Janus helical thermoelectric hydrogel fibers and methods of making the same

Abstract

The application discloses a Janus spiral thermoelectric hydrogel fiber and a preparation method thereof. The preparation method comprises the following steps: dissolving first sodium polyacrylate in an alkaline solution to obtain sodium polyacrylate hydrogel; dissolving carbon nanotubes and an anionic surfactant in the alkaline solution to obtain a carbon nanotube solution, and dissolving second sodium polyacrylate in the carbon nanotube solution to obtain a composite hydrogel; extruding the sodium polyacrylate hydrogel and the composite hydrogel into a coagulation bath by using a wet spinning device to obtain a Janus hydrogel fiber, and applying a pre-strain to the Janus hydrogel fiber to obtain a Janus spiral hydrogel fiber; and doping and modifying the Janus spiral hydrogel fiber by using a PEI solution to obtain the Janus spiral thermoelectric hydrogel fiber. The preparation method of the Janus spiral thermoelectric hydrogel fiber is simple, convenient and easy to operate, raw material cost is low and the raw material is easy to obtain, and the Janus spiral thermoelectric hydrogel fiber can be used for large-scale preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermoelectric hydrogel fibers, in particular to a Janus spiral thermoelectric hydrogel fiber and a preparation method thereof. BACKGROUND

[0002] In recent years, thermoelectric (TE) technology can convert waste heat energy into electrical energy using the Seebeck effect, and solid-state thermoelectric generators (TEGs) have the advantages of no noise, no pollution and quiet operation in the conversion process, so TEGs have attracted the attention of researchers. Currently, TEGs are developing towards miniaturization, integration and multifunctionalization to meet the needs of wearable devices and micro energy systems. However, the rigidity and brittleness of traditional TEGs limit their application in the wearable field. Therefore, in order to meet the ergonomics, wearable TEGs need to have a certain flexibility.

[0003] The basic structure of TEG is that p-type material and n-type material are connected in series, where the carrier in p-type material is a hole with positive electricity; the carrier in n-type material is an electron with negative electricity. When a temperature difference is generated between the two ends of TEG, the carrier migrates from the hot end to the cold end, thereby forming a potential difference. To achieve efficient TE conversion and apply it to practice, the key is to improve the energy conversion efficiency of TE devices, which largely depends on the material properties. The dimensionless thermoelectric figure of merit (ZT) is a standard for measuring the efficiency of materials and devices, defined as ZT=σS2T / κ, where T(K) is the absolute temperature, S(μV / K) is the Seebeck coefficient (positive for p-type and negative for n-type), σ(S / m) and κ(W / m·K) represent the electrical conductivity and thermal conductivity, respectively. An ideal thermoelectric material needs to have high S and σ, while κ is low. Therefore, some scholars have combined thermoelectric materials with organic polymers to achieve the desired effect, for example, integrating carbon nanotubes (CNTs) into an organic conductive polymer matrix to form a CNT / polymer composite material, which has high thermoelectric performance and low thermal conductivity. Moreover, CNT materials have adjustable p / n properties, which can modify the original p-type material to n-type material through n-type dopant, laying a foundation for realizing p / n alternating fibers.

[0004] However, the existing technology of CNT / polymer composite material prepared thermoelectric film has poor stretchability and air permeability, and still lacks in out-of-plane temperature difference capture and mechanical properties (such as stretching and shearing); the stretchability of thermoelectric fibers is limited, and it needs to rely on textiles as a substrate to prepare thermoelectric textiles to collect the out-of-plane temperature difference. At the same time, most wearable thermoelectric devices cannot conform to the dynamic skin of the human body, and the resistance increases and the thermoelectric performance decreases when subjected to tensile strain. SUMMARY

[0005] To solve the above technical problems, the present application aims to provide a preparation method of Janus helical thermoelectric hydrogel fiber.

