Implantable electrical contact device

Abstract

The present invention relates to an implantable electrical contact device comprising at least one electrode element arrangement, which is completely integrated into a carrier substrate made of a biocompatible, electrically insulating material and has at least one freely accessible electrode surface directly or indirectly surrounded by the biocompatible, electrically insulating carrier substrate. The invention is characterized in that, within a subspace not containing the at least one electrode element arrangement, the carrier substrate completely surrounds at least one space containing at least one material having an elastic modulus that differs from the elastic modulus of the material associated with the carrier substrate.

Description

Technical Field

[0001] The present invention relates to an implantable electrical contact device comprising at least one electrode element arrangement, which is completely integrated into a carrier substrate made of a biocompatible, electrically insulating material and has at least one freely accessible electrode surface which is directly or indirectly surrounded by the biocompatible, electrically insulating carrier substrate. Background Art

[0002] Implantable electrical contact devices of the type in question are used to apply electrical signals to and / or obtain electrical signals from tissue surfaces in the body, in particular the surfaces of blood vessels, muscles or nerve fibers. A particular challenge for the in vivo positioning of such implantable electrical contact devices is to secure the contact device as gently and smoothly as possible to the internal body surface without damaging or irritating the internal body surface over a long period of time. However, this places high demands on the securing of the implant side of the electrical contact device to the corresponding tissue surface, in particular since the tissue surface is subject to movement and shape changes due to changes in temperature and pressure in the body, which should not, or as far as possible, be hindered by the medical implant. At the same time, the local surface contact between the electrode surfaces of the electrode elements applied on the implant side should be formed with a surface contact pressure that is as constant as possible and defined, in order to ensure electrical transmission characteristics that are as constant as possible.

[0003] In addition to various different forms of implantable electrode devices, so-called skin-mounted electrodes, which are applied circularly around a nerve fiber bundle, allow for electrical nerve stimulation and localized acquisition of electrical neural signals along the nerve fiber bundle. Due to the wrapping formed by the circular opening of the skin-mounted electrode, the latter can be radially molded to the nerve fiber bundle from the outside, while following radial changes in the shape of the nerve fiber bundle.

[0004] The electrode element of an implantable electrical contact device, designed as a skin-mounted electrode for contacting a nerve fiber bundle, is applied to a biocompatible, electrically insulating, sheet-like carrier substrate, which can be shaped from a flat surface into the shape of a straight hollow cylinder by surface wrapping and / or surface curvature. In this state of the skin-mounted electrode, the freely accessible electrode surface of the electrode element is located on the inner side of the carrier substrate shaped as a hollow cylinder and, in the implanted state, rests directly on the epineurium of the nerve fiber bundle.

[0005] EP0843574B1 describes a known skin-mounted electrode whose sheet-like carrier substrate is configured in the form of an interdigitated structure. By bending the sheet, the flexible fingers assume the shape of a straight hollow cylinder, the diameter of which can be flexibly varied by the corresponding fingers, whose ends are freely and variably interlocked. To create and support the hollow cylindrical shape, the sheet-like carrier substrate is provided with at least one layer of shape-memory material or mechanically prestressed material.

[0006] An alternative design for producing an implantable skin-wound electrode device is described in document EP3204105B1. In this case, the skin-wound electrode configured as a wound electrode comprises a sheet-like, flexible, biocompatible carrier substrate, preferably in the form of a polyimide film, on the upper side of one carrier substrate, an electrode device consisting of a plurality of individual electrode elements is applied. The individual electrode elements of the electrode device are in direct surface contact with the epineurium of the nerve fiber bundle, in particular when the carrier substrate is rolled into a straight cylindrical winding shape by appropriately incorporating mechanical prestress into the membrane. By means of windings open at one end, winding layers of the sheet-like carrier substrate that slide loosely against each other are at least partially formed, by means of which individual diameter variations of the hollow cylindrical skin-wound electrode device surrounding the nerve fiber bundle are possible.

[0007] The contact pressure with which the electrode surfaces each come into contact with the epineurium of the nerve fiber bundle is essentially determined by the elastic material properties of the entire sheet-like carrier substrate.

[0008] DE 202010015346 U1 proposes an electrode arrangement in which a single piece of nitinol strip protrudes through the entire substrate for shaping purposes within the electrode within a strand-shaped substrate. The nitinol strip has an elastic modulus that differs from that of the carrier substrate and functions as a spine to support the shape of the electrode assembly.

