Method for manufacturing a sensor cap with a membrane

Abstract

Method for manufacturing a sensor cap (7, 13) with at least one base body (16) and a membrane (8, 15) for a sensor, in particular optochemical (10) or electrochemical (1), for determining and / or monitoring the concentration of an analyte (2) in a measuring medium (3), comprising the following process steps - Providing a membrane (8,14) permeable to the measuring medium (3) and / or to at least one analyte (2) contained in the measuring medium (3) with a surface (O) intended for contact with the measuring medium (3) - Providing a base body (16) with at least one sub-area (18) intended for connection with the membrane (8,14), and - Welding at least a part of the membrane (8,14) and the base body (16), wherein the membrane (8,14) is applied at least partially to the at least one part (18) of the base body (16) and a tight connection is made between the base body (16) and the membrane (8,14) with respect to the measuring medium (3), - wherein the base body (16) and the membrane (8,14) are made of the same material, - wherein the base body (16) and the membrane (8,14) are welded together by means of ultrasonic welding.

Description

[0001] The invention relates to a method for producing a sensor cap with at least one base body and a membrane for a sensor, in particular an optochemical or electrochemical sensor, for determining the concentration of an analyte in a measuring medium, in particular a gaseous or liquid, or a measured variable dependent on the concentration of the analyte in the measuring medium. Furthermore, the present invention relates to a sensor cap produced by a method according to the invention and to a sensor with a corresponding sensor cap. In the following, an analyte is understood to mean any form of ion or gas contained in a liquid or in a gas / gas mixture.

[0002] Optochemical and electrochemical sensors often comprise a membrane that, in a continuous measurement principle, is brought into contact with a measuring medium, such as a measuring gas or a measuring liquid, to record measured values. Depending on whether the sensor is optochemical or electrochemical, the membrane serves a different function and is specifically designed for its use. In the case of optochemical sensors, for example, the membrane is often a thin film composed of one or more superimposed layers, particularly polymer layers.The individual layers exhibit different properties necessary for the functionality of the respective sensor. In particular, one of the sensor-specific layers, especially functional layers, is designed such that it is at least partially permeable to the measuring medium and / or to an analyte contained in the measuring medium. In the case of electrochemical sensors, however, the membrane is often a porous layer, in particular one with pores or openings, which is at least partially permeable to the measuring medium or at least to an analyte contained therein.

[0003] Many electrochemical, particularly amperometric, sensors have an electrolyte chamber separated from the measuring medium by a membrane. In amperometric sensors for determining a gas concentration in a liquid, such as electrochemical O2, Cl2, CO2, H2S, NH3, or SO2 sensors, the membrane serves as a diffusion barrier through which the analyte diffuses from the measuring medium into the electrolyte chamber. One such sensor is described, for example, in DE 10 2008 039465 A1.

[0004] DE 196 10 192 C2 discloses a method for manufacturing a sensor cap for an electrochemical sensor. However, this method has the disadvantage of using a hot-welding process with two heated annular dies and different materials for the base body and membrane.

[0005] Optochemical sensors, e.g., optochemical oxygen, ozone, or carbon dioxide sensors, are often based on analyte-induced fluorescence or luminescence quenching of an organic dye, or fluorophore, matched to the analyte. This fluorophore is typically contained, particularly dissolved, in a functional layer of the membrane, which in turn is applied to a substrate, e.g., a glass slide or an optical fiber, to form a sensor spot. Upon contact with the respective measuring medium, the interaction of the fluorophore with the analyte causes the fluorescence or luminescence intensity of the fluorophore to decrease as a function of the analyte concentration in the measuring medium. Different designs for optochemical sensors are known, for example, from documents WO 2005 / 100957 A1 and DE 100 51 220 A1.

