Coated electrical conductor and method for manufacturing it

Abstract

The invention relates to an electrical conductor, in particular a medical electrode, comprising a substrate with a surface on which a first layer comprising a platinum-iridium alloy and a second layer comprising a conductive polymer are arranged. The invention further relates to a method for manufacturing such an electrical conductor, in particular for manufacturing a medical electrode.

Description

[0001] The invention relates to an electrical conductor, in particular a medical electrode, comprising a substrate with a surface on which a first layer comprising a platinum-iridium alloy and a second layer comprising a conductive polymer are arranged.

[0002] The invention further relates to a method for manufacturing such an electrical conductor, in particular for manufacturing a medical electrode. Background of the invention

[0003] Medical devices, and in particular active implantable medical devices, generally include electrodes for the electrical stimulation of body tissue or for measuring electrical signals generated by it. Examples of body tissue include muscles and nerves. These electrodes also include electrical conductors.

[0004] There are several important requirements for the aforementioned electrical conductors. A first requirement is that the conductor should have a very low impedance, especially at lower frequencies in the range of 0.1 Hz to 100 Hz. This low-frequency range is of particular importance for the medical devices mentioned above. A very low impedance is essential to ensure a good signal-to-noise ratio. Another requirement is that the conductor should have a high charge storage capacity. A further requirement is that the conductor should exhibit long-term stability. This means that the electrical properties, such as impedance and charge storage capacity, should not change substantially over time.This is important for medical devices used for stimulation, as the electrical signal should not change over time. This long-term stability is also important for medical devices used for mapping and sensing, as it affects the measurement accuracy of the medical device.

[0005] Electrical conductors very often consist of a substrate but no coating layer. The absence of a coating layer has the disadvantage that these electrical conductors exhibit very high electrical impedance, especially at lower frequencies in the range of 0.1 Hz to 100 Hz. Uncoated electrical conductors also have low charge storage capacity and a low signal-to-noise ratio.

[0006] It is known, for example, from US 10,219,715 B2, that the electrical properties of an electrical conductor, such as impedance and charge storage capacity, can be improved by using laser ablation to structure the substrate. However, even in this case, the impedance remains too high, especially in the range of 0.1 Hz to 100 Hz, and the charge storage capacity remains too low.

[0007] The substrate can be coated with an electrically conductive polymer to improve the aforementioned electrical properties, as disclosed, for example, in US 2019 / 0159833 A1. However, achieving adhesion of the electrically conductive polymer to the substrate is difficult, especially when the electrical conductor is subjected to mechanical stresses and forces. Consequently, sections of the electrically conductive polymer frequently detach from the substrate. The adhesion of a polymer coating can be improved by laser-structuring the substrate, as disclosed, for example, in EP 3500419 B1. But even in this case, adhesion remains problematic. This lack of adhesion not only affects the patient but also the electrical properties and long-term stability of the electrical conductor.

[0008] To improve the adhesion of the electrically conductive polymer to the substrate, the substrate can comprise a metal, such as iron, silver, copper, nickel, palladium, platinum, gold, iridium, titanium, hafnium, niobium, tantalum, cobalt, chromium, zirconium, rhenium, tungsten, molybdenum, or an alloy, such as a platinum alloy, such as a platinum-iridium alloy, or steel. This can improve the adhesion between the substrate and the conductive polymer, as described, for example, in US 11,495,369 B2.

[0009] In the paper “Long-Term Stable Adhesion for Conducting Polymers in Biomedical Applications: IrOx and Nanostructured Platinum Solve the Chronic Challenge”, ACS Appl. Mater. Interfaces 2017, 9, 189-197 by Boehler et al., the adhesion of conductive polymers, such as poly(3,4-ethylenedioxythiophene) (PEDOT), to iridium oxide is described. However, such adhesion to iridium in the form of an alloy is denied.

[0010] Significant efforts continue to be made to provide electrical conductors, especially medical electrodes, which have low impedance combined with high mechanical strength. Tasks

[0011] One object of the present invention is to overcome at least some of the disadvantages arising from the prior art.

[0012] Another objective of the invention is to provide an electrical conductor that has a reduced impedance.

[0013] Another objective of the invention is to provide an electrical conductor that has an increased charge storage capacity.

[0014] A further object of the invention is to provide an electrical conductor that exhibits increased robustness against damage resulting from mechanical forces and stresses. Examples of damage resulting from mechanical forces include damage that occurs, for example, when the electrical conductor is inserted into or removed from the body of a mammal or handled by an operator.

[0015] Another object of the invention is to provide an electrical conductor which has improved adhesion of a conductive polymer to its surface.

[0016] Another objective of the invention is to provide an electrical conductor that exhibits improved long-term stability.

[0017] A further object of the invention is to provide a method for producing an electrical conductor by means of which at least some of the problems already described are at least partially solved. Preferred embodiments of the invention

[0018] A contribution to at least partially fulfilling at least one of the aforementioned objects is made by the features of the independent claims. The dependent claims provide preferred embodiments that contribute to at least partially fulfilling at least one of the objects.

