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

Abstract

A preparation method and application of a wide-range flexible capacitive pressure sensor, comprising: obtaining high modulus medium material parameter information based on single-layer flexible pressure sensor test results; performing simulation analysis based on the high modulus medium parameter information to determine the best modulus gradient range between media; determining low modulus medium material parameters according to the obtained best modulus gradient range data; selecting low modulus polymer powder and high modulus polymer powder according to the low modulus medium material parameters and the high modulus medium material parameters respectively to prepare low modulus medium films and high modulus medium films; assembling the low modulus medium films, the high modulus medium films and flexible electrodes in a sandwich structure, and leading out wires to obtain a double-layer flexible pressure sensor. The present application ensures that force can be smoothly converted between the two modulus media, avoiding the force transmission failure phenomenon due to modulus mismatch between media.

Description

Technical Field

[0001] This invention belongs to the field of flexible pressure sensor technology, specifically a method for preparing and applying a wide-range flexible capacitive pressure sensor. Background Technology

[0002] Based on the current research status of wide-range pressure sensors, traditional ceramic and MEMS pressure sensors, while achieving high sensitivity within a relatively wide detection range (10 MPa), suffer from complex fabrication processes, high costs, and, due to technological limitations, generally lack flexibility, limiting their application to planar detection and preventing conformal attachment to the measured object, thus impacting sensor accuracy. Therefore, flexible pressure sensors, with their excellent bending, ductility, and flexibility, have been proposed, showing great promise in various application fields. However, extensive research indicates a persistent trade-off between high sensitivity and wide detection range in flexible pressure sensors, making it difficult to achieve both simultaneously. To expand the sensor's detection range and improve sensitivity, a multilayer dielectric scheme has been proposed. This scheme utilizes the modulus differences between the dielectric layers to sequentially detect stresses at different ranges, enhancing the sensor's ability to sense minute stress changes while achieving a wide detection range, thus achieving a balance between wide detection range, high sensitivity, and low resolution. However, experiments on a double-layer flexible pressure sensor reveal that when there is a significant difference in modulus between the upper and lower dielectric layers, force transmission between the layers is severely hindered, leading to force transmission failure. This phenomenon not only reduces the sensitivity of the flexible pressure sensor, but also limits the sensor's effective linear detection range. Summary of the Invention

[0003] The purpose of this invention is to provide a method for manufacturing a wide-range flexible capacitive pressure sensor and its application, so as to solve the above-mentioned problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for fabricating a wide-range flexible capacitive pressure sensor includes:

[0006] Based on the test results of a single-layer flexible pressure sensor, parameter information of high-modulus medium material is obtained.

[0007] Simulation analysis is performed based on the parameter information of high modulus media to determine the optimal modulus gradient range between media.

[0008] Based on the obtained optimal modulus gradient range data, determine the parameters of the low modulus medium material;

[0009] Based on the parameters of low-modulus and high-modulus dielectric materials, low-modulus polymer powder and high-modulus polymer powder are selected respectively to prepare low-modulus dielectric films and high-modulus dielectric films.

[0010] A low-modulus dielectric film, a high-modulus dielectric film, and a flexible electrode are assembled in a sandwich structure, and wires are led out to obtain a double-layer flexible pressure sensor.

[0011] Furthermore, based on the test results of a single-layer flexible pressure sensor, parameter information of the high-modulus medium material is obtained, including:

[0012] The test results of the single-layer flexible pressure sensor were evaluated to determine the high-modulus medium material. The parameters of the high-modulus medium include Young's modulus, relative permittivity, and Poisson's ratio of the medium layer.

[0013] Furthermore, simulation analysis is performed based on the parameter information of the high-modulus medium, including:

[0014] Based on the capacitive sensing structure, a double-layer flexible pressure sensor model was constructed in multiphysics simulation software, and simulation and finite element analysis were 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 module of the double-layer flexible pressure sensor model includes a solid mechanics module and an electrostatic module.

[0015] Furthermore, the simulation results include deformation displacement images of the sensor under stress, displacement change curves of various medium surfaces of the sensor, and capacitance change curves of the sensor.