[0006] A measuring membrane suitable for an optochemical or electrochemical sensor is known, for example, from DE 10 2014 112 972 A1. The measuring membrane comprises a sensor element having at least one functional layer with a sensor-specific substance and a substrate material. The sensor element is fully embedded in a matrix, and the matrix consists of a material that is accessible to the analyte at least in a partial area facing the medium and adjacent to the sensor element.

[0007] In many cases, the membrane is part of a sensor cap, which has a base body, in particular a cylindrical one, to which the membrane is glued or frequently clamped at the end in one end region. With such fastening methods, however, leaks often occur in the area of ​​the sensor cap during continuous operation of the respective sensor, especially over time. In the case of a glued membrane, for example, the adhesive can be attacked and at least partially dissolved by the respective analyte, e.g. chlorine or chlorine oxide. With clamped membranes, wrinkles can occur at the edges and / or the membrane can be destroyed as a result of the clamping. The present invention is therefore based on the object of providing a particularly durable and robust sensor cap for a sensor, in particular an optochemical or electrochemical sensor.

[0008] This object is achieved by the method for producing a sensor cap according to claim 1, by the sensor cap according to claim 9 and the sensor according to claim 14. Advantageous embodiments are specified in the dependent claims.

[0009] With regard to the method, the object according to the invention is achieved by a method for producing a sensor cap with at least one base body and a membrane for a, in particular optochemical or electrochemical, sensor for determining and / or monitoring the concentration of an analyte in a measuring medium, comprising the following method steps - Providing a membrane permeable to the measuring medium and / or to at least one analyte contained in the measuring medium, with a surface intended for contact with the measuring medium, - Providing a base body with at least one partial area intended for connection to the membrane, and - welding at least part of the membrane and the base body, wherein the membrane is at least partially applied to the at least one partial area of ​​the base body and a connection which is tight with respect to the measuring medium is created between the base body and the membrane, - the base body and the membrane are made of the same material, - whereby the base body and the membrane are welded together by ultrasonic welding.

[0010] A wide variety of membrane designs are possible, each of which can be adapted to the intended application, for example, the respective analyte or a specific sensor principle. In one design, the membrane is at least partially designed in the form of a porous structure, in particular one with pores.Alternatively, the membrane can also be designed at least partially as a thin film, which is constructed in particular from one or more layers, in particular functional layers, arranged one above the other, which layers can have at least partially identical or differently dimensioned base areas, wherein at least one layer is provided for welding the membrane to the base body, and / or wherein the layer provided for welding is designed such that it runs at least partially along an end face of the base body facing the measuring medium, or along the end face and at least partially along at least one lateral surface of the base body facing the measuring medium, or essentially completely or extending into an inner region of the base body along a surface of the base body facing the measuring medium.

[0011] For electrochemical sensors, the membrane is preferably designed at least partially as a porous structure, in particular one with pores. It can, for example, be made at least partially from at least one polymer. The geometric dimensions are preferably adapted to the geometry of the base body of the sensor cap or to the respective sensor. The membrane often has a substantially circular base area.

[0012] In the case of an optochemical sensor, however, the membrane is preferably a thin film, which in particular comprises one or more superimposed layers, in particular functional layers. One layer exhibits at least partial selective permeability to the analyte, while other layers ensure the chemical and / or mechanical stability of the membrane or can be designed to fluoresce, phosphoresce, or absorb light upon appropriate excitation. At least one layer is also provided for welding. This can, in particular, be the layer that has the surface intended for contact with the measuring medium.The base areas of the layer(s) forming the sensor spot and the layer intended for welding can fundamentally be dimensioned differently; in particular, the layer intended for welding can have a larger base area than the other layers. In this case, the membrane is welded, for example, not only to a surface, in particular the one bordering the base body at the end, but also at least partially to a lateral surface of the base body. In particular, at least the layer intended for welding can completely cover the base body on the surface facing the measuring medium.