[0019] A first embodiment of the invention is an electrical conductor, in particular a medical electrode, with a surface on which a first layer is arranged, comprising a platinum-iridium alloy, preferably consisting of a platinum-iridium alloy, and a second layer, comprising a conductive polymer, in particular an electrically conductive polymer, preferably consisting of a conductive polymer, and is arranged on the first layer. characterized by the fact that The platinum-iridium alloy has an iridium content of at least 30 percent by weight based on the total mass of the platinum-iridium alloy.

[0020] In a preferred embodiment of the electrical conductor, the platinum-iridium alloy has an iridium content of at most 50 percent by weight, based on the total mass of the platinum-iridium alloy. This preferred embodiment is a second embodiment of the invention, which is preferably dependent on the first embodiment of the invention.

[0021] In a preferred embodiment of the electrical conductor, the platinum-iridium alloy has an iridium content in the range of 30-50 percent by weight, preferably in the range of 30-45 percent by weight, and more preferably in the range of 35-45 percent by weight, based on the total mass of the platinum-iridium alloy. This preferred embodiment is a third embodiment of the invention, which is preferably dependent on the first or the second embodiment of the invention.

[0022] In a preferred embodiment of the electrical conductor, the platinum-iridium alloy is galvanically, or in other words electrochemically, deposited on the surface of the substrate. This preferred embodiment is a fourth embodiment of the invention, which is preferably dependent on the first to third embodiments of the invention.

[0023] In a preferred embodiment of the electrical conductor, the platinum-iridium alloy has a surface, in particular a surface facing the second layer, with a mean roughness value R a in a range of 0.05 µm to 0.5 µm, preferably in a range of 0.1 µm to 0.4 µm, more preferably in a range of 0.1 µm to 0.3 µm, most preferably in a range of 0.2 µm to 0.3 µm. This preferred embodiment is a fifth embodiment of the invention, which is preferably dependent on one of the preceding embodiments of the invention.

[0024] In a preferred embodiment of the electrical conductor, the first layer, preferably the platinum-iridium alloy, has a layer thickness of at most 3 µm. This preferred embodiment is a sixth embodiment of the invention, which is preferably dependent on one of the preceding embodiments of the invention.

[0025] In a preferred embodiment of the electrical conductor, the first layer, preferably the platinum-iridium alloy, has a layer thickness of at least 300 nm. This preferred embodiment is a seventh embodiment of the invention, which is preferably dependent on one of the preceding embodiments of the invention.

[0026] In a preferred embodiment of the electrical conductor, the substrate comprises gold or platinum; preferably, the substrate consists of gold or platinum. This preferred embodiment is an eighth embodiment of the invention, which is preferably dependent on one of the preceding embodiments of the invention.

[0027] In a preferred embodiment of the electrical conductor, the second layer comprises PEDOT, preferably Amplicoat®. This preferred embodiment is a ninth embodiment of the invention, which is preferably dependent on one of the preceding embodiments of the invention.

[0028] A tenth embodiment of the invention is a method for producing an electrical conductor according to one of the preceding embodiments, comprising the following steps: i) Providing the substrate with the surface; ii) Applying the first layer to the surface; iii) Applying the second layer to the first layer.

[0029] In a preferred embodiment of the method, the first layer is applied to the surface by a galvanic, or in other words, an electrochemical, coating process. This preferred embodiment is an eleventh embodiment of the invention, which is preferably dependent on the tenth embodiment of the invention.

[0030] In a preferred embodiment of the method, the second layer, in particular the conductive polymer, is applied to the first layer by electrochemical or chemical polymerization, by dip coating, or by inkjet printing. This preferred embodiment is a twelfth embodiment of the invention, which is preferably dependent on the tenth or eleventh embodiment of the invention. General

[0031] For each of the embodiments described herein, whose elements "have" or "comprise" a particular feature (e.g., a material), a further embodiment is always considered in which the element in question consists solely of the feature, i.e., it does not include any other components. The word "comprise" or "comprise" is used synonymously with the word "have" or "have" herein.

[0032] If an element in an embodiment is designated in the singular, an embodiment containing several such elements is also considered. The use of a plural term for an element generally also includes an embodiment containing only a single corresponding element.

[0033] Unless otherwise stated or clearly excluded from the context, it is generally possible, and hereby expressly considered, that features of different embodiments may also be present in the other embodiments described herein. Likewise, it is generally considered that all features described herein in connection with a method are also applicable to the products and devices described herein, and vice versa. For the sake of brevity, not all of these considered combinations are explicitly listed in every case. Technical solutions that are known to be equivalent to the features described herein are also generally considered to be within the scope of the invention.

[0034] In this description, range specifications also include values ​​referred to as limits. A specification such as "in the range from X to Y" with respect to a quantity A therefore means that A can take on the values ​​X, Y, and values ​​between X and Y. Similarly, a range limited on one side, such as "up to Y" for a quantity A, means that A can take on the values ​​Y and less than Y.

