Flexible capacitive three-dimensional force sensor and preparation method thereof

Abstract

The invention provides a flexible capacitive three-dimensional force sensor and a preparation method thereof. The sensor sequentially comprises a flexible substrate, a bottom pole plate, a composite dielectric layer, a top pole plate and a packaging layer from bottom to top, wherein at least three bottom pole plates are arranged and are arranged in a triangular shape; when the packaging layer is subjected to external force, the force is sequentially transmitted to the top electrode plate and the composite dielectric layer through the packaging layer, the composite dielectric layer deforms under the force, the capacitance value between the bottom electrode plate and the top electrode plate is changed, and the capacitance value between the bottom electrode plate and the top electrode plate is measured according to the change of the capacitance value between different bottom electrode plates and top electrode plates before and after the force is applied. And analyzing to obtain the direction and the magnitude of the external force. According to the flexible capacitance type three-dimensional force sensor, the three-common-plate capacitor structure is adopted, when the force is applied, the numerical value of the tangential force can be measured through the relative displacement and the opposite area of the upper and lower electrode plates of the three capacitors, the direction of the force is determined through the increase and decrease change of the capacitors, and therefore three-dimensional force detection is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-end equipment manufacturing, and in particular to a flexible capacitive three-dimensional force sensor and a preparation method thereof. Background Art

[0002] Flexible three-dimensional force sensors usually have good biocompatibility, environmental adaptability and the potential for low-cost mass production. These characteristics can promote their innovative applications in multiple high-end equipment fields such as personalized health management, precision medicine, virtual reality / augmented reality (VR / AR) experience, smart textiles, smart homes, etc., providing users with a more natural, intuitive and safe human-computer interaction method. In addition, with the development of Internet of Things technology, flexible three-dimensional force sensors can also be used as one of the key components to help build a more intelligent and efficient environmental monitoring system, such as air quality monitoring, hydrogeological disaster warning, etc.

[0003] With the rapid development of science and technology, the demand for high-precision and multifunctional pressure sensors in the fields of human-computer interaction, wireless health detection, consumer electronics and environmental monitoring is increasing. Especially in the field of three-dimensional force detection, traditional rigid force sensors are limited in their wide application in emerging application fields such as wearable devices, robot tactile perception, and intelligent medical assistance devices due to their large size, lack of flexibility, easy breakage, and heavy weight. Therefore, the development of flexible three-dimensional force sensors with high sensitivity, fast response time, wide detection range, good stability and long life has become the focus of current research. Summary of the invention

[0004] In view of this, the present invention proposes a flexible capacitive three-dimensional force sensor and a preparation method thereof, so as to realize the detection of three-dimensional force by the flexible sensor.

[0005] In a first aspect, the present invention provides a flexible capacitive three-dimensional force sensor, wherein the sensor comprises, from bottom to top, a flexible substrate, a bottom electrode plate, a composite dielectric layer, a top electrode plate, and a packaging layer; at least three bottom electrodes are provided, and are arranged in a triangular shape;

[0006] When the packaging layer is subjected to an external force, the force is transmitted to the top electrode plate and the composite dielectric layer in sequence through the packaging layer. The composite dielectric layer is deformed under the action of the force, causing the capacitance value between the bottom electrode plate and the top electrode plate to change. By measuring the changes in the capacitance values ​​between different bottom electrodes and the top electrode plate before and after the force is applied, the direction and magnitude of the external force are analyzed and obtained.

[0007] By adopting the above technical solution, the flexible capacitive three-dimensional force sensor realizes fast and accurate detection of external force through the change of capacitance value caused by the deformation of the composite dielectric layer. It has high sensitivity and fast response time and is suitable for real-time monitoring and dynamic application scenarios. In particular, the deformation of the composite dielectric layer when subjected to force can accurately reflect the magnitude and distribution of the force, and the bottom electrode is arranged in a triangular shape, which can simultaneously detect forces in three directions and realize accurate measurement of three-dimensional force, providing a reliable means for force detection in complex environments, and significantly improving the application performance and reliability of sensors in human-computer interaction, wireless health detection, consumer electronics, and environmental monitoring.

[0008] Furthermore, the plurality of bottom plates are arranged in an isosceles triangle.

[0009] Furthermore, the plurality of bottom plates are arranged in an equilateral triangle.

[0010] By adopting the above technical solution, the force detection points can be evenly distributed, ensuring that the force detection in three directions is more balanced and accurate, and effectively improving the measurement accuracy and reliability of three-dimensional force.

