A stress sensor and its preparation method, and a stress sensing device

Abstract

The embodiment of the present application provides a stress sensor and a preparation method thereof, and a stress sensing device. When the upper substrate or the lower substrate of the stress sensor is subjected to pressure, the elastic insulating protrusion structure of the tunneling layer is deformed, so that the distance between the low-square-resistance layer and the high-square-resistance layer is shortened, and a tunneling effect occurs, generating a tunneling current, and the magnitude of the tunneling current is proportional to the magnitude of the pressure. The present invention fills a tunneling layer between the high-square-resistance layer and the low-square-resistance layer instead of a traditional gasket structure, thereby greatly reducing the thickness of the stress sensor, reducing the minimum stress trigger threshold, and improving the sensitivity of the sensor, which can realize the extraction of weak signals and effectively extend the life of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor equipment, and in particular to a stress sensor and a preparation method thereof, and a stress sensing device. Background Art

[0002] Stress sensors are a common type of sensor in the field of sensors. Usually, the structure of stress sensors determines the corresponding relationship between their electrical signals and stress magnitude. At present, the characteristic response curve of stress sensors is basically a linear design, and the stress magnitude is proportional to the strength of the electrical signal. This means that the electrical signal obtained when measuring small stresses may be small, which makes the transmission circuit have higher requirements for the extraction ability of weak signals. In order to improve the signal-to-noise ratio, a gasket structure is set in the structure of some sensors, so that the sensing material is in a non-conductive state when not under stress, and is directly connected to the electrode when under stress to form a conductive loop. The corresponding electrical signal of this stress sensor is manifested as a transition from infinite resistance to small resistance, and the signal change amplitude is large. Although this type of sensor can achieve a very large electrical change, its structural difficulty lies in the fact that the gasket has a certain height, which introduces a minimum response stress threshold. Only when the external stress is greater than this threshold, the sensor will respond, making it impossible to measure very weak stress with high precision. In addition, most of them use double-sided tape as sensor gasket. On the one hand, the thickness of the double-sided tape is relatively thick (about 75 to 125um); on the other hand, the double-sided tape is very easy to age during long-term use, and the viscosity and rebound performance are seriously degraded, even causing sensor failure. Summary of the invention

[0003] Based on this, the purpose of the present invention is to provide a stress sensor and a preparation method thereof, and a stress sensing device, which replaces the traditional gasket structure with a tunneling layer to greatly reduce the thickness of the sensor and improve the sensitivity of the sensor, thereby effectively extending the life of the sensor.

[0004] In a first aspect, the present invention provides a stress sensor, comprising a first detection electrode, a second detection electrode and a stress sensing device;

[0005] The stress sensing device comprises a lower substrate, a high square resistance layer, a tunneling layer, a low square resistance layer and an upper substrate stacked in sequence, and the first detection electrode and the second detection electrode are respectively connected to two ends of the high square resistance layer;

[0006] The tunneling layer includes a plurality of elastic insulating protrusion structures. When there is external pressure acting on the stress sensing device, the protrusion structure is deformed, so that the distance between the high square resistance layer and the low square resistance layer is reduced, and the resistance value between the first detection electrode and the second detection electrode is reduced.

[0007] Furthermore, the tunneling layer further includes an island structure, which is made of a metal material and fills a gap between the protrusion structure located on one side of the low-square-resistance layer.

[0008] Furthermore, the bottom of the protruding structure is connected to the low square resistance layer, the top of the protruding structure extends toward the high square resistance layer, and the cross section of the protruding structure gradually decreases in the direction extending from the low square resistance layer to the high square resistance layer.

[0009] Furthermore, the height difference between any two of the protruding structures is less than 20 um, and the height difference between the top of the island structure and an end of the protruding structure away from the low-resistance layer is less than 30 um.

[0010] Furthermore, the sheet resistance between the high sheet resistance layer and the low sheet resistance layer differs by at least one order of magnitude and the sheet resistance of the low sheet resistance layer is less than 30 ohms / mil.

