Moisture-environment-resistant liquid metal-based electromagnetic shielding film and preparation method thereof

Abstract

The invention discloses a humid-environment-resistant liquid metal-based electromagnetic shielding film and a preparation method thereof, and relates to the technical field of electromagnetic shielding materials. The method comprises the following steps: firstly, adding metals Ga, In and Sn into an oil bath pan, mixing and melting to obtain liquid metal; the preparation method comprises the following steps: adding polyvinyl alcohol into deionized water, heating in a water bath, and uniformly mixing to obtain a polyvinyl alcohol solution; the preparation method comprises the following steps: adding nickel powder and liquid metal into a polyvinyl alcohol solution, carrying out ultrasonic pulverization in an ice bath, and slowly adding a borax solution at the same time to obtain PLM-Ni composite hydrogel; and spin-coating the PLM-Ni composite hydrogel on the surface of a substrate, drying, and collecting to obtain the PLM-Ni composite film. According to the prepared liquid metal-based electromagnetic shielding film resistant to the humid environment, the problem that the electromagnetic shielding function fails due to the fact that the electromagnetic shielding film is prone to being damaged in the humid environment is solved, the water resistance and the self-healing capacity of the film are improved, meanwhile, the preparation technology is simplified, the cost is reduced, and the preparation efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic shielding materials, and in particular to a liquid metal-based electromagnetic shielding film resistant to humid environments and a preparation method thereof. Background Art

[0002] At present, the increasing popularity of wearable smart electronic devices leads to serious electromagnetic interference, which not only destroys the functions of electronic devices, but also has adverse effects on human health. Therefore, the development of flexible wearable electromagnetic shielding materials has become the key to solving this problem. With the emergence of 5G technology and the growing demand for high-frequency bands in IoT applications, the demand for high-performance, lightweight and enhanced flexibility electromagnetic shielding film materials has also increased significantly. However, electromagnetic shielding films are easily damaged in humid environments, which makes the electromagnetic shielding function ineffective. Therefore, it becomes crucial to enhance their moisture resistance and self-healing capabilities. Summary of the invention

[0003] The object of the present invention is to provide a liquid metal-based electromagnetic shielding film resistant to humid environments and a preparation method thereof, so as to solve the problem that existing electromagnetic shielding materials are easily damaged in humid environments.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for preparing a liquid metal-based electromagnetic shielding film resistant to humid environments, characterized in that it comprises the following steps:

[0005] S1. Add metal Ga, In, and Sn into an oil bath, mix and melt to obtain liquid metal;

[0006] S2. Add polyvinyl alcohol to deionized water and heat in a water bath to mix well to obtain a polyvinyl alcohol solution;

[0007] S3. Add nickel powder and liquid metal to the polyvinyl alcohol solution, and perform ultrasonic grinding in an ice bath, and slowly add borax solution to obtain a PLM-Ni composite hydrogel;

[0008] S4. Spin-coat the PLM-Ni composite hydrogel on the substrate surface and collect it after drying to obtain the PLM-Ni composite film.

[0009] A further technical solution is to mix the metals Ga, In and Sn in a mass ratio of 68:22:10, and mix and melt them in an oil bath at 120° C. for 1 hour.

[0010] A further technical solution is that in step S2, the amount of polyvinyl alcohol added is 0.5 g / 10 mL of deionized water, the water bath temperature is 90° C., and the mixing is performed by magnetic stirring for 10 hours.

[0011] A further technical solution is that in step S3, the amount of nickel powder added is 0.3-2.6 g / 10 mL of deionized water, and the amount of liquid metal added is 50 μL / 10 mL of deionized water.

[0012] A further technical solution is that the ultrasonic crushing time is 10 minutes.

[0013] A further technical solution is that the concentration of the borax solution is 4%, and the added amount is 500 μL / 10 mL of deionized water.

[0014] A further technical solution is that the drying is performed at 80° C. for 30 minutes.

[0015] Reaction mechanism: The present invention uses polyvinyl alcohol (PVA), borax, liquid metal (LM) and nickel as raw materials. PVA polymer is a biocompatible material with a complex network structure that can form a self-healing hydrogel matrix. The borate molecules in the borax act as cross-linking agents through a dynamic process, and the hydroxyl groups in the PVA chain form tight hydrogen bonding sites with the borax molecules through hydrogen bonds and reconnect to form a liquid metal-based hydrogel composite material with multiple polymer networks with the liquid metal. Based on the dynamic organic / inorganic cross-linking process, the present invention uses a simple spin coating process to achieve the preparation of liquid metal-based electromagnetic shielding films.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention uses a liquid metal-based electromagnetic shielding film prepared from polyvinyl alcohol (PVA), borax, liquid metal (LM) and nickel. The film has high electromagnetic shielding performance while being foldable, magnetic, moisture-resistant, and able to heal quickly after contacting water. It has great potential in applications such as "magnetic switches" and electromagnetic shielding.

