Sensor Device and Method for Producing a Sensor Device

Abstract

In an embodiment a sensor device includes a sensor element, a media supply configured to transport a medium to the sensor element and a surface, wherein the surface is configured to be exposed to the medium during operation of the sensor device, and wherein the surface comprises a surface structure configured to reduce a wettability of the surface by the medium.

Claims

1.-17. (canceled)

18. A sensor device comprising: a sensor element; a media supply configured to transport a medium to the sensor element; and a surface, wherein the surface is configured to be exposed to the medium during operation of the sensor device, and wherein the surface comprises a surface structure configured to reduce a wettability of the surface by the medium.

19. The sensor device according to claim 18, wherein the surface is hydrophobic or superhydrophobic caused by the surface structure.

20. The sensor device according to claim 18, wherein the surface structure comprises a microstructure.

21. The sensor device according to claim 20, wherein the microstructure comprises elevations and/or depressions having circular and/or elongate cross sections.

22. The sensor device according to claim 21, wherein the elevations and/or the depressions have a spacing of less than or equal to 500 μm.

23. The sensor device according to claim 21, wherein the elevations and/or the depressions have a height or a depth of less than or equal to 250 μm.

24. The sensor device according to claim 18, wherein the surface structure comprises a nanostructure.

25. The sensor device according to claim 18, wherein the surface structure comprises a hierarchical micro-nanostructure.

26. The sensor device according to claim 18, wherein the sensor element comprises a membrane and the surface is at least a part of the membrane.

27. The sensor device according to claim 18, wherein the surface is at least part of the media supply.

28. The sensor device according to claim 27, wherein the surface is at least a part of a channel, of a conduit and/or of a storage volume for the medium.

29. The sensor device according to claim 18, wherein the sensor device is a pressure sensor.

30. The sensor device according to claim 18, wherein the entire surface comprises the surface structure.

31. The sensor device according to claim 18, wherein the surface is at least partially a metal surface.

32. The sensor device according to claim 18, wherein the surface comprises different materials.

33. A method for producing the sensor device according to claim 18, the method comprising: producing the surface structure by pulsed laser radiation.

34. The method according to claim 33, wherein the pulsed laser radiation comprises laser pulses with a pulse duration of less than or equal to 100 ns.

35. A sensor device comprising: a sensor element; a media supply configured to transport a medium to the sensor element; and a surface, wherein the surface is configured to be exposed to the medium during operation of the sensor device, wherein the surface comprises a surface structure configured to reduce a wettability of the surface by the medium, and wherein the surface with the surface structure is free of a coating configured to reduce a wetting.

36. The sensor device according to claim 35, wherein the surface is free of a material having a lower wettability in comparison with the uncoated surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further advantages, advantageous embodiments and refinements may be found in the exemplary embodiments described below in connection with the figures, in which:

[0028] FIGS. 1A to 1C show schematic representations of a sensor device and of a method for producing the sensor device according to one exemplary embodiment;

[0029] FIGS. 2A to 2C show schematic representations of surface structures of a sensor device according to further exemplary embodiments; and

[0030] FIGS. 3A and 3B show results of experimental measurements for surface structures produced by means of the method.

[0031] In the exemplary embodiments and figures, elements which are the same or of the same type, or which have the same effect, may respectively be provided with the same references. The elements represented and their size proportions with respect to one another are not to be regarded as true to scale. Rather, individual elements, for example layers, component parts, components and regions, may be represented exaggeratedly large for better representability and/or for better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0032] A sensor device 100 and a method for producing the sensor device 100 according to one exemplary embodiment are shown in FIGS. 1A to 1C. The sensor device 100 is, in particular, provided and adapted to measure one or more parameters of a medium 99, which may for example be selected from a pressure, a temperature and optical properties.

[0033] Purely by way of example, the sensor device 100 of the exemplary embodiment shown is a pressure sensor, which may for example be used in the scope of an exhaust gas measurement in a motor vehicle. Correspondingly, the medium 99 may purely by way of example comprise or be an exhaust gas of a gasoline or diesel engine. Furthermore, the medium 99 may also at least partially comprise air. This may, in particular, be the case at a time before the engine is started and/or shortly after starting of the engine. In particular, the medium 99 may also at least partially comprise moisture, which is for example contained in the air and/or in the exhaust gas, so that the possibility may arise that the medium 99 forms a condensate at low temperatures. Even though the description below relates to a particular configuration of the sensor device 100, it applies equally for other types of sensor, including in combination with other media.

[0034] As is shown in FIG. 1A, the sensor device 100 comprises a sensor element 1 which constitutes the active part of the sensor device 100. In the exemplary embodiment shown, the sensor element 1 is a pressure sensor chip, which may for example be based on silicon and which comprises a membrane that deforms under the effect of pressure due to the medium 99. As an alternative thereto, the sensor element 1 may for example also comprise a ceramic or metal membrane.

