Intelligent wearable high-sensitivity visual mechanical sensor and preparation method thereof

Abstract

The invention provides an intelligent wearable high-sensitivity visual mechanical sensor and a preparation method thereof. The preparation method comprises the following steps: firstly, mixing a liquid crystal monomer, a chiral agent, a cross-linking agent, a chain extender, a photoinitiator and a catalyst, and carrying out prepolymerization reaction to obtain a first solution; then coating the first solution on the film-shaped PU adhesive to enable the cholesteric liquid crystal to complete evaporation-induced self-assembly, and then irradiating and curing under an ultraviolet lamp to obtain a color-changing film; and finally hot-pressing the color-changing film on the fabric to obtain the intelligent wearable high-sensitivity visual mechanical sensor. The color-changing film and the textile are combined through the PU adhesive, amino in the PU adhesive reacts with carbon-carbon double bonds in the color-changing layer by controlling the chemical composition of the color-changing layer, the color-changing layer and the PU adhesive are combined more firmly, the PU adhesive can permeate into the textile in the hot pressing process, and the color-changing effect is improved. The color-changing layer, the middle layer and the textile are tightly combined, and the wearable force response visual sensor better fitting the three-dimensional curved surface of the human body is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible electronic device preparation, and particularly relates to an intelligent wearable highly sensitive visual mechanical sensor and a preparation method thereof. Background Art

[0002] In the field of intelligent wearable technology, flexible mechanical sensors have the broadest application prospects. Flexible mechanical sensors can efficiently convert the physical and mechanical stimuli suffered by the human body during movement into accurate and quantifiable signals, thereby realizing the real-time monitoring of the mechanical effects of the human physiological state and external environmental changes. This characteristic has enabled its in-depth application in many professional fields such as medical health, sports, health monitoring, and advanced human-computer interaction. Considering the complex motion patterns exhibited by the human body during movement and the various external impact forces that may be suffered, developing a multi-stress mode flexible sensor that can accurately capture both the change in motion amplitude and external force stimulation has become an urgent need in the current field of intelligent wearable technology. This need not only promotes the further innovation of sensor technology but also provides the possibility to improve the accuracy and comprehensiveness of human motion monitoring.

[0003] Researchers have carried out a large amount of basic research work in the field of wearable sensing. Lacus et al. reported a preparation method of a sticky multicolor mechanical chromogenic label (《ACS applied materials&interfaces》2024, 16: 14144 - 14151). In this method, the assembly, curing, and cutting of cholesteric liquid crystal are first completed on the surface of PVA, and then glue is applied to the color-changing layer to realize its application on different object surfaces. This label can visually display mechanical changes, but its preparation process is complex, the adhesion of the sticky label on rough flexible surfaces such as fabrics is not good enough, it cannot monitor the amplitude of human movement, and when its strain reaches 50%, the color can change from red to green, which is not sensitive enough.

[0004] Patent CN118065156A discloses a stretchable color-changing flexible fabric and a preparation method and application thereof. In this preparation method, a nano-dopant is added to the chiral liquid crystal polymer precursor solution. The nano-dopant assists the self-assembly of liquid crystal monomer molecules, and finally a highly saturated structural color is obtained. Combining the stretchable color-changing characteristics of the chiral liquid crystal polymer material, a stretchable color-changing flexible fabric is realized. However, this method requires surface plasma treatment and silane coupling agent graft modification of the intermediate coating layer, the preparation method is cumbersome, the efficiency is low, and the cyclic color-changing performance of the flexible fabric is unknown.

[0005] In view of this, it is necessary to design an intelligent wearable highly sensitive visual mechanical sensor and a preparation method thereof to solve the above problems. Summary of the Invention

[0006] The present application provides an intelligent wearable highly sensitive visual mechanical sensor and a preparation method thereof. The preparation method first prepares a force-responsive and color-changing liquid crystal elastomer material, and then combines it with a textile using PU glue. By controlling the chemical composition of the color-changing layer, the amino group in the PU glue reacts with the carbon-carbon double bond in the color-changing layer, making the combination between the color-changing layer and the PU glue more firm. The hot pressing process enables the PU glue to penetrate into the textile, realizing the tight combination among the color-changing layer, the intermediate layer, and the textile, and preparing a wearable force-responsive visual sensor that fits better with the three-dimensional curved surface of the human body.

