Electrochromic indicator sheet for optimizing viologen optical memory effect based on viscous liquid metal

Abstract

The invention discloses an electrochromic indicator sheet for optimizing viologen optical memory effect based on viscous liquid metal, and belongs to the technical field of functional materials and electrochromism. The electrochromic indicating sheet comprises lower-layer conductive glass, a multifunctional viscous liquid metal layer, a viologen integrated electrochromic electrolyte layer and upper-layer conductive glass which are sequentially arranged from bottom to top. According to the invention, a plasticine-like liquid metal conductive material capable of being coated is introduced, real-time electric leakage indication is realized through viologen discoloration, historical state recording is realized through irreversible consumption of liquid metal, viologen discoloration and consumption of the liquid metal form a dual visual feedback mechanism, the probability of occurrence and observation of an electric leakage phenomenon can be increased, and the reliability of electric leakage detection is improved. Meanwhile, the situation that the initial electric leakage phenomenon is not observed, the viologen self-oxidation indicating color disappears after a period of time, and electric leakage is mistakenly deemed not to occur is avoided. MuA-level micro leakage current can be detected, the response speed reaches a second level, and early insulation degradation and transient pulse leakage risks are accurately captured.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of functional materials and electrochromic technology, and particularly relates to an electrochromic indicator sheet based on a viscous liquid metal (LM) and MXene composite conductive layer for optimizing the optical memory effect of viologen and a preparation method. BACKGROUND

[0002] In the current field of electrical safety monitoring, leakage detection technology is crucial to ensure equipment reliability and personal safety. Traditional leakage indicators mainly rely on mechanical tripping mechanisms, LED / buzzing alarms, or digital ammeters, but have significant limitations. Mechanical tripping mechanisms rely on leakage currents reaching mA-level thresholds to trigger, making it difficult to warn of early-stage insulation degradation-induced μA-level micro-leakage, and the response is delayed and lacks sensitivity. Digital ammeters can quantitatively display, but require professional operation and cannot capture transient pulse currents, while LED alarms and thermal labels rely on continuous power supply or thermal conduction responses, and have defects such as ambiguous positioning, high misjudgment rate, etc. In addition, the rigid structure design makes it difficult for traditional devices to adapt to curved surfaces or small spaces, and their stability significantly decreases in complex working conditions such as humidity, salt spray, and wide temperature range. With the rapid development of new energy storage systems, smart grids, and high-density electronic devices, there is an increasing demand for a new type of leakage monitoring solution with high sensitivity, passive self-sustaining, intuitive visualization, and flexible adaptation.

[0003] Currently, viologen, as a typical electrochromic material, has been widely studied and applied in intelligent display, visual sensing, safety warning, energy storage, and state indication due to its low driving voltage, distinct color transition characteristics (usually from light yellow to deep blue), and good reversible color-changing ability. However, it still faces many technical challenges in practical applications, especially in the aspect of optical memory effect. After experiencing an external voltage reduction, the deep blue reduced state formed by viologen is easily disturbed by oxygen, water vapor, or other oxidizing substances in the environment without continuous power supply, leading to reverse oxidation and rapid color fading, with a half-life generally less than 72 hours, which seriously affects its practicality in scenarios requiring long-term state retention.

[0004] To overcome the above problems, existing research attempts to delay the reverse oxidation process of viologen by optimizing the electrolyte system (such as introducing high-viscosity gel or hydrophobic ionic liquid), or to enhance the electron transport efficiency and interface coupling stability by using high-conductivity two-dimensional materials (such as MXene, graphene) to modify the electrode. However, these solutions still have many limitations. On the one hand, solid-state electrolytes often have low ionic conductivity and slow response speed. On the other hand, the complex device structure increases the difficulty of packaging and is less suitable for flexible or large-area preparation, which limits the engineering promotion. In addition, there is currently a lack of a solution that can continuously maintain the reduced state color of viologen without continuous external power supply, providing long-lasting and traceable color change signal feedback. Especially in the application scenarios of leakage indication and state monitoring, which require "single event long-term recording", the existing technical solutions cannot meet the dual demands of "passive persistent recording + intuitive color display". Therefore, it is urgent to develop an electrochromic system with simple structure, easy to process, and capable of realizing continuous electron supply and multi-modal visual feedback, to break through the core technical bottleneck of short service life and easy fading of viologen materials, and lay a solid foundation for their application in high-reliability visual perception and intelligent safety monitoring. SUMMARY

