Optically secure non-iridescent structural color ink for 3D printing and method of making the same

Abstract

The present application belongs to the technical field of structural color materials, and specifically relates to optical anti-counterfeiting non-iridescent structural color ink for 3D printing and a preparation method thereof. The present application mixes core-shell structure colloidal particles containing polydopamine as an intermediate layer and polymer soft shell as an outer shell with a small molecule organic matrix to form non-iridescent structural color ink with high viscosity and excellent rheological properties. The structural color ink prepared by the present application has optical anti-counterfeiting properties, that is, it displays black under natural light and displays beautiful colors under strong light. By changing the particle size or volume fraction of the colloidal particles, structural color ink in the full visible light range can be prepared. By combining the prepared ink with 3D printing, various complex and shape customizable patterns can be prepared. The preparation method of the present application is simple, has strong repeatability, does not pollute the environment, is convenient for large-scale preparation, and has application prospects in the fields of anti-counterfeiting labels, encryption coding and wide-angle display.

Description

Technical Field

[0001] This invention belongs to the field of structural color materials technology, specifically relating to optical anti-counterfeiting non-iridescent structural color ink and its preparation method. Background Technology

[0002] Structural color, also known as physical color, is a vibrant color produced by manipulating the direction of light propagation within a specific arrangement of nanometer or micrometer structures, resulting in physical interactions. Unlike pigment colors, which suffer from drawbacks such as non-recyclability and environmental pollution, structural colors offer numerous advantages, including long-term stability, sustainable production, environmental friendliness, and dynamic, wide-range color adjustment. Generally, structural colors are generated primarily through thin-film interference, light scattering, grating diffraction, and photonic crystals. While photonic crystals constructed from ordered arrays promote the development of high-reflectivity, high-saturation, and angle-dependent structural colors under Bragg reflection, their applications in wide-angle displays and sensors are somewhat limited. Artificial perturbation can effectively manipulate amorphous structures with short-range order but long-range disorder, leading to the generation of non-iridescent structural colors under coherent light scattering. A key characteristic of these structural colors is that their color does not change with the viewing angle. However, the presence of amorphous sequences in amorphous structures inevitably leads to strong incoherent multiple scattering, resulting in a decline in the quality of structural colors, such as reduced saturation, whitening, and weakened brightness. This significantly limits the application of non-iridescent structural color materials in photonic devices. To address this issue, black substances such as polypyrrole, graphene, carbon black, or PDA are typically added. Their strong light absorption and wide absorption range are utilized to suppress incoherence and multiple scattering, thereby improving the saturation of the structural color. Therefore, we can combine black light-absorbing substances with colloidal particles to prepare high-quality non-iridescent structural color materials.

[0003] Structural color inks are novel materials that utilize the arrangement of colloidal particles or block copolymers within a matrix to form specific structures, thereby controlling light propagation and exhibiting a beautiful optical appearance. Generally, high-fidelity, stable, and diverse structural color patterns or components can be created using structural color inks through methods such as 3D printing, inkjet printing, direct ink writing, or fused deposition modeling. Among these, 3D printing, as an emerging printing technology, can manufacture arbitrary geometric shapes without the need for stencil prefabrication, etching, or masking required by traditional processes, and has been used to construct complex three-dimensional graphics. By combining 3D printing technology with structural color inks, printed devices with structural color appearances have potential applications in areas such as anti-counterfeiting labels and encryption codes. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a non-iridescent structural color ink for optical anti-counterfeiting that can be used in 3D printing.

[0005] The non-iridescent structural color ink provided by this invention is obtained by blending colloidal particles coated with a soft shell and containing a PDA intermediate layer with a small molecule organic matrix. During the shear mixing process, the strong interaction between the swollen soft shell and the matrix generates high viscosity and strong interparticle forces, forming a short-range ordered but long-range disordered structure. At the same time, the high viscosity and excellent rheological properties give the structural color ink the feasibility of 3D printing. In addition, due to the strong light absorption properties of PDA, the prepared structural color ink appears black under natural light, but exhibits a bright color under strong light, which can be used in the field of anti-counterfeiting structural color ink.

[0006] The method for preparing non-iridescent structural color ink provided by this invention involves blending colloidal particles coated with a soft shell and containing a PDA interlayer with a small molecule organic matrix. The specific steps are as follows:

[0007] (1) Preparation of core-shell structured colloidal particles

[0008] Colloidal particles are coated with a polydopamine (PDA) intermediate layer of a certain thickness, and then the nanoparticles are coated with a polymer soft shell to form core-shell structured colloidal particles.

