WO2014146959A1

WO2014146959A1 - Humidity sensor with water-permeable protective layer and method for protecting the sensor using the protective layer

Info

Publication number: WO2014146959A1
Application number: PCT/EP2014/054914
Authority: WO
Inventors: Reinhard Neul; Fabian Henrici
Original assignee: Robert Bosch Gmbh
Priority date: 2013-03-18
Filing date: 2014-03-13
Publication date: 2014-09-25
Also published as: DE102013204663A1

Abstract

Disclosed is a humidity sensor (100) for determining the humidity of a measuring medium (160) in an environment of the humidity sensor (100). The humidity sensor (100) has at least one humidity-sensitive sensor element (140). At least one property of the sensor element (140) is dependent on the humidity of the measuring medium (160). The humidity sensor (100) has a protective layer (150), by means of which the at least one sensor element (140) is separated from the environment of the humidity sensor (100) such that a substance exchange occurs between the measuring medium (160) and the at least one sensor element (140) via the protective layer (150) alone. The protective layer (150) is designed to be permeable to water (162) in the measuring medium (160) and to be impermeable to other substances (164) in the measuring medium (160).

Description

5 description

title

MOISTURE SENSOR WITH WATERPERMEABLY PROTECTIVE LAYER AND PROCESS FOR PROTECTING THE

SENSORS

- n THROUGH THE PROTECTIVE LAYER

State of the art

The present invention relates to a humidity sensor for determining a humidity of a measuring medium in an environment of the humidity sensor,

to a method of protecting a humidity sensor and to using graphene oxide as a protective layer for a humidity sensor.

Humidity sensors are often exposed to aggressive media, such as dirt, acids or other pollutants and are before such media too

protect. However, moisture sensors should be accessible to the moisture to be detected in surrounding media.

DE 10 2006 033 251 A1 discloses a protective device for a humidity sensor in an aggressive atmosphere.

Disclosure of the invention

Against this background, an improved humidity sensor for determining a humidity of a measuring medium in an environment of the humidity sensor,

an improved method for protecting a humidity sensor and an advantageous use of graphene oxide as a protective layer for a moisture sensor presented according to the main claims. Advantageous embodiments emerge from the respective subclaims and the following description. According to embodiments of the present invention, a humidity sensor having an advantageous protective layer can be provided. Provided, for example, is an at least partial coating or coating of a moisture sensor with a layer which specifically passes only moisture. In particular, a graphene oxide layer is suitable for this purpose. In particular, the moisture sensor is provided with a protective layer which allows moisture to pass well, but keeps unwanted pollutants from the sensor.

An advantage of embodiments of the present invention is a reliable protection of a humidity sensor by the protective layer z. B. off

Graphene oxide, which is especially permeable to water and thus keeps unwanted pollutants from the sensor. Therefore, an improved protection of the sensor against harmful or a function of the sensor affecting environmental influences can be achieved, wherein a contact of the sensor is maintained to the substance to be detected in the surrounding medium. In particular, embodiments of the present invention also relate to an advantageous use of a graphene oxide membrane or coating to protect a moisture sensor from damage by acids, dirt, and the like.

A humidity sensor for determining a humidity of a measuring medium in an environment of the humidity sensor has the following features: at least one moisture-sensitive sensor element, wherein at least one property of the sensor element can be influenced by the humidity of the measuring medium; and a protective layer, by means of which the at least one sensor element can be separated from the environment of the humidity sensor, so that a mass transfer between the measuring medium and the at least one sensor element takes place exclusively via the protective layer, wherein the protective layer is designed to be permeable to water in the measuring medium and to be substantially impermeable to other substances in the measurement medium.

The humidity sensor may be provided in particular for automotive applications or automotive applications. Thus, the humidity sensor can be used, for example, in conjunction with a vehicle, in order to to determine moisture. The vehicle may be a motor vehicle, in particular a road-bound motor vehicle, such as a passenger car, a truck or any other commercial vehicle. The sensor element may be a well-known element for detection of moisture. The sensor element may for example be based on a capacitive measuring arrangement. The at least one property of the sensor element, which can be influenced by the moisture of the measured medium, may be a conductivity, for example an electrical or dielectric conductivity of the sensor element. The sensor element or a material of the sensor element is designed to change its property when it is exposed to moisture or brought into contact with moisture. The sensor element may comprise, for example, a moisture-absorbing material, for example a polymer. The property or a change of the property can be detected metrologically. As a result, it can be detected whether the sensor element is influenced by moisture or not. If necessary, it can also be recognized by what amount of moisture the sensor element is influenced. The protective layer of the humidity sensor or for the humidity sensor can be designed to be permeable or permeable to water vapor in the measuring medium. On the other hand, the protective layer of the moisture sensor or, for the moisture sensor, can be designed to be substantially impermeable or impermeable to other substances or molecules, in particular also in the gaseous state, in the measuring medium. By "substantially impermeable" is meant a complete impermeability or negligibly low permeability.