[0011] Furthermore, the composite dielectric layer includes a planar layer and a pyramid layer, the planar layer is arranged between the bottom electrode plate and the top electrode plate, and the pyramid layer is arranged between the bottom electrode plate and the planar layer and / or between the top electrode plate and the planar layer.

[0012] In the present invention, by setting a double pyramid layer structure, the following effects can be obtained:

[0013] First, the structure can optimize the force distribution, so that the sensor maintains a better linear response in a larger pressure range. This means that the relationship between the output signal and the input pressure obtained during the measurement process is more linear, which is convenient for subsequent signal processing and analysis.

[0014] Second, the double-layer pyramid structure can reduce the hysteresis caused by the elasticity and viscosity of the material itself, thereby improving the response speed and accuracy of the sensor under dynamic pressure changes.

[0015] Third, because the double-layer structure can better disperse the pressure applied to the sensor, the strength and stability of the overall structure are enhanced, reducing the risk of damage caused by overload.

[0016] Fourth, the design of the double pyramidal layer helps to maintain consistent performance at different temperatures, because the influence of thermal expansion on sensor performance can be reduced by selecting the structure and materials between the two pyramidal layers.

[0017] Fifth, during the micromachining process, the double-layer pyramid design can provide more design freedom in the process of control and adjustment, making the manufacturing of the microstructure more precise, thereby improving the overall performance of the sensor.

[0018] In the present invention, the plane layer is used to support the double pyramid layer. The doping of the plane layer material and the pyramid layer material increases the dielectric constant of the composite dielectric layer. At the same time, the composite double pyramid layer will produce stress concentration when subjected to force, resulting in greater deformation, further improving the sensitivity of the sensor. This structural design enables the sensor to show higher accuracy and reliability in three-dimensional force detection in complex environments.

[0019] By introducing a micro-prism structure on the surface of a flexible electrode (including a top plate and / or a bottom plate), the facing area of ​​the two plates of the flexible electrode can be increased and the surface spacing can be reduced under the action of pressure, thereby obtaining a larger capacitance change rate and improving sensitivity; the dielectric constant can be limitedly changed through the planar layer-double prism structure multi-dielectric layer, thereby improving the sensitivity of the sensor. This structure can obtain a high-sensitivity capacitive pressure sensor.

[0020] Furthermore, any of the pyramid layers is provided with three pyramids, and any of the pyramids has a top end face and a bottom end face arranged along its own axial direction, and the area of ​​the top end face is smaller than the area of ​​the bottom end face.

[0021] Furthermore, the top end surface is close to one side of the planar layer and / or the top electrode plate; the bottom end surface is close to one side of the bottom electrode plate and / or the planar layer.

[0022] Furthermore, the material of the prism is a PI flexible material modified by nano-barium titanate (BT), and a γ-aminopropyltriethoxysilane (KH550) modifier is used. KH550 reacts chemically with hydroxyl groups and is grafted on the surface of barium titanate. The mass ratio of KH550, BT, and PI is 3:60:337. KH550 helps to improve the dispersibility of BT in the BT / PI composite material, thereby producing a smaller capacitor structure and improving the overall dielectric constant. At 10KHz, the relative dielectric constant of ordinary PI film is only 3.5, while the dielectric constant of the unmodified BT / PI composite film is 16.9 when the volume fraction of nano-barium titanate particles is 15%, and the dielectric constant of the BT / PI composite film modified with KH550 is 25.78.

[0023] Furthermore, the raw materials of the planar layer include multi-walled carbon nanotubes, polydimethylsiloxane, a curing agent, sodium bicarbonate and isopropyl alcohol, and the mass ratio thereof is 10:20:2:33:100; the material of the flexible substrate and / or the packaging layer is selected from one of polyimide, polydimethylsiloxane or polyester; the material of the bottom plate and / or the top plate is selected from one of gold, silver or copper.

[0024] By adopting the above technical scheme, the prism layer uses PI flexible material modified by nano-barium titanate, which can significantly improve the dielectric constant and enhance the capacitance change rate. At the same time, stress concentration is generated when subjected to force, causing greater deformation, further improving the sensitivity and response speed of the sensor; the planar layer is composed of multi-walled carbon nanotubes (MWCNTs), polydimethylsiloxane (PDMS), curing agent, sodium bicarbonate (NaHCO3), and isopropanol. Sodium bicarbonate is used as a pore-forming agent. The platform layer material is doped to increase the dielectric constant and also provide stable support for the double prism layer; the flexible substrate and packaging layer use one of polyimide, polydimethylsiloxane or polyester to ensure the flexibility and durability of the overall structure; the bottom plate and the top plate use one of gold, silver or copper to ensure good conductivity and mechanical properties.