[0018] 2. The present invention uses polyvinyl alcohol (PVA), borax, liquid metal (LM) and nickel as raw materials, based on a dynamic organic / inorganic cross-linking process, and uses a simple spin coating process to achieve the preparation of a liquid metal-based electromagnetic shielding film. The preparation process is simple, efficient, and conducive to large-scale production.

[0019] 3. The liquid metal-based electromagnetic shielding film resistant to humid environments prepared by the present invention solves the problem that the electromagnetic shielding film is easily damaged in a humid environment, resulting in failure of the electromagnetic shielding function, improves the water resistance and self-healing ability of the film, and at the same time simplifies the preparation process, reduces costs, and improves preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are the XRD diagrams of the PLM-8Ni prepared in Example 4 of the present invention and the PLM and PVA samples of the control examples.

[0021] Figure 2 This is the SEM image of the PLM-8Ni sample of Example 4 of the present invention.

[0022] Figure 3 This is a diagram of the electromagnetic shielding performance of PLM-1Ni of Example 1, PLM-2Ni of Example 2, and PLM-4Ni of Example 3 of the present invention.

[0023] Figure 4 It is a graph showing the electromagnetic shielding performance of the PLM-8Ni sample of Example 4 of the present invention and the PLM and PVA samples of the control examples.

[0024] Figure 5 It is the average SET value of the PLM-8Ni sample of Example 4 of the present invention exposed to an 80% humidity environment for different time periods.

[0025] Figure 6 It is the average SET value of the PLM-8Ni sample of Example 4 of the present invention after being exposed to different humidity environments for five minutes.

[0026] Figure 7 This is the conductivity test of PLM-8Ni sample in a humid environment. DETAILED DESCRIPTION

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0028] The following examples are only used to further illustrate the present invention, but do not constitute any limitation to the present invention. The materials used in the following examples were purchased from conventional chemical reagent companies and raw material suppliers.

[0029] Example 1

[0030] A method for preparing a liquid metal-based electromagnetic shielding film resistant to humid environments comprises the following steps:

[0031] 1) Melting a mixture of Ga:In:Sn=68wt%:22wt%:10wt% in an oil bath at 120°C for 1 hour to obtain liquid metal;

[0032] 2) 0.5% polyvinyl alcohol (PVA) was magnetically stirred in 10 ml of deionized water at 90°C for 10 hours to obtain a polyvinyl alcohol solution;

[0033] 3) adding 0.322 g Ni and 50 μL liquid metal to the polyvinyl alcohol solution obtained in 2), and subjecting the solution to ultrasonic grinding in an ice bath (P=70%, t=10 min);

[0034] 4) Slowly add 500 μL of 4 wt% borax solution while ultrasonicating;

[0035] 5) The PLM-Ni composite hydrogel obtained in 4) is evenly spin-coated on the surface of the substrate using a spin coater;

[0036] 6) Dry at 80°C for 30 minutes and collect the PLM-Ni composite film, which is labeled as PLM-1Ni.

[0037] Embodiment 2:

[0038] The difference from Example 1 is that in step 3), the nickel is changed to 0.644 g, and the obtained hydrogel film is marked as PLM-2Ni; the rest is the same as Example 1.

[0039] Embodiment 3:

[0040] The difference from Example 1 is that the nickel in step 3) is changed to 1.288 g, and the obtained hydrogel film is marked as PLM-4Ni; the rest is the same as Example 1.

[0041] Embodiment 4:

[0042] The difference from Example 1 is that the nickel in step 3) is changed to 2.576 g, and the obtained hydrogel film is marked as PLM-8Ni; the rest is the same as Example 1.

[0043] Figure 1 is the XRD pattern of the PLM-8Ni sample in Example 4. Figure 1 It can be seen that the introduction of nickel particles into the PLM-8Ni product of the present invention leads to the appearance of several obvious diffraction peaks in the XRD spectrum of the PLM-8Ni film, which is consistent with the standard diffraction peaks of nickel (PDF#04-0850).

[0044] Comparative Example 1:

[0045] The difference from Example 4 is that in step 3), 0 μL of liquid metal is taken and the sample is recorded as PVA; the rest is the same as Example 1.

