavity generates a high shear rate, triggering the shear-thickening fluid matrix to transform from a liquid sol state to a solidified state. This restricts the relative sliding between the metal wires and increases the stiffness of the braided layer. As a result, the microcatheter body can maintain compliant navigation characteristics when the working flow rate threshold is not reached, and obtain rigid support when puncture of lesions is required. This solves the problem that microcatheters cannot balance distal compliance with puncture propulsion force.

[0037] 3. This invention utilizes the viscoelastic memory properties of the polymer material at the visible tip and the thixotropic properties of the shear-thickening fluid matrix, combined with the progressive hardness design of the torsion control section, anti-bending section, and coaxial section along the axial direction of the microcatheter body. This allows the visible tip to elastically return to its original inner diameter after the fluid injection pressure is removed, and the shear-thickening fluid matrix to return to a liquid sol state. This ensures that the microcatheter can quickly release its rigidity and restore its flexibility after completing the puncture, which is beneficial for subsequent guidewire exchange operations and reduces the risk of mechanical damage to the blood vessel wall. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the appearance of the microcatheter in one embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of a microcatheter in one embodiment of the present invention;

[0040] Figure 3 This is a cross-sectional view of a microcatheter in one embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of the outer segment of a microcatheter in one embodiment of the present invention;

[0042] Figure 5 This is a flowchart of a method for using a microchannel-targeted coronary microcatheter in one embodiment of the present invention.

[0043] Among them, 100 is the main body of the microcatheter; 101 is the visible tip; 102 is the coaxial section; 103 is the anti-bending section; 104 is the torsion control section; 111 is the outer layer of the catheter; 112 is the braided layer; 113 is the inner layer of the catheter; and 114 is the lumen. Detailed Implementation

[0044] The technical solutions in 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.

[0045] See attached document Figure 1 -Appendix Figure 4This invention provides a microchannel targeted coronary microcatheter, including a microcatheter body 100, with a visible tip 101 fixedly connected to the distal end of the microcatheter body 100; an inner layer 113 forming a guide cavity 114 is disposed inside the microcatheter body 100, a braided layer 112 is disposed outside the inner layer 113, and an outer layer 111 is disposed outside the braided layer 112; the inner surface of the inner layer 113 is provided with alternating hydrophilic and hydrophobic strips extending spirally along the axial direction, the hydrophilic and hydrophobic strips being configured to induce a tangential velocity component along the spiral direction in the fluid when the fluid flow rate in the guide cavity 114 exceeds a working flow rate threshold; the braided layer... 112 is woven from metal wires, and the gaps between the metal wires are filled and encapsulated with a shear-thickening fluid matrix. The shear-thickening fluid matrix is ​​configured to be in a liquid sol state at low shear rates. Under high shear rates induced by high-frequency micro-vibrations induced by fluid flow in the guide cavity 114, it restricts the relative sliding between the metal wires by undergoing phase change solidification. The visible head end 101 is made of a polymer material with radial gradient modulus. The visible head end 101 includes an inner wall layer and an outer wall layer. The elastic modulus of the inner wall layer is smaller than that of the outer wall layer. The inner wall layer is configured to contract towards the central axis to form a tapered sharpening structure when the fluid flow rate in the guide cavity 114 increases, causing the internal cavity static pressure to decrease.

[0046] Specifically, the microcatheter body 100 is a slender tubular structure, with a Luer connector at the proximal end for connecting an external pressurization device. The inner layer 113 serves as a lining layer and is made of a low-friction coefficient material such as polytetrafluoroethylene or high-density polyethylene to facilitate guidewire passage. The fluid control structure on the inner surface of the inner layer 113 is fabricated using micro / nano processing or differentiated coating technology. When the injected contrast agent or saline flow rate is low, the fluid is in a laminar flow state; when the flow rate exceeds the set working flow rate threshold, hydrophilic and hydrophobic bands with different wettability generate differentiated viscous resistance at the fluid boundary layer, inducing the fluid to rotate and form a high-speed helical jet. The braided layer 112 is cross-woven from stainless steel wire such as 304 stainless steel or nickel-titanium alloy wire, and the shear-thickening fluid matrix encapsulated within the gaps of the braided layer 112 serves as a damping material. In normal navigation mode, the shear-thickening fluid matrix is ​​in a liquid state, and relative sliding occurs between the metal wires, keeping the microcatheter body 100 compliant. When the high-speed helical jet generates turbulent pulsations that cause high-frequency micro-vibrations in the wall of the microcatheter body 100, the shear-thickening fluid matrix undergoes a phase change and solidifies, limiting the relative displacement of the metal wire intersection points and improving the thrust transmission performance and flexural strength of the microcatheter body 100. The visible tip 101 is doped with imaging materials such as platinum-iridium alloy powder or tungsten powder, which facilitates the positioning of the visible tip 101 under X-rays.

