Preparation method of PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with core-sheath structure

Abstract

The application discloses a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure. The PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with the core-sheath structure is continuously prepared by adopting a thermal induction coaxial dry spinning method, wherein the core layer is liquid crystal, and the sheath layer is PDMS. The core-sheath structure effectively prevents the leakage of the temperature-sensitive material. The core layer liquid crystal exhibits multicolor reversible changes of yellow-green-blue-purple between 34 DEG C and 38 DEG C. The high-transparency PDMS of the sheath layer completely covers the liquid crystal inside, avoids the loss of the core layer, and can directly observe the color change of the core layer liquid crystal under natural light by naked eyes. The fiber-based temperature sensor exhibits excellent flexibility and weavability, and has wide application value in the fields of medical health and intelligent clothes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fiber materials, and relates to a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure. BACKGROUND

[0002] Environmental temperature is one of the key factors affecting human daily activities. High or low temperature can cause an increase in physiological discomfort of the human body, thereby destroying the homeostatic balance of the human body, leading to the occurrence of abnormal conditions such as fever, chills, heat stroke, and hormone disorder. Traditional temperature sensors are large in size and rigid, which limits their application in the field of intelligent textiles and wearable devices. In contrast, fibers and yarns with temperature sensing function are not only flexible and light in weight, but also have textile processability, and have become key materials for preparing new flexible temperature sensors. In particular, the thermochromic flexible temperature sensor can transmit information through color change, which not only can actively sense the environmental temperature and accurately capture the signal, but also does not require subsequent processing of the signal, and has the advantages of timely feedback, color visibility, and simplicity. At present, there are three basic preparation methods for the thermochromic flexible temperature sensor: one is thermochromic microcapsules, which encapsulate the thermochromic material in a high molecular polymer, but this method weakens the color of the temperature-sensitive material; the second is a thermochromic film, which coats the temperature-sensitive material on the surface of the textile substrate by immersion coating, screen printing and other methods. However, the film is usually hard in hand feeling and poor in air permeability, and the uniformity of the coating is difficult to control, and it is easy to fall off after long-term use; the third is a thermochromic fiber, which directly combines the thermochromic material with the textile material, shortens the process flow, and the prepared fiber has the advantages of good washing resistance and durable color change effect.

[0003] In patent CN105821522A, the inventors use wet spinning to prepare a thermochromic blended fiber, however, there is a risk of gradual leakage of the temperature-sensitive material. The inventors of patents CN111005089A and CN110205705A use a polymer as the sheath layer and a mixture of the polymer and the thermochromic microcapsules as the core layer to prepare a thermochromic composite fiber with a core-sheath structure. This method wraps the temperature-sensitive microcapsules in a high polymer sheath layer to avoid leakage of the microcapsules, but this fiber also has obvious limitations: the polymer sheath layer such as polyamide will still hinder the color display of the core layer to some extent, and the color change of the temperature-sensitive microcapsules is relatively single. Liquid crystal materials can display rich colors according to temperature changes. Patent CN107938013A invents a static electrospinning core-sheath nanofiber with a liquid crystal core, however, the fiber can only be observed under a polarizing microscope to show obvious rainbow colors, and the naked eye cannot distinguish the color change.

[0004] Therefore, it is necessary and challenging to develop a thermochromic fiber-based temperature sensor that can be observed by the naked eye. SUMMARY

[0005] The application aims to provide a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, and solve the above problems.

[0006] The technical scheme of the application is:

[0007] A preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, characterized by comprising the following steps:

[0008] (1) mixing PDMS prepolymer and curing agent, and obtaining sheath layer PDMS spinning solution after vacuum degassing;

[0009] (2) heating cholestanol oleic alcohol carbonate and cholestanol nonanoate in a water bath, and obtaining homogeneous core layer liquid crystal spinning solution through magnetic stirring under constant temperature after complete melting;

[0010] (3) injecting the sheath layer PDMS spinning solution and the core layer liquid crystal spinning solution into the sheath layer and the core layer of a coaxial needle tube respectively for heat-induced coaxial dry spinning, rapidly solidifying the sheath layer PDMS spinning solution in a high-temperature oil bath to wrap the core layer liquid crystal, and obtaining continuous PDMS / liquid crystal composite fiber with a core-sheath structure through a winding device;

[0011] (4) placing the PDMS / liquid crystal composite fiber into an oven for continuous drying to completely solidify the fiber, and obtaining a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure.

[0012] Further, in step (1), the mass ratio of the PDMS prepolymer to the curing agent is 10:1.

[0013] Further, in step (2), the mass ratio of the cholestanol oleic alcohol carbonate to the cholestanol nonanoate is 1:1.

[0014] Further, in step (2), the temperature of the constant temperature is 85℃, and the stirring time is 10 min.

