A soft magnetic guide wire with strong deflection properties and its preparation method

Abstract

This invention provides a novel soft magnetic guidewire with deflection properties and its preparation method. Silicone is mixed and stirred with pre-magnetized neodymium iron boron magnetic powder to obtain a silicone rubber precursor, eliminating air trapped within the precursor. The silicone rubber precursor is injected into a hollow cylindrical mold, and concentric guidewires are placed inside the mold. The precursor is then cured to form a magnetic guidewire. PDMS mixed with a curing agent is coated onto the contact surface between the cured magnetic guidewire and the concentric guidewire. The magnetic guidewire is immersed in a hydrophilic coating solution; it is then magnetized in a magnetizer; and finally cooled using an ice water cooler. This invention provides a magnetic guidewire with strong deflection properties. Building upon properties such as super-lubricity, biocompatibility, flexibility, elasticity, and magnetism, the magnetic guidewire significantly improves deflection performance, thereby enhancing the safety and operability of the magnetic guidewire during in vivo navigation and reducing surgical time and risks.

Description

Technical Field

[0001] This invention provides a soft magnetic guide wire with strong deflection properties and its preparation method, belonging to the field of medical device technology. Background Technology

[0002] Disposable medical catheters / guidewires are the most frequently used routine surgical instruments in minimally invasive surgery. In magnetic navigation surgical robot-assisted minimally invasive surgery, the magnetic navigation surgical robot system uses a specially designed guidewire with a permanent magnet or ferromagnetic object at the distal end. The external large magnet generates a gradient magnetic field space in the patient's torso. By controlling the angle and distance of the external magnet, the force generated on the distal magnet of the guidewire is changed, thereby changing the orientation of the distal end of the guidewire and achieving the purpose of distal guidance.

[0003] After entering the human body, the magnetic guide wire needs to pass through a series of vascular bifurcations to reach the lesion site, which places high demands on the deflection performance of the magnetic guide wire. When the lesion location in the patient's body is complex and ordinary magnetic guide wires are difficult to penetrate, magnetic guide wires with strong deflection performance must be selected for interventional surgery. When the magnetic guide wire has strong deflection performance, it can not only pass through complex intravascular bifurcations more easily, but also adapt to complex anatomical structures and move in rapidly changing intravascular environments.

[0004] In the existing technology, most researchers do not consider the optimization design of deflection performance when designing magnetic wires. The few studies that exist usually improve the deflection performance of magnetic wires by integrating one or more permanent magnets inside the magnetic wire, increasing the magnetic powder content as much as possible, and optimizing the PDMS ratio. However, there are still technical defects such as poor safety performance and insufficient consideration of details.

[0005] One existing technique (S. Jeon, AK Hoshiar, K. Kim, S. Lee, E. Kim, S. Lee, J.-y. Kim, BJ Nelson, H.-J. Cha, B.-J. Yi, et al., “A magnetically controlled soft microrobotsteering a guidewire in a three-dimensional phantom vascular network,” Softrobotics, vol. 6, no. 1, pp. 54–68, 2019) first places two micro NdFeB permanent magnets coaxially with a spring coil in a cylindrical mold. Then, prepared polydimethylsiloxane (PDMS) is injected into the mold, and the magnetic guidewire is prepared after the PDMS cures. During the PDMS curing process, the two micro NdFeB permanent magnets are connected to the spring coil through the PDMS. The micro NdFeB permanent magnet at the head end enhances the magnetic response capability at the head end of the magnetic guidewire, while the micro NdFeB permanent magnet at the tail end enhances the magnetic response capability at the tail end.

[0006] The disadvantages of this technology are:

[0007] Disadvantage 1: Friction between the tip and the vessel wall. Using NdFeB permanent magnets as the magnetic response device for the magnetic guide wire results in unnecessary friction between the guide wire and the vessel wall during intravascular navigation due to differences in hardness, density, and weight between NdFeB permanent magnets and PDMS. This increases the probability of intraoperative bleeding and postoperative complications.

