Device and Method for Preparing Photonic Crystal Opal-Inverse Films Based on Microfluidic Chips

Abstract

The present invention discloses a device and method for preparing a photonic crystal inverse opal film based on a microfluidic chip. The device includes a cover plate, a bonding layer, and a bottom plate. The bonding layer is located between the cover plate and the bottom plate and connects the cover plate and the bottom plate into an integral structure. The cover plate is provided with a liquid addition hole A and a liquid addition hole B. The bonding layer is provided with a through hole A and a through hole B. The bottom plate is provided with a liquid storage tank A and a liquid storage tank B. The liquid addition hole A, the liquid storage tank A, and the through hole A are communicated with each other. The liquid addition hole B, the liquid storage tank B, and the through hole B are communicated with each other. The bonding layer is provided with a receiving cavity, which is a self-assembly area, and its top is an open end and is communicated with the outside air. The bonding layer is also provided with a tee-channel structure composed of a channel A, a channel B, and a channel C. Using this device to prepare a photonic crystal inverse opal film has the advantages of high forming quality, high speed, and low cost. In addition, it can also eliminate problems such as cracks generated during processes such as template drying and calcination, and high-performance products can be prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of photonic crystal inverse opal films, and particularly relates to a device and method for preparing photonic crystal inverse opal films based on a microfluidic chip. Background Art

[0002] Photonic crystals are a kind of photonic nanomaterials with photonic bandgap characteristics composed of periodically modulated dielectric materials. Light with specific wavelengths or frequencies in the photonic bandgap is prohibited from propagating through the photonic crystal. With the increasingly wide application of photonic crystal thin films as photonic materials and structural color substances, such as photonic ink systems, photonic rubber sheets, crystal lasers, bio / chemical sensors, and biomimetic materials, people's interest in colloidal crystal thin films has been continuously increasing, and the development of the preparation technology of photonic crystal thin films has become an important topic.

[0003] Using a photonic crystal as a template and filling it with a medium to form a porous structure with equally excellent optical properties is called a photonic crystal inverse opal. Among them, hydrogels are widely used as inverse opal materials. The preparation of the photonic crystal template is a prerequisite for the preparation of its inverse opal structure. Photonic crystals are generally prepared by the "bottom-up" self-assembly method. The self-assembly method is a simple, economical, and effective method. It is a process in which colloidal tissues spontaneously form an ordered arrangement, and it is to use a colloid or suspension of submicron spheres to prepare opal-like photonic crystals through the self-assembly process.

[0004] Among the common thin film self-assembly preparation methods, methods represented by the dip-coating method, spin-coating method, gravity method, and natural evaporation method are difficult to evaporate the solvent quickly, and the formed time of the prepared thin film is relatively long. For example, the formation of a thin film of the size of a glass slide generally takes more than ten hours or even several days. In addition, during the preparation process, such methods are easily affected by factors such as environmental temperature, humidity, and colloid concentration. The thin films under a long formation cycle often have uneven film thickness and uneven quality; self-assembly methods such as the centrifugation method and electrophoretic deposition method can shorten the formation time of the thin film, but they require additional driving forces, and the preparation system is often relatively complex. Therefore, developing a photonic crystal thin film preparation scheme with high forming quality, high speed, and low cost is a major challenge in this field.

[0005] Before filling the inverse opal material, it is generally necessary to completely dry the photonic crystal thin film template. Research shows that during the drying stage of the photonic crystal, under the constraint of a rigid substrate, the drying-induced shrinkage of colloidal particles generates capillary stress, which leads to the formation of cracks. In addition, cracks are sometimes formed during the transfer and calcination processes. These will undoubtedly reduce the quality of the inverse opal structure. It can be seen that how to effectively avoid cracks caused during the process from template assembly to inverse opal material filling is a key issue in the inverse opal thin film preparation technology. Summary of the Invention

[0006] A microfluidic chip is a device that manipulates and controls small - volume fluids through micro - channels with cross - sectional dimensions ranging from dozens to hundreds of micrometers, and realizes different functions by using different micro - channel structures. The self - assembly preparation technology of photonic crystal membranes based on microfluidic systems is a new and efficient method. The purpose of the present invention is to provide a device and method for preparing photonic crystal inverse opal membranes based on microfluidic chips. The photonic crystal inverse opal membranes prepared by it have the advantages of high forming quality, high speed, low cost, etc., and eliminate the cracks generated during processes such as template drying and calcination, providing a high - performance platform for the research of photonic crystal inverse opal membranes.

