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

Abstract

The application provides a smart wearable high-sensitivity visual mechanical sensor and a preparation method thereof. The preparation method comprises the following steps: firstly, mixing liquid crystal monomers, a chiral agent, a cross-linking agent, a chain extender, a photo initiator and a catalyst to perform a prepolymerization reaction to obtain a first solution; then, coating the first solution on a thin film PU glue to complete evaporation-induced self-assembly of cholesteric liquid crystals, and then irradiating and curing under a UV lamp to obtain a color-changing film; finally, hot-pressing the color-changing film on a fabric to obtain the smart wearable high-sensitivity visual mechanical sensor. The PU glue is used to combine the color-changing film and the textile, the chemical composition of the color-changing layer is controlled to make the amino group in the PU glue react with the carbon-carbon double bond in the color-changing layer, the color-changing layer is combined with the PU glue more firmly, the PU glue can penetrate into the textile in the hot-pressing process, the color-changing layer, the intermediate layer and the textile are tightly combined, and the wearable force response visual sensor which is more fitted to the three-dimensional surface of the human body is prepared.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic device fabrication technology, specifically to a smart wearable high-sensitivity visual mechanical sensor and its fabrication method. Background Technology

[0002] Within the realm of smart wearable technology, flexible mechanical sensors possess the broadest application prospects. These sensors efficiently convert the physical and mechanical stimuli experienced by the human body during movement into precise, quantifiable signals, enabling real-time monitoring of the mechanical effects of changes in the human physiological state and external environment. This characteristic has led to their widespread application in various professional fields, including healthcare, sports, health monitoring, and advanced human-computer interaction. Considering the complex movement patterns exhibited by the human body during movement and the various external impacts it may experience, developing a multi-stress-mode flexible sensor capable of simultaneously and accurately capturing changes in movement amplitude and external force stimuli has become an urgent need in the field of smart wearable technology. This need not only drives further innovation in sensor technology but also provides the possibility of improving the accuracy and comprehensiveness of human motion monitoring.

[0003] Researchers have conducted extensive fundamental research in the field of wearable sensing. Lacus et al. reported a method for preparing an adhesive multicolor mechanical color-changing tag (ACS Applied Materials & Interfaces 2024, 16: 14144-14151). This method involves first assembling, curing, and cutting cholesteric liquid crystals on a PVA surface, then applying adhesive to the color-changing layer to enable its application on various object surfaces. This tag can visually display mechanical changes, but its preparation process is complex. The adhesiveness of the tag is insufficient on rough, flexible surfaces such as fabrics, making it unable to monitor the amplitude of human movement. Furthermore, the color changes from red to green only when the strain reaches 50%, indicating insufficient sensitivity.

[0004] Patent CN118065156A discloses a stretch-sensitive color-changing flexible fabric, its preparation method, and its applications. This preparation method involves adding nano-dopersive agents to a chiral liquid crystal polymer precursor solution. The nano-dopersive agents assist in the self-assembly of liquid crystal monomer molecules, ultimately yielding a highly saturated structural color. This method combines the stretch-sensitive color-changing characteristics of chiral liquid crystal polymer materials to achieve a stretchable and color-changing flexible fabric. However, this method requires surface plasma treatment and silane coupling agent grafting modification of the intermediate coating layer, making the preparation process cumbersome, inefficient, and the cyclic color-changing performance of the flexible fabric unknown.

[0005] In view of this, it is necessary to design an intelligent wearable high-sensitivity visual mechanical sensor and its fabrication method to solve the above problems. Summary of the Invention

[0006] This application provides a smart wearable high-sensitivity visual mechanical sensor and its fabrication method. The fabrication method first prepares a force-responsive, force-sensitive color-changing liquid crystal elastomer material, and then uses PU adhesive to combine it with textiles. By controlling the chemical composition of the color-changing layer, the amino groups in the PU adhesive react with the carbon-carbon double bonds in the color-changing layer, making the color-changing layer and PU adhesive more firmly bonded. The hot-pressing process allows the PU adhesive to penetrate into the textiles, achieving a tight bond between the color-changing layer, the intermediate layer, and the textiles, thus fabricating a wearable force-responsive visual sensor that better conforms to the three-dimensional curved surface of the human body.

[0007] This sensor detects mechanical changes by changing color. Compared to traditional sensors that require current monitoring equipment, it is more portable, more sensitive, has a wider range of applications, and a longer lifespan.

