Rigid-flexible matrix digital controllable intelligent material and preparation method thereof

Abstract

The invention discloses a rigid-flexible matrix digital controllable intelligent material, and belongs to the technical field of novel intelligent materials. The rigid-flexible matrix digital controllable intelligent material is of a layered laminated structure: (1) an upper packaging layer; the upper electrode layer is provided with a plurality of interdigital electrodes extending in the first direction; the functional layer comprises a flexible matrix and a plurality of microcapsules dispersed in the flexible matrix, and each microcapsule comprises a shell and an electrorheological fluid inner core or other dielectric objects encapsulated in the shell; (4) a lower electrode layer; (5) preparing a lower packaging layer; wherein the electrode system is configured to be capable of independently applying an electric field to a specific unit in the matrix so as to reversibly change the mechanical property of the functional layer in the corresponding area. The giant electrorheological working fluid in the microcapsule generates reversible yield stress and viscoelastic modulus transition under the action of a local electric field, and an unselected area is kept in an initial rheological state; the electrode patterning enables a horizontal field and a vertical field to be integrated, and controlled field intensity distribution is formed at pixel intersection points.

Description

Technical Field

[0001] This invention relates to the field of novel smart materials technology, and in particular to a rigid-flexible matrix digitally controllable smart material and its preparation method. Background Technology

[0002] Flexible electroactive devices generally employ a stacked approach of surface protection - electrode - functional sandwich - electrode - functional layer - adhesive layer to strike a balance between mechanical compliance and electric field control capability. Structurally, these composite materials tend to sandwich the functional sandwich between two sets of staggered, interdigitated electrodes, achieving localized electric fields and regionalized responses by applying voltage to selected rows / columns of electrodes. A transparent or semi-transparent protective layer is then placed on the outermost layer to provide wear resistance and environmental protection. This framework provides a basic carrier for achieving matrix-based, pixel-level digitally addressable control, but it places higher demands on the interfacial compatibility, dielectric loss control, and environmental stability of the material system.

[0003] Humid and hot environments are one of the primary stress sources for flexible electroactive composite systems. In practical applications, water vapor permeation alters the dielectric environment of the functional interlayer and induces leakage and performance drift. Therefore, the water vapor transmission rate of the surface protective material becomes a key indicator for stability design. While general-purpose flexible protective layers, such as thermoplastic polyurethane (TPU), possess processing and mechanical advantages, their water vapor transmission rate is often high without densification measures, making it difficult to maintain low loss and low leakage under humid and hot loads. Under the same test aperture, the water vapor transmission rate of pure TPU samples is significantly higher than that of samples treated with densification strategies. Simply relying on thickening or thinning does not bring linear improvement; thick films may experience a decrease in barrier properties due to internal stress and micropore defects, while thin films show a significant increase in water vapor transmission rate due to shortened diffusion paths. Multilayer heterogeneous structures are prone to delamination under repeated deformation, and the electrode-functional layer interface is prone to failure under high-voltage electric fields. The uniformity of the dispersion of active materials in the functional layer, the integrity of microcapsules, and precise alignment processes all pose challenges to batch-to-batch consistency. This phenomenon indicates that macroscopic thickness cannot replace the regulation of microscopic density and interface quality. Summary of the Invention

[0004] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to address the common problems of insufficient barrier, high dielectric loss, poor batch-to-batch consistency, and unstable pixel-level addressable response of flexible electroactive matrix materials under humid and long-term bias conditions. The aim is to significantly reduce water vapor permeation, suppress the effects of interface polarization and leakage current, and improve repeatability by constructing a dense network of modified COF sheets that is highly compatible with the substrate on the TPU surface, and working in conjunction with the matrix structure of row and column cross-finger electrodes and their microcapsule sandwich layers, while maintaining the mechanical compliance of the device. This enables the matrix unit to achieve lower water vapor permeability and Tanδ, stable ε′, and maintain repeatable local electric field control and current-varying response under a unified test aperture, thereby achieving a comprehensive optimization of environmental stability and digital controllability.

[0005] To achieve the above objectives, the present invention provides a rigid-flexible matrix digitally controllable smart material and its preparation method.

[0006] A rigid-flexible matrix digitally controllable smart material, having a layered composite structure, comprising: (1) Upper encapsulation layer; (2) An upper electrode layer having a plurality of interdigitated electrodes extending along a first direction; (3) A functional layer comprising a flexible matrix and a plurality of microcapsules dispersed therein, the microcapsules comprising a shell and an electrorheological fluid core or other dielectric material encapsulated therein; (4) The lower electrode layer is provided with a plurality of interdigitated electrodes extending along the second direction, wherein the first direction and the second direction are perpendicular to each other, thereby forming an electrode system together with the upper electrode layer that can perform matrix addressing of the functional layer. (5) Lower encapsulation layer; The electrode system is configured to independently apply an electric field to specific units in the matrix to reversibly alter the mechanical properties of the corresponding functional layer.

[0007] The upper encapsulation layer and / or the lower encapsulation layer are made of thermoplastic polyurethane. The functional layer and the electrode layer, and / or the structural layers are bonded together by an optically transparent adhesive layer.

[0008] The functional layer is formed by solidifying a slurry of microcapsules and a flexible matrix; wherein the volume fraction of the microcapsules in the functional layer is 20-30 vol%. The optically transparent adhesive layer is 3M™ Optically Clear Adhesive 8211 with a thickness of 10-20µm.

[0009] It also includes a flexible sensor layer, which is disposed between the lower electrode layer and the lower encapsulation layer.

