Electrode for application to human skin

Description

[0001] The invention relates to an electrode according to the preamble of claim 1. The invention further relates to a method for manufacturing an electrode.

[0002] These medical skin electrodes can be used as measuring electrodes to detect electrical signals from the human body. They can also be used as therapeutic electrodes to deliver electrical currents to the body. For this purpose, the electrodes are adhered to the skin and generally have an electrically conductive gel or other contact medium on their underside, which is galvanically connected to a terminal element of the electrode. An electrical signal conductor can be connected to this terminal element, allowing currents to be drawn from or supplied to the electrode.

[0003] One type of electrode has a protruding, electrically conductive connecting element on the upper side facing away from the skin, with a connection point that is usually essentially spherical, to which a neck is attached.

[0004] In previous designs of this type of electrode, the connection element was a two-part design. The upper part (upper stud) serves as a contact and anchor element for standard signal conductors, such as ECG leads. Essentially below the electrode body, on the side facing the skin, is a lower stud (eyelet) that receives electrical potentials directly from the gel (contact medium) or transfers them to the gel. The eyelet is connected to the stud both electrically and mechanically, generally by riveting the two parts together, such that the electrode material is firmly clamped between a flange-like, laterally projecting retaining area of ​​the stud and a similar retaining area of ​​the eyelet.Such a design offers, on the one hand, good mechanical retention of the connecting element on the electrode carrier and, on the other hand, allows the eyelet to be manufactured from materials that possess electrically favorable properties for a signal electrode. For example, it can be coated with silver, whereby the silver layer is then completely or at least partially covered by a layer of silver / silver chloride (Ag / AgCl) in the area that contacts the gel. It is also possible for the eyelet not to directly contact the gel. In these so-called off-center signal electrodes, a transverse conductor is provided to connect the eyelet to the gel.

[0005] Such an off-center signal electrode is known, for example, from WO 2006 / 053366 A1.

[0006] US patent 4,777,954 A discloses a medical electrode with a two-part connector.

[0007] In DE 20 2007 006 112 U1, an electrode is shown in which the connecting element is arranged on the signal line. The electrode has an opening into which the connecting element located on the signal line is inserted.

[0008] WO 01 / 17423 A2 shows an electrode with a one-piece connection element. The connection element is attached by means of a flange, and a contact medium for contacting the skin is applied directly to the connection element.

[0009] WO 2016 / 001393 A1 again reveals an electrode with a two-part connection element.

[0010] US 4 117 846 A discloses an electrode with a lateral offset and a transverse conductor that is directly galvanically connected to the terminal element.

[0011] With such state-of-the-art electrodes, the contact point with the skin often does not always meet the desired requirements in terms of various factors. Furthermore, state-of-the-art electrodes are expensive – and even slight price differences can be significant for such mass-produced items.

[0012] The object of the invention is therefore to create an electrode of the type mentioned above that can be manufactured more cost-effectively and that, despite the cost-effective manufacturing, provides good mechanical anchoring of the connecting element in the electrode as well as good electrical properties.

[0013] According to the invention, this is achieved by an electrode according to claim 1.

[0014] In contrast to the previously common two-part construction, in which the connection element consists of two riveted parts (stud and eyelet), the invention provides a single connection element that, on the one hand, provides the connection point for the detachable connection of a signal conductor and, on the other hand, is connected (preferably galvanically) to the electrical transverse conductor. This single connection element can itself be made of several materials, for example, nickel-plated brass or a plastic doped with a conductive material (especially carbon fibers). However, unlike the previous two-part construction consisting of an eyelet and a stud, it constitutes a structural unit in the sense of a single part.

[0015] A particularly preferred embodiment of the connecting element is such that it has a substantially spherical head, a neck with a reduced diameter adjoining it, and a flange-like, laterally projecting retaining area at the end of the neck opposite the head. Standard signal conductors can be easily and detachably connected via the spherical head. The reduced-diameter neck is guided through an opening in the carrier (preferably without lateral contact), while the flange-like, laterally projecting retaining area is connected, preferably bonded, to the underside of the carrier or to a layered transverse conductor attached to it. The flange-like, laterally projecting retaining area securely holds the connecting element to the carrier material, even under high tensile loads.

[0016] To ensure a secure hold even under compressive loads on the connecting element, it is preferably provided that the connecting element has a laterally projecting retaining area which is arranged between a support layer and the carrier, wherein the support layer extends laterally beyond the retaining area of ​​the connecting element and is firmly connected to the carrier there - preferably bonded.

