Visual multifunctional humidity-strain sensor and preparation method and application thereof

Abstract

The invention provides a visual multifunctional humidity-strain sensor and a preparation method and application thereof, and belongs to the technical field of humidity-strain sensor preparation. The preparation method provided by the invention comprises the following steps: uniformly mixing a perovskite solution with a polymer solution to obtain a perovskite polymer composite spinning solution; dissolving a hydrophilic conductive material and a hydrophilic polymer in a hydrophilic solvent to obtain a uniform composite conductive spinning solution; and then, through combination of a wet spinning method and an impregnation method, the perovskite polymer composite spinning solution is firstly extruded into a coagulating bath for preliminary curing and fiber forming, then the perovskite polymer composite spinning solution is immediately immersed into the composite conductive spinning solution, and finally heat treatment is performed to obtain the visual multifunctional humidity-strain sensor with the skin-core structure. The sensor is adjustable in fluorescence color and resistance, high in fluorescence intensity, good in uniformity and stability, good in electronic temperature resistance of the conducting layer, good in storage stability, excellent in humidity and strain response performance, high in response speed, high in sensitivity and small in sensing hysteresis.

Description

Technical Field

[0001] The present invention relates to the technical field of humidity-strain sensor preparation, and particularly relates to a visual multifunctional humidity-strain sensor, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of sensors and their manufacturing technologies, as well as the continuous improvement of human needs, integration, multifunctionality, intelligence, and miniaturization have become important directions in current sensor research. Among them, by combining the flexible characteristics of textiles, a multifunctional flexible sensing device obtained by integrating multiple sensing elements with different functions not only has good flexibility and ductility, can be freely bent or even folded to be adaptively adjusted according to the application scenario, but also can measure multiple parameters simultaneously to reflect the overall state of the sample to be measured, and has broad application prospects in related fields from intelligent wearable devices to medical and health monitoring.

[0003] In the prior art, there have been many studies on flexible sensors, but there are still many technical problems to be solved. On the one hand, although there are currently highly sensitive flexible sensors, the interface mismatch between the conductive material and the flexible substrate may cause peeling or interlayer separation of the conductive layer under mechanical external forces, thereby affecting the durability of the sensor; on the other hand, the manufacturing of flexible sensors is generally complex and expensive, which limits their commercial applications. Therefore, in order to meet various requirements in practical applications, how to prepare a multifunctional high-performance flexible sensor with a fiber substrate in a simple and low-cost manner remains a huge challenge.

[0004] In view of this, it is necessary to design a visual multifunctional humidity-strain sensor, a preparation method thereof, and an application thereof to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a visual multifunctional humidity-strain sensor based on perovskite fluorescent filaments, a preparation method thereof, and an application thereof, and combines the wet spinning method and the impregnation method to prepare a visual multifunctional humidity-strain sensor with a core-shell structure. The humidity-strain sensor realizes visualization and high stretchability through a high-fluorescence-brightness perovskite polymer composite elastic core layer, and obtains good conductivity through a hydrophilic composite conductive layer to realize humidity sensing and stretch sensing.

[0006] In a first aspect, an embodiment of the present application provides a preparation method of a visual multifunctional humidity-strain sensor, including the following steps:

[0007] S1, uniformly mixing a perovskite solution and a polymer solution to obtain a perovskite polymer composite spinning solution;

[0008] S2. Dissolve the hydrophilic conductive material and the hydrophilic polymer in a hydrophilic solvent to obtain a uniform composite conductive spinning solution;

[0009] S3. Using the wet spinning method, extrude the perovskite polymer composite spinning solution obtained in step S1 into a coagulation bath to preliminarily solidify and form fibers to obtain a core layer. When the core layer is not completely solidified and dried, quickly immerse it in the composite conductive spinning solution obtained in step S2 so that the outside of the core layer is fully and evenly coated with a conductive layer to obtain a primary composite fiber, and then perform heat treatment to dry and solidify the primary composite fiber and further crystallize the core layer material. After natural cooling, a core-shell structured visual multifunctional humidity-strain sensor is obtained.

[0010] Further, in the perovskite solution in step S1, the concentration of the perovskite is 0.005 - 4.0 mmol / mL, and the perovskite is a mixture of AX and PbX 2 ; wherein, the molar ratio of AX to PbX 2 is 1:(0.5 - 2), A is one or more of cesium, methylamine, and ethylamine, and X is one or more of I, Cl, and Br; the solvent of the perovskite solution is one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone.

[0011] Further, in the polymer solution in step S1, the concentration of the polymer is 5 - 50 wt%, and the polymer is polyurethane, polyacrylonitrile, or polyvinyl chloride; the solvent of the polymer solution is one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone; in step S1, the volume ratio of the perovskite solution to the polymer solution is 1:(1 - 30).

[0012] Further, in step S2, the hydrophilic conductive material is one or more of carbon nanotubes, carbon black, graphene, MXene, silver nanowires, and silver nanoparticles, the hydrophilic polymer is one or more of sodium polyacrylate, polyvinyl alcohol, and polyethylene glycol, and the hydrophilic solvent is water, ethanol, or isopropanol.

[0013] Further, the concentration of the hydrophilic conductive material in the composite conductive spinning solution is 0.1 - 20 wt%, and the concentration of the hydrophilic polymer in the composite conductive spinning solution is 0.01 - 5 wt%.

