All-silicone rubber dielectric elastomer actuator, method of manufacture and applications

Abstract

The application discloses a full-silicon rubber dielectric elastomer driver, a preparation method and application, the dielectric elastomer driver is sequentially from top to bottom a soft electrode layer, a dielectric composite film and a hard electrode layer, the soft electrode layer and the hard electrode layer form an asymmetric electrode structure; the dielectric composite film is prepared into a composite film, namely a CCSR film, by a solution blending method through silicon rubber SR and silane coupling modified carbon black, namely CTES@CB particles; under the action of an applied electric field, the dielectric composite film is deformed under the action of Maxwell electro-elastic force, the hard electrode layer limits the deformation of the corresponding side, and the soft electrode layer releases the deformation of the corresponding side, so that the driver generates enhanced out-of-plane driving displacement. The application provides a preparation technology of a high-dielectric-constant and high-breakdown-strength silicon rubber dielectric film, proposes a strategy of releasing normal deformation by an asymmetric electrode, obtains a DEA driver with enhanced out-of-plane deformation, and realizes continuous dynamic display of a Braille pattern.

Description

Technical Field

[0001] This invention belongs to the field of artificial muscles, specifically relating to an enhanced surface deformation driven by an all-silicone rubber dielectric elastomer and its applications in pumps, valves, artificial heart valves, Braille displays, etc. Background Technology

[0002] According to data released by the World Health Organization, there are approximately 36 million blind people worldwide. Due to visual impairment, blind people cannot learn and read like sighted people. They can only rely on touch, hearing, and residual vision to obtain information about their environment. Braille is a type of text specifically designed for the blind. Each character consists of six raised bumps arranged in three rows and two columns, which can be combined to form different characters. Blind people can obtain textual information from Braille books through tactile perception using their fingers. However, recent commercial paper Braille books are too cumbersome to use, and the content of the books cannot be refreshed, failing to help blind people obtain real-time information. Recently, various novel Braille display devices based on electroactive polymers and electronic technology have been developed, including dielectric elastomer drivers (DEAs) monitored by flexible thin-film transistors, temperature-controlled bistable electroactive polymer drivers, water-coupled dielectric elastomer drivers, and compact dielectric elastomer tubular drivers. Dielectric elastomers are electroactive polymers that can undergo large deformations under an electric field and immediately return to their original size after the electric field is removed. Braille devices made of dielectric elastomers are flexible and refreshable, providing better tactile and electrical feedback for real-time information.

[0003] Dielectric elastomer actuators are hailed as "artificial muscles." In certain fields, they can replace electric motors, solving driving problems that are difficult for electric motors to handle, while avoiding the size constraints and heat generation issues of electric motors. DEA (electrode-dielectric polymer-electrode) employs a sandwich structure, offering advantages such as light weight, large driving strain, fast response (millisecond-level), and high electromechanical conversion efficiency. The dielectric polymer (DE) accounts for over 90% of the weight of the DEA composite film, and its electromechanical coupling performance directly determines the electric driving behavior of the actuator.

[0004] Polyacrylate (PAA), silicone rubber (SR), and polyurethane (PU) are commonly used dielectric elastomers (DEAs). Among them, 3M's VHB4910 elastomer is a typical representative of PAA, but it suffers from high viscoelasticity, large mechanical losses, and severe electromechanical instability. PU molecules contain numerous hydrogen bonds, resulting in a high elastic modulus that limits large deformations. SR has low viscoelasticity, low mechanical losses, and good biocompatibility, making it an ideal matrix for commercial DEAs. However, SR has a low dielectric constant and low driving strain (<15%), limiting its practical applications.

[0005] To improve the driving performance of silicone rubber dielectric elastomers, various modification schemes have been proposed in the prior art, such as high-dielectric silicone rubber composite dielectric elastomer technology and silicone rubber dielectric elastomer technology using plasticizing modification or organic / inorganic synergistic modification. Patent CN113621236 discloses a high-performance composite dielectric elastomer, its preparation method, and its application. This mainly involves introducing high-dielectric fillers such as barium titanate and carbon-based materials into a silicone rubber matrix to increase the dielectric constant of the material and enhance the electro-deformation capability of the actuator. While this type of scheme can improve dielectric performance to some extent, it usually relies on high filler content, which can easily lead to decreased silicone rubber elasticity, increased elastic modulus, and increased dielectric loss. Furthermore, it may suffer from problems such as uneven filler dispersion and insufficient interfacial compatibility, thereby affecting the output performance, cycle stability, and service life of the actuator.

[0006] Patent CN115109417B discloses a high dielectric constant, low modulus, self-healing silicone rubber dielectric elastomer, its preparation method, and its applications. This method primarily reduces the material modulus and improves actuation sensitivity and deformation by introducing plasticizers, flexible modified components, or surface-modified nanofillers. While this approach can reduce the actuation voltage and improve actuation response to some extent, it often suffers from problems such as easy plasticizer migration, insufficient long-term material stability, decreased mechanical strength, and limited durability. It is difficult to simultaneously achieve high dielectric properties, low actuation voltage, excellent mechanical properties, and long-term reliability, thus still failing to meet the comprehensive performance requirements of all-silicone rubber dielectric elastomer actuators in applications such as refreshable Braille displays.

