Hybrid structure electrospun friction nanogenerator, preparation method thereof and spinning device

Abstract

The application discloses a hybrid structure electrostatic spinning friction nanogenerator in the technical field of nanogeneration, and a preparation method and a spinning device thereof, and aims to solve the problems that part of electrostatic spinning nanofibers are prone to delamination in the application process in the prior art, and the TPU / CB bead string structure nanofiber and PVDF-TrFE nanofiber blended fiber membrane are prepared in batches by using a special free liquid surface spinning device. The application can effectively improve the shortcoming that the PVDF and copolymer nanofiber are prone to delamination in the use process, and the existence of the bead string structure is also beneficial to improving the air permeability and surface roughness of the membrane and improving the electric output property of the triboelectric nanogenerator.

Description

Technical Field

[0001] This invention relates to a hybrid electrospinning triboelectric nanogenerator, its preparation method, and spinning equipment, belonging to the field of nano-power generation technology. Background Technology

[0002] Wearable electronic devices offer advantages such as being able to be integrated into clothing or worn as accessories without implantation. They not only functionally replace traditional large medical electronic devices, reducing the need for medical professionals and improving quality of life, but also consume considerable power and require a stable power source to operate. Traditional batteries require frequent charging, and their inherent rigidity also limits the flexibility and lightweight design of wearable devices.

[0003] Self-powered technology is a novel energy supply technology that requires no external energy supply and maintains its operation by collecting energy in the working environment. Among them, triboelectric nanogenerators (TENGs), which are low-cost, structurally diverse, have stable output power, and high energy conversion efficiency, are used to collect mechanical energy such as human movement, wind energy, and water energy, and convert it into electrical energy, which is then integrated into flexible wearable electronic products to solve the battery dependence of wearable devices.

[0004] Currently, there are two main approaches to improving the output performance of triboelectric nanogenerators (TENGs): one is to increase surface charge by selecting optimal friction materials or introducing electrets; the other is to increase the roughness of the friction layer to improve its specific surface area during contact. Besides the output performance of TENGs, wearing comfort is also crucial. Therefore, using nanofiber membranes (NFMs) with high specific surface area, aspect ratio, porosity, and abundant contact sites not only improves the electrical output performance and breathability of TENGs but also provides a larger contact area. Furthermore, the unique structure of NFMs can improve sensitivity and response speed, both of which are essential for sensors.

[0005] However, some electrospun nanofibers (such as PVDF and its copolymers) are prone to delamination during contact with other materials, and this delamination is irreversible, affecting their durability and stability during use, which limits their application in wearable sensors. To suppress the delamination defect of some polymer nanofiber membranes, researchers often use hybrid spinning methods, but this may result in poor polymer blending properties, making it difficult to improve the original defects. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hybrid electrospun triboelectric nanogenerator, its preparation method, and spinning equipment, which can effectively improve the disadvantage of PVDF and its copolymer nanofibers being prone to delamination during use.

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a hybrid-structured electrospinning triboelectric nanogenerator, comprising the following steps:

[0009] The polyvinylidene fluoride-trifluoroethylene copolymer was dispersed in a mixed solvent of N,N-dimethylformamide / acetone, and stirred for a time a to obtain a polyvinylidene fluoride-trifluoroethylene copolymer spinning solution.

[0010] Carbon black was added to a mixed solvent of N,N-dimethylformamide / acetone, and the mixture was sonicated to obtain a CB-N,N-dimethylformamide / acetone solution; polyurethane was added to the CB-N,N-dimethylformamide / acetone solution, and the mixture was stirred for time b to obtain a polyurethane / carbon black spinning solution.

[0011] Electrospinning was performed by mixing a polyvinylidene fluoride-trifluoroethylene copolymer spinning solution and a polyurethane / carbon black spinning solution to obtain a nanofiber membrane with a hybrid structure.

[0012] After cutting the nanofiber membrane, conductive fabric is pasted onto its surface to obtain the negative electrode material of the nanogenerator.

