Preparation method and application of a self-powered device based on reduced graphene oxide / polydopamine self-healing hydrogel

Abstract

The present invention belongs to the field of energy harvesting, and discloses a preparation method and application of a self-powered device based on reduced graphene oxide / polydopamine self-healing hydrogel. The power generation device uses a reduced graphene oxide / polydopamine composite hydrogel with self-healing properties to achieve energy conversion. When the hydrogel contains a sodium chloride solution and undergoes mechanical deformation under an external force, the hydrogel self-powered device can generate an ionic current. The self-powered device connects metal copper sheets to both ends of the hydrogel containing the sodium chloride solution as electrodes, and is encapsulated with polydimethylsiloxane. When the hydrogel in the self-powered device is subjected to an external pressure, a current can be output. The present invention can be used for collecting various forms of mechanical energy around the human body and converting it into electrical energy for driving wearable electronic devices. The device of the present invention is simple to manufacture, and the materials used have good biocompatibility. It can convert mechanical energy under external pressure into electrical energy and has a wide range of applications in flexible electronic devices.

Description

Technical Field

[0001] The present invention belongs to the field of energy harvesting, and particularly relates to a preparation method and application of a self-powered device based on reduced graphene oxide / polydopamine self-healing hydrogel. Background Art

[0002] Flexible and wearable electronic devices have attracted considerable interest in human physiological activity monitoring and personal health management due to their ability to continuously, long-term, real-time, and comfortably monitor physiological and biochemical signals. To achieve continuous and long-term monitoring performance, wearable electronic devices require a long-life and reliable power source as a driving power supply. So far, most wearable devices are powered by batteries. However, traditional batteries that require regular charging and eventual replacement exhibit lifespan limitations, single-use problems, and safety issues. Therefore, the development of sustainable and flexible power generation devices is urgently needed.

[0003] In recent years, a series of advanced self-powered technologies such as piezoelectric nanogenerators, triboelectric nanogenerators, and nanofluidic generators have been developed. With these technologies, various forms of energy around the human body can be harvested and converted into electrical energy for driving wearable electronic devices. Some flexible conductive polymer hydrogels have been used in these self-powered technologies, and graphene-based hydrogels have better conductivity and great application potential in self-powered devices. A nanofluidic generator based on a graphene hydrogel film reported currently consists of a layered graphene hydrogel film obtained by vacuum filtering a graphene dispersion placed in a container filled with sodium chloride solution. Although this device has a certain current output, the graphene sheets in the used graphene hydrogel film are only simply stacked, with weak interaction forces, poor stability in solution, and easy to break, affecting the device lifespan. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a self-powered device based on reduced graphene oxide / polydopamine self-healing hydrogel and a preparation method thereof. Based on the self-polymerization reaction of dopamine (DA) and the reduction self-assembly of graphene oxide (GO), reduced graphene oxide / polydopamine hydrogel is obtained. The hydrogel is filled with sodium chloride solution inside and connected to a copper electrode to form a flexible self-powered device. The materials used have good current output and self-healing characteristics.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A preparation method of a self-powered device based on reduced graphene oxide / polydopamine self-healing hydrogel includes the following steps:

[0007] S1. Prepare reduced graphene oxide / polydopamine hydrogel through a hydrothermal reduction reaction;

[0008] Graphene oxide (GO) was added to deionized water and ultrasonically dispersed to prepare a graphene oxide suspension;

[0009] A dopamine hydrochloride solution and a tris-HCl buffer solution were respectively prepared, and then the pH of the dopamine hydrochloride solution was adjusted with the tris-HCl buffer solution to oxidize and self-polymerize the dopamine hydrochloride solution into a polydopamine solution;

[0010] Finally, the polydopamine solution was mixed with the graphene oxide suspension. The mixed solution was sealed in a glass test tube and heated in a water bath to obtain a reduced graphene oxide / polydopamine hydrogel. In this process, the graphene oxide was reduced by dopamine to become reduced graphene oxide (rGO). The prepared hydrogel was dialyzed with deionized water for purification to remove the remaining impurities, and then soaked in an NaCl solution;

[0011] S2. The reduced graphene oxide / polydopamine hydrogel after being soaked in step S1 was fixed between two copper electrodes and then connected with wires;

[0012] S3. The assembled reduced graphene oxide / polydopamine hydrogel was encapsulated to obtain a self-powered hydrogel device.

