Pyroelectric gel film, preparation method thereof and application of pyroelectric gel film in flexible electronic device
By constructing a crystalline pyroelectric gel material in a gel system, the problems of slow response speed and insufficient mechanical flexibility in flexible electronic devices are solved, achieving rapid and sensitive response to various stimuli, and making it suitable for flexible electronic devices.
Patent Information
- Application Number
- CN202511130532.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-13
- Publication Date
- 2025-11-18
AI Technical Summary
Among existing flexible electronic devices, those based on ions as signal transmission carriers have slow response speeds and low sensitivity, and the mechanical flexibility of pyroelectric materials is insufficient, making it difficult to meet the integration requirements of flexible scenarios.
By introducing polymer segments containing polar groups and ionic salts or small molecule fillers into the gel system, a crystalline structure is constructed to prepare a novel pyroelectric gel material, which is then applied to two-end structure devices to utilize the response induced by stimuli such as light, temperature, deformation, and humidity.
It achieves rapid and sensitive response to various stimuli such as light, temperature, deformation and humidity, improving the electrical performance and mechanical flexibility of the device, and is suitable for the field of flexible electronic devices.
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Figure CN120966170A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of pyroelectric functional materials and flexible electronic devices. Specifically, it belongs to pyroelectric gel thin film and its preparation method and flexible electronic device application. BACKGROUND
[0002] Biological skin has multiple functions such as tactile perception, high flexibility, stretchability and self-healing. Inspired by this, the development of conductive elastomers that can simulate the functions of biological skin systems has attracted widespread attention [Adv. Funct. Mater. 2022, 32, 2110417]. In recent years, researchers have developed flexible conductive materials such as hydrogels and ionic gels based on the transmission mechanism of biological signals, taking ions as signal transmission carriers [Adv. Mater. 2024, 36, 2403937]. Such gel materials have high stretchability and self-healing ability, and show broad application prospects in stretchable ionic devices and electronic skin. However, devices based on ions as signal transmission carriers still face challenges such as slow response speed and low sensitivity [Nat. Commun. 2024, 15, 3086].
[0003] Pyroelectric effect is a physical mechanism that can output electrical signals without external voltage under temperature change conditions, and has been widely used in infrared detection, non-contact sensing, self-driven devices and energy harvesting [Small 2021, 17, 2103960]. However, the current mainstream pyroelectric materials are mostly inorganic crystals (such as lead titanate, zinc oxide and barium titanate), which have excellent pyroelectric properties but lack mechanical flexibility, making it difficult to meet the integration needs of flexible scenarios and limiting their application in new generation of flexible electronic systems [Nature 2022, 607, 480-485; The Innovation 2022, 3, 100204]. To overcome these problems, the present application introduces polar group-containing polymer segments and ionic salts or small molecule fillers based on the intrinsic flexibility and component adjustable characteristics of gel materials, and constructs a crystalline structure in the gel system, thereby giving it a significant pyroelectric response, and preparing a new type of pyroelectric gel material. The two-terminal structure device based on the pyroelectric gel can respond to multiple stimuli such as light, temperature, deformation and humidity, and has broad application potential in the field of flexible electronics. SUMMARY
[0004] In view of the problems of slow response speed, low sensitivity of gel-based flexible devices with ions as signal transmission carriers, and the lack of mechanical flexibility of pyroelectric materials, which makes it difficult to meet the integration needs of flexible scenarios, the present application prepares pyroelectric gel materials through a combination of component regulation and molecular structure design strategy, and applies them to the field of flexible electronic devices such as light detectors, temperature sensors, strain sensors and humidity sensors.
[0005] The pyroelectric gel film component in the present application comprises amorphous polyvinyl alcohol, crystalline polyvinyl alcohol, organic solvent, deionized water and ionic salt; after the two ends of the pyroelectric gel film are connected with electrodes, the device current will change under the conditions of light, strain, environmental temperature or humidity change; the light-heat effect or the change of environmental temperature causes the film to spontaneously polarize and generate induced charges on the surface; the deformation response is that the film generates current by molecular polarization and ion migration under pressure or bending deformation; the humidity response is that the film absorbs water molecules to cause the formation of ion concentration difference in the gel, forming a potential difference to generate ion current.
[0006] In order to construct the pyroelectric gel material, polyvinyl alcohol, ionic salt, organic solvent and deionized water are used as precursors; after the above precursors are heated, stirred and dissolved, they are placed in a vacuum oven for defoaming, and then a pyroelectric gel film with crystalline domain structure is prepared by freeze-thaw cycle treatment.