[0009] Document US2008 / 0004673A1 discloses an elastically deformable skin-mounted electrode, in which a shape memory material, such as Nitinol, is added to the skin-mounted electrode for forming purposes. Summary of the Invention

[0010] The object of the present invention is to further develop an implantable electrical contact device comprising at least one electrode element arrangement which is fully integrated into a carrier substrate made of a biocompatible, electrically insulating material and has at least one freely accessible electrode surface which is directly or indirectly surrounded by the biocompatible, electrically insulating carrier substrate, such that the contact pressure of the at least one electrode surface on the in vivo tissue surface can be individually adjusted without changing or substantially changing the spatial dimensions of the carrier substrate, in particular the thickness of the carrier substrate. It should be possible to individually configure the contact pressure in the surface along which the carrier substrate contacts the in vivo tissue surface, i.e., to adjust the contact pressure in a position-dependent manner along the contacting carrier substrate surface.

[0011] The solution to the object forming the basis of the invention is set forth in claim 1. Further advantageous developments of the inventive idea form the subject matter of the dependent claims and can be gathered from the further description, in particular with reference to the illustrated embodiments.

[0012] Unlike the obvious variation measure, which is to first increase the material thickness of the sheet-like carrier substrate in order to bring about a greater local material stiffness and a corresponding increase in the surface contact force, the implantable electrical contact device according to the present solution is characterized in that, within a subspace that does not contain at least one electrode element device, the carrier substrate directly or indirectly encloses at least one space, which at least one space contains at least one material having an elastic modulus that is different from the elastic modulus of the material assigned to the carrier substrate.

[0013] The measures according to the present solution essentially allow the surface elasticity or surface stiffness of the sheet-like carrier substrate to be individually adjusted or specified without changing, or substantially changing, the thickness of the sheet-like carrier substrate. In particular, this makes it possible to produce an implantable electrical contact device whose electrode surface presses against the body tissue surface with a higher pressure than the remaining sheet-like carrier substrate.

[0014] In this way, a durable, stable electrical contact with constant electrical properties is ensured, while in other areas, the sheet-like carrier substrate is in contact with the nerve fiber bundle with sufficiently low contact forces for fixation purposes, in a tissue-friendly manner. To this end, at least one material with a higher elastic modulus than the material's elastic modulus is selected for filling the space. Similarly, the surface stiffness can be locally reduced in areas of the carrier substrate by selecting at least one material with a lower elastic modulus than the material of which the carrier substrate is made for filling the space. Depending on the material selection and the available space within the sheet-like carrier substrate, any desired stiffness gradient can be generated within the carrier substrate.

[0015] In a preferred form of embodiment, the sheet-like carrier substrate comprises a neutral fiber which separates a subspace of the carrier substrate containing the at least one electrode element arrangement from a subspace of the carrier substrate containing the at least one space.

[0016] The at least one space is completely surrounded by the biocompatible, electrically insulating material of the carrier substrate and, with respect to its dimensions, oriented relative to the longitudinal direction of the sheet, is significantly smaller than that of the sheet-like carrier substrate. This allows for unproblematic use of the implantable electrical contact device according to the invention in vivo, particularly since the at least one material applied to the carrier substrate does not come into contact with the in vivo environment.

[0017] Preferably, when projected orthogonally onto the electrode surface, the at least one space at least partially, preferably completely, overlaps the electrode surface. In this way, it is ensured that at least the carrier substrate region containing the electrode surface is locally pressed against the in vivo tissue surface with an increased or individually adapted contact force.

[0018] Typically, the sheet-like carrier substrate is made of a polymer, such as polyimide, liquid crystal polymer (LCP), parylene, or PDMS. Typically, such materials have an elastic modulus between 1 GPa and 2 GPa. When a metallic material is used to fill the at least one space, a significant stiffness gradient can be incorporated into the sheet-like carrier substrate. The following table shows the elastic moduli associated with various metallic materials:

[0019] Material Elastic modulus GPa gold 78 copper 100 to 130 aluminum 70 nickel 195 to 205 ceramics 160 to 440 graphene About 1,000

[0020] In addition to the solid materials not listed in the table above, other materials that contribute to local reinforcement of the polymeric carrier substrate, have an elastic modulus lower than that of the carrier substrate, and can be inserted into or enclosed within at least one space within the carrier substrate are also conceivable. For example, gels, liquids, or gases that can be inserted into the carrier substrate are also suitable for this purpose. Furthermore, when using gases or liquids, their assigned elastic moduli can be determined by the filling pressure of the corresponding gaseous or liquid material into the at least one space within the sheet-like carrier substrate.

