Preparation method of multifunctional composite nanofiber membrane, single-electric-stage triboelectric sensor and application

Abstract

This invention belongs to the field of nanoenergy technology, and particularly relates to a method for preparing a multifunctional composite nanofiber membrane, a single-electrode triboelectric sensor, and its applications. The method includes the following steps: combining degummed and impurity-removed silk fibroin with a mixed solvent composed of anhydrous calcium chloride and formic acid, and stirring at room temperature to form a silk fibroin solution; adding TiO2 to the silk fibroin solution, and then adding phase change materials (PCMs) after stirring, followed by stirring and ultrasonic treatment to prepare a PCMs / TiO2 / silk fibroin spinning solution; and using solution jet spinning technology to convert the spinning solution into a silk fibroin-based composite nanofiber membrane. This composite nanofiber membrane has an adaptive temperature regulation function of daytime cooling and nighttime heat preservation, especially when applied to model cars, achieving daytime cooling up to 22°C. Simultaneously, the composite membrane also possesses excellent triboelectric properties and can be used to prepare a single-electrode triboelectric sensor with a maximum output power of approximately 272 μW / m. 2 It can realize sensing and monitoring functions in outdoor applications.

Description

Technical Field

[0001] This invention belongs to the field of nanoenergy, and particularly relates to a method for preparing a multifunctional composite nanofiber membrane, a single-electrode triboelectric sensor and its application. Background Technology

[0002] Traditional electricity-based cooling technologies consume vast amounts of energy and generate significant carbon emissions, which in turn contribute to frequent extreme weather events and a pronounced greenhouse effect. Nanofiber membranes prepared using passive radiative cooling (PRC) technology can avoid this vicious cycle by reflecting sunlight (AW 0.3-2.5 μm) and dissipating their own heat through transparent windows in the atmosphere (AW 8-13 μm), thus attracting widespread attention.

[0003] However, current nanofiber membranes with passive radiation cooling function suffer from problems such as high manufacturing cost, complex manufacturing process, excessive cooling at night, and limited functionality.

[0004] For example, Chinese patent CN111996679B discloses a colored radiative cooling flexible composite film and its preparation method. This composite film uses inefficient electrospinning technology, which, although it suffers from nighttime overcooling, lacks additional functions. Chinese patent CN115926235B discloses a radiative cooling bacterial cellulose nanocomposite film with adjustable solar transmittance and its preparation method. Although this composite film has radiative cooling and heat insulation properties, its preparation process is complex and cumbersome, and it also lacks additional functions. Wang et al. used traditional inefficient electrospinning technology to prepare composite fiber membranes with good flexibility and daytime radiative cooling function (X.Wang, X.Liu, Z.Li, H.Zhang, Z.Yang, H.Zhou, T.Fan, Scalable Flexible Hybrid Membranes with Photonic Structures for DaytimeRadiative Cooling, Adv FunctMaterials). 30(2020)1907562.https: / / doi.org / 10.1002), the composite fiber membrane prepared by electrospinning technology has low efficiency and cannot solve the problem of nighttime supercooling, achieve temperature adaptive regulation, and does not have other functions, with limited functionality; Cai et al. developed a new type of cellulose composite membrane with excellent mechanical properties and UV durability using solvent-induced phase separation technology (C.Cai,F.Chen,Z.Wei,C.Ding,Y.Chen,Y.Wang,Y.Fu,Large scalable,anti-ultraviolet,strong cellulose film with well-defined dual-pores for longtime daytime radiative cooling,ChemicalEngineering Journal). 476(2023)146668.https: / / doi.org / 10.1016 / j.cej.2023.146668), the preparation process of this cellulose composite membrane is complex and cumbersome, inefficient, difficult to industrialize, and does not solve the problem of nighttime overcooling. Apart from having a long-term passive radiation cooling function, it does not have other functions.

