Sensor for detecting gas and method for manufacturing same

Abstract

To provide a sensor for detecting percutaneous gas such as CO2, and a method of manufacturing the sensor.SOLUTION: A sensor 1 includes: at least one radiation source 3 for discharging a radiation; at least one detector 4 for detecting the radiation discharged by the radiation source 3; and at least one measurement chamber 6 for receiving sample gas. The radiation source 3, the detector 4, and the measurement chamber 6 are arranged so that at least part of the radiation propagates along a route passing through the measurement chamber 6. The sensor 1 further includes a casing 7, in which the radiation source 3, the detector 4, and the measurement chamber 6 are arranged. The sensor 1 includes a contact surface 8 that can be directed toward a measurement part. The sensor 1 still further includes at least one gas access channel 9 that allows the gas to move to the measurement chamber 6 from the contact surface 8. The casing 7 preferably has high thermal conductivity exceeding 10 W / m / k, and preferably includes a metal material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sensor for detecting a gas, in particular a sensor for detecting CO2, and to a method for manufacturing the sensor. [Background technology]

[0002] Current systems for measuring gases use different measurement principles. In medical technology, mainly electrochemical sensors are used for the measurement of gases that have diffused transcutaneously, i.e. through the skin of a human patient or an animal. Current sensors for the measurement of transcutaneous CO2 are very sensitive and exhibit good response times. Electrochemical sensors for the measurement of transcutaneous gases are known, for example, from WO 2008 / 132205.

[0003] In certain clinical situations involving extracorporeal blood circulation, it is even possible to measure blood gases directly from the patient's bloodstream by using transcutaneous gas sensors.

[0004] An optical sensor for transcutaneous gas measurements is known, for example, from WO 2015 / 011103. Summary of the Invention [Problem to be solved by the invention]

[0005] Transcutaneous gas can refer to a mixture of gases. Transcutaneous gases can typically be CO2, O2, H2O, N2, and anesthetic gases.

[0006] Instead of transcutaneous gases, such sensors can also measure the concentration of non-transcutaneous gases, e.g., gases from the extracorporeal blood stream. In the context of this application, the term "sample gas" refers to a gas that can be measured by the sensor regardless of its origin. The expression "measurand gas" as used herein is equivalent to the term "sample gas".

[0007] In this application, the term contact surface is intended to denote the surface of the sensor that is in direct or indirect contact with the measurement site, which is typically the patient's skin or the blood vessels surrounding the blood flow. One or several additional gas-permeable membranes and contact liquids or gels may be present between the contact surface of the sensor and the measurement site, at least during the measurement. The contact surface is typically formed mainly by a part of the surface of the casing and an area that allows gas diffusion into the measurement chamber. For example, the contact surface may be formed by a combination of a part of the casing, a gas-permeable membrane such as a gas access channel seal, and the surface of a zone related to the sensor assembly, such as an epoxy. A casing with a contact surface means a casing whose specific surface part forms at least a part of the contact surface when the sensor is fully assembled.

[0008] One of the main technical challenges in transcutaneous gas sensing is related to the fact that the rate at which gases permeate tissue and skin is very low. Therefore, if a sensor for transcutaneous gas measurement relies on the equilibrium between the concentration of gas in a measurement chamber and the respective concentration in the skin, the volume of such a measurement chamber must be extremely small in order to achieve an acceptable response (equilibrium completion) time. Furthermore, for optical sensors with such small measurement chambers, it is a challenge to direct the optical radiation with sufficient light intensity to and through the measurement chamber. Another constraint is the small area of ​​the measurement site, which is typically the earlobe of an adult patient or the thigh of a newborn.

[0009] Typically, only small amounts of sample gas are available, so the sensor must be able to detect unwanted gas leaks or It is very sensitive to possible disturbances such as poor absorption of the measurement radiation.

[0010] In this application, the term measurement radiation means radiation generated by a radiation source, which radiation propagates through a measurement chamber and is detectable by a detector. Typically, at least a portion of the measurement radiation propagating through the measurement chamber can be absorbed by the sample gas present in the measurement chamber. If the sensor is a sensor for measuring CO2, the measurement radiation preferably has a wavelength in the range of 3.5 to 4.5 μm or within that range, although other wavelengths or wavelength bands may be used to measure other gases or other properties of CO2.

[0011] The presence of the sample gas in the measurement chamber can cause absorption of the measurement radiation and thus absorption of the measurement signal. The measurement chamber is defined mainly by its confinement surfaces, except at (usually small) locations where the sample gas needs to enter and leave the measurement chamber. At such locations, no material surface may be present and the measurement chamber boundary is defined as a smooth extension of the adjacent material surfaces corresponding to the material surfaces it would be expected to have in the absence of gas access openings.

[0012] The measurement chamber is typically defined by the surfaces of several components, for example the measurement chamber may be formed by parts of the surfaces of the optical module support, the mirror, the radiation entrance window and the radiation exit window.

[0013] The sensor for detecting gas may comprise a mirror that forms part of the measurement chamber and has at least a part of one surface that is reflective for the measurement radiation. The mirror may be added to the assembly at a suitable stage, for example after applying a surface coating to some of the surfaces of the measurement chamber. This mirror may be porous so that it is permeable to the atoms and molecules of the sample gas, but may be liquid-tight. If such a porous liquid-tight mirror forms part of the contact surface of the sensor, this is advantageous because the transdermal gas has to travel only a very short distance from the skin surface to the measurement chamber, which helps to keep the response time of the sensor short.

[0014] The optical module support may be included in the sensor. The optical module support may carry at least one of the radiation source, the detector, the wavelength sensitive element, the mirror. These components may be located on or within the optical module support. The optical module support may also encompass at least a portion of the measurement chamber. The optical module support with such sensor components constitutes an optical module. The optical module may also include further components or features, such as radiation entrance and exit windows, radiation window seals along the radiation entrance and / or exit windows, coatings, adhesives, films, or gas access channels. When appropriately connected and driven, the optical module may function as an optical measurement unit, such that it can generate measurement radiation and provide an absorption measurement signal. The optical module may form the basis of a single parameter sensor or may be combined with other sensing units and / or further optical modules to form a multi-parameter sensor.

[0015] One or several gas access channels may be present in the sensor. They form a diffusion path for the molecules of the sample gas that leads from the measurement chamber to the sensor surface, typically the contact surface of the sensor. During the measurement, the gas access channels ensure that the sample gas can diffuse efficiently into or out of the measurement chamber, which allows equilibration of the gas concentration with the ambient concentration (typically the concentration in the skin) within a useful response time. Preferably, the gas access channels are not completely filled with solid or liquid so that the sample gas can easily move through them.

[0016] During patient measurements, a large amount of humidity can be present in the measurement chamber. Water condensation in the measurement chamber must be avoided, since liquid water tends to absorb and deflect the measurement radiation.

[0017] A water trap can be incorporated into the sensor or a disposable portion of the sensor to capture water molecules from the sample gas mixture and reduce humidity, however, the small size of the sensor makes assembly difficult and the water trap may only have a limited capacity.

[0018] The object of the present invention is to avoid the drawbacks of the state of the art and to provide a robust sensor for detecting gases, in particular for determining the concentration of gas species in small gas mixtures, and a method for detecting gases, in particular for determining the concentration of gas species in small gas mixtures, which does not require frequent calibration, gives accurate results within an acceptable response time, and is easy and cheap to manufacture.

[0019] Response time in this context is understood as the time required for the sensor to reach 90% of a stable measurement after application to the patient. Acceptable response times are less than 10 minutes, preferably less than 5 minutes, more preferably less than 2.5 minutes. [Means for solving the problem]

[0020] According to the invention, these objects are achieved by means of a sensor and a method according to the independent claims.

[0021] According to a first aspect of the present invention, there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO2.

[0022] The sensor comprises at least one radiation source for emitting radiation, at least one detector for detecting radiation emitted by the radiation source, and at least one measurement chamber for receiving a sample gas, which are preferably arranged on or within an optical module support to form an optical module.

[0023] The radiation source, the detector, and the measurement chamber are positioned such that at least a portion of the radiation propagates along a path, the path passing through the measurement chamber.

[0024] Preferably, the sensor further comprises a mirror arranged such that the radiation path includes reflection at the mirror. Preferably, the mirror is arranged on or in the optical module support, in particular in the same optical module support as the radiation source and the detector.

[0025] The sensor further comprises a casing, in which the radiation source, the detector, the measurement chamber and optionally further components such as an optical module or a mirror are arranged. The sensor, in particular the casing, has a contact surface that can be oriented towards the measurement site and is intended to be in close contact with the patient's skin during the transcutaneous measurement.

[0026] The sensor may comprise at least one gas access channel that allows the sample gas, preferably a transcutaneous gas, to travel from the contact surface into the measurement chamber. Preferably, the sensor comprises more than one gas access channel, for example two, three or four gas access channels. Preferably, at least some of the gas access channels are located on or in the optical module support.

