Method for producing a multifunctional dielectric elastomer and dielectric elastomer film

Abstract

This invention provides a method for preparing a multifunctional dielectric elastomer and a dielectric elastomer film. The method includes: Step 1: preparing a carbon dot (CDs) solution; Step 2: adding silica particles to the carbon dot (CDs) solution to obtain a CDs-silica suspension and mixing it uniformly; Step 3: providing PDMS, adding the CDs-silica suspension to the PDMS and mixing it uniformly to obtain a precursor, adding the precursor to a mold and heating to cure, thereby obtaining a CDs-PDMS composite film with fluorescence emission properties. This invention fills the dielectric elastomer matrix with carbon dot particles and achieves uniform dispersion of the carbon dots in the matrix. As nano-conductive particles, the carbon dots can improve the dielectric constant of the dielectric elastomer. Simultaneously, the uniformly dispersed carbon dots possess fluorescence emission properties after ultraviolet excitation. Therefore, by filling with carbon dots, both the dielectric properties of the dielectric elastomer and its fluorescence emission properties can be improved, thus preparing a multifunctional dielectric elastomer.

Description

Technical Field

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

[0002] A dielectric elastomer actuator (DEA) consists of a dielectric elastomer (DE) film and flexible electrodes on the upper and lower surfaces of the film. The electro-actuation performance of a DEA is primarily affected by two components: the electrodes and the DE film. The electro-actuation performance of a DEA is mainly influenced by the dielectric constant of the DE film. and film elastic modulus Y The influence of both increasing the dielectric constant of the DE film and decreasing its elastic modulus can improve the deformation of the DEA.

[0003] Currently, among the methods of improving the dielectric properties of dielectric elastomers by using conductive particles as fillers, the conductive particles used to improve the properties of dielectric elastomers mainly include metal particles, carbon-based particles, and conductive polymer particles. Metal particles include silver, copper, nickel, etc., carbon-based particles include carbon black, carbon nanotubes, graphene, etc., and conductive polymer particles include polyaniline, etc.

[0004] Existing technologies often require high particle filling rates to improve the performance of dielectric elastomers (DEAs). However, high filling rates can lead to several problems: for example, particles are prone to agglomeration within the matrix, causing the DEA to break down under high electric fields. Higher filling rates also increase the Young's modulus of the DEA, thus affecting its electro-actuation performance. Furthermore, the functions of particles used in existing technologies are relatively limited; metal and ceramic particles can only improve the dielectric properties of DEAs, offering limited benefits in expanding their application range. Summary of the Invention

[0005] This invention provides a method for preparing a multifunctional dielectric elastomer and a dielectric elastomer film, thereby addressing at least one of the problems existing in related technologies. To achieve this objective, this invention is implemented through the following technical solutions.

[0006] This invention provides a method for preparing a multifunctional dielectric elastomer, comprising: step 1: preparing a carbon dot CDs solution; step 2: adding silica particles to the carbon dot CDs solution to obtain a CDs-silica suspension and mixing it uniformly; step 3: providing PDMS, adding the CDs-silica suspension to PDMS and mixing it uniformly to obtain a precursor, adding the precursor to a mold and heating to cure it to obtain a CDs-PDMS composite film with fluorescence emission properties.

[0007] Furthermore, the carbon dot CDs used to prepare the carbon dot CDs solution include: carbon quantum dots, graphene quantum dots, and carbonized polymer dots.

[0008] Furthermore, the CDs filling rate in the CDs-PDMS composite film is less than 0.040 wt%, preferably, the CDs filling rate in the CDs-PDMS composite film is 0.025 wt% (mass percentage), and the silica filling rate is 1-2 wt%.

[0009] Furthermore, the ratio of PDMS matrix to curing agent is 10:1-20:1. Furthermore, the dielectric constant of the CDs-PDMS composite film is 4.8-6.4, and the elastic modulus is 0.1-0.2 MPa.

