Method for producing a composite dielectric elastomer membrane and dielectric elastomer membrane actuator

Abstract

The application provides a preparation method of a composite dielectric elastomer film and a dielectric elastomer film actuator. The preparation method comprises the following steps: step 1: mixing BTRU@CDs giant electro-rheological particles with an electro-rheological liquid dispersion phase to obtain a suspension; step 2: uniformly mixing silicone rubber with the suspension to obtain a composite dielectric elastomer prepolymer, wherein the mass ratio of the silicone rubber to the suspension is 15:1 to 1:1, and the mass ratio of the BTRU@CDs giant electro-rheological particles in the composite dielectric elastomer prepolymer is 5-40%; and step 3: film forming is performed on the composite dielectric elastomer prepolymer to obtain a composite dielectric elastomer film. The composite dielectric elastomer film prepared by the preparation method of the composite dielectric elastomer film has better actuating performance, better mechanical performance and better cycle stability than traditional rubber elastomers. The problems of high driving voltage, large pre-stretching ratio, limited actuating strain, poor fatigue resistance and easy breakdown of existing dielectric elastomer materials are solved.

Description

Technical Field

[0001] This invention relates to the field of actuators, and more particularly to a method for preparing a composite dielectric elastomer film and a dielectric elastomer film actuator. Background Technology

[0002] Dielectric elastomers (DEs) are electronically active polymers that can change shape under an electric field. Due to their softness, fast response, high energy density, and actuation response close to that of natural muscles, they have been dubbed the next generation of "artificial muscles" and are widely researched and applied in fields such as bionics, flexible robotics, medical rehabilitation, and aerospace. Dielectric elastomer actuators (DEAs) consist of a DE film sandwiched between two flexible electrodes, and their working principle can be explained using the Maxwell effect. However, existing DE materials face several challenges, including high driving voltage, large pre-stretch ratio, limited actuation strain, poor fatigue resistance, and susceptibility to breakdown, which significantly restricts their application scope.

[0003] For example, in the field of flexible robotics, the most widely used and mature dielectric elastomer (DE) materials for actuators are the commercially available acrylates VHB 4905 and VHB 4910, both sourced from Minnesota Mining and Manufacturing (3M). VHB exhibits excellent actuation properties: high areal strain (380%-400%), Maxwell stress (7.2 MPa), and energy density (3.4 MJ / m²). 3 However, its disadvantages include high viscosity and poor cycling stability. Currently, increasing the dielectric constant of DE materials is the main way to improve their electromechanical responsiveness. Adding fillers with high dielectric constants to the polymer matrix is ​​one way to solve this problem, such as adding inorganic ceramic particles TiO2 and BaTiO3, conductive particles carbon black (CB), carbon nanotubes, etc. However, adding high concentrations of ceramics or conductive particles to the matrix inevitably has some problems: the former often requires a high filling amount (around 50%), and is accompanied by serious particle agglomeration and dispersibility issues, while the latter often has too low breakdown strength and is prone to percolation breakdown. These problems are not conducive to the practical application of DE materials. Summary of the Invention

[0004] This invention provides a method for preparing a composite dielectric elastomer film, a composite dielectric elastomer film for a film actuator, a dielectric elastomer film actuator, and a crawling actuator based on the composite dielectric elastomer film, to at least solve one of the problems existing in the related art. To achieve this objective, this invention is implemented through the following technical solutions.

[0005] The first aspect of this invention provides a method for preparing a composite dielectric elastomer film, comprising:

[0006] Step 1: Premix BTRU@CDs giant electrorheological particles with the electrorheological fluid dispersion to obtain a suspension. The BTRU@CDs giant electrorheological particles are urea-encapsulated barium titanyl oxalate particles (BTRU) modified with carbon quantum dots (CDs) obtained by coprecipitation method. The mass ratio of the BTRU@CDs giant electrorheological particles to the electrorheological fluid dispersion is 3:1 to 1:1.

[0007] Step 2: Mix the silicone rubber with the suspension to obtain a composite dielectric elastomer prepolymer, wherein the mass ratio of the silicone rubber to the suspension is 15:1 to 1:1, and the BTRU@CDs giant electrorheological particles account for 5-40% of the mass ratio of the composite dielectric elastomer prepolymer.

[0008] Step 3: The composite dielectric elastomer prepolymer is film-formed to obtain a composite dielectric elastomer film.

