A thermally induced multi-color-changing nanofiber membrane temperature sensor and a preparation method thereof

Abstract

The application provides a thermochromic multi-color-changing nanofiber membrane temperature sensor and a preparation method thereof. A thermochromic powder is fully mixed with a TPU polymer to prepare a spinning solution, and a nanofiber membrane with a thermochromic function is prepared by an electrostatic spinning method, and then the nanofiber membrane is packaged by using PDMS to obtain a thermochromic nanofiber membrane temperature sensor with a temperature indicating function. The application also prepares a thermochromic multi-color-changing nanofiber membrane temperature sensor capable of changing multiple colors with temperature changes by using a two-step electrostatic spinning and re-packaging process, and the color change has no limitation of color system and color span, thereby solving the problem that the application range of the thermochromic material is restricted due to the limited color changing range of the thermochromic material itself, that is, when the color changes, it is usually in a relatively narrow range of similar color tones or similar colors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature sensors, and particularly relates to a thermochromic multi-color-changing nanofiber membrane temperature sensor and a preparation method thereof. BACKGROUND

[0002] The obvious color change as a feature that can be directly recognized by the naked eye of human beings, such as can be applied to the temperature identification scene in the life and industrial field, will have great convenience. The thermochromic capsule has the feature of showing obvious different colors with the change of temperature, and this feature is reversible, which provides a new method basis for various temperature sensors in life and industry. At present, a plurality of temperature change powders or temperature change pigments made of thermochromic materials have appeared on the market. Based on these materials, some simple thermochromic film products with temperature sensor function also appear in life. These products usually only simply mix the thermochromic material with the original functional carrier, and have the problems of low thermochromic sensitivity, easy failure, and color change with the limitation of color system and color span.

[0003] Some processes start from the capsule structure to design various reliable core-shell structures to ensure the thermochromic performance of the prepared film body. For example, the Chinese invention patent with the patent application number CN202210634405.5 discloses a kind of thermochromic composite nanomaterial and its preparation method, which takes vanadium dioxide as the core, polydiacetylene derivative as the shell, and obtains thermochromic vanadium dioxide nanoparticles. The composite film prepared from the nanoparticles can show obvious red-blue color change under photo-thermal induction. However, it is more complicated to solve the problem of obvious color change from the structure and material of the thermochromic capsule itself, and the cost is high. In addition, in order to make the prepared thermochromic film sensor have good mechanical properties, the content of thermochromic material in the whole preparation solution is often reduced, which leads to the problems of unobvious color change, easy failure, etc. SUMMARY

[0004] The purpose of the present application is to provide a thermochromic multi-color-changing nanofiber membrane temperature sensor, which has good thermochromic sensitivity and mechanical properties, and its color does not have the limitation of color system and color span.

[0005] Another purpose of the present application is to provide a preparation method of a thermochromic multi-color-changing nanofiber membrane temperature sensor, which adopts electrospinning or step-by-step electrospinning to prepare a nanofiber membrane, and encapsulates it with PDMS, without the need for additional auxiliary equipment and processing, simple operation and controllable parameters, suitable for industrialized mass production.

[0006] The technical problem of the present application is solved by adopting the following technical scheme.

[0007] The application provides a preparation method of a thermochromic multi-color-changing nanofiber membrane temperature sensor.

[0008] S1, thermoplastic polyurethane elastomer rubber (TPU) powder is dissolved in a dimethylformamide (DMF) / tetrahydrofuran (THF) mixed solution, then a first thermochromic temperature-changing powder is added, and after mixing, stirring is performed for 9-11 hours to obtain a first spinning solution;

[0009] S2, thermoplastic polyurethane elastomer rubber powder is dissolved in a dimethylformamide / tetrahydrofuran mixed solution, then a second thermochromic temperature-changing powder is added, and after mixing, stirring is performed for 9-11 hours to obtain a second spinning solution, wherein the first thermochromic temperature-changing powder and the second thermochromic temperature-changing powder are different in color at a normal temperature and in color-changing critical temperature.

[0010] S3, the first spinning solution is subjected to electrospinning to obtain a nanofiber membrane, then the second spinning solution is subjected to electrospinning and the spinning fibers are stacked on the nanofiber membrane to obtain a thermochromic nanofiber composite membrane.