[0008] Disadvantage 2: Poor safety. In this technology, the magnetic guide wire is made up of a variety of materials with incompatible physical properties, such as PDMS, micro NdFeB permanent magnets, and spring coils. The internal structure is complex, the hardness and mechanical properties of different parts are inconsistent, and the connection between different components is not firm. This makes the magnetic guide wire very easy to break or fall off when navigating in blood vessels.

[0009] Disadvantage 3: Uneven distribution of deflection performance. Although the existing technology [1] uses two high-grade (N52) neodymium iron boron permanent magnets to improve the deflection performance of the magnetic wire, the controlled magnetic response only exists in the part where the permanent magnet is located. In the parts where there is no permanent magnet, such as the elastic link between permanent magnets made of PDMS and the micro spring coil, the control and deflection performance are often ignored.

[0010] The second existing technology (Y. Kim, G.A. Parada, S. Liu, and X. Zhao, “Ferromagnetic softcontinuum robots,” Science Robotics, vol. 4, no. 33, 2019.) first involves uniformly mixing unmagnetized NdFeB powder with PDMS at a 1:1 mass ratio to obtain a magnetic fluid. Then, the magnetic fluid is evacuated to remove internal air bubbles. Subsequently, the magnetic fluid is injected into a silicone tube using a micro-injector. Next, a custom-designed micro NdFeB permanent magnet is inserted into one end of the silicone tube, and a conventional guide wire is inserted into the other end to complete the magnetic guide wire fabrication. Finally, the prepared magnetic guide wire is placed in an oven and baked at 55°C for 18 hours to completely solidify it. This technical solution uses both neodymium iron boron permanent magnets and magnetofluid as magnetic response devices for magnetic guide wires. However, it still has problems such as discontinuous internal structure, inconsistent mechanical properties, and easy detachment of the head end. In addition, the configuration of magnetofluid is fixed at 1:1, and no targeted optimization design is made for the formulation of magnetofluid. The overall deflection performance of the magnetic guide wire is not adequately considered.

[0011] The disadvantages of this technology are:

[0012] Disadvantage 1: Friction between the tip and the vessel wall. Because NdFeB permanent magnets are used as the magnetic response device for the magnetic guide wire, and the properties of NdFeB permanent magnets, such as hardness, density, and weight, differ from those of magnetic fluids, the magnetic guide wire will generate unnecessary friction with the vessel wall during intravascular navigation, increasing the probability of intraoperative bleeding and postoperative complications.

[0013] Disadvantage 2: Poor safety. The magnetic wire prepared by this technology integrates multiple materials with inconsistent physical properties, such as PDMS, neodymium iron boron powder, and micro NdFeB permanent magnets. The internal structure is complex, and the hardness and mechanical properties of different parts are inconsistent. The connection between the neodymium iron boron permanent magnet and the magnetofluid is not firm, which makes the neodymium iron boron permanent magnet at the tip very easy to break or fall off during intravascular navigation.

[0014] Disadvantage 3: Inconsistent deflection performance. Although the second prior art, compared with the first prior art, uses a high-grade neodymium iron boron permanent magnet and a magnetic fluid as a magnetic response device for the magnetic guide wire, it partially makes up for the disadvantage 3 of the prior art [1]. However, the deflection performance of the magnetic fluid and the neodymium iron boron permanent magnet is not consistent. Under the same magnetic field strength, the permanent magnet per unit volume has a larger deflection amplitude than the magnetic fluid per unit volume. This makes the internal deflection performance of the magnetic guide wire prepared by the second prior art inconsistent. It is manifested that under the same magnetic field strength, the deflection amplitude of the permanent magnet at the head end is greater than that of the magnetic fluid at the tail end.

