Structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal and preparation method and application thereof

Abstract

The application discloses a structural color pressure-sensitive film based on a hollow polymer colloidal photonic crystal and a preparation method and application thereof, and belongs to the technical field of force-induced color-changing materials. The preparation method of the structural color pressure-sensitive film comprises the following steps: (1) uniformly dispersing core-shell nano colloidal particles in an organic solvent to obtain a colloidal particle dispersion liquid; the shell layer of the core-shell nano colloidal particles is a polymer material, and the core layer is an inorganic oxide; (2) coating the colloidal particle dispersion liquid on the surface of a flexible substrate, and obtaining a precursor photonic crystal film after heating; and after removing the core layer of the core-shell nano colloidal particles in the precursor photonic crystal film by acid treatment etching, the structural color pressure-sensitive film is obtained. The preparation method of the structural color pressure-sensitive film is simple, the conditions are mild, and no pigment dye molecules are needed; by utilizing the pressure deformation and shape memory characteristics of a single hollow polymer colloidal particle itself and the inherent structural color characteristics of a photonic crystal, the structural color pressure-sensitive film can realize the regulation and memory of rich and high-saturation structural colors under the action of pressure.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of force-induced color-changing materials, and particularly relates to a structural color pressure-sensitive film based on a hollow polymer colloidal photonic crystal as well as a preparation method and application thereof. BACKGROUND

[0002] The pressure-sensitive paper, also known as pressure-sensing paper or pressure-sensitive paper, is usually composed of a color-developing agent layer, a color-developing agent layer and a substrate. When the pressure-sensitive paper is placed between two contact surfaces and pressure or impact force is applied, the pigment molecules in the color-developing agent layer will diffuse to the color-developing agent layer to develop color, and different stress sizes will show different color development concentrations on the paper. Due to the flexibility, thinness, wide application scenarios, simplicity, economy and other characteristics of the pressure-sensitive paper, it is widely used in lithium battery, automobile industry, electronic manufacturing industry, human-machine engineering and other industries for testing pressure, pressure distribution, flatness and the like.

[0003] A pressure-sensitive film is disclosed in Chinese patent document CN104713669A, which includes a substrate, a color-developing layer and a color-forming layer stacked in order from top to bottom. The other surface of the substrate opposite to the surface adjacent to the color-developing layer is used to bear the pressure of the equipment. The color-forming layer includes at least one color-forming unit, each of which includes at least two color capsules having different pressure threshold values from each other and working when the pressure they bear reaches their pressure threshold values. The color-developing layer presents corresponding colors according to the working conditions of the color capsules, and each color corresponds to a set pressure value. Chinese patent document CN208224101U discloses a pressure-sensitive paper, which includes a first substrate and a second substrate arranged oppositely. The surface of the first substrate has a color-developing substance, and the surface of the second substrate has a color-producing substance. The color-developing substance can react with the color-producing substance to generate a chemical substance of a preset color, and the chemical substance can recover to the color-producing substance after contacting with air for a preset time.

[0004] At present, the main limitation of the pressure-sensitive paper is that it usually develops color through the diffusion and penetration of the color-developing substance in the color-developing layer, which easily causes a reduction in resolution and cannot realize high-precision pressure distribution testing of the micro-nano structure surface pressure. Secondly, after using the pressure-sensitive paper for pressure testing, only the depth of a single pigment color or a few preset colors is used to obtain the size of different pressures, which is not conducive to accurately reading the pressure value by the naked eye, and it is even more difficult to obtain the visual distribution of the three-dimensional pressure of the object surface, resulting in low measurement accuracy. In addition, since the pigment dye used in most pressure-sensitive papers at present causes serious pollution in the production process, and the pigment molecules are easily faded under long-term light and other conditions, it is not conducive to preservation, and therefore there is an urgent need to develop a high-resolution, high-precision, pressure distribution color visual, green and environmentally friendly pressure-sensitive paper.

