Fluid power generation fiber with two-phase gradient structure, preparation method and application

Abstract

The invention discloses a fluid power generation fiber with a two-phase gradient structure and a preparation method and application thereof, and belongs to the technical field of fiber materials, the fluid power generation fiber comprises a porous network-shaped cellulose sponge layer at a core part and a carbon black nanoparticle accumulation layer located outside the core part; the cellulose sponge layer is provided with micron-sized pores, and the pores are reduced from the center to the edge; the carbon black nano-particle accumulation layer is provided with nano-scale pores; the cellulose micro-nano channels with negative charges form overlapped double electric layers, when fluid is directionally transmitted in the fiber, ions with positive charges are promoted to move to form current, and a certain potential difference is accumulated and generated, so that continuous green power generation can be realized by utilizing the interaction between the fluid and the fiber, and power can be supplied to small electronic equipment; the method is expected to play an important role in a portable wearable self-powered system.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber materials, and in particular relates to a fluid power generation fiber with a two-phase gradient structure, a preparation method and an application thereof. Background Art

[0002] Natural biomass materials such as cellulose and chitin have abundant reserves and a wide range of sources, becoming new biodegradable and renewable fiber raw materials that replace fossil raw materials. At present, there are two main methods for constructing regenerated fibers: top-down and bottom-up strategies. Top-down refers to separating and extracting nanofibrils or nanocrystals from raw materials as spinning precursors; bottom-up means dissolving natural fibers and then letting them gel to grow into fibers. The dissolution and gel process is simple, fast, and low-cost, and is a common method for constructing fiber materials.

[0003] Common fiber construction methods include dry spinning, wet spinning, microfluidic spinning, dry-jet wet spinning, etc. The fiber structure prepared by the traditional spinning process is single, and only the characteristics of the spinning raw materials themselves are used to meet the application. At present, more and more application scenarios require fibers with special structures. Microfluidic spinning technology can prepare fibers with specific structures through precise control of the spinning flow channel, giving fibers new applications in the fields of light, heat, electricity, etc.

[0004] Using the energy generated by the interaction between flowing liquids and solids, some generators, sensors and energy harvesting devices have emerged. The working mechanism of these devices mostly relies on streaming potential, that is, when the electrolyte passes through a narrow channel in a directional manner, a current is generated, and then the opposite charges at both ends of the channel continue to accumulate, generating a potential difference. For example, the volatile liquid power generation device proposed in CN 204190653U and the carbon material-based power generation device and its manufacturing method proposed in CN 105591166 B both use the interaction between fluids and carbon materials to achieve continuous high-voltage power output, but the specific device limits the use scenario. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a fluid power generation fiber with a two-phase gradient structure, wherein the fluid power generation fiber includes a porous network-like cellulose sponge layer in the core and a carbon black nanoparticle accumulation layer outside the core; the negatively charged cellulose micro-nano channels form overlapping double electric layers, and when the fluid is transmitted in a direction in the fiber, it will promote the movement of positively charged ions to form an electric current, and accumulate to generate a certain potential difference. Therefore, the interaction between the fluid and the fiber can achieve continuous green power generation, which can power small electronic devices and is expected to play an important role in portable, wearable and self-powered systems.

[0006] The present invention also provides a method for preparing a fluid power generation fiber with a two-phase gradient structure, and prepares the fluid power generation fiber with a two-phase gradient structure based on microfluidic chip technology.

[0007] The present invention also provides an application of a fluid power generation fiber with a two-phase gradient structure as a fluid power generation material. The fluid power generation fiber can generate electricity in a fluid with ionization properties and can provide power for small electronic devices.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a fluid power generation fiber with a two-phase gradient structure, which includes a porous network cellulose sponge layer in the core and a carbon black nanoparticle accumulation layer outside the core; the cellulose sponge layer has micron-scale pores, and the pores decrease from the center to the edge; the carbon black nanoparticle accumulation layer has nanoscale pores.

[0010] The diameter of the fluid power generation fiber is 150 μm to 350 μm.

[0011] The central axial fluid transmission rate of the fluid power generation fiber is 2-5 mm / s, the edge axial fluid transmission rate is 0.2-0.4 mm / s, and the radial fluid transmission rate is 0.1-0.4 mm / s.

