Preparation method and application of flexible fluorescent piezoelectric composite film with optical touch sensing coupling

Abstract

The application relates to the technical field of sensors, in particular to a preparation method and application of a flexible fluorescent piezoelectric composite film with photo-tactile perception coupling, which comprises the following steps: first mixing CQDs and deionized water according to a preset first mass ratio to obtain a CQDs suspension; mixing a fluorine-containing piezoelectric polymer, a water-soluble pore-forming agent, a volatile auxiliary agent and N, N-dimethylformamide to obtain a pore-forming precursor mixed solution; depositing the pore-forming precursor mixed solution on a conductive surface of an electrode and performing first heat treatment to obtain a pore-forming agent dense film; and placing the pore-forming agent dense film into the CQDs suspension to perform immersion treatment and obtain a flexible fluorescent piezoelectric composite film. The porous structure is shaped to support the dispersion implantation of single quantum state CQDs, so that the composite film and the device thereof are endowed with fluorescent light perception function; the beta piezoelectric phase in the fluorine-containing piezoelectric polymer is formed through synchronous polarization induction, so that the composite film and the device thereof are endowed with high sensitivity.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, specifically to a method for preparing and applying a flexible fluorescent piezoelectric composite film with photosensitive coupling. Background Technology

[0002] With the rapid development of flexible electronics, wearable devices, and intelligent human-computer interaction technologies, multifunctional flexible sensing materials capable of simultaneously sensing optical and mechanical tactile signals have attracted widespread attention. Existing flexible sensors mostly focus on the detection of single physical quantities, such as relying solely on the piezoelectric effect to achieve pressure or strain sensing, or utilizing only the fluorescence / photoelectric effect to achieve optical signal detection. These methods are insufficient to meet the demands for simultaneous sensing and fusion of multimodal information in complex application scenarios.

[0003] Fluorinated piezoelectric polymers (such as PVDF and its derivatives) are widely used in flexible pressure sensing and energy harvesting due to their excellent flexibility, chemical stability, and piezoelectric properties. However, traditional piezoelectric polymer films mainly convert mechanical stimuli into electrical signals, resulting in relatively limited functionality and a lack of direct response to light stimuli. On the other hand, carbon quantum dots (CQDs) offer advantages such as simple fabrication, tunable fluorescence properties, and good biocompatibility, showing promising applications in optical sensing and fluorescence displays. However, when used alone, they often struggle to simultaneously achieve flexibility, mechanical stability, and piezoelectric response characteristics.

[0004] In the existing technology, CQDs have been introduced into fluorinated piezoelectric polymer matrices to construct PVDF / CQDs composite films that combine fluorescence response and piezoelectric properties, in order to achieve the coordinated perception of optical signals and tactile signals.

[0005] However, the limited controllability of the pore structure in PVDF and the weakening of the β-piezoelectric phase-induced effect prevent the composite film from imparting high sensitivity to the sensor. Therefore, the application of PVDF / CQDs composite films in flexible antennal sensors still faces significant challenges that need to be addressed. Summary of the Invention

[0006] (a) Purpose of the invention The purpose of this invention is to provide a method for preparing and applying a flexible fluorescent piezoelectric composite film with photosensitive coupling. By shaping a porous structure to support the diffuse implantation of single quantum states (CQDs), the composite film and its device are endowed with fluorescent photosensitive function. By inducing the formation of a β-piezoelectric phase in a fluorinated piezoelectric polymer through synchronous polarization, the composite film and its device are endowed with high sensitivity.

[0007] (II) Technical Solution To address the above problems, this invention provides a method for preparing a flexible fluorescent piezoelectric composite film with photosensitive coupling, comprising: CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. A fluorinated piezoelectric polymer, a water-soluble pore-forming agent, a volatile auxiliary agent, and N,N-dimethylformamide are mixed to obtain a pore-forming precursor mixture. The pore-forming precursor mixture is deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of pore-forming agent. The pore-forming agent-dense film is immersed in the CQDs suspension for impregnation treatment to obtain a flexible fluorescent piezoelectric composite film.

[0008] In another aspect of the present invention, preferably, the preset first mass ratio is 1:(5000~100000), and the first mixing time is 6~24h.

