Hydrophilic sensor cap containing a DLC coating

Abstract

Method for producing a hydrophilic cover layer (1) of a sensor membrane (2) which has a contact angle q of < 90° with water, comprising - providing a sensor membrane (2) comprising a medium-facing silicone film (3), - Coating the silicone film (3) with diamond-like carbon (DLC), wherein the coating step is selected from physical vapor deposition (PVD), chemical vapor deposition (CVD), for example by ECR (electron cyclotron resonance)-CVD, laser evaporation and sputtering, preferably magnetron sputtering, whereby a cover layer (1) is formed which, during operation, comes into contact with the medium and comprises the diamond-like carbon coating (5) and the silicone film (3), - Treating the cover layer (1) with a sterilizing agent.

Description

The invention relates to a sensor membrane or a sensor spot, a sensor cap containing the sensor membrane and a sensor containing the sensor cap.Optical sensors are sensors which are based on an optochemical reaction with the measurement medium. An optochemical analyte sensor, e.g. an oxygen sensor or carbon dioxide sensor, is based on the principle of the analyte-induced luminescence quenching of an indicator, in particular an organic luminescent dye or fluorescent or phosphorescent dye matched for a specified analyte, which is usually introduced into a polymer matrix. The sensor unit of such a sensor comprises in particular a substrate, e.g. a glass plate or an optical fiber, to which the polymer / dye mixture tuned for a predetermined analyte is applied as a solid film. The respective underlying measurement principles are known from a large number of publications. Corresponding sensors are manufactured and sold by the applicant in a wide variety of configurations.Gaseous analytes such as oxygen are introduced, for example, with a pager into biotechnological fermentation processes, for example in the field of the production of biologicals, in order to culture higher cell densities and thus to increase the yield of the product. As "spars", gas distributors of different geometries are referred to, which are used for introducing gases in process environments or reaction vessels. A pager is often located at the bottom of the reaction vessel, near the agitator or as a unit with the agitator. Sensors, on the other hand, can be installed at different locations of the reaction vessel. Common installation positions of sensors are, inter alia, from above through the cover or end plate of the reaction vessel or from the side through the wall of the reactor vessel. A sensor is often introduced into the reaction vessel via a flange located on the reaction vessel, the sensor being introduced into the reaction vessel directly or in the interior of a so-called sensor fitting, depending on the configuration. In the case of the fermenter, for example, air or oxygen bubbles are introduced into the aqueous measurement medium located therein by the pager and distributed in the entire fermenter, in particular in the measurement medium, with the aid of the stirrer. These gas bubbles can have different sizes and, as already mentioned, are deposited on the optical sensor and / or on the sensor element and cause error values, for example due to measurement peaks, incorrect measurements and / or even overloading.The object according to the present invention is to provide a sensor cap in which the accumulation of oxygen is reduced and thus a signal of the sensor with less interference is achieved, and to provide a method for producing the hydrophilic membrane.The object is achieved by the DLC-coated hydrophilic sensor membrane according to the invention or by the sensor spot according to the invention, a sensor cap containing a sensor membrane according to the invention or the sensor spot according to the invention.The invention relates to a method for producing a hydrophilic covering layer of a sensor membrane which has a contact angle q of <90° with water, comprising- providing a sensor membrane comprising a silicone film facing the medium during operation,coating the silicone film with diamond-like carbon (DLC), wherein the coating step is selected from physical vapor deposition (PVD), chemical vapor deposition (CVD), for example by ECR (electron cyclotron resonance) CVD, laser evaporation and sputtering, preferably magnetron sputtering, whereby a covering layer comprising the diamond-like carbon coating and the silicone film, which is in contact with the medium during operation, is formed,treating the cover layer with a sterilizing agent.In a preferred embodiment, the diamond-like carbon is doped with silicon, titanium, hexane or nitrogen, more preferably with nitrogen.In a preferred embodiment, the sensor membrane has a silicon oxide layer on the side facing the medium during operation.In a preferred embodiment, the chemical vapor deposition is plasma assisted vapor deposition.The invention also relates to a hydrophilic sensor membrane for an optical sensor for measuring an analyte in a measurement medium comprising:an analyte-permeable hydrophilic covering layer which is in contact with the medium during operation and comprises a silicone film having a DLC coating with a thickness of 0.01 to 10 μm, preferably 0.025 to 5 μm, more preferably 0.5 μm to 5 μm, which is obtained by the method according to the invention or an embodiment thereof, wherein the covering layer has a contact