[0006] A further object of the present application is to provide a Janus helical thermoelectric hydrogel fiber, which can be used as an integrated fiber-based thermoelectric device, without the need for other textiles as a substrate, to directly form a three-dimensional helical structure to build a vertical temperature gradient between the human body and the environment, thereby achieving effective collection of thermal energy from the human body. Moreover, the fiber has super-stretchable and excellent strain-insensitive properties, and can maintain stable energy collection at dynamic joint parts.

[0007] The above object of the present application is achieved by the following technical solutions:

[0008] The present application provides a preparation method of Janus helical thermoelectric hydrogel fiber, comprising the following steps:

[0009] (1) Dissolve the first sodium polyacrylate in an alkaline solution to obtain a sodium polyacrylate hydrogel; dissolve carbon nanotubes (CNT) and an anionic surfactant in an alkaline solution to obtain a carbon nanotube solution, and dissolve the second sodium polyacrylate in the carbon nanotube solution to obtain a composite hydrogel;

[0010] (2) Extrude the sodium polyacrylate hydrogel and the composite hydrogel obtained in step (1) into a coagulation bath using a wet spinning device to obtain a Janus hydrogel fiber;

[0011] (3) Apply a pre-strain to the Janus hydrogel fiber obtained in step (2) to obtain a Janus helical hydrogel fiber;

[0012] (4) Dope modify the Janus helical hydrogel fiber in step (3) using a polyethyleneimine (PEI) solution to obtain the Janus helical thermoelectric hydrogel fiber.

[0013] The Janus hydrogel fiber with arbitrary cross-sectional shape and length can be prepared by regulating and controlling the two-phase spinning needle, and the mechanical asymmetric characteristics of the two-phase gel fiber can be utilized to adjust the size of the pre-strain to form spiral coils with different diameters, and the mechanical properties of the Janus spiral hydrogel fiber are improved by orders of magnitude compared with the Janus hydrogel fiber. The Janus spiral hydrogel fiber has excellent tensile property (strain > 1500%) due to the unique spiral structure, and the fiber material internal structure does not change when the fiber is stretched by external force and changes from spiral to straight state. The PEI solution is used as an n-type dopant to modify the Janus spiral hydrogel fiber, and the original positive hole in the CNT is modified into a negative electron, and the modified p / n alternating Janus spiral thermoelectric hydrogel fiber realizes the series connection of multiple p / n junctions, can accurately control the formation logarithm of the p / n junction, and achieves the effect of electrical series connection and thermal parallel connection, and after the integration of the wearable thermoelectric device, the skin and air layer in the vertical direction can be constructed when placed on the skin, and the stable output signal can be obtained without the stretching of the body joint, so that the human body heat can be collected with the maximum efficiency. The n-type modification can convert the in-plane temperature difference of the fiber into the out-of-plane temperature difference, and the voltage is improved by several times. The preparation method of the Janus spiral thermoelectric hydrogel fiber is simple, convenient and easy to operate, the raw material cost is low and easy to obtain, and can be used for large-scale preparation.

[0014] Further, in step (1), when preparing the sodium polyacrylate hydrogel, the molecular weight of the first sodium polyacrylate is 6-30 million Da, the pH value of the alkaline solution is 9-13.5, the alkaline solution is one or more of sodium hydroxide solution, sodium carbonate solution and sodium bicarbonate solution, and the concentration of the alkaline solution is 0.1-0.5 mol / L.

[0015] Further, in step (1), when preparing the composite hydrogel, the mass ratio of the anionic surfactant to the carbon nanotube is (0.05-0.5):1, the mass ratio of the second sodium polyacrylate to the carbon nanotube is 1:(0.05-0.7), the molecular weight of the second sodium polyacrylate is 6-30 million Da, the pH value of the alkaline solution is 9-13.5, the alkaline solution is one or more of sodium hydroxide solution, sodium carbonate solution and sodium bicarbonate solution, and the concentration of the alkaline solution is 0.2-1.5 mol / L.

[0016] Further, in step (1), the anionic surfactant is sodium dodecyl sulfate.

[0017] Further, in step (1), the carbon nanotubes can be single-walled carbon nanotube powder, or a single-walled carbon nanotube dispersion prepared by dissolving single-walled carbon nanotube powder in a solvent, wherein the solvent is water and / or N,N-dimethylformamide (DMF).

