Resistive pressure sensor and method of manufacturing the same

Abstract

This invention discloses a resistive pressure sensor and its fabrication method. The adjustable intrinsic conductive coating has high and adjustable conductivity, solving the current loss problem caused by materials with high bulk resistance and low dielectric constant. Simultaneously, the adjustable intrinsic conductive coating has a controllable surface microstructure, solving the sensitivity reduction problem caused by the deformation saturation of the elastomer surface microstructure, thereby improving the linear testing range of the pressure sensor. The applicable pressure testing range of the fabricated pressure sensor is related to the surface roughness, conductivity, spacing of the coplanar electrodes of the conductive coating, and the mechanical properties and surface structure of the selected elastomer, thus improving the designability of the sensor. The adjustable intrinsic conductive coating is chemically bonded to the elastomer substrate or coplanar electrodes without altering the surface structure and overall shape of the elastomer substrate or coplanar electrodes, thereby improving the stability of the sensor.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, and in particular to a resistive pressure sensor and its fabrication method. Background Technology

[0002] With the development of emerging fields such as the Internet of Things, biomedicine, and artificial intelligence, flexible sensors, characterized by their flexibility, foldability, and wearability, are gradually demonstrating significant application value. Flexible pressure sensors are an important component of flexible sensors. Among them, flexible piezoresistive sensors have attracted widespread attention and research due to their advantages such as simple fabrication, low power consumption, strong anti-interference ability, and sensitivity to static forces.

[0003] The interface contact model is a novel flexible piezoresistive sensing model. The relationship between contact resistance and interface parameters is: R∝(ρ / F)·K, where ρ is the resistivity of the contact surface, F is the pressure applied to the surface, and K is a function of surface roughness and elasticity. By adjusting the conductivity, surface roughness, elasticity, and other properties of the piezoresistive layer, the contact resistance change of the pressure sensor under pressure load can be optimized, i.e., the piezoresistive performance.

[0004] Existing contact piezoresistive sensors mostly optimize device performance from the perspective of deformable structural design. For example, special surface structures are prepared on the surface of elastomers using physicochemical methods. However, the deformation of these surface microstructures is prone to saturation, resulting in a generally narrow detection range for such piezoresistive sensors. Alternatively, three-dimensional sponges can be combined with conductive materials (carbon-based materials, metal nanomaterials, and conductive polymers, etc.) through mixing or coating. However, in this composite approach, the electrical stability of the conductive material is easily affected by the viscoelasticity of the three-dimensional sponge. Furthermore, the detection range and sensitivity of such sensors are limited by the mechanical properties and deformation behavior of the three-dimensional sponge.

[0005] However, as the demand for intelligent monitoring technology continues to increase, the requirements for sensors are also constantly rising. Therefore, it is necessary to comprehensively study the impact of the key components of pressure sensors on their pressure-sensitive performance in order to develop sensor devices with high sensitivity, wide detection range, and high accuracy.

[0006] There is an urgent need to develop a resistive pressure sensor and its fabrication method to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to design a resistive pressure sensor and its fabrication method in order to solve the above-mentioned problems.

[0008] The present invention achieves the above objectives through the following technical solutions:

[0009] Resistive pressure sensors include:

[0010] Elastic voltage-conducting resistive layer; the elastic voltage-conducting resistive layer includes an elastomer substrate and at least one layer of a first adjustable intrinsic conductive coating.

[0011] At least two microstructured coplanar electrodes; the microstructured coplanar electrodes include a second adjustable intrinsic conductive coating, a coplanar conductive electrode, and a coplanar electrode substrate; the at least two microstructured coplanar electrodes are laterally spaced and placed between the elastic conductive voltage resistive layer and the coplanar electrode substrate;

[0012] The resistive pressure sensor is arranged from one side to the other as follows: an elastomer substrate, a first adjustable intrinsic conductive coating, a second adjustable intrinsic conductive coating, a coplanar conductive electrode, and a coplanar electrode substrate are connected in sequence; wherein the first adjustable intrinsic conductive coating and the second adjustable intrinsic conductive coating are in electrical contact.

