Integrated preparation method and application of PN-type thermoelectric fiber

Abstract

The present invention provides an integrated preparation method and application of a P-N type structure thermoelectric fiber. First, a P-type thermoelectric spinning solution and an N-type thermoelectric spinning solution are prepared respectively, and the two are respectively injected into the first spinning channel and the second spinning channel of a dual-channel microfluidic chip at a predetermined extrusion speed. The two spinning channels are alternately circulated and input into a transition spinning tube, and then enter a coagulation bath through a spinneret for coagulation and molding. Finally, the fibers are dried and wound to obtain a continuous P-N type structure thermoelectric fiber. The present invention improves the dual-channel microfluidic chip, controls the extrusion speed of the thermoelectric spinning solution, regulates the thermoelectric fiber formation process and the formed fiber structure, and forms a plurality of continuous P-N knot fibers in one step, thereby realizing the integrated spinning of the P-N type structure thermoelectric fiber. This method is different from the traditional step-by-step preparation method of the P-N thermoelectric fiber. It is simple and fast, has strong feasibility, is suitable for industrial mass production, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of PN type thermoelectric fiber preparation, and in particular to an integrated preparation method and application of PN type structured thermoelectric fibers. Background Art

[0002] With the development of smart devices and rising demands for sensory capabilities, wearable devices have a huge market potential. The miniaturization and integration of electronic devices have enabled significant progress in wearable electronics technology. However, the integration of electronic devices with wearable fabrics can easily increase the burden on the fabric and reduce comfort. Therefore, smart textiles made from functional fibers have become a research hotspot and trend in recent years. Their excellent wearing comfort and special functionality have brought significant changes to the field of wearable electronic devices. Thermoelectric fibers, as functional fibers, are functional materials that can generate electrical energy from ambient temperature differences. PN-type thermoelectric materials can form a series thermoelectric path using P-type and N-type materials, enhancing power generation efficiency. Combining PN-type thermoelectric materials with fibers can produce PN-type thermoelectric fiber materials with high thermoelectric performance.

[0003] In the prior art, an invention patent (application number CN 202110533460.0) discloses an ultra-flexible self-generating yarn, an all-fiber-based ultra-flexible temperature difference self-generating fabric and a preparation method thereof. The all-fiber-based ultra-flexible temperature difference self-generating fabric preferably coats P-type thermoelectric materials and N-type thermoelectric materials on the base yarn by an intermittent coating method to prepare several P-type thermoelectric material areas and N-type thermoelectric material areas, so that they form a passage and enhance the power generation efficiency. The invention patent (application number CN202011133205.9) discloses a flexible thermoelectric fiber based on a woven PN-type structure and its preparation method. First, a P-type thermoelectric solution and an N-type thermoelectric paste are prepared separately, and the textile fiber is wrapped around a threaded column. It is divided into two symmetrical sides with the axial direction of the threaded column as the center. One side is immersed in the P-type thermoelectric solution to obtain a P-type thermoelectric region, and then the other side of the textile fiber is coated with an N-type thermoelectric paste to obtain an N-type thermoelectric region; finally, a conductive adhesive is coated at the junction between the P-type thermoelectric region and the N-type thermoelectric region to obtain a flexible thermoelectric fiber with a PN-type structure.

[0004] In the above method, the thermoelectric material is compounded on the surface of the fiber substrate by a special coating or immersion method. The resulting PN-type thermoelectric fiber has weak integrity and poor mechanical properties. The thermoelectric material is compounded on the fiber surface, which damages the flexibility and comfort of the fiber, affecting the subsequent application of the thermoelectric fiber. Moreover, the preparation process of the PN-type thermoelectric fiber is complicated and cannot be prepared in an integrated manner, making it difficult to achieve industrial mass production.

[0005] In view of this, it is necessary to design an improved integrated preparation method and application of PN-type structured thermoelectric fibers to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide an integrated preparation method and application of PN-type structured thermoelectric fibers. By improving the dual-channel microfluidic chip, regulating the thermoelectric fiber formation process and the formed fiber structure, multiple continuous PN knot fibers are formed in one step, realizing the integrated spinning of PN-type structured thermoelectric fibers. This preparation method is simple, rapid, highly feasible, and has good prospects for industrial application.