[0012] The fluid power generation fiber can generate electricity in a fluid with ionization properties. The fluid with ionization properties is any one or more of sea water, lake water, human sweat, and salt solution.

[0013] The present invention also provides a method for preparing the fluid power generation fiber having a two-phase gradient structure, the method comprising the following steps:

[0014] S1. preparing a mixed aqueous solution Ⅰ, wherein the mixed aqueous solution Ⅰ is a mixed aqueous solution of an inorganic base and urea; the mixed aqueous solution Ⅰ is used as a solvent;

[0015] S2. preparing a mixed suspension II, wherein the mixed suspension II is a mixed suspension obtained by dispersing carbon black nanoparticles in a mixed aqueous solution I and then ball milling the mixture; the mixed suspension II is used as a sheath injection agent;

[0016] S3. preparing a mixed aqueous solution III, wherein the mixed aqueous solution III is a mixed aqueous solution of an inorganic acid and a metal salt of the inorganic acid; the mixed aqueous solution III is used as a coagulation bath;

[0017] S4. Under cooling conditions, dissolving the fiber raw material in the mixed aqueous solution I, and degassing by centrifugation to obtain solution A;

[0018] S5. Add a crosslinking agent to the solution A, cool the reaction, and centrifuge to degas to obtain a solution B;

[0019] S6. Pump solution B and mixed suspension II into the core channel and sheath channel of the microfluidic chip respectively, and then collect the outflow material in the mixed aqueous solution III, and obtain the fluid power generation fiber with a two-phase gradient structure through centrifugation, washing and drying.

[0020] In step S1, the inorganic base is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide, preferably lithium hydroxide.

[0021] In step S1, the mass percentage concentrations of the inorganic base and urea in the mixed aqueous solution I are 7-15% and 3-30%, respectively, preferably 8% and 15%, respectively.

[0022] In step S2, the mass percentage concentration of carbon black nanoparticles in the mixed suspension II is 1-2%, preferably 2%.

[0023] In step S2, the rotation speed of the ball mill is 500-800 rpm, and the ball milling time is 25-35 min.

[0024] In step S3, the inorganic acid is sulfuric acid; the metal salt of the inorganic acid is sodium sulfate; in the mixed aqueous solution III, the mass percentage concentrations of the inorganic acid and the metal salt of the inorganic acid are 5-10% and 1-5.5%, respectively, preferably 5% and 5%, respectively.

[0025] In step S4, the fiber raw material is at least one of cellulose, chitin, chitosan, and cotton linters; the mass percentage concentration of the fiber raw material in the mixed aqueous solution I is 1.0 to 5.0%, preferably 1.0 to 2.0%.

[0026] In step S4, the cooling includes cooling the solvent and the fiber raw material at a temperature of about -20 to -30°C for 2 to 5 hours, respectively, and then mixing and stirring the fiber raw material and the cooled solvent, with the stirring temperature being ≤ room temperature.

[0027] In step S5, the ratio of the solution A to the cross-linking agent is 100 g: (1.0-2.0) ml; the cross-linking agent is epichlorohydrin.

[0028] In step S5, the cooling reaction is carried out at a temperature of -10 to 0°C for 1.5 to 2 hours.

[0029] In step S6, the pumping speed of the solution B is 200-350 μL / min; the pumping speed of the mixed suspension II is 250-400 μL / min.

[0030] In step S6, the pumping speed must satisfy mixed suspension II ≥ solution B.

[0031] In step S6, the microfluidic chip includes a core channel 100, a sheath channel 200 and a mixing channel 300; the core channel 100 and the mixing channel 300 are on the same vertical line and are interconnected, and the sheath channel 200 is on a horizontal line and is arranged in a cross pattern with the core channel 100 and the mixing channel 300. Figure 3 shown.

[0032] The application of the fluid power generation fiber with a two-phase gradient structure as a fluid power generation material can be used as a fluid power generation material in small electronic devices.

[0033] The fluid power generation fiber with a two-phase gradient structure provided by the present invention comprises a porous network-like cellulose sponge layer in the core and a carbon black nanoparticle accumulation layer outside the core; the cellulose sponge layer has micron-scale pores, and the pores decrease from the center to the edge; the carbon black nanoparticle accumulation layer has nanoscale pores. Negatively charged cellulose micro-nano channels form overlapping double electric layers. When the fluid is transmitted in a directional manner in the fiber, it will promote the movement of positively charged ions to form current and accumulate a certain potential difference. Therefore, the interaction between the fluid and the fiber can achieve continuous green power generation, can power small electronic devices, and is expected to play an important role in portable wearable self-powered systems.