[0021] In another preferred embodiment, at least two materials with different elastic moduli are incorporated into at least one space, preferably in the form of a layered sequence of two solid materials, preferably in the form of two different metal layers. By combining several substances with mutually different elastic moduli, a random distribution of the elastic moduli can be achieved within the carrier substrate.

[0022] In another embodiment, preferably for local reinforcement of the carrier substrate, a transducer material is used as the material filling the at least one space, which can be modified by an external action, for example, by an external energy field, so as to change its shape and / or elasticity. Suitable transducer materials are, for example, bimetallic materials, shape memory alloys, piezoelectric ceramics, electrostrictive ceramics, magnetostrictive alloys, electrorheological fluids or magnetorheological fluids, or similar materials.

[0023] Implantable electrical contact devices typically have a flat carrier substrate that is suitably sized in shape and size for application to tissue or nerve fiber bundles in the body. The typical area of ​​the carrier substrate, which can be folded and / or wrapped in a single or multiple overlapping manner depending on the application, is between a few square millimeters and a few square centimeters, for example between 4 square millimeters and 20 square centimeters, preferably from 10 mm to 20 mm. 2 Up to 6cm 2 Most sheet-like carrier substrates have a substrate thickness of several micrometers to several hundred micrometers, for example, 2 micrometers to 650 micrometers, preferably 10 micrometers to 100 micrometers.

[0024] At least one space, which is completely, i.e. sealed, surrounded by the carrier substrate material and preferably has a cubic or cuboid shape, the dimensions of which are much smaller than the dimensions of the carrier substrate in its longitudinal direction. The at least one space contains at most 17 mm 3 Volume. A space filled with a material having an elastic modulus different from that of the carrier substrate can only locally affect the characteristics of the carrier substrate in the area surrounding the space. Due to the small size of at least one space relative to the size of the carrier substrate, the material contained in the space does not exert a supporting force that affects the overall spatial shape of the carrier substrate. Even in the case where multiple spaces are distributed within the carrier substrate and filled with at least one material, and each space is arranged in an isolated manner and spaced apart from each other, spatial regions with multiple elastic moduli different from that of the carrier substrate partially act in a hardening or softening manner, but do not act in a manner that defines the shape of the space because the space cannot form a coherent supporting effect.

[0025] Therefore, one example of an embodiment envisions a plurality of first spaces, each space being filled with at least one material, and the plurality of first spaces being distributed in the carrier substrate along a first straight line or along a first plane in an array-like manner and spaced apart from each other.

[0026] In another embodiment, in addition to the plurality of first spaces, a plurality of second spaces, each of which is filled with at least one material, are distributed within the carrier substrate along a second line or along a second plane, spaced apart from one another. Preferably, the first and second lines, or the first and second planes, are oriented parallel to one another.

[0027] In addition to the plurality of first and second spaces filled with at least one material, another example of embodiment envisages a plurality of further spaces, each filled with at least one material, which are distributed along further straight lines or along further planes spaced apart from one another within the carrier substrate.

[0028] By means of such a plurality of spaces filled with material, areas of the sheet-like carrier substrate can be specified with individually defined hardness and / or stiffness.

[0029] In particular, in the case of skin-engraving electrode devices that can be wrapped around a nerve fiber bundle, the carrier substrate region that is in direct contact with the nerve fiber bundle and / or the carrier substrate wrapping near the nerve fiber bundle can be designed to have the lowest possible surface stiffness, because in this region of the carrier substrate, there are no spaces filled with material, or only spaces filled with a material with an elastic modulus that is significantly lower than the elastic modulus of the carrier substrate material. In the radially adjacent carrier substrate regions of the skin-engraving electrode device, spaces filled with a material whose elastic modulus is selected to be greater than the elastic modulus of the carrier substrate material are included. In this way, a radially acting, increased external contact pressure can be exerted on the inner carrier substrate layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will now be described by way of example without limiting the general inventive concept, with reference to the accompanying drawings.