[0015] The third existing technology (Kim Y, Genevriere E, Harker P, et al. Telerobotic neurovascular interventions with magnetic manipulation[J]. Science Robotics, 2022, 7(65): eabg9907) improves the deflection performance of magnetic wires by optimizing the PDMS ratio. In this technology, neodymium iron boron microparticles with an average particle size of 5 μm are uniformly mixed with PDMS and its curing agent. After permanently magnetizing the neodymium iron boron microparticles with an average particle size of 5 μm, a paste with shear yielding and shear dilution characteristics is prepared. The paste is placed into a magnetic wire mold by extrusion and then heated and cured to complete the preparation of the magnetic wire. During the PDMS ratio optimization process, the deflection performance of magnetic wires with different PDMS ratios under the same magnetic field strength was tested. Finally, the PDMS ratio that causes the magnetic wire to deflect to the maximum was selected as the optimal ratio.

[0016] The disadvantages of this technology are:

[0017] Disadvantage 1: It only applies to PDMS, which is not the optimal design material for magnetic wires. This technical solution only optimizes the design for the PDMS ratio, and does not make corresponding optimization designs for other flexible materials, such as Ecoflex 00-10 silicone produced by Smooth-On. Summary of the Invention

[0018] Therefore, the present invention provides a novel soft magnetic guide wire with deflection performance, which can significantly improve the deflection performance of the magnetic guide wire while meeting the requirements of safety, flexibility, elasticity and magnetic properties.

[0019] Deflection performance definition: Under the same magnetic field strength, the larger the deflection angle of the magnetic wire, the better the deflection performance of the magnetic wire, and vice versa.

[0020] A soft magnetic guide wire with strong deflection properties is prepared by means of the following steps:

[0021] Step 1: Pre-magnetization stage

[0022] First, weigh a certain amount of NdFeB magnetic powder and put it into a magnetizer for magnetization. After magnetization, use an ice water machine to cool it down, thus completing the pre-magnetization stage of the NdFeB magnetic powder.

[0023] The magnetizer has a voltage of 3000 volts, a capacitor capacity of 3000UF, an axial magnetization direction, a magnetic field strength of 5T, and a magnetization time of 1 second.

[0024] The particle size of neodymium iron boron magnetic powder is 100-5000 mesh, preferably 2000 mesh;

[0025] Step 2: Mix the silicone with pre-magnetized neodymium iron boron magnetic powder until homogeneous to obtain the silicone rubber precursor.

[0026] The mass ratio of silicone to pre-magnetized neodymium iron boron magnetic powder is 1:0.1 to 5, preferably 1:1.

[0027] Step 3: Use a vacuum pump to remove the air mixed in the silicone rubber precursor; after vacuum treatment, inject the silicone rubber precursor into a hollow cylindrical mold, and place concentric guide wires inside the mold at the same time.

[0028] The mold is made of TPU material, which is biocompatible, and has an inner diameter of 0.4 mm and an outer diameter of 0.7 mm.

[0029] The concentric guidewire has a diameter of 0.3 mm and is made of Nitinol material;

[0030] Step 4: The mold containing the silicone rubber precursor and the concentric guide wire is left to stand vertically at 26 degrees Celsius for 48 hours to completely solidify into a magnetic guide wire.

[0031] Step 5: Apply PDMS mixed with a quantitative curing agent to the contact surface of the cured magnetic wire and the concentric wire. After coating, place the magnetic wire in an oven to dry, and obtain the magnetic wire; the sides and head of the magnetic wire have a biocompatible layer composed of a mold, and the contact surface of the magnetic wire and the concentric wire has a biocompatible layer composed of PDMS.

[0032] The drying conditions are: 25-150℃, 0.5-48 hours, preferably drying at 170℃ for 30 minutes.

[0033] Step Six: Place the prepared magnetic wire in a hydrophilic coating solution and immerse it to complete the preparation of the hydrophilic coating on the magnetic wire. Thus, the magnetic wire comprises a silicone rubber precursor composed of a mixture of silica gel and neodymium iron boron particles, a biocompatible coating, and an outermost hydrophilic coating.

[0034] The hydrophilic coating material is any one or a mixture of the following:

[0035] Polyvinylpyrrolidone;

[0036] Composite hydrogel based on gelatin and sodium alginate;

[0037] A photosensitive hydrogel based on gelatin and modified by methacrylation;

[0038] Composite hydrogels based on collagen and chitosan;

[0039] Photosensitive hydrogel based on polyethylene glycol diacrylate chemical modification

[0040] based on F-127 hydrogel;

[0041] The concentration of the hydrophilic coating solution is 1%-60% by volume, preferably 10%;

[0042] Soaking conditions are: 10–100℃, 0.1–5 hours; preferably, soaking at room temperature for 30 minutes.

