A highly biocompatible implantable ultra-fine stranded conductor and its manufacturing method

Abstract

This invention provides a highly biocompatible implantable ultra-fine stranded conductor and its manufacturing method. The conductor is formed by stranding several composite monofilaments together. The composite monofilaments are composed of a core wire made of a high-strength inert alloy material and a high-purity silver and corrosion-resistant layer sequentially wrapped around the core wire. This allows the stranded conductor to maintain excellent biocompatibility, conductivity, signal transmission, fatigue resistance, and oxidation and corrosion resistance in the body for a long time, and it also has good solderability, meeting the long-term implantation requirements of biomedicine.

Description

Technical Field

[0001] This invention relates to the field of biomedical implantable conductor technology, and in particular to a highly biocompatible implantable ultrafine stranded conductor and its manufacturing method. Background Technology

[0002] Long-term implants require reliable biocompatibility, especially given the significant development and application of electrical signal transmission in implant therapy in recent years. This necessitates that cables transmitting signals or currents possess high transmission efficiency, flexibility, fatigue resistance, and biocompatibility. Furthermore, implant size is often limited by volume, and the presence of multiple signal pathways places extremely high demands on the electromechanical performance of conductors suitable for long-term implantation.

[0003] Chinese patent CN201210558926.3 discloses a biomedical heating composite material and its preparation method. The method involves cleaning the surfaces of a nickel-chromium alloy rod and a titanium or titanium alloy tube until the new metal surface is exposed. Then, the nickel-chromium alloy rod is fitted into the titanium or titanium alloy tube and placed inside an explosive composite sleeve to achieve precise positioning, with a tube-rod gap of 0.5-2 mm. Explosives with a thickness of 5-20 mm are evenly distributed between the outside of the titanium or titanium alloy tube and the explosive composite sleeve. The biomedical heating composite material is manufactured through an explosive composite process and appropriate heat treatment. After multiple drawing processes, it is made into a biomedical heating composite filament.

[0004] The aforementioned existing biomedical heating composite materials are used in the preparation of medical (physiotherapy) devices that require heating or implantation of heating in biological and human bodies. They are required to have high resistance properties for use in biomedical heating. For the biomedical field, there is an urgent need to propose a biomedical implantable conductor material that can be implanted in the body for a long time and transmit signals. Summary of the Invention

[0005] One of the objectives of this invention is to address the shortcomings of existing technologies by providing a highly biocompatible implantable ultra-fine stranded conductor. This conductor is formed by stranding several composite monofilaments together. Each composite monofilament consists of a core wire made of a high-strength inert alloy material and a high-purity silver and corrosion-resistant layer sequentially wrapped around the core wire. This allows the stranded conductor to maintain excellent biocompatibility, conductivity, signal transmission, fatigue resistance, and oxidation and corrosion resistance in the body for a long period of time, while also exhibiting good solderability, thus meeting the long-term implantation requirements in biomedicine.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A highly biocompatible implantable ultra-fine stranded conductor is composed of several composite monofilaments twisted together. The composite monofilaments are composed of a core wire of high-strength inert alloy material, a high-purity silver layer wrapped around the core wire, and a corrosion-resistant layer wrapped around the high-purity silver layer, so that the stranded conductor can maintain its strength and transmit signals in the body for a long time.

[0008] The core wire is a nickel-based alloy; the silver content in the high-purity silver layer is not less than 99.99% by mass.

[0009] As an improvement, the nickel-based alloy is an alloy that is corrosion-resistant and biocompatible in living organisms.

[0010] As an improvement, the composition of the nickel-based alloy by weight is as follows: nickel 40-60%, cobalt 0-40%, chromium 19-21%, molybdenum 9-10.5%, carbon ≤0.025%, manganese ≤0.15%, titanium ≤1.0%, and niobium 0.5-8%.

[0011] As an improvement, the core wire has a tensile strength of 1600-1800 MPa and an elongation of ≥20%.

[0012] As an improvement, the high-purity silver layer is formed by a bottom-drawing solid / liquid composite continuous casting method.

[0013] As an improvement, the corrosion-resistant layer is a gold-plated layer with a gold content of not less than 99.99% by mass.

[0014] As an improvement, the diameter of the composite wire monofilament is 0.025-0.035mm; wherein the cross-sectional area of ​​the core wire accounts for 50-75% of the total area, and the cross-sectional area of ​​the high-purity silver layer accounts for 23-30% of the total area.

[0015] Preferably, the diameter of the stranded conductor composed of 7 composite wires twisted together is 0.02-0.1 mm.