[0005] These studies have only addressed some of the problems faced by passively radiatively cooled nanofiber membranes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a multifunctional composite nanofiber membrane, a triboelectric sensor, and its applications. Utilizing a simple, efficient, low-cost, and scalable solution jet spinning technology, a silk fibroin-based composite nanofiber membrane is prepared by combining titanium dioxide (TiO2) and phase change microcapsules (PCMs) with adaptive temperature regulation functions (daytime cooling and nighttime heat preservation) and triboelectric properties. This membrane is then used as a friction layer to prepare a single-electrode triboelectric sensor for application.

[0007] The technical solution provided by this invention is as follows:

[0008] This invention provides a method for preparing a multifunctional composite nanofiber membrane, comprising the following steps:

[0009] The degummed and impurity-removed silk fibroin was combined with a mixed solvent consisting of anhydrous calcium chloride and formic acid and stirred at room temperature to form a silk fibroin solution.

[0010] TiO2 was added to a silk fibroin solution, and then phase change material PCMs were added after stirring. The solution was then stirred and sonicated to prepare a PCMs / TiO2 / silk fibroin spinning solution.

[0011] The spinning solution is converted into a silk fibroin-based composite nanofiber membrane using solution jet spinning technology.

[0012] Furthermore, the mass ratio of anhydrous calcium chloride to degummed and impurity-removed silk fibroin in the silk fibroin solution is 1:6-1:9.

[0013] Furthermore, the silk fibroin solution has a mass fraction of 15-20 wt%.

[0014] Furthermore, the amount of TiO2 added in the PCMs / TiO2 / silk fibroin spinning solution is 5-15 wt%, and the amount of PCMs added is 1-5 wt%.

[0015] Furthermore, the solution jet spinning technology uses a coaxial spinning needle with a specification of 17+22G. The inner channel of the needle is connected to the spinning solution, and the outer channel is connected to the airflow. The nylon receiving net is fixed on a grounded metal porous plate, and the needle is 35-45cm away from the receiving net.

[0016] Furthermore, during the solution jet spinning process, the airflow pressure is maintained at 0.2-0.25 MPa, the auxiliary electric field voltage is 10-15 kV, and the spinning solution flow rate is controlled at 5-10 ml / h.

[0017] Furthermore, during the solution jet spinning process, the ambient humidity is 50-65% and the ambient temperature is 20-25℃.

[0018] Furthermore, the TiO2 is rutile type with a particle size of 250-350 nm, and the PCMs have a particle size of 1-3 μm and a phase transition temperature of 25-30 °C.

[0019] The present invention also provides a single-electrode triboelectric sensor, which includes a first friction layer, a second friction layer, and an electrode layer. The first friction layer and the second friction layer are respectively formed on the upper and lower surfaces of the electrode layer. The first friction layer and the second friction layer are multifunctional composite nanofiber membranes prepared according to the preparation method of the multifunctional composite nanofiber membrane described above. The electrode layer uses highly conductive graphite powder as the electrode material. The highly conductive graphite powder has a particle size of 10-30 μm and a carbon content of 99.9%.

[0020] The present invention also provides an application of a single-electrode triboelectric sensor in a car model, wherein the single-electrode triboelectric sensor is the single-electrode triboelectric sensor described above, and the sensor is configured to monitor the scratches and collisions of different parts of the model car.

[0021] Beneficial effects

[0022] This invention employs a novel nanofiber preparation technology—solution jet spinning—that is efficient, simple, low-consumption, safe, and scalable, to prepare multifunctional composite nanofiber membranes. Compared with traditional methods such as electrospinning and coating, this technology improves the ability to scale up production and application.

[0023] This invention uses silk fibroin as a substrate and incorporates TiO2 and PCMs through internal loading to prepare a silk fibroin-based composite nanofiber membrane. Silk fibroin, as a substrate, possesses excellent flexibility, and the silk fibroin nanofibers can uniformly encapsulate TiO2 and PCMs particles while forming a nanofiber network. The addition of TiO2 increases the reflectivity of the composite nanofiber membrane, thereby enhancing its passive radiative cooling effect. The addition of PCMs can store and manage the cooling energy generated by passive radiative cooling, thus enabling the composite nanofiber membrane to possess adaptive temperature regulation functions of daytime cooling and nighttime heat preservation. Indoor thermal simulation test results show that when the composite nanofiber membrane is exposed to 700-800 W / m², it exhibits excellent thermal performance. 2 Under indoor infrared light, the temperature under the membrane is about 4-9.9°C lower than the surrounding environment, indicating that it has a daytime cooling effect. When the lights are off to simulate nighttime, the temperature under the membrane is about 1.5-2.2°C higher than the surrounding environment, and the cooling rate is even lower, indicating that it has a nighttime heat preservation effect. Moreover, when this composite nanofiber membrane is applied to a model car, it can also achieve a cooling effect of about 22°C and a heat preservation effect of about 4°C.