[0010] Furthermore, the preparation method of carbon quantum dots (CQDs) includes: Step 01: Prepare a citric acid solution and add ethylenediamine to obtain a mixed solution, with the citric acid concentration being 0.05-0.2 g / ml and the ethylenediamine concentration being 0.15-5%; Step 02: Place the mixed solution in an autoclave and heat it at 150-250℃ for 4-8 hours, then cool it to room temperature and remove the mixed solution; Step 03: Centrifuge the mixed solution to remove impurities and perform dialysis; Step 04: Freeze-dry the dialyzed mixed solution to obtain carbon quantum dot (CQD) particles.

[0011] Furthermore, the mixing method in step 2 is ultrasonic stirring.

[0012] Furthermore, the excitation wavelength of the CDs-PDMS composite film with fluorescence emission properties is 340nm-360nm.

[0013] Furthermore, the concentration of the carbon quantum dot (CD) solution is 0.1-5 mg / ml.

[0014] Another aspect of the present invention provides a dielectric elastomer film, which is prepared by the method for preparing a multifunctional dielectric elastomer according to the first aspect of the present invention.

[0015] Furthermore, the pre-stretch ratio of the dielectric elastomer film is 1.1-1.5, and the thickness of the dielectric elastomer film is 0.2-1.0 mm.

[0016] The embodiments of the present invention have the following beneficial effects: (1) In this embodiment of the invention, carbon dots (CDs) are filled into a dielectric elastomer matrix, and the carbon dots are uniformly dispersed in the matrix. As nano-conductive particles, the filling of carbon dots can improve the dielectric constant of the dielectric elastomer. At the same time, the uniformly dispersed carbon dots have fluorescence emission properties after ultraviolet excitation. Therefore, by filling carbon dots, the dielectric properties of the dielectric elastomer and its fluorescence emission properties can be improved at the same time, thus preparing a multifunctional dielectric elastomer.

[0017] (2) The filling of CDs generates many microcapacitors on the PDMS surface, resulting in a large polarization capacitance, which enhances interfacial polarization and improves the dielectric constant. The dielectric constant of pure PDMS is 3.34, while that of CDs can reach up to 6.4. The dielectric constant of the composite film is 92% higher than that of pure PDMS.

[0018] (3) The present invention achieves improved dielectric properties of DEA at a low filling rate. The filling rate of CDs is less than 0.040wt%, which is much lower than the filling rate of the prior art. The extremely low filling rate also reduces the influence of particle filling on Young's modulus and avoids the problem of breakdown under high electric field strength caused by particle agglomeration in the matrix.

[0019] (4) In this embodiment of the invention, silica and CDs are used to form a suspension. Because silica contains a large number of hydroxyl groups on its surface and has a particle size of about 30 nm, it has many micropores and a large surface energy. Although the physical properties of silica determine that it is difficult to dissolve in water, the hydroxyl groups and the large surface energy give it excellent dispersibility in water. Its solid particles can be uniformly distributed in water due to factors such as density and buoyancy to form an opaque suspension. The dispersed silica has a low degree of soft aggregation in water and has good compatibility with organic polymer materials. After the CDs solution is mixed with silica, it becomes a colloid with a unique morphology. This colloid avoids the aggregation of CDs particles, maintains its fluorescence performance, and has a certain affinity with the PDMS matrix. This colloid can be filled into PDMS by physical mixing (e.g., ultrasonic stirring) to finally achieve uniform dispersion of CDs in PDMS. On the other hand, the surface of silica has some pores. Under the action of water, well-dispersed CD particles can form bonds with silica, allowing CDs to be distributed on the silica surface and in the pores, thus promoting the uniform dispersion of CDs. More importantly, silica particles themselves have a high dielectric constant and a large surface capacitance. The internal pores increase their specific surface area, which can form more microcapacitors under an electric field, thereby improving the dielectric constant of the composite film.

[0020] (5) In the embodiments of the present invention, CDs particles and silica particles are mixed and then filled into the PDMS dielectric elastomer matrix. The beneficial effects of the combination of CDs, silica and PDMS are mainly: CDs have excellent water solubility and can be uniformly dispersed in water. Silica has excellent dispersibility in water. The suspension prepared by mixing silica and CDs solution not only achieves uniform dispersion of CDs and ensures the fluorescence performance of CDs, but also has good compatibility with PDMS matrix. It can be mixed with matrix and then cured, so that CDs that are originally incompatible with PDMS can be filled into PDMS.

