Multifunctional hydrogel and preparation method thereof

Abstract

The application provides a multifunctional hydrogel and a preparation method thereof, and the preparation method comprises the following steps: (1) preparing a transparent conductive film on a silica gel substrate to form a transparent conductive film layer; (2) contacting the transparent conductive film layer with a mixed solution, then sequentially performing fermentation and freeze-thaw treatment on the mixed solution, and solidifying the mixed solution to form a hydrogel layer; and (3) peeling off the silica gel substrate; in the step (2), when the mixed solution comprises a carbon-based material, polyvinyl alcohol, glucose, water and yeast, a carbon-based material-PVA / transparent electrode composite hydrogel structure is obtained after the silica gel substrate is peeled off; and when the mixed solution comprises polyvinyl alcohol, glucose, water and yeast, a PVA / transparent electrode composite hydrogel structure is obtained after the silica gel substrate is peeled off. The application develops a multifunctional, flexible and transparent composite hydrogel structure which has the advantages of simple process, strong designability of patterns and the simultaneous realization of efficient interface water evaporation and friction power generation, and has important significance for expanding the integrated application of energy conversion and heat management systems.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically providing a multifunctional hydrogel and its preparation method. Background Technology

[0002] With the increasing demand for sustainable energy solutions, interfacial photothermal evaporation technology has attracted much attention due to its potential for low energy consumption and high efficiency in fields such as seawater desalination and wastewater treatment. Meanwhile, triboelectric nanogenerator (TENG), as an emerging method of mechanical energy harvesting, shows great promise for self-powered sensing systems and wearable electronic devices because it can convert low-frequency, irregular mechanical energy in the environment into electrical energy.

[0003] Current technologies still have certain shortcomings. On the one hand, traditional hydrogel-structured interfacial water evaporation devices have poor performance, and the temperature difference relies solely on solar energy for heat generation. On the other hand, although triboelectric nanogenerators have made some progress in flexibility and transparency, their triboelectric layer materials often need to balance good triboelectric properties with mechanical properties, and commonly used materials are prone to wear during long-term use. In addition, current technologies lack a technical solution that can seamlessly integrate efficient interfacial water evaporation and stable triboelectric nanogenerator capabilities onto a single flexible and transparent platform. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in the prior art. Therefore, one objective of this invention is to propose a multifunctional hydrogel and its preparation method to address the poor performance of existing interfacial water evaporation devices and the inability to balance the electrical and mechanical properties of triboelectric nanogenerators, while simultaneously achieving efficient fabrication of evaporation devices or triboelectric generators.

[0005] In a first aspect, the present invention provides a method for preparing a multifunctional hydrogel, comprising:

[0006] (1) A transparent conductive film is prepared on a silicone substrate to form a transparent conductive film layer;

[0007] (2) The transparent conductive film layer is brought into contact with the mixture, and then the mixture is subjected to fermentation and freeze-thaw treatment in sequence, and the mixture is solidified to form a hydrogel layer;

[0008] (3) Peel off the silicone substrate;

[0009] In step (2), when the mixture includes carbon-based materials, polyvinyl alcohol, glucose, water and yeast, the carbon-based material-PVA / transparent electrode composite hydrogel structure is obtained after the silicone substrate is peeled off.

[0010] When the mixture includes polyvinyl alcohol, glucose, water and yeast, a PVA / transparent electrode composite hydrogel structure is obtained after peeling off the silicone substrate.

[0011] The preparation method provided by this invention first prepares a transparent conductive film (such as silver nanowires) on silica gel, and then coats it with a polymer composite material (carbon-based material - PVA or PVA) using nanoimprinting technology. The polymer composite material is then cured through fermentation, refrigeration, and freeze-thaw processes to form a hydrogel. Finally, the hydrogel / transparent electrode composite structure is obtained by peeling. The transparent electrode of this device can be led out. When water evaporates at the interface, the transparent electrode layer generates Joule heat when energized. Combined with the patterned surface, the specific surface area is increased, significantly improving the evaporation efficiency. When this film is used in a triboelectric nanogenerator, the PVA hydrogel acts as a positive friction layer, exhibiting excellent flexibility and surface friction. This invention has a simple process, strong pattern designability, and the resulting device combines transparency, flexibility, and multifunctionality, showing broad prospects in the fields of energy conversion and thermal management.