[0013] Either the layer(s) forming the sensor spot is / are applied separately to the base body, with the layer intended for welding being welded to the base body over the sensor spot. Thus, only part of the membrane is welded to the base body. Alternatively, the layers forming the sensor spot can be applied first to the layer intended for welding, which is then welded to the base body. In any case, the membrane is understood below to mean the entirety of the layers.

[0014] By joining the membrane and the base body by welding, a material-tight, long-lasting connection is advantageously achieved between the membrane and the base body. The result is an essentially one-piece sensor cap that is impermeable to the measuring medium and / or, if applicable, to an electrolyte, which is particularly advantageous for applications with high hygiene requirements. The method according to the invention also enables a simple and reliable manufacturing process. Besides the base body and the membrane, no further elements such as sealing rings or the like are required, as is the case with a clamped membrane. Welding processes without the use of filler metals are particularly preferred. The materials for the membrane and the base body can each be optimally adapted in terms of their mechanical and chemical properties to the intended application of the respective sensor.They are therefore typically chemically resistant to the analyte. If these are directly bonded together, the chemical resistance of the sensor cap remains comparable to the chemical resistance of the base body and the membrane. However, if an additional material is required to create a bonded connection, such as in the case of adhesive bonding or some welding processes, this material must be carefully selected, or the best compromise must be found with regard to various, sometimes conflicting requirements, such as adhesive properties or chemical resistance. This can disadvantageously result in reduced chemical stability of the material with respect to the measuring medium compared to the base body and the membrane.

[0015] According to the invention, the membrane is at least partially applied to at least one partial area of ​​the base body. This at least one partial area can be, for example, a cutout or section of at least one surface of the base body. The at least one partial area can be planar or curved. Furthermore, the wall of the base body can be specifically processed, for example, structured, in the at least one partial area.

[0016] In an advantageous embodiment of the method according to the invention, the base body is designed such that it has at least one frontal opening delimited by a wall of the base body, wherein the at least one partial area is defined by the wall of the base body in the area of ​​the opening, and / or wherein the base body is made of a translucent or transparent material, at least in the at least one partial area. The first variant is particularly suitable for an electrochemical, in particular amperometric, sensor, while the second variant is preferably used for optochemical sensors.

[0017] In the case of a cylindrical base body, the partial area can, for example, be defined by one of the two circular, planar surface areas of the cylinder. If the cylinder has a circular opening at at least one of the two opposite ends, the partial area can in turn be defined by the boundary of one of these two openings through the wall of the base body.

[0018] To create the integral connection, the membrane and the base body are then welded together. In particular, the membrane is welded to or onto at least one partial area of ​​the base body. The membrane preferably covers the partial area at least partially, in particular completely, and / or completely closes an opening in the base body if the partial area represents the boundary of an opening in the wall of the base body.

[0019] In a further preferred embodiment of the method, the geometry and / or the material of the base body is / are selected such that at least one hygiene standard is met. Particular reference is made here to the common standards for hygienic applications, such as ASME, BPE, 3A, or EHEDG. For applications in the dairy product sector, the materials selected for manufacturing the respective sensors must, for example, be stable against fat residues at high temperatures. In particular, the cleanability tests, sterilization tests, and bacterial impermeability tests specified and certified by EHEDG (EL-Class 1, EL-Aseptic, EL-Class 2, or ED) are worth mentioning here. Other common requirements and approvals in this context include, for example, ASME-BPE (cleanability after treatment at 130°C, 100h), ASME, BPE, and safety with regard to FDA, USP Class VI (87 / 88 / 381).

[0020] When using plastics, particular care must be taken to ensure that the materials used have a low level of roughness. In this regard, it is advantageous if the base body is manufactured as a one-piece component, particularly as an injection-molded part, and / or if the base body is made of a material with a roughness of less than 0.8 µm, or if at least one surface of the base body is provided with a coating with a roughness of less than 0.8 µm. The limit value for surface roughness of 0.8 µm applies to hygienic applications. For aseptic applications, the predeterminable limit value for roughness is preferably even 0.38 µm.