[0007] This sensor senses mechanical changes in the form of color changes. Compared with traditional sensors that require current monitoring devices, it is more portable, more sensitive, has a wider application range, and a longer service life.

[0008] In a first aspect, an embodiment of the present application provides a preparation method for an intelligent wearable highly sensitive visual mechanical sensor, including the following steps:

[0009] S1. Dissolve liquid crystal monomer RM257 and a chiral agent in the solvent dichloromethane, then add crosslinking agent PETMP, chain extender EDDET, and photoinitiator I-651, and finally add catalyst DPA. Stir evenly and let stand for 20 - 30 min for prepolymerization reaction to obtain a first solution.

[0010] S2. Apply the first solution obtained in step S1 onto a film-like PU glue, and then place it in a closed space at an environmental temperature of 30 °C ± 2 for 4 - 6 h to complete the evaporation-induced self-assembly of the cholesteric liquid crystal. Finally, irradiate it under a UV lamp with a wavelength of 365 nm and an intensity of 20 - 50 mW / cm 2 for 20 - 30 min for curing to obtain a color-changing film.

[0011] S3. Use the hot pressing method to hot press the color-changing film obtained in step S2 onto a fabric to obtain an intelligent wearable highly sensitive visual mechanical sensor.

[0012] Further, in step S1, the mass fraction of dichloromethane in the first solution is 45 - 50%.

[0013] Further, in step S1, the addition amount of PETMP is 2 - 3 wt% of the reaction system.

[0014] Further, the chiral agent is LC756; the mass ratio of LC756 to RM257 is (0.045 - 0.060):1.

[0015] Further, the chiral agent includes two kinds, LC756 and S5011. Among them, the mass ratio of LC756 to S5011 is 1:(0.91 - 1).

[0016] Further, in step S3, the hot pressing temperature is 100-120°C.

[0017] Further, in the first solution, the mass fraction of RM257 is (35-39)%, and the mass fraction of the chiral agent is (1.5-1.8)%.

[0018] In a second aspect, the embodiments of the present application provide an intelligent wearable highly sensitive visual mechanical sensor, which is prepared by any one of the foregoing technical solutions. The intelligent wearable highly sensitive visual mechanical sensor has a three-layer structure, which is a flexible fabric layer, a connection layer, and a liquid crystal layer from bottom to top in sequence; the connection layer is obtained by the reaction of amino groups in PU glue with carbon-carbon double bonds in the discoloration film, and the intelligent wearable highly sensitive visual mechanical sensor realizes dynamic color change of red, yellow, green, and blue under external force stretching.

[0019] Further, the thickness of the flexible fabric layer is 0.5-0.8 mm, the thickness of the connection layer is 0.05-0.07 mm, and the thickness of the liquid crystal layer is 0.04-1 mm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The preparation method of the intelligent wearable highly sensitive visual mechanical sensor provided by the present application controls the modulus of the liquid crystal layer to be consistent with that of the fabric layer by controlling the crosslinking degree of the prepolymer, thereby improving the color change sensitivity, fatigue resistance, and color change cycle reversibility stability. Specifically, the main influencing factor of the prepolymer crosslinking degree is the addition amount of the crosslinking agent (PETMP). In the addition range of 0-14 μl, the liquid crystal crosslinking degree increases with the increase of the crosslinking agent addition amount.