[0014] Further, in step S3, the coagulation bath is water at room temperature, and the temperature of the heat treatment is lower than or equal to 180°C.

[0015] In a second aspect, embodiments of the present application provide a visual multifunctional humidity-strain sensor, which is prepared by using the preparation method described in any one of the foregoing solutions. The visual multifunctional humidity-strain sensor has a core-shell structure. Among them, the core layer is a composite fluorescent elastic material prepared by using perovskite and a polymer, and the skin layer is a composite conductive material prepared by using an aqueous conductive material and a hydrophilic polymer. The skin layer is a humidity-strain sensing layer. The visual multifunctional humidity-strain sensor has a photoluminescence property, and the fluorescence emitted by the core layer under ultraviolet light irradiation penetrates the skin layer structure, making the fluorescence of the visual multifunctional humidity-strain sensor visible.

[0016] Further, the photoluminescence color of the visual multifunctional humidity-strain sensor is regulated by changing the type and proportion of element X contained in the core layer. The visual multifunctional humidity-strain sensor is stored in air with constant temperature and humidity for 30 days, and the fluorescence intensity decay rate of the photoluminescence is less than 5%. The visual multifunctional humidity-strain sensor is repeatedly stretched to a length strain of 200% and cycled 1000 times, and the fluorescence intensity decay rate of the photoluminescence is less than 5%.

[0017] Further, the resistance of the visual multifunctional humidity-strain sensor is regulated by changing the proportion of the conductive material in the skin layer, and the regulation range of the resistance is between 100Ω and 1MΩ. The normalized resistance change rate of the visual multifunctional humidity-strain sensor in an environment with a humidity of 23-95%RH is greater than or equal to 120%. The visual multifunctional humidity-strain sensor is stored in air with constant temperature and humidity for 24 days, and the normalized resistance change rate is less than 10%. When the storage temperature is raised from 15°C to 45°C, the normalized resistance change rate of the visual multifunctional humidity-strain sensor is less than 10%.

[0018] In a third aspect, embodiments of the present application provide an application of a visual multifunctional humidity-strain sensor prepared by using the preparation method described in any one of the foregoing solutions or the visual multifunctional humidity-strain sensor described in any one of the foregoing solutions. The visual multifunctional humidity-strain sensor is used for monitoring human physiological activities, flexible pattern display, encryption and anti-counterfeiting, detecting skin humidity, non-contact switches, and danger warning.

[0019] The beneficial effects of the present application are as follows:

[0020] The present application provides a visual multifunctional humidity-strain sensor, a preparation method thereof and an application. The visual multifunctional humidity-strain sensor with a core-shell structure is prepared by combining the wet spinning method and the impregnation method. The humidity-strain sensor realizes visualization and high stretchability through a high-fluorescence-brightness perovskite polymer composite elastic core layer, and obtains good conductivity through a hydrophilic composite conductive layer, realizing humidity sensing and stretch sensing.

[0021] (1) The visual multifunctional humidity-strain sensor prepared in the present application has excellent humidity and strain response performances, a fast response speed, high sensitivity and a small sensing hysteresis. The normalized resistance change rate of the visual multifunctional humidity-strain sensor in an environment with a humidity of 23-95% RH is greater than or equal to 120%. When the strain range is between 0-95%, GF 1 can reach 2.9; when the strain range is between 95-200%, GF 2 can reach 27. The response / recovery time of the visual multifunctional humidity-strain sensor to strain can reach 0.2 s / 0.3 s.

[0022] (2) The preparation method of the visual multifunctional humidity-strain sensor provided in the present application has a low cost, a simple process, is easy to scale up production, and can regulate the fluorescence color of the visual multifunctional humidity-strain sensor by adjusting the raw material ratio and type of perovskite, and regulate the resistance of the visual multifunctional humidity-strain sensor by adjusting the proportion of the conductive material in the cortex.

[0023] (3) The visual multifunctional humidity-strain sensor prepared in the present application has excellent luminous brightness and a wide color gamut, and the fluorescence color is rich and adjustable, including blue, green, red, yellow, etc. The fluorescence of the visual multifunctional humidity-strain sensor can penetrate the cortex, making the sensor present clear and bright fluorescence, realizing visual display, and having high fluorescence intensity, good uniformity and stability. The visual multifunctional humidity-strain sensor is placed in air with fixed temperature and humidity for 30 days, and the fluorescence intensity and fluorescence uniformity of photoluminescence basically remain unchanged, and the decline rate of the fluorescence intensity is less than 5%. The sensor is repeatedly stretched to a length deformation of 200% and cycled 1000 times, and the decline rate of the fluorescence intensity of photoluminescence is less than 5%.

[0024] (4) The visual multifunctional humidity-strain sensor prepared in the present application has a wide resistance regulation range, between 100 Ω - 1 MΩ, and the conductive layer has good electron heat resistance and good storage stability. The visual multifunctional humidity-strain sensor is placed in air with fixed temperature and humidity for 24 days, and the normalized resistance change rate is less than 10%; when the storage temperature is raised from 15 °C to 45 °C, the normalized resistance change rate of the sensor is less than 10%.

[0025] (5) The visual multi-functional humidity-strain sensor prepared in this application has good mechanical properties and can be used in the fields of monitoring human physiological activities, flexible pattern display, encryption and anti-counterfeiting, detecting skin humidity, non-contact switches, and danger warning.