[0009] In another aspect of the present invention, preferably, the mixing of the fluorinated piezoelectric polymer, the water-soluble pore-forming agent, the volatile auxiliary agent, and N,N-dimethylformamide to obtain the pore-forming precursor mixture comprises: The volatile auxiliary agent and N,N-dimethylformamide are mixed in a second mixture at a preset second mass ratio to obtain a first mixture. The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain a second mixture; The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture; The third mixture is defoamed to obtain a pore-forming precursor mixture.

[0010] In another aspect of the present invention, preferably, the volatile auxiliary agent includes at least one selected from ethanol, isopropanol, ethylene glycol, and acetone; The preset second mass ratio is 1:(1~5); The second mixing temperature is room temperature, and the second mixing time is 0.1~0.5h.

[0011] In another aspect of the present invention, preferably, the water-soluble pore-forming agent includes at least one of starch, raffinose, chitosan, maltose, dextrin, and fructose; The preset third mass ratio is 1:(30~300); The temperature of the third mixing is room temperature, and the time of the third mixing is 1 to 5 hours.

[0012] In another aspect of the present invention, preferably, the fluorinated piezoelectric polymer comprises at least one of PVDF, PVDF-HFP, PVDF-TrFE, and other derivatives; The preset fourth mass ratio is 1:(10~20); The temperature of the fourth mixing is 60~100℃, and the time of the fourth mixing is 2~10h; The defoaming treatment includes standing at room temperature for 10-30 minutes.

[0013] In another aspect of the present invention, preferably, the conductive surface of the electrode is subjected to oxygen plasma treatment for a time of 5 to 15 minutes. The deposition process includes any one of the following: spin coating, electrospinning, casting, screen printing, coating, 3D printing, and doctor blade coating. The temperature of the first heat treatment is 50~70℃, and the time of the first heat treatment is 20~60min.

[0014] In another aspect of the present invention, preferably, the step of immersing the pore-forming agent dense film in the CQDs suspension for impregnation treatment to obtain a flexible fluorescent piezoelectric composite film includes: The pore-forming agent dense film is immersed in the CQDs suspension for impregnation treatment to obtain the first composite film; The first composite membrane is cleaned with ethanol to obtain the second composite membrane; The second composite film is subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite film.

[0015] In another aspect of the present invention, preferably, the temperature of the impregnation treatment is room temperature, and the time of the impregnation treatment is 12-24 hours; The temperature of the second heat treatment is 100~120℃, and the time of the second heat treatment is 1~2h.

[0016] In another aspect of the present invention, preferably, is the application of the photosensitive coupled flexible fluorescent piezoelectric composite film prepared by the method described above in a flexible tactile sensor.

[0017] (III) Beneficial Effects The above-described technical solution of the present invention has the following beneficial technical effects: This invention constructs a composite membrane with a microporous structure by depositing a mixture of fluorinated piezoelectric polymer, a water-soluble pore-forming agent, a volatile auxiliary agent, and N,N-dimethylformamide. The membrane is then immersed in a CQDs suspension for impregnation, allowing the CQDs to penetrate into the membrane along the pore channels under the Kirkendall diffusion effect. The CQDs preferentially undergo chemical adsorption and stable anchoring on the pore walls and polymer backbone surface. This achieves uniform dispersion and efficient loading of CQDs in the composite membrane without compromising the overall flexibility and mechanical properties of the membrane, effectively avoiding CQDs aggregation and fluorescence quenching. Simultaneously, it enhances the content and orientation of the β-piezoelectric phase in the fluorinated piezoelectric polymer. The branched functional groups of the water-soluble pore-forming agent and the polar functional groups such as hydroxyl, carboxyl, amino, and sulfonic acid groups on the CQDs surface jointly induce the ordered orientation of the fluorinated piezoelectric polymer molecular chains. The hydroxyl groups enriched on the substrate surface after oxygen plasma treatment further enhance the interfacial polarization effect, effectively compensating for the limited effect of a single induced polarization method, thereby significantly improving the sensitivity of the composite membrane. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of one embodiment of the present invention; Figure 2 This is a SEM image of the composite membrane from Example 1; Figure 3 This is a macroscopic photograph of the composite film of Example 1 under 254nm ultraviolet excitation; Figure 4 This is the FT-IR spectrum of the composite film in Example 1; Figure 5 This is the output voltage-time curve of the sensor assembled with the composite membrane in Example 1; Figure 6 This is the output voltage-time curve of the sensor assembled with the composite film in Example 1 when sensing finger bending; Figure 7 This is the output voltage-force curve of the sensor assembled with the composite membrane in Example 1; Figure 8 This is a sensitivity diagram of the sensor assembled with the composite film in Example 1 under different lighting conditions; Figure 9 This is a comparative output voltage-force curve of a sensor assembled with a pure PVDF-HFP film. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0020] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example 1 A method for preparing a flexible fluorescent piezoelectric composite film with phototactile sensing coupling. Figure 1 An overall flowchart of one embodiment of the present invention is shown, as follows: Figure 1 As shown, it includes: CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. The preset first mass ratio is 1:(5000~100000) to ensure the dispersion of CQDs in the aqueous medium and the subsequent membrane permeation effect. The mixing can be carried out by magnetic stirring, ultrasonic dispersion or a combination thereof. The first mixing time is 6~24h to fully realize the uniform dispersion of CQDs in water and form a stable suspension to prevent aggregation or precipitation.