[0035] The sensor element 1 is located in a housing 2, which may for example comprise or consist of plastic, metallic and/or ceramic materials. The medium 99 can be fed to the sensor element 1 through a media supply 21, for example in the form of a conduit formed by a connecting piece. As shown by way of example in FIG. 1A, the sensor element 1 may be located in a volume 20 of the housing 2 which is closed by a cover 3. The volume 20 may have a reference pressure, in relation to which the pressure of the medium 99 is measured. As an alternative thereto, it may also be possible for the volume 20 to be open to the surroundings or likewise to be connected to the exhaust gas system, so that the sensor element 1 can measure a corresponding differential pressure. In this case, the surface of the sensor element 1 which faces toward the volume 20, and/or the surfaces of the walls forming the volume 20, and optionally of a supply conduit or media supply, may be configured as or in a similar way as described below for the media supply 21 and the side of the sensor element 1 facing toward the media supply 21. The sensor device 100 is represented in a greatly simplified way in the exemplary embodiment shown, and may comprise further or alternative parts and components conventional for corresponding sensor devices.

[0036] The sensor device 100 comprises surfaces 4 which face toward the medium 99 during regular operation. In the exemplary embodiment shown, the surfaces 4 are formed by an inner wall of the media supply 21 and by the side of the sensor element 1 facing toward the media supply 21, in which case the latter side may in particular be formed by the membrane of the sensor element 1. If the temperature in the media supply 21 and/or in the region of the sensor element 1 falls to a sufficiently low value, it may be the case that at least a part of the medium 99 condenses on at least a part of the surfaces 4 or, at even lower temperatures, freezes, which may lead to the problems described in the general part above. In order to avoid this, the sensor device 100 comprises at least one surface 4 with a surface structure 40, which is indicated in a detail in FIG. 1B and which reduces a wettability of the surface 4 with the medium 99 or at least one component contained in the medium 99. In particular, the surface 4 with the surface structure 4 may be superhydrophobic caused by the surface structure 40. This may particularly preferably mean that the contact angle between water and the surface 4 with the surface structure 40 is greater than or equal to 110° or even greater than or equal to 135° or even greater than or equal to 150°. In particular, the superhydrophobic effect of the surface 4 may be caused only by the surface structure 40.

[0037] The surface 4 with the surface structure 40 is, in particular, free of a coating that reduces the wetting. In other words, the surface 4 is not formed by a material such as, for example, Teflon or another fluoropolymer, which has been applied deliberately in order to reduce the wettability. Rather, the surface 4 with the surface structure 40 may be a surface of a part or a component of the sensor device 100 which would have a high wettability without the surface structure 40. The material of the surface 4 with the surface structure 40 is therefore, in particular, the material of the corresponding part or of the corresponding component of the sensor device 100 and may, depending on the material from which the part or the component of the sensor device 100 having the surface 4 with the surface structure 40 is made, comprise or be for example a semiconductor material, a metal or a metal alloy, a plastic, a ceramic material or combinations comprising these.

[0038] For example, the surface 4 with the surface structure 40 which is indicated in FIG. 1B may be a surface of the sensor element 1. In the exemplary embodiment shown, the surface 4 with the surface structure 40 may particularly preferably be part of the membrane of the sensor element 1. In other words, the surface 4 with the surface structure 40 may be formed by a surface of the membrane facing toward the media supply 21 and therefore toward the medium 99 during operation of the sensor device 100. If the sensor element 1 is a silicon-based chip, the surface with the surface structure may comprise or consist of silicon or an oxide or nitride of silicon. In the case of a ceramic membrane or metal membrane, the surface 4 with the surface structure 40 may correspondingly be a ceramic or metal surface.

[0039] As an alternative or in addition, the surface 4 with the surface structure 40 may be at least part of the media supply 21. For example, the surface 4 with the surface structure 40 may be at least a part of the inner wall of the connecting piece shown in FIG. 1A. If the housing 2, and in particular the connecting piece, is made from a ceramic material or a plastic, the surface 4 with the surface structure 40 may correspondingly be a ceramic or plastic surface. In the case of a metal housing 2, the surface 4 with the surface structure 40 may correspondingly also be a metal surface.

[0040] Particularly preferably, the entire surface of the sensor device 100 exposed to the medium 99 during operation of the sensor device 100, i.e. all the surfaces 4 exposed to the medium 99 during operation, may also comprise the surface structure 40. Correspondingly, the wettability of all surfaces 4 of the sensor device 100 which come in contact with the medium 99 during operation may be reduced because of the surface structure 40. The advantages described in the general part above may be achievable by the reduced wettability of the surface 4 with the surface structure 40.

[0041] The surface structure 40 may comprise a microstructure and/or a nanostructure, i.e. as shown in FIG. 1B it may comprise a multiplicity of elevations 41 and/or depressions 42 in the surface 4, which may have characteristic sizes in the range of greater than or equal to 0.1 μm and less than or equal to 500 μm in the case of a microstructure, and in the range of greater than or equal to 1 nm and less than or equal to 100 nm.