[0011] In a second aspect, the present invention further provides a method for preparing a stress sensor, comprising the following steps:

[0012] S1: providing an upper substrate, a lower substrate and a tunneling layer, wherein the tunneling layer comprises a plurality of elastic insulating protrusion structures;

[0013] S2. Print or evaporate a high square resistance layer with a thickness ranging from 5um to 100um on one side of the lower substrate, and keep it warm at a temperature range of 30°C to 200°C for 10 to 180 minutes;

[0014] S3, printing or vapor-depositing a low square resistance layer with a thickness ranging from 5um to 100um on one side of the upper substrate, and keeping it warm at a temperature range of 30°C to 200°C for 10 to 180 minutes;

[0015] S4, printing a tunneling layer on the surface of the cooled low-square-resistance layer, keeping it still for 10 minutes to 300 minutes, and keeping it warm in the temperature range of 30° C. to 200° C. for 10 minutes to 180 minutes;

[0016] S5, facing the side of the lower substrate with the high square resistance layer toward the side of the upper substrate with the tunnel layer, and pressing the upper substrate and the lower substrate face to face;

[0017] S6. Form a first detection electrode and a second detection electrode on both sides of the high square resistance layer by riveting or printing.

[0018] Furthermore, the bottom of the protruding structure is attached to the low square resistance layer, the top of the protruding structure extends toward the high square resistance layer, and the cross section of the protruding structure gradually decreases in the direction extending from the low square resistance layer to the high square resistance layer;

[0019] The gap between the protrusion structure located on one side of the low-resistance layer is filled with an island structure by glue coating or spraying, and the island structure is made of at least one of the following materials: copper, silver, gold, platinum or alloy.

[0020] Furthermore, the height difference between any two of the protruding structures is less than 20 um, and the height difference between the top of the island structure and an end of the protruding structure away from the low-resistance layer is less than 30 um.

[0021] Furthermore, the sheet resistance between the high sheet resistance layer and the low sheet resistance layer differs by at least one order of magnitude and the sheet resistance of the low sheet resistance layer is less than 30 ohms / mil.

[0022] In a third aspect, the present invention further provides a stress sensing device, comprising a plurality of stress sensors as described in the first aspect, wherein the plurality of stress sensors are connected in series or in parallel.

[0023] A stress sensor and a preparation method thereof, as well as a stress sensing device provided in the embodiments of the present application, when the upper substrate or the lower substrate is subjected to pressure, the elastic insulating protrusion structure of the tunneling layer is deformed, so that the distance between the low-square-resistance layer and the high-square-resistance layer is shortened, resulting in a tunneling effect, generating a tunneling current, and the magnitude of the tunneling current is proportional to the magnitude of the pressure; the present invention fills a tunneling layer between the high-square-resistance layer and the low-square-resistance layer instead of a traditional gasket structure, thereby greatly reducing the thickness of the stress sensor, reducing the lower limit of the minimum stress trigger threshold, and improving the sensitivity of the sensor, thereby being able to extract weak signals and effectively extending the life of the sensor.

[0024] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a stress sensor in an exemplary example;

[0026] Figure 2 is a schematic structural diagram of a stress sensor tunneling layer in an exemplary example;

[0027] Figure 3 is a circuit diagram of a stress sensor in an exemplary example when it is not subjected to external stress;

[0028] Figure 4 is a circuit diagram of a stress sensor subjected to external stress in an exemplary example;

[0029] Figure 5 is a schematic diagram of the tunneling behavior of electrons in a stress sensor in an exemplary example;

[0030] Figure 6A three-dimensional topography image of a tunneling layer of a stress sensor in an exemplary example;

[0031] Figure 7 FIG. 4 is a planar topography diagram of a tunneling layer of a stress sensor in an illustrative example. DETAILED DESCRIPTION

[0032] The present invention will now be more fully described with reference to the accompanying drawings in the text which follow, in which embodiments of the present invention are shown. However, the present invention may be embodied in a variety of different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are intended to convey the scope of the present invention to those skilled in the art.