[0005] The purpose of the present application is to provide an electrochromic indicator sheet based on thick liquid metal optimized viologen optical memory effect and a preparation method, aiming to solve the technical problems of poor optical memory effect, short fading half-life of existing viologen electrochromic materials, and unstable interface of electrochromic devices.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] An electrochromic indicator sheet based on thick liquid metal optimized viologen optical memory effect, comprising a lower conductive glass, a multifunctional thick liquid metal layer, a viologen integrated electrochromic electrolyte layer and an upper conductive glass arranged in order from bottom to top.

[0008] The multifunctional thick liquid metal layer is formed by mixing liquid metal and nanomaterial dispersion liquid through solvent-assisted stirring method, and presents thick state.

[0009] The viologen integrated electrochromic electrolyte layer comprises viologen electrochromic material, skeleton polymer, electrolyte and solvent.

[0010] Further, the upper conductive glass and the lower conductive glass are transparent conductive oxide (TCO) glass, metal-based conductive glass or conductive polymer coating glass.

[0011] Further, the upper conductive glass and the lower conductive glass are flexible or rigid, and the conductive surfaces are placed opposite to each other, respectively serving as the positive electrode and the negative electrode of the device.

[0012] Further, in the multifunctional viscous liquid metal layer, the liquid metal is one or more of gallium (Ga), gallium-indium-tin alloy (GaInSn), gallium-indium alloy (EGaIn), etc., and the nanomaterial is one or more of MXene, graphene, transition metal sulfide, black phosphorus, SiO2, CaF2, and TiO2; the mass percentage of the liquid metal is 95%-99%, and the mass percentage of the nanomaterial is 1%-5%.

[0013] Further, the thickness of the multifunctional viscous liquid metal layer is 100-250 microns.

[0014] Further, the multifunctional viscous liquid metal layer is formed by transferring the viscous liquid metal to the surface of the lower conductive glass by physical film forming methods such as spraying, spin coating, blade coating, and dip coating.

[0015] Further, in the viologen integrated electrochromic electrolyte layer, the viologen-based electrochromic material is 1,1'-dimethyl-4,4'-bipyridinium dichloride (methyl viologen), butyl viologen, cyanophenyl viologen, or monosubstituted benzyl viologen, with a mass percentage of 0.5-1.5%; the backbone polymer is one or more of polymethyl methacrylate, polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride, and poly(vinylidene fluoride-co-hexafluoroethylene), with a mass percentage of 30-40%; the electrolyte is a lithium salt such as lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium chloride, with a mass percentage of 2-3%; and the solvent is one or more of propylene carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl pyrrolidone, fluorinated ethylene carbonate, ethyl acetate, and acetonitrile, with a mass percentage of 55-65%.

[0016] Further, the indicating color of the electrochromic indicator sheet is not limited to the transition from light yellow to blue, but different viologen molecules can be selected to prepare indicator sheets with different indicating colors, as different viologens exhibit different characteristic colors in the oxidized and reduced states.

[0017] A method for preparing an electrochromic indicator sheet based on the optimization of the optical memory effect of viologen by using a viscous liquid metal, comprising the following steps:

[0018] Step 1. Preparation of a hydrophilic nanomaterial dispersion;

[0019] The nanomaterial is added to the dispersant, and stirring is performed to prepare a hydrophilic nanomaterial dispersion with a concentration of 1-5 mg / ml;

[0020] Step 2. Preparation of a viscous liquid metal clay that can be coated;

[0021] The liquid metal is added to the hydrophilic nanomaterial dispersion prepared in step 1, and stirred at 40℃ for 9h to obtain a viscous liquid metal rubber that can be coated; wherein the mass percentage of the liquid metal is 95% to 99%, and the mass percentage of the nanomaterial is 1% to 5%;

