A temperature / light-sensitive flexible electrochemical gel actuator and its preparation and control method

Abstract

The present invention relates to a temperature / light-sensitive flexible electrochemical gel actuator and a preparation and control method, belonging to the technical field of ionic electroactive polymer preparation. Its structure includes two layers of conductive gel electrode films and a gel electrolyte interlayer film in the middle; the electrode film is prepared by casting a PEDOT:PSS solution into a film, and the electrolyte film is prepared by mixing and dissolving PVDF-HFP and an ionic liquid and then casting it into a film. Finally, the flexible actuator is prepared by hot pressing. The device has the advantages of integrated sensing and driving, high sensitivity, weak voltage drive, low cost, and simple preparation. This flexible actuator has broad application prospects in the fields of soft robots, artificial muscles, biomedicine, and intelligent wearable sensing.

Description

Technical Field

[0001] The invention relates to a temperature / light-sensitive flexible electrochemical gel actuator and a preparation and control method thereof, belonging to the technical field of preparation of ionic electroactive polymers. Background Art

[0002] Sensors and actuators are widely used in production and daily life and occupy an extremely important position. Flexible actuators are key components of flexible mechatronics. Among the emerging science and technology of this century, flexible mechatronics is one of the core technologies in important future development areas of humanity, such as bionic robotics, artificial intelligence, and wearable medical devices. Unlike traditional rigid mechatronics, flexible mechatronics abandons complex mechanical transmission devices and typically uses functional polymers or polymer-based composites as a basis to achieve complex terminal motion. Ionic electroactive polymers, the main material used in flexible actuators, not only have the advantages of low-voltage drive, fast response, large strain and stress, but also combine actuation and sensing functions. Currently, this material is also widely used in actuator exploration projects and has a wide range of applications.

[0003] The core of flexible electronic devices is the sensing material. This actuator exhibits mechanical properties and biocompatibility similar to human skin. Using the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid) (PEDOT:PSS) as an electrode film, a device integrating sensing and actuation was fabricated. This device mimics the movements of living organisms in nature, achieving a true biomimetic effect. This device offers advantages such as miniaturization, integrability, high sensitivity, a long detection range, and convenient signal extraction. By sensing temperature changes and providing timely feedback, it holds broad application prospects in soft robotics, artificial muscles, biomedicine, and smart wearable sensing, and holds significant practical significance. Summary of the Invention

[0004] The present invention proposes a structure, preparation and control method of a temperature / light-sensitive flexible electrochemical gel actuator, which utilizes the sensing and actuation functions of ion gel materials to achieve integrated temperature perception and drive. It has the advantages of high flexibility, high sensitivity, large working range and good stability, and is of great significance for promoting the application of flexible intelligent materials and the development of flexible machine electronic technology.

[0005] The thermo- and light-sensitive flexible electrochemical gel actuator comprises an upper electrode film, a lower electrode film, and an electrolyte layer located between the upper and lower electrode films. The electrolyte layer is a mixture of polyvinylidene fluoride copolymer (PVDF-HFP) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI). The actuator generates a thermoelectric potential under the influence of a temperature gradient and undergoes bending deformation when a voltage is applied.

[0006] The preparation of the temperature / light-sensitive flexible electrochemical gel actuator comprises the following steps:

[0007] Preparation of electrode film: Take the PEDOT:PSS solution, stir it, add the initiator, stir it evenly, and inject it into a customized mold. Let it stand at room temperature to allow it to evaporate naturally and form. Place the formed electrode film in an oven dryer, heat and dry it, and then anneal it at high temperature. The electrode film is prepared.

[0008] The mass percentage concentration of the PEDOT:PSS solution is 1.2%, the initiator is 1-butyl-3-methylimidazole p-toluenesulfonate, and the amount of initiator added is 1% of the solid content of the PEDOT:PSS solution; the standing time at room temperature is 24 hours, the heating and drying temperature is 60°C, the time is 120 minutes, and the high-temperature annealing temperature is 150°C, and the time is 30 minutes.

[0009] Preparation of the electrolyte layer: Take PVDF-HFP, add N,N-dimethylformamide, and stir at 80°C until fully dissolved; take the ionic liquid EMIMTFSI and add it to the fully dissolved solution, stir at room temperature until evenly dispersed, then inject it into the mold, place it in a fume hood, and heat it to fully evaporate the organic solvent. The electrolyte layer is prepared.

[0010] The ratio of the PVDF-HFP, N,N-dimethylformamide and ionic liquid EMIMTFSI is 1 g:10 ml:4 g.

[0011] Preferably, the 1-butyl-3-methylimidazole p-toluenesulfonate as an initiator can weaken the interaction between PEDOT and PSS, promote the separation and recombination of PEDOT:PSS molecular chains, and improve the electrode conductivity.

[0012] Preferably, PVDF-HFP is selected as the raw material for making the electrolyte layer. Compared with other commercial polymer materials, it has outstanding properties such as high mechanical strength, thermal stability, chemical resistance and high hydrophobicity. Compared with softer and mechanically lower perfluorocarbon polymers, PVDF-HFP has higher mechanical and impact strength, and has excellent creep resistance under long-term stress and cyclic loading fatigue.