[0034] In the preparation method of the fluid power generation fiber with a two-phase gradient structure provided by the present invention, microfluidic technology is used for preparation. Figure 3 In the microfluidic chip shown, solution B containing fiber raw materials is pumped into the core channel 100, and mixed suspension II containing carbon black nanoparticles is pumped into the sheath channel 200, and then the two are mixed in the mixing channel 300, and then flow out to the mixed aqueous solution III for solidification, and after centrifugation, washing, and drying, a fluid power generation fiber with a two-phase gradient structure is obtained. Since the core channel and the sheath channel are interconnected, coupled with the dynamic diffusion effect, the systems in the two channels will contact each other during the spinning process, and the fiber raw material (cellulose) is wrapped and squeezed by the carbon black nanoparticles to form a relatively dense outer layer, and there is a region where cellulose and carbon black nanoparticles are closely interwoven. The oriented shearing effect makes the fibers align and grow along the extension direction of the mixing channel 300; the cellulose in the core channel is squeezed and washed by the sheath injection agent, and the pores decrease from the center to the edge, forming a gradient structure.

[0035] The fluid power generation fiber with a two-phase gradient structure provided by the present invention has a negatively charged cellulose micro-nano channel in the core and a carbon black nano channel to form an overlapping double electric layer. When one end of the fiber is immersed in the fluid, the negatively charged cellulose channel will cause the water molecules in the fluid to be ionized, and the overlapping double electron layer only allows positively charged ions to pass through. During the transmission process, the ions continuously rub against the outer carbon black nano particles to induce charge separation. The good hydrophilicity of cellulose causes water to carry positive ions and quickly transmit along the fiber axis, thereby forming a flowing current in the fiber axis. The directional movement of the ions forms an instantaneous and stable potential difference at both ends of the fiber, thereby realizing fluid power generation.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The fluid power generation fiber provided by the present invention has a novel structure. By immersing it in a fluid with ionizing properties, it can achieve green power generation and power small electronic devices. It is expected to play an important role in portable, wearable, self-powered systems.

[0038] The preparation method of the fluid power generation fiber provided by the present invention is simple, and the two-phase structure of the prepared fluid power generation fiber is controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a SEM image of the fluid power generation fiber obtained in Example 1;

[0040] Figure 2 This is a SEM image of the fluid power generation fiber obtained in Example 1;

[0041] Figure 3 The schematic diagram of the structure of the microfluidic chip used in the present invention, in which 100 is a core channel; 200 is a sheath channel; 300 is a mixing channel;

[0042] Figure 4 The electrical performance test results of the fluid power generation fiber obtained in Example 1;

[0043] Figure 5 The water transmission performance test results of the fluid power generation fiber obtained in Example 1;

[0044] Figure 6 This is a SEM image of the fluid power generation fiber obtained in Example 2;

[0045] Figure 7 This is a SEM image of the fluid power generation fiber obtained in Example 3;

[0046] Figure 8 This is the SEM image of the regenerated fiber obtained in Comparative Example 1;

[0047] Fig. 9 The strength test results of the fluid power generation fibers obtained in Examples 1 to 3 are shown;

[0048] Fig.10 This is the evaluation result of the performance of powering small electronic devices after the fluid power generation fibers are connected in series in the application example. DETAILED DESCRIPTION

[0049] The present invention is described in detail below with reference to the embodiments.