[0007] The ionic salt can be one of organic salts choline chloride, sodium citrate and sodium sulfate. The ionic salt can improve the conductivity of the gel film, and also can promote the formation of pyroelectric properties of the film, and the overall electrical properties of the pyroelectric gel film device will be improved.
[0008] The organic solvent can be one of ethylene glycol, butanediol, glycerol, oxalic acid and citric acid. Among them, 1,4-butanediol and glycerol can improve the mechanical properties of the gel as a secondary network, and also can improve the stability of the film as a water-retaining agent. In addition, these organic solvents also help the polarization performance of the film.
[0009] The preparation method of the pyroelectric gel film mainly consists of the following steps:
[0010] (1) The raw materials of the pyroelectric gel precursor are weighed according to the mass ratio: polyvinyl alcohol monomer: 10-20%, deionized water: 50-60%, organic solvent: 20-30%, ionic salt: 0.2-1%;
[0011] (2) The raw materials in (1) are added to a glass bottle in a certain mass ratio, heated and stirred in a water bath at 60-95℃, the stirring speed is 500-1000 rpm, and the stirring time is 2-6 hours, to obtain a homogeneous mixture solution;
[0012] (3) The mixed solution is cooled in air, and then placed in a vacuum oven at a temperature of 60-90℃ for 2-4h for degassing treatment;
[0013] (4) The degassed homogeneous transparent solution is injected into a polytetrafluoroethylene mold and slowly cooled at room temperature. Then the sample is frozen in a refrigerator at -4 to -30 °C for 6 to 10 h, and the film is thawed at room temperature for 0.5 to 2 h after freezing. The freezing-thawing process is repeated 1 to 4 times. During the freezing process, deionized water freezes, causing the gel to phase separate and form a polymer crystalline structure, and a pyroelectric gel film is obtained.
[0014] The present application develops a flexible electronic device integrating multiple functions based on the pyroelectric gel film.
[0015] Preparation method one: two electrodes (one of which is a copper electrode, and the other is one of a copper, gold, silver or indium oxide electrode) are placed on both sides of the mold, and then the pyroelectric gel precursor solution is injected into the mold. Subsequently, the mold containing the electrodes and the precursor solution is placed in a refrigerator, and the freezing-thawing process is repeated according to the above conditions.
[0016] Preparation method two: a copper electrode is placed at the bottom of the mold, and then the pyroelectric gel precursor solution is injected into the mold and subjected to the freezing-thawing process. Subsequently, the other electrode (one of a copper, gold, silver or indium oxide electrode) is transferred to the surface of the gel.
[0017] Through the two methods, a two-terminal structure device based on a pyroelectric gel with a vertical or planar structure can be obtained, which has response functions to light, temperature, deformation and humidity. The device has light or temperature response due to the light-heat effect or environmental temperature change, which causes the film to spontaneously polarize and generate induced charges on the surface electrode, forming a pyroelectric current. The deformation response is that the film generates an electric current under pressure or bending deformation, etc. The humidity response is that the film absorbs water molecules, which causes the formation of an ion concentration difference in the gel, forming an electric potential difference to generate an ionic current. BRIEF DESCRIPTION OF DRAWINGS
[0018] Figure 1 It is a physical map of the pyroelectric gel film of Example 2.
[0019] Figure 2 It is an XRD pattern of the pyroelectric gel film of Example 2.
[0020] Figure 3 It is a pyroelectric coefficient curve of the pyroelectric gel film of Example 2, and the pyroelectric coefficient is 0.011 μC cm - 2 K -1 .
[0021] Figure 4 It is a tensile-fracture curve of the pyroelectric gel film, and the elongation at break is greater than 180%.
[0022] Figure 5 This is an initial-stretched image of the pyroelectric gel film.
[0023] Figure 6 The tensile-fracture curves of the pyroelectric gel film before and after self-healing are shown.
[0024] Figure 7 The photoresponse of the pyroelectric gel photodetector at different wavelengths.
[0025] Figure 8 This is a time-current plot of the response of a pyroelectric gel photodetector to different light intensities at a wavelength of 455 nm.
[0026] Figure 9 The responsivity and specific detectivity of the pyroelectric gel photodetector at different light intensities at a wavelength of 455 nm are presented.
[0027] Figure 10 This is the temperature response curve of the pyroelectric gel device.
[0028] Figure 11 The pressure response curve of the pyroelectric gel device is shown.
[0029] Figure 12 The humidity response curve of the pyroelectric gel device is shown. Detailed Implementation
[0030] The invention and its applications will be further described in detail below with reference to examples and accompanying drawings.