[0022] Step 3. Preparation of an integrated electrochromic electrolyte;

[0023] The viologen electrochromic material, the skeleton polymer and the electrolyte salt are blended in a solvent, and ultrasonic is applied until complete dissolution to obtain an integrated electrochromic electrolyte;

[0024] Step 4. Preparation of an electrochromic indicator sheet;

[0025] 4.1 The conductive glass is sequentially ultrasonically cleaned in detergent, acetone, deionized water and anhydrous ethanol;

[0026] 4.2 The cleaned conductive glass is blown dry with nitrogen, and then treated with ultraviolet-ozone for 30min to ensure a clean and clean surface;

[0027] 4.3 The viscous liquid metal rubber that can be coated prepared in step 2 is scraped on the conductive glass treated in 4.2 with a four-side scraper;

[0028] 4.4 A piece of clean conductive glass is placed on the conductive glass scraped with liquid metal rubber in 4.3, and the conductive surfaces of the two pieces of conductive glass are oppositely arranged; the integrated electrochromic electrolyte obtained in step 3 is injected between the two pieces of conductive glass, and the conductive glass is packaged to obtain an electrochromic indicator sheet based on the viscous liquid metal optimized viologen optical memory effect.

[0029] Further, in step 1, the nanomaterial is one or more of MXene, graphene, transition metal sulfide, black phosphorus, SiO2, CaF2, TiO2; the dispersant is one or more of water, ethanol, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and the like.

[0030] Further, in step 3, the viologen electrochromic material is methyl viologen, butyl viologen, cyanophenyl viologen or monosubstituted benzyl viologen; the electrolyte salt is lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium chloride and the like.

[0031] Further, in step 3, different reduction potential viologen electrochromic materials can also be added to realize multi-color display to indicate the degree of leakage. Preferably, the different reduction potential viologen electrochromic materials are 4,4'-(6-(1-4-vinylbenzyl)pyridine)-1,3,5-triazine-2,4-diyl bis(1-benzylpyridine) with a mass ratio of 1:1, or (TPBE) and 1,1'-dimethyl-4,4'-bipyridinium dichloride (MDL) with a mass ratio of 1:1.

[0032] The working principle of the electrochromic indicator sheet based on the optimization of the viologen optical memory effect of the viscous liquid metal provided by the present application realizes the multiple visual response mechanism under the leakage condition as follows:

[0033] 1. Excellent coatability and interface adaptability:

[0034] Ethanol and trace amounts of residual water can create a hydrogen bond environment for the dispersion of MXene, while reducing the yield stress of LM, promoting the formation of a slip layer between LM and MXene. Mechanical stirring causes the LM to break into small droplets. After stirring and dispersion, the liquid metal is easily oxidized to form an oxide layer. MXene acts as a seed to induce the oxide layer to uniformly coat its surface. As the oxide layer gradually increases, the viscosity of the system increases significantly. Ethanol self-volatilizes during the stirring process, ultimately forming a coatable LM / MXene rubber structure. This solves the problem of pure LM flowing in the system. The LM rubber has good rheological properties and interface adhesion ability, and can be conveniently squeegee-coated on the surface of ITO conductive glass, providing a stable and continuous conductive channel for the device.

[0035] 2. Normal state self-protection:

[0036] Under normal non-leakage conditions, liquid metal is easily self-oxidized to form a surface oxide layer (Ga2O3 / In2O3, thickness 2-5 nm), which prevents the internal liquid metal from being further oxidized. Viologen, as an electrochromic material, is light yellow in normal state and has a reduction coloring property. After reduction, it turns dark blue. In the initial state without current passing through, the oxide layer on the surface of the liquid metal prevents contact with the viologen and no reaction occurs, maintaining the system in equilibrium and no color change, keeping the system light yellow and ensuring that the indicator is in a static and stable state, ensuring a low-noise background.