[0010] The electrorheological fluid core mentioned above includes, but is not limited to, giant electrorheological fluids. Electrorheological fluid systems based on inorganic particles, polymer particles, or liquid crystals can also be used, as long as their rheological properties can be reversibly controlled by an electric field. The electrode layer can be prepared by etching copper foil, printing conductive silver paste, or transferring two-dimensional materials such as graphene. The upper and lower electrode layers are fabricated on a flexible substrate using laser direct forming (LDS) technology, with an electrode thickness of 5-15µm and a linewidth / spacing of 20-100µm.

[0011] A further preferred rigid-flexible matrix digitally controllable smart material includes a structure of layers stacked sequentially from top to bottom: a) Thermoplastic polyurethane protective layer; b) A first interdigital electrode, wherein the first interdigital electrodes are arranged along the column direction to form a first interdigital electrode array; c) Microcapsule carrier layer, wherein microcapsules are dispersed in the microcapsule carrier layer, each microcapsule including a shell and a core, the core being a giant electrorheological fluid working fluid; d) Second interdigital electrode, the second interdigital electrode is arranged along the row direction to form a second interdigital electrode, and is orthogonally superimposed on the first interdigital electrode array in the projection, so as to form an addressable matrix unit together with the microcapsule carrier layer; e) Flexible sensors; and f) Adhesive layer.

[0012] The microcapsule carrier layer is sandwiched between the first interdigital electrode array and the second interdigital electrode array. By applying voltage to the selected row and column electrodes, a local electric field is generated in the corresponding matrix unit to reversibly control the rheological properties of the giant electrorheological fluid working fluid, thereby realizing digital regional control of the material.

[0013] The thermoplastic polyurethane protective layer is a transparent or semi-transparent layer used to protect the electrodes and microcapsules and provide surface abrasion resistance and protection.

[0014] The thickness of the thermoplastic polyurethane protective layer and the thickness of the adhesion layer are independently selected according to the application scenario, without affecting the limitation on the size of the microcapsule core and the thickness of the shell. The thickness of the thermoplastic polyurethane protective layer used in this invention is 20-80µm; The microcapsule support layer is formed by solidifying a slurry of microcapsules and a flexible matrix; the volume fraction of microcapsules in the microcapsule support layer is 20-30 vol%; and the thickness of the microcapsule support layer is 70-90 µm.

[0015] The first and second interdigital electrodes are fabricated on a flexible substrate using laser direct forming (LDS) technology. The electrode thickness is 5-15µm, and the line width and spacing are 20-100µm.

[0016] The first interdigital electrode array and the second interdigital electrode array are disposed on opposite sides of the microcapsule carrier layer.

[0017] The adhesive layer is made of thermoplastic polyurethane; the thickness of the adhesive layer is 20-60µm.

[0018] The structural layers are bonded together by an optically transparent adhesive layer.

[0019] The optically transparent adhesive layer is 3M™ Optically Clear Adhesive 8211 with a thickness of 10-20µm.

[0020] The method for preparing the thermoplastic polyurethane protective layer is as follows: Add 0.5-0.7g of 1,3,5-tricarboxymethyl phloroglucinol and 0.2-0.4g of p-phenylenediamine to a 20-50 mL mixture, wherein the mixture is composed of m-trimethylbenzene and 1,4-dioxane in a volume ratio of (1-3):(1-3). Then add 0.1-0.6 mL of 3-6M glacial acetic acid and heat to 100-120℃ for 48-72 h under a nitrogen atmosphere. After the reaction, ultrasonically clean and dry the mixture sequentially with dioxane, tetrahydrofuran, and methanol to obtain COF powder. Add 0.4-0.6g of COF powder to 80-100 mL of a mixed solution of N-methylpyrrolidone and isopropanol (N-methylpyrrolidone to isopropanol volume ratio of 5-7:1-3) and mix thoroughly. Ultrasonically treat the mixture at 20-25℃ and 100-200 W for 30-60 minutes. After processing at 5000-10000 rpm for 10-20 min, and then at 3000×g for 10-30 min to remove coarse agglomerates and collect the supernatant, the precipitate was collected after processing at 10000×g for 10-30 min. Finally, the precipitate was redispersed in 50-100 mL of ethanol to obtain a COF nanosheet dispersion for later use. Add 0.5-1g of 3,3,3-trifluoropropyltriethoxysilane to 30-80mL of 80-90wt% ethanol aqueous solution and mix well. Add 0.01-0.1mL of glacial acetic acid, then add the above COF nanosheet dispersion. Stir at room temperature and heat to 50-60℃ for 1-2h. After the reaction is complete, centrifuge, wash and dry to obtain modified COF. Polycaprolactone-type TPU was added to a mixed solution of N,N-dimethylformamide and methyl ethyl ketone and treated at 50-60℃ for 1-3 hours to obtain a polycaprolactone-type TPU solution with a solid content of 10-20wt%. Then, modified COF was added at a dry film content of 0.5-1wt%, and the mixture was stirred and degassed for 5-10 minutes. The TPU was then coated onto a PET carrier at a linear speed of 1-1.5 m / min with a gap of 50-80 µm and dried in stages: 50-60℃ for 5-10 minutes, 70-80℃ for 1-10 minutes, and 90-100℃ for 1-10 minutes. Finally, the TPU was stretched at 1.40× at 70-80℃ and held for 2-5 minutes to set the shape before cooling.

[0021] Modified COF nanosheets construct a tortuous diffusion path within TPU, reducing the penetration of moisture and small molecules, thereby stabilizing the dielectric environment of the microcapsules and GER, and suppressing leakage and performance drift under humid and hot conditions; simultaneously, they enhance scratch resistance and chemical abrasion resistance. After exposure to humid heat, the matrix maintains addressability and multi-level response, with high retention rates of yield stress and response time, and controlled growth in leakage and dielectric loss. The interlayer modulus gradient and the flexible adhesive layer absorb the thermal expansion and contraction mismatch, reducing stress concentration points and preventing peeling and cracking. No abnormal dielectric breakdown or partial discharge propagation occurs under long-term bias, and the breakdown field strength and creepage tolerance meet the predetermined application safety margin.