[0012] In some embodiments of the present invention, in step (1), the material of the transparent conductive film includes silver nanowires, carbon nanotubes, graphene, silver nanoparticles, copper nanowires, or copper nanoparticles.

[0013] In some embodiments of the present invention, in step (1), the method of preparing the transparent conductive film on the silicone substrate includes at least one of spin coating and spray coating.

[0014] The transparent conductive film is fitted to the shape of the silicone; see reference for details. Figure 1 The structure can be a regular concave-convex structure, or other structures can be used. The specific structure is determined by those skilled in the art based on the actual principle. Next, by transferring the pattern of the silicone and the transparent conductive film on it onto the hydrogel, in principle, within a fixed horizontal area, the pattern can increase the specific surface area, thereby increasing the contact area between the evaporation layer and the air. The larger the contact area, the more it helps to increase the evaporation area of ​​water.

[0015] Those skilled in the art will understand that the specific distribution of the transparent conductive film and hydrogel is limited by the shape of the silicone. Therefore, those skilled in the art can set different silicone shapes to obtain different distribution methods on the surface of the transparent conductive film / hydrogel.

[0016] Furthermore, a suitable patterned substrate is selected and the surface pattern is transferred onto the silicone, thereby enabling the preparation of different silicone materials through the substrate.

[0017] In some embodiments of the present invention, the ratio of silicone to curing agent is 10:1, and then the silicone is heated and cured before being peeled off from the pattern substrate.

[0018] In some embodiments of the present invention, in step (2), the fermentation temperature is 40-48°C, and the fermentation time is 1.5-3 hours. Controlling the fermentation temperature and time within the above range can effectively improve fermentation efficiency, promote the metabolic activity of beneficial microorganisms or enzymes, and achieve full fermentation in a shorter time.

[0019] In some embodiments of the present invention, step (2) includes freezing and thawing.

[0020] The crosslinking structure and mechanical properties of carbon-based material-PVA hydrogel or PVA / transparent electrode composite hydrogel were regulated by fermentation and freeze-thaw treatment.

[0021] In some embodiments of the present invention, in step (2), the freezing temperature is -25℃ to -15℃ and the freezing time is 10-15h.

[0022] In some embodiments of the present invention, the thawing temperature is room temperature and the thawing time is 1-3 hours.

[0023] In some embodiments of the present invention, the freezing and thawing cycles are repeated 2-4 times.

[0024] In some embodiments of the present invention, the carbon-based material includes carbon nanotubes or graphene.

[0025] In some embodiments of the present invention, the number-average molecular weight of the polyvinyl alcohol is 1700-1800.

[0026] In some embodiments of the present invention, in step (2), when the mixture includes carbon-based material, polyvinyl alcohol, glucose, water and yeast, the mass ratio of the carbon-based material, the polyvinyl alcohol, the glucose and the water is 5: (80-120): (8-12): (350-450).

[0027] In some embodiments of the present invention, in step (2), the other components of the mixture except for the yeast are placed in a heat-collecting constant temperature magnetic stirrer and stirred for a certain period of time to ensure that the components are fully dissolved and mixed evenly. After cooling, the yeast is added.

[0028] In some embodiments of the present invention, in step (2), when the mixture includes polyvinyl alcohol, glucose, water and yeast, the mass ratio of the polyvinyl alcohol, the glucose and the water is (80-120):(8-12):(350-450).

[0029] In some embodiments of the present invention, the yeast in the mixture has a mass fraction of 0.1-3%.