[0021] In a further advantageous embodiment of the method, the membrane and / or the base body are each manufactured at least partially from a plastic, in particular a fluoroplastic such as PTFE or PVDF. The plastic can be adapted to a specific sensor application and optimized, in particular, with regard to its chemical resistance or similar.

[0022] According to the invention, the base body and the membrane are at least partially made of the same material. Using the same material for the base body and the membrane further simplifies the welding process to be used, since no problems, particularly manufacturing-related ones, are to be expected with regard to the compatibility of the two components, for example, with regard to the welding process, in particular with regard to the respective melting temperatures and / or chemical compatibility.

[0023] According to the invention, the base body and the membrane are welded together using ultrasonic welding. Ultrasonic welding is a so-called friction welding process in which a high-frequency mechanical vibration, which occurs between the components to be welded, leads to at least local heating through molecular and interfacial friction. In the case of metals, this leads to interlocking and interlocking of the components, while in the case of thermoplastics, softening or local melting of the components is achieved.Given that welding describes the permanent joining of components using heat, and that ultrasound-based joining processes are also always based on heating the components using ultrasound, various variants of the known ultrasound-based joining processes are understood below as variants of a welding process, in particular ultrasonic hot stamping, ultrasonic thermoforming, ultrasonic riveting, or ultrasonic punching. In this regard, reference should also be made to the article by J. Sackmann et al., "Review on ultrasonic fabrication of polymer micro devices," Ultrasonics (2014), doi: http: / / dx.doi.org.10.1016 / j.ultras.2014.08.007, which is hereby incorporated by reference.

[0024] According to a further embodiment of the method, at least one further functional layer is applied to a surface of the membrane, in particular by means of a coating process such as the so-called chemical vapor deposition (CVD) or physical vapor deposition (PVD) process. This additional functional layer can, for example, be applied to the surface of the membrane intended for contact with the medium and / or to the surface of the membrane facing away from the medium and, in particular, can be specifically adapted to the intended use of the sensor. In the case of an optochemical sensor, for example, a darkening layer can be applied to the surface intended for contact with the measuring medium. An additional layer on the surface of the membrane facing the measuring medium can also be advantageous with regard to requirements from common standards for hygiene requirements, such as ASME, BPE, 3A or EHEDG.

[0025] The object according to the invention is further achieved by a sensor cap with at least one base body and a membrane, in particular for an electrochemical or optochemical sensor, which sensor cap is produced according to an embodiment of the method according to the invention.

[0026] A preferred embodiment of the sensor cap according to the invention includes that the base body is at least partially substantially cylindrical, cubic, conical, frustoconical, conical, hemispherical, obliquely cylindrical, concave or convex.

[0027] According to a further preferred embodiment, the membrane has at least partially a planar, conical, pyramidal or ellipsoidal geometry.

[0028] Such geometric considerations regarding the base body and / or the membrane are advantageous for a variety of reasons. For example, the sensor can be optimized with respect to the flow behavior of the respective measuring medium in the respective application and / or with respect to specific hygiene requirements. A suitable choice of geometry can also prevent the potential accumulation of bubbles in the area of ​​the sensitive membrane.

[0029] It is advantageous if at least one section, in particular an edge region, of the membrane and / or at least a part of the partial region of the base body is substantially planar, and / or wherein at least the section of the membrane and / or the part of the partial region of the base body at least partially has a structured surface. The welded connection is then made along the planar sections of the membrane and at least the partial region of the base body. The structured sections, in particular the structures, also called concentrators, melt locally during the welding process.

[0030] A particularly preferred embodiment of the sensor cap includes a line parallel to the partial area of ​​the base body and a longitudinal axis of the base body having an angle other than 90° to each other. This embodiment therefore essentially involves a sensor cap with a flush, beveled front. Finally, the object of the invention is also achieved by a sensor, in particular an electrochemical or optochemical sensor, for determining and / or monitoring the concentration of an analyte in a measuring medium, comprising a sensor cap according to the invention.