[0013] In step S1,

[0014] The ultrasonic time was 30 min and the ultrasonic power was 300 W; the concentration of the graphene oxide suspension was 3 - 5 mg / mL.

[0015] The concentration of the dopamine hydrochloride solution was 3 - 5 mg / mL, the concentration of the tris-HCl buffer solution was 10 mmol / L; the pH was adjusted to 8.0.

[0016] The volume ratio of the polydopamine solution to the graphene oxide suspension was 8:10.

[0017] The temperature of the water bath heating was 80 °C and the time was 8 - 12 h.

[0018] The dialysis time was 48 h.

[0019] The concentration of the NaCl solution was 0.1 mol / L, the soaking temperature was room temperature, and the soaking time was 24 h.

[0020] In step S3, the reduced graphene oxide / polydopamine hydrogel and the copper electrode were encapsulated with polydimethylsiloxane PDMS.

[0021] Application of the self-healing hydrogel self-powered device based on reduced graphene oxide / polydopamine prepared by the present invention in flexible electronic devices.

[0022] The generation mechanism of the present invention is as follows:

[0023] Since the surface of reduced graphene oxide (rGO) contains fixed immobile negatively charged functional groups, the channels of the hydrogel are filled with sodium chloride solution. Cations in the solution are attracted to the surface of negatively charged reduced graphene oxide (rGO) due to electrostatic force, forming an electric double layer, while anions move in the solution under the action of external force. The power-generating hydrogel can be regarded as a charge filter to separate cations and anions. When pressure is applied to the hydrogel, the deformation of the hydrogel causes the liquid in its nanochannels to flow. The liquid flow drives the mobile negative ions to migrate through the hydrogel channels, forming a net ionic current, and an ionic current of corresponding magnitude can be generated according to the magnitude of the external force.

[0024] The beneficial effects of the present invention are as follows:

[0025] (1) The rGO nanosheets inside the reduced graphene oxide / polydopamine hydrogel of the present invention form a three-dimensional porous structure through crosslinking to achieve the cross-transport of water and ions in the pores, and polydopamine endows the hydrogel with the property of rapid self-healing.

[0026] (2) A self-powered device based on the reduced graphene oxide / polydopamine self-healing hydrogel of this patent utilizes the anisotropic three-dimensional continuous microchannel structure of the hydrogel. Based on the streaming potential theory, a large streaming current is obtained by driving the ions in the liquid to flow in the hydrogel by external force, realizing the conversion of mechanical energy in the surrounding environment into electrical energy. Description of the Drawings

[0027] Figure 1 It is the preparation flow chart of the hydrogel of the present invention;

[0028] Figure 2 It is the schematic diagram of the principle of hydrogel power generation of the present invention;

[0029] Figure 3 It is the schematic assembly diagram of the hydrogel power generation device of the present invention;

[0030] Figure 4 It is the scanning electron micrograph of the hydrogel of the present invention;

[0031] Figure 5 It is the I-V diagram of the hydrogel of the present invention before and after self-healing;

[0032] Figure 6 It is the curve graph of the current change generated by the hydrogel power generation device of the present invention under different external forces. Detailed Embodiments

[0033] The present invention will be further described below in conjunction with the drawings and specific embodiments, but the protection scope of the present invention is not limited thereto. Example 1

[0034] As Figure 1 shown, reduced graphene oxide / polydopamine hydrogel was prepared.

[0035] 10 ml of graphene oxide (GO) suspension with a concentration of 5 mg / ml was prepared, and the graphene oxide (GO) suspension was ultrasonicated for 30 min. 10 mmol / L tris-HCl buffer solution was prepared, and 8 ml of dopamine hydrochloride solution with a concentration of 3 mg / ml was prepared. When the pH was adjusted to about 8.0, the graphene oxide (GO) suspension and the dopamine hydrochloride solution were mixed and heated in a water bath at 80 °C for 8 h to obtain reduced graphene oxide / polydopamine hydrogel. The prepared hydrogel was dialyzed with deionized water for 2 days for purification to remove the remaining impurities in the hydrogel. Then the hydrogel was immersed in 0.1 mol / L sodium chloride solution for 1 day and taken out for standby.

[0036] As Figure 2 shown, the working principle of the self-powered hydrogel device. The channels of the reduced graphene oxide / polydopamine hydrogel are filled with sodium chloride solution. Cations in the sodium chloride solution are attracted to the surface of negatively charged reduced graphene oxide (rGO) due to electrostatic force to form an electric double layer, while anions migrate in the solution with the fluid flow caused by external force to form a net ionic current.