[0024] A fluorinated piezoelectric polymer, a water-soluble pore-forming agent, a volatile auxiliary agent, and N,N-dimethylformamide are mixed to obtain a pore-forming precursor mixture; in this embodiment, it includes: A volatile auxiliary agent and N,N-dimethylformamide are mixed in a second process at a preset second mass ratio to obtain a first mixture. The volatile auxiliary agent includes at least one of ethanol, isopropanol, ethylene glycol, and acetone. The preset second mass ratio is 1:(1~5). The second mixing temperature is room temperature, and the second mixing time is 0.1~0.5 h. Each part of volatile auxiliary agent corresponds to 1~5 parts of N,N-dimethylformamide to ensure that the auxiliary agent is fully dissolved in the solvent system and to adjust the solution viscosity. The mixing process is carried out at room temperature and can be carried out by magnetic stirring, mechanical stirring, or ultrasonic dispersion to obtain a uniform and transparent first mixture.

[0025] A water-soluble pore-forming agent and the first mixture are mixed a third time at a preset third mass ratio to obtain a second mixture. The water-soluble pore-forming agent includes at least one of starch, raffinose, chitosan, maltose, dextrin, and fructose. The preset third mass ratio is 1:(30~300). The third mixing temperature is room temperature, and the third mixing time is 1~5 hours. The water-soluble pore-forming agent acts as a soft template to form a microporous structure during subsequent membrane heat treatment and solvent exchange, and provides stable adsorption sites for CQDs. Each part of pore-forming agent corresponds to 30~300 parts of the first mixture to ensure uniform pore structure and controllable pore size. The mixing process is carried out at room temperature for 1~5 hours. Low-speed stirring or intermittent ultrasonic oscillation can be used to prevent the pore-forming agent from agglomerating and to ensure its full dissolution or uniform dispersion in the solution, thereby laying the foundation for the subsequent microporous structure shaping of the composite membrane.

[0026] The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture. The fluorinated piezoelectric polymer includes at least one of PVDF, PVDF-HFP, PVDF-TrFE, and other derivatives, and its function is to provide piezoelectric response in the composite film. The preset fourth mass ratio is 1:(10~20). The fourth mixing temperature is 60~100℃, and the fourth mixing time is 2~10h. Each part of polymer corresponds to 10~20 parts of the second mixture to ensure that the polymer is fully dissolved and obtains a suitable viscosity. The mixing temperature is controlled at 60~100℃, and the mixing time is 2~10 hours. Uniform dissolution can be achieved by magnetic stirring or mechanical stirring, so that the polymer chains are fully integrated with the pore-forming agent and auxiliary agents to form a uniform and viscous third mixture. At the same time, it promotes the initial ordered arrangement of polymer molecular chains and provides a precursor structure for subsequent β-phase piezoelectric polarization.

[0027] The third mixture is defoamed to obtain the pore-forming precursor mixture. The defoaming process includes allowing it to stand at room temperature for 10–30 minutes. To eliminate air bubbles and micropores generated during mixing, the third mixture needs to be defoamed to obtain the final pore-forming precursor mixture. The defoaming process involves allowing the liquid to stand at room temperature, allowing air bubbles to rise and release naturally, ensuring a smooth membrane surface and continuous, uniform pore structure during membrane coating, while avoiding membrane defects and mechanical property degradation caused by air bubbles. If necessary, gentle vacuum suction or low-speed centrifugation can be combined to further improve the defoaming effect and obtain a higher quality pore-forming precursor mixture.