[0011] S4, the thermochromic nanofiber composite membrane is packaged by using PDMS to obtain the thermochromic multi-color-changing nanofiber membrane temperature sensor.

[0012] The application provides a thermochromic nanofiber membrane temperature sensor, which is prepared according to the preparation method.

[0013] The application provides a preparation method of a thermochromic nanofiber membrane temperature sensor, which comprises the following steps:

[0014] The thermochromic nanofiber membrane is packaged by using PDMS to obtain the thermochromic nanofiber membrane temperature sensor, wherein the mixed solution is one of a mixed solution of thermoplastic polyurethane elastomer rubber powder and a dimethylformamide / tetrahydrofuran solution and a mixed solution of polyvinylidene fluoride and dimethylacetamide.

[0015] The application provides a thermochromic nanofiber membrane temperature sensor, which is prepared according to the preparation method.

[0016] The thermochromic nanofiber membrane temperature sensor and the preparation method thereof have the following beneficial effects:

[0017] The thermochromic powder prepared from the thermochromic microcapsules is fully mixed with a TPU polymer to form a spinning solution, and a thermochromic functional nanofiber membrane is prepared by one-step electrospinning or step-by-step electrospinning, and then the nanofiber membrane is encapsulated by PDMS to obtain a thermochromic multi-color nanofiber membrane temperature sensor with temperature indication function. The color change of the thermochromic multi-color nanofiber membrane sensor obtained by the present application depends on the raw material itself, and the color change under temperature induction can be easily realized by changing the color, and the color change span is not limited, so that most powder type thermochromic particles can be used in the preparation method of the present application, and the universality is higher. In addition, due to the advantages of nanofibers prepared by electrospinning, good thermochromic sensitivity can be obtained without adding a large amount of thermochromic raw materials. In addition, the use of TPU as a carrier can ensure the mechanical properties of the nanofiber membrane sensor, and the practicality is higher. The thermochromic nanofiber membrane temperature sensor of the present application can be applied to the preparation of electrically controlled thermochromic display screen, surface thermal imaging, wearable flexible sensor and the like, and has great market potential.

[0018] The thermochromic multi-color nanofiber membrane temperature sensor capable of multi-color change with temperature change is prepared by the process of two-step electrospinning and encapsulation, and the color change has no limitation of color system and color span, thereby solving the problem that the color change range of the thermochromic material itself is limited, that is, when the color change occurs, it is usually in a relatively narrow range of similar color tone or similar color, and the application range is restricted. Moreover, the step-by-step electrospinning process does not need to use additional and special auxiliary equipment, and no additional treatment is needed during the electrospinning superposition process, and the spinning solution can be directly replaced and electrospun, which is convenient to operate. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 The preparation flow chart of the thermochromic multi-color nanofiber membrane temperature sensor of the present application;

[0021] Figure 2 The thermochromic nanofiber composite membrane picture of the embodiment 1 of the present application;

[0022] Figure 3 The color change effect schematic diagram of the thermochromic multi-color nanofiber membrane temperature sensor at different temperatures;

[0023] Figure 4 SEM images of the thermochromic powder and the thermochromic nanofiber composite film of Example 1;

[0024] Figure 5 This is a stress-strain curve of the thermochromic nanofiber membrane sensor of Embodiment 1 of the present invention;

[0025] Figure 6 This is a schematic diagram illustrating the display of hidden elements in an image;

[0026] Figure 7 This is a schematic diagram of an electronically controlled thermocoupled display screen.

[0027] Figure 8 This is a schematic diagram of surface thermal imaging;

[0028] Figure 9 This is a schematic diagram of the wearable sensor before and after movement. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0030] The thermochromic nanofiber membrane temperature sensor and its preparation method according to embodiments of the present invention will be described in detail below.

[0031] Reference Figure 1 As shown in the figure, the method for preparing a thermochromic nanofiber membrane temperature sensor provided by the present invention includes the following steps:

[0032] S1. Dissolve thermoplastic polyurethane elastomer rubber powder in a dimethylformamide / tetrahydrofuran mixed solution, then add the first thermochromic powder and mix, stir for 9-11 hours to obtain the first spinning solution.