[0018] In specific embodiments, in step (1), sodium polyacrylate is dissolved in an alkaline solution, and a sodium polyacrylate hydrogel is obtained after heating and stirring and centrifugation; carbon nanotubes and an anionic surfactant are dissolved in an alkaline solution, and a carbon nanotube solution is obtained after ultrasonic dispersion under ice bath conditions; sodium polyacrylate is dissolved in the carbon nanotube solution, and a composite hydrogel is obtained after heating and stirring and centrifugation.

[0019] Further, in the process of dissolving sodium polyacrylate in an alkaline solution, the temperature for heating and stirring is 50-80℃, the time for heating and stirring is 3-9h, the stirring speed for heating and stirring is 200-600r / min, the speed for centrifugation is 800-4000r / min, and the time for centrifugation is 30-90min.

[0020] Further, the time for ultrasonic dispersion is 20-60min, and the working cycle is 3 / 5s (on / off).

[0021] Further, in the process of dissolving sodium polyacrylate in the carbon nanotube solution, the temperature for heating and stirring is 50-80℃, the time for heating and stirring is 3-9h, the stirring speed for heating and stirring is 200-600r / min, the speed for centrifugation is 800-4000r / min, and the time for centrifugation is 30-90min.

[0022] Further, in step (2), the extrusion speeds of the sodium polyacrylate hydrogel and the composite hydrogel are the same.

[0023] Further, in step (2), the extrusion speeds of the sodium polyacrylate hydrogel and the composite hydrogel are both 3-15mL / h.

[0024] Further, in step (2), the coagulation bath is an aqueous solution of an organic solvent, wherein the organic solvent is selected from one or more of methanol, ethanol and propylene glycol, and the volume percentage of the organic solvent in the aqueous solution of the organic solvent is 50%-100%.

[0025] In specific embodiments, in step (2), a parallel double-needle wet spinning device is used to extrude the sodium polyacrylate hydrogel and the composite hydrogel into the coagulation bath at the same speed, to obtain a Janus hydrogel fiber.

[0026] Further, in step (3), a pre-strain of 100%-800% is applied.

[0027] Further, in step (3), the spiral diameter (outer diameter) of the Janus spiral hydrogel fiber is 1.1-11 mm.

[0028] Further, in step (4), the content of polyethyleneimine in the polyethyleneimine solution is 1-40 wt%, preferably 10-30 wt%.

[0029] Further, in step (4), the solvent of the polyethyleneimine solution is an aqueous solution of an organic solvent, the organic solvent is ethanol and / or N,N dimethylformamide (DMF), and the volume percentage of the organic solvent in the aqueous solution of the organic solvent is 50%-100%.

[0030] Further, in step (4), the doping modification is performed by selective coating.

[0031] The second aspect of the present application provides a Janus spiral thermoelectric hydrogel fiber prepared by the method of the first aspect.

[0032] The Janus spiral thermoelectric hydrogel fiber prepared by the present application can directly establish the temperature gradient along the thickness direction between the human body and the external environment without weaving as an integrated fiber-based thermoelectric device, and the fiber has the characteristics of controllable p / n pair number and adjustable diameter, and the diameter and p / n pair number of the spiral fiber can be adjusted according to actual needs. In addition, the Janus spiral hydrogel fiber with alternating p / n has excellent strain-insensitive characteristics and can maintain stable heat energy collection under dynamic stretching. In addition, the fiber can not only be used as an energy collector, but also can be used as a temperature sensor device due to its sensitive response to temperature changes.