[0013] Preferably, the spacing between two adjacent coplanar electrodes of the microstructure is 50 μm to 1 mm.

[0014] Preferably, both the first adjustable intrinsic conductive coating and the second adjustable intrinsic conductive coating comprise conductive polymer materials.

[0015] Preferably, the conductive polymer material is polypyrrole, polyaniline, or polyethylene dioxythiophene.

[0016] Preferably, the elastomer substrate is formed as a planar structure, a micro / nano structure, or a porous structure.

[0017] A method for fabricating a resistive pressure sensor, characterized in that the fabrication method includes the following steps:

[0018] S1. Select a coplanar electrode substrate and prepare at least two coplanar conductive electrodes on it. Then, prepare an adjustable intrinsic conductive coating on each coplanar conductive electrode to obtain a microstructured coplanar electrode.

[0019] S2. Select an elastomer substrate and prepare at least one layer of tunable intrinsic conductive coating on it to obtain an elastic voltage-resistance layer.

[0020] S3. An elastic conductive voltage resistive layer is electrically contacted with a microstructure coplanar electrode to form a resistive pressure sensor.

[0021] Specifically, methods for preparing tunable intrinsic conductive coatings on coplanar conductive electrodes include electrochemical oxidation; methods for preparing tunable intrinsic conductive coatings on elastomer substrates include at least one of chemical oxidation and electrochemical oxidation.

[0022] Furthermore, the electrochemical oxidation method includes at least one of the constant voltage method, constant current method, step voltage method, step current method, and cyclic voltammetry method; the performance control of the tunable intrinsic conductive coating in the electrochemical oxidation method includes changing at least one of the voltage, current, type and concentration of doped ions, and preparation time; the performance control of the tunable intrinsic conductive coating in the chemical oxidation method includes changing at least one of the precursor composition of the reaction solution, the precursor concentration of the reaction solution, the acidity or alkalinity of the reaction solution, the temperature of the reaction environment, and the reaction time.

[0023] The beneficial effects of this invention are as follows:

[0024] The resistive pressure sensor provided by this invention has a simple fabrication method. The adjustable intrinsic conductive coating has high conductivity and adjustable conductivity, which solves the current loss problem caused by materials with high bulk resistance and low dielectric constant. At the same time, the adjustable intrinsic conductive coating has an adjustable surface microstructure, which solves the sensitivity reduction problem caused by the deformation saturation of the microstructure on the surface of the elastomer, thereby improving the linear testing range of the pressure sensor.

[0025] The adjustable intrinsic conductive coating has no requirements for the selection of elastomer and coplanar electrodes. The pressure test range applicable to the prepared pressure sensor is related to the surface roughness, conductivity, spacing of microstructure coplanar electrodes, and mechanical properties and surface structure of the selected elastomer, thereby improving the designability of the sensor.

[0026] Adjustable intrinsic conductive coatings are adsorbed onto elastomer substrates or coplanar electrodes using chemical bonding methods, without altering the surface structure and overall shape of the elastomer substrate or coplanar electrode substrate, thereby improving the stability of the sensor device.

[0027] The method for fabricating the resistive pressure sensor described in this application is simple, easy to process, and low in cost. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the resistive pressure sensor in this invention;

[0029] Figure 2 These are images showing different surface microstructure morphologies of the conductive coating with adjustable intrinsic properties in this embodiment of the invention; a is sample 1, b is sample 2, and c is sample 3.

[0030] Figure 3 In the figure, a is the performance test curve of the resistive pressure sensor based on the adjustable intrinsic conductive coating in Example 1 under a pressure range of 0-200 kPa; b is the real-time response curve of the resistive pressure sensor based on the adjustable intrinsic conductive coating in Example 1 when detecting the bending motion of a human finger.