[0016] As an improvement, the composite wire monofilament has a conductivity ≥20% IACS, resistivity ≤9Ω.m, axial breaking force ≥9N, tensile strength ≥1800MPa, elongation ≥2%, and internal corrosion resistance ≥10 years.

[0017] As an improvement, the composite wire monofilament has a conductivity of 20-50% IACS, a resistivity of 8.5-9Ω.m, and an axial tensile strength ≥10N.

[0018] Another objective of this invention is to address the shortcomings of existing technologies by providing a method for manufacturing a highly biocompatible implantable ultra-fine stranded conductor. This method involves manufacturing a core wire, a composite silver-cast high-purity silver layer, a composite corrosion-resistant layer, an ultra-fine composite monofilament, and stranding the conductor to achieve ultra-fine size implantable ultra-fine stranded conductor production. This method ensures that the conductor maintains excellent biocompatibility, conductivity, signal transmission, fatigue strength, and oxidation and corrosion resistance in the body for extended periods, thus meeting the long-term implantation requirements in biomedicine.

[0019] To achieve the above objectives, the present invention provides the following technical solution:

[0020] A method for manufacturing a highly biocompatible implantable ultra-fine stranded conductor includes the following steps:

[0021] S1, Manufacturing core wires;

[0022] S2. Manufacturing composite monofilaments, including:

[0023] 2.1 High-purity silver coating: A high-purity silver layer is uniformly coated onto the outside of the core wire using a bottom-drawing solid / liquid composite continuous casting method;

[0024] 2.2 Drawing: The wire coated with a high-purity silver layer is drawn multiple times to reduce its diameter;

[0025] 2.3 Secondary drawing: The wire is heat-treated and precision drawn to obtain composite monofilaments with a diameter of 0.025-0.035mm;

[0026] S3. Manufacturing extremely fine stranded conductors, including:

[0027] 3.1 Twisting: Multiple composite wire monofilaments obtained in step S2 are untwisted and twisted together to form a stranded wire;

[0028] 3.2 Pulling: Pull the stranded wire diameter to 0.02-0.1mm;

[0029] It also includes gold plating treatment, which involves gold plating the composite wire obtained in step 2.2, or gold plating the stranded wire obtained in step 3.2.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) The core wire in this invention has high strength, high fatigue resistance and high conductivity. Nickel-based alloy has good tensile strength and biocompatibility. Nickel and cobalt have good strength and corrosion resistance, etc. However, cobalt is expensive and not economical. Increasing the nickel content and decreasing the cobalt content in the alloy can ensure the strength and corrosion resistance of the alloy while taking into account the economy. In addition, chromium and molybdenum bring good strength and corrosion resistance to the alloy, and the increase of niobium further improves the strength of the alloy.

[0032] (2) The composite wire monofilament of the present invention is formed by high-strength inert alloy-silver-gold from the inside out. The high-purity silver layer coating is beneficial to improving the transmission rate and localization of high-frequency signals. Silver will not cause irritation to the human body. However, silver ions are easy to oxidize and precipitate. Therefore, a corrosion-resistant layer is wrapped around it. The corrosion-resistant layer of the present invention is a gold-plated layer. Gold and tin have good welding affinity, which is beneficial to improving the welding reliability between the conductor and the implanted device. The gold-plated layer is also beneficial to improving the conductivity of the conductor.

[0033] (3) In this invention, the high-purity silver layer is formed by the bottom-drawing solid / liquid composite continuous casting method, which can achieve continuous, directional, metallurgical grade, and strong bonding silver layer coating. The coated silver layer is uniform and dense, and can effectively realize the drawing process of ultra-fine wire with multi-layer coating structure. The process is efficient and stable.

[0034] The stranded conductor product of this invention is particularly suitable for medical fields such as nerve implantation, analgesia, electrical pulse therapy, cardiac implantation, and Parkinson's disease, and can be implanted in the body for more than ten years. Attached Figure Description

[0035] Figure 1 This is a schematic cross-sectional view of the composite wire monofilament of the present invention;

[0036] Figure 2 This is a schematic diagram of the cross-sectional view of the single filament of the composite line of the present invention from a microscope (magnified 100 times);

[0037] Figure 3 This is a schematic diagram of the surface of the stranded conductor in Embodiment 1 of the present invention, viewed from a microscope (50x magnification).

[0038] Figure 4 This is a schematic diagram of the surface microscopic view (50x magnification) of the stranded conductor portion in Embodiment 1 of the present invention.