[0043] Step 7: Saturation Magnetization Stage. Place the magnetic wire into the magnetizer for magnetization; and after magnetization is completed, use an ice water machine to cool it down.

[0044] The magnetizer has a voltage of 3000 volts, a capacitor capacity of 3000UF, an axial magnetization direction, a magnetic field strength of 5T, and a magnetization time of 1 second.

[0045] This invention provides a magnetic guide wire with strong deflection performance. By designing the optimal mass ratio of silicone and neodymium iron boron powder, the formed magnetic guide wire not only possesses properties such as super-slipperiness, biocompatibility, flexibility, elasticity, and magnetism, but also significantly improves deflection performance. This can significantly improve the safety and operability of the magnetic guide wire during in vivo navigation, and reduce surgical operation time and operational risks. Detailed Implementation

[0046] The specific technical solutions of the present invention will be described with reference to the embodiments.

[0047] Example 1

[0048] A soft magnetic guide wire with strong deflection properties is prepared by means of the following steps:

[0049] Step 1: Pre-magnetization stage. First, weigh a certain weight of 2000-mesh neodymium iron boron (NdFeB) magnetic powder and place it into a MA-3030 magnetizer manufactured by Shenzhen Jiuju Automation Co., Ltd. Set the magnetizer voltage parameters to 3000 volts, the capacitor capacity to 3000UF, the magnetization direction to axial magnetization, the magnetization magnetic field strength to 5T, and the magnetization time to 1 second. After magnetization, use an LS-1P chiller manufactured by Shenzhen Jiuju Automation Co., Ltd. to cool down the powder, thus completing the pre-magnetization stage of the neodymium iron boron magnetic powder.

[0050] Step 2: Mix Smooth-On's Ecoflex 00-10 or Ecoflex 00-50 silicone with pre-magnetized 2000-mesh neodymium iron boron magnetic powder until homogeneous to obtain the silicone rubber precursor.

[0051] Step 3: Use a vacuum pump to remove air mixed in the silicone rubber precursor. After vacuum treatment, inject the silicone rubber precursor into a hollow cylindrical mold, and simultaneously place a concentric guidewire (0.3mm diameter, Nitinol material, Reflex steerable guidewire, Cordis Corporation, USA) inside the mold. The mold is made of TPU material, is biocompatible, and has an inner diameter of 0.4mm and an outer diameter of 0.7mm to maximize the fit to clinical guidewire sizes.

[0052] Step 4: The TPU mold containing the silicone rubber precursor and concentric guide wires is left to stand vertically at 26 degrees Celsius for 48 hours to fully cure.

[0053] Step 5: Coat the contact surface between the cured magnetic wire and the concentric wire with PDMS mixed with a quantitative curing agent. After coating, place the magnetic wire in an oven and dry it at 170°C for 30 minutes to complete the magnetic wire preparation. The sides and head of the magnetic wire have a biocompatible layer composed of TPU, and the contact surface between the magnetic wire and the concentric wire has a biocompatible layer composed of PDMS.

[0054] Step Six: Place the prepared magnetic wire in a 10% polyvinyl pyrrolidone (PVP) solution (by volume) and immerse it completely at 26°C for 30 minutes to complete the preparation of the hydrophilic coating on the magnetic wire. Thus, the magnetic wire comprises a silicone rubber precursor composed of a mixture of Ecoflex 00-10 and NdFeB particles, a biocompatible coating, and an outermost hydrophilic PVP coating.