[0033] The present application has the following advantages:

[0034] (1) The present application uses a PEI solution as an n-type dopant to modify the Janus spiral hydrogel fiber to n-type. The modified Janus spiral thermoelectric hydrogel fiber with alternating p / n realizes the series connection of multiple p / n junctions, can accurately control the formation of the p / n junction number, achieves the effect of electrical series connection and thermal parallel connection, and after integration of wearable thermoelectric devices, can construct the temperature difference between the skin and the air layer in the vertical direction when placed on the skin, and can stably output signals without stretching of the body joints, thereby collecting human heat with maximum efficiency. After n-type modification, the fiber can convert the in-plane temperature difference into an out-of-plane temperature difference, and the voltage is improved by several times. The preparation method of the Janus spiral thermoelectric hydrogel fiber provided by the present application is simple, convenient and easy to operate, the raw material cost is low and easy to obtain, and can be used for large-scale preparation.

[0035] (2) The Janus spiral thermoelectric hydrogel fiber prepared by this invention, as an integrated fiber-based thermoelectric device, can directly establish a temperature gradient along the thickness direction between the human body and the external environment without weaving. Furthermore, this fiber has controllable p / n logarithm and adjustable diameter, allowing adjustment of the spiral fiber diameter and p / n logarithm according to actual needs. Moreover, the p / n alternating Janus spiral hydrogel fiber exhibits excellent strain insensitivity, maintaining stable heat collection under dynamic stretching. In addition, this fiber can not only serve as an energy harvester but also, due to its sensitive response to temperature changes, can be used as a temperature sensor. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the preparation process of the Janus helical thermoelectric hydrogel fiber of the present invention.

[0037] Figure 2 This is a schematic diagram illustrating the preparation of the Janus hydrogel fiber of the present invention.

[0038] Figure 3 This is a diagram illustrating the formation mechanism of the Janus helical hydrogel fibers of the present invention.

[0039] Figure 4 This is a schematic diagram of n-type modification of Janus helical hydrogel fibers by selectively coating them with PEI solution.

[0040] Figure 5 The strain-resistance change rate curve of the Janus helical thermoelectric hydrogel fiber prepared in Example 1 is shown.

[0041] Figure 6 The images show physical pictures and mechanical property curves of Janus spiral hydrogel fibers with different spiral diameters; wherein, (a) is a physical picture of Janus spiral hydrogel fibers with different spiral diameters, and (b) is a mechanical property curve of Janus hydrogel fiber, Janus spiral hydrogel fiber with a spiral diameter of 5 mm in Example 1 and Janus spiral hydrogel fiber with a spiral diameter of 3 mm in Example 2.

[0042] Figure 7 The Seebeck coefficient data of Janus thermoelectric hydrogel fibers obtained by modifying Janus hydrogel fibers with different contents of PEI in Example 1 is shown in the figure.

[0043] Figure 8 The diagram shows the Janus spiral thermoelectric hydrogel fiber placed on a heating plate or arm for voltage testing; (a) shows the actual image and infrared image of the Janus spiral thermoelectric hydrogel fiber placed on the heating plate, and (b) shows the Janus spiral thermoelectric hydrogel fiber worn on the arm for voltage testing. DETAILED DESCRIPTION

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] The application will be further described with reference to the drawings and specific examples in which the application is not limited, and the examples are not to be construed as limiting the application.

[0046] The experimental methods used in the following examples are conventional methods, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0047] The application provides a preparation method of Janus spiral thermoelectric hydrogel fiber, and a preparation flowchart thereof is shown in Figure 1 The preparation method specifically comprises the following steps:

[0048] (1) dissolving sodium polyacrylate in a sodium hydroxide solution to obtain a sodium polyacrylate hydrogel; dissolving carbon nanotubes and an anionic surfactant in the sodium hydroxide solution to obtain a carbon nanotube solution, and dissolving sodium polyacrylate in the carbon nanotube solution to obtain a composite hydrogel;

[0049] (2) extruding the sodium polyacrylate hydrogel and the composite hydrogel obtained in step (1) into a coagulation bath by using a parallel double-needle wet spinning device to obtain a Janus hydrogel fiber, and a preparation schematic diagram thereof is shown in Figure 2 ;

[0050] (3) applying a pre-strain to the Janus hydrogel fiber obtained in step (2) to obtain a Janus spiral hydrogel fiber, and a formation mechanism diagram thereof is shown in Figure 3 ;

[0051] (4) doping and modifying the Janus spiral hydrogel fiber in step (3) by using a PEI solution, and a schematic diagram of n-type modification by selective coating is shown in Figure 4 , to obtain the Janus spiral thermoelectric hydrogel fiber.