[0009] (2) Preparation of non-iridescent structural color inks

[0010] The core-shell structured colloidal particles obtained in step (1) are mixed with a small molecule organic matrix at a certain volume fraction. After mixing and shearing, a non-iridescent structural color ink is obtained.

[0011] Furthermore,

[0012] In step (1), the colloidal particles include, but are not limited to, silica (SiO2), titanium dioxide (TiO2), polystyrene (PS), polyacrylic acid (PAA), polymethacrylic acid (PMAA), polymethyl methacrylate (PMA), polymethyl methacrylate (PMMA), polyglycidyl methacrylate (PGMA), polyhydroxyethyl methacrylate (PHEMA), polylactic acid (PLA), polycaprolactone (PCL), polystyrene / divinylbenzene (PS-DVB), polyethyleneimine (PEI), polyacrylamide (PAAM), polyvinyl alcohol (PVA), poly(N-isopropylacrylamide) (PNIPAM), poly(1-vinylimidazolium) (PVIM), and poly(tert-butylaminoethyl methacrylate) (TBAEMA).

[0013] In step (1), the particle size of the colloidal nanoparticles can be controlled between 100 and 300 nm. As a further preferred option, when the particle size of the nanoparticles is between 120 and 240 nm, a non-iridescent structural color ink in the full visible light range can be obtained.

[0014] In step (1), the thickness of the intermediate PDA layer can be controlled to be 2 to 30 nm. As a further preferred option, when the thickness of the intermediate PDA layer is 5 to 20 nm, a non-iridescent structural color ink in the full visible light range can be obtained.

[0015] In step (1), the polymer soft shell surrounding the colloidal particles includes, but is not limited to, hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), hydroxypropyl methacrylate (HPMA), acrylic acid (AA), ethyl acrylate (EA), ethyl methacrylate (EMA), methacrylic acid (MAA), n-butyl acrylate (n-BA), n-butyl methacrylate (n-BMA), isobutyl methacrylate (i-BMA), isooctyl acrylate (2-EHA), n-octyl acrylate (OA), glycidyl methacrylate (GMA), and isopropyl methacrylate (i-PMA).

[0016] In step (2), the small molecule organic matrix includes, but is not limited to, hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA), acrylic acid (AA), methacrylic acid (MAA), ethyl acrylate (EA), ethyl methacrylate (EMA), butyl acrylate (BA), n-butyl methacrylate (BMA), methyl methacrylate (MMA), methyl acrylate (MA), hydroxybutyl acrylate (4-HBA), isobutyl methacrylate (i-BMA), etc.

[0017] In step (2), the volume fraction of the colloidal particles can be controlled between 21.7% and 48.9%. As a further preferred option, high-quality structural color ink can be obtained when the volume fraction of the colloidal particles is controlled between 25.6% and 38.6%.

[0018] In step (2), the obtained structural color ink can be used in 3D printing technology to prepare complex, fine and customizable structural color devices.

[0019] Compared with the prior art, the main technical features and beneficial effects of this invention are as follows:

[0020] (1) The present invention uses colloidal particles coated with a soft shell and containing a PDA intermediate layer and a small molecule organic matrix to obtain structural color ink. The method is simple to operate, highly repeatable, and does not pollute the environment, making it easy to prepare on a large scale. By adjusting the particle size of the colloidal particles or the content of the colloidal particles and the small molecule organic matrix, structural color ink with a full visible spectrum range can be obtained, and the color is single and does not contain other impurity colors.

[0021] (2) The structural color ink prepared by the present invention has non-iridescent properties and exhibits no angle dependence mainly because the soft shell of the colloidal particles is fully swollen in the presence of small molecule organic matrix. While having high viscosity, it generates strong interparticle forces. During the mixing and shearing process, these nanoparticles tend to adhere to each other, eventually forming a short-range ordered but long-range disordered nanostructure. This provides a new idea for the preparation of non-iridescent structural color ink.

[0022] (3) The structural color ink prepared by the present invention has a PDA intermediate layer in the colloidal particles of the building unit, which has strong light absorption and wide range of light absorption characteristics. This makes the ink appear black under natural light, but exhibits a beautiful structural color feature under strong light. This has potential application value in anti-counterfeiting labels, encrypted information, and customized coding.