[0015] Further, in step (3), the temperature of the high-temperature oil bath is 120-190℃.

[0016] Further, in step (3), the inner diameter of the outer needle of the coaxial needle is 0.61 mm, and the inner and outer diameters of the inner needle are 0.25 mm and 0.49 mm respectively.

[0017] Further, in step (3), the outer needle of the coaxial needle is located above the oil bath liquid surface, and the inner needle protrudes from the outer needle and is immersed below the oil bath liquid surface.

[0018] Further, in step (3), the flow rate of the sheath layer PDMS spinning solution is 4-16 mL / h, and the flow rate of the core layer liquid crystal spinning solution is 1.0-5.0 mL / h.

[0019] Further, in step (3), the winding speed of the winding device is 40-130 m / h.

[0020] Further, in step (4), the drying temperature of the oven is 60℃, and the time is 30 min.

[0021] The application provides a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure.

[0022] The fiber can be directly used as a temperature sensor, the core layer liquid crystal changes color with temperature, and the sheath layer high-transparency PDMS completely covers the liquid crystal inside, which avoids the loss of the core layer and enables the color change to be observed by the naked eye under natural light. In addition, the high elasticity of the PDMS endows the fiber-based temperature sensor with excellent flexibility and weavability, which provides a possibility for further development of the temperature sensor in the fields of medical health and intelligent clothing. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The application provides a preparation process diagram of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, wherein 1 is a core layer liquid crystal spinning solution, 2 is a sheath layer PDMS spinning solution, 3 is a coaxial needle, 4 is a high-temperature oil bath, and 5 is a PDMS / liquid crystal composite fiber collected by a winding device.

[0024] Figure 2 The application provides a morphology electron microscope diagram of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, wherein (a) is a fiber cross section, and (b) is a fiber surface.

[0025] Figure 3 The application provides a photo of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure. DETAILED DESCRIPTION

[0026] The application aims to provide a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure.

[0027] To achieve the above-mentioned purpose, the application realizes the technical scheme as follows.

[0028] The application provides a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, and the specific steps are as follows.

[0029] Step 1, PDMS prepolymer and curing agent are fully mixed according to a mass ratio of 10:1, and the sheath layer PDMS spinning solution (PDMS stands for polydimethylsiloxane, which is composed of two components of prepolymer A and curing agent B, the main component of A is polydimethylsiloxane with a vinyl side chain, and B is polydimethylsiloxane with a hydrogen group, and cross-linking is generated by the contact of the two to solidify) is obtained after vacuum degassing.

[0030] Step 2, cholesteryl oleic carbonate (COC) and cholesteryl pelargonate (CP) with a mass ratio of 1:1 are heated in a water bath, and after being completely melted, the homogeneous core layer liquid crystal spinning solution is obtained by magnetic stirring at 85℃ for 10 minutes.

[0031] Step 3, the sheath layer PDMS spinning solution and the core layer liquid crystal spinning solution are respectively injected into the sheath layer and the core layer of the coaxial needle tube for heat-induced coaxial dry spinning, the sheath layer PDMS spinning solution is rapidly solidified in a high-temperature oil bath at 120-190℃, and the core layer liquid crystal is wrapped, and after being collected by a winding device, the continuous PDMS / liquid crystal composite fiber with a core-sheath structure is obtained. The outer needle of the coaxial needle used in the application has an inner diameter of 0.61mm, and the inner needle has an inner diameter of 0.25mm and an outer diameter of 0.49mm. In order to improve the flowability of PDMS and liquid crystal, the outer needle of the coaxial needle is located above the oil bath liquid surface, and the inner needle is inserted into the oil bath liquid surface below. The flow rate of PDMS is 4-16mL / h, the flow rate of liquid crystal is 1.0-5.0mL / h, and the winding speed is 40-130m / h.

[0032] Step 4, the continuous PDMS / liquid crystal composite fiber with core-sheath structure is placed in an oven at 60℃ for 30 min to continue drying and curing the fiber completely. The fiber with core-sheath structure can be directly used as a temperature sensor to sensitively detect the change of temperature.

[0033] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the technical solutions of the present application are further described below in combination with specific examples. However, the present application is not limited to the listed examples, and any other known changes within the scope of the claimed rights of the present application are also included.

[0034] The term "one embodiment" or "an embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one implementation of the present application. The appearances of "in one embodiment" at different places in the specification do not necessarily refer to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

[0035] Example 1

[0036] The following example demonstrates a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with core-sheath structure. The specific steps are as follows:

[0037] (1) The PDMS prepolymer and curing agent are mixed at a mass ratio of 10:1, and the sheath layer PDMS spinning solution is obtained after vacuum degassing.