[0052] The test methods of the related properties in the following examples and comparative examples are as follows:

[0053] Resistivity: The resistance of the fiber before stretching was measured by a precision LCR digital bridge (TH2832), and recorded as R0. Then the resistance of the fiber after applying 100% ~ 1500% strain was recorded as R, and the resistance change rate R / R0 under different strains was obtained.

[0054] Mechanical properties: Janus hydrogel fibers with a clamping length of 2 cm, 3 mm diameter spiral fibers and 5 mm diameter spiral fibers were prepared respectively. Tensile test was carried out by using a wing microcomputer control electronic universal material testing machine (HY-0580), and the tensile speed was 30 mm / min. The stress-strain curve of fiber tensile fracture was obtained.

[0055] Seebeck coefficient: The two ends of the thermoelectric fiber were fixed on two refrigeration sheets respectively. The refrigeration sheets were pressurized by a direct current stabilized power supply (UTP3305), so that one end was heated and the other end was cooled. The temperature difference between the two ends of the thermoelectric fiber was constructed. The thermoelectric voltage generated by the fiber was measured by means of nanovoltmeter (2182A). The corresponding voltage generated by different temperature differences was recorded, and the linear relationship between temperature difference and voltage was obtained. The slope was the Seebeck coefficient.

[0056] Electrical conductivity: The resistance R of the fiber with a length L of 1 cm was measured by a precision LCR digital bridge (TH2832), and the cross-sectional area S of the fiber was measured. The electrical conductivity was obtained by the formula L / RS.

[0057] Example 1

[0058] A preparation method of a Janus spiral thermoelectric hydrogel fiber, comprising the following steps:

[0059] (1) 0.365 g of sodium polyacrylate powder was dissolved in 10 mL of 0.2 mol / L sodium hydroxide solution. It was stirred at a rate of 450 r / min on a heating table at 80℃ for 6 h, and then centrifuged at a speed of 2000 r / min for 45 min to obtain a uniform sodium polyacrylate hydrogel. 0.073 g of single-walled carbon nanotube powder was dissolved in 10 mL of 1 mol / L sodium hydroxide solution mixed with 0.0219 g of sodium dodecyl sulfate, and placed in an ultrasonic cell crusher for ultrasonic dispersion for 50 min, with a working cycle of 3 / 5 s (on / off). Then 0.365 g of sodium polyacrylate powder was dissolved in the single-walled carbon nanotube solution after ultrasonic dispersion, and it was stirred at a rate of 450 r / min on a heating table at 80℃ for 6 h, and then centrifuged at a speed of 2000 r / min for 45 min to obtain a uniform composite hydrogel.

[0060] (2) The polyacrylic acid sodium hydrogel and the composite hydrogel obtained in step (1) are extruded into a methanol coagulation bath at a rate of 9 mL / h by using a parallel double needle wet spinning device to perform phase separation to form a Janus hydrogel fiber, and a fiber collector collects the Janus hydrogel fiber at a matching rate.

[0061] (3) The Janus hydrogel fiber obtained in step (2) is placed in an environment with an air humidity of 65% for 8 h of moisture absorption, and a pre-strain of 200% is applied to form a Janus spiral hydrogel fiber with a spiral diameter of 5 mm.

[0062] (4) PEI with a molecular weight of 600 Da is dissolved in a 50% ethanol aqueous solution to obtain a PEI solution with a PEI content of 20 wt%, and the Janus spiral hydrogel fiber in step (3) is drop-coated and doped with the PEI solution as an n-type modification dopant to obtain a 30-pair p / n alternating Janus spiral thermoelectric hydrogel fiber.