[0055] Step 7: Saturation Magnetization Stage. Place the magnetic wire into the MA-3030 magnetizer manufactured by Shenzhen Jiuju Automation Co., Ltd. Use the CS-120 magnetizer fixture manufactured by Shenzhen Jiuju Automation Co., Ltd. to fix the magnetic wire. Set the magnetizer voltage parameters to 3000 volts, the capacitor capacity to 3000UF, the magnetization direction to axial magnetization, the magnetization magnetic field strength to 5T, and the magnetization time to 1 second. After magnetization, use the LS-1P chiller manufactured by Shenzhen Jiuju Automation Co., Ltd. to cool down the wire. After cooling, remove the magnetic wire to complete the saturation magnetization stage of the magnetic wire.

[0056] This invention designs the optimal mass ratio of Ecoflex 00-10 silicone to 2000-mesh neodymium iron boron powder, which significantly improves the deflection performance of the molded magnetic wire. This can significantly improve the safety and operability of the magnetic wire during in vivo navigation, and reduce surgical operation time and risks.

[0057] This invention uses 2000-mesh NdFeB microparticles instead of micro-permanent magnets as the magnetic response material at the tip of the magnetic wire. The 2000-mesh NdFeB microparticles have a diameter of approximately 6.5 micrometers. After being mixed with Ecoflex 00-10 type silicone, the magnetic wire has the same internal mechanical properties and a continuous structure. This eliminates the problem of the tip naturally sagging due to differences in hardness, density, and weight found in existing technologies. Furthermore, because the magnetic wire prepared by this invention is structurally continuous, there are no joints between the NdFeB microparticles and the Ecoflex 00-10 type silicone, avoiding the poor safety issues at the joints caused by differences in mechanical properties at the joints found in existing technologies. Therefore, this invention offers better safety compared to existing technologies.

[0058] This invention uses Ecoflex 00-10 type silicone as the design material for magnetic wires. Ecoflex 00-10 type silicone has better elasticity than PDMS, which can make the prepared magnetic wires have stronger deflection ability. Furthermore, this invention has designed the optimal ratio of Ecoflex 00-10 type silicone to 2000 mesh NdFeB magnetic powder through testing, so that the prepared magnetic wires have the best deflection performance.

[0059] Regarding deflection performance, the magnetic guide wire with strong deflection performance obtained in this invention was compared through deflection tests. The test results are as follows:

[0060] Deflection performance test comparison experiment 1: First, 10 magnetic wires with different mass ratios but the same size, composition, and no biocompatible or hydrophilic coatings on their surfaces were prepared. The silicone rubber precursors of these 5 magnetic wires were all composed of Ecoflex 00-10 silicone and 2000-mesh NdFeB particles. The mass ratios of Ecoflex 00-10 silicone to 2000-mesh NdFeB particles were 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, and 1:2, respectively. Then, the 10 magnetic wires with different mass ratios were placed in a uniform magnetic field environment, and the deflection angles of the 10 magnetic wires under the same magnetic field strength (5 millite) were tested and recorded. The test results are shown in Table 1.

[0061] Table 1. Test results of magnetic wire deflection with different mass ratios.

[0062]

[0063] Test results show that as the mass ratio of Ecoflex 00-10 silicone to 2000-mesh NdFeB particles increases from 1:0.2 to 1:1.4, the deflection angle of the magnetic wire under the same magnetic field strength increases from 4 degrees to 17 degrees. The deflection performance increases with the increase in the content of 2000-mesh NdFeB particles. However, when the mass ratio of Ecoflex 00-10 silicone to 2000-mesh NdFeB particles exceeds 1:1.4, the deflection performance of the magnetic wire decreases with increasing mass ratio. This is because a higher mass ratio results in a higher NdFeB particle content in the magnetic wire, while a lower proportion of Ecoflex 00-10 silicone means that the small amount of Ecoflex 00-10 silicone cannot provide the flexibility and elasticity required for a larger deflection. Consequently, the magnetic wire deflects in a near-straight line rather than a bent state. Therefore, a mass ratio of 1:1.4 is chosen as the formulation to achieve the best deflection performance.