[0037] 3. When the device is applied with voltage under leakage, the triple synergistic response mechanism triggered by leakage:

[0038] (1) Electrochromic trigger: under the action of an external electric field during leakage, the viologen material is first reduced to dark blue at the cathode, completing the first color response;

[0039] (2) Oxidation film breakdown, activation of reducing agent release: further breakdown of the LM surface oxidation film by external voltage, exposing the liquid metal and directly contacting with the viologen, LM continuously releases electrons, further reducing the viologen and maintaining it in a blue stable state, significantly delaying the color fading process;

[0040] (3) Visual enhancement indication mechanism: the LM / MXene original state is silver-white, existing as a bottom coating layer. When the liquid metal oxidation film is broken down and continuously reacts with the viologen after being oxidized, gray-black precipitates or floccules appear on the surface, forming a second visual feedback, indicating the metal consumption process, which helps users identify that the system has experienced a leakage, even if the subsequent color of the viologen gradually fades, the historical triggering traces can still be judged by the precipitates.

[0041] 4. Leakage degree multicolor indication:

[0042] The reduction potential of 4,4'-(6-(1-4-vinylbenzyl)pyridine)-1,3,5-triazine-2,4-diyl bis(1-benzylpyridine) is -0.8V (vs. Ag / AgCl), which is preferentially reduced at low voltage, and the color changes from light yellow (oxidized state) to dark green (reduced state); the reduction potential of 1,1'-dimethyl-4,4'-bipyridinium dichloride is -1.8V (vs. Ag / AgCl), which requires higher voltage to activate, and the color changes from transparent (oxidized state) to blue (reduced state).

[0043] Low voltage (0~ -0.8V): only TBPE is partially reduced, showing light yellow-green (slight leakage);

[0044] Medium-low voltage (-0.8~ -1.2V): MDL is partially reduced, showing blue-green (moderate leakage);

[0045] Medium voltage (-1.2V~ -1.8V): TBPE is fully reduced, and MDL is partially reduced, showing a superimposed absorption peak in dark green;

[0046] High voltage (-1.8~ -2.5V): both viologens are completely reduced, the absorption peaks are superimposed, forming a deep blue color (severe leakage).

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] 1. The present application innovatively introduces a rubbery paste-like liquid metal conductive material that can be coated, not only realizes real-time leakage indication through viologen discoloration, but also realizes historical state recording through irreversible consumption of liquid metal, and the viologen discoloration and consumption of liquid metal constitute a double visual feedback mechanism, which can increase the probability of occurrence and observation of leakage phenomenon, while avoiding the case that the initial leakage phenomenon is not observed and the viologen self-oxidation indicating color disappears after a period of time, mistakenly thinking that there has been no leakage. The device can detect a small leakage current of μA level, and the response speed reaches seconds, breaking through the limitations of low sensitivity and slow response of traditional mechanical or thermal schemes, and accurately capturing early insulation deterioration and transient pulse leakage risk. By adding multiple viologen molecules, multi-level color change (such as transparent→green→blue) can be achieved to intuitively distinguish the severity of leakage. The overall device can be prepared into a flexible film, which can be attached to curved surfaces or narrow spaces such as cables and battery modules, breaking through the installation limitations of rigid devices and having significantly better adaptability than traditional rigid sensors.

[0049] 2. The device of the present application has both passive characteristics and a material system suitable for printing process, can realize large-area, low-cost distributed deployment, and is used for accurate positioning of leakage points in high-density areas, avoiding the high cost and low coverage of traditional centralized monitoring scheme, and providing a more cost-effective intelligent safety monitoring solution for smart grids, new energy equipment and other fields. The overall structure of the device is reasonably designed, and the preparation process is mature and reliable. Large-scale production can be realized through existing industrial processes, and the device has good engineering prospects, and is particularly suitable for application in fields such as power safety, intelligent sensing, and industrial automation, which have high reliability requirements for leakage detection. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The structure diagram of the electrochromic indicating sheet based on the thick liquid metal optimized viologen optical memory effect of the present application;

[0051] Figure 2 The actual leakage indication effect display diagram of the electrochromic indicating sheet based on the thick liquid metal optimized viologen optical memory effect of the present application;

[0052] Figure 3 The multi-color color change layer effect display diagram of the electrochromic indicating sheet based on the thick liquid metal optimized viologen optical memory effect of the present application;

[0053] Figure 4 The multi-color device indication effect display diagram of the electrochromic indicating sheet based on the thick liquid metal optimized viologen optical memory effect of the present application. DETAILED DESCRIPTION

[0054] The present application will be further described in detail below in conjunction with specific embodiments and drawings, and the specific embodiments described herein are only used to explain the present application, but the embodiments of the present application are not limited thereto.