[0031] Example 1
[0032] (1) Weigh 1.5g of polypropylene powder, 0.015g of choline chloride, 3g of ethylene glycol and 6g of deionized water into a glass bottle. Heat and stir in a water bath at 60°C for 6 hours, then cool it to room temperature. After that, place the solution in an oven at 90°C for 2 hours to degas it and obtain a uniform and transparent solution.
[0033] (2) Place the two thin copper electrodes on either side of the PTFE mold, ensuring that the contact area with the prepared gel is 25 mm². 2 Then, the pyroelectric gel precursor solution was injected into the mold, and then the gel was formed by the freeze-thaw cycle method: the sample was frozen in a refrigerator at -4°C for 10 h, and the film was thawed at room temperature for 0.5 h after freezing. This freeze-thaw process was repeated 4 times to obtain the pyroelectric gel film.
[0034] Example 2
[0035] (1) 1.5 g of polypropylene powder, 0.03 g of choline chloride, 3 g of butanediol, and 6 g of deionized water were weighed into a glass bottle, heated and stirred in a water bath at 75°C for 5 hours, and then cooled to room temperature. The solution was then degassed in an oven at 80°C for 2.5 hours to obtain a uniform and transparent solution.
[0036] (2) Two thin copper electrodes were placed on either side of the PTFE mold to ensure contact with the prepared gel with an area of 25 mm 2 The pyroelectric gel precursor solution was then injected into the mold, and then a gel was formed by a freeze-thaw cycle method: the sample was frozen in a refrigerator at -10°C for 8 hours, and then the film was thawed at room temperature for 1 hour. This freeze-thaw process was repeated 3 times to obtain a pyroelectric gel film. The actual picture of the pyroelectric gel film is shown in Figure 1
[0037] Example 3
[0038] (1) 1.5 g of polypropylene powder, 0.06 g of choline chloride, 3 g of glycerol, and 6 g of deionized water were weighed into a glass bottle, heated and stirred in a water bath at 80°C for 3 hours, and then cooled to room temperature. The solution was then degassed in an oven at 70°C for 3 hours to obtain a uniform and transparent solution.
[0039] (2) Two thin copper electrodes were placed on either side of the PTFE mold, and then the pyroelectric gel precursor solution was injected into the mold, and then a gel was formed by a freeze-thaw cycle method: the sample was frozen in a refrigerator at -15°C for 7 hours, and then the film was thawed at room temperature for 1.5 hours. This freeze-thaw process was repeated 3 times to obtain a pyroelectric gel film.
[0040] Example 4
[0041] (1) 1.5 g of polypropylene powder, 0.03 g of sodium citrate, 3 g of glycerol, and 6 g of deionized water were weighed into a glass bottle, heated and stirred in a water bath at 95°C for 2 hours, and then cooled to room temperature. The solution was then degassed in an oven at 65°C for 3.5 hours to obtain a uniform and transparent solution.
[0042] (2) One thin copper electrode was placed at the bottom of the PTFE mold, and then the pyroelectric gel precursor solution was injected into the mold, and then a gel was formed by a freeze-thaw cycle method: the sample was frozen in a refrigerator at -23°C for 6 hours, and then the film was thawed at room temperature for 2 hours. This freeze-thaw process was repeated 2 times to obtain a pyroelectric gel film. Then a thin copper electrode with an area half of the gel area was attached to the top layer to prepare a vertical structure photodetector based on the pyroelectric gel film.
[0043] Example 5
[0044] (1) 1.5 g of polypropylene powder, 0.03 g of sodium citrate, 3 g of oxalic acid, and 6 g of deionized water were weighed into a glass bottle, heated and stirred in a water bath at 95°C for 2 hours, and then placed in a room temperature environment to cool completely. Subsequently, the solution was degassed in an oven at 60°C for 4 hours to obtain a uniform and transparent solution.
[0045] (2) Two thin copper electrodes were placed on either side of the PTFE mold to ensure that the contact area with the prepared gel was 40 mm 2 Then, the pyroelectric gel precursor solution was injected into the mold, and then the gel was formed by a freeze-thaw cycle method: the sample was frozen in a refrigerator at -30°C for 6 h, and then the film was thawed at room temperature for 2 h. This freeze-thaw process was repeated once to obtain a pyroelectric gel film.
[0046] Example 6
[0047] (1) 1.5 g of polypropylene powder, 0.03 g of sodium sulfate, 3 g of oxalic acid, and 6 g of deionized water were weighed into a glass bottle, heated and stirred in a water bath at 95°C for 2 hours, and then placed in a room temperature environment to cool completely. Subsequently, the solution was degassed in an oven at 60°C for 4 hours to obtain a uniform and transparent solution.