[0028] Through the above multi-step mixing and defoaming treatment, the final pore-forming precursor mixture has a uniform component distribution, suitable viscosity and stability, and can be directly used for deposition on the conductive surface of the electrode for film formation and heat treatment operations to construct a controllable pore structure, providing a solid material basis for CQDs impregnation and composite film fluorescence light sensing and high-sensitivity piezoelectric tactile sensing.

[0029] The pore-forming precursor mixture is deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense pore-forming film. The conductive surface of the electrode is then treated with oxygen plasma for 5-15 minutes. Prior to deposition, the conductive surface of the electrode is treated with oxygen plasma for 5-15 minutes, which can be performed in a vacuum plasma device. This treatment introduces active hydroxyl (-OH) functional groups onto the electrode surface, improving the interfacial wettability and adhesion between the electrode and the composite film, while providing a favorable interface for subsequent PVDF molecular chain orientation and β-piezoelectric phase induction. The deposition process includes any one of the following: spin coating, electrospinning, casting, screen printing, coating, 3D printing, and doctor blade coating. Spin coating obtains a uniform film layer by controlling the rotation speed and time; electrospinning can obtain a nanofiber-like film structure; casting, doctor blade coating, and coating are suitable for preparing large-area uniform films; and screen printing and 3D printing are suitable for forming complex patterned or microstructured films. The temperature of the first heat treatment is 50~70℃ and the time of the first heat treatment is 20~60min, so that the solvent can fully evaporate and the film can be initially solidified. At the same time, the pore-forming agent forms a tightly arranged preliminary pore structure in the film, resulting in a flat and dense pore-forming agent dense film, which provides pore support for the subsequent uniform impregnation of CQDs.

[0030] The pore-forming agent-dense film is immersed in the CQDs suspension for impregnation treatment to obtain a flexible fluorescent piezoelectric composite film, comprising: The pore-forming agent-dense membrane is immersed in the CQDs suspension for impregnation treatment to obtain a first composite membrane. The impregnation treatment temperature is room temperature, and the impregnation treatment time is 12-24 hours. The impregnation process is carried out at room temperature for 12-24 hours, allowing the CQDs to diffuse inward along the membrane pores under the action of Kirkendall diffusion effect, and preferentially adsorb onto the pore walls and polymer backbone surface to form a stable chemical bond, thereby achieving uniform distribution of CQDs in the membrane and avoiding aggregation and fluorescence quenching.

[0031] The first composite membrane is cleaned with ethanol to obtain the second composite membrane. After impregnation, the first composite membrane is cleaned with ethanol to remove unadsorbed CQDs and residual solvent on the surface to obtain the second composite membrane, thereby further improving the fluorescence stability and surface smoothness of the membrane.

[0032] The second composite film is subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite film. The temperature of the second heat treatment is 100~120℃, and the time is 1~2 hours. The second heat treatment further removes residual moisture and solvent by heating, while promoting the interfacial bonding and partial molecular chain rearrangement between CQDs and the PVDF framework, enhancing the mechanical strength and flexibility of the film, and facilitating the formation of the β-piezoelectric phase of PVDF, thereby obtaining the final flexible fluorescent piezoelectric composite film. This composite film not only maintains good flexibility and mechanical stability, but also possesses highly sensitive tactile sensing function and stable fluorescence light sensing function, and can be directly used in flexible sensors and multimodal sensing devices.

[0033] Furthermore, this embodiment also provides the application of the photosensitive coupled flexible fluorescent piezoelectric composite film prepared by the method described above in a flexible tactile sensor.

[0034] Example 1 CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. The preset first mass ratio is 1:30000, and the first mixing time is 12h. A volatile auxiliary agent and N,N-dimethylformamide are mixed in a second mixture at a preset second mass ratio to obtain a first mixture; the volatile auxiliary agent is ethanol; the preset second mass ratio is 1:2.5; the second mixing temperature is room temperature, and the second mixing time is 0.2 h; The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain a second mixture; the water-soluble pore-forming agent is raffinose; the preset third mass ratio is 1:56; the third mixing temperature is room temperature, and the third mixing time is 2 hours.