[0005] Photonic crystal materials have a unique periodic structure and exhibit structural color with high color saturation, green environmental protection and never fading. Among them, the force-induced color-changing photonic crystal can realize the dynamic regulation of structural color under the action of external force, and is expected to be applied to pressure-sensitive paper with three-dimensional pressure visual color distribution function. Most of the force-induced color-changing photonic crystals currently use opal structure combined with elastic filler to achieve high sensitivity of force-induced color-changing characteristics. It has been reported that a three-dimensional opal photonic crystal array is constructed by using SiO2 colloidal particles, and then embedded in a polydimethylsiloxane elastomer to prepare a transparent photonic crystal film with force-induced color-changing properties ([1] Yang Liu, Yi Cheng Zhou, Yu Yuan Yao, et al. Force-induced color-changing regulation and anti-counterfeiting application of transparent photonic crystal film [J]. Fine Chemicals, 2022, 39(9): 7.).

[0006] However, when the force-induced color-changing photonic crystal is applied to pressure-sensitive paper, the following problems still exist: (1) the shape and structural color of the elastic photonic crystal film will return to the initial state after the external force is removed, and the long-term maintenance and memory of the pressure deformation cannot be realized; (2) when using shape memory polymers, most of them can only switch between colored and colorless memory states under the action of external force, which cannot meet the continuous color-changing demand under different pressure in actual application scenarios, greatly limiting its application in pressure-sensitive paper. Therefore, a new type of photonic crystal high-saturation structural color material with shape memory and force-induced color-changing properties needs to be prepared to expand its application in pressure-sensitive paper. SUMMARY

[0007] The application provides a preparation method of a structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals, which is simple and efficient, easy to prepare and mass-produce, and integrates color generation and color development layers, has force-induced deformation color-changing properties and shape memory properties, can convert external pressure intensity and pressure distribution applied to the film into structural color hue information and regional color distribution information, realize three-dimensional pressure distribution color visualization, and can long-term save.

[0008] The specific technical solutions are as follows:

[0009] A preparation method of a structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals, comprising the following steps:

[0010] (1) uniformly dispersing core-shell nano colloidal particles in an organic solvent to obtain a colloidal particle dispersion liquid; the shell layer of the core-shell nano colloidal particle is a polymer material, and the core layer is an inorganic oxide;

[0011] (2) coating the colloidal particle dispersion liquid on the surface of the flexible substrate, and obtaining the precursor photonic crystal thin film after heating; and removing the core layer of the core-shell nanocolloid in the precursor photonic crystal thin film by acid treatment etching to obtain the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal.

[0012] The polymer material includes, but is not limited to, phenolic resin, polyacrylate, polyurethane, etc.

[0013] The inorganic oxide includes, but is not limited to, silicon dioxide, triiron tetroxide, cerium oxide, zinc oxide, etc.

[0014] Preferably, the core-shell nanocolloid is SiO2@phenolic resin (RF) core-shell nanocolloid, which is prepared by the following method:

[0015] S01: tetraethyl orthosilicate is injected into a mixed solution of ethanol, water and ammonia water, and SiO2 colloidal particles are obtained after reaction, which are centrifuged, washed and then surface-modified with PVP to obtain PVP-grafted SiO2 colloidal particles;

[0016] S02: resorcinol, formaldehyde and ammonia water are sequentially added to the PVP-grafted SiO2 colloidal particle aqueous solution, and the mixture is heated to prepare SiO2@RF core-shell nanocolloid.

[0017] Preferably, the particle size of the core-shell nanocolloid is 100-1000 nm, and the shell thickness is 10-100 nm.

[0018] Further preferably, the particle size of the core-shell nanocolloid is 100-300 nm, and the shell thickness is 10-50 nm. Under the above preferred particle size, the photonic crystal layer thin film obtained by assembling the colloidal particles is located in the visible light region.