[0017] Forces exerted on the connecting element by pressure loads are absorbed on the one hand by the bonding of the holding area to the underside of the carrier or the cross conductor provided there, and on the other hand by the support layer, which directs these forces laterally into the carrier.

[0018] The electrical properties of the holding element are not subject to stringent requirements in the invention. It can therefore be made of inexpensive material, such as a simple sheet of metal. The holding element itself does not need to possess any special electrical properties, as only the transverse conductor, which is in contact with the electrical contact medium, can exhibit these properties that are advantageous for bioelectrodes.

[0019] To achieve low noise and depolarization in defibrillation at an electrode, redox couples are currently used. These can be oxidized or reduced, thereby accepting or donating at least one electron. Currently, a wide variety of substances are used for this depolarization. Silver / silver chloride and tin / tin chloride are the most common. However, for the present invention, any redox couple that enables electrode depolarization is conceivable. The redox couples can be actively added or possibly generated in situ through reactions.

[0020] Since, for example, silver / silver chloride is a relatively expensive substance, it is sufficient if, according to the invention, the transverse conductor has at least two different electrically conductive materials, one of which is galvanically connected to the connecting element and another of which is galvanically connected to the contact medium.

[0021] Further cost savings can be achieved by constructing the cross conductor from at least two different materials. The actual cross conductor can be made of relatively inexpensive materials, such as metal or plastic reinforced with conductive carbon fibers, while a second material, such as silver / silver chloride, can be used at the transition area to the electrical contact medium (especially gel), which is critical for the favorable electrical properties of the bioelectrode. It is sufficient for this material to be present only locally in this area.

[0022] The invention is based on the fundamental idea of ​​designing the connection element for the signal conductor in such a way that it is securely anchored in the electrode, while electrical properties are less critical, thus allowing the use of cost-effective materials. Conversely, the more expensive materials intended for efficient electrical signal conduction can only be used in the electrically critical area at the interface with the electrical contact medium (gel). This task is performed by the cross conductor. In short, the electrically conductive connection element, aside from the basic property of electrical conductivity, is primarily responsible for the "mechanics." The cross conductor, on the other hand, does not require any special mechanical properties and only needs to be made of suitable materials in the area of ​​the interface with the electrical contact medium (gel).Therefore, the cross conductor is responsible for the "electrical" functions without any special mechanical tasks.

[0023] Further advantages and details of the invention are explained in more detail with reference to the following description of figures: The Figure 1 The figure shows, in a schematic bottom view (later the side facing the skin), the manufacturing steps of an exemplary embodiment of an electrode according to the invention up to the finished electrode. Figure 2 shows a corresponding top view, although only some of the process steps are depicted in a top view. Figure 3 shows the sequence of cuts according to line AA of the Figure 1 The illustration is schematic and intended for better visualization. In reality, the layer sequence may have different dimensions, as is common with medical electrodes. Figures 4, 5 and 6 They essentially show the same representations as in the Figures 1, 2 and 3, however, for a different embodiment. The Figures 7 and 8 The diagram shows the underside of exemplary embodiments of an electrical connection element.

[0024] With reference to the Figures 1 to 3 The process for manufacturing an embodiment of an electrode according to the invention for application to human skin will now be explained in more detail.

[0025] The starting point is an electrically non-conductive substrate 1. The substrate material serves to anchor the electrical components of the electrode. It can, for example, consist of a (flexible) film (e.g., made of PET or TPU) which is applied to the substrate shown in the drawing. Figure 1 The underside facing upwards is coated with an adhesive 2, which can be, for example, self-adhesive (pressure sensitive adhesive) or thermo-activated (hot melt).

[0026] In a next step, a strip-shaped transverse conductor 3 is attached to this carrier material, in particular by bonding. According to a preferred embodiment of the invention, the transverse conductor has two differently electrically conductive materials, one of which is subsequently galvanically connected to the electrical connection element and the other of which is galvanically connected to the contact medium (gel).

[0027] The illustrated embodiment consists of a black, strip-shaped conductor made of a plastic doped with conductive carbon fibers. In the area of ​​the subsequent contact point with the electrical contact medium (gel), this transverse conductor 3 (first material with a second electrically conductive material) is coated, for example, with a layer 3a of silver / silver chloride or tin / tin chloride or another redox couple.

[0028] This layer 3a, intended to provide favorable electrical properties between the contact point and the subsequent gel, is only present where the gel will later be applied. Otherwise, a "normal" conductor 3, which is significantly less expensive, is sufficient to establish the electrical connection with the electrical terminal element described below.

