A microfluidic chip-based photonic crystal film preparation device and method

Abstract

The application discloses a photonic crystal film preparation device and method based on a micro-fluidic chip, and the device comprises a bottom plate, a cover plate, a supporting pad and a self-assembly plate; the cover plate is connected with the bottom plate to form an integral structure; the cover plate is provided with a through liquid storage groove and micropores, and the liquid storage groove and the micropores are communicated through a flow channel; the self-assembly plate is detachably connected with the cover plate through the supporting pad, a self-assembly area which is communicated with the outside air is formed between the self-assembly plate and the cover plate, and the micropores are communicated with the center of the cavity. In the process of preparing the photonic crystal film, the colloidal emulsion is filled into the self-assembly area by capillary force to form a colloidal liquid film, the solvent is evaporated from the edge of the self-assembly area, and meanwhile, the monodisperse nanometer microspheres are self-assembled from outside to inside to obtain the photonic crystal film. The device can be recycled, and multiple thickness films can be prepared simultaneously. The photonic crystal film preparation method by using the device has the advantages of high forming quality, high speed and low cost.

Description

Technical Field

[0001] This invention relates to the field of colloidal photonic crystal film preparation technology, and in particular to a photonic crystal film preparation device and method based on a microfluidic chip. Background Technology

[0002] Photonic crystals are photonic nanomaterials with photonic bandgap properties, composed of periodically modulated dielectric materials. Light with specific wavelengths or frequencies is prevented from propagating through a photonic crystal within its bandgap. With the increasing application of photonic crystal films as photonic materials and structural color substances, such as photonic ink systems, photonic rubber sheets and crystal lasers, biological / chemical sensors, and biomimetic materials, interest in colloidal crystal films is growing, making the development of photonic crystal film fabrication technology an important research topic.

[0003] Photonic crystal films are generally prepared using microfabrication methods such as "top-down" photolithography and "bottom-up" self-assembly methods. "Top-down" methods such as photolithography, electron beam etching, holography, and sacrificial template methods require expensive high dielectric constant materials and have relatively complex processes, which increases the cost of obtaining a completely bandgap photonic crystal.

[0004] Self-assembly is a simple, economical, and effective method, a process in which colloidal structures spontaneously form an ordered arrangement. Opal-like photonic crystals are prepared using submicron spherical colloids or suspensions through self-assembly. Common thin-film self-assembly methods, such as Czochralski, spin-coating, gravity coating, and natural evaporation, struggle to quickly evaporate the solvent, resulting in long film formation times; for example, forming a film the size of a glass slide can take tens of hours or even days. Furthermore, these methods are susceptible to environmental factors such as temperature, humidity, and colloidal concentration, often leading to uneven film thickness and inconsistent quality during long formation cycles. While centrifugation and electrophoretic deposition can shorten formation time, they require additional driving force, making the preparation systems relatively complex. Therefore, developing a high-quality, fast, and low-cost self-assembly scheme for photonic crystal films is a major challenge in this field. Moreover, obtaining films of varying thicknesses requires adjusting parameters and even device dimensions, and necessitates multiple preparation processes, significantly reducing efficiency. It is evident that developing a method capable of simultaneously preparing thin films of various thicknesses is of great significance. Summary of the Invention

[0005] Microfluidic chips are devices that manipulate and control small volumes of fluid through microchannels with cross-sectional dimensions of tens to hundreds of micrometers, and utilize different microchannel structures to achieve different functions. The self-assembly fabrication technology of photonic crystal films based on microfluidic systems is a novel and efficient method. The purpose of this invention is to provide a device and method for fabricating photonic crystal films based on microfluidic chips. The fabrication of photonic crystal films using this method offers advantages such as high forming quality, high speed, low cost, reusability, and the ability to fabricate films of various thicknesses in a single operation, providing a high-performance platform for photonic crystal research.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a photonic crystal film fabrication device based on a microfluidic chip, comprising a base plate, a cover plate, and a self-assembly plate; the cover plate and the base plate are connected as an integral structure; one end of the cover plate is provided with a through liquid storage tank, and the other end of the cover plate is provided with a plurality of micropores; a flow channel for connecting the liquid storage tank and the micropores is formed between the base plate and the cover plate; a plurality of self-assembly plates corresponding one-to-one with the micropores are placed on the top of the cover plate, and the self-assembly plates cover the micropores; a support pad for supporting the self-assembly plates is placed on the cover plate, and the distance between the self-assembly plates and the cover plate can be controlled by controlling the height of the support pad; a limiting protrusion is also fixed on the cover plate, the height of the limiting protrusion is higher than the self-assembly plate, and the limiting protrusion is located at the side edge of the self-assembly plate; a self-assembly area communicating with the outside air is formed between the self-assembly plate and the cover plate, and the micropores are connected to the geometric center of the self-assembly area.