[0027] The casing comprises or consists entirely of a material with high thermal conductivity. The thermal conductivity is preferably greater than 10 W / m / k. The material is preferably metal or ceramic. Particularly well suited are metal alloys such as aluminum, copper or titanium alloys, for example brass, or ceramics based on alumina, zirconia, silicone or boron nitride or silicon carbide.

[0028] The casing can be used to efficiently transport thermal energy during use. Thermal energy is typically generated intentionally by a controllable heating element such as a heating resistor, but waste heat generated by other components such as amplifiers, microprocessors, etc. also contribute to the generated thermal energy. The thermal energy generated by the heating element and further components needs to be transported to the contact surface of the sensor to warm the patient's skin at the measurement site. Typically, such heating elements and other heat-generating components are located in the sensor at a location away from the contact surface, for reasons such as proximity to a power supply or availability of space. A good thermally conductive casing allows the generated heat to flow through the casing to the patient's skin rather than inside the sensor. This reduces the temperature gradient in the sensor.

[0029] According to a second aspect of the present invention there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO. Preferably the sensor is as described above.

[0030] The sensor comprises at least one radiation source for emitting radiation, at least one detector for detecting radiation emitted by the radiation source, and at least one measurement chamber for receiving a sample gas, which are preferably arranged on or within an optical module support to form an optical module.

[0031] The radiation source, the detector, and the measurement chamber are positioned such that at least a portion of the radiation propagates along a path, the path passing through the measurement chamber.

[0032] Preferably, the sensor further comprises a mirror for reflecting radiation emitted by the radiation source arranged such that the radiation path includes reflection at the mirror. Preferably, the mirror is arranged on or in the optical module support, in particular in the same optical module support as the radiation source and the detector.

[0033] The sensor further comprises a casing, in which the radiation source, the detector, the measurement chamber and optionally further components such as an optical module or a mirror are arranged. The sensor, in particular the casing, has a contact surface that can be oriented towards the measurement site and is intended to be in close contact with the patient's skin during the transcutaneous measurement.

[0034] The sensor may comprise at least one gas access channel that allows the sample gas, preferably a transcutaneous gas, to travel from the contact surface into the measurement chamber. Preferably, the sensor comprises more than one gas access channel, for example two, three, four or more gas access channels. As many as hundreds or thousands of gas access channels can be realized, as long as the diameter and volume of the gas access channels allow.

[0035] The radiation source is disposed in a radiation source compartment in the sensor, for example in a radiation source compartment formed in an optical module support. The radiation source compartment is preferably separated from the measurement chamber by a radiation entrance window. The radiation source compartment is typically gas-filled. A radiation window seal along the radiation entrance window can reduce or avoid gas exchange between the measurement chamber and the radiation source compartment.

[0036] The sensor comprises at least one ventilation channel leading from the radiation source compartment to the environment. Preferably, at least a portion of the ventilation channel leads through the casing. Preferably, if present, at least a portion of the ventilation channel leads through the optical module support.

[0037] The ventilation channel reduces the risk of accumulation of relevant amounts of unwanted gas in the radiation source compartment. For example, a leaky radiation window seal along the radiation entrance window may allow sample gas to diffuse from the measurement chamber into the radiation source compartment over time. Additionally, unwanted gas can be generated in the radiation source compartment, for example, by degradation of adhesives due to irradiation from the radiation source, or by out-gassing or out-diffusion of volatile atoms or molecules from sensor components in or near the radiation source compartment.

[0038] The presence of the ventilation channel ensures a constant gas exchange with the environment and allows unwanted gases to escape from the source compartment, thus ensuring an unbiased measurement. The rate at which unwanted gases appear in the source compartment must be slower than the rate at which they disappear into the environment. Since the rate of the former is usually low, the rate of the latter does not need to be particularly high.

[0039] The ventilation channel may be formed by a tube, preferably made of metal such as steel or a polymer, which may lead from the source compartment through the casing wall of the sensor, or alternatively to an opening in the casing or cap of the sensor.

[0040] In a preferred embodiment of this aspect, the sensor comprises a vent channel seal for sealing the vent channel. The vent channel seal is gas permeable to some extent, thus allowing unwanted gas to escape from the source compartment over time. The vent channel seal prevents contaminants such as dust or particles from entering the vent channel and the source compartment, which may lead to source problems or measurement failures. Preferably, the vent channel seal is liquid-tight, such that liquids and cleaning agents such as application gels, sweat or alcohol are also prevented from entering the vent channel and the source compartment under normal clinical use conditions.

[0041] Preferably, the vent channel seal allows gases, such as CO2 and H2O, within the source compartment to equilibrate with environmental concentrations within less than a month, preferably within a few hours to a few days.

[0042] Preferably, the ventilation channel seal is designed so that the rate at which unwanted gas diffuses from the radiation source compartment into the environment is substantially higher (e.g., 10 times higher) than the rate at which unwanted gas appears in the radiation source compartment, e.g., due to diffusion from the measurement chamber through the radiation window seal or outgassing or generation within the radiation source compartment.

[0043] The ventilation channel seal may have any suitable shape, and is preferably used in the form of a plug, disc or cap.

[0044] Preferably, the vent channel seal comprises or is made from a material that can be applied as a viscous liquid or paste and hardens into a solid gas permeable material. Preferably, polymers typically available as adhesives are used, particularly silicone, epoxy, acrylic, cyanoacrylate, or urethane compounds.

[0045] Additionally or alternatively, the vent channel seal may include or be made of a solid, non-porous, gas-permeable material, particularly solid materials including silicone, fluoropolymers, or polyolefin compounds such as PDMS or PTFE or PP.

[0046] Additionally or alternatively, the ventilation channel seal may also comprise a porous material such as a sintered ceramic, sintered polymer, or sintered metal, particularly a sintered fluoropolymer such as PTFE, sintered steel, or sintered titanium.

[0047] Additionally or alternatively, the ventilation channel seal may also be formed from a support material having pore voids or holes. The insulating layer may include or may be made of a gas permeable layer such as a conductive layer, a foil, a membrane, or a coating.

[0048] In a further preferred embodiment, the detector is disposed within the detector compartment and the sensor may comprise a ventilation channel from the detector compartment to the environment, similar to the ventilation channel of the radiation source compartment described above. In particular, the detector ventilation channel may be covered by a ventilation channel seal. The sensor may comprise a detector ventilation channel instead of or in addition to the radiation source ventilation channel.

[0049] This is particularly useful when there is an emission window seal along the emission window that merely slows down gas exchange between the measurement chamber and the detector compartment to some extent.

[0050] According to a third aspect of the present invention there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO. Preferably the sensor is as described above.

[0051] The sensor comprises at least one radiation source for emitting radiation, at least one detector for detecting radiation emitted by the radiation source, a mirror for reflecting the radiation, and at least one measurement chamber for receiving a sample gas, which are preferably arranged on or within an optical module support to form an optical module.

[0052] The radiation source, detector, mirror and measurement chamber are arranged such that at least a portion of the radiation propagates along a path that passes through the measurement chamber and includes reflection off the mirror.

[0053] The sensor has a contact surface that is orientable towards the measurement site and is intended to be in intimate contact with the patient's skin during transcutaneous measurement.

[0054] The sensor may comprise at least one gas access channel that allows the sample gas, preferably a transcutaneous gas, to travel from the contact surface into the measurement chamber. Preferably, the sensor comprises more than one gas access channel, for example two, three or four gas access channels.

[0055] The mirror is positioned away from the contact surface. If the mirror is not located on the contact surface, it is not strongly cooled by the skin during use, and therefore the risk of condensation on the mirror surface is reduced, even in case of contact with a moist sample gas.

[0056] For example, the mirror may be disposed on a layer of epoxy or some other material such that the contact surface is largely or completely separated from the mirror by the layer.

[0057] The sensor preferably comprises a casing. Sensor components such as an optical module are arranged within the casing. At least a part of the contact surface may be formed by a part of a surface of the casing. The mirror may be arranged in a part of the casing such that the mirror and the contact surface are at least separated by the part of the casing.

[0058] Such a highly thermally conductive casing can act as a heat shield between the skin and the measurement chamber and / or mirror, especially when the inside of the sensor is at a higher temperature than the contact surface, so that during a patient measurement, the skin primarily cools the casing rather than directly cooling the mirror.

[0059] When measuring the concentration of a humid sample gas, the risk of condensation in the measurement chamber, especially on the mirror, is reduced because the mirror is at approximately the same temperature as the rest of the measurement chamber surface and is therefore less affected by the temperature of the contact surface.

[0060] Alternatively or additionally, the sensor further comprises a casing. The mirror is then arranged at a distance from the casing. The mirror is thermally decoupled from the casing. In particular, a thermal insulation layer may be arranged between the mirror and the casing.

[0061] The insulating layer is preferably made of a material with low thermal conductivity, preferably less than 10 W / m / k, more preferably less than 0.1 W / m / k. Alternatively, the insulating layer may be formed by a gas such as air.

