CN113539392B - A kind of preparation method of structural color microsphere shell based on FDTD - Google Patents

Abstract

The present invention provides a method for preparing a structural color microsphere shell based on FDTD, comprising the following steps: Step 1, the structure of the designed structural color microsphere shell includes an inner phase, a shell layer covering the inner phase, and an outer phase located outside the shell layer. , set the refractive index of each component, and build a microsphere shell model based on the structure of the structural color microsphere shell based on the FDTD algorithm. By changing the structural parameters of the microsphere shell model, the reflection spectrum of the structural color microsphere shell is simulated to establish the structure The relationship between the parameters and the structural color, and the corresponding structural parameters are determined according to the structural color that the structural color microsphere shell needs to produce; Step 2, the multiphase fluid is introduced into the capillary microfluidic chip, and the flow rate of the external phase solution is adjusted according to the structural parameters. , the flow rate of the shell material solution and the gas pressure of the inner phase gas, to prepare the liquid layer microsphere shell; step 3, according to the difference of the shell layer material solution, adopt the corresponding curing method to solidify the liquid layer microsphere shell to obtain a stable separation from the liquid environment The presence of structural color microsphere shells.

Description

A kind of preparation method of structural color microsphere shell based on FDTD

technical field

The invention belongs to the field of structural color materials, in particular to a method for preparing a structural color microsphere shell based on FDTD.

Background technique

Humans can perceive colorful colors because the optic nerve cells of the human eye have specific stimulus responses to different frequencies of light (350-750nm). The spectral distribution that makes humans perceive color comes from the interaction between the medium and light. According to the different mechanisms of color generation, it can be divided into pigment coloring and structural coloring (Rep.Prog.Phys.2008,71,076041.). Pigment coloration comes from the absorption of specific wavelengths of light by objects. Structural color formation comes from some basic physical optical processes, such as reflection, refraction, interference, diffraction, scattering, etc. (RSCAdv. 2013, 3, 14865.). Structurally colored objects can control the spatial distribution of light, so structurally colored materials usually have an iridescent effect, that is, the color changes significantly with the change of viewing angle.

Compared with the chemical coloring method often used in the manufacturing industry, structural color-forming materials have the characteristics of high saturation, high brightness, adjustable color, long-term color development, and green preparation process. great application prospects. Structural color materials with iridescent effect are also often used in anti-counterfeiting, information preservation and other fields. Common color-forming structures such as thin-film interference, diffraction gratings, and photonic crystals have been fully studied and extended to the preparation of multi-functional materials such as uniform color-developing films and colloidal inks (Adv.Opt.Mater.2020,8,2000234.) . In order to obtain more broad-spectrum light modulation methods, researchers are still looking for new micro-nano structures to obtain structural color phenomena with different spatial distributions, and FDTD is favored by researchers as an efficient technical means for predicting structural color.

FDTD is a numerical calculation method that converts Maxwell's equations into difference equations by meshing (Comput.Phys.Commun.2010, 181, 687.), which can quickly calculate the target structure through the transient response of the target structure to the incident pulsed plane wave Scattering properties over a wide frequency range. Therefore, FDTD is often used to study the reflection properties of structural color materials (Phys. Rev. E 2009, 80, 051924.).

Microfluidics is an emerging technology that precisely controls fluid flow at the micrometer scale. It has the characteristics of high precision, easy regulation and low cost, and is often used in the preparation of structural color materials. The monodispersity of the microstructures prepared by this method is good. Controlling the consistency of structural color units from the micron scale can further improve the purity of structural color materials and enhance the overall advantages of materials.

In the prior art, the analysis of structural color is relatively complicated, the reflection spectrum of structural color material cannot be obtained by rapid analysis, the process of preparing structural color material is relatively complicated, and the degree of controllability is low, and there is no combination of FDTD algorithm and microfluidic control. technology to prepare structured light materials.

SUMMARY OF THE INVENTION

The present invention is made to solve the above-mentioned problems, and the purpose is to provide a method for preparing structural color microsphere shells based on FDTD.