[0007] To achieve the above-mentioned purpose, the present invention provides an integrated preparation method of a PN-type structured thermoelectric fiber, which uses a dual-channel microfluidic chip to perform integrated preparation of the PN-type structured thermoelectric fiber, comprising the following steps:

[0008] S1, preparing a P-type thermo-electrospinning solution and an N-type thermo-electrospinning solution respectively;

[0009] S2, injecting the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution in step S1 into the first spinning channel and the second spinning channel of the dual-channel microfluidic chip at a predetermined extrusion speed, and alternately circulating from the first spinning channel and the second spinning channel into the transition spinning tube, and then entering the coagulation bath through the spinneret for coagulation and forming, and finally drying and winding to obtain a continuous PN-type structure thermoelectric fiber;

[0010] Of the spinning holes of the first spinning channel and the second spinning channel, one is an oblique spinning hole and the other is a flat spinning hole, and the opening direction of the oblique spinning hole is away from the flat spinning hole; the spinning channel with the oblique spinning hole is vertically inserted into the transition spinning tube, and the spinning channel with the flat spinning hole is horizontally inserted into the transition spinning tube along the axis of the transition spinning tube.

[0011] As a further improvement of the present invention, the transition spinning tube is a light-transmitting tube, and an ultraviolet light emitting device is provided on the outside of the transition spinning tube. Photocuring is performed at the moment when the P-type thermoelectric spinning liquid and the N-type thermoelectric spinning liquid are alternately input into the transition spinning tube to achieve pre-forming at the junction of the two thermoelectric spinning liquids.

[0012] As a further improvement of the present invention, along the axial direction of the transition spinning tube, the horizontal distance between the oblique spinning port and the flat spinning port is 1 to 2 mm, and the vertical distance between them is 0 to 1 mm.

[0013] As a further improvement of the present invention, in step S2, the extrusion speeds of the P-type thermo-electrospinning solution and the N-type thermo-electrospinning solution are pre-set according to their viscosities respectively.

[0014] As a further improvement of the present invention, the P-type thermoelectric spinning solution includes PEDOT:PSS solution, carbon nanotubes, polyurethane, N,N-dimethylformamide, dimethyl sulfoxide and sodium dodecyl sulfate; the N-type thermoelectric spinning solution includes PEDOT:PSS solution, carbon nanotubes, polyurethane, N,N-dimethylformamide, dimethyl sulfoxide, sodium dodecyl sulfate and N-type dopant polyetherimide.

[0015] As a further improvement of the present invention, the extrusion speed of the P-type thermoelectric spinning solution is 8 to 14 mm / h, and the extrusion speed of the P-type thermoelectric spinning solution is 12 to 16 mm / h.

[0016] As a further improvement of the present invention, in the P-type thermospinning solution and the N-type thermospinning solution, the PEDOT:PSS solution accounts for 10wt% to 90wt% of the total mass of the thermospinning solution, and the solid content of the polyurethane is 3 to 5 times that of PEDOT:PSS; in the N-type thermospinning solution, the content ratio of the polyetherimide to the carbon nanotubes is (0.1 to 1):1.

[0017] As a further improvement of the present invention, in step S2, the first spinning channel and the second spinning channel are both hydrophobically treated glass capillaries with an inner diameter of 0.1 to 0.5 mm and a length of 5 to 20 mm; the coagulation bath is an isopropyl alcohol / water mixed solution.

[0018] As a further improvement of the present invention, the transition spinning tube is a glass capillary with an inner diameter of 0.5 to 0.9 mm and a length of 10 to 60 mm; the spinneret is a capillary with an inner diameter of 0.1 to 0.5 mm.