[0007] Therefore, it is still necessary to provide an all-silicone rubber dielectric elastomer actuator and its preparation method to improve its dielectric and driving performance while ensuring the material's flexibility and stability, thereby better meeting the application needs of fields such as refreshable Braille displays. Summary of the Invention

[0008] To address the problems of high viscoelasticity, high elastic modulus, large mechanical loss, and small driving strain in existing technologies, this invention provides an all-silicone rubber dielectric elastomer actuator that utilizes enhanced surface deformation for Braille display. CB is surface-modified using a silane coupling agent (cyanoethyltriethoxysilane, CTES) to obtain CTES@CB particles with a core-shell structure. Soft and hard electrodes are fixed on both sides of the CCSR film to suppress deformation on the hard electrode side and release deformation on the soft electrode side, highlighting surface deformation. The all-silicone rubber structural design, with covalent bonds between the electrodes and the substrate film, overcomes the mechanical mismatch problem between the constituent films and eliminates electrode failure and fatigue drawbacks, resulting in a DEA exhibiting high stability. Based on this, 2×3 and 3×4 DEA array actuators were fabricated, successfully achieving continuous dynamic display of Braille. This invention provides a fabrication technique for high dielectric constant and high breakdown strength silicone rubber dielectric films, proposes a strategy for releasing normal deformation through asymmetric electrodes, obtains a DEA actuator with enhanced surface deformation, and realizes continuous dynamic display of Braille patterns. It can be used in pumps, valves, artificial heart valves, Braille displays, etc.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A silicone rubber dielectric elastomer actuator comprises, from top to bottom, a soft electrode layer, a dielectric composite film, and a hard electrode layer, with the soft electrode layer and hard electrode layer forming an asymmetric electrode structure. The dielectric composite film is prepared by solution blending of silicone rubber SR and silane coupling agent CTES-modified carbon black CB (CTES@CB particles) to form a composite film, namely a CCSR film. Under the action of an applied electric field, the dielectric composite film deforms under the action of Maxwell electro-coercivity. The hard electrode layer restricts the deformation on its corresponding side, while the soft electrode layer releases the deformation on its corresponding side, thereby enabling the actuator to generate enhanced out-of-plane driving displacement.

[0011] Furthermore, the dielectric composite film has a thickness of 0.29-0.32 mm, an elastic modulus of 0.21-0.73 MPa, and a dielectric constant of 2.65-10.31.

[0012] Furthermore, the soft electrode layer was obtained by ultrasonically dispersing a single-walled carbon nanotube (SWCNT) dispersion and a silicone rubber (SR) prepolymer, followed by spraying. This layer, named SSR, had a thickness of 2.01–4.00 μm and a resistivity of 1.4–10.08 kΩ·sq. -1 The content of SWCNT is 0.2~1.8 phr, that is, the mass fraction of SWCNT in SR colloid is 0.2~1.8%; the hard electrode layer is a conductive silicone grease-coated electrode, named CSR, with a thickness of 20.57-31.00 μm and a resistance of 7.13-12.04 kΩ·sq.-1 .

[0013] Furthermore, the dielectric composite film is prepared as a CCSR film by solution blending of SR and silane coupling agent modified carbon black CB, i.e., CTES@CB particles. The specific steps are as follows:

[0014] (1) Preparation of CTES@CB particles: CB was surface modified by using silane coupling agent cyanoethyltriethoxysilane (CTES) to obtain CTES@CB particles with core-shell structure;

[0015] (2) Preparation of SR prepolymer: Dissolve SR colloid in tetrahydrofuran (THF), stir mechanically until uniform, add curing agent, and continue mechanical stirring to obtain SR prepolymer;

[0016] (3) Preparation of CCSR membrane: CTES@CB particles are added to the solution and ultrasonically dispersed. Then, SR prepolymer is added and mechanically stirred to mix evenly. The resulting mixture is poured into a circular polytetrafluoroethylene mold and heated in a vacuum drying oven until the solvent is completely evaporated to obtain CCSR membrane.

[0017] Furthermore, the amount of curing agent is 1%-2% of the mass of SR, and the content of CTES@CB particles is 0.5~2.5 phr, that is, the mass fraction of CTES@CB particles in SR colloid is 0.5~2.5%.

[0018] Furthermore, under AC signal conditions with an electric field strength higher than 23.57 V / μm and a frequency greater than 0.25 Hz, it can generate out-of-plane actuation displacements of 0–6.21 mm; the mechanical sensitivity is 12.61–15.78 MPa. -1 .

[0019] The present invention also provides a method for preparing the all-silicone rubber dielectric elastomer actuator as follows:

[0020] Step 1: Prepare SSR electrode paste. The electrode prepared from this SSR electrode paste is a soft electrode.

[0021] Step 2: Prepare CSR electrode colloid, and the electrode prepared from the CSR electrode colloid is a hard electrode;

[0022] Step 3, DEA preparation: The CCSR film is laid flat on a glass plate, covered with a circular mask, and the CSR electrode colloid is uniformly coated on the surface of the CCSR film to obtain a CSR|CCSR double layer film, which is then dried for later use; using the same mask, the SSR electrode paste is uniformly sprayed onto the CCSR film surface of the CSR|CCSR double layer film at a pressure of 120 kPa using a spraying process, and after complete curing, the asymmetric electrode DEA (CSR|CCSR|SSR) is obtained.

[0023] This invention also provides the application of the aforementioned all-silicone rubber dielectric elastomer actuator as a Braille display actuator. The Braille display includes a driving section and a control module. The driving section consists of the aforementioned all-silicone rubber dielectric elastomer actuator, a pressure regulating valve, an air pump, and a constant-pressure air chamber. The asymmetric electrode of the all-silicone rubber dielectric elastomer actuator is connected to the control module. The all-silicone rubber dielectric elastomer actuator is fixed above the constant-pressure air chamber for pre-deformation. The constant-pressure air chamber is connected to the pressure regulating valve and the air pump. The pressure regulating valve controls the air pressure to 600 Pa to maintain a constant air pressure in the air chamber. The control section consists of a signal generation unit, a power amplifier, a programmable logic controller (PLC), a digital output module (IO terminals), and a six-channel relay module. The signal generated by the signal generation unit is amplified and then enters the control module. The programmable logic controller (PLC) generates corresponding multi-channel digital control signals in a loop according to the preset logic and sends them to the digital output module (IO terminal) to drive two sets of six-channel relay modules respectively. Each relay acts as a high-voltage switch controlled by a low-voltage signal, accurately and independently driving the corresponding DEA small driver to complete the continuous and dynamic display of Braille patterns.

[0024] Furthermore, the all-silicone rubber dielectric elastomer actuator is a CCSR film array DEA fabricated using 2×3 and 3×4 circular array masks with ϕ=5 mm and a spacing of 2 mm.