[0022] The microcapsule has an outer diameter of 50 μm ± 5 μm and a shell thickness of 2-4 μm.

[0023] The microcapsule preparation method includes the following steps: 1) Solution preparation: Weigh 9-11 g of toluene-2,4-diisocyanate and add it to 90-100 g of anhydrous cyclohexane. Stir well to obtain an organic shell solution. Weigh 1-2g of polyvinyl alcohol and add it to 90-110mL of water. Heat and stir at 80-100℃ until completely dissolved. After cooling to room temperature, add 4-6g of ethylenediamine and stir evenly to obtain the outer aqueous phase solution. 2) Microfluidic control of droplets and collection: Three syringes were respectively filled with giant electrorheological fluid, organic shell solution, and outer aqueous phase solution, and connected to the three inlets of the flow-focusing microfluidic chip; the flow rates were adjusted and stabilized under a microscope as follows: Giant electrorheological fluid: 1-6 mL per hour; Organic shell solution: 1-5 mL per hour; Outer aqueous phase solution: 10-20 mL per hour; A double emulsion droplet is formed in the chip channel, consisting of a core of giant electrorheological fluid, a middle organic layer containing diisocyanate, and an outer aqueous phase. The droplets are continuously produced and collected, and magnetically stirred to obtain an emulsion droplet suspension. 3) Interface aggregation and solidification: The collected emulsion droplet suspension was placed in a constant temperature water bath at 40-50℃ and shaken at 100-200 times per minute for 1-3 hours to obtain the initial microcapsules. 4) Cleaning and drying: The microcapsules were filtered through a 0.45-micron microporous membrane; they were rinsed alternately with water and anhydrous ethanol to remove unreacted monomers and polyvinyl alcohol residues; the pre-formed microcapsules were vacuum dried at 40-50℃ for 12-24 hours to obtain dried giant electrorheological fluid capsules; they were stored under sealed, light-proof and dry conditions.

[0024] The method for preparing the giant electrorheological fluid includes the following steps: 1) Place 300-500g of dimethyl silicone oil in an ice-water bath at 0-5℃ and stir for 5-10 minutes. Then add 9-11g of 4A molecular sieve, increase the speed and continue stirring. Then separate and remove the 4A molecular sieve. Add 1-3g of Span 80 and stir evenly. 2) Add 99-101g of urea-coated titanium-based inorganic material, shear and disperse, then increase the rotation speed to continue shearing; 3) Insert the ultrasonic probe into the mixture; set it to 800-1000W, turn it on for 1-5 seconds and turn it off for 1-3 seconds, for a total of 30-60 minutes; 4) Transfer to a vacuum planetary mixer, at 50-70℃ and -0.098MPa, degas at 10-50rpm / 50-60rpm for 60-120min, release the vacuum, discharge the material, and obtain a uniform and fine giant electrorheological fluid.

[0025] The method for preparing urea-coated titanium-based inorganic materials includes the following steps: S1 is prepared by adding 9-11g of titanium-based inorganic material to 800-1000mL of saturated urea solution at 60-70℃ and ultrasonically dispersing for 30-60min. S2 is heated to 80-90℃, stirred at 100-300rpm, connected to a vertical condenser for atmospheric distillation and collection of the distillate, and kept at a constant temperature for 1-6 hours to obtain a concentrated slurry; S3 cools the above concentrated slurry to 0-5°C and lets it stand for 12-24 hours to promote the recrystallization of urea on the surface of nanowires to form a coating layer. S4 filtration, ethanol washing, vacuum drying at 60-70℃ and -0.095MPa for 12-24h, and passing through a 100-200 mesh sieve to obtain urea-coated titanium-based inorganic material.

[0026] The titanium-based inorganic material mentioned therein is at least one of titanium dioxide and barium titanate.

[0027] The method for preparing the titanium dioxide includes the following steps: Step (1) Tetrabutyl titanate was added to NaOH aqueous solution and the temperature was controlled to obtain a milky white sodium titanate precursor suspension; Step (2) The above suspension is transferred into a polytetrafluoroethylene-lined high-pressure reactor and hydrothermally treated to obtain a white product; Step (3) Centrifuge the product and wash it until neutral to obtain hydrogen-form titanate nanowires; Step (4) Dry the hydrogen-form titanate nanowires and calcine them to obtain titanium dioxide.

[0028] This invention not only protects a rigid-flexible matrix digitally controllable smart material, but also its preparation method, variable stiffness devices containing the material, and their applications in various equipment. A method for preparing a rigid-flexible matrix digitally controllable smart material includes the following steps: Step 1: Provide the lower electrode layer; Step 2: Coat the lower electrode layer with a slurry containing the microcapsules and an uncured flexible matrix, and cure it to form a functional layer; Step 3: Provide an upper electrode layer and align and stack it with the functional layer so that the interdigitated directions of the upper and lower electrodes are perpendicular to each other; Step 4: Perform vacuum hot pressing lamination to bond the upper encapsulation layer, upper electrode layer, functional layer, lower electrode layer, and lower encapsulation layer into one unit.

[0029] The material structure of the present invention can be regarded as a digital mechanical pixel array. By addressing the row and column electrodes, pixel-based programming control of the surface stiffness of the material can be achieved, thereby dynamically changing its support force, shape self-adaptation ability and vibration transmission characteristics.

