A stretchable conductive composite film, its preparation method and application

Abstract

This invention discloses a stretchable conductive composite film, its preparation method, and its applications, belonging to the fields of stretchable organic electronics and temperature sensing technology. The preparation method involves uniformly dispersing pyrrole monomers into a polyurethane matrix via an air / glycerol interface assembly method, followed by chemical oxidation synthesis. The pyrrole monomers undergo oxidative polymerization between polyurethane molecular chains, resulting in the growth and entanglement of the synthesized polypyrrole polymer chains within the polyurethane molecular chains, forming a stretchable conductive composite film with a polyurethane / polypyrrole interpenetrating network structure. The polypyrrole and polyurethane interpenetrating network structure of this invention ensures that the conductive pathway of the stretchable temperature sensor is not significantly disrupted under tensile and other strain conditions. Therefore, the stretchable temperature sensor of this invention exhibits strain-insensitive temperature sensing performance, maintaining stable temperature sensing performance under both tensile and bending deformations.

Description

Technical Field

[0001] This invention relates to the fields of stretchable organic electronics and temperature sensing technology, and in particular to a stretchable conductive composite film, its preparation method, and its application. Background Technology

[0002] Body temperature is an important physiological indicator for the human body, and acute illnesses are often accompanied by abnormal fluctuations in body temperature. Therefore, patients with serious illnesses need to monitor their vital signs through real-time body temperature monitoring. This necessitates the development of wearable electronic temperature detection products for continuous, real-time body temperature monitoring.

[0003] To achieve real-time body temperature monitoring and provide more possibilities for personalized health management and monitoring the health status of more special populations, it is necessary to develop a temperature sensor that can fit snugly against the skin and is comfortable to wear. Currently, most thermometers on the market are rigid and lack wearing comfort; commonly used thermometers such as mercury thermometers have long response times, making continuous monitoring impossible and resulting in significant efficiency deficiencies. Furthermore, the range of human body temperature variation is narrow, requiring thermometers with an accuracy of 0.1℃ to meet the requirements. Therefore, there is a need to develop high-precision temperature measurement products, which are not adequately met by commonly available infrared thermometers and thermocouples.

[0004] With the rapid development of flexible electronics, stretchable electronics, as a further development trend, has received widespread attention. Human skin has a certain degree of deformation, necessitating the development of deformable electronic products. In the field of wearable sensors, stretchable sensors offer better wearing comfort, conformability, and resistance to strain interference, exhibiting significant advantages and broader application prospects in body temperature monitoring. Therefore, designing a stretchable, high-precision temperature sensor is of great importance.

[0005] Polypyrrole (PP) is an organic conductive polymer with flexibility, a wide and tunable conductivity range, and environmental stability, making it an attractive candidate for applications in organic electronics. As a p-type semiconductor material, PPP's carrier transitions are temperature-dependent; increasing temperature enhances carrier transition capability, increases carrier density and mobility, and consequently reduces resistance, making it an excellent functional material for flexible temperature sensors. More importantly, PPP exhibits good biocompatibility, which is crucial for wearable electronics. Furthermore, PPP is easy to synthesize, with a simple preparation process and low cost, making it suitable for mass production and possessing significant commercial value. However, PPP's excellent chemical stability, exhibiting insolubility and infusibility, while providing excellent environmental stability, also introduces processing difficulties. PPP is incompatible with solution preparation methods (such as spin coating and inkjet printing), thus hindering its composite with other materials. To fabricate stretchable temperature sensors based on polypyrrole, the mechanical properties of polypyrrole are insufficient to support its electrical properties under stretching. Therefore, it is often combined with stretchable elastomer materials to create stretchable conductors that balance conductivity and stretchability. Common composite strategies include: 1) Physically attaching polypyrrole to the surface of the elastomer to form a stretchable conductor with a polypyrrole coating. However, polypyrrole has poor adhesion, and the interaction between it and the elastomer is weak. Therefore, even under small stretching, slippage and delamination can occur, leading to large cracks and electrical failure. 2) Blending polypyrrole as a filler with the elastomer. However, this easily leads to particle agglomeration and uneven distribution, resulting in poor conductivity of the composite material. Furthermore, stress concentration at agglomerated areas during stretching makes them more prone to cracking. Additionally, compatibility between materials and the time-consuming and labor-intensive processing significantly limit its production and application. Summary of the Invention

[0006] The purpose of this invention is to address the problems of existing temperature detection products being non-stretchable, difficult to adapt to various skin deformations, having poor wearing comfort, long response time, and low accuracy, and to provide a method for preparing a stretchable conductive composite film.