[0025] In a second aspect, the present invention relates to a method for preparing the above-mentioned flexible capacitive three-dimensional force sensor, wherein the method is to assemble in order a flexible substrate, a bottom electrode plate, a composite dielectric layer, a top electrode plate and a packaging layer;

[0026] Alternatively, the method comprises assembling in the order of packaging layer, top electrode plate, composite dielectric layer, bottom electrode plate and flexible substrate.

[0027] Furthermore, the bottom plate and / or the top plate are processed by one of magnetron sputtering, vacuum evaporation or electroplating.

[0028] Furthermore, the present invention relates to the application of the above-mentioned flexible capacitive three-dimensional force sensor in force analysis.

[0029] In a third aspect, the present invention provides a method for force analysis, comprising: arranging the flexible capacitive three-dimensional force sensors in an array and performing wiring detection for detecting large-area force analysis.

[0030] The flexible capacitive three-dimensional force sensor provided by the present invention has the following beneficial effects compared with the prior art:

[0031] 1. The flexible capacitive three-dimensional force sensor of the present invention adopts a three-common-plate capacitor structure. When subjected to force, the value of the tangential force can be measured by the relative displacement of the upper and lower plates of the three capacitors and the facing area, and its direction can be determined by the increase or decrease of the capacitor.

[0032] 2. The flexible capacitive three-dimensional force sensor of the present invention combines a plane layer with a micro-prism multi-media layer. Compared with the force on the plane dielectric layer, the micro-prism structure obviously has a smaller force area, and the deformation generated when subjected to the same degree of pressure will be greater. The stress is still mainly concentrated on the upper end of the sensor, which will produce a huge deformation, while the tangential stress of the plane structure is borne by the entire layer. In addition, the plane dielectric layer and the micro-prism structure use different materials to form a composite dielectric layer, which can change the spacing and dielectric constant to improve the sensitivity of the sensor. Therefore, when subjected to the same force, the strain generated by the plane layer and the micro-prism multi-media layer sensor is much greater than that of the plane structure sensor, and the relative area change between the capacitor plates is also greater. Therefore, the tangential force sensitivity of this type of sensor is also much greater than that of the plane structure sensor.

[0033] 3. The composite dielectric layer of the present invention, on the one hand, the double micro-prism dielectric layer adopts PI flexible material, and barium titanate nanoparticles BaTiO3 are added to improve the dielectric constant. The dielectric constants of PI, barium titanate and air are different. When an external force is applied, the deformation of the material will cause a change in the dielectric constant. The air is compressed, which causes the dielectric constant of the dielectric layer to increase, and the capacitance change rate also increases. On the other hand, the porous carbon system / PDMS plane layer is prepared by a solution blending method to produce a porous conductive composite material with good electrical and mechanical properties. This three-dimensional porous material has a large deformation amount and a high effective dielectric constant under the same external force, and can be used as a composite dielectric layer to design a high-performance flexible capacitive tactile sensor.

[0034] 4. The method for preparing a flexible capacitive three-dimensional force sensor of the present invention is easy to implement, convenient to integrate and has a small finished product volume. When analyzing the force of a large area, the sensor can be arranged in an array, for example: 2*2, 3*3, 4*4, etc., and wiring detection can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 The structure diagram of the flexible capacitive three-dimensional force sensor provided by the present invention; in the figure, 1 is a flexible substrate; 2 is a bottom electrode plate; 3 is a composite dielectric layer; 31 is a plane layer; 32 is a prism layer; 4 is a top electrode plate; 5 is a packaging layer;

[0037] Figure 2 A plan view of the flexible capacitive three-dimensional force sensor provided by the present invention;

[0038] Figure 3 A schematic diagram of measuring vertical force of the flexible capacitive three-dimensional force sensor provided by the present invention;