[0047] See attached document Figure 1 -Appendix Figure 4The angle between the helix of the hydrophilic and hydrophobic strips and the central axis of the catheter is between 15 and 45 degrees; the width of a single hydrophilic or hydrophobic strip is between 10 and 100 micrometers; the contact angle of the surface material of the hydrophilic strip is between 0 and 30 degrees, and the contact angle of the surface material of the hydrophobic strip is between 120 and 180 degrees; the shear-thickening fluid matrix is ​​a nano-silica suspension dispersed in polyethylene glycol; the shear-thickening fluid matrix has thixotropic properties and is configured to recover from a solidified state to a liquid sol state after the high-frequency micro-vibration is removed; the visible tip 101 has an initial relaxed state and an activated sharpening state; in the initial relaxed state, the visible tip 101 maintains its original inner diameter, which is greater than or equal to the inner diameter of the lumen 114 at the microcatheter body 100; In the activated sharpening state, the visible tip 101 is in a radially contracted state driven by the transwall pressure difference, and is configured to recover to the initial relaxed state by the viscoelasticity of the material after the fluid pressure is removed; the microcatheter body 100 includes a torsion control section 104, a flexural strength section 103, and a coaxial section 102 in sequence from near to far along the axial direction, and the material hardness of the outer layer 111 of the torsion control section 104, the flexural strength section 103, and the coaxial section 102 decreases in sequence; the outer surface of the outer layer 111 of the catheter is coated with a hydrophilic coating; the inner layer 113 of the catheter is made of polytetrafluoroethylene or high-density polyethylene; the metal wire is stainless steel wire or nickel-titanium alloy wire; the outer layer 111 of the catheter is made of polyether block polyamide or nylon; the visible tip 101 is made of thermoplastic polyurethane or polyether block polyamide, and its interior is doped with a developer selected from platinum-iridium alloy powder or tungsten powder.

[0048] Specifically, the helical parameters of the hydrophilic and hydrophobic strips are designed to improve the generation efficiency of the tangential velocity component while ensuring fluid flux. The angle between the helix of the hydrophilic and hydrophobic strips and the central axis of the microcatheter body 100 is between 15 and 45 degrees, and the width of a single strip in both types of strips is between 10 and 100 micrometers. The surface of the hydrophilic strips is coated with a hydrophilic polymer, and the contact angle of the surface material is between 0 and 30 degrees. The surface of the hydrophobic strips is coated with a micro / nano-structured superhydrophobic coating, and the contact angle of the surface material is between 120 and 180 degrees. The shear-thickening fluid matrix is ​​a non-Newtonian fluid formed by dispersing nano-silica particles in polyethylene glycol. The reversible sol-gel transition properties of the shear-thickening fluid matrix enable dynamic adjustment of the stiffness of the microcatheter body 100. The visual tip 101 is made of thermoplastic polyurethane or polyether block polyamide. The deformation mechanism of the visual tip 101 is based on the principle of fluid mechanics: when high-pressure injection causes the internal flow velocity of the visual tip 101 to increase, the static pressure in the lumen of the visual tip 101 decreases and falls below the physiological pressure in the blood vessel, forming a trans-wall pressure difference pointing towards the central axis. Since the inner wall layer of the visual tip 101 has a low modulus and the outer wall layer has a high modulus, the trans-wall pressure difference drives the inner wall layer of the visual tip 101 to collapse inward, making the visual tip 101 present a tapered and sharpened structure, which is conducive to insertion into narrow microchannels. The outer layer 111 of the catheter is made of polyether block polyamide or nylon. The hardness of the outer layer 111 is gradually adjusted by adjusting the material formulation. For example, the hardness of the torsion control section 104 is set to 72D to provide support, the hardness of the flexural section 103 is set to 55D for transition, and the hardness of the coaxial section 102 is set to 40D to provide flexibility. The hydrophilic coating on the surface of the outer layer 111 of the catheter reduces the frictional resistance in the blood vessel.