[0007] To achieve the above - mentioned purpose, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a device for preparing photonic crystal inverse opal membranes based on microfluidic chips, including a cover plate, a bonding layer, and a bottom plate; the bonding layer is located between the cover plate and the bottom plate and connects the cover plate and the bottom plate into an integral structure; the cover plate is provided with a liquid - adding hole A and a liquid - adding hole B, the bonding layer is provided with a through - hole A and a through - hole B, and on the side wall of the bottom plate facing the bonding layer, there are a liquid storage tank A and a liquid storage tank B. The liquid - adding hole A, the liquid storage tank A, and the through - hole A are mutually connected, and the liquid - adding hole B, the liquid storage tank B, and the through - hole B are mutually connected; the bonding layer is also provided with a self - assembly area, and the self - assembly area is a cavity located between the through - hole A and the through - hole B. The top of the cavity is an open end communicating with the outside air; the bonding layer is also provided with a flow channel A, a flow channel B, and a flow channel C; the flow channel C is in the vertical direction and communicates with the bottom of the cavity; the flow channel A connects the through - hole A and the flow channel C, and the included angle formed between the end of the flow channel A close to the flow channel C and the flow channel C is an acute angle; the flow channel B connects the through - hole B and the flow channel C, and the included angle formed between the end of the flow channel B close to the flow channel C and the flow channel C is an obtuse angle. Preferably, the widths of the flow channel A, the flow channel B, and the flow channel C are 50 - 200μm.

[0009] As a preferred technical solution, the bonding layer is provided with auxiliary evaporation areas on both sides of the open end of the cavity. The auxiliary evaporation areas have chambers communicating with the cavity. The setting of the chambers in the auxiliary evaporation areas can increase the contact area between the liquid in the cavity and the outside air, improve the evaporation speed of the solvent, and shorten the preparation period of the photonic crystal membrane.

[0010] As a preferred technical solution, the materials of the cover plate and the bottom plate are independently selected from one of high - molecular polymer materials such as polymethyl methacrylate, polydimethylsiloxane, or polystyrene; the material of the bonding layer is a pressure - sensitive double - sided adhesive, which can realize the bonding of the microfluidic chip at room temperature, and has stable bonding and low cost; the thickness of the pressure - sensitive double - sided adhesive is 10μm - 100μm to ensure that sufficient capillary force is generated in the self - assembly area to completely suck the colloidal emulsion into the cavity, and the area of the cavity is 0.1 - 5 cm 2 .

[0011] The second aspect of the present invention is to provide a method for preparing a photonic crystal inverse opal film based on a microfluidic chip, which is completed by using the photonic crystal film preparation device described in the first aspect above, and includes the following steps:

[0012] Perform hydrophilic treatment on the photonic crystal film preparation device by plasma treatment to enhance the capillary force inside the fluid chip pipeline. Add an excessive volume of colloidal emulsion containing monodisperse silica nanospheres into the liquid storage tank A from the liquid addition hole A. The colloidal emulsion enters the flow channel A under the action of capillary force. Part of the colloidal emulsion entering the flow channel A enters the flow channel B, and the other part enters the flow channel C. The colloidal emulsion entering the flow channel B stops at the connection between the flow channel B and the liquid storage tank B. The colloidal emulsion entering the flow channel C fills into the accommodation cavity to form a colloidal liquid film. Then cover the liquid addition hole A with a tape with micropores to ensure the air pressure balance in the liquid storage tank A and the evaporation from the micropores can be ignored. Seal the liquid addition hole B with a tape to avoid the evaporation of the emulsion from here. Place the photonic crystal inverse opal film preparation device in an oven with a constant temperature of 40-80°C with the open end of the accommodation cavity facing upwards, so that the solvent in the colloidal liquid film evaporates, and at the same time, the monodisperse nanospheres self-assemble to obtain a photonic crystal film template. Remove the tapes on the liquid addition hole A and the liquid addition hole B, and seal the liquid addition hole A with a tape, so that the operation of the emulsion in the liquid storage tank A and the flow channel A stagnates due to air pressure. Add the precursor solution into the liquid storage tank B from the liquid addition hole B. The precursor solution is connected to the flow channel B. Cover the liquid addition hole B with a tape with holes to ensure the air pressure balance in the liquid storage tank B and the evaporation from the micropores can be ignored. The solvent in the self-assembly area continuously evaporates at the open end, and the capillary force sucks the precursor solution in the liquid storage tank B into the self-assembly area through the flow channel B and the flow channel C. Since the density of the precursor solution is greater than that of the colloidal emulsion, and the included angle between the flow channel B and the flow channel C is an obtuse angle, the mixing of the precursor solution with the colloidal emulsion in the flow channel B can be reduced during the flow from low to high, and the included angle between the flow channel A and the flow channel C is an acute angle, which can prevent the precursor solution from entering the flow channel A. After the solvent in the self-assembly area completely evaporates, the precursor solution is filled into the photonic crystal film template by capillary force traction. Irradiate the precursor solution with an ultraviolet lamp to cure it. After curing, remove the template with a hydrofluoric acid solution to obtain the photonic crystal inverse opal film.