[0048] (2) Two thin copper electrodes were placed on either side of the PTFE mold to ensure that the contact area with the prepared gel was 40 mm 2 Then, the pyroelectric gel precursor solution was injected into the mold, and then the gel was formed by a freeze-thaw cycle method: the sample was frozen in a refrigerator at -30°C for 6 h, and then the film was thawed at room temperature for 2 h. This freeze-thaw process was repeated once to obtain a pyroelectric gel film.
[0049] Example 7
[0050] (1) 1.5 g of polypropylene powder, 0.03 g of sodium sulfate, 3 g of oxalic acid, and 6 g of deionized water were weighed into a glass bottle, heated and stirred in a water bath at 95°C for 2 hours, and then placed in a room temperature environment to cool completely. Subsequently, the solution was degassed in an oven at 60°C for 4 hours to obtain a uniform and transparent solution.
[0051] (2) Two thin copper electrodes were placed on either side of the PTFE mold to ensure that the contact area with the prepared gel was 40 mm 2 Then, the pyroelectric gel precursor solution was injected into the mold, and then the gel was formed by a freeze-thaw cycle method: the sample was frozen in a refrigerator at -30°C for 6 h, and then the film was thawed at room temperature for 2 h. This freeze-thaw process was repeated once to obtain a pyroelectric gel film.
[0052] By comparing the properties of pyroelectric gels prepared under various conditions, the inventors found that the pyroelectric gel film with the best performance, stability, and sensitivity could be obtained under the conditions of Example 2. The following are the material characterization results of Example 2:
[0053] (1) The pyroelectric gel prepared in Example 2 was cut into cuboids of 20mm × 10mm × 1mm, as shown below. Figure 1 As shown, the pyroelectric gel exhibits high transparency.
[0054] (2) To study the structural properties of the organic gel, the inventors conducted X-ray diffraction (XRD) analysis to distinguish between crystalline and amorphous regions. For example... Figure 2 As shown, the XRD patterns reveal diffraction peaks at 2θ = 19.1°, 24.8°, and 40.3°, corresponding to crystalline and amorphous structures in the polypropylene organic gel and pyroelectric gel, respectively. The similarity of crystal structures among these samples indicates that the introduction of glycerol and choline chloride has a relatively small impact on the formation of crystal structures in the organic gel. Furthermore, the disappearance of the choline chloride diffraction peak indicates that it formed a homogeneous phase in the PVA organic gel. Since crystalline regions can serve as rigid, highly functional crosslinking points, increasing crystallinity helps improve the elastic properties of the material.
[0055] (3) The pyroelectric gel device was heated under zero bias conditions to test its pyroelectric performance. For example... Figure 3 As shown, a sharp pyroelectric current peak of approximately 6 nA was observed during the temperature rise. By integrating the current over time, the temperature-dependent pyroelectric coefficient Pi can be calculated using the following formula:
[0056]
[0057] Its performance is comparable to that of some traditional pyroelectric materials.
[0058] (4) Figure 4 and Figure 5 The organic gel exhibits excellent mechanical properties, with stress reaching 505 kPa and strain reaching 183%, demonstrating the material's outstanding deformability and mechanical strength, reflecting its dense and stable internal physical cross-linked network structure. Figure 6 The self-healing properties of the organic gel were further verified. By comparing the tensile properties before and after the injury, it can be seen that its mechanical properties are basically restored after healing, indicating that the gel has good self-repair ability. This behavior is mainly attributed to the synergistic effect of strong hydrogen bonds and interionic interactions between gel components.
[0059] (5) Figure 7The optical response characteristics of the pyroelectric photodetector in a wide spectral range are shown. The device produces significant photocurrent response in the wavelength range of 365 to 590 nm, and exhibits an enhanced current response at 455 nm. However, in the 625 to 1300 nm band, the photocurrent is significantly weakened, indicating that the device has low sensitivity to infrared light. This is mainly due to the fact that short-wavelength (i.e. high-frequency) light carries more energy and has stronger excitation ability. Therefore, the thermal energy generated by infrared irradiation is insufficient, resulting in a significant decrease in photocurrent. As shown in Figure 8 , under 455 nm laser irradiation, as the laser intensity increases from 0.45 μW / cm 2 to 17.28 μW / cm 2 , the peak photocurrent of the device increases from 0.9 nA to 8.3 nA. The device is significantly superior to previously reported gel-based detectors that rely on ion migration mechanisms in terms of detectable light intensity range and response speed, highlighting the unique advantages of pyroelectric gels. Further, the performance of the device was evaluated by calculating two key parameters - the photoelectric responsivity (R) and the detection rate (D*), as shown in Figure 9 , the photoelectric responsivity first increases and then decreases with the increase of light power density, reaching a maximum value of 42.06 mA / W at a wavelength of 455 nm. The specific detectivity shows a similar trend to the photoelectric responsivity, reaching a maximum value of about 7.65 x 10 2 Jones at a light intensity of 0.78 μW / cm 10 .