[0022] (2) By controlling the viscosity, crosslinking degree, and evaporation rate of the prepolymer to control the evaporation-induced self-assembly process of the liquid crystal layer, making its assembly regular. When preparing the prepolymer solution, the viscosity is controlled by controlling the content of the solvent (DCM). When the solvent content is about 50 wt%, it is most beneficial to the assembly of the liquid crystal layer. By controlling the temperature (30°C ± 2) in the evaporation-induced self-assembly process to control the evaporation rate, the liquid crystal assembly is more regular. When the temperature is too high, the evaporation is too fast, and the time from the appearance to the solidification of the cholesteric liquid crystal phase is short, which will cause the liquid crystal molecules not to have enough time for sufficient self-assembly, thus affecting the order and stability of the liquid crystal phase; when the temperature is too low, the evaporation is slow, and the evaporation-induced self-assembly process of the liquid crystal molecules in the solvent may become too slow, resulting in a decrease in the self-assembly efficiency.

[0023] (3) In this application, the initial pitch is regulated by adding different chiral reagents and adjusting the ratio of chiral reagent to liquid crystal unit, so as to control the color and color-changing ability of the liquid crystal layer. When only chiral reagent a (LC756) is added, the prepared liquid crystal is dextrorotatory. When the mass ratio of chiral reagent a to liquid crystal unit (RM257) is 0.045:1, 0.049:1, 0.052:1, 0.060:1, the initial color of the liquid crystal layer is red, yellow, green, and blue. Adding an appropriate amount of chiral reagent b (S5011) can prepare a left-handed cholesteric liquid crystal. When the ratio of chiral reagent a to b is 1:0.910, 1:0.940, 1:0.975, 1:1.000, the initial color of the liquid crystal layer is red, yellow, green, and blue.

[0024] (4) In this application, PU glue is used to combine the liquid crystal layer with the fabric. The amino group in PU reacts with the liquid crystal layer chemically to enhance the interfacial force between the color-changing layer and the fabric layer, making the composite structure firm and having good performance. A hot-melt adhesive with a specific melting temperature (100 - 120 °C) and containing amino groups is selected, which not only ensures the firmness of the three-layer structure combination, but also can make the hot-melt adhesive serve as the assembly base of the color-changing layer, and will not damage the liquid crystal assembly structure at the hot-bonding temperature, simplifying the preparation process of the composite fabric and improving the preparation efficiency.

[0025] 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 implementation manners of this application are listed below. Brief Description of the Drawings

[0026] 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, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic structural diagram of the intelligent wearable highly sensitive visual mechanical sensor of the present invention.

[0028] Figure 2 It is a cross-sectional scanning electron microscope image of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1.

[0029] Figure 3 It is the initial color image of the intelligent wearable highly sensitive visual mechanical sensors prepared in Examples 1 - 4.

[0030] Figure 4Color changes of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1 with increasing strain: (a) Physical diagram; (b) Spectrogram.

[0031] Figure 5 Color change diagram of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1 with the bending angle of finger joints changing.

[0032] Figure 6 Stress-strain diagram of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1 for five stretching cycles.

[0033] Figure 7 Liquid crystals with different initial colors prepared in Examples 9 - 12. Detailed implementation manners

[0034] Hereinafter, embodiments of the technical solutions of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and thus are only examples and cannot be used to limit the protection scope of the present application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill 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 accompanying drawing descriptions are intended to cover non-exclusive inclusion.

[0036] 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, "a plurality" means more than two unless otherwise specifically and clearly defined.

[0037] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places 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 will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0038] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship describing associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, in this text, the character " / " generally represents an "or" relationship between the associated objects before and after.

[0039] In the description of the embodiments of the present application, the term "plurality" refers to two or more (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0040] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "linkage", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0041] The embodiments of the present application provide a preparation method for an intelligent wearable highly sensitive visual mechanical sensor, including the following steps:

[0042] S1, dissolve the liquid crystal monomer RM257 and the chiral agent in the solvent dichloromethane, then add the cross-linking agent PETMP, the chain extender EDDET, and the photoinitiator I-651, and finally add the catalyst DPA, stir evenly, stand for 20 - 30 min, and carry out a prepolymerization reaction to obtain a first solution;

[0043] Among them, the mass fraction of dichloromethane in the first solution is 45 - 50%.

[0044] The addition amount of PETMP is 2 - 3 wt% of the entire reaction system.