[0062] It is further preferred that the insulating layer has a low solubility for the sample gas such that the sample gas is absorbed into the insulating layer at no more than a small rate.

[0063] Preferred materials for the insulating layer include polymers such as epoxies or other potting materials.

[0064] According to a fourth aspect of the present invention there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO. Preferably the sensor is as described above.

[0065] The sensor comprises at least one radiation source for emitting radiation, at least one detector for detecting radiation emitted by the radiation source, a mirror for reflecting the radiation, and at least one measurement chamber for receiving a sample gas, which are preferably arranged on or within an optical module support to form an optical module.

[0066] The radiation source, detector, mirror and measurement chamber are arranged such that at least a portion of the radiation propagates along a path that passes through the measurement chamber and includes reflection off the mirror.

[0067] The sensor has a contact surface that is orientable towards the measurement site and is intended to be in intimate contact with the patient's skin during transcutaneous measurement.

[0068] The sensor comprises at least one gas access channel that allows the sample gas, preferably a transcutaneous gas, to travel from the contact surface into the measurement chamber. Preferably, the sensor comprises more than one gas access channel, for example two, three or four gas access channels.

[0069] At least one gas access channel wall is located away from the edge of the mirror and does not penetrate the mirror, preferably all gas access channel walls are located away from the edge of the mirror and do not penetrate the mirror.

[0070] If the gas access channel does not pass through or directly around the mirror, it is easier to securely attach and seal the mirror during sensor assembly. For example, if the mirror is attached using adhesive, the risk of adhesive flowing into the gas access channel and / or into the measurement chamber is reduced. Adhesive that flows into the gas access channel or into the measurement chamber may impede or even block the exchange of sample gas or may excessively absorb measurement radiation.

[0071] Furthermore, preferably, as mentioned above, a thermal barrier is arranged between the mirror and the casing. In this case, it may be beneficial to apply this insulating layer in the form of a liquid adhesive, for example an epoxy adhesive, which transforms into a solid material on curing.

[0072] The openings of the gas access channels at the contact surface are preferably arranged on a closed line, in particular on a circle, surrounding the mirror, which simplifies the assembly of the sensor (in particular the mounting of the mirror) and allows the collection of gas from an extended gas collection area.

[0073] In a preferred embodiment of this aspect, part of the gas access channel may lead along part of the mirror, in particular along part of the inner surface of the mirror, i.e. the surface facing the measurement chamber.

[0074] The creation of the gas access channel and the attachment of the mirror may be separate and independent process steps, which reduces manufacturing complexity and demands and increases the reliability of the manufactured parts.

[0075] Preferably, the gas access channel starts from the measurement chamber and then runs along the inner surface of the mirror, but does not extend to the edge of the mirror, which allows the mirror to be sealed liquid-tight, as described above. The part of the gas access channel that runs along the inner surface of the mirror is well accessible during manufacturing and before the mirror is attached, which allows the formation of a small opening of the gas access channel to the measurement chamber. A large opening would result in excessive loss of measurement radiation into the channel, and thus a decrease in the measurement signal quality.

[0076] Furthermore, those parts of the gas access channel that are not routed along the inner surface of the mirror are preferably routed through a material with high thermal conductivity, such as the bulk material of the optical module support, so that the risk of cold spots on the gas access channel surface causing condensation is reduced.

[0077] Preferably, the gas access channel, the measurement chamber and the mirror are located on or in the optical module support.

[0078] Preferably, an optical module support with high thermal conductivity is used, to which the mirror may be attached and the gas access channel always passes through the surface or inside of the optical module support, which makes it easier to keep the gas access channel and the inner surface of the measurement chamber at a uniform temperature.

[0079] According to a fifth aspect of the present invention there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO. Preferably the sensor is as described above.

[0080] The sensor comprises at least one radiation source for emitting radiation, at least one detector for detecting radiation emitted by the radiation source, a mirror for reflecting the radiation, and at least one measurement chamber for receiving a sample gas, which are preferably arranged on or within an optical module support to form an optical module.

[0081] The radiation source, detector, mirror and measurement chamber are arranged such that at least a portion of the radiation propagates along a path that passes through the measurement chamber and includes reflection off the mirror.

[0082] The sensor has a contact surface that is orientable towards the measurement site and is intended to be in intimate contact with the patient's skin during transcutaneous measurement.

[0083] The sensor preferably comprises at least one gas access channel that allows the sample gas, preferably a transcutaneous gas, to travel from the contact surface into the measurement chamber. Preferably, the sensor comprises more than one gas access channel, for example two, three or four gas access channels.

[0084] The mirror consists of a deformable material, and preferably is furthermore highly reflective to the measurement radiation, inert, non-porous and / or has good thermal conductivity, most preferably having all of these properties.

[0085] The mirror may comprise, and preferably consist of, a solid but deformable material. The material may be relatively soft, preferably with a hardness of less than 100HV5, more preferably less than 60HV5, most preferably less than 30HV5. The material can then be mechanically and plastically deformed with relatively low forces, allowing mirror attachment by deformation. Preferably, the deformable mirror can be plastically deformed at temperatures below 150°C, more preferably at lower temperatures, most preferably at room temperature.

[0086] The mirror preferably exhibits a high reflectivity for the measurement radiation, at least on its inner surface which is the surface facing the measurement chamber, Preferably, the reflectivity of the mirror for wavelengths within the wavelength range of the measurement radiation is greater than 80%, more preferably greater than 92%, even more preferably greater than 97%.

[0087] The mirror material is preferably inert, which ensures that the material does not corrode or chemically react with the transdermal gas, the sample gas, water or water vapour, gases or liquids associated with irrigation, particularly alcohol or alcoholic vapours, or ambient gases, particularly oxygen.

[0088] The mirror material is preferably well thermally conductive, preferably with a thermal conductivity higher than 30 W / m / k, more preferably above 100 W / m / k, most preferably above 200 W / m / k, to ensure a uniform mirror temperature. Ideally, the part of the inner surface of the mirror that forms part of the measurement chamber is at the same temperature as the remaining measurement chamber surface. Thus, there are no cold spots on the mirror and condensation on the inner surface of the mirror is prevented.

[0089] The mirror may include a support material and one or more coatings. For example, the support may be made of a material that exhibits high reflectivity but limited corrosion resistance, and the support is coated with one or several protective coating layers that do not excessively absorb the measurement radiation. As another example, the support may be made of a highly deformable material with low reflectivity coated with a layer of an inert material with high reflectivity or coated with one or more interference layers that reflect the measurement radiation.

[0090] The mirror preferably consists of a single material, in which case there is no risk of delamination of parts of the coating and contamination of the measurement chamber during deformation of the mirror.

[0091] The mirror material especially comprises at least one of Au, Ag, Cu, Mo, W or Al. Preferably, the material consists of one of these elements in high purity form. The material may also be a high purity alloy mainly composed of one of these elements, for example an Au-Cu, Au-Ag, Au-Pd, Cu-Ag-Pd or Au-Cu-Pt-Ag alloy. In particular, high purity Au (99% or more pure) is a suitable material.

[0092] Alternatively, the mirror may comprise or consist of a thermoplastic polymer such as ABS or POM having a coating, e.g., Au or an interference layer. The polymer may be, for example, a heat treated tube. By using a roller, it can be deformed by applying heat.

[0093] In a preferred embodiment of this aspect, the mirror is attached by deformation of the mirror. In this way, the mirror can be attached in a quick single step. No further assembly steps or materials such as adhesives are necessary. In particular, the mirror is attached by plastic deformation, preferably crimping, such that material from the lateral volume of the mirror is displaced into one or several suitable recesses, preferably undercuts. Preferably, the mirror is attached to the optical module support. The deformation process can result in a tight contact between the mirror and the holder, typically between the mirror and the optical module support, which allows an efficient exchange of thermal energy and thus ensures that all surfaces of the measurement chamber are at a uniform temperature.

[0094] The deformation can be achieved by applying pressure using a suitably shaped stamp die, without or with the application of heat to support the mirror deformation.

[0095] After attachment by deformation, the interface between the mirror and the optical module support may optionally be sealed. A liquid-tight seal can be achieved, for example, by application of a high viscosity adhesive.

[0096] According to a sixth aspect of the present invention there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO. Preferably the sensor is as described above.

[0097] The sensor comprises at least one radiation source for emitting radiation, at least one detector for detecting radiation emitted by the radiation source, and at least one measurement chamber for receiving a sample gas, which are preferably arranged on or within an optical module support to form an optical module.

[0098] The sensor preferably further comprises a mirror, preferably disposed on or in the optical module support, defining part of the measurement chamber boundary.

[0099] The radiation source, the detector, and the measurement chamber are positioned such that at least a portion of the radiation propagates along a path, the path passing through the measurement chamber.

[0100] The sensor has a contact surface that is orientable towards the measurement site and is intended to be in intimate contact with the patient's skin during transcutaneous measurement.

