A capacitive sensor based on multi-stage compression deformation and its preparation method

Abstract

The present invention belongs to the field of sensor technology, and specifically discloses a capacitive sensor based on multi-stage compression deformation and a preparation method thereof, wherein the capacitive sensor includes an upper electrode layer and a lower electrode layer; a deformable corrugated structure is provided between the upper electrode layer and the lower electrode layer, and the deformable corrugated structure includes three deformation regions with the same structure; three cavities are provided in the deformation region, and the three cavities are respectively filled with a first dielectric layer, a second dielectric layer, and a third dielectric layer; magnetic adsorption units are provided on the outside of adjacent deformation regions. The present invention adopts the above-mentioned capacitive sensor based on multi-stage compression deformation and a preparation method thereof, and the sensor realizes a wide-range, multi-resolution pressure measurement capability; the sensor can present different sensitivity characteristics within different pressure ranges, can flexibly switch working modes, and adapt to various measurement requirements from low pressure to ultra-high pressure, solving the technical problem that traditional capacitive sensors are difficult to simultaneously take into account wide range and high resolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a capacitive sensor based on multi-stage compression deformation and a preparation method thereof. Background Art

[0002] Capacitive sensors have been widely used in the measurement of various physical quantities such as displacement, pressure, humidity, liquid level, and proximity switches due to their simple structure, high sensitivity, low power consumption, and fast response speed. Traditional capacitive sensors, such as parallel plate capacitor structures, usually have a linear or single nonlinear relationship between the change in capacitance and the change in the distance between the plates or the change in the dielectric constant. However, in many practical application scenarios, such as systems that need to simultaneously monitor small pressure changes and withstand large impact pressures, or situations where high-precision judgment of specific key positions is required during large-scale displacement monitoring, traditional capacitive sensors face challenges. Their measurement range and resolution often restrict each other, making it difficult to meet the requirements of wide range and high resolution at the same time, especially when different resolutions are required in different sections within the range.

[0003] To expand the measurement range or increase sensitivity within a specific range, existing technologies may employ complex signal processing circuits or a combination of multiple sensors with different ranges. This increases system complexity, cost, and potential failure points. Furthermore, achieving controllable, phased sensing response characteristics through sensor structural design to accommodate more complex measurement requirements and simplify subsequent signal processing is a promising area of ​​research in sensor technology.

[0004] Therefore, it is of great practical significance and application value to develop a capacitive sensor in this field that has a novel structure and can achieve wide-range and multi-resolution measurement through its own multi-level deformation characteristics. Summary of the Invention

[0005] The purpose of the present invention is to provide a capacitive sensor based on multi-stage compression deformation and a preparation method thereof. The sensor achieves wide-range, multi-resolution pressure measurement capabilities through an innovative multi-layer corrugated structure and a combination of materials with different dielectric properties. The sensor can present different sensitivity characteristics within different pressure ranges, and through the selective activation of the magnetic adsorption unit, it can flexibly switch the working mode to adapt to various measurement requirements from low pressure to ultra-high pressure, solving the technical problem that traditional capacitive sensors are difficult to simultaneously take into account wide range and high resolution.

[0006] To achieve the above objectives, the present invention provides a capacitive sensor based on multi-stage compression deformation, comprising an upper electrode layer and a lower electrode layer, the upper and lower electrode layers being arranged parallel to each other; a deformable corrugated structure is provided between the upper and lower electrode layers, the deformable corrugated structure comprising three deformation regions with identical structures; three cavities are provided within the three deformation regions with identical structures, the three cavities being filled with a first dielectric layer, a second dielectric layer, and a third dielectric layer, respectively; and magnetic adsorption units are provided on the outer sides of adjacent deformation regions;

[0007] The upper and lower electrode layers are both made of conductive materials. The deformable corrugated structure is made of a composite material containing electromagnetic shielding material, which is used to reduce the impact of external electromagnetic interference on sensor measurements. The first, second, and third dielectric layers each contain different types or contents of dielectric materials, so that the multiple dielectric layers have preset and different dielectric properties that match the compression response characteristics of the deformation region in which they are located. The magnetic adsorption unit is made of NdFeB N35-N52 grade permanent magnets, which can realize the merging of adjacent deformation regions.

[0008] The three deformable regions of the deformable corrugated structure can be compressed under the action of the magnetic adsorption unit, changing the thickness of the corresponding multiple dielectric layers and the degree of change in the overall dielectric properties, resulting in a characteristic change in the overall capacitance value of the sensor, thereby achieving wide-range and multi-resolution pressure measurement;

[0009] The working modes of this capacitive sensor include the following 4 modes:

[0010] (a) Low-pressure measurement mode: The magnetic adsorption unit is deactivated, leaving the three structurally identical deformation regions in their initial uncompressed state. This configures the sensor for measuring low pressures between 5 and 100 kPa. When measuring pressure in this mode, the sensor's capacitive response is primarily contributed by the first, second, and third dielectric layers.

[0011] (b) Medium-pressure measurement mode: The magnetic attraction unit for pre-compressing the first deformation region is activated, causing the first deformation region to be pre-compressed, while the second and third deformation regions remain in their initial uncompressed state. This configures the sensor for measuring medium pressures between 100 and 500 kPa. When measuring pressure in this mode, the sensor's capacitive response is primarily contributed by the second and third dielectric layers, while the contribution of the pre-compressed first dielectric layer is reduced.

[0012] (c) High-pressure measurement mode: The magnetic attraction units for pre-compressing the first and second deformation regions are activated, causing the first and second deformation regions to be pre-compressed while the third deformation region remains in its initial uncompressed state. This configures the sensor for measuring high pressures between 500 and 2000 kPa. When measuring pressure in this mode, the sensor's capacitive response is primarily contributed by the third dielectric layer, while the contribution of the pre-compressed first and second dielectric layers is reduced.