[0049] See attached document Figure 1 -Appendix Figure 5 This invention provides a method for using a microchannel targeted coronary microcatheter, which is based on the aforementioned microchannel targeted coronary microcatheter and includes the following steps:

[0050] S100, push the microcatheter 100 along the guidewire to the proximal end of the coronary lesion, keep the fluid injection pressure in the lumen 114 less than the working pressure threshold required to generate eddy current, keep the inner layer 113 of the catheter in a laminar flow state, and keep the shear-thickening fluid matrix in the braided layer 112 in a liquid sol state, and use the flexibility of the microchannel-targeted coronary microcatheter for navigation.

[0051] S200. When approaching the occluded lesion and the guidewire cannot pass through, the fluid injection pressure in the lumen 114 is increased to above the working pressure threshold. The hydrophilic and hydrophobic stripes on the surface of the inner layer 113 of the catheter are used to induce the fluid to generate a high-speed spiral jet, forming a vortex nucleus at the outlet of the visible tip 101, thereby aligning with the microchannel entrance.

[0052] S300. While maintaining the fluid injection pressure above the working pressure threshold, the negative pressure generated by the high-speed spiral jet drives the inner wall layer of the visible head end 101 to contract toward the central axis to form a conical sharpening shape. At the same time, the high-frequency micro-vibration induced by the fluid flow triggers the shear thickening fluid matrix in the braided layer 112 to undergo phase change solidification, thereby improving the stiffness of the braided layer 112.

[0053] S400. While maintaining the fluid injection pressure above the working pressure threshold, apply axial thrust, loosen the microchannel tissue with high-speed spiral jet, and pass through the lesion with the support provided by the sharpened visible tip 101 and the hardened braided layer 112.

[0054] S500. After confirming that the lesion has been penetrated, the fluid injection pressure is removed, allowing the visible tip 101 to elastically return to its original diameter, and the shear-thickened fluid matrix to return to a liquid sol state.

[0055] The following section provides a detailed explanation of each of the above steps, taking into account specific structural features:

[0056] In step S100, the operator manipulates the microcatheter 100 for routine navigation. At this time, the external pressurization device connected to the microcatheter 100 is in an unpressurized or low-pressure state, and the fluid injection pressure has not reached the threshold for triggering catheter functional deformation. The hydrophilic and hydrophobic strips on the inner surface of the catheter inner layer 113 are not activated by the fluid, and the fluid maintains a stable laminar flow state when flowing through the lumen 114. At the same time, the shear-thickening fluid matrix filling the gaps in the braided layer 112 exhibits low viscosity liquid sol characteristics due to the shear rate being below the critical value. In this state, relative sliding can occur between the wires, and the microcatheter 100 as a whole exhibits low bending stiffness, which can conform to the tortuous coronary vessel path, helping to reduce advancement resistance and reduce mechanical damage to the vessel wall.

[0057] In step S200, when the microcatheter 100 approaches the lesion (such as a chronically occluded lesion) and the conventional guidewire has difficulty locating the entry point, the operator increases the fluid injection pressure beyond the working pressure threshold using a pressurization device. At this time, the flow velocity within the guide cavity 114 increases, and the fluid boundary layer flows through alternating hydrophilic and hydrophobic bands. Due to the difference in viscous resistance to the fluid from different wettable surfaces, the fluid is driven by a force along the helical tangential direction, converting some of the axial momentum into tangential momentum, thereby forming a high-speed helical jet. When the high-speed helical jet exits the visible tip 101, a vortex with a central negative pressure is formed near the central axis of the flow field. Utilizing the hydrodynamic characteristic that the vortex tends to deflect towards the region of least fluid resistance, the outlet of the visible tip 101 can automatically align with the microchannel entry point on the lesion surface.