[0101] The sensor comprises at least one gas access channel that allows the sample gas, preferably a transcutaneous gas, to travel from the contact surface into the measurement chamber. Preferably, the sensor comprises more than one gas access channel, for example two, three or four gas access channels.

[0102] Each gas access channel has an access opening, which is the opening at the end of the gas access channel, specifically the end facing the contact surface. The other opening of the gas access channel terminates in the measurement chamber. The access opening can have the same cross section as the respective gas access channel near the access opening. Alternatively, the access opening can also expand or contract towards its contact surface end.

[0103] The access opening is located near the contact surface of the sensor and is covered by an access opening seal that is liquid-tight or liquid-repellent, yet permeable to the sample gas.

[0104] Preferably, the surface of the access opening seal forms a smooth plane with the surface of the casing such that the sensor has a smooth contact surface. Alternatively, the surface of the access opening seal protrudes slightly from the contact surface by a few millimeters or less, preferably 0.3 mm or less, more preferably 0.1 mm or less. Alternatively, the surface of the access opening seal is slightly below the plane formed by the contact surface, preferably 0.3 mm or less, more preferably 0.1 mm or less.

[0105] At least a portion of the gas access channel may be disposed within a casing of the sensor and may be formed such that the access opening is disposed within or near the casing wall.

[0106] When the surface of the access opening seal forms a smooth plane with the contact surface or stands only slightly above or below the contact surface, the build-up of contaminants such as contact gels, sweat, particulate matter, or other undesirable materials is largely prevented while being easily cleaned.

[0107] Alternatively, several access openings may be covered by one access opening seal, for example all access openings may be covered by a single access opening seal.

[0108] In a preferred embodiment of this aspect, the access opening seal may comprise a substrate such as a plate or disk or foil or grid or mesh having holes or a porous structure, optionally coated or infiltrated with a gas permeable material.

[0109] The access opening seal may have a specially designed surface, such as a microstructured or plasma treated surface, that renders the surface liquid repellent or liquid tight, which is particularly useful when the access opening seal does not include a coating.

[0110] Preferably, the access opening seal comprises a coating that does not contain holes or other openings. Thus, the access opening seal may span holes or voids in the substrate. Such a seal does not allow liquids or other contaminants to enter the gas access channel under normal use conditions. Thus, such an access opening seal is practically liquid-tight. Preferably, the coating is made of a material that has high permeability to the sample gas, for example a fluoropolymer such as PTFE, FEP, PFA, or a further fluoropolymer, or a polyolefin such as PP, PE, PMP, or PB, or a silicone such as PDMS, or a further polymer that is preferably thermoplastic and has low crystallinity, so that the response time of the sensor remains short.

[0111] Such a coating may be present on one side of the substrate. Alternatively, the coating may further extend completely or partially into the voids and openings of the substrate. For example, the coating may extend over holes or voids in the substrate to which a layer within the substrate may be secured, or the coating may cover one or both sides of the substrate and extend partially or completely into the voids and holes in the substrate.

[0112] Alternatively, the coating may only be present in holes or voids in the substrate, with no coating covering the substrate surface, in which case the coating does not necessarily have to be a continuous layer, but preferably the coating fills all voids in the substrate to the extent that there is no path through the access opening seal that penetrates neither the substrate material nor the coating material, such that liquids or particulate matter cannot penetrate the seal.

[0113] The access opening seal is a non-continuous coating having pores at locations where the substrate also has holes or pores. If the coating includes a discontinuous coating, it may be made of a material that has some or even no permeability to the sample gas. Such an access opening seal may be liquid-repellent but not liquid-tight, since liquid may pass through the seal, especially when sufficient pressure is applied and when relatively large holes are present in the coating. However, during normal clinical use, this may be sufficient to protect the gas access channel from the ingress of liquid or particles, especially if an additional protective membrane is present between the access opening seal and the measurement site on the patient's skin, at least during use. Preferably, such a discontinuous coating is hydrophobic and / or oleophobic.

[0114] The substrate of the access opening seal preferably comprises or consists of a metal, ceramic or polymer material. Preferably, the substrate is made of or coated with a material that exhibits good biocompatibility, for example stainless steel, titanium alloy, aluminum oxide, zirconium oxide, glass such as borosilicate glass or soda lime glass, or polymers such as POM, ABS, epoxy, PTFE, FEP, PFA, further fluoropolymers, PP, PE, PMP or PB, or silicones such as PDMS.

[0115] The access opening seal may be used in combination with an additional membrane, typically a replaceable and non-porous membrane that extends over the contact surface, particularly if it is only liquid repellent rather than liquid tight.

[0116] In a further preferred embodiment of this aspect, the substrate of the access opening seal includes protrusions and the coating is disposed at least between the protrusions. The material of the protrusions is more wear resistant than the material of the coating. Alternatively, rather than a substrate with protrusions, the substrate may have recesses. Preferably, the coating also covers the protrusions so that the coating forms a smooth surface, especially if the coating has non-stick properties.

[0117] Between applications to the patient, the sensor needs to be cleaned. Due to the unavoidable abrasive effect of the repeated cleaning or wiping process, the coating of the access opening seal can be affected and damaged over time. The protrusions are more resistant to wear than the coating, thus protecting the coating between them. If a hole in the substrate is located between the protrusions, the part of the coating that seals the hole remains intact, and therefore the sealing function is not compromised even if the top part of the coating wears off.

[0118] The protrusions may be formed by hillocks on the substrate of the access opening seal or may be an inherent part of the substrate. The hillocks may protrude, for example, by 0.1 μm to 500 μm, preferably a few microns to tens of microns, may have a lateral extension, for example, a diameter of 1 μm to 500 μm, preferably a few microns to tens of microns, and may be spaced apart, for example, by 1 μm to 500 μm, preferably a few tens of microns to about 100 microns.

[0119] Alternatively, the protrusions may be formed by a roughened surface having a surface roughness Ra>1 μm, in which case the size and arrangement of the protrusions are irregular.

[0120] Alternatively, protrusions may be formed in irregular shapes, for example by the material remaining when multiple recesses are formed in the material, for example the recesses may be circular in size and formed by etching, but there are corresponding protrusions that are not recessed.

[0121] Preferably, the protrusions are formed such that an undercut is formed, which helps secure the coating to the substrate, which makes the access opening seal more durable.

[0122] In a further preferred embodiment of this aspect, the access opening seal comprises a seal mechanical fastening. The seal may include at least one anchor, such as one or several "L" or "T" shaped legs that allow for a secure fit. For example, the anchor may be embedded in a potting material, preferably epoxy. This is particularly useful when the seal includes a non-stick coating, making it difficult to adhere, thereby allowing for a secure fit.

[0123] In a further preferred embodiment of this aspect, an additional liquid-tight membrane can be placed between the access opening seal and the access opening of the gas access channel. This approach is particularly beneficial when the access opening seal is porous or contains holes, since the membrane ensures perfect liquid-tightness, while the liquid-repellent surface can prevent clogging of the holes or pores in the seal's substrate. Furthermore, the seal's substrate protects the underlying membrane from mechanical damage.

[0124] In a further preferred embodiment of this aspect, the cross-sectional area of ​​the access opening of the gas access channel is larger than the cross-sectional area of ​​the portion of the gas access channel adjacent to the access opening. Preferably, the cross-sectional area of ​​the gas access channel is fairly small because the gas access channel contributes to the total gas-accessible volume, and a large gas-accessible volume increases the sensor response time. The access opening may preferably be fairly wide (particularly wider than the cross-sectional area of ​​the gas access channel) to allow diffusion of sample gas into the gas access channel from a relatively large area, which helps to reduce the response time. The area of ​​the access opening seal is preferably of similar size or wider than the access opening at the interface with the seal.

[0125] Preferably, the maximum cross-sectional area of ​​an access opening is at least two times larger than the cross-sectional area of ​​the gas access channel near the access opening, more preferably at least 5 to 50 times larger. The cross-sectional area of ​​the access opening seal is preferably only slightly larger, and preferably less than two times, than the cross-sectional area of ​​the access opening at the interface with the seal.

[0126] In a further preferred embodiment, the access opening can include a star-shaped, or snowflake-shaped, or lattice-like structure that includes shallow cavities that extend away from the gas access channel. These cavities serve to guide the sample gas into the gas access channel after it diffuses through the access opening seal. This is particularly advantageous when the access opening seal is in intimate contact with the component that comprises the cavities and the gas access channel, for example when the access opening seal is in intimate contact with the optical module support. Tight or narrow contacts prevent or slow down gas diffusion. Thus, the channel-like cavities provide space for the diffusing gas and reduce the sensor response time. The cavities may also have different shapes / structures, and as long as they are connected to the gas access channel, they serve to guide the sample gas into the gas access channel.

[0127] Preferably, the depth of the described cavities is less than 500 μm, more preferably less than 100 μm, most preferably less than 50 μm.