[0035] Some of the described characteristics are linked to the term "essentially." The term "essentially" means that, under real-world conditions and manufacturing techniques, a mathematically exact interpretation of terms such as "superposition," "perpendicular," "diameter," or "parallelism" can never be exact, but only within certain manufacturing tolerances. For example, "essentially perpendicular axes" include an angle of 85 to 95 degrees to each other, and "essentially equal volumes" encompass a deviation of up to 5% by volume. A "device consisting essentially of plastic," for example, comprises a plastic content of ≥95% to ≤100% by weight. "An essentially complete filling of volume B," for example, encompasses a filling of ≥95% to ≤100% by volume of the total volume of B. Detailed description

[0036] A first object of the invention relates to an electrical conductor, in particular a medical electrode, with a surface on which a first layer is arranged, comprising a platinum-iridium alloy, preferably consisting of a platinum-iridium alloy, and a second layer, comprising a conductive polymer, preferably consisting of a conductive polymer, and is arranged on the first layer. characterized by the fact that The platinum-iridium alloy has an iridium content of at least 30 percent by weight based on the total mass of the platinum-iridium alloy.

[0037] The electrical conductor is preferably a medical electrode for a medical device. Therefore, the electrical conductor preferably has the shape of a conductor for a medical device. Examples of preferred shapes are cylindrical, annular, flat, spherical, needle-like, cubic, rectangular, or a combination of two or more of these. An annular, flat, or cylindrical shape is particularly preferred. Most preferably, the electrical conductor is a ring electrode for a medical device or an electrode for a stent.

[0038] The electrical conductor can have the dimensions of a known electrode for a medical device. In one embodiment, it is preferred that the electrical conductor has a width in the range of 0.1 mm to 30.0 mm, more preferably in the range of 0.1 mm to 20.0 mm, and further preferably in the range of 0.1 mm to 10.0 mm. In another embodiment, it is preferred that the electrical conductor has a diameter in the range of 0.1 mm to 30.0 mm, more preferably in the range of 0.1 mm to 20.0 mm, and further preferably in the range of 0.1 mm to 10.0 mm.

[0039] In a further embodiment, it is preferred that the electrical conductor has a length in the range of 0.1 mm to 60.0 mm, more preferably in the range of 0.1 mm to 40.0 mm and further preferably in the range of 0.1 mm to 20.0 mm.

[0040] In a further embodiment, it is preferred that the electrical conductor has a height in the range of 0.1 mm to 30.0 mm, more preferably in the range of 0.1 mm to 20.0 mm and further preferably in the range of 0.1 mm to 10.0 mm.

[0041] A first layer is arranged on the surface, particularly the radially outer surface, of the substrate. Preferably, substantially the entire surface, especially the radially outer surface, of the substrate is covered by the first layer.

[0042] The first layer comprises a platinum-iridium alloy. Preferably, the first layer consists essentially of the platinum-iridium alloy.

[0043] A second layer is arranged on top of the first layer, particularly radially on the outer surface of the first layer. Preferably, the first layer is substantially completely covered by the second layer.

[0044] The first layer is therefore preferably present as an intermediate layer between the substrate and the second layer.

[0045] The second layer comprises a conductive, in particular electrically conductive, polymer. Preferably, the second layer consists essentially of the conductive polymer.

[0046] The platinum-iridium alloy of the first layer has an iridium content of at least 30% by weight, based on the total mass of the platinum-iridium alloy. In other words, the platinum-iridium alloy consists of at least 30% by weight of iridium. The remaining weight percentage of the platinum-iridium alloy is platinum and other optional components, preferably consisting essentially of platinum and iridium, with iridium comprising at least 30% by weight and platinum comprising at most 70% by weight.

[0047] An iridium content of at least 30% by weight, based on the total mass of the platinum-iridium alloy, offers the surprising advantage that the second layer, particularly the conductive polymer of the second layer, exhibits improved adhesion to the first layer. Platinum-iridium alloys with lower iridium content, on the other hand, show significantly reduced adhesion of conductive polymers to their surface. Good adhesion is crucial to ensure the longest possible lifespan of the electrical conductor, especially when used as a medical electrode, and particularly when used as an implanted medical electrode.

[0048] In one embodiment of the electrical conductor, it is preferred that the platinum-iridium alloy has an iridium content of at most 50% by weight, based on the total mass of the platinum-iridium alloy. In other words, the platinum-iridium alloy consists of at most 50% by weight of iridium. The remaining percentage by weight of the platinum-iridium alloy is platinum and other optional components, with the platinum-iridium alloy preferably consisting substantially of platinum and iridium, wherein iridium constitutes a proportion of at most 50% by weight and platinum a proportion of at least 50% by weight.

[0049] An iridium content of no more than 50 percent by weight, based on the total mass of the platinum-iridium alloy, has the surprising advantage of giving the platinum-iridium alloy a comparatively high mechanical strength, and in particular, comparatively low brittleness. Platinum-iridium alloys with a higher iridium content, on the other hand, exhibit significantly reduced mechanical strength, especially increased brittleness, which would shorten the service life of the electrical conductor, particularly when used as a medical electrode, especially when used as an implanted medical electrode.

[0050] Furthermore, a higher iridium content than 50 percent by weight at the time of the invention would negatively affect the manufacturing costs of the electrical conductor due to the higher cost of iridium compared to platinum.

[0051] Preferably, the platinum-iridium alloy has an iridium content of at least 30 percent by weight and at most 50 percent by weight based on the total mass of the platinum-iridium alloy.