[0007] Another object of the present invention is to provide a stretchable conductive composite film obtained by the above preparation method.

[0008] Another object of the present invention is to provide the application of the above-mentioned stretchable conductive composite film in a stretchable temperature sensor.

[0009] The technical solution adopted to achieve the purpose of this invention is:

[0010] A method for preparing a stretchable conductive composite film involves uniformly dispersing pyrrole monomers into a polyurethane matrix via a gas-liquid interface self-assembly method, followed by chemical oxidation synthesis, in which the pyrrole monomers undergo oxidative polymerization between polyurethane molecular chains, resulting in the growth and entanglement of the synthesized polypyrrole molecular chains between the polyurethane molecular chains, thus forming a stretchable conductive composite film with a polyurethane / polypyrrole interpenetrating network structure.

[0011] In the above technical solution, the polyurethane matrix is ​​a polyether-type thermoplastic polyurethane matrix.

[0012] In the above technical solution, the preparation method includes the following steps:

[0013] Step 1: Disperse pyrrole monomer and polyurethane uniformly in tetrahydrofuran to obtain a mixed solution. Drop the mixed solution onto the sealed glycerol surface and release the seal to allow the tetrahydrofuran to evaporate. At the same time, the pyrrole monomer is uniformly dispersed between the polyurethane molecular chains and floats on the glycerol surface to form a pyrrole monomer / polyurethane film.

[0014] Step 2: The pyrrole monomer / polyurethane film obtained in Step 1 is lifted from the glycerol surface and placed in an oxidant solution for chemical oxidation synthesis. The pyrrole monomer is polymerized in situ between the molecular chains of polyurethane to form polypyrrole, resulting in a thermoplastic polyurethane / polypyrrole film with a polyurethane / polypyrrole interpenetrating network structure.

[0015] Step 3: The thermoplastic polyurethane / polypyrrole film obtained in Step 2 is taken out of the oxidant solution, excess oxidant on the surface is washed away, and then dried to obtain a stretchable conductive composite film.

[0016] In the above technical solution, in step 1, the mass ratio of the pyrrole monomer to the polyurethane is (0.5~2):1, preferably, the mass ratio of the pyrrole monomer to the polyurethane is 1:1.

[0017] In the above technical solution, step 1 is performed in a yellow light or dark environment, and step 2 is performed in a yellow light or dark environment.

[0018] In the above technical solution, in step 2, the pyrrole monomer / polyurethane film is lifted from the glycerol surface using a pretreated glass slide.

[0019] In the above technical solution, the pretreatment process is as follows: after rinsing the glass slide clean, it is then ultrasonically cleaned with deionized water, acetone, and ethanol in sequence, and then the glass slide is sequentially hydroxylated and hydrophobically modified.

[0020] In the above technical solution, in step 2, the temperature of the chemical oxidation synthesis is 0-25°C, and the time of the chemical oxidation synthesis is 5-20 min. Preferably, the time is 5 min, 10 min, or 20 min, and more preferably, the time is 5 min.

[0021] In the above technical solution, in steps 2 and 3, the oxidant solution is a mixed solution of oxidant and water; the molar concentration of the oxidant solution is not less than 0.5 M, preferably 0.62 M; the oxidant is ferric chloride, copper chloride, persulfate or hydrogen peroxide.

[0022] Another aspect of the present invention includes a stretchable conductive composite film obtained by the preparation method, wherein the thickness of the stretchable conductive composite film is 40 µm.

[0023] Another aspect of the present invention includes the application of the stretchable conductive composite film in a stretchable temperature sensor, the stretchable temperature sensor comprising a stretchable conductive composite film and electrodes disposed on opposite sides of the stretchable conductive composite film, wherein conductive silver paste is coated between the electrodes and the stretchable conductive composite film.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention is the first to apply the air / glycerol interface assembly method (gas-liquid interface self-assembly method) to the composite of polypyrrole and polyurethane. Pyrrole monomers are uniformly dispersed in the gaps between polyurethane networks, and then the pyrrole monomers are polymerized in situ between polyurethane molecular chains to form high-molecular-weight polypyrrole, forming an interpenetrating network structure of polypyrrole and polyurethane. This ingeniously solves the problem of difficult processing of polypyrrole composite materials. Compared with the direct mixing method, it greatly improves the dispersion uniformity of polypyrrole in the elastic matrix and avoids the stress concentration problem introduced by the agglomeration of polypyrrole particles. Moreover, the formation of the interpenetrating network structure of polypyrrole and polyurethane greatly improves the mechanical tensile properties of polypyrrole, and obtains a stretchable conductive composite film with both high tensile strength and high conductivity. At the same time, the synthesis of polypyrrole can be completed by simply soaking in an oxidant. The preparation method is simple, quick, and low-cost, and suitable for mass production.