[0013] (d) Ultra-high pressure measurement mode: The magnetic adsorption units used to pre-compress the first, second, and third deformation regions are all activated, so that the first, second, and third deformation regions are all pre-compressed, thereby configuring the sensor to be suitable for measuring ultra-high pressures of 2000-5000 kPa. When performing pressure measurements in this mode, the capacitive response of the sensor is mainly contributed by the pre-compressed first, second, and third dielectric layers under extreme compression.

[0014] A method for preparing a capacitive sensor based on multi-stage compression deformation comprises the following steps:

[0015] Step S1, forming an upper electrode layer and a lower electrode layer by using a conductive material;

[0016] Step S2: preparing a deformable corrugated structure between the electrode layer and the lower electrode layer;

[0017] Step S3, preparing a first dielectric layer, a second dielectric layer and a third dielectric layer in the deformation area of ​​the deformable corrugated structure;

[0018] Step S4: using NdFeB N35-N52 grade permanent magnets to make a magnetic adsorption unit, and setting the magnetic adsorption unit outside the adjacent deformation area;

[0019] Step S5: The capacitive sensor based on multi-stage compression deformation is configured to pre-compress one or more deformation areas by selectively activating the magnetic adsorption unit, and to configure several working modes to adapt to different measurement requirements.

[0020] Preferably, step S2 is specifically as follows:

[0021] Step S21, weighing the following components by mass percentage: 92.0% to 98.5% of a matrix, 1.0% to 5.0% of an electromagnetic shielding filler, and 0.5% to 2.0% of a dispersant;

[0022] Step S22, pre-dispersion of electromagnetic shielding filler: adding the surface functionalized electromagnetic shielding filler powder and the dispersant to half the mass of the matrix, and performing preliminary dispersion using high-energy ultrasonic treatment to form a uniform and stable electromagnetic shielding filler concentrated slurry or premix;

[0023] Step S23, mixing and degassing: the concentrated slurry or premix of the electromagnetic shielding filler and the remaining half of the matrix are mixed in a centrifugal mixer at 1000-1200 rpm for 10-20 minutes. The mixing process must be carried out under vacuum conditions to completely remove bubbles in the material and tiny bubbles that may be introduced during the mixing process;

[0024] Step S24, molding and curing: Using a liquid injection molding process, the degassed homogeneous mixture is injected into a precisely designed mold with a target corrugated shape through an injection system. The mold temperature is set at 130°C to 160°C, the injection pressure is 50-100 MPa, and the holding time is 30-90 seconds.

[0025] Step S25, post-processing: After the product is completely solidified in the mold, the mold is cooled to below 60°C, and the mold is opened to remove the formed deformable corrugated structure.

[0026] The material composition of the deformable corrugated structure and its preparation method can achieve excellent flexibility, precise shape retention and high-efficiency broadband electromagnetic shielding function.

[0027] Preferably, in step S21, the substrate is liquid silicone rubber (LSR) with a Shore A hardness of 40 to 60; the electromagnetic shielding filler is a two-dimensional transition metal carbon / nitride (MXene) with a surface functionalization treatment, specifically Ti3C2T x , after surface modification with vinyltriethoxysilane; the lateral size of the two-dimensional transition metal carbon / nitride flakes is 0.5~5μm, and the thickness is less than 5nm; the dispersant is the non-ionic surfactant TritonX-100, which assists the uniform dispersion of MXene in the LSR prepolymer.

[0028] Preferably, step S3 is specifically as follows:

[0029] Step S31, preparing a first dielectric layer;

[0030] (a) Weigh the following components by mass percentage: matrix 60%-75%, ionic liquid 25%-40%, stabilizer 0.5%-2%;

[0031] (b) Premixing: Under an inert atmosphere, half the mass of the matrix and the stabilizer were mixed in a planetary mixer at 500-1000 rpm for 8-10 minutes to obtain a mixture A.

[0032] (c) Adding the ionic liquid: Slowly add the ionic liquid dropwise to the mixture A and continue mixing at 800-1000 rpm for 15 minutes to ensure that a uniform milky white or translucent dispersion is formed;

[0033] (d) adding the remaining half of the matrix and mixing at 1000-1200 rpm for 3 min to obtain mixture B;

[0034] (e) Degassing: Degas the mixture B in a vacuum chamber for 15–20 min, or until no bubbles are released.

[0035] (f) Filling: The degassed mixture B is precisely injected into the designated cavity of the first deformation region and cured at room temperature for 1–2 hours to form the first dielectric layer.

[0036] The prepared first dielectric layer utilizes the high polarity and ion migration ability of the ionic liquid itself to provide an extremely high dielectric constant, and encapsulates it in an ultra-soft elastomer matrix to form an ion gel with an extremely low Young's modulus and an extremely high dielectric constant to achieve ultra-high sensitivity under low pressure;

[0037] Step S32: preparing a second dielectric layer;

[0038] (a) Weigh the following components by mass percentage: base 70%-85%, functional filler 20%-30%, foaming agent 0.5%-5%, foam stabilizer 0.5%-1%, coupling agent 0.5%-0.8%;

[0039] (b) Premixing: Mix half the mass of the matrix, functional filler, foam stabilizer, and coupling agent in a planetary mixer at 1200-1500 rpm for 15-20 minutes to ensure uniform dispersion.

[0040] (c) Add the remaining half of the matrix and continue mixing at 1200-1500 rpm for 3 minutes;

[0041] (d) Adding a foaming agent: Cool the mixture to room temperature, add the foaming agent, and mix at a low speed of 300 to 500 rpm for 5 to 8 minutes;

[0042] (e) Degassing: The mixture was statically degassed in a vacuum chamber for 15–20 min, or until no obvious bubbles escaped;

[0043] (f) Molding foaming and vulcanization: The degassed mixture was quickly injected into the second dielectric layer mold preheated to 115°C, and a pressure of 5 MPa was applied. The temperature and pressure were maintained for 25 minutes.