The present invention provides a method for preparing a structural color microsphere shell based on FDTD, which has such characteristics and includes the following steps: Step 1, the structure of the designed structural color microsphere shell includes an inner phase, a shell layer covering the inner phase, and a For the outer phase outside the shell, set the refractive indices of the inner phase, the shell and the outer phase, and build the microsphere shell model based on the structure of the structural color microsphere shell based on the FDTD algorithm. By changing the structural parameters of the microsphere shell model, the simulation obtains The reflection spectrum of the structural color microsphere shell is used to establish the relationship between the structural parameters and the structural color, and the corresponding structural parameters are determined according to the structural color that the structural color microsphere shell needs to produce;

In step 2, the multiphase fluid is introduced into the capillary microfluidic chip, and the flow rate of the outer phase solution, the flow rate of the shell material solution and the gas pressure of the inner phase gas are correspondingly adjusted according to the structural parameters to prepare a liquid layer microsphere shell;

Step 3, according to the difference of the shell layer material solution, adopt the curing method corresponding to the shell layer material solution to solidify the liquid layer microsphere shell to obtain a structural color microsphere shell that is stably separated from the liquid environment,

Among them, the inner phase gas is high-purity nitrogen gas, the outer phase solution is polyvinyl alcohol aqueous solution, the shell material solution is hydrogel precursor or nano-silica colloid, and the structural parameters include the radius of the microsphere shell, the thickness of the shell layer and the degree of deviation , in step 2, the radius is changed by adjusting the flow rate of the outer phase solution and the pressure of the inner phase, and the thickness of the shell layer is changed by adjusting the flow rate of the shell material solution.

In the method for preparing structural color microsphere shells based on FDTD provided by the present invention, it may also have the following characteristics: wherein, in step 1, the microsphere shell model is a two-dimensional microsphere shell in the z-x plane, and the Among the structural parameters, the radius is 26μm-34μm, the shell thickness is 0.6μm-1.2μm, and the degree of deviation is that the two sphere centers of the microsphere shell model have a deviation of 0μm-xμm in the vertical direction z, and x is the thickness of the shell layer. .

In the method for preparing structural color microsphere shells based on FDTD provided by the present invention, it may also have the following characteristics: wherein, in step 1, the medium refractive index of the inner phase in the microsphere shell model is set to be 1, and the The refractive index is 1.45 and the refractive index of the outer phase is 1.34.

The FDTD-based structural color microsphere shell preparation method provided by the present invention may also have the following characteristics: wherein, in step 1, by changing the structural parameters of the microsphere shell model, the reflection spectrum of the microsphere shell is obtained by simulation The specific process is as follows: The reflection spectrum is obtained by setting the plane wave light source and the monitor. The plane wave light source is a broad-spectrum Gaussian pulse, and the pulse length is less than 33fs. The electric field polarization direction of the plane wave light source is perpendicular to the plane of the microsphere shell model, and the monitor is a point monitor. The device is set at the center of the thickness of the edge shell to monitor the electric field intensity Ey at the set place. The wavelength range for monitoring is 350nm-750nm. The plane wave light source emits incident pulses and passes through the microsphere shell model, and the transmission through the shell is monitored by the monitor. After receiving the pulse, the ratio of the incident pulse spectrum to the received pulse spectrum is taken as the reflection spectrum.

In the preparation method of FDTD-based structural color microsphere shell provided by the present invention, it can also have the following characteristics: wherein, in step 3, when the shell material solution is nano-silica colloid, it is cured by solvent volatilization, corresponding to Silica microsphere shells that exist stably out of the liquid environment are obtained, and when the shell material solution is a hydrogel precursor, the hydrogel microsphere shells that exist stably out of the liquid environment are correspondingly obtained by curing under ultraviolet light.

The FDTD-based method for preparing structural color microsphere shells provided by the present invention may also have the feature that the structural color of the liquid layer microsphere shells changes with time until the inner phase gas is completely dissolved into the surrounding environment.