[0023] (4) The structural color ink prepared by the present invention has excellent rheological properties and can be directly used in 3D printing technology to prepare optical anti-counterfeiting non-iridescent structural color devices of arbitrary shapes, which has application prospects in the field of wide-angle display. Attached Figure Description

[0024] Figure 1 Macroscopic photographs and reflection spectra of the four non-iridescent structural color inks (blue, green, yellow, and orange) used in Examples 1, 2, 3, and 4 under natural and strong light illumination.

[0025] Figure 2 These are photographs of the four non-iridescent structural color inks—blue, green, yellow, and orange—used in Examples 1, 2, 3, and 4, taken from different angles.

[0026] Figure 3 The images are scanning electron microscope (SEM) images of the four non-iridescent structural color inks (blue, green, yellow, and orange) in Examples 1, 2, 3, and 4, and the Fast Fourier Transform (FFT) images based thereon, showing a structure that is ordered in the short range but disordered in the long range.

[0027] Figure 4 Macroscopic photographs and reflection spectra of the four non-iridescent structural color inks (purple, cyan, green, and yellow) used in Examples 5, 6, 7, and 8 under natural light and strong light.

[0028] Figure 5 These are photographs of the four non-iridescent structural color inks—purple, cyan, green, and yellow—used in Examples 5, 6, 7, and 8, taken from different angles.

[0029] Figure 6Macroscopic photographs and reflectance spectra of four non-iridescent structural color inks (blue, cyan, yellow-green, and yellow) formed at different colloidal particle volume fractions in Examples 9, 10, 11, and 12, under strong light irradiation.

[0030] Figure 7 Macroscopic photographs and reflectance spectra of four non-iridescent structural color inks—blue, cyan, blue-green, and yellow-green—formed by mixing colloidal particles with different small-molecule organic matrices in Examples 13, 14, 15, and 16, under strong light irradiation.

[0031] Figure 8 The pattern with optical anti-counterfeiting features is prepared by 3D printing using the structural color ink described in Examples 1-8 in Example 17. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments and accompanying drawings. However, it should be understood that other embodiments made by other personnel in the art based on the embodiments in this application without creative effort are all within the protection scope of this application.

[0033] Example 1

[0034] (1) 200 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 171 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 180 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0035] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%, resulting in a non-iridescent structural color ink for optical anti-counterfeiting. This ink appears black under natural light and blue under strong light, with a maximum reflection wavelength of 468 nm. The structural color ink exhibits similar blue colors at different angles (0°, 10°, 20°, 30°, 40°); (macroscopic photos and reflection wavelengths are shown in the image). Figure 1 As shown in Example 1, photos from different angles are as follows: Figure 2 (As shown in Example 1).

[0036] Example 2

[0037] (1) 200 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 171 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.15 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 189 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0038] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and green under strong light, with a maximum reflection wavelength of 509 nm. The structural color ink exhibited similar green photos at different angles (0°, 10°, 20°, 30°, 40°); (macroscopic photos and reflection wavelengths are shown in the image below). Figure 1 As shown in Example 2, photos from different angles are as follows: Figure 2 (As shown in Example 2).

[0039] Example 3

[0040] (1) 200 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was reacted at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 171 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.20 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 195 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0041] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and yellow under strong light, with a maximum reflection wavelength of 553 nm. The structural color ink exhibited similar yellow colors in photographs taken at different angles (0°, 10°, 20°, 30°, 40°); (macroscopic photographs and reflection wavelengths are shown in the figure). Figure 1 As shown in Example 3, photos from different angles are as follows: Figure 2 (As shown in Example 3).

[0042] Example 4

[0043] (1) 200 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 171 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.25 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 208 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0044] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and orange under strong light, with a maximum reflection wavelength of 605 nm. The structural color ink exhibited similar orange colors at different angles (0°, 10°, 20°, 30°, 40°); (macroscopic photos and reflection wavelengths are shown in the image). Figure 1 As shown in Example 4, photos from different angles are as follows: Figure 2 (As shown in Example 4).