[0024] The composite nanofiber membrane prepared in this invention also possesses excellent triboelectric properties, with an output voltage exceeding 4.5V, which meets the requirements of practical applications. Therefore, it is used as a friction layer to assemble a single-electrode triboelectric sensor. This sensor exhibits stable output voltage, reaching up to 8V, and also demonstrates good electrical output cycle stability, maintaining relative stability over 1000 cycles. The maximum output power density of this sensor is approximately 272 μW / m². 2 It can be used for sensing and monitoring in outdoor applications. When applied to model cars, it can also monitor scratches and collisions on different parts of the car, issue hazard warnings, and prevent serious consequences. Attached Figure Description

[0025] Figure 1 This is a flow chart of the preparation process of the multifunctional composite nanofiber membrane of the present invention;

[0026] Figure 2 This is an electron microscope image of the multifunctional composite nanofiber membrane prepared in Example 1 of the present invention;

[0027] Figure 3 This is an electron microscope image of the single-electrode triboelectric sensor obtained in Example 4 of the present invention;

[0028] Figure 4 This is an electron microscope image of the silk fibroin nanofibers prepared in Comparative Example 4 of the present invention.

[0029] Figure 5 This is a schematic diagram of the indoor thermal simulation testing device of the present invention;

[0030] Figure 6 This is a schematic diagram of the triboelectric testing device of the present invention;

[0031] Figure 7 The results of indoor thermal simulation tests are for the multifunctional composite nanofiber membranes prepared in Examples 1-3 of this invention.

[0032] Figure 8 Comparison of indoor thermal simulation test results of the multifunctional composite nanofiber membranes prepared in Example 1 and Comparative Examples 1-2 of the present invention;

[0033] Figure 9 The results of thermal simulation tests are as follows: The multifunctional composite nanofiber membrane prepared in Example 1 of this invention is applied to a model car.

[0034] Figure 10 The triboelectric test results are for the multifunctional composite nanofiber membranes prepared in Examples 1-3 of this invention.

[0035] Figure 11 The triboelectric test results are for the single-electrode triboelectric sensor prepared in Example 4 of this invention.

[0036] Figure 12 The cyclic stability test curve of the single-electrode triboelectric sensor prepared in Example 4 of the present invention is shown.

[0037] Figure 13 This is a graph showing the functional relationship between the output power density and the external load resistance of the single-electrode triboelectric sensor prepared in Embodiment 4 of the present invention.

[0038] Figure 14 This is a simulation test of the sensing performance of the single-electrode triboelectric sensor prepared in Example 4 of the present invention on a model car.

[0039] Figure labeling: 1. Silkworm cocoon; 2. Degumming pan; 3. Drying oven; 4. Anhydrous calcium chloride; 5. Formic acid; 6. Degummed and impurity-removed silk fibroin; 7. Mixed solvent composed of anhydrous calcium chloride and formic acid; 8. Silk fibroin solution; 9. PCMs / TiO2 / silk fibroin spinning solution; 10. Peristaltic pump; 11. Air compressor; 12. Coaxial spinning needle; 13. Airflow; 14. Silk fibroin-based composite nanofiber membrane; 15. Nylon receiving net; 16. R95e type Philips lamp (simulated light source; its infrared light intensity is 700-800W / m²). 2 17. Temperature measuring point; 18. Friction material (rubber sheet or skin); 19. Single electrode triboelectric sensor; 121. Coaxial needle inner channel (spinning solution channel); 122. Coaxial needle outer channel (airflow channel). Detailed Implementation

[0040] This invention provides a method for preparing a multifunctional composite nanofiber membrane. Employing a highly efficient and scalable solution-jet spinning technique, the method uses silk fibroin as a substrate, combined with titanium dioxide (TiO2) and phase change microcapsules (PCMs), to prepare a silk fibroin-based composite nanofiber membrane possessing both adaptive temperature regulation and triboelectric properties. The specific steps include:

[0041] (1) The degummed and impurity-removed silk fibroin is combined with a mixed solvent 7 consisting of anhydrous calcium chloride and formic acid, and stirred at room temperature to form a silk fibroin solution 8.