[0039] Figure 5 This is a schematic diagram of the welding state of the stranded conductor in Embodiment 1 of the present invention;

[0040] Figure 6 This is a test diagram of the welding affinity of the stranded conductor in Embodiment 1 of the present invention;

[0041] Figure 7 This is a schematic diagram of the surface of the stranded conductor in Comparative Example 1 of the present invention, viewed from a microscope (magnified 50 times).

[0042] Figure 8 This is a schematic diagram of the product surface under a microscope (magnified 50 times) during the manufacturing process of composite wire monofilament drawing in Comparative Example 2 of the present invention;

[0043] Figure 9 and Figure 10 This is a schematic diagram of the process flow of the present invention;

[0044] Figure 11 This is a schematic diagram of the structure of the downward continuous casting device of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] Example 1: A Highly Biocompatible Implantable Ultra-Fine Stranded Conductor

[0048] like Figure 1-Figure 2 As shown, the stranded conductor is composed of several composite wire monofilaments twisted together. The composite wire monofilament is composed of a core wire 1 made of high-strength inert alloy material, a high-purity silver layer 2 wrapped around the core wire 1, and a corrosion-resistant layer 3 wrapped around the high-purity silver layer 2, so that the stranded conductor can maintain its strength and transmit signals in the body for a long time.

[0049] The core wire 1 is made of a nickel-based alloy that is corrosion-resistant and biocompatible in living organisms. In this embodiment, the composition of the nickel-based alloy by mass percentage is: nickel 40-60%, chromium 19-21%, molybdenum 9-10.5%, carbon ≤0.025%, manganese ≤0.15%, titanium ≤1.0%, and niobium 0.5-8%.

[0050] The core wire 1 has a tensile strength of 1600-1800MPa and an elongation of ≥20%.

[0051] In this embodiment, the mass percentage of silver in the high-purity silver layer 2 is not less than 99.99%.

[0052] The nickel-based alloy has a melting point of 1400℃. The high-purity silver layer 2 is formed by bottom-feed solid / liquid composite continuous casting.

[0053] In this embodiment, the corrosion-resistant layer 3 is preferably a gold-plated layer with a gold content of not less than 99.99% by mass.

[0054] In this embodiment, the diameter of the composite wire monofilament is 0.025-0.035mm; wherein the cross-sectional area of ​​the core wire 1 accounts for 50-75% of the total area, and the cross-sectional area of ​​the high-purity silver layer 2 accounts for 25-30% of the total area.

[0055] Preferably, the thickness of the high-purity silver layer 2 is 3-5 μm, and the thickness of the electroplated gold layer is 0.05-0.5 μm.

[0056] Since excessive silver layer thickness leads to decreased overall strength and insufficient thickness leads to decreased conductivity, the cross-sectional area of ​​the high-purity silver layer 2 is preferably 25-30% of the total area. The diameter of the composite wire monofilament is 0.025-0.035mm, enabling the fabrication of extremely fine stranded conductors, which are particularly suitable for signal transmission wires used in biological systems. Figures 3-4 As shown, the diameter of the stranded conductor composed of 7 composite wires twisted together is 0.02-0.1 mm, and more preferably 0.025-0.08 mm.

[0057] In this embodiment, the composite wire monofilament has a conductivity ≥20-50% IACS, a resistivity of 8.5-9Ω.m, an axial breaking force ≥10N, a tensile strength ≥1800MPa, an elongation ≥2%, and an internal corrosion resistance ≥10 years.

[0058] This embodiment also provides a method for manufacturing a highly biocompatible implantable ultra-fine stranded conductor, such as... Figures 9-10 As shown, it includes the following steps:

[0059] S1, Manufacturing core wire 1;

[0060] In step S1, the process of manufacturing the core wire using a nickel-based alloy is as follows:

[0061] 1.1 Continuous casting: The nickel-cobalt alloy is smelted in an oxygen-free environment and continuously cast to obtain a nickel-cobalt alloy bar. The preferred size of the nickel-chromium alloy bar is 20 mm.

[0062] 1.2 Hot rolling: Hot rolling of nickel-cobalt alloy bars at a temperature of 550-650℃ reduces their diameter to 8mm and then rapidly cools them to room temperature. This process of reducing the diameter and then rapidly cooling them yields nickel-cobalt bar billets with refined grains.

[0063] 1.3 Wire drawing: The hot-rolled nickel-cobalt alloy fine-grained rod blank is drawn to obtain an alloy rod of a certain diameter, wherein the diameter is drawn from 8mm to 4mm;

[0064] 1.4 Polishing and Cleaning: Polish and clean the surface of the nickel-cobalt alloy rod;

[0065] S2. Manufacturing composite monofilaments, including:

[0066] 2.1 High-purity silver coating layer 2: A high-purity silver layer 2 is uniformly coated on the outside of the core wire 1 using a bottom-drawing solid / liquid composite continuous casting method; wherein the melting point of the core wire 1 is about 1400℃, and the temperature of the silver solution is about 900℃.