[0008] As a preferred technical solution, the number of microholes and corresponding self-assembly areas on the cover plate is 1 to 10, and the ratio of the number of microholes, support pads and limiting protrusions is 1:4:2.

[0009] As a preferred technical solution, the materials of the cover plate and the base plate are independently selected from polymethyl methacrylate, polydimethylsiloxane, or polystyrene; the material of the self-assembly plate is polymethyl methacrylate, polydimethylsiloxane, polystyrene, or glass; the thickness of the base plate is 0.5-2mm; and the bonding method between the base plate and the cover plate is thermoforming, plasma bonding, or ultrasonic bonding.

[0010] As a preferred technical solution, the cover plate has a thickness of 2-5 mm; the cross-section of the flow channel and micropores are both square, with a side length of 50-500 μm; the height of the support pad is 5 μm-100 μm, and the support pads in the same self-assembly area have the same height. The size of the self-assembly area and the thickness of the film are controlled by adjusting the height of the support pad; the height of the limiting protrusion is 1.5-3 mm; the thickness of the self-assembly plate is 1-2 mm, and the area is 0.1-5 cm². 2 .

[0011] The second aspect of the present invention provides a method for fabricating a photonic crystal film based on a microfluidic chip, which is accomplished using the photonic crystal film fabrication apparatus described in the first aspect above, and includes the following steps:

[0012] A colloidal emulsion containing monodisperse nanospheres is added to a storage tank. Under capillary action, the colloidal emulsion enters the flow channels and micropores and stops at the top of the micropores. One end of the storage tank is gently lifted, and the colloidal emulsion enters from the micropores under gravity and fills each self-assembly region to form a colloidal liquid film. A limiting protrusion is used to restrict the movement of the self-assembly plate when the device is tilted. The storage tank is sealed with tape, and pores are left in the tape to allow the storage tank to communicate with the outside air. The photonic crystal film preparation device is placed horizontally in an oven with a constant temperature of 40-80°C. The solvent in the colloidal liquid film evaporates from the edge of the self-assembly region, while the monodisperse nanospheres self-assemble from the outside to the inside, obtaining photonic crystal films of different thicknesses.

[0013] As a preferred technical solution, one end of the liquid storage tank is raised to an angle of 30° to 60° with the horizontal plane.

[0014] As a preferred technical solution, the colloidal emulsion containing monodisperse nanospheres is prepared by the following method: the monodisperse nanospheres are diluted in a solvent and ultrasonically dispersed to form a relatively stable colloidal emulsion; more preferably, the monodisperse nanospheres are silica or titanium dioxide, and the diameter of the monodisperse 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 to 1:5; the mass percentage of monodisperse nanospheres in the colloidal emulsion is 5%-10%. The colloidal emulsion is preheated in a constant temperature oven at 40-80℃ for 30-60 min to remove gas from the solvent and reduce the occurrence of bubbles during self-packaging.

[0015] Compared with existing methods, the beneficial effects of the present invention are as follows:

[0016] 1) High Quality: The filled self-assembly region allows for precise control of the photonic crystal film's thickness and pattern. Furthermore, the film thickness is unaffected by environmental temperature changes during self-assembly, resulting in a photonic crystal film with uniform thickness. The self-assembly of the photonic crystal within the device ensures consistent contact between the assembled portion and the colloidal emulsion at the assembly interface, preventing excessive stress caused by rapid evaporation and reducing defects such as cracks. Experiments have demonstrated that the nanospheres exhibit uniform arrangement, good continuity, and excellent optical properties.

[0017] 2) High speed: The self-assembly method within the self-assembly region can increase the evaporation rate to a greater extent without reducing the quality of the photonic crystal film. The method of this invention adopts the addition of a certain proportion of ethanol to the solvent of the colloidal material and increases the evaporation temperature to increase the evaporation rate, which greatly shortens the preparation cycle.