[0019] Preferably, in the colloidal particle dispersion liquid, the volume fraction of the core-shell nanocolloid is 15%-40%, and the organic solvent is at least one selected from the group consisting of ethanol, ethylene glycol, diethylene glycol, propylene carbonate, dimethylformamide and dimethyl sulfoxide.

[0020] The flexible substrate includes, but is not limited to, polyethylene terephthalate film, polydimethylsiloxane film, polyurethane film, etc.

[0021] Preferably, in step (2), the coating method is selected from blade coating or spraying; and the heating condition is 30-100°C for 1.5-2h.

[0022] Preferably, the acid treatment etching method is hydrofluoric acid etching, specifically: the precursor photonic crystal thin film is immersed in a hydrofluoric acid solution with a volume fraction of 1%-10% for 5-60 min, and the core layer of the core-shell nanocolloid in the precursor photonic crystal thin film is etched and removed.

[0023] The application further provides a preparation method of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals.

[0024] Under the action of pressure, the hollow polymer colloidal particles in the photonic crystal layer are deformed, so that the lattice spacing of the structural color pressure-sensitive film is reduced, resulting in a blue shift of the structural color, and the reflection peak displacement is linearly related to the size of the applied pressure, thereby realizing pressure sensing.

[0025] The hollow polymer colloidal particles in the photonic crystal layer have the properties of force-induced deformation and shape memory, so that the structural color pressure-sensitive film can realize high-resolution pattern transfer on the surface of an object under the action of pressure, and can long-term store the color distribution information under the action of gradient pressure after the pressure is removed.

[0026] Preferably, the thickness of the photonic crystal layer is 1-50 μm, and the thickness of the flexible substrate layer is 50-500 μm.

[0027] The application further provides an application of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals in the fields of pressure-sensitive paper, intelligent sensing, flexible devices and the like.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] (1) The application uses hollow polymer colloidal particles as assembly units to construct a photonic crystal structural color pressure-sensitive film with force-induced color change characteristics, which has not been reported in the prior art. The structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals provided by the application can record red, orange, yellow, green, blue-violet and other color displays under different pressure actions on a single film, and has the characteristics of visualizing the size and distribution of pressure on the surface of an object.

[0030] (2) Compared with the existing pressure-sensitive paper, the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals provided by the application can realize the regulation and memory of rich and high-saturation structural colors under the action of pressure, and can directly identify the color and chroma information of the film by the naked eye to obtain the visualized distribution of three-dimensional pressure on the surface of an object.

[0031] (3) The preparation method of the structural color pressure-sensitive film based on the hollow polymer colloidal photonic crystal is simple, mild, easy to mass produce, and does not need to use pigment dye molecules, and the product structural color pressure-sensitive film utilizes the pressure deformation, shape memory and recovery characteristics of a single hollow polymer colloidal particle itself and the inherent structural color characteristics of the photonic crystal, integrates the color forming layer and the color forming layer, has the advantages of high pressure imprint resolution, rich color control, high color saturation, green environmental protection and the like. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Fig. 1 is a TEM image of SiO2@RF core-shell nanocolloid particles and an optical image of a structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals, wherein a and d are Example 3, b and e are Example 2, and c and f are Example 1.

[0033] Figure 2 Fig. 2 is a schematic diagram of the force-induced color change principle of the structural color pressure-sensitive film based on the hollow polymer colloidal photonic crystal, and b-d are cross-sectional SEM images of the structural color pressure-sensitive film based on the hollow polymer colloidal photonic crystal under different pressures in Example 1.

[0034] Figure 3 Fig. 3 is an optical image of the structural color pressure-sensitive film based on the hollow polymer colloidal photonic crystal in Example 1 after being in contact with the surface of a cylindrical template and being subjected to different pressures, b is a statistical diagram of the change of the reflection peak in the pressurized area, c is a diagram of the relationship between the reflection peak position and the applied pressure, and d is a diagram of the relationship between the film thickness and the applied pressure.