[0030] The present invention also provides a variable stiffness device comprising a variable stiffness device with a digitally controllable smart material of a rigid-flexible matrix.

[0031] The variable stiffness devices mentioned therein include, but are not limited to: variable stiffness joints for robots, support elements for wearable exoskeletons, actuation elements for active suspension in automobiles, adaptive energy-absorbing protective equipment, and force feedback interfaces for virtual reality devices.

[0032] The beneficial effects of this invention are: 1. Compared with existing technologies, the first and second interdigital electrodes are orthogonally arranged along columns or rows, with the microcapsule carrier layer sandwiched between them. A voltage is applied to selected columns and rows, creating a restricted and repeatable local high field in the intersection region. The giant electrorheological working fluid within the microcapsules undergoes reversible yield stress and viscoelastic modulus transitions under the local electric field, while unselected areas retain their initial rheological state. Copper electrodes are placed adjacent to the microcapsule layer, with a protective layer and adhesive layer providing insulation and mechanical support on the outside. Electrode patterning integrates horizontal and vertical fields, forming a controlled field strength distribution at pixel intersections.

[0033] 2. Compared to existing technologies, modified COF nanosheets construct a tortuous diffusion path within polyurethane, reducing the penetration of moisture and small molecules, thereby stabilizing the dielectric environment of the microcapsules and GER, and suppressing leakage and performance drift under humid heat; simultaneously, it improves scratch resistance and chemical abrasion resistance. After exposure to humid heat, the matrix retains addressability and multi-level response, with high retention rates of yield stress and response time, and controlled growth in leakage and dielectric loss. The mismatch between the interlayer modulus gradient and the flexible adhesive layer absorbs thermal expansion and contraction, reducing stress concentration points and preventing peeling and cracking. Under long-term bias, there is no abnormal dielectric breakdown or partial discharge propagation, and the breakdown field strength and creepage tolerance meet the predetermined application safety margin. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the rigid-flexible matrix digitally controllable smart material of the present invention. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0036] The thermoplastic polyurethane protective layer used in Example 1 is Elastollan® C85A, manufactured by BASF (BASF Polyurethanes GmbH). The polycaprolactone-type TPU used in Example 2 and the comparative example was Pearlthane™ 11T92E, manufactured by Lubrizol Advanced Materials, Inc. Flow-focused microfluidic chip (Suzhou Wenhao Microfluidics Technology Co., Ltd., Model: 3.2.002.00.036) - Focused PDMS chip with a channel depth of 50 μm and a linewidth of 100 μm, PDMS-glass slide bonding.

[0037] Other raw materials not mentioned are all common raw materials. The above content is only for the purpose of illustrating the present invention and should not be construed as a strict limitation of the present invention. Those skilled in the art can directly purchase the same / similar raw materials from the market or prepare them themselves.

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1 A rigid-flexible matrix digitally controllable smart material, comprising a structure stacked sequentially from top to bottom: a) Thermoplastic polyurethane protective layer; b) A first interdigital electrode, wherein the first interdigital electrodes are arranged along the column direction to form a first interdigital electrode array; c) Microcapsule carrier layer, wherein multiple microcapsules are dispersed in the microcapsule carrier layer, each microcapsule includes a shell and a core, the core being a giant electrorheological fluid working fluid, the outer diameter of the microcapsule is 50μm±5μm, and the thickness of the shell is 2-4μm; d) Second interdigital electrode, the second interdigital electrode is arranged along the row direction to form a second interdigital electrode array, and is orthogonally superimposed on the first interdigital electrode array in projection, thereby forming an addressable matrix unit together with the microcapsule carrier layer; e) Flexible sensors; and f) Adhesive layer.

[0040] The microcapsule carrier layer is sandwiched between the first interdigital electrode array and the second interdigital electrode array. By applying voltage to the selected row and column electrodes, a local electric field is generated in the corresponding matrix unit to reversibly control the rheological properties of the giant electrorheological fluid working fluid, thereby realizing digital regional control of the material.

[0041] The microcapsule support layer is formed by curing a slurry of microcapsules and a flexible matrix. The specific preparation method involves uniformly mixing N,N-dimethylformamide and methyl ethyl ketone at a mass ratio of 7:3 and heating to 50°C. Then, 12 wt% of TPU (Elastollan® C85A, manufacturer: BASF (BASF Polyurethanes GmbH)) is added and stirred continuously for 50 min. Next, 25 vol% of microcapsules are added, and the mixture is stirred for 6 min and degassed for 12 min. A 120 μm wet film is then applied via slit coating. Finally, the film is dried at 70°C for 45 min, then heated to 85°C for 90 min and dried to set the shape. The thickness of the microcapsule support layer is 80 µm. The thermoplastic polyurethane protective layer is made of thermoplastic polyurethane and has a thickness of 50±3 µm.

[0042] The first interdigital electrode array and the second interdigital electrode array are disposed on opposite sides of the microcapsule carrier layer.

[0043] The first and second interdigital electrodes are fabricated on a flexible substrate using a laser direct forming (LDS) process. The electrodes have a thickness of 10µm and a line width and spacing of 80µm.

[0044] The adhesive layer is made of thermoplastic polyurethane, Elastollan® C85A, manufactured by BASF (BASF Polyurethanes GmbH); the thickness of the adhesive layer is 50µm.

[0045] The structural layers are bonded together by an optically transparent adhesive layer.

[0046] The optically transparent adhesive layer is 3M™ Optically Clear Adhesive 8211 with a thickness of 10µm.