[0029] In a further step, a bore 4 is provided through the electrical transverse conductor 3 and the support 1. This can be done, for example, by punching. Subsequently, the electrically conductive connection element 5 is inserted, which has a substantially spherical connection point 5a for the detachable connection of a commercially available signal conductor (not shown) and which protrudes beyond the top surface 1a of the support 1.

[0030] In the illustrated embodiment, the electrical connection element has a neck 5b with a reduced diameter following the essentially spherical head 5a, at which a flange-shaped holding area 5c is located at the end facing away from the head 5a.

[0031] Overall, the laterally projecting, flange-shaped retaining area 5c is essentially disc-shaped. On the one hand, it serves for electrical contact with the transverse conductor 3, in which the latter is "clamped" between the support 1 and the disc-shaped flange 5c. On the other hand, the disc-shaped flange provides mechanical support for the electrical connection element, particularly against tensile loads that can be exerted on the head 5a, and thus on the entire connection element 5, by a signal cable.

[0032] Preferably, an electrically conductive adhesive is provided between the transverse conductor 3 and the connecting element 5 or a flange 5c projecting laterally from it.

[0033] In contrast to the previously used riveted two-part connection elements consisting of a top-protruding stud (upper knob) and the bottom-mounted eyelet (lower knob), the invention employs a connection element 5 that consists of a single part. This part connects to the electrical transverse conductor 3 on one side and has the connection point 5a for the detachable connection of a signal conductor (not shown) on the other. This enables cost-effective manufacturing of the electrode because the usually expensive eyelet (lower knob) can be omitted. The one-piece design of the connection element is sufficient for mechanical anchoring.

[0034] The requirements for the electrical properties are minimal. This allows for the use of simple designs, such as a deep-drawn metal part as the connection element 5. The somewhat more complex electrical tasks are therefore not performed by the usual eyelet (bottom knob), but rather by the end of the transverse conductor 3 that connects to the subsequently applied electrical contact medium (gel). This results in a separation of functions. Apart from its basic property of being electrically conductive, the electrical connection element is primarily responsible for the mechanical retention within the electrode, while the transverse conductor is largely relieved of mechanical functions. This allows for the selection of cost-effective materials. In particular, it is possible to use more expensive—and electrically advantageous—materials only at point 3a, where contact with the gel will later occur.

[0035] The electrically conductive connecting element can – as already mentioned – consist of a deep-drawn metal sheet. In this case, it is at least partially hollow inside. However, it can also consist of a conductive plastic, for example ABS doped with conductive carbon fibers.

[0036] Ideally, the connecting element should be designed to be essentially rotationally symmetrical. Other variations are also possible.

[0037] To permanently fix the electrical connection element 5c in the electrode and, in particular, to secure it against pressure loads on the head 5a, a support layer 6 is applied in a next step. This support layer 6 can, for example, consist of a double-sided adhesive tape applied to the surface in the Figure 1 The lower side is bonded to the connecting element 5 (specifically to the plate-shaped holding area 5c) and to areas of the underside 1a of the carrier 1.

[0038] Pressure can be applied to the layers, causing them to conform to their contours and bond together. The in Figure 3 The cross-section shown after the application of support layer 6, with the edges shown there, is merely a schematic representation. In reality, the layer thicknesses are usually less and the layer profiles are much more rounded.

[0039] The double-sided adhesive tape 6, which is bonded on one side to the carrier 1, the electrical cross conductor 3 and the holding area 5c of the electrical connection element 5, is now bonded on the other side with a plaster layer 7, wherein the plaster layer is preferably able to be adhered to the skin by means of a patient-side coating of biocompatible adhesive in order to fix the electrode.

[0040] Contrary to the illustrated embodiments, the support layer can also be formed directly by the paving layer (without an interposed double-sided adhesive tape). It is also possible to bond the paving layer to the carrier 1 and the holding area 5c of the connecting element 5 via a layer of self-adhesive or a thermo-activated adhesive applied to it.

[0041] Now back to the example implementation according to the Figures 1 to 3 The plaster material 7 shown there is firmly bonded to the carrier 1 not only via the double adhesive tape 6 but also via the adhesive on the underside 2.

[0042] The adhesive material ultimately serves to fix the electrode to the patient's skin. Suitable adhesive materials can consist of, for example, a film (e.g., PE), a foam strip (e.g., PE foam), or non-woven fabrics. The adhesive materials are usually coated on the patient side with a biocompatible adhesive 7a.