[0052] In one embodiment of the electrical conductor, the platinum-iridium alloy has an iridium content in the range of 30-50% by weight, preferably in the range of 30-45% by weight, and more preferably in the range of 35-45% by weight, based on the total mass of the platinum-iridium alloy. These ranges represent a good compromise between improved adhesion of the second layer, in particular the conductive polymer of the second layer, to the first layer, in particular the platinum-iridium alloy of the first layer, and the mechanical strength of the first layer, in particular the platinum-iridium alloy of the first layer. Such iridium content thus surprisingly ensures an increased service life of the electrical conductor, especially when used as a medical electrode, and particularly when used as an implanted medical electrode.

[0053] The first layer can be applied to the substrate in various ways, and thus, depending on the application method, it can have a differently defined surface facing the second layer. Differently defined surfaces facing the second layer can affect the adhesion of the second layer to the first.

[0054] For example, the first layer can be glued, soldered, sintered, vapor-coated or rolled onto the substrate.

[0055] In one embodiment of the electrical conductor, the first layer, in particular the platinum-iridium alloy, is deposited electrochemically onto the surface of the substrate. An advantage of this method is that the substrate is subjected to only minimal mechanical stress during the deposition of the first layer. Furthermore, an electrochemically deposited platinum-iridium alloy can be used for a wide range of applications due to its surface roughness, particularly its mean roughness value Rm. a , leading to improved adhesion of the second layer to the first layer.

[0056] In one embodiment of the electrical conductor, the first layer, in particular the platinum-iridium alloy, has a surface with a mean roughness value R ain a range of 0.05–0.5 µm, preferably in a range of 0.1–0.4 µm, more preferably in a range of 0.1–0.3 µm, and most preferably in a range of 0.2–0.3 µm. The aforementioned ranges refer to the mean value of the mean roughness R. a Preferably, the mean roughness value R a a minimum value in the range of 0.05–0.2 µm and a maximum value in the range of 0.2–0.6 µm. Such ranges for the mean roughness R a They represent a good compromise between improved adhesion of the second layer to the first layer and the mechanical stability of the first layer, especially the platinum-iridium alloy of the first layer. The larger the mean roughness value R aThe more durable the first layer, particularly the platinum-iridium alloy, the greater the risk of detachment due to mechanical stress. For example, vertical elements of the first layer, especially the platinum-iridium alloy, protruding from its surface, could be detached by mechanical stress, such as friction. This would negatively affect the service life of the electrical conductor, particularly when used as a medical electrode, especially when used as an implanted medical electrode.

[0057] In one embodiment of the electrical conductor, the first layer, in particular the platinum-iridium alloy, has a layer thickness of at most 3 µm, for example at most 2 µm or at most 1 µm. In some embodiments, the first layer has a layer thickness of at most 900, 800, 700, 600 or at most 500 nm.

[0058] In one embodiment of the electrical conductor, the first layer has a thickness of at least 300 nm, more preferably at least 400, 500, 600, 700, 800, 900 or 1000 nm. In some embodiments, the first layer has a thickness in the range of 500–1000 nm or in the range of 800–2000 nm.

[0059] The thickness of a layer can be determined by evaluating electron microscopic cross-sectional images, whereby the average distance between the profile lines along the opposing interfaces of the layer to be determined is calculated using suitable image processing software. Further details on determining layer thickness using electron microscopy are described, for example, in Giurlani et al., Coatings 2020, 10, 1211; doi:10.3390 / coatings10121211.

[0060] The substrate may comprise or consist of different materials, as long as these are suitable for constructing an electrical conductor, in particular for constructing a medical electrode, especially an implantable medical electrode.

[0061] In one embodiment of the electrical conductor, the substrate comprises a metal, a metal alloy, or a combination thereof. A preferred metal is selected from the group consisting of iron, silver, copper, nickel, palladium, platinum, gold, iridium, titanium, hafnium, niobium, tantalum, cobalt, chromium, zirconium, rhenium, tungsten, molybdenum, and combinations, for example, mixtures, preferably alloys, of at least two of these metals. A particularly preferred metal is gold or platinum. A particularly preferred alloy is steel. In one embodiment, it is preferred that the substrate comprises or consists of a platinum alloy, preferably a platinum-iridium alloy, such as PtIr10 or PtIr20.

[0062] The second layer can comprise or consist of different conductive polymers, particularly electrically conductive polymers. For example, the second layer can comprise or consist of one, two, three, or more different conductive polymers.

[0063] A “conductive polymer” is understood to mean, in particular, an “electrically conductive polymer”.

[0064] In one embodiment, the conductive polymer, in particular the electrically conductive polymer, is cationic. In one embodiment, it is preferred that the conductive polymer comprises at least one or all of the following: a polyacetylene, a poly(vinyl alcohol), a poly(fluorene), a polyphenylene, a polyphenylenevinylene, a polypyrene, a polyazulene, a polynaphthalene, a poly(pyrrole), a polycarbazole, a polyindole, a polyazepine, a polyaniline, a polyacene, a polythiophene, a polythiophenevinylene, a poly(p-phenylene sulfide), a polypyridine, or functionalized derivatives, precursors, or mixtures thereof.