[0042] (2) Add TiO2 to silk fibroin solution 8, and add phase change material PCMs after stirring. Then stir and sonicate to prepare PCMs / TiO2 / silk fibroin spinning solution 9.

[0043] (3) The spinning solution is converted into a silk fibroin-based composite nanofiber membrane 14 by using solution jet spinning technology.

[0044] In step (1), the specific steps for degumming and removing impurities from the silk fibroin are as follows: Deionized water is added to the degumming pot 2 and heated. Anhydrous sodium carbonate is weighed and added when the water is about to boil, allowing it to dissolve completely. Silkworm cocoons 1 are weighed and added after the water boils. The mixture is stirred every 10 minutes and boiled for 30 minutes. After removal, it is repeatedly rubbed and washed 3 times with deionized water and dried in a 60℃ oven 3 to obtain degummed and impurity-removed silk fibroin 6. The mass ratio of anhydrous calcium chloride 4 to degummed and impurity-removed silk fibroin 6 in the silk fibroin solution 8 is 1:6-1:9; the mass fraction of the silk fibroin solution 8 is 15-20 wt%.

[0045] In practical applications, in the mixed solvent 7 composed of anhydrous calcium chloride and formic acid, anhydrous calcium chloride 4 was purchased from Sinopharm Chemical Reagent Co., Ltd., and formic acid 5 with a concentration of ≥98% was purchased from Shanghai Titan Technology Co., Ltd.

[0046] In step (2), the amount of TiO2 added to the PCMs / TiO2 / silk fibroin spinning solution 9 is 5-15wt%, and the amount of PCMs added is 1-5wt%. The TiO2 is rutile with a particle size of 250-350nm, and the PCMs have a particle size of 1-3μm and a phase transition temperature of 25-30℃.

[0047] In step (3), the solution jet spinning technology uses a coaxial spinning needle 12 with a specification of 17+22G. The inner channel 121 of the coaxial needle is connected to the spinning solution, and the outer channel 122 of the coaxial needle is connected to the airflow 13. The nylon receiving net 15 is fixed on a grounded metal porous plate, and the needle is 35-45cm away from the receiving net. During the solution jet spinning process, the airflow pressure is 0.2-0.25MPa, the auxiliary electric field voltage is 10-15kV, and the spinning solution flow rate is 5-10ml / h. During the solution jet spinning process, the ambient humidity is 50-65% and the ambient temperature is 20-25℃.

[0048] This invention also provides a single-electrode triboelectric sensor, comprising a first friction layer, a second friction layer, and an electrode layer. The first and second friction layers are formed on the upper and lower surfaces of the electrode layer, respectively. The first and second friction layers are multifunctional composite nanofiber membranes prepared according to the aforementioned method. The electrode layer uses highly conductive graphite powder as the electrode material, with a particle size of 10-30 μm and a carbon content of 99.9%. The specific preparation process of this single-electrode triboelectric sensor is as follows: firstly, the first friction layer is prepared using solution jet spinning technology; then, highly conductive graphite powder is applied to one side of the first friction layer as the electrode layer using a spraying method; finally, the second friction layer is deposited on the other side of the electrode layer using solution jet spinning technology, thereby forming the single-electrode triboelectric sensor.

[0049] In practical applications, the superconducting graphite powder was purchased from Suzhou CarbonFeng Graphene Technology Co., Ltd.

[0050] The present invention also provides an application of a single-electrode triboelectric sensor in a car model, wherein the single-electrode triboelectric sensor is the single-electrode triboelectric sensor described above, and the sensor is configured to monitor the scratches and collisions of different parts of the model car.