[0033] S2. Dissolve thermoplastic polyurethane elastomer rubber powder in a dimethylformamide / tetrahydrofuran mixed solution, then add the second thermochromic powder and mix, stirring for 9-11 hours to obtain the second spinning solution. The first thermochromic powder and the second thermochromic powder have different color change critical temperatures and a large color range.

[0034] Furthermore, in a preferred embodiment of the present invention, the mass-to-volume ratio of the thermoplastic polyurethane elastomer rubber powder to the dimethylformamide / tetrahydrofuran mixed solution is 0.15–0.2:1 (g / mL).

[0035] Further, in the preferred embodiment of the present application, the volume ratio of dimethylformamide and tetrahydrofuran in the mixed solution of dimethylformamide and tetrahydrofuran is 0.8-1.2:1. Preferably, the volume ratio of DMF and THF is 1:1.

[0036] Further, in the preferred embodiment of the present application, the mass ratio of the thermoplastic polyurethane elastomer rubber powder and the first thermally induced color-changing powder is 1:4-4.2, and the mass ratio of the thermoplastic polyurethane elastomer rubber powder and the second thermally induced color-changing powder is 1:4-4.2.

[0037] S3, after electrospinning of the first spinning solution, a nanofiber membrane is obtained, then the second spinning solution is electrospun and the spinning fibers are stacked on the nanofiber membrane to obtain a thermally induced color-changing nanofiber composite membrane.

[0038] Further, in the preferred embodiment of the present application, the step of electrospinning includes: injecting the first spinning solution or the second spinning solution into a disposable syringe for electrospinning on a silicon wafer as a receiving plate, wherein the size of the electrospinning needle of the disposable syringe is 20-22G, the disposable syringe is connected to a positive voltage of 7.2-7.8kV, the silicon wafer is connected to a negative voltage of 1.5-2kV, the receiving distance is 12-16cm, and the injection pump liquid supply speed is 25-29μL / min. Preferably, the first spinning solution or the second spinning solution is injected into a 2.5mL disposable syringe for electrospinning on a silicon wafer as a receiving plate, wherein the size of the electrospinning needle of the disposable syringe is 21G, the disposable syringe is connected to a positive voltage of 7.5kV, the silicon wafer is connected to a negative voltage of 1.7kV, the receiving distance is 14cm, and the injection pump liquid supply speed is 27μL / min.

[0039] S4, the thermally induced color-changing nanofiber composite membrane is encapsulated by PDMS to obtain a thermally induced multi-color-changing nanofiber membrane temperature sensor.

[0040] Further, in the preferred embodiment of the present application, the step of encapsulating the thermally induced color-changing nanofiber composite membrane by PDMS is: covering the PDMS on the surface of the thermally induced color-changing nanofiber composite membrane and spin coating for 50-70s in a film applicator, then standing and drying to obtain the thermally induced multi-color-changing nanofiber membrane temperature sensor.

[0041] Further, in the preferred embodiment of the present application, the step of standing and drying is: after spin coating of the thermally induced color-changing nanofiber composite membrane in the film applicator, standing for 50-70min at room temperature and then placing in a drying cabinet for drying at 70-90℃ for 1.5-2.5h.

[0042] The application further provides a thermochromic nanofiber membrane temperature sensor prepared according to the preparation method.

[0043] The application provides a preparation method of a thermochromic nanofiber membrane temperature sensor, which comprises the following steps:

[0044] The thermochromic powder is mixed with the mixed solution, and then electrospinning is performed to obtain a thermochromic nanofiber membrane, and then the thermochromic nanofiber membrane is packaged by using PDMS to obtain the thermochromic nanofiber membrane temperature sensor, wherein the mixed solution is one of a mixed solution of thermoplastic polyurethane elastomer rubber powder and dimethylformamide / tetrahydrofuran solution, and a mixed solution of polyvinylidene fluoride and dimethylacetamide.

[0045] The application provides a thermochromic nanofiber membrane temperature sensor prepared according to the preparation method.