[0063] Figure 5 The strain-resistance change rate curve of the Janus spiral thermoelectric hydrogel fiber prepared in Example 1 is shown in FIG. 2, from which it can be seen that, when the spiral fiber is stretched, the resistance does not change before the fiber is straightened due to the effective dispersion of strain by the spiral structure, and the fiber exhibits a strain-insensitive property; when the strain continues to increase, the fiber changes internally, and thus the resistance increases. Figure 5

[0064] Example 2

[0065] A method for preparing a Janus spiral thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that, in step (3), the Janus hydrogel fiber obtained in step (2) is placed in an environment with an air humidity of 65% for 8 h of moisture absorption, and a pre-strain of 250% is applied to form a Janus spiral hydrogel fiber with a spiral diameter of 3 mm.

[0066] Figure 6 The actual photos and mechanical property curve of the Janus spiral hydrogel fibers with different spiral diameters; wherein (a) is the actual photo of the Janus spiral hydrogel fibers with different spiral diameters, and (b) is the mechanical property curve of the Janus hydrogel fiber, the Janus spiral hydrogel fiber with a spiral diameter of 5 mm in Example 1, and the Janus spiral hydrogel fiber with a spiral diameter of 3 mm in Example 2. From (b) in FIG. 3, it can be seen that the mechanical property of the Janus spiral hydrogel fiber is improved by an order of magnitude compared with the Janus hydrogel fiber. Figure 6

[0067] Example 3

[0068] ​​A preparation method of a Janus helical thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that in step (4), the content of PEI in the PEI solution is 5wt%.

[0069] Example 4

[0070] A preparation method of a Janus helical thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that in step (4), the content of PEI in the PEI solution is 10wt%.

[0071] Example 5

[0072] A preparation method of a Janus helical thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that in step (4), the content of PEI in the PEI solution is 30wt%.

[0073] Example 6

[0074] A preparation method of a Janus helical thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that in step (4), the content of PEI in the PEI solution is 40wt%.

[0075] Example 7

[0076] A preparation method of a Janus helical thermoelectric hydrogel fiber, comprising the following steps:

[0077] (1) 0.365 g of sodium polyacrylate powder is dissolved in 10 mL of 0.2 mol / L sodium hydroxide solution, which is stirred at a rate of 450 r / min on a heating table at 80℃ for 6 h, and then centrifuged at a speed of 2000 r / min for 45 min to obtain a uniform sodium polyacrylate hydrogel; 0.1825 g of single-walled carbon nanotube powder is dissolved in 10 mL of 1 mol / L sodium hydroxide solution mixed with 0.0548 g of sodium dodecyl sulfate, and is ultrasonically dispersed in an ultrasonic cell crusher for 50 min, with a working cycle of 3 / 5 s (on / off), then 0.365 g of sodium polyacrylate powder is dissolved in the single-walled carbon nanotube solution after ultrasonic completion, which is stirred at a rate of 450 r / min on a heating table at 80℃ for 6 h, and then centrifuged at a speed of 2000 r / min for 45 min to obtain a uniform composite hydrogel.

[0078] (2) The sodium polyacrylate hydrogel and the composite hydrogel obtained in step (1) are extruded into a methanol coagulation bath at a rate of 9 mL / h using a parallel double-needle wet spinning device to perform phase separation, forming a Janus hydrogel fiber, and a fiber collector collects the Janus hydrogel fiber at a matching rate.

[0079] (3) The Janus hydrogel fiber obtained in step (2) is placed in an environment with an air humidity of 65% to absorb moisture for 8 h, and a pre-strain of 100% is applied to form a Janus spiral hydrogel fiber with a spiral diameter of 5 mm.

[0080] (4) PEI with a molecular weight of 600 Da is dissolved in a 50% ethanol aqueous solution to obtain a PEI solution with a PEI content of 20 wt%, and the Janus spiral hydrogel fiber in step (3) is drop-coated and doped with the PEI solution as an n-type modified dopant to obtain a Janus spiral thermoelectric hydrogel fiber with 30 pairs of p / n alternation.