[0128] In further preferred embodiments, additionally or alternatively, wide or grid-like shallow cavities may be placed in the access opening seal, such as the star-shaped, snowflake-shaped, or grid-like cavities described above for the access opening, which may be easier to manufacture than if these structures were machined into the optical module or corresponding component.

[0129] For example, the access opening seal may include a cavity that is slightly narrower than the seal itself so that after the seal is assembled, a small gap exists between the seal and the periphery of the access opening to facilitate gas diffusion into the gas access channel.

[0130] According to a seventh aspect of the present invention there is provided a sensor for detecting a gas, preferably a transcutaneous gas, in particular gaseous CO. Preferably the sensor is as described above.

[0131] The sensor comprises an optical module support. The optical module support forms at least a portion of the measurement chamber. Further surfaces may define the remaining measurement chamber boundary. Typically, the main measurement chamber boundary of the sensor is formed by surface portions of the optical module support, the mirror, and the radiation entrance and exit windows.

[0132] The optical module support has at least one opening, in particular an opening that allows the coating to be applied on at least some of the surfaces that serve as measurement chamber surfaces, preferably on at least all surfaces of the optical module support that serve as measurement chamber surfaces. The opening is typically wide enough to allow reliable application of the coating. For example, the area of ​​the opening may be similar to or larger than the maximum cross-section of the measurement chamber, reducing the risk of shadowing during the application process.

[0133] The sensor preferably comprises a closure component, which can at least partially close said opening of the optical module support after application of the coating. Preferably, a mirror as described above can be used as the closure component. Preferably, the closure component exhibits a high reflectivity, preferably more than 90%, for the measurement radiation. For example, the mirror may be mounted such that a part of its inner surface forms part of the measurement chamber surface. Advantageously, a small open space between the closure component and the optical module support may remain open for the purpose of gas transfer to and from the measurement chamber. Preferably, such a small open space forms part of a gas access channel.

[0134] The sensor preferably comprises at least one radiation entrance window, which is preferably arranged in the optical module support. The radiation source can be mounted near the radiation entrance window, for example in a partial or complete radiation source section arranged in the optical module support, and the detector section is separated from the measurement chamber by the radiation entrance window.

[0135] The sensor preferably comprises at least one radiation exit window, which is preferably arranged in the optical module support. A detector for detecting the measurement radiation may be mounted near the radiation exit window, for example in a partial or complete detector section in which the optical module support is arranged, which is separated from the measurement chamber by the radiation exit window.

[0136] The optical module support may comprise or consist of a material with high thermal conductivity, preferably higher than 30 W / m / k, more preferably above 100 W / m / k, most preferably above 200 W / m / k, which makes temperature stabilization of the optical module easier and makes the temperature within the optical module more uniform.

[0137] In a further preferred embodiment of this aspect, if a coating that is reflective for the measurement radiation is applied, the optical module support may be manufactured from a material with a lower reflectivity, which broadens the material choice and makes it possible to manufacture the optical module support from a material that is particularly suitable for the applied manufacturing process or a particularly cheap material.

[0138] At least some of the surfaces of the optical module support that also serve as measurement chamber surfaces can receive a reflective coating, with or without additional buffer or barrier layers. Preferably, the reflective coating comprises Ag, Au, Cu, Al, W, or Mo, preferably with a purity of greater than 99%. Preferred deposition methods include electroplating, PVD (sputtering, evaporation), CVD, and ALD.

[0139] In the case of particularly not sufficiently inert coatings, at least one protective layer can be applied onto the reflective coating, which can comprise, for example, silicon oxide, silicon nitride or aluminum oxide, which is sufficiently transparent to the measurement radiation.

[0140] In a further preferred embodiment of this aspect, the optical module support comprises at least a part of at least one gas access channel, allowing the sample gas, preferably a transcutaneous gas, to pass through the gas access channel to and from the measurement chamber.

[0141] The sample gas typically presents at the contact surface of the sensor, e.g., after diffusion from the skin, and migrates into the gas access channels, preferably through one or more gas permeable seals and / or membranes that protect each gas access channel from contamination and clogging, e.g., through an access opening seal as described above.

[0142] Advantageously, the optical module support comprises a portion of at least one gas access channel. Preferably, this includes a major portion of all gas access channels of the sensor. Preferably, the channel portion does not terminate at the contact surface, but only close to the contact surface, allowing the access opening seal to be assembled onto the access opening of the channel such that the surface of the seal is at the same level as the rest of the contact surface, thus allowing the formation of a smooth contact surface without depressions or protrusions.

[0143] In this way, one or more gas access paths are formed leading from near the contact surface to the measurement chamber, along which molecules of the sample gas can diffuse from the sensor environment to the measurement chamber and vice versa.

[0144] The optical module support may include at least one mounting location for a heat source and / or a temperature sensor, which facilitates temperature stabilization of the optical module.

[0145] Thus, the optical module may comprise the main elements of a sensor required for gas measurement, such as an optical module support, a radiation source, a detector, a measurement chamber, and a gas access channel. This module may be placed in a casing that provides a protective housing and an interface to the patient, and may be connected to drive and readout electronics.

[0146] The optical module support may include an opening that is closed with a closing component such as a mirror, and it further comprises a mounting and sealing zone near the opening.

[0147] The mounting and sealing zone is located in an area where there is no gas access channel, typically between the edge of the closure component and an opening, such as a gas access channel or a measurement chamber opening. For example, a mirror can be used as the closure component, the edge of which is intended to be placed in an undercut of the optical module support. In this case, the mounting and sealing zone is located between the undercut and the gas access channel opening.

[0148] Such mounting and sealing zones facilitate liquid-tight or gas-tight mounting of the mirror to the optical module support.

[0149] Furthermore, the attachment and sealing zone allows for mechanical attachment of the closure component to the optical module support such that a good thermal contact is established between the closure component and the optical module support. Preferably, the mirror as described above is pressed into the undercut, for example by crimping, such that the mirror material is pressed into the undercut, thus ensuring a good mechanical contact between the mirror and the optical module support, thereby ensuring a good thermal contact. It is attached to the optical module support by plastic deformation.

[0150] In a further preferred embodiment of this aspect, the optical module support is preferably provided with an undercut near or in the above-mentioned mounting and sealing zone, preferably leading all around the optical module opening, for example in a circular shape.

[0151] A closure component, for example a mirror as described above, can then be attached by plastic deformation. The closure component can seal the opening in the optical module support such that a high viscosity liquid, such as an adhesive, preferably no liquid can flow into the gas access channel or opening at all.

[0152] Alternatively, the closure components may be attached by gluing, preferably using a high viscosity adhesive.

[0153] In further preferred embodiments of this aspect, the optical module support is formed from a metallic material such as aluminum, brass, bronze, copper, titanium, stainless steel, silver, gold, or from an alloy containing primarily such metals, or from a ceramic material such as aluminum oxide, zirconium oxide, or aluminum nitride, or from a polymeric material such as epoxy, PEEK, LCP, POM, or ABS.

[0154] The optical module support can be manufactured by mechanical processes such as drilling, milling, stamping, deep drawing, erosion, grinding or polishing, optical processes involving lasers such as laser ablation or laser melting, chemical processes such as etching, casting or molding, additive manufacturing processes such as laser melting or laser sintering or thermal sintering, stereolithography, or 3D printing processes involving two-photon absorption, or a combination of such processes.

[0155] In a further preferred embodiment of this aspect, the sensor has a contact surface and the optical module support is arranged within the casing such that no part of the optical module support forms part of the contact surface. Preferably, at least an access opening seal as described above is arranged between the contact surface of the sensor and the optical module support.

[0156] Preferably, the optical module support is thermally isolated from the casing. An insulating layer may be arranged between the main part of the optical module support and the casing. The layer may comprise or consist of a material having a low thermal conductivity, preferably less than 10 W / m / k, more preferably less than 1 W / m / k.

[0157] In at least one preferred embodiment of the sensor as described above, the sensor comprises a measurement chamber, the measurement chamber having a surface with high reflectivity for the measurement radiation. Preferably, all surfaces of the measurement chamber except the surfaces of the radiation entrance window or the radiation exit window, such as the relevant surfaces of the optical module support and mirrors, are highly reflective.

[0158] Preferably, the reflectivity of the measurement chamber surfaces for wavelengths within the range of wavelengths of the measurement radiation is greater than 80%, more preferably greater than 92%, even more preferably greater than 97%.

[0159] Preferably, at least some of the surfaces of the measurement chamber are coated with a reflective coating. This allows components such as the optical module support or the mirror to be made using materials with insufficient reflectivity. One or more protective coatings may be applied. In this way, materials that are particularly suitable or inexpensive for manufacturing can be selected.

[0160] In at least one preferred embodiment of the sensor as described above, any space in the sensor that is not required for measurement, such as the volume between the optical module and the sensor casing, may be filled with a material that has no or little solubility in the gas. This may be achieved, for example, by potting with epoxy. Filling the empty space with a material that has no or little solubility in the gas reduces the exchange of sample gas even if there is a leak.