[0013] By using negative electrode materials to assemble nanogenerators, an electrospinning triboelectric nanogenerator was obtained.

[0014] Furthermore, the mass percentage of the polyvinylidene fluoride-trifluoroethylene copolymer spinning solution ranges from 5 to 10 wt%, and the mass percentage of the polyurethane / carbon black spinning solution ranges from 15 to 20 wt%.

[0015] Furthermore, all stirring was carried out at room temperature, with stirring time a being 6–8 hours and stirring time b being 4–6 hours.

[0016] Furthermore, the conductive fabric is a conductive fabric with a nickel-copper coating, which serves as the electrode for assembling the TENG.

[0017] Furthermore, the assembly of the nanogenerator is completed using negative electrode materials, including: attaching the positive and negative electrode materials of the nanogenerator to both sides of an arch shape folded from paper, and mounting it on a linear motor.

[0018] Secondly, the present invention provides a hybrid electrospinning triboelectric nanogenerator, prepared by any of the preparation methods described above.

[0019] Thirdly, the present invention provides a spinning device, including a liquid supply device, a liquid storage device, a roller, and a high-voltage power supply. The liquid storage device is used to store polyvinylidene fluoride-trifluoroethylene copolymer spinning solution and polyurethane / carbon black spinning solution. The positive terminal of the high-voltage power supply is connected to the liquid storage device, and its negative terminal is connected to the roller.

[0020] Optionally, the liquid storage device is mounted on a slide rail device, which can drive the liquid storage device to move at a constant speed, and the direction of movement is perpendicular to the rotation direction of the drum.

[0021] Optionally, the liquid storage device is provided with a polypropylene plate inside, which is used to divide the inside of the liquid storage device into two parts, which are used to place the polyvinylidene fluoride-trifluoroethylene copolymer spinning solution and the polyurethane / carbon black spinning solution, respectively.

[0022] Optionally, the liquid storage device uses a concave copper tube.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0024] This invention redesigns the free-float spinning equipment and prepares a fiber membrane with a TPU / CB beaded nanofiber structure and a PVDF-TrFE nanofiber blend structure. This solves the problem of easy delamination of pure PVDF and its copolymer nanofibers during use. The presence of the beaded structure helps to improve the membrane's air permeability and surface roughness, locks in the PVDF-TrFE nanofibers, inhibits fiber delamination, and improves the electrical output of the triboelectric nanogenerator. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the electrospinning equipment for nanofiber membranes in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram showing the proportion of PVDF-TrFE spinning solution in an embodiment of the present invention;

[0027] Figure 3 These are schematic images of different types of nanofibers in the embodiments of the present invention, where a to e are schematic SEM images: (a) TPU / CB beaded nanofibers, (b) PVDF-TrFE nanofibers, (c) TBP HNFMs with a mass ratio of 6:1, (d) TBP HNFMs with a mass ratio of 2:1, (e) TBP HNFMs with a mass ratio of 1:2, (f) images of different types of nanofibers, and (g) schematic diagram comparing the mechanical stability of different types of nanofibers.

[0028] Figure 4These are schematic SEM images of cross sections of TBP HNFMs with different mass ratios after cutting, as shown in the embodiments of the present invention, where (a) 6:1, (b) 2:1, and (c) 1:2.

[0029] Figure 5 This is a schematic diagram of the structure of the electrostatic triboelectric nanogenerator assembled in an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram showing the output performance of TBP HNFMs with different mass ratios and the output performance of TENG in an embodiment of the present invention, wherein (a) to (c) are the output performance of TBP HNFMs with different mass ratios, and (d) to (f) are the changes in the corresponding output performance of TENG under different external forces;

[0031] Figure 7 This is a test schematic diagram of the capacitor charging system using TENG in an embodiment of the present invention, wherein (a) TENG charging curves for different capacitors; (b) charging a 2.2μF capacitor by tapping and clapping with a finger; (c) tapping the TENG with a finger to charge a 10μF capacitor for powering a stopwatch; and (d) tapping the TENG with a finger to charge a 22μF capacitor for powering a thermometer and hygrometer.