[0019] The present invention also provides an application of a PN-type structured thermoelectric fiber, which is prepared by any of the integrated preparation methods described above. The application of the PN-type structured thermoelectric fiber includes serving as a power source for a sensing device, and application in smart clothing and wearable electronic devices.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention provides an integrated preparation method and application of PN-type structured thermoelectric fibers. The integrated preparation of PN-type structured thermoelectric fibers is performed using a dual-channel microfluidic chip. P-type and N-type thermoelectric spinning solutions are injected into the first and second spinning channels of the dual-channel microfluidic chip at predetermined extrusion rates, respectively. The solutions are then alternately circulated from the first and second spinning channels into a transition spinning tube. The fibers are then fed through a spinneret into a coagulation bath for coagulation and formation. Finally, the fibers are dried and wound to produce continuous PN-type structured thermoelectric fibers. By improving the dual-channel microfluidic chip, the present invention controls the extrusion rate of the thermoelectric spinning solution, regulates the thermoelectric fiber formation process and the resulting fiber structure, and forms multiple continuous PN-type knot fibers in a single step, achieving the integrated spinning of PN-type structured thermoelectric fibers. This preparation method is simple, rapid, highly feasible, and has good prospects for industrial application.

[0022] 2. The present invention sets the two spinning channels of the dual-channel microfluidic chip as an oblique spinning port and a flat spinning port, respectively, and controls the degree of combination of the ejected P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution by limiting their positions, so as to form a PN junction at the mixing point of the two, thereby realizing the one-step spinning of the PN-type structure thermoelectric fiber. In addition, the present invention uses a light-transmitting glass tube as a transition spinning tube, and provides an ultraviolet light emitting device on the outside of the transition spinning tube. At the moment when the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution are alternately input into the transition spinning tube, light curing is performed, realizing the pre-forming of the junction of the two thermoelectric spinning solutions, so as to control the fusion between them and avoid excessive mixing of the two thermoelectric spinning solutions, successfully preparing the PN junction of the thermoelectric fiber, and finally obtaining a large-scale continuous PN-type structure thermoelectric fiber. The PN-type structure thermoelectric fiber can be assembled with fabric or self-woven into fabric as a thermoelectric device, which has important scientific value and broad application prospects in the wearable field.

[0023] 3. Both the P-type and N-type thermoelectric spinning solutions of the present invention utilize PEDOT:PSS as the thermoelectric material and incorporate polyurethane, improving the spinnability of the spinning solution. This allows for the successful production of integrated thermoelectric fibers using spinning technology. The addition of carbon nanotubes further enhances the thermoelectric performance of the resulting PN-type thermoelectric fibers. The present preparation method allows for the direct production of thermoelectric fibers with a continuous PN-type structure. Unlike conventional, step-by-step preparation methods for PN thermoelectric fibers, this method is simple and easy to implement, suitable for industrial mass production, and possesses promising application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a physical picture of the PN-type thermoelectric fiber prepared in Example 1 of the present invention.

[0025] Figure 2This is a microstructure diagram of the PN-type thermoelectric fiber prepared in Example 1 of the present invention.

[0026] Figure 3 This is the microstructure diagram of the PN-type thermoelectric fiber prepared in Comparative Example 1. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0029] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0030] A method for preparing an integrated PN-type structure thermoelectric fiber using a dual-channel microfluidic chip includes the following steps:

[0031] S1, preparing a P-type thermo-electrospinning solution and an N-type thermo-electrospinning solution respectively;

[0032] S2. The P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution in step S1 are respectively injected into the first spinning channel and the second spinning channel of the dual-channel microfluidic chip at a predetermined extrusion speed, and are alternately circulated from the first spinning channel and the second spinning channel into the transition spinning tube, and then enter the coagulation bath through the spinneret for coagulation and forming, and finally dried and wound to obtain a continuous PN-type structure thermoelectric fiber; wherein the extrusion speeds of the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution are pre-set according to their viscosities.

[0033] The present invention improves the dual-channel microfluidic chip and controls the extrusion speed of the thermoelectric spinning solution to regulate the thermoelectric fiber formation process and the formed fiber structure, thereby forming multiple continuous PN knot fibers in a one-step method, thereby realizing the integrated spinning of PN-type thermoelectric fibers. The preparation method of the present invention can directly produce thermoelectric fibers with a continuous PN-type structure. Unlike the traditional step-by-step preparation method of PN thermoelectric fibers, this method is simple and easy to implement, suitable for industrial mass production, and has good application prospects.

