Preparation method and application of wide-range flexible capacitive pressure sensor

Abstract

The invention discloses a preparation method and application of a wide-range flexible capacitive pressure sensor, and the method comprises the steps: obtaining the parameter information of a high-modulus dielectric material based on a test result of a single-layer flexible pressure sensor; simulation analysis is carried out based on the high-modulus medium parameter information, and the optimal modulus gradient range between the media is determined; according to the obtained optimal modulus gradient range data, low-modulus dielectric material parameters are determined; respectively selecting low-modulus polymer powder and high-modulus polymer powder according to the parameters of the low-modulus dielectric material and the parameters of the high-modulus dielectric material to prepare a low-modulus dielectric film and a high-modulus dielectric film; and assembling the low-modulus dielectric film, the high-modulus dielectric film and the flexible electrode according to a sandwich structure, and leading out a lead to obtain the double-layer flexible pressure sensor. According to the invention, smooth conversion of force between two kinds of modulus media is ensured, and the phenomenon of force conduction failure caused by modulus mismatch between the media is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensors, and in particular relates to a preparation method and application of a wide-range flexible capacitive pressure sensor. Background Art

[0002] According to the current research status of wide-range pressure sensors, although traditional ceramic and MEMS pressure sensors have achieved high sensitivity within a wide detection range (10 MPa), their sensor preparation process is complex and costly. In addition, due to process limitations, the sensors are generally not flexible, making them only suitable for plane detection and unable to be conformally attached to the object being measured, which has a certain impact on the sensor test accuracy. Therefore, flexible pressure sensors have been proposed due to their excellent bendability, ductility, flexibility and other characteristics, showing great application prospects in various application fields. However, a large number of research works have shown that there is always a mutual restriction between high sensitivity and wide detection range in flexible pressure sensors, and it is difficult to have both. In order to expand the detection range of the sensor and improve the sensitivity, a multi-layer medium scheme has been proposed. This scheme uses the modulus difference between each layer of medium to realize the function of sequentially detecting stress in different ranges, and on the basis of achieving wide range detection, it improves the sensor's ability to sense small stress changes, so that the sensor can achieve the goal of wide detection range, high sensitivity and low resolution. However, based on the experimental results of the double-layer flexible pressure sensor, when there is a large difference in the modulus of the upper and lower media, the conduction of force between the medium layers will be seriously hindered, and force conduction failure will occur. This phenomenon not only reduces the sensitivity of the flexible pressure sensor, but also limits the effective linear detection range of the sensor. Summary of the invention

[0003] The object of the present invention is to provide a preparation method and application of a wide-range flexible capacitive pressure sensor to solve the above-mentioned problems.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing a wide-range flexible capacitive pressure sensor, comprising: Based on the test results of the single-layer flexible pressure sensor, the parameter information of the high modulus dielectric material is obtained; Based on the high modulus medium parameter information, simulation analysis is performed to determine the optimal modulus gradient range between media; Determine the low modulus dielectric material parameters based on the obtained optimal modulus gradient range data; According to the parameters of the low modulus dielectric material and the parameters of the high modulus dielectric material, low modulus polymer powder and high modulus polymer powder are selected respectively to prepare a low modulus dielectric film and a high modulus dielectric film; The low modulus dielectric film, the high modulus dielectric film and the flexible electrode are assembled in a sandwich structure, and the wires are led out to obtain a double-layer flexible pressure sensor.

[0005] Furthermore, based on the test results of the single-layer flexible pressure sensor, the parameter information of the high modulus dielectric material is obtained, including: Evaluate the test results of the single-layer flexible pressure sensor and determine the high modulus dielectric material. The high modulus dielectric parameter information includes Young's modulus, relative dielectric constant and Poisson's ratio of the dielectric layer.

[0006] Furthermore, simulation analysis is performed based on the high modulus medium parameter information, including: Based on the capacitive sensing structure, a double-layer flexible pressure sensor model is constructed in the multi-physics field simulation software, and simulation and finite element analysis are performed on it. The capacitive sensor structure model consists of a top electrode, a low modulus dielectric layer, a high modulus dielectric layer, and a bottom electrode from top to bottom; the simulation modules of the double-layer flexible pressure sensor model include a solid mechanics module and an electrostatic module.

[0007] Furthermore, the simulation results include a deformation displacement image of the sensor when subjected to stress, a displacement change curve of each medium surface of the sensor, and a capacitance change curve of the sensor.