[0026] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically exemplified below. Brief Description of the Drawings

[0027] In order to illustrate the technical solution of this application more clearly, the drawings used in this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 Digital photos of the visual multi-functional humidity-strain sensor prepared in Example 1 of this application when stretched to different deformation states under natural light and ultraviolet light;

[0029] Figure 2 Resistance change diagram of the visual multi-functional humidity-strain sensor prepared in Example 1 of this application when stored in air at a temperature of 15 °C and a relative humidity of 23% for 24 days;

[0030] Figure 3 Digital photos of the visual multi-functional humidity-strain sensors prepared in Examples 1-3 of this application under natural light and ultraviolet light irradiation, from left to right are Example 1 (green), Example 2 (red), and Example 3 (blue);

[0031] Figure 4 Digital photo of integrating the visual multi-functional humidity-strain sensor into a fabric substrate in Application Example 1 of this application;

[0032] Figure 5 Relative resistance change diagram obtained by applying the visual multi-functional humidity-strain sensor to respiratory pattern detection in Application Example 2 of this application;

[0033] Figure 6 Resistance change diagram of the visual multi-functional humidity-strain sensor prepared in Example 4 of this application when stored in air at a temperature of 15 °C and a relative humidity of 69% for 24 days;

[0034] Figure 7Resistance change diagram of the visual multifunctional humidity-strain sensor prepared in Example 4 of this application when the ambient temperature is increased from 15°C to 45°C in air with a relative humidity of 69%. Detailed implementation manners

[0035] The embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0037] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality of" is two or more (including two), unless otherwise specifically defined.

[0038] Referring to "embodiment" herein means that a specific feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0039] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0040] There have been many studies on flexible sensors in the prior art, but there are still many technical problems to be solved. On the one hand, although there are already high-sensitivity flexible sensors, the interface mismatch between the conductive material and the flexible substrate may cause peeling or interlayer separation of the conductive layer under mechanical external forces, thereby affecting the durability of the sensor; on the other hand, the manufacturing of flexible sensors is generally complex and expensive, which limits their commercial applications. Therefore, in order to meet various requirements in practical applications, it is still a great challenge to prepare a multifunctional high-performance flexible sensor with a fiber substrate in a simple and low-cost manner.

[0041] To solve the above technical problems, the present application provides a visual multifunctional humidity-strain sensor, a preparation method thereof and an application thereof. A visual multifunctional humidity-strain sensor with a core-shell structure is prepared by combining the wet spinning method and the dipping method. The preparation cost is low, the process is simple, and it is easy to scale up production. The prepared humidity-strain sensor realizes visualization and high stretchability through a high-fluorescence-brightness perovskite polymer composite elastic core layer, and obtains good conductivity through a hydrophilic composite conductive layer, realizing humidity sensing and stretch sensing.

[0042] In a first aspect, an embodiment of the present application provides a preparation method of a visual multifunctional humidity-strain sensor, including the following steps.

[0043] S1, uniformly mixing a perovskite solution and a polymer solution to obtain a perovskite polymer composite spinning solution.

[0044] In some embodiments, the volume ratio of the perovskite solution to the polymer solution is 1:(1 - 30).

[0045] Among them, the concentration of perovskite in the perovskite solution is 0.005 - 4.0 mmol / mL, and the perovskite is a mixture of AX and PbX 2 The molar ratio of AX to PbX 2 is 1:(0.5 - 2), A is one or more of cesium, methylamine, and ethylamine, and X is one or more of I, Cl, and Br. The solvent of the perovskite solution is one or more of DMF, DMSO, NMP, and GBL.

[0046] The polymer in the polymer solution is PU, PAN or PVC, and the concentration of the polymer is 5 - 50 wt%. The solvent of the polymer solution is one or more of DMF, DMSO, NMP, and GBL.

[0047] S2, dissolving a hydrophilic conductive material and a hydrophilic polymer in a hydrophilic solvent to obtain a uniform composite conductive spinning solution.

[0048] In some embodiments, the hydrophilic conductive material is one or a mixture of carbon nanotubes, carbon black, graphene, MXene, silver nanowires, and silver nanoparticles. The concentration of the hydrophilic conductive material in the composite conductive spinning solution is 0.1-20 wt%.

[0049] In some embodiments, the hydrophilic polymer is PAAS, PVA, or PEG, and the concentration of the hydrophilic polymer in the composite conductive spinning solution is 0.01-5 wt%. The solvent used in step S2 is water, ethanol, or isopropanol.

[0050] S3. Using the wet spinning method, extrude the perovskite polymer composite spinning solution obtained in step S1 into a coagulation bath to preliminarily solidify and form fibers, obtaining a core layer. When the core layer is not completely solidified and dried, quickly immerse it in the composite conductive spinning solution obtained in step S2 to fully and uniformly coat the outside of the core layer with a conductive layer, obtaining a primary composite fiber. Then, perform heat treatment to dry and solidify the primary composite fiber and further crystallize the core layer material. After natural cooling, a core-shell structured visual multifunctional humidity-strain sensor is obtained.

[0051] In some embodiments, the coagulation bath is water at room temperature. The heat treatment temperature of the primary composite fiber is lower than or equal to 180 °C. Further, the heat treatment temperature is 50-180 °C, and the heat treatment time is adjusted within the range of 10 min-24 h according to the heat treatment temperature. Specifically, the heat treatment time shortens with the increase of the heat treatment temperature and lengthens with the decrease of the heat treatment temperature. In the actual preparation process, ensure that the primary composite fiber is completely dried and solidified during the heat treatment.