[0051] The following detailed description, in conjunction with embodiments, illustrates the preparation method and application of a multifunctional composite nanofiber membrane and a single-electrode triboelectric sensor provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] Step (1): Add 0.303g of anhydrous calcium chloride 4 to 10g of formic acid 5 and stir until completely dissolved to obtain a mixed solvent. Then add the degummed and impurity-removed silk fibroin to the mixed solvent and stir continuously at 20°C for 1 hour to obtain silk fibroin solution 8. Preferably, the mass ratio of anhydrous calcium chloride 4 to degummed and impurity-removed silk fibroin 6 is 1:6, and the mass fraction of the silk fibroin solution is 15wt%. The specific steps for degumming and impurity removal of the silk fibroin are as follows: Add deionized water to degumming pot 2 and heat it. Weigh anhydrous sodium carbonate and add it when the water is about to boil to dissolve it completely. Weigh silkworm cocoon 1 and add it after the water boils. Stir once every 10 minutes and boil for 30 minutes. After removing it, wash it repeatedly with deionized water 3 times and dry it in an oven at 60°C to obtain degummed and impurity-removed silk fibroin 6.

[0054] Step (2): Add 5 wt% TiO2 to the silk fibroin solution 8 and stir for 5 minutes. Then add 5 wt% PCMs and stir continuously at 20°C for 1 hour. Then sonicate the mixed solution for 30 minutes to obtain PCMs / TiO2 / silk fibroin spinning solution 9. The TiO2 is rutile with a particle size of 300 nm and the PCMs has a particle size of 2 μm and a phase transition temperature of 28°C.

[0055] Step (3): Using solution jet spinning technology, PCMs / TiO2 / silk fibroin spinning solution 9 is used to make silk fibroin-based composite nanofiber membrane 14. The specific steps are as follows: the inlet pipe of the peristaltic pump 10 is inserted into the prepared spinning solution, and the outlet end is connected to a single coaxial spinning needle 12. The needle specification is 17+22G. The inner channel 121 of the coaxial needle is connected to the spinning solution, and the outer channel 122 of the coaxial needle is connected to the airflow 13. The nylon mesh receiving net 15 is fixed on the grounded metal porous plate. The needle is 40cm away from the receiving net. The flow rate of the spinning solution is 10mL / h. The airflow pressure of the air compressor 11 is 0.2MPa. The auxiliary electric field voltage is 10kV. The ambient humidity is controlled at 50%-65%, and the temperature is 25℃.

[0056] Example 2

[0057] The only difference between Example 2 and Example 1 is that the mass fraction of PCMs added in step (2) is 3%.

[0058] Example 3

[0059] The only difference between Example 3 and Example 1 is that the mass fraction of PCMs added in step (2) is 1%.

[0060] Example 4

[0061] Using highly conductive graphite powder as the electrode layer material and the multifunctional composite nanofiber membrane prepared in Example 1 as the friction layer material, the electrode layer was prepared by spraying, and the friction layer was prepared by solution jet spinning technology. Finally, a single-electrode triboelectric sensor was obtained, with the electrode layer in the middle and the friction layers on both sides. The highly conductive graphite powder had a particle size of 10-30 μm and a carbon content of 99.9%. The specific preparation process was as follows: first, the first friction layer was prepared using solution jet spinning technology; then, highly conductive graphite powder was sprayed onto one side of the first friction layer as the electrode layer; finally, the second friction layer was deposited on the other side of the electrode layer using solution jet spinning technology, thus forming a single-electrode triboelectric sensor.

[0062] Comparative Example 1

[0063] The only difference between Comparative Example 1 and Example 1 is that PCMs were not added in step (2).

[0064] Comparative Example 2

[0065] The difference between Comparative Example 2 and Example 1 is that the silk fibroin solution 8 obtained in step (1) is directly used as the spinning solution to spin silk fibroin fiber membrane.