[0055] Example 1

[0056] A preparation method of an electrochromic indicator based on optimization of viologen optical memory effect by viscous liquid metal, specifically comprising the following steps:

[0057] Step 1. Preparation of Ti3C2T x MXene solution;

[0058] 1.1 Pour 20 mL of HF (40 wt%) and 20 mL of HCl (37 wt%) into a polytetrafluoroethylene beaker and stir until uniform, then add 2 g of Ti3AlC2 powder to the polytetrafluoroethylene beaker in small amounts one by one, and stir and heat at 45°C for 12-24 h;

[0059] 1.2 Centrifuge the mixed solution obtained in step 1.1 and wash with deionized water for multiple cycles (5000 rpm, 10 min) until the supernatant is close to neutral (pH>5), separate to obtain the precipitate;

[0060] 1.3 Add 40 mL of distilled water and 2 g of LiCl to the precipitate obtained in step 1.2, and stir intercalation at room temperature for 12 h;

[0061] 1.4 Peel off the single-layer / few-layer MXene by multiple expansion centrifugation (5000 rpm, 1 min) to increase the yield, and then collect the upper suspension by low-speed centrifugation (3000 rpm, 10 min) to obtain a single-layer / few-layer MXene dispersion;

[0062] Step 2. Preparation of LM / MXene coatable clay:

[0063] Add liquid metal EGaIn to the MXene dispersion obtained in step 1 and stir at 40°C for 9 h to obtain LM / MXene coatable clay; wherein the mass percentage content of liquid metal EGaIn is 99%, and the mass percentage content of nanomaterial MXene is 1%;

[0064] Step 3. Preparation of integrated electrochromic electrolyte;

[0065] Blend methyl viologen, polymethyl methacrylate and lithium perchlorate in N,N-dimethylformamide solvent, and ultrasonic for 1 h until completely dissolved to obtain an integrated electrochromic electrolyte;

[0066] Step 4. Preparation of electrochromic indicator;

[0067] 4.1 Ultrasonically clean the conductive glass in washing-up liquid, acetone, deionized water and anhydrous ethanol for 10 min;

[0068] 4.2 The cleaned conductive glass is blown dry with nitrogen, and then treated with ultraviolet-ozone for 30 min to ensure a clean and clear surface;

[0069] 4.3 The LM / MXene-coated putty prepared in step 2 is scraped onto the conductive glass treated in step 2 using a 250-μm-thick four-sided coater;

[0070] 4.4 A piece of cleaned conductive glass is placed on the conductive glass scraped with the liquid metal putty in step 3, with the conductive surfaces oppositely arranged; the integrated electrochromic electrolyte obtained in step 3 is filled between the two pieces of conductive glass, and then encapsulated to obtain an electrochromic indicator sheet based on a viscous liquid metal-optimized viologen optical memory effect.

[0071] In the present application, the liquid metal acts as a reducing agent, and together with the viologen, forms a special electrochemical reaction system. The electric field can break through the oxide thin layer and break the system balance. The viologen is reduced at the cathode to obtain electrons, and the color changes from light yellow to dark blue. Subsequently, the liquid metal and the viologen undergo a redox reaction, continuously providing electrons until the liquid metal is completely consumed, and the system color is stably maintained at the blue state. The stable color change time of this embodiment can reach 7 days. The LM / MXene structure of the present application effectively optimizes the reaction process, delays the reverse oxidation of the viologen to the colorless state, significantly improves the optical memory effect and long-term stability, and the color change result is shown in FIG. 2. Figure 2

[0072] Example 2

[0073] A method for preparing a multi-color flexible electrochromic indicator sheet based on a viscous liquid metal-optimized viologen optical memory effect, specifically comprising the following steps:

[0074] Step 1. Preparation of CaF2 ethanol dispersion:

[0075] CaF2 powder (particle size 50-100 μm) is added to an ethanol solvent, and ultrasonic treatment is performed at 25°C for 12-24 hours;

[0076] Step 2. Preparation of LM / CaF2-coated putty;

[0077] A gallium-indium alloy is added to the CaF2 ethanol dispersion obtained in step 1, and stirred at 40°C for 9 h to obtain LM / CaF2-coated putty; wherein the mass percentage of the gallium-indium alloy is 99%, and the mass percentage of CaF2 is 1%;

[0078] Step 3. Synthesis of 4,4'-(6-(1-3-butene)pyridine)-1,3,5-triazine (TPBE);

[0079] ​In a 100 ml beaker, 4.98 g of 2,4,6-tris(4-pyridine)1,3,5-triazine (TPT) (16 mmol) and 0.57 g of 4-bromo-1-butene (12 mmol) were added. The reaction mixture was heated to 100 °C with stirring and reacted for 2 hours. After cooling to room temperature, a black solution with a grayish-white precipitate was obtained. After filtering to remove the precipitate, the black solution was poured into 800 ml of ethyl acetate, yielding a yellow precipitate. This precipitate was repeatedly washed with ethyl acetate and dried to remove the solvent, yielding a yellow solid, TPBE.

[0080] Step 4. Prepare an integrated multicolor electrochromic indicator layer of 4,4'-(6-(1-4-vinylbenzyl)pyridine)-1,3,5-triazine-2,4-dimethylbis(1-benzylpyridine) and 1,1'-dimethyl-4,4'-bipyridine onium salt dichloride;

[0081] 0.3g TPBE, 0.3g 1,1'-dimethyl-4,4'-bipyridinium salt dichloride, 1g polymethyl methacrylate and 1.06g lithium perchlorate were mixed in 10mL N,N-dimethylformamide solvent and sonicated for 1h until completely dissolved to obtain an integrated multicolor electrochromic indicator layer;

[0082] Step 5. Prepare a flexible integrated multicolor electrochromic leakage current indicator sheet;

[0083] 5.1 The flexible ITO glass was ultrasonically cleaned in detergent, acetone, deionized water and anhydrous ethanol for 10 minutes in sequence.

[0084] 5.2 Dry the cleaned flexible ITO glass with nitrogen gas, and then treat the conductive glass with ultraviolet light and ozone for 30 minutes to ensure that the surface is clean and hygienic.

[0085] 5.3 The LM / CaF2 coatable putty obtained in step 2 was applied to the flexible ITO glass treated in step 5.2 using a 250 μm thick four-sided preparation tool;

[0086] 5.4 On the flexible ITO glass coated with liquid metal putty in 5.3, cover it with another cleaned flexible ITO glass, with the conductive surfaces of the flexible ITO glass facing each other; fill the space between the two flexible ITO glass pieces with the integrated electrochromic electrolyte obtained in step 4, and encapsulate it to obtain a multicolor flexible electrochromic leakage current indicator based on the optimized viologen optical memory effect of viscous liquid metal. The multicolor viologen color-changing effect is shown in the attached figure. Figure 3 As shown in the attached image, the color-changing effect of the device is as follows. Figure 4 As shown.

[0087] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. An electrochromic indicator based on optimization of viologen optical memory effect in a viscous state of liquid metal, characterized in that, The device comprises a lower conductive glass, a multifunctional viscous liquid metal layer, a viologen integrated electrochromic electrolyte layer and an upper conductive glass arranged in sequence from bottom to top. The multifunctional viscous liquid metal layer is formed by mixing liquid metal and nanomaterial dispersion liquid through solvent assisted stirring method. The viologen integrated electrochromic electrolyte layer comprises viologen electrochromic material, skeleton polymer, electrolyte and solvent.

2. The electrochromic indicator based on the optimization of the viologen optical memory effect in the viscous state of liquid metal according to claim 1, characterized by the fact that The upper and lower conductive glasses are transparent conductive oxide glass, metal-based conductive glass or conductive polymer coated glass.