[0052] In a second aspect, an embodiment of the present application provides a visual multifunctional humidity-strain sensor, which is prepared according to the preparation method in the foregoing solution, and the visual multifunctional humidity-strain sensor has a core-shell structure. Among them, the core layer is a composite fluorescent elastic material prepared by using perovskite and a polymer, and the skin layer is a composite conductive material prepared by using a hydrophilic conductive material and a hydrophilic polymer, and the skin layer is a humidity-strain sensing layer. The visual multifunctional humidity-strain sensor has a photoluminescence property, and the fluorescence emitted by the core layer under ultraviolet light irradiation penetrates the skin layer structure, making the fluorescence of the visual multifunctional humidity-strain sensor visible.

[0053] In some embodiments, the photoluminescence color of the visual multifunctional humidity-strain sensor provided by the present application is regulated by changing the type and proportion of element X contained in the core layer. Further, the regulation range of the photoluminescence color is the blue light color gamut, the green light color gamut, the red light color gamut, and the yellow light color gamut.

[0054] In some embodiments, the visual multifunctional humidity-strain sensor is placed in air with fixed temperature and humidity for 30 days. The fluorescence intensity and fluorescence uniformity of photoluminescence remain basically unchanged, and the decline rate of fluorescence intensity is less than 5%. The visual multifunctional humidity-strain sensor is repeatedly stretched to a length deformation of 200%, and after 1000 cycles, the decline rate of the fluorescence intensity of photoluminescence is less than 5%.

[0055] In some embodiments, the resistance of the visual multifunctional humidity-strain sensor provided in this application is regulated in the range of 100 Ω - 1 MΩ by changing the proportion of the conductive material in the cortex. The normalized resistance change rate of the visual multifunctional humidity-strain sensor in an environment with a humidity of 23 - 95% RH is greater than or equal to 120%.

[0056] In some embodiments, the visual multifunctional humidity-strain sensor is placed in air with fixed temperature and humidity for 24 days, and the normalized resistance change rate is less than 10%. When the storage temperature is raised from 15 °C to 45 °C, the normalized resistance change rate of the visual multifunctional humidity-strain sensor is less than 10%.

[0057] In a third aspect, an embodiment of this application provides an application of a visual multifunctional humidity-strain sensor, and the visual multifunctional humidity-strain sensor is used for monitoring human physiological activities, flexible pattern display, encryption and anti-counterfeiting, detecting skin humidity, non-contact switch, and danger warning.

[0058] In some embodiments, the visual multifunctional humidity-strain sensor provided in this application is applied to the fields of flexible pattern display and encryption and anti-counterfeiting. By combining and weaving visual multifunctional humidity-strain sensors with different fluorescence colors onto a flexible substrate, a flexible pattern can be obtained, and the flexible pattern presents different patterns under natural light and ultraviolet light. By combining the specific pattern presented under ultraviolet light with a specific arrangement combination, a specific digital combination or a specific letter combination / word can be obtained.

[0059] The following lists some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application and should not be construed as a limitation to this application. For those without specific techniques or conditions noted in the embodiments, the techniques or conditions described in the literature in this field or according to the product specification are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0060] Example 1

[0061] Example 1 provides a preparation method for a visual multifunctional humidity-strain sensor, including the following steps:

[0062] S1. First, prepare the perovskite solution. The specific steps are as follows: Mix CsBr and PbBr 2 in a molar ratio of 1:1 to obtain perovskite, and add the perovskite to DMF to obtain a perovskite solution with a concentration of 0.04 mmol / mL. Then, prepare the polymer solution (PU solution). The specific steps are as follows: Add PU to DMF to obtain a PU solution with a concentration of 20 wt%. Finally, uniformly mix the perovskite solution and the PU solution in a volume ratio of 2:5 to obtain a perovskite polymer composite spinning solution.

[0063] S2. Add the hydrophilic conductive material CNT and the hydrophilic polymer PAAS to deionized water and mix evenly to obtain a composite conductive spinning solution with a CNT concentration of 1 wt% and a PAAS concentration of 1 wt%.

[0064] S3. Using the wet spinning method, extrude the perovskite polymer composite spinning solution obtained in step S1 into a coagulation bath (water at room temperature) to preliminarily solidify and form fibers, obtaining a core layer. When the core layer is not completely solidified and dried, quickly immerse it in the composite conductive spinning solution obtained in step S2 to fully and evenly coat the outside of the core layer with a conductive layer, obtaining a primary composite fiber. Then, perform heat treatment at 60 °C for 0.5 h to dry and solidify the primary composite fiber. At the same time, the heat treatment also promotes the crystallization of the perovskite material in the light-emitting layer (core layer). After natural cooling, a core-shell structured visual multifunctional humidity-strain sensor is obtained.

[0065] The photoluminescence color of the visual multifunctional humidity-strain sensor prepared in Example 1 is green. Stretch this sensor by hand to deformation rates of 0%, 50%, 100%, 150%, and 200% respectively. Please refer to Figure 1 as shown. The digital photos of this visual multifunctional humidity-strain sensor stretched to different deformation states under natural light and ultraviolet light are shown. It can be seen that this sensor has good stretchability and still has good fluorescence uniformity under the stretched state. As the deformation rate increases, the fluorescence intensity of the sensor decreases.