According to one embodiment, the protective layer may comprise graphene oxide. In particular, the protective layer can consist of graphene or graphene oxide. Such a graphene oxide layer may be permeable to water or moisture, but impermeable to other gases or molecules. Such an embodiment offers the advantage that a protection of the sensor element and optionally also further detection features of the humidity sensor can be increased from harmful environmental influences, but without limiting a detection function of the sensor element. Graphene oxide is gas-tight but permeable to water molecules and has good tensile strength and rigidity. Also, the protective layer may be formed as a membrane. Thus, a protective membrane of graphene or graphene oxide can be provided. The protective membrane can be designed to enclose or encase the at least one moisture-sensitive sensor element, if appropriate, also other detection features of the moisture sensor or to surround it at least partially. Such an embodiment offers the advantage that a membrane, in particular a graphene oxide membrane, is distinguished by good mechanical properties and a sensor element can be surrounded and protected in a simple manner by means of such a membrane.

Furthermore, the protective layer may be formed as a coating of the at least one sensor element. Thus, a coating of graphene or graphene oxide can be provided. Such an embodiment offers the advantage that even by means of a coating, in particular with graphene oxide, the sensor element can be protected in a simple manner.

Advantageously, the protective layer can be arranged so as to extend over at least one side of the at least one sensor element. For example, the protective layer may partially or completely cover a surface, a surface and a side surface or a surface and a peripheral edge of the sensor element. In this case, at least one side of the sensor element can be coated or covered with the protective layer. Such an embodiment has the advantage that both a large-scale water exchange with the environment of the humidity sensor and a large-scale protection of the moisture sensor or in particular the at least one sensor element from contamination, harmful substances and the like can be made possible.

In particular, the at least one sensor element may comprise a moisture-sensitive polymer material. In this case, the sensor element can be designed to

To store water. Such an embodiment offers the advantage that a polymer sensor element enables a simple dependency and detectability of the humidity of the measuring medium on the basis of the amount of stored water. Depending on the amount of stored water, the property, for example, a permittivity or conductivity of the

Change polymer material. In addition, the at least one sensor element can have two electrodes. Between the electrodes, a moisture-absorbing material of the sensor element may be arranged. Here, the two electrodes may be in contact with the moisture absorbing material. The material can thus form a dielectric of a capacitor arrangement. By a voltage measurement at the electrodes or a current measurement between the electrodes, a moisture-induced change in a dielectric conductivity of the material can be detected. From the change in the dielectric conductivity can in turn be concluded on the moisture that has caused the change.

In this case, the two electrodes can be formed as two parallel or obliquely arranged plate electrodes or as two finger-shaped interdigitated interdigital electrodes. The two electrodes may also be formed as two electrically conductive layers. The two plate electrodes arranged parallel or inclined with respect to one another may be part of a plate capacitor, wherein the moisture sensor may have a capacitive evaluation or detection. In this case, the moisture of the measuring medium can be detected, for example, by incorporating water into the at least one sensor element or a polymer layer between the two electrodes or conductive layers of the sensor element. An altered incorporation of water or the electrical conductivity dependent thereon changes a capacitance of the plate capacitor, which in turn can be detected electrically. Such an embodiment offers the advantage that a simple and reliable and accurate determination of the humidity of the medium to be measured is made possible.

According to one embodiment, a carrier may be provided on which the at least one sensor element is mounted. In this case, the protective layer can be arranged to extend over all but one side of the at least one sensor element. In this case, the protective layer may be attached to the carrier. Furthermore, the protective layer can be arranged spanning the at least one sensor element and optionally the two electrodes. Thus, the at least one sensor element may be attached on one side to the carrier and be surrounded on the other sides of the protective layer. Such an embodiment offers the advantage that an uncomplicated structure of a safely protected against undesired environmental influences protected humidity sensor is.

A method for protecting a humidity sensor, which is provided for determining a humidity of a measuring medium in an environment of the humidity sensor, comprises the following steps:

Providing at least one moisture-sensitive sensor element, wherein at least one property of the sensor element is dependent on the humidity of the measured medium; and

Arranging a protective layer for separating the at least one sensor element from the surroundings of the humidity sensor at the at least one sensor element, so that a mass transfer between the measuring medium and the at least one sensor element takes place exclusively via the protective layer, wherein the protective layer is designed to permeate water in the measuring medium and to be substantially impermeable to other substances in the measurement medium.