[0013] As a preferred technical solution, the colloidal emulsion containing monodisperse silica nanospheres is prepared by the following method: Dilute the silica nanospheres in a solvent and disperse them ultrasonically to form a relatively stable colloidal emulsion; Further preferably, the diameter of the silica nanospheres is 180 - 500 nm; The solvent is a mixed solvent composed of ethanol and water, and the volume ratio of ethanol to water is 1:1 - 1:5; The mass percentage of silica nanospheres in the colloidal emulsion is 5% - 10%. Preheat the colloidal emulsion in a constant temperature oven at 40 - 80 °C for 5 - 10 min before adding it to the storage tank A to remove the gas in the solvent and reduce the appearance of bubbles during the self-assembly process; The volume of the colloidal emulsion added to the storage tank A is 200 - 500 μl.

[0014] As a preferred technical solution, the precursor is prepared by the following method: The precursor solution is an aqueous solution containing a hydrophilic polymer material and a photoinitiator; Further preferably, the hydrophilic polymer material is at least one of hydrogel solutions such as polyethylene glycol, polyacrylic acid, and polymethacrylic acid; The content of the hydrophilic polymer material is 20% - 80%; The photoinitiator is a kind of ultraviolet photoinitiator; The content of the photoinitiator is 1% - 3%; The volume of the precursor solution added to the storage tank B is 50 - 200 μl.

[0015] As a preferred technical solution, the mass percentage of hydrofluoric acid is 2% - 5%.

[0016] Compared with the existing methods, the beneficial effects of the present invention are as follows:

[0017] 1) High quality: The filling type self-assembly area can precisely control the thickness and pattern of the photonic crystal film, and the film thickness during self-assembly is not affected by factors such as environmental temperature changes, and a photonic crystal film with uniform thickness can be obtained. The self-assembly method of the photonic crystal inside the device keeps the assembled part and the colloidal emulsion in full contact all the time, avoiding excessive stress caused by too fast evaporation and reducing the appearance of defects such as cracks. Experiments prove that the nano-spheres are arranged uniformly, have good continuity, and good optical properties.

[0018] 2) Fast speed: The self-assembly method inside the self-assembly area can significantly increase the evaporation speed without reducing the quality of the photonic crystal film. The method of the present invention adopts methods such as adding a certain proportion of ethanol to the solvent of the colloid, setting an auxiliary evaporation area, and increasing the oven temperature to increase the evaporation speed, greatly shortening the preparation cycle.

[0019] 3) Low cost: The device of the present invention is designed based on a microfluidic chip, which can accurately calculate and control the dosage of the colloidal emulsion, reducing the ineffective loss of nano-spheres. Moreover, the materials of the cover plate and the bottom plate are polymer polymers, with a simple structure, easy to process, low manufacturing cost, and suitable for large-scale production.

[0020] 4) Dry-free filling: After the self-assembly of the template film is completed, due to the difference in specific gravity between the two solutions, the precursor solution gradually replaces the unevaporated solvent in the film. The film remains wet throughout the process, effectively avoiding the appearance of cracks and improving the quality of the photonic crystal inverse opal film. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 The front view and the schematic diagram of the self-assembly principle of the photonic crystal inverse opal film preparation device in the embodiment of the present invention;

[0023] Figure 2 is Figure 1 The top view of the photonic crystal inverse opal film preparation device;

[0024] Figure 3 is Figure 1 The exploded view of the structure of the photonic crystal inverse opal film preparation device;

[0025] Figure 4 The scanning electron microscope image of the silica photonic crystal film template prepared in Example 1 of the present invention;

[0026] Figure 5 The reflection spectrum diagram of the silica photonic crystal film template prepared in Example 1 of the present invention.