[0009] Furthermore, the preparation steps of the BTRU@CDs giant electrorheological particles include:

[0010] Step 11: Prepare the reaction solution, including: preparing a mixed solution of barium chloride and rubidium chloride at 50-70℃, wherein the mass concentration of barium chloride is 0.1-0.5 g / ml and the mass concentration of rubidium chloride is 0.001-0.01 g / ml; preparing an aqueous solution of titanium tetrachloride with a concentration of 0.1-0.4 g / ml, adding the aqueous solution of titanium tetrachloride to the mixed solution of barium chloride and rubidium chloride at 50-70℃, and mixing evenly to obtain mixed solution A; dissolving urea and carbon quantum dots in deionized water to obtain a urea mixed solution, wherein the mass concentration of urea is 0.1-0.4 g / ml and the mass concentration of carbon quantum dots is 0.001-0.01 g / ml; preparing an oxalic acid solution with a concentration of 0.1-0.4 g / ml at 50-70℃; and mixing the urea mixed solution and the oxalic acid solution evenly to obtain mixed solution B.

[0011] Step 12: Perform a coprecipitation reaction, including: when the temperature of the mixed solution A and the mixed solution B reaches 50-70℃, slowly pour the mixed solution A into the mixed solution B, add ice-cold deionized water at the same time, and continue stirring until the solution is milky white and flocculent. Wash with deionized water until the pH value of the supernatant is 2-4.

[0012] Step 13: Filter and freeze-dry the washed solution to obtain powdered particles.

[0013] Furthermore, the composite dielectric elastomer film has a thickness of 0.5-1 mm, an elastic modulus of 100-250 kPa, a dielectric constant of 2.7-10, a pre-stretching ratio of 110-180% during film formation, a driving voltage of 0.5-15 kV, an out-of-plane actuation displacement of 0.05-4 mm, and a maximum area strain of 10-50%.

[0014] Furthermore, the BTRU@CDs giant electrorheological particles account for 15-30% of the mass of the composite dielectric elastomer prepolymer, preferably 15%.

[0015] Furthermore, the silicone rubber mixture has a viscosity of 2.7-50 Pa·s, an elastic modulus of 50-800 kPa, an elongation at break of 200-1000%, and a dielectric constant of 2.5-5.

[0016] A second aspect of the present invention provides a composite dielectric elastomer film for a thin film actuator, wherein the composite dielectric elastomer film is prepared according to the above-described preparation method.

[0017] A third aspect of this invention provides a dielectric elastomer thin-film actuator, which is an articulated bending structure comprising: a composite dielectric elastomer layer, a first flexible frame, and a second flexible frame. The composite dielectric elastomer layer includes: the aforementioned composite dielectric elastomer thin film for the thin-film actuator, and flexible carbon grease electrodes attached to the upper and lower surfaces of the composite dielectric elastomer thin film. The first flexible frame is attached to the lower surface of the composite dielectric elastomer layer, and a first perforation pattern is provided at the center of the first flexible frame, the first perforation pattern corresponding to the shape and position of the flexible carbon grease electrode. The second flexible frame includes two separate sub-frames, both attached to the upper surface of the composite dielectric elastomer layer. The portions of the two sub-frames close to each other are respectively provided with second perforation patterns, the two second perforation patterns corresponding in shape and position to the first perforation pattern.

[0018] Furthermore, the flexible carbon grease electrode is circular or elliptical, the two sub-frames of the second flexible frame are separated by a distance of 3-10 mm, and the thickness of the second flexible frame is greater than the thickness of the first flexible frame.

[0019] A fourth aspect of the present invention provides a crawling actuator based on a composite dielectric elastomer film, comprising: a dielectric elastomer film actuator according to a third aspect of the present invention, a front foot and a rear foot, wherein the front foot and the rear foot are respectively attached to two opposite edges of the dielectric elastomer film actuator, the two opposite edges are respectively parallel to the bending axis of the dielectric elastomer film actuator, the front foot and the rear foot are sharp angles or serrated, and the number of sharp angles or serrations of the front foot and the rear foot are different, and crawling is achieved by the difference in contact friction between the front foot and the rear foot and the drive of an external high voltage power supply.

[0020] Furthermore, the ratio of the number of sharp corners or serrations of the front foot and the rear foot is 5:1 to 2:1. The dielectric elastomer film actuator resonates at a specific frequency of the applied high voltage power supply to generate the maximum bending angle. The bending angle is the bending angle of the articulated bending structure of the dielectric elastomer film actuator.

[0021] The embodiments of the present invention have the following beneficial effects:

[0022] (1) Urea-encapsulated barium titanyl oxalate particles (BaTiO(C2O4)2@urea, BTRU) were synthesized using an improved co-precipitation method, and carbon quantum dots (CDs) were further added to obtain shell-structured BTRU@CDs giant electrorheological particles. In this process, barium titanyl oxalate was the core, urea was the shell, and the carbon quantum dots were bonded to the urea-encapsulated barium titanyl oxalate particles by forming amide bonds. The modified BTRU@CDs particles were incorporated into silicone rubber to prepare composite DE materials. On the one hand, since CDs have good semiconductor properties, BTRU and CDs can form a "microcapacitor structure" under an electric field and produce a synergistic effect, which can significantly improve the dielectric properties of the material compared to single BTRU particles. On the other hand, due to the negative charge of both BTRU and CDs particles, the agglomeration problem of BTRU itself was improved to a certain extent under the action of electrostatic repulsion.

