A method for amplifying electrically driven deformation using geometric structure

Abstract

This invention provides a method for amplifying electrically driven deformation using geometric structures, comprising the following steps: (1) preparing a material that can be driven under the action of an electric field, wherein the driving direction is determined by the direction of the electric field; (2) processing the material prepared in step (1) into a three-dimensional actuator with a certain three-dimensional geometric shape; (3) coating electrodes on the three-dimensional actuator prepared in step (2) and then performing electrical driving to obtain a three-dimensional actuator with amplified deformation. The method provided by this invention greatly reduces the driving voltage and increases the safety of the application; at the same time, controllable out-of-plane deformation can be obtained without additional processing; on the other hand, by obtaining a three-dimensional actuator through simple processing methods, deformation can be significantly amplified, greatly expanding the application field.

Description

Technical Field

[0001] This invention belongs to the field of novel functional materials, and specifically relates to a method for amplifying electrically driven deformation using geometric structures. Background Technology

[0002] Electroactive polymers can generate actuation under an external electric field, and due to their flexibility and actuation behavior similar to biological muscles, they are often referred to as "artificial muscles" (Q. Zhang, MRS Bull., 2008, 33: 173-181.). Among them, dielectric elastomers (DEs) have broad prospects in soft robotics and other fields due to their fast response speed and large actuation strain, but their applications are still limited by two aspects. First, the actuation electric field of DE materials is approximately 20-100 V / μm. A high actuation electric field not only means the need for large-volume power supply components, but also increases the safety of device operation. In addition, its deformation mode is in-plane expansion deformation caused by Maxwell stress generated under the action of an electric field. This small-area strain must be amplified by methods such as fixed pre-stretching, increasing the dielectric constant, and decreasing the elastic modulus (Q. Pei, Acc. Chem. Res., 2019, 52: 316-325). At the same time, for robotic applications, it is also important to convert in-plane expansion deformation into out-of-plane controllable deformation. This transformation can be achieved by applying a rigid frame (J. Zhu, Adv. Funct. Mater., 2019, 29: 1901908), embedding rigid fibers (DR. Clarke, Adv. Mater., 2015, 27: 6814-6819.), designing electrodes (JA. Lewis, Adv. Funct. Mater., 2020, 30: 1907375.), and designing anisotropic actuating materials (M. Sitti, Sci. Adv., 2019, 5: eaay0855.). However, in these methods, the designed device can only complete the actuation from two-dimensional to three-dimensional space with a single initial shape, and cannot be changed after the design is completed.

[0003] On the other hand, ionomer-metal composites (IPMC) (K. Asaka, Advanced Robotics., 2008, 22: 913-928), polyelectrolyte hydrogels (J. Tang, Nanoscale, 2019, 11: 2231-2237), polyvinyl chloride (PVC) gels (S. Cai, ACS Appl. Mater. Interfaces, 2021, 13: 24164-24172), and space charge conduction dielectrics (T. Hirai, J. Appl. Phys. 2003, 94: 2494) can all produce bending deformations with the electric field direction controlling the deformation direction under low electric field driving. However, the deformation mode can only achieve simple deformation from two-dimensional plane to three-dimensional plane, and the deformation amount is limited.

[0004] Therefore, it is necessary to design an electrically driven material that can produce large controllable out-of-plane deformation under a low electric field and has a complex three-dimensional shape. Summary of the Invention

[0005] The purpose of this invention is to provide a method for amplifying electrically driven deformation using geometric structures, which can generate large controllable out-of-plane deformation even under a relatively low electric field (2-10V / μm).

[0006] This invention provides the following technical solution:

[0007] A method for amplifying electrically driven deformation using geometric structures, the method comprising the following steps:

[0008] (1) Prepare materials that can be driven under the action of an electric field, and the driving direction is determined by the direction of the electric field;

[0009] (2) The material prepared in step (1) is processed into a three-dimensional actuator with a certain three-dimensional geometry;

[0010] (3) After coating the three-dimensional actuator prepared in step (2) with electrodes, perform electric drive to obtain the deformed and amplified three-dimensional actuator.