[0035] Figure 4 Fig. 4 is an optical image of the structural color pressure-sensitive film based on the hollow polymer colloidal photonic crystal in Example 1 after being subjected to pressure deformation and being recovered to the initial state by solvent swelling and drying, and b and c are the reflection spectrum changes of the un-deformed area and the pressure-deformed area under the action of the solvent, respectively.

[0036] Figure 5 Fig. 5 is an optical microscopic image of the high-resolution pattern and pressure distribution of the structural color pressure-sensitive film based on the hollow polymer colloidal photonic crystal in Example 1 in contact with a circular high-resolution template and subjected to 2 MPa and 8 MPa pressures, respectively, a and c are the high-resolution pattern and pressure distribution, and b and d are the high-resolution pattern and pressure distribution when a square high-resolution template is used. DETAILED DESCRIPTION

[0037] The present application will be further illustrated below in conjunction with the examples and drawings. It should be understood that these examples are only used to illustrate the present application, and are not used to limit the scope of the present application.

[0038] The preparation method of the SiO2@RF core-shell nanocolloid particles used in the examples is as follows:

[0039] S01 tetraethyl orthosilicate is injected into a mixed solution of ethanol, water and ammonia water, and after reaction, SiO2 colloidal particles are obtained. After centrifugal separation and washing, surface PVP modification is performed to obtain PVP grafted SiO2 colloidal particles;

[0040] S02 resorcinol, formaldehyde and ammonia water are sequentially added to the PVP grafted SiO2 colloidal particle aqueous solution, and heating reaction is performed to obtain SiO2@RF core-shell nanogel particles.

[0041] Specifically, taking the preparation of SiO2@RF core-shell nanogel particles with a SiO2 inner core diameter of 150 nm and an RF shell layer thickness of 18 nm as an example, 100 mL of ethanol, 7 mL of water and 4 mL of ammonia water are mixed and stirred for 15 min to form a uniform solution. Subsequently, 8 mL of tetraethyl orthosilicate is quickly injected into the above solution, and after 3 h of reaction, SiO2 colloidal particles are formed. After centrifugal separation and washing with ethanol for three times, the SiO2 colloidal particles are finally dispersed in 10 mL of water. Subsequently, 1 mL of the above SiO2 colloidal particle aqueous solution is added to a polyvinylpyrrolidone (PVP) aqueous solution with a concentration of 5 mg / mL, and the SiO2 colloidal particle surface is modified with PVP by stirring at room temperature for 6 h. PVP grafted SiO2 colloidal particles are obtained. The above PVP grafted SiO2 colloidal particles are centrifugally separated and ultrasonically dispersed in 28 mL of water. Then, 30 mg of resorcinol, 42 μL of formaldehyde and 100 μL of ammonia water (2.8 wt%) are sequentially added. The above mixture is reacted at 60°C for 2 h, and then the temperature is increased to 100°C for continuous reaction for 2 h to obtain SiO2@RF core-shell nanogel particles.

[0042] Example 1

[0043] SiO2@RF core-shell nanogel particles with a SiO2 inner core diameter of 225 nm and an RF shell layer thickness of 32 nm are uniformly dispersed in propylene carbonate solvent to form a colloidal dispersion liquid with a particle volume fraction of 30%;

[0044] 100 μL of the above colloidal dispersion liquid is dropped onto a black polyethylene terephthalate (PET) substrate, and a colloidal dispersion liquid is uniformly spread on the PET substrate by using a doctor blade method to form a liquid film with a thickness of about 30 μm. After standing at room temperature for 15 min, the colloidal dispersion liquid is crystallized to form a thin film. After heating at 90°C for 30 min to completely volatilize the solvent, a precursor photonic crystal thin film is obtained. In the precursor photonic crystal thin film, the photonic crystal layer is composed of SiO2@RF core-shell nanogel particles.