[0023] (2) The composite dielectric elastomer film prepared by the method provided in this embodiment of the invention exhibits superior actuation performance compared to traditional rubber elastomers. Concentration gradient experiments demonstrate that, in a preferred embodiment, for example, the actuation displacement of the composite dielectric elastomer film filled with 15 wt.% BTRU@CDs particles can be increased by 683% compared to a pure rubber matrix. Furthermore, the composite dielectric elastomer film provided in this embodiment of the invention possesses superior mechanical properties and cycle stability, to a certain extent solving the problems of particle agglomeration and low breakdown strength when filled with nano-ceramic particles and conductive particles.

[0024] (3) The dielectric constant of the DE composite increases with the increase of BTRU@CDs particle concentration, which is attributed to the overall polarization enhancement of the composite caused by the increase of BTRU@CDs particle concentration. However, when the BTRU@CDs particle concentration increases, the dielectric loss of the system also increases continuously, and the energy conversion rate decreases, which is detrimental to improving the actuation performance of DE. The embodiments of the present invention, through the study of the dielectric mechanism of DE composite and combined with experimental verification, found that when the mass ratio of BTRU@CDs giant electrorheological particles to composite dielectric elastomer prepolymer is 5-40%, preferably 15-30%, especially when the particle concentration is 15%, the actuation performance of DE composite is better. The reason is that: on the one hand, the electromechanical properties of DE material are coordinated at this concentration; on the other hand, from an energy perspective, 15% DE material has lower dielectric loss and higher breakdown strength, thus exhibiting stronger electroactivity.

[0025] (4) The composite dielectric elastomer film made by doping silicone rubber with BTRU@CDs particles, compared with commercial VHB materials, does not require a large stretch ratio in the film-making process (e.g., a stretch ratio of only 150% × 125%), and has excellent cycle stability. It does not show significant performance degradation after hundreds of thousands of cycles of continuous operation, and the film is flexible overall, without the need for a high proportion of rigid constraints. In contrast, commercial VHB materials often require a pre-stretch ratio of 400% × 400% to provide a large driving force and avoid electromechanical instability. In practical applications, they have strong viscous loss, which are currently insurmountable difficulties for acrylate materials.

[0026] (5) From a device design perspective, most flexible crawling robots currently have complex control mechanisms. They generally require separate voltage control for the front and rear "feet" to control movement in a certain direction, or a combination of two or more control mechanisms, such as combining dielectric elastomer actuators with electroadhesion mechanisms to achieve crawling. However, the crawling actuator based on a composite dielectric elastomer film provided in this invention achieves forward movement or crawling by simply controlling the difference in friction between the front and rear feet of the actuator. Furthermore, by adjusting the driving frequency of the external high-voltage power supply, the dielectric elastomer film actuator resonates to generate the maximum bending angle, i.e., the maximum electro-actuation effect. The principle is that when energized, the composite dielectric elastomer layer is actuated, and the film expands, resulting in a decrease in bending tension. In the current structure, this area expansion is converted into bending deformation perpendicular to the joint gap, and the entire bending structure opens around the joint axis. Finally, due to the difference in contact friction between the front and rear feet and the driving force of the external high-voltage power supply, the crawling actuator moves forward towards the head with greater friction during the repeated opening and closing of the angle. That is, the crawling actuator based on composite dielectric elastomer film provided by the embodiments of the present invention can control crawling by using only one dielectric elastomer actuator (composed of a single dielectric elastomer film) and a simple setting of friction difference.

[0027] (6) The crawling actuator based on composite dielectric elastomer film according to the present invention has the advantages of simple structure, light weight, small size, simple control, fast response, fast crawling speed and long cycle life. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 Infrared spectra of three types of particles: BTRU@CDs giant electrorheological particles, BTRU giant electrorheological particles, and pure carbon quantum dot CDs.

[0030] Figure 2 TEM images of different particles: (a)-(e) are BTRU@CDs particles, (f) are CDs particles;

[0031] Figure 3 The trends of (a) dielectric constant and (b) dielectric loss as a function of frequency for dielectric elastomer films with different particle contents;

[0032] Figure 4 (a) The conductivity as a function of frequency and (b) The breakdown strength of composite dielectric elastomer films with different particle contents are shown.

[0033] Figure 5 The actuated displacement of the composite dielectric elastomer film varies with particle content;

[0034] Figure 6 (a) Actuation displacement of B@CDs / 0030 with a particle content of 15 wt.% at different frequencies, and (b) Actuation displacement variation trend after 500,000 cycles at the resonant frequency.

[0035] Figure 7 This is a schematic diagram showing the composition and structure of a flexible crawling actuator based on a composite dielectric elastomer film.