[0037] As Figure 3 shown, the assembly schematic diagram of the self-powered hydrogel device. The reduced graphene oxide / polydopamine hydrogel was made into a block with a specification of 10 mm×7 mm×5 mm, and the hydrogel was fixed between two copper electrodes. The copper electrode specifications were 7 mm×5 mm×1.5 mm, and the resistivity was <0.018 Ω·mm 2 / m.

[0038] As Figure 3 shown, further, the copper electrodes and the hydrogel between them were encapsulated with polydimethylsiloxane (PDMS) to complete the assembly of the device.

[0039] Furthermore, when the hydrogel was cut into two pieces and then contacted with each other, it could self-heal into a whole, and the shapes of the I-V curves before and after healing were almost the same. During the repeated cutting and healing process, the reduced graphene oxide / polydopamine hydrogel showed good self-healing ability.

[0040] Connect the assembled devices in series and connect them to a high-precision source meter with copper wires to form a loop for testing the power generation ability. When there is no external force on the self-powered hydrogel device, the source meter does not detect any current generation. When a pressure of 2 g is applied to the hydrogel device, an ionic current of 0.4 μA can be generated instantaneously by the hydrogel device; when the external force is removed, the current returns to zero again. When a pressure of 5 g is applied to the hydrogel device, an ionic current of 0.8 μA can be generated instantaneously, and the current returns to zero after the external force is removed. During the repeated pressing of the hydrogel device, the device exhibits good current output characteristics. Example 2

[0041] This example is basically the same as Example 1, except that:

[0042] When preparing the mixed solution, the concentration of the dopamine hydrochloride solution is 4 mg / ml, and the concentration of the graphene oxide (GO) suspension is 5 mg / ml; the volume ratio of the graphene oxide (GO) suspension to the dopamine (DA) solution is 5:4; the water bath heating time of the mixed solution is 10 h. The prepared hydrogel is dialyzed with deionized water for 48 h for purification to remove the remaining impurities in the hydrogel. Then the hydrogel is soaked in 0.1 mol / L sodium chloride solution for 2 days and taken out for standby.

[0043] As Figure 3 shown, the reduced graphene oxide / polydopamine hydrogel is prepared into a block with a specification of 10 mm×7 mm×5 mm, and the hydrogel is fixed between two copper electrodes. The copper electrode has a specification of 7 mm×5 mm×1.5 mm, and the resistivity is <0.018 Ω·mm 2 / m.

[0044] As Figure 3 shown, further encapsulate the copper electrodes and the hydrogel between them with polydimethylsiloxane (PDMS), connect the wires, and complete the assembly of the device.

[0045] As Figure 4 shown, the reduced graphene oxide (rGO) nanosheets inside the self-powered hydrogel form a three-dimensional porous structure through crosslinking, which can realize the cross-transport of water and ions in the pores.

[0046] As Figure 5 (a) shown, the hydrogel can still re-heal after being sheared, and the shapes of the two I-V curves are almost the same after healing, as Figure 5 (b) shown. During the repeated shearing and healing process, the graphene / polydopamine hydrogel exhibits good self-healing ability.

[0047] Connect the assembled devices in series and connect them to a high-precision source meter with copper wires to form a loop for testing the power generation ability. When no external force is applied to the self-powered hydrogel device, the source meter does not detect any current generation. When a pressure of 2 g is applied to the hydrogel device, the self-powered hydrogel device can instantaneously generate an ionic current of 0.5 μA. After removing the external force, the current returns to zero. When a pressure of 5 g is applied to the hydrogel device, the self-powered hydrogel device can generate an ionic current of 1.25 μA, as Figure 6 shown. During the repeated pressing and power generation process of the self-powered hydrogel device, the hydrogel has good self-healing properties and stability for sensing and power generation. Example 3

[0048] This example is basically the same as Example 1, except that:

[0049] When preparing the mixed solution, the concentration of the dopamine hydrochloride solution is 5 mg / ml, and the concentration of the graphene oxide (GO) suspension is 5 mg / ml; the ratio of the graphene oxide (GO) suspension to the dopamine (DA) solution is approximately 5:4, and the mixed solution is heated in a water bath for 12 h. The prepared hydrogel is dialyzed with deionized water for 48 h for purification to remove the remaining impurities in the hydrogel. Then the hydrogel is soaked in a 0.1 mol / L sodium chloride solution for 2 days and taken out for standby.

