High-biocompatibility implanted superfine stranded wire conductor and manufacturing method thereof

Abstract

The invention provides a high-biocompatibility implanted superfine stranded wire conductor and a manufacturing method thereof, a plurality of composite wire monofilaments are stranded to form the stranded wire conductor, and each composite wire monofilament is formed by compounding a core wire made of a high-strength inert alloy material, high-purity silver and a corrosion-resistant layer, the stranded wire conductor has the characteristics of excellent biocompatibility, conductivity, signal transmission, fatigue resistance, oxidation corrosion resistance and the like in a living body for a long time, has good welding affinity, and meets the long-term implantation requirement of biomedical use.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical implantable conductors, and in particular to an implantable ultra-fine stranded conductor with high biocompatibility and a manufacturing method thereof. Background Art

[0002] Long-term human implants require reliable biocompatibility. In particular, electrical signal transmission has seen significant development and application in implantable therapeutics in recent years. This requires cables that transmit signals or current to possess high transmission efficiency, flexibility, fatigue resistance, and biocompatibility. Furthermore, implant size is often limited by volume, and the complex signal pathways create extremely high electromechanical performance requirements for long-term implantable conductors.

[0003] Chinese patent CN201210558926.3 discloses a biomedical heating composite material and its preparation method. The surfaces of a nickel-chromium alloy rod and a titanium or titanium alloy tube are cleaned until the new metal surface is exposed; the nickel-chromium alloy rod is then sleeved into a titanium or titanium alloy tube and placed in an explosive composite casing to achieve precise positioning, with a tube-rod gap of 0.5-2mm; explosives with a thickness of 5-20mm are evenly distributed between the outer side of the titanium or titanium alloy tube and the explosive composite casing. The biomedical heating composite material is manufactured through an explosive composite process and an appropriate heat treatment process, and then through multiple drawing processes, it is made into a biomedical heating composite wire.

[0004] The above-mentioned biomedical heating composite materials in the prior art are used in the preparation of medical (physiotherapy) equipment for organisms and human bodies that require heating or implanted heating. They are required to have high resistance performance and be used for biomedical heating. In 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 purposes of the present invention is to address the shortcomings of the existing technology and provide a highly biocompatible implantable ultra-fine stranded conductor. The stranded conductor is formed by twisting together several composite wire monofilaments. The composite wire monofilaments are composed of a core wire of a high-strength inert alloy material and a high-purity silver and corrosion-resistant layer wrapped around the outside of the core wire in sequence. The stranded conductor can maintain excellent biocompatibility, conductivity, signal transmission, fatigue resistance, and anti-oxidation and corrosion properties in the body for a long time, and has good welding affinity to meet the needs of long-term biomedical implantation.

[0006] To achieve the above object, the present invention provides the following technical solutions: A highly biocompatible, implantable, ultra-fine stranded conductor. The stranded conductor is composed of a plurality of composite monofilaments twisted together. The composite monofilaments are composed of a core wire of a 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. This allows the stranded conductor to maintain strength and transmit signals in the body for a long time. The core wire is a nickel-based alloy; the mass percentage of silver in the high-purity silver layer is not less than 99.99%.

[0007] As an improvement, the nickel-based alloy is an alloy that is corrosion-resistant and biocompatible in vivo.

[0008] As an improvement, the composition of the nickel-based alloy is as follows by weight: 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%.

[0009] As an improvement, the tensile strength of the core wire is 1600-1800 MPa and the elongation is ≥20%.

[0010] As an improvement, the high-purity silver layer is formed by coating through a bottom-draw solid / liquid composite continuous casting method.

[0011] As an improvement, the corrosion-resistant layer is a gold-plated layer, and the mass percentage of gold is not less than 99.99%.

[0012] As an improvement, the diameter of the composite wire monofilament is 0.025-0.035 mm; the ratio of the cross-sectional area of ​​the core wire to the total area is 50-75%, and the ratio of the cross-sectional area of ​​the high-purity silver layer to the total area is 23-30%.

[0013] Preferably, the diameter of the stranded conductor formed by twisting 7 composite wire monofilaments is 0.02-0.1 mm.