[0018] 3) Low cost: The device of this invention is based on a microfluidic chip design, which can accurately calculate and control the amount of colloidal emulsion used, reducing the ineffective loss of nanospheres. Furthermore, the cover plate and base plate are made of high-molecular polymers, which have a simple structure, are easy to process, and have low manufacturing costs, making them suitable for large-scale production.

[0019] 4) Recycling: The self-assembled plate and the cover plate form a detachable connection. After preparation, the device can be recycled after cleaning and drying, which improves preparation efficiency.

[0020] 5) Simultaneous fabrication of films of different thicknesses: By adjusting the height of the support pad in different self-assembly zones, films of corresponding thicknesses can be fabricated simultaneously in different self-assembly zones. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a top view of the photonic crystal film fabrication apparatus in an embodiment of the present invention;

[0023] Figure 2 for Figure 1 A cross-sectional view (AA) of the apparatus for fabricating medium-photonic crystal films;

[0024] Figure 3 for Figure 1 Isometric view of the apparatus for fabricating medium-photonic crystal films;

[0025] Figure 4 This is a scanning electron microscope image of the photonic crystal film prepared in an embodiment of the present invention;

[0026] Figure 5 The image shows the reflection spectrum of the photonic crystal film prepared according to an embodiment of the present invention.

[0027] Reference numerals: 1-Cover plate, 2-Support pad, 3-Self-assembly plate, 4-Self-assembly area, 5-Limiting protrusion, 6-Micropore, 7-Flow channel, 8-Liquid storage tank, 9-Base plate. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Example

[0030] refer to Figures 1 to 3A photonic crystal film fabrication device based on a microfluidic chip includes a base plate 9, a cover plate 1, and a self-assembly plate 3. The cover plate 1 is connected to the base plate 9 as an integral structure. The cover plate 1 has a through liquid storage tank 8 and micropores 6, and the liquid storage tank 8 is connected to the micropores 6 through a flow channel 7. Several self-assembly plates 3 corresponding one-to-one with the micropores 6 are placed on the top of the cover plate 1, and the self-assembly plates 3 cover the micropores. A support pad 2 for supporting the self-assembly plates is placed on the cover plate 1, and the distance between the self-assembly plates 3 and the cover plate 1 can be controlled by controlling the height of the support pad 2. A limiting protrusion 5 is also fixed on the cover plate 1. The height of the limiting protrusion 5 is higher than that of the self-assembly plates 3, and the limiting protrusion 5 is located at the side edge of the self-assembly plates 3. A self-assembly region 4 that is connected to the outside air is formed between the self-assembly plates 3 and the cover plate 1, and the micropores 6 are connected to the geometric center of the self-assembly region 4.

[0031] The aforementioned photonic crystal film fabrication device can be obtained through the following process:

[0032] PMMA sheets are machined into base plates and cover plates of the required dimensions using laser cutting and CNC milling. The base plate is 1mm thick, and the cover plate is 3mm thick. The cover plate has three self-assembly zones with corresponding support pad heights of 10μm, 50μm, and 100μm. After ultrasonic cleaning and drying, the base plate and cover plate are connected by plasma bonding. The self-assembly plate is 1mm thick and has an area of ​​1cm². 2 The glass plates, after being cleaned and dried, are placed on the support pads of each self-assembly area.

[0033] The method for preparing a photonic crystal film based on the above-mentioned photonic crystal film preparation apparatus includes the following steps:

[0034] Monodisperse silica microspheres with a particle size of 240 nm were added to a mixed solvent of alcohol and water at a volume ratio of 1:4 and ultrasonically dispersed to obtain a 5% (w / w) colloidal emulsion. The colloidal emulsion was preheated in a constant temperature oven at 80°C for 30 minutes to remove gases from the solvent and reduce the formation of air bubbles during self-assembly. The colloidal emulsion was added to a storage tank using a pipette. Under capillary action, the emulsion entered the channels and micropores and stopped at the top of the micropores. One end of the storage tank was raised to a 30° angle with the tabletop. Under gravity, the colloidal emulsion entered through the micropores and filled the self-assembly region to form a colloidal liquid film. A limiting protrusion was used to prevent the self-assembly plate from sliding during tilting. The storage tank was sealed with tape, with pores left in the tape to allow the tank to communicate with the outside air. The photonic crystal film preparation device was placed horizontally in a constant temperature oven at 80°C. The solvent in the colloidal liquid film evaporated from the edge of the self-assembly region, while the monodisperse nanospheres self-assembled from the outside to the inside, thus obtaining photonic crystal films of different thicknesses.