[0031] Figure 4 This is the IV curve of the resistive pressure sensor based on the adjustable intrinsic conductive coating in Example 2 under a pressure range of 0-1 MPa.

[0032] Figure 5 The image shows the performance test curves of the resistive pressure sensor based on the adjustable intrinsic conductive coating in Example 2 under a pressure range of 0-1 MPa.

[0033] In the figure: 1. Elastic conductive resistive layer; 11. Elastomer substrate; 12. First adjustable intrinsic conductive coating; 2. Microstructured coplanar electrode; 21. Second adjustable intrinsic conductive coating; 22. Coplanar conductive electrode; 3. Coplanar electrode substrate. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] like Figure 1 As shown, the resistive pressure sensor includes:

[0042] Elastic voltage-conducting layer 1; the elastic voltage-conducting layer 1 includes an elastomer substrate 11 and at least one first adjustable intrinsic conductive coating 12.

[0043] At least two microstructured coplanar electrodes 2; the microstructured coplanar electrodes 2 include a second adjustable intrinsic conductive coating 21 and a coplanar conductive electrode 22; the at least two microstructured coplanar electrodes 2 are laterally spaced and placed between the elastic conductive voltage resistive layer 1 and the coplanar electrode substrate 3;

[0044] The coplanar electrode substrate 3; the resistive pressure sensor is arranged from one side to the other as follows: an elastomer substrate 11, a first adjustable intrinsic conductive coating 12, a second adjustable intrinsic conductive coating 21, a coplanar conductive electrode 22, and the coplanar electrode substrate 3 are connected in sequence; wherein, the first adjustable intrinsic conductive coating 12 and the second adjustable intrinsic conductive coating 21 are in electrical contact.

[0045] In some embodiments, the spacing between two adjacent microstructure coplanar electrodes 2 (here referring to the distance between the second adjustable intrinsic conductive coatings in the two microstructure coplanar electrodes or the distance between the coplanar conductive electrode supports) is 50 μm-1 mm.

[0046] In some embodiments, both the first adjustable intrinsic conductive coating 12 and the second adjustable intrinsic conductive coating 21 comprise conductive polymer materials.

[0047] In some embodiments, the conductive polymer material is polypyrrole, polyaniline, or polyethylene dioxythiophene.

[0048] In some embodiments, the elastomer substrate 11 is formed as a planar structure, a micro / nano structure, or a porous structure.

[0049] A method for fabricating a resistive pressure sensor, characterized in that the fabrication method includes the following steps:

[0050] S1. Select a coplanar electrode substrate 3, and prepare at least two coplanar conductive electrodes 22 on it. Then, prepare an adjustable intrinsic conductive coating on each coplanar conductive electrode 22 to obtain a microstructured coplanar electrode 2.

[0051] S2. Select an elastomer substrate 11 and prepare at least one layer of tunable intrinsic conductive coating on it to obtain an elastic voltage-resistance layer.

[0052] S3. The elastic conductive voltage resistive layer is electrically contacted with the microstructure coplanar electrode 2 to form a resistive pressure sensor.

[0053] In some embodiments, the method for preparing an intrinsically conductive coating with adjustable properties on a coplanar conductive electrode 22 includes an electrochemical oxidation method; the method for preparing an intrinsically conductive coating with adjustable properties on an elastomer substrate 11 includes at least one of a chemical oxidation method and an electrochemical oxidation method.

[0054] In some embodiments, the electrochemical oxidation method includes at least one of the constant voltage method, constant current method, step voltage method, step current method, and cyclic voltammetry method; the performance regulation of the tunable intrinsic conductive coating in the electrochemical oxidation method includes changing at least one of the voltage, current, type and concentration of doped ions, and preparation time; the performance regulation of the tunable intrinsic conductive coating in the chemical oxidation method includes changing at least one of the precursor composition of the reaction solution, the precursor concentration of the reaction solution, the acidity or alkalinity of the reaction solution, the reaction ambient temperature, and the reaction time.