[0021] (6) The specific silica filling rate also has a significant impact on the implementation of the present invention: when the silica filling rate is too low, it may not be able to fully exert its advantage of promoting CD dispersion, so CDs will be unevenly dispersed and CDs will agglomerate inside PDMS; when the silica content is too high, the compatibility between the suspension and the matrix will become worse, and even the phenomenon of silica agglomeration inside the matrix will occur. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a flowchart illustrating the preparation method of the CDs-PDMS composite film according to Embodiment 1 of the present invention. Figure 2 The preparation process of carbon quantum dots (CQDs) in Example 1 of this invention is as follows; Figure 3 The image shows a photograph (left) of the CQDs-silica suspension from Embodiment 1 of the present invention and a photograph (right) of the precursor after the suspension and PDMS are uniformly mixed under 360nm ultraviolet light. Figure 4 Optical micrographs of CQDs-PDMS composite films with different CQDs contents prepared in Example 1 of this invention: a. 0.005wt%; b. 0.010wt%; c. 0.015wt%; d. 0.020wt%; e. 0.025wt%; f. 0.030wt%; g. 0.035wt%; h. 0.040wt% Figure 5 This is a microscopic morphology diagram of the dielectric elastomer actuator prepared in Example 2; Figure 6 This is a SEM image of the single-walled carbon nanotube electrode from Example 2; Figure 7Photographs of CQDs-PDMS composite films with different CQDs contents under visible light (left) and ultraviolet light (right): a. pure PDMS; b. 0.005wt%; c. 0.010wt%; d. 0.015wt%; e. 0.020wt%; f. 0.025wt%; g. 0.030wt%; h. 0.035wt%; i. 0.040wt% Figure 8 The effect of CQDs content on the fluorescence emission spectrum of CQDs-PDMS composite films under different excitation wavelengths: (a) 300 nm; (b) 320 nm; (c) 340 nm; (d) 360 nm; (e) 380 nm; (f) 400 nm; (g) 420 nm; Figure 9 The dielectric constant (top) and dielectric loss (bottom) of the CQDs-PDMS composite film; Figure 10 The effect of electric field strength and CQDs content on DEA electro-actuation performance; Figure 11 The effect of frequency and CQDs content on DEA electro-actuated displacement; Figure 12 The effect of CQDs content on DEA electrical breakdown strength; Figure 13 Stress-strain curves of composite films with different CQD contents are shown. Figure 14 The effect of CQDs content on Young's modulus. Detailed Implementation

[0024] 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.

[0025] In this invention, carbon dot (CDs) particles are filled into a dielectric elastomer matrix, achieving uniform dispersion of the carbon dots within the matrix. As nano-conductive particles, the carbon dots enhance the dielectric constant of the dielectric elastomer. Simultaneously, the uniformly dispersed carbon dots exhibit fluorescence emission properties upon ultraviolet excitation. Therefore, by filling with carbon dots, both the dielectric properties of the dielectric elastomer and its fluorescence emission properties can be simultaneously improved, resulting in a multifunctional dielectric elastomer.

[0026] Example 1

[0027] Based on the above ideas, embodiments of the present invention provide a method for preparing a multifunctional dielectric elastomer. Figure 1 This is a flowchart illustrating the preparation method of the CDs-PDMS composite film according to an embodiment of the present invention. Figure 1 As shown, the preparation method includes the following steps: Step 1: Prepare carbon quantum dot (CDs) solution. Specifically, dissolve carbon dot particles in deionized water to prepare a carbon dot solution with a concentration range of 0.1-5 mg / ml.

[0028] The carbon dot CDs used to prepare the carbon dot CDs solution include: carbon quantum dots, graphene quantum dots, and carbonized polymer dots. In this embodiment, carbon quantum dots (CQDs) are used as an example to introduce the concept of the present invention. Figure 2 This describes the preparation process of carbon quantum dots (CQDs) according to an embodiment of the present invention. Figure 2 As shown, the process for preparing carbon quantum dots (CQDs) using the hydrothermal method includes steps 01-04: Step 01: Prepare a citric acid solution and add ethylenediamine to obtain a mixed solution. The concentration of citric acid is 0.05-0.2 g / ml, and the concentration of ethylenediamine is 0.15-5%. Specifically, dissolve 4.2 g of citric acid in 40 ml of deionized water, sonicate for 10 min and stir. After the citric acid is completely dissolved, add 1.34 ml of ethylenediamine, sonicate for 10 min and stir.