[0025] This invention modifies the SR (Silicone Resin) membrane by constructing a core-shell structure filler to significantly improve its dielectric properties and driving capability. Based on this, soft electrodes (single-walled carbon nanotube-modified silicone rubber) and hard electrodes (carbon black-modified silicone rubber) are constructed on both sides of the composite film, forming an asymmetric electrode structure all-silicone rubber DEA. Further, 2×3 and 3×4 array actuators are constructed to achieve continuous dynamic display of Braille.

[0026] The advantages of this invention compared to existing technologies are as follows:

[0027] 1. Compared to pure silicone rubber film (pure SR), the composite film prepared in this invention has a higher dielectric constant and higher mechanical sensitivity; the composite film electric actuator prepared in this invention, due to the improved mechanical properties, dielectric properties, and breakdown strength of the composite film, can generate stable and large displacement drive under low electric fields. Specifically:

[0028] (1) The dielectric properties of the CCSR composite film proposed in this invention are significantly improved, and the dielectric constant is greatly improved compared with that of silicone rubber, which is beneficial to the electrical actuation performance of the CCSR composite film electric actuator under low voltage.

[0029] (2) The mechanical properties of the CCSR composite film proposed in this invention are significantly improved. Compared with the pure SR composite film, it is beneficial to the stability and fast recovery capability of the CCSR composite film electric actuator. It has high mechanical sensitivity and high breakdown voltage.

[0030] (3) The CCSR composite film electric actuator proposed in this invention can work stably under low electric field and respond to changes in frequency and voltage, and has good controllability.

[0031] 2. This invention fixes soft and hard electrodes on both sides of the CCSR film, respectively, suppressing deformation on the hard electrode side and releasing deformation on the soft electrode side, thus highlighting surface deformation. DEA achieves significant surface deformation.

[0032] 3. This invention has fabricated 2×3 and 3×4 small DEA array drivers, successfully realizing continuous dynamic Braille display, and verifying the application prospects of asymmetric electrode DEA in pumps, valves, artificial heart valves, Braille displays and other fields. Attached Figure Description

[0033] Figure 1 It serves as the driver and testing platform for DEA.

[0034] Figure 2 For driving and Braille display platform.

[0035] Figure 3 Infrared spectral curves of the CTES@CB and CCSR composite film.

[0036] Figure 4 Mechanical property analysis of CCSR membrane.

[0037] Figure 5 Comparison of Young's modulus for DEA multilayer films.

[0038] Figure 6 The dielectric properties curve of the CCSR film is shown.

[0039] Figure 7 This is a scanning electron microscope image of the CCSR composite film.

[0040] Figure 8 Displacement curves for CCSR composite membrane actuators.

[0041] Figure 9 It is a CCSR film DEA array device.

[0042] Figure 10 This is the DEA array control module.

[0043] Figure 11 Braille patterns driven by asymmetric electrodes, consisting of 2×3 or 3×4 DEA actuators.

[0044] 1 is a programmable logic controller (PLC) based on preset logic, 2 is a digital output module (IO terminal), 3 is a six-channel relay, 4 is a CCSR membrane DEA array, 5 is a constant pressure air chamber, 6 is a pressure regulating valve, and 7 is an air pump. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.

[0046] Carbon black (CB, 30-40 nm) was purchased from Suzhou Shengernuo Technology Co., Ltd.; silicone rubber (SR, 1688) and curing agent were purchased from Jinan Xingfeilong Chemical Co., Ltd.; 2-cyanoethyltriethoxysilane (CTES) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; oily single-walled carbon nanotube dispersion (SWCNT, 0.4 wt%) was purchased from Dongguan Kelude New Energy Technology Co., Ltd.; CB particle-filled conductive silica gel (LR3162 A / B) was purchased from Wacker Chemie; dibutyltin dilaurate (DBTDL) was purchased from Sigma Aldrich; tetrahydrofuran (THF), anhydrous ethanol and other reagents were all of analytical grade.

[0047] The core-shell structure of CTES@CB particles was observed using a high-resolution transmission electron microscope (JEM-2100, Japan). Fourier transform infrared spectroscopy (FTIR IS50, USA) and Raman spectroscopy (inVia, UK) were used to determine the relevant chemical composition. The dynamic viscoelasticity of the membrane was measured using a rotational rheometer (HAAKEMARS, USA) at frequencies ranging from 0.1 to 40 Hz. The static viscoelasticity and mechanical properties of the membrane were tested using a universal tensile testing machine (UTM2202, China). Stress relaxation was performed at a constant strain of 200%, and strain relaxation was performed under a constant stress of 50 g for 20 min. Conductivity parameters were measured using a four-probe conductivity meter (RTS-9, China). The dielectric parameters of the CCSR composite membrane were measured using an impedance analyzer (Ailent 4294A, USA). The microstructure of the DEA was observed using a field emission scanning electron microscope (JSM-7001F, Japan).

[0048] Example 1

[0049] Preparation of pure SR membrane (sample 1)

[0050] The SR prepolymer was poured into a circular polytetrafluoroethylene mold (ϕ = 90 mm) and vacuum-sealed.

[0051] After removing the bubbles, the film was vulcanized at room temperature for 24 h to obtain a pure SR composite film, which was designated as sample 1.

[0052] Example 2

[0053] The preparation method of the CCSR membrane in this embodiment is as follows:

[0054] (1) Preparation of CTES@CB particles

[0055] 1.5 g CTES, 3 g CB, and 2 drops of dibutyltin dilaurate (DBTDL) catalyst were continuously added to 30 mL THF solution, and the mixture was magnetically stirred at 60 °C for 10 h to obtain black CTES@CB. The mixture was washed with THF and dried under vacuum for later use.

[0056] (2) Preparation of SR prepolymer

[0057] Add 2.5 g of SR colloid to 6.0 mL of THF solution, stir mechanically until homogeneous, then add 0.05 g of curing agent and continue stirring mechanically to obtain SR prepolymer for later use.

[0058] (3) Preparation of CCSR membrane (sample 2)

[0059] Add 0.013 g of CTES@CB particles to 10 mL of THF solution, disperse by ultrasonication, then add SR prepolymer (containing 2.5 g of SR colloid) and mix thoroughly by mechanical stirring. Pour the mixture into a circular polytetrafluoroethylene mold (ϕ = 90 mm), remove air bubbles under vacuum, and vulcanize at room temperature for 24 h to obtain a black CCSR film with a mass fraction of 0.5 phr (the mass fraction of CTES@CB particles to SR colloid) and a thickness between 290-320 μm, designated as Sample 2.