[0161] At the same time, a filling process can be used to form a thermal insulation layer between the optical module support and the casing, as described above.

[0162] In at least one preferred embodiment of the sensor as described above, the radiation source emits radiation having at least two wavelengths, preferably in the range of 3.5 to 4.5 μm. Preferably, the sensor comprises a wavelength sensitive element for separating the at least two wavelengths. For example, the wavelength sensitive element may be an interference filter or an absorption filter.

[0163] Preferably, the wavelength sensitive element is located close to the detection surface of the detector, for example between the detection surface and the radiation exit window. Alternatively, the wavelength sensitive element may be located close to the radiation source, for example between the radiation source and the radiation entrance window. Alternatively, the wavelength sensitive element may be formed by the radiation entrance window or the radiation exit window, or by a combination of both, for example by a coating of a suitable surface of the window.

[0164] It may be advantageous to incorporate the wavelength sensitive element into the detector to form one component. In at least one preferred embodiment of the sensor as described above, the radiation source is arranged such that at least a portion of the emitted radiation propagates through the measurement chamber along a plurality of paths, at least a first and a second path. At least one of the paths includes reflection at a mirror. The detector is arranged such that radiation propagating along the first path impinges on a first detection surface and radiation propagating along the second path impinges on a second detection surface. A wavelength-sensitive element additionally arranged in the optical path may serve to separate wavelengths of the measurement radiation.

[0165] Advantageously, at least a part of the measurement radiation propagates from the radiation source to the detection surface in a non-imaging manner. In at least one preferred embodiment of the sensor as described above, the sensor comprises an additional liquid-tight membrane covering an area of ​​the sensor that cannot be exposed to liquid. Preferably, the additional membrane covers at least a part of the contact surface of the sensor. The additional membrane may be attached to a casing of the sensor.

[0166] The additional membrane may be replaceable. In at least one preferred embodiment of the above-mentioned sensors, the sensor comprises a receiving interface for the additional membrane. The receiving interface is preferably arranged in the casing and is formed so that the additional membrane can be arranged on at least a part of the contact surface, at least during use of the sensor. For example, the additional membrane can be integrated in the patient applicator, in which case the additional membrane can be a disposable membrane that prevents direct contact between the skin and the casing. Alternatively, the additional membrane can be a disposable membrane that can remain attached to the casing for one or more consecutive measurements.

[0167] In a preferred embodiment of at least one of the sensors as described above, the sensor has a size and shape to fit into a small volume. The sensor (without communication and power cables and connectors) preferably fits into an imaginary cylinder with a diameter of 30 mm and a height of 20 mm or a 15 cm 3 More preferably, the sensor fits into a virtual volume of 20 mm diameter and 16 mm height or 5 cm 3 Most preferably, the sensor is 17 mm in diameter and 17 mm in height. 13mm cylinder or 3cm 3 The scalar fits into a virtual volume of

[0168] Furthermore, all measurement radiation propagating along the optical path from the radiation source to the detector is confined to this volume, in particular the optical fiber guiding the measurement radiation in and out of the sensor is not connected to the sensor.

[0169] Preferably, the total length of the shortest complete optical path from the radiation source through the measurement chamber to the detection surface, i.e. the shortest path followed by the measurement radiation, does not exceed 20 mm, preferably does not exceed 10 mm, most preferably does not exceed 5 mm. Such a miniaturized design is advantageous for the manufacture of transcutaneous sensors.

[0170] The shortest complete optical path followed by the measurement radiation not only passes through gas-accessible volumes such as the measurement chamber or unfilled spaces between, for example, the radiation entrance window and the radiation source, but also through filled (non-gas-accessible) volumes such as the radiation entrance window or the radiation exit window. Preferably, the length of the part of this shortest complete optical path through the measurement chamber with respect to the total length of all parts of this path through the gas-accessible volumes is at least 50%, more preferably at least 60%, most preferably at least 75%. Such a design increases the reliability of the measurement results.

[0171] Furthermore, the sensor preferably generates the measurement radiation only in the sensor itself, most preferably in the optical module, and therefore the measurement radiation is not transported to the sensor via means such as a waveguide.

[0172] Preferably, after an initial warm-up phase, the average power delivered to the sensor during typical measurement conditions is less than 5W, more preferably less than 2W, and most preferably less than 1W.

[0173] Preferably, the radiation source of the sensor is a thermal radiator emitting broadband blackbody type radiation. Alternatively, the radiation source may also consist of one or several LEDs, for example mid-IR LEDs, or tunable or non-tunable lasers.

[0174] Preferably, the radiation detector of the sensor is a detector such as a photosensitive element or photodiode, a (micro)bolometer or a pyrometer. The detector is made of a material suitable for the wavelength of the measurement radiation.

[0175] According to an eighth aspect of the present invention there is provided a method for manufacturing a sensor, in particular a sensor as described above. The optical module support is provided with an opening that provides access to at least a portion of the measurement chamber. At least a portion of the optical module support is then coated through the opening with at least one coating having a high reflectivity for the measurement radiation. The reflective coating may be formed by materials and methods as described above.

[0176] The opening is then closed with a mirror such that at least a portion of the surface of the mirror forms part of the measurement chamber surface.

[0177] At least one radiation source is provided for emitting radiation and is positioned such that at least a portion of the radiation is reflected by the mirror.

[0178] Preferably, the mirror is attached by deformation, in particular by plastic deformation. The mirror may for example be deformed by a stamp die. The edge of the mirror may be pressed into an undercut in the optical module support, thereby mechanically attaching it to the optical module support. The object is fixed objectively.

[0179] Advantageously, the method comprises the further step of providing a radiation entrance window in the optical module support, which separates the measurement chamber from the radiation source of the sensor. The radiation source is preferably mounted in a radiation source compartment arranged in the optical module support. Preferably, the optical module support further comprises a radiation exit window, which separates the measurement chamber from the detector of the one or more sensors. The detector is preferably mounted in a detector compartment arranged in the optical module support.

[0180] Preferably, the at least one radiation source and the at least one detector are arranged on or in the optical module support such that at least a portion of the radiation emitted by the radiation source propagates from the radiation source through the measurement chamber towards the detector, is reflected by a mirror and impinges on a detection surface of the detector.

[0181] Advantageously, the method comprises the further step of providing at least a main part of the above-mentioned at least one gas access channel in the optical module support.

[0182] The method may include the further step of covering the access opening of the gas access channel with an access opening seal that is permeable to the sample gas but liquid-tight or at least liquid-repellent.

[0183] The method may include the further step of providing a casing as described above.The optical module support may be disposed within the casing.

[0184] In a preferred embodiment of the method, the optical module support is formed by a machining process, an optical or chemical process, casting or molding, an additive manufacturing process, or a combination of such processes.

[0185] The invention will now be further described with reference to preferred embodiments and the following drawings. [Brief description of the drawings]

[0186] [Figure 1] FIG. 1 is a schematic cross-sectional view of a first example of a sensor according to the present invention. [Diagram 2] 4 is a schematic cross-sectional view of a further example of a sensor according to the invention; [Diagram 3] 1 is a schematic cross-sectional view of a portion of an optical module support prior to assembly. [Figure 4] 1 is a schematic cross-sectional view of a portion of an optical module support showing a mirror assembly. [Diagram 5] FIG. 13 is a schematic cross-sectional view of a portion of the optical module after the mirror is assembled. [Figure 6] 4 is a schematic cross-sectional view of a portion of a further example of a sensor according to the invention; [Figure 7] 4 is a schematic cross-sectional view of a portion of a further example of a sensor according to the invention; [Figure 8] 4 is a schematic cross-sectional view of a portion of a further example of a sensor according to the invention; [Figure 9] 4 is a schematic cross-sectional view of a portion of a further example of a sensor according to the invention; [Figure 10] 4 is a schematic cross-sectional view of a portion of a further example of a sensor according to the invention; [Figure 11] FIG. 13 is a schematic diagram of a portion of an optical module showing an example of an access opening for a gas access channel. [Figure 12] 13 is a schematic diagram of a portion of an optical module showing further examples of access openings for the gas access channels. FIG. [Figure 13] 4 is a schematic cross-sectional view of a portion of a further example of a sensor according to the invention; [Figure 14] 1 is a schematic cross-sectional view of an example of an access opening seal. [Figure 15] 13 is a schematic cross-sectional view of a further example of an access opening seal; [Figure 16] 13 is a schematic cross-sectional view of a further example of an access opening seal; [Figure 17] 13 is a schematic cross-sectional view of a further example of an access opening seal; [Figure 18] 13 is a schematic cross-sectional view of a further example of an access opening seal; [Figure 19] FIG. 2 is a schematic cross-sectional view of an example of an optical module. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0187] Identical parts or parts with the same function have the same reference numbers in all figures. 1 shows a schematic cross-sectional view of a sensor 1 for detecting gas, in particular for detecting transcutaneous CO2. The sensor 1 comprises an optical module 2. The optical module 2 comprises an optical module support 19, a radiation source 3 in the form of a thermal emitter or an LED for emitting radiation, a detector 4 in the form of an infrared photovoltaic or photoconductive detector for detecting the radiation emitted by the radiation source 3, a wavelength-sensitive element 41 formed by an interference filter, a mirror 5 for reflecting the radiation, a measuring chamber 6 for receiving a sample gas, a radiation entrance window 20 and a radiation exit window 21.