The method for protecting a humidity sensor can be carried out in order to advantageously manufacture the above-mentioned moisture sensor or to advantageously protect a moisture sensor. In the step of providing, a base device of the humidity sensor may also be provided, wherein the at least one moisture-sensitive sensor element is a part of the basic device. Such a basic device may further comprise a carrier, to which the at least one sensor element is attached, and two electrodes, between which the at least one sensor element is arranged. In the arranging step, the protective layer may be formed as a membrane over the at least one sensor element or as a coating of the at least one sensor element.

It is also advantageous to use graphene oxide as a protective layer for a moisture sensor. Graphene oxide may be permeable to water or moisture, but impermeable to other gases or molecules. By using graphene oxide as a protective layer for a moisture sensor, protection of the moisture sensor against damaging environmental influences can be increased. without, however, restricting a detection function of the humidity sensor. Graphene oxide is gas-tight and permeable to water molecules and has good tensile strength and rigidity.

The invention will be described by way of example with reference to the accompanying drawings. Show it:

1 shows a humidity sensor according to an embodiment of the present invention;

FIGS. 2A and 2B show a humidity sensor according to a further exemplary embodiment of the present invention; and

3 is a flowchart of a method according to an embodiment of the present invention.

In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similarly acting, wherein a repeated description of these elements is omitted.

1 shows a schematic sectional view of a humidity sensor 100 according to an embodiment of the present invention. The humidity sensor 100 has a carrier 110, a first electrode 120, a second electrode 130, a sensor element 140 and a protective layer 150. The humidity sensor 100 is arranged in or exposed to a surrounding measuring medium 160. The measuring medium 160 contains moisture or moisture in the form of water 162 or water molecules and other substances 164, such as dirt, acids and / or the like.

According to the embodiment of the present invention shown in FIG. 1, the first electrode 120 is arranged on the carrier 110. Between the first electrode 120 and the second electrode 130, the sensor element 140 is arranged. Thus, the first electrode 120 is disposed between the carrier 110 and the second electrode 130. The protective layer 150 is attached to the carrier. the first electrode 120 and the second electrode 130 and the sensor element 140 are arranged and enveloped.

The first electrode 120 and the second electrode 130 are referred to as

Capacitor plates formed. The sensor element 140 comprises a polymer which is designed to absorb a moisture or moisture. The moisture originates here from the water 162 of the measuring medium 160. The measuring medium 160 surrounds the humidity sensor 100. The humidity sensor 100 is designed to determine a humidity of the measuring medium 160. The protective layer 150 of the humidity sensor 100 has, for example, graphene oxide, although this is not explicitly illustrated graphically in FIG. 1.

The protective layer 150 of the humidity sensor 100 is designed to be permeable to the water 162 or the water molecules of the measuring medium 160. This is symbolized in FIG. 1 by a bidirectional arrow which extends between the measuring medium 160 and the sensor element 140 as well as through the protective layer 150. The protective layer 150 of the humidity sensor 100 is designed to be impermeable to the other substances 164 of the measuring medium 160. This is symbolized in FIG. 1 by an arrow which runs in the measuring medium 160 outside the protective layer 150, the arrow pointing to the

Protective layer 150 impinges and from the protective layer 150 back into the measuring medium 160 shows. The water 162 penetrating the protective layer 150 is taken up by the sensor element 140. In this case, a dielectric conductivity of the sensor element 140 depends on a quantity of the stored water 162. By way of example, this can be detected capacitively by means of the first electrode 120 and the second electrode 130, so that the humidity of the measuring medium 160 can be determined.

The moisture sensor 100 in FIGS. 2A and 2B, for example, corresponds to the mode of operation and components of the moisture sensor from FIG. 1, with the exception that in FIGS. 2A and 2B the components of the humidity sensor 100 have a different arrangement / or molding.

FIG. 2A shows a schematic plan view of a humidity sensor 100 according to a further exemplary embodiment of the present invention. Shown are in the schematic plan view of the humidity sensor 100, a first electrode 120, a second electrode 130, a sensor element 140 and a section line AA. According to the exemplary embodiment of the present invention illustrated in FIGS. 2A and 2B, the first electrode 120 and the second electrode 130 are formed as interdigital electrodes or form an interdigital structure or intermeshing structure. The sensor element 140 is disposed between the first electrode 120 and the second electrode 130. The sensor element 140 extends serpentinely between the first electrode 120 and the second electrode 130. FIG. 2B shows a cross-sectional view of the moisture sensor 100 shown in FIG. 2A along the section line AA. Shown are in the

Cross-sectional view of the humidity sensor 100, a carrier 1 10, the first electrode 120, the second electrode 130, the sensor element 140 and a protective layer 150th

In this case, the first electrode 120, the second electrode 130 and the sensor element 140 are attached to the carrier 110. In this case, the sensor element 140 is arranged between the first electrode 120 and the second electrode 130. The protective layer 150 extends from the first electrode 120 to the second electrode 130 across the sensor element 140. Thus, the sensor element

140 between the carrier 1 10 and the protective layer 150 is arranged. In the cross-sectional illustration of FIG. 2B, the sensor element 140 is surrounded by the carrier 110, the first electrode 120, the second electrode 130 and the protective layer 150.