[0031] It should be noted that the embodiments relating to the method according to the invention are also applicable mutatis mutandis to the sensor cap according to the invention and the sensor according to the invention and vice versa.

[0032] In the following, the figures Fig. 1 to Fig. The invention is explained in more detail in the exemplary embodiments shown in Figure 4.

[0033] They show: Fig. 1 schematic representation of an (a) electrochemical and (b) optochemical sensor according to the state of the art, Fig. 2 a schematic representation of a sensor cap for (a) an electrochemical sensor and (b), (c) for an optochemical sensor in two different designs, Fig. 3 a perspective view of a base body according to the invention and a membrane before the welding process; and Fig. 4 different geometries for a membrane cap according to the invention.

[0034] Fig. 1a shows a schematic representation of an electrochemical sensor 1 for determining and / or monitoring the concentration of an analyte 2 in a gaseous or liquid measuring medium 3 in a container 4. The sensor comprises a sensor tube 5 within which a measuring electrode 6 is arranged and on which a membrane cap 7 with a membrane 8 is arranged on the side facing the medium. The measuring electrode 6 projects into an electrolyte chamber 9 filled with an electrolyte 9a, which is sealed by the membrane 8 on the medium side, and touches the membrane 8 at least in a partial area. This allows the membrane 8 to be slightly curved. A similar structure of an electrochemical sensor is known, for example, from document US2913386.

[0035] A schematic representation of an optochemical sensor 10 for determining and / or monitoring the concentration of an analyte 2 in a gaseous or liquid measuring medium 3 in a container 4 is again shown in Fig. 1b. The sensor 10 comprises a sensor tube 11 with an optical fiber 12. On the side of the sensor tube 11 facing the measuring medium 3, the sensor tube 11 is closed by a membrane 14, which is arranged flush with a membrane cap 13 with a sensor spot 15.

[0036] Fig. 2a shows, by way of example, a cylindrical sensor cap 7, often also referred to as a membrane cap, which is particularly suitable for an electrochemical sensor. In this example, the sensor cap 7 comprises a cylindrically shaped base body 16, which has an opening 17 delimited by its wall in the area of ​​the end face S facing the measuring medium 3. The partial area 18 to be welded is in this case defined by the wall of the base body 16 in the area of ​​the opening 17. The membrane 8, here in the form of a porous structure, can either be enclosed in the opening, as shown in the drawing. However, it is also possible, for example, to apply the membrane 8 to the end face S of the base body 16.

[0037] Fig. 2b and Fig. 2c show two, particularly suitable for an optochemical sensor, similar to the one in Fig. 2a designed sensor caps 13. In contrast to the Fig. 2a, the base body 16 for an optochemical sensor does not include an opening 17.

[0038] Shown here, but not mandatory, the end face S of the base body 16 facing the measuring medium 3 includes a suitably dimensioned recess for accommodating the sensor spot 20. In this case, this is a flush-mounted membrane cap 13. The base body 16 can be manufactured, for example, as an injection-molded part from a transparent or translucent plastic, especially PVDF. The degree of transparency can be influenced, for example, by the wall thickness or thickness of the material.

[0039] It should be noted at this point that for the illustrated embodiments from Fig. 2b, but also for those according to Fig. 2c, the membrane 14 encompasses both the sensor spot 20 and the layer 20c. After the welding process, however, the layer 20c intended for welding and the partial area 18 of the base body 16 intended for welding are at least partially fused together. Then, distinguishing between the base body 16 and the layer 20c intended for welding can be at least partially difficult. The sensor-specific functions of the membrane 14 are always performed by the other layers 20a, 20b, which form the sensor spot 20 for the embodiment shown here.