[0034] In some specific embodiments, the extrusion speed of the P-type thermo-electrospinning solution is 8 to 14 mm / h, and the extrusion speed of the P-type thermo-electrospinning solution is 12 to 16 mm / h.

[0035] Specifically, a dual-channel microfluidic chip that realizes the integrated preparation method of the above-mentioned PN-type structure thermoelectric fiber includes a first spinning channel, a second spinning channel, a transition spinning tube connected to the first spinning channel and the second spinning channel, and a spinneret at the end of the transition spinning tube; wherein the spinning port of the first spinning channel and the spinning port of the second spinning channel, one is an oblique spinning port, and the other is a flat spinning port, and the opening direction of the oblique spinning port is away from the flat spinning port; the spinning channel with the oblique spinning port is vertically inserted into the transition spinning tube, and the spinning channel with the flat spinning port is horizontally inserted into it from the end of the transition spinning tube along the axis of the transition spinning tube; the spinneret is connected to the other end of the transition spinning tube.

[0036] Along the axial direction of the transition spinning tube, the horizontal distance between the oblique spinning port and the flat spinning port is 1 to 2 mm, and the vertical distance is 0 to 1 mm; in this way, the spinning ports of the two spinning channels are respectively set as the oblique spinning port and the flat spinning port, and by limiting the positions of the two, the degree of combination of the P-type thermoelectric spinning liquid and the N-type thermoelectric spinning liquid ejected from the spinning port is controlled to form a PN junction at the mixing point of the two, thereby realizing the one-step spinning of PN-type structured thermoelectric fibers.

[0037] In particular, the transition spinning tube is a light-transmitting tube, and an ultraviolet light emitting device is provided on the outside of the transition spinning tube. When the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution are alternately input into the transition spinning tube, light curing is performed to achieve the pre-forming of the junction of the two thermoelectric spinning solutions. The present invention uses a light-transmitting glass tube as the transition spinning tube and provides an ultraviolet light emitting device on the outside thereof, achieving the pre-forming of the junction of the two thermoelectric spinning solutions to control the fusion between them and avoid excessive mixing of the two thermoelectric spinning solutions. The PN junction of the thermoelectric fiber is successfully prepared, and finally a large-scale continuous PN-type structure thermoelectric fiber is obtained. The PN-type structure thermoelectric fiber can be assembled with fabric or self-woven into fabric as a thermoelectric device, and has important scientific value and broad application prospects in the wearable field.

[0038] Specifically, the P-type thermospinning solution includes a PEDOT:PSS solution, carbon nanotubes (CNTs), polyurethane (PU), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and sodium dodecyl sulfate (SDS); the N-type thermospinning solution includes a PEDOT:PSS solution, carbon nanotubes (CNTs), polyurethane (PU), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), sodium dodecyl sulfate (SDS), and an N-type dopant, polyetherimide (PEI). In both the P-type and N-type thermospinning solutions, the PEDOT:PSS solution accounts for 10% to 90% by weight of the total mass of the thermospinning solution, and the solid content of the polyurethane is 3 to 5 times that of the PEDOT:PSS solution. In the N-type thermospinning solution, the content ratio of polyetherimide to carbon nanotubes is (0.1 to 1):1.

[0039] The P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution of the present invention both use PEDOT:PSS as the thermoelectric material and add polyurethane to improve the spinnability of the spinning solution, successfully utilizing spinning technology to produce integrated thermoelectric fibers; by adding carbon nanotubes, the thermoelectric performance of the prepared PN-type structured thermoelectric fibers is further improved.

[0040] In some specific embodiments, the preparation process of the P-type thermoelectric spinning solution is as follows:

[0041] SS1. CNTs were dispersed in DMF by cell crushing to prepare a CNT dispersion, and PEDOT:PSS solids were dispersed in DMSO by cell crushing to prepare a PEDOT:PSS dispersion; the solid content of the CNT dispersion was 0.1 to 0.3 wt%;

[0042] SS2. The two solutions are mixed in a cell crusher, and finally polyurethane (PU) particles are added and stirred to form a P-type thermoelectric spinning solution.