[0050] Example 1

[0051] A method for preparing a fluid power generation fiber with a two-phase gradient structure, the steps are as follows:

[0052] S1. Weigh 80 g of lithium hydroxide and 150 g of urea, add 770 mL of ultrapure water, stir and dissolve to obtain a mixed aqueous solution I;

[0053] S2. 98 g of the mixed aqueous solution Ⅰ and 2 g of carbon black nanoparticles were mixed and ball-milled at 500 rpm for 30 min to obtain a mixed suspension Ⅱ;

[0054] S3. Prepare a mixed aqueous solution of sulfuric acid and sodium sulfate to obtain a mixed aqueous solution III, wherein the concentration of sulfuric acid is 10wt%, the concentration of sodium sulfate is 5wt%;

[0055] S4. 95 g of mixed aqueous solution I and 5 g of cotton linters (natural cellulose) were placed at -25 °C and cooled for 2 h;

[0056] S5. The mixed aqueous solution Ⅰ after cooling in step S4 was mixed with cotton linters and stirred at 1500 rad / min for 5 min to obtain a transparent cellulose solution;

[0057] S6. The cellulose solution obtained in step S5 is centrifuged to obtain solution A, wherein the centrifugal speed is 8000 rad / min, the time is 10 min, and the temperature is 0°C;

[0058] S7. Add crosslinking agent epichlorohydrin to solution A at a ratio of 1.0 mL crosslinking agent / 100 g solution A, and stir on a cold well at -5 °C at a speed of 300 rad / min for 2 h;

[0059] S8. Centrifuge the mixed system obtained in step S7 to obtain solution B, wherein the centrifugal speed is 6000 rad / min, the time is 5 min, the temperature is 0°C, and then the solution B is refrigerated at 5°C;

[0060] S9. Figure 3In the microfluidic chip shown, the cooled solution B is pumped into the core channel 100 at a propulsion speed of 300 μL / min, and the mixed suspension II is pumped into the sheath channel 200 at a propulsion speed of 350 μL / min, and they are ejected from the outlet of the mixing channel 300 into the mixed aqueous solution III for solidification; the solidified material is collected by a roller, and the rotation speed of the roller is 10 rpm;

[0061] S10. The solidified material in step S9 is washed in ultrapure water until the residual acid solution is removed;

[0062] S11. Freeze the cleaned material in liquid nitrogen and freeze-dry for 3 hours to obtain the fluid power generation fiber.

[0063] The SEM image of the fluid power generation fiber obtained in this embodiment is as follows: Figures 1-2 The schematic diagram of the chip structure is shown in Figure 3 shown.

[0064] Example 2

[0065] This embodiment prepares a fluid power generation fiber, and the specific preparation process is different from that of embodiment 1 as follows:

[0066] (1) In step S4, 96 g of mixed aqueous solution I (solvent) and 4 g of cotton linters (natural cellulose) were placed at -70 °C and cooled for 2 h;

[0067] (2) In step S7, the addition ratio of the cross-linking agent epichlorohydrin is 1.5 mL of the cross-linking agent / 100 g of solution A;

[0068] (3) In step S9, the propulsion speed of the cooled solution B is 350 μL / min; the propulsion speed of the mixed suspension II is 400 μL / min.

[0069] The SEM image of the fluid power generation fiber obtained in this embodiment is as follows: Figure 6 shown.

[0070] Example 3

[0071] This embodiment prepares a fluid power generation fiber, and the specific process is different from that of embodiment 1 as follows:

[0072] (1) In step S2, 99 g of the mixed aqueous solution I and 1 g of carbon black nanoparticles were mixed and ball-milled at 500 rpm for 30 min to obtain a mixed suspension II;

[0073] (2) In step S8, the propulsion speed of the cooled solution B is 350 μL / min; the propulsion speed of the mixed suspension II is 400 μL / min.

[0074] The SEM image of the fluid power generation fiber obtained in this embodiment is as follows: Figure 7 shown.

[0075] Comparative Example 1

[0076] This comparative example prepares a regenerated fiber, which differs from Example 1 in that:

[0077] (1) In step S9, the cooled solution B is pumped into the core channel 100 at a propulsion speed of 200 μL / min, sprayed out from the outlet of the mixing channel 300, and solidified in the mixed aqueous solution III; no solution is injected into the sheath channel 200.

[0078] (2) Before step S10, the material solidified in step S9 is immediately placed in the mixed suspension II and immersed for 10 minutes, and then step S10 is performed.

[0079] The SEM image of the regenerated fiber obtained in this comparative example is as follows Figure 8 shown.

[0080] Test example

[0081] This test example tests the morphology, fluid power generation performance, water transmission rate, and fiber strength of the fibers obtained in Examples 1 to 3 and Comparative Example 1.

[0082] The morphology test is carried out with the aid of a scanning electron microscope; particle distribution software is used to calculate the diameter of the fiber on the acquired scanning electron microscope image.