[0029] Step 02: Place the mixed solution in an autoclave and heat at 150-250℃ for 4-8 hours. After cooling to room temperature, remove the mixed solution. Specifically, after the solute has fully dissolved, transfer the mixed solution to a 200ml stainless steel autoclave lined with polytetrafluoroethylene and heat it in an oven at 200℃ for 6 hours. After the autoclave cools to room temperature, remove it.

[0030] Step 03: Centrifuge the mixed solution to remove impurities and then perform dialysis. Specifically, pour the solution from the reaction vessel into a centrifuge tube and centrifuge at 10,000 rpm for 5 minutes to remove impurities that have settled to the bottom. Then, dialyze the brown liquid in deionized water. During the dialysis process, change the deionized water every two hours for a total of 48 hours.

[0031] Step 04: The dialyzed solution is freeze-dried to obtain carbon quantum dot (CQD) particles. Specifically, the dialyzed solution is placed in a freeze dryer at a cold well temperature of -50°C for 72 hours. CQD particles are then obtained after freeze-drying.

[0032] Step 2: Add silica particles to the carbon quantum dot (CQDs) solution at a concentration of 1-3 wt% to obtain a CQDs-silica suspension and mix thoroughly. The silica particles are produced through the dehydration of silicic acid. This process is difficult to achieve complete dehydration, resulting in a large number of hydroxyl groups on the silica surface. Furthermore, the silica particles have a diameter of 30 nm, numerous micropores, and a high surface energy. Although the physical properties of silica make it difficult to dissolve in water, the hydroxyl groups and high surface energy give it excellent dispersibility in water. Due to factors such as density and buoyancy, the solid particles can be uniformly distributed in water to form an opaque suspension. The dispersed silica exhibits low soft aggregation in water and good compatibility with organic polymers. When CQDs solution is mixed with silica, it becomes a colloid with a unique morphology. This colloid avoids the aggregation of CQDs particles, maintains their fluorescence properties, and has a certain affinity for the PDMS matrix. This colloid can be filled into PDMS through physical mixing (such as ultrasonic stirring), ultimately achieving uniform dispersion of CQDs in PDMS.

[0033] Step 3: Provide PDMS. Add CQDs-silica suspension to PDMS and mix evenly to obtain a precursor. Add the precursor to a mold and heat to cure, obtaining a CQDs-PDMS composite film with fluorescent emission properties. Specifically, add 186 polydimethylsiloxane (186PDMS) to a measuring cup as the matrix. The mass ratio of matrix to curing agent is 10:1-20:1, for example, 15:1. Add CQDs-silica suspension to PDMS and stir to mix evenly to form the precursor. Then, vacuum to remove air bubbles. Use a triangle ruler to apply the precursor into a 0.5mm deep PMMA mold and heat at 60℃ for 5 hours to cure, obtaining a CQDs-PDMS composite film. Figure 3 The images show a CQDs-silica suspension (left) and a precursor (right) after uniform mixing of the suspension and PDMS under 360nm ultraviolet light, representing an embodiment of the present invention. Figure 3 It can be clearly seen that the prepared CDs-PDMS composite film can emit fluorescence under ultraviolet light excitation.

[0034] Example 2

[0035] This embodiment provides a dielectric elastomer film prepared according to the preparation method of Embodiment 1, and electrodes are coated on the upper and lower surfaces of the dielectric elastomer film to obtain a dielectric elastomer actuator. Specifically, 2 ml of deionized water and 18 ml of isopropanol are added to a centrifuge tube as solvents, 10 mg of single-walled carbon nanotube particles are dissolved in the solvents, sonicated for 120 minutes, and centrifuged at 7500 rpm for 15 minutes. The supernatant is then poured out as the single-walled carbon nanotube electrode for spraying.