The FDTD-based method for preparing structural color microsphere shells provided by the present invention may also have the following characteristics: wherein, the structural color microsphere shells have an aspherical symmetric core-shell structure, and the thickness of the shell layer of the structural color microsphere shells The thinnest part is less than 100 nm, the thickest part is more than 1 μm, and the outer diameter of the spherical shell of the structural color microsphere shell is 10 μm-100 μm.

The role and effect of the invention

According to a method for preparing structural color microsphere shells based on FDTD involved in the present invention, because a corresponding microsphere shell model is constructed according to the structure of the structural color microsphere shell based on the FDTD algorithm to establish the relationship between the structural parameters and the structural color, the FDTD algorithm It has high stability, fast calculation speed, small memory occupation, can efficiently obtain the electric field distribution at any position in the microsphere shell structure, and is convenient for analyzing the generation of optical interference; and the preparation method of the invention is simple, high in controllability and low in cost, It can be expanded to prepare a variety of structural color microsphere shells with different functions. In addition, the structural color microsphere shell prepared by the present invention is an aspherical symmetric core-shell structure, and has a novel color-forming structure. The structure has less requirements on the types of constituent materials and physical and chemical properties, and can increase the reflectivity of incident light and improve the structure. Through this structure, the spatial distribution of light can be modulated, and it has important application prospects in various fields such as micro-nano photonic devices and structural color anti-counterfeiting.

Description of drawings

Fig. 1 is the side structure schematic diagram of the microsphere shell model in the embodiment of the present invention;

Fig. 2 is the FDTD model diagram of the microsphere shell model in the embodiment of the present invention;

3 is the reflection spectrum corresponding to the microsphere shell model with a radius of 30 μm, a shell thickness of 0.9 μm, and a deviation degree of 0.8 μm in the embodiment of the present invention;

4 is a light microscope comparison diagram of the liquid layer microsphere shells corresponding to the shell material solution flow rates of 1300 μL/h and 1500 μL/h in the embodiment of the present invention;

Fig. 5 is the light microscope view of hydrogel microsphere shell in the embodiment of the present invention;

Fig. 6 is the electron microscope picture of hydrogel microsphere shell in the embodiment of the present invention;

Fig. 7 is the light microscope view of silica microsphere shell in the embodiment of the present invention;

FIG. 8 is an electron microscope image of the silica microsphere shell in the embodiment of the present invention.

Detailed ways

In order to make the technical means and effects realized by the present invention easy to understand, the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

<Example>

A method for preparing a FDTD-based structural color microsphere shell of the present embodiment includes the following steps:

Step 1, the structure of the structural color microsphere shell is designed, including the inner phase, the shell layer covering the inner phase, and the outer phase located outside the shell layer, and the refractive indices of the inner phase, the shell layer and the outer phase are set, and based on the FDTD algorithm, according to the structure color The structure of the microsphere shell is constructed to obtain the microsphere shell model. By changing the structural parameters of the microsphere shell model, the reflection spectrum of the structural color microsphere shell is simulated to establish the relationship between the structural parameters and the structural color. The structural color to be generated determines the corresponding structural parameters.

The inner phase, the shell layer and the outer phase are prepared from the inner phase gas, the shell layer material solution and the outer phase solution, respectively.

The inner phase gas is high-purity nitrogen gas, the outer phase solution is a polyvinyl alcohol aqueous solution, and the shell material solution is a hydrogel precursor or nano-silica colloid.

In step 1, the microsphere shell model is a two-dimensional microsphere shell in the z-x plane,

FIG. 1 is a schematic side view of a microsphere shell model in an embodiment of the present invention.

As shown in FIG. 1 , the microsphere shell model includes a shell layer 1 covering the inner phase, an inner phase 2 , and an outer phase 3 located outside the shell layer.

In this embodiment, the microsphere shell model is constructed by using the software MEEP based on the FDTD algorithm.