[0043] It should be noted that N-type thermoelectrospinning solution can be produced by adding an appropriate amount of PEI to a P-type thermoelectrospinning solution. The cell disruption of CNT or PEDOT:PSS dispersions requires a power of 300-600W for 1-2 hours. To prepare the PEDOT:PSS solid, the freeze-drying time for the PEDOT:PSS aqueous solution is 48-72 hours.

[0044] In step S2, both the first and second spinning channels are hydrophobically treated glass capillaries with an inner diameter of 0.1-0.5 mm and a length of 5-20 mm. The coagulation bath is an isopropyl alcohol / water mixture. The transition spinning tube is a glass capillary with an inner diameter of 0.5-0.9 mm and a length of 10-60 mm. The spinneret is a capillary with an inner diameter of 0.1-0.5 mm.

[0045] In some specific embodiments, the hydrophobic treatment includes placing the glass capillary in an ethanol solution for water bath ultrasonic treatment to wash away impurities on the inner wall; and treating the cleaned glass capillary with 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTs), specifically placing the glass capillary and PFOTs in a vacuum drying vessel, evacuating to -0.1 MPa, maintaining the vacuum, and standing for 2 to 6 hours to allow PFOTs vapor to form a hydrophobic film on the inner wall of the capillary.

[0046] The present invention also provides an application of a PN-type structured thermoelectric fiber. The PN-type structured thermoelectric fiber is prepared by the above-mentioned integrated preparation method of the PN-type structured thermoelectric fiber. The application of the PN-type structured thermoelectric fiber includes being used as a power source to power a sensing device, and being used in smart clothing and wearable electronic devices.

[0047] Example 1

[0048] This embodiment provides an integrated preparation method for a PN-type structured thermoelectric fiber, which uses a dual-channel microfluidic chip to perform integrated preparation of the PN-type structured thermoelectric fiber, including the following steps:

[0049] S1, preparing a P-type thermo-electrospinning solution and an N-type thermo-electrospinning solution respectively;

[0050] S11, CNTs were dispersed in DMF by cell crushing to obtain a CNT dispersion, and PEDOT:PSS solids were dispersed in DMSO by cell crushing to obtain a PEDOT:PSS dispersion; the solid content of the CNT dispersion was 0.2 wt %.

[0051] S12, mixing the two solutions in a cell crusher, and finally adding polyurethane (PU) particles and stirring to prepare a P-type thermoelectric spinning solution;

[0052] S13, adding an appropriate amount of PEI to the P-type thermo-electrospinning solution to obtain the N-type thermo-electrospinning solution;

[0053] In the P-type and N-type thermospinning solutions, the PEDOT:PSS solution accounts for 40 wt% of the total mass of the thermospinning solution, and the solid content of polyurethane is 4 times that of PEDOT:PSS. In the N-type thermospinning solution, the content ratio of polyetherimide to carbon nanotubes is 0.3:1.

[0054] S2, injecting the P-type thermoelectric spinning solution in step S1 into the first spinning channel of the dual-channel microfluidic chip at an extrusion rate of 10 mm / h, and injecting the N-type thermoelectric spinning solution into the second spinning channel of the dual-channel microfluidic chip at an extrusion rate of 14 mm / h; and alternately circulating from the first spinning channel and the second spinning channel into the transition spinning tube, and then entering the coagulation bath through the spinneret for coagulation and molding, and finally drying and winding to obtain a continuous PN-type structure thermoelectric fiber;

[0055] Among them, the spinning mouth of the first spinning channel is a flat spinning mouth, and the spinning mouth of the second spinning channel is an oblique spinning mouth, and the opening direction of the oblique spinning mouth is back to the flat spinning mouth; the second spinning channel with the oblique spinning mouth is vertically inserted into the transition spinning tube, and the first spinning channel with the flat spinning mouth is horizontally inserted from the end of the transition spinning tube along the axis of the transition spinning tube; the spinneret is connected to the other end of the transition spinning tube; along the axis direction of the transition spinning tube, the horizontal distance between the oblique spinning mouth and the flat spinning mouth is 1.0 mm, and the vertical distance is 0.5 mm.