[0038] (2) The cholesteryl oleic carbonate (COC) and cholesteryl pelargonate (CP) with a mass ratio of 1:1 are placed in a water bath for heating. After complete melting, the homogeneous core layer liquid crystal spinning solution is obtained by magnetic stirring at 85℃ for 10 min.

[0039] (3) The sheath layer PDMS spinning solution and the core layer liquid crystal spinning solution are injected into the sheath layer and the core layer of the coaxial needle tube for heat-induced coaxial dry spinning. The sheath layer PDMS spinning solution is rapidly solidified at a high temperature of 140℃ in the oil bath to wrap the core layer liquid crystal. After collection by the winding device, the continuous PDMS / liquid crystal composite fiber with core-sheath structure is obtained. In this example, the inner diameter of the outer needle of the coaxial needle is 0.61 mm, and the inner and outer diameters of the inner needle are 0.25 mm and 0.49 mm, respectively. The outer needle is located above the oil bath liquid surface, and the inner needle protrudes from the outer needle and is immersed below the oil bath liquid surface. The flow rate of PDMS is 8 mL / h, the flow rate of liquid crystal is 2.0 mL / h, and the winding speed is 40 m / h. The preparation flow chart of the fiber is shown in Figure 1

[0040] (4) The PDMS / liquid crystal composite fiber is placed in an oven for 30 min to continue drying and curing the fiber completely. ​

[0041] Temperature / °C 33 34 35 36 37 38 Color Colorless Pale yellow Orange yellow Green Blue violet Pale violet

[0042] Table 1

[0043] The PDMS / liquid crystal composite fiber temperature sensor with core-sheath structure obtained by the above preparation method and process parameters has a diameter of 479.97±32 μm, and the cross section and surface morphology thereof can be seen from Figure 2 , Figure 2 Figure 1 is a scanning electron microscope image of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to the present application. As shown in Figure 2 , it can be seen that the surface of the fiber sensor is smooth and has obvious core-sheath structure. Please refer to Figure 3 , Figure 3 Figure 2 is a photograph of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to the present application. As shown in Figure 3 , the sheath layer PDMS gives the sensor excellent light transmittance, which can make the color change of the core layer of the sensor fully exhibit; the core layer is completely wrapped inside the fiber, effectively preventing the core layer from leaking. Please refer to Table 1, which is a temperature responsiveness schematic table of the sample of Example 1. As shown in Table 1, the sensor exhibits different color changes in the temperature range of 33-38℃.

[0044] Example 2

[0045] The following example shows a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, and the specific steps are as follows:

[0046] (1) The PDMS prepolymer and the curing agent are fully mixed according to a mass ratio of 10:1, and the sheath layer PDMS spinning solution is obtained after vacuum degassing.

[0047] (2) The cholesteryl cocoate (COC) and cholesteryl pelargonate (CP) with a mass ratio of 1:1 are placed in a water bath for heating, and after completely melting, the homogeneous core layer liquid crystal spinning solution is obtained by magnetic stirring at 85℃ constant temperature for 10 min.

[0048] (3) The sheath layer PDMS spinning solution and the core layer liquid crystal spinning solution are respectively injected into the sheath layer and the core layer of the coaxial needle tube for heat-induced coaxial dry spinning. The sheath layer PDMS spinning solution is rapidly solidified at a high temperature of 140 DEG C in an oil bath, and the core layer liquid crystal is wrapped. After being collected by a winding device, a continuous PDMS / liquid crystal composite fiber with a core-sheath structure is obtained. The inner diameter of the outer needle of the coaxial needle used in the present application is 0.61 mm, and the inner diameter and the outer diameter of the inner needle are 0.25 mm and 0.49 mm respectively. The outer needle is located above the oil bath liquid surface, and the inner needle is protruded from the outer needle and immersed below the oil bath liquid surface. The flow rate of PDMS is 10 mL / h, the flow rate of liquid crystal is 3.0 mL / h, and the winding speed is 70 m / h.

[0049] (4) The PDMS / liquid crystal composite fiber is placed in an oven for further drying for 30 min to completely solidify the fiber.

[0050] Temperature / °C 33 34 35 36 37 38 Color Colorless Pale yellow Yellow green Green Violet Pale violet

[0051] Table 2

[0052] The PDMS / liquid crystal composite fiber with a core-sheath structure obtained by the above preparation method and process parameters is a temperature sensor with a diameter of 457.01 ± 39 μm. Please refer to Table 2, which is a temperature response table of the sample of Example 2. As shown in Table 2, different color changes are exhibited in the temperature range of 33 DEG C to 38 DEG C.

[0053] Example 3

[0054] The following example shows a preparation method of a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, and the specific steps are as follows:

[0055] (1) The PDMS prepolymer and the curing agent are fully mixed according to a mass ratio of 10:1, and the sheath layer PDMS spinning solution is obtained after vacuum degassing.