[0045] The precursor photonic crystal film is transferred into a hydrofluoric acid solution with a volume fraction of 5% and soaked for 15 min, so that the SiO2 core layer is completely etched, finally, the film is taken out and washed with deionized water and ethanol for three times respectively, and quickly dried at 90°C to obtain the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals.

[0046] In the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in the example, the thickness of the photonic crystal layer is about 9 μm, and the thickness of the flexible substrate layer is 250 μm; the inside of the photonic crystal layer is a three-dimensional assembly structure composed of highly ordered arrangement of hollow phenolic resin colloidal particles; because the difference between the refractive index of air inside the hollow phenolic resin colloidal particles and the refractive index of phenolic resin is large, a high-saturation orange-red structural color is presented.

[0047] In the example, the TEM image of the SiO2@RF core-shell nanocolloid particle used is shown as c in Figure 1 The optical photograph of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared is shown as f in Figure 1

[0048] Example 2

[0049] SiO2@RF core-shell nanocolloid particles with a SiO2 inner core diameter of 150 nm and a RF shell layer thickness of 30 nm are uniformly dispersed in propylene carbonate solvent to form a colloidal dispersion liquid with a colloidal particle volume fraction of 30%;

[0050] 100 μL of the above colloidal dispersion liquid is dropped on a black PET substrate, and the colloidal dispersion liquid is uniformly spread on the PET substrate to form a liquid film with a thickness of about 30 μm by using a doctor blade method, and the colloidal dispersion liquid is allowed to stand at room temperature for 15 min, and after the colloidal dispersion liquid is crystallized to form a film, the solvent is completely volatilized by heating at 90°C for 30 min, to obtain a precursor photonic crystal film, wherein the photonic crystal layer is composed of SiO2@RF core-shell nanocolloid particles;

[0051] The precursor photonic crystal film is transferred into a hydrofluoric acid solution with a volume fraction of 5% and soaked for 15 min, so that the SiO2 core layer is completely etched, finally, the film is taken out and washed with deionized water and ethanol for three times respectively, and quickly dried at 90°C to obtain the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals.

[0052] In the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in the example, the thickness of the photonic crystal layer is about 9 μm, and the thickness of the flexible substrate layer is 250 μm; the inside of the photonic crystal layer is a three-dimensional assembly structure composed of highly ordered arrangement of hollow phenolic resin colloidal particles; because the difference between the refractive index of air inside the hollow phenolic resin colloidal particles and the refractive index of phenolic resin is large, a high-saturation orange-red structural color is presented.​

[0053] The TEM image of the SiO2@RF core-shell nanogel used in this example is shown in Fig. 1a, and the optical photograph of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in this example is shown in Fig. 1e. Figure 1 Figure 1 The TEM image of the SiO2@RF core-shell nanogel used in this example is shown in Fig. 1a, and the optical photograph of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in this example is shown in Fig. 1e.

[0054] Example 3

[0055] The SiO2@RF core-shell nanogel with a SiO2 core of 150 nm in diameter and a RF shell of 18 nm in thickness was uniformly dispersed in propylene carbonate solvent to form a colloidal dispersion with a nanogel volume fraction of 30%;

[0056] 100 μL of the above colloidal dispersion was dropped onto a black PET substrate, and the colloidal dispersion was uniformly spread on the PET substrate by blade coating to form a liquid film with a thickness of about 30 μm. After standing at room temperature for 15 min, the colloidal dispersion was crystallized to form a film, and the film was heated at 90°C for 30 min to completely evaporate the solvent, thereby obtaining a precursor photonic crystal film. In the precursor photonic crystal film, the photonic crystal layer was composed of SiO2@RF core-shell nanogel.

[0057] The precursor photonic crystal film was transferred to a hydrofluoric acid solution with a volume fraction of 5% and soaked for 15 min to completely etch the SiO2 core layer. Finally, the film was taken out and washed with deionized water and ethanol three times, respectively, and quickly dried at 90°C to obtain the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals.