[0014] As an improvement, the electrical conductivity of the composite wire monofilament is ≥20% IACS, the resistivity is ≤9Ω.m, the axial breaking force is ≥9N, the tensile strength is ≥1800MPa, the elongation is ≥2%, and the in vivo corrosion resistance is ≥10 years.

[0015] As an improvement, the electrical conductivity of the composite wire monofilament is 20-50% IACS, the resistivity is 8.5-9Ω.m, and the axial breaking force is ≥10N.

[0016] Another object of the present invention is to address the shortcomings of the existing technology and provide a method for manufacturing a highly biocompatible implantable ultra-fine stranded wire conductor. By manufacturing a core wire, a composite silver-cast high-purity silver layer, a composite corrosion-resistant layer, manufacturing an ultra-fine composite wire monofilament, and manufacturing a highly biocompatible implantable ultra-fine stranded wire conductor by twisting, the production of ultra-fine-sized highly biocompatible implantable ultra-fine stranded wire conductors is achieved, which satisfies the conductor's long-term excellent biocompatibility, conductivity, signal transmission, fatigue resistance, and anti-oxidation corrosion properties in the body, thereby meeting the needs of long-term biomedical implantation.

[0017] To achieve the above object, the present invention provides the following technical solutions: A method for manufacturing an implantable ultra-fine stranded conductor with high biocompatibility, comprising the following steps: S1, manufacturing core wire; S2. Manufacturing composite monofilament, including: 2.1. High-purity silver coating: A high-purity silver layer is uniformly coated on the outside of the core wire using a bottom-draw solid / liquid composite continuous casting method; 2.2. Drawing: The wire coated with high-purity silver layer is subjected to multiple diameter reduction drawing; 2.3. Secondary drawing: The wire is heat treated and precision drawn to obtain a composite wire monofilament with a diameter of 0.025-0.035mm; S3. Manufacturing of very fine stranded conductors, including: 3.1. Twisting: Untwisting and twisting the multiple composite wire monofilaments obtained in step S2 to form a stranded wire; 3.2. Drawing: Pull the stranded wire to a diameter of 0.02-0.1mm; The method further includes gold plating, wherein the composite wire prepared in step 2.2 is gold plated, or the stranded wire prepared in step 3.2 is gold plated.

[0018] The beneficial effects of the present invention are: (1) The core wire of the present invention has high strength, high fatigue resistance, and high conductivity. The nickel-based alloy has good tensile strength and biocompatibility. Nickel and cobalt have good strength and corrosion resistance. However, cobalt is expensive and has poor economic efficiency. By increasing the nickel content and reducing the cobalt content in the alloy, the strength and corrosion resistance of the alloy are guaranteed while taking into account the economic efficiency. In addition, chromium and molybdenum bring good strength and corrosion resistance to the alloy, and the addition of niobium further improves the strength of the alloy.

[0019] (2) The composite wire monofilament of the present invention is formed into a structure of high-strength inert alloy-silver-gold from the inside out, wherein the coating of the high-purity silver layer is beneficial to improving the transmission rate and integration properties of high-frequency signals, and silver does not cause irritation to the human body, but silver ions are easily oxidized and precipitated, so a corrosion-resistant layer is wrapped on the outside. The corrosion-resistant layer of the present invention adopts 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.

[0020] (3) The high-purity silver layer in the present invention is formed by coating through a bottom-draw solid / liquid composite continuous casting method, which can achieve continuous, directional, metallurgical-grade, and strongly bonded silver layer coating. The coated silver layer has a uniform and dense thickness and effectively realizes the drawing processing of ultra-fine wires with a multi-layer coating structure, and the process is efficient and stable.