[0064] Deflection performance test comparison experiment 2: First, four magnetic wires of the same size and mass ratio (1:1.4) were prepared, none of which had biocompatible or hydrophilic coatings on their surfaces. The silicone rubber precursors of these four magnetic wires were composed of: Ecoflex 00-10 silicone rubber + 2000-mesh NdFeB microparticles, Ecoflex 00-20 silicone rubber + 2000-mesh NdFeB microparticles, Ecoflex 00-30 silicone rubber + 2000-mesh NdFeB microparticles, and Ecoflex 00-50 silicone rubber + 2000-mesh NdFeB microparticles, respectively. Then, the four magnetic wires with different mass ratios were placed in a uniform magnetic field environment, and the deflection angles of the four magnetic wires under the same magnetic field strength (5 millitrile) were tested and recorded. The test results are shown in Table 2.

[0065] Table 2. Magnetic wire deflection test results for different silicone compositions

[0066]

[0067]

[0068] Test results show that Ecoflex 00-10 performs best in the Ecoflex series. Magnetic wires made based on Ecoflex 00-10 can achieve a larger deflection angle under the same magnetic field strength. This is because Ecoflex 00-10 has a smaller elastic modulus (up to 8 psi) and the lowest hardness (Shore hardness of 0-10). The better flexibility allows Ecoflex 00-10 to carry more 2000-mesh NdFeB powder under the same conditions, while losing less of the elasticity required for magnetic wire deflection.

[0069] Deflection performance test comparison experiment 3: First, prepare two magnetic wires of the same size, neither of which has a biocompatible coating or a hydrophilic coating on its surface. The silicone rubber precursor compositions of these two magnetic wires are: Ecoflex 00-10 type silicone rubber + 2000 mesh NdFeB microparticles, and PDMS + 2000 mesh NdFeB microparticles, respectively. The magnetic wire based on Ecoflex 00-10 type silicone rubber was manufactured with a mass ratio of Ecoflex 00-10 type silicone rubber to 2000 mesh NdFeB microparticles of 1:1.4; the magnetic wire based on PDMS was manufactured with a volume ratio of PDMS to 2000 mesh NdFeB microparticles of 4:1. Then, two magnetic wires with different mass ratios and different silica gel compositions were placed in the same uniform magnetic field environment. The deflection angles of the two magnetic wires under the same magnetic field strength (5 millite) were tested and recorded. The test results showed that the magnetic wire prepared based on the mass ratio of Ecoflex 00-10 silica gel to 2000-mesh NdFeB particles of 1:1.4 could deflect 17 degrees, while the magnetic wire prepared based on the volume ratio of PDMS to 2000-mesh NdFeB particles of 4:1 could deflect approximately 15 degrees. It can be seen that the magnetic wire prepared based on the mass ratio of Ecoflex 00-10 silica gel to 2000-mesh NdFeB particles of 1:1.4 has better deflection performance.

[0070] Example 2

[0071] The preparation method is the same as in Example 1, except that Ecoflex 00-10 silicone is replaced with Ecoflex 00-50 silicone.

[0072] This invention uses 2000-mesh NdFeB microparticles instead of micro permanent magnets as the magnetic response material at the tip of the magnetic wire. The diameter of the 2000-mesh NdFeB microparticles is about 6.5 micrometers. After being mixed with Ecoflex 00-50 type silicone, the internal mechanical properties of the magnetic wire are the same and the structure is continuous. There is no problem of the tip naturally drooping due to differences in hardness, density and weight in the prior art. Since the magnetic wire prepared by this invention is continuous in structure, there is no connection between the NdFeB microparticles and Ecoflex 00-50 type silicone, which avoids the problem of poor tensile performance at the connection due to differences in mechanical properties at the connection in the prior art [1]. Therefore, this invention has better safety compared with the prior art.

[0073] All operations of this invention can be performed at room temperature, eliminating the need for complex temperature control and effectively lowering the barrier to entry for magnetic wire preparation and production. Furthermore, since the curing of Ecoflex 00-50 silicone can be carried out at room temperature, vacuuming (step three) can be performed, whereas the TPU material in the prior art needs to remain in a molten state and cannot be vacuumed. Therefore, the magnetic wire prepared by this invention has a uniform internal material and does not produce the fine pores found in the prior art, avoiding safety issues in magnetic wire operation caused by pores.