[0027] Figure 6 The scanning electron microscope image of the photonic crystal hydrogel inverse opal film prepared in Example 2 of the present invention;

[0028] Figure 7 The reflection spectrum diagram of the photonic crystal hydrogel inverse opal film prepared in Example 2 of the present invention.

[0029] Reference numerals: 1 - cover plate, 2 - liquid addition hole A, 3 - bonding layer, 4 - through hole A, 5 - auxiliary evaporation area, 6 - self-assembly area, 7 - bottom plate, 8 - liquid storage tank A, 9 - liquid storage tank B, 10 - liquid addition hole B, 11 - flow channel A, 12 - flow channel C, 13 - flow channel B, 14 - through hole B. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with embodiments, so that those skilled in the art can better understand the present invention and implement it, but the exemplified embodiments are not intended to limit the present invention.

[0031] In addition, in the preparation processes of the following embodiments, unless otherwise specified, they are all conventional means in the prior art in this field. Therefore, they will not be described in detail hereinafter; the parts in the following embodiments all refer to parts by weight.

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] Reference Figures 1 to 3 A device for preparing a photonic crystal inverse opal film based on a microfluidic chip, comprising a cover plate 1, a bonding layer 3 and a bottom plate 7; the bonding layer 3 is located between the cover plate 1 and the bottom plate 7 and connects the cover plate 1 and the bottom plate 7 into an integral structure; the cover plate 7 is provided with a liquid adding hole A 2 and a liquid adding hole B 10, the bonding layer 3 is provided with a through hole A 4 and a through hole B 14, and a liquid storage tank A 8 and a liquid storage tank B 9 are arranged on the side wall of the bottom plate 7 facing the bonding layer 3. The liquid adding hole A 2, the liquid storage tank A 7 and the through hole A 4 are communicated with each other, and the liquid adding hole B 10, the liquid storage tank B 9 and the through hole B 14 are communicated with each other; the bonding layer is provided with a receiving cavity 6, and the receiving cavity 6 is located between the through hole A 4 and the through hole B 14. The receiving cavity 6 is a self-assembly area, and its top is an open end and is communicated with the outside air; the bonding layer 3 is further provided with a flow channel A 11, a flow channel B 13 and a flow channel C 12; the flow channel C 12 is in the vertical direction and is communicated with the bottom of the receiving cavity 6; the flow channel A 11 connects the through hole A 4 and the flow channel C 12, and the included angle formed between the end of the flow channel A 11 close to the flow channel C 12 and the flow channel C 12 is an acute angle; the flow channel B 13 connects the through hole B 14 and the flow channel C 12, and the included angle formed between the end of the flow channel B 13 close to the flow channel C 12 and the flow channel C 12 is an obtuse angle. Further, the bonding layer 3 is provided with auxiliary evaporation areas 5 on both sides of the open end of the receiving cavity, and the auxiliary evaporation areas 5 have chambers communicated with the receiving cavity 6.

[0034] The above-mentioned device for preparing a photonic crystal film can be obtained through the following process:

[0035] The bottom plate and the cover plate with required sizes are cut and processed from PMMA plates by laser and numerically controlled milling machines. The thickness of the bottom plate is 3 mm, and the thickness of the cover plate is 1 mm. After ultrasonic cleaning, it is dried for standby. The pressure-sensitive double-sided tape with a protective film is cut into the required pattern by laser to obtain the bonding layer, and a self-assembly area is formed on the bonding layer. The thickness of the bonding layer is 100 μm. In the front view, the widths of the flow channel A, the flow channel B and the flow channel C are all 100 μm, and the area of the receiving cavity is 1 cm 2。The flow channel C is in the vertical direction. The included angle between the connection of the flow channel A and the flow channel C is 60°, and the included angle between the connection of the flow channel B and the flow channel C is 105°. The bottom plate and the cover plate are bonded through the bonding layer to form a three-layered photonic crystal film preparation device.