[0008] In a first aspect, embodiments of this application provide a method for fabricating a smart wearable high-sensitivity visual mechanical sensor, comprising the following steps:

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

[0010] S2, the first solution obtained in step S1 is coated onto a thin film of PU adhesive, and then placed in a sealed space at an ambient temperature of 30℃±2 for 4-6 hours to allow the cholesteric liquid crystal to complete evaporation-induced self-assembly. Finally, it is placed at 365nm and 20-50mW / cm 2 The color-changing film was prepared by curing it under ultraviolet light for 20-30 minutes.

[0011] S3. The color-changing film obtained in step S2 is hot-pressed onto the fabric using a hot-pressing method to obtain a smart wearable high-sensitivity visual mechanical sensor.

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

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

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

[0015] Furthermore, the chiral agent includes two types: LC756 and S5011, wherein the mass ratio of LC756 to S5011 is 1:(0.91-1).

[0016] Furthermore, in step S3, the hot pressing temperature is 100-120℃.

[0017] Furthermore, 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] Secondly, this application provides a smart wearable high-sensitivity visual mechanical sensor, prepared by any of the aforementioned technical solutions. This smart wearable high-sensitivity visual mechanical sensor has a three-layer structure, consisting of a flexible fabric layer, a connecting layer, and a liquid crystal layer from bottom to top. The connecting layer is formed by the reaction of amino groups in PU adhesive with carbon-carbon double bonds in the color-changing film. The smart wearable high-sensitivity visual mechanical sensor achieves dynamic color changes to red, yellow, green, and blue under external tensile force.

[0019] Furthermore, the thickness of the flexible fabric layer is 0.5-0.8 mm, the thickness of the connecting 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 method for preparing the intelligent wearable high-sensitivity visual mechanical sensor provided in this 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 precursor, thereby improving the color change sensitivity, fatigue resistance and color change cycle reversible stability. Specifically, the main influencing factor of the crosslinking degree of the precursor is the amount of crosslinking agent (PETMP) added. Within the addition range of 0-14 μl, the crosslinking degree of the liquid crystal increases with the increase of the amount of crosslinking agent added.

[0022] (2) The evaporation-induced self-assembly process of the liquid crystal layer is controlled by adjusting the viscosity, crosslinking degree, and evaporation rate of the precursor, resulting in more orderly assembly. When preparing the precursor solution, the viscosity is controlled by adjusting the solvent (DCM) content; a solvent content of approximately 50 wt% is most favorable for liquid crystal layer assembly. The evaporation rate is controlled by adjusting the temperature (30℃±2) during the evaporation-induced self-assembly process, leading to more orderly liquid crystal assembly. Excessive temperature results in rapid evaporation, shortening the time from the appearance to solidification of the cholesteric liquid crystal phase, which leaves insufficient time for sufficient self-assembly of the liquid crystal molecules, thus affecting the orderliness and stability of the liquid crystal phase. Conversely, excessively low temperature leads to slow evaporation, potentially causing the evaporation-induced self-assembly process of the liquid crystal molecules in the solvent to become too slow, resulting in reduced self-assembly efficiency.

[0023] (3) This application controls the initial pitch by adding different chiral reagents and adjusting the ratio of chiral reagent to liquid crystal module, thereby controlling 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 module (RM257) is 0.045:1, 0.049:1, 0.052:1, and 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 levorotatory cholesteric liquid crystal. When the ratio of chiral reagent a to b is 1:0.910, 1:0.940, 1:0.975, and 1:1.000, the initial color of the liquid crystal layer is red, yellow, green, and blue.

[0024] (4) This application uses PU adhesive to bond the liquid crystal layer to the fabric. The amine groups in PU react chemically with the liquid crystal layer to improve the interfacial force between the color-changing layer and the fabric layer, making the composite structure strong and with good performance. The selection of hot melt adhesive with a specific hot melt temperature (100-120℃) and containing amino groups ensures the strong bonding of the three-layer structure and allows the hot melt adhesive to serve as the assembly substrate for the color-changing layer. Moreover, the liquid crystal assembly structure will not be damaged 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 better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0026] To more clearly illustrate the technical solution of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of the intelligent wearable high-sensitivity visual mechanical sensor of the present invention.

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

[0029] Figure 3 This is the initial color map of the intelligent wearable high-sensitivity visual mechanical sensor obtained in Examples 1-4.

[0030] Figure 4The color change of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1 as strain increases: (a) physical image; (b) spectrum.

[0031] Figure 5 This is a color change graph of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1 as the bending angle of the finger joint changes.

[0032] Figure 6 The stress-strain diagram of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1 after five tensile cycles is shown.

