TWI797572B - Humidity sensor - Google Patents

Abstract

A humidity sensor includes a substrate, a single electrode structure, and a sensing layer or a three-dimensional sensing structure. The sensing layer or the three-dimensional sensing structure is disposed on the substrate. The single electrode structure is disposed on the surface of the sensing layer or the three-dimensional sensing structure, and relative humidity is obtained according to the resistance value of the two ends of the single electrode structure.

Description

humidity sensor

The present invention relates to a sensor, and in particular to a humidity sensor.

Generally, humidity sensors are divided into resistive and capacitive humidity sensors. The resistive humidity sensor uses the characteristic that the sensing layer itself is affected by humidity to cause its own resistance to change. By measuring the resistance of the sensing layer itself to convert it into relative humidity, its response speed is fast, compared with capacitance The measurement cost of the type humidity sensor is low, but the resistance measured by the resistance type humidity sensor has no linear relationship with the relative humidity, and it needs to be processed by logarithm operation, so the interchangeability is poor. The capacitive humidity sensor uses the characteristic that the sensing layer itself is affected by humidity to cause its own dielectric constant to change, so that the capacitance value also changes with humidity. Therefore, the relative humidity can be obtained by measuring the capacitance value of the sensing layer. Among them, the capacitance value has a linear relationship with the relative humidity, so the interchangeability is good, but the response speed of the capacitive humidity sensor is slower, and the measurement cost is higher than that of the resistive humidity sensor.

The invention provides a humidity sensor, which is a resistive humidity sensor with a linear relationship between resistance and relative humidity.

The humidity sensor of the present invention includes a substrate, a sensing layer and a single electrode structure. The sensing layer is arranged on the substrate. The single electrode structure is disposed on the surface of the sensing layer, and the relative humidity is obtained according to the resistance values at both ends of the single electrode structure.

In an embodiment of the present invention, the above-mentioned single electrode structure is a linear electrode, and the water absorption thickness expansion rate of the sensing layer is less than 10%.

In an embodiment of the present invention, the above-mentioned single electrode structure is a serpentine electrode or a spiral electrode, and the water absorption thickness expansion rate of the sensing layer is between 0% and 10%.

In an embodiment of the present invention, the ratio of the thickness of the above-mentioned single electrode structure to the thickness of the sensing layer is less than 1.

The humidity sensor of the present invention includes a substrate, a three-dimensional sensing structure and a single electrode structure. The stereoscopic sensing structure is disposed on the substrate, and the surface of the stereoscopic sensing structure is non-planar. The single electrode structure is arranged on the surface of the three-dimensional sensing structure, and the relative humidity is obtained according to the resistance values at both ends of the single electrode structure.

In an embodiment of the present invention, the above-mentioned stereoscopic sensing structure is a cone structure, a quadrangular pyramid structure or a pyramid structure.

In an embodiment of the present invention, the ratio of the thickness of the above-mentioned single electrode structure to the maximum thickness of the stereoscopic sensing structure is less than 1.

In an embodiment of the present invention, the above-mentioned single electrode structure is a linear electrode, and the water absorption thickness expansion rate of the three-dimensional sensing structure is less than 10%.

In an embodiment of the present invention, the above-mentioned single electrode structure is a serpentine electrode or a spiral electrode, and the water absorption thickness expansion rate of the three-dimensional sensing structure is between 0% and 10%.

In an embodiment of the present invention, the above-mentioned single electrode is not in contact with the substrate.

Based on the above, the humidity sensor of the present invention includes a sensing layer or a three-dimensional sensing structure disposed between the substrate and a single electrode structure. By measuring the resistance value of the single electrode structure, the sensing layer or three-dimensional sensing structure can be obtained. The stress change of the single electrode structure can be used to obtain the relative humidity, and the resistance value of the single electrode structure has a linear relationship with the relative humidity. Therefore, the resistance value of the single electrode structure does not need to be logarithmically calculated to obtain the relative humidity, and the resistance humidity sensor with good interchangeability can be realized. It solves the problem that traditional resistive humidity sensors need to logarithmically calculate the resistance value to obtain relative humidity.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

The following examples are listed and described in detail with the accompanying drawings, but the provided examples are not intended to limit the scope of the present invention. In addition, the drawings are for illustrative purposes only and are not drawn to original scale. In order to facilitate understanding, the same elements in the following description will be described with the same symbols.