[0043] In a final manufacturing step of the electrode according to the Figures 1 to 3The electrical contact medium is introduced into a designated recess 7b in the patch material 7. The electrical contact medium enables the (preferably ion-based) conduction of body-generated electrical potentials or device-generated measurement or stimulation currents from the body surface (skin) to the electrical contact element and vice versa. The contact medium can, for example, consist of a chloride-doped gel, which is either in a more or less liquid form (more or less gelled) or as a cross-linked polymer matrix (hydrogel). However, it is also possible to produce the electrical contact medium using other means, such as a conductive adhesive or a sponge filled with saline solution.

[0044] In any case, the electrical contact medium 8, as the last step in the Figures 1 to 3shown, inserted into recess 7b. It contacts the end area 3a there (second material of the transverse conductor, in particular silver / silver chloride).

[0045] The interaction of the specially designed end region of the transverse conductor 3, in particular the coating with silver / silver chloride or another suitable material on the one hand, and the material of the electrically conductive contact medium 8 on the other hand, makes it possible to achieve favorable electrical properties of the electrode, such as noise-free signal transmission or depolarizing effects, whereby the use of the relatively expensive second material 3a at the end of the transverse conductor 3 can be limited to the area where contact with the contact medium 8 occurs. This further reduces costs.

[0046] Overall, the manufacturing process according to the Figures 1 to 3a "decentralized" electrode in which the connecting element 5 on the one hand and the contact medium 8 (gel) on the other hand are arranged at laterally offset locations (distance d) on the carrier 1.

[0047] The embodiment according to the Figures 1 to 3 The essential procedural steps are the following: Attaching, preferably by thermo-activated bonding, a strip-shaped transverse conductor to the underside of an electrically non-conductive carrier facing the skin; producing, preferably by punching out, a continuous opening through the transverse conductor and the carrier; inserting a one-piece connecting element from the underside of the carrier into the opening, such that a connection point for a signal conductor protrudes on the opposite top side of the carrier and the connecting element rests against the transverse conductor with a laterally projecting - preferably plate-shaped - retaining area; covering the retaining area of ​​the connecting element with a support layer, which is bonded to the carrier laterally next to the retaining area.

[0048] Finally, the following steps are taken to complete the electrode: Applying - preferably bonding - a skin-side adhesive patch layer to the carrier and / or the support layer, introducing an electrical contact medium - preferably a gel - into a recess of the patch layer, such that the underlying transverse conductor is contacted.

[0049] In the Figures 4 to 6 In the illustrated embodiment, most of the process steps correspond to those in Figures 1 to 3 They are identical, which is why the same reference symbols denote the same parts.

[0050] The difference lies essentially in step 5. Here, according to the Figure 4 Two incisions 9 are made through the entire assembly. In the next step 6, the paving material 7 is then only glued in the upper area and at the bottom on the "wings" (for example by local thermal activation), but not in the area of ​​the tab which remains movable as a result.

[0051] Overall, the exemplary embodiment according to the Figures 4 to 6 A movable tab 10 supports the connecting element 5 with the connection point 5a. This movable tab can compensate for tensile loads on the signal conductor (not shown) and thus on the connection point 5a, preventing these loads from being fully transferred to the electrode. Overall, this improves the adhesion of the electrode to the patient's skin.

[0052] In Figure 7 Figure 1 shows an embodiment of a holding area 5c, which projects laterally from the connecting element 5 in a flange-like manner. This holding area or flange has bores 5d. When the electrode is bonded, adhesive penetrates these bores, thereby improving the adhesion and resistance to rotation of the connecting element to the parts of the rest of the electrode.

[0053] The in serves the same purpose Figure 8The illustrated embodiment shows indentations 5e on the circumferential edge of the plate-shaped holding area. The hot melt adhesive also penetrates these indentations, thus improving adhesion.

[0054] The signal conductor, not shown, is of a known design and typically consists of an insulated, flexible cable leading from an evaluation unit or power supply unit to the electrode. The signal conductor itself is not part of the electrode, but rather separate from it and its connection element. At its electrode-side end, the signal conductor usually has a coupling piece, allowing it to be mechanically and electrically detachable to the connection point of the electrode's connection element, which is preferably pre-mounted on the electrode and permanently connected to it.