[0188] The optical module support 19 is made, for example, of a copper alloy, ie a material having a thermal conductivity of 100 W / m / k or more. The optical module support 19 does not extend to the contact surface 8.

[0189] The mirror 5 is made, for example, of gold, which is a highly reflective, deformable, inert, non-porous and / or well thermally conductive material. It closes the opening of the optical module support 19 and is attached to the optical module support 19 by plastic deformation such that good thermal contact is established between the mirror 5 and the optical module support 19.

[0190] The radiation source 3 , detector 4 , mirror 5 and measurement chamber 6 are arranged such that at least a portion of the radiation propagates through the measurement chamber 6 along a path that includes reflection off the mirror 5 .

[0191] The measurement chamber 6 has surfaces that are highly reflective to the measurement radiation. In this embodiment, the high reflectivity is achieved by a highly reflective coating of, for example, gold on these surfaces. The coating can be applied through an opening in the optical module support 19 before mounting the mirror 5.

[0192] The sensor 1 further comprises a casing 7 in which the optical module 2 is arranged. The casing 7 is made of a metallic material, in particular a copper, aluminum or titanium alloy, having a high thermal conductivity, preferably above 10 W / m / k.

[0193] The sensor 1 has a contact surface 8 which is orientable towards the measurement site and which is intended to be in intimate contact with the patient's skin during a transcutaneous measurement.

[0194] The sensor 1 has a gas access channel 9 that allows gas to travel from the contact surface 8 to the measurement chamber 6. The gas access channel 9 is arranged so that it does not pass through or directly around the mirror 5. The gas access channel 9 leads to the measurement chamber 6 from near the contact surface 8 and is arranged to extend along a portion of the inner surface 24 of the mirror 5 (see FIG. 4). This portion is selected so that the gas access channel 9 does not reach the edge 25 of the mirror 5 (see also FIG. 4). The gas access channel 9 is mainly arranged in the optical module support 19.

[0195] The radiation source 3 is arranged in the radiation source section 10 . The sensor 1 comprises at least one ventilation channel 11 leading from the source compartment 10 to the environment 22 .

[0196] The sensor 1 allows gas trapped within the source compartment 10 to escape to the environment 22. While providing a liquid-tight but gas-permeable vent channel seal 12 to protect the vent channel 11 from liquids or particles, the seal 12 is made of a polymer such as silicone, for example.

[0197] The detector 4 is arranged in the detector section 27 . The mirror 5 is disposed at a distance 13 from the contact surface 8 and is covered by a portion 14 of the casing 7 .

[0198] The mirror 5 is thermally decoupled from the casing 7. A thermal insulation layer 15, for example made of epoxy, is arranged between the mirror 5 and the part 14 of the casing 7.

[0199] The gas access channel 9 terminates in an access opening 17 located near the contact surface 8 of the sensor 1. The access opening 17 is covered by an access opening seal 18 that is gas permeable but liquid tight or liquid repellent. The seal is formed, for example, by a titanium, steel, or glass substrate and a polymer coating, such as a fluoropolymer, silicone, or polyolefin. The otherwise empty space between the access opening seal 18 and the casing 7 is filled with a potting material 37, such as epoxy. The access opening seal 18 and the potting material 37 are formed and positioned such that they form a fairly smooth contact surface 8 with a portion of the casing 7.

[0200] Any empty space inside the sensor, such as between the optical module 19 and the casing 7, is potted with a potting material 16, in particular an epoxy.

[0201] The sensor 1 may be provided with an additional membrane 26, at least during use, to improve the reliability of the sensor in wet or humid environments. The additional membrane 26 is attached to the casing 7 of the sensor 1 and is replaceable.

[0202] The sensor may further include a cover or cap 35, preferably made from a polymer, that closes and protects the top of the sensor.

[0203] 2 shows a schematic cross-sectional view of a further example of the sensor 1. Furthermore, the optical module 2 comprises a radiation window seal 34 along at least a part of the radiation entrance window 20 and the radiation exit window 21 to prevent gas exchange between the measurement chamber 6 and the radiation source section 10 or the detector section 27.

[0204] The sensor 1 further comprises a ventilation channel 11 that passes through the optical module support 19. The ventilation channel 11 originates from the source compartment. The ventilation channel seal 12 allows unwanted gas present in the source compartment 10 to diffuse from the source compartment 10 to the sensor environment 22. The ventilation channel 11 may extend to some extent into the ventilation channel seal 12.

[0205] 3 shows a schematic cross-sectional view of a portion of the optical module support 19 prior to assembly. The optical module support 19 comprises a major portion of the gas access channel 9 (see FIG. 1). The optical module support 19 comprises an opening 28 that allows the application of a reflective coating 29 onto a surface that defines a significant portion of the surface of the measurement chamber 6 (see FIG. 1).

[0206] The reflective coating 29 is made, for example, of gold or silver in combination with a protective coating, which is highly reflective to the measurement radiation.

[0207] A surface treatment on the surface that should be covered by the mirror 5 (see Figures 4 and 5) and that is located between a part of the gas access channel 9 in the optical module support 19 and the undercut 33. A mounting and sealing zone 30 is provided on the optical module support 19 .

[0208] FIG. 4 shows a schematic cross-sectional view of a portion of the optical module support 19 showing how the mirror 5 is assembled, with the opening 28 being closed by the mirror 5 .

[0209] The mirror 5 is placed on the optical module support 19 such that the edge 25 of the mirror 5 is located near the undercut 33 and the inner surface 24 of the mirror covers part of the gas access channel 9. Plastic deformation of the mirror 5 is then achieved by pressing the mirror 5 with a stamp die 31 such that material from the lateral volume 32 of the mirror is displaced into the undercut 33 (see FIG. 5 ).

[0210] FIG. 5 shows a schematic cross-sectional view of a part of the optical module 2 after assembly of the mirror 5 on the optical module support 19 by compression bonding.

[0211] A lateral volume 32 of the mirror 5 is displaced into an undercut 33 of the optical module support 19 , whereby said mirror 5 is fixed in the undercut 33 and a good thermal contact to the optical module support 19 is achieved.

[0212] A portion of the gas access channel 9 leads into the measurement chamber 6 along the inner surface 24 of the mirror.

[0213] FIG. 6 shows a schematic cross-sectional view of a part of a further example of the sensor 1. The optical module 2, which comprises at least the optical module support 19 and the mirror 5, is arranged in a casing 7. Between the optical module 2 and the casing 7, in particular between the mirror 5 and the part 14 of the casing 7, a thermal insulation layer 15 is provided.

[0214] The gas access channel 9 extends from the measurement chamber 6 along part of the inner surface 24 of the mirror 5, then through the optical module support 19 but not around the edge of the mirror 5, near the contact surface 8 of the sensor 1. The gap between the optical module support 19 and the casing 7 is filled with a potting material 37, which may be different or the same as the material used as the thermal insulation layer 15. The access opening 17 of the gas access channel 9 widens near the end of the gas access channel.

[0215] An additional membrane 26 is present near the contact surface of the sensor, at least during use, to prevent the gas access channel from becoming clogged with contaminants such as liquids, pastes or particles.

[0216] FIG. 7 shows a schematic cross-sectional view of a part of a further example of the sensor 1. In this embodiment, the access opening 17 of the gas access channel 9 is covered by the access opening seal 18. Any gap between the access opening seal 18 and the casing 7 is potted with a potting material 37. The casing 7, potting material 37, and access opening seal 18 are arranged such that a smooth contact surface 8 is formed.

[0217] A thermal insulating epoxy layer 15 is disposed between the mirror 5 and the access opening seal 18 such that the mirror is thermally isolated from the contact surface 8 .

[0218] The access opening seal 18 is much wider than the access opening 17 of the gas access channel 9. If the sensor has one or more further gas access channels with their respective access openings, the access opening seal 18 can be used to cover and protect such further access openings as well.

[0219] FIG. 8 shows a schematic cross-sectional view of a part of a further example of the sensor 1. A gas access channel 9, which extends mostly through the optical module support 19, terminates near the contact surface 8. An access opening 17 of the gas access channel 9 widens toward an access opening seal 18 where the access opening 17 is covered. The widening of the access opening 17 aids in the migration of sample gas into the gas access channel 9 after diffusing through the access opening seal 18.

[0220] The access opening seal 18 includes an anchor 36. The anchor 36 is embedded in a potting material 37, preferably epoxy, so that the anchor 36 is mechanically secured.