[0056] See also Figure 1 As shown, Figure 1 This is a photo of the PN-type thermoelectric fiber prepared in Example 1. It should be noted that in practice, there is no color difference between the P-type and N-type thermoelectric spinning solutions. In this example, a color-enhancing material that does not affect performance was added to the P-type thermoelectric spinning solution to distinguish the P-type and N-type thermoelectric regions of the fiber and the PN junction between them. The photo of the PN-type thermoelectric fiber demonstrates that this method successfully produced thermoelectric fibers with a continuous PN structure.

[0057] See also Figure 2 As shown, Figure 2 This is the microstructure diagram of the PN-type structure thermoelectric fiber prepared in Example 1. It can be seen from the figure that the overall structure of the PN-type structure thermoelectric fiber is uniform. Due to the rapid transition between the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution, the formed thermoelectric fiber successfully forms a PN junction, and the boundary between the P-type thermoelectric region and the N-type thermoelectric region is clear.

[0058] Example 2

[0059] This embodiment provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that in step S12, the added polyurethane is acrylate (PUA). The rest is roughly the same as Example 1 and will not be repeated here.

[0060] Example 3

[0061] This embodiment provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 2, the difference is that the transition spinning tube is a light-transmitting tube, and an ultraviolet light emitting device is provided on the outside of the transition spinning tube. Photocuring is performed at the moment when the P-type thermoelectric spinning liquid and the N-type thermoelectric spinning liquid are alternately input into the transition spinning tube; the rest is roughly the same as Example 2 and will not be repeated here.

[0062] Comparative Example 1

[0063] Comparative Example 1 provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that the spinning holes of the first spinning channel and the second spinning channel are both flat-mouth spinning holes. The rest is roughly the same as Example 1 and will not be repeated here.

[0064] See also Figure 3 As shown, Figure 3 This is a microscopic image of the PN-type thermoelectric fiber prepared in Comparative Example 1. As can be seen from the figure, the overall structure of the PN-type thermoelectric fiber prepared in Comparative Example 1 is uneven, and the transition state between the P-type thermoelectric region and the N-type thermoelectric region is long, which affects the thermoelectric performance of the PN-type thermoelectric fiber.

[0065] Comparative Example 2

[0066] Comparative Example 2 provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that the horizontal distance between the flat spinning port of the first spinning channel and the oblique spinning port of the second spinning channel is 0. The rest is roughly the same as Example 1 and will not be repeated here.

[0067] Comparative Example 3

[0068] Comparative Example 2 provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that the horizontal distance between the flat spinning port of the first spinning channel and the oblique spinning port of the second spinning channel is 4 mm, and the vertical distance is 2.5 mm. The rest is roughly the same as Example 1 and will not be repeated here.

[0069] Comparative Example 4

[0070] Comparative Example 4 provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that the extrusion speed of the P-type thermoelectric spinning solution is 5 mm / h, and the extrusion speed of the N-type thermoelectric spinning solution is 10 mm / h. The rest is roughly the same as Example 1 and will not be repeated here.

[0071] Comparative Example 5

[0072] Comparative Example 5 provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that the extrusion speed of the P-type thermoelectric spinning solution is 16 mm / h, and the extrusion speed of the N-type thermoelectric spinning solution is 18 mm / h. The rest is roughly the same as Example 1 and will not be repeated here.

[0073] Comparative Example 6

[0074] Comparative Example 6 provides an integrated preparation method for PN-type structured thermoelectric fibers. Compared with Example 1, the difference is that polyurethane is not added to the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution. The rest is roughly the same as Example 1 and will not be repeated here.

[0075] In Comparative Example 6, in the absence of polyurethane, the spun fibers were difficult to shape after the coagulation bath, had an uneven fiber structure, and had poor performance.

[0076] The PN-type structured thermoelectric fibers prepared in Examples 1 to 2 and Comparative Examples 1 to 5 were tested for thermoelectric properties and mechanical properties, and the results are shown in the following table.