The structural parameters include the radius of the microsphere shell, the thickness of the shell layer, and the degree of deviation,

Among the structural parameters of the microsphere shell model, the radius is 26μm-34μm, the shell thickness is 0.6μm-1.2μm, and the degree of deviation is that the two sphere centers of the microsphere shell model have a deviation of 0μm-xμm in the vertical direction z, x is the shell thickness.

In the microsphere shell model, the medium refractive index of the inner phase is set to 1, the refractive index of the shell layer is 1.45, and the refractive index of the outer phase is 1.34.

FIG. 2 is an FDTD model diagram of a microsphere shell model in an embodiment of the present invention.

As shown in Figure 2, in step 1, by changing the structural parameters of the microsphere shell model, the specific process of simulating the reflection spectrum of the microsphere shell is as follows:

The reflection spectrum is obtained by setting the plane wave light source 4 and the monitor 5,

The plane wave light source 4 is a broad-spectrum Gaussian pulse, the pulse length is less than 33fs, the electric field polarization direction of the plane wave light source 4 is perpendicular to the plane of the microsphere shell model,

The monitor 5 is a point monitor, set at the center of the thickness of the edge shell, and used to monitor the electric field intensity Ey at the set place, and the monitored wavelength range is 350nm-750nm,

The plane wave light source 4 is turned on, the plane wave light source 4 sends out incident pulses and passes through the microsphere shell model, and the received pulses transmitted through the shell layer within the observation time are monitored by the monitor 5 . Since the incident pulse on the sidewall in this structure propagates through the shell and is retroreflected from the sidewall at the symmetrical end, the incident pulse spectrum and the received pulse spectrum are directly regarded as the reflection spectrum of the entire microsphere shell model.

In this embodiment, the reflection spectrum of a microsphere shell model with a radius of 30 μm, a shell thickness of 0.9 μm, and a deviation degree of 0.8 μm is also tested. Reflectance spectra corresponding to the microsphere shell model with a degree of 0.8 μm.

As shown in Figure 3, when the radius of the microsphere shell model is 30 μm, the thickness of the shell layer is 0.9 μm, and the degree of deviation is 0.8 μm, it can be clearly seen that there are reflection spectrum peaks at 370 nm and 580 nm, indicating that the light waves of the corresponding wavelengths Constructive interference within the structure can produce corresponding structural colors.

In step 2, a multiphase fluid is introduced into the capillary microfluidic chip, and the flow rate of the outer phase solution, the flow rate of the shell material solution and the pressure of the inner phase gas are adjusted correspondingly according to the structural parameters to prepare a liquid layer microsphere shell.

In this example, a capillary with a certain diameter is prepared by using a capillary pulling needle, and then combined with a specific surface chemical modification to make the capillary hydrophilic/hydrophobic, and the capillary is aligned with a square tube to prepare a confocal-flow focusing microfluidic chip. Based on the prepared capillary microfluidic chip, a microfluidic pump and a pressure regulator are used to control the liquid flow rate and gas pressure flowing into the channel. Under the appropriate flow rate and pressure, liquid-layer microsphere shells with uniform size can be prepared.

In this embodiment, the specific process of introducing multiphase fluid into the capillary microfluidic chip to obtain the liquid layer microsphere shell is as follows:

Step 2-1: First, a capillary microfluidic chip is prepared by capillary pulling method and surface chemical modification.

Step 2-2, prepare the shell material solution and the external phase solution,

Step 2-3: Pass the shell material solution and the outer phase solution into the capillary microfluidic chip in different directions, and control the flow rate of the outer phase solution to be 40000-50000 μL/h, and the flow rate of the shell material solution to be 1000-2000 μL/h. When the gas pressure of the phase gas is 10-20 psi, a large batch of monodisperse liquid-layered microsphere shells can be prepared, and a cover glass is covered on the surface of the liquid-layered microsphere shells to ensure the smoothness of the liquid surface and prevent the shells from cracking. Liquid-layered microsphere shells with the same color distribution.

In steps 2-4, the radius is changed by adjusting the flow rate of the outer phase solution and the pressure of the inner phase, and the thickness of the shell layer is changed by adjusting the flow rate of the shell material solution.