[0066] Comparative Example 3

[0067] The only difference between Comparative Example 3 and Example 1 is that the mass fraction of PCMs added in step (2) is 7%. Comparative Example 3 cannot prepare a multifunctional composite nanofiber membrane. This is because when the mass fraction of added PCMs is 7%, the content of PCMs particles is too high, the coaxial spinning needle is prone to clogging, and the process of spinning a multifunctional composite nanofiber membrane is difficult.

[0068] Comparative Example 4

[0069] The difference between Comparative Example 4 and Example 1 is that in step (1), the mass ratio of anhydrous calcium chloride 4 to degummed and impurity-removed silk fibroin 6 is 1:3. Figure 4 As shown, when the mass ratio of anhydrous calcium chloride 4 to degummed and impurity-removed silk fibroin 6 is 1:3, the prepared silk fibroin nanofiber membrane has fibers that adhere to each other, and the fiber morphology is severely damaged. The spun nanofiber membrane has poor film-forming effect, so subsequent steps cannot be carried out and multifunctional composite nanofiber membranes cannot be prepared.

[0070] In Examples 1-3 and Comparative Examples 1-2 above, the specific steps for the indoor thermal simulation test of the samples are as follows:

[0071] The sample membrane was cut into 4cm x 4cm pieces and placed on a table for indoor thermal simulation testing. A Philips R95e 16 lamp (model R95e, 100W) was used as the sunlight simulation light source. The lamp was placed 35cm away from the sample. The temperature under the membrane and the ambient temperature were measured during the 600s between the lamp being on and off (simulating daytime conditions and nighttime conditions, respectively). A schematic diagram of the indoor thermal simulation testing setup is shown below. Figure 5 As shown, a solar power meter was used to test the power of the light source during the test.

[0072] like Figure 7 As shown, when the composite nanofiber membrane is exposed to 700-800 W / m 2 Under indoor infrared light, the temperature under its membrane is about 4-9.9℃ lower than the surrounding environment, indicating that it has a daytime cooling effect; when the lights are off to simulate nighttime, the temperature under its membrane is about 1.5-2.2℃ higher than the surrounding environment, and the cooling rate is even lower, indicating that it has a nighttime heat preservation effect. Figure 8 As shown, the cooling ranges of the composite nanofiber membranes prepared in Example 1 and Comparative Examples 1 and 2 are approximately 8.3-9.9℃, 3.2-4.2℃, and 1.6-2.6℃, respectively, indicating that the composite nanofiber membrane prepared in Example 1 has a better daytime cooling effect compared to Comparative Examples 1-2. At the same time, the composite nanofiber membrane prepared in Example 1 has a better heat preservation effect and a slower cooling rate. Its membrane temperature is about 0.7-1.1℃ higher than that of Comparative Example 1 and about 0.9-1.5℃ higher than that of Comparative Example 2.

[0073] The sample from Example 1 was applied to a model car, and indoor thermal simulation tests were conducted. The specific steps were as follows:

[0074] The sample film was placed on top of a small car model for application testing. The rear seat armrest served as temperature measurement point 17. A Philips R95e lamp 16 was used as a simulated sunlight source, illuminating the sample at a distance of 35cm. The temperature at the measurement point and the ambient temperature were measured during the 600s between the lamp being on and off (the lamp being on simulates daytime conditions, and the lamp being off simulates nighttime conditions). The power of the light source was measured using a solar power meter during the test.

[0075] like Figure 9 As shown, when the composite nanofiber membrane is applied to a model car, it can achieve a cooling effect of about 22°C and a heat preservation effect of about 4°C, and the cooling rate of the covered membrane is slower than that of the uncovered membrane.

[0076] The specific steps for testing the triboelectric properties of the samples in Examples 1-3 above are as follows:

[0077] Place the 3cm × 3cm sample on a self-built multi-frequency contact separation platform in the laboratory, such as Figure 6 As shown, the friction material 18 is a 3cm×3cm rubber sheet. The open-circuit voltage of the sensor under the set frequency and pressure is tested using a Keithley 6514 electrometer, and the data is recorded using a digital multimeter (DMM7510).

[0078] like Figure 10 As shown, the composite nanofiber membrane has excellent triboelectric properties. Under the set conditions of 16N and 2Hz, the output voltage is measured to be above 4.5V, which can meet the needs of practical applications.