[0065] In one embodiment, it is preferred that the conductive polymer is derived from a functionalized derivative of EDOT selected from the group consisting of hydroxymethyl-EDOT, EDOT-vinyl, EDOT-ether-allyl, EDOTCOOH, EDOT-MeOH, EDOT-silane, EDOT-vinyl, EDOT-acrylate, EDOT-sulfonate, EDOT-amine, EDOT-amide, and combinations thereof. For example, the functionalized derivative of 3,4-ethylenedioxythiophene (EDOT) can be selected from the group consisting of hydroxymethyl-EDOT, EDOT-vinyl, EDOT-ether-allyl, EDOT-acrylate, and combinations thereof.

[0066] In one embodiment, it is preferred that the second layer comprises or consists of PEDOT.

[0067] In one embodiment, it is preferred that the conductive polymer comprises an anionic photoreactive crosslinking agent. In this embodiment, it is preferred that the crosslinking agent has at least two photoreactive groups. In a further embodiment of the invention, it is preferred that the anionic photoreactive crosslinking agent comprises a compound of formula I: Xi~Y~X2, wherein Y is a radical containing at least one acidic group or a salt of an acidic group, and Xi and X2 are each independently radicals containing a latent photoreactive group. Examples of a photoreactive group are an aryl ketone or a quinone. In a further embodiment of the invention, it is preferred that spacers are part of Xi or X2, preferably together with the latent photoreactive group.

[0068] In one embodiment, it is preferred that the compound of formula IY contains a radical comprising at least one acidic group or a salt thereof. Examples of acidic groups include sulfonic acids, carboxylic acids, phosphonic acids, and the like. Examples of salts of such groups include sulfonate, carboxylate, and phosphate salts. As an example, the crosslinking agent can comprise a sulfonic acid or sulfonate group.

[0069] In a further embodiment of the invention, it is preferred that such a photoreactive crosslinking agent is anionic. Examples of counterions include alkali, alkaline earth metals, ammonium, protonated amines, and the like.

[0070] In one embodiment, it is preferred that the conductive polymer comprises an anionic photoreactive hydrophilic polymer. In this embodiment, it is preferred that the hydrophilic polymer is anionic. Examples of anionic hydrophilic polymers are homopolymers, copolymers, terpolymers, and the like. In another embodiment of the invention, if the electrically conductive polymer comprises at least one anionic hydrophilic polymer, it is preferred that the anionic hydrophilic polymer is derivatized with photoreactive groups.

[0071] In a further embodiment, it is preferred that the anionic hydrophilic polymer comprises polymers containing polyacrylamide and photoreactive groups (“photo-PA”). In a further embodiment of the invention, it is preferred that the anionic hydrophilic polymer comprises polyacrylamide and sulfonate groups. For example, the anionic hydrophilic polymer comprises acrylamido-2-methylpropanesulfonate (AMPS) groups and polyethylene glycol segments.

[0072] The terms “latent photoreactive group” and “photoreactive group” are used interchangeably and refer to a chemical entity that is sufficiently stable to remain in an inactive state (i.e., ground state) under normal storage conditions, but can undergo a transformation from the inactive state to an activated state when exposed to a suitable energy source. Unless otherwise specified, references to photoreactive groups herein are preferably to include the reaction products of the photoreactive groups.

[0073] In another embodiment, it is preferred that photoreactive groups are selected to respond to different proportions of actinic radiation. For example, groups can be selected that can be photoactivated using either ultraviolet or visible radiation. Examples of photoreactive groups include azides, diazos, diazirines, ketones, and quinones. In a further embodiment of the invention, it is preferred that the photoreactive group comprises an aryl ketone, such as acetophenone, benzophenone, anthrone, and anthrone-like heterocycles (i.e., heterocyclic analogs of anthrone, such as those with N, O, or S in the 10-position) or their substituted (e.g., ring-substituted) derivatives. Examples of aryl ketones include heterocyclic derivatives of anthrone, including acridone, xanthone, and thioxanthone, and their ring-substituted derivatives.Other suitable photoreactive groups include quinone, such as anthraquinone.

[0074] Electrically conductive polymers are well known to those skilled in the art and are commercially available under the trade names Orgacon®, available from Agfa-Gevaert NV (Belgium), or Amplicoat®, available from Heraeus Deutschland GmbH & Co. KG (Germany).

[0075] Another object of the invention relates to a method for manufacturing an electrical conductor, in particular a medical electrode, especially an implantable medical electrode, according to one of the preceding embodiments, comprising the following steps: i) Providing the substrate with the surface; ii) Applying the first layer to the surface; iii) Applying the second layer to the first layer.

[0076] The first layer can be applied using various methods. For example, it can be applied via wet-chemical redox reactions. Preferably, the first layer, especially the platinum-iridium alloy, can be applied to the substrate electroplated, i.e., using an electroplating process. This allows the thickness of the first layer to be controlled and adjusted cost-effectively. Furthermore, the surface roughness, especially the mean roughness Rm, can be precisely controlled. a The surface roughness of the first layer, particularly of the platinum-iridium alloy, is controlled. The selection of suitable process conditions and their relationship to the resulting surface roughness, especially the mean roughness value R, are crucial. aThis process is described in numerous publications in the specialist literature. Suitable process conditions can be found, for example, in Petrossians et al., Journal of The Electrochemical Society, 158 (5), D269-D276 (2011).