[0032] Figure 8 This is a voltage diagram of the TENG self-powered sensor applied to various human movements in an embodiment of the present invention;

[0033] In the diagram: 1. Roller, 2. High-voltage power supply, 3. Liquid storage device, 4. Spacing adjustment device, 5. Slide rail device, 6. Liquid supply device. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0037] Example 1:

[0038] This invention provides a method for preparing a hybrid-structured electrospun triboelectric nanogenerator, comprising the following steps:

[0039] Preparation of spinning solution for polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE):

[0040] Polyvinylidene fluoride-trifluoroethylene copolymer was dispersed in a mixed solvent of N,N-dimethylformamide / acetone (mass percentage 4:6) and stirred at room temperature for 7 h to obtain a 6 wt% polyvinylidene fluoride-trifluoroethylene copolymer spinning solution.

[0041] Preparation of polyurethane / carbon black (TPU / CB) spinning solution:

[0042] Add 3 wt% carbon black to a mixed solvent of N,N-dimethylformamide / acetone (mass percentage 7:3), and sonicate for 30 minutes to obtain a CB-N,N-dimethylformamide / acetone solution; add 15 wt% polyurethane to the CB-N,N-dimethylformamide / acetone solution, and stir at room temperature for 4 hours to obtain a polyurethane / carbon black spinning solution.

[0043] Combination Figure 2 By comparing the spinning yield of TPU / CB NFM and PVDF-TrFE NFM under the same area, the proportion of the spinning area occupied by the spinning solution of the two was designed according to the spinning yield. The central angle of the fan-shaped area occupied by the PVDF-TrFE spinning solution was set as α. When α is 90°, the mass ratio of TPU / CB NFM and PVDF-TrFE NFM in the final mixed NFM is 6:1.

[0044] Electrospinning was performed using a spinning device with the spinning voltage set to 50kV and the receiving distance of the roller to 18cm, resulting in TPU / CB-PVDF fiber membranes (TBP HNFMs) with a uniform mixture of the two fibers.

[0045] Example 2:

[0046] The difference between this embodiment and Embodiment 1 is that α is set to 180°, and the mass ratio of TPU / CB NFM and PVDF-TrFE NFM in the obtained hybrid fiber membrane is 2:1.

[0047] Example 3:

[0048] The difference between this embodiment and Embodiment 1 is that α is set to 288°, and the mass ratio of TPU / CB NFM and PVDF-TrFE NFM in the obtained hybrid fiber membrane is 1:2.

[0049] Comparative Example 1:

[0050] Preparation of TPU / CB beaded nanofiber membrane:

[0051] Add 3 wt% carbon black to a mixed solvent of N,N-dimethylformamide / acetone (mass percentage 7:3), and sonicate for 30 minutes to obtain a CB-N,N-dimethylformamide / acetone solution; add 15 wt% polyurethane particles to the CB-N,N-dimethylformamide / acetone solution, and stir at room temperature for 4 hours to obtain a polyurethane / carbon black spinning solution.

[0052] TPU / CB beaded nanofiber membranes were obtained by electrospinning using a spinning device.

[0053] Comparative Example 2:

[0054] Preparation of PVDF-TrFE nanofiber membranes:

[0055] Polyvinylidene fluoride-trifluoroethylene copolymer was dispersed in a mixed solvent of N,N-dimethylformamide / acetone (mass percentage 4:6) and stirred at room temperature for 6 h to obtain a 6 wt% polyvinylidene fluoride-trifluoroethylene copolymer spinning solution.

[0056] PVDF-TrFE nanofiber membranes were obtained by electrospinning using a spinning device.