[0021] The stranded conductor product of the present invention is particularly suitable for medical fields such as neural implantation, analgesia, electric pulse therapy, cardiac implantation, Parkinson's disease, etc., and can be implanted in a living body for a long time for more than ten years. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the cross-sectional structure of the composite wire monofilament of the present invention; Figure 2 Schematic diagram of a cross-section of a single filament of the composite yarn of the present invention from a microscope perspective (magnified 100 times); Figure 3 Schematic diagram of the surface of the stranded conductor in Example 1 of the present invention from a microscope perspective (magnified 50 times); Figure 4 A schematic diagram of a partially decomposed surface microscope view (50 times magnification) of a stranded wire conductor in Example 1 of the present invention; Figure 5 Schematic diagram of the welding state of the stranded conductor in the first embodiment of the present invention; Figure 6 This is a test diagram of the welding affinity of the stranded conductor in Example 1 of the present invention; Figure 7 A schematic diagram of a surface microscope view (50 times magnification) of a stranded conductor in Comparative Example 1 of the present invention; Figure 8 Schematic diagram of the product surface from a microscope perspective (50 times magnification) during the drawing process of a composite wire monofilament in Comparative Example 2 of the present invention; Figure 9 and Figure 10 It is a schematic diagram of the process flow of the present invention; Figure 11 It is a schematic structural diagram of the downward continuous casting device of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0025] Example 1: A highly biocompatible implantable ultra-fine stranded conductor like Figure 1-Figure 2 As shown, the stranded conductor is composed of a plurality of composite wire monofilaments twisted together, wherein the composite wire monofilament is composed of a core wire 1 of a high-strength inert alloy material, a high-purity silver layer 2 wrapped around the outside of the core wire 1, and a corrosion-resistant layer 3 wrapped around the outside of the high-purity silver layer 2. This allows the stranded conductor to maintain strength and transmit signals in the body for a long time; The core wire 1 is made of a nickel-based alloy that is corrosion-resistant and biocompatible in vivo. In this embodiment, the composition of the nickel-based alloy is as follows by mass percentage: nickel 40-60%, chromium 19-21%, molybdenum 9-10.5%, carbon ≤0.025%, manganese ≤0.15%, titanium ≤1.0%, and niobium 0.5-8%.

[0026] The core wire 1 has a tensile strength of 1600-1800 MPa and an elongation of ≥20%.

[0027] In this embodiment, the mass percentage of silver in the high-purity silver layer 2 is not less than 99.99%.

[0028] The melting point of the nickel-based alloy is 1400° C. The high-purity silver layer 2 is formed by cladding in a bottom-draw solid / liquid composite continuous casting manner.

[0029] In this embodiment, the corrosion-resistant layer 3 is preferably a gold-plated layer, and the mass percentage of gold is not less than 99.99%.

[0030] In this embodiment, the diameter of the composite wire monofilament is 0.025-0.035 mm; the ratio of the cross-sectional area of ​​the core wire 1 to the total area is 50-75%, and the ratio of the cross-sectional area of ​​the high-purity silver layer 2 to the total area is 25-30%.

[0031] 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.

[0032] Since too large a thickness of the silver layer will lead to a decrease in overall strength, and too small a thickness will lead to a decrease in conductivity, it is preferred that the ratio of the cross-sectional area of ​​the high-purity silver layer 2 to the total area is 25-30%; the diameter of the composite wire monofilament is 0.025-0.035 mm, which can realize the production of extremely fine stranded conductors, and is particularly suitable for wire conductors used for signal transmission in vivo; Figure 3-Figure 4 As shown, the diameter of the stranded conductor composed of 7 composite wire monofilaments is 0.02-0.1 mm, and more preferably 0.025-0.08 mm.

[0033] In this embodiment, the electrical conductivity of the composite wire monofilament is ≥20-50% IACS, the resistivity is 8.5-9Ω.m, the axial breaking force is ≥10N, the tensile strength is ≥1800MPa, the elongation is ≥2%, and the in vivo corrosion resistance is ≥10 years.