In addition, terms such as "comprising", "including", and "having" used in the text are all open terms, which means "including but not limited to".

It should be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, and/or or parts thereof shall not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a "first element," "component," "region," "layer," or "section" discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein.

In addition, the directional terms mentioned in the text, such as "up" and "down", are only used to refer to the directions of the drawings, and are not used to limit the present invention.

FIG. 1 is a layered diagram of a humidity sensor according to a first embodiment of the present invention.

Referring to FIG. 1 , the humidity sensor 10 a includes a substrate 100 , a sensing layer 110 and a single electrode structure 120 . The substrate 100 may include a rigid substrate or a flexible substrate, and the present invention is not limited thereto. The sensing layer 110 is disposed on the substrate 100 , and the single electrode structure 120 is disposed on the surface 111 of the sensing layer 110 and attached to the sensing layer 110 . The projection range of the single electrode structure 120 on the substrate 100 does not exceed the projection range of the sensing layer 110 on the substrate 100 , that is, the single electrode structure 120 and the substrate 100 are not in contact with each other.

The sensing layer 110 is basically a plane with a uniform thickness t1, for example, can be formed by spin coating, dip coating or other suitable methods. The material of the sensing layer 110 can be a water-absorbing swellable material whose swelling degree increases linearly with the increase of relative humidity, such as polyimide, sodium polystyrenesulfonate (sodium polystyrenesulfonate), polymethyl methacrylate ( poly(methyl methacrylate, PMMA), cellulose acetate-butyrate, benzocyclobutene or other suitable materials, the present invention is not limited thereto. The water absorption thickness expansion rate of the sensing layer 110 can be less than 10%, so as to avoid the collapse of the single electrode structure 120 beyond its tolerable stress range, that is, to avoid irreversible deformation of the single electrode structure 120, and at the same time, the single electrode structure 120 The signal change of the structure 120 can be relatively stable, that is, there will not be too large resistance change to cause too large signal change. The water absorption thickness expansion rate of the aforementioned sensing layer 110 refers to the thickness expansion rate obtained by converting the mass expansion rate. Further, the water absorption thickness expansion rate is measured by measuring the difference between the mass of the material before and after water absorption, which is The mass increase caused by water, the density of permeated water can push back the increased volume of the material, and then the thickness change can be calculated from the area of the material to obtain the thickness expansion rate of water absorption, where the thickness expansion rate of water absorption is 0%, which means that it is in the Water absorption thickness expansion in the absence of humidity.

The shape of the single electrode structure 120 is not particularly limited, as long as the deformation of the sensing layer 110 can be sensed and the resistance value of the single electrode structure 120 can be measured. In the first embodiment, the single electrode structure 120 is a linear electrode extending along the x direction, but the present invention is not limited thereto. In some embodiments, the single electrode structure 120 may be a serpentine or spiral electrode. The material of the single electrode structure 120 may include gold, silver, copper, platinum, aluminum, or alloys of the aforementioned metals, but the invention is not limited thereto. The single electrode structure 120 basically has a uniform thickness t2, and can be formed, for example, by screen printing, physical/chemical vapor deposition or other suitable methods. The thickness t2 of the single electrode structure 120 is smaller than the thickness t1 of the sensing layer 110 , and the ratio of the thickness t2 of the single electrode structure 120 to the thickness t1 of the sensing layer 110 is less than 1.

Since the sensing layer 110 will linearly expand or contract as the relative humidity changes, and the single electrode structure 120 is attached to the surface 111 of the sensing layer 110, it will generate stress together with the deformation of the sensing layer 110. The change of the stress of the sensing layer 110 can be obtained by measuring the resistance value of the two ends of the single electrode structure 120, and then the relative humidity can be obtained. That is to say, based on the structure of the humidity sensor 10a of this embodiment, the relative humidity can be obtained according to the resistance value of the two ends of the single electrode structure 120, and the relative humidity and the resistance value of the two ends of the single electrode structure 120 have the same relationship. Linear relationship, so it solves the shortcomings of traditional resistance hygrometers that need to undergo logarithmic operations and poor interchangeability, and still maintains the advantages of fast response and low measurement cost of traditional resistance hygrometers. In other words, the humidity sensor 10a of the present invention has both the advantages of the traditional resistive humidity sensor and the capacitive humidity sensor.