[0040] Fig. Figure 2b first shows two different configurations I and II for the membrane 14. As best seen in Fig. As can be seen in Figure 2b I, the membrane 14, which is designed in the form of a thin film, comprises a plurality of superimposed layers 20a, 20b, 20c for the membrane cap 13 suitable for an optochemical sensor 10. The layers 20a, 20b here form, by way of example, the sensor spot 20, in particular the optical one. The number and arrangement of the individual layers 20a, 20b..., is each adapted for a specific sensor or for a specific application. It goes without saying that the membrane 14 can also comprise more than the two layers 20a, 20b shown here as an example for the sake of simplicity. Furthermore, the membrane 14 comprises a layer 20c intended for welding, which for both embodiments shown, although this is not absolutely necessary, has a larger base area A' than the layers 20a, 20b forming the sensor spot 20, with the base area A being identical here for both layers 20a, 20b.It should be noted that many different designs are conceivable for the relationship between the dimensions of the sensor spot 20 and the layer intended for welding, all of which fall within the scope of the present invention. In the case of design I, the layer 20c intended for welding runs at least substantially completely along an end face S of the base body 16 facing the medium. Alternatively, the layer 20c, as shown in design II, can also run along the lateral surface M of the base body, i.e. essentially completely along the surface of the base body 16 facing the measuring medium 3. As indicated by the dashed continuation of the layer 20c, the layer 20c can also extend into an inner region of the base body 16. In this case, a vacuum welding process is particularly suitable for producing the sensor cap 13.This latter variant, in which the layer 20c intended for welding completely surrounds the surface of the base body 16 facing the measuring medium 3 and extends into an inner region of the base body, is a particularly advantageous embodiment of the present invention. The membrane cap 13 thus created has a surface particularly suitable for applications with high hygiene requirements, which is integrally bonded to the base body by welding. In particular, the formation of waves and / or corrugations along the surface is prevented.

[0041] To produce a sensor cap 13, Fig. 2c, two different variants are explained by way of example. Both variants are suitable for a wide variety of configurations of the individual layers 20a, 20b, 20c forming the membrane 14, in particular for configurations I and II of Fig. 2b. All methods known to the person skilled in the art, such as doctor blade coating, spray coating, spin coating, etc., can be used as methods for producing a sensor spot 20.

[0042] According to embodiment III, the sensor spot 20 is first applied to the layer 20c intended for welding. One manufacturing variant for a corresponding membrane consists in applying the individual, different layers 20a, 20b, ..., which are in particular polymers, individually and successively to the layer 20c intended for welding. An exemplary arrangement of the layers 20a, 20b, ... comprises a transparent silicone layer applied to the layer 20c after a suitable plasma treatment of the latter, followed by an optically insulating black silicone layer, a silicone layer with a fluorescent indicator, and another transparent layer. However, the two transparent layers and the optically insulating layer are not absolutely necessary for an optochemical sensor.

[0043] An alternative manufacturing process concerns the embodiment IV of Fig. 2c. Here, the sensor spot 20 is first applied to the base body 16. In this case, at least the area of ​​the base body 16 to which the sensor spot 20 is applied first undergoes a suitable plasma treatment. Subsequently, the layers 20a, 20b,... forming the sensor spot 20 are applied in a suitable sequence. A suitable sequence, similar to embodiment III, would be, for example, the application of a transparent layer, followed by a silicone layer with a fluorescent indicator, an optically insulating layer, and another transparent layer.

[0044] In optochemical and / or electrochemical sensors, the base body 16 forming the membrane cap 7, 13 and the membrane 8, 14 are often made of plastic. In this case, the use of an ultrasound-based joining process, such as ultrasonic welding, is particularly advantageous. Therefore, the following description refers to a membrane cap 7, 13 manufactured by ultrasonic welding.