[0016] Furthermore, the optimal modulus gradient evaluation criterion is that the sensor deformation displacement image does not show obvious layering and the displacement of each medium surface of the sensor reaches its maximum at full scale.

[0017] Furthermore, the low-modulus polymer powder is dissolved in an organic solvent and the polymer solution is treated; the high-modulus polymer powder is dissolved in an organic solvent and the polymer solution is treated.

[0018] Further processing of the polymer solution includes filtration, dispersion of conductive particles, and preparation of a mixed solution.

[0019] Furthermore, the sandwich structure, from top to bottom, includes: an upper encapsulation layer, a top electrode, a low-modulus dielectric, a high-modulus dielectric, a bottom electrode, and a lower encapsulation layer.

[0020] A wide-range flexible capacitive pressure sensor is prepared by the aforementioned method for preparing a wide-range flexible capacitive pressure sensor.

[0021] An application of a wide-range flexible capacitive pressure sensor for wearable electronic devices and health monitoring.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] In this invention, the flexible dielectric layer employs a modulus gradient design, bonding two materials with a certain modulus difference to form the flexible dielectric of the sensor. Unlike a single-layer dielectric, the bilayer dielectric composed of different moduli can detect stresses within different ranges sequentially through modulus differences. Specifically, when the stress is low, the low-modulus dielectric responds and captures minute stress changes; as the pressure load increases, the high-modulus dielectric comes into play, enabling the detection of large stresses.

[0024] Unlike traditional dual-layer media sensors, the difference between the two moduli of the flexible media in this invention is obtained through simulation and finite element analysis. This ensures that the force can be smoothly converted between the two moduli, avoiding the force transmission failure caused by the mismatch between the media moduli. It also ensures that the capacitance change rate of the flexible pressure sensor increases linearly with the increase of pressure within a certain range, guaranteeing that the sensor can achieve high sensitivity and low resolution over an ultra-wide detection range. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the sensor structure of the present invention;

[0026] Figure 2 This is the simulation model of the flexible sensor of the present invention;

[0027] Figure 3 This is a simulated force transmission failure image of the double-layer flexible sensor of this invention;

[0028] Figure 4 This is a graph showing the relationship between capacitance change rate and stress in Example 1;

[0029] Figure 5 This is a diagram showing the detection results of minute stress changes in Example 1.

[0030] Figure description: 1-Upper encapsulation layer; 2-Top electrode; 3-Low modulus dielectric; 4-High modulus dielectric; 5-Bottom electrode; 6-Lower encapsulation layer. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Example 1: A method for fabricating a wide-range flexible capacitive pressure sensor, comprising:

[0033] Based on the test results of a single-layer flexible pressure sensor, parameter information of high-modulus medium material is obtained.

[0034] Simulation analysis is performed based on the parameter information of high modulus media to determine the optimal modulus gradient range between media.

[0035] Based on the obtained optimal modulus gradient range data, determine the parameters of the low modulus medium material;

[0036] Based on the parameters of low-modulus and high-modulus dielectric materials, low-modulus polymer powder and high-modulus polymer powder are selected respectively to prepare low-modulus dielectric films and high-modulus dielectric films.

[0037] A low-modulus dielectric film, a high-modulus dielectric film, and a flexible electrode are assembled in a sandwich structure, and wires are led out to obtain a double-layer flexible pressure sensor.

[0038] Example 2: A method for fabricating a wide-range flexible capacitive pressure sensor, specifically including:

[0039] The modulus gradient optimization design method includes the following steps:

[0040] Step 1: Evaluate the test results of the single-layer flexible pressure sensor to determine the high-modulus medium material;

[0041] Step 2: Obtain parameter information for high modulus media;

[0042] Step 3: Based on the capacitive sensing structure, construct a sensor model in multiphysics simulation software, and perform simulation and finite element analysis to determine the optimal modulus gradient range between the media.

[0043] Step 4: Determine the parameters of the low-modulus medium material based on the obtained optimal modulus gradient data.