[0042] As indicated in FIG. 1C, in order to produce the sensor device, the surface structure is produced by means of pulsed laser radiation, which is indicated by means of the broken arrow with the reference 201. In particular, short-pulse laser irradiation or preferably ultrashort-pulse laser irradiation may be carried out, in particular by using a laser 200, for instance a nanosecond laser or preferably a picosecond laser or particularly preferably a femtosecond laser. This may mean that the pulsed laser radiation 201, which is shone onto the surface 4, comprises laser pulses with a pulse duration of less than or equal to 100 ns or preferably less than or equal to 100 fs or less than or equal to 50 fs or less than or equal to 30 fs.

[0043] Parameters of the laser radiation 201, for example selected from wavelength, energy, beam width, fluence, degree of polarization, forward advance rate, pulse frequency, pulse number, pulse duration, angle of incidence and scan conduit offset, may be adjusted depending on the material of the surface 4 in which the surface structure is produced, in order to achieve a desired material ablation in order to generate the surface structure. Furthermore, for example, an interference technique may be used in order to produce periodic microstructures and/or nanostructures.

[0044] By the use of the pulsed laser radiation 201, which may correspondingly be adjusted according to the surface material to be processed and the desired surface structure, it may be possible to produce identical or different surface structures on different surfaces, i.e. surfaces of different materials. This may be done during or after the production of a part or a component of the sensor device in an in-line process step. Correspondingly, the pulsed laser irradiation may be carried out as a method step inserted into the conventional production process.

[0045] The elevations 41 and/or depressions 42 of the surface structure 40 may, for example, have circular and/or elongate cross sections. For example, the surface structure 40 may comprise circular and/or elliptical elevations and/or depressions, i.e. hole-like depressions and/or hill- or island-like elevations, which may for example be columnar, cylindrical and/or conical in shape. The surface structure 40 may furthermore comprise elongate, branching or non-branching ridges and/or trenches extending along the surface 4, which may intersect or not intersect or be parallel. The elevations 41 and/or depressions 42 may at least partially or all be shaped and/or distributed periodically and therefore regularly, or may at least partially or all be shaped and/or arranged irregularly.

[0046] Three exemplary embodiments of the surface structure 40 are shown purely by way of example in FIGS. 2A to 2C. It may, as indicated in FIG. 2A, for example comprise mutually parallel, periodically arranged depressions 42 in the form of channels. As an alternative thereto, the channels may for example also be formed irregularly and/or not straight and/or intersecting. As shown in FIG. 2B, the surface structure 40 may also comprise hole-like depressions 42, for example with a round cross section as shown in FIG. 2B. Furthermore, other shapes as described above and in the general part are possible. Between the depressions 42 shown, the surface 4 may be planar or comprise elevations. Furthermore, it may also be possible for correspondingly shaped elevations 41 to be formed on the surface 4 instead of the depressions 42 shown. As is indicated in FIG. 2C, the surface structure 40 may also comprise a so-called hierarchical micro-nanostructure, i.e. a combination of a microstructure and a nanostructure. To this end, the surface structure 40 may comprise elevations 41 and/or depressions 42, on the surfaces of which nanostructures having corresponding elevations 41′ and/or depressions 42′ are formed. The characteristic sizes of the surface structures 40 shown may be as described above in the general part. In particular, the shapes and characteristic sizes of the surface structure 40 may be selected in such a way that a sufficiently low wettability is achieved in respect of the medium which is in contact with the surface 4 with the surface structure 40 during operation, in order to reduce or even entirely prevent the problems of the prior art described above and achieve the advantages described above.

[0047] In experimental measurements, surface structures were produced on stainless steel membranes (stainless steel 1.4435) in the manner described. The membranes had a diameter of 12 mm and a thickness of 20 μm, and a surface structure was produced in their respective surface by means of a focused femtosecond laser beam with a pulse duration of 30 fs, a central wavelength of 800 nm and linearly polarized laser light. The parameters of energy E or fluence θ.sub.0, the forward advance rate V and the pulse number N were in this case varied. In FIG. 3A, these parameters of nine experimental measurements carried out and the contact angle α for water due to the respectively generated surface structure are indicated in a table. In FIG. 3B, corresponding images of water drops are shown, the number respectively in the upper right corner indicating the experiment number # from the table in FIG. 3A and the angle information on the respective right-hand side of the image specifying the contact angle likewise given in the table. From the table and the images, it is clear that the contact angle of a water drop on the membranes depends greatly on the laser parameters selected, and that a pronounced lotus effect can be achieved by a suitable selection of the laser parameters, depending on the material of the surface, as may be seen in the experiments with the numbers 1 and 5.

[0048] The features and exemplary embodiments described in connection with the figures may be combined with one another according to further exemplary embodiments, even though not all combinations are explicitly described. Furthermore, the exemplary embodiments described in connection with the figures may as an alternative or in addition comprise further features according to the description in the general part.

[0049] By the description of the invention with the aid of the exemplary embodiments, the invention is not restricted to the latter. Rather, the invention comprises any new feature and any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or this combination is not itself explicitly specified in the patent claims or exemplary embodiments.