Thus, Fig. 2B shows a humidity sensor 100, in which on the carrier 1 10, the z. As a semiconductor substrate or other carrier material, the electrodes 120 and 130, z. B. in the form of an interdigital structure, whereby other structures are possible, are arranged. Gaps between the electrodes 120 and 130 are connected to the sensor element 140 and a moisture-sensitive layer, for. As a polymer layer, filled and covered with the protective layer 150.

3 shows a flow chart of a method 300 for protecting a humidity sensor, which is provided for determining a humidity of a measuring medium in an environment of the humidity sensor, according to an embodiment. Example of the present invention. In this case, the method 300 has a step of providing 310 at least one moisture-sensitive sensor element. In this case, at least one property of the sensor element is dependent on the humidity of the measuring medium. The method 300 also includes a step of arranging 320 a protective layer for separating the at least one sensor element from the environment of the humidity sensor on the at least one sensor element, so that a mass transfer between the measuring medium and the at least one sensor element takes place exclusively via the protective layer. In this case, the protective layer is designed to be permeable to water in the measuring medium and to be substantially impermeable to other substances in the measuring medium. The method 300 for protecting a humidity sensor can be carried out in order to advantageously manufacture the moisture sensor shown and described in FIGS. 1 and 2A and 2B or to protect a moisture sensor in an advantageous manner.

The embodiments described and shown in the figures are chosen only by way of example. Different embodiments may be combined together or in relation to individual features. Also, an embodiment can be supplemented by features of another embodiment. Furthermore, method steps can be repeated and executed in a different order than in the order described.

Claims

claims

1 . A humidity sensor (100) for determining a humidity of a measuring medium (160) in an environment of the humidity sensor (100), wherein the humidity sensor (100) has the following features: at least one moisture-sensitive sensor element (140), wherein at least one characteristic of the sensor element (140) of the humidity of the measuring medium (160) can be influenced; and a protective layer (150), by means of which the at least one sensor element (140) can be separated from the surroundings of the humidity sensor (100) so that a mass transfer between the measuring medium (160) and the at least one sensor element (140) occurs exclusively via the protective layer (150 ), wherein the protective layer (150) is adapted to be permeable to water (162) in the measurement medium (160) and to be substantially impermeable to other substances (164) in the measurement medium (160).

The humidity sensor (100) of claim 1, wherein the protective layer (150) comprises graphene oxide.

3. Moisture sensor (100) according to one of the preceding claims, wherein the protective layer (150) is formed as a membrane.

4. Moisture sensor (100) according to one of the preceding claims, wherein the protective layer (150) is formed as a coating of the at least one sensor element (140).

5. Moisture sensor (100) according to one of the preceding claims, wherein the protective layer (150) is arranged to extend over at least one side of the at least one sensor element (140). Moisture sensor (100) according to one of the preceding claims, wherein the at least one sensor element (140) comprises a moisture-sensitive polymer material.

Moisture sensor (100) according to one of the preceding claims, in which the at least one sensor element (140) has two electrodes (120, 130).

Humidity sensor (100) according to claim 7, wherein the two electrodes (120, 130) are formed as two parallel or obliquely arranged plate electrodes or as two finger-interdigitated interdigital electrodes.

Moisture sensor (100) according to one of claims 7 or 8, with a carrier (110) to which the at least one sensor element (140) is attached, wherein the protective layer (150) extends over all but one side of the at least one sensor element (10). 140) is arranged extending.

A method (300) for protecting a humidity sensor (100) provided for determining a humidity of a measurement medium (160) in an environment of the humidity sensor (100), the method (300) comprising the steps of:

Providing (310) at least one moisture-sensitive sensor element (140), wherein at least one property of the sensor element (140) is dependent on the humidity of the measuring medium (160); and

Arranging (320) a protective layer (150) for separating the at least one sensor element (140) from the surroundings of the humidity sensor (100) at the at least one sensor element (140) so that a mass transfer between the measuring medium (160) and the at least one sensor element ( 140) exclusively via the protective layer (150), the protective layer (150) being designed to be permeable to water (162) in the measuring medium (160) and substantially to other substances (164) in the measuring medium (160) to be impermeable. Use of Graphene Oxide as Protective Layer (150) for a Humidity Sensor (100).