[0066] Stretch the visual multifunctional humidity-strain sensor prepared in Example 1 by hand to a deformation rate of 200%, then release it to rebound to its original shape, and then stretch and rebound again. After 1000 cycles, the fluorescence intensity decay rate of this sensor is measured to be 1.8%.

[0067] Example 2

[0068] The difference between Example 2 and Example 1 is that in step S1, the perovskite is MAPbI 3(MA methylamine ion), and the rest is basically the same as that in Example 1, which will not be elaborated here. The photoluminescence color of the visual multifunctional humidity-strain sensor prepared in Example 2 is red light.

[0069] Example 3

[0070] The difference between Example 3 and Example 1 is that in step S1, the perovskite is CsPbCl 1.5 Br 1.5 , and the rest is basically the same as that in Example 1, which will not be elaborated here. The photoluminescence color of the visual multifunctional humidity-strain sensor prepared in Example 3 is blue light.

[0071] The sensing performance and conductive performance of the visual multifunctional humidity-strain sensor provided by this application are only related to the composite conductive layer and have nothing to do with the core layer (light-emitting layer). The sensing performances of the visual multifunctional humidity-strain sensors prepared in Examples 1-3 are consistent. Therefore, only the performance of the visual multifunctional humidity-strain sensor prepared in Example 1 is tested as follows:

[0072] (1) The initial resistance of the visual multifunctional humidity-strain sensor is tested to be 60±2 kΩ.

[0073] (2) Place the visual multifunctional humidity-strain sensor in the air at a temperature of 15°C and a relative humidity of 23% for 24 days, and test the normalized resistance change of the visual multifunctional humidity-strain sensor during the storage process. The test results are shown in Figure 2 . It can be seen that the visual multifunctional humidity-strain sensor prepared in Example 1 has good storage stability. After being stored in the air for 24 days, the normalized resistance change rate is less than 2%.

[0074] (3) Place the visual multifunctional humidity-strain sensor in the air with a relative humidity of 23%, and increase the ambient temperature from 15°C to 45°C. Test the normalized resistance change of the visual multifunctional humidity-strain sensor during the heating process, and the obtained normalized resistance change rate is 5%. It can be seen that the visual multifunctional humidity-strain sensor has good heat resistance.

[0075] (4) Test the humidity sensing performance of the visual multifunctional humidity-strain sensor: Place the visual multifunctional humidity-strain sensor in a humidity chamber with a pre-set relative humidity (RH = 23%, 35%, 45%, 55%, 65%, 75%, 85% and 95%). Use an electrochemical workstation to record the resistance change generated when the sensor responds in different humidity environments, and calculate the resistance change rate (△R = [(R x -R 0 ) / R 0 )× 100%, where R x is the real-time resistance, and R 0 is the initial resistance). Test results: In an environment with a humidity of 23 - 95% RH, the relative resistance change rate of the visual multifunctional humidity-strain sensor is 130%, and the humidity hysteresis value is 3.5%.

[0076] (5) Test the strain sensing performance of the visual multifunctional humidity-strain sensor: Use a tensile tester to stretch the visual multifunctional humidity-strain sensor with different deformations, and use an electrochemical workstation to record the resistance changes generated by the sensor due to different deformations, and calculate the GF value (GF = [(R x - R 0 ) / R 0 / ε, where ε is the strain and GF is the ratio of the relative resistance change to the strain). Test results: When the strain range is between 0 - 95%, GF 1 = 2.9; when the strain range is between 95 - 200%, GF 2 = 27; the response / recovery time of the visual multifunctional humidity-strain sensor to strain is 0.2 s / 0.3 s.

[0077] Please refer to Figure 3 the digital photos of the visual multifunctional humidity-strain sensors prepared in Examples 1 - 3 under natural light and ultraviolet light irradiation shown below. From left to right, they are Example 1 (green), Example 2 (red), and Example 3 (blue).

[0078] Place the visual multifunctional humidity-strain sensors prepared in Examples 1 - 3 in air at a temperature of 15 °C and a relative humidity of 23% for 30 days, and test the change in their fluorescence intensity. Among them, the decline rate of the fluorescence intensity is shown in the following table.

[0079]

[0080]

[0081] Application Example 1

[0082] Application Example 1 provides an application of a visual multifunctional humidity-strain sensor in the fields of flexible pattern display and anti-counterfeiting. The visual multifunctional humidity-strain sensors prepared in Examples 1-3 are woven together onto a black flexible substrate to present the number 8. Among them, the visual multifunctional humidity-strain sensor prepared in Example 1 is woven into two vertical lines to form the digital pattern "1"; the visual multifunctional humidity-strain sensor prepared in Example 2 is woven into one horizontal line at the top, two horizontal lines in the middle, two horizontal lines at the bottom, and one vertical line on the right side of the aforementioned horizontal lines to form the digital pattern "3"; the visual multifunctional humidity-strain sensor prepared in Example 3 is woven to obtain an intersecting horizontal line and a vertical line to form the digital pattern "7"; at the same time, the digital patterns "1", "3", and "7" are combined to obtain the digital number "8" in double-line font.