Claims

1. An electrode for application to human skin, comprising an electrically non-conductive carrier, which has an electrically conductive connecting element projecting from the top side of the carrier remote from the skin, the connecting element having a connection location for releasably connecting a separate signal conductor, wherein a transverse conductor extending at least partially on the underside of the carrier, and being arranged so as to electrically connect the connecting element to a contact medium facing the skin, wherein the connecting element (5) is formed of a single part which one on hand is in connected relationship with the transverse conductor (3) and on the other hand has the connection location (5a) for releasably connecting the separate signal conductor, wherein the connecting element (5) on the one hand and the contact medium (8) on the other hand are arranged at laterally mutually displaced locations (distance d) on the carrier (1), wherein the connecting element (5) projects through an opening (4) in the carrier (1), preferably with a neck (5b) that tapers in diameter, and that the connecting element (5), apart from any lateral contact in the area of the opening, is connected to the carrier (1) only on the underside of the carrier facing the skin, with a flat transverse conductor (3) interposed between them, characterized in that the transverse conductor (3) comprises at least two different electrically conductive materials, one of which (3) is galvanically connected to the connecting element (5) and another of which (3a) is galvanically connected to the contact medium (8).

2. The electrode according to claim 1, characterized in that the connecting element (5) comprises a metal, preferably a deep-drawn metal sheet, or conductive plastic, preferably with ABS doped with conductive carbon fibers.

3. The electrode according to claim 1 or 2, characterized in that the connecting element (5) has a substantially spherical head (5a), a reduced-diameter neck (5b) adjoining the head, and a laterally projecting flange-shaped holding region (5c) that is arranged at an end of the neck (5b) remote from the head (5a).

4. The electrode according to one of claims 1 to 3, characterized in that the contact medium (8), preferably arranged in a recess (7b) of a plaster layer (7), is a gel, preferably doped with chlorides, is designed as a conductive adhesive or a saline-filled sponge.

5. The electrode according to one of claims 1 to 4, characterized in that the connecting element (5) has a laterally protruding holding area (5c) which is arranged between a support layer (6) and the carrier (1), wherein the support layer (6) extends laterally beyond holding area (5c) of the connecting element (5) and is firmly connected there to the carrier (1), preferably by being glued.

6. The electrode according to claim 5, characterized in that the support layer (6) is designed as double-sided adhesive tape or as tape made of a thermally activatable adhesive or as tape made of a thermoplastic material suitable for direct thermoplastic connection to the carrier, which is glued on one side to the connecting element (5) and the carrier (1).

7. The electrode according to claim 5, characterized in that the support layer (6) is formed by a plaster layer (7), wherein the player layer can be glued to the skin, preferably by means of a patient-side coating of biocompatible adhesive (7a), in order to fix the electrode in place.

8. The electrode according to one of claims 1 to 7, characterized in that the transverse conductor (3) is designed as a preferably strip-shaped layer made of a first electrically conductive material, which is provided with, preferably coated with, a second electrically conductive material (3a) in the area of the contact medium (8) and preferably only there.

9. The electrode according to claim 8, characterized in that the first electrically conductive material (3) is a metal or a metal alloy, a plastic film which is conductive throughout or superficially, for example through conductive carbon fibers, or a textile material which is conductive throughout or superficially.

10. The electrode according to claim 8 or 9, characterized in that the second material (3a) is formed by a pair of silver / silver chloride or tin / tin chloride or another redox pair suitable for depolarizing the electrode.

11. The electrode according to one of claims 1 to 10, characterized in that the carrier (1) and the support layer (6) connected thereto has at least one incision (9) in a region beside the connecting element, which incision allows mobility of the connecting element (5) with respect to a plaster layer (7) provided for gluing to the skin.

12. The electrode according to one of claims 1 to 11, characterized in that the connecting element (5) is pre-mounted on the electrode and permanently connected thereto.

13. A method of producing an electrode for application to human skin according to one of claims 1 to 12, comprising the following steps: - Applying, preferably thermoactivated bonding, of a strip-shaped transverse conductor to the underside of the electrically non-conductive carrier facing the skin; - Producing, preferably punching a through opening through the transverse conductor and the carrier; - Introducing a one-piece connecting element from the underside of the carrier into the through opening, such that the connection location for a signal conductor projects from the opposite top side of the carrier and the connecting element bears with a laterally projecting, preferably plate-shaped, holding region against the transverse conductor; and - Covering the holding region of the connecting element with a support layer which is glued to the carrier laterally beside the holding region.

14. The method according to claim 13, characterized through the following further steps: - Applying, preferably by gluing, a plaster layer which is adhesive on the underside of the carrier or the support layer facing the skin; and - Introducing an electrical contact medium, preferably a gel, into a recess in the plaster layer such that the underlying transverse conductor is contacted.