[0045] In Fig. Figure 3 shows a perspective view of an embodiment according to the invention for a base body 16 and a membrane 8 before the welding process. In this example, the base body 16 has, as in Fig. 2a has an opening 17 on the medium side on its front side limited by its wall. The example can be easily applied to a membrane cap 13 closed on the medium side, as in Fig. 2b, transferred.

[0046] The part 18 of the base body 16 to be welded is as shown in Fig. 2a is given by the wall of the base body 16 defining the opening 17. In a section 19 of the partial area 18, the base body has a structured surface 21. Here, so-called concentrators are incorporated into the base body 16, which melt during the welding process and ensure a materially bonded connection between the base body 16 and the membrane 8, 14.

[0047] Particularly for applications of the sensor with high hygienic requirements, an additional functional layer 22 can be applied in the area of ​​the surface O of the membrane 8 intended for contact with the measuring medium 3. Alternatively, the surface O of the membrane 8, 14 facing the measuring medium 3 can also be specifically functionalized, for example, by plasma treatment or corona treatment. The method according to the invention makes it possible to produce a plurality of membrane caps 7, 13 with different geometries, which are particularly advantageous for different areas of application. An exemplary selection is shown in Fig. 4 shown.

[0048] Fig. 4a shows a cylindrical base body 16, which is concave in the area facing the membrane 8, 14. In another embodiment, as in Fig. As shown in Fig. 4c, the base body is also cylindrical, but in the area facing the membrane 8, 14 it is pyramidal, tapering towards the membrane 8, 14.

[0049] In the design according to Fig. 4b, the membrane 8, 14 is mounted centrally on the base body. The planar, annular edge region 23 forms the portion 18 of the membrane 8, 14 intended for welding. However, such an edge region 23 is not absolutely necessary. Alternatively, a cylindrical base body 16 with a curvature can be used, as in the example according to Fig. 4e. In this case, the membrane 8,14 is also curved.

[0050] A further embodiment according to the invention for a membrane cap 7,13 is shown in Fig.4d. Here, the boundary surface S of the base body 16 facing the membrane, which at least partially forms the partial area 18 intended for welding, regardless of whether it has an opening 17 or not, is designed such that the angle between a line A parallel to the partial area 18 and a longitudinal axis L of the base body 16 is at an angle other than 90°. The side 24 of the membrane cap facing the measuring medium is therefore beveled in this embodiment.

[0051] It goes without saying that in addition to the described examples of a membrane cap 7, 13 according to the invention, many other embodiments are also possible, all of which fall under the scope of the present invention. Reference symbol 1 electrochemical sensor 2 Analyt 3 Measuring medium 4 containers 5 Sensor tube 6 measuring electrode 7 Membrane cap 8 Membran 9 Electrolyte chamber, filled with an electrolyte 9a 10 optochemical sensor 11 Sensor tube 12 optical fibers 13 Membrane cap 14 Membran 15 Sensor spot 16 basic bodies 17 Opening in the base body 18 Partial area, for welding process 19 Porous structure, especially one with pores 20 Sensor spot with functional layers 20a, 20b and a layer 20c intended for welding,... with base area A, A',... 21 Section of the base body with structured surface, concentrators 22 Functional layer 23 planar section of the membrane 24 Side of the membrane cap facing the measuring medium S, M End face and lateral surface of the base body O Surface intended for contact with the measuring medium I Longitudinal axis of the base body a line parallel to the subarea