[0045] In the first solution, the mass fraction of the liquid crystal monomer RM257 is 35 - 39%, and the mass fraction of the chiral agent is 1.5 - 1.8%.

[0046] The present application regulates the size of the initial pitch by adding different chiral reagents and adjusting the ratio of the chiral reagent / liquid crystal unit, so as to realize the regulation of the color and color change ability of the liquid crystal layer.

[0047] Specifically, when the chiral agent is LC756, the prepared liquid crystal is dextrorotatory.

[0048] Control the mass ratio of LC756 to RM257 to be (0.045 - 0.060):1. Specifically, when the mass ratio of the chiral reagent LC756 to the liquid crystal unit (RM257) is 0.045, 0.049, 0.052, or 0.060, the initial color of the liquid crystal layer is red, yellow, green, or blue.

[0049] When the chiral agent includes both LC756 and S5011, a left-handed cholesteric liquid crystal can be prepared.

[0050] Specifically, when the ratio of the chiral reagent LC756 to S5011 is 1:0.910, 1:0.940, 1:0.975, or 1:1.000, the initial color of the liquid crystal layer is red, yellow, green, or blue.

[0051] S2, Coat the first solution obtained in step S1 onto the thin-film PU glue, and then place it in a closed space to maintain an environmental temperature of 30°C ± 2 for 4 - 6 hours to complete the evaporation-induced self-assembly of the cholesteric liquid crystal. Finally, irradiate and cure it under a UV lamp of 365 nm and 20 - 50 mW / cm 2 for 20 - 30 minutes to prepare a color-changing film;

[0052] S3, Use the hot pressing method to hot press the color-changing film obtained in step S2 onto the fabric to obtain a smart wearable highly sensitive visual mechanical sensor.

[0053] Among them, the hot pressing temperature is 100 - 120°C. By controlling the hot pressing temperature, the PU glue can penetrate into the fabric interior to improve the interfacial force, and at this temperature, the color-changing layer can still maintain the cholesteric phase and have the color-changing function. If the hot pressing temperature is too low, the PU glue cannot melt and penetrate into the fabric structure; if the hot pressing temperature is too high, the liquid crystal phase of the cholesteric liquid crystal is easily damaged at high temperature, and the force-induced color-changing function cannot be achieved.

[0054] In the second aspect, the embodiments of the present application provide a smart wearable highly sensitive visual mechanical sensor prepared by the foregoing technical solution. This smart wearable highly sensitive visual mechanical sensor has a three-layer structure, which is, from bottom to top, a flexible fabric layer, a connection layer, and a liquid crystal layer; among them, the connection layer is obtained by the reaction of the amino group in the PU glue with the carbon-carbon double bond in the color-changing film. This smart wearable highly sensitive visual mechanical sensor realizes dynamic color change of red, yellow, green, and blue under external force stretching.

[0055] Among them, the thickness of the flexible fabric layer is 0.5 - 0.8 mm, the thickness of the connection layer is 0.05 - 0.07 mm, and the thickness of the liquid crystal layer is 0.04 - 1 mm.

[0056] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation of the present application. For those embodiments where specific technologies or conditions are not indicated, the technologies or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchases.

[0057] I. Preparation method

[0058] Example 1

[0059] Please refer to Figure 1 As shown, this example provides a preparation method for an intelligent wearable highly sensitive visual mechanical sensor, including the following steps:

[0060] S1. Mix 0.27 g of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene (RM257) and 0.012 g of (3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-((4-(((4-acryloyloxy)butoxy)carbonyl)oxy)benzoate) (LC756) with 100 μl of dichloromethane (DCM), heat to 80 °C, and after the solute is completely dissolved, cool to 25 °C. Add 14 μl of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), 65 μl of 3,6-dioxa-1,8-octanedithiol (EDDET), and 0.002 g of 2,2-dimethoxy-2-phenylacetophenone (I-651) to the solution, and finally add 1.3 μl of di-n-propylamine (DPA) as a catalyst for the first-stage Michael addition reaction. Stir the solution for 5 min and let it stand for 20 minutes to pre-polymerize the reaction;

[0061] S2. Use a film applicator to evenly coat the solution on the thin-film PU glue, then place it in a closed space and keep the ambient temperature at 30 °C for 4 h to complete the evaporation-induced self-assembly of the cholesteric liquid crystal. Finally, irradiate and cure it under a UV lamp at 365 nm and 50 mW / cm 2 to prepare a color-changing film.