[0036] Figure 8 The curves showing the variation of the subtraction angle Δθ(a) of the dielectric elastomer thin film actuator under different electric fields and (b) different frequencies;

[0037] Figure 9 This is a physical diagram showing the change in the angular size of a dielectric elastomer film actuator at different frequencies. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the various embodiments of the present invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0039] Example 1

[0040] This embodiment provides a method for preparing a composite dielectric elastomer film, including:

[0041] Step 1: Using a high-energy ball mill, BTRU@CDs giant electrorheological particles and an electrorheological fluid dispersion phase (e.g., dimethyl silicone oil) are premixed at a specific mass ratio to obtain a uniformly dispersed suspension. The mass ratio of BTRU@CDs giant electrorheological particles to dimethyl silicone oil is 3:1 to 1:1. The BTRU@CDs giant electrorheological particles are urea-coated barium titanate particles modified with carbon quantum dots obtained by co-precipitation. The specific preparation method is as follows:

[0042] Step 11: Prepare the reaction solution, including: preparing a mixed solution of barium chloride and rubidium chloride at 50-70℃, wherein the mass concentration of barium chloride is 0.1-0.5 g / ml and the mass concentration of rubidium chloride is 0.001-0.01 g / ml; preparing a titanium tetrachloride aqueous solution with a concentration of 0.1-0.4 g / ml, adding the titanium tetrachloride aqueous solution to the mixed solution of barium chloride and rubidium chloride at 50-70℃, and mixing thoroughly to obtain mixed solution A; dissolving urea and carbon quantum dots in deionized water to obtain a urea mixed solution, wherein the mass concentration of urea is 0.1-0.4 g / ml and the mass concentration of carbon quantum dots is 0.001-0.01 g / ml; preparing an oxalic acid solution with a concentration of 0.1-0.4 g / ml at 50-70℃; mixing the urea mixed solution and the oxalic acid solution thoroughly to obtain mixed solution B;

[0043] Step 12: Perform coprecipitation reaction, including: when the temperature of mixed solution A and mixed solution B reaches 50-70℃, slowly pour mixed solution A into mixed solution B, add ice-cold deionized water at the same time, and continue stirring until the solution is milky white flocculent. Wash with deionized water until the pH value of the supernatant is 2-4.

[0044] Step 13: The washed solution is filtered and freeze-dried to obtain powdered particles, denoted as BTRU@CDs giant electrorheological particles.

[0045] Step 2: The silicone rubber and suspension are mixed evenly to obtain a composite dielectric elastomer prepolymer. The mass ratio of silicone rubber to suspension is 15:1 to 1:1, ensuring that the BTRU@CDs giant current rheological particles account for 5-40% of the mass ratio of the composite dielectric elastomer prepolymer. In this embodiment, the silicone rubber used is Ecoflex 0030, a commercial silicone rubber from Smooth-On, USA. Ecoflex 0030 is an AB two-component silicone rubber, with a fixed mixing ratio of 1:1 for components A and B. The mixed silicone rubber and the suspension obtained in Step 1 are stirred evenly at a certain mass ratio, and excess air bubbles are removed using a vacuum pump to obtain the composite dielectric elastomer prepolymer. The elastic modulus after curing is approximately 68.95 kPa.

[0046] Step 3: The composite dielectric elastomer prepolymer is coated to obtain a composite dielectric elastomer film. In this embodiment, a film-forming machine is used for film formation. Specifically, relevant parameters are set on an automatic coating machine, and the composite dielectric elastomer prepolymer is poured onto a PET substrate for coating. The parameters set on the automatic coating machine include: expected film thickness of 0.5-1 mm, coating speed of 10-100 mm / s, coating distance of 10-50 cm, and substrate heating temperature of 25-60 °C. After coating, a composite dielectric elastomer film with uniform thickness is obtained after the prepolymer cures. The composite dielectric elastomer film according to embodiments of the present invention has a thickness of 0.5-1 mm, an elastic modulus of 100-250 kPa, a dielectric constant of 2.7-10 at a frequency of 1 Hz, a pre-stretching ratio of 110-180% during film formation, a driving voltage of 0.5-15 kV, an out-of-plane actuation displacement of 0.05-4 mm, and a maximum area strain of 10-50%.

[0047] Example 2

[0048] This embodiment provides a composite dielectric elastomer film for a thin film actuator. The composite dielectric elastomer film is prepared according to the preparation method provided in Example 1 and is denoted as B@CDs / 0030.

[0049] The mechanism by which the composite dielectric elastomer film of the present invention can be actuated is as follows: under an external high voltage power supply, positive and negative charges accumulate on the upper and lower surfaces of the composite dielectric elastomer film to generate Maxwell force, which causes the composite dielectric elastomer film to expand in the plane and thus actuate.

[0050] The performance of the BTRU@CDs giant electrorheological particles used to prepare the composite dielectric elastomer film was further characterized.