[0030] In a second aspect, the present invention proposes a carbon-based material-PVA / transparent electrode composite hydrogel structure, which is prepared by the above method.

[0031] In a third aspect, the present invention proposes a PVA / transparent electrode composite hydrogel structure, which is prepared by the above method.

[0032] In a fourth aspect, the present invention provides an interfacial water evaporation device comprising the aforementioned carbon-based material-PVA / transparent electrode composite hydrogel structure. The interfacial water evaporation device further comprises positive and negative electrodes, preferably having at least two lead-out points located at the edge of the pattern of the transparent conductive thin film layer.

[0033] Electrothermal Joule heating is applied to a carbon-based material-PVA / transparent electrode composite hydrogel structure to preheat the surface and create a temperature difference while increasing the specific surface area for interfacial water evaporation. Compared to traditional interfacial water evaporation devices, the interfacial water evaporation device of this invention has two advantages: First, it can generate heat through electro-excitation, improving the performance of interfacial water evaporation while simultaneously generating heat through solar irradiation. Second, it increases the specific surface area of ​​the device through pattern transfer, thereby enhancing its water vapor dissipation.

[0034] In a fifth aspect, the present invention provides a triboelectric nanogenerator comprising the aforementioned PVA / transparent electrode composite hydrogel structure. The triboelectric nanogenerator further comprises electrodes, preferably having at least one electrode lead-out point located at the edge of the pattern of the transparent conductive thin film layer.

[0035] PVA hydrogel is used as the positive friction layer and assembled with the negative friction layer material to form a triboelectric nanogenerator. The PVA hydrogel as the positive friction layer has excellent flexibility and surface friction, thereby improving the mechanical and electrical performance of the generator and further extending its service life.

[0036] The electrodes drawn out from the positive and negative friction layers are connected to the energy storage device through a circuit to form an integrated structure device for power generation, energy storage and application.

[0037] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0038] This invention achieves the preparation of composite thin films with both efficient interfacial water evaporation and stable triboelectric nano-power generation functions on the same platform through a set of patterned transfer and peeling processes. It has the advantages of simple process, strong pattern designability, transparent and flexible device and low cost.

[0039] The method of this invention achieves improved device performance at a low cost. Furthermore, the introduction of surface patterns using nanoimprint technology is simple, easy to operate, and significantly enhances device performance. In interfacial water evaporation devices, adding a transparent conductive thin film layer enables electrothermal assistance. In the field of triboelectric nanogenerators, hydrogel technology further enhances flexibility while maintaining self-heating capabilities. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the fabrication process of the interfacial water evaporation device in Embodiment 1 of the present invention;

[0041] Figure 2 This is a schematic diagram of the fabrication process of the triboelectric nanogenerator in Example 2 of the present invention;

[0042] Figure 3 This is a SEM image of the patterned surface of the AgNWs / PVA composite structure in an embodiment of the present invention. Detailed Implementation

[0043] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0044] Example 1

[0045] This embodiment provides an interfacial water evaporation device with a CNTs-PVA / AgNWs composite hydrogel structure, which can be referenced. Figure 1 The specific preparation process is as follows:

[0046] (1) Select a patterned substrate with the target micro / nano pattern, such as Figure 1 As shown in A;

[0047] (2) Mix PDMS prepolymer and curing agent uniformly at a mass ratio of 10:1, pour onto a patterned substrate, heat to cure, and then peel off to obtain a patterned silicone mold, such as Figure 1 As shown in B and C;

[0048] (3) A transparent conductive film of silver nanowires (AgNWs) was prepared on the patterned surface of the obtained patterned silicone mold by spin coating. The spin coating speed was controlled at 1000 rpm and the time was 30 s. Annealing was then performed to enhance conductivity. Figure 1 As shown in D;

[0049] (4) According to the mass fraction of 5:100:10:400 (CNTs:PVA:glucose:deionized water), carbon nanotubes, polyvinyl alcohol (molecular weight 1700-1800), glucose and deionized water are placed in a heat-collecting constant temperature magnetic stirrer and stirred and heated at 90°C for 2 hours to fully dissolve and mix the components.