[0083] Please refer to Figure 4 as shown in the digital photo of the visual multifunctional humidity-strain sensor integrated onto the fabric substrate. Among them, Figure 4 a is taken under natural light, Figure 4 b is taken under ultraviolet light. The pattern color obtained in Application Example 1 is similar to the black background under natural light, and different colored numbers are obtained under ultraviolet light irradiation, that is, the green number "1", the red number "3", the blue number "7", and the colored number "8". Specific digital combinations can be obtained by combining specific permutations and combinations. For example, when the password is set to "red green blue color", the obtained digital combination is 3178.

[0084] Application Example 2

[0085] Application Example 2 provides an application of a visual multifunctional humidity-strain sensor in testing the breathing mode. The sensor is installed inside the mask. When wearing the mask and breathing, the sensor responds to the humidity change to generate a real-time resistance change.

[0086] Please refer to Figure 5 as shown in the relative resistance change graph obtained from the breathing mode detection. It can be seen that the impact of mouth breathing on the relative resistance change is much greater than that of nose breathing because breathing through the mouth releases more water molecules, resulting in a greater resistance change of the visual multifunctional humidity-strain sensor. Similarly, the change in breathing speed can be further detected by analyzing the amplitude of the resistance change.

[0087] Example 4

[0088] Example 4 provides a preparation method for a visual multifunctional humidity-strain sensor, including the following steps:

[0089] S1, first, prepare the perovskite solution. The specific steps are to mix CsBr and PbBr 2The perovskite is obtained by mixing in a molar ratio of 1:1. The perovskite is added to a DMF-DMSO mixed solvent (V DMF :V DMSO = 9:1) to obtain a perovskite solution with a concentration of 0.04 mmol / mL. Then, a polymer solution (PU solution) is prepared. The specific steps are as follows: PU is added to a DMF-DMSO mixed solvent (V DMF :V DMSO = 9:1) to obtain a PU solution with a concentration of 20 wt%. Finally, the perovskite solution and the PU solution are uniformly mixed in a volume ratio of 2:5 to obtain a perovskite polymer composite spinning solution.

[0090] S2, CNT and CB are mixed in a molar ratio of 10:1 to obtain a conductive material. The conductive material and the hydrophilic polymer PAAS are added to deionized water and mixed evenly to obtain a composite conductive spinning solution with a conductive material concentration of 1 wt% and a PAAS concentration of 0.75 wt%.

[0091] S3, using the wet spinning method, the perovskite polymer composite spinning solution obtained in step S1 is extruded into a coagulation bath (water at room temperature) to be preliminarily solidified into fibers to obtain a core layer. When the core layer is not completely solidified and dried, it is quickly immersed in the composite conductive spinning solution obtained in step S2 so that the outside of the core layer is fully and evenly coated with a conductive layer to obtain a composite fiber precursor. Then, it is heat-treated at 60 °C for 0.5 h to dry and solidify the composite fiber precursor. At the same time, the heat treatment also promotes the crystallization of the perovskite material in the light-emitting layer (core layer). After natural cooling, a core-shell structured visual multifunctional humidity-strain sensor is obtained.

[0092] The photoluminescence color of the visual multifunctional humidity-strain sensor prepared in Example 4 is green. The performance of the visual multifunctional humidity-strain sensor prepared in Example 4 is tested as follows:

[0093] (1) The initial resistance of the visual multifunctional humidity-strain sensor is tested to be 80 ± 3 kΩ.

[0094] (2) The sensor is placed in air at a temperature of 15 °C and a relative humidity of 69% for 24 days, and the normalized resistance change of the sensor during storage is tested. The test results are shown in Figure 6 It can be seen that the visual multifunctional humidity-strain sensor prepared in Example 4 has good storage stability. After being stored in air for 24 days, the normalized resistance change rate is 4%.

[0095] (3) The sensor is placed in air with a relative humidity of 69%, and the environmental temperature is raised from 15 °C to 45 °C. The normalized resistance change of the sensor during the heating process is tested. The test results are shown in Figure 7As shown, it can be seen that the visual multifunctional humidity-strain sensor prepared in Example 4 has good temperature stability. When the temperature rises from 15 °C to 45 °C, the normalized resistance change rate is 4%.

[0096] (4) Test the humidity sensing performance of the visual multifunctional humidity-strain sensor. Test results: In an environment with a humidity of 23 - 95% RH, the relative resistance change rate of the sensor is 127%, and the humidity hysteresis value is 3.8%.

[0097] (5) Test the strain sensing performance of the visual multifunctional humidity-strain sensor. Test results: When the strain range is between 0 - 95%, GF 1 = 2.9; when the strain range is between 95 - 200%, GF 2 = 25; the response / recovery time of the sensor to strain is 0.3 s / 0.3 s.

[0098] Example 5

[0099] The difference between Example 5 and Example 4 is that the hydrophilic polymer used in step S2 is PEG, and the concentration of PEG in the composite conductive spinning solution is 0.5 wt%. The rest is basically the same as in Example 4 and will not be elaborated here.

[0100] The visual multifunctional humidity-strain sensor prepared in Example 5 is black under natural light and has a fluorescent color of green under ultraviolet light illumination. The initial resistance of the visual multifunctional humidity-strain sensor is tested to be 90 ± 5 kΩ. The visual multifunctional humidity-strain sensor is placed in air at a temperature of 15 °C and a relative humidity of 69% for 24 days, and the normalized resistance change rate is 8%.