[0050] As Figure 3 shown, the reduced graphene oxide / polydopamine hydrogel is prepared into a block with a specification of 10 mm × 7 mm × 5 mm, and the hydrogel is fixed between two copper electrodes. The conductive glue has a specification of 7 mm × 5 mm × 1.5 mm, and the resistivity is <0.018 Ω·mm 2 / m.

[0051] As Figure 3 shown, further encapsulate the copper electrodes and the hydrogel between them with polydimethylsiloxane (PDMS), connect the wires, and complete the assembly of the device.

[0052] Furthermore, when the hydrogel is cut into two pieces and then brought into contact with each other, it can self-heal into a whole, and the shapes of the I-V curves before and after healing are almost the same. During the repeated cutting and healing process, the graphene / polydopamine hydrogel shows good self-healing ability.

[0053] Connect the assembled devices in series and connect them to a high-precision source meter with copper wires to form a loop for testing the power generation ability. When no external force is applied to the self-powered hydrogel device, the source meter does not detect any current generation. When a pressure of 2 g is applied to the hydrogel device, the self-powered hydrogel can instantaneously generate an ionic current of 0.45 μA. After removing the external force, the current reading returns to zero. When a pressure of 5 g is applied to the hydrogel device, the self-powered hydrogel device can instantaneously generate an ionic current of 1.0 μA. After removing the external force, the current returns to zero again. During the repeated pressing and power generation process of the self-powered hydrogel device, the hydrogel has good self-healing properties and the stability of sensing and power generation.

[0054] The above-described embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and optimization improvements made under the substantial content of the present invention shall be included within the protection scope of the present invention.

[0055] The described embodiments are the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Without departing from the substantial content of the present invention, any obvious improvements, substitutions, or variations that can be made by those skilled in the art fall within the protection scope of the present invention.

Claims

1. A preparation method of a self-powered device based on a reduced graphene oxide / polydopamine self-healing hydrogel, characterized in that, It includes the following steps: S1. Prepare reduced graphene oxide / polydopamine hydrogel through a hydrothermal reduction reaction; Add graphene oxide GO to deionized water and disperse it by ultrasonic treatment to obtain a graphene oxide suspension; Prepare a dopamine hydrochloride solution and a tris-HCl buffer solution respectively, and then adjust the pH of the dopamine hydrochloride solution with the tris-HCl buffer solution to oxidize and self-polymerize the dopamine hydrochloride solution into a polydopamine solution; Finally, mix the polydopamine solution with the graphene oxide suspension, seal the mixed solution in a glass test tube, and heat it in a water bath to obtain a reduced graphene oxide / polydopamine hydrogel. In this process, the graphene oxide is reduced to reduced graphene oxide rGO. Dialyze the prepared hydrogel with deionized water for purification to remove the remaining impurities, and then soak it in an NaCl solution; S2. Fix the reduced graphene oxide / polydopamine hydrogel soaked in step S1 between two copper electrodes and connect them with wires; S3. Package the reduced graphene oxide / polydopamine hydrogel with the assembled electrodes.

2. The preparation method according to claim 1, wherein In step S1, the ultrasonic time is 30 min and the ultrasonic power is 300 W; the concentration of the graphene oxide suspension is 3 - 5 mg / mL.

3. The preparation method according to claim 1, wherein In step S1, the concentration of the dopamine hydrochloride solution is 3 - 5 mg / mL, and the concentration of the tris-HCl buffer solution is 10 mmol / L; adjust the pH to 8.

0.

4. The preparation method according to claim 1, characterized in that, In step S1, the volume ratio of the polydopamine solution to the graphene oxide suspension is 8:

10.

5. The preparation method according to claim 1, characterized in that, In step S1, the temperature of the water bath heating is 80 °C and the time is 8 - 12 h; the dialysis time is 48 h.

6. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the NaCl solution is 0.1 mol / L, the soaking temperature is room temperature, and the soaking time is 24 h.

7. The preparation method according to claim 1, wherein In step S3, the reduced graphene oxide / polydopamine hydrogel and the copper electrodes are packaged with polydimethylsiloxane PDMS.

8. Application of the self-powered device based on the reduced graphene oxide / polydopamine self-healing hydrogel prepared by the preparation method according to any one of claims 1 - 7 in flexible electronic devices.

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