[0050] (5) After the above solution cools to 30°C, add 1% yeast by mass and stir well. Then, cast the resulting liquid CNTs-PVA composite material onto a patterned silicone mold with a transparent conductive layer of silver nanowires, as shown below. Figure 1 As shown in E;

[0051] (6) Ferment the sample in a constant temperature chamber at 45℃ for 2 hours to allow the yeast to produce gas and form a porous structure;

[0052] (7) Place the fermented sample in a -20℃ freezer for 12 hours, then thaw it at room temperature for 2 hours. Repeat this freeze-thaw cycle 3 times to solidify the PVA into a stable hydrogel.

[0053] (8) The cured CNTs-PVA hydrogel, along with the silver nanowire film at its bottom, was peeled off from the silicone mold as a whole to obtain a patterned CNTs-PVA / transparent electrode composite hydrogel structure. Its surface morphology is complementary to the patterned structure of the silicone mold, such as... Figure 1 As shown in F;

[0054] (9) Introduce two positive and negative electrode lead-out points at the edge of the transparent electrode pattern of the obtained composite film;

[0055] (10) Connect the positive and negative electrodes to an external DC power supply via wires, such as Figure 1 As shown in G.

[0056] After the power is turned on, the carbon nanotube network in the CNTs-PVA layer generates Joule heat under the action of current. Combined with the huge specific surface area provided by the patterned surface, it realizes the rapid evaporation of interfacial water. The Joule heat power is controlled by adjusting the input voltage, thereby regulating the evaporation rate. This forms a highly efficient water evaporation structure device that integrates electrothermal and solar energy interfacial evaporation.

[0057] The evaporation performance of the vapor device was studied by using only the hydrogel layer in the CNTs-PVA / transparent electrode composite hydrogel structure of Example 1, i.e. without the silver nanowire film. The results showed that the device of Example 1 of the present invention improved the evaporation rate of water by 7%-8% compared with the device without the silver nanowire film.

[0058] Example 2

[0059] This embodiment provides a triboelectric nanogenerator based on a PVA / transparent electrode composite hydrogel structure. The specific fabrication process is as follows, which can be referred to... Figure 2 :

[0060] (1) Select a patterned substrate with the target micro / nano pattern, such as Figure 2 As shown in A;

[0061] (2) Mix PDMS prepolymer and curing agent uniformly at a mass ratio of 10:1, pour onto a patterned substrate, heat to cure, and then peel off to obtain a patterned silicone mold, such as Figure 2 As shown in B and C;

[0062] (3) On the patterned surface of the obtained patterned silicone mold, a transparent conductive film of silver nanowires (AgNWs) was prepared by spin coating. The spin coating speed was controlled at 1500 rpm and the time was 30 s to form a transparent conductive layer, such as... Figure 2 As shown in D;

[0063] (4) Add polyvinyl alcohol and glucose to deionized water in a mass fraction ratio of 10:40:1 (PVA: deionized water: glucose), place them in a heat-collecting constant temperature magnetic stirrer and stir and heat at 90°C for 2 hours to fully dissolve PVA;

[0064] (5) After the solution cools to 30°C, add 1% yeast by mass and stir well. Then, cast the resulting liquid PVA-based composite material onto a patterned silicone mold with a pre-prepared transparent conductive layer of silver nanowires, such as... Figure 2 As shown in E;

[0065] (6) Ferment the sample in a constant temperature chamber at 40℃ for 2 hours to allow the yeast to produce gas and form a porous structure, thereby increasing the surface roughness;

[0066] (7) Place the fermented sample in a -20℃ freezer for 12 hours, then thaw it at room temperature for 2 hours. Repeat this freeze-thaw cycle 3 times to solidify the PVA into a stable hydrogel.