[0074] Regarding tensile strength, the tensile strength tests of the magnetic guide wire with tensile properties obtained in this invention are compared below, and the test results are as follows:

[0075] Tensile Strength Test Comparison Experiment 1: Tensile strength tests were conducted on the magnetic guide wires with tensile properties obtained in this invention within the Ecoflex series products. First, four magnetic guide wires of identical size and mass ratio, with no biocompatible or hydrophilic coatings on their surfaces, were prepared. The silicone rubber precursor compositions of these four magnetic guide wires were: Ecoflex 00-10 silicone rubber + 2000-mesh NdFeB microparticles, Ecoflex 00-20 silicone rubber + 2000-mesh NdFeB microparticles, Ecoflex 00-30 silicone rubber + 2000-mesh NdFeB microparticles, and Ecoflex 00-50 silicone rubber + 2000-mesh NdFeB microparticles, respectively. Then, according to the ASTM D412 standard test method, the tensile strength of the four magnetic guide wires stretched to the fracture point was tested using an electronic universal testing machine. Test results show that Ecoflex 00-10 silicone + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 3.4 MPa, Ecoflex 00-20 silicone + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 6.7 MPa, Ecoflex 00-30 silicone + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 9.8 MPa, and Ecoflex 00-50 silicone + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 13.7 MPa. It can be seen that, among products in the same series, the magnetic wire made of Ecoflex 00-50 silicone + NdFeB microparticles exhibits better tensile properties.

[0076] Comparative Experiment 2 on Tensile Strength Testing: First, four magnetic wires of identical size and mass ratio, with no biocompatible or hydrophilic coatings on their surfaces, were prepared. The silicone rubber precursor compositions of these four magnetic wires were: Ecoflex 00-50 silicone rubber + 2000-mesh NdFeB microparticles, PDMS + 2000-mesh NdFeB microparticles, TPU + 2000-mesh NdFeB microparticles, and two-component silicone rubber BL-620 + 2000-mesh NdFeB microparticles, respectively. Then, according to the ASTM D412 standard test method, the tensile strength of the four magnetic wires stretched to the fracture point was tested using an electronic universal testing machine. Test results show that Ecoflex 00-50 silicone + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 13.7 MPa, PDMS + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 0.8 MPa, TPU + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 12 MPa, and two-component silicone rubber BL-620 + 2000-mesh NdFeB microparticles can withstand a maximum tensile stress of approximately 3.5 MPa. It can be seen that, compared with PDMS, TPU, and two-component silicone rubber BL-620, the magnetic wire made of Ecoflex 00-50 silicone + 2000-mesh NdFeB microparticles exhibits better tensile properties.

[0077] Tensile Strength Test Comparison Experiment 3: First, five magnetic wires with different mass ratios but identical dimensions, compositions, and surfaces without biocompatible or hydrophilic coatings were prepared. The silicone rubber precursors of these five magnetic wires were all composed of Ecoflex 00-50 silicone rubber and 2000-mesh NdFeB microparticles, with mass ratios of Ecoflex 00-50 silicone rubber to 2000-mesh NdFeB microparticles of 1:0.5, 1:1, 1:1.5, 1:2, and 1:2.5, respectively. Then, according to the ASTM D412 standard test method, the tensile strength of the five magnetic wires stretched to the fracture point was tested using an electronic universal testing machine. Test results show that the magnetic wire with a mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles of 1:0.5 can withstand a maximum tensile stress of approximately 12.3 MPa; the magnetic wire with a mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles of 1:1 can withstand a maximum tensile stress of approximately 13.7 MPa; the magnetic wire with a mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles of 1:1.5 can withstand a maximum tensile stress of approximately 12.5 MPa; the magnetic wire with a mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles of 1:2 can withstand a maximum tensile stress of approximately 10.3 MPa; and the magnetic wire with a mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles of 1:2.5 can withstand a maximum tensile stress of approximately 8.8 MPa. It can be seen that as the mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles increases from 1:0.5 to 1:1, the tensile strength of the magnetic wire improves. This is because the ratio of silicone to 2000-mesh NdFeB particles in the magnetic wire is more balanced at this point. However, when the mass ratio of Ecoflex 00-50 silicone to 2000-mesh NdFeB particles exceeds 1:1, the tensile strength of the magnetic wire decreases with increasing mass ratio. This is because as the mass ratio increases, the NdFeB particle content in the magnetic wire increases, resulting in higher overall hardness, making the material more brittle and less flexible and elastic. Correspondingly, the tensile strength of the magnetic wire also decreases. Therefore, a mass ratio of 1:1 is chosen as the optimal formulation.