[0047] The microcapsule preparation method includes the following steps: 1) Solution preparation: Weigh 10 g of toluene-2,4-diisocyanate and add it to 90 g of anhydrous cyclohexane and stir until homogeneous to obtain an organic shell solution. Weigh 1g of polyvinyl alcohol (Kuraray POVAL™ 205) and add it to 99 mL of water. Heat and stir at 90 °C until completely dissolved. After cooling to room temperature, add 5g of ethylenediamine and stir until homogeneous to obtain the outer aqueous phase solution. 2) Microfluidic control of droplets and collection: Three syringes were respectively filled with giant electrorheological fluid, organic shell solution, and outer aqueous phase solution, and connected to the three inlets of the flow-focusing microfluidic chip; the flow rates were adjusted and stabilized under a microscope as follows: Giant electrorheological fluid: 5 mL per hour; Organic shell solution: 3 mL per hour; Outer aqueous phase solution: 15 mL per hour; Double emulsions are formed in the chip channel, with a core of giant electrorheological fluid, an organic layer containing diisocyanate in the middle, and an outer aqueous phase. They are continuously produced and collected in a beaker containing 50 mL of the outer aqueous phase solution. The emulsion is magnetically stirred at 200 rpm to prevent aggregation, resulting in an emulsion suspension. 3) Interface aggregation and solidification: The collected emulsion droplet suspension was placed in a 40 ℃ constant temperature water bath and shaken 100 times per minute for 2 hours to obtain the initial microcapsules; 4) Cleaning and drying: The microcapsules were filtered through a 0.45-micron microporous membrane; they were rinsed alternately with water and anhydrous ethanol to remove unreacted monomers and polyvinyl alcohol residues; the pre-formed microcapsules were vacuum dried at 40 °C for 12 h to obtain dried microcapsules; and stored under sealed, light-proof, and dry conditions.

[0048] The method for preparing the giant electrorheological fluid includes the following steps: 1) Add 500g of dimethyl silicone oil with a viscosity of 100cSt to a beaker and control the temperature in an ice-water bath at 5℃; mechanically stir at 500rpm for 5min, add 10g of 4A molecular sieve, increase the stirring speed to 2000rpm for 30min, then separate and remove the 4A molecular sieve; then add 3g of Span 80 and stir evenly. 2) Add 100g of urea-coated titanium dioxide nanowire powder, shear at 5000rpm for 10min, then increase to 12000rpm and shear for 30min; 3) Transfer the mixture to a wide-mouth container, insert the ultrasonic probe, set it to 800W, turn it on for 5 seconds and turn it off for 3 seconds, for a total of 30 minutes to complete dispersion and degassing; 4) Transfer to a vacuum planetary mixer, and degas for 60 minutes at 60℃ and -0.098MPa, with a revolution of 30 rpm and a rotation of 50 rpm. Release the vacuum, discharge the material, and obtain a uniform and fine giant electrorheological fluid.

[0049] The preparation method of urea-coated titanium dioxide nanowire powder includes the following steps: S1 At 65℃, 10g of anatase titanium dioxide nanowire powder was added to 1000mL of saturated urea solution and ultrasonically dispersed (600W, 3s on / 2s off) for 30min. S2 is heated to 80℃, stirred at 200rpm, connected to a vertical condenser for atmospheric distillation and collection of the distillate, and kept at a constant temperature for 5 hours to obtain a concentrated slurry. S3 cools the above concentrated slurry to 4°C and lets it stand for 12 hours to promote the recrystallization of urea on the surface of nanowires to form a coating layer. S4 filtration, ethanol washing, vacuum drying at 60℃ and −0.095MPa for 12h, and passing through a 200-mesh sieve to obtain urea-coated titanium dioxide nanowire powder.

[0050] The preparation method of the anatase titanium dioxide nanowire powder includes the following steps: Step (1) Add 240 mL of tetrabutyl titanate to 600 mL of 10 mol / L NaOH aqueous solution at a rate of 5 mL / min and mix well. Heat to 40 °C. After the addition is complete, continue stirring for 60 min to obtain a milky white sodium titanate precursor suspension. Step (2) The above suspension was transferred into a polytetrafluoroethylene-lined high-pressure reactor and heated to 180°C at 2°C / min and kept at that temperature for 24 hours. The heating was stopped and the mixture was allowed to cool naturally to room temperature to obtain a white product. Step (3) Transfer the product to a 500 mL centrifuge cup, centrifuge at 10000 rpm for 15 min, and discard the supernatant; add 400 mL of water and sonicate for 5 min, then centrifuge again, repeat until the supernatant pH=7; then disperse the precipitate in 2 L 0.1 M HCl solution, stir at 300 rpm for 2 h, and then wash with water until the supernatant pH=7 to obtain hydrogen-form titanate nanowires; Step (4) The hydrogen-type titanate nanowires were dried at 80°C for 24 hours, ground into a fine powder, placed in an alumina crucible, heated to 500°C at 5°C / min and held for 2 hours, then cooled to 200°C at 2°C / min and cooled to room temperature with the furnace to obtain anatase titanium dioxide nanowire powder.