[0031] Figure 1a 、 1b , 1c each show a longitudinal section through a carrier substrate with an electrode arrangement and at least one space. DETAILED DESCRIPTION

[0032] Figure 1a A longitudinal section through a sheet-like carrier substrate 1, preferably in the form of a polyimide film, is shown, having a carrier substrate top side 2 and an opposing carrier substrate bottom side 3. Embedded within carrier substrate 1 is an electrode arrangement comprising at least one electrode element 4, which contacts power supply and outlet leads 5 extending within carrier substrate 1. Electrode element 4 includes a freely accessible electrode surface 6. Optionally, but advantageously, electrode element 4 protrudes beyond carrier substrate top side 2 and, in the implanted state, faces toward a tissue surface (not shown) within the body, so that electrode surface 6 comes into surface contact with the tissue surface.

[0033] The sheet-like carrier substrate 1 comprises a neutral fiber 7 which divides the carrier substrate 1 into an upper subspace 8 and a lower subspace 9. The upper subspace 8 contains the electrode arrangement, while the lower subspace of the carrier substrate 1 comprises at least one space 10 which is completely surrounded by the material of the carrier substrate 1 and contains at least one material 11 having an elastic modulus E1 which is different from the elastic modulus E1 of the carrier substrate 1. T .

[0034] In the example of embodiment shown in FIG1 . Figure 1a In an orthogonal projection onto the carrier substrate top side 2 , the space 10 is arranged partially below the electrode element 4 in a completely overlapping manner.

[0035] A preferred material selection involves the use of a metallic substance 11 within space 10, preferably in the form of an integral metallic layer, which is completely surrounded by the biocompatible, electrically insulating material of carrier substrate 1. Metallic substance 11 can locally reinforce carrier substrate 1. When the carrier substrate is designed as a skin-engraved electrode device, this local reinforcement can achieve a localized increase in the contact pressure between electrode element 4 and an in vivo tissue surface, preferably in the form of nerve fiber bundles. The additional infusion or integration of material 11 within space 10 is independent of any increase in carrier substrate thickness d.

[0036] The arrangement, size and spatial configuration of the space 10 within the carrier substrate can be selected differently.

[0037] Figure 1b An alternative example of embodiment is shown which envisages a plurality of separate spaces 10 ′ within the carrier substrate 1 , which are either uniformly filled with one material 11 or each filled with a different material, depending on the desired setting of the stiffness of the carrier substrate 1 in the region of at least one electrode element 4 . Figure 1b , a plurality of spaces 10' are arranged along a plane e1 extending parallel to the neutral fiber 7. Alternative arrangements of a plurality of individual spaces 10' are also conceivable, for example in two or more planes e1, e2, etc. extending parallel to each other.

[0038] Figure 1c A further example of an embodiment is shown, which has at least two spaces 10″, wherein each space is respectively applied laterally next to an electrode element 4 when projected orthogonally onto the carrier substrate top 2. In this case, if the spaces 10′ are filled with a material having a higher elastic modulus than the elastic modulus of the carrier substrate 1, the carrier substrate 1 has a lower stiffness in the region of the electrode arrangement than in regions laterally adjacent to the electrode arrangement.

[0039] Common to all possible examples of embodiment is the fact that, by providing one or more spaces within the carrier substrate 1, each space being filled with at least one material, without increasing the thickness of the sheet-like carrier substrate, a randomly generated stiffness gradient can be defined within the carrier substrate 1. In particular, since the materials used to fill the individual spaces can be freely selected and, in addition to solids, these materials can also include gases, in particular liquids or gel-like substances, the surface stiffness properties of the entire carrier substrate can be individually and finely controlled.

[0040] It is also possible to use textile or fibrous materials which can be integrated individually or layered in a locally limited manner within the carrier substrate. For example, in the case of a textile layer, it can be surrounded by the biocompatible, electrically non-conductive material of the carrier substrate like a matrix.

[0041] According to this solution, at least one space within the carrier substrate is provided, which is filled with a material having an elastic modulus different from that of the carrier substrate. This arrangement can also serve to compensate for mechanical stresses that arise within the carrier substrate due to the integration of the electrode arrangement within the carrier substrate. Such mechanical stresses can lead to excessive material stresses within the carrier substrate and ultimately limit the lifespan of the implantable electrical contact device. More specifically, the design of the implantable electrical contact device in the form of a known skin-mounted electrode leads to inherent material mechanical stresses that can be fully or at least largely compensated by the at least one space within the carrier substrate filled with the material.