[0044] (g) Demolding and filling: While maintaining pressure, the second dielectric layer mold is cooled to below 60°C. After demolding, the obtained second dielectric layer is precisely placed and fixed in the second deformation area cavity;

[0045] The prepared second dielectric layer has a medium modulus and a medium and stable dielectric constant. It introduces a closed-pore structure with a porosity of 25-30% and specific dielectric fillers to optimize the compression response curve and capacitance change gradient in the range of 0.5-5 MPa.

[0046] Step S33, preparing a third dielectric layer;

[0047] (a) Weigh the following components by mass percentage: matrix 63%-74.5%, functional filler 25%-35%, vulcanizing agent 0.5%, processing aid 0.5%;

[0048] (b) Rolling: Using a two-roll mixer, control the roller temperature at 40°C to 70°C and roll-coat the substrate;

[0049] (c) Add functional fillers and processing aids in batches and mix thoroughly for 15 to 25 minutes. After achieving uniform dispersion, reduce the roller temperature to below 30°C, quickly and evenly add the vulcanizing agent, pass it through the roller 3 to 5 times to mix evenly, and then quickly remove the sheet;

[0050] (d) Standing: The mixture is stood at room temperature for 4 to 12 hours to relax the internal stress;

[0051] (e) Orientation molding: Using an injection molding machine, the mold design includes appropriate gates and runners to generate a strong shear flow field when filling the third dielectric layer cavity, prompting the functional filler layer to be oriented along the flow direction and parallel to the electrode plate. The holding pressure is set to 10-15 MPa to complete the initial vulcanization.

[0052] (f) Demolding and post-vulcanization: After demolding, the product is placed in an oven at 200°C for post-vulcanization for 4–6 hours to remove peroxide decomposition products and complete cross-linking to obtain the third dielectric layer. Finally, the third dielectric layer is precisely placed and fixed in the cavity of the third deformation region.

[0053] The prepared third dielectric layer utilizes the high strength of high-temperature vulcanized silicone rubber and is filled with oriented functional fillers. It has a high Young's modulus and high pressure resistance, and maintains stable dielectric response and mechanical integrity under high pressure not exceeding 2000kPa.

[0054] Preferably, in step S31, the matrix is ​​Ecoflex 00-30, a platinum-catalyzed addition-type silicone rubber with an extremely low crosslinking density; the ionic liquid is 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid; and the stabilizer is hydroxyl-terminated polydimethylsiloxane (PDMS-OH);

[0055] In step S32, the substrate is a medium-hardness room-temperature vulcanized RTV-2 silicone rubber with a Shore A hardness of 20-30, Wacker Elastosil RT 601 A / B, or an equivalent. The functional filler is micron-sized strontium titanate (SrTiO3) powder with a D50 particle size of 1-5 μm, which must be dried at 120°C for 4-6 hours before use. The foaming agent is toluenesulfonyl hydrazide (TSH), which has a decomposition temperature of approximately 105-115°C. The foam stabilizer is nano-sized zinc oxide (ZnO) with an average particle size of less than 100 nm. The coupling agent is vinyl trimethoxy silane (VTMS), which is used to pre-treat the surface of the SrTiO3 and enhance its interfacial bonding with the substrate.

[0056] In step S33, the substrate is a high-hardness, high-temperature vulcanized HTV silicone rubber with a Shore A hardness of 40 to 55; the functional filler is boron nitride nanosheets (BNNS) that have been surface-functionalized with aminosilane, have a sheet diameter of 1 to 5 μm, a thickness of less than 10 nm, and an aspect ratio greater than 100; the vulcanizing agent is diisopropylbenzene peroxide (BIPB) with an active content of 40%; and the processing aid is low-viscosity vinyl silicone oil.

[0057] Preferably, in step S1, the length and width of the upper electrode layer and the lower electrode layer are both 10 mm to 20 mm, and the thickness is 0.1 to 1 mm;

[0058] In step S3, the wall thickness of the deformable corrugated structure is 1 mm to 3 mm, and the height of a single deformation area is 3 mm to 8 mm;

[0059] In step S4, the thickness of the magnetic adsorption unit is 0.1-0.3 mm.

[0060] The present invention adopts the above-mentioned capacitive sensor based on multi-stage compression deformation and its preparation method, and the beneficial effects are as follows:

[0061] (1) The present invention achieves an ultra-wide pressure measurement range of 5 to 5000 kPa or even higher through an innovative multi-stage compression deformation structure design, far exceeding the range limitations of traditional capacitive sensors. That is, a single sensor unit can meet the full range of accurate monitoring requirements from micro pressure to extremely high pressure.

[0062] (2) The present invention achieves the ability to dynamically switch between four different working modes without replacing or adjusting the hardware through the selective activation of the magnetic adsorption unit, providing flexibility and adaptability for multi-scenario applications;

[0063] (3) The dielectric layer of the present invention has sensitive values ​​for different ranges. A specific working state is selected according to the working environment. Based on the differential contribution design of multiple dielectric layers, the capacitance response of the sensor under different pressures shows nonlinear changes, thereby improving the measurement accuracy and sensitivity.

[0064] (4) The present invention utilizes the synergistic effects of sensor material technologies such as ionic liquids to enhance dielectric properties, functional fillers to provide controllable dielectric constants, and closed-cell structures to optimize compression curves, thereby achieving customized dielectric and mechanical responses in various pressure ranges.

[0065] (5) The capacitive sensor based on multi-stage compression deformation in the present invention has the advantages of simple structure, wide measurement range, high resolution and flexible adjustment.