[0039] Figure 4 Schematic diagram of measuring tangential force of the flexible capacitive three-dimensional force sensor provided by the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1 As shown, the present invention designs a flexible capacitive three-dimensional force sensor composed of three common-plate capacitors, which is divided into five parts, including from bottom to top: a flexible substrate 1, a bottom plate 2, a composite dielectric layer 3, a top plate 4 and a packaging layer 5. Among them, the bottom plate 2 is provided with at least three, and is arranged in a triangular shape; the composite dielectric layer 3 includes a plane layer 31 and a prism layer 32, the plane layer 31 is arranged between the bottom plate 2 and the top plate 4, and the prism layer 32 is arranged between the bottom plate 2 and the plane layer 31 and / or between the top plate 4 and the plane layer 31; any of the prism layers 32 is provided with three prisms, and any of the prisms has a top end face and a bottom end face arranged along its own axial direction, and the area of ​​the top end face is smaller than the area of ​​the bottom end face; the top end face is close to the side of the plane layer 31 and / or the top plate 4; the bottom end face is close to the side of the bottom plate 2 and / or the plane layer 31.

[0042] For sensors, pressure is usually measured by the distance between the plates, the dielectric constant and the change in the facing area. The relative displacement of the upper and lower plates of the capacitor and the facing area can be used to measure the magnitude of the tangential force, and the increase or decrease of the three capacitors can be used to determine the direction of the tangential force. Among them, the formula for measuring pressure with a capacitive sensor is:

[0043]

[0044] In formula (I), C represents the capacitance value, ε0 represents the vacuum dielectric constant, and ε r It represents the dielectric constant of the dielectric layer between the capacitor plates, S represents the area between the capacitor plates, and d represents the distance between the capacitor plates. According to its principle, the detection of external force can be achieved by changing the area, spacing and dielectric constant of the dielectric layer.

[0045] In the present invention, when the encapsulation layer 5 is acted upon by an external force, the force is sequentially transmitted to the top plate 4 and the composite dielectric layer 3 through the encapsulation layer 5, and the composite dielectric layer 3 is deformed under the force, causing the capacitance value between the bottom plate 2 and the top plate 4 to change. By measuring the change in the capacitance value between different bottom plates 2 and the top plate 4 before and after the force is applied, the direction and magnitude of the external force are analyzed. Among them, the method for measuring the capacitance value includes:

[0046] An extended thin wire is added from one side of the bottom electrode plate 2 and the top electrode plate 4 to facilitate the connection of the test wire to realize the measurement of the capacitance value.

[0047] The sensor uses three capacitors with common plates to detect tangential force. The top plate 4 serves as the common plate of the three capacitors and also as the force-bearing plate. When no force is applied, the distance d between the three bottom plates 2 and the top plate 4 is the same as the facing area S. When subjected to tangential force, the common plates are relatively displaced in the direction of the tangential force, causing the facing area of ​​the plates of the three capacitors to change, and the capacitance value changes accordingly. Figure 2 A brief description is given below:

[0048] When the sensor is subjected to a force or force component perpendicular to the electrode plate (Z axis), the composite dielectric layer 3 is compressed, resulting in a change in the distance between the electrode plates. At this time, the planar layer 31 and the prism layer 32 structure in the composite dielectric layer 3 further change the dielectric constant of the dielectric layer and the contact area of ​​the electrode plate, thereby causing a significant change in the capacitance value of the sensor. Therefore, when different external forces are applied, different capacitance values ​​will be generated. By establishing a pressure-capacitance relationship, the magnitude of the pressure and the direction of the force can be accurately calculated, and real-time display can be achieved through programming.

[0049] When the sensor is subjected to a force or force component parallel to the plate (X-axis or Y-axis), the force conditions of each layer of the sensor are different, resulting in different tangential displacements of the composite dielectric layer 3 and the plate. This displacement causes the effective area between the upper and lower plates of the capacitive sensor to change, thereby causing a corresponding change in the capacitance value. By detecting the change in the capacitance value, the magnitude and direction of the force or force component parallel to the plate can be accurately measured.

[0050] In the present invention, due to the application of external force, the dielectric constant of many materials will change. This phenomenon is called piezoelectric effect or mechanical strain effect. In some materials (such as piezoelectric materials, polarized materials, etc.), the mechanical stress applied by the outside world will cause the polarization state inside the material to change, thereby changing its dielectric constant.

[0051] Conversely, low dielectric constant materials may result in smaller capacitance changes, thus reducing sensitivity. So we try to increase the dielectric constant as much as possible.

[0052] Therefore, the present invention uses the following materials when preparing the flexible capacitive three-dimensional force sensor:

[0053] In the present invention, the flexible substrate 1 and / or the encapsulation layer 5 may be made of one of polyimide (PI), polydimethylsiloxane (PDMS) or polyester (PET) materials.