FIG. 2 is a layered schematic diagram of a humidity sensor according to a second embodiment of the present invention. The layered schematic diagram of FIG. 2 is roughly similar to the layered schematic diagram of FIG. 1, so the same components recorded in the second embodiment and the first embodiment can refer to the aforementioned related content, so the same configurations in the first and second embodiments , which will not be repeated here.

In FIG. 2, the humidity sensor 10b of this embodiment is different from the first embodiment in that the single electrode structure 120 of the humidity sensor 10b is a serpentine electrode with continuous electrodes extending along the x direction and along the y direction. structure. The projection range of the single electrode structure 120 on the substrate 100 is within the projection range of the sensing layer 110 on the substrate 100 . Since the single electrode structure 120 is a continuous structure extending along the x-direction and along the y-direction, it can sense the two-dimensional stress change of the sensing layer 110, so that the stress sensing of the humidity sensor 10b is improved and the resistance is increased, thereby enabling The sensitivity of the humidity sensor 10b is improved, and it is easy to miniaturize.

FIG. 3 is a layered schematic diagram of a humidity sensor according to a third embodiment of the present invention. FIG. 4 is a schematic cross-sectional view along line A-A of FIG. 3 .

Please refer to FIG. 3 , the humidity sensor 20 a includes a substrate 200 , a three-dimensional sensing structure 210 and a single electrode structure 220 . The substrate 200 may include a rigid substrate or a flexible substrate, and the present invention is not limited thereto. The stereoscopic sensing structure 210 is disposed on the substrate 100 , wherein the surface 211 of the stereoscopic sensing structure 210 is non-planar. The single electrode structure 220 is disposed on the surface 211 of the three-dimensional sensing structure 210 and bonded to the three-dimensional sensing structure 210 . The projection range of the single electrode structure 220 on the substrate 200 does not exceed the projection range of the stereoscopic sensing structure 210 on the substrate 200 , that is, the single electrode structure 220 and the substrate 200 do not contact each other.

Please refer to FIG. 3 and FIG. 4 at the same time. The three-dimensional sensing structure 210 can be a structure with a thicker middle thickness and a thinner peripheral area, such as a conical structure, a quadrangular pyramid structure or a pyramid structure. In FIG. 3, the three-dimensional sensing structure 210 is a quadrangular pyramid structure, but the present invention is not limited thereto. The three-dimensional sensing structure 210 can be formed by 3D printing, but the present invention is not limited thereto. The aforementioned thickness of the stereoscopic sensing structure 210 refers to the vertical distance from the surface 211 of the stereoscopic sensing structure 210 to the surface of the substrate 200 . In FIG. 4 , the included angle between the surface 211 of the stereoscopic sensing structure 210 and the substrate 200 is between 30∘˜90∘. The material of the three-dimensional sensing structure 210 can be a water-swellable material whose swelling degree increases linearly with the increase of relative humidity, such as polyimide, sodium polystyrenesulfonate (sodium polystyrenesulfonate), polymethylmethacrylate (polymethyl methacrylate), cellulose acetate butyrate (CAB), benzocyclobutene (benzocyclobutene) or other suitable materials, the present invention is not limited thereto. The water absorption thickness expansion rate of the three-dimensional sensing structure 210 is less than 10%, so as to avoid the collapse of the single electrode structure 220 beyond its bearable stress range, that is, to avoid irreversible deformation of the single electrode structure 220. At the same time, the single electrode structure 220 The signal change of the structure 220 can be relatively stable, that is, there will not be too large a change of the resistance to cause the signal change to be too large. The water-absorbing thickness expansion rate of the aforementioned three-dimensional sensing structure 210 refers to the thickness expansion rate obtained by converting the mass expansion rate. Further, the water-absorbing thickness expansion rate is obtained by measuring the difference between the mass of the material before and after water absorption, that is, The increase in mass caused by water, the density of water can be used to push back the increased volume of the material, and then the thickness of the material can be calculated from the area of the material to obtain the water absorption thickness expansion rate, where the water absorption thickness expansion rate is 0%. Water absorption thickness expansion rate in a humidity-free environment.