[0013] Preferably, the electrolyte layer is 190 μm thick, and the electrode layers on the upper and lower surfaces are both 35 μm thick. The prepared electrode film and the electrolyte layer are pressed together by hot pressing to obtain a flexible actuator.

[0014] Preferably, the connection between the flexible actuator and the external circuit uses an Au electrode as a contact to avoid corrosion of the metal electrode at the connection by the ionic liquid.

[0015] Preferably, the excitation source of the flexible actuator adopts an electric field of 1-2V to electrically drive it.

[0016] Preferably, the customized mold is a polytetrafluoroethylene mold, which has the characteristics of being resistant to high temperatures, acids, alkalis, and various organic solvents.

[0017] The control method for a temperature- and light-sensitive flexible electrochemical gel actuator described in this invention is characterized by: when a heat source approaches the actuator, a temperature difference is generated between the upper and lower surfaces, resulting in a thermoelectric potential due to ion diffusion. The device is connected to an external circuit control system. When the thermoelectric potential reaches a certain threshold, a voltage is applied to the actuator, causing bending and straightening, thus providing feedback to external stimuli.

[0018] The technical principle of the present invention is as follows: Figure 2 As shown, according to the Soret effect, ions diffuse under the action of a temperature gradient. Since the migration rates of positive and negative ions are inconsistent, a thermoelectric potential is generated when there is a temperature difference between the upper and lower surfaces, so it can be used as a temperature sensor. Under the action of an electric field, positive and negative ions will also migrate. Since the volumes of positive and negative ions are different, one side will expand and the other side will shrink, thus presenting a curved state, so it can be used as a driver. The conductive polymer flexible driver material provided by the present invention is made of a commercially available PEDOT:PSS solution as the main material for making an electrode film. The electrode film is prepared by a casting method. Compared with the traditional flexible electrode preparation, the present invention not only has low production cost and simple process, but also greatly improves the conductivity and tensile properties of the prepared electrode film by adding a conductive agent and an initiator. PVDF-HFP and EMIMTFSI are mixed in a certain proportion to prepare an electrolyte layer. Within the range of low voltage (1-2V), it can achieve advantages such as large strain, stress, fast response speed, and large swing displacement. The device has high sensitivity, and its Seebeck coefficient reaches 2mv / k, which can sense small temperature changes. This conductive polymer flexible actuator has broad application prospects in the fields of soft robotics, artificial muscles, biomedicine, and smart wearable sensing and has important practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the drive structure;

[0020] Figure 2 Schematic diagram of the device's sensing and driving principles, where (a) is the driver's thermal sensing principle; (b) is the driver's electrically driven deformation principle;

[0021] Figure 3 The complete process of “seeking benefits and avoiding harm” of bionic flowers;

[0022] Figure 4 Positional awareness of array-type distributed drives. DETAILED DESCRIPTION

[0023] In the specific implementation process, in order to present the technical solution of the present invention more clearly and completely, the present invention will be clearly and completely described below with reference to specific examples. The examples described are only part of the examples of the present invention and cannot represent all examples.

[0024] Unless otherwise specified, materials and reagents used in the examples are commercially available or can be obtained by methods well known to those skilled in the art. Specific experimental methods and operating conditions generally followed conventional process conditions, those described in manuals, or those recommended by the manufacturer.

[0025] Example 1: A method for preparing a flexible driver with a layered structure and a highly conductive polymer, specifically: taking out the prepared electrode film and soaking it in an organic solvent alcohol for 30 minutes, then soaking it in deionized water for 30 minutes, cutting the electrode film soaked in deionized water into regular strips with scissors, soaking it in the ionic liquid EMIMTFSI for 30 minutes, and heating it in an oven to remove excess water in the film, so as to better allow the ionic liquid to enter the film. The driver is made by hot pressing. The three-layer structure of the driver is electrode film (upper) 1, electrolyte layer (middle) 2, electrode film (lower) 3. After the three layers of the driver are placed layer by layer, they are transferred to a glass slide, and the three-layer structure is pressed tightly by two glass slides. The glass slide is then placed in an 80°C oven and heated for 60 minutes. After heating, it is taken out and cut into the shape of a flower. The flexible electrode is clamped on the upper and lower surfaces in the center of the device. In order to avoid corrosion of the connection by the ionic liquid, an Au electrode is used as the contact electrode, and a copper wire is used to connect to the external electrical control system. Simulating the opening and closing of a bionic flower, such as Figure 3 As shown in the figure, when the palm is close to the upper surface of the flower, a temperature difference is generated between the upper and lower surfaces, thereby generating a thermoelectric potential. The controller captures the voltage signal and, depending on the voltage, the excitation source provides a voltage of 1-2V, thereby achieving the purpose of driving and completing the complete process of "seeking benefits and avoiding harm".