[0101] The humidity sensing performance and strain sensing performance of the visual multifunctional humidity-strain sensor prepared in Example 5 are tested as follows:

[0102] (1) Humidity sensing performance. In an environment with a humidity of 23 - 95% RH, the relative resistance change rate of the sensor is 125%, and the humidity hysteresis value is 7%.

[0103] (2) Strain sensing performance. When the strain range is between 0 - 95%, GF 1 = 2.8; when the strain range is between 95 - 200%, GF 2 = 27; the response / recovery time of the sensor to strain is 0.5 s / 0.8 s.

[0104] Example 6

[0105] Example 6 is different from Example 4 in that the conductive material used in step S2 is CNT, and the concentration of CNT in the composite conductive spinning solution is 12 wt%. The rest is basically the same as that of Example 4 and will not be elaborated here.

[0106] The visual multifunctional humidity-strain sensor prepared in Example 6 is black under natural light and has a fluorescent color of green under ultraviolet light illumination. The initial resistance of the visual multifunctional humidity-strain sensor is tested to be 800 ± 25 Ω. The visual multifunctional humidity-strain sensor is placed in air at a temperature of 15 °C and a relative humidity of 69% for 24 days, and the normalized resistance change rate is 7%.

[0107] The humidity sensing performance and strain sensing performance of the visual multifunctional humidity-strain sensor prepared in Example 6 are tested as follows:

[0108] (1) Humidity sensing performance. In an environment with a humidity of 23 - 95% RH, the relative resistance change rate of the sensor is 123%, and the humidity hysteresis value is 4%.

[0109] (2) Strain sensing performance. When the strain range is between 0 - 95%, GF 1 = 2.0; when the strain range is between 95 - 200%, GF 2 = 20; the response / recovery time of the sensor to strain is 0.3 s / 0.3 s.

[0110] Example 7

[0111] Example 7 is different from Example 4 in that the conductive material used in step S2 is CNT with a concentration of 0.5 wt%. The rest is basically the same as that of Example 4 and will not be elaborated here.

[0112] The visual multifunctional humidity-strain sensor prepared in Example 7 is black under natural light and has a fluorescent color of green under ultraviolet light illumination. The initial resistance of the visual multifunctional humidity-strain sensor is tested to be 500 ± 20 kΩ. The visual multifunctional humidity-strain sensor is placed in air at a temperature of 15 °C and a relative humidity of 69% for 24 days, and the normalized resistance change rate is 6%.

[0113] The humidity sensing performance and strain sensing performance of the visual multifunctional humidity-strain sensor prepared in Example 7 are tested as follows:

[0114] (1) Humidity sensing performance. In an environment with a humidity of 23 - 95% RH, the relative resistance change rate of the sensor is 122%, and the humidity hysteresis value is 5%.

[0115] (2) Strain sensing performance. When the strain range is between 0 - 95%, GF1 = 2.1; When the strain range is between 95 - 200%, GF 2 = 21; The response / recovery time of the sensor to strain is 0.3 s / 0.4 s.

[0116] Example 8

[0117] The difference between Example 8 and Example 4 is that the conductive material used in step S2 is AgNW, and its concentration in the composite conductive spinning solution is 0.5 wt%; the polymer is PVA, and its concentration in the composite conductive spinning solution is 0.5 wt%. The rest is basically the same as in Example 4 and will not be elaborated here.

[0118] The visual multifunctional humidity-strain sensor prepared in Example 8 is silver-white under natural light and has a fluorescent color of green under ultraviolet light illumination. The initial resistance of the visual multifunctional humidity-strain sensor is tested to be 10 ± 1 kΩ. The visual multifunctional humidity-strain sensor is placed in air at a temperature of 15 °C and a relative humidity of 69% for 24 days, and the normalized resistance change rate is 8.2%.

[0119] The humidity sensing performance and strain sensing performance of the visual multifunctional humidity-strain sensor prepared in Example 7 are tested as follows:

[0120] (1) Humidity sensing performance. In an environment with a humidity of 23 - 95% RH, the relative resistance change rate of the sensor is 123%, and the humidity hysteresis value is 5%.

[0121] (2) Strain sensing performance. When the strain range is between 0 - 95%, GF 1 = 2.0; When the strain range is between 95 - 200%, GF 2 = 21; The response / recovery time of the sensor to strain is 0.3 / 0.4 s.

[0122] The preparation methods of Examples 1 - 8 and the summary of the initial resistances of the corresponding visual multifunctional humidity-strain sensors are shown in the following table.

[0123]

[0124] In summary, the present application provides a visual multifunctional humidity-strain sensor and a preparation method thereof. The visual multifunctional humidity-strain sensor with a core-shell structure is prepared by combining the wet spinning method and the impregnation method, and the applications of the sensor in the fields of flexible pattern display, anti-counterfeiting, and breathing pattern detection are provided. The fluorescence color and resistance of the visual multifunctional humidity-strain sensor prepared in the present application are controllable, the fluorescence intensity is high, the uniformity and stability are good, and the conductive layer has good electron heat resistance and storage stability. The sensor has excellent humidity and strain response performances, a fast response speed, high sensitivity, and a small sensing hysteresis. The normalized resistance change rate of the visual multifunctional humidity-strain sensor in an environment with a humidity of 23-95% RH is greater than or equal to 120%. 1 can reach 2.9; when the strain range is between 95-200%, GF 2 can reach 27. The response / recovery time of the visual multifunctional humidity-strain sensor to strain can reach 0.2 s / 0.3 s.