[0046] Comparative Example 2:

[0047] The difference from Example 2 is that in step 3), 0 g of nickel is taken and the sample is recorded as PLM; the rest is the same as Example 1.

[0048] Electromagnetic shielding performance test:

[0049] The prepared PLM-Ni composite film with electromagnetic wave shielding performance was taken as a sample, and the dielectric and electromagnetic properties of the material were analyzed using a vector network analyzer (VNA, Agilent N5234A). The specific method is: the sample was cut into 22.86×10.16mm block samples for testing, and the shielding performance of different samples was simulated and tested using a vector network analyzer.

[0050] like Figure 3 As shown, the average electromagnetic shielding SET value of the PLM-1Ni film of Example 1 is 4.89dB; the average electromagnetic shielding SET value of the PLM-2Ni film of Example 2 is 9.47dB; the average electromagnetic shielding SET value of the PLM-4Ni film of Example 3 is 17.19dB; the average electromagnetic shielding SET value of the PLM-8Ni film of Example 4 is 53.3dB (blocking 99.99953% of electromagnetic waves), which is significantly higher than the comparative example PVA film sample and (average electromagnetic shielding SET = 0.21dB). The above results show that the electromagnetic shielding SET is affected by the nickel content, and the average electromagnetic shielding SET value of the PLM-8Ni composite film performs best.

[0051] like Figure 4 As shown, the PVA and PLM samples prepared in Control Example 1 and Control Example 2 have very poor electromagnetic shielding performance, which indicates that nickel and liquid metal play an important role in the electromagnetic shielding performance of the film.

[0052] Moisture resistance test

[0053] Compared with the original PLM-8Ni film sample, the SET, SER, and SEA values ​​decreased under different ambient humidity conditions with a fixed exposure time of 5 min, e.g. Figure 6 As shown. At humidity levels of 50%, 70%, and 90%, the average SET was 50.9dB, 48.7dB, and 40.9dB, respectively. Exposed to different humidity environments, the SET value of the PLM-8Ni film exceeded the commercial standard threshold of ≥20dB. The electromagnetic shielding performance of the PLM-8Ni film exposed to an ambient humidity level set at 80% was compared to the original PLM-8Ni film. The average SET was 52.9dB, 46.0dB, and 45.7dB at exposure times of 1 minute, 4 minutes, and 16 minutes, respectively, as shown Figure 5 As shown. Exceeding the commercial standard threshold ≥ 20dB. The conductivity of PLM-8Ni film was tested in a humid environment, as shown Figure 7As shown. At first, the circuit was normal (LED was on), and even when the ambient humidity was 46.2%, the LED was still on. When the ambient humidity was 86.6%, the LED suddenly dimmed, but still emitted a faint light. The conductive related functions can still be maintained under a certain humidity. The good adaptability of the PLM-8Ni composite film to a humid environment is mainly due to its complete conductive network structure.

[0054] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a liquid metal-based electromagnetic shielding film resistant to humid environments, characterized in that The steps include: S1. Add metal Ga, In, and Sn into an oil bath, mix and melt to obtain liquid metal; S2. Add polyvinyl alcohol to deionized water and heat in a water bath to mix well to obtain a polyvinyl alcohol solution; S3. Add nickel powder and liquid metal to the polyvinyl alcohol solution, and perform ultrasonic grinding in an ice bath, and simultaneously add borax solution dropwise to obtain a PLM-Ni composite hydrogel; S4. Spin-coat the PLM-Ni composite hydrogel on the substrate surface and collect it after drying to obtain the PLM-Ni composite film.

2. The method according to claim 1, characterized in that: The metals Ga, In, and Sn were mixed in a mass ratio of 68:22:10, and mixed and melted in an oil bath at 120° C. for 1 hour.

3. The method according to claim 1, characterized in that: In the step S2, the amount of polyvinyl alcohol added is 0.5 g / 10 mL of deionized water, the water bath temperature is 90° C., and the mixing is performed by magnetic stirring for 10 hours.

4. The method according to claim 1, characterized in that: In the step S3, the amount of nickel powder added is 0.3-2.6 g / 10 mL of deionized water, and the amount of liquid metal added is 50 μL / 10 mL of deionized water.

5. The method according to claim 1, characterized in that: The ultrasonic pulverization time is 10 minutes.

6. The method according to claim 1, characterized in that: The concentration of the borax solution is 4%, and the added amount is 500 μL / 10 mL of deionized water.

7. The method according to claim 1, characterized in that: The drying is performed at 80° C. for 30 minutes.

8. A liquid metal-based electromagnetic shielding film resistant to humid environments, characterized in that: Prepared according to the method according to any one of claims 1 to 7.

Images