[0011] Applying dielectric elastomers to robotics requires methods such as pre-stretching or chemical modification to increase deformation. Simultaneously, it's necessary to convert the in-plane expansion deformation of the dielectric elastomer under electrical actuation into controllable out-of-plane deformation. Previous methods have all required additional external structures or complex multilayer electrode designs, making them quite complicated. Furthermore, the driving voltage is relatively high, approaching the material's breakdown voltage, which introduces safety risks into practical applications.

[0012] Materials such as ionomer-polymer-metal composites (IPMC), polyelectrolyte hydrogels, polyvinyl chloride (PVC) gels, and space charge-conducting dielectrics can all produce bending deformations with the electric field direction controlling the deformation direction under low electric field driving. However, the deformation mode can only achieve simple deformation from two-dimensional plane to three-dimensional plane, and the deformation amount is limited.

[0013] This invention provides a method for amplifying electrically driven deformation using geometric structures, based on materials possessing the characteristic of controlling the direction of driven deformation under the influence of an electric field. First, a material is prepared that can be driven under an electric field, with the driving direction determined by the electric field direction. Then, this material is processed to obtain an actuator with a specific three-dimensional geometry. Finally, electrodes are coated for electrically driven deformation, which is amplified at the actuator's hinge. This strong geometric effect stems from the change in bending stiffness. For planar actuators, the bending stiffness is uniform. For simple three-dimensional actuators bending along the short side, the bending stiffness of the long side will significantly exceed that of the short side, becoming the favorable driving direction. Upon further driving, the bending of the long side will generate positive feedback. Therefore, the bending drive will be significantly amplified along the bending direction.

[0014] In step (1), the mechanism for preparing the material that can be driven under the action of an electric field is selected from the space charge conduction mechanism, the ion migration mechanism, or the plasticizer molecule migration mechanism of polyvinyl chloride (PVC) gel actuator.

[0015] Preferably, the material that can be driven under the action of an electric field by utilizing the space charge conduction mechanism is a material containing polyurethane, polycaprolactone or thiol base, which may be a copolymer of one or more of these with other monomers.

[0016] Preferably, the material that utilizes the ion migration mechanism to achieve driving under the action of an electric field is the ion migration inside the polyelectrolyte hydrogel and the ion polymer metal composite (IPMC) under the action of an external electric field.

[0017] The processing method for processing the material into a three-dimensional actuator with a certain three-dimensional geometry in step (2) is selected from processing using the properties of the membrane itself, processing using 3D printing technology, or fixing using an external frame, etc.

[0018] Preferably, the processing using 3D printing technology includes laser sintering, material jetting, material extrusion, photopolymerization, and other processing technologies.

[0019] Preferably, the processing method utilizing the membrane's own characteristics is selected from processing by utilizing the dynamic covalent bond exchange within the membrane, processing by utilizing the orientation of liquid crystal units within the membrane, or processing by utilizing the thermally reversible properties of physical cross-linking.

[0020] Preferably, the dynamic covalent bonds used in the processing via dynamic covalent bond exchange within the membrane include chemical bonds that can undergo reversible exchange under stimuli such as light, heat, or humidity. Examples include ester bonds, urethane bonds, disulfide bonds, borate ester bonds, and diselenyl bonds. By fixing the three-dimensional shape and then subjecting it to stress relaxation under certain conditions, the three-dimensional shape can be obtained.

[0021] Preferably, the orientation method used in the processing by aligning the liquid crystal units inside the film includes solvent-assisted orientation or secondary crosslinking orientation.

[0022] Further preferably, the solvent-assisted orientation method includes solvents such as toluene, dichloromethane, and N,N-dimethylformamide. The liquid crystal elastomer is constructed in a three-dimensional shape under solvent-rich conditions, and the three-dimensional shape can be fixed after the solvent is evaporated at a suitable temperature.

[0023] Preferably, the physical crosslinking process utilizing the thermally reversible properties of physical crosslinking includes using hard segments in the thermoplastic polymer as crosslinking points, or crosslinking involving hydrogen bonds and metallic bonds in the material. Three-dimensional shape reconstruction can be achieved through heat treatment.