[0033] Unless otherwise defined, the terms (including technical and scientific terms) used herein should be understood to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. Moreover, it is understood that the terms used herein should be understood to have the same meaning as that in this specification and the relevant art, and should not be interpreted by an ideal or overly formal meaning, unless explicitly provided in this document.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0035] In view of the technical problems mentioned in the background technology, the present invention provides a stress sensor, including a first detection electrode, a second detection electrode and a stress sensing device. Figure 1 As shown, Figure 1It is a schematic diagram of the structure of a stress sensing device in an embodiment, including a lower substrate 1, a high square resistance layer 2, a tunneling layer 3, a low square resistance layer 4 and an upper substrate 5 stacked in sequence, and the first detection electrode and the second detection electrode are respectively connected to the two ends of the high square resistance layer, so that when the first detection electrode and the second detection electrode are connected to power on both sides, the first detection electrode, the second detection electrode and the high square resistance layer 2 form a current path. The upper substrate 5 and the lower substrate are located on the outside of the stress sensing device, which are used to protect the square resistance layer and tunneling layer structure inside it, and ensure that there is no electronic exchange with the square resistance layer structure. The upper and lower substrates can be made of insulating materials such as silicon and rubber. The first detection electrode and the second detection electrode are made of conductive materials with low resistivity, and are used to connect external detection equipment to measure the resistance or current at both ends of the stress sensing device.

[0036] like Figure 2 As shown, Figure 2 Schematic diagram of the structure of the tunneling layer 3. The tunneling layer 3 includes a plurality of elastic insulating protrusion structures 31. When there is external pressure acting on the stress sensing device, the protrusion structure is deformed, so that the distance between the high square resistance layer 2 and the low square resistance layer 4 is reduced, and the resistance value between the first detection electrode and the second detection electrode is reduced. The external pressure is the pressure applied to the outside of the stress sensing device and causes the protrusion structure 31 to deform, such as the external pressure formed by pressing the pressure sensing device with a finger. Specifically, the external pressure can be a force applied in the vertical direction of the lower substrate 1 or a component force applied in the vertical direction of the lower substrate 1, so that the protrusion structure 31 is squeezed and deformed; it can also be a force applied in the vertical direction of the upper substrate 5 or a component force applied in the vertical direction of the upper substrate 5, so that the protrusion structure 31 is squeezed and deformed.

[0037] like Figure 3 As shown, when there is no external pressure acting on the stress sensing device, that is, when F=0, both ends of the high square resistance layer 2 in the stress sensing device are connected to a power supply, and the current flows from the positive electrode of the power supply through the high square resistance layer 2 to the negative electrode of the power supply. At this time, the resistance value in the circuit is the resistance value of the high square resistance layer 2 connected to the circuit.

[0038] like Figure 4As shown, when there is external pressure acting on the stress sensing device, that is, when F>0, the two ends of the high square resistance layer 2 in the stress sensing device are still connected to the power supply, but the current no longer flows only through the high square resistance layer 2; because the protrusion structure 31 is squeezed and deformed, the distance between the high square resistance layer 2 and the low square resistance layer 4 is reduced. At this time, the distance between the high square resistance layer 2 and the low square resistance layer 4 reaches the minimum threshold distance for the electron tunneling effect to occur. The electrons in the high square resistance layer 2 will have a probability of tunneling along the direction of the electric line, that is, tunneling from the high square resistance layer 2 to the low square resistance layer 4. From a macroscopic point of view, at this time, the current flows through the high square resistance layer 2 and the low square resistance layer 4 at the same time, and the smaller the distance between the high square resistance layer 2 and the low square resistance layer 4, the greater the probability of the electron tunneling behavior, and the current passing through the low square resistance layer 4 is larger. At this time, the resistance value of the stress sensing device is reduced, that is, the pressure applied to the stress sensing device is inversely proportional to the resistance value of the stress sensing device, and is directly proportional to the current passing through the stress sensing sensor device.

[0039] Specifically, the high square resistance layer 2 can be made of a low conductivity material, such as at least one semiconductor material with low conductivity, such as tungsten oxide, zinc oxide, carbon nanotubes, graphene, carbon fiber, carbon-based composite cloth, etc. The low square resistance layer 4 can be made of a high conductivity material, for example, it can be made of at least one material such as copper, silver, gold, platinum or alloy. The conductivity of the high square resistance layer 2 needs to be significantly smaller than the conductivity of the low square resistance layer 2. In some practical applications, the square resistance between the high square resistance layer 2 and the low square resistance layer 4 differs by at least one order of magnitude and the square resistance of the low resistance layer is less than 30 ohms / mil.