[0035] The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture; the fluorinated piezoelectric polymer is PVDF-HFP, and the preset fourth mass ratio is 1:11.4; the fourth mixing temperature is 80℃, and the fourth mixing time is 5h; The third mixture was defoamed to obtain the pore-forming precursor mixture; the defoaming treatment included standing at room temperature for 10 minutes.

[0036] The pore-forming precursor mixture was deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of pore-forming agent. The conductive surface of the electrode was then subjected to oxygen plasma treatment for 10 minutes. The deposition process was spin coating, with a spin coating speed of 1000 rpm and a spin coating time of 60 seconds. The temperature of the first heat treatment was 60°C and the time of the first heat treatment was 30 minutes.

[0037] The pore-forming agent dense film was immersed in CQDs suspension for impregnation treatment to obtain the first composite film. The impregnation treatment temperature was room temperature and the impregnation treatment time was 12 hours. The first composite membrane was cleaned with ethanol to obtain the second composite membrane; The second composite film is subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite film. The temperature of the second heat treatment is 120°C and the time of the second heat treatment is 1 hour.

[0038] When applied to flexible tactile sensors, the following process is used: the composite film deposited on the surface of the ITO-PEN electrode is placed with the conductive surface facing upwards, and then the conductive surface of the blank ITO-PEN electrode is placed downwards and offset over its upper surface. The uncovered parts of the two electrodes are used as leads. Silicone is applied around the edges for fixation, and the wires are fixed to the leads of the two electrodes with conductive silver paste, thus obtaining a flexible tactile sensor.

[0039] Figure 2 The SEM morphology of the composite membrane of Example 1 is shown, as follows. Figure 2 As shown, the composite membrane of Example 1 has a well-developed porous structure, indicating that the method of this embodiment has a strong pore-forming ability. Moreover, when it is used as a porous framework, it is easy for CQDs to enter its interior and be uniformly adsorbed on the surface of the framework, thereby avoiding Foster energy transfer caused by aggregation and ultimately ensuring the excitation of the fluorescence photosensing ability of CQDs. Figure 3 A macroscopic photograph of the composite film of Example 1 under 254 nm ultraviolet excitation is shown, as follows. Figure 3 As shown, the composite film of Example 1 fully inherits the red fluorescence from the highly diffusely distributed single quantum state CQDs, realizing the effective coupling of fluorescence light sensing function. Figure 4 The FT-IR spectrum of the composite film of Example 1 is shown, as follows. Figure 4 As shown, the composite membrane of Example 1 exhibited a significant adsorption peak at a wavenumber of 838 cm⁻¹, indicating that the composite membrane of Example 1 contains a large amount of β-piezoelectric phase from PVDF with piezoelectric response, thus achieving effective coupling of tactile sensing function. Figure 5 The output voltage-time curve of the sensor assembled with the composite membrane in Example 1 is shown, as follows: Figure 5 As shown, the sensor can continuously output a stable voltage under repeated force of 4N, and has the ability to be self-powered by the composite membrane. Figure 6 The output voltage-time curve of the sensor assembled with the composite film in Example 1 when sensing finger bending is shown; as follows: Figure 6 As shown, this demonstrates that the composite membrane and its sensor possess high flexibility. Figure 7 The output voltage-force curve of the sensor assembled with the composite membrane in Example 1 is shown, as follows: Figure 7As shown, the sensor prepared in Example 1 exhibits an excellent direct proportional relationship between the output voltage and the applied force, with corresponding sensitivities of 2.29V / N and 0.987, demonstrating high-sensitivity tactile sensing capabilities derived from the composite membrane. Figure 8 The sensitivity diagrams of the composite film-assembled sensor of Example 1 under different illumination conditions are shown, as follows. Figure 8 As shown, the sensor prepared in Example 1 has a light-sensing function from the composite film.

[0040] Example 2 CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. The preset first mass ratio is 1:5000 and the first mixing time is 6 hours. A volatile auxiliary agent and N,N-dimethylformamide are mixed in a second mixture at a preset second mass ratio to obtain a first mixture; the volatile auxiliary agent is ethanol; the preset second mass ratio is 1:1; the second mixing temperature is room temperature, and the second mixing time is 0.1 h; The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain a second mixture; the water-soluble pore-forming agent is starch; the preset third mass ratio is 1:30; the third mixing temperature is room temperature, and the third mixing time is 1 hour.