[0066] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a schematic diagram of the overall structure of a capacitive sensor based on multi-stage compression deformation and a preparation method thereof in Example 1 of the present invention;

[0068] Figure 2 Schematic diagram of three deformation regions of the deformable corrugated structure in Example 1 of a capacitive sensor based on multi-stage compression deformation and a preparation method thereof according to the present invention;

[0069] Figure 3 Schematic diagram of the dielectric layer filling deformation region in Example 1 of a capacitive sensor based on multi-stage compressive deformation and a method for preparing the same according to the present invention; (a) is a schematic diagram of the outer shape of the capacitive sensor based on multi-stage compressive deformation; (b) is a schematic diagram of the three dielectric layers within the capacitive sensor based on multi-stage compressive deformation;

[0070] Figure 4 Schematic diagram of the state of the sensor in different working modes in Example 1 of a capacitive sensor based on multi-stage compression deformation and a preparation method thereof of the present invention;

[0071] Figure 5 The pressure-capacitance response curves under different pressure ranges in Example 1 of a capacitive sensor based on multi-stage compression deformation and a preparation method thereof according to the present invention are shown; among them, (a) is the low-pressure measurement mode; (b) is the medium-pressure measurement mode; (c) is the high-pressure measurement mode; and (d) is the ultra-high-pressure measurement mode.

[0072] Reference numerals

[0073] 1. Magnetic adsorption unit; 2. Deformable corrugated structure; 3. Upper electrode layer; 4. First dielectric layer; 5. Second dielectric layer; 6. Third dielectric layer; 7. Lower electrode layer. DETAILED DESCRIPTION

[0074] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0075] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0076] Example 1

[0077] A capacitive sensor based on multi-level compression deformation is used in human physiological signal monitoring equipment. Different pressure sensitivities are required for monitoring different physiological signals of the human body: light contact pressure monitoring (5-100kPa) is suitable for basic physiological parameter collection, medium pressure monitoring (100-500kPa) is suitable for muscle tension and deep tissue assessment, high pressure monitoring (500-2000kPa) is suitable for joint movement and athletic ability assessment, and ultra-high pressure monitoring (2000-5000kPa) is suitable for collecting biomechanical parameters under extreme exercise conditions.

[0078] like Figure 1 As shown, the capacitive sensor based on multi-stage compression deformation in this embodiment includes an upper electrode layer 3 and a lower electrode layer 7, which are arranged parallel to each other and are composed of conductive materials. A deformable corrugated structure 2 is provided between the upper electrode layer 3 and the lower electrode layer 7. The length and width of the upper electrode layer 3 and the lower electrode layer 7 of the sensor in this embodiment are both 12 mm, and the thickness is 0.2 mm. It is made of a flexible printed circuit board and the surface is covered with a biocompatible protective layer to ensure safety and comfort when in contact with the human body.

[0079] like Figure 2-Figure 3 As shown, the deformable corrugated structure 2 includes three deformation regions with the same structure; the three deformation regions with the same structure are the first deformation region, the second deformation region, and the third deformation region. Three cavities are provided in the three deformation regions with the same structure, and the three cavities are filled with the first dielectric layer 4, the second dielectric layer 5, and the third dielectric layer 6 respectively.

[0080] Magnetic adsorption units 1 are provided on the outside of adjacent deformation areas. The magnetic adsorption units 1 are annular and there are 6 of them in total. They are installed on the outer edges corresponding to the upper and lower boundaries of each deformation area.

[0081] The composition (mass percentage) of the deformable corrugated structure 2 in this embodiment is: 93.5% of liquid silicone rubber LSR with a Shore A hardness of 45, VTES surface-modified MXene (Ti3C2T x ) 4.5% (lateral size 2μm, thickness 3nm), TritonX-100 2.0%.

[0082] The fabrication process for the deformable corrugated structure 2 is as follows: (a) MXene pre-dispersion: Surface-functionalized MXene and Triton X-100 are added to half the mass of liquid silicone rubber (LSR) and treated with high-energy ultrasonication to form a uniform and stable premix. (b) Mixing and degassing: The premixed solution is mixed with the remaining half of the liquid silicone rubber (LSR) in a centrifugal mixer at 1100 rpm for 15 minutes, and bubbles are thoroughly removed under vacuum. (c) Molding and curing: The mixture is injected into a mold with the target corrugated shape using liquid injection molding at a mold temperature of 145°C, an injection pressure of 75 MPa, and a holding time of 60 seconds. (d) After complete curing, the mold is cooled to 55°C and the mold is opened to remove the formed corrugated structure. The wall thickness of the formed corrugated structure is 1.5 mm, and the height of each deformation region is 4 mm. The magnetic adsorption unit 1 is made of NdFeB N42 grade permanent magnets with a thickness of 0.15 mm.

[0083] The material formulas of the three dielectric layers in this embodiment are as follows:

[0084] The first dielectric layer 4 has a composition (mass percentage): Ecoflex 00-30 70%, 1-ethyl-3-methylimidazolium tetrafluoroborate 29%, and PDMS-OH 1%.

[0085] Preparation steps for the first dielectric layer 4: (a) Under an inert atmosphere, mix half the mass of Ecoflex 00-30 and PDMS-OH in a planetary mixer at 800 rpm for 9 minutes; (b) slowly add the ionic liquid dropwise and mix at 900 rpm for 15 minutes until a uniform milky white dispersion is formed; (c) add the remaining half the mass of Ecoflex 00-30 and mix at 1100 rpm for 3 minutes; (d) degas in a vacuum chamber for 18 minutes until no bubbles are formed; (e) inject into the first deformation region cavity and cure at room temperature for 1.5 hours to obtain the first dielectric layer 4. The resulting dielectric layer has an extremely high dielectric constant and ultra-low Young's modulus, making it suitable for monitoring light contact pressures (5-100 kPa).

[0086] The formula composition of the second dielectric layer 5 (mass percentage) is: 71.7% of medium hardness room temperature vulcanized RTV-2 silicone rubber (Shore A hardness 25), 25% of micron-sized strontium titanate (SrTiO3) powder (D50 particle size 2μm), 2.0% of toluenesulfonyl hydrazide (TSH), 0.7% of nano-sized zinc oxide (ZnO) (particle size 90nm), and 0.6% of vinyltrimethoxysilane (VTMS).