[0034] This embodiment also provides a method for manufacturing a highly biocompatible implantable ultra-fine stranded conductor, such as Figure 9-10 As shown, the following steps are included: S1, manufacturing core wire 1; In step S1, the steps of manufacturing the core wire using nickel-based alloy are as follows: 1.1. Continuous casting: Smelting nickel-cobalt alloy in an oxygen-free state and continuously casting to obtain nickel-cobalt alloy rods. The preferred nickel-chromium alloy rods have a size of 20 mm. 1.2. Hot rolling: hot rolling nickel-cobalt alloy rods at a temperature of 550-650°C, reducing their diameter to 8mm and rapidly cooling them to room temperature. After the diameter is reduced, they are rapidly cooled to obtain nickel-cobalt rod blanks with refined grains; 1.3. Wire drawing: After hot rolling, nickel-cobalt alloy fine grain rod billets are drawn to obtain alloy rods of a certain diameter, wherein the diameter is drawn from 8mm to 4mm; 1.4. Polishing and cleaning: polish and clean the surface of nickel-cobalt alloy rod; S2. Manufacturing composite monofilament, including: 2.1. Coating with high-purity silver layer 2: A high-purity silver layer 2 is uniformly coated on the outside of the core wire 1 using a bottom-draw solid / liquid composite continuous casting method; the melting point of the core wire 1 is approximately 1400°C, and the temperature of the silver solution is approximately 900°C; The step 2.1 specifically includes: like Figure 11 As shown, a down-draw continuous casting device is used to pass a cleaned core wire rod through an inert gas-protected furnace and the other end through the center of a crystallizer 41. The silver is melted to a liquid temperature of approximately 980-1150°C. The core wire rod is then pulled through a cooling continuous casting mold 42, where the silver liquid adheres to the core wire rod and cools in the continuous casting mold to form a silver casting layer that uniformly wraps around the outer wall of the core wire rod. The thickness of the silver casting layer is determined by the size of the core wire rod or the size of the continuous casting mold. 2.2. Drawing: The wire coated with the high-purity silver layer 2 is subjected to multiple diameter-reducing drawing to further enhance the bonding strength between the core wire 1 and the high-purity silver layer 2 and improve the conductor hardness; 2.3. Secondary drawing: The wire is subjected to multiple heat treatments and precision drawing, with an annealing temperature of 800-900°C to obtain a composite wire monofilament with a diameter of 0.025-0.035mm; S3. Manufacturing of very fine stranded conductors, including: 3.1. Twisting: Untwisting and twisting multiple composite wire monofilaments obtained in step S2 to form a stranded wire. Preferably, seven composite wire monofilaments are twisted. 3.2. Drawing: The wire diameter of the stranded wire is drawn to 0.02-0.1 mm, preferably to 0.025-0.08 mm; It also includes gold plating, wherein the composite wire obtained in step 2.2 is gold plated, or the stranded wire obtained in step 3.2 is gold plated. The order of setting the gold plating process is determined according to customer requirements.

[0035] Example 2: A highly biocompatible implantable ultra-fine stranded conductor In this embodiment, the composition of the nickel-based alloy is as follows by mass percentage: 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%.

[0036] 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 the first embodiment.

[0037] Comparative Example 1: A highly biocompatible implantable ultra-fine stranded conductor The composite wire monofilament is composed of a core wire 1 of high-purity silver, an MP35N layer wrapped around the core wire 1, and a biocompatible corrosion-resistant layer wrapped around the MP35N layer, wherein MP35N is a commercially available material, such as MP35N TM , which is equivalent to UNS R30035 (covered by ASTMF562-02), and the corrosion-resistant layer is a fluorine-containing plastic polymer material. The diameter of the composite wire monofilament is 0.033mm, and the diameter of the stranded wire obtained by twisting 7 strands is 0.1mm. Figure 7 shown.

[0038] Comparative Example 2: A highly biocompatible implantable ultra-fine stranded conductor The corrosion-resistant layer 3 is plated with titanium (silver-white). The rest is the same as in the first embodiment.

[0039] The performance parameters of the composite wire monofilaments of Examples 1 and 2 and Comparative Examples 1 and 2 were tested using conventional testing methods in the art, as shown in Table 1 below.

[0040] Table 1: Comparison of performance parameters of various embodiments

[0041] The results in Table 1 show that the composite wire monofilaments of Examples 1 and 2 of the present invention all exhibit high strength, high fatigue resistance, and high electrical conductivity, with conductivity ≥20-50% IACS, resistivity 8.5-9 Ω.m, axial breaking force ≥10N, tensile strength ≥1800 MPa, elongation ≥2%, and in vivo corrosion resistance exceeding 10 years. Because nickel, cobalt, chromium, and molybdenum in nickel-based alloys provide excellent strength and corrosion resistance, and the addition of niobium further improves the alloy's strength, nickel-based alloys exhibit excellent tensile strength and biocompatibility.