In this example, different liquid-layer microsphere shells were obtained by adjusting the flow rate of the shell material solution to 1300 μL/h and 1500 μL/h, and the structural colors were compared. FIG. 4 is the shell material solution in the embodiment of the present invention. Light microscope comparison of liquid-layer microsphere shells corresponding to flow rates of 1300 μL/h and 1500 μL/h.

As shown in Figure 4, the liquid layer microsphere shells obtained by changing the flow rate of the shell material solution have different structural colors.

The structural color of the liquid-layered microsphere shell changes with time until the inner phase gas is completely dissolved into the surrounding environment.

Step 3, according to the difference of the shell layer material solution, adopt the curing method corresponding to the shell layer material solution to solidify the liquid layer microsphere shells to obtain the structural color microsphere shells that are stably separated from the liquid environment.

When the shell material solution is a hydrogel precursor, by curing under ultraviolet light, a structural color microsphere shell that is stably separated from the liquid environment is obtained. In this embodiment, the specific process is as follows:

Using the hydrogel precursor as the shell material solution, the hydrogel precursor microsphere shell was prepared according to step 2. After covering the surface of the sample with a cover glass, it was irradiated with ultraviolet light for 2-3 minutes to obtain a cured microsphere. The hydrogel microsphere shell, Fig. 5 is the light microscope view of the hydrogel microsphere shell in the embodiment of the present invention,

As shown in Figure 5, the cured hydrogel microsphere shell still has structural color phenomenon.

Then the solidified structural color microsphere shells were washed and dried with deionized water, and the microsphere shells were observed by SEM.

As shown in Figure 6, it can be seen that the diameter of the microsphere shell is 25 μm, the thickness of the shell layer of the microsphere shell is not uniform, the thinnest part is less than 100 nm, and the thickness of the shell layer is greater than 1 μm in some places.

In step 3, when the shell material solution is nano-silica colloid, it is cured by solvent volatilization, correspondingly obtaining a silica microsphere shell that is stably separated from the liquid environment. In this embodiment, the specific process is as follows:

Using nano-silica colloid as the shell material solution, prepare silica colloid microsphere shells according to step 2, place the sample in a ventilated environment for more than 8 hours, and wait until the solvent of the colloid is completely volatilized to prepare silica microspheres. Spherical shell, the microsphere shell is washed and dried with deionized water, and the silica microsphere shell that is separated from the liquid environment and exists stably can be obtained.

As shown in Figure 7, the cured silica microsphere shell still has structural color phenomenon.

The silica microsphere shells were then observed by SEM, and FIG. 8 is an electron microscope image of the silica microsphere shells in the embodiment of the present invention.

As shown in Figure 8, the diameter of the silica microsphere shell is about 30 μm.

The structural color microsphere shell prepared by the FDTD-based structural color microsphere shell preparation method of this embodiment has an aspherical symmetric core-shell structure,

The thinnest part of the shell thickness of the structural color microsphere shell is less than 100 nm, the thickest part is more than 1 μm, and the outer diameter of the spherical shell of the structural color microsphere shell is 10 μm-100 μm.

Action and effect of the embodiment

According to a method for preparing structural color microsphere shells based on FDTD involved in this embodiment, because the corresponding microsphere shell model is constructed according to the structure of the structural color microsphere shell based on the FDTD algorithm to establish the relationship between structural parameters and structural color, FDTD The algorithm has high stability, fast calculation speed, and small memory occupation, and can efficiently obtain the electric field distribution at any position in the microsphere shell structure, which is convenient for analyzing the generation of optical interference; and the preparation method of this embodiment is simple, highly controllable, and cost-effective. It can be expanded to prepare a variety of structural color microsphere shells with different functions. In addition, the structural color microsphere shells prepared in this example have an aspherical symmetric core-shell structure and have a novel color-forming structure. This structure has less requirements on the types of constituent materials and physicochemical properties, and can increase the reflectivity of incident light and improve the The brightness of structural color, through which the spatial distribution of light can be modulated, has important application prospects in various fields such as micro-nano photonic devices and structural color anti-counterfeiting.