[0060] (6) In order to systematically evaluate the comprehensive performance of the pyroelectric gel of the present application in the perception of various environmental stimuli, the inventors designed and implemented temperature, pressure and humidity response tests. In the temperature response experiment, as shown in Figure 10 , as the ambient temperature gradually increases, the device produces a significant positive current peak (about 5.4 nA) at about 304.8 K, and quickly recovers after the signal peak, demonstrating high sensitivity to small temperature changes and excellent repeat stability. In the pressure response test, as shown in Figure 11 , when a constant external force is applied, the output current of the device quickly rises and remains stable within a few seconds, and quickly recovers to the initial value after the pressure is removed, showing good reversibility and fast response characteristics. In the humidity response experiment, as shown in Figure 12 , the device can show clear and distinguishable current stepwise growth with the periodic change of environmental humidity, and reach a peak value of about 3.7 nA, and the signal is stable and controllable. These results show that the pyroelectric gel can achieve sensitive, stable and fast response when dealing with different types of environmental stimuli, laying a solid foundation for its application in flexible electronic devices such as light detectors, temperature sensors, strain sensors and humidity sensors.
Claims
1. A pyroelectric gel film, characterized in that, The gel film comprises amorphous polyvinyl alcohol, crystalline polyvinyl alcohol, organic solvent, deionized water, and ionic salt; the pyroelectric gel film has pyroelectric properties; after electrodes are connected to both ends of the pyroelectric gel film, changes in device current will occur under conditions of light, strain, ambient temperature, or humidity; the photothermal effect or changes in ambient temperature cause the film to spontaneously polarize and generate induced charges on the surface. Deformation response is the current generated by molecular polarization and ion migration of the thin film under deformation such as pressure or bending; humidity response is the ion concentration difference formed in the gel after the thin film adsorbs water molecules, which in turn generates an ion current due to the potential difference.
2. The pyroelectric gel film according to claim 1, characterized in that: The pyroelectric gel film has stretchable properties.
3. A method for preparing a pyroelectric gel film according to claim 1, characterized in that... The raw materials and their mass percentages for the gel are: polyvinyl alcohol 10-20%, deionized water 50-60%, organic solvent 20-30%, and ionic salt 0.2-1%. Its preparation method includes the following steps: (1) Add the above raw materials into a glass bottle in a certain mass ratio, place it in a water bath at 60-95℃ and heat and stir, with a stirring speed of 500-1000 rpm and a stirring time of 2-6 hours to obtain a homogeneous mixture solution. (2) The mixture solution in step (1) is placed in air to cool, and then placed in a vacuum oven at a temperature of 60-90°C to degas, so as to obtain a uniform and transparent solution. (3) The uniform transparent solution in step (2) is injected into the polytetrafluoroethylene mold. First, it is cooled at room temperature. Then, the cooled sample is placed in a refrigerator at -4 to -30°C for 6 to 10 hours. After freezing, the film is thawed at room temperature for 0.5 to 2 hours. The freezing-thawing process is repeated 1 to 4 times to prepare the pyroelectric gel film.
4. The method for preparing a pyroelectric gel according to claim 3, characterized in that: The ionic salt is one of choline chloride, sodium citrate, and sodium sulfate.
5. The method for preparing a pyroelectric gel according to claim 3, characterized in that: The organic solvent is one of ethylene glycol, butanediol, glycerol, oxalic acid, and citric acid.
6. The method for preparing a pyroelectric gel according to claim 3, characterized in that: After the cyclic freezing-thawing process in step (3), the pyroelectric gel film will undergo phase separation, forming a polymer crystalline structure that improves the toughness and pyroelectric properties of the gel film.
7. The application of the pyroelectric gel film according to claim 1, characterized in that, After electrodes are connected to both ends of the pyroelectric gel film, the prepared two-end structure device can be used for the detection of light, temperature, pressure or humidity.
8. The application of a pyroelectric gel film according to claim 6, characterized in that, One of the electrodes used is a copper electrode, and the other is one of copper, gold, silver or indium oxide electrodes.