[0060] Example 3

[0061] The preparation method of the CCSR membrane in this embodiment is as follows:

[0062] (1) The preparation of CTES@CB particles is the same as in Example 2.

[0063] (2) The preparation of SR prepolymer is the same as in Example 2.

[0064] (3) Preparation of CCSR film (sample 3): 0.023 g CTES@CB particles were added to 10 mL THF solution and ultrasonically dispersed. Then, SR prepolymer (containing 2.5 g SR colloid) was added and mechanically stirred until homogeneous. The mixture was poured into a circular polytetrafluoroethylene mold (ϕ = 90 mm), vacuumed to remove air bubbles, and then vulcanized at room temperature for 24 h to obtain a black CCSR film with a mass fraction of 1 phr and a thickness between 290-320 μm, which was designated as sample 3.

[0065] Example 4

[0066] The preparation method of the CCSR membrane in this embodiment is as follows:

[0067] (1) The preparation of CTES@CB particles is the same as in Example 2.

[0068] (2) The preparation of SR prepolymer is the same as in Example 2.

[0069] (3) Preparation of CCSR film (sample 4): 0.038 g CTES@CB particles were added to 10 mL THF solution, ultrasonically dispersed, and then SR prepolymer (containing 2.5 g SR colloid) was added and mechanically stirred until homogeneous. The mixture was poured into a circular polytetrafluoroethylene mold (ϕ = 90 mm), vacuumed to remove air bubbles, and then vulcanized at room temperature for 24 h to obtain a black CCSR film with a mass fraction of 1.5 phr and a thickness between 290-320 μm, designated as sample 4. Specifically, the array CCSR film was prepared by adding 0.03 g CTES@CB particles to 10 mL THF solution, ultrasonically dispersing, adding SR prepolymer (containing 2.0 g SR colloid), and mechanically stirring until homogeneous. The mixture was poured into a circular polytetrafluoroethylene mold (ϕ = 90 mm), vacuumed to remove air bubbles, and then vulcanized at room temperature for 24 h to obtain a black CCSR film with a mass fraction of 1.5 phr and a thickness between 150-170 μm.

[0070] Example 5

[0071] The preparation method of the CCSR membrane in this embodiment is as follows:

[0072] (1) The preparation of CTES@CB particles is the same as in Example 2.

[0073] (2) The preparation of SR prepolymer is the same as in Example 2.

[0074] (3) Preparation of CCSR film (sample 5): 0.051 g CTES@CB particles were added to 10 mL THF solution and ultrasonically dispersed. Then, SR prepolymer (containing 2.5 g SR colloid) was added and mechanically stirred until homogeneous. The mixture was poured into a circular polytetrafluoroethylene mold (ϕ = 90 mm), vacuumed to remove air bubbles, and then vulcanized at room temperature for 24 h to obtain a black CCSR film with a mass fraction of 2 phr and a thickness between 290-320 μm, which was designated as sample 5.

[0075] Example 6

[0076] The preparation method of the CCSR membrane in this embodiment is as follows:

[0077] (1) The preparation of CTES@CB particles is the same as in Example 2.

[0078] (2) The preparation of SR prepolymer is the same as in Example 2.

[0079] (3) Preparation of CCSR film (sample 6): 0.064 g CTES@CB particles were added to 10 mL THF solution and ultrasonically dispersed. Then, SR prepolymer (containing 2.5 g SR colloid) was added and mechanically stirred until homogeneous. The mixture was poured into a circular polytetrafluoroethylene mold (ϕ = 90 mm), vacuumed to remove air bubbles, and then vulcanized at room temperature for 24 h to obtain a black CCSR film with a mass fraction of 2.5 phr and a thickness between 290-320 μm, which was designated as sample 6.

[0080] 1. Chemical structure analysis of CTES@CB and CCSR membranes

[0081] The surface of CB is rich in active hydroxyl groups, which can undergo a silane coupling reaction with CTES to graft a silane molecular film onto the CB surface, forming core-shell structured CTES@CB particles. Figure 3 a). High-resolution TEM showed that the CB particles were well dispersed, with diameters between 65-78 nm; the particle surface was covered with an organic film approximately 3 nm thick, exhibiting distinct core-shell structure characteristics. Figure 3 a) FTIR was used to monitor the formation process of CTES@CB. It showed that the CB particles contained a large number of active groups: 3674, 1742, and 1657 cm⁻¹. -1 Absorption peaks for the stretching vibrations of -OH, -COOH, and C=C bonds appeared at 2250 cm⁻¹, respectively. After CTES modification, the stretching vibration peak of the OH bond disappeared, and the peak at 2250 cm⁻¹ disappeared. -1 A new sharp absorption peak is observed, which is a characteristic absorption peak of the C≡N bond. This indicates that CTES has been grafted onto the CB surface.

[0082] The infrared spectrum of the CCSR composite film not only showed the characteristic peaks of SR, but also the characteristic peaks of CTES@CB particles. Figure 3 b). Moreover, the intensity of its characteristic peaks increases with the increase of CTES@CB. For example, the relative peak area of ​​the C≡N bond (2250 cm⁻¹) -1 Peak area / 704 cm -1 The peak area gradually increased from 0.64 for the CCSR0.5 film to 0.87 for the CCSR2.5 film, suggesting that CTES@CB particles have filled the interior of the SR.

[0083] 2. Mechanical property analysis of CCSR membrane

[0084] Tensile tests demonstrated the chemical compatibility between CTES@CB particles and the SR matrix. Tensile test results for the CCSR film showed that both the tensile strength and tensile modulus increased continuously with increasing CTES@CB content. Figure 4 For example, the breaking strength and tensile modulus of sample 4 were 2.76 MPa and 0.43 MPa, respectively, while those of sample 6 increased to 3.48 MPa and 0.73 MPa, representing increases of 26.09% and 69.77%, respectively. Since rigid fillers inevitably disrupt the continuity and flexibility of the matrix polymer chains, the elongation at break decreases with increasing CTES@CB particle content. However, the uniquely uniformly distributed crosslinking sites within silicone rubber effectively suppress stress concentration, and all CCSR films maintained high elongation at break; for example, sample 4 exhibited an elongation at break of 448%.