The shape of the single electrode structure 220 is not particularly limited, as long as the deformation of the three-dimensional sensing structure 210 can be sensed and the resistance value of the single electrode structure 220 can be measured. In FIG. 3 , the single electrode structure 220 is a linear electrode extending along the x direction, but the present invention is not limited thereto. In some embodiments, the single electrode structure 220 may be a serpentine or spiral electrode. The material of the single electrode structure 220 may include gold, silver, copper, platinum, aluminum, or alloys of the aforementioned metals, but the invention is not limited thereto. The single electrode structure 220 basically has a uniform thickness t4, and can be formed, for example, by screen printing, physical/chemical vapor deposition or other suitable methods. The thickness t4 of the single electrode structure 220 is smaller than the maximum thickness t3 of the three-dimensional sensing structure 210 , and the ratio of the thickness t4 of the single electrode structure 220 to the maximum thickness t3 of the three-dimensional sensing structure 210 is less than 1.

Since the three-dimensional sensing structure 210 will linearly expand or contract as the relative humidity changes, and the single electrode structure 220 is attached to the surface 211 of the three-dimensional sensing structure 210, it will follow the deformation of the three-dimensional sensing structure 210, Stress changes occur together, and the stress changes of the sensing layer 210 can be obtained by measuring the resistance values at both ends of the single electrode structure 220 , and then the relative humidity can be obtained. That is to say, based on the structure of the humidity sensor 20a of this embodiment, the relative humidity can be obtained according to the resistance value of the two ends of the single electrode structure 220, and the relative humidity and the resistance value of the two ends of the single electrode structure 220 have the same relationship. Linear relationship, so it solves the shortcomings of traditional resistance hygrometers that need to undergo logarithmic operations and poor interchangeability, and still maintains the advantages of fast response and low measurement cost of traditional resistance hygrometers. And because the thickness of the three-dimensional sensing structure 210 is not a single thickness, the single electrode structure 220 can sense the stress change of the three-dimensional sensing structure 210 in the x direction and the z direction, improve the stress sensing, and improve the sensitivity of the humidity sensor 20a .

FIG. 5 is a layered schematic diagram of a humidity sensor according to a fourth embodiment of the present invention. The layered schematic diagram of Figure 5 is roughly similar to the layered schematic diagram of Figure 3, so the same components recorded in the fourth embodiment and the third embodiment can refer to the aforementioned related content, so the same configurations in the third and fourth embodiments , which will not be repeated here. FIG. 6 is a schematic cross-sectional view of the line B-B in FIG. 5 .

In FIGS. 5 and 6, the humidity sensor 20b of this embodiment is different from the third embodiment in that the single electrode structure 220 of the humidity sensor 20b is a serpentine electrode with Extended continuous structure, the water absorption thickness expansion rate of the three-dimensional sensing structure 210 can be between 0% and 10%, so as to avoid irreversible deformation of the single electrode structure 220, and at the same time, the signal change of the single electrode structure 220 can be relatively stable, that is There will be no excessive resistance changes that cause excessive signal changes. Since the single electrode structure 220 is a continuous structure extending along the x-direction and the y-direction and the thickness of the three-dimensional sensing structure 210 is not a single thickness, the single electrode structure 220 can sense the three-dimensional stress change of the three-dimensional sensing structure 210, making the humidity The stress sensing of the sensor 20b is improved and the resistance is increased, thereby improving the sensitivity of the humidity sensor 20b and making it easier to miniaturize.

FIG. 7 is a layered diagram of a humidity sensor according to a fifth embodiment of the present invention. The layered schematic diagram of FIG. 7 is roughly similar to the layered schematic diagram of FIG. 3 , so the same components recorded in the fifth embodiment and the third embodiment can refer to the aforementioned related content, so the same configurations in the third and fifth embodiments , which will not be repeated here.

In FIG. 7, the humidity sensor 20c of this embodiment is different from the third embodiment in that the three-dimensional sensing structure 210 of the humidity sensor 20c is a conical structure, and the single electrode structure 220 is attached to the three-dimensional sensing The surface 211 of the structure 210 is similar to that shown in the cross-sectional view of FIG. 4 . The projection range of the single electrode structure 220 on the substrate 200 does not exceed the projection range of the stereoscopic sensing structure 210 on the substrate 200 . Since the thickness of the three-dimensional sensing structure 210 is non-uniform, the single electrode structure 220 can sense the stress change of the three-dimensional sensing structure 210 in the x-direction and the z-direction, thereby improving stress sensing and improving the sensitivity of the humidity sensor 20c .