The above embodiments are preferred cases of the present invention, and are not intended to limit the protection scope of the present invention.

Claims (3)

1. A preparation method of a structural color microsphere shell based on FDTD is characterized by comprising the following steps:

step 1, designing a structure of a structural color microsphere shell to comprise an internal phase, a shell layer for coating the internal phase and an external phase positioned outside the shell layer, setting refractive indexes of the internal phase, the shell layer and the external phase, constructing and obtaining a microsphere shell model according to the structure of the structural color microsphere shell based on an FDTD algorithm, simulating and obtaining a reflection spectrum of the structural color microsphere shell by changing structural parameters of the microsphere shell model to establish the relation between the structural parameters and the structural color, and determining the corresponding structural parameters according to the structural color required to be generated by the structural color microsphere shell;

step 2, introducing a multi-phase fluid into the capillary microfluidic chip, and correspondingly adjusting the flow rate of the external phase solution, the flow rate of the shell material solution and the air pressure of the internal phase gas according to the structural parameters to prepare a liquid layer microsphere shell;

step 3, curing the liquid layer microsphere shell by adopting a curing mode corresponding to the shell material solution according to the difference of the shell material solution to obtain the structural color microsphere shell which stably exists in a liquid environment,

wherein the inner phase gas is high-purity nitrogen, the outer phase solution is a polyvinyl alcohol aqueous solution, the shell material solution is a hydrogel precursor or a nano silicon dioxide colloid,

the structural parameters comprise the radius of the microsphere shell, the shell layer thickness and the deviation degree,

in the step 2, the radius is changed by adjusting the flow rate of the external phase solution and the internal phase air pressure, the thickness of the shell layer is changed by adjusting the flow rate of the shell layer material solution,

in the step 1, the microsphere shell model is a two-dimensional microsphere shell in a z-x plane,

in the structural parameters of the microsphere shell model, the radius is 26-34 μm, the shell thickness is 0.6-1.2 μm, the deviation degree is that the two sphere centers of the microsphere shell model have the deviation of 0-x μm in the vertical direction z, and x is the shell thickness,

in the step 1, the specific process of obtaining the reflection spectrum of the microsphere shell through simulation by changing the structural parameters of the microsphere shell model is as follows: the reflection spectrum is obtained by providing a plane wave light source and a monitor,

the plane wave light source is a wide-spectrum Gaussian pulse, the pulse length is less than 33fs, the electric field polarization direction of the plane wave light source is vertical to the plane of the microsphere shell model,

the monitor is a point monitor, is arranged at the thickness center of the edge shell layer and is used for monitoring the electric field intensity Ey at the arranged position, the monitored wavelength range is 350nm-750nm,

the plane wave light source emits incident pulses, the incident pulses pass through the microsphere shell model, the monitor monitors received pulses transmitted by the shell, the ratio of the incident pulse spectrum to the received pulse spectrum is used as the reflection spectrum,

in the step 3, when the shell material solution is nano-silica colloid, the solvent is volatilized to solidify, and a silica microsphere shell which is separated from the liquid environment and stably exists is correspondingly obtained,

and when the shell material solution is a hydrogel precursor, curing under ultraviolet illumination to correspondingly obtain the hydrogel microsphere shell which is stably in a liquid environment.

2. The method of making an FDTD-based structurally colored microsphere shell according to claim 1, wherein:

wherein the structural color of the liquid layer microsphere shell changes over time until the inner phase gas is completely dissolved to the surrounding environment.

3. The method of making an FDTD-based structurally colored microsphere shell according to claim 1, wherein:

the structural color microsphere shell is of an asymmetric core-shell structure, the thinnest part of the shell layer thickness of the structural color microsphere shell is less than 100nm, the thickest part of the shell layer thickness of the structural color microsphere shell is more than 1 mu m, and the outer diameter of the microsphere shell of the structural color microsphere shell is 10 mu m-100 mu m.

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