[0026] 2. The stretchable conductive composite film of this invention is made of all-organic materials, making it green, environmentally friendly, and pollution-free. It has low material cost, making it suitable for large-scale use; and it possesses good biocompatibility, a necessary condition for wearable electronic devices.

[0027] 3. The principle of the air / glycerol interface assembly method of the present invention is that the evaporation of the solvent tetrahydrofuran and its dissolution in glycerol reduce the local surface tension, thereby forming a circular surface tension gradient near the droplet. This gradient induces Marangoni flow from the center to the edge, thereby driving the diffusion of the solute polyurethane and pyrrole monomer.

[0028] 4. Regarding the basic performance of temperature sensing, the stretchable temperature sensor of this invention exhibits excellent linearity R within the human body temperature range of 25-42 °C. 2 =0.999, high linearity makes subsequent signal processing simpler and more reliable; at the same time, the present invention achieves high precision by controlling the oxidation degree of polypyrrole, so that the resolution of the stretchable temperature sensor reaches 0.1℃. Moreover, the stretchable temperature sensor of the present invention has the advantages of response and recovery time of up to 1.3 s, good stability, conformal fit and comfortable wear.

[0029] 5. The stretchable temperature sensor of this invention is a thin-film structure composed of elastic polyurethane and the polymer polypyrrole. The elastic polyurethane acts as the stretchable functional material, forming an entangled network structure with the polypyrrole, which greatly improves stretchability. The polypyrrole acts as the thermosensitive functional material, and its temperature sensing mechanism is based on the thermal resistance effect: as the temperature increases, the carrier density increases, the mobility increases, and the resistance decreases. As the temperature decreases, the carrier density decreases, and the resistance increases. Therefore, the sensor's resistance changes with temperature. By calculating the relationship between the rate of change of resistance and temperature, the temperature can be detected.

[0030] 6. In the stretchable conductive composite film of the present invention, the polyurethane is a polyether-type thermoplastic polyurethane. Thermoplastic polyurethane is chosen because it possesses elasticity, flexibility, high tensile strength, and biocompatibility, and is a porous elastomer with good air permeability. Thermoplastic polyurethane is divided into polyester type and polyether type. Polyether type is chosen because it has better elasticity and hydrolysis resistance compared to polyester type. Elasticity is crucial for achieving stretchability; as a wearable sensor, it is often affected by external moisture such as sweat, requiring good hydrolysis resistance.

[0031] 7. The polypyrrole and polyurethane interpenetrating network structure of the present invention ensures that the conductive path of the stretchable temperature sensor is not significantly damaged under tensile strain. Therefore, the stretchable temperature sensor of the present invention has strain-insensitive temperature sensing performance and can maintain stable temperature sensing performance under deformations such as tension and bending. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the preparation method of the present invention.

[0033] Figure 2 This is a schematic diagram of the polyurethane / polypyrrole interpenetrating network structure of the present invention.

[0034] Figure 3 The image shows a cross-sectional characterization of the stretchable conductive composite film of the present invention, where a is an SEM image and b is an EDS image.

[0035] Figure 4 A photograph of the stretchable conductive composite film of Example 1 shaped into a butterfly and attached to the wrist.

[0036] Figure 5 The water vapor transmission rate is the water vapor permeability of the stretchable conductive composite film of Example 1.

[0037] Figure 6 The graphs show the relative resistance variation of the stretchable temperature sensors according to Embodiments 10 to 12 of the present invention.

[0038] Figure 7 This is a schematic diagram of the structure of the stretchable temperature sensor of the present invention.

[0039] Wherein: 1: Stretchable conductive composite film, 2: Copper tape, 3: Conductive silver paste.

[0040] Figure 8 The temperature response graphs for different chemical oxidation synthesis times in Examples 7 to 9 of the present invention are shown.