[0083] Test of power generation performance: Use Keithley 2400 ammeter to obtain electrical performance data. One end of the dried fluid power generation fiber is immersed in 0.5 mol / L NaCl solution, and the other end is exposed to the air. Both ends are contacted with test electric pens coated with ink (eliminating redox reaction).

[0084] Test of water transmission rate in fiber: Use an upright fluorescence microscope to observe and photograph, drop a water solution containing fluorescent particles on the fiber, and record the process and speed of the solution transmission along the axial and radial directions of the fiber;

[0085] The test method for fiber strength is: at a temperature of 25°C and a relative humidity of 65%, a fiber mechanical properties tester is used with a test rate of 1 mm / min to perform a tensile test on the fluid power generation fiber and the regenerated fiber with a clamping length of 10 mm.

[0086] The above test results are as follows:

[0087] Morphology test results: The morphology of the fluid power generation fiber obtained in Example 1 is as follows Figures 1-2 As shown, the morphology of the fluid power generation fiber obtained in Example 2 is as follows Figure 6 As shown, the morphology of the fluid power generation fiber obtained in Example 3 is as follows Figure 7As shown; the morphology of the regenerated fiber obtained in Comparative Example 1 is as shown Figure 8 The above SEM images show that according to the preparation method provided by the present invention, the obtained fluid power generation fiber is in the form of a thin and long filament with an outer layer wrapped with carbon black nanoparticles, as shown in FIG. Figure 2 As shown; perpendicular to the fiber extension direction, there are two components with different morphology, structure and chemical composition, such as Figure 1 , 6 As shown in Figures 1 and 7, the diameters of the fluid power generation fibers are 265 μm, 310 μm, and 245 μm, respectively, including a porous network cellulose sponge layer in the center layer and an edge portion formed by the accumulation of carbon black nanoparticles in the outer layer, and the average pore size of the center portion is larger than that of the edge portion. The diameter of the regenerated fiber obtained in Comparative Example 1 is larger, as shown in Figures 2 and 3. Figure 8 As shown, the pore size of the cellulose layer inside the generated material is evenly distributed, and there is no interlaced area between carbon black and cellulose, which limits the electrical properties of the regenerated fiber and its application in the field of powering small electronic devices.

[0088] Test results of power generation performance: The test results of electrical properties of the fluid power generation fibers obtained in Examples 1 to 3 and the regenerated fibers obtained in Comparative Example 1 are shown in Table 1.

[0089] Table 1 Electrical properties of the fibers.

[0090]

[0091] Fiber strength test results: The strength test results of the fluid power generation fibers obtained in Examples 1 to 3 are shown in the figure below: Fig. 9 As shown, the strength range is 17.62~26.78MPa.

[0092] Test results of water transmission rate in fibers: The test results of water transmission rate of the fluid power generation fibers obtained in Examples 1 to 3 and the regenerated fibers obtained in Comparative Example 1 are shown in Table 2.

[0093] Table 2 Water transmission rate in fibers

[0094]

[0095]

[0096] The water transport performance test results of the fluid power generation fiber obtained in Example 1 are as follows: Figure 5 shown.

[0097] As can be seen from Table 2, the water transmission rate of the central axial direction of the fluid power generation fiber prepared by the present invention is 2-5 mm / s, the water transmission rate of the edge axial direction is 0.2-0.4 mm / s, and the water transmission rate of the radial direction is 0.1-0.4 mm / s. It can be seen that after one end of the fluid power generation fiber prepared by the present invention is immersed in the fluid, the fluid can not only be directional transmitted along the axial direction of the fiber, but also there is radial liquid diffusion during the transmission process. The negatively charged cellulose channel can fully promote the ionization of the fluid water molecules, and the overlapping double electron layer only allows positively charged ions to pass through. During the transmission process, the ions are constantly rubbed with the outer carbon black nanoparticles to induce charge separation. The good hydrophilicity of cellulose promotes the rapid transmission of water along the fiber axis with positive ions, and then forms a flowing current in the fiber axis. The directional movement of ions forms an instantaneous and stable potential difference at both ends of the fiber, realizing fluid power generation. However, the regenerated fiber prepared in Comparative Example 1 has a larger diameter and uniform internal pores, so the liquid is only transmitted along the fiber axis. The larger liquid flux slows down the liquid transmission speed, and the fluid power generation performance is reduced.