[0033] Figure 7 These are liquid crystals with different initial colors obtained in Examples 9-12. Detailed Implementation

[0034] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings 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 used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0039] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0040] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0041] This application provides a method for fabricating a smart wearable high-sensitivity visual mechanical sensor, comprising the following steps:

[0042] S1, dissolve the liquid crystal monomer RM257 and chiral agent in the solvent dichloromethane, then add the crosslinking agent PETMP, chain extender EDDET and photoinitiator I-651, and finally add the catalyst DPA. Stir well, let stand for 20-30 minutes, and carry out the prepolymerization reaction to obtain the first solution.

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

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

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

[0046] This application controls the initial pitch by adding different chiral reagents and adjusting the ratio of chiral reagents to liquid crystal modules, thereby controlling the color and color-changing ability of the liquid crystal layer.

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

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

[0049] When the chiral agents include both LC756 and S5011, a levo-cholesterol phase liquid crystal can be prepared.

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

[0051] S2, the first solution obtained in step S1 is coated onto a thin film of PU adhesive, and then placed in a sealed space at an ambient temperature of 30℃±2 for 4-6 hours to allow the cholesteric liquid crystal to complete evaporation-induced self-assembly. Finally, it is placed at 365nm and 20-50mW / cm 2 The color-changing film was prepared by curing it under ultraviolet light for 20-30 minutes.

[0052] S3. The color-changing film obtained in step S2 is hot-pressed onto the fabric using a hot-pressing method to obtain a smart wearable high-sensitivity visual mechanical sensor.

[0053] The hot-pressing temperature is 100-120℃. By controlling the hot-pressing temperature, the PU adhesive can penetrate into the fabric to improve interfacial forces, and the color-changing layer can still maintain the cholesteric phase and thus retain its color-changing function at this temperature. If the hot-pressing temperature is too low, the PU adhesive cannot melt and penetrate into the fabric structure; if the hot-pressing temperature is too high, the high temperature can easily destroy the liquid crystal phase of the cholesteric liquid crystal, thus failing to achieve the mechanochromic function.

[0054] Secondly, this application provides a smart wearable high-sensitivity visual mechanical sensor, prepared using the aforementioned technical solution. This smart wearable high-sensitivity visual mechanical sensor has a three-layer structure, consisting of a flexible fabric layer, a connecting layer, and a liquid crystal layer from bottom to top. The connecting layer is formed by the reaction of amino groups in the PU adhesive with carbon-carbon double bonds in the color-changing film. This smart wearable high-sensitivity visual mechanical sensor achieves dynamic color changes to red, yellow, green, and blue under external stretching.

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

[0056] The following are 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 limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0057] I. Preparation Method

[0058] Example 1

[0059] Please see Figure 1 As shown, this embodiment provides a method for fabricating a smart wearable high-sensitivity visual mechanical sensor, including the following steps:

[0060] S1, 0.27 g of 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene (RM257) and 0.012 g of (3R,3aR,6S,6aR)-hexahydrofurano[3,2-b]furan-3,6-diylbis(4-((4-((((4-acryloyloxy)butoxy)carbonyl)oxy)benzoate) (LC756) were mixed with 100 μl of dichloromethane (DCM), heated to 80 °C, and cooled to 25 °C after the solute was completely dissolved. Then, 14 μl of pentaerythritol tetrakis(3-mercaptopropionic acid) ester (PETMP), 65 μl of 3,6-dioxa-1,8-octanedithiol (EDDET), and 0.002 g of [unspecified ingredient] were added to the solution. 2,2-Dimethoxy-2-phenylacetophenone (I-651) was added, and finally 1.3 μl of di-n-propylamine (DPA) was added as a catalyst for the first-stage Michael addition reaction. The solution was stirred for 5 min and allowed to stand for 20 min to allow the reaction to prepolymerize.

[0061] S2, using a coating applicator, the solution is evenly coated onto a thin film of PU adhesive, and then placed in a sealed space at an ambient temperature of 30°C for 4 hours to allow the cholesteric liquid crystal to complete evaporation-induced self-assembly. Finally, it is placed at 365nm and 50mW / cm². 2 The color-changing film was prepared by curing under ultraviolet light.

[0062] S3. The prepared color-changing film is cut to size according to the usage environment and requirements, and then hot-pressed onto the fabric using a hot-pressing method to obtain a smart wearable high-sensitivity visual mechanical sensor. (Image of the actual product follows.) Figure 3 As shown in (a) above. The fabric is an elastic fabric containing spandex.

[0063] Comparative Example 1

[0064] Comparative Example 1 provides a method for fabricating a smart wearable high-sensitivity visual mechanical sensor. The difference from Example 1 is that, after step S1, the solution obtained in step S1 is directly coated onto a fabric and placed in a sealed space at an ambient temperature of 30°C for 4 hours to allow the cholesteric liquid crystal to complete evaporation-induced self-assembly. Finally, it is placed at 365 nm and 50 mW / cm². 2 Cured under ultraviolet light.