[0036] The CQDs-PDMS composite film is removed from the mold and pre-stretched by 1.1-1.5 times using a rigid support. A mask is then attached to its surface, with the shape and size of the cutout in the center of the mask matching the inner diameter of the PMMA circular mold. The film is fixed on an 80°C heating platform. Heating is used to rapidly vaporize isopropanol to prevent it from forming microdroplets on the film surface, which would cause the single-walled carbon nanotube particles to aggregate. Single-walled carbon nanotube electrodes are then sprayed onto the upper and lower surfaces of the film using a spray gun, with the distance between the spray gun tip and the film controlled at 20cm. The sheet resistance of the electrodes is tested during the spraying process. 20ml-30ml of electrodes are sprayed onto each side of the film to ensure that the sheet resistance of the electrodes is less than 50kΩ. Conductive adhesive is used to lead out the electrodes. The CQDs-PDMS composite film is then fixed using a PMMA circular mold, thus creating a CQDs-PDMS dielectric elastomer actuator, i.e., a multifunctional dielectric elastomer actuator.

[0037] Example 3

[0038] This embodiment further tests the prepared sample's microstructure, optical properties, mechanical properties, dielectric properties, and other properties through various characterization and testing methods.

[0039] Figure 4 This is an optical micrograph of the CQDs-PDMS composite thin film prepared in Example 1. Figure 4 As shown, under a 100x optical microscope, no obvious particle aggregation was observed in the CQDs-PDMS composite film, indicating that the particles were well dispersed within the matrix. Silica particles are amorphous white powders, non-toxic, odorless, and non-polluting. Their microstructure is spherical, exhibiting flocculent and network-like particle structures. Silica particles are produced through the dehydration of silicic acid. This process is difficult to achieve complete dehydration, resulting in a large number of hydroxyl groups on the silica surface. Furthermore, the particle size is 30 nm, with numerous micropores and a relatively high surface energy. Although the physical properties of silica determine its poor water solubility, the hydroxyl groups and high surface energy give it excellent dispersibility in water. Due to factors such as density and buoyancy, the solid particles can be uniformly distributed in water to form an opaque suspension. The dispersed silica exhibits low soft aggregation in water and good compatibility with organic polymer materials. When CQDs solution is mixed with silica, it becomes a colloid with a unique morphology. This colloid not only avoids the aggregation of CQDs particles and maintains their fluorescence properties, but also has a certain affinity with the PDMS matrix. This colloid can be filled into PDMS through physical mixing, ultimately achieving uniform dispersion of CQDs in PDMS.

[0040] Figure 5The image shows the microstructure of the dielectric elastomer actuator prepared in Example 2. The three-layer structure of electrode-DE-electrode is shown in the left image, and the junction of the electrode and DE is shown in the right image. As shown in Figure 5, this dielectric elastomer actuator has a typical DEA three-layer structure, with a composite film in the middle layer and single-walled carbon nanotube electrodes on both sides. The total thickness of the DEA is approximately 340 μm, of which the composite film thickness is approximately 300 μm and the electrode thickness is approximately 20 μm.

[0041] Figure 6 This is a SEM (scanning electron microscope) image of the single-walled carbon nanotube electrode from Example 2. Figure 6 As shown, the single-walled carbon nanotube particles have a cross-sectional diameter of approximately 150 nm and a length of approximately 500 nm. SEM characterization results indicate that the CQDs and silica particles are uniformly distributed within the PDMS matrix with minimal aggregation, suggesting that the suspension of these two types of particles with water exhibits good compatibility with PDMS.

[0042] Figure 7 Images of CQDs-PDMS composite films with different CQDs contents under visible light (left) and ultraviolet light (right) are shown. The CQDs contents are as follows: a. pure PDMS; b. 0.005wt%; c. 0.010wt%; d. 0.015wt%; e. 0.020wt%; f. 0.025wt%; g. 0.030wt%; h. 0.035wt%; i. 0.040wt%. Figure 7 As shown, the composite film with a thickness of 1 mm has relatively poor transparency due to its thickness. Under visible light, its color is yellowish-brown, similar to the CQDs solution, and its transparency gradually decreases with increasing CQDs content. Under ultraviolet light, the composite film exhibits significant fluorescence emission, indicating that the CQDs in the PDMS did not undergo fluorescence quenching, achieving uniform dispersion of CQDs within the PDMS.