[0051] (1) FTIR (Full-Time Infrared Spectroscopy)

[0052] To determine the difference in chemical structure of BTRU@CDs giant current rheostat particles before and after modification, total reflectance infrared spectroscopy was performed on the particles, with a measurement range of 4000 cm⁻¹. -1 -400cm -1 ,like Figure 1 As shown. Figure 1 The infrared spectra of three types of particles are shown: BTRU@CDs giant current rheostat particles, BTRU giant current rheostat particles, and pure carbon quantum dots. The characteristic absorption peak positions of the two types of particles (BTRU@CDs particles and BTRU particles) before and after modification are basically the same, both around 1670 cm⁻¹. -1 The nearby band corresponds to the amide I band, a characteristic peak of the amide group -(C=O)NH-. The peak intensity corresponding to BTRU@CDs particles is approximately 1.8 times that of BTRU particles, indicating an increased number of C=O bonds in the former. This FTIR result demonstrates that new amide bonds are formed and bonded together between CDs and BTRU, completing the modification of BTRU by CDs.

[0053] (2) Transmission electron microscopy (TEM) test

[0054] The coating structure of the modified BTRU@CDs particles was observed using TEM, such as... Figure 2 As shown. From Figure 2 In (a)-(e), a core-shell granular structure can be clearly observed, but differences exist between the core-shell structures of different particles. For example... Figure 2 The outer shell of the particles in (d) is relatively transparent, while Figure 2 (e) A distinct black boundary exists between the core and shell; this black boundary is the introduced CDs, and its size is similar to... Figure 2 The size (1-3 nm) of CDs in (f) is consistent with this. The above results indicate that CDs-modified particles, namely BTRU@CDs giant electrorheological particles, were successfully prepared.

[0055] Example 3

[0056] This embodiment uses the composite dielectric elastomer film prepared in Example 2 to fabricate a ring-shaped thin-film actuator. The ring-shaped thin-film actuator is a device used to test the out-of-plane actuation displacement of a dielectric elastomer. The fabrication steps are as follows:

[0057] a. The cured composite dielectric elastomer film (thickness 0.5-1mm) is pre-stretched by 120% × 120% biaxially and fixed on a rigid frame with polyimide double-sided tape on the edge.

[0058] b. Subsequently, a PET mask with a circular pattern is applied to the surface of the pre-stretched film. A suitable amount of carbon grease electrode ink is then applied using a doctor blade ink pad printing machine, with 10-20 pad printing passes per area until the entire central circle of the mask is completely covered.

[0059] c. After the carbon grease electrode has cured, add acrylic rings to the corresponding electrode positions on the upper and lower surfaces of the film. Use the matching nuts and screws to fix the ring frame to the film. Use a knife to separate the film from the original rigid frame, allowing the lightweight acrylic rings to replace the original rigid frame and maintain the pre-stretching of the film.

[0060] At this point, the annular thin-film actuator has been successfully fabricated and can be used to test out-of-plane actuated displacement.

[0061] Example 4

[0062] This embodiment further conducts out-of-plane actuation displacement tests on the annular thin-film actuator prepared in Example 3, aiming to quantitatively test the actuation performance of different composite dielectric elastomer thin films. Test principle: Applying a small prestress to the film surface causes the thin-film actuator to convert area expansion into relatively significant vertical vibration (out-of-plane actuation displacement). Specific test steps are as follows:

[0063] a. Connect the upper and lower poles of the manufactured ring actuator to the positive and negative poles of the power supply through conductive tape, and place it directly below the sensor;

[0064] b. Apply prestress to the surface of the annular thin-film actuator. In this embodiment, different amounts of prestress are represented by applying different numbers of magnets to the thin-film surface. The mass of a single small magnet used is 3.8g. For simplicity, the number of magnets applied is represented by x_Mag, that is, one magnet is represented as 1_Mag, which represents the prestress (Fpre).

[0065] It is 37.2mN, and so on.

[0066] c. Turn on the laser displacement sensor and program, complete initialization and zeroing.

[0067] Then turn on the power, slowly adjust the voltage, and start the test after the actuator is running smoothly.

[0068] Example 5

[0069] This embodiment investigates the dielectric properties, conductivity, and breakdown strength of the composite dielectric elastomer film of Example 2 with different BTRU@CDs particle contents (5%-30%). Simultaneously, the out-of-plane actuation displacement of the annular thin-film actuator prepared using the method of Example 3 is tested, thereby evaluating the actuation performance of the samples with different BTRU@CDs particle contents.