[0041] Figure 9 The signal-to-noise ratio and noise of the stretchable temperature sensor of Embodiments 7 to 9 of the present invention when detecting a temperature change of 0.1°C.

[0042] Figure 10 The step detection curve is shown for the stretchable temperature sensor in Example 7.

[0043] Figure 11 The image shows the relative resistance change curve of the stretchable temperature sensor in Example 7.

[0044] Figure 12 The response time is that of the stretchable temperature sensor in Example 7.

[0045] Figure 13 The temperature cycling test stability of the stretchable temperature sensor in Example 7 is shown in Figure a, where a is a magnified view from 2750s to 4950s and b is a magnified view from 11000s to 13200s.

[0046] Figure 14The diagram shows the tensile properties and temperature response of the stretchable temperature sensor in Example 7. In the diagram, a is the temperature response curve under 0% and 30% stretching; b is the stepped cyclic curve of 35-60℃ under 0% and 30% stretching; c is the temperature response after 0, 10, 100, and 500 bending cycles; and d is the curve of the stretchable temperature sensor attached to the outer wall of a measuring cup with a bending radius of 3.5mm to monitor water temperature changes in real time. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0048] Example 1

[0049] A method for preparing a stretchable conductive composite film includes the following steps:

[0050] like Figure 1 As shown, in step 1, 1 g of pyrrole monomer (pale yellow liquid) and 1 g of polyether thermoplastic polyurethane (solid TPU) are dispersed in 9 mL of tetrahydrofuran. The mixture is stirred at 320 rpm / s for 72 h on a turntable at room temperature and in the dark to achieve uniform dispersion and obtain a mixed solution. 18 mL of glycerol is placed in a petri dish with a diameter of 6 cm and a height of 1.5 cm. The dish is sealed with plastic wrap, and a small hole is made in the middle of the plastic wrap. In a windless environment, 400 µL of the mixed solution is pipetted onto the surface of the glycerol through the small hole. The plastic wrap is removed to release the seal, and the tetrahydrofuran solvent is allowed to evaporate. At the same time, the pyrrole monomer is uniformly dispersed in the polyurethane matrix and floats on the surface of the glycerol to form a pyrrole monomer / polyurethane film.

[0051] Step 2: Scrub a 3.8*3.8 cm glass slide with detergent for 2 minutes, rinse thoroughly, and then ultrasonically clean it sequentially with deionized water, acetone, and ethanol for 10 minutes each. Treat with oxygen plasma for 3 minutes to hydroxylate both sides of the glass slide. Immerse the glass slide in a 1:1000 mixture of octadecyltrichlorosilane and n-heptane solvent for 10 minutes. Remove and dry with a nitrogen gun, then ultrasonically clean with chloroform solvent for 10 minutes to remove excess hydroxyl groups, obtaining a pretreated glass slide. When the film changes from completely transparent to 40% transparent, use the pretreated glass slide to slowly lift the pyrrole monomer / polyurethane film obtained in Step 1 from the glycerol surface from one side to the other (avoiding air bubbles between the glass slide and the film). Then, place the glass slide vertically in a 20 mL container with a molar concentration of 0.62. In a mixed solution of ferric chloride and water, a pyrrole monomer / polyurethane film is immersed and chemically oxidized at 20°C for 5 minutes. The pyrrole monomer polymerizes in situ between the polyurethane molecular chains to form polypyrrole, resulting in a thermoplastic polyurethane / polypyrrole film with a polyurethane / polypyrrole interpenetrating network structure (e.g., ...). Figure 2 (as shown)

[0052] Step 3: Using the pretreated glass slide, the thermoplastic polyurethane / polypyrrole film obtained in step 2 is lifted out of the ferric chloride solution, rinsed with secondary water for 1 min to remove excess ferric chloride from the surface, and then dried in an oven at 80°C for 6 h. The film is then mechanically peeled off the glass slide to obtain a stretchable conductive composite film with a thickness of 40 μm.

[0053] Depend on Figure 2 It is evident that applying the air / glycerol interface assembly method to the composite of polypyrrole and polyurethane ingeniously solves the difficult processing problem of polypyrrole composites and greatly improves the dispersion uniformity of polypyrrole in polyurethane. This interpenetrating network structure allows for more space for deformation of the molecular chain network during stretching without being destroyed, effectively dissipating stress during stretching and significantly improving the mechanical properties of polypyrrole.