[0079] The specific steps for testing the triboelectric performance of the single-electrode triboelectric sensor in Example 4 above are as follows:

[0080] A 3cm × 3cm sensor sample was placed on a self-built multi-frequency contact separation platform in the laboratory, such as... Figure 6 As shown, the friction material 18 is human skin (i.e., the human body imitates the movement of the contact separation platform, causing friction between the human skin and the sensor). The open-circuit voltage and short-circuit current of the sensor under the set frequency and pressure are tested using a Keithley 6514 electrometer, and the data is recorded using a digital multimeter (DMM7510).

[0081] like Figure 11-12 As shown, a single-electrode triboelectric sensor 19 is assembled using a composite nanofiber membrane as a friction layer. The sensor has a stable output voltage, and the voltage value measured under the set conditions of 8N and 3Hz can reach 8V. Moreover, the sensor also has good electrical output cycle stability and can remain relatively stable within 1000 cycles.

[0082] The single-electrode triboelectric sensor 19 in Example 4 above was subjected to an output power density test. The specific steps of the test are as follows:

[0083] The output power density was calculated by measuring the short-circuit current of the sensor under different load resistances at a compression force of 8N and a frequency of 3Hz, and the calculation formula is W = I. 2 R / A, where W is the output power density, I is the short-circuit current, R is the load resistance, and A is the sensor surface area (3cm×3cm).

[0084] like Figure 13 As shown, the maximum output power density is achieved at a load resistance of 50 MΩ, which is approximately 272 μW / m. 2 .

[0085] The single-electrode triboelectric sensor 19 from Embodiment 4 above is applied to a model car. The specific steps for triboelectric testing using this sensor are as follows:

[0086] The sensor is used on the exterior of a car. It is attached to the front, rear, side doors and roof of a model car. The electrical signal output value of the sensor is tested when the front, rear, side and top of the model car collide with a human body.

[0087] like Figure 14 As shown, the single-electrode triboelectric sensor 19 can be applied to the external sensing and monitoring of a car model. When the front of the car repeatedly collides with a human body, it generates regular voltage fluctuations, with a peak value of approximately 0.4V. This scenario simulates the sensor's monitoring when the front of the car collides with a human body during the car's start-up or slow-moving process. When the car is stationary and the roof is hit by a falling object, it also generates regular voltage fluctuations of 0.3-0.4V, which can be used to detect falling objects on the roof of the car when no one is inside. When the car reverses and collides with a human body, it generates a specific waveform of about 1.5-2V, and repeated collisions also show regular output voltage peaks, which can be used for collision accident monitoring and early warning when the vehicle is reversing. In addition, the output voltage waveform change when the car door repeatedly rubs and scrapes against a human body was simulated. The test results show that a similar waveform of 8-10V is generated, which can represent the situation of friction and scraping at the car door. The collision test results at different parts of the car show that the triboelectric sensor covering the car surface can monitor a variety of accident scenarios and prevent more serious consequences, showing good application prospects in the sensing and monitoring of outdoor equipment.

[0088] All other testing methods are conventional, and the materials and reagents used are commercially available.

[0089] Figure 1 This is a process flow diagram of the preparation method of the multifunctional composite nanofiber membrane of the present invention. The preparation apparatus of the multifunctional composite nanofiber membrane of the present invention includes a degumming pan 2, an oven 3, a peristaltic pump 10, an air compressor 11, a coaxial spinning needle 12, a nylon receiving net 15, etc.