[0046] The thermochromic powder prepared from the thermochromic microcapsules is fully mixed with a TPU polymer to prepare a spinning solution, and a nanofiber membrane with a thermochromic function is manufactured by using an electrospinning method, and then the nanofiber membrane is packaged by using PDMS to obtain a thermochromic nanofiber membrane temperature sensor with a temperature indicating function.

[0047] The features and performances of the application are further described in detail in combination with the embodiments.

[0048] Embodiment 1

[0049] The application provides a thermochromic nanofiber membrane temperature sensor prepared according to the following method:

[0050] (1) Preparation of the electrospinning solution: 1.7g of TPU powder is dissolved in 10mL of a dimethylformamide / tetrahydrofuran mixed solution, 7g of first thermochromic powder with a color change critical temperature of 65℃ (blue) is mixed with the solution, and the mixed solution is stirred at room temperature for 10 hours to obtain a uniform first spinning solution for standby use.

[0051] The 1.7 g TPU powder was dissolved in 10 mL of a dimethylformamide / tetrahydrofuran mixed solution, and 7 g of a second thermochromic powder (red) with a color change critical temperature of 45°C was mixed with the solution. The mixed solution was stirred at room temperature for 10 hours to obtain a uniform second spinning solution for standby. The volume ratio of DMF to THF was 5:5.

[0052] (2) Stepwise superimposed electrospinning: The first spinning solution was injected into a disposable syringe with a capacity of 2.5 mL, and a 21G electrospinning needle was selected with a positive voltage of 7.5 kV. A silicon wafer was used as a receiving plate to facilitate the stripping of the nanofiber membrane after electrospinning was completed, and the silicon wafer was connected to a negative voltage of 1.7 kV. The receiving distance was 14 cm, and the liquid supply speed of the injection pump was 27 μL / min. Electrospinning was performed according to the above process parameters to obtain a nanofiber membrane. Then, the spinning solution was replaced with the second spinning solution, and electrospinning was continued according to the previous parameters to superimpose the spinning fibers on the nanofiber membrane, thereby obtaining a thermochromic nanofiber composite membrane.

[0053] (3) PDMS was coated on the surface of the thermochromic nanofiber composite membrane, and was spin-coated in a coating machine for 60 s. After spin-coating was completed, the sample was placed at room temperature for 1 h, and then was placed in a drying oven for 2 h at 80°C to solidify the PDMS. After encapsulation, a thermochromic nanofiber membrane temperature sensor with a thickness of 0.5 mm was obtained.

[0054] Example 2

[0055] The thermochromic nanofiber membrane temperature sensor provided in this example was prepared according to the following method:

[0056] (1) Preparation of electrospinning solution: 1.7 g of TPU powder was dissolved in 10 mL of a dimethylformamide / tetrahydrofuran mixed solution, and 7 g of a first thermochromic powder (orange yellow) with a color change critical temperature of 38°C was mixed with the solution. The mixed solution was stirred at room temperature for 10 hours to obtain a uniform first spinning solution for standby. The volume ratio of DMF to THF was 5:5.

[0057] The 1.7 g TPU powder was dissolved in 10 mL of a dimethylformamide / tetrahydrofuran mixed solution, and 7 g of a second thermochromic powder (red) with a color change critical temperature of 45°C was mixed with the solution. The mixed solution was stirred at room temperature for 10 hours to obtain a uniform second spinning solution for standby. The volume ratio of DMF to THF was 5:5.

[0058] (2) Step-by-step electrospinning: The first spinning solution was injected into a disposable syringe with a capacity of 2.5 mL, and an electrospinning needle with a size of 21G was selected, connected to a positive voltage of 7.5 kV; a silicon wafer was used as the receiving plate to facilitate the stripping of the nanofiber membrane after electrospinning was completed, and the silicon wafer was connected to a negative voltage of 1.7 kV; the receiving distance was 14 cm; the liquid supply speed of the injection pump was 27 μL / min, and electrospinning was performed according to the above process parameters to obtain a nanofiber membrane. Then, the spinning solution was replaced with the second spinning solution, and electrospinning was continued according to the previous parameters to make the spinning fibers superimposed on the nanofiber membrane, thereby obtaining a thermochromic nanofiber composite membrane.