[0077] Table 1 Performance test results of PN type thermoelectric fibers of Examples 1 to 2 and Comparative Examples 1 to 5

[0078] Conductivity (S / cm) Seebeck coefficient (μV / k) Mechanical properties (Mpa, %) Example 1 P-type: 35.7; N-type: 69.3 P type: 27.5; N type: -22.4 Stress: 28.5 Strain: 70.4 Example 2 P-type: 30.2; N-type: 61.4 P-type: 18.6; N-type: -19.2 Stress: 21.3 Strain: 61.6 Example 3 P type: 32.9; N type: 67.5 P-type: 20.6; N-type: -23.7 Stress: 21.8 Strain: 65.6 Comparative Example 1 P type: 33.0; N type: 62.1 P-type: 17.4; N-type: -18.9 Stress: 27.1 Strain: 62.3 Comparative Example 2 P-type: 31.7; N-type: 59.9 P-type: 23.1; N-type: -20.4 Stress: 30.1 Strain: 69.2 Comparative Example 3 P-type: 35.4; N-type: 72.2 P-type: 21.2; N-type: -20.6 Stress: 24.2 Strain: 73.4 Comparative Example 4 P-type: 37.2; N-type: 66.8 P-type: 22.1; N-type: -21.4 Stress: 26.7 Strain: 70.8 Comparative Example 5 P type: 29.3; N type: 50.1 P type: 18.4; N type: -18.8 Stress: 28.8 Strain: 50.1

[0079] As shown in Table 1, a comparison of Example 2 and Example 3 shows that the thermoelectric and mechanical properties of the PN-type structured thermoelectric fibers prepared after photocuring are significantly improved, indicating that photocuring can affect the transition state between the P-type thermoelectric region and the N-type thermoelectric region, improving the PN structure of the fiber. Comparing the test results of Example 1 with those of Comparative Example 1, the Seebeck coefficient of Comparative Example 1 is lower than that of the example, indicating that the oblique spinning nozzle configuration helps avoid the problem of low Seebeck coefficient of thermoelectric fibers caused by excessive mixing of P and N-type thermoelectric spinning solutions. As can be seen from Example 1 and Comparative Examples 2-3, the electrical conductivity and Seebeck coefficient of Example 1 are higher than those of Comparative Examples 2-3, indicating that the distance between the spinning channels affects the thermoelectric properties of the fiber. Comparing Example 1 with Comparative Examples 4-5 shows that when the injection speed is too low, the Seebeck coefficient is significantly reduced; when the injection speed is too high, the fiber unevenness increases, and the thermoelectric and mechanical properties deteriorate. In addition, an inappropriate injection speed can lead to excessive fusion of P and N and uneven fiber morphology.