angle q of <90° C. with water,a reflector layer which comprises TiO2 and is arranged on the side of the covering layer facing away from the medium,an analyte-sensitive pigment layer arranged on the side of the reflector layer facing away from the medium during operation, wherein the sensor membrane contains at least one luminophoric dye, wherein the luminescence of the analyte-sensitive pigment layer depends on the concentration of the analyte, anda glass substrate arranged on the side of the analyte-sensitive pigment layer facing away from the medium during operation, wherein the glass substrate preferably consists of fused silica.A hydrophilic sensor membrane is a sensor membrane whose contact angle q with water is <90°.The contact angle q refers to the angle between the force vectors of the gaseous, liquid and solid phases on a planar surface. The force vectors are the result of different interfacial effects such as cohesive and adhesive forces in and between the fabrics, and surface tensions. In the present invention, the contact angle q refers to a contact angle with water.The Young's equation forms the basis for the calculation of the surface tension.YSG=interface tension between solid and gas phasesYSL=interface tension between solid and liquid phasesYGL = Interfacial Tension between Liquid and Gas PhaseA hydrophilic membrane is obtained by coating the layer facing the medium during operation with a DLC (diamond-like carbon) layer. The layer facing the medium preferably consists of a hydrophilic sensor membrane made of silicone. The DLC preferably consists of a-C:H:X according to VDI 2840.In a preferred embodiment of the method according to the invention or of the sensor membrane according to the invention, the DLC coating ( 5) covers 70-98%, preferably 70-90%, of the surface of the silicone film.The nature of DLC layers is studied by means of thermoplastically gravimetric (TGA) and differential thermal analyses (DTA). Phase identification and microstructural studies are performed using X-ray diffraction (XRD), Raman, and scanning electron microscopy (SEM), electro-dispersive X-ray spectroscopy (EDS).When sensors are used in such fermentation processes, it is also necessary for the sensor used in the process to be a hygienic sensor which meets the regulatory requirements for biotechnologically produced products, for example biologicals.The invention therefore also relates to a sensor cap containing the sensor membrane and to a sensor which are of hygienic design.The sterilizing agent preferably used in the invention is selected from:a chemical disinfectant selected from: sodium hypochlorite, acetic acid, hydrogen peroxide;g-radiation for g-sterilization and / orSuperheated steam at 120-140°C.In one embodiment, the contact angle q of the hydrophilic outer layer ( 3) with water is <50°, preferably <20°, more preferably <10°, even more preferably <5°.In one embodiment, the layer thickness of the hydrophilic outer layer ( 3) is between 2 and 5 μm, preferably 2 and 4 μm, more preferably 3 μm.In one embodiment, the layers of the sensor membrane ( 2) are bonded to one another adhesively and / or covalently.In one embodiment, the analyte-sensitive luminescent dye is an analyte-sensitive fluorescent or phosphorescent dye, wherein the analytea gas dissolved in the medium selected from O 2, CO 2, O 3, NH 3 and nitrogen oxides, the gas preferably being O 2,a cation dissolved in the medium selected from a hydronium ion, Na +, K +, NH 4+, Ca 2+, and Mg 2+, preferably a hydronium ionan anion dissolved in the medium selected from chloride ions and nitrate ions, andan organic molecule selected from glucose, lactose and lactate.In a preferred embodiment, the analyte is selected from a gas dissolved in the medium, preferably selected from O 2, CO 2, O 3, NH 3 and nitrogen oxides, wherein the gas is preferably O 2.The invention also relates to a sensor cap for an optochemical sensor for determining and / or monitoring at least one analyte present in a medium, comprisinga cylindrical internal component comprising a hydrophilic sensor membrane according to the invention or an embodiment thereof, anda sleeve-shaped outer component which bounds the inner component and consists of stainless steel, preferably of 1.4435 stainless steel,wherein the inner component and the outer component are detachably mechanically connected to one another, preferably via a screw connection.In one embodiment of the sensor cap, between the inner component and the outer component on the surface of the sensor cap which, during operation, contacts the medium, a sealing ring is accommodated in a receptacle of the outer casing, which sealing ring is configured to seal the inner component and the sleeve-shaped component against the measurement medium without any gaps.The invention also relates to an optical sensor for determining or monitoring at least one analyte located in a medium, having a sensor cap or an embodiment thereof, and an electronic component which are detachably connected to one another, wherein the electronic component consists of a first module having a light source and a detector and of a second module having a transceiver.In one embodiment of the sensor, the sensor cap is connected to the electronic component in a mechanically detachable manner, preferably via a screw connection.In one embodiment of the sensor, the first and the second module are connected to one another via