[0125] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same function and effect as the technical idea within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various deformations that can be conceived by those skilled in the art are applied to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a visual multifunctional humidity-strain sensor, characterized in that: The steps include: S1, uniformly mixing the perovskite solution and the polymer solution to obtain a perovskite polymer composite spinning solution; S2, dissolving a hydrophilic conductive material and a hydrophilic polymer in a hydrophilic solvent to obtain a uniform composite conductive spinning solution; S3, using a wet spinning method, extruding the perovskite polymer composite spinning solution obtained in step S1 into a coagulation bath to preliminarily solidify it into fibers to obtain a core layer, and quickly immersing the core layer in the composite conductive spinning solution obtained in step S2 before it is completely solidified and dried, so that the outside of the core layer is fully and evenly covered with a conductive layer to obtain a composite fiber filament, and then performing a heat treatment to dry and solidify the composite fiber filament and further crystallize the core layer material, and after natural cooling, a visual multifunctional humidity-strain sensor with a skin-core structure is obtained.

2. The method for preparing the visualized multifunctional humidity-strain sensor according to claim 1, characterized in that: In the perovskite solution described in step S1, the concentration of perovskite is 0.005-4.0mmol / mL, and the perovskite is a mixture of AX and PbX2; wherein the molar ratio of AX to PbX2 is 1:(0.5-2), A is a mixture of one or more of cesium, methylamine, and ethylamine, and X is a mixture of one or more of I, Cl, and Br; the solvent of the perovskite solution is a mixture of one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone.

3. The method for preparing the visualized multifunctional humidity-strain sensor according to claim 1, characterized in that: In the polymer solution described in step S1, the concentration of the polymer is 5-50wt%, and the polymer is polyurethane, polyacrylonitrile or polyvinyl chloride; the solvent of the polymer solution is a mixture of one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone; in step S1, the volume ratio of the perovskite solution to the polymer solution is 1:(1-30).

4. The method for preparing the visualized multifunctional humidity-strain sensor according to claim 1, characterized in that: In step S2, the hydrophilic conductive material is a mixture of one or more of carbon nanotubes, carbon black, graphene, MXene, silver nanowires, and silver nanoparticles; the hydrophilic polymer is a mixture of one or more of sodium polyacrylate, polyvinyl alcohol, and polyethylene glycol; and the hydrophilic solvent is water, ethanol, or isopropanol.

5. The method for preparing the visualized multifunctional humidity-strain sensor according to claim 1, characterized in that: The concentration of the hydrophilic conductive material in the composite conductive spinning solution is 0.1-20 wt %, and the concentration of the hydrophilic polymer in the composite conductive spinning solution is 0.01-5 wt %.

6. The method for preparing the visualized multifunctional humidity-strain sensor according to claim 1, characterized in that: In step S3, the coagulation bath is water at room temperature, and the temperature of the heat treatment is lower than or equal to 180°C.

7. A visual multifunctional humidity-strain sensor, characterized in that: The visualized multifunctional humidity-strain sensor is prepared according to the preparation method described in any one of claims 1-6, and the visualized multifunctional humidity-strain sensor is a skin-core structure; wherein the core layer is a composite fluorescent elastic material prepared by using perovskite and polymer, and the skin layer is a composite conductive material prepared by using aqueous conductive material and hydrophilic polymer, and the skin layer is a humidity-strain sensing layer; the visualized multifunctional humidity-strain sensor has photoluminescent properties, and the fluorescence emitted by the core layer under ultraviolet light penetrates the skin structure, so that the fluorescence of the visualized multifunctional humidity-strain sensor is visible.

8. The visual multifunctional humidity-strain sensor according to claim 7, characterized in that: The photoluminescence color of the visualized multifunctional humidity-strain sensor is regulated by changing the type and proportion of the X element contained in the core layer; the visualized multifunctional humidity-strain sensor is stored in air with constant temperature and humidity for 30 days, and the decrease rate of the photoluminescence fluorescence intensity is less than 5%; the visualized multifunctional humidity-strain sensor is repeatedly stretched to a length deformation of 200%, and after 1000 cycles, the decrease rate of the photoluminescence fluorescence intensity is less than 5%.

9. The visual multifunctional humidity-strain sensor according to claim 7, characterized in that: The resistance of the visual multifunctional humidity-strain sensor is regulated by changing the proportion of conductive materials in the cortex, and the resistance regulation range is between 100Ω-1MΩ; the normalized resistance change rate of the visual multifunctional humidity-strain sensor in an environment with a humidity of 23-95% RH is greater than or equal to 120%; the visual multifunctional humidity-strain sensor is stored in air with fixed temperature and humidity for 24 days, and the normalized resistance change rate is less than 10%; when the storage temperature is increased from 15°C to 45°C, the normalized resistance change rate of the visual multifunctional humidity-strain sensor is less than 10%.

10. An application of a visualized multifunctional humidity-strain sensor prepared by the preparation method according to any one of claims 1 to 6 or a visualized multifunctional humidity-strain sensor according to any one of claims 7 to 9, characterized in that: The visualized multifunctional humidity-strain sensor is used for monitoring human physiological activities, flexible pattern display, encryption and anti-counterfeiting, detecting skin humidity, non-contact switching and danger warning.

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