[0057] Example 4:

[0058] like Figure 1 As shown, this embodiment provides a spinning device, including a liquid storage device, a roller, and a high-voltage power supply. The liquid storage device is mounted on a spacing adjustment device, which is used to adjust the distance between the liquid storage device and the roller. The spacing adjustment device is mounted on a slide rail device, which can drive the spacing adjustment device and the liquid storage device to move left and right at a uniform speed, and the direction of movement is perpendicular to the rotation direction of the roller.

[0059] The roller serves as a receiving device. The positive terminal of the high-voltage power supply is connected to the liquid storage device, and the negative terminal is connected to the roller. An electric field of a certain intensity is formed between the positive and negative terminals, causing the spinning solution on the surface of the liquid storage device to ripple, similar to forming a Taylor cone, and further stretching it into nanofibers.

[0060] The liquid storage device uses a concave copper tube, inside which is a polypropylene plate. Since polypropylene itself is non-conductive, it will not interfere with the preparation and formation of the two fibers. The polypropylene plate can cut the internal cavity of the concave copper tube into two parts, which are respectively connected to the liquid supply devices storing PVDF-TrFE spinning solution and TPU / CB spinning solution.

[0061] The performance of the fiber membranes obtained in Examples 1-3 and Comparative Examples 1-2 will be analyzed below with reference to the accompanying drawings.

[0062] like Figure 3 As shown, Figure 3 (a) and (b) are SEM images of TPU / CB beaded nanofibers and PVDF-TrFE nanofibers, respectively. Under independent electrospinning conditions, each component has a good morphology. Figure 3 (c-e) are SEM images of TBPHNFMs at different mass ratios. TPU / CB beaded nanofibers and PVDF nanofibers can be clearly seen in the fiber membranes obtained by mixing at different mass ratios, indicating that TBP HNFMs mixed at different ratios have good morphology and dispersibility. Furthermore, TPU / CB beaded nanofibers and PVDF-TrFE nanofibers have achieved an interactive structure, and the number of beads gradually decreases as the mass ratio of PVDF-TrFE nanofibers increases.

[0063] Furthermore, the mechanical stability of pure electrospun PVDF-TrFE nanofiber membranes and TBP HNFMs is as follows: Figure 3 As shown in (f~g), the pure PVDF-TrFE nanofiber membrane exhibits obvious delamination when in contact with a finger, indicating poor mechanical stability. With the addition of TPU / CB NFM, the delamination phenomenon gradually weakens until it is completely eliminated, and the mechanical stability improves.

[0064] like Figure 4 As shown, Figure 4 The SEM cross-sectional images of TPU HNFMs with different mass ratios show that TPU / CB NFM is uniformly distributed in each layer of the fiber membrane, which can suppress the delamination of PVDF-TrFE NFM to a certain extent.

[0065] To demonstrate the good mixing of TPU / CB NFM and PVDF-TrFE NFM, EDS was used to track the distribution of F element through elemental color mapping. The contents of C, N, O, and F elements in TBP HNFMs with different mass ratios are shown in Table 1.

[0066] Table 1: EDS analysis of elemental content in TBP HNFMs with different mass ratios

[0067]

[0068]

[0069] As can be seen from the data in Table 1, the proportion of F element increases with the increase of PVDF-TrFE mass ratio, because F element only exists in PVDF-TrFE.

[0070] The nanofiber membranes prepared in Examples 1-3 were used as negative electrode materials and assembled into an electrospun triboelectric nanogenerator. The specific steps are as follows:

[0071] like Figure 5 As shown, after cutting the nanofiber membrane, a conductive fabric with a nickel-copper coating is pasted onto its surface to obtain the negative electrode material of the nanogenerator; the positive electrode material of the nanogenerator (composed of a nanofiber membrane with a porous structure of polylactic acid / chitosan / aloe vera) and the negative electrode material are pasted onto both sides of an arch shape folded from A4 paper, and then mounted on a linear motor to obtain TENG.