[0065] Experiments show that the fabric has a loose and porous structure. After coating, the solution will penetrate into the fabric and cannot be assembled on the surface of the fabric, resulting in the liquid crystal layer being colorless and unable 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 fabricating a smart wearable high-sensitivity visual mechanical sensor. Compared with Example 1, the difference lies in changing the amount of raw materials used in step S1, as shown in the table below. The rest is largely the same as in Example 1 and will not be repeated 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 This is a cross-sectional scanning electron microscope image of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1. It can be seen that the upper layer of PU adhesive is tightly bonded to the liquid crystal layer, and the lower layer has penetrated into the fabric, providing excellent adhesion. This indicates that the prepared composite fabric structure is stable, the liquid crystal layer is not easily detached, and it has a long service life. Furthermore, the thickness of both the liquid crystal layer and the PU adhesive is approximately 60 μm, and the overall composite layer is relatively thin, making it suitable for various complex curved surfaces.

[0070] Figure 3 The images show the initial color diagrams of the intelligent wearable high-sensitivity visual mechanical sensors prepared in Examples 1-4. It can be seen that by changing the amount of chiral reagent added, composite fabrics with different initial colors can be prepared. In practical applications, the rich variety of colors allows the composite fabrics to be used as intelligent wearable sensors in a wider range of applications and more diverse usage scenarios.

[0071] Figure 4The color change of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1 with increasing strain is shown in the images: (a) physical image; (b) spectral diagram. It can be seen that the surface color of the composite fabric changes from red to blue with increasing strain when stretched. Specifically, it turns green at a strain of 0.34. Compared with the preparation method reported by Lacus et al. (ACS Applied Materials & Interfaces 2024, 16: 14144-14151, where the strain is around 50%, it is more sensitive. This sensor can exhibit a larger spectral shift at lower strains.

[0072] Figure 5 This is a color change graph of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1 as the finger joint bending angle changes. It can be seen that when the finger is bent, the surface of the composite fabric changes color with the applied force, enabling sensitive response to human movement.

[0073] Figure 6 The image shows the stress-strain diagram of the intelligent wearable high-sensitivity visual mechanical sensor prepared in Example 1 after five tensile cycles. It can be seen that after multiple tensile and recovery cycles, the fabric maintains relatively stable mechanical properties, without significant strength decrease or deformation increase, and without significant performance fluctuations or degradation, exhibiting good fatigue resistance.

[0074] Experiments show that when the amount of chiral reagent is too small, it cannot induce the liquid crystal monomers to assemble, thus failing to achieve a helical structure. The film surface appears white, and the film does not change color when stretched. When the amount of chiral reagent is too large, the pitch of the liquid crystal monomers assembled is too small, resulting in a reflection wavelength on the film surface that is too small, exceeding the visible light wavelength range. Consequently, the surface also fails to display color, and the film does not change color when stretched.

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

[0076] Examples 5-8 and Comparative Examples 4-5 provide a method for fabricating a smart wearable high-sensitivity visual mechanical sensor. Compared with Example 1, the difference lies in changing the amount of raw materials used in step S1, as shown in the table below. The rest is largely the same as in Example 1 and will not be repeated 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] Experiments show that the degree of crosslinking of the precursor can be controlled by adjusting the amount of crosslinking agent (PETMP), thereby maintaining consistency between the modulus of the liquid crystal layer and the fabric layer, and achieving synchronous color change between the color-changing layer and the fabric layer. Within the addition range of 1-14 μl, the degree of crosslinking of the liquid crystal increases with the increase of the amount of crosslinking agent. When the amount of PETMP continues to increase, the crosslinking inside the film becomes too excessive, preventing the liquid crystal monomers from undergoing helical assembly, resulting in the film surface failing to display color and thus failing to achieve the mechanochromic function.

[0079] When preparing the precursor solution, the viscosity is controlled by adjusting the solvent content (DCM). A solvent mass fraction of approximately 45-50 wt% is most favorable for liquid crystal layer assembly. When the DCM mass fraction is below 45%, the viscosity of the precursor solution is too high, resulting in excessive resistance to liquid crystal assembly and an inability to form a regular assembly structure. When the DCM mass fraction is above 50%, the viscosity of the precursor solution is too low, leading to a low polymerization rate and low mechanical strength and modulus of the resulting film, which cannot match the modulus of the fabric. Consequently, the composite fabric exhibits low color change sensitivity, failing to meet application requirements.