[0059] (3) PDMS was coated on the surface of the thermochromic nanofiber composite membrane and spin-coated in a film applicator for 60 s. After spin-coating was completed, it was left to stand at room temperature for 1 h, and then placed in a drying cabinet for 2 h at 80°C to solidify the PDMS. After encapsulation, a thermochromic multi-color-changing nanofiber membrane temperature sensor was obtained.

[0060] Example 3

[0061] (1) Preparation of electrospinning solution: 1.7 g of TPU powder was dissolved in 10 mL of a dimethylformamide / tetrahydrofuran mixed solution, and 7 g of a thermochromic powder with a critical temperature of 65°C (blue) was mixed with it. The mixed solution was stirred at room temperature for 10 hours to obtain a uniform spinning solution for standby use. The volume ratio of DMF to THF was 5:5.

[0062] (2) Electrospinning: The spinning solution was injected into a disposable syringe with a capacity of 2.5 mL, and an electrospinning needle with a size of 21G was selected, connected to a positive voltage of 7.5 kV; a silicon wafer was used as the receiving plate to facilitate the stripping of the nanofiber membrane after electrospinning was completed, and the silicon wafer was connected to a negative voltage of 1.7 kV; the receiving distance was 14 cm; the liquid supply speed of the injection pump was 27 μL / min, and a thermochromic nanofiber membrane was obtained.

[0063] (3) PDMS was coated on the surface of the thermochromic nanofiber membrane and spin-coated in a film applicator for 60 s. After spin-coating was completed, it was left to stand at room temperature for 1 h, and then placed in a drying cabinet for 2 h at 80°C to solidify the PDMS. After encapsulation, a thermochromic nanofiber membrane temperature sensor was obtained.

[0064] Example 4

[0065] (1) Preparation of electrospinning solution: 1.7 g of TPU powder was dissolved in 10 mL of a dimethylformamide / tetrahydrofuran mixed solution, and 7 g of a thermochromic powder with a critical temperature of 38°C (orange yellow) was mixed with it. The mixed solution was stirred at room temperature for 10 hours to obtain a uniform spinning solution for standby use. The volume ratio of DMF to THF was 5:5.

[0066] (2) Electrospinning: The spinning solution was injected into a disposable syringe with a capacity of 2.5 mL, and an electrospinning needle with a size of 21G was selected, and a positive voltage of 7.5 kV was connected; a silicon wafer was used as a receiving plate to facilitate the stripping of the nanofiber membrane after electrospinning was completed, and the silicon wafer was connected to a negative voltage of 1.7 kV; the receiving distance was 14 cm; the liquid supply speed of the injection pump was 27 μL / min, and the thermochromic nanofiber membrane was obtained.

[0067] (3) PDMS was coated on the surface of the thermochromic nanofiber membrane, and spin coating was performed in a homogenizer for 60 s. After spin coating was completed, the sample was placed at room temperature for 1 h, and then placed in a drying cabinet for 2 h at 80°C to solidify the PDMS. After encapsulation was completed, a thermochromic nanofiber membrane temperature sensor with a thickness of 0.3 mm was obtained.

[0068] Example 5

[0069] (1) Preparation of electrospinning solution: 1.7 g of TPU powder was dissolved in 10 mL of a mixed solution of dimethylformamide / tetrahydrofuran, and then 7 g of thermochromic powder with a critical temperature of 35°C (pink) was mixed with the solution. The mixed solution was stirred at room temperature for 10 hours to obtain a uniform spinning solution for standby use. The volume ratio of DMF to THF was 5:5.

[0070] (2) Electrospinning: The spinning solution was injected into a disposable syringe with a capacity of 2.5 mL, and an electrospinning needle with a size of 21G was selected, and a positive voltage of 7.5 kV was connected; a silicon wafer was used as a receiving plate to facilitate the stripping of the nanofiber membrane after electrospinning was completed, and the silicon wafer was connected to a negative voltage of 1.7 kV; the receiving distance was 14 cm; the liquid supply speed of the injection pump was 27 μL / min, and the thermochromic nanofiber membrane was obtained.