[0080] In summary, the present invention provides an integrated preparation method and application for PN-type thermoelectric fibers. This method utilizes a dual-channel microfluidic chip for the integrated preparation of PN-type thermoelectric fibers. By improving the dual-channel microfluidic chip, controlling the extrusion rate of the thermoelectric spinning solution, and regulating the thermoelectric fiber formation process and resulting fiber structure, multiple continuous PN-junction fibers are formed in a single step, achieving the integrated spinning of PN-type thermoelectric fibers. The present invention configures the two spinning channel spinning ports of the dual-channel microfluidic chip as oblique and flat spinning ports, respectively. By defining the positions of the two ports, the degree of bonding between the ejected P-type and N-type thermoelectric spinning solutions is controlled, forming a PN junction at the junction of the two, thereby achieving the one-step spinning of PN-type thermoelectric fibers. In addition, by selecting a light-transmitting glass tube as a transition spinning tube and providing an ultraviolet light emitting device on the outside of the transition spinning tube, light curing is performed at the moment when the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution are alternately input into the transition spinning tube, thereby achieving pre-forming at the junction of the two thermoelectric spinning solutions to control the fusion between them and avoid excessive mixing of the two thermoelectric spinning solutions. The PN junction of the thermoelectric fiber is successfully prepared, and finally a large-scale continuous PN-type structure thermoelectric fiber is obtained. The PN-type structure thermoelectric fiber can be assembled with fabric or self-woven into fabric as a thermoelectric device, and has important scientific value and broad application prospects in the wearable field. The preparation method of the present invention can directly produce a thermoelectric fiber with a continuous PN-type structure. Unlike the traditional step-by-step preparation method of PN thermoelectric fiber, this method is simple and fast, has strong feasibility, is suitable for industrial mass production, and has good application prospects.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An integrated preparation method for PN-type thermoelectric fibers, characterized in that: The integrated preparation of PN-type structured thermoelectric fibers using a dual-channel microfluidic chip includes the following steps: S1, preparing a P-type thermo-electrospinning solution and an N-type thermo-electrospinning solution respectively; S2, injecting the P-type thermoelectric spinning solution and the N-type thermoelectric spinning solution in step S1 into the first spinning channel and the second spinning channel of the dual-channel microfluidic chip at a predetermined extrusion speed, and alternately circulating from the first spinning channel and the second spinning channel into the transition spinning tube, and then entering the coagulation bath through the spinneret for coagulation and forming, and finally drying and winding to obtain a continuous PN-type structure thermoelectric fiber; Of the spinning holes of the first spinning channel and the second spinning channel, one is an oblique spinning hole and the other is a flat spinning hole, and the opening direction of the oblique spinning hole is away from the flat spinning hole; the spinning channel with the oblique spinning hole is vertically inserted into the transition spinning tube, and the spinning channel with the flat spinning hole is horizontally inserted into the transition spinning tube along the axis of the transition spinning tube; along the axis of the transition spinning tube, the horizontal distance between the oblique spinning hole and the flat spinning hole is 1-2 mm, and the vertical distance is 0-1 mm; The extrusion speed of the P-type thermoelectric spinning solution is 8~14 mm / h, and the extrusion speed of the P-type thermoelectric spinning solution is 12~16 mm / h; The transition spinning tube is a light-transmitting tube, and an ultraviolet light emitting device is provided on the outside of the transition spinning tube. When the P-type thermoelectric spinning liquid and the N-type thermoelectric spinning liquid are alternately input into the transition spinning tube, light curing is performed to achieve pre-forming of the junction of the two thermoelectric spinning liquids.

2. The integrated preparation method of PN-type thermoelectric fiber according to claim 1, characterized in that: In step S2 , the extrusion speeds of the P-type thermo-electrospinning solution and the N-type thermo-electrospinning solution are pre-set according to their viscosities.

3. The integrated preparation method of PN-type thermoelectric fiber according to claim 2, characterized in that: The P-type thermoelectric spinning solution includes PEDOT:PSS solution, carbon nanotubes, polyurethane, N,N-dimethylformamide, dimethyl sulfoxide and sodium lauryl sulfate; the N-type thermoelectric spinning solution includes PEDOT:PSS solution, carbon nanotubes, polyurethane, N,N-dimethylformamide, dimethyl sulfoxide, sodium lauryl sulfate and N-type dopant polyetherimide.

4. The integrated preparation method of the PN-type thermoelectric fiber according to claim 3, characterized in that: In the P-type thermospinning solution and the N-type thermospinning solution, the PEDOT:PSS solution accounts for 10wt% to 90wt% of the total mass of the thermospinning solution, and the solid content of the polyurethane is 3 to 5 times that of the PEDOT:PSS. In the N-type thermospinning solution, the content ratio of the polyetherimide to the carbon nanotube is (0.1 to 1):

1.

5. The integrated preparation method of PN type structure thermoelectric fiber according to claim 1, characterized in that: In step S2, the first spinning channel and the second spinning channel are both glass capillaries after hydrophobic treatment, with an inner diameter of 0.1-0.5 mm and a length of 5-20 mm; the coagulation bath is an isopropyl alcohol / water mixed solution.

6. The integrated preparation method of PN-type thermoelectric fiber according to claim 5, characterized in that: The transition spinning tube is a glass capillary with an inner diameter of 0.5-0.9 mm and a length of 10-60 mm; the spinneret is a capillary with an inner diameter of 0.1-0.5 mm.

7. An application of a PN type structure thermoelectric fiber, characterized in that: The PN-type structured thermoelectric fiber is prepared by the integrated preparation method according to any one of claims 1 to 6. Applications of the PN-type structured thermoelectric fiber include serving as a power source for a sensing device, and being used in smart clothing and wearable electronic devices.

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