[0042] The nickel-based alloy is coated with a high-purity silver layer, which is beneficial to improving the transmission rate of high-frequency signals and the conductivity of the extremely fine stranded conductor. At the same time, the pure gold layer is plated on the outside. Due to the good welding affinity between gold and tin, it is also beneficial to improve the conductivity of the conductor. Figure 5-Figure 6 This is a test diagram of a naturally suspended conductor obtained by twisting 7 composite wire strands in Example 1 and welding it to a device weighing 250 g. It can be seen that the welding affinity is excellent.

[0043] 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. Since nickel and tin are not mutually soluble, welding is difficult and effective welding is almost impossible to achieve. The signal transmission is unreliable. Therefore, it cannot be widely promoted as a stranded wire conductor for long-term implantation in the human body. In addition, its high-purity silver is used as the core wire and the MP35N is used as the outer layer. Therefore, the transmission rate of high-frequency signals is poor, the resistivity is high, and the conductivity is poor.

[0044] In the second comparative example, the corrosion-resistant layer 3 is plated with titanium. Since titanium has a high hardness, it is easy to break during the drawing process of the composite wire. Figure 8 , it can be seen that its surface morphology is peeling or even broken.

[0045] In summary, the stranded wire conductor of the present invention has high conductivity, corrosion resistance, relatively stable signal transmission performance and high welding affinity.

[0046] 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 in the scope of protection of the present invention.

Claims

1. A highly biocompatible implantable ultra-fine stranded conductor, characterized in that: The stranded conductor is composed of a plurality of composite wire monofilaments twisted together, wherein the composite wire monofilament is composed of a core wire (1) of a high-strength inert alloy material, a high-purity silver layer (2) wrapped around the outside of the core wire (1), and a corrosion-resistant layer (3) wrapped around the outside of the high-purity silver layer (2), so that the stranded conductor maintains strength in a living body for a long time and transmits signals; The core wire (1) is a nickel-based alloy; the mass percentage of silver in the high-purity silver layer (2) is not less than 99.99%; the high-purity silver layer (2) is formed by coating in a bottom-draw solid / liquid composite continuous casting method; The diameter of the composite wire monofilament is 0.025-0.035 mm, wherein the ratio of the cross-sectional area of ​​the core wire (1) to the total area is 50-75%, and the ratio of the cross-sectional area of ​​the high-purity silver layer (2) to the total area is 25-30%.

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 vivo.

3. The highly biocompatible implantable ultra-fine stranded conductor according to claim 2, characterized in that: The composition of the nickel-based alloy is as follows by mass percentage: 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%.

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

5. The highly biocompatible implantable ultra-fine stranded conductor according to any one of claims 1 to 3, characterized in that: The corrosion-resistant layer (3) is a gold-plated layer, and the mass percentage of gold is not less than 99.99%.

6. The highly biocompatible implantable ultra-fine stranded conductor according to claim 1, characterized in that: The diameter of the stranded conductor composed of 7 composite wire monofilaments is 0.02-0.1mm.

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

8. The highly biocompatible implantable ultra-fine stranded conductor according to claim 7, characterized in that: The electrical conductivity of the composite wire monofilament is 20-50% IACS, the resistivity is 8.5-9Ω.m, and the axial breaking force is ≥10N.

9. A method for manufacturing a highly biocompatible implantable ultra-fine stranded conductor, characterized in that: The following steps are involved: S1, manufacturing core wire (1); S2. Manufacturing composite monofilament, including: 2.

1. Coating with high-purity silver layer (2): using a bottom-draw solid / liquid composite continuous casting method to uniformly coat the outer surface of the core wire (1) with a high-purity silver layer (2); 2.

2. Drawing: The wire coated with the high-purity silver layer (2) is subjected to multiple diameter-reducing drawing; 2.

3. Secondary drawing: The wire is heat treated and precision drawn to obtain a composite wire monofilament with a diameter of 0.025-0.035mm; S3. Manufacturing of very fine stranded conductors, including: 3.

1. Twisting: Untwisting and twisting the multiple composite wire monofilaments obtained in step S2 to form a stranded wire; 3.

2. Drawing: Pull the stranded wire to a diameter of 0.02-0.1mm; The method further includes gold plating, wherein the composite wire prepared in step 2.2 is gold plated, or the stranded wire prepared in step 3.2 is gold plated.

Images