[0045] Example 5

[0046] (1) 220 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was reacted at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 165 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 176 nm. These nanoparticles were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0047] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and purple under strong light, with a maximum reflection wavelength of 432 nm. The structural color ink exhibited similar purple colors in photographs taken at different angles (0°, 10°, 20°, 30°, 40°). (Macroscopic photographs and reflection wavelengths are shown in the image.) Figure 4 As shown in Example 5, photos from different angles are as follows: Figure 5 (As shown in Example 5).

[0048] Example 6

[0049] (1) 170 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 182 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 209 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0050] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and cyan under strong light, with a maximum reflection wavelength of 476 nm. The structural color ink exhibited similar cyan photos at different angles (0°, 10°, 20°, 30°, 40°); (macroscopic photos and reflection wavelengths are shown in the image). Figure 4 As shown in Example 6, photos from different angles are as follows: Figure 5 (As shown in Example 6).

[0051] Example 7

[0052] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0053] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and green under strong light, with a maximum reflection wavelength of 518 nm. The structural color ink exhibited similar green photos at different angles (0°, 10°, 20°, 30°, 40°): (Macroscopic photos and reflection wavelengths are shown in the image below). Figure 4 As shown in Example 7, photos from different angles are as follows: Figure 5 (As shown in Example 7).

[0054] Example 8

[0055] (1) 100 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 223 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 255 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0056] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 95 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears black under natural light and yellow under strong light, with a maximum reflection wavelength of 557 nm. The structural color ink exhibited similar yellow colors in photographs taken at different angles (0°, 10°, 20°, 30°, 40°); (macroscopic photographs and reflection wavelengths are shown in the figure). Figure 4 As shown in Example 8, photos from different angles are as follows: Figure 5 (As shown in Example 8).

[0057] Example 9

[0058] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0059] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 63 μL hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of the SiO2@PDA@PHEMA nanoparticles was 43.6%, resulting in a non-iridescent structural color ink for optical anti-counterfeiting. Under strong light, the ink appears blue, with a maximum reflection wavelength of 425 nm. (Photos and reflection wavelengths are shown below.) Figure 6 (As shown in Example 9).

[0060] Example 10

[0061] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0062] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 78 μL hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of the SiO2@PDA@PHEMA nanoparticles was 38.6%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appeared cyan under strong light, with a maximum reflection wavelength of 482 nm. (Photo and reflection wavelength are shown below.) Figure 6 As shown in the image.

[0063] Example 11

[0064] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0065] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 116 μL hydroxyethyl methacrylate (HEMA) were thoroughly mixed until homogeneous. At this point, the volume fraction of the SiO2@PDA@PHEMA nanoparticles was 29.7%, resulting in a non-iridescent structural color ink for optical anti-counterfeiting. This ink appears yellow-green under strong light, with a maximum reflection wavelength of 545 nm. (Photo and reflection wavelength are shown below.) Figure 6 As shown in Figure 11.

[0066] Example 12

[0067] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0068] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 143 μL of hydroxyethyl methacrylate (HEMA) were thoroughly mixed until the volume fraction of the SiO2@PDA@PHEMA nanoparticles was 25.6%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which appears yellow under strong light and has a maximum reflection wavelength of 566 nm. (Photo and reflection wavelength are shown below.) Figure 6 As shown in the image.

[0069] Example 13

[0070] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0071] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) were completely mixed with 91 μL of acrylic acid (AA), resulting in a volume fraction of 34.0% for the SiO2@PDA@PHEMA nanoparticles. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which displays blue under strong light and has a maximum reflection wavelength of 441 nm. (Photo and reflection wavelength are shown below.) Figure 7 As shown in the image.

[0072] Example 14

[0073] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0074] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) were completely mixed with 100 μL of methacrylic acid (MAA), resulting in a volume fraction of 34.0% for the SiO2@PDA@PHEMA nanoparticles. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which displays a cyan color under strong light and has a maximum reflection wavelength of 491 nm. (Photo and reflection wavelength are shown below.) Figure 7 As shown in the image.

[0075] Example 15

[0076] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0077] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) were completely mixed with 91 μL of hydroxyethyl acrylate (HEA), resulting in a volume fraction of 34.0% for the SiO2@PDA@PHEMA nanoparticles. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which displays a blue-green color under strong light, with a maximum reflection wavelength of 512 nm. (Photo and reflection wavelength are shown below.) Figure 7 As shown in the image.