[0056] (2) The cholesteryl oleic carbonate (COC) and cholesteryl pelargonate (CP) with a mass ratio of 1:1 are placed in a water bath for heating. After being completely melted, the homogeneous core layer liquid crystal spinning solution is obtained by magnetic stirring at a constant temperature of 85 DEG C for 10 min.

[0057] (3) The sheath layer PDMS spinning solution and the core layer liquid crystal spinning solution are respectively injected into the sheath layer and the core layer of the coaxial needle tube for heat-induced coaxial dry spinning. The sheath layer PDMS spinning solution is rapidly solidified at a high temperature of 140℃ in an oil bath, and the core layer liquid crystal is wrapped, and after being collected by a winding device, a continuous PDMS / liquid crystal composite fiber with a core-sheath structure is obtained. The inner diameter of the outer needle of the coaxial needle used in the present application is 0.61mm, and the inner diameter and the outer diameter of the inner needle are 0.25mm and 0.49mm respectively. The outer needle is located above the oil bath liquid surface, and the inner needle is protruded from the outer needle and immersed below the oil bath liquid surface. The flow rate of PDMS is 14mL / h, the flow rate of liquid crystal is 2.5mL / h, and the winding speed is 60m / h;

[0058] (4) The PDMS / liquid crystal composite fiber is placed in an oven for further drying for 30min to completely solidify the fiber.

[0059] Temperature / °C 33 34 35 36 37 38 Color Colorless Pale yellow Orange yellow Green Violet Pale violet

[0060] Table 3

[0061] The PDMS / liquid crystal composite fiber with a core-sheath structure obtained by the above preparation method and process parameters is a temperature sensor with a diameter of 528.47±19μm, please refer to Table 3, which is a temperature response table of the sample of Example 3. As shown in Table 3, different color changes are exhibited in the temperature range of 33℃-38℃. The sample of the present embodiment has uniform diameter and no beads, and presents obvious uniform color, which can be used to flexibly monitor physiological signals such as human body temperature, and can be widely applied in the fields of temperature monitoring and flexible sensing.

[0062] In summary, the preparation method of the PDMS / liquid crystal composite fiber with a core-sheath structure in the present application is simple, the color change of the prepared sensor is reversible, rich and visible to the naked eye, and the sensor has excellent mechanical properties such as high elasticity and durability, and can be directly combined with textiles, and has great application prospect in the field of intelligent textiles.

[0063] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure, characterized in that, Includes the following steps: (1) The PDMS prepolymer and curing agent are thoroughly mixed and then degassed under vacuum to obtain the sheath PDMS spinning solution; (2) Cholesterol oleyl carbonate and cholesterol nonanoate are placed in a water bath and heated until they are completely melted. Then, a homogeneous core layer liquid crystal spinning solution is obtained by magnetic stirring under constant temperature. (3) The sheath PDMS spinning solution and the core liquid crystal spinning solution are respectively injected into the sheath and core of the coaxial needle tube for thermally induced coaxial dry spinning. The sheath PDMS spinning solution is rapidly solidified in a high-temperature oil bath, encapsulating the core liquid crystal. After being collected by a winding device, a continuous PDMS / liquid crystal composite fiber with a core-sheath structure is obtained. (4) The PDMS / liquid crystal composite fiber is placed in an oven and dried to completely solidify the fiber, thereby obtaining a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure.

2. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (1), the mass ratio of the PDMS prepolymer to the curing agent is 10:

1.

3. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (2), the mass ratio of cholesterol oleyl carbonate to cholesterol nonanoate is 1:

1.

4. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (2), the constant temperature is 85°C and the stirring time is 10 min.

5. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (3), the temperature of the high-temperature oil bath is 120-190℃.

6. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (3), the inner diameter of the outer needle of the coaxial needle is 0.61 mm, and the inner and outer diameters of the inner needle of the coaxial needle are 0.25 mm and 0.49 mm, respectively.

7. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 6, characterized in that: In step (3), the outer needle of the coaxial needle is located above the surface of the oil bath, and the inner needle of the coaxial needle protrudes from the outer needle and is submerged below the surface of the oil bath.

8. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (3), the flow rate of the sheath PDMS spinning solution is 4-16 mL / h, and the flow rate of the core liquid crystal spinning solution is 1.0-5.0 mL / h.

9. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (3), the winding speed of the winding device is 40-130 m / h.

10. The method for fabricating a PDMS / liquid crystal composite fiber-based high-transparency temperature sensor with a core-sheath structure according to claim 1, characterized in that: In step (4), the drying temperature of the oven is 60°C and the drying time is 30 min.

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