[0077] In one embodiment of the method, the application of the second layer, in particular the conductive polymer, to the first layer can be carried out, for example, by dip coating or inkjet printing. In another embodiment of the method, the curing of the conductive polymer can be carried out, if necessary, by chemical or electrochemical polymerization. The curing of PEDOT and its derivatives can preferably be carried out electrochemically.

[0078] Another aspect of the invention relates to the use of an embodiment of the electrical conductor described herein, in particular as a medical electrode, especially as an implantable medical electrode.

[0079] Another aspect of the invention relates to the use of an embodiment of the method described herein for the production of an electrical conductor.

[0080] In a further aspect of the invention, an electrical medical device is provided, comprising an electrical conductor according to one of the preceding embodiments.

[0081] The electrical medical device can be, for example, a lead for use with a pulse generator, pacemaker, cardiac resynchronization device, mapping catheter, sensor, or stimulator. Leads are electrical conductors that can be used, for example, in medical applications such as cardiac stimulation, neuromodulation, deep brain stimulation, spinal cord stimulation, or gastric stimulation. In one embodiment, the lead is configured and / or intended to be connected to a generator of an active implantable device. A lead can also be used in a medical device to receive an electrical signal from the body of a living being. A stimulator is a medical device that can produce a physiological effect by delivering an electrical signal to the body of a living being.For example, a neurostimulator can cause an electrical signal in a nerve cell (e.g., an action potential) by delivering an electrical signal to a nerve cell.

[0082] Another embodiment relates to a microelectrode array comprising a plurality of electrical conductors according to the invention.

[0083] Another aspect of the invention relates to a diagnostic method in or on the body of a living being, comprising the recording of an electrical signal by means of the electrical conductor described herein.

[0084] Another aspect of the invention relates to the use of the electrical conductor described herein in a diagnostic procedure in or on the body of a living being, comprising the recording of an electrical signal by means of the electrical conductor.

[0085] Another aspect of the invention relates to a therapeutic method in or on the body of a living being, comprising the delivery of an electrical signal by means of the electrical conductor described herein.

[0086] Another aspect of the invention relates to the use of the electrical conductor described herein in a therapeutic procedure in or on the body of a living being, comprising the emission of an electrical signal by means of the electrical conductor.

[0087] The therapeutic procedure may involve delivering an electrical signal to nerve cells or muscle cells in the area of ​​an organ, for example, heart, muscle, stomach or brain.

[0088] The diagnostic procedure may involve recording an electrical signal from nerve cells or muscle cells in the area of ​​an organ, for example, the heart, muscle, or brain.

[0089] A further aspect of the invention relates to an electrode comprising at least one electrical conductor according to the invention. It is preferred that the electrode be suitable for use in an implantable medical device, and more preferably in an active implantable medical device (AIMD). In one embodiment, the electrode according to the present invention is suitable for use in a temporary or short-term medical device such as a catheter. In another embodiment, the electrode is suitable for use in a conductor for a medical device.

[0090] The features disclosed for the electrical conductor are also disclosed for the method for manufacturing the electrical conductor and all other aspects of the invention, and vice versa. Method description

[0091] To determine the mean roughness R a3D images were acquired on the surface of the corresponding electrical conductor in substrate form using the µsurf custom confocal microscope (NanoFocus AG, Germany). These images encompassed the reference section S. The microscopic 3D images were then analyzed using the µSoft Analysis Premium software (7.4.8872; NanoFocus AG, Germany). First, any deflection of the substrate in the 3D images was corrected (using a 2-degree polynomial). Then, the reference section S (for example, with a width of 0.0315 mm) was defined, and the roughness profile along the reference section S was obtained using a Gaussian filter (0.08 mm). At least three parallel reference sections S of equal length were selected. The reference sections S had a length of at least 20% of the substrate's circumference.The mean roughness value R was determined from the roughness profiles obtained along the reference sections S. a according to the version of the standard DIN EN ISO 4287 valid on the filing date.

[0092] To determine the mechanical strength of a conductive polymer layer applied to a surface, a swipe test was performed. For this purpose, electrical conductors in substrate form (diameter at least 5 cm) were prepared and immersed in a phosphate-buffered saline solution (PBS solution) for 15 minutes at room temperature. The substrates were then sequentially fixed to a Y-shaped, movable sample stage using adhesive tape (Scotch Magic Tape). A holder for a rod was positioned above the sample stage in its initial position and directly above the substrate. The rod was freely movable in the vertical direction and could be placed on the substrate. A 10 x 10 mm piece of foam soaked in PBS solution was attached to the end of the rod facing the substrate before the rod was carefully lowered onto the substrate fixed to the sample stage.The rod, positioned in this way, exerted an initial weight of 43 g on the substrate. The sample stage was then moved back and forth 10 times in the Y-direction, so that the rod was moved across the substrate with its weight force each time. After the substrate was detached and dried, it was photographed under a microscope at appropriate magnification using normal light.

[0093] The entire process was then repeated, with the rod being weighted incrementally by 10 g each time (by attaching two 5 g washers). The process was preferably repeated until the conductive polymer began to detach. Since the electrical polymer used was Amplicoat®, available from Heraeus Deutschland GmbH & Co. KG, which appears black under normal light, the detachment was clearly visible.