FIG. 8 is a layered diagram of a humidity sensor according to a sixth embodiment of the present invention. The layered schematic diagram of FIG. 8 is roughly similar to the layered schematic diagram of FIG. 7, so the same components recorded in the sixth embodiment can refer to the foregoing content, and the same configurations in the fifth and sixth embodiments will not be repeated here. .

In FIG. 8, the humidity sensor 20d of this embodiment is different from the fifth embodiment in that the single electrode structure 220 of the humidity sensor 20d is a spiral electrode, which surrounds the three-dimensional sense in a counterclockwise or clockwise direction. The measuring structure 210 is attached to the surface 211 of the three-dimensional sensing structure 210, similar to that shown in the cross-sectional view of FIG. 6 . The projection range of the single electrode structure 220 on the substrate 200 does not exceed the projection range of the stereoscopic sensing structure 210 on the substrate 200 . Since the single electrode structure 220 is a spiral continuous structure and the thickness of the three-dimensional sensing structure 210 is not a single thickness, the single electrode structure 220 can sense the three-dimensional stress change of the three-dimensional sensing structure 210, so that the stress sense of the humidity sensor 20d The measurement is improved and the resistance is increased, thereby improving the sensitivity of the humidity sensor 20d and making it easier to miniaturize. The water absorption thickness expansion rate of the three-dimensional sensing structure 210 can also be between 0% and 10%, so as to avoid irreversible deformation of the single electrode structure 220. At the same time, the signal change of the single electrode structure 220 can be relatively stable, that is, there will not be too much The change in resistance causes the signal to change too much.

To sum up, the humidity sensor of the present invention includes a sensing layer or a three-dimensional sensing structure disposed between the substrate and a single electrode structure. By measuring the resistance value of the single electrode structure, the sensing layer or three-dimensional sensing structure can be obtained. Measure the stress change of the structure, and then obtain the relative humidity, and the resistance value of the single electrode structure has a linear relationship with the relative humidity. The demand for the humidity sensor solves the problem that the traditional resistive humidity sensor needs to logarithmically calculate the resistance value to obtain the relative humidity, and maintains the advantages of the traditional resistive humidity sensor with fast response speed and low measurement cost .

Although the present invention has been disclosed above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention should be defined by the scope of the appended patent application.

10a, 10b, 20a, 20b, 20c, 20d: humidity sensor 100, 200: Substrate 110: Sensing layer 111, 211: surface 120, 220: single electrode structure 210: Stereo sensing structure A-A, B-B: section line t1, t2, t3, t4: Thickness x, y: direction θ: included angle

FIG. 1 is a layered diagram of a humidity sensor according to a first embodiment of the present invention. FIG. 2 is a layered schematic diagram of a humidity sensor according to a second embodiment of the present invention. FIG. 3 is a layered schematic diagram of a humidity sensor according to a third embodiment of the present invention. FIG. 4 is a schematic cross-sectional view along line A-A of FIG. 3 . FIG. 5 is a layered schematic diagram of a humidity sensor according to a fourth embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of the line B-B in FIG. 5 . FIG. 7 is a layered diagram of a humidity sensor according to a fifth embodiment of the present invention. FIG. 8 is a layered diagram of a humidity sensor according to a sixth embodiment of the present invention.

10a: Humidity sensor

100: Substrate

110: Sensing layer

111: surface

120:Single electrode structure

t1, t2: Thickness

x, y: direction

Claims (6)

A humidity sensor, comprising: a substrate; a three-dimensional sensing structure disposed on the substrate, the surface of the three-dimensional sensing structure is non-planar; and a single electrode structure disposed on the three-dimensional sensing structure surface, and the relative humidity is obtained according to the resistance value of the two ends of the single electrode structure. The humidity sensor according to claim 1, wherein the three-dimensional sensing structure is a cone structure, a quadrangular pyramid structure or a pyramid structure. The humidity sensor as claimed in claim 1, wherein the ratio of the thickness of the single electrode structure to the maximum thickness of the three-dimensional sensing structure is less than 1. The humidity sensor according to claim 1, wherein the single electrode structure is a linear electrode, and the water absorption thickness expansion rate of the three-dimensional sensing structure is less than 10%. The humidity sensor according to claim 1, wherein the single electrode structure is a serpentine electrode or a spiral electrode, and the water absorption thickness expansion rate of the three-dimensional sensing structure is between 0% and 10%. The humidity sensor as claimed in claim 1, wherein the single electrode structure is not in contact with the substrate.

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