[0008] Furthermore, the optimal modulus gradient evaluation criterion is that the deformation displacement image of the sensor does not show obvious stratification and the displacement of each medium surface of the sensor reaches the maximum under full scale.

[0009] Furthermore, the low modulus polymer powder is dissolved in an organic solvent and the polymer solution is treated, and the high modulus polymer powder is dissolved in an organic solvent and the polymer solution is treated.

[0010] Furthermore, the polymer solution treatment includes filtering, dispersing conductive particles and preparing a mixed solution.

[0011] Furthermore, the sandwich structure includes, from top to bottom, an upper packaging layer, a top electrode, a low modulus dielectric, a high modulus dielectric, a bottom electrode and a lower packaging layer.

[0012] A wide-range flexible capacitive pressure sensor is prepared by the preparation method of a wide-range flexible capacitive pressure sensor.

[0013] A wide-range flexible capacitive pressure sensor is used in wearable electronic devices and health and medical monitoring.

[0014] Compared with the prior art, the present invention has the following technical effects: In the present invention, the flexible medium layer adopts a modulus gradient design, and two materials with a certain modulus difference are bonded together to form a flexible medium of the sensor. Unlike a single-layer medium, a double-layer medium composed of different moduli can detect stresses in different ranges in sequence through modulus differences. Specifically, when the stress is small, the low-modulus medium responds and captures small stress changes; as the pressure load increases, the high-modulus medium plays a role and realizes the detection of large stresses.

[0015] Unlike traditional double-layer dielectric sensors, the difference between the two moduli of the flexible medium of the present invention is obtained through reasonable configuration through simulation and finite element analysis, ensuring that the force can be smoothly converted between the two modulus media, avoiding the force conduction failure caused by modulus mismatch between the media, and ensuring that the capacitance change rate of the flexible pressure sensor increases linearly with the increase of pressure within a certain range, ensuring that the sensor achieves the goals of higher sensitivity and lower resolution within an ultra-wide detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the sensor of the present invention; Figure 2 It is a simulation model of the flexible sensor of the present invention; Figure 3 This is a simulated force conduction failure image of the double-layer flexible sensor of the present invention; Figure 4 is a graph showing the relationship between capacitance change rate and stress in Example 1; Figure 5 This is a diagram showing the detection results of slight stress changes in Example 1.

[0017] Description of the drawings: 1-upper packaging layer; 2-top electrode; 3-low modulus dielectric; 4-high modulus dielectric; 5-bottom electrode; 6-lower packaging layer. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Embodiment 1, a method for preparing a wide-range flexible capacitive pressure sensor, comprising: Based on the test results of the single-layer flexible pressure sensor, the parameter information of the high modulus dielectric material is obtained; Based on the high modulus medium parameter information, simulation analysis is performed to determine the optimal modulus gradient range between media; Determine the low modulus dielectric material parameters based on the obtained optimal modulus gradient range data; According to the parameters of the low modulus dielectric material and the parameters of the high modulus dielectric material, low modulus polymer powder and high modulus polymer powder are selected respectively to prepare a low modulus dielectric film and a high modulus dielectric film; The low modulus dielectric film, the high modulus dielectric film and the flexible electrode are assembled in a sandwich structure, and the wires are led out to obtain a double-layer flexible pressure sensor.

[0020] Embodiment 2, a method for preparing a wide-range flexible capacitive pressure sensor, specifically comprising: The modulus gradient optimization design method comprises the following steps: Step 1, evaluate the test results of the single-layer flexible pressure sensor and determine the high modulus dielectric material; Step 2, obtaining high modulus medium parameter information; Step 3: Based on the capacitive sensing structure, a sensor model is constructed in the multi-physics field simulation software, and simulation and finite element analysis are performed on it to determine the optimal modulus gradient range between media. Step 4: Determine the low modulus dielectric material parameters based on the obtained optimal modulus gradient data.

[0021] Preferably, in step 1, the evaluation criterion for the high modulus dielectric layer is that the sensor is applicable to a wide range of detection, especially detection within a higher stress range, and has a higher sensitivity within a wide detection range.

[0022] Preferably, in step 2, the high modulus medium parameter information includes Young's modulus, relative dielectric constant and Poisson's ratio of the medium layer.

[0023] Preferably, in step 3, the capacitive sensor structure model is, from top to bottom, a top electrode, a low modulus dielectric layer, a high modulus dielectric layer, and a bottom electrode.

[0024] Preferably, in step 3, the simulation module of the double-layer flexible pressure sensor model includes a solid mechanics module and an electrostatic module.