[0221] FIG. 9 shows a schematic cross-sectional view of a part of a further example of the sensor 1. The access opening 17 of the gas access channel 9 is covered with a liquid-tight membrane 42, made for example of a fluoropolymer, silicone, or polyolefin, which is covered with an access opening seal 18, made for example of a metal, glass, or ceramic substrate and polymer coating.

[0222] FIG. 10 shows a schematic cross-sectional view of a part of a further example of the sensor 1. The access opening 17 is wider than the gas access channel 9 and includes a shallow cavity 43 that extends along its interface with the access opening seal 18. This shallow cavity 43 aids in the migration of sample gas into the gas access channel 9 after diffusing through the access opening seal 18. The shallow cavity 43 or access opening 17 may be formed to reside under a major portion of the access opening seal 18.

[0223] 11 shows a schematic top view of a portion of the optical module support 19, specifically an example of an access opening 17 of the gas access channel 9. The access opening 17 includes a shallow cavity 43 that extends from the end of the gas access channel 9 in a star-shaped pattern.

[0224] Such a star-shaped shallow cavity 43 has an advantage over a simple shallow cylindrical cavity because the access opening seal 18 is mechanically supported over most of its area, whereas in a cylindrical cavity it is not. This is particularly relevant when the shallow cavity extends over a large area.

[0225] 12 shows a schematic top view of a portion of the optical module support 19, specifically a further example of an access opening 17 of the gas access channel 9. The access opening 17 comprises shallow cavities 43 arranged in a grid-like pattern near the ends of the gas access channels 9.

[0226] The grid-like arrangement of shallow cavities 43 aids gas movement towards the gas access channels 9 even for large area, i.e., large access opening seals, while the additional gas accessible volume created by the shallow cavities 43 remains small. Furthermore, the large access opening seals also remain well mechanically supported by the optical module support 19.

[0227] FIG. 13 shows a schematic cross-sectional view of a part of a further example of the sensor 1. The access opening 17 of the gas access channel 9 is not significantly wider than the adjacent portions of the gas access channel 9 .

[0228] The access opening seal 18 includes a shallow cavity 44 extending along a portion of its interface with the access opening seal 18. This shallow cavity 44 aids in the migration of sample gas into the gas access channel 9 after diffusing through the access opening seal 18 in the same manner as the shallow cavity in the access opening 17, as described above (FIGS. 10-12). A star or grid pattern, or any other pattern toward the gas access channel 9 may be formed in the main portion of the access opening seal 18 .

[0229] FIG. 14 shows a schematic cross-sectional view of one example of an access opening seal 18. The access opening seal 18 includes a base plate 38 that includes a hole that passes from the top surface to the bottom surface of the base plate 38. The base plate 38 includes a protrusion 39.

[0230] A gas permeable coating 40 is disposed at least between the protrusions 39. The material of the protrusions 39 may be, for example, titanium, steel, glass, or a ceramic that is more wear resistant than the material of the gas permeable coating 40.

[0231] Preferably, gas-permeable coating 40 also covers the protrusions. This is particularly advantageous, for example, when coating 40 is a fluoropolymer that has non-stick or easy-to-clean properties.

[0232] FIG. 15 shows a schematic cross-sectional view of a further example of an access opening seal 18 . Here, gas permeable coating 40 is disposed at least between protrusions 39 and partially or completely within the holes.

[0233] FIG. 16 shows a schematic cross-sectional view of a further example of an access opening seal 18 . The substrate 38 includes larger holes at the top of the access opening seal 18 and smaller holes that lead from the bottom of the larger holes to the underside of the access opening seal 18. Each larger hole may have one or more smaller holes. The larger holes may be conically shaped so that an undercut is created. Between the larger holes, the substrate 38 includes a protrusion 39.

[0234] The gas permeable coating 40 is disposed at least between the protrusions 39 in the larger holes. Thus, the gas permeable coating 40 of the larger holes is protected from abrasion while at the same time being held in place due to the conical shape of the larger holes. The smaller holes may be small enough in diameter that the gas permeable coating 40 does not easily penetrate into them during the coating process. This allows the thickness of the gas permeable coating 40 to be reduced, which reduces the diffusion time of the sample gas from the measurement site into the gas access channel.

[0235] The access opening seal 18 further comprises a shallow cavity 43 on the bottom surface which connects the small holes and leads to the access openings of the gas access channels in the fully assembled sensor. The shape of the shallow cavity 43 can be cylindrical, star-shaped, lattice-like, or any other shape.

[0236] FIG. 17 shows a schematic cross-sectional view of a further example of an access opening seal 18 . The access opening seal 18 includes a porous substrate 38 formed by molten particles. There are no direct channels extending from the top surface to the bottom surface of the substrate, or only a few such channels. Instead, many voids between components of the porous substrate 38 are interconnected to form diffusion channels of arbitrary shape. The irregular structure of the substrate 38 results in protrusions 39.

[0237] Gas permeable coating 40 is disposed at least between protrusions 39. The material of protrusions 39 is more wear resistant than the material of gas permeable coating 40. Gas permeable coating 40 may extend partially or completely into the voids of the substrate.

[0238] FIG. 18 shows a schematic cross-sectional view of a further example of an access opening seal 18 . A gas permeable coating 40 made of a material as described above is disposed within the holes, or at least some of the holes, of the substrate 38. The material of the substrate 38 is more abrasion resistant than the material of the permeable coating 40, so the substrate protects the coating from damage.

[0239] 19 shows a schematic cross-sectional view of an example of an optical module 2. The optical module 2 comprises an optical module support 19, preferably made from a copper alloy, which is a good thermally conductive material. The mirror 5 is attached to the optical module support 19 as described above. A gas access channel 9 passes through the optical module support 19, between the optical module support 19 and the inner surface 24 of the mirror 5. Sample gas present at the access opening 17 of the gas access channel 9 can diffuse into the measurement chamber 6 in a way that does not lead directly around the edge of the mirror 5.

[0240] The optical module 2 further comprises a radiation entrance window 20 and a radiation exit window 21. A radiation window seal 34 separates the measurement chamber 6 from the radiation source section 10 and the detector section 27, both of which are essentially machined into the optical module support 19, so that gas exchange between the measurement chamber 6 and the radiation source section 10 or the detector section 27 is strongly limited. The measurement radiation emitted by the radiation source 3 can propagate through the radiation entrance window 20 into the measurement chamber 6, where it undergoes reflection at the mirror 5 and / or at a surface of the measurement chamber 6. The measurement radiation can further propagate through the radiation exit window 21 through the wavelength-sensitive element 41 and may then be absorbed by the detection surface of the detector 4. The radiation may propagate in a non-imaging manner.

[0241] The optical module 2 further comprises at least a portion of a ventilation channel 11 through which unwanted gas present in the source chamber 10 can escape.

Claims

1. A sensor (1) for detecting a gas, comprising: The sensor (1) at least one radiation source (3) for emitting radiation; at least one detector (4) for detecting radiation emitted by said radiation source; At least one measuring chamber (6) for receiving said gas to be measured; Equipped with the radiation source (3), the radiation entrance window, the measurement chamber (6), the mirror, the radiation exit window, and the detector (4) are arranged such that at least a portion of the radiation emitted by the radiation source (3) propagates along a path passing through the radiation entrance window into the measurement chamber (6), being reflected by the mirror, and passing through the radiation exit window towards the detector (4); said sensor (1) comprising an optical module support (19) which forms part of said measuring chamber and comprises an opening (28), said sensor comprising a closure component for closing said opening (28), i.e. said mirror, the measurement chamber of the sensor is formed by an optical module support, the mirror, and surface portions of the radiation entrance window and the radiation exit window; A small open space between the mirror and the optical module support remains open for the purpose of gas transfer to and from the measurement chamber.

2. The sensor (1) of claim 1, wherein the optical module support (19) includes at least a portion of at least one gas access channel (9) and allows the gas to be measured to travel through the gas access channel (9) to the measurement chamber (6).

3. 3. The sensor (1) according to claim 1 or 2, wherein the optical module support (19) comprises a mounting and sealing zone (30) near the opening (28) to enable mechanical mounting of the closure component to the optical module support (19).

4. The sensor (1) according to any one of claims 1 to 3, wherein the optical module support (19) comprises an undercut (33) in which the lateral volume (32) of the closure component can be arranged.

5. The optical module support (19) -metallic materials, - ceramic materials, and - Polymer materials The sensor (1) according to any one of claims 1 to 4, made from a material selected from the group consisting of:

6. 6. The sensor (1) according to claim 1, wherein the sensor has a contact surface (8), and the optical module support (19) is arranged within the casing (7) such that no part of the optical module support forms part of the contact surface (8).

7. A sensor (1) described in any one of claims 1 to 6, wherein the optical module support (19) and at least a portion of the mirror have a reflectivity for measurement radiation on the surface directed toward the measurement chamber (6).

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