[0087] The second dielectric layer 5 is prepared in the following steps: (a) Mix half the mass of medium-hardness room-temperature vulcanized RTV-2 silicone rubber, strontium titanate, zinc oxide, and a coupling agent in a planetary mixer at 1400 rpm for 18 minutes until uniformly dispersed; (b) Add the remaining half the mass of medium-hardness room-temperature vulcanized RTV-2 silicone rubber and mix at 1300 rpm for 3 minutes; (c) Cool to room temperature, add tosylhydrazine, and mix at 400 rpm for 6 minutes; (d) Vacuum degas for 17 minutes until no bubbles are present; (e) Inject the mixture into a mold preheated to 115°C and apply a pressure of 5 MPa for 25 minutes; (f) Cool the mold to 55°C, demold it, and place it in the cavity of the second deformation zone. The resulting dielectric layer exhibits excellent response characteristics in the medium pressure range (100-500 kPa).

[0088] The formula composition of the third dielectric layer 6 (mass percentage) is: 68% high-temperature vulcanized HTV silicone rubber with a Shore A hardness of 50, 31% aminosilane-functionalized boron nitride nanosheets (BNNS) (sheet diameter 4μm, thickness 7nm, aspect ratio >100), 0.5% diisopropylbenzene peroxide (BIPB) (40% active content), and 0.5% low-viscosity vinyl silicone oil.

[0089] The third dielectric layer 6 is prepared in the following steps: (a) using a two-roll mill to roll-mold the high-temperature vulcanized HTV silicone rubber at a roll temperature of 50°C; (b) adding BNNS and vinyl silicone oil in portions and mixing for 20 minutes until uniformly dispersed. The roll temperature is lowered to 25°C, and then BIPB is added and thinly passed through four times to mix thoroughly before being removed from the sheet; (c) the layer is allowed to stand at room temperature for 8 hours to relax internal stress; (d) using an injection molding machine, shear flow is generated through the designed gate and runners to align the BNNS along the flow direction, and the initial vulcanization is completed at a holding pressure of 12 MPa; (e) after demolding, the layer is post-cured in a 200°C oven for 5 hours before being placed and fixed in the cavity of the third deformation zone. The resulting dielectric layer exhibits reliable response characteristics in the high-pressure range (500-2000 kPa) and ultra-high-pressure range (2-5 MPa).

[0090] like Figure 4 As shown, the sensor prepared in this embodiment realizes four working modes of human physiological monitoring scenarios:

[0091] (1) Low-pressure measurement mode: All magnetic adsorption units 1 are inactive, and the three deformation areas are in their initial uncompressed state. The sensor provides a high-sensitivity response within the pressure range of 5 to 100 kPa through the combined action of the first dielectric layer 4, the second dielectric layer 5, and the third dielectric layer 6, and is suitable for monitoring basic physiological parameters such as skin surface pulse and skin elasticity.

[0092] (2) Medium-pressure measurement mode: Manually activate the magnetic adsorption unit 1 of the first deformation area, causing the first deformation area to be compressed, while the second and third deformation areas remain in their initial state. The contribution of the compressed first dielectric layer 4 to the measurement is greatly reduced. The sensor mainly provides a stable response within the pressure range of 100-500 kPa through the second dielectric layer 5 and the third dielectric layer 6, which is suitable for evaluating muscle tension and deep tissue elasticity.

[0093] (3) High-pressure measurement mode: The user activates the magnetic attraction unit 1 of the first and second deformation zones, causing these zones to be pre-compressed, while the third deformation zone remains in its initial state. The sensor provides a reliable response within a pressure range of 500-2000 kPa, primarily through the third dielectric layer 6, and is suitable for monitoring joint range of motion, stability, and force output.

[0094] (4) Ultra-high pressure measurement mode: The user activates all magnetic adsorption units 1, so that all three deformation areas are pre-compressed. The sensor provides a stable response in the ultra-high pressure range of 2~5MPa, which is used to monitor the impact force, explosive force and joint bearing capacity in extreme sports.

[0095] like Figure 5 The following is a graph of the ΔC / C and pressure-capacitance response curves for this embodiment. ΔC / C exhibits a linear trend in different modes, demonstrating that better performance can be achieved by changing the sensor mode of the present invention. The four curves correspond to the sensor's low-pressure, medium-pressure, high-pressure, and ultra-high-pressure measurement modes, forming a complete multi-range, high-resolution measurement system. To ensure the accuracy and reliability of the measurement results, this embodiment systematically calibrates the sensor.

[0096] During the calibration process, a high-precision standard pressure sensor is used as a reference. At each pressure point, the pressure reading of the standard sensor and the capacitance change value (ΔC / C) of the sensor of the present invention are simultaneously recorded. Through this calibration method, an accurate correspondence between the capacitance change and the actual pressure value is established, allowing the sensor of the present invention to accurately convert the capacitance signal into the actual pressure value. After analysis and processing, the calibration data is formed as follows Figure 5 The pressure-capacitance response curves shown are actually calibrated transfer functions, providing a reliable measurement basis for subsequent applications.

[0097] Clearly, all four curves follow the same basic pattern: the ΔC / C value increases continuously with increasing pressure. This consistent trend allows precise mathematical fitting of the curves within each independent measurement mode, establishing a stable model of the pressure-capacitance relationship. This fitability provides a reliable foundation for data processing and pressure calculation in practical applications. It should be noted that at the sensor mode switching points (such as 100 kPa, 500 kPa, and 2 MPa), changes in the pre-compression state of the deformation region can cause jumps in the sensor output characteristics. However, due to the excellent fitability of the curves within each mode, these jumps can be resolved through a simple algorithm conversion, achieving a smooth transition of measurement data between different modes. This approach greatly simplifies system complexity, enabling full-range measurements from low to ultra-high pressure without replacing the sensor, offering significant advantages over traditional methods that require physical replacement of different sensors.

[0098] Example 2

[0099] This embodiment provides a capacitive sensor based on multi-stage compression deformation for use in an injection molding machine pressure monitoring system. The injection molding machine needs to switch between different pressure stages during the production cycle, and traditional pressure sensors find it difficult to simultaneously meet the high-precision measurement requirements of multiple pressure ranges.