[0040] In a preferred embodiment, Figure 2 As shown, the tunneling layer 3 further includes an island structure 32, which is made of a metal material and fills the gap between the protrusion structure 31 on one side of the low square resistance layer 4. The island structure 32 can be made of a metal film or metal particles with excellent conductivity, and preferably, can be a metal material such as copper, silver, gold, platinum or an alloy. Figure 5 As shown, when there is external pressure acting on the stress sensing device, the electrons in the high square resistance layer 2 tunnel to the low square resistance layer 4 through the island structure 32. Therefore, the island structure 32 increases the minimum threshold distance between the high square resistance layer 2 and the low square resistance layer 4 for the electron tunneling effect to occur, thereby increasing the sensitivity of the stress sensing device and enabling it to capture weaker signals.

[0041] In a preferred example, the bottom of the protrusion structure 31 is connected to the low-resistance layer 4, the top of the protrusion structure 31 extends toward the high-resistance layer 2, and the cross section of the protrusion structure 31 gradually decreases in the direction from the low-resistance layer 4 to the high-resistance layer 2. That is, the protrusion structure 31 is roughly conical, and its side section is as follows: Figure 2In other examples, the protrusion structure may also be columnar, or inverted quadrangular pyramidal, etc. The heights of different protrusion structures 31 may be the same. In another example, the heights of any two protrusion structures 31 may be different, and the height difference between them is less than 20 um.

[0042] The height of the island structure 32 is not higher than any protrusion structure 31 , and the height difference between the top of the island structure 32 and the end of the protrusion structure 31 away from the low-resistance layer 4 is less than 30 um.

[0043] In a specific example, the morphology of the tunneling layer 3 of a stress sensor described in an embodiment of the present application is as follows: Figure 6 and Figure 7 shown.

[0044] A stress sensor provided by an embodiment of the present application, when the upper substrate or the lower substrate is subjected to pressure, the elastic insulating protrusion structure of the tunneling layer is deformed, so that the distance between the low-square-resistance layer and the high-square-resistance layer is shortened, resulting in a tunneling effect, generating a tunneling current, and the magnitude of the tunneling current is proportional to the magnitude of the pressure, thereby realizing the detection of stress. At the same time, the embodiment of the present application fills the tunneling layer between the high-square-resistance layer and the low-square-resistance layer instead of the traditional gasket structure, thereby greatly reducing the thickness of the stress sensor, reducing the minimum stress trigger threshold lower limit, improving the sensor sensitivity, and realizing the extraction of weak signals and effectively extending the life of the sensor.

[0045] The present application also provides a method for preparing a stress sensor, comprising the following steps:

[0046] S1: providing an upper substrate, a lower substrate and a tunneling layer, wherein the tunneling layer comprises a plurality of elastic insulating protrusion structures;

[0047] S2. Print or evaporate a high square resistance layer with a thickness ranging from 5um to 100um on one side of the lower substrate, and keep it warm at a temperature range of 30°C to 200°C for 10 to 180 minutes;

[0048] S3, printing or vapor-depositing a low square resistance layer with a thickness ranging from 5um to 100um on one side of the upper substrate, and keeping it warm at a temperature range of 30°C to 200°C for 10 to 180 minutes;

[0049] S4, printing a tunneling layer on the surface of the cooled low-square-resistance layer, keeping it still for 10 minutes to 300 minutes, and keeping it warm in the temperature range of 30° C. to 200° C. for 10 minutes to 180 minutes;

[0050] S5, facing the side of the lower substrate with the high square resistance layer toward the side of the upper substrate with the tunnel layer, and pressing the upper substrate and the lower substrate face to face;

[0051] S6. Form a first detection electrode and a second detection electrode on both sides of the high square resistance layer by riveting or printing.

[0052] In a preferred embodiment, the bottom of the protrusion structure is attached to the low-square-resistance layer, the top of the protrusion structure extends toward the high-square-resistance layer, and the cross-section of the protrusion structure gradually decreases in the direction extending from the low-square-resistance layer to the high-square-resistance layer;

[0053] The gap between the protrusion structure located on one side of the low-resistance layer is filled with an island structure by glue coating or spraying, and the island structure is made of at least one of the following materials: copper, silver, gold, platinum or alloy.

[0054] In a preferred embodiment, the height difference between any two of the protruding structures is less than 20 um, and the height difference between the top of the island structure and the end of the protruding structure away from the low-resistance layer is less than 30 um.