[0071] (3) PDMS was coated on the surface of the thermochromic nanofiber membrane, and spin coating was performed in a homogenizer for 60 s. After spin coating was completed, the sample was placed at room temperature for 1 h, and then placed in a drying cabinet for 2 h at 80°C to solidify the PDMS. After encapsulation was completed, a thermochromic nanofiber membrane temperature sensor with a thickness of 0.3 mm was obtained.

[0072] Test Example 1

[0073] In this test example, the thermochromic nanofiber composite membrane prepared in Example 1 was observed at room temperature. As shown in FIG. 1, it is the picture of the thermochromic nanofiber composite membrane of Example 1 of the present application. As can be seen from FIG. 1, Figure 2 the front of the thermochromic nanofiber composite membrane is red and the back is blue, and the color layering can be clearly seen in the cross-section of the membrane, and the thickness is 0.3 mm. Since PDMS is not used for infiltration and encapsulation, the front of the thermochromic nanofiber composite membrane becomes white after reaching the critical temperature of 45°C, and the blue color of the bottom layer cannot be displayed. Figure 2 ​

[0074] Test Example 2

[0075] In this test example, the thermochromic multiple color-changing nanofiber membrane temperature sensor prepared in Example 1 was heated to study its color-changing effect. As shown in Figure 3 The color-changing effect of the thermochromic multiple color-changing nanofiber membrane temperature sensor at different temperatures is shown in the figure. From Figure 3 It can be seen that when the temperature reaches 45℃, the thermochromic multiple color-changing nanofiber membrane temperature sensor changes from red to blue; when the temperature reaches 65℃, the thermochromic multiple color-changing nanofiber membrane temperature sensor changes from blue to white. The present application has prepared a flexible sensor that can change multiple colors with temperature gradient changes, and the color change has no color system limitation, thereby providing a new solution to the current thermochromic product color change with a narrow color and color system span.

[0076] Test Example 3

[0077] In this test example, scanning electron microscopy (SEM, SIGMA 500, Germany) was used to observe the thermochromic powder and the thermochromic nanofiber composite film of Example 1. The thermochromic powder was prepared by microcapsule encapsulation technology. As shown in Figure 4 The SEM images of the thermochromic powder and the thermochromic nanofiber composite film of Example 1 are shown in the figure. Among them, Figure 4 (a) and Figure 4 (b) are SEM images of the thermochromic powder at different magnifications; Figure 4 (c) and Figure 4 (d) are SEM images of the thermochromic nanofiber composite film at different magnifications. From Figure 4 (a) and Figure 4 (b) can be seen, the thermochromic capsules are spherical, and the thermochromic material is encapsulated in the sphere; the surface of the sphere is a shell with a thickness of about 0.2-0.5 μm, which is not easy to dissolve and melt, and is used to protect the internal thermochromic material from erosion. There will be a pit on the surface of the protective layer, which may be caused by the encapsulation process. The diameter of the sphere is mostly in the range of 2-7 μm as indicated in the product parameter. From Figure 4 (c) and Figure 5 (d) can be seen, after sufficient stirring and mixing with the spinning solution, the thermochromic powder is uniformly and widely distributed in the nanofiber, and is tightly wrapped inside the dense and disordered TPU nanofiber in single or multiple agglomerates. The TPU nanofiber intertwines to form a disordered network, and the single fiber diameter is between 100-200 nm.

[0078] Test Example 4

[0079] For flexible sensors, sufficient mechanical properties are essential to ensure their practicality. Therefore, this experimental example conducts a tensile test on the thermochromic multicolor nanofiber membrane temperature sensor prepared in Example 1 to study its mechanical properties. Considering that the thermochromic multicolor nanofiber membrane temperature sensor is not a narrow strip in most applications, this experimental example uses a thermochromic nanofiber composite membrane with a length of 1 cm, a width of 1 cm, and a thickness of 0.5 mm, which is cured and encapsulated in PDMS, as the sample for tensile testing.