[0054] In the present invention, the bottom electrode plate 2 and / or the top electrode plate 4 are both made of metal materials, including but not limited to metals with good conductivity such as gold, silver or copper.

[0055] In the present invention, for the prism layer 32, the prism uses a PI flexible material modified by nano-barium carbonate. The modification condition is to use a γ-aminopropyltriethoxysilane (KH550) modifier. KH550 reacts chemically with hydroxyl groups to be grafted on the surface of barium titanate. KH550 helps to improve the dispersibility of BT in the BT / PI composite material, thereby producing a smaller capacitor structure and improving the overall dielectric constant. The nano-barium carbonate is selected from 50nm nano-barium carbonate from Aladdin Reagent Company; the selection of the PI flexible material includes but is not limited to polyimide solutions from plastic polymer material stores. At 10KHz, the relative dielectric constant of ordinary PI film is only 3.5, while the dielectric constant of the unmodified BT / PI composite film is 16.9 when the volume fraction of nano-barium titanate particles is 15%, and the dielectric constant of the BT / PI composite film modified with KH550 is 25.78.

[0056] In the present invention, the planar layer 31 is a porous carbon / PDMS planar layer, and its constituent raw materials include multi-walled carbon nanotubes (MWCNTs), polydimethylsiloxane (PDMS), a curing agent, sodium bicarbonate (NaHCO3), and isopropyl alcohol (IPA), and the ratio is 10:20:2:33:100; the multi-walled carbon nanotubes are selected from Suzhou Carbonfeng with an inner diameter of 3-5nm, an outer diameter of 8-15nm, and a length of 3-12um; the polydimethylsiloxane is selected from Dow Corning's SYLGARD 184; the curing agent is a PDMS curing agent, and a curing agent matched with Dow Corning's SYLGARD 184 is selected; the sodium bicarbonate is selected from Sinopharm Reagent AR (analytical grade), and the isopropyl alcohol is selected from Lanxiang Chemical AR (analytical grade). The distance between the plates changes. According to the tunnel effect and effective conductive path theory, the distance between the carbon-based conductive particles decreases and a new effective conductive path is formed. The tunnel effect is enhanced, and the electrical properties of the porous composite conductive material change, which leads to an increase in the dielectric constant of the composite dielectric layer.

[0057] The following are specific examples of the present invention. Unless otherwise specified, the sources of materials involved in the examples are all commercially available conventional materials.

[0058] Embodiment 1

[0059] This embodiment provides a method for preparing a flexible capacitive three-dimensional force sensor, comprising the following steps:

[0060] Step 1: Preparation of the material for the prism layer 32

[0061] 0.75 g of KH550 solid, 15 g of BT solid, and 84.25 g of PI solution were weighed into a beaker using an electronic balance, and dispersed in an ultrasonic cleaner for 1 hour to finally obtain a uniformly mixed KH550 / BT / PI composite solution.

[0062] The prepared solution was poured into a machined polytetrafluoroethylene micro-prism three-dimensional structure mold and heated on a heating table at 100°C for about 1 minute to semi-solidify (a state between solid and liquid);

[0063] Step 2: Preparation of planar layer 31 material

[0064] Use an electronic balance to weigh 10g of multi-walled carbon nanotubes (MWCNTs), 20g of polydimethylsiloxane (PDMS), 2g of curing agent, 33g of sodium bicarbonate (NaHCO3), and 100g of isopropanol solution, put them into a clean beaker, stir them evenly and ultrasonically disperse them for 1 hour; then put them into a pre-prepared mold and heat them on a heating table at 60°C for about 30 minutes to solidify them (solid state), and then use tweezers to gently take out the planar layer 31 material.

[0065] Step 3: Material selection

[0066] In this embodiment, the flexible substrate 1 is made of PI film, the encapsulation layer 5 is made of PI film, and the top electrode plate 4 and the bottom electrode plate 2 are made of metal gold.