[0072] Combination Figure 6 (a)~(c), Figure 6 Figures (a) to (c) show the output performance of TBP HNFMs with different mass ratios. As can be seen from the figures, the output performance first decreases and then increases with the increase of the PVDF-TrFE nanofiber ratio. TBP HNFMs containing a high proportion of PVDF-TrFE nanofibers exhibit better output performance. In this case, the PVDF-TrFE nanofibers play a dominant role in the electrical performance output. However, a lower proportion of TPU / CB NFM makes it difficult to completely fix the PVDF-TrFE nanofibers, resulting in poor mechanical stability of the fiber membrane. Figure 3 As shown in (g).

[0073] Conversely, when TBP HNFM contains a high proportion of TPU / CB NFM, its electrical output performance is comparable to that of a high proportion of PVDF-TrFE nanofibers. This is due to the higher surface roughness of the friction layer caused by the presence of the beaded structure. Furthermore, its electrical output performance is a result of the combined effect of TPU / CB beaded nanofibers and PVDF-TrFE nanofibers.

[0074] In summary, considering the balance between triboelectric properties and tensile properties, the optimal parameter is set to 6:1 TBP HNFMs.

[0075] Combination Figure 6 (d) to (e) show the changes in the TENG's output performance under different external forces. With increasing applied force, the output voltage changes significantly, while the current increases slowly. To accurately analyze the TENG's sensitivity, a linear simulation was used to derive the relationship between pressure and voltage output, as shown in the figure. Figure 6 As shown in (f), a voltage of 26.6V can be displayed even under a force of 1N, indicating that the prepared TENG can be easily captured. The voltage output changes rapidly as the applied force gradually increases, because the increased pressure causes significant deformation of the beaded structure, increasing the effective contact area between the positive friction layer and the fiber. The results show that the TENG exhibits a pressure-responsive behavior.

[0076] To compare the output performance of the TENG, its charging capability with capacitors of different capacitances was also investigated to demonstrate its potential for powering small electronic devices. In this experiment, a full-wave bridge rectifier was used to convert the AC power generated by the 2cm×2cm TENG into DC power. Figure 7 (a) shows the curves obtained by continuously charging different capacitors (2.2, 6.8, 10, 22, and 33 μF) for 200 s with a force of 3 N and a frequency of 3 Hz under no external load. As the capacitance increases, the charging rate gradually decreases, and the maximum potential obtained also gradually decreases, with potentials of 4.5, 2.73, 1.88, 0.82, and 0.69 V obtained, respectively.

[0077] Furthermore, to verify the practical application of TENG, pressure was applied to TENG through continuous finger tapping and clapping, and the charging curve of 2.2μF within 200s was tested, as shown below. Figure 7 As shown in (b), the force of clapping with your hand is significantly greater than that of clapping with your fingers, therefore the charging speed of clapping with your hand is significantly faster than that of clapping with your fingers. Similarly, TENG can also be used to charge other movements of the human body. Figure 7 (c) is a graph showing the power supply of the stopwatch after the 10μF capacitor is charged by tapping the TENG with a finger. Figure 7 (d) shows the charge-discharge curve of the 22μF capacitor driven by the TENG. By rapidly tapping the TENG with a finger, the capacitor voltage reaches 1.84V within 400s. The energy stored in this capacitor can be used to power a thermometer and hygrometer, and its charge-discharge curve is shown.

[0078] Therefore, due to TENG's flexibility and shape adaptability, it can be attached to the human body surface as a wearable sensor. An assembled negative friction layer measuring 2cm x 2cm was attached to the fingertip to monitor the output of finger taps of varying intensities, such as... Figure 8 As shown in (a), during continuous tapping, the output voltage exhibits a repeatable, stable, and synchronized signal. Furthermore, by attaching a friction layer to both gloves and detecting the voltage at different clapping frequencies, good synchronization of the clapping can be detected regardless of the clapping speed. Figure 8 (b)). For example Figure 8 As shown in (c), two friction layers were attached to the test subject's underarm clothing and inner elbow, respectively, generating corresponding continuous voltage signals during gentle arm raising / lowering. Subsequently, the TENG was assembled into a mask for detecting human respiratory status, such as... Figure 8 As shown in (d), there is a significant difference in the voltage output signal detected during normal breathing and rapid breathing. These results demonstrate the great potential of TENG as a wearable electronic device.