[0100] The sensor structure of this embodiment is the same as that of the first embodiment, and also includes an upper electrode layer 3 and a lower electrode layer 7, a deformable corrugated structure 2, three dielectric layers and a magnetic adsorption unit 1. Its basic working principle is consistent with that of the first embodiment.

[0101] However, there are the following differences in specific parameters and formulations:

[0102] Dimensional Parameters: In this embodiment, both the upper electrode layer 3 and the lower electrode layer 7 are made of a 0.3mm-thick flexible printed circuit board (FPCB), with a length and width of 15mm. The surface is coated with a 5μm-thick gold layer to improve conductivity and withstand the corrosive gases in the injection molding environment. The wall thickness of the deformable corrugated structure 2 is 2mm, and the height of a single deformable area is 5mm. The magnetic attraction unit 1 is 0.2mm thick and is made of NdFeB N40 grade permanent magnets.

[0103] The material composition of the deformable corrugated structure 2 (by mass percentage) is: 94.5% of liquid silicone rubber LSR with a Shore A hardness of 50, 4.0% of surface functionalized MXene, and 1.5% of non-ionic surfactant TritonX-100.

[0104] The first dielectric layer 4's composition (by weight percentage) is: 65% platinum-catalyzed addition-type silicone rubber Ecoflex 00-30, 33% 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid, and 2% high-molecular-weight hydroxyl-terminated polydimethylsiloxane. This formulation ensures that the first dielectric layer 4 is designed for pressure detection in the 5-100 kPa range, achieving a sensitivity of up to 120 pF / kPa.

[0105] The second dielectric layer 5's composition (by mass percentage) is: 74% Wacker Elastosil RT 601 A / B, 23% micronized strontium titanate powder, 1.5% toluenesulfonyl hydrazide, 0.8% nano-sized zinc oxide, and 0.7% vinyltrimethoxysilane. This material is optimized for detecting pressures between 100 and 500 kPa, with a sensitivity of 25 pF / kPa.

[0106] The third dielectric layer 6 consists of (by mass percentage): 69% high-temperature vulcanized HTV silicone rubber with a Shore A hardness of 50, 30% boron nitride nanosheets, 0.5% dicumyl peroxide, and 0.5% low-viscosity vinyl silicone oil. This material is designed for pressure monitoring in the 500-2000 kPa range and above, with a sensitivity of 5 pF / kPa.

[0107] In this embodiment, the preparation process of the deformable corrugated structure 2 and the three dielectric layers is the same as that described in the first embodiment.

[0108] The sensor of this embodiment can also be configured into four working modes (low pressure, medium pressure, high pressure and ultra-high pressure measurement modes). Its principle is the same as that of the first embodiment, but the application scenarios are targeted at different pressure stages in the production cycle of the injection molding machine:

[0109] Low pressure measurement mode (5~100kPa): used to accurately monitor and control injection rate and flow;

[0110] Medium pressure measurement mode (100~500kPa): used to ensure uniform filling and stable compaction of molten material in the mold;

[0111] High pressure measurement mode (500~2000kPa): used to ensure product molding quality and mold safety;

[0112] Ultra-high pressure measurement mode (2~5MPa): used to monitor pressure conditions under extreme conditions.

[0113] In summary, based on Example 1 and Example 2, the three dielectric layers in the present invention play different but mutually coordinated roles in the overall performance of the sensor, forming a complete wide-range, multi-resolution measurement system, wherein: the first dielectric layer 4 adopts an ionic liquid-enhanced ultra-soft elastomer design, which has an extremely low Young's modulus and can produce significant deformation under the action of small pressure. The introduction of ionic liquid greatly improves the dielectric constant of the material, so that a large capacitance change can be produced even under small deformation. When the external pressure is lower than 100kPa, the first dielectric layer 4 is the main contributor to the capacitance response, providing an ultra-high sensitivity of up to 120pF / kPa. This enables the sensor to accurately capture small pressure changes, such as pulse fluctuations and shallow tissue elasticity changes in physiological signal monitoring. The ion migration mechanism of ionic liquid in the elastic matrix further enhances the dielectric response capability of the material under dynamic pressure changes.

[0114] The second dielectric layer 5 utilizes an elastic foam structure reinforced with functional fillers. Its Young's modulus is moderate, providing optimal response within the medium pressure range (100-500 kPa). Strontium titanate (SrTiO3), a high-dielectric-constant filler (εr ≈ 300), works synergistically with the closed-cell foam structure to create a unique compression response. As pressure increases, the progressive collapse of the foam structure produces a nonlinear compression curve. Simultaneously, the reduced spacing between filler particles leads to a nonlinear increase in the dielectric constant. These two effects combine to produce a stable sensitivity of approximately 25 pF / kPa. In the low-pressure range (<0.5 MPa), the high stiffness of the second dielectric layer 5 limits its deformation and contributes little. However, when pressure exceeds 100-500 kPa, the closed-cell structure becomes substantially compacted, the compression capacity approaches saturation, and the sensitivity gradually decreases.

[0115] The third dielectric layer 6 is designed from a high-strength elastomer reinforced with oriented fillers, optimized for the high-pressure range of 500-2000 kPa. Boron nitride nanosheets (BNNS) form a highly oriented structure in a flow-oriented process, arranged perpendicular to the electrodes. This structure barely deforms at low pressures and contributes little to capacitance. However, at high pressures, the decreasing spacing between the nanosheets produces a significant change in dielectric constant, resulting in a sensitivity of approximately 5 pF / kPa. Particularly in the ultrahigh-pressure range (>2 MPa), even when the first and second dielectric layers 4 and 5 are nearly fully compacted, the third dielectric layer 6 still provides a measurable capacitance change, ensuring the sensor's continued functionality under extreme conditions.

[0116] The differentiated contributions of the three dielectric layers across different pressure ranges enable a "relay" response mechanism. As pressure increases from low to high, the sensor's primary sensitive area gradually transitions from the first dielectric layer 4 to the second dielectric layer 5, and then to the third dielectric layer 6. This design ensures the sensor maintains appropriate sensitivity across its entire ultra-wide measurement range, avoiding the "accuracy dilemma" often faced by traditional sensors in wide-range measurements: either high accuracy but a narrow range, or a wide range but low accuracy.