[0051] Example 2 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thermoplastic polyurethane protective layer is different. The thermoplastic polyurethane protective layer is a modified polyurethane protective layer, and its preparation method is as follows: 0.63 g of 1,3,5-tricarboxymethyl phloroglucinol and 0.32 g of p-phenylenediamine were added to a 20 mL mixture, which consisted of m-trimethylbenzene and 1,4-dioxane in a 1:1 volume ratio. Then, 0.5 mL of 6M glacial acetic acid was added, and the mixture was heated to 120 °C for 72 h under a nitrogen atmosphere. After the reaction, the mixture was ultrasonically cleaned and dried sequentially with dioxane, tetrahydrofuran, and methanol to obtain COF powder. 0.5 g of COF powder was added to 100 mL of a mixed solution of N-methylpyrrolidone and isopropanol (N-methylpyrrolidone to isopropanol volume ratio 7:3), mixed thoroughly, and ultrasonically treated at 25 °C and 200 W for 60 min. This was followed by shearing at 8000 rpm for 10 min, treatment at 3000×g for 10 min to remove coarse agglomerates and collection of the supernatant, treatment at 10000×g for 30 min to collect the precipitate, and finally redispersed in 50 mL of water. mL of ethanol was used to obtain a COF nanosheet dispersion for later use; 1 g of 3,3,3-trifluoropropyltriethoxysilane was added to 50 mL of 90 wt% ethanol aqueous solution and mixed evenly. 0.1 mL of glacial acetic acid was added, followed by the above COF nanosheet dispersion. The mixture was stirred at room temperature and heated to 50 °C for 1 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the modified COF. Polycaprolactone-type TPU was added to a mixed solution of N,N-dimethylformamide and methyl ethyl ketone (N,N-dimethylformamide to methyl ethyl ketone volume ratio of 1:1) and treated at 55℃ for 2 hours. Then, modified COF was added at 0.8 wt% of the dry film, and the mixture was stirred to remove bubbles for 5 minutes. The TPU was then coated onto a PET carrier at a linear speed of 1.3 m / min and a gap of 80 µm. The TPU was dried in stages: 60℃ for 5 minutes, then heated to 80℃ for 8 minutes, and then heated to 95℃ for 5 minutes. Finally, the TPU was stretched at 1.40× at 80℃ and held for 2 minutes to set the shape. After cooling, the thickness was 50±3 µm.

[0052] Comparative Example 1 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thermoplastic polyurethane protective layer is different. The thermoplastic polyurethane protective layer is a modified polyurethane protective layer, and its preparation method is as follows: Polycaprolactone-type TPU was added to a mixed solution of N,N-dimethylformamide and butanone (N,N-dimethylformamide to butanone volume ratio 1:1), treated at 55℃ for 2 h, and stirred to remove bubbles for 5 min. Then it was coated on a PET carrier at a linear speed of 1.3 m / min and a gap of 80 µm, and dried in stages: dried at 60℃ for 5 min, dried at 80℃ for 8 min, dried at 95℃ for 5 min, and finally stretched at 1.40× at 80℃, held for 2 min to set the shape, and the thickness after cooling was 50±3 µm.

[0053] Comparative Example 2 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thermoplastic polyurethane protective layer is different. The thermoplastic polyurethane protective layer is a modified polyurethane protective layer, and its preparation method is as follows: 0.63 g of 1,3,5-tricarboxymethyl phloroglucinol and 0.32 g of p-phenylenediamine were added to a 20 mL mixture, wherein the mixture was composed of m-trimethylbenzene and 1,4-dioxane in a volume ratio of 1:1. Then, 0.5 mL of 6M glacial acetic acid was added, and the mixture was heated to 120 °C for 72 h under a nitrogen atmosphere. After the reaction, the mixture was ultrasonically cleaned and dried sequentially with dioxane, tetrahydrofuran, and methanol to obtain COF powder. 0.5 g of COF powder was added to a 100 mL mixed solution of N-methylpyrrolidone and isopropanol (N-methylpyrrolidone to isopropanol volume ratio of 7:3) and mixed evenly. The mixture was ultrasonically treated at 25 °C and 200 W for 60 min, followed by shearing at 8000 rpm for 10 min, treatment at 3000 × g for 10 min to remove coarse agglomerates and collection of supernatant, and treatment at 10000 × g for 30 min. The precipitate was collected and dried to obtain COF nanosheets for later use. Polycaprolactone-type TPU was added to a mixed solution of N,N-dimethylformamide and butanone (volume ratio of N,N-dimethylformamide to butanone was 1:1) and treated at 55℃ for 2 h. Then, COF nanosheets were added at 0.8 wt% of the dry film, and the mixture was stirred to remove bubbles for 5 min. The nanosheets were then coated onto a PET carrier at a linear speed of 1.3 m / min with a gap of 80 µm. The nanosheets were dried in stages: 60℃ for 5 min, 80℃ for 8 min, and 95℃ for 5 min. Finally, the nanosheets were stretched at 1.40× at 80℃ and held for 2 min to set the shape. After cooling, the thickness was 50±3 µm.

[0054] Comparative Example 3 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thermoplastic polyurethane protective layer is different. The thermoplastic polyurethane protective layer is a modified polyurethane protective layer, and its preparation method is as follows: 0.63 g of 1,3,5-tricarboxymethyl phloroglucinol and 0.32 g of p-phenylenediamine were added to a 20 mL mixture, which consisted of m-trimethylbenzene and 1,4-dioxane in a 1:1 volume ratio. Then, 0.5 mL of 6M glacial acetic acid was added, and the mixture was heated to 120 °C for 72 h under a nitrogen atmosphere. After the reaction, the mixture was ultrasonically cleaned and dried sequentially with dioxane, tetrahydrofuran, and methanol to obtain COF powder. 0.5 g of COF powder was added to 100 mL of a mixed solution of N-methylpyrrolidone and isopropanol (N-methylpyrrolidone to isopropanol volume ratio 7:3), mixed thoroughly, and ultrasonically treated at 25 °C and 200 W for 60 min. This was followed by shearing at 8000 rpm for 10 min, treatment at 3000×g for 10 min to remove coarse agglomerates and collection of the supernatant, treatment at 10000×g for 30 min to collect the precipitate, and finally redispersed in 50 mL of water. mL of ethanol was used to obtain a COF nanosheet dispersion for later use; 1 g of 3,3,3-trifluoropropyltriethoxysilane was added to 50 mL of 90 wt% ethanol aqueous solution and mixed evenly. 0.1 mL of glacial acetic acid was added, followed by the above COF nanosheet dispersion. The mixture was stirred at room temperature and heated to 50 °C for 1 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the modified COF. Polycaprolactone-type TPU was added to a mixed solution of N,N-dimethylformamide and butanone (volume ratio of N,N-dimethylformamide to butanone was 1:1) and treated at 55°C for 2 hours. Then, modified COF was added at 0.2 wt% of the dry film, and the mixture was stirred to remove bubbles for 5 minutes. The TPU was then coated onto a PET carrier at a linear speed of 1.3 m / min and a gap of 80 µm. The TPU was dried in stages: 60°C for 5 minutes, then heated to 80°C for 8 minutes, and then heated to 95°C for 5 minutes. Finally, the TPU was stretched at 1.40 × 100°C for 2 minutes to set the shape. After cooling, the TPU thickness was 50 ± 3 µm.