[0055] In a preferred embodiment, the sheet resistance between the high sheet resistance layer and the low sheet resistance layer differs by at least one order of magnitude and the sheet resistance of the low sheet resistance layer is less than 30 ohms / mil.

[0056] The embodiment of the present application further provides a stress sensing device, comprising a plurality of stress sensors according to any of the above embodiments, wherein the plurality of stress sensors are connected in series or in parallel with each other. The stress sensing device can realize stress detection over a larger area.

[0057] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A stress sensor, Features: It includes a first detection electrode, a second detection electrode and a stress sensing device; The stress sensing device comprises a lower substrate, a high square resistance layer, a tunneling layer, a low square resistance layer and an upper substrate stacked in sequence, and the first detection electrode and the second detection electrode are respectively connected to two ends of the high square resistance layer; The tunneling layer includes a plurality of elastic insulating protrusion structures, and when there is external pressure acting on the stress sensing device, the protrusion structure is deformed, so that the distance between the high square resistance layer and the low square resistance layer is reduced, and the resistance value between the first detection electrode and the second detection electrode is reduced; The tunneling layer further includes an island structure, which is made of a metal material and fills a gap between the protrusion structures located on one side of the low-square-resistance layer.

2. A stress sensor according to claim 1, Features: The bottom of the protrusion structure is connected to the low square resistance layer, the top of the protrusion structure extends toward the high square resistance layer, and the cross section of the protrusion structure gradually decreases in the direction extending from the low square resistance layer to the high square resistance layer.

3. A stress sensor according to claim 2, Features: The height difference between any two of the protruding structures is less than 20 um, and the height difference between the top of the island structure and the end of the protruding structure away from the low-resistance layer is less than 30 um.

4. A stress sensor according to claim 1, Features: The sheet resistance between the high sheet resistance layer and the low sheet resistance layer differs by at least one order of magnitude, and the sheet resistance of the low sheet resistance layer is less than 30 ohm / mil.

5. A method for preparing a stress sensor, It is characterized in that The steps include: S1: providing an upper substrate, a lower substrate and a tunneling layer, wherein the tunneling layer comprises a plurality of elastic insulating protrusion structures; S2. Print or evaporate a high square resistance layer with a thickness ranging from 5um to 100um on one side of the lower substrate, and keep it warm at a temperature range of 30°C to 200°C for 10 to 180 minutes; S3, printing or vapor-depositing a low square resistance layer with a thickness ranging from 5um to 100um on one side of the upper substrate, and keeping the temperature within the range of 30°C to 200°C for 10 to 180 minutes; S4, printing a tunneling layer on the surface of the cooled low-square-resistance layer, keeping it still for 10 minutes to 300 minutes, and keeping it warm in the temperature range of 30° C. to 200° C. for 10 minutes to 180 minutes; S5, facing the side of the lower substrate with the high square resistance layer toward the side of the upper substrate with the tunnel layer, and pressing the upper substrate and the lower substrate face to face; S6, respectively manufacturing a first detection electrode and a second detection electrode on both sides of the high square resistance layer by riveting or printing; The bottom of the protrusion structure is attached to the low-square-resistance layer, the top of the protrusion structure extends toward the high-square-resistance layer, and the cross-section of the protrusion structure gradually decreases in the direction extending from the low-square-resistance layer to the high-square-resistance layer; The gap between the protrusion structure located on one side of the low-resistance layer is filled with an island structure by glue coating or spraying, and the island structure is made of at least one of the following materials: copper, silver, gold, platinum or alloy.

6. The method for preparing a stress sensor according to claim 5, Features: The height difference between any two of the protruding structures is less than 20 um, and the height difference between the top of the island structure and the end of the protruding structure away from the low-resistance layer is less than 30 um.

7. The method for preparing a stress sensor according to claim 6, Features: The sheet resistance between the high sheet resistance layer and the low sheet resistance layer differs by at least one order of magnitude, and the sheet resistance of the low sheet resistance layer is less than 30 ohm / mil.

8. A stress sensing device, Features: It comprises a plurality of stress sensors according to any one of claims 1 to 4, wherein the plurality of stress sensors are connected in series or in parallel.

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