[0080] By controlling the temperature (30℃±2) during the evaporation-induced self-assembly process, the evaporation rate can be controlled to make the liquid crystal assembly more orderly. If the temperature is too high, the evaporation is too fast, and the time from the appearance to solidification of the cholesteric liquid crystal phase is too short, which will not allow the liquid crystal molecules enough time to perform sufficient self-assembly, thus affecting the order and stability of the liquid crystal phase. If the temperature is too low, the evaporation is slow, and the evaporation-induced self-assembly process of liquid crystal molecules in the solvent may become too slow, resulting in a decrease in self-assembly efficiency.

[0081] In summary, this application controls the evaporation-induced self-assembly process of the liquid crystal layer by controlling the viscosity, crosslinking degree, and evaporation rate of the precursor, making the assembly more regular and resulting in a sensor with a more sensitive response to external forces and higher surface color saturation.

[0082] Examples 9-12

[0083] Examples 9-12 provide a method for preparing a smart wearable high-sensitivity visual mechanical sensor. Compared with Example 1, the difference is that two chiral reagents, LC756 and S5011, are added in step S1. The specific amounts of the raw materials are shown in the table below. The rest is roughly the same as in Example 1 and will not be repeated here.

[0084]

[0085] Experiments show that when the ratio of LC756 to S5011 is 1:0.910, 1:0.940, 1:0.975, and 1:1.000, the initial colors of the liquid crystal layer are red, yellow, green, and blue, respectively. Figure 7 As shown.

[0086] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing an intelligent wearable high-sensitivity visual mechanical sensor, characterized in that, Includes the following steps: S1, dissolve the liquid crystal monomer RM257 and chiral agent in the solvent dichloromethane, then add the crosslinking agent PETMP, chain extender EDDET and photoinitiator I-651, and finally add the catalyst DPA. Stir well, let stand for 20-30 minutes, and carry out the prepolymerization reaction to obtain the first solution. S2, the first solution obtained in step S1 is coated onto a thin film of PU glue, and then placed in a closed space to maintain an ambient temperature of 30°C±2 for 4-6h, so that the cholesteric liquid crystal completes evaporation-induced self-assembly, and finally placed under a 365 nm, 20-50 mW / cm 2 UV lamp for irradiation and curing for 20-30 min to prepare a color-changing film; S3. The color-changing film obtained in step S2 is hot-pressed onto the fabric using a hot-pressing method to obtain a smart wearable high-sensitivity visual mechanical sensor. During the hot-pressing process, some PU adhesive penetrates into the fabric. The amino groups in the PU adhesive react with the carbon-carbon double bonds in the color-changing film to form a connecting layer. The upper layer of the connecting layer is tightly bonded to the liquid crystal layer, and the lower layer has penetrated into the fabric, so that the color-changing layer is tightly bonded to the textile.

2. The method for fabricating the intelligent wearable high-sensitivity 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 method of claim 1, wherein the method further comprises the steps of: coating the substrate with a layer of a conductive material; and coating the layer of the conductive material with a layer of a dielectric material. In step S1, the amount of PETMP added is 2-3 wt% of the reaction system.

4. The method of claim 1, wherein the method further comprises: The chiral agent is LC756; the mass ratio of LC756 to RM257 is (0.045-0.060):

1.

5. The method of claim 1, wherein the method further comprises: The chiral agent includes two types: LC756 and S5011, wherein the mass ratio of LC756 to S5011 is 1:(0.91-1).

6. The method of claim 1, wherein the method further comprises: In step S3, the hot pressing temperature is 100-120℃.

7. The method of claim 1, wherein the method further comprises the steps of: coating the substrate with a layer of a conductive material; and coating the layer of the conductive material with a layer of a dielectric material. 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 high-sensitivity visual mechanical sensor, characterized in that, The intelligent wearable high-sensitivity visual mechanical sensor is prepared by the preparation method according to any one of claims 1-7; the intelligent wearable high-sensitivity visual mechanical sensor has a three-layer structure, consisting of a flexible fabric layer, a connecting layer, and a liquid crystal layer from bottom to top; the connecting layer is obtained by the reaction of amino groups in PU adhesive with carbon-carbon double bonds in the color-changing film; the intelligent wearable high-sensitivity visual mechanical sensor achieves dynamic color changes of red, yellow, green, and blue under external force stretching; the strain response of the intelligent wearable high-sensitivity visual mechanical sensor is as low as 34%. 9.The smart wearable high-sensitivity visual mechanical sensor of claim 8, wherein, The thickness of the flexible fabric layer is 0.5-0.8 mm, the thickness of the connecting layer is 0.05-0.07 mm, and the thickness of the liquid crystal layer is 0.04-1 mm.

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