3. The electrochromic indicator based on the optimization of the viologen optical memory effect in the viscous state of liquid metal according to claim 1, characterized by the fact that In the multifunctional viscous liquid metal layer, the liquid metal is one or more of gallium, gallium indium tin alloy and gallium indium alloy, and the nanomaterial is one or more of MXene, graphene, transition metal sulfide, black phosphorus, SiO2, CaF2 and TiO2; the mass percentage of the liquid metal is 95-99%, and the mass percentage of the nanomaterial is 1-5%.

4. The electrochromic indicator based on the optimization of the viologen optical memory effect in the viscous state of liquid metal according to claim 1, characterized by the fact that The thickness of the multifunctional viscous liquid metal layer is 100-250 microns.

5. The electrochromic indicator based on the optimization of the viologen optical memory effect in the viscous state of liquid metal according to claim 1, characterized by the fact that The multifunctional viscous liquid metal layer is formed by transferring the viscous liquid metal to the surface of the lower conductive glass by spraying, spin coating, blade coating or dipping.

6. The electrochromic indicator based on the optimization of the viologen optical memory effect in the viscous state of liquid metal according to claim 1, characterized by the fact that In the viologen integrated electrochromic electrolyte layer, the viologen electrochromic material is methyl viologen, butyl viologen, cyanophenyl viologen or monosubstituted benzyl viologen, with a mass percentage of 0.5-1.5%; the skeleton polymer is one or more of polymethyl methacrylate, polyvinyl alcohol, polyethylene oxide, polyvinylidene fluoride and poly(vinylidene fluoride-co-hexafluoroethylene), with a mass percentage of 30-40%; the electrolyte is lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate or lithium chloride, with a mass percentage of 2-3%; and the solvent is one or more of propylene carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl pyrrolidone, fluorinated ethylene carbonate, ethyl acetate and acetonitrile, with a mass percentage of 55-65%.

7. The electrochromic indicator based on the optimization of the viologen optical memory effect in the viscous state of liquid metal according to claim 1, characterized by the fact that The viologen electrochromic material is a multi-color display material with different reduction potentials to indicate the degree of leakage.

8. A method for preparing an electrochromic indicator based on the optimization of the viologen optical memory effect in a viscous state of liquid metal, characterized by the fact that, The method comprises the following steps: Step 1. Preparation of hydrophilic nanomaterial dispersion liquid The nanomaterial is added to the dispersant and stirred to obtain a hydrophilic nanomaterial dispersion liquid with a concentration of 1-5 mg / mL; Step 2. Preparation of viscous state coatable liquid metal putty The liquid metal is added to the hydrophilic nanomaterial dispersion liquid prepared in step 1 and stirred to obtain viscous state coatable liquid metal putty; wherein the mass percentage of the liquid metal is 95-99%, and the mass percentage of the nanomaterial is 1-5%; Step 3. Preparation of integrated electrochromic electrolyte The viologen electrochromic material, skeleton polymer and electrolyte salt are blended in the solvent and ultrasonically treated until completely dissolved to obtain an integrated electrochromic electrolyte; Step 4. Preparation of electrochromic indicator sheet 4.1 The viscous state coatable liquid metal putty prepared in step 2 is blade coated onto a clean conductive glass; 4.2 Cover another clean conductive glass on the conductive glass coated with liquid metal putty in 4.1, and the conductive surfaces of the two conductive glasses are opposite; fill the integrated electrochromic electrolyte obtained in step 3 between the two conductive glasses, encapsulate, and obtain an electrochromic indicator based on the optimization of viologen optical memory effect of viscous liquid metal.

9. The method for preparing the electrochromic indicator based on the optimization of viologen optical memory effect by using viscous liquid metal according to claim 8, characterized in that, In step 1, the nanomaterial is one or more of MXene, graphene, transition metal sulfide, black phosphorus, SiO2, CaF2, and TiO2; and the dispersant is one or more of water, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide.

10. The method for preparing the electrochromic indicator based on the optimization of viologen optical memory effect by using viscous liquid metal according to claim 8, characterized in that, In step 3, different viologen electrochromic materials with different reduction potentials are added to realize multi-color display to indicate the degree of leakage.

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