[0062] S3. Cut the prepared color-changing film according to the usage environment and requirements, and use the hot pressing method to hot press it on the fabric to obtain an intelligent wearable highly sensitive visual mechanical sensor. The physical diagram is as shown in Figure 3 (a) in. Among them, the fabric is a stretch fabric containing spandex.

[0063] Comparative Example 1

[0064] Comparative Example 1 provides a method for preparing an intelligent wearable highly sensitive visual mechanical sensor. Compared with Example 1, the difference lies in that after step S1, the solution obtained in step S1 is directly coated on the fabric, and it is placed in a closed space to maintain an environmental temperature of 30 °C for 4 h to complete the evaporation-induced self-assembly of the cholesteric liquid crystal. Finally, it is placed under an ultraviolet lamp with a wavelength of 365 nm and a power density of 50 mW / cm 2 for curing by irradiation.

[0065] It can be seen from the experiment that the fabric has a loose and porous structure. After coating, the solution will penetrate into the fabric and cannot be assembled on the fabric surface, resulting in a colorless liquid crystal layer and the inability to achieve the effect of force-induced color change.

[0066] Examples 2-4 and Comparative Examples 2-3

[0067] Examples 2-4 and Comparative Examples 2-3 provide a method for preparing an intelligent wearable highly sensitive visual mechanical sensor. Compared with Example 1, the difference lies in changing the dosage of raw materials in step S1, as shown in the following table. The rest is roughly the same as in Example 1 and will not be elaborated here.

[0068] Serial number RM257 / g LC756 / g PETMP / μl EDDET / μl I-651 / g DPA / μl Example 1 / (a) 0.27 0.012 14 65 0.002 1.3 Example 2 / (b) 0.27 0.014 14 65 0.002 1.3 Example 3 / (c) 0.27 0.015 14 65 0.002 1.3 Example 4 / (d) 0.27 0.016 14 65 0.002 1.3 Comparative Example 2 0.27 0.0108 14 65 0.002 1.3 Comparative Example 3 0.27 0.0229 14 65 0.002 1.3

[0069] Figure 2 Figure 18 is a cross-sectional scanning electron microscope image of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1. It can be seen that the upper layer of the PU adhesive is closely attached to the liquid crystal layer, and the lower layer has penetrated into the fabric, playing a good pasting role. This shows that the prepared composite fabric has a stable structure, the liquid crystal layer is not easy to fall off, and the service life is long. Moreover, the thicknesses of both the liquid crystal layer and the PU adhesive are about 60 μm, and the overall composite layer is relatively thin, which can be applied to a variety of complex curved surfaces.

[0070] Figure 3 Figure 22 is the initial color map of the intelligent wearable highly sensitive visual mechanical sensors prepared in Examples 1-4. It can be seen that by changing the addition amount of the chiral reagent, composite fabrics with different initial colors can be prepared. In practical applications, the rich colors can make the composite fabric have a wider range of uses and more diverse usage scenarios as an intelligent wearable sensor.

[0071] Figure 4Color change of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1 with increasing strain: (a) Physical picture; (b) Spectrogram. It can be seen that when the composite fabric is stretched, the surface color can change from red to blue with the increase of strain. Among them, when the strain reaches 0.34, it turns green. Compared with the preparation method reported by Lacus et al. (《ACS applied materials & interfaces》2024, 16: 14144 - 14151, whose strain is about 50% when it is green), it is more sensitive, and this sensor can have a larger spectral shift at a lower strain.