[0058] In step S300, as the fluid injection pressure remains above the working pressure threshold, the microcatheter 100 exhibits a dual response in terms of shape and stiffness. On one hand, the increased jet velocity flowing through the visible tip 101 leads to a decrease in the hydrostatic pressure of the internal fluid, falling below the physiological pressure of the external vascular environment, creating a trans-wall pressure differential pointing towards the axis. Since the elastic modulus of the inner wall layer of the visible tip 101 is less than that of the outer wall layer, this pressure differential drives the inner wall layer to collapse inward preferentially, causing the tip to contract into a tapered, sharpened shape, reducing the cross-sectional area of ​​the tip. On the other hand, the turbulent pulsations inside the high-speed spiral jet induce high-frequency micro-vibrations in the catheter wall, subjecting the shear-thickening fluid matrix within the braided layer 112 to high-frequency shearing. When the shear rate exceeds a critical value, the shear-thickening fluid matrix undergoes a phase transition, changing from a liquid sol to a solidified state, restricting the relative displacement of the metal wire. At this point, the stiffness of the catheter shaft increases, entering a rigid mode suitable for puncture.

[0059] In step S400, the operator performs a puncture using the rigid mode of the microcatheter 100. A high-speed spiral jet ejected from the visible tip 101 first applies hydrodynamic impact to the lesion tissue, loosening the micropores on the fibrous cap or calcified tissue surface through the shearing effect of the swirling flow. Subsequently, the operator applies axial thrust, and the sharpened visible tip 101 embeds itself into the fluid-loosened microchannel entrance using a mechanical wedge effect. During this process, the hardened braided layer 112 provides axial support, reducing the risk of the microcatheter 100 buckling or kinking when encountering resistance, ensuring that the thrust is transmitted to the tip, achieving physical penetration of the lesion.

[0060] In step S500, once it is confirmed that the microcatheter 100 has passed through the lesion and entered the true lumen of the blood vessel, the operator stops pressurizing, and the fluid injection pressure drops. As the flow rate decreases, the flow field returns to laminar flow, and the micro-vibration of the vessel wall stops. Utilizing the viscoelastic memory properties of the polymer material, the visible tip 101 gradually elastically returns to its original large-diameter state after the transwall pressure difference is eliminated, thus eliminating lumen narrowing. Simultaneously, the shear-thickened fluid matrix undergoes microstructural rearrangement due to the decrease in shear rate, reliquefying into a sol state and releasing the locking of the metal wire. The microcatheter 100 returns to a compliant state, facilitating subsequent microwire exchange, contrast agent injection, or delivery of other therapeutic devices, and also facilitating safe catheter withdrawal.

Claims

1. A microchannel targeted coronary microcatheter, comprising a microcatheter body (100), characterized in that, The distal end of the microcatheter body (100) is fixedly connected to a visible tip (101). The microcatheter body (100) has an inner catheter layer (113) that surrounds the guide cavity (114) inside, a braided layer (112) is provided on the outside of the inner catheter layer (113), and an outer catheter layer (111) is provided on the outside of the braided layer (112). The inner surface of the inner layer (113) of the conduit is provided with hydrophilic strips and hydrophobic strips that extend spirally along the axial direction and are arranged alternately. The hydrophilic strips and the hydrophobic strips are configured to induce the fluid to generate a tangential velocity component along the spiral direction when the fluid flow rate in the cavity (114) exceeds the working flow rate threshold. The braided layer (112) is made of metal wires, and the gaps between the metal wires are filled and encapsulated with a shear-thickening fluid matrix. The shear-thickening fluid matrix is ​​configured to be in a liquid sol state at a low shear rate and to restrict the relative sliding between the metal wires by phase change solidification at a high shear rate induced by the high-frequency micro-vibration generated by the fluid flow in the guide cavity (114). The visible head end (101) is made of a polymer material with a radial gradient modulus. The visible head end (101) includes an inner wall layer and an outer wall layer. The elastic modulus of the inner wall layer is less than that of the outer wall layer. The inner wall layer is configured to contract toward the central axis to form a tapered sharpened structure when the fluid flow rate in the guide cavity (114) increases, causing the static pressure in the cavity to decrease.

2. The microchannel targeted coronary microcatheter according to claim 1, characterized in that, The angle between the helix of the hydrophilic strip and the hydrophobic strip and the central axis of the conduit is between 15 degrees and 45 degrees, and the width of a single strip in the hydrophilic strip and the hydrophobic strip is between 10 micrometers and 100 micrometers.

3. The microchannel targeted coronary microcatheter according to claim 1, characterized in that, The surface material of the hydrophilic strip has a contact angle between 0 and 30 degrees, and the surface material of the hydrophobic strip has a contact angle between 120 and 180 degrees.