[0070] (1) Dielectric properties

[0071] Figure 3 (a) and (b) show 1-10 respectively. 7The dielectric constant (ε) of the composite dielectric elastomer film B@CDs / 0030 in the Hz frequency range r The trends of dielectric loss (tanδ) and frequency variation. Figure 3 In (a), as the frequency increases, the ε of samples with different particle concentrations... r The dielectric properties gradually decrease and then tend to stabilize. This is mainly because the dielectric properties of materials at low frequencies depend on interfacial polarization. As the frequency increases further, interfacial polarization weakens, and dipole polarization becomes dominant. Figure 3 In (b), at low frequencies, the dielectric loss of the composite dielectric elastomer film is mainly due to conductivity loss caused by leakage current. At 1 Hz, the tanδ of 0030 is 0.10, while the tanδ of B@CDs / 0030 with particle concentrations of 15 wt.% and 30 wt.% are 0.17 and 0.37, respectively, representing increases of 70% and 270% compared to the pure silicone rubber matrix (denoted as 0030). As the frequency further increases, the dielectric loss of different samples at 10 Hz... 3 -10 4 A significant dielectric loss peak appears in the Hz range, mainly due to the loss caused by the orientation polarization of molecular dipoles.

[0072] In summary, the dielectric constant of the composite dielectric elastomer film B@CDs / 0030 increases with increasing BTRU@CDs particle concentration, which is attributed to the enhanced overall polarization caused by the increased particle concentration. However, as the particle concentration increases, the dielectric loss of the system also increases, and the energy conversion efficiency decreases, which is detrimental to improving the actuation performance of the DE.

[0073] (2) Conductivity and breakdown strength

[0074] Figure 4 The figures show (a) conductivity versus frequency and (b) breakdown strength of composite dielectric elastomer films with different particle contents. Figure 4 (a) It can be seen that the higher the particle concentration, the greater the conductivity of the composite dielectric elastomer film. The highest conductivity of 30wt.% B@CDs / 0030 is only 2.39×10⁻⁶. -10 S / cm, this value is still far lower than the conductivity of a conductor (10). -7 The S / cm indicates that the composite dielectric elastomer film filled with BTRU@CDs nanoparticles has good electrical insulation properties. Figure 4(b) shows the basic trend of the electrical breakdown strength of the composite dielectric elastomer film with particle concentration: initially relatively stable, then significantly decreasing. The average breakdown strength of the 15 wt.% sample was 24.6 kV, which was only 10.6% lower than that of the pure silicone rubber matrix, demonstrating good particle dispersion in the matrix. Subsequently, the breakdown strength of the composite dielectric elastomer film decreased significantly. This is due to the increased number of defects such as voids within the system, and the accumulation of charge between particles, which easily leads to material breakdown.

[0075] (3) Actuation performance

[0076] Figure 5 The actuated displacements of composite dielectric elastomer films with particle contents ranging from 0 to 30 wt.% are shown. All actuated displacements for all samples in the figure were measured at 1 Hz with a 1-Mag preload (equivalent to a prestress of 37.24 mN). Figure 5 It can be seen that, under a constant electric field, the composite dielectric elastomer film with a BTRU@CDs particle concentration of 15 wt.% exhibits the highest actuation displacement, which is 683% higher than that of the pure silicone rubber matrix at 10 kV / mm. The reason for the significant increase in actuation displacement of this sample is twofold: firstly, the electromechanical properties of the sample are well-coordinated at this concentration; secondly, from an energy perspective, the 15 wt.% sample has lower dielectric loss (tanδ) and higher breakdown strength, thus exhibiting stronger electroactivity.

[0077] Further testing was conducted on the composite dielectric elastomer film with a particle filling content of 15 wt.%. Figure 6 (a) Electrical response of a composite dielectric elastomer film with a particle filling of 15 wt.% at different frequencies. Test conditions were 8.75 kV / mm and a preload of Mag₂ (74.5 mN). Figure 6 It was found that the 15wt.%B@CDs / 0030 thin film achieved resonance at 11Hz, reaching the maximum actuation displacement of approximately 3.17mm. Further testing of the cyclic actuation performance of the 15wt.%B@CDs / 0030 thin film at this resonance frequency was conducted. After 500,000 cycles, the film sample showed only a 9.5% decrease in performance compared to the initial 100,000 cycles. These results demonstrate that the DE composite thin film exhibits high cyclic stability, which will be beneficial for designing and developing stable actuator devices.