[0024] Preferably, the fixation using an external frame includes fixing the pre-stretched membrane material with a rigid plastic such as polyethylene terephthalate (PET) or a soft rubber such as polyacrylate (VHB) with a certain structure, which can form a three-dimensional structure after rebound.

[0025] The three-dimensional geometry in step (2) is selected from complex three-dimensional geometry that is partially or entirely composed of curved and twisted basic shapes.

[0026] The electrodes in step (3) are selected from carbon electrodes, metal electrodes and their composite electrodes.

[0027] The voltage for electric drive in step (3) is 2-10V / μm.

[0028] Preferably, the carbon electrode includes conductive carbon paste, single-walled carbon nanotube electrodes, etc.

[0029] The present invention provides a method for amplifying electrically driven deformation using geometric structures, the main principle of which includes two parts:

[0030] Materials are prepared that exhibit the property that the direction of deformation is determined by the direction of the electric field under electric field driving. This property can be achieved through space charge conduction in dielectrics, ion conduction in hydrogels, ion conduction in ion-polymer metal composites, and migration of small plasticizer molecules in polyvinyl chloride gels. Specifically, under an applied electric field, injected charges, charged ions, or small plasticizer molecules in the material tend to concentrate on one side of the positive or negative electrode, thus macroscopically causing the outer surface of that side to expand, resulting in bending deformation of the device to the other side.

[0031] This material is used to fabricate actuators with specific three-dimensional geometries. While the bending deformation of the aforementioned planar actuators is directionally controllable, the deformation is still relatively small. However, after fabricating a three-dimensional actuator composed of twisting or bending, the deformation will be geometrically amplified at the bending point. The principle behind this lies in the change in bending stiffness. For example, for a simple three-dimensional actuator bending along the short side, the bending stiffness of the long side will significantly exceed that of the short side, becoming a favorable driving direction.

[0032] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0033] Compared to dielectric elastomers, commonly used materials in artificial muscles, this type of material significantly reduces the driving voltage (2-10V / μm), increasing application safety. Furthermore, controllable out-of-plane deformation can be achieved without additional processing. On the other hand, by obtaining a three-dimensional actuator through simple processing methods, deformation can be significantly amplified, greatly expanding the application areas. Attached Figure Description

[0034] Figure 1 A schematic diagram of the planar actuator prepared in Example 1;

[0035] Figure 2 A schematic diagram of the bending actuator prepared in Example 1;

[0036] Figure 3 A schematic diagram of the planar actuator prepared in Example 2;

[0037] Figure 4 This is a schematic diagram of the bending actuator prepared in Example 2. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the scope expressed in the embodiments.

[0039] Example 1 (Dynamic Covalent Bond Exchange System)

[0040] raw material:

[0041] 5-Norbornene-2-methanol: TCI;

[0042] ε-caprolactone: TCI;

[0043] Dibutyltin dilaurate: TCI;

[0044] 2,2-Dimethoxy-2-phenylacetophenone: TCI;

[0045] Ethyl vinyl ether: TCI;

[0046] 2-Ethyltin(II) hexanoate: Sigma Aldrich;

[0047] 2-Ethyl isocyanate methacrylate: Macklin;

[0048] Anhydrous tetrahydrofuran: Macklin;

[0049] Grubb catalyst: Shanghai Keqin Technology Co., Ltd.

[0050] The preparation method is as follows:

[0051]

[0052] Weigh 0.83 g of 5-norbornene-2-methanol, 20 g of ε-caprolactone, and 0.10 g of tin(II) 2-ethylhexanoate, place them in a 50 ml flask, and purge with nitrogen for protection. Stir the mixture at 120°C for 8 hours. Dilute with 20 ml of dichloromethane, then pour into cold methanol to precipitate the product. Repeat this dissolution and precipitation process three times to remove unreacted monomers and catalysts. Dry the resulting product (N-PCL) in a vacuum oven at room temperature for 24 hours for later use.

[0053] Dissolve 15g of N-PCL in 60ml of anhydrous tetrahydrofuran, transfer to a 100ml flask, and purge with nitrogen for protection. Dissolve 0.083g of Grubb catalyst in 1.66ml of anhydrous tetrahydrofuran, then add to the flask and mix with the reactants. Incubate the mixture at 25°C with magnetic stirring for 2 hours, then quench with 0.68g of ethyl vinyl ether. Continue stirring for 2 hours, then precipitate the solid product in cold methanol. Further dissolve the product in dichloromethane and purify it by precipitation with cold methanol, repeating this process twice. After filtration, dry the resulting brush-like prepolymer under vacuum at room temperature for 24 hours.