[0072] Figure 5 Color change diagram of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1 with the change of the bending angle of finger joints. It can be seen that when the finger bends, the surface of the composite fabric produces color changes with the change of the force applied, and it can achieve sensitive sensing of human movements.

[0073] Figure 6 Stress-strain diagram of five stretching cycles of the intelligent wearable highly sensitive visual mechanical sensor prepared in Example 1. It can be seen that after multiple stretching and recovery cycles, the fabric can maintain relatively stable mechanical properties, without obvious strength decline or deformation increase, without obvious performance fluctuations or degradation, and has good fatigue resistance.

[0074] It is known from experiments that when the amount of the chiral reagent is too small, it cannot induce the assembly of liquid crystal monomers, and the helical structure cannot be realized. The surface of the film presents white, and the film cannot produce color changes when it is stretched. When the amount of the chiral reagent is too large, the pitch formed by the assembly of liquid crystal monomers is too small, and the reflection wavelength on the surface of the film is too small, exceeding the visible light wavelength range, and the surface cannot present color either, and the film cannot produce color changes when it is stretched.

[0075] Examples 5 - 8 and Comparative Examples 4 - 5

[0076] Examples 5 - 8 and Comparative Examples 4 - 5 provide a preparation method of an intelligent wearable highly sensitive visual mechanical sensor. Compared with Example 1, the difference lies in changing the amount of raw materials in step S1, as shown in the following table. The rest is roughly the same as Example 1 and will not be elaborated here.

[0077] Serial number RM257 / g LC756 / g PETMP / μl EDDET / μl I-651 / g DPA / μl Example 5 0.27 0.012 1 65 0.002 1.3 Example 6 0.27 0.012 5 65 0.002 1.3 Example 7 0.27 0.012 10 65 0.002 1.3 Example 8 0.27 0.012 14 65 0.002 1.3 Comparative Example 4 0.27 0.012 20 65 0.002 1.3 Comparative Example 5 0.27 0.012 30 65 0.002 1.3

[0078] It can be known from experiments that the crosslinking degree of the prepolymer can be controlled by controlling the addition amount of the crosslinking agent (PETMP), and then the modulus of the liquid crystal layer can be controlled to be consistent with that of the fabric layer, so as to realize the synchronous color change of the color-changing layer and the fabric layer. In the addition range of 1-14 μl, the liquid crystal crosslinking degree increases with the increase of the crosslinking agent addition amount. When the addition amount of PETMP continues to increase, the crosslinking degree inside the film is too large, so that the liquid crystal monomers cannot be assembled in a spiral shape, and the film surface cannot present color, and the mechanochromic function cannot be realized.

[0079] When preparing the prepolymer solution, the viscosity is controlled by controlling the content of the solvent (DCM). When the mass fraction of the solvent is about 45-50 wt%, it is most beneficial to the assembly of the liquid crystal layer. When the mass fraction of DCM is lower than 45%, the viscosity of the prepolymer solution is too high, and the resistance to liquid crystal assembly is too large, and a regular assembly structure cannot be formed; when the mass fraction of DCM is higher than 50%, the viscosity of the prepolymer solution is too low, the polymerization reaction rate is too low, the mechanical strength and modulus of the formed film are low, and they cannot match the modulus of the fabric, and the color change sensitivity of the composite fabric is low, which cannot meet the application requirements.

[0080] By controlling the temperature (30 °C ± 2) during the evaporation-induced self-assembly process to control the volatilization rate, the liquid crystal assembly is more regular. When the temperature is too high, the volatilization is too fast, and the time from the appearance to the solidification of the cholesteric liquid crystal phase is short, which will cause the liquid crystal molecules not to have enough time for sufficient self-assembly, thus affecting the order and stability of the liquid crystal phase. When the temperature is too low, the volatilization is slow, and the evaporation-induced self-assembly process of the liquid crystal molecules in the solvent may become too slow, resulting in a decrease in the self-assembly efficiency.