[0054] Depend on Figure 3 As can be seen in the SEM image, the brighter granular particles are polypyrrole, while the smoother, darker matrix is ​​polyurethane. It can be observed that polypyrrole is interspersed within the polyurethane matrix.

[0055] In the EDS cross-sectional elemental distribution map, oxygen is a characteristic element of polyurethane, and chlorine is a characteristic element of polypyrrole. It can be seen that the distribution of chlorine corresponds very well with the SEM image. Figure 3 The uneven brightness in b is due to the varying heights and undulations, which is caused by the cross-section of the stretchable conductive composite film. Figure 3 This demonstrates that polypyrrole is uniformly dispersed in the TPU matrix, forming a polyurethane / polypyrrole interpenetrating network structure.

[0056] Depend on Figure 4 It is known that the stretchable conductive composite film of the present invention is made into a butterfly shape by laser etching. Since its thickness is only 40µm, it can be attached to the surface of human skin, making it comfortable to wear, breathable, and not stuffy. It can continuously monitor human body temperature for a long time.

[0057] Example 2

[0058] A method for preparing a stretchable conductive composite film. The difference between the preparation method in this embodiment and that in Example 1 is that chemical oxidation synthesis is performed for 10 minutes in step 2.

[0059] Example 3

[0060] A method for preparing a stretchable conductive composite film. The preparation method of this embodiment differs from that of Example 1 only in that, in step 1, the mass ratio of polyurethane to pyrrole monomer is 2:1; and in step 2, chemical oxidation synthesis is carried out for 10 minutes.

[0061] Example 4

[0062] A method for preparing a stretchable conductive composite film. The preparation method of this embodiment differs from that of Example 1 only in that, in step 1, the mass ratio of polyurethane to pyrrole monomer is 1:2; and in step 2, chemical oxidation synthesis is carried out for 10 min.

[0063] Example 5

[0064] A method for preparing a stretchable conductive composite film. The preparation method of this embodiment differs from that of Example 1 only in that, in step 1, the mass ratio of pyrrole monomer to polyurethane is 1:1; and in step 2, chemical oxidation synthesis is carried out for 10 minutes.

[0065] Example 6

[0066] A method for preparing a stretchable conductive composite film. The preparation method of this embodiment differs from that of Example 1 only in that, in step 1, the mass ratio of pyrrole monomer to polyurethane is 1:1; and in step 2, chemical oxidation synthesis is carried out for 20 minutes.

[0067] Example 7

[0068] like Figure 7 As shown, this embodiment provides a method for preparing a stretchable temperature sensor: the stretchable conductive composite film 1 obtained in Example 1 is cut into a rectangle of 1.5*1.5 cm, and copper tape 2 (copper tape width 5 mm) is used as electrodes on opposite sides. Conductive silver paste 3 is coated on the connection between the copper tape 2 and the stretchable conductive composite film 1 to obtain a stretchable temperature sensor.

[0069] Example 8

[0070] This embodiment provides a method for preparing a stretchable temperature sensor: the stretchable conductive composite film 1 obtained in Example 5 is cut into a rectangle of 1.5*1.5 cm, and copper tape 2 (copper tape width 5 mm) is used as electrodes on opposite sides. Conductive silver paste 3 is coated on the connection between the copper tape 2 and the stretchable conductive composite film 1 to obtain a stretchable temperature sensor.

[0071] Example 9

[0072] This embodiment provides a method for preparing a stretchable temperature sensor: the stretchable conductive composite film 1 obtained in Example 6 is cut into a rectangle of 1.5*1.5 cm, and copper tape 2 (copper tape width 5 mm) is used as electrodes on opposite sides. Conductive silver paste 3 is coated on the connection between the copper tape 2 and the stretchable conductive composite film 1 to obtain a stretchable temperature sensor.

[0073] Example 10

[0074] This embodiment provides a method for preparing a stretchable temperature sensor, which is the same as in Example 7, using the stretchable conductive composite film obtained in Example 2 to prepare the stretchable temperature sensor.

[0075] Example 11

[0076] This embodiment provides a method for preparing a stretchable temperature sensor, which is the same as in Example 7, using the stretchable conductive composite film obtained in Example 3 to prepare the stretchable temperature sensor.

[0077] Example 12

[0078] This embodiment provides a method for preparing a stretchable temperature sensor, which is the same as in Example 7, using the stretchable conductive composite film obtained in Example 4 to prepare the stretchable temperature sensor.