4. The microchannel targeted coronary microcatheter according to claim 1, characterized in that, The shear-thickening fluid matrix is ​​a nano-silica suspension dispersed in polyethylene glycol; The shear-thickening fluid matrix has thixotropic properties and is configured to return from a solidified state to a liquid sol state after the high-frequency micro-vibration is removed.

5. The microchannel targeted coronary microcatheter according to claim 1, characterized in that, The visual head end (101) has an initial relaxed state and an activated sharpening state; In the initial relaxed state, the visible tip (101) maintains its original inner diameter, which is greater than or equal to the inner diameter of the lumen (114) at the microcatheter body (100); In the activated sharpening state, the visible head end (101) is in a radially contracted state driven by the transwall pressure difference and is configured to recover to the initial relaxed state by utilizing the viscoelasticity of the material after the fluid pressure is removed.

6. The microchannel targeted coronary microcatheter according to claim 1, characterized in that, The microcatheter body (100) includes, from near to far along the axial direction, a torsion control section (104), a flexural resistance section (103), and a coaxial section (102). The material hardness of the outer layer (111) of the catheter corresponding to the torsion control section (104), the flexural resistance section (103), and the coaxial section (102) decreases sequentially. The outer surface of the outer layer (111) of the catheter is coated with a hydrophilic coating.

7. The microchannel targeted coronary microcatheter according to claim 1, characterized in that, The inner layer (113) of the catheter is made of polytetrafluoroethylene or high-density polyethylene; the metal wire is stainless steel wire or nickel-titanium alloy wire; the outer layer (111) of the catheter is made of polyether block polyamide or nylon; the polymer material used in the visual tip (101) is specifically thermoplastic polyurethane or polyether block polyamide, and the visual tip (101) is doped with a developer selected from platinum-iridium alloy powder or tungsten powder.

8. A method for using a microchannel targeted coronary microcatheter, characterized in that, The microchannel targeted coronary microcatheter as described in any one of claims 1 to 7 comprises the following steps: S100. Push the microchannel-targeted coronary microcatheter along the guidewire to the proximal end of the coronary lesion. During the pushing process, keep the fluid injection pressure in the lumen (114) less than the working pressure threshold required to generate eddy current, so that the inner layer (113) of the catheter maintains laminar flow characteristics and the shear-thickening fluid matrix located in the braided layer (112) is in a liquid sol state. S200. When approaching the occluded lesion and the guidewire cannot pass through, the fluid injection pressure in the guide lumen (114) is increased to above the working pressure threshold. The hydrophilic and hydrophobic stripes on the surface of the inner layer (113) of the catheter are used to induce the fluid to generate a high-speed spiral jet, forming a vortex nucleus at the outlet of the visible tip (101), and the vortex nucleus is used to align with the microchannel inlet. S300. While maintaining the fluid injection pressure above the working pressure threshold, the negative pressure generated by the high-speed spiral jet drives the visible head end (101) to contract toward the central axis to form a conical sharpening shape. At the same time, the high-frequency micro-vibration induced by the high-speed spiral jet triggers the shear thickening fluid matrix in the braided layer (112) to undergo phase change solidification. S400. While maintaining the fluid injection pressure above the working pressure threshold, apply axial thrust and use the visible tip (101) in the tapered sharpening state and the braided layer (112) in the solidified state to pass through the lesion. S500. After confirming that the fluid has passed through the lesion, the fluid injection pressure is removed, so that the visible tip (101) is restored to its original diameter, and the shear-thickening fluid matrix is ​​restored to the liquid sol state.

9. The method of using a microchannel targeted coronary microcatheter according to claim 8, characterized in that, In step S200, the high-speed helical jet is formed by the tangential velocity component generated when the fluid flows through the hydrophilic strip and the hydrophobic strip; In step S300, the contraction of the visible head end (101) is driven by the transwall pressure difference formed by the decrease in internal static pressure caused by the high-speed spiral jet.

10. The method of using a microchannel targeted coronary microcatheter according to claim 8, characterized in that, In step S300, the phase change solidification of the shear-thickening fluid matrix is ​​triggered by the high-frequency micro-vibration induced by the high-speed helical jet on the inner wall of the conduit (113); In step S500, as the fluid injection pressure is removed, the visible tip (101) recovers by utilizing the viscoelastic memory properties of the material.

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