[0041] The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture; the fluorinated piezoelectric polymer is PVDF; the preset fourth mass ratio is 1:10; the fourth mixing temperature is 60℃ and the fourth mixing time is 2h; the third mixture is defoamed to obtain a pore-forming precursor mixture; the defoaming treatment includes standing at room temperature for 10min.

[0042] A pore-forming precursor mixture is deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of the pore-forming agent; the conductive surface of the electrode is subjected to oxygen plasma treatment for 5 minutes; the deposition process is electrospinning; the temperature of the first heat treatment is 50°C and the time of the first heat treatment is 20 minutes.

[0043] A pore-forming agent-dense membrane was immersed in a CQDs suspension to obtain a first composite membrane. The immersion temperature was room temperature and the immersion time was 12 hours. The first composite membrane was then cleaned with ethanol to obtain a second composite membrane. The second composite membrane was then subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite membrane. The second heat treatment temperature was 100°C and the second heat treatment time was 1 hour.

[0044] When applied to flexible tactile sensors, the following process is used: the composite film deposited on the surface of the ITO-PEN electrode is placed with the conductive surface facing upwards, and then the conductive surface of the blank ITO-PEN electrode is placed downwards and offset over its upper surface. The uncovered parts of the two electrodes are used as leads. Silicone is applied around the edges for fixation, and the wires are fixed to the leads of the two electrodes with conductive silver paste, thus obtaining a flexible tactile sensor.

[0045] Example 3 CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. The preset first mass ratio is 1:100000 and the first mixing time is 24h. A volatile auxiliary agent and N,N-dimethylformamide are mixed in a second mixture at a preset second mass ratio to obtain a first mixture; the volatile auxiliary agent is ethylene glycol; the preset second mass ratio is 1:5; the second mixing temperature is room temperature, and the second mixing time is 0.5 h; The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain the second mixture; the water-soluble pore-forming agent is maltose; the preset third mass ratio is 1:300; the third mixing temperature is room temperature, and the third mixing time is 5 hours.

[0046] The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mass ratio according to a preset fourth mass ratio to obtain a third mixture. The fluorinated piezoelectric polymer includes PVDF-TrFE, and the preset fourth mass ratio is 1:20. The fourth mixing temperature is 100℃ and the fourth mixing time is 10h. The third mixture is defoamed to obtain a pore-forming precursor mixture. The defoaming treatment includes standing at room temperature for 30min.

[0047] A pore-forming precursor mixture was deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of the pore-forming agent. The conductive surface of the electrode was then subjected to oxygen plasma treatment for 15 minutes. The deposition process was a casting method. The temperature of the first heat treatment was 70°C and the time of the first heat treatment was 60 minutes.

[0048] The pore-forming agent-dense membrane was immersed in the CQDs suspension to obtain a first composite membrane. The immersion temperature was room temperature and the immersion time was 24 hours. The first composite membrane was then cleaned with ethanol to obtain a second composite membrane. The second composite membrane was then subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite membrane. The second heat treatment temperature was 120°C and the second heat treatment time was 2 hours.

[0049] When applied to flexible tactile sensors, the following process is used: the composite film deposited on the surface of the ITO-PEN electrode is placed with the conductive surface facing upwards, and then the conductive surface of the blank ITO-PEN electrode is placed downwards and offset over its upper surface. The uncovered parts of the two electrodes are used as leads. Silicone is applied around the edges for fixation, and the wires are fixed to the leads of the two electrodes with conductive silver paste, thus obtaining a flexible tactile sensor.

[0050] Example 4 CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. The preset first mass ratio is 1:50000, and the first mixing time is 15h. A volatile auxiliary agent and N,N-dimethylformamide were mixed in a second mixture at a preset second mass ratio to obtain a first mixture; the volatile auxiliary agent was acetone; the preset second mass ratio was 1:3; the second mixing temperature was room temperature, and the second mixing time was 0.4 h; The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain the second mixture; the water-soluble pore-forming agent is dextrin; the preset third mass ratio is 1:150; the third mixing temperature is room temperature, and the third mixing time is 3 hours.

[0051] The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture; the fluorinated piezoelectric polymer includes PVDF-HFP; the preset fourth mass ratio is 1:18; the fourth mixing temperature is 75℃ and the fourth mixing time is 6h; the third mixture is defoamed to obtain a pore-forming precursor mixture; the defoaming treatment includes standing at room temperature for 25min.