[0067] Step 2.1 specifically includes:

[0068] like Figure 11 As shown, a bottom-drawing continuous casting device is used to pass the clean core wire 1 bar through the furnace protected by inert gas, and the other end through the center of the crystallizer 41; the silver melts at a liquid temperature of about 980-1150℃, and the core wire 1 bar is pulled through the continuous casting mold 42 with cooling, so that the silver liquid adheres to the core wire 1 bar and cools in the continuous casting mold to form a silver casting layer that is uniformly wrapped around the outer wall of the core wire 1 bar. The thickness of the silver casting layer is determined by the size of the core wire 1 bar or the size of the continuous casting mold.

[0069] 2.2 Drawing: The wire coated with high-purity silver layer 2 is drawn multiple times to reduce its diameter; this further enhances the bonding force between the core wire 1 and the high-purity silver layer 2 and increases the conductor hardness;

[0070] 2.3 Secondary drawing: The wire undergoes multiple heat treatments and precision drawing, with an annealing temperature of 800-900℃, to obtain composite monofilaments with a diameter of 0.025-0.035mm;

[0071] S3. Manufacturing extremely fine stranded conductors, including:

[0072] 3.1 Twisting: Multiple composite wire monofilaments obtained in step S2 are untwisted and twisted to form a stranded wire, preferably seven composite wire monofilaments are twisted together;

[0073] 3.2 Pulling: Pull the diameter of the stranded wire to 0.02-0.1mm, and further optimize it to 0.025-0.08mm;

[0074] It also includes gold plating, which involves plating the composite wire obtained in step 2.2 or the stranded wire obtained in step 3.2 with gold. The order of the gold plating process depends on the customer's requirements.

[0075] Example 2: A highly biocompatible implantable ultra-fine stranded conductor

[0076] In this embodiment, the composition of the nickel-based alloy by mass percentage is: nickel 35-50%, cobalt 10-35%, chromium 19%, molybdenum 9.5%, carbon ≤0.025%, manganese ≤0.15%, titanium ≤1.0%, and niobium 0.5-8%.

[0077] In this embodiment, the diameter of the composite wire monofilament is 0.033 mm, and the diameter of the stranded wire obtained by twisting 7 strands is 0.1 mm. The rest is the same as in Embodiment 1.

[0078] Comparative Example 1: A Highly Biocompatible Implantable Ultra-Fine Stranded Conductor

[0079] The composite wire consists of a high-purity silver core wire 1, an MP35N layer wrapped around the core wire 1, and a biocompatible and corrosion-resistant layer wrapped around the MP35N layer. The MP35N is a commercially available material. TM It is equivalent to UNS R30035 (covered by ASTM F562-02), and the corrosion-resistant layer is a fluoropolymer material. The diameter of the single filament in the composite wire is 0.033mm, and the diameter of the stranded wire obtained by twisting 7 strands is 0.1mm. Figure 7 As shown.

[0080] Comparative Example 2: A Highly Biocompatible Implantable Ultra-Fine Stranded Conductor

[0081] The corrosion-resistant layer 3 is titanium-plated (silver-white). The rest is the same as in Example 1.

[0082] The composite monofilaments of Examples 1 and 2 and Comparative Examples 1 and 2 were tested for various performance parameters using conventional testing methods in the art, as shown in Table 1 below.

[0083] Table 1: Comparison of performance parameters for each embodiment

[0084]

[0085] Table 1 shows that the composite monofilaments in Examples 1 and 2 of this invention possess high strength, high fatigue resistance, and high conductivity, with conductivity ≥20-50% IACS, resistivity 8.5-9 Ω·m, axial breaking force ≥10N, tensile strength ≥1800MPa, elongation ≥2%, and internal corrosion resistance exceeding 10 years. Because nickel, cobalt, chromium, and molybdenum contribute to the good strength and corrosion resistance of the nickel-based alloy, and the addition of niobium further improves the alloy's strength, the nickel-based alloy exhibits good tensile strength and biocompatibility.

[0086] The high-purity silver coating on the nickel-based alloy improves the transmission rate of high-frequency signals and enhances the conductivity of the ultra-fine stranded conductor. Simultaneously, a pure gold plating layer further improves conductivity due to the excellent solderability between gold and tin. (See attached image.) Figures 5-6 The image shows a test result of a stranded conductor obtained by twisting 7 strands of composite wire monofilaments in Example 1 and a device weighing 250g after welding, which is naturally suspended. It can be seen that the welding affinity is excellent.

