Preparation method of power generation device based on two-dimensional nano material

Abstract

The invention discloses a preparation method of a power generation device based on a two-dimensional nano material, and belongs to the technical field of nano power generation devices. The power generation device prepared by the invention comprises a substrate, a plurality of two-dimensional material nanobelts are prepared on the substrate, a plurality of wrinkles are formed on the two-dimensional material nanobelts, one or more wrinkles form a power generation unit, electrodes are prepared at two ends of the power generation unit, and the power generation device is formed. Under the action of external mechanical force, the flexural electric field of the wrinkle structure serving as the power generation unit can be changed under pressure stress or tensile stress, so that stable current is obtained. By using the flexoelectric effect, as the size of the material is reduced to nanoscale, the material can be matched with a nano-electronic device and a circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of nano power generation devices, and in particular relates to a method for preparing a power generation device based on two-dimensional nanomaterials. Background Art

[0002] There are many methods for converting mechanical energy into electrical energy using various physical effects. The most common method is to use electromagnetic induction to generate current by moving a coil in a magnetic field, thus converting mechanical motion into electrical energy. Another example is to use the triboelectric effect to collect and convert static electricity generated when two different materials come into contact and separate. With the help of the thermoelectric effect, the temperature difference is converted into electrical energy through the Seebeck effect to realize a thermoelectric generator. Or, using the piezoelectric effect, piezoelectric materials such as quartz and PZT can convert mechanical vibration or pressure into electrical energy. These methods usually have the following problems: (1) There must be moving parts in the generator, such as electromagnetic induction and triboelectric generation; (2) There must be a temperature gradient in the environment, such as a thermoelectric generator; (3) There are strict restrictions on the materials, and they must be specific thermoelectric or piezoelectric materials. Summary of the invention

[0003] The present invention proposes a method for preparing a power generation device based on the flexoelectric effect of two-dimensional nanomaterials.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for preparing a power generation device based on two-dimensional nanomaterials, characterized in that the power generation device includes a substrate, a plurality of two-dimensional material nanobelts are prepared on the substrate, a plurality of wrinkles are formed on the two-dimensional material nanobelts, the single or multiple wrinkles are a power generation unit, and electrodes are prepared at both ends of the power generation unit, and the specific steps include:

[0006] 1) Preparing a PDMS film: Specifically, a PDMS base material and a curing agent are mixed, the mixed PDMS is placed in a vacuum chamber for degassing, the degassed PDMS is poured onto a mold, and the PDMS is evenly coated on the mold surface using a scraper or a roller to ensure that there are no bubbles and the thickness is uniform before curing, the curing temperature is between 60-80° C. After the curing is completed, the PDMS film is peeled off from the mold;

[0007] 2) peeling off and transferring the two-dimensional material to the surface of the PDMS film, etching the two-dimensional material film, and forming a number of two-dimensional material nanobelts;

[0008] 3) placing the PDMS film covered with the two-dimensional material nanobelt into liquid nitrogen to form multiple wrinkles on the two-dimensional material nanobelt;

[0009] 4) The PDMS film is transferred to the substrate surface, one or more wrinkles on the two-dimensional material nanobelt are a power generation unit, and electrodes are prepared at both ends of the power generation unit to form a power generation device.

[0010] Furthermore, the substrate is Si / SiO2, silicon carbide, sapphire or boron nitride.

[0011] Furthermore, the two-dimensional material is MoS2, graphene or metal oxide semiconductor film, etc., with a thickness of 1-10nm.

[0012] Furthermore, the electrode material is a metal material such as gold, silver, palladium or platinum, and the electrode thickness is 50-100nm.

[0013] Furthermore, in step 2), the two-dimensional material crystal is placed in the middle of the tape by mechanical stripping technology, and the tape is repeatedly folded and torn to obtain a two-dimensional material film, and the number of repeated folding and tearing is 3-10 times.

[0014] Furthermore, in step 2), a layer of photoresist is coated on the PDMS surface covered with the two-dimensional material film, and exposed and developed to form a nanobelt pattern, and the two-dimensional material film is etched by dry etching technology to produce two-dimensional material nanobelts.

[0015] Furthermore, in step 3), the time of being placed in liquid nitrogen is 5-20 seconds.

[0016] Furthermore, in step 4), a mask method is used to prepare the electrode or a transfer method is used to obtain the electrode.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention utilizes the flexoelectric effect. The folds on the two-dimensional material are curved and there is a flexoelectric field. The folds are used as power generation units. Under the action of external mechanical forces (such as friction, AFM, centrifugal force, etc.), the folds produce asymmetric flexoelectric effects, which can generate electrical signals and pulse currents. The power generation device of the present invention is not limited by the symmetry of the material, that is, the flexoelectric effect is different from the piezoelectric effect. The piezoelectric effect usually only appears in non-centrosymmetric materials, while the flexoelectric effect is based on the asymmetry of the material. The flexoelectric effect significantly increases as the material size decreases to the nanoscale, and the electrical effect is significantly improved when the strain gradient is larger (about 10 6 The present invention uses nanometer-scale thick two-dimensional materials to realize small-sized and sensitive power generation devices, and converts mechanical energy into electrical energy with minimal external stress changes, thereby obtaining a micro power source that matches nanoelectronic devices and circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A schematic diagram of the structure of a power generation device based on two-dimensional nanomaterials in a specific embodiment of the present invention;