[0094] It will be apparent to those skilled in the art that, instead of the swipe test described here, other equivalent means can be used in a similar manner to determine the mechanical strength of surfaces. Examples

[0095] The invention is further illustrated below by means of examples, which, however, are not to be understood as limiting. It will be apparent to those skilled in the art that other equivalent means can be used in a similar manner instead of the features described here.

[0096] The following applies to comparative examples 1 and 2 as well as to examples 1 and 2 according to the invention. An electrical conductor in the form of a disc was provided. The disc has a diameter of 5 cm and a height of 0.1 cm and has a substantially smooth surface which was neither etched nor coated in any way by any other method.

[0097] The following applies to comparative example 2 and example 2 according to the invention. The disk was electroplated with a layer of a platinum-iridium alloy. These layers have a thickness of approximately 2 µm and a mean roughness value R a from approximately 0.2 µm.

[0098] Finally, all discs were coated with a conductive polymer (Amplicoat®, available from Heraeus Deutschland GmbH & Co. KG, Hanau, Germany) according to the manufacturer's instructions. In Comparative Example 1 and Example 1 according to the invention, the conductive polymer was applied directly to the surface of the discs. In Comparative Example 2 and Example 2 according to the invention, the conductive polymer was applied to the platinum-iridium alloy layer.

[0099] The mechanical strength of the applied layer of conductive polymer was then determined using the swipe test. A higher weight value before the conductive polymer was detached correlated with higher mechanical strength.

[0100] Additional details for each of the respective examples are given below and in Table 1. Comparative example 1

[0101] The disk consists of a platinum-iridium alloy with an iridium content of 10% by weight of the total mass of the platinum-iridium alloy (Ptlr10), and there is no additional intermediate layer between the surface of the disk and the conductive polymer. This example therefore simulates an electrical conductor with a first layer of such a low-iridium platinum-iridium alloy, where the first layer is essentially smooth. Comparison example 2

[0102] As in Comparative Example 1, the disk consists of a platinum-iridium alloy with an iridium content of 10% by weight based on the total mass of the platinum-iridium alloy (Ptlr10). The electroplated intermediate layer described above is formed between the disk and the conductive polymer. This intermediate layer, like the disk, consists of a Ptlr10 alloy. This example thus simulates an electrical conductor with an electroplated first layer of Ptlr10 with a mean roughness value R. a of 0.2 µm. Example according to the invention 1

[0103] This example is similar to Comparative Example 1, wherein the disk consists of a platinum-iridium alloy with an iridium content of 40 percent by weight based on the total mass of the platinum-iridium alloy (PtIr40). This example therefore simulates an electrical conductor with a first layer made of a PtIr40 alloy according to the invention, wherein the first layer is substantially smooth. Example 2 according to the invention

[0104] As in Example 1 of the invention, the disk consists of a PtIr10 alloy, wherein the electroplated intermediate layer described above is formed between the disk and the conductive polymer. The intermediate layer consists of a Ptlr40 alloy. This example therefore simulates an electrical conductor with a first layer made of a Ptlr40 alloy according to the invention, wherein the first layer is electroplated and has a mean roughness of 0.2 µm. Table 1: Determination of the mechanical load-bearing capacity of the conductive polymer layer on different layers. Comparative example 1 Comparison example 2 Example according to the invention 1 Example 2 according to the invention Material of the simulated first layer Ptlr10 Ptlr10 Ptlr40 Ptlr40 Galvanically deposited first layer no Yes no Yes Average roughness R a the simulated first layer Essentially smooth 0.2 µm Essentially smooth 0.2 µm Weight at which conductive polymer layer delaminates 93 g 143 g 133 g > 203 g

[0105] A direct comparison of Comparative Example 1 to Inventive Example 1 and a direct comparison of Comparative Example 2 to Inventive Example 2 shows that the improvement in the mechanical stability of the electrical conductor is primarily due to the high iridium content of the platinum-iridium alloy and only secondarily to the surface roughness of the layer on which the conductive polymer was applied. The first layer of the Inventive Examples, in particular the electroplated first layer of Inventive Example 2, thus allows the construction of more durable, mechanically stable electrical conductors, especially medical electrodes. Figures

[0106] The invention is further illustrated below by means of exemplary figures. The invention is not limited to the figures.

[0107] They show Fig. 1 an electron microscopic cross-sectional image of an electronic conductor according to the invention, Fig. 2 an electron micrograph of an electroplated first layer in a top view, Fig. 3 Test results of a swipe test of the inventive example 2 in overhead view, Fig. 4 Test results of a swipe test of comparison example 1 under supervision, and Fig. 5. A flowchart of a process for manufacturing an electrical conductor. Description of the characters

[0108] Fig.Figure 1 shows an electron microscopic cross-sectional image of an electrical conductor 100 according to the invention. The electrical conductor 100 comprises a substrate 110 made of a platinum-iridium alloy with an iridium content of 10% by weight based on the total mass of the platinum-iridium alloy (PtIr10) and a surface area 115. A platinum-iridium alloy with an iridium content of 40% by weight based on the total mass of the platinum-iridium alloy (PtIr40) was electroplated onto the surface 115 of the substrate 110 as a first layer 120. In the embodiment shown, the first layer 120 consists of the platinum-iridium alloy with the iridium content of 40% by weight based on the total mass of the platinum-iridium alloy. The first layer 120 has a layer thickness between 0.8 µm and 1.2 µm.On the side of the first layer 120 facing away from the substrate 110, a conductive polymer in the form of Amplicoat®, available from Heraeus Deutschland GmbH & Co. KG, is applied as a second layer 130. In the embodiment shown, the second layer 130 consists of the conductive polymer. The second layer 130 has a thickness of between 0.8 µm and 1.5 µm.