Claims

[1] Method for producing a sensor cap (7, 13) with at least one base body (16) and a membrane (8, 15) for a sensor, in particular an optochemical (10) or electrochemical (1), for determining and / or monitoring the concentration of an analyte (2) in a measuring medium (3), comprising the following method steps - Providing a membrane (8, 14) permeable to the measuring medium (3) and / or to at least one analyte (2) contained in the measuring medium (3) with a surface (O) intended for contact with the measuring medium (3) - providing a base body (16) with at least one partial area (18) intended for connection to the membrane (8, 14), and - welding at least part of the membrane (8, 14) and the base body (16), wherein the membrane (8, 14) is at least partially applied to the at least one partial area (18) of the base body (16) and a connection which is tight with respect to the measuring medium (3) is produced between the base body (16) and the membrane (8, 14), - wherein the base body (16) and the membrane (8,14) are made of the same material, - wherein the base body (16) and the membrane (8,14) are welded together by ultrasonic welding. [2] Method according to claim 1, wherein the membrane (8,14) is at least partially designed in the form of a porous structure (8), in particular one having pores. [3] Method according to claim 1, wherein the membrane (8, 14) is at least partially designed as a thin film (14), which is constructed in particular from one or more layers (20a, 20b, 20c), in particular functional layers, arranged one above the other, and which Layers (20a, 20b, 20c) can have at least partially identical or differently dimensioned base areas (A), wherein at least one layer (20c) is provided for welding the membrane (8, 14) to the base body (16), and / or wherein the layer (20c) provided for welding is designed such that it runs at least partially along an end face (S) of the base body (16) facing the measuring medium (3), or along the end face (S) and at least partially along at least one lateral surface (M) of the base body facing the measuring medium, or substantially completely or extending into an inner region of the base body (16) along a surface (S,M) of the base body (16) facing the measuring medium (3). [4] Method according to at least one of the preceding claims, wherein the base body (16) is designed such that it has at least one front-side opening (17) delimited by a wall of the base body, wherein the at least one partial region (18) is defined by the wall of the base body (16) in the region of the opening (17), and / or wherein the base body (16) is made of a translucent or transparent material at least in the at least one partial area (18). [5] Method according to at least one of the preceding claims, wherein the geometry and / or the material of the base body is / are selected such that at least one hygiene standard is met. [6] Method according to claim 4, wherein the base body (16) is produced as a one-piece component, in particular as an injection-molded part, and / or the base body (16) is made of a material with a roughness of less than 0.8 µm, or wherein at least one surface of the base body is provided with a coating, which coating has a roughness of less than 0.8 µm. [7] Method according to at least one of the preceding claims, wherein the membrane (8, 14) and / or the base body (16) is / are each made at least partially from a plastic, in particular a fluoroplastic, such as PTFE or PVDF. [8] Method according to at least one of the preceding claims, wherein at least one further functional layer (22) is applied to a surface (O) of the membrane (8, 14), in particular by means of a coating process such as the CVD or PVD process. [9] Sensor cap (7,13) with at least one base body (16) and a membrane (8,14), in particular for an electrochemical (1) or optochemical (10) sensor, wherein the sensor cap (7,13) is produced by a method according to at least one of the preceding claims, wherein the base body (16) and the membrane (8,14) are at least partially made of the same material. [10] Sensor cap (7,13) according to claim 9, wherein the base body (16) is at least partially substantially cylindrical, cubic, conical, frustoconical, conical, hemispherical, obliquely cylindrical, concave or convex. [11] Sensor cap according to at least one of claims 9 or 10, wherein the membrane (8,14) has at least partially a planar, conical, pyramidal or ellipsoidal geometry. [12] Sensor cap (7, 13) according to at least one of claims 9 to 11, wherein at least one section (23), in particular an edge region, of the membrane (8, 14) and / or at least a part of the partial region (18) of the base body (16) are designed to be substantially planar, and / or wherein at least the section (23) of the membrane (8, 14) and / or the part of the partial region (18) of the base body (16) at least partially have a structured surface (21). [13] Sensor cap (7, 13) according to at least one of claims 9 to 12, wherein a line A parallel to the partial region (18) of the base body (16) and a longitudinal axis L of the base body (16) have an angle different from 90° to one another. [14] Sensor, in particular electrochemical (1) or optochemical (10) sensor, for determining and / or monitoring the concentration of an analyte (2) in a measuring medium (3), with a sensor cap (7, 13) according to one of claims 9 to 13.

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