[0020] Figure 2 Schematic diagram of the principle of converting mechanical energy into electrical energy by the flexoelectric effect of the power generation unit of the present invention: (a) Schematic diagram of charge distribution caused by wrinkle strain; (b) Schematic diagram of the change of charge distribution caused by external force and its enhancement ("asymmetric and enhanced charge distribution") of wrinkles under the action of external force;

[0021] Figure 3 A flow chart of the preparation of a power generation device based on two-dimensional nanomaterials according to a specific embodiment of the present invention;

[0022] Wherein: 1-substrate; 2-power generation unit; 3-electrode. DETAILED DESCRIPTION

[0023] The structure of the power generation device of the present invention is specifically as follows: comprising a substrate, a plurality of two-dimensional material nanobelts are prepared on the substrate, a plurality of wrinkles are formed on the two-dimensional material nanobelts, and a plurality of wrinkles are formed on the two-dimensional material nanobelts. Figure 1 , a plurality of wrinkles on a two-dimensional material nanobelt is a power generation unit, and electrodes are prepared at both ends of the power generation unit to form a power generation device.

[0024] For the wrinkle structure on the two-dimensional film material, the bending degree of the wrinkle and the degree of stress coupling, that is, the stress gradient, are proportional to the flexural electric field. The flexural electric field will cause charge accumulation at the bending part of the wrinkle. Usually, positive charge will accumulate at the compressive stress part, while negative charge will accumulate at the tensile stress part, such as Figure 2 As shown in a. In the asymmetric case, wrinkles have a certain flexural electric field. When subjected to external mechanical forces (such as friction, AFM, centrifugal force), the wrinkles as power generation units will undergo stress gradient changes to varying degrees. Compared with the initial state (without external stress), the flexural electric effect at the compressive stress or tensile stress site will produce an asymmetric charge distribution, such as Figure 2 As shown in b.

[0025] refer to Figure 3 The process flow of preparing the power generation device of the present invention is as follows:

[0026] 1. Preparation of PDMS film:

[0027] Mix the PDMS base and curing agent in a ratio of 10:1. Mix in a clean container and stir with a stirring rod or magnetic stirrer until the mixture turns white. Place the mixed PDMS in a vacuum chamber for degassing to remove bubbles generated during the mixing process. After degassing, the PDMS is uniform and transparent. The degassing time needs to be controlled between 10 minutes and 30 minutes. Pour the degassed PDMS onto the prepared mold. The mold surface can be a silicon wafer, plastic plate or other material. The mold surface usually needs to be pre-treated with mold glue or similar substances to facilitate subsequent demolding. Use a scraper or roller to evenly apply the PDMS on the mold surface, ensuring that there are no bubbles and the thickness is consistent.

[0028] The coated PDMS is placed in an oven for curing. The curing temperature is usually between 60-80°C, and the curing time may range from several hours to 24 hours. During the curing process, PDMS will change from a liquid to an elastomer. After curing is completed, the PDMS film is peeled off from the mold. This process can be achieved by manual peeling or using a release agent. Before the subsequent steps, the PDMS film needs to be cleaned with isopropyl alcohol or other solvents to remove residual release agents or other contaminants on the surface of the residual film. After cleaning, the PDMS film is dried for subsequent processes. After cleaning, the PDMS film is dried and cut into samples of appropriate sizes for subsequent processes.

[0029] 2. Peel off and transfer the two-dimensional material to the PDMS membrane surface:

[0030] The two-dimensional material of the present invention can be: MoS2, graphene or metal oxide semiconductor film, etc. Taking MoS2 as an example, the specific steps are to prepare a MoS2 material film or directly purchase MoS2 crystals, and then place the MoS2 crystals in the middle of the tape through mechanical stripping technology. The tape is repeatedly folded and torn to obtain a MoS2 film sample with a thickness of 1-10nm. Usually, the number of repeated folding and tearing is 3-10 times (related to the viscosity of the tape). The tape is pressed against the surface of the PDMS film to transfer the MoS2 film to the PDMS surface.

[0031] 3. Etching 2D material thin film to form 2D material nanoribbons:

[0032] Using oxygen plasma etching, or using gallium ion focused ion beam (FIB) etching, helium ion etching and other methods, directly etch the surface of the MoS2 film to form a two-dimensional material nanobelt. Specifically, taking oxygen plasma etching as an example, the steps include: when etching, first apply a layer of photoresist on the surface of the PDMS containing the MoS2 film, and expose and develop to form a MoS2 nanobelt pattern. The MoS2 film is etched using oxygen plasma etching technology. During the etching process, the endpoint detection technology is used to monitor the changes in light intensity or other signals to determine whether the etching is completed. After the etching is completed, cleaning and annealing are required to remove residues and repair damage to the surface of the MoS2 material.