[0055] Comparative Example 4 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thermoplastic polyurethane protective layer is different. The thermoplastic polyurethane protective layer is a modified polyurethane protective layer, and its preparation method is as follows: 0.63 g of 1,3,5-tricarboxymethyl phloroglucinol and 0.32 g of p-phenylenediamine were added to a 20 mL mixture, which consisted of m-trimethylbenzene and 1,4-dioxane in a 1:1 volume ratio. Then, 0.5 mL of 6M glacial acetic acid was added, and the mixture was heated to 120 °C for 72 h under a nitrogen atmosphere. After the reaction, the mixture was ultrasonically cleaned and dried sequentially with dioxane, tetrahydrofuran, and methanol to obtain COF powder. 0.5 g of COF powder was added to 100 mL of a mixed solution of N-methylpyrrolidone and isopropanol (N-methylpyrrolidone to isopropanol volume ratio 7:3), mixed thoroughly, and ultrasonically treated at 25 °C and 200 W for 60 min. This was followed by shearing at 8000 rpm for 10 min, treatment at 3000×g for 10 min to remove coarse agglomerates and collection of the supernatant, treatment at 10000×g for 30 min to collect the precipitate, and finally redispersed in 50 mL of water. mL of ethanol was used to obtain a COF nanosheet dispersion for later use; 1 g of 3,3,3-trifluoropropyltriethoxysilane was added to 50 mL of 90 wt% ethanol aqueous solution and mixed evenly. 0.1 mL of glacial acetic acid was added, followed by the above COF nanosheet dispersion. The mixture was stirred at room temperature and heated to 50 °C for 1 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the modified COF. Polycaprolactone-type TPU was added to a mixed solution of N,N-dimethylformamide and butanone (volume ratio of N,N-dimethylformamide to butanone was 1:1) and treated at 55°C for 2 hours. Then, modified COF was added at 1.6 wt% of the dry film, and the mixture was stirred to remove bubbles for 5 minutes. The TPU was then coated onto a PET carrier at a linear speed of 1.3 m / min and a gap of 80 µm. The TPU was dried in stages: 60°C for 5 minutes, then heated to 80°C for 8 minutes, and then heated to 95°C for 5 minutes. Finally, the TPU was stretched at 1.40 × 100°C and held for 2 minutes to set the shape. After cooling, the thickness was 50 ± 3 µm.

[0056] Comparative Example 5 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thickness of the thermoplastic polyurethane protective layer is different. The thickness of the protective layer in Comparative Example 5 is 80±5 µm.

[0057] Comparative Example 6 A rigid-flexible matrix digitally controllable smart material is basically the same as that in Example 1, except that the thickness of the thermoplastic polyurethane protective layer is different. The thickness of the protective layer in Comparative Example 5 is 30±3 µm.

[0058] Test Example 1 The water vapor transmission rate of the thermoplastic polyurethane protective layer was tested according to the test method in GB / T21529-2008. Table 1

[0059] The thermoplastic polyurethane protective layer of each embodiment was used as the test sample, and the test was carried out in accordance with GB / T 1409-2006 "Recommended methods for measuring the permittivity and dielectric loss factor of electrical insulation materials at power frequency, audio frequency and high frequency (including meter wave wavelength)".

[0060] Table 2 As shown in Table 1-2, Example 2, based on Example 1, used 3,3,3-trifluoropropyltriethoxysilane to modify the surface of COF nanosheets, and added TPU matrix at 0.8 wt% of the dry film, resulting in a final protective layer thickness of 50 ± 3 µm. This group achieved a water vapor transmission rate of 2.35 g·day. -1 ·m -2 With Tanδ = 0.0048, ε′ = 3.28, and RSD = 1.4%, the surface modification is superior to the reference sample in all indicators, showing that the surface modification can achieve both a denser diffusion tortuous path and a lower interfacial polarization loss.

[0061] Comparative Example 1 did not involve the addition of COF and belonged to a filler-free TPU membrane system. The corresponding data are water vapor transmission rate = 5.20 g·day⁻¹·m⁻², Tanδ = 0.0105, ε′ = 3.40, and RSD = 2.5%. Compared with Example 2, both barrier properties and dielectric stability are lower, indicating that without the construction of a layered tortuous diffusion network and interface compatibility control, water vapor and loss channels are more easily formed.

[0062] Comparative Example 2: The addition of unmodified COF reduced the water vapor permeability to 4.10 g·day. -1 ·m -2 The values ​​were: Tanδ = 0.0089, ε′ = 3.45, and RSD = 2.2%. Compared with pure TPU, there is an improvement, but there is still a significant gap compared with Example 2. This suggests that without fluorosilane modification, the interfacial compatibility and dispersion uniformity are insufficient, which easily leads to micro-defects and polarization hotspots, thereby limiting the synergistic effect of barrier and loss optimization.