a detachable plug connection unit, wherein the plug connection unit is designed to transmit energy and / or data by means of a galvanically separated, in particular inductive interface, wherein the detachable plug connection unit is preferably a bayonet lock, wherein energy, unidirectionally from the second module to the first module, and data, in particular data on the analyte concentration, are transmitted bidirectionally between the first and the second module.The invention also relates to an optical analysis system comprising an optical sensor according to the invention or an embodiment thereof, wherein the second module of the optical sensor is electrically connected to a data processing unit via a connection.In all embodiments, the hygiene sensors conform to USP87 and / or USP88 Class IV. Moreover, complete traceability of all media contacting parts is required. In all embodiments, the parts of the hygiene sensor cap and the hygiene sensor FDA are conformal and free of animal components (TSE Frei).In a preferred embodiment, the sensors meet the requirements of EHEDG and 3A to be fully sanitary.The preferred materials for the sensor are:the sensor sheath is stainless steel;in the case of the sealing element, preferably sealing ring, more preferably O-ring FKM, FFKM, EPDM, silicone, or other elastomeric plastics;the sheath of the sensor cap is stainless steel, titanium or a NiMo28, for example Hastelloy B and further nickel-based alloys;in the outer medium-contacting layer of the sensor element silicone.All the embodiments of the modular system and of the measurement system described above can each be combined with one another, provided that this is technically possible.The invention is explained in more detail in the following description with reference to the exemplary embodiments shown in the drawing.The following are shown: FIG. 1 : a sensor membrane according to the invention. FIGS. 2 a- b : a sensor cap in an arrangement of the sensor element which is horizontal with respect to the longitudinal axis of the sensor (a) and (b) an arrangement of the sensor cap which is angled with respect to the longitudinal axis of the sensor, wherein the angle a is between 20° and 40°, preferably 30°. FIG. 3 : an optical sensor with an inductive interface.FIG. 1 shows the sensor membrane according to the invention comprising a DLC-coated covering layer (1). In the sensor membrane according to FIG. 1, the sensor layers are attached one above the other on a glass carrier, wherein the glass carrier, which preferably consists of quartz glass, is arranged on the side facing away from the medium during operation of the sensor. On the medium side of the glass support (9), the analyte-sensitive pigment layer (7) containing the luminescent dye (8) is arranged. On the medium side of the analyte-sensitive pigment layer (7), a TiO 2 reflector layer (6) is arranged. On the medium side of the TiO 2- reflector layer (6), a cover layer (3) is arranged, which is permeable to the analyte to be measured, but impermeable to the measurement medium in which the analyte is present dissolved, for example water. A DLC coating is applied to the cover layer ( 3).The sensor caps ( 10) from FIGS. 2 aand 2 bcomprise the sensor membrane ( 1) according to the invention from FIG. 1. The sensor cap consists of an inner component ( 11), which comprises the sensor membrane, and of a sheath-like outer component ( 12). The inner component (11) and the outer component (12) are connected to one another via a releasable mechanical connection, wherein the mechanical connection is preferably a screw connection.The sensor caps (10) are also connected to the electronics component (16) of the optical sensor via a detachable mechanical connection (22), preferably via a screw connection.The sensor (15) according to FIG. 3 comprises the sensor cap (10) and the electronic component (16), wherein the electronic module consists of a first module (17) comprising the light source (18) and the detector (19) and a second module (20) containing the transceiver (21). The first (17) and the second module (20) are connected to one another via a mechanical plug-in connection unit (23), wherein the mechanical plug-in connection unit (23) comprises an inductive interface. Preferably, the mechanical plug-in connection unit ( 23) is a bayonet connection.Reference numerals are not to be understood as limiting the scope of the subject matter protected by the claims. They are intended merely to make the claims more readily understood.Reference numerals denote reference numerals1 DLC-coated hydrophilic cover layer 2 hydrophilic sensor membrane 3 silicone film 4 measurement medium 5 DLC coating 6 TiO 2- reflector layer 7 analyte-sensitive pigment layer 8 luminophoric dye 9 glass substrate 10 sensor cap 11 inner component of the sensor cap 12 outer component of the sensor cap 13 mechanical connection, screw connection, between the inner and outer components of the sensor cap 14 sealing ring 15 optical sensor 16 electronic component of the sensor 17 first module 18 light source 19 light detector 20 second module 21 transceiver 22 mechanical connection, Screw connection between the sensor cap and the electronic component 23 Detachable plug connection unit 24 Electrical connection 25 Data processing unit 26 Optical analysis system L Longitudinal axis of the sensor cap a Angle transversely to the longitudinal axis of the sensor cap