[0052] The pore-forming precursor mixture was deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of pore-forming agent; the conductive surface of the electrode was subjected to oxygen plasma treatment for 13 min; the deposition process was a coating method; the temperature of the first heat treatment was 65℃ and the time of the first heat treatment was 50 min.

[0053] A pore-forming agent-dense membrane was immersed in a CQDs suspension to obtain a first composite membrane. The immersion temperature was room temperature and the immersion time was 18 hours. The first composite membrane was then cleaned with ethanol to obtain a second composite membrane. The second composite membrane was then subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite membrane. The second heat treatment temperature was 105°C and the second heat treatment time was 1.6 hours.

[0054] When applied to flexible tactile sensors, the following process is used: the composite film deposited on the surface of the ITO-PEN electrode is placed with the conductive surface facing upwards, and then the conductive surface of the blank ITO-PEN electrode is placed downwards and offset over its upper surface. The uncovered parts of the two electrodes are used as leads. Silicone is applied around the edges for fixation, and the wires are fixed to the leads of the two electrodes with conductive silver paste, thus obtaining a flexible tactile sensor.

[0055] Example 5 CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. The preset first mass ratio is 1:60000 and the first mixing time is 22h. A volatile auxiliary agent and N,N-dimethylformamide were mixed in a second mixture at a preset second mass ratio to obtain a first mixture; the volatile auxiliary agent was ethanol; the preset second mass ratio was 1:3.5; the second mixing temperature was room temperature, and the second mixing time was 0.4 h. The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain a second mixture; the water-soluble pore-forming agent is fructose; the preset third mass ratio is 1:210; the third mixing temperature is room temperature, and the third mixing time is 3.5h.

[0056] The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture; the fluorinated piezoelectric polymer is PVDF; the preset fourth mass ratio is 1:16; the fourth mixing temperature is 85℃ and the fourth mixing time is 7h; the third mixture is defoamed to obtain a pore-forming precursor mixture; the defoaming treatment includes standing at room temperature for 19min.

[0057] A pore-forming precursor mixture is deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of pore-forming agent; the conductive surface of the electrode is subjected to oxygen plasma treatment for 11 min; the deposition process is a scraper method; the temperature of the first heat treatment is 58°C and the time of the first heat treatment is 36 min.

[0058] A pore-forming agent-dense membrane was immersed in a CQDs suspension to obtain a first composite membrane. The immersion temperature was room temperature and the immersion time was 18 hours. The first composite membrane was then cleaned with ethanol to obtain a second composite membrane. The second composite membrane was then subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite membrane. The second heat treatment temperature was 115°C and the second heat treatment time was 1 hour.

[0059] When applied to flexible tactile sensors, the following process is used: the composite film deposited on the surface of the ITO-PEN electrode is placed with the conductive surface facing upwards, and then the conductive surface of the blank ITO-PEN electrode is placed downwards and offset over its upper surface. The uncovered parts of the two electrodes are used as leads. Silicone is applied around the edges for fixation, and the wires are fixed to the leads of the two electrodes with conductive silver paste, thus obtaining a flexible tactile sensor.

[0060] Comparative Example A pure PVDF-HFP membrane was prepared as a comparison. The process was basically the same as that in Example 1, except that it was free of water-soluble pore-forming agent and CQDs.

[0061] Ethanol and N,N-dimethylformamide were mixed at a mass ratio of 1:2.5 and magnetically stirred at room temperature for 0.2 h to obtain mixture a; then PVDF-HFP and mixture a were mixed at a mass ratio of 1:11.4 and magnetically stirred at 80 °C to obtain solution b; finally, solution b was allowed to stand at room temperature for 10 min to obtain PVDF-HFP solution.

[0062] The conductive surface of the ITO-PEN electrode was subjected to oxygen plasma treatment for 10 min; then, PVDF-HFP solution was spin-coated onto the conductive surface of the ITO-PEN electrode at a spin speed of 1000 rpm for 60 s to obtain pure film a; pure film a was then kept at 60℃ for 30 min to obtain pure film b; pure film b was then placed in deionized water and soaked at room temperature for 12 h to obtain pure film c; pure film c was then washed with ethanol and kept at 120℃ for 1 h to obtain pure PVDF-HFP film. Figure 9 The output voltage-force curve of a sensor assembled with a pure PVDF-HFP film is shown as a comparative example. Figure 9 As shown, the sensitivity of the comparative sensor is 0.59V / N, which is much lower than that of the sensor assembled with PVDF-HFP / CQDs composite film (2.29V / N), confirming that this embodiment can significantly improve the sensitivity of the composite film.