[0079] Application Example 1

[0080] A water vapor transmission rate experiment was conducted on the stretchable conductive composite film prepared in Example 1: First, a 2.5cm*2.5cm stretchable conductive composite film was tightly covered over the mouth of a cylindrical permeation cup containing a certain amount of deionized water. The diameter of the cup mouth was 2cm. The permeation cup was placed in a sealed box with constant temperature and humidity. Water-absorbing calcium chloride powder was placed in the box to absorb the water vapor volatilized from the permeation cup. The weight of the permeation cup was recorded after 0, 1, 2, 3, and 4 days, and the weight change curve over time was obtained, as shown in the figure. Figure 5As shown, the weight loss represents the mass of water vapor that evaporates through the stretchable conductive composite film. The greater the mass loss per unit time and per unit area of ​​the permeable cup opening, the better the air permeability of the stretchable conductive composite film. The water vapor permeability of normal human skin is 240-1920 g / m². 2 / day, by Figure 5 It can be seen that the water vapor transmission rate of the stretchable conductive composite film prepared in Example 1 is 936.3 g / m. 2 / day, which is consistent with the water vapor permeability of normal human skin. The high water vapor permeability is attributed to the porous structure of the stretchable conductive composite film made by the air / glycerin interface assembly method.

[0081] Application Example 2

[0082] The resistance of the stretchable temperature sensors obtained in Examples 10-12 was tested using a 2450 source meter. The initial resistance R0 (resistance when the original length was 1 cm) was recorded first, and then recorded again every time the length was stretched by 10%. The results are as follows: Figure 6 As shown, by Figure 6 It is known that when the mass ratio of pyrrole monomer to polyurethane is 1:1, the stretchable temperature sensor exhibits minimal relative resistance change, with almost constant resistance within 30% of the human body strain range, demonstrating excellent tensile properties. This is attributed to the favorable ratio of polypyrrole to polyurethane, resulting in a sparse yet robust network of polypyrrole within the polyurethane matrix. A network that is too dense would have a high mechanical modulus, making it prone to cracking under tensile strain. Conversely, a network that is too sparse would have poor electrical conductivity, causing the distance between polypyrrole chains to increase under tensile strain, thus disrupting the conductive pathways.

[0083] Application Example 3

[0084] The stretchable temperature sensors from Examples 7 to 9 were respectively attached to the temperature-changing platform of the temperature-changing device. The temperature-changing device was adjusted to heat from 25°C to 120°C at a heating rate of 8°C / min. Simultaneously, a 2450Ω source meter was used to continuously test the change in resistance with temperature. Figure 8 As shown. By Figure 8 It can be seen that when the oxidation synthesis time is 5 min, the resistance of the stretchable temperature sensor prepared in Example 7 changes the most with temperature.

[0085] Application Example 4

[0086] The stretchable temperature sensors from Examples 7-9, with different chemical oxidation synthesis times, were placed on the temperature-changing platform of the variable-temperature device. The device was adjusted to heat from 37°C to 37.1°C at a rate of 3°C / min. The resistance change of this 0.1°C temperature change was measured using a 2450 source meter, which is the temperature response signal. Subsequently, the temperature was controlled at 37.1°C and held for 3 minutes. The resistance was recorded, and the drift resistance was calculated, which is the noise. The ratio of the response signal to the noise is the signal-to-noise ratio. The results are as follows: Figure 9 As shown, when the signal-to-noise ratio is greater than 3, 0.1℃ can be distinguished. Figure 9 It can be seen that the stretchable temperature sensor prepared from the stretchable conductive composite film obtained when the polymerization time is 5 min has an accuracy of 0.1℃.

[0087] Application Example 5

[0088] The stretchable temperature sensor from Example 7 was attached to the temperature-changing platform of the temperature-changing device. The heating rate of the temperature-changing device was adjusted to 3°C / min, with an initial temperature of 36.1°C. The temperature was increased by 0.1°C and held for 3 minutes at each subsequent increase, continuing this process until the temperature reached 37°C. The resistance change was continuously monitored using a 2450 source meter. Figure 10 As shown, by Figure 10 It can be seen that within the range of 36.1-37℃, each temperature step is held for 3 minutes, indicating that the stretchable temperature sensor can stably respond to a temperature change of 0.1℃. Furthermore, when held at the same temperature, the resistance remains stable without significant drift, demonstrating the sensor's excellent temperature sensing stability.