[0025] Preferably, in step 4, the simulation results include a deformation displacement image of the sensor when subjected to stress, a displacement change curve of each medium surface of the sensor, and a capacitance change curve of the sensor. Preferably, in step 4, the optimal modulus gradient evaluation criterion is that the deformation displacement image of the sensor does not show obvious stratification and the displacement of each medium surface of the sensor reaches the maximum under full scale.

[0026] A method for preparing a double-layer flexible capacitive pressure sensor comprises the following steps: Step 1, dissolving low modulus polymer powder with an organic solvent and treating the polymer solution; Step 2, using the solution obtained in step 1 to prepare a film to obtain a low modulus dielectric film; Step 3, dissolving the high modulus polymer powder with an organic solvent and treating the polymer solution; Step 4, using the solution obtained in step 3 to prepare a film to obtain a high modulus dielectric film; Step 5, preparing a flexible electrode on the flexible packaging layer; Step 6: Assemble the dielectric films with different moduli obtained in steps 2 and 4 and the flexible packaging layer with electrodes obtained in step 5 in a "sandwich" structure, and lead out wires to obtain a double-layer flexible pressure sensor.

[0027] Preferably, in steps 1 and 3, the polymer solution treatment scheme includes but is not limited to filtering, dispersing conductive particles, and preparing a mixed solution.

[0028] Preferably, in step 6, the “sandwich” structure includes, from top to bottom, an upper packaging layer 1, a top electrode 2, a low modulus dielectric 3, a high modulus dielectric 4, a bottom electrode 5 and a lower packaging layer 6.

[0029] Embodiment 3, a method for preparing a wide-range, flexible capacitive pressure sensor based on modulus gradient design, comprising the following steps: Step 1, determine the high modulus dielectric layer. By comparing the stress detection results of single-layer flexible pressure sensors prepared with MWCNTs / P(VDF-TrFE) composite films of different mass ratios, it is found that the composite film with a MWCNTs mass ratio of 0.2-0.5 wt% has the highest sensitivity in the range of 0.1-10 MPa. Therefore, the composite film with this mass ratio is selected as the high modulus dielectric layer; Step 2: Obtain high modulus medium parameter information: The Young's modulus of the MWCNTs / P(VDF-TrFE) composite film was measured to be 1.6 GPa and the dielectric constant was 12.5 using an optical microscopic tensile stress in-situ tester and an LCR meter.

[0030] Step 3: Build a double-layer flexible pressure sensor model. Create a three-dimensional spatial structure model, set the medium parameters, simulation ports, boundary conditions, etc. Then, mesh the sensor model, set the simulation range (0.1-10 MPa) and simulation step (0.1 MPa) in the solver, and then click Calculate to perform finite element simulation.

[0031] Step 4: Analyze the simulation results. Analyze the deformation displacement images, surface displacement curves of each medium, and capacitance change curves of different modulus gradient sensor models after being subjected to 10 MPa stress. The analysis results show that when the upper modulus is 0.04-0.06GPa and the modulus gradient is 1.54-1.56 GPa, Figure 3As shown in the figure, the deformation displacement image of the sensor shows obvious stratification, and the surface displacement of the lower medium decreases significantly compared with other modulus gradients. When the upper modulus is 0.09-0.11 GPa and the modulus gradient is 1.49-1.51 GPa, the deformation displacement image of the sensor does not show stratification, and compared with other modulus gradients, the surface displacements of the upper and lower media reach the maximum. Therefore, it is determined to use materials with similar modulus as the low modulus medium of the sensor. Through experiments, it was finally determined to use P (VDF-TrFE-CTFE) pure polymer film with a modulus of 0.09 GPa as the low modulus medium.

[0032] Step 5, preparation of a double-layer flexible pressure sensor. The dielectric materials of each layer determined by the above steps are used to prepare dielectric films. In this embodiment, MWCNTs / P (VDF-TrFE) composite film and P (VDF-TrFE-CTFE) pure polymer film are prepared respectively. Afterwards, the conductive silver paste is printed on the flexible packaging material PI tape by screen printing to prepare a flexible electrode. Finally, the double-layer flexible dielectric film and the flexible packaging layer with upper and lower electrodes are assembled in a "sandwich" structure.

[0033] Based on the above steps, a double-layer flexible capacitive pressure sensor with a modulus gradient design can be prepared.