[0087] In contrast, in Comparative Example 1, high-purity silver is used as the core wire and MP35N is used as the outer layer. MP35N is a nickel-based alloy. Because nickel and tin are not compatible, welding is difficult and almost impossible to achieve effective welding. The signal transmission is unreliable, so it cannot be widely used as a stranded conductor for long-term implantation in the human body. In addition, its high-purity silver core wire and MP35N outer layer result in poor transmission rate of high-frequency signals, high resistivity, and poor conductivity.

[0088] In Comparative Example 2, the corrosion-resistant layer 3 is titanium-plated. Due to the high hardness of titanium, the single filaments in the composite wire are prone to breakage during the drawing process. (See Appendix) Figure 8 It can be seen that its surface morphology exhibits peeling and even fracture.

[0089] In summary, the stranded conductor in this invention has high conductivity, corrosion resistance, relatively stable signal transmission performance, and high solderability.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly biocompatible implantable ultra-fine stranded conductor, characterized in that, The stranded conductor is composed of several composite wire monofilaments twisted together. The composite wire monofilament is composed of a core wire (1) of high strength inert alloy material, a high-purity silver layer (2) wrapped around the core wire (1), and a corrosion-resistant layer (3) wrapped around the high-purity silver layer (2), so that the stranded conductor can maintain its strength and transmit signals in the body for a long time. The core wire (1) is a nickel-based alloy, and the composition of the nickel-based alloy by mass percentage is: nickel 40-60%, cobalt 0-40%, chromium 19-21%, molybdenum 9-10.5%, carbon ≤0.025%, manganese ≤0.15%, titanium ≤1.0%, niobium 0.5-8%; the high-purity silver layer (2) has a silver mass percentage of not less than 99.99%; the high-purity silver layer (2) is formed by bottom-feed solid / liquid composite continuous casting; the corrosion-resistant layer (3) is a gold-plated layer, and the gold mass percentage is not less than 99.99%; The diameter of the composite wire monofilament is 0.025-0.035mm, wherein the cross-sectional area of ​​the core wire (1) accounts for 50-75% of the total area, and the cross-sectional area of ​​the high-purity silver layer (2) accounts for 25-30% of the total area.

2. The highly biocompatible implantable ultra-fine stranded conductor according to claim 1, characterized in that, The nickel-based alloy is an alloy that is corrosion-resistant and biocompatible in living organisms.

3. The highly biocompatible implantable ultra-fine stranded conductor according to claim 1, characterized in that, The core wire (1) has a tensile strength of 1600-1800MPa and an elongation of ≥20%.

4. The highly biocompatible implantable ultra-fine stranded conductor according to claim 1, characterized in that, The diameter of the stranded conductor, which is composed of 7 composite wires twisted together, is 0.02-0.1 mm.

5. The highly biocompatible implantable ultra-fine stranded conductor according to claim 1, characterized in that, The composite wire monofilament has a conductivity ≥20% IACS, resistivity ≤9Ω.m, axial breaking force ≥9N, tensile strength ≥1800MPa, elongation ≥2%, and internal corrosion resistance ≥10 years.

6. The highly biocompatible implantable ultra-fine stranded conductor according to claim 5, characterized in that, The composite wire monofilament has a conductivity of 20-50% IACS, a resistivity of 8.5-9Ω.m, and an axial tensile strength ≥10N.

7. A method for manufacturing a highly biocompatible implantable ultra-fine stranded conductor, characterized in that, Includes the following steps: S1, Manufacturing core wire (1); S2. Manufacturing composite monofilaments, including: 2.

1. High-purity silver coating (2): A high-purity silver coating (2) is uniformly formed on the outside of the core wire (1) by using a bottom-drawing solid / liquid composite continuous casting method. 2.2 Drawing: The wire coated with the high-purity silver layer (2) is drawn multiple times to reduce its diameter; 2.3 Secondary drawing: The wire is heat-treated and precision drawn to obtain composite monofilaments with a diameter of 0.025-0.035mm; S3. Manufacturing extremely fine stranded conductors, including: 3.1 Twisting: Multiple composite wire monofilaments obtained in step S2 are untwisted and twisted together to form a stranded wire; 3.2 Pulling: Pull the stranded wire diameter to 0.02-0.1mm; It also includes gold plating treatment, which involves gold plating the composite wire obtained in step 2.2, or gold plating the stranded wire obtained in step 3.2.

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