[0117] By activating different levels of pre-compression through the magnetic adsorption unit 1, the contribution of a specific dielectric layer can be selectively "shielded" according to actual needs, so that the sensitivity characteristics of the sensor best match the current measurement task, realizing programmable adjustment of the sensing performance.

[0118] Therefore, the present invention adopts the above-mentioned capacitive sensor based on multi-stage compression deformation and its preparation method. The sensor achieves wide-range, multi-resolution pressure measurement capabilities through an innovative multi-layer corrugated structure and a combination of materials with different dielectric properties; the sensor can present different sensitivity characteristics within different pressure ranges, and through the selective activation of the magnetic adsorption unit, it can flexibly switch the working mode to adapt to various measurement requirements from low pressure to ultra-high pressure, solving the technical problem that traditional capacitive sensors are difficult to simultaneously take into account wide range and high resolution.

[0119] Finally, it should be noted that 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 preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A capacitive sensor based on multi-stage compression deformation, characterized in that: The device comprises an upper electrode layer and a lower electrode layer, the upper electrode layer and the lower electrode layer being arranged parallel to each other; a deformable corrugated structure is provided between the upper electrode layer and the lower electrode layer, the deformable corrugated structure comprising three deformation regions with identical structures; three cavities are provided within the three deformation regions with identical structures, the three cavities being filled with a first dielectric layer, a second dielectric layer, and a third dielectric layer respectively; and magnetic adsorption units are provided on the outer sides of adjacent deformation regions; The upper electrode layer and the lower electrode layer are both made of conductive materials; the deformable corrugated structure is made of a composite material containing electromagnetic shielding material; the first dielectric layer, the second dielectric layer, and the third dielectric layer each contain different types or contents of dielectric materials; and the magnetic adsorption unit is made of NdFeB N35-N52 grade permanent magnets. The working modes of this capacitive sensor include the following 4 modes: (a) Low-pressure measurement mode: The magnetic adsorption unit is deactivated, leaving the three structurally identical deformation regions in their initial uncompressed state. This configures the sensor for measuring low pressures between 5 and 100 kPa. When measuring pressure in this mode, the sensor's capacitive response is primarily contributed by the first, second, and third dielectric layers. (b) Medium-pressure measurement mode: The magnetic attraction unit for pre-compressing the first deformation region is activated, causing the first deformation region to be pre-compressed, while the second and third deformation regions remain in their initial uncompressed state. This configures the sensor for measuring medium pressures between 100 and 500 kPa. When measuring pressure in this mode, the sensor's capacitive response is primarily contributed by the second and third dielectric layers, while the contribution of the pre-compressed first dielectric layer is reduced. (c) High-pressure measurement mode: The magnetic attraction units for pre-compressing the first and second deformation regions are activated, causing the first and second deformation regions to be pre-compressed while the third deformation region remains in its initial uncompressed state. This configures the sensor for measuring high pressures between 500 and 2000 kPa. When measuring pressure in this mode, the sensor's capacitive response is primarily contributed by the third dielectric layer, while the contribution of the pre-compressed first and second dielectric layers is reduced. (d) Ultra-high pressure measurement mode: The magnetic adsorption units used to pre-compress the first, second, and third deformation regions are all activated, so that the first, second, and third deformation regions are all pre-compressed, thereby configuring the sensor to be suitable for measuring ultra-high pressures of 2000-5000 kPa. When performing pressure measurements in this mode, the capacitive response of the sensor is mainly contributed by the pre-compressed first, second, and third dielectric layers under extreme compression.

2. The method for preparing a capacitive sensor based on multi-stage compression deformation according to claim 1, characterized in that: The following steps are involved: Step S1, forming an upper electrode layer and a lower electrode layer by using a conductive material; Step S2: preparing a deformable corrugated structure between the electrode layer and the lower electrode layer; Step S3, preparing a first dielectric layer, a second dielectric layer and a third dielectric layer in the deformation area of ​​the deformable corrugated structure; Step S4: using NdFeB N35-N52 grade permanent magnets to make a magnetic adsorption unit, and setting the magnetic adsorption unit outside the adjacent deformation area; Step S5: The capacitive sensor based on multi-stage compression deformation is configured to pre-compress one or more deformation areas by selectively activating the magnetic adsorption unit, and to configure several working modes to adapt to different measurement requirements.

3. A method for preparing a capacitive sensor based on multi-stage compression deformation according to claim 2, characterized in that: Step S2 is specifically as follows: Step S21, weighing the following components by mass percentage: 92.0% to 98.5% of a matrix, 1.0% to 5.0% of an electromagnetic shielding filler, and 0.5% to 2.0% of a dispersant; Step S22, pre-dispersion of electromagnetic shielding filler: adding the surface functionalized electromagnetic shielding filler powder and the dispersant to half the mass of the matrix, and performing preliminary dispersion using high-energy ultrasonic treatment to form a uniform and stable electromagnetic shielding filler concentrated slurry or premix; Step S23, mixing and degassing: the concentrated slurry or premix of the electromagnetic shielding filler and the remaining half of the matrix are mixed in a centrifugal mixer at 1000-1200 rpm for 10-20 minutes. The mixing process must be carried out under vacuum conditions to completely remove bubbles in the material and tiny bubbles that may be introduced during the mixing process; Step S24, molding and curing: Using a liquid injection molding process, the degassed homogeneous mixture is injected into a precisely designed mold with a target corrugated shape through an injection system. The mold temperature is set at 130°C to 160°C, the injection pressure is 50-100 MPa, and the holding time is 30-90 seconds. Step S25, post-processing: After the product is completely solidified in the mold, the mold is cooled to below 60°C, and the mold is opened to remove the formed deformable corrugated structure.