[0089] In summary, as shown in Application Examples 1 through 5, the chemical oxidation synthesis time affects the degree of oxidation of polypyrrole, thus influencing its activation energy. As a p-type semiconductor material, as the chemical oxidation synthesis time increases, the degree of oxidation of polypyrrole increases, the activation energy increases, the Fermi level gradually moves away from the conduction band, and the energy required to release holes increases. For temperature sensors based on the thermal resistance effect, the number of holes excited per unit of heat decreases, thus reducing the change in resistance.

[0090] Application Example 6

[0091] The stretchable temperature sensor from Example 7 was attached to the temperature-changing platform of the temperature-changing device. The temperature-changing device was adjusted to heat from 25°C to 42°C at a heating rate of 8°C / min. Simultaneously, a 2450 source meter was used to continuously measure the resistance change with temperature to obtain the temperature response curve. Here, R0 is the initial resistance of the stretchable temperature sensor at 25°C. The temperature response curve was linearly fitted using Origin software to obtain the linear fitting curve, as shown below. Figure 11 As shown, by Figure 11It can be seen that within the human body temperature range (25-42℃), the temperature sensitivity of the stretchable temperature sensor is 0.4%, and the linearity R... 2 =0.999, the good linearity shows that the stretchable temperature sensor has reliable temperature sensing capability, and subsequent signal processing will be simpler, which is of great significance for practical applications.

[0092] Application Example 7

[0093] The stretchable temperature sensor from Example 7 was attached to the temperature-changing platform of the temperature-changing device. The temperature-changing device was adjusted to heat from 37°C to 37.1°C at a heating rate of 200°C / min, held at that temperature for 20 seconds, and then rapidly cooled down to 37°C by introducing liquid nitrogen. Simultaneously, a 2450 source meter was used to continuously measure the change in resistance over time, where R0 is the initial resistance at 37°C. Figure 12 As shown, by Figure 12 It is evident that by controlling the degree of oxidation of polypyrrole through regulating the chemical oxidation synthesis time, the stretchable temperature sensor can achieve a detection accuracy of 0.1℃, with short response and recovery times of only 1.8 s and 1.3 s, respectively, making high-precision continuous body temperature monitoring possible. Furthermore, the stretchable temperature sensor exhibits excellent durability and reliability, maintaining stable temperature sensing performance even after multiple consecutive temperature cycles.

[0094] Application Example 8

[0095] The stretchable temperature sensor from Example 7 was attached to the temperature-changing platform of the temperature-changing device. The temperature-changing device was adjusted to increase the temperature from 36°C to 42°C (the temperature range of the human body) at a rate of 6°C / min, and cyclicated 150 times within the temperature range. The resistance change was continuously measured using a 2450 source meter, where R0 is the initial resistance at 36°C. The results are as follows: Figure 13 As shown, the consistency of the cyclic test reflects the stability and reliability of the temperature sensor. Figure 13 It can be seen that the stretchable temperature sensor of the present invention exhibits strain-insensitive temperature sensing performance, indicating that it has good application prospects in the fields of human health monitoring and electronic skin.

[0096] Application Example 9

[0097] The stretchable temperature sensor from Example 7 was attached to the temperature control platform of the temperature control device. The temperature control device was adjusted to heat from 27°C to 100°C at a rate of 8°C / min, and the resistance change with temperature was measured using a 2450 source meter. The stretchable temperature sensor was then stretched by 30% and attached to the temperature control platform again to test the temperature response described above. The results are as follows. Figure 14 As shown in 'a'.

[0098] The stretchable temperature sensor from Example 7 was attached to the temperature-changing platform of the temperature control device. The temperature control device was adjusted to a temperature-changing rate of 6°C / min, causing the temperature to change sequentially in steps of 35°C, 40°C, 35°C, 45°C, 35°C, 50°C, 35°C, 55°C, 35°C, and 60°C. Each temperature was held for 1 minute, and the resistance change with temperature was measured using a 2450Ω source meter. The temperature sensor was stretched by 30% and then attached to the temperature-changing platform again to test the above-mentioned step temperature response. The results are as follows. Figure 14 As shown in b in the figure.