[0081] In summary, the present application controls the evaporation-induced self-assembly process of the liquid crystal layer by controlling the viscosity, crosslinking degree and volatilization rate of the prepolymer, making its assembly regular, so that the finally obtained sensor is more sensitive to external forces and has a higher surface color saturation.

[0082] Examples 9-12

[0083] Examples 9-12 provide a preparation method of an intelligent wearable highly sensitive visual mechanical sensor. Compared with Example 1, the difference is that two chiral reagents LC756 and S5011 are added in step S1, and the usage amounts of the raw materials are shown in the following table. The rest is roughly the same as in Example 1 and will not be elaborated here.

[0084]

[0085] It can be known from experiments that when the ratio of LC756 to S5011 is 1:0.910, 1:0.940, 1:0.975, 1:1.000, the initial color of the liquid crystal layer is red, yellow, green, blue, as Figure 7 shown.

[0086] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and embodiments having the same composition in essence as the technical idea and achieving the same effects within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A preparation method of an intelligent wearable highly sensitive visual mechanical sensor, characterized in that, It includes the following steps: S1. Dissolve liquid crystal monomer RM257 and chiral agent in the solvent dichloromethane, then add crosslinking agent PETMP, chain extender EDDET and photoinitiator I-651, and finally add catalyst DPA. Stir evenly and let stand for 20 - 30 min to carry out prepolymerization reaction to obtain the first solution; S2. Apply the first solution obtained in step S1 to the film-shaped PU glue, and then place it in a closed space to maintain an environmental temperature of 30°C ± 2 for 4 - 6 h to complete the evaporation-induced self-assembly of the cholesteric liquid crystal. Finally, irradiate it under a UV lamp with a wavelength of 365 nm and an intensity of 20 - 50 mW / cm 2 for 20 - 30 min to cure and prepare the color-changing film; S3. Use the hot pressing method to hot press the color-changing film obtained in step S2 onto the fabric to obtain the intelligent wearable highly sensitive visual mechanical sensor.

2. The preparation method of the intelligent wearable highly sensitive visual mechanical sensor according to claim 1, characterized in that, In step S1, the mass fraction of dichloromethane in the first solution is 45 - 50%.

3. The preparation method of the intelligent wearable highly sensitive visual mechanical sensor according to claim 1, wherein In step S1, the addition amount of PETMP is 2 - 3 wt% of the reaction system.

4. The preparation method of the intelligent wearable highly sensitive visual mechanical sensor according to claim 1, characterized in that, The chiral agent is LC756; the mass ratio of LC756 to RM257 is (0.045 - 0.060):

1.

5. The preparation method of the intelligent wearable highly sensitive visual mechanical sensor according to claim 1, characterized in that The chiral agent includes two kinds, LC756 and S5011, wherein the mass ratio of LC756 to S5011 is 1:(0.91 - 1).

6. The preparation method of the intelligent wearable highly sensitive visual mechanical sensor according to claim 1, characterized in that In step S3, the hot pressing temperature is 100 - 120 °C.

7. The preparation method of the intelligent wearable highly sensitive visual mechanical sensor according to claim 1, characterized in that, In the first solution, the mass fraction of RM257 is (35 - 39)%, and the mass fraction of the chiral agent is (1.5 - 1.8)%.

8. An intelligent wearable highly sensitive visualizable mechanical sensor, characterized in that, Prepared by the preparation method according to any one of claims 1 - 7; the intelligent wearable highly sensitive visual mechanical sensor is a three-layer structure, which is successively a flexible fabric layer, a connection layer and a liquid crystal layer from bottom to top; the connection layer is obtained by the reaction of the amino group in PU glue with the carbon-carbon double bond in the color-changing film, and the intelligent wearable highly sensitive visual mechanical sensor realizes dynamic color change of red, yellow, green and blue under external tensile force.

9. The intelligent wearable highly sensitive visualizable mechanical sensor according to claim 8, wherein The thickness of the flexible fabric layer is 0.5 - 0.8 mm, the thickness of the connection layer is 0.05 - 0.07 mm, and the thickness of the liquid crystal layer is 0.04 - 1 mm.

Images