[0036] A method for preparing a photonic crystal inverse opal film based on the above photonic crystal film preparation device, comprising the following steps:

[0037] Template preparation: Monodisperse silica microspheres with a particle size of 240 nm are added to a mixed solvent with a volume ratio of alcohol to water of 1:4, and ultrasonically dispersed evenly to obtain a colloidal emulsion with a mass fraction of 5%. The colloidal emulsion is preheated in a constant temperature oven at 80 °C for 10 min to remove the gas in the solvent and reduce the appearance of bubbles during the self-assembly process. The photonic crystal inverse opal film preparation device is hydrophilized by plasma treatment. 300 μl of the colloidal emulsion is added to the liquid storage tank A with a pipette. The colloidal emulsion flows from one end of the flow channel A to the flow channel B under the action of capillary force. Since a capillary stop valve with a variable cross-section is formed at the connection between the flow channel B and the liquid storage tank B, the colloidal emulsion stops here. The other end fills into the accommodation cavity in the self-assembly area through the flow channel C to form a colloidal liquid film. Then, the liquid addition hole A is covered with a tape with micropores to ensure the air pressure balance in the liquid storage tank A and the evaporation from the micropores can be ignored. The liquid addition hole B is sealed with a tape to avoid evaporation of the emulsion from here; with the open end of the accommodation cavity facing upward, the photonic crystal inverse opal film preparation device is placed in an oven with a constant temperature of 80 °C. The solvent in the colloidal emulsion evaporates at the open ends of the self-assembly area and the auxiliary evaporation area, and the silica microspheres start to self-assemble from the opening and gradually stack downward. After 15 min, a silica photonic crystal film template is obtained.

[0038] Preparation of inverse opal film: Remove the tape on the liquid addition holes A and B, and seal the liquid addition hole A with tape, so as to stagnate the operation of the emulsion in the liquid storage tank A and the flow channel A through air pressure. Mix α-hydroxyisobutyrophenone: polyethylene glycol diacrylate: polyethylene glycol 200: water in a volume ratio of 1:40:40:19 to obtain a precursor solution. Add 50 μl of the precursor solution into the liquid storage tank B from the liquid addition hole B. The precursor solution is connected to the flow channel B. Cover the liquid addition hole B with a perforated tape to ensure the air pressure balance in the liquid storage tank B and the evaporation from the micropores can be ignored; the solvent in the self-assembly area continuously evaporates at the open end, and the capillary force sucks the precursor solution in the liquid storage tank B into the self-assembly area through the flow channel B and the flow channel C. Since the density of the precursor solution is greater than that of the colloidal emulsion, and the included angle at the connection of the flow channel B and the flow channel C is an obtuse angle, the precursor solution can be reduced from mixing with the colloidal emulsion in the flow channel B during the flow from low to high, while the included angle at the connection of the flow channel A and the flow channel C is an acute angle, which can prevent the precursor solution from entering the flow channel A. After the solvent in the self-assembly area is completely evaporated, the precursor solution is filled into the photonic crystal film template by the traction of the capillary force; the precursor solution is cured by irradiating with an ultraviolet lamp, and the silica template is removed by soaking in a 4% hydrofluoric acid solution for 4 h to obtain a photonic crystal inverse opal film.

[0039] Figure 4 The microscopic morphology of the prepared silica photonic crystal film template. As shown in the figure, it can be seen that the silica microspheres are arranged regularly and uniformly, and the contact between the spheres is tight and the continuity is good during the self-assembly process.

[0040] Figure 5 The reflection spectrum of the prepared silica photonic crystal film template, and the reflection peak is 560 nm.

[0041] Figure 6 The microscopic morphology of the prepared photonic crystal hydrogel inverse opal film.

[0042] Figure 7 The reflection spectrum of the prepared photonic crystal hydrogel inverse opal film, and the reflection peak is 594 nm.

[0043] It should be noted that the above embodiments only give one implementation scheme of the present invention, and the devices or methods that meet the following conditions can still achieve the purpose of the present invention.

[0044] For the thickness of the bonding layer, in addition to 50 μm in the above embodiments, thickness values such as 10 μm, 30 μm, or 100 μm can also achieve the purpose of the present invention.

[0045] For the colloidal emulsion, the monodisperse nano-microspheres therein can be silica, or titanium dioxide, etc.; the diameter of the monodisperse nano-microspheres can be 180 nm, 300 nm, 500 nm, etc.; the volume ratio of ethanol to water in the solvent can also be 1:1 or 1:5; the mass percentage of the monodisperse nano-microspheres in the colloidal emulsion can also be 8% or 10%.