[0067] Step 4: Preparation of sensor

[0068] (1) Hexamethyldisilazane (HMDS) is pre-coated on the encapsulation layer 5 and the flexible substrate 1 film respectively to enhance the adhesion between the substrate and the metal, and then a photoresist is coated on the encapsulation layer 5 and the flexible substrate 1 film, and a mask is used for exposure to form a desired electrode pattern, and the unexposed part of the photoresist is removed by development to expose the substrate;

[0069] (2) depositing magnetron sputtering technology sputtering on the substrate exposed in step (1) by magnetron sputtering method Cr adhesion layer, Au metal layer, forming a bottom plate 2 and a top plate 4;

[0070] (3) pouring the semi-cured micro-prism layer onto the already cured plane layer and performing final curing to form an upper prism layer 32;

[0071] (4) Repeat the steps of preparing the micro-prism layer 32 on the dielectric layer, but pour the semi-cured micro-prism layer in the opposite direction onto the already cured planar layer - the upper micro-prism layer, and perform final curing to form the lower prism layer 32;

[0072] (5) Assemble the flexible substrate 1, the bottom electrode 2, the composite dielectric layer 3, the top electrode 4 and the packaging layer 5 in sequence from bottom to top, ensuring that the layers are tightly fitted and free of bubbles, thereby obtaining a flexible capacitive three-dimensional force sensor.

[0073] Embodiment 2

[0074] This embodiment provides a method for preparing a flexible capacitive three-dimensional force sensor, comprising the following steps:

[0075] Step 1: Preparation of the material for the prism layer 32

[0076] 0.75 g of KH550 solid, 15 g of BT solid, and 84.25 g of PI solution were weighed into a beaker using an electronic balance, and dispersed in an ultrasonic cleaner for 1 hour to finally obtain a uniformly mixed KH550 / BT / PI composite solution.

[0077] The prepared solution was poured into a machined polytetrafluoroethylene micro-prism three-dimensional structure mold and heated on a heating table at 100°C for about 1 minute to semi-solidify (a state between solid and liquid);

[0078] Step 2: Preparation of planar layer 31 material

[0079] Use an electronic balance to weigh 10g of multi-walled carbon nanotubes (MWCNTs), 20g of polydimethylsiloxane (PDMS), 2g of curing agent, 33g of sodium bicarbonate (NaHCO3), and 100g of isopropanol solution, put them into a clean beaker, stir them evenly and ultrasonically disperse them for 1 hour; then put them into a pre-prepared mold and heat them on a heating table at 60°C for about 30 minutes to solidify them (solid state), and then use tweezers to gently take out the planar layer 31 material.

[0080] Step 3: Material selection

[0081] In this embodiment, the flexible substrate 1 is made of PDMS film, the encapsulation layer 5 is made of PI film, and the top electrode plate 4 and the bottom electrode plate 2 are made of metallic silver.

[0082] Step 4: Preparation of sensor

[0083] (1) Hexamethyldisilazane (HMDS) is pre-coated on the encapsulation layer 5 and the flexible substrate 1 film respectively to enhance the adhesion between the substrate and the metal, and then a photoresist is coated on the encapsulation layer 5 and the flexible substrate 1 film, and a mask is used for exposure to form a desired electrode pattern, and the unexposed part of the photoresist is removed by development to expose the substrate;

[0084] (2) depositing a metal layer - silver on the substrate exposed in step (1) by vacuum evaporation at a deposition rate of 1 nm / s to form a bottom electrode 2 and a top electrode 4;

[0085] (3) pouring the semi-cured micro-prism layer onto the already cured plane layer 31 and performing final curing to form an upper prism layer 32;

[0086] (4) Repeat the steps of preparing the micro-prism layer on the dielectric layer, but pour the semi-cured micro-prism layer in the opposite direction onto the already cured planar layer - the upper micro-prism layer, and perform final curing to form the lower prism layer 32;

[0087] (5) Assemble the flexible substrate 1, the bottom electrode 2, the composite dielectric layer 3, the top electrode 4 and the packaging layer 5 in sequence from bottom to top, ensuring that the layers are tightly fitted and free of bubbles, thereby obtaining a flexible capacitive three-dimensional force sensor.

[0088] Embodiment 3

[0089] This embodiment provides a method for preparing a flexible capacitive three-dimensional force sensor, comprising the following steps:

[0090] Step 1: Preparation of the material for the prism layer 32

[0091] Use an electronic balance to weigh 0.75 g of KH550 solid, 15 g of BT solid, and 84.25 g of PI solution, respectively, and put them into a beaker. Then disperse them in an ultrasonic cleaner for 1 hour to finally obtain a uniformly mixed KH550 / BT / PI solution.