[0080] like Figure 5 The figure shown is a stress-strain curve of the thermochromic nanofiber membrane sensor of Embodiment 1 of the present invention. From... Figure 6 It can be seen that the tensile strength of the thermochromic nanofiber membrane sensor of the above dimensions is 3.03 MPa, and the tensile strain is 189%. After PDMS encapsulation, the tensile strength of the thermochromic nanofiber membrane sensor is significantly improved, with its tensile strength increasing by nearly three times compared to the unencapsulated thermochromic nanofiber composite membrane. The ductility of this thermochromic nanofiber membrane sensor appears to be relatively reduced, but the reduction is small, and it can still be stretched to nearly 1.9 times its own length. This experiment basically verifies that the thermochromic nanofiber membrane sensor meets the possible tensile requirements for flexible sensor applications in terms of mechanical properties.

[0081] Experimental Example 5

[0082] Utilizing the color-changing properties of thermochromic nanofiber membrane sensors, text or patterns can be easily hidden / displayed against the same background. This experimental example applies thermochromic nanofiber membranes to an electronically controlled thermochromic display screen, specifically including the following steps:

[0083] A spinning solution was prepared by uniformly mixing a solution of polyvinylidene fluoride (PVDF) and dimethylacetamide (DMAC) with a thermochromic powder having a thermochromic critical temperature of 45°C. The lettering "XMUT" was etched into aluminum foil as a mask, which was then attached to a standard A4 sheet of paper as a spinning receiving plate. After electrospinning, removing the mask revealed the thermochromic "XMUT" lettering on the white paper. When heated to 45°C, the thermochromic lettering quickly turned a pinkish-white color similar to the white paper, achieving a hidden lettering effect. Figure 7 (As shown). The PVDF thermochromic nanofiber membrane is simply encapsulated with PU waterproof tape and then pasted onto a heating circuit board to serve as a display screen. This heating circuit board is designed with an electronically controlled heating circuit featuring digital patterns.

[0084] like Figure 7 The image shown is a schematic diagram of an electronically controlled thermal display screen. From... Figure 8It can be seen that when the switch button is pressed, the digital pattern formed by the heating wires on the circuit board will be heated in a certain order, so that the numbers 1, 2 and 3 can appear on the display screen in turn. Among them, since the heating wires in the heating circuit have a certain heating and cooling time, each number needs about 2s from the heating wire starts to heat to the number completely appears, and from completely appears to the number disappears.

[0085] Test Example 6

[0086] The thermochromic nanofiber film sensor has the advantage of not needing to go through signal processing, and can directly present the temperature gradient in the form of color difference. In this test example, the thermochromic nanofiber film sensor of Example 3 is made into a sensor array, which can be used for temperature imaging of the surface to be measured. By laying the thermochromic nanofiber film sensor array with a thermochromic critical temperature of 65℃ (blue to white) on the heating platform, the temperature difference of each part of the surface of the heating platform during heating can be observed (as shown in the figure). Figure 8

[0087] As Figure 8 The surface thermal imaging schematic diagram is shown. As Figure 9 It can be seen that when the heating platform displays a temperature of 65℃, the central part of the sensor array is completely colored, while the edge still remains blue. The image formed by this set of array sensors can be used to easily determine the actual range of the instantaneous temperature on the heating platform.

[0088] Test Example 7

[0089] The thermochromic nanofiber film serving as a temperature sensor only serves as a front-end characterization in temperature index detection and analysis. In this test example, the thermochromic nanofiber film temperature sensors prepared in Examples 4 and 5 are respectively attached to the same position on the bodies of multiple subjects, and then the physiological characteristics of the subjects are analyzed through the color change of the sensors after the subjects perform the same amount of intense exercise, and the color difference of the sensors is recognized by the back-end electronic equipment and converted into data for further analysis. It should be noted that if the temperature sensor is directly attached to the arm or back of the hand for convenience of detection, the surface temperature of such position will not generally change much after intense exercise under the condition that the ambient temperature remains unchanged, and the temperature rise is about 1-2℃. In such a narrow temperature change range, unless the thermochromic sensor has a color change critical temperature close to the original skin surface temperature, the thermochromic nanofiber film cannot show a very obvious color difference. Therefore, the specific steps of this test include:

[0090] ​Two pieces of the thermochromic nanofiber film with thickness of about 0.3mm were taken, one of which had a critical temperature of 35℃ and was pink at room temperature, and the other had a critical temperature of 38℃ and was orange at room temperature. The two pieces of the nanofiber film were used as wearable temperature sensors and were attached to the back of the hand. The color change of the sensors was observed when the wearable temperature sensors were just worn and when the wearable temperature sensors were worn and ran at a speed of about 200m / min for 30min.