[0058] In the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in this example, the thickness of the photonic crystal layer was about 9 μm, and the thickness of the flexible substrate layer was 250 μm. The interior of the photonic crystal layer was a three-dimensional assembly structure composed of highly ordered arrangement of hollow phenolic resin nanogels. Since the difference between the refractive index of air inside the hollow phenolic resin nanogel and the refractive index of phenolic resin was large, a high-saturation purple structural color was presented.

[0059] The TEM image of the SiO2@RF core-shell nanogel used in this example is shown in Fig. 1a, and the optical photograph of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in this example is shown in Fig. 1e. Figure 1 Figure 1 The TEM image of the SiO2@RF core-shell nanogel used in this example is shown in Fig. 1a, and the optical photograph of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals prepared in this example is shown in Fig. 1e.

[0060] Example 4

[0061] The preparation method of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystals in this example was different from that in Example 1 only in that the volume fraction of the core-shell nanogel in the colloidal dispersion was 25%, and the precursor photonic crystal film was soaked in a hydrofluoric acid solution with a volume fraction of 3% for 20 min.​​

[0062] Sample analysis

[0063] (1) Deformation color change principle of structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal

[0064] The pressure-sensitive property of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal is mainly due to the change of the lattice constant of the colloidal crystal film caused by the deformation of the hollow polymer colloidal particles themselves under the action of pressure, thereby changing the structural color. The hollow polymer colloidal particles deform under the action of pressure, and their shape gradually changes from the initial spherical shape to a concave shape under the action of pressure, and finally changes to a flat "disc" structure, as shown in a of Figure 2 .

[0065] The cross-sectional SEM images of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal in Example 1 under different pressures are shown in b-d of Figure 2 , which further verifies the flattening deformation effect of the hollow polymer colloidal particles under the action of pressure. The thickness of the colloidal crystal film decreases from the initial 9.01 μm to the final 3.64 μm, verifying the shrinkage of the photonic crystal lattice. At the same time, the structural color of the structural color pressure-sensitive film changes from orange red to the final purple, proving the deformation color change property of the structural color pressure-sensitive film.

[0066] (2) Pressure sensing property of structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal

[0067] Taking the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal prepared in Example 1 as an example, when a cylindrical template is in contact with the orange red structural color pressure-sensitive film and a pressure of 0-10 MPa is applied, as shown in a of Figure 3 , the contact area of the film and the cylindrical template gradually changes from the initial orange red to yellow green, green, blue purple, and purple, indicating that the structural color pressure-sensitive film can realize wide-range regulation of structural color under the action of different pressures. As shown in b-d of Figure 3 , the corresponding reflection spectrum and thickness of the film are inversely proportional to the pressure, and the reflection peak position changes from the initial 712 nm to the final 403 nm. This linear response behavior indicates that the structural color pressure-sensitive film can be used for quantitative sensing in the pressure range of 0-10 MPa.

[0068] (3) Shape memory and recovery performance of structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal

[0069] As mentioned above, the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal prepared by the present application can be deformed to different deformation states and structural colors by external pressure. In addition, the structural color pressure-sensitive film can maintain any deformation state for a long time without any change when the external pressure is removed. This is because the hollow polymer colloidal particles themselves have shape memory characteristics, so that the structural color pressure-sensitive film can be "frozen" in different structural color states.

[0070] In addition, if the deformed structural color pressure-sensitive film is immersed in a solvent of swellable polymer, such as ethylene glycol, diethylene glycol, dimethyl sulfoxide, etc., the reflection peak of the structural color pressure-sensitive film gradually red shifts within 5 min, and the structural color of the deformed area tends to be consistent with the initial state. After the solvent is completely volatilized, the corresponding structural color pressure-sensitive film returns to the initial color, as shown in a-c of Figure 4 This is because the polymer network in the hollow polymer colloidal particles swells to restore the colloidal particles from the deformed state to the initial spherical state.