Claims

Method for producing the hydrophilic covering layer (1) of a sensor membrane (2) which has a contact angle q of < 90° with water, comprising - providing a sensor membrane (2) comprising a silicone film (3) facing the medium, - coating the silicone film (3) with diamond-like carbon (DLC), wherein the coating step is selected from physical vapor deposition (PVD), chemical vapor deposition (CVD), for example by ECR (electron cyclotron resonance) CVD, laser evaporation and sputtering, preferably magnetron sputtering, whereby a covering layer (1) which contacts the medium during operation and comprises the diamond-like carbon coating (5) and the silicone film (3) is formed, - treating the covering layer (1) with a sterilizing agent.The method of claim 1, wherein the chemical vapor deposition is plasma assisted vapor deposition.The method according to claim 1 or 2, wherein the diamond-like carbon is doped with silicon, titanium, hexane or nitrogen, preferably with nitrogen.Method according to any one of claims 1 to 3, wherein the DLC coating (5) covers 70-98%, preferably 70-90%, of the surface of the silicone film.Hydrophilic sensor membrane (2) for an optical sensor for measuring an analyte in a measurement medium (4) comprising: - an analyte-permeable hydrophilic cover layer (1) which is in contact with the medium during operation and contains a silicone film with a DLC coating (5) having a thickness of 0.01 to 10 μm, preferably 0.025 to 5 μm, further preferably 0.5 μm to 5 μm, which is obtained by the method according to one of Claims 1 to 4, wherein the cover layer (1) has a contact angle q of < 90°C with water, - a reflector layer (6) which contains TiO2 and is arranged on the side of the cover layer (1) facing away from the medium, - an analyte-sensitive pigment layer (7) arranged on the side of the reflector layer (6) facing away from the medium during operation, wherein the sensor membrane contains at least one luminophoric dye (8), wherein the luminescence of the analyte-sensitive pigment layer (7) depends on the concentration of the analyte (4), and - a glass substrate (9) arranged on the side of the analyte-sensitive pigment layer facing away from the medium during operation, wherein the glass substrate preferably consists of quartz glass.The hydrophilic sensor membrane according to claim 5, wherein the DLC coating (5) covers 70-98%, preferably 70-90%, of the surface of the silicone film.Hydrophilic sensor membrane (2) according to claim 5 or 6, wherein the contact angle q of the hydrophilic cover layer (3) with water is < 50°, preferably < 20°, more preferably <10°, even more preferably < 5°.Hydrophilic sensor membrane according to one of claims 5 to 7, wherein the layer thickness of the hydrophilic cover layer (3) is between 2 and 5 μm, preferably 2 and 4 μm, more preferably 3 μm.Hydrophilic sensor membrane (2) according to any one of claims 5 to 8, wherein the layers of the sensor membrane (2) are bonded together adhesively and / or covalently.Hydrophilic sensor membrane (2) according to one of claims 5 to 9, wherein the analyte-sensitive luminescent dye is an analyte-sensitive fluorescent or phosphorescent dye, wherein the analyte - is a gas dissolved in the medium, selected from O 2, CO 2, O 3, NH 3 and nitrogen oxides, wherein the gas is preferably O 2 - is a cation dissolved in the medium, selected from a hydronium ion, Na +, K +, NH 4+, Ca 2+, and Mg 2+, preferably a hydronium ion - is an anion dissolved in the medium, selected from chloride ions and nitrate ions and an organic molecule selected from glucose, lactose and lactate.The hydrophilic sensor membrane according to claim 10, wherein the analyte is selected from a gas dissolved in the medium, preferably selected from O 2, CO 2, O 3, NH 3, nitric oxides, more preferably wherein the gas is O 2.Sensor cap (10) for an optochemical sensor for determining and / or monitoring at least one analyte present in a medium, comprising a cylindrical inner component (11) comprising a hydrophilic sensor membrane according to one of claims 5 to 11 and a sleeve-shaped outer component (12), which borders the inner component and consists of stainless steel, preferably of 1.4435 stainless steel, wherein the inner component and the outer component (12) are detachably connected to one another mechanically, preferably via a screw connection (13).Sensor cap (10) according to claim 12, wherein between the inner component (11) and the sleeve-shaped outer component (12) on the surface of the sensor cap which contacts the medium during operation, a sealing ring (14) is accommodated in a receptacle of the outer component (12), which is configured to seal the inner component (11) and the sleeve-shaped outer component (12) against the measurement medium without any gaps.Optical sensor (15) for determining or monitoring at least one analyte present in a medium, having a sensor cap (10) according to Claim 12 or 13, and an electronics component (16) which are detachably connected to one another, wherein the electronics component consists of a first module (17) having a light source (18) and a detector (19) and of a second module (20 having a transceiver (21).Optical sensor (15) according to claim 14, wherein the sensor cap (10) is connected to the electronic component (16) mechanically, preferably via a screw connection (22), in a releasable manner.Optical sensor (14) according to claim 14 or 15, wherein the first (17) and the second module (18) are connected to one another via a detachable plug connection unit (22), wherein the plug connection unit (22) is designed to transmit energy and / or data by means of a galvanically separated, in particular inductive, interface, wherein the detachable plug connection unit is preferably a bayonet lock (22), wherein energy, unidirectionally from the second module to the first module, as well as data, in particular data on the analyte concentration, are transmitted bidirectionally between the first and the second module.Optical analysis system (25) comprising an optical sensor according to any one of claims 14 to 16, wherein the second module of the optical sensor (14) is electrically connected to a data processing unit (24) via a connection (23).

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