[0067] (8) The cured PVA hydrogel, along with the silver nanowire film at its bottom, is peeled off from the silicone mold as a whole to obtain a patterned PVA / AgNWs composite hydrogel structure, which serves as a positive friction layer. Its surface morphology is complementary to the patterned structure of the silicone mold, such as... Figure 2 As shown in F;

[0068] (9) The electrodes are drawn out to form the positive friction layer of a wearable flexible transparent triboelectric nanogenerator, such as Figure 2 As shown in G.

[0069] SEM images of the patterned surface of the AgNWs / PVA composite structure prepared by this invention are shown below. Figure 3 As shown.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a multifunctional hydrogel, characterized in that, include: (1) A transparent conductive film is prepared on a silicone substrate to form a transparent conductive film layer; (2) The transparent conductive film layer is brought into contact with the mixture, and then the mixture is subjected to fermentation and freeze-thaw treatment in sequence, and the mixture is solidified to form a hydrogel layer; (3) Peel off the silicone substrate; In step (2), when the mixture includes carbon-based materials, polyvinyl alcohol, glucose, water and yeast, the carbon-based material-PVA / transparent electrode composite hydrogel structure is obtained after the silicone substrate is peeled off. When the mixture includes polyvinyl alcohol, glucose, water and yeast, the silicone substrate is peeled off to obtain a PVA / transparent electrode composite hydrogel structure.

2. The method according to claim 1, characterized in that, In step (1), the material of the transparent conductive film includes silver nanowires, carbon nanotubes, graphene, silver nanoparticles, copper nanowires, or copper nanoparticles. And / or, the transparent conductive film is prepared on the silicone substrate by at least one of spin coating and spray coating.

3. The method according to claim 1, characterized in that, In step (2), the fermentation temperature is 40-48℃ and the fermentation time is 1.5h-3h; And / or, the freeze-thaw process includes freezing and thawing.

4. The method according to claim 3, characterized in that, In step (2), the freezing temperature is -25℃ to -15℃, and the freezing time is 10-15h; And / or, the thawing temperature is room temperature, and the thawing time is 1-3 hours; And / or, the freezing and thawing cycles are repeated 2-4 times.

5. The method according to claim 1, characterized in that, The carbon-based material includes carbon nanotubes or graphene; And / or, the number average molecular weight of the polyvinyl alcohol is 1700-1800.

6. The method according to any one of claims 1-5, characterized in that, In step (2), when the mixture includes carbon-based material, polyvinyl alcohol, glucose, water and yeast, the mass ratio of the carbon-based material, the polyvinyl alcohol, the glucose and the water is 5:(80-120):(8-12):(350-450). In step (2), when the mixture includes polyvinyl alcohol, glucose, water and yeast, the mass ratio of polyvinyl alcohol, glucose and water is (80-120):(8-12):(350-450). And / or, in the mixture, the mass fraction of the yeast is 0.1-3%.

7. A carbon-based material-PVA / transparent electrode composite hydrogel structure, characterized in that, It is prepared by any one of the methods described in claims 1-6.

8. A PVA / transparent electrode composite hydrogel structure, characterized in that, It is prepared by any one of the methods described in claims 1-6.

9. An interfacial water evaporation device, characterized in that, Includes the carbon-based material-PVA / transparent electrode composite hydrogel structure as described in claim 7; The interface water evaporation device further includes positive and negative electrodes, preferably with at least two lead-out points located at the edge of the pattern of the transparent conductive thin film layer.

10. A triboelectric nanogenerator, characterized in that, Includes the PVA / transparent electrode composite hydrogel structure as described in claim 8; The triboelectric nanogenerator also includes electrodes, preferably having at least one electrode lead-out point located at the edge of the pattern of the transparent conductive thin film layer.

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