[0055] The resistive pressure sensor provided by this invention operates based on the interface contact model principle. Under external pressure load, the contact area between the microstructured coplanar electrode 2 and the elastic conductive voltage resistive layer changes, and the elastic conductive voltage resistive layer deforms, causing a change in contact resistance. When a voltage is applied to the circuit, by monitoring the change in current value, the differences in the current-voltage curves of the pressure sensor under different pressure loads can be obtained, thereby achieving accurate pressure detection. Because the adjustable intrinsic conductive coating has adjustable conductivity, the bulk resistance and initial contact resistance of the elastic conductive voltage resistive layer can be set according to actual needs. Simultaneously, because the adjustable intrinsic conductive coating has adjustable surface microstructure, the contact resistance change of the elastic conductive voltage resistive layer during the deformation saturation stage can be increased, thereby achieving high sensitivity of the pressure sensor over a wide pressure range.

[0056] Example 1

[0057] A schematic diagram of the resistive pressure sensor involved in this embodiment can be found in [reference needed]. Figure 1 As shown, the microstructure morphology of different surfaces of the tunable intrinsic conductive coating can be found in the following diagrams. Figure 2 As shown, the fabrication process of the resistive pressure sensor based on an adjustable intrinsic conductive coating includes:

[0058] Step 1: Fabrication of the coplanar microstructure electrode 2:

[0059] Using gold as the conductive material and polyimide as the coplanar electrode substrate 3, a coplanar conductive electrode 22 with an electrode width of 200 μm and an electrode spacing of 200 μm was prepared. A certain volume of a mixed aqueous solution of pyrrole monomer and sodium dodecylbenzenesulfonate was prepared as the electrolyte. The coplanar conductive electrode 22 was placed in the electrolyte and connected to an electrochemical workstation through a wire. A constant potential of 2.5 V was applied, and the reaction was carried out for 60 s to obtain a second tunable intrinsic conductive coating 21. After that, the coplanar electrode composite was taken out, soaked and washed in water for 5 min, and then vacuum dried at 60 °C for 4 h to form a microstructured coplanar electrode 2.

[0060] Step 2: Fabrication of the elastic conductive-voltage resistive layer:

[0061] A silicone rubber substrate with a thickness of 700 μm, a closed surface, and a porous interior was selected as the elastomer substrate 11. It was treated with Ar / N2 plasma with a power of 30 W for 5 min. The treated silicone rubber substrate was immersed in a pyrrole monomer solution for 30 min. Then, an oxidant FeCl3·6H2O aqueous solution was added, and the reaction was allowed to stand at 4 °C for 12 h to obtain the first layer of first tunable intrinsic conductive coating 12.

[0062] The elastic silicone rubber of the composite first tunable intrinsic conductive coating 12 was immersed and washed three times in clean water, and then vacuum dried at 60°C for 4 hours. It was then placed in a mixed electrolyte of pyrrole monomer and sodium dodecylbenzenesulfonate, connected to an electrochemical workstation via a wire, and a constant potential of 0.8V was applied. The reaction was carried out for 1200 seconds to obtain the second layer of the first tunable intrinsic conductive coating 12. After that, the elastic conductive composite was taken out, immersed and washed three times in clean water, and then vacuum dried at 60°C for 4 hours to form an elastic conductive voltage resistive layer 1.

[0063] Step 3: Pressure sensor fabrication:

[0064] A pressure sensor is formed by electrically contacting the microstructured coplanar electrode 2 with the elastic conductive voltage resistive layer 1 and encapsulating them with polyimide tape.

[0065] See Figure 3 In section 'a', the pressure sensor performance test in this embodiment is described in the reference section. Figure 3 In this embodiment, b represents the pressure sensor that detects the bending motion of a human finger in real time.

[0066] Example 2

[0067] A schematic diagram of the pressure sensor involved in this embodiment can be found in [reference]. Figure 1 As shown, the microstructure morphology of different surfaces of the conductive coating with tunable intrinsic properties can be found in the following diagrams. Figure 2As shown.