[0099] The stretchable temperature sensor of Example 7 was attached to the temperature control platform of the temperature control device. The temperature control device was adjusted to heat from 27°C to 67°C at a rate of 8°C / min. The resistance change with temperature was measured using a 2450 source meter (No. 0). The temperature sensor was then bent 10 times (No. 10), 100 times (No. 100), and 500 times (No. 500), and the temperature response was tested again on the temperature control platform. Each bending radius was 5mm. The results are as follows. Figure 14 As shown in c in the figure.

[0100] The stretchable temperature sensor from Example 7 was attached to the wall of a glass with a bending radius of 3.5 cm. Water at 33°C was poured in, and the glass was allowed to cool naturally to room temperature (23°C). The resistance change with temperature was measured using a 2450 source meter. The results are as follows: Figure 14 As shown in d.

[0101] Figure 14 R0 in the figure represents the initial resistance before any stretching or bending occurs.

[0102] Depend on Figure 14 It can be seen that the stretchable temperature sensor of Example 7, when stretched by 30%, bent 500 times, and when attached to the cup wall in a bent state, has almost no change in temperature response and can still remain stable. This shows that the stretchable conductive composite film of the present invention has strain insensitive properties and can maintain stable temperature sensing performance under deformations such as stretching and bending.

[0103] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of making a stretchable conductive composite film, characterized by, The pyrrole monomer is uniformly dispersed into the polyurethane matrix by the gas-liquid interface self-assembly method, and then the pyrrole monomer is oxidized and polymerized between the polyurethane molecular chains by the chemical oxidation synthesis method. The synthesized polypyrrole molecular chains grow and entangle between the polyurethane molecular chains, forming a stretchable conductive composite film with a polyurethane / polypyrrole interpenetrating network structure. The polyurethane matrix is a polyether type thermoplastic polyurethane.

2. The production method according to claim 1, characterized by, The method comprises the following steps: In step 1, the pyrrole monomer and the polyurethane are uniformly dispersed in tetrahydrofuran to obtain a mixed solution. The mixed solution is dropped onto the surface of sealed glycerol, and the glycerol is unsealed to volatilize the tetrahydrofuran while the pyrrole monomer is uniformly dispersed between the polyurethane molecular chains and floats on the surface of the glycerol, forming a pyrrole monomer / polyurethane film. In step 2, the pyrrole monomer / polyurethane film obtained in step 1 is taken out of the surface of the glycerol and placed in an oxidant solution for chemical oxidation synthesis. The pyrrole monomer is in-situ polymerized into polypyrrole between the molecular chains of the polyurethane, obtaining a thermoplastic polyurethane / polypyrrole film with a polyurethane / polypyrrole interpenetrating network structure. In step 3, the thermoplastic polyurethane / polypyrrole film obtained in step 2 is taken out of the oxidant solution, and the excess oxidant on the surface is washed away, and then dried to obtain a stretchable conductive composite film.

3. The production method according to claim 2, characterized by, In step 1, the mass ratio of the pyrrole monomer to the polyurethane is (0.5-2):

1.

4. The production method according to claim 2, characterized by, In step 1, the process is carried out in a yellow light or dark environment, and in step 2, the process is carried out in a yellow light or dark environment.

5. The preparation method according to claim 2, characterized in that, In step 2, the pyrrole monomer / polyurethane film is taken out of the surface of the glycerol by a pretreated glass sheet. The pretreatment process comprises the following steps: the glass sheet is cleaned, then ultrasonic cleaned with deionized water, acetone and ethanol in sequence, and then the glass sheet is subjected to hydroxylation and hydrophobic modification in sequence.

6. The preparation method according to claim 2, characterized in that, In step 2, the temperature of the chemical oxidation synthesis is 0-25℃, and the time of the chemical oxidation synthesis is 5-20 min.

7. The preparation method according to claim 2, characterized in that, In steps 2 and 3, the oxidant solution is a mixed solution of an oxidant and water; the molar concentration of the oxidant solution is not less than 0.5 M; and the oxidant is ferric chloride, cupric chloride, persulfate or hydrogen peroxide.

8. The stretchable conductive composite film obtained by the production method according to any one of claims 1 to 7, wherein The thickness of the stretchable conductive composite film is 40 µm.

9. Use of the stretchable conductive composite film according to claim 8 in a stretchable temperature sensor, characterized in that, The stretchable temperature sensor comprises a stretchable conductive composite film and electrodes arranged on opposite sides of the stretchable conductive composite film, and conductive silver paste is coated between the electrodes and the stretchable conductive composite film.

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