[0085] 3. Analysis of the electrical and mechanical properties of asymmetric electrodes

[0086] Preparation of SSR electrode paste: Add 3.0 g of SWCNT dispersion to 10.0 mL of THF solution, and after ultrasonic dispersion, pour in the SR prepolymer (containing 1.2 g of SR colloid). After mechanical stirring, an SSR electrode paste with a mass fraction of 1.0 phr (the mass fraction of SWCNT in SR colloid) is obtained. Using the same method, SSR electrode pastes with mass fractions of 0.2, 0.6, 1.4, and 1.8 phr are obtained. The electrodes prepared from these pastes are soft electrodes, denoted as SSR0.2, SSR0.6, SSR1.0, SSR1.4, and SSR1.8, respectively.

[0087] Preparation of CSR electrode colloid: The hard electrode was prepared using two-component conductive silicone. 10.0 g of each of the conductive silicone components A and B were weighed, diluted with 30.0 g of silicone oil, mechanically stirred at room temperature for 1 h, and then vacuum-treated to remove air bubbles, yielding the CSR electrode colloid.

[0088] The CCSR film prepared in Example 4 was laid flat on a glass plate, and a circular mask (ϕ=25 mm) was placed on top of it. The CSR electrode colloid was uniformly coated on the surface of the CCSR film to obtain a CSR|CCSR bilayer film, which was then dried for later use. Using the same mask, the SSR electrode paste with different SWCNT mass fractions was uniformly sprayed onto the CCSR film surface of the CSR|CCSR bilayer film at a pressure of 120 kPa using a spraying process. After complete curing, the asymmetric electrode DEA (CSR|CCSR|SSR) was obtained.

[0089] As the SWCNT content increases, the sheet resistance of the SSR film electrode gradually decreases, from 10.08 kΩ·sq -1 Reduced to 1.4 kΩ·sq -1Among them, when the SWCNT content is 1 phr, the SSR film exhibits ideal conductivity, with a sheet resistivity of 2.37 kΩ·sq. -1 The sheet resistivity of the CSR film is 10.04 kΩ·sq. -1 The modulus of the CSR membrane with a single-sided loading on the CCSR substrate was 4.25 times that of the SSR membrane. Furthermore, based on sample 4, the Young's modulus of the CSR membrane with a single-sided loading on the CCSR substrate was 1.75 times that of the SSR membrane with a single-sided loading on the CCSR substrate, and the modulus of the CSR membrane with a double-sided loading on the CCSR substrate was 2.12 times that of the SSR membrane with a double-sided loading on the CCSR substrate. Figure 5 The SSR film contains 1.0 phr of SWCNT (the mass fraction of SWCNT in the SR colloid). This suggests that the Young's modulus of the CSR film is much higher than that of the SSR film, indicating a mechanical and electrical asymmetry between the electrodes on both sides of the CSR|CCSR|SSR film. The electrode resistance and mechanical properties of the CCSR multilayer film are summarized in Tables 1 and 2 below:

[0090] Table 1. Summary of Electrode Resistance

[0091]

[0092] Table 2. Summary of Mechanical Properties of CCSR Multilayer Films

[0093]

[0094] 4. Dielectric property analysis of CCSR film

[0095] With the increase of CTES@CB content, the dielectric constant of CCSR film continues to increase. Figure 6 a) The data increased from 2.65 in sample 1 to 10.31 in sample 6, an increase of 2.89 times. Reasons: 1) Under the applied electric field, the charge accumulated between CB and SR undergoes interfacial polarization, generating a large interfacial capacitance; 2) The cyano group has a large dipole moment (~3.5 D), much higher than common polar groups such as hydroxyl and ester groups, resulting in strong induced orientation polarization. All dielectric loss values ​​are limited (< 0.35 @ 1 kHz), reducing the risk of thermal and electrical breakdown.

[0096] With the increase of CTES@CB content, the breakdown strength of the composite film continuously improved, with sample 4 reaching the maximum breakdown strength of 51.74 V / μm. Figure 6 The increase in breakdown strength is due to the siloxane coating on the CB surface. The CTES shell not only improves the chemical compatibility between the filler and the matrix, but also prevents the agglomeration of CB particles and reduces the leakage current between CB particles.

[0097] Example 7

[0098] This embodiment describes a method for preparing a silicone rubber dielectric elastomer actuator (DEA), and the steps are as follows:

[0099] Step 1: Preparation of SSR electrode paste. Add 3.0 g of SWCNT dispersion to 10.0 mL of THF solution, and after ultrasonic dispersion, pour in the SR prepolymer (containing 1.2 g of SR colloid). After mechanical stirring until homogeneous, the SSR electrode paste is obtained. The electrode prepared from this SSR electrode paste is a soft electrode.

[0100] Step 2: Preparation of CSR electrode colloid. The hard electrode is prepared using two-component conductive silicone. 10.0 g of each of the conductive silicone components A and B are weighed, diluted with 30.0 g of silicone oil, mechanically stirred at room temperature for 1 h, and then vacuum-treated to remove air bubbles, yielding the CSR electrode colloid.

[0101] Step 3: Prepare DEA.

[0102] The CCSR film prepared in Example 4 was laid flat on a glass plate, and a circular mask (ϕ=25 mm) was placed on top of it. The CSR electrode colloid was uniformly coated on the surface of the CCSR film to obtain a CSR|CCSR bilayer film, which was then dried for later use. Using the same mask, the SSR electrode paste was uniformly sprayed onto the CCSR film surface of the CSR|CCSR bilayer film at a pressure of 120 kPa using a spraying process. After complete curing, the asymmetric electrode DEA (CSR|CCSR|SSR) was obtained.