Claims

1. A method for preparing a soft magnetic guide wire with strong deflection properties, characterized in that, Includes the following steps: Step 1: Pre-magnetization stage Neodymium iron boron magnetic powder is placed in a magnetizer for magnetization; after magnetization, it is cooled down using an ice water machine to complete the pre-magnetization stage of the neodymium iron boron magnetic powder. Step 2: Mix the silicone with pre-magnetized neodymium iron boron magnetic powder until homogeneous to obtain the silicone rubber precursor; Step 3: Use a vacuum pump to remove the air mixed in the silicone rubber precursor; after vacuum treatment, inject the silicone rubber precursor into a hollow cylindrical mold, and place concentric guide wires inside the mold at the same time. Step 4: The mold containing the silicone rubber precursor and the concentric guide wire is left to stand vertically at 26 degrees Celsius for 48 hours to completely solidify into a magnetic guide wire. Step 5: Coat the contact surface of the cured magnetic wire and the concentric wire with PDMS mixed with curing agent; after coating, place the magnetic wire in an oven to dry, and obtain the magnetic wire; the side and head of the magnetic wire have a biocompatible layer composed of mold, and the contact surface of the magnetic wire and the concentric wire has a biocompatible layer composed of PDMS. Step 6: Place the prepared magnetic wire in a hydrophilic coating solution and immerse it to complete the preparation of the hydrophilic coating of the magnetic wire; at this point, the magnetic wire includes a silicone rubber precursor made of a mixture of silicone and neodymium iron boron particles, a biocompatible coating, and an outermost hydrophilic coating. Step 7: Saturation magnetization stage; place the magnetic wire into the magnetizer for magnetization; and use an ice water machine to cool it down after magnetization is completed.

2. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, In step one, the magnetizer voltage is 3000 volts, the capacitor capacity is 3000UF, the magnetization direction is axial, the magnetic field strength is 5T, and the magnetization time is 1 second.

3. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, The neodymium iron boron magnetic powder has a particle size of 100-5000 mesh.

4. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, In step two, the mass ratio of silicone to pre-magnetized neodymium iron boron magnetic powder is 1:0.1 to 5.

5. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, In step three, the mold is made of TPU material, which is biocompatible, with an inner diameter of 0.4 mm and an outer diameter of 0.7 mm.

6. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, The concentric guidewire has a diameter of 0.3 mm and is made of nickel-titanium alloy.

7. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, In step five, the drying conditions are: 25–150℃, 0.5–48 hours.

8. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, In step six, the hydrophilic coating material is any one or a mixture of the following: Polyvinylpyrrolidone; Composite hydrogel based on gelatin and sodium alginate; A photosensitive hydrogel based on gelatin and modified by methacrylation; Composite hydrogels based on collagen and chitosan; Photosensitive hydrogel based on polyethylene glycol diacrylate chemical modification based on F-127 hydrogel; The concentration of the hydrophilic coating solution is 1%-60% by volume; Soaking conditions: 10-100℃, 0.1-5 hours.

9. The method for preparing a soft magnetic guide wire with strong deflection performance according to claim 1, characterized in that, In step seven, the magnetizer voltage is 3000 volts, the capacitor capacity is 3000UF, the magnetization direction is axial, the magnetic field strength is 5T, and the magnetization time is 1 second.

10. A soft magnetic guide wire with strong deflection properties obtained by the preparation method according to any one of claims 1 to 9.

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