[0035] Figure 4The figure shows the microstructure of the prepared silica photonic crystal film. As shown, the silica microspheres are arranged in a regular and uniform manner, and the contact between the spheres is tight and the continuity is good during the self-assembly process.

[0036] Figure 5 The reflection spectra of silica photonic crystal films of different thicknesses were obtained. It can be seen that the optical bandgap properties of the films prepared by different self-assembly regions are consistent. The bandgap position is 530-595nm, the reflection peak is 560±1nm, and the half width at half maximum is 46±2nm.

[0037] It should be noted that the above embodiments only provide one implementation scheme of the present invention, and the purpose of the present invention can still be achieved by devices or methods that meet the following conditions.

[0038] Regarding the height of the support pad, in addition to the 10μm, 50μm, and 100μm mentioned in the above embodiments, thickness values ​​such as 20μm, 30μm, or 60μm can also achieve the purpose of this invention.

[0039] For colloidal emulsions, the monodisperse nanospheres can be silica or titanium dioxide, etc.; the diameter of the monodisperse nanospheres can be 180 nm, 300 nm or 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 monodisperse nanospheres in the colloidal emulsion can also be 8% or 10%.

[0040] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A device for fabricating photonic crystal films based on microfluidic chips, characterized in that: The device includes a base plate and a cover plate, which are connected to the base plate as a single unit. One end of the cover plate has a through-hole liquid storage tank, and the other end has several micro-holes. A flow channel is formed between the base plate and the cover plate to connect the liquid storage tank and the micro-holes. Several self-assembly plates corresponding to the micro-holes are placed on the top of the cover plate, and the self-assembly plates cover the micro-holes. A support pad is placed on the cover plate to support the self-assembly plates. The distance between the self-assembly plates and the cover plate can be controlled by controlling the height of the support pad. A self-assembly zone that is connected to the outside air is formed between the self-assembly plates and the cover plate. A limiting protrusion is also fixed on the cover plate. The height of the limiting protrusion is higher than that of the self-assembly plates and is located at the side edge of the self-assembly plates. The height of the support pad is 5μm to 100μm.

2. The photonic crystal film fabrication device based on a microfluidic chip according to claim 1, characterized in that: The number of micropores is 1 to 10.

3. The photonic crystal film fabrication device based on a microfluidic chip according to claim 1, characterized in that: The ratio of the number of micropores, support pads, and limiting posts is 1:4:

2.

4. The photonic crystal film fabrication device based on a microfluidic chip according to claim 1, characterized in that: The cover plate and the bottom plate are each made of polymethyl methacrylate, polydimethylsiloxane, or polystyrene; the self-assembly plate is made of polymethyl methacrylate, polydimethylsiloxane, polystyrene, or glass.

5. The photonic crystal film fabrication device based on a microfluidic chip according to claim 1, characterized in that: The height of the support pad is 5μm~100μm, and the support pads located at the bottom of the same self-assembly plate have the same height.

6. A method for fabricating a photonic crystal film based on a microfluidic chip, characterized in that: It is accomplished using the photonic crystal film fabrication apparatus as described in any one of claims 1 to 5, and includes the following steps: A colloidal emulsion containing monodisperse nanospheres is added to a storage tank. Under capillary action, the colloidal emulsion enters the flow channels and micropores and stops at the top of the micropores. One end of the storage tank is lifted, and the colloidal emulsion enters from the micropores under gravity and fills the self-assembly region to form a colloidal liquid film. The storage tank is sealed with tape, with pores left in the tape to allow the storage tank to communicate with the outside air. The photonic crystal film preparation device is placed horizontally in an oven. The solvent in the colloidal liquid film evaporates from the periphery of the self-assembly region, while the monodisperse nanospheres self-assemble from the outside in, thus obtaining a photonic crystal film. During the preparation process, photonic crystal films of different thicknesses can be obtained by controlling the height of the support pad.

7. The method for fabricating a photonic crystal film based on a microfluidic chip according to claim 6, characterized in that: One end of the liquid storage tank is raised to an angle of 30° to 60° with the horizontal plane.

8. The method for fabricating a photonic crystal film based on a microfluidic chip according to claim 6, characterized in that: The