[0103] The cross-sectional morphology of the CCSR composite DEA film was observed using scanning electron microscopy. Due to the difference in conductivity, the three-layer DEA film (CSR|CCSR|SSR) exhibits an asymmetric sandwich structure: the top layer is an SSR electrode with a thickness of 2.86 μm; the middle layer is a CCSR1.5 composite film (sample 4) with a thickness of 297 μm; and the bottom layer is a CSR electrode with a thickness of 28.57 μm. Figure 7 a). Cross-sectional view of CCSR ( Figure 7 b) shows that due to the CTES coating, a large number of CTES@CB particles are uniformly dispersed inside the CCSR film, with no obvious aggregation between particles, and no obvious pores or defects were observed. From the planar and cross-sectional views of the SSR electrode ( Figure 7 As shown in c-7e, a large number of SWCNTs are intertwined, forming a three-dimensional conductive network; SR acts as a binder, firmly bonding the SWCNTs to the base film. From the planar and cross-sectional views of the CSR electrode ( Figure 7 (f-7h) shows that: irregular CB particles are uniformly distributed in the CSR electrode; a large number of CB particles approach each other to form multiple current channels.

[0104] Comparing the cross-sectional SEM images of the upper SSR electrode and the lower CSR electrode, the upper SSR electrode shows a sparse arrangement of SWCNTs with numerous voids, resulting in a lower elastic modulus and classifying it as a soft electrode. The lower electrode, on the other hand, is dense and thick, leading to a higher elastic modulus and classifying it as a hard electrode. Since both the SR in the electrode and the SR in the substrate film are siloxanes, they exhibit high chemical compatibility. Therefore, regardless of the SSR|CCSR interface (…),… Figure 7 d), or the CSR|CCSR interface ( Figure 7 g) All interface connections are dense and show no signs of detachment. This dense structure is beneficial for stable electromechanical behavior during DEA driving.

[0105] Example 8

[0106] Preparation process of symmetrical electrode DEA

[0107] Step 1: The preparation of the SSR electrode paste is the same as in Example 7.

[0108] Step 2: The preparation of the CSR electrode colloid is the same as in Example 7.

[0109] Step 3: Prepare the symmetrical electrode DEA.

[0110] The CCSR films prepared in Examples 1-6 were laid flat on a glass plate, and a circular mask (ϕ=25 mm) was placed on top of them. CSR electrode colloid was uniformly coated on the surface of the CCSR film to obtain a CSR|CCSR bilayer film, which was then dried for later use. Using the same mask, CSR electrode colloid was coated on the surface of the CCSR film of the CSR|CCSR bilayer film. After complete curing, a symmetrical electrode DEA (CSR|CCSR|CSR) was obtained.

[0111] The CCSR films prepared in Examples 1-6 were laid flat on a glass plate, and a circular mask (ϕ=25 mm) was placed on top of them. The SSR electrode paste was uniformly sprayed onto the surface of the CCSR film using a spraying process at a pressure of 120 kPa. After complete curing, an SSR|CCSR double-layer film was obtained. Using the same mask, the SSR electrode paste was uniformly sprayed onto the surface of the CCSR film of the SSR|CCSR double-layer film using a spraying process at a pressure of 120 kPa. After complete curing, a symmetrical electrode DEA (SSR|CCSR|SSR) was obtained.

[0112] like Figure 8As shown, to analyze the electro-actuation performance of the CCSR composite film electro-actuator, a CCSR film DEA with an electrode diameter (ϕ=25mm) was prepared. This CCSR film DEA4 was fixed above a constant pressure chamber 5 for pre-deformation. The constant pressure chamber 5 is connected to a pressure regulating valve 6 and an air pump 7. The pressure regulating valve 6 controls the air pressure to 600 Pa to maintain a constant chamber pressure. With the increase of CTES@CB content, the displacement output of the three DEAs all showed a trend of first increasing and then decreasing. Figure 8 For example, under an electric field excitation of 33.67 V / μm, the output displacement of the asymmetric electrode-driven DEA increased from 3.2 mm in sample 1 to 6.21 mm in sample 4, and then decreased to 5.61 mm in sample 6. Compared with the output displacements of the three electrode DEAs in sample 1 (2.33, 2.83, 3.20 mm), the output displacement of the film DEA in sample 4 increased by 84.98%, 69.96%, and 94.06%, respectively. According to the spherical cap model, the surface deformation displacement of the DEA can be converted into area strain. Correspondingly, under an electric field of 33.67 V / μm, the area deformation of the three electrode DEAs in sample 4 was 42.97%, 28.07%, and 24.99%, respectively, which increased by 32.41%, 14.37%, and 12.77% compared with the film DEA in sample 1 (10.56%, 13.70%, and 16.22%). The data are shown in the table below:

[0113] Table 3. Summary of the driving performance of CCSR membrane DEA

[0114]

[0115] Example 9

[0116] This embodiment describes a method for fabricating a DEA array device using an all-silicone rubber dielectric elastomer actuator. The steps are as follows:

[0117] Step 1: Preparation of SSR electrode paste. Add 3.0 g of SWCNT dispersion to 10.0 mL of THF solution, and after ultrasonic dispersion, pour in the SR prepolymer (containing 1.2 g of SR colloid). After mechanical stirring until homogeneous, the SSR electrode paste is obtained. The electrode prepared from this SSR electrode paste is a soft electrode.

[0118] Step 2: Preparation of CSR electrode colloid. The hard electrode was prepared using two-component conductive silicone (LR3162 A / B, Wacker Chemie). 10.0 g of each of the conductive silicone components A and B were weighed, diluted with 30.0 g of silicone oil, mechanically stirred at room temperature for 1 h, and then vacuum-treated to remove air bubbles, yielding the CSR electrode colloid.

[0119] Step 3: Fabricate the DEA array device.

[0120] The CCSR film (150-170 μm thick) prepared in Example 4 was laid flat on a glass plate, and covered with 2×3 and 3×4 circular array masks (ϕ=5 mm) with a spacing of 2 mm. CSR electrode colloid was uniformly coated onto the surface of the CCSR film to obtain a CSR|CCSR bilayer film, which was then dried for later use. Using the same mask, SSR electrode paste was uniformly sprayed onto the CCSR film surface of the CSR|CCSR bilayer film at a pressure of 120 kPa using a spraying process. After complete curing, an asymmetric electrode DEA (CSR|CCSR|SSR) array device (such as...) was obtained. Figure 9 (As shown).