[0081] Comparative Example 1

[0082] A preparation method of a Janus spiral thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that in step (4), oleylamine is dissolved in a 50% ethanol aqueous solution to obtain an oleylamine solution with an oleylamine content of 20 wt%, and the Janus spiral hydrogel fiber in step (3) is drop-coated and doped with the oleylamine solution as an n-type modified dopant to obtain a Janus spiral thermoelectric hydrogel fiber with 30 pairs of p / n alternation.

[0083] Comparative Example 2

[0084] A preparation method of a Janus spiral thermoelectric hydrogel fiber, which is basically the same as the preparation method of Example 1, except that in step (4), sodium borohydride is dissolved in a 50% ethanol aqueous solution to obtain a sodium borohydride solution with a sodium borohydride content of 20 wt%, and the Janus spiral hydrogel fiber in step (3) is drop-coated and doped with the sodium borohydride solution as an n-type modified dopant to obtain a Janus spiral thermoelectric hydrogel fiber with 30 pairs of p / n alternation.

[0085] Comparative Example 3

[0086] A preparation method of a Janus spiral thermoelectric hydrogel fiber, comprising the following steps:

[0087] (1) 0.365 g of sodium polyacrylate powder is dissolved in 10 mL of 0.2 mol / L sodium hydroxide solution, which is stirred at a rate of 450 r / min on a heating table at 80℃ for 6 h, and then centrifuged at a speed of 2000 r / min for 45 min to obtain a uniform sodium polyacrylate hydrogel; 0.365 g of sodium polyacrylate powder is dissolved in 10 mL of a single-walled carbon nanotube water dispersion, which is stirred at a rate of 450 r / min on a heating table at 80℃ for 6 h, and then centrifuged at a speed of 2000 r / min for 45 min to obtain a uniform composite hydrogel.

[0088] (2) Using parallel double needle head wet spinning device, the polyacrylic acid sodium hydrogel and the composite hydrogel obtained in step (1) are extruded into a methanol coagulation bath at a rate of 9 mL / h for phase separation to form a Janus hydrogel fiber, and a fiber collector collects the Janus hydrogel fiber at a matching rate.

[0089] (3) The Janus hydrogel fiber obtained in step (2) is placed in an environment with an air humidity of 65% for 8h of moisture absorption, and a pre-strain of 200% is applied to form a Janus spiral hydrogel fiber with a spiral diameter of 5mm.

[0090] (4) PEI with a molecular weight of 600Da is dissolved in a 50% ethanol aqueous solution to obtain a PEI solution with a PEI content of 20wt%, and the Janus spiral hydrogel fiber in step (3) is drop-coated and doped with the PEI solution as an n-type modification dopant to obtain a 30-pair p / n alternating Janus spiral thermoelectric hydrogel fiber.

[0091] Test Example 1

[0092] The Janus hydrogel fiber in Example 1 is immersed in a PEI solution with different PEI contents for modification to obtain a Janus thermoelectric hydrogel fiber, and the thermoelectric properties, the Seebeck coefficient and the electrical conductivity of the Janus thermoelectric hydrogel fiber are tested, and the test results are shown in Figure 7 and Table 1, from Figure 7 As can be seen from

[0093] Table 1

[0094] PEI content Conductivity (S / m) 0 wt% 143 5 wt% 30 10 wt% 39.3 20 wt% 61 30 wt% 45.8 40 wt% 26.2

[0095] Test Example 2

[0096] The Janus spiral thermoelectric hydrogel fibers prepared in Examples 1-7 and Comparative Examples 1-3 are tested for thermoelectric properties, and the test method is to place the Janus spiral thermoelectric hydrogel fiber on a heating plate (air temperature is 20℃) or an arm at 45℃ to test the voltage generated, and the test schematic diagram is shown in Figure 8 , and the test results are shown in Table 2:

[0097] Table 2

[0098] Voltage (mV) Example 1 7.12 Example 2 4.58 Example 3 5.14 Example 4 5.87 Example 5 5.33 Example 6 4.65 Example 7 7.35 Comparative Example 1 1.33 Comparative Example 2 2.65 Comparative Example 3 3.53