[0092] The prepared solution was poured into a machined polytetrafluoroethylene micro-prism three-dimensional structure mold and heated on a heating table at 100°C for about 1 minute to semi-solidify (a state between solid and liquid);

[0093] Step 2: Preparation of planar layer 31 material

[0094] Use an electronic balance to weigh 10g of multi-walled carbon nanotubes (MWCNTs), 20g of polydimethylsiloxane (PDMS), 2g of curing agent, 33g of sodium bicarbonate (NaHCO3), and 100g of isopropanol solution, put them into a clean beaker, stir them evenly and ultrasonically disperse them for 1 hour; then put them into a pre-prepared mold and heat them on a heating table at 60°C for about 30 minutes to solidify them (solid state), and then use tweezers to gently take out the planar layer 31 material.

[0095] Step 3: Material selection

[0096] In this embodiment, the flexible substrate 1 is made of PDMS film, the encapsulation layer 5 is made of PET film, the top electrode plate 4 is made of metal gold, and the bottom electrode plate 2 is made of metal copper.

[0097] Step 4: Preparation of sensor

[0098] (1) Hexamethyldisilazane (HMDS) is pre-coated on the encapsulation layer 5 and the flexible substrate 1 film respectively to enhance the adhesion between the substrate and the metal, and then a photoresist is coated on the encapsulation layer 5 and the flexible substrate 1 film, and a mask is used for exposure to form a desired electrode pattern, and the unexposed part of the photoresist is removed by development to expose the substrate;

[0099] (2) Depositing a metal layer - gold / copper on the substrate exposed in step (1) by electroplating, the specific conditions are: pH 9, temperature 55 ° C, current density 0.5A / dm 2 , plating time is 30min; copper plating conditions are: PH 5, temperature 45℃, current density 1.5A / dm 2 , the plating time is 15 minutes, forming a top electrode plate 4 and a bottom electrode plate 2;

[0100] (3) pouring the semi-cured micro-prism layer onto the already cured plane layer and performing final curing to form an upper prism layer 32;

[0101] (4) Repeat the steps of preparing the micro-prism layer on the dielectric layer, but pour the semi-cured micro-prism layer in the opposite direction onto the already cured planar layer - the upper micro-prism layer, and perform final curing to form the lower prism layer 32;

[0102] (5) Assemble the flexible substrate 1, the bottom electrode 2, the composite dielectric layer 3, the top electrode 4 and the packaging layer 5 in sequence from bottom to top, ensuring that the layers are tightly fitted and free of bubbles, thereby obtaining a flexible capacitive three-dimensional force sensor.

[0103] Embodiment 4

[0104] Based on the above-mentioned first embodiment, this embodiment provides a method for three-dimensional force measurement, which specifically includes:

[0105] (1) Vertical force measurement: refer to the attached Figure 3 , when positive pressure (force in the Z-axis direction) is applied, when the force is compressed to the upper micro-prism 32, the distance between the dielectric layers decreases, and the area facing each other between the plates increases. It can be obtained from the formula that the capacitance values ​​of the three capacitors increase; when the force is compressed to the dielectric layer plane layer 31, the distance between the dielectric layers decreases, and the area facing each other between the plates increases. The dielectric constant increases due to the doping of each material in the two dielectric layers and the assembly of the two layers. It can be obtained from the formula that the capacitance values ​​of the three capacitors increase; when the force is compressed to the lower micro-prism 32, the distance between the dielectric layers decreases, and the area facing each other between the plates increases. The dielectric constant increases due to the doping of each material in the three dielectric layers and the assembly of the three layers. It can be obtained from the formula that the capacitance values ​​of the three capacitors C1, C2, and C3 increase;

[0106] (2) Tangential force measurement: refer to the attached Figure 4 When a tangential force is applied along the positive direction of the y-axis, as the tangential force increases, the positive relative displacement of the common electrode along the Y-axis increases, and the area of ​​C1 facing the common electrode increases, causing its capacitance to gradually increase, while the capacitance values ​​of C2 and C3 gradually decrease. This is because the application of the tangential force causes the common electrode to displace along the positive direction of the y-axis, increasing the area of ​​C1 facing the common electrode and reducing the areas of C2 and C3 facing the common electrode. Therefore, the capacitance of C1 increases, while the capacitance of C2 and C3 decreases. The force applied in the negative direction of the Y-axis is the opposite. When a tangential force is applied along the positive direction of the x-axis, the capacitance of C2 and C3 decreases and increases due to the decrease and increase of the area of ​​the capacitance facing the common electrode caused by the tangential force applied along the positive direction of the x-axis. The capacitance of C1 remains unchanged because the area of ​​the common electrode facing the common electrode remains unchanged. When a tangential force is applied along the negative direction of the x-axis, the capacitances of C2 and C3 are opposite, while those of C1 are the same. Therefore, the sensor can well determine the direction of the tangential force.