4. A method for preparing a capacitive sensor based on multi-stage compression deformation according to claim 3, characterized in that: In step S21, the substrate is liquid silicone rubber with a Shore A hardness of 40 to 60; the electromagnetic shielding filler is a two-dimensional transition metal carbon / nitride with a surface functionalization treatment, specifically Ti3C2T x , after surface modification with vinyltriethoxysilane; the lateral size of the two-dimensional transition metal carbon / nitride sheet is 0.5~5μm and the thickness is less than 5nm; The dispersant is the non-ionic surfactant Triton X-100.

5. A method for preparing a capacitive sensor based on multi-stage compression deformation according to claim 2, characterized in that: Step S3 is specifically as follows: Step S31, preparing a first dielectric layer; (a) Weigh the following components by mass percentage: matrix 60%-75%, ionic liquid 25%-40%, stabilizer 0.5%-2%; (b) Premixing: Under an inert atmosphere, half the mass of the matrix and the stabilizer were mixed in a planetary mixer at 500-1000 rpm for 8-10 minutes to obtain a mixture A. (c) Adding the ionic liquid: Slowly add the ionic liquid dropwise to the mixture A and continue mixing at 800-1000 rpm for 15 minutes to ensure that a uniform milky white or translucent dispersion is formed; (d) adding the remaining half of the matrix and mixing at 1000-1200 rpm for 3 min to obtain mixture B; (e) Degassing: Degas the mixture B in a vacuum chamber for 15–20 min, or until no bubbles are released. (f) Filling: The degassed mixture B is precisely injected into the designated cavity of the first deformation region and cured at room temperature for 1–2 hours to form the first dielectric layer. Step S32: preparing a second dielectric layer; (a) Weigh the following components by mass percentage: base 70%-85%, functional filler 20%-30%, foaming agent 0.5%-5%, foam stabilizer 0.5%-1%, coupling agent 0.5%-0.8%; (b) Premixing: Mix half the mass of the matrix, functional filler, foam stabilizer, and coupling agent in a planetary mixer at 1200-1500 rpm for 15-20 minutes to ensure uniform dispersion. (c) Add the remaining half of the matrix and continue mixing at 1200-1500 rpm for 3 minutes; (d) Adding a foaming agent: Cool the mixture to room temperature, add the foaming agent, and mix at a low speed of 300 to 500 rpm for 5 to 8 minutes; (e) Degassing: The mixture was statically degassed in a vacuum chamber for 15–20 min, or until no obvious bubbles escaped; (f) Molding foaming and vulcanization: The degassed mixture is quickly injected into the second dielectric layer mold preheated to 115°C, and a pressure of 5 MPa is applied. This temperature and pressure are maintained for 25 minutes. (g) Demolding and filling: While maintaining pressure, the second dielectric layer mold is cooled to below 60°C. After demolding, the obtained second dielectric layer is precisely placed and fixed in the second deformation area cavity; Step S33: preparing a third dielectric layer; (a) Weigh the following components by mass percentage: matrix 63%-74.5%, functional filler 25%-35%, vulcanizing agent 0.5%, processing aid 0.5%; (b) Rolling: Using a two-roll mixer, control the roller temperature at 40°C to 70°C and roll-coat the substrate; (c) Add functional fillers and processing aids in batches and mix thoroughly for 15 to 25 minutes. After achieving uniform dispersion, reduce the roller temperature to below 30°C, quickly and evenly add the vulcanizing agent, pass it through the roller 3 to 5 times to mix evenly, and then quickly remove the sheet; (d) Standing: The mixture is stood at room temperature for 4 to 12 hours to relax the internal stress; (e) Orientation molding: Using an injection molding machine, the mold design includes appropriate gates and runners to generate a strong shear flow field when filling the third dielectric layer cavity, prompting the functional filler layer to be oriented along the flow direction and parallel to the electrode plate. The holding pressure is set to 10-15 MPa to complete the initial vulcanization. (f) Demolding and post-vulcanization: After demolding, the product is placed in an oven at 200°C for post-vulcanization for 4–6 hours to remove peroxide decomposition products and complete cross-linking to obtain the third dielectric layer. Finally, the third dielectric layer is precisely placed and fixed in the cavity of the third deformation region.

6. A method for preparing a capacitive sensor based on multi-stage compression deformation according to claim 5, characterized in that: In step S31, the substrate is Ecoflex 00-30, a platinum-catalyzed addition-type silicone rubber with an extremely low crosslinking density; the ionic liquid is 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid; and the stabilizer is hydroxyl-terminated polydimethylsiloxane; In step S32, the substrate is a medium-hardness room-temperature vulcanized RTV-2 silicone rubber with a Shore A hardness of 20-30, Wacker Elastosil RT 601 A / B, or an equivalent; the functional filler is micron-sized strontium titanate powder with a D50 particle size of 1-5 μm, which must be dried at 120° C. for 4-6 hours before use; the foaming agent is toluenesulfonyl hydrazide with a decomposition temperature of 105-115° C.; the foam stabilizer is nano-sized zinc oxide with an average particle size of less than 100 nm; and the coupling agent is vinyltrimethoxysilane. In step S33, the substrate is a high-hardness high-temperature vulcanized HTV silicone rubber with a Shore A hardness of 40 to 55; the functional filler is boron nitride nanosheets, which have been surface-functionalized with aminosilane, have a sheet diameter of 1 to 5 μm, a thickness of less than 10 nm, and an aspect ratio greater than 100; the vulcanizing agent is dicumyl peroxide with an active content of 40%; and the processing aid is low-viscosity vinyl silicone oil.

7. A method for preparing a capacitive sensor based on multi-stage compression deformation according to claim 2, characterized in that: In step S1, the length and width of the upper electrode layer and the lower electrode layer are both 10 mm to 20 mm, and the thickness is 0.1 mm to 1 mm; In step S3, the wall thickness of the deformable corrugated structure is 1 mm to 3 mm, and the height of a single deformed area is 3 mm to 8 mm; In step S4, the thickness of the magnetic adsorption unit is 0.1-0.3 mm.

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