[0042] Reference Signs List

[0043] 1 Carrier substrate

[0044] 2 Carrier substrate upper side

[0045] 3 Underside of carrier substrate

[0046] 4 Motor components

[0047] 5 Power and outlet leads

[0048] 6 Electrode surface

[0049] 7 Neutral Fiber

[0050] 8 Subspace containing electrode element devices

[0051] 9 contains at least one subspace of the space

[0052] 10, 10', 10" space

[0053] 11 Materials

[0054] e1 and e2 are used for the layout of the space

[0055] d Sheet thickness of carrier substrate

[0056] E1 elastic modulus of the material

[0057] E T Elastic modulus of carrier substrate

Claims

1. An implantable electrical contact device comprising: at least one electrode element arrangement, which is originally fully integrated into a carrier substrate made of a biocompatible, electrically insulating material and has at least one freely accessible electrode surface which is directly or indirectly surrounded by the biocompatible, electrically insulating carrier substrate, wherein the carrier substrate comprises neutral fibers (7) which separate the carrier substrate into an upper subspace (8) and a lower subspace (9), the upper subspace containing the at least one electrode arrangement and the lower subspace containing the at least one space (10); A transducer material is arranged in the at least one space (10), wherein the transducer material provides a local reinforcement, has an elastic modulus higher than the elastic modulus assigned to the carrier substrate material, and changes shape or elasticity by an external energy field; wherein an orthogonal projection of the at least one space (10) on the electrode surface at least partially overlaps with the electrode surface, a longitudinal length of the at least one space is smaller than a longitudinal length of the carrier substrate, an upper subspace of the carrier substrate is free of transducer material, and the electrical contact device is configured to locally increase a contact pressure applied from the electrical contact device to the surface of the tissue in the body at the electrode surface.

2. The implantable electrical contact device according to claim 1, It is characterized in that The at least one space further comprises at least one material having an elastic modulus that differs from the elastic modulus of the material assigned to the carrier substrate.

3. The implantable electrical contact device according to claim 1 or 2, It is characterized in that The carrier substrate is made of a polymer that is one of the following polymers: polyimide, liquid crystal polymer (LCP), parylene, or PDMS.

4. The implantable electrical contact device according to claim 1 or 2, It is characterized in that The carrier substrate is designed in a sheet-like manner and has a carrier substrate top side comprising the at least one freely accessible electrode surface and an opposite carrier substrate bottom side, and The at least one space has an extension parallel to the orientation of the carrier substrate top side and the carrier substrate bottom side.

5. The implantable electrical contact device according to claim 2, It is characterized in that The at least one material is in gaseous, liquid or solid state.

6. The implantable electrical contact device according to claim 1 or 2, It is characterized in that At least two materials having different elastic moduli are also contained within the at least one space.

7. The implantable electrical contact device according to claim 1 or 2, It is characterized in that The transducer material is a material from the following material group: bimetallic material, shape memory alloy, piezoelectric ceramic, electrostrictive ceramic, magnetostrictive alloy, electrorheological fluid or magnetorheological fluid.

8. The implantable electrical contact device according to claim 1 or 2, It is characterized in that The at least one space encloses a maximum of 17 mm 3 volume of space.

9. The implantable electrical contact device according to claim 1 or 2, It is characterized in that In terms of the size of the at least one space in the longitudinal direction of the sheet, the size of the at least one space is at least one order of magnitude smaller.

10. The implantable electrical contact device according to claim 1 or 2, It is characterized in that The dimensions of the at least one space and the material contained in the at least one space are selected such that the at least one space and the material contained in the at least one space cannot exert any force capable of influencing the spatial shape of the implantable electrical contact device.

11. The implantable electrical contact device according to claim 2, It is characterized in that A plurality of first spaces respectively filled with the at least one material are distributed in the carrier substrate along a first straight line or along a first plane in an array-like manner and spaced apart from each other.

12. The implantable electrical contact device according to claim 11, It is characterized in that A plurality of second spaces respectively filled with the at least one material are distributed in the carrier substrate along a second straight line or along a second plane in an array-like manner and spaced apart from each other.

13. The implantable electrical contact device according to claim 12, It is characterized in that The first straight line and the second straight line or the first plane and the second plane are oriented parallel to each other.

14. The implantable electrical contact device according to claim 12 or 13, It is characterized in that A plurality of additional spaces, each filled with the at least one material, are distributed in the carrier substrate along another straight line or along another plane in an array-like manner and spaced apart from one another.

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