[0107] Embodiment 5

[0108] This embodiment provides a method for force analysis based on the above-mentioned embodiment 2, specifically including: for large-area force analysis, we can use 2*2, 3*3, 4*4 and other structures according to the specific area size, apply vertical force and tangential force measurement respectively, each sensor unit can independently measure vertical force and tangential force, and then process the force information of each sensor to obtain the overall force information. The advantages of array arrangement are: full coverage: through array arrangement, the force area can be fully covered to provide continuous force distribution information; high precision: multiple sensor units work together to improve the accuracy and reliability of measurement; flexibility: array arrangement allows sensors to adapt to different shapes and sizes of force areas, providing flexible measurement solutions.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible capacitive three-dimensional force sensor, characterized in that: The sensor comprises, from bottom to top, a flexible substrate (1), a bottom electrode plate (2), a composite dielectric layer (3), a top electrode plate (4) and a packaging layer (5); at least three bottom electrode plates (2) are provided and arranged in a triangular shape; When the packaging layer (5) is acted upon by an external force, the force is sequentially transmitted to the top electrode plate (4) and the composite dielectric layer (3) through the packaging layer (5). The composite dielectric layer (3) is deformed under the action of the force, causing the capacitance value between the bottom electrode plate (2) and the top electrode plate (4) to change. By measuring the change in the capacitance value between different bottom electrodes (2) and the top electrode plate (4) before and after the force is applied, the direction and magnitude of the external force applied are analyzed and obtained.

2. The flexible capacitive three-dimensional force sensor according to claim 1, characterized in that: The plurality of bottom plates (2) are arranged in an isosceles triangle.

3. The flexible capacitive three-dimensional force sensor according to claim 1, characterized in that: The composite dielectric layer (3) comprises a planar layer (31) and a pyramid layer (32); the planar layer (31) is arranged between the bottom electrode plate (2) and the top electrode plate (4); and the pyramid layer (32) is arranged between the bottom electrode plate (2) and the planar layer (31) and / or between the top electrode plate (4) and the planar layer (31).

4. The flexible capacitive three-dimensional force sensor according to claim 3, characterized in that: Any of the pyramid layers (32) is provided with three pyramids, and any of the pyramids has a top end face and a bottom end face arranged along its own axial direction, and the area of ​​the top end face is smaller than the area of ​​the bottom end face.

5. The flexible capacitive three-dimensional force sensor according to claim 4, characterized in that: The top end surface is close to one side of the planar layer (31) and / or the top electrode plate (4); and the bottom end surface is close to one side of the bottom electrode plate (2) and / or the planar layer (31).

6. The flexible capacitive three-dimensional force sensor according to claim 3, characterized in that: The material of the prism is a PI flexible material modified by nano-barium titanate; The planar layer (31) is composed of raw materials including multi-walled carbon nanotubes, polydimethylsiloxane, a curing agent, sodium bicarbonate and isopropanol, with a mass ratio of 10:20:2:33:100; The material of the flexible substrate (1) and / or the encapsulation layer (5) is selected from one of polyimide, polydimethylsiloxane or polyester; The material of the bottom electrode plate (2) and / or the top electrode plate (4) is selected from one of gold, silver or copper.

7. A method for preparing a flexible capacitive three-dimensional force sensor as described in any one of claims 1 to 6, wherein the method comprises assembling in sequence from bottom to top a flexible substrate (1), a bottom electrode plate (2), a composite dielectric layer (3), a top electrode plate (4) and a packaging layer (5).

8. The method according to claim 7, characterized in that The bottom electrode plate (2) and / or the top electrode plate (4) is processed by one of magnetron sputtering, vacuum evaporation or electroplating.

9. Application of the flexible capacitive three-dimensional force sensor prepared by the method according to any one of claims 7 to 8 in force analysis.

10. A method for force analysis, characterized in that: Using the flexible capacitive three-dimensional force sensor as described in any one of claims 1 to 6 comprises: arranging the flexible capacitive three-dimensional force sensors in an array and performing wiring detection for detecting force analysis over a large area.

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