[0043] Figure 8 The effect of CQDs content on the fluorescence emission spectrum of CQDs-PDMS composite films under different excitation wavelengths was investigated. The excitation wavelengths were: (a) 300 nm; (b) 320 nm; (c) 340 nm; (d) 360 nm; (e) 380 nm; (f) 400 nm; (g) 420 nm. Figure 8As shown, composite films with different CQDs contents were excited using ultraviolet light in the range of 300-420 nm with 20 nm intervals, and their fluorescence emission spectra were tested. With increasing CQDs content, the fluorescence emission intensity first increased and then decreased, with the optimal filling rate being 0.025 wt%, at which point the strongest emission peak was observed. This indicates that when the content is below 0.025 wt%, particle aggregation is minimal and does not affect the film's fluorescence emission performance; the limiting factor is the CQDs content. When the content exceeds 0.025 wt%, particle aggregation and aggregation quenching gradually occur, leading to a gradual decrease in fluorescence intensity. With increasing excitation wavelength, the fluorescence emission intensity first increases and then decreases. The optimal excitation wavelength for the composite film is 340 nm-360 nm; excitation wavelengths that are too high or too low are not conducive to the generation of excited-state molecules.

[0044] Figure 9 The dielectric constant (top) and dielectric loss (bottom) of the CQDs-PDMS composite film are shown. Figure 9 As shown above, the dielectric constant of the composite films all exhibits a decreasing trend with increasing frequency. This decrease in dielectric constant is due to the hysteresis of electronic (or dipole) polarization to changes in the electric field; therefore, the dielectric constant always decreases with increasing frequency. With increasing CQDs content, the dielectric constant of the composite films gradually increases, and this increase is more pronounced in the low-frequency region. This is because the filling of CQDs generates many microcapacitors on the PDMS surface, producing a larger polarization capacitance, enhancing interfacial polarization, and increasing the dielectric constant. The dielectric constant of pure PDMS is 3.34, while that after CQDs filling can reach a maximum of 6.41, representing a 92% improvement in dielectric constant compared to pure PDMS. Figure 9 (Below) is the dielectric loss of the composite film. As the CQDs content increases, the dielectric loss of the composite film continues to increase. The dielectric loss and dielectric constant follow the law of "increasing and decreasing at the same time". As the frequency increases, the dielectric loss gradually decreases.

[0045] Figure 10 The effect of electric field strength and CQDs content on the electro-actuation performance of DEA. For example... Figure 10 As shown, after fabricating a DEA by spraying SWCNT electrodes onto the surface of a CQDs-PDMS composite film, its electro-actuated displacement was tested. With increasing CQDs content, the electro-actuated displacement of the DEA continuously increased due to the improved dielectric constant. At lower fill rates, the improvement in dielectric constant was limited; however, with increasing voltage, the displacement increase became more significant. Through CQDs filling, the electro-actuated displacement of the DEA fabricated from the composite film increased by 10-20 times compared to pure PDMS.

[0046] Single-walled carbon nanotube (SWN) electrodes are attached to the film surface by spraying a solution. Compared to commonly used carbon ester electrodes, the adsorption force between SWN particles and the film is weaker. With the increase of CQDs content and voltage, the electro-actuated displacement shows a continuous increasing trend. However, there is a limit to this displacement. As the deformation of the film gradually increases, the distance between the SWN particles attached to the film surface also gradually increases, and this change in distance is irreversible. This leads to an increase in electrode resistance. The increase in resistance, in turn, causes a decrease in the surface electric field of the elastomer and uneven resistance distribution. The decrease in surface electric field leads to a decrease in electro-actuation performance. At a voltage of 2.5 kV, the electro-actuated displacement shows a decreasing trend as the CQDs content increases from 0.025 wt%. Uneven resistance distribution can cause excessively large local electric fields, which can easily form conductive paths and cause electrical breakdown.