[0068] The preparation method of the resistive pressure sensor based on the adjustable intrinsic conductive coating provided in this embodiment is basically the same as that in Embodiment 1, except that: the width of the coplanar conductive electrode 22 is 500 μm and the electrode spacing is 500 μm; the thickness of the elastomer substrate 11 is 2 mm, and both its interior and surface have a porous structure with a size of 200 μm-500 μm; the first adjustable intrinsic conductive coating 12 on it is a single layer, prepared by chemical oxidation; the conductivity of the adjustable intrinsic conductive coating is controlled by adjusting the concentration of pyrrole monomer and oxidant FeCl3·6H2O in the reaction solution.

[0069] See Figure 4 and Figure 5 This embodiment describes the performance test of a pressure sensor. The test range of this pressure sensor can reach up to 1 MPa, and its linearity R... 2 >0.9.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A resistive pressure sensor, characterized by include: Elastic voltage-conducting resistive layer; the elastic voltage-conducting resistive layer includes an elastomer substrate and at least one layer of a first adjustable intrinsic conductive coating. At least two microstructured coplanar electrodes; the microstructured coplanar electrodes include a second adjustable intrinsic conductive coating, a coplanar conductive electrode, and a coplanar electrode substrate; the at least two microstructured coplanar electrodes are laterally spaced and placed between the elastic conductive voltage resistive layer and the coplanar electrode substrate; The resistive pressure sensor is arranged from one side to the other as follows: an elastomer substrate, a first adjustable intrinsic conductive coating, a second adjustable intrinsic conductive coating, a coplanar conductive electrode, and a coplanar electrode substrate are connected in sequence; wherein the first adjustable intrinsic conductive coating and the second adjustable intrinsic conductive coating are in electrical contact.

2. The resistive pressure sensor of claim 1, wherein, The spacing between two adjacent coplanar electrodes of microstructures is 50 μm-1 mm.

3. The resistive pressure sensor of claim 1, wherein, Both the first tunable intrinsic conductive coating and the second tunable intrinsic conductive coating include conductive polymer materials.

4. The resistive pressure sensor of claim 3, wherein, The conductive polymer material is polypyrrole, polyaniline, or polyethylene dioxythiophene.

5. The resistive pressure sensor of claim 1, wherein, The elastomer substrate can be planar, micro / nano structured, or porous.

6. Method for the production of a resistive pressure sensor for the production of a resistive pressure sensor according to any one of claims 1 to 5, characterized in that The preparation method includes the following steps: S1. Select a coplanar electrode substrate and prepare at least two coplanar conductive electrodes on it. Then, prepare an adjustable intrinsic conductive coating on each coplanar conductive electrode to obtain a microstructured coplanar electrode. S2. Select an elastomer substrate and prepare at least one layer of tunable intrinsic conductive coating on it to obtain an elastic voltage-resistance layer. S3. An elastic conductive voltage resistive layer is electrically contacted with a microstructure coplanar electrode to form a resistive pressure sensor.

7. The method for manufacturing a resistive pressure sensor according to claim 6, characterized in that, Methods for preparing tunable intrinsic conductive coatings on coplanar conductive electrodes include electrochemical oxidation; methods for preparing tunable intrinsic conductive coatings on elastomer substrates include at least one of chemical oxidation and electrochemical oxidation.

8. The method of manufacturing a resistive pressure sensor according to claim 7, characterized in that, Electrochemical oxidation methods include at least one of constant voltage method, constant current method, step voltage method, step current method, and cyclic voltammetry method; the performance control of tunable intrinsic conductive coatings in electrochemical oxidation methods includes changing at least one of voltage, current, type and concentration of doped ions, and preparation time; the performance control of tunable intrinsic conductive coatings in chemical oxidation methods includes changing at least one of the following: precursor composition of reaction solution, precursor concentration of reaction solution, acidity or alkalinity of reaction solution, reaction environment temperature, and reaction time.

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