[0026] Example 2: The structure, preparation, and control method of a temperature / light-sensitive flexible electrochemical gel actuator in this embodiment are the same as those in Example 1. The specific steps are as follows: take out the prepared electrode film and soak it in organic solvent alcohol for 30 minutes, then soak it in deionized water for 30 minutes. Cut the electrode film soaked in deionized water into regular strips with scissors, soak it in the ionic liquid EMIMTFSI, and heat it in a 60°C forced air drying oven for 3 hours to remove excess moisture in the film and better allow the ionic liquid to penetrate into the film. The actuator is made by hot pressing. The three-layer structure of the actuator is an electrode film (top), an electrolyte layer (middle), and an electrode film (bottom). After the three layers of the actuator are placed layer by layer, they are transferred to a glass slide, and the three-layer structure is pressed tightly by two glass slides. The glass slide is then placed in an 80°C oven and heated for 60 minutes. After heating, it is removed. The device was cut into four strips measuring 30mm x 6mm and 260μm thick (the electrolyte layer was 190μm thick, and the upper and lower electrode layers were 35μm thick each). A custom screen printing screen was used, and the film was placed under the screen. Silver paste was then printed as the conductive medium, and after drying, the flexible circuit board was obtained.

[0027] Arrange the cut components on the four sides of the flexible circuit board, package them and connect them to the external electrical control system. Figure 4 .

[0028] When a finger approaches one of the devices, a corresponding thermoelectric potential is generated, and the finger's specific position can be determined based on the magnitude of the thermoelectric potential. A multi-channel voltage monitoring and control module eliminates the need for a separate control unit and electric field, enabling independent acquisition and control of electrical signals from each device. Based on the potential, appropriate feedback is generated, and the excitation source applies voltage to the device, completing the drive process.

[0029] Although the embodiments disclosed in this application are as described above, the contents described are merely embodiments adopted to facilitate understanding of this application and are not intended to limit this application. Any person skilled in the art to which this application belongs may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this application. However, the scope of patent protection of this application shall still be based on the scope defined by the attached claims.

Claims

1. A control method for a temperature / light-sensitive flexible electrochemical gel actuator, characterized in that: The temperature / light-sensitive flexible electrochemical gel actuator includes an upper electrode film, a lower electrode film, and an electrolyte layer located between the upper electrode film and the lower electrode film. The electrolyte layer is a mixture of polyvinylidene fluoride copolymer (PVDF-HFP) and 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide (EMIMTFSI). The temperature / light-sensitive flexible electrochemical gel actuator generates a thermoelectric potential under the action of a temperature gradient and bends and deforms when a voltage is applied. When a heat source approaches the actuator, a temperature difference is generated between the upper and lower surfaces of the actuator, and a thermoelectric potential is generated due to the diffusion of ions. The device is connected to an external circuit control system. When the thermoelectric potential reaches a certain threshold, a voltage is applied to the actuator to achieve bending and straightening movements, thereby realizing feedback to external stimuli.

2. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 1, characterized in that: The electrolyte layer had a thickness of 190 μm.

3. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 1, characterized in that: The thickness of the upper electrode film and the lower electrode film are both 35 μm.

4. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 1, characterized in that: The connection between the temperature / light-sensitive flexible electrochemical gel actuator and the external circuit uses an Au electrode as a contact point to prevent the ionic liquid from corroding the metal electrode at the connection point.

5. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 1, characterized in that: The excitation source of the temperature / light-sensitive flexible electrochemical gel actuator adopts an electric field of 1-2V to electrically drive it.

6. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 1, characterized in that: The preparation method of the temperature / light-sensitive flexible electrochemical gel actuator comprises the following specific steps: (1) Preparation of electrode film: Take the PEDOT:PSS solution, stir it, add the initiator, stir it evenly, and inject it into a customized mold. Let it stand at room temperature to allow it to evaporate naturally and form. Place the formed electrode film in an oven dryer, heat and dry it, and then anneal it at high temperature. The electrode film is prepared. (2) Preparation of the electrolyte layer: Take PVDF-HFP, add N,N-dimethylformamide, place it at 80°C and stir until it is fully dissolved; take the ionic liquid EMIMTFSI and add it to the fully dissolved solution, stir it at room temperature until it is evenly dispersed, then inject it into the mold, place it in a fume hood, and heat it to fully evaporate the organic solvent. The electrolyte layer is prepared; (3) The prepared electrode film and electrolyte layer are pressed together by hot pressing to obtain a flexible actuator.

7. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 6, characterized in that: In step (1), the mass percentage concentration of the PEDOT:PSS solution is 1.2%, and the initiator is 1-butyl-3-methylimidazole p-toluenesulfonate; the standing time at room temperature is 24 hours, the heating and drying temperature is 60°C, the time is 120 minutes, and the high-temperature annealing temperature is 150°C, the time is 30 minutes; and the customized mold is a polytetrafluoroethylene mold.

8. The control method of a temperature / light-sensitive flexible electrochemical gel actuator according to claim 6, characterized in that: In step (2), the ratio of PVDF-HFP, N,N-dimethylformamide and ionic liquid EMIMTFSI is 1g:10ml:4g.

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