[0090] Deionized water was added to degumming pot 2 and heated. Anhydrous sodium carbonate was weighed and added when the water was about to boil, and then dissolved completely. Silkworm cocoons 1 were weighed and added after the water boiled. The mixture was stirred every 10 minutes and boiled for 30 minutes. After boiling, the cocoons were removed and repeatedly rubbed with deionized water 3 times. They were then dried in an oven at 60°C to obtain degummed and impurity-removed silk fibroin 6. The degummed and impurity-removed silk fibroin 6 was then added to a mixed solvent 7 composed of anhydrous chloride and formic acid. The mixture was stirred at room temperature to form a silk fibroin solution 8. TiO2 was added to the silk fibroin solution 8 and stirred. After mixing, phase change material PCMs is added, followed by stirring and ultrasonic treatment to prepare PCMs / TiO2 / silk fibroin spinning solution 9. The inlet pipe of peristaltic pump 10 is inserted into the prepared PCMs / TiO2 / silk fibroin spinning solution 9, and the outlet end is connected to a single coaxial spinning needle 12. The inner channel 121 of the coaxial needle is connected to the spinning solution, and the outer channel 122 of the coaxial needle is connected to the airflow 13. The nylon mesh receiving net 15 is fixed on a grounded metal porous plate, and airflow is provided by air compressor 11 to obtain silk fibroin-based composite nanofiber membrane 14.

[0091] Figure 2 This is an electron microscope image of the multifunctional composite nanofiber membrane prepared in Example 1 of this invention. Figure 3 This is an electron microscope image of the single-electrode triboelectric sensor prepared in Embodiment 4 of the present invention. Figure 4 This is an electron microscope image of the silk fibroin nanofibers prepared in Comparative Example 4 of this invention.

[0092] Although the above embodiments have described the present invention in detail, the above description is only a preferred embodiment of the present invention. The present invention is not limited to the above embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification, such as the ratio of anhydrous calcium chloride and degummed and impurity-removed silk fibroin, the concentration of silk fibroin solution, etc., all fall within the substantial scope of this specification and should be protected by the present invention.

Claims

1. A method for preparing a multifunctional composite nanofiber membrane, characterized in that, Includes the following steps: The degummed and impurity-removed silk fibroin was combined with a mixed solvent consisting of anhydrous calcium chloride and formic acid and stirred at room temperature to form a silk fibroin solution. TiO2 was added to a silk fibroin solution, and then phase change material PCMs were added after stirring. The solution was then stirred and sonicated to prepare a PCMs / TiO2 / silk fibroin spinning solution. The spinning solution is converted into a silk fibroin-based composite nanofiber membrane using solution jet spinning technology. The mass ratio of anhydrous calcium chloride to degummed and impurity-removed silk fibroin in the silk fibroin solution is 1:6-1:

9. The silk fibroin solution has a mass fraction of 15-20 wt%. The amount of TiO2 added in the PCMs / TiO2 / silk fibroin spinning solution is 5-15 wt%, and the amount of PCMs added is 1-5 wt%. The solution jet spinning technology uses a coaxial spinning needle with a specification of 17+22G. The inner channel of the needle is connected to the spinning solution, and the outer channel is connected to the airflow. The nylon receiving net is fixed on a grounded metal porous plate, and the needle is 35-45cm away from the receiving net. During the solution jet spinning process, the airflow pressure is maintained at 0.2-0.25 MPa, the auxiliary electric field voltage is 10-15 kV, and the spinning solution flow rate is controlled at 5-10 ml / h. The TiO2 is rutile type with a particle size of 250-350 nm, and the PCMs have a particle size of 1-3 μm and a phase transition temperature of 25-30 °C.

2. The method for preparing the multifunctional composite nanofiber membrane according to claim 1, characterized in that, During the solution jet spinning process, the ambient humidity is 50-65% and the ambient temperature is 20-25℃.

3. A single-electrode triboelectric sensor, characterized in that, The triboelectric sensor includes a first friction layer, a second friction layer, and an electrode layer. The first friction layer and the second friction layer are respectively formed on the upper and lower surfaces of the electrode layer. The first friction layer and the second friction layer are multifunctional composite nanofiber membranes prepared by the preparation method of the multifunctional composite nanofiber membrane according to any one of claims 1-2. The electrode layer uses highly conductive graphite powder as the electrode material. The highly conductive graphite powder has a particle size of 10-30 μm and a carbon content of 99.9%.

4. An application of a single-electrode triboelectric sensor in a car model, characterized in that, The single-electrode triboelectric sensor is the single-electrode triboelectric sensor as described in claim 3, which is configured to monitor scratches and collisions at different parts of a model car.

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