[0091] As shown in Figure 9 the schematic diagram of the wearable sensor before and after exercise. Among them Figure 9 (i) is a schematic diagram of the structure of the wearable sensor before exercise, Figure 9 (ii) is a schematic diagram of the structure of the wearable sensor after exercise. From ​ it can be seen that, since the critical temperature of the pink nanofiber film is close to the temperature of the back of the hand at room temperature, which is 31-33℃, the color of the film has become lighter after being attached. The orange nanofiber film has not changed color significantly because its critical temperature is relatively high. After wearing the wearable sensor and running at a speed of about 200m / min for 30min, the state of the two sensors was observed again, and it was found that the temperature of the back of the hand had increased to about 36℃, the pink nanofiber film had completely changed to transparent or white (white is due to the fact that there is sweat that is not in close contact with the skin), and the orange nanofiber film had only changed color slightly. Of course, it should be noted that if the wearable sensor is attached to some parts of the body that change temperature more dramatically during exercise, such as the palm, armpit, etc., the above problem will be improved a lot.

[0092] The above-described embodiments are part of the embodiments of the present application, but not all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

Claims

1. A method for preparing a thermochromic nanofiber membrane temperature sensor, characterized in that, Includes the following steps: S1. Dissolve thermoplastic polyurethane elastomer rubber powder in a dimethylformamide / tetrahydrofuran mixed solution, then add the first thermochromic powder and mix, stirring for 9-11 hours to obtain the first spinning solution. S2. Dissolve thermoplastic polyurethane elastomer rubber powder in a dimethylformamide / tetrahydrofuran mixed solution, then add the second thermochromic powder and mix, stir for 9-11 hours to obtain the second spinning solution. The first thermochromic powder and the second thermochromic powder have different color change critical temperatures and different colors at room temperature. S3. After the first spinning solution is electrospun, a nanofiber membrane is obtained. Then, the second spinning solution is electrospun and the spun fibers are superimposed on the nanofiber membrane to obtain a thermochromic nanofiber composite membrane. S4. The thermochromic nanofiber composite film is encapsulated using PDMS to obtain a thermochromic multicolor nanofiber film temperature sensor.

2. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the thermoplastic polyurethane elastomer rubber powder to the dimethylformamide / tetrahydrofuran mixed solution is 0.15~0.2:1 (g / mL).

3. The preparation method according to claim 1, characterized in that, In the dimethylformamide / tetrahydrofuran mixed solution, the volume ratio of dimethylformamide to tetrahydrofuran is 0.8~1.2:

1.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the thermoplastic polyurethane elastomer rubber powder to the first thermochromic powder is 1:4~4.2, and the mass ratio of the thermoplastic polyurethane elastomer rubber powder to the second thermochromic powder is 1:4~4.

2.

5. The preparation method according to claim 1, characterized in that, In step S3, the electrospinning step includes: injecting the first spinning solution or the second spinning solution into a disposable syringe, and performing electrospinning with a silicon wafer as the receiving plate. The disposable syringe has an electrospinning needle size of 20~22G, and is connected to a positive voltage of 7.2~7.8kV; the silicon wafer is connected to a negative voltage of 1.5~2kV; the receiving distance is 12~16cm, and the injection pump supply speed is 25~29μL / min.

6. The preparation method according to claim 1, characterized in that, In step S4, the step of encapsulating the nanofiber membrane with PDMS is as follows: the PDMS is covered on the surface of the thermochromic nanofiber composite membrane and spin-coated in a spin coater for 50-70 seconds, then left to stand and dry to obtain the thermochromic nanofiber membrane temperature sensor.

7. The preparation method according to claim 6, characterized in that, The steps of settling and drying are as follows: after the thermochromic nanofiber composite film is spin-coated in the spin coater, it is settling at room temperature for 50-70 minutes and then placed in a drying cabinet and dried at 70-90℃ for 1.5-2.5 hours.

8. A thermochromic multicolor nanofiber membrane temperature sensor, characterized in that, Prepared by the preparation method according to any one of claims 1 to 7.

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