[0063] Comparative Examples 3-4 were prepared by adding different amounts of modified COF. With the modification implemented, the filler content was reduced to 0.2 wt%, and a water vapor transmission rate of 3.90 g·day was observed. -1 ·m -2 The Tanδ was 0.0078, ε′ was 3.38, and RSD was 1.9%. This represents an improvement over the unfilled or unmodified system, but due to the low loading, the continuous and effective sheet barrier is insufficient to sufficiently lengthen the water vapor diffusion path, and the interfacial synergy is not optimal. When the loading was increased to 1.6 wt%, the water vapor permeability increased to 4.60 g·day. -1 ·m -2 Tanδ increased to 0.0116, ε′ to 3.60, and RSD to 3.1%. High filling caused lamellar agglomeration and the formation of local conductive and polarization channels, which weakened the compactness of the barrier layer and aggravated dielectric loss and inter-sample fluctuations.

[0064] Comparative Examples 5-6 show that improving the coating thickness does not lead to linear and proportional micro-densification. Solvent residue, internal stress, and porosity control become more difficult, resulting in no significant benefit to barrier properties and dielectric stability. When the protective layer becomes thinner, the effective diffusion path is significantly shortened and the defect amplification effect becomes more pronounced, manifesting as a significant decline in barrier performance and an increase in dielectric loss, with repeatability deteriorating simultaneously.

[0065] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A rigid-flexible matrix digitally controllable smart material, characterized in that, It has a layered, stacked structure, including: (1) Upper encapsulation layer; (2) An upper electrode layer having a plurality of interdigitated electrodes extending along a first direction; (3) A functional layer comprising a flexible matrix and a plurality of microcapsules dispersed therein, the microcapsules comprising a shell and an electrorheological fluid core or other dielectric material encapsulated therein; (4) The lower electrode layer is provided with a plurality of interdigitated electrodes extending along a second direction, the second direction being perpendicular to the first direction, thereby forming an electrode system together with the upper electrode layer that can perform matrix addressing of the functional layer. (5) Lower encapsulation layer; The electrode system is configured to independently apply an electric field to specific units in the matrix to reversibly alter the mechanical properties of the corresponding functional layer.

2. The rigid-flexible matrix digitally controllable smart material as described in claim 1, characterized in that, The upper and / or lower encapsulation layers are made of thermoplastic polyurethane.

3. The rigid-flexible matrix digitally controllable smart material as described in claim 1, characterized in that, The functional layer and the electrode layer, and / or the structural layers are bonded together by an optically transparent adhesive layer.

4. The rigid-flexible matrix digitally controllable smart material as described in claim 1, characterized in that, It also includes a flexible sensor layer disposed between the lower electrode layer and the lower encapsulation layer.

5. The rigid-flexible matrix digitally controllable smart material as described in claim 1, characterized in that, The microcapsule preparation method includes the following steps: 1) Solution preparation: Toluene-2,4-diisocyanate was added to cyclohexane and stirred until homogeneous to obtain an organic shell solution. Weigh out polyvinyl alcohol and add it to water. Heat the mixture and cool it to room temperature. Then add ethylenediamine and stir until homogeneous to obtain an outer aqueous phase solution. 2) Microfluidic control of droplets and collection: Three syringes were filled with giant electrorheological fluid, organic shell solution, and outer aqueous phase solution, respectively, and connected to the three inlets of the flow-focusing microfluidic chip. A double emulsion droplet is formed in the chip channel, consisting of a core of giant electrorheological fluid, a middle organic layer containing diisocyanate, and an outer aqueous phase. The droplets are continuously produced and collected, and magnetically stirred to prevent aggregation, resulting in an emulsion droplet suspension. 3) Interface aggregation and solidification: The collected emulsion droplet suspension was placed in a constant temperature water bath for treatment to obtain pre-formed microcapsules. 4) Cleaning and drying: Store under the following conditions: filtration, washing, drying, sealing, protection from light, and dryness.

6. The rigid-flexible matrix digitally controllable smart material as described in claim 1 or 5, characterized in that, The preparation method of the giant electrorheological fluid includes the following steps: 1) At 0-5℃, mix dimethyl silicone oil with 4A molecular sieve, then separate and remove the 4A molecular sieve; then add Span 80 and stir evenly. 2) Add urea to coat titanium-based inorganic materials, and shear and disperse them to obtain the giant electrorheological fluid.

7. The rigid-flexible matrix digitally controllable smart material as described in claim 1, characterized in that, The electrorheological fluid core includes, but is not limited to, giant electrorheological fluid, and may also be an electrorheological fluid system based on inorganic particles, polymer particles or liquid crystal.

8. The rigid-flexible matrix digitally controllable smart material as described in claim 1, characterized in that, The upper and lower electrode layers are fabricated on a flexible substrate film using a laser direct forming process. The electrode thickness is 5-15 μm, and the line width and spacing are 20-100 μm.

9. A method for preparing a rigid-flexible matrix digitally controllable smart material as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Provide the lower electrode layer; Step 2: Coat the lower electrode layer with a slurry containing the microcapsules and an uncured flexible matrix, and cure it to form a functional layer; Step 3: Provide an upper electrode layer and align and stack it with the functional layer so that the interdigitated directions of the upper and lower electrodes are perpendicular to each other; Step 4: Perform vacuum hot pressing lamination to bond the upper encapsulation layer, upper electrode layer, functional layer, lower electrode layer, and lower encapsulation layer into one unit.

10. A variable stiffness device, characterized in that, It comprises a rigid-flexible matrix digitally controllable smart material as described in any one of claims 1-8.

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