[0071] The above results show that the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal prepared by the present application not only has the force-induced color change characteristics, but also has the shape memory and reversible characteristics.

[0072] (4) High-resolution pressure distribution display of object surface based on structural color pressure-sensitive film of hollow polymer colloidal photonic crystal

[0073] Benefiting from the regulation of the structural color of the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal, which is derived from the change of the micro-morphology of the hollow polymer colloidal particles, the structural color pressure-sensitive film can realize high-resolution pressure distribution memory and pattern display of micro-nano structure.

[0074] As shown in a-d of Figure 5 When a micrometer-level patterned array substrate is used as a template to contact the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal prepared in Example 1 and the external force is removed after 5 seconds of pressure application, the template is separated from the structural color pressure-sensitive film. It can be clearly observed that the pattern on the template is left on the structural color pressure-sensitive film. The green area in the structural color pressure-sensitive film is the raised area in the template, and the orange area in the structural color pressure-sensitive film is the concave area in the template, which shows that the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal prepared by the present application can well transfer the topography of the object surface, and the color difference can be directly observed by naked eye to intuitively distinguish the micro-nano structure of the template surface without using other scanning and electronic analysis systems, which preliminarily verifies the feasibility of pressure distribution visualization.

[0075] Further increasing the pressure with the same template, it can be observed that the shape of the pattern does not change significantly, while the structural color further blue shifts, thus the size of the external force on the surface can be analyzed according to the difference in color hue of the structural color. When micro-nano structures with different shapes and sizes are used as templates, similar pressure distribution memory effects are exhibited, and the highest resolution can reach several microns, indicating that the structural color pressure sensing film realizes the visualization of high-resolution pressure distribution.

[0076] The above embodiments are used to explain the technical solutions of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the present application. Any modification, supplement or similar substitution within the principle range of the present application should be included in the protection scope of the present application.

Claims

1. Use of a structural color pressure-sensitive film based on a hollow polymeric colloidal photonic crystal as a pressure-sensitive paper for pressure distribution visualization, characterized in that, The structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal comprises a photonic crystal layer and a flexible substrate layer, and the preparation method comprises the following steps: (1) uniformly dispersing core-shell nano colloidal particles in an organic solvent to obtain a colloidal particle dispersion liquid; the shell layer of the core-shell nano colloidal particles is a polymer material, and the core layer is an inorganic oxide; (2) coating the colloidal particle dispersion liquid on the surface of a flexible substrate, and obtaining a precursor photonic crystal film after heating; after removing the core layer of the core-shell nano colloidal particles in the precursor photonic crystal film by acid treatment etching, the structural color pressure-sensitive film based on hollow polymer colloidal photonic crystal is obtained; the thickness of the photonic crystal layer is 1-50 μm; the thickness of the flexible substrate layer is 50-500 μm; the flexible substrate is a polyethylene terephthalate film, a polydimethylsiloxane film or a polyurethane film; the polymer material is a phenolic resin.

2. Use according to claim 1, characterized in that, the inorganic oxide comprises silicon dioxide, triiron tetroxide, cerium oxide or zinc oxide.

3. Use according to claim 1, characterized in that, the particle size of the core-shell nano colloidal particles is 100-1000 nm, and the shell layer thickness is 10-100 nm.

4. Use according to claim 1, characterized in that, the coating method is selected from the group consisting of doctor blade coating and spraying.

5. Use according to claim 1, characterized in that, the acid treatment etching method is a hydrofluoric acid etching method, specifically: immersing the precursor photonic crystal film in a hydrofluoric acid solution with a volume fraction of 1%-10% for 5-60 min to etch and remove the core layer of the core-shell nano colloidal particles in the precursor photonic crystal film.

Images