[0063] Table 1 shows the sensitivities of the assembled sensors in Examples 1-5 and the comparative examples. Table 1. Sensitivity of the assembled sensors in Examples 1-5 and the comparative examples. In summary, the sensors prepared using the composite films prepared by the method of this embodiment all exhibit better sensitivity than the comparative examples.

[0064] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

[0065] The present invention has been described above with reference to embodiments thereof. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

[0066] Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit and scope of the invention.

[0067] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a flexible fluorescent piezoelectric composite film with photosensitive coupling, characterized in that, include: CQDs and deionized water are mixed at a preset first mass ratio to obtain a CQDs suspension. A fluorinated piezoelectric polymer, a water-soluble pore-forming agent, a volatile auxiliary agent, and N,N-dimethylformamide are mixed to obtain a pore-forming precursor mixture. The pore-forming precursor mixture is deposited on the conductive surface of the electrode and subjected to a first heat treatment to obtain a dense film of pore-forming agent. The pore-forming agent-dense film is immersed in the CQDs suspension for impregnation treatment to obtain a flexible fluorescent piezoelectric composite film.

2. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 1, characterized in that, The preset first mass ratio is 1:(5000~100000), and the first mixing time is 6~24h.

3. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 1, characterized in that, The step involves mixing a fluorinated piezoelectric polymer, a water-soluble pore-forming agent, a volatile auxiliary agent, and N,N-dimethylformamide to obtain a pore-forming precursor mixture, comprising: The volatile auxiliary agent and N,N-dimethylformamide are mixed in a second mixture at a preset second mass ratio to obtain a first mixture. The water-soluble pore-forming agent and the first mixture are mixed in a third mixture at a preset third mass ratio to obtain a second mixture; The fluorinated piezoelectric polymer and the second mixture are mixed in a fourth mixture at a preset fourth mass ratio to obtain a third mixture; The third mixture is defoamed to obtain a pore-forming precursor mixture.

4. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 3, characterized in that, The volatile auxiliary agent includes at least one of ethanol, isopropanol, ethylene glycol, and acetone; The preset second mass ratio is 1:(1~5); The second mixing temperature is room temperature, and the second mixing time is 0.1~0.5h.

5. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 3, characterized in that, The water-soluble pore-forming agent includes at least one of starch, raffinose, chitosan, maltose, dextrin, and fructose; The preset third mass ratio is 1:(30~300); The temperature of the third mixing is room temperature, and the time of the third mixing is 1 to 5 hours.

6. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 3, characterized in that, The fluorinated piezoelectric polymer includes at least one of PVDF, PVDF-HFP, PVDF-TrFE and other derivatives; The preset fourth mass ratio is 1:(10~20); The temperature of the fourth mixing is 60~100℃, and the time of the fourth mixing is 2~10h; The defoaming treatment includes standing at room temperature for 10-30 minutes.

7. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 1, characterized in that, The conductive surface of the electrode is treated with oxygen plasma for 5 to 15 minutes. The deposition process includes any one of the following: spin coating, electrospinning, casting, screen printing, coating, 3D printing, and doctor blade coating. The temperature of the first heat treatment is 50~70℃, and the time of the first heat treatment is 20~60min.

8. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 1, characterized in that, The step of immersing the pore-forming agent-dense film in the CQDs suspension for impregnation treatment to obtain a flexible fluorescent piezoelectric composite film includes: The pore-forming agent dense film is immersed in the CQDs suspension for impregnation treatment to obtain the first composite film; The first composite membrane is cleaned with ethanol to obtain the second composite membrane; The second composite film is subjected to a second heat treatment to obtain a flexible fluorescent piezoelectric composite film.

9. The method for preparing the flexible fluorescent piezoelectric composite film with photosensitive coupling according to claim 8, characterized in that, The immersion treatment is performed at room temperature for 12 to 24 hours. The temperature of the second heat treatment is 100~120℃, and the time of the second heat treatment is 1~2h.

10. The application of the photosensitive coupled flexible fluorescent piezoelectric composite film prepared by the method of any one of claims 1-9 in a flexible tactile sensor.

Images