[0079] 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 technical principles 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 for preparing a hybrid-structured electrospinning triboelectric nanogenerator, characterized in that, Includes the following steps: The polyvinylidene fluoride-trifluoroethylene copolymer was dispersed in a mixed solvent of N,N-dimethylformamide / acetone, and stirred for a time a to obtain a polyvinylidene fluoride-trifluoroethylene copolymer spinning solution. Carbon black was added to a mixed solvent of N,N-dimethylformamide / acetone, and the mixture was sonicated to obtain a CB-N,N-dimethylformamide / acetone solution; polyurethane was added to the CB-N,N-dimethylformamide / acetone solution, and the mixture was stirred for time b to obtain a polyurethane / carbon black spinning solution. Electrospinning was performed by mixing a polyvinylidene fluoride-trifluoroethylene copolymer spinning solution and a polyurethane / carbon black spinning solution to obtain a nanofiber membrane with a hybrid structure. After cutting the nanofiber membrane, conductive fabric is pasted onto its surface to obtain the negative electrode material of the nanogenerator. By using negative electrode materials to assemble nanogenerators, an electrospinning triboelectric nanogenerator was obtained.

2. The method for preparing the hybrid-structured electrospinning triboelectric nanogenerator according to claim 1, characterized in that, The mass percentage range of the polyvinylidene fluoride-trifluoroethylene copolymer spinning solution is 5–10 wt%, and the mass percentage range of the polyurethane / carbon black spinning solution is 15–20 wt%.

3. The method for preparing the hybrid-structured electrospinning triboelectric nanogenerator according to claim 1, characterized in that, All stirring was carried out at room temperature, with stirring time a being 6–8 hours and stirring time b being 4–6 hours.

4. The method for preparing the hybrid-structured electrospinning triboelectric nanogenerator according to claim 1, characterized in that, The conductive fabric is a conductive fabric with a nickel-copper coating.

5. The method for preparing the hybrid-structured electrospinning triboelectric nanogenerator according to claim 1, characterized in that, The assembly of a nanogenerator using negative electrode materials includes: attaching the positive and negative electrode materials of the nanogenerator to both sides of an arch shape folded from paper, and then mounting it on a linear motor.

6. A hybrid electrospinning triboelectric nanogenerator, characterized in that, It is prepared by the method for preparing the hybrid structure electrospinning triboelectric nanogenerator according to any one of claims 1 to 5.

7. A spinning apparatus for preparing a hybrid electrospun triboelectric nanogenerator according to any one of claims 1 to 5, characterized in that, It includes a liquid supply device, a liquid storage device, a roller, and a high-voltage power supply. The liquid storage device is used to store polyvinylidene fluoride-trifluoroethylene copolymer spinning solution and polyurethane / carbon black spinning solution, respectively. The positive terminal of the high-voltage power supply is connected to the liquid storage device, and its negative terminal is connected to the roller.

8. The spinning equipment according to claim 7, characterized in that: The liquid storage device is mounted on the spacing adjustment device, which is used to adjust the distance between the liquid storage device and the drum. The spacing adjustment device is slidably connected to the slide rail device, which can drive the spacing adjustment device and the liquid storage device to move at a constant speed, and the direction of movement is perpendicular to the rotation direction of the drum.

9. The spinning equipment according to claim 7, characterized in that: The liquid storage device is equipped with a polypropylene plate, which divides the interior of the liquid storage device into two parts, which are respectively connected to a liquid supply device containing a polyvinylidene fluoride-trifluoroethylene copolymer spinning solution and a polyurethane / carbon black spinning solution.

10. The spinning equipment according to claim 7, characterized in that: The liquid storage device uses a concave copper tube.

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