[0078] Example 6

[0079] This embodiment further provides a dielectric elastomer film actuator based on the composite dielectric elastomer film of Embodiment 2. Figure 7 This is a schematic diagram illustrating the composition and structure of a flexible crawling actuator based on a composite dielectric elastomer film. Among them, Figure 7The image above shows an exploded structural diagram of the main body of the flexible crawling actuator—the dielectric elastomer film actuator. For example... Figure 7 As shown, the dielectric elastomer film actuator has an articulated (or origami-like) bending structure, comprising: a composite dielectric elastomer layer, a first flexible frame (i.e., Figure 7 The PET frame 1) and the second flexible frame (i.e. Figure 7 The PET frame 2 in the example. The composite dielectric elastomer layer includes: the composite dielectric elastomer film provided in Example 2 (i.e., Figure 7 The composite dielectric elastomer film (DE film) and flexible carbon grease electrodes attached to the upper and lower surfaces of the composite dielectric elastomer film are described. A first flexible frame is attached to the lower surface of the composite dielectric elastomer layer as a substrate. A perforated pattern (I) is provided at the center of the first flexible frame, corresponding to the shape and position of the flexible carbon grease electrode. In this embodiment, the flexible carbon grease electrode is circular or elliptical, and the perforated pattern (I) is also a corresponding circular or elliptical shape. A second flexible frame serves as a reinforcing layer, comprising two separate sub-frames, both attached to the upper surface of the composite dielectric elastomer layer. Perforated patterns (II) are provided on the adjacent portions of the two sub-frames, and the overall shape and position of the two perforated patterns (II) correspond to the shape and position of the perforated pattern (I). In this embodiment, the perforated pattern (II) is also generally circular or elliptical. In this embodiment, the thickness of the composite dielectric elastomer film is 0.5-1 mm, the thickness of the flexible carbon grease electrode is 3-20 μm, the distance between the two sub-frames of the second flexible frame is 3-10 mm, and the thickness of the second flexible frame is greater than the thickness of the first flexible frame. For example, the thickness of the first flexible frame is 0.05-0.15 mm, and the thickness of the second flexible frame is greater than 0.2 mm. The purpose is to serve as a reinforcing layer to provide stronger support and holding force for the flexible crawling actuator, and to avoid irregular deformation of the actuator's four corners curling up due to excessive pre-stretching ratio of the composite dielectric elastomer film.

[0080] Example 7

[0081] This embodiment further provides a crawling actuator based on a composite dielectric elastomer film, building upon Embodiment Six. Figure 7 As shown in the figure below, the crawling actuator includes: a dielectric elastomer film actuator according to Embodiment Six. Figure 7 The actuator body, front feet, and rear feet are respectively attached to two opposite edges of the dielectric elastomer film actuator. Figure 7 The front and rear feet (head and tail) are parallel to the bending axis of the dielectric elastomer film actuator. The front and rear feet are pointed or serrated, and the number of pointed or serrated feet is different. Crawling is achieved by the difference in contact friction between the front and rear feet and the drive of an external high voltage power supply.

[0082] Furthermore, the ratio of the number of sharp corners or serrations of the front and rear feet is 5:1 to 2:1. The dielectric elastomer film actuator resonates at a specific frequency of the applied high voltage power supply to generate the maximum bending angle, which is the bending angle of the articulated bending structure of the dielectric elastomer film actuator.

[0083] The crawling mechanism of this flexible crawling actuator is as follows: In the unpowered state, the actuator exhibits natural bending, for example, under a pre-stretch ratio of 150% × 125% (length × width) during film fabrication, the natural bending angle is approximately 90°. This is because the tension contraction of the pre-stretched film releases elastic energy, a portion of which is stored in the flexible frame, causing the structure to bend naturally. When powered, the composite dielectric elastomer layer is actuated, causing the film to expand and reducing the bending tension. In the current structure, this area expansion is converted into bending deformation perpendicular to the joint gap, and the entire bending structure opens around the joint axis. Ultimately, due to the difference in contact friction between the front and rear feet and the drive of the external high-voltage power supply, the crawling actuator shifts towards the head, where the friction is greater, during the repeated opening and closing of the bending angle.

[0084] Example 8

[0085] This embodiment provides a performance test of the flexible crawling actuator of Embodiment Seven. To better illustrate the crawling effect of the crawling actuator, the bending angle change (Δθ) of its dielectric elastomer film actuator under different voltages and frequencies was tested beforehand. Figure 8 (a) shows the opening angle variation curves of the dielectric elastomer thin film actuator under different electric fields at 0.1 Hz. When the field strength increases to a certain extent (approximately 12 kV / mm), the increase in opening angle slows down. This bending actuator can achieve an angle change of 13.07° at 16 kV / mm. Figure 8 (b) shows the change curve of the dielectric elastomer thin film actuator in the frequency range of 0-15Hz under an electric field of 14kV / mm. Figure 9 The actual diagrams show the changes in the aperture angle of the dielectric elastomer thin film actuator at four frequencies: 0.1Hz, 4Hz, 8Hz, and 12Hz. Figure 9 It can be seen that the dielectric elastomer film actuator has different electrical responses depending on the power supply frequency. When the frequency reaches around 8Hz, the dielectric elastomer film actuator resonates, and the change in Δθ is the largest, approximately 23.31°.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A crawling actuator based on a composite dielectric elastomer film, characterized in that, The actuator includes a dielectric elastomer film actuator, front feet, and rear feet. The dielectric elastomer film actuator has an articulated bending structure, comprising: a composite dielectric elastomer layer, a first flexible frame, and a second flexible frame. The composite dielectric elastomer layer includes: a composite dielectric elastomer film, and flexible carbon grease electrodes attached to the upper and lower surfaces of the composite dielectric elastomer film; The first flexible frame is attached to the lower surface of the composite dielectric elastomer layer. A hollow pattern is provided at the center of the first flexible frame, and the hollow pattern corresponds to the shape and position of the flexible carbon grease electrode. The second flexible frame includes two separate sub-frames, both attached to the upper surface of the composite dielectric elastomer layer. The portions of the two sub-frames that are close to each other are respectively provided with a second hollow pattern. The two second hollow patterns as a whole correspond to the shape and position of the first hollow pattern. The front and rear feet are respectively attached to two opposite edges of the dielectric elastomer film actuator. These two opposite edges are parallel to the bending axis of the actuator. The front and rear feet are serrated, and the number of serrations differs between them. Crawling is achieved through the difference in contact friction between the front and rear feet and the drive of an external high-voltage power supply. The composite dielectric elastomer film is prepared by the following method, including: Step 1: Premix BTRU@CDs giant electrorheological particles with the electrorheological fluid dispersion phase to obtain a suspension. The BTRU@CDs giant electrorheological particles are urea-encapsulated barium titanyl oxalate particles modified with carbon quantum dots obtained by co-precipitation method. The mass ratio of the BTRU@CDs giant electrorheological particles to the electrorheological fluid dispersion phase is 3:1 to 1:

1. Step 2: Mix the silicone rubber with the suspension to obtain a composite dielectric elastomer prepolymer, wherein the mass ratio of the silicone rubber to the suspension is 15:1 to 1:1, and the BTRU@CDs giant electrorheological particles account for 5-40% of the mass ratio of the composite dielectric elastomer prepolymer. Step 3: The composite dielectric elastomer prepolymer is film-formed to obtain the composite dielectric elastomer film.

2. The crawling actuator based on a composite dielectric elastomer film according to claim 1, characterized in that, The flexible carbon grease electrode is circular or elliptical, the two sub-frames of the second flexible frame are separated by a distance of 3-10 mm, and the thickness of the second flexible frame is greater than the thickness of the first flexible frame.

3. The crawling actuator based on a composite dielectric elastomer film according to claim 1, characterized in that, The ratio of the number of serrations between the front and rear feet is 5:1 to 2:

1. The dielectric elastomer film actuator resonates at a specific frequency of the applied high voltage power supply to generate the maximum bending angle. The bending angle is the bending angle of the articulated bending structure of the dielectric elastomer film actuator.

4. The crawling actuator based on a composite dielectric elastomer film according to claim 1, characterized in that, The preparation steps of the BTRU@CDs giant electrorheological particles include: Step 11: Prepare the reaction solution, including: preparing a mixed solution of barium chloride and rubidium chloride at 50-70℃, wherein the mass concentration of barium chloride is 0.1-0.5 g / ml and the mass concentration of rubidium chloride is 0.001-0.01 g / ml; preparing an aqueous solution of titanium tetrachloride with a concentration of 0.1-0.4 g / ml, adding the aqueous solution of titanium tetrachloride to the mixed solution of barium chloride and rubidium chloride at 50-70℃, and mixing evenly to obtain mixed solution A; dissolving urea and carbon quantum dots in deionized water to obtain a urea mixed solution, wherein the mass concentration of urea is 0.1-0.4 g / ml and the mass concentration of carbon quantum dots is 0.001-0.01 g / ml; preparing an oxalic acid solution with a concentration of 0.1-0.4 g / ml at 50-70℃; and mixing the urea mixed solution and the oxalic acid solution evenly to obtain mixed solution B. Step 12: Perform a coprecipitation reaction, including: when the temperature of the mixed solution A and the mixed solution B reaches 50-70℃, slowly pour the mixed solution A into the mixed solution B, add ice-cold deionized water at the same time, and continue stirring until the solution is milky white and flocculent. Wash with deionized water until the pH value of the supernatant is 2-4. Step 13: Filter and freeze-dry the washed solution to obtain powdered particles.

5. The crawling actuator based on a composite dielectric elastomer film according to claim 1, characterized in that, The composite dielectric elastomer film has a thickness of 0.5-1 mm, an elastic modulus of 100-250 kPa, a dielectric constant of 2.7-10, a pre-stretching ratio of 110-180% during film formation, a driving voltage of 0.5-15 kV, an out-of-plane actuation displacement of 0.05-4 mm, and a maximum area strain of 10-50%.

6. The crawling actuator based on a composite dielectric elastomer film according to claim 1, characterized in that, The BTRU@CDs giant current rheotropic particles account for 15-30% of the mass of the composite dielectric elastomer prepolymer.

7. The crawling actuator based on a composite dielectric elastomer film according to claim 1, characterized in that, The silicone rubber mixture has a viscosity of 2.7-50 Pa·s, an elastic modulus of 50-800 kPa, an elongation at break of 200-1000%, and a dielectric constant of 2.5-5.

Images