[0099] As can be seen from Table 2, the helix diameter of Example 2 is reduced, and the temperature difference between the top and bottom of the coil is reduced, thus the output voltage is reduced. The data of Examples 3-6 show that too high or too low PEI content will affect the output voltage of the fiber. After mixing with low concentration PEI, a small amount of electrons is injected into the CNT, but the CNT is not completely modified, so the voltage is low. When high concentration PEI is mixed, the oily PEI wraps the CNT, affecting the transport of holes, and the output voltage is also reduced. In Example 7, the carbon nanotubes are used as thermoelectric materials in the fiber, and the Seebeck coefficient as the intrinsic parameter of the material is less affected by the content of the carbon nanotubes. However, the resistance of the fiber will decrease with the increase of the content of the carbon nanotubes. When the content of the carbon nanotubes is 20%, the resistance of the fiber is 7.9 kΩ / cm; when the content increases to 50%, the resistance decreases to 312 Ω / cm, which can improve the current and output power of the thermoelectric fiber. Comparative Example 1 uses oleylamine and Comparative Example 2 uses sodium borohydride as n-type dopant, which has no obvious modification effect. In Comparative Example 2, the Seebeck coefficient of the single-walled carbon nanotube aqueous slurry and the sodium polyacrylate wet-spun thermoelectric fiber is small, about 16 μV / K (the Seebeck coefficient of the carbon nanotube powder in Example 1 is 36 μV / K), so after being prepared into a p / n alternating Janus spiral thermoelectric hydrogel fiber, the voltage generated is also small.

[0100] As can be seen from Figure 8 Example 2, when the p / n alternating Janus spiral thermoelectric hydrogel fiber of Example 2 is placed on the skin, it can collect human body heat and generate an output voltage of 2.89 mV.

[0101] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art should understand that on the basis of the above description, other different forms of changes or variations can also be made. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A method for preparing Janus spiral thermoelectric hydrogel fibers, characterized in that, Includes the following steps: (1) Dissolve the first sodium polyacrylate in an alkaline solution to obtain sodium polyacrylate hydrogel; Carbon nanotubes and anionic surfactants are dissolved in an alkaline solution to obtain a carbon nanotube solution. Sodium polyacrylate is then dissolved in the carbon nanotube solution to obtain a composite hydrogel. (2) The sodium polyacrylate hydrogel and composite hydrogel obtained in step (1) are extruded into a coagulation bath using a wet spinning device to obtain Janus hydrogel fibers. (3) Apply pre-strain to the Janus hydrogel fiber obtained in step (2) to obtain Janus spiral hydrogel fiber; (4) The Janus spiral hydrogel fiber in step (3) is modified by doping with polyethyleneimine solution to obtain the Janus spiral thermoelectric hydrogel fiber.

2. The preparation method according to claim 1, characterized in that, In step (1), the molecular weight of the first sodium polyacrylate is 600 to 3000 million Da, and the molecular weight of the second sodium polyacrylate is 600 to 3000 million Da.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the anionic surfactant to the carbon nanotube is (0.05 to 0.5):

1.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the second sodium polyacrylate to carbon nanotubes is 1:(0.05-0.7).

5. The preparation method according to claim 1, characterized in that, In step (2), the extrusion speed of both the sodium polyacrylate hydrogel and the composite hydrogel is 3 to 15 mL / h.

6. The preparation method according to claim 1, characterized in that, In step (2), the coagulation bath is an aqueous solution of an organic solvent, which is selected from one or more of methanol, ethanol and propylene glycol.

7. The preparation method according to claim 1, characterized in that, In step (3), a pre-strain of 100% to 800% is applied.

8. The preparation method according to claim 1, characterized in that, In step (3), the helical diameter of the Janus helical hydrogel fiber is 1.1 to 11 mm.

9. The preparation method according to claim 1, characterized in that, In step (4), the content of polyethyleneimine in the polyethyleneimine solution is 1 to 40 wt%.

10. Janus spiral thermoelectric hydrogel fiber prepared by the method according to any one of claims 1 to 9.

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