[0121] Application Example 1

[0122] The dielectric elastomer driver DEA array device prepared in Example 9 is used as a Braille display driver. The Braille display driver includes a driving section and a control module.

[0123] The driving section of the Braille display consists of a full silicone rubber dielectric elastomer actuator (CCSR film array DEA), a pressure regulating valve, an air pump, and a constant-pressure air chamber. Specifically, the asymmetric electrode DEA (CSR|CCSR|SSR) is fixed above the constant-pressure air chamber 5 for pre-deformation. The constant-pressure air chamber 5 is connected to the pressure regulating valve 6 and the air pump 7. The pressure regulating valve 6 controls the air pressure to 600 Pa to maintain a constant air pressure in the air chamber 5. This device is used for dynamic Braille display, and the array structure is 2×3 and 3×4 array.

[0124] like Figure 10 The diagram shows the DEA array control module. The control section consists of a signal generation unit, a power amplifier, a programmable logic controller (PLC), a digital output module (IO terminals), and a six-channel relay module. The asymmetric electrodes of the CCSR film array DEA are connected to the IO terminals of the DEA array control module.

[0125] During the experiment, a signal generator was first used to generate drive signals. The signal generator provides an adjustable input signal, typically an AC signal, the frequency and amplitude of which can be adjusted according to experimental requirements. The signal generated by the signal generation unit is amplified and then enters the control module. The programmable logic controller (PLC) 1, based on preset logic, cyclically parses and generates corresponding multi-channel digital control signals, which are sent to the digital output module (IO terminal) 2 to drive two sets of six-channel relay modules 3. Each relay acts as a high-voltage switch controlled by a low-voltage signal, precisely and independently driving the corresponding DEA mini-driver.

[0126] The drive system consists of a power amplifier (TREK, USA) and a signal generator (RIGOL, China). Figure 1) can generate a sinusoidal electrical signal with a voltage range of 0 - 10.0 kV and a frequency range of 0.1 - 10 Hz. In this experiment, the DEA film was fixed above a constant-pressure chamber of 600 Pa for pre-deformation. After the DEA received the electrical signal, it bent upward, and its deflection displacement was collected by a laser displacement sensor (Keyence, Japan), with the light spot focused on the center of the film. The response and recovery times were tested under a square-wave signal with a duty cycle of 0.5, a frequency of 0.25 Hz, and a voltage of 7.0 kV. The force output was tested by an electronic balance (OHAUS, USA). A Xiaomi mobile phone (15 Pro, China) recorded the driving video of the DEA and the dynamic Braille display.

[0127] As Figure 2 , the control module associates 2×3 and 3×4 DEA arrays with the Braille control system. The signal generated by the signal generation unit enters the control module after being amplified by the power amplifier. The programmable logic controller (PLC) 1 analyzes and generates corresponding multi-channel digital control signals in a loop according to the preset logic, and sends them to the digital output module (IO terminal) 2 to drive two groups of six-channel relay modules 3 respectively. Each relay acts as a high-voltage switch controlled by a low-voltage signal, accurately and independently driving the corresponding DEA small driver to complete the continuous and dynamic display of the Braille pattern.

[0128] Using this system, display tests were carried out on representative Chinese characters, numbers, and letters respectively. Figure 11 It shows Braille patterns driven by asymmetric electrodes and composed of 2×3 or 3×4 DEA drivers. The surface deformation of each DEA driver is controlled by a programmable Braille display system. Using this system, display tests were carried out on four Chinese characters "中、国、科、学", four numbers "二、〇、二、六", and four Braille letters "Z、U、L、I" respectively. The blue Braille display screen gave the Braille patterns associated with the above Chinese characters (or letters, numbers). Under the electric field drive, the relevant DEA drivers underwent surface deformation and bent upward synchronously, with basically the same bending amplitude, jointly forming a pattern matching the display screen. At the same time, under the control of the system, the DEA array continuously displayed the corresponding Braille patterns, successfully achieving the dynamic display of Braille, demonstrating the application space of asymmetric electrode DEA in fields such as pumps, valves, artificial heart valves, and enhanced virtual reality.

[0129] To improve the dielectric constant of the composite film (SR), this invention proposes a strategy of filling the SR with carbon black (CB) nanoparticles. The aim is to utilize the microcapacitance of a large number of CB particles to enhance the dielectric constant of the composite film. However, due to the significant difference in surface energy, the exposed CB particles have poor chemical compatibility with the SR matrix, leading to problems such as filler agglomeration and the formation of micropores. This results in localized concentration of the electric field within the film, inducing premature electrical breakdown. To address this, a silane coupling agent (cyanoethyltriethoxysilane, CTES) is used to modify the surface of CB, resulting in CTES@CB particles with a core-shell structure. Surface modification yielded three positive effects: 1) Grafting CTES onto the CB surface prevented CB particle aggregation and reduced leakage current between CB particles; 2) CTES exhibited high chemical compatibility with SR, increasing CB dispersion in SR, facilitating the filling of large doses of CB, while simultaneously reducing defects within the composite film; 3) The cyano groups in CTES are strongly polarizing groups, generating strong induced orientation capacitance, which couples with the interfacial polarization effect of CB, further enhancing the dielectric constant. Consequently, the CTES@CB-filled SR (CCSR) composite film exhibited a high dielectric constant (10.31) and breakdown strength (51.74 V / μm), representing improvements of 289% and 24.67%, respectively, compared to the pure SR film.