[0109] Fig. Figure 2 shows an electron micrograph of a first layer 120' according to the invention in top view. The second layer 120' consists of a platinum-iridium alloy with an iridium content of 40% by weight based on the total mass of the platinum-iridium alloy (Ptlr40) and was electroplated onto a substrate (not visible) and has a surface with elevations and depressions. The mean roughness R a The thickness of the first layer shown, 120', is 0.254 µm.

[0110] Fig.Figure 3 shows the results of the swipe test of example 2 according to the invention (see Table 1). It is clearly evident that no detachment of the conductive polymer (black) occurred up to a weight value of 203 g.

[0111] Fig. Figure 4 shows the results of the swipe test for comparison example 1 (see Table 1). Up to a weight of 83 g, no detachment of the electrical polymer (black) occurs. At a weight of 93 g, some of the electrical polymer has been rubbed off, and the first layer (silver-colored) beneath the electrical polymer is visible.

[0112] Fig. Figure 5 shows a flowchart of a process 200 for the production of an electrical conductor 100 according to the invention, comprising steps 210 to 230.

[0113] In step 210, a substrate 110 with a surface area 115 is provided.

[0114] In step 220, a first layer 120 is applied to the surface 115 of the substrate 110. For example, the application in step 220 is carried out by an electroplating process.

[0115] In step 230, a second layer 130 is applied to the first layer 120, in particular to the side of the first layer 120 facing away from the substrate 110. The application of the second layer 130 to the first layer 120 can be carried out, for example, by electrochemical or chemical polymerization, by dip coating, or by inkjet printing, or a combination thereof. Reference sign 100 electrical conductors 110 substrate 115 Surface area substrate 120, 120' first shift 130 second shift 200 procedures 210 Provide 220 Applying the first layer 230 Applying the second layer QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 10,219,715 B2

[0006] US 2019 / 0159833 A1

[0007] EP 3500419 B1

[0007] US 11,495,369 B2

[0008] Cited non-patent literature

[0000] Long-Term Stable Adhesion for Conducting Polymers in Biomedical Applications: IrOx and Nanostructured Platinum Solve the Chronic Challenge", ACS Appl. Mater. Interfaces 2017, 9, 189-197 by Boehler

[0009] Giurlani et al, Coatings 2020, 10, 1211; doi:10.3390 / coatings10121211

[0059] Petrossians et al, Journal of The Electrochemical Society, 158 (5), D269-D276 (2011

[0076] DIN EN ISO 4287

[0091]

Claims

[1] An electrical conductor (100) comprising a substrate (110) having a surface (115) on which a first layer (120, 120') comprising a platinum-iridium alloy is disposed, and a second layer (130) comprising a conductive polymer is disposed on the first layer (120, 120'), characterized by that the platinum-iridium alloy has an iridium content of at least 30 percent by weight based on the total mass of the platinum-iridium alloy. [2] Electrical conductor (100) according to claim 1, wherein the platinum-iridium alloy has an iridium content of at most 50 weight percent based on the total mass of the platinum-iridium alloy. [3] Electrical conductor (100) according to claim 1 or 2, wherein the platinum-iridium alloy has an iridium content in a range of 30-50 weight percent, preferably in a range of 30-45 weight percent, more preferably in a range of 35-45 weight percent, based on the total mass of the platinum-iridium alloy. [4] Electrical conductor (100) according to one of the preceding claims, wherein the platinum-iridium alloy is galvanically deposited on the surface (115) of the substrate (110). [5] Electrical conductor (100) according to one of the preceding claims, wherein the platinum-iridium alloy has a surface with a mean roughness R a in a range of 0.05 µm to 0.5 µm. [6] Electrical conductor (100) according to one of the preceding claims, wherein the first layer (120, 120') has a layer thickness of at most 3 µm. [7] Electrical conductor (100) according to claim 6, wherein the first layer (120, 120') has a layer thickness of at least 300 nm. [8] Electrical conductor (100) according to one of the preceding claims, wherein the substrate (110) comprises or consists of gold or platinum. [9] Electrical conductor (100) according to one of the preceding claims, wherein the second layer (130) comprises or consists of PEDOT. [10] Method (200) for producing an electrical conductor (100) according to one of the preceding claims, comprising the following steps: i) providing (210) the substrate (110) with the surface (115); ii) applying (220) the first layer (120, 120') to the surface (115); iii) applying (230) the second layer (130) to the first layer (120, 120'). [11] The method (200) of claim 10, wherein the first layer (120, 120') is applied to the surface (115) by a galvanic coating process. [12] Method (200) according to claim 10 or 11, wherein the application (230) of the second layer (130) to the first layer (120, 120') is carried out by electrochemical or chemical polymerization, by means of dip coating or by means of inkjet printing.

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