[0044] Preferably, in step 1, the evaluation criterion for the high modulus dielectric layer is that the sensor is suitable for a wide range of detection, especially for detection in a high stress range, and has high sensitivity over a wide detection range.

[0045] Preferably, in step 2, the high-modulus dielectric parameter information includes the Young's modulus, relative permittivity, and Poisson's ratio of the dielectric layer.

[0046] Preferably, in step 3, 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.

[0047] Preferably, in step 3, the simulation module of the double-layer flexible pressure sensor model includes a solid mechanics module and an electrostatic module.

[0048] Preferably, in step 4, the simulation results include the deformation displacement image of the sensor under stress, the displacement change curves of the sensor's various medium surfaces, and the sensor capacitance change curve.

[0049] Preferably, in step 4, the optimal modulus gradient evaluation criterion is that the sensor deformation displacement image does not show obvious layering and the displacement of each medium surface of the sensor reaches its maximum at full scale.

[0050] The fabrication method of a double-layer flexible capacitive pressure sensor includes the following steps:

[0051] Step 1: Dissolve the low-modulus polymer powder in an organic solvent and treat the polymer solution.

[0052] Step 2: Use the solution obtained in Step 1 to prepare a low-modulus dielectric film;

[0053] Step 3: Dissolve the high-modulus polymer powder in an organic solvent and treat the polymer solution.

[0054] Step 4: Use the solution obtained in Step 3 to prepare a high-modulus dielectric film;

[0055] Step 5: Fabricate flexible electrodes in the flexible encapsulation layer;

[0056] Step 6: Assemble the dielectric films with different moduli obtained in Steps 2 and 4 and the flexible encapsulation layer with electrodes obtained in Step 5 according to the "sandwich" structure, and lead out the wires to obtain a double-layer flexible pressure sensor.

[0057] Preferably, in steps 1 and 3, the polymer solution treatment scheme includes, but is not limited to, filtration, dispersing conductive particles, and preparing a mixed solution.

[0058] Preferably, in step 6, the "sandwich" structure comprises, from top to bottom, an upper encapsulation layer 1, a top electrode 2, a low-modulus dielectric 3, a high-modulus dielectric 4, a bottom electrode 5, and a lower encapsulation layer 6.

[0059] Example 3: A method for fabricating a wide-range, flexible capacitive pressure sensor based on modulus gradient design, comprising the following steps:

[0060] 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 membranes of different mass ratios, it was found that the composite membrane with a MWCNTs mass ratio of 0.2-0.5 wt% had the highest sensitivity in the range of 0.1-10 MPa. Therefore, this mass ratio composite membrane was selected as the high-modulus dielectric layer.

[0061] Step 2: Obtain high modulus dielectric parameters. The Young's modulus of the MWCNTs / P(VDF-TrFE) composite film was measured to be 1.6 GPa and the dielectric constant to be 12.5 using an optical microscopic in-situ tensile stress analyzer and an LCR meter.

[0062] Step 3: Construct a double-layer flexible pressure sensor model. Establish a three-dimensional spatial structure model, setting various medium parameters, simulation ports, boundary conditions, etc. Then, mesh the sensor model and set the simulation range (0.1-10 MPa) and simulation step size (0.1 MPa) in the solver. Click "Calculate" to perform the finite element simulation.

[0063] Step 4: Analyze the simulation results. Analyze the deformation displacement images, surface displacement curves, and capacitance change curves of sensor models with different modulus gradients after being subjected to a stress of 10 MPa. The analysis results show that when the upper layer modulus is 0.04-0.06 GPa and the modulus gradient is 1.54-1.56 GPa, as... Figure 3 As shown, the sensor deformation displacement image exhibits obvious layering, and the surface displacement of the lower medium decreases significantly compared to other modulus gradients. When the upper layer modulus is 0.09-0.11 GPa and the modulus gradient is 1.49-1.51 GPa, the sensor deformation displacement image does not show layering, and the surface displacement of both the upper and lower media reaches its maximum compared to other modulus gradients. Therefore, materials with similar moduli are selected as the low-modulus medium for the sensor. Through experiments, a P(VDF-TrFE-CTFE) pure polymer film with a modulus of 0.09 GPa was ultimately chosen as the low-modulus medium.