[0078] Example 16

[0079] (1) 120 μL of SiO2 seed solution, 8 mL of ammonia (NH3·H2O), 240 mL of anhydrous ethanol (EtOH), and 60 mL of water (H2O) were mixed together in a 500 mL reaction flask. Then, 16 mL of tetraethyl orthosilicate (TEOS) was injected into the solution at a rate of 1.9 mL / h using a syringe pump. After complete injection of TEOS, the solution was allowed to react at room temperature for another 6 hours. Finally, SiO2 colloidal nanoparticles with a particle size of 201 nm were obtained by centrifugation and washing three times with ethanol and deionized water. Then, 0.40 g of silica particles (SiO2) and 0.10 g of dopamine hydrochloride (DA·HCl) were reacted in 100 mL of TrisBuffer solution (10 mM, pH = 8.5) for 30 hours to obtain SiO2@PDA nanoparticles with a particle size of 232 nm. These were also washed three times with ethanol and deionized water by centrifugation. Finally, 100 mg of SiO2@PDA nanoparticles were dispersed in 100 mL of acetonitrile (ACN) and sonicated for 5 minutes. Then, 475 μL of hydroxyethyl methacrylate (HEMA), 120 mg of methylene bisacrylamide (MBA) and 12 mg of azobisisobutyronitrile (AIBN) were added and sonicated for 10 minutes. The dispersion was then refluxed at 110 °C for 2 hours to precipitate. The obtained SiO2@PDA@PHEMA nanoparticles were washed three times each with ethanol and deionized water and then dried in a vacuum oven for 6 hours.

[0080] (2) The 100 mg SiO2@PDA@PHEMA nanoparticles obtained in step (1) and 99 μL of hydroxybutyl acrylate (4-HBA) were thoroughly mixed until the volume fraction of the SiO2@PDA@PHEMA nanoparticles was 34.0%. This yielded a non-iridescent structural color ink for optical anti-counterfeiting, which displays a yellow-green color under strong light, with a maximum reflection wavelength of 546 nm. (Photo and reflection wavelength are shown below.) Figure 7 As shown in the image.

[0081] Example 17

[0082] The non-iridescent structural color ink from the above embodiments was used in 3D printing to prepare complex and customizable patterns. At room temperature, using a 0.26 mm printing nozzle and 10 mm·s... -1 The printing speed enables the printing of various patterns, such as pentagonal shapes and butterflies; in addition, simple English words and Chinese characters can also be printed accurately, and these patterns display the same structural color when viewed from different angles. (Photos are shown.) Figure 8 As shown.

Claims

1. A method for preparing an optical anti-counterfeiting non-iridescent structural color ink for 3D printing, characterized in that, The specific steps are as follows: (1) Preparation of core-shell structured colloidal particles Colloidal particles are coated with a polydopamine (PDA) interlayer, and then the composite nanoparticles are coated with a polymer soft shell to form core-shell structured colloidal particles; wherein the particle size of the colloidal nanoparticles is 100~300 nm, and the thickness of the PDA is 2~30 nm. (2) Preparation of non-iridescent structural color inks The core-shell structured colloidal particles obtained in step (1) are mixed with a small molecule organic matrix at a volume fraction of 21.7% to 48.9%, and after mixing and shearing, a non-iridescent structural color ink is obtained. The polymer soft shell material in step (1) is selected from hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, acrylic acid, ethyl acrylate, ethyl methacrylate, methacrylic acid, n-butyl acrylate, n-butyl methacrylate, isobutyl methacrylate, isooctyl acrylate, glycidyl methacrylate, and isopropyl methacrylate. The material of the small molecule organic matrix in step (2) is selected from hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, ethyl acrylate, ethyl methacrylate, butyl acrylate, n-butyl methacrylate, methyl methacrylate, methyl acrylate, hydroxybutyl acrylate, and isobutyl methacrylate.

2. The preparation method according to claim 1, characterized in that, The colloidal particles mentioned in step (1) are selected from silica, titanium dioxide, polystyrene, polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, polylactic acid, polycaprolactone, polystyrene / divinylbenzene, polyethyleneimine, polyacrylamide, polyvinyl alcohol, poly-N-isopropylacrylamide, poly-1-vinylimidazole, and polytert-butylaminoethyl methacrylate.

3. A non-iridescent structural color ink obtained by the preparation method described in claim 1 or 2.

4. The application of the non-iridescent structural color ink as described in claim 3 in 3D printing technology to prepare complex, delicate, and customizable wide-viewing-angle structural color devices.

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