[0098] Application Examples

[0099] The fluid power generation fiber prepared in Example 1 was connected in series with conductive glue and wires to an LED display screen to power small electronic devices. The electrical signal test data is as follows: Fig.10 The results show that the fluid power generation fiber provided by the present invention has excellent fluid power generation performance. When the number of series connection is six, the open circuit voltage and short circuit current are 3.12V and 3.13μA respectively, which can power commercial LED display screens.

[0100] By comparison, the regenerated fibers obtained in Comparative Example 1, under the same test conditions, have inferior fluid power generation performance to the fluid power generation fibers provided by the present invention (Table 1). This indicates that the fluid power generation fibers provided by the present invention, due to their special structure, are more suitable for realizing continuous power generation by utilizing the interaction between liquid and fiber, and have broad application prospects in the field of powering small electronic devices.

[0101] The above-mentioned detailed description of a fluid power generation fiber with a two-phase gradient structure, its preparation method and application with reference to the embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A fluid power generation fiber with a two-phase gradient structure, characterized in that: The fluid power generation fiber includes a porous network cellulose sponge layer in the core and a carbon black nanoparticle accumulation layer outside the core; the cellulose sponge layer has micron-scale pores, and the pores decrease from the center to the edge; the carbon black nanoparticle accumulation layer has nanoscale pores.

2. The fluid power generation fiber according to claim 1, characterized in that: The diameter of the fluid power generation fiber is 150 μm to 350 μm.

3. The fluid power generation fiber according to claim 1, characterized in that: The central axial fluid transmission rate of the fluid power generation fiber is 2-5 mm / s, the edge axial fluid transmission rate is 0.2-0.4 mm / s, and the radial fluid transmission rate is 0.1-0.4 mm / s.

4. The fluid power generation fiber according to claim 1, characterized in that: The fluid power generation fiber can generate electricity in a fluid with ionization properties.

5. The method for preparing a fluid power generation fiber having a two-phase gradient structure according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: S1. preparing a mixed aqueous solution Ⅰ, wherein the mixed aqueous solution Ⅰ is a mixed aqueous solution of an inorganic base and urea; S2. preparing a mixed suspension II, wherein the mixed suspension II is a mixed suspension obtained by dispersing carbon black nanoparticles in a mixed aqueous solution I and then ball milling; S3. Preparing a mixed aqueous solution III, wherein the mixed aqueous solution III is a mixed aqueous solution of an inorganic acid and a metal salt of the inorganic acid; S4. Under cooling conditions, dissolving the fiber raw material in the mixed aqueous solution I, and degassing by centrifugation to obtain solution A; S5. Add a crosslinking agent to the solution A, cool the reaction, and centrifuge to degas to obtain a solution B; S6. Pump solution B and mixed suspension II into the core channel and sheath channel of the microfluidic chip respectively, and then collect the outflow material in the mixed aqueous solution III, and obtain the fluid power generation fiber with a two-phase gradient structure through centrifugation, washing and drying.

6. The preparation method according to claim 5, characterized in that: The inorganic base is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide; the mass percentage concentration of the inorganic base and urea in the mixed aqueous solution I is 7-15% and 3-30% respectively; in the mixed suspension II, the mass percentage concentration of the carbon black nanoparticles is 1-2%.

7. The preparation method according to claim 5, characterized in that: In step S3, the inorganic acid is sulfuric acid; the metal salt of the inorganic acid is sodium sulfate; in the mixed aqueous solution III, the mass percentage concentrations of the inorganic acid and the metal salt of the inorganic acid are 5-10% and 1-5.5%, respectively.

8. The preparation method according to claim 5, characterized in that: In step S4, the fiber raw material is at least one of cellulose, chitin, chitosan, and cotton linters; and the mass percentage concentration of the fiber raw material in the mixed aqueous solution I is 3.0-5.0 wt%.

9. The preparation method according to claim 5, characterized in that: In step S5, the ratio of the solution A to the cross-linking agent is 100 g: (1.0-2.0) ml; the cross-linking agent is epichlorohydrin.

10. Use of the fluid power generation fiber with a two-phase gradient structure as claimed in any one of claims 1 to 4 as a fluid power generation material.

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