[0064] Step 5: Fabrication of the dual-layer flexible pressure sensor. Dielectric films are fabricated using the dielectric materials determined in the previous steps. In this embodiment, MWCNTs / P(VDF-TrFE) composite films and P(VDF-TrFE-CTFE) pure polymer films are fabricated. Then, conductive silver paste is screen-printed onto PI tape, a flexible encapsulation material, to fabricate flexible electrodes. Finally, the dual-layer flexible dielectric films and the flexible encapsulation layer with upper and lower electrodes are assembled in a "sandwich" structure.

[0065] Based on the above steps, a double-layer flexible capacitive pressure sensor with a modulus gradient design can be fabricated.

[0066] Test Example 1:

[0067] This invention employs a pressure testing system to perform pressure testing on the aforementioned prepared double-layer flexible pressure sensor. The system mainly consists of an electric pressure frame and a digital display push-pull force gauge. It primarily determines the sensor's detectable pressure range by comparing and analyzing pressure values ​​with capacitance data, and calculates the sensor's detectable stress range by combining this with the pressure head area.

[0068] Test results are as follows Figure 4 As shown, Example 1 achieves high sensitivity and low resolution within an ultra-wide linear detection range (0.05-12 MPa). Furthermore, due to the modulus gradient design, the sensor does not exhibit force transmission failure under modulus adaptation conditions, maintaining good linearity, indicating that this dual-layer hybrid medium flexible pressure sensor possesses excellent sensing performance.

[0069] Test Example 2:

[0070] The ability of a flexible pressure sensor with a dual-layer hybrid medium to detect minute stress changes was tested using objects of different masses. Masses of 0.196 g, 0.020 g, and 0.005 g were placed sequentially on the sensing area of ​​the flexible pressure sensor for testing. These three masses exhibited a clear gradient, and their relatively small size makes them suitable for evaluating the sensor's ability to detect minute stress changes.

[0071] Test results are as follows Figure 5 As shown, when three tiny objects were placed on the flexible pressure sensor, the sensor capacitance exhibited a significant response. Notably, when faced with a tiny object with a mass of 0.005 g, the double-layer flexible pressure sensor of this invention demonstrated excellent performance, not only successfully detecting its presence but also providing a rapid response with an average capacitance change rate of 0.068%, indicating its promising application prospects in the field of micro-stress measurement.

[0072] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

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

2. The method for fabricating a wide-range flexible capacitive pressure sensor according to claim 1, characterized in that, Based on the test results of a single-layer flexible pressure sensor, parameter information of the high-modulus medium material was obtained, including: The test results of the single-layer flexible pressure sensor were evaluated to determine the high-modulus medium material. The parameters of the high-modulus medium include Young's modulus, relative permittivity, and Poisson's ratio of the medium layer.

3. The method for fabricating a wide-range flexible capacitive pressure sensor according to claim 1, characterized in that, Simulation analysis based on high modulus medium parameter information includes: Based on the capacitive sensing structure, a double-layer flexible pressure sensor model was constructed in multiphysics simulation software, and simulation and finite element analysis were performed on it. The double-layer flexible pressure sensor 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 module of the double-layer flexible pressure sensor model includes a solid mechanics module and an electrostatic module.

4. The method for fabricating a wide-range flexible capacitive pressure sensor according to claim 3, characterized in that, The simulation results include the deformation and displacement images of the sensor under stress, the displacement change curves of the sensor's various medium surfaces, and the sensor's capacitance change curve.

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

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

7. The method for fabricating a wide-range flexible capacitive pressure sensor according to claim 6, characterized in that, Polymer solution treatment includes filtration, dispersion of conductive particles, and preparation of mixed solutions.

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

9. A wide-range flexible capacitive pressure sensor, characterized in that, The wide-range flexible capacitive pressure sensor is prepared by any one of claims 1 to 8.

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

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