[0034] Test Example 1: The present invention uses a pressure testing system to perform pressure testing on the double-layer flexible pressure sensor prepared above. The system is mainly composed of an electric pressure frame and a digital display push-pull force gauge. The pressure range that the sensor can detect is obtained by comparing and analyzing the pressure value and the capacitance data, and the stress range that the sensor can detect is calculated in combination with the pressure head area.

[0035] Test results such as Figure 4 As shown, Example 1 achieves higher sensitivity and lower resolution in an ultra-wide linear detection range (0.05-12 MPa). And due to the modulus gradient design, the sensor does not experience force conduction failure under modulus adaptation and maintains good linearity, indicating that the double-layer mixed medium flexible pressure sensor has excellent sensing performance.

[0036] Test Example 2: The detection capability of the double-layer mixed medium flexible pressure sensor for small stress changes was tested using objects of different masses. Mass blocks of 0.196 g, 0.020 g, and 0.005 g were placed in the sensing area of ​​the flexible pressure sensor for testing. These three masses showed a clear gradient and were small in mass, which is suitable for evaluating the sensor's ability to detect small stress changes.

[0037] Test results such as Figure 5As shown in the figure, when three kinds of tiny mass objects are placed on the flexible pressure sensor, the sensor capacitance shows a significant response effect. It is worth noting that when facing a tiny object with a mass of 0.005 g, the double-layer flexible pressure sensor of the present invention shows its excellent performance, not only successfully detecting its existence, but also giving a fast response, and its average capacitance change rate is 0.068%, indicating that it has certain application prospects in the field of tiny stress measurement.

[0038] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a wide-range flexible capacitive pressure sensor, characterized in that: include: Based on the test results of the single-layer flexible pressure sensor, the parameter information of the high modulus dielectric material is obtained; Based on the high modulus medium parameter information, simulation analysis is performed to determine the optimal modulus gradient range between media; Determine the low modulus dielectric material parameters based on the obtained optimal modulus gradient range data; According to the parameters of the low modulus dielectric material and the high modulus dielectric material, low modulus polymer powder and high modulus polymer powder are selected respectively to prepare low modulus dielectric film and high modulus dielectric film; The low modulus dielectric film, the high modulus dielectric film and the flexible electrode are assembled in a sandwich structure, and the wires are led out to obtain a double-layer flexible pressure sensor.

2. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 1, characterized in that: Based on the test results of the single-layer flexible pressure sensor, the parameter information of the high modulus dielectric material is obtained, including: Evaluate the test results of the single-layer flexible pressure sensor and determine the high modulus dielectric material. The high modulus dielectric parameter information includes Young's modulus, relative dielectric constant and Poisson's ratio of the dielectric layer.

3. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 1, characterized in that: Simulation analysis based on high modulus medium parameter information, including: Based on the capacitive sensing structure, a double-layer flexible pressure sensor model is constructed in the multi-physics field simulation software, and simulation and finite element analysis are performed on it. The capacitive sensor structure model consists of a top electrode, a low modulus dielectric layer, a high modulus dielectric layer, and a bottom electrode from top to bottom; the simulation modules of the double-layer flexible pressure sensor model include a solid mechanics module and an electrostatic module.

4. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 3, characterized in that: The simulation results include the deformation displacement image of the sensor when subjected to stress, the displacement change curve of each medium surface of the sensor, and the capacitance change curve of the sensor.

5. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 3, characterized in that: The optimal modulus gradient evaluation criterion is that the deformation displacement image of the sensor does not show obvious stratification and the displacement of each medium surface of the sensor reaches the maximum under full scale.

6. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 1, characterized in that: The low modulus polymer powder is dissolved in an organic solvent and the polymer solution is treated, and the high modulus polymer powder is dissolved in an organic solvent and the polymer solution is treated.

7. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 6, characterized in that: The polymer solution processing includes filtering, dispersing conductive particles and preparing a mixed solution.

8. The method for preparing a wide-range flexible capacitive pressure sensor according to claim 1, characterized in that: The sandwich structure includes, from top to bottom, an upper packaging layer, a top electrode, a low modulus dielectric, a high modulus dielectric, a bottom electrode, and a lower packaging layer.

9. A wide-range flexible capacitive pressure sensor, characterized in that: The sensor is manufactured by the method for preparing a wide-range flexible capacitive pressure sensor as described in any one of claims 1 to 8.

10. An application of the wide-range flexible capacitive pressure sensor as claimed in claim 9, characterized in that: Used in wearable electronic devices and health and medical monitoring.

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