[0054] Ethyl 2-isocyanate methacrylate (14.55 mg), brush prepolymer (1 g), and dibutyltin dilaurate (0.5%) were dissolved together in toluene (1 g), mixed, and stirred for 4 h under nitrogen protection at 65 degrees Celsius. This mixture was then used directly in the next synthesis step.

[0055] After adding 0.5% photoinitiator to the above solution, place it between two glass plates separated by a silicone rubber gasket and clamp it. Cure in a UV curing oven for 180 seconds, and then vacuum dry the cured polymer film at 70 degrees Celsius for 24 hours for later use.

[0056] The sample is clamped between two aluminum sheets (thickness: 0.1 mm). The three-layer sandwich film is then manually deformed into a preset arbitrary three-dimensional geometry and fixed with a fixture. It is then annealed at 140 degrees Celsius for 2 hours to complete the dynamic covalent bond exchange. The fixture and aluminum sheets are removed, and the polymer film is heated to 80 degrees Celsius to obtain the final three-dimensional permanent shape.

[0057] After coating with carbon nanotube electrodes, connecting to a high-voltage power supply allows for driving, with a driving voltage of 2-10V / μm.

[0058] like Figure 1 The image shows a comparison of the planar actuator before and after actuation with carbon nanotube electrodes.

[0059] like Figure 2 The image shows a comparison of the bending actuator before and after being driven with carbon nanotube electrodes.

[0060] Example 2 (Liquid Crystal System)

[0061] raw material:

[0062] Polycaprolactone (molecular weight 2500): Macklin, structure as follows:

[0063]

[0064] 1,4-Bis[4-(6-Acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (RM82): BaYi Space Company; Structure as follows:

[0065]

[0066] 3,6-Dioxa-1,8-octanedithiol: TCI;

[0067] 2,2-Dimethoxy-2-phenylacetophenone: TCI;

[0068] Toluene: Chinese medicine.

[0069] Preparation method:

[0070] Weigh RM82 (0.5g), diacrylate-modified polycaprolactone (0.186g), and 3,6-dioxa-1,8-octanedithiol (0.149g) into a culture bottle, add 0.5% photoinitiator and 0.25g toluene, and stir to dissolve. Then, place the mixture between two glass slides separated by a silicone rubber gasket and clamp it. After curing under UV light for 300 seconds, remove the film.

[0071] In the presence of solvent, the sample is clamped between two aluminum sheets (thickness: 0.1 mm). The three-layer sandwich film is then manually deformed into a predetermined arbitrary three-dimensional geometry and fixed with a clamp. It is then heated at 60 degrees Celsius for 8 hours to evaporate the solvent and fix the three-dimensional shape. The clamp and aluminum sheets are removed, and the polymer film is heated to 80 degrees Celsius and then placed at room temperature to obtain the final three-dimensional permanent shape.

[0072] After coating with carbon nanotube electrodes, connecting to a high-voltage power supply allows for driving, with a driving voltage of 2-10V / μm.

[0073] like Figure 3 The image shows a comparison of the planar actuator before and after actuation with carbon nanotube electrodes.

[0074] like Figure 4 The image shows a comparison of the bending actuator before and after being driven with carbon nanotube electrodes.

[0075] Example 3 (3D Printing System)

[0076] raw material:

[0077] RYOJI High-Quality Polyurethane Acrylates: Guangzhou Lihou Trading Co., Ltd.;

[0078] 3,6-Dioxa-1,8-octanedithiol: TCI;

[0079] 2,2-Dimethoxy-2-phenylacetophenone: TCI;

[0080] N,N-Dimethylformamide (DMF): Chinese medicine.

[0081] Preparation method:

[0082] Polyurethane acrylate and 3,6-dioxa-1,8-octanedithiol were mixed in a glass beaker at a molar ratio of 1:1, along with 50 wt% DMF and 3 wt% 2,2-dimethoxy-2-phenylacetophenone as photoinitiators. The mixture was stirred at room temperature for 30 minutes to form a clear solution.