[0047] Figure 11 The effect of frequency and CQDs content on the electrically actuated displacement of the DEA. For example... Figure 11 As shown, both the magnitude and frequency of the driving voltage affect the electro-actuated displacement of the DEA. At a voltage of 2.5 kV, the electro-actuated displacement of DEAs with different CQD contents at different frequencies was tested. At lower frequencies, the CQD content has a more significant effect on displacement. As the frequency increases, the electro-actuated displacement of the DEA shows an overall decreasing trend. This is because after the driving frequency increases, the DEA begins the next stage of motion before reaching its maximum displacement. Above 15 Hz, the effect of CQDs on displacement is relatively small, and the displacement of all samples is close to 0 mm. In the frequency range of 8-15 Hz, the displacement of the DEA has a peak at 11 Hz, indicating that this frequency is the resonant frequency of the DEA. The DEA vibrates with a larger amplitude at 11 Hz than at other frequencies; 11 Hz is a resonance point for the DEA.

[0048] Figure 12 The effect of CQDs content on DEA electrical breakdown strength. For example... Figure 12 As shown, with the addition of CQDs and the increase of their content, the breakdown strength of DEA gradually decreases. After the CQDs content increases, they inevitably accumulate to a certain extent inside the film. Under the action of an electric field, they are prone to generate conductive paths, causing DEA breakdown. The higher the CQDs content, the greater the possibility of aggregation, the more severe the aggregation, and the lower the breakdown strength.

[0049] Figure 13 Stress-strain curves of composite films with different CQD contents are shown. Figure 14 The effect of CQDs content on Young's modulus. For example... Figure 13 and Figure 14As shown, with the increase of CQDs content, the Young's modulus of the composite film increased slightly, indicating that the filling of CQDs and silica particles had little impact on the mechanical properties of the composite film. Firstly, the particle filling rate was low; in this embodiment, the silica filling rate was 0.2 wt%, and the CQDs filling rate did not exceed 0.040 wt%. Secondly, both types of particles have small particle sizes, resulting in minimal impact on the modulus of the matrix. Furthermore, they were added to the PDMS matrix in a suspension manner, leading to low particle agglomeration and good compatibility with the matrix.

[0050] 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 method for producing a multifunctional dielectric elastomer, characterized by, include: Step 1: Prepare carbon dot CDs solution; The concentration of the carbon dot CDs solution is 0.1-5 mg / ml; Step 2: Add silica particles to the carbon dot CDs solution to obtain a CDs-silica suspension and mix it evenly; Step 3: Provide PDMS, add CDs-silica suspension to PDMS and mix evenly to obtain a precursor, add the precursor to a mold and heat to cure, to obtain a CDs-PDMS composite film with fluorescence emission properties; The carbon dots (CDs) used to prepare carbon dot solutions are carbon quantum dots. In the CDs-PDMS composite film, the mass filling rate of CDs is less than 0.040%, and the mass filling rate of silica is 1-3%.

2. The method for producing a multifunctional dielectric elastomer according to claim 1, characterized by, The mass filling rate of CDs in the CDs-PDMS composite film is 0.025 wt%.

3. The method for producing a multifunctional dielectric elastomer according to claim 1, characterized by, The dielectric constant of the CDs-PDMS composite film is 4.8-6.4, and the elastic modulus is 0.1-0.2 MPa.

4. The method for producing a multifunctional dielectric elastomer according to claim 1, characterized by, Methods for preparing carbon quantum dots include: Step 01: Prepare a citric acid solution and add ethylenediamine to obtain a mixed solution. The concentration of citric acid is 0.05-0.2 g / ml, and the concentration of ethylenediamine is 0.15-5%. Step 02: Place the mixed solution in an autoclave and heat at 150-250℃ for 4-8 hours. After cooling to room temperature, remove the mixed solution. Step 03: Centrifuge the mixed solution to remove impurities and then perform dialysis. Step 04: The dialysis mixture is freeze-dried to obtain carbon quantum dot particles.

5. The method of claim 1, wherein the multifunctional dielectric elastomer is prepared by the steps of: The excitation wavelength of the CDs-PDMS composite film with fluorescence emission properties is 340nm-360nm.

6. A dielectric elastomer film prepared by the method for preparing a multifunctional dielectric elastomer according to any one of claims 1-5.

7. The dielectric elastomer film of claim 6, wherein, The pre-stretch ratio of the dielectric elastomer film is 1.1-1.5, and the thickness of the dielectric elastomer film is 0.20-1.0 mm.

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