[0033] 4. Put the PDMS film covered with the two-dimensional material nanobelt into liquid nitrogen, and several wrinkles will form on the surface of the two-dimensional material nanobelt:

[0034] The PDMS film containing MoS2 nanobelts was placed in liquid nitrogen and taken out after being placed for 5 seconds. Since the temperature of liquid nitrogen is 77K, it is lower than room temperature (300K). Due to the large difference in thermal shrinkage coefficient between the MoS2 film and PDMS, PDMS will shrink significantly, resulting in a large number of wrinkles on the surface of the MoS2 nanobelts. The direction of wrinkles is related to the amount of deformation, and wrinkles are more likely to form in the long axis direction of the MoS2 nanobelt. Use an optical microscope to check whether wrinkles are generated and whether the wrinkle morphology meets the expected requirements.

[0035] 5. Transfer the PDMS film to the surface of the insulating Si / SiO2 substrate and prepare the metal electrode:

[0036] First, align the PDMS with the substrate, and contact the PDMS surface without MoS2 nanobelts with the insulating substrate. After placement, use the adhesion of the PDMS itself to bond it to the substrate, thereby transferring the PDMS film to the substrate surface. The electrode is prepared by a mask method or obtained by a transfer method. The metal electrode can be a metal material such as gold (Au), silver (Ag), palladium (Pd) or platinum (Pt), and gold (Au) is selected. The specific steps for preparing the electrode in this embodiment are as follows:

[0037] 1) If multiple wrinkles on the two-dimensional material nanobelt are a power generation unit, electrodes are directly prepared at both ends of the two-dimensional material nanobelt. Specifically, the required electrode pattern is first obtained by CAM image processing, and a high-precision mask is obtained, and then etching, demolding and cleaning are performed to obtain the required gold electrode. Use an optical microscope or a scanning electron microscope (SEM) to check whether the size of the electrode meets the expectations and whether the wrinkles are complete in shape after the electrode is prepared.

[0038] 2) If a single wrinkle on a two-dimensional material nanobelt is a power generation unit, electrodes are prepared at both ends of the wrinkle, specifically using a probe-assisted transfer method, and the specific steps include: first preparing a gold electrode placed on a silicon / silicon oxide substrate and etching it, then using a probe to gently lift up one end of the etched electrode, and then transferring the electrode to the target material, and finally obtaining the desired gold electrode. Use an optical microscope or scanning electron microscope (SEM) to check whether the size of the electrode is as expected and whether the wrinkle is complete in shape after the electrode is prepared.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. A person skilled in the art may modify or make equivalent substitutions for the technical solutions of the present invention without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for preparing a power generation device based on two-dimensional nanomaterials, characterized in that: The power generation device includes a substrate, a plurality of two-dimensional material nanobelts are prepared on the substrate, a plurality of wrinkles are formed on the two-dimensional material nanobelts, the single or multiple wrinkles are a power generation unit, and electrodes are prepared at both ends of the power generation unit. The specific preparation steps include: 1) Preparing a PDMS film: Specifically, a PDMS base material and a curing agent are mixed, the mixed PDMS is placed in a vacuum chamber for degassing, the degassed PDMS is poured onto a mold, and the PDMS is evenly coated on the mold surface using a scraper or a roller to ensure that there are no bubbles and the thickness is uniform before curing, the curing temperature is between 60-80° C. After the curing is completed, the PDMS film is peeled off from the mold; 2) peeling off and transferring the two-dimensional material to the surface of the PDMS film, etching the two-dimensional material film, and forming a number of two-dimensional material nanobelts; 3) placing the PDMS film covered with the two-dimensional material nanobelt into liquid nitrogen to form multiple wrinkles on the two-dimensional material nanobelt; 4) The PDMS film is transferred to the substrate surface, one or more wrinkles on the two-dimensional material nanobelt are a power generation unit, and electrodes are prepared at both ends of the power generation unit to form a power generation device.

2. The preparation method according to claim 1, characterized in that The substrate is Si / SiO2, silicon carbide, sapphire or boron nitride.

3. The preparation method according to claim 1, characterized in that: The two-dimensional material is MoS2, graphene or a metal oxide semiconductor film, and its thickness is 1-10nm.

4. The preparation method according to claim 1, characterized in that: The electrode is made of gold, silver, palladium or platinum metal material, and has a thickness of 50-100 nm.

5. The preparation method according to claim 1, characterized in that: In step 2), the two-dimensional material crystal is placed in the middle of the tape by mechanical stripping technology, and the tape is repeatedly folded and torn to obtain a two-dimensional material film, and the number of repeated folding and tearing is 3-10 times.

6. The preparation method according to claim 1, characterized in that: In step 2), a layer of photoresist is coated on the surface of the PDMS covering the two-dimensional material film, and exposure and development are performed to form a nanobelt pattern. The two-dimensional material film is etched using dry etching technology to produce two-dimensional material nanobelts.

7. The preparation method according to claim 1, characterized in that: In step 3), the time of being placed in liquid nitrogen is 5-20 seconds.

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