[0083] The DLP printer is assembled from an electric motor and a commercial projector (DELL 1609WX). The printed 3D shape models were created using AutoCAD. All printed models were printed using a 100μm slice thickness and a 20-second exposure time, and then post-cured in a UV chamber for 5 minutes to obtain the final 3D shape.

[0084] After coating with carbon nanotube electrodes, connecting to a high-voltage power supply allows for driving at voltages of 2-10V / μm.

Claims

1. A method for amplifying electrically driven deformation using geometric structure, characterized by, The method includes the following steps: (1) Prepare materials that can be driven under the action of an electric field, and the driving direction is determined by the direction of the electric field; (2) The material prepared in step (1) is processed into a three-dimensional actuator with a certain three-dimensional geometry; (3) After coating the three-dimensional actuator prepared in step (2) with electrodes, perform electric drive to obtain the deformed and amplified three-dimensional actuator; The preparation of the material that can be driven under the action of an electric field in step (1) specifically includes: 5-norbornene-2-methanol, ε-caprolactone, and tin(II) 2-ethylhexanoate were weighed and placed in a flask, protected with nitrogen, and stirred to obtain a brush-like prepolymer N-PCL. Ethyl 2-isocyanate methacrylate, the brush-like prepolymer, and dibutyltin dilaurate were dissolved together in toluene, mixed, and stirred under nitrogen protection. After adding a photoinitiator, the mixture was placed between two glass plates separated by a silicone rubber gasket and clamped, then cured in a UV curing oven. The cured polymer film was then vacuum dried to obtain a material that can be driven by an electric field. Alternatively, weigh RM82, diacrylate-modified polycaprolactone, and 3,6-dioxa-1,8-octanedithiol into a culture bottle, add a photoinitiator, and add toluene, then stir to dissolve. Subsequently, it was placed between two glass plates separated by a silicone rubber gasket and clamped; after curing under a UV lamp, the film was removed; a material that can be driven under the action of an electric field was obtained; Alternatively, polyurethane acrylate and 3,6-dioxa-1,8-octanedithiol are mixed in a glass beaker at a molar ratio of 1:1, along with 50 wt% DMF and 3 wt% 2,2-dimethoxy-2-phenylacetophenone as photoinitiators. The mixture is stirred at room temperature for 30 minutes to form a transparent solution, thereby obtaining a material that can be driven under the action of an electric field. The three-dimensional geometry in step (2) is selected from complex three-dimensional geometry that is partially or entirely composed of curved and twisted basic shapes; The voltage for electric drive in step (3) is 2-10 V / µm.

2. The method for amplifying electrically driven deformation using geometric structures according to claim 1, characterized in that, The processing method for processing the material into a three-dimensional actuator with a certain three-dimensional geometry in step (2) is selected from processing using the properties of the membrane itself, processing using 3D printing technology, or fixing using an external frame.

3. The method for amplifying electrically driven deformation using geometric structures according to claim 2, characterized in that, The processing methods utilizing the membrane's inherent properties are selected from processing by utilizing the dynamic covalent bond exchange within the membrane, processing by utilizing the orientation of liquid crystal units within the membrane, or processing by utilizing the thermally reversible properties of physical cross-linking.

4. The method for amplifying electrically driven deformation using geometric structures according to claim 3, characterized in that, The dynamic covalent bonds in the processing utilizing the dynamic covalent bond exchange within the membrane include chemical bonds that can undergo reversible exchange under the stimulation of light, heat, or humidity; the orientation methods in the processing utilizing the orientation of liquid crystal units within the membrane include solvent-assisted orientation or secondary crosslinking orientation; the physical crosslinking in the processing utilizing the thermally reversible properties of physical crosslinking includes hard segments in thermoplastic polymers as crosslinking points, or materials containing hydrogen bonds and metallic bonds.

5. The method for amplifying electrically driven deformation using geometric structures according to claim 1, characterized in that, The electrodes in step (3) are selected from carbon electrodes, metal electrodes and their composite electrodes.

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