[0130] The mechanical properties of electrodes always suppress the normal deformation of DEA. This invention designs soft and hard electrodes fixed on both sides of a CCSR film, aiming to suppress deformation on the hard electrode side and release deformation on the soft electrode side, thus highlighting out-of-plane deformation. The soft electrode is derived from single-walled carbon nanotube (SWCNT) filled SR (SSR), and the hard electrode is derived from CB filled SR (CSR). After thermal crosslinking, a three-layer (CSR|CCSR|SSR) all-silicone rubber DEA is obtained. Under an electric field excitation of 33.67 V / μm, the DEA exhibits 42.97% out-of-plane strain, far exceeding the strain of existing SR-based DEA. Simulation was performed using COMSOL multiphysics finite element method (FEA) software. The calculated results (43.3%) highly matched the experimental results, verifying the surface deformation enhancement mechanism of the asymmetric electrode DEA. Due to the all-silicone rubber structural design, covalent bonds exist between the electrode and the substrate film, overcoming the mechanical mismatch problem between the constituent films and eliminating electrode failure and fatigue drawbacks. The DEA fabricated in this way exhibits high stability: the relative displacement drift (RDS) is only 5.36% within a 4000 s working time, lower than most DEA actuators. Based on this, two DEA array actuators, 2×3 and 3×4, were fabricated, successfully realizing continuous dynamic display of Braille patterns. This invention provides a fabrication technology for high dielectric constant and high breakdown strength silicone rubber dielectric films, proposes a strategy for releasing normal deformation of asymmetric electrodes, obtains a DEA actuator with enhanced surface deformation, and realizes continuous dynamic display of Braille patterns.

[0131] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A fully silicone rubber dielectric elastomer actuator, characterized in that, The dielectric elastomer actuator consists of a soft electrode layer, a dielectric composite film, and a hard electrode layer from top to bottom. The soft electrode layer and the hard electrode layer form an asymmetric electrode structure. The dielectric composite film is prepared by solution blending of silicone rubber SR and silane coupling agent CTES modified carbon black CB (CTES@CB particles) to form a composite film, namely a CCSR film. Under the action of an applied electric field, the dielectric composite film deforms under the action of Maxwell electro-coercivity. The hard electrode layer restricts the deformation on its corresponding side, and the soft electrode layer releases the deformation on its corresponding side, thereby enabling the actuator to generate enhanced out-of-plane driving displacement.

2. The all-silicone rubber dielectric elastomer actuator according to claim 1, characterized in that, The dielectric composite film has a thickness of 0.29-0.32 mm, an elastic modulus of 0.21-0.73 MPa, and a dielectric constant of 2.65-10.

31.

3. The all-silicone rubber dielectric elastomer actuator according to claim 1, characterized in that, The soft electrode layer, named SSR, is obtained by ultrasonically dispersing a single-walled carbon nanotube (SWCNT) dispersion with a silicone rubber (SR) prepolymer and then spraying the resulting mixture. The thickness ranges from 2.01 to 4.00 μm, and the resistivity is 1.4–10.08 kΩ·sq. -1 The content of SWCNT is 0.2~1.8 phr, that is, the mass fraction of SWCNT in SR colloid is 0.2~1.8%; the hard electrode layer is a conductive silicone grease-coated electrode, named CSR, with a thickness of 20.57-31.00 μm and a resistance of 7.13-12.04 kΩ·sq. -1 .

4. The all-silicone rubber dielectric elastomer actuator according to claim 1, characterized in that, The dielectric composite film is prepared by solution blending SR and silane coupling agent modified carbon black CB (CTES@CB particles) to form a CCSR film. The specific steps are as follows: (1) Preparation of CTES@CB particles: CB was surface modified by using silane coupling agent cyanoethyltriethoxysilane (CTES) to obtain CTES@CB particles with core-shell structure; (2) Preparation of SR prepolymer: Dissolve SR colloid in tetrahydrofuran (THF), stir mechanically until uniform, add curing agent, and continue mechanical stirring to obtain SR prepolymer; (3) Preparation of CCSR membrane: CTES@CB particles are added to the solution and ultrasonically dispersed. Then, SR prepolymer is added and mechanically stirred to mix evenly. The resulting mixture is poured into a circular polytetrafluoroethylene mold and heated in a vacuum drying oven until the solvent is completely evaporated to obtain CCSR membrane.

5. The all-silicone rubber dielectric elastomer actuator according to claim 4, characterized in that, The amount of curing agent is 1%-2% of the mass of SR, and the content of CTES@CB particles is 0.5~2.5 phr, that is, the mass fraction of CTES@CB particles in SR colloid is 0.5~2.5%.

6. The all-silicone rubber dielectric elastomer actuator according to claim 1, characterized in that, Under AC signals with an electric field strength higher than 23.57 V / μm and a frequency greater than 0.25 Hz, it can generate out-of-plane actuated displacements of 0–6.21 mm; the mechanical sensitivity is 12.61–15.78 MPa. -1 .

7. The preparation method of the all-silicone rubber dielectric elastomer actuator according to any one of claims 1-6 is as follows: Step 1: Prepare SSR electrode paste. The electrode prepared from this SSR electrode paste is a soft electrode. Step 2: Prepare CSR electrode colloid, and the electrode prepared from the CSR electrode colloid is a hard electrode; Step 3, DEA preparation: The CCSR film is laid flat on a glass plate, covered with a circular mask, and the CSR electrode colloid is uniformly coated on the surface of the CCSR film to obtain a CSR|CCSR double layer film, which is then dried for later use; using the same mask, the SSR electrode paste is uniformly sprayed onto the CCSR film surface of the CSR|CCSR double layer film at a pressure of 120 kPa using a spraying process, and after complete curing, the asymmetric electrode DEA (CSR|CCSR|SSR) is obtained.

8. The application of the all-silicone rubber dielectric elastomer actuator according to any one of claims 1-6 as a Braille display actuator.

9. The application according to claim 8, characterized in that, The Braille display includes a driving part and a control module. The driving part consists of a silicone rubber dielectric elastomer actuator as described in any one of claims 1-6, a pressure regulating valve, an air pump, and a constant pressure air chamber. The asymmetric electrode of the silicone rubber dielectric elastomer actuator is connected to the control module. The silicone rubber dielectric elastomer actuator is fixed above the constant pressure air chamber for pre-deformation. The constant pressure air chamber is connected to the pressure regulating valve and the air pump. The pressure regulating valve controls the air pressure to 600 Pa to maintain a constant air pressure in the air chamber.

10. The application according to claim 8, characterized in that, The all-silicone rubber dielectric elastomer actuator is a CCSR film array DEA fabricated using 2×3 and 3×4 circular array masks with ϕ=5 mm and a spacing of 2 mm.

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