[0046] Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A device for preparing a photonic crystal inverse opal film based on a microfluidic chip, characterized in that: It includes a cover plate, a bonding layer and a bottom plate; the bonding layer is located between the cover plate and the bottom plate and connects the cover plate and the bottom plate into an integral structure; The cover plate is provided with a liquid adding hole A and a liquid adding hole B, the bonding layer is provided with a through hole A and a through hole B, and the side wall of the bottom plate facing the bonding layer is provided with a liquid storage tank A and a liquid storage tank B. The liquid adding hole A, the liquid storage tank A and the through hole A communicate with each other, and the liquid adding hole B, the liquid storage tank B and the through hole B communicate with each other; The bonding layer is provided with a receiving cavity, the receiving cavity is located between the through hole A and the through hole B, the receiving cavity is a self-assembly area, the top of which is an open end and communicates with the outside air; the bonding layer is also provided with a flow channel A, a flow channel B and a flow channel C; the flow channel C is in the vertical direction and communicates with the bottom of the receiving cavity; the flow channel A connects the through hole A and the flow channel C, and the included angle formed between the end of the flow channel A close to the flow channel C and the flow channel C is an acute angle; the flow channel B connects the through hole B and the flow channel C, and the included angle formed between the end of the flow channel B close to the flow channel C and the flow channel C is an obtuse angle.

2. The preparation device of the photonic crystal inverse opal film based on a microfluidic chip according to claim 1, wherein: The bonding layer is provided with auxiliary evaporation areas on both sides of the top of the receiving cavity, and the auxiliary evaporation areas have cavities communicating with the receiving cavity.

3. The apparatus for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 1, characterized in that: The materials of the cover plate and the bottom plate are independently selected from polymethyl methacrylate, polydimethylsiloxane or polystyrene; the material of the bonding layer is a pressure-sensitive double-sided adhesive, and the thickness of the pressure-sensitive double-sided adhesive is 10μm - 100μm.

4. The apparatus for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 1, wherein: The widths of the flow channel A, the flow channel B and the flow channel C are 50 - 200μm.

5. A method for preparing a photonic crystal inverse opal film based on a microfluidic chip, characterized in that: It is completed by using the photonic crystal inverse opal film preparation device according to any one of claims 1 to 4, including the following steps: Perform hydrophilic treatment on the photonic crystal inverse opal film preparation device, add the colloidal emulsion containing monodisperse silica nanospheres from the liquid adding hole A into the liquid storage tank A. The colloidal emulsion enters the flow channel A under the action of capillary force. A part of the colloidal emulsion entering the flow channel A enters the flow channel B, and the other part enters the flow channel C. The colloidal emulsion entering the flow channel B stops at the connection between the flow channel B and the liquid storage tank B. The colloidal emulsion entering the flow channel C fills into the receiving cavity to form a colloidal liquid film. Then cover the liquid adding hole A with a tape with micropores, and seal the liquid adding hole B with a tape; with the open end of the receiving cavity facing up, place the photonic crystal inverse opal film preparation device in an oven to evaporate the solvent in the colloidal liquid film, and at the same time, the monodisperse nanospheres perform self-assembly to obtain a photonic crystal film template; remove the tapes on the liquid adding hole A and the liquid adding hole B, seal the liquid adding hole A with a tape, add the precursor solution from the liquid adding hole B into the liquid storage tank B. The precursor solution communicates with the flow channel B, and cover the liquid adding hole B with a tape with holes; the solvent in the self-assembly area continuously evaporates at the open end, and the capillary force sucks the precursor solution in the liquid storage tank B into the self-assembly area through the flow channel B. After the solvent in the self-assembly area completely evaporates, the precursor solution is filled into the photonic crystal film template by the traction of the capillary force; cure the precursor solution, and remove the template with hydrofluoric acid solution to obtain the photonic crystal inverse opal film.

6. The method for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 5, wherein: The colloidal emulsion containing monodisperse silica nanospheres is prepared by the following method: The monodisperse silica nanospheres are added to a solvent for dilution, and ultrasonic dispersion is carried out to form a colloidal emulsion; the diameter of the monodisperse silica nanospheres is 180 - 500 nm; the solvent is a mixed solvent composed of ethanol and water; the volume ratio of ethanol to water is 1:1 - 1:

5.

7. The method for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 6, characterized in that: The mass percentage of the monodisperse nanospheres in the colloidal emulsion is 5% - 10%.

8. The method for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 5, characterized in that: The constant temperature of the oven is 40 - 80 °C.

9. The method for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 5, characterized in that: The precursor solution is an aqueous solution containing a hydrophilic polymer material and a photoinitiator; the hydrophilic polymer material is at least one of polyethylene glycol, polyacrylic acid, and polymethacrylic acid.

10. The method for preparing a photonic crystal inverse opal film based on a microfluidic chip according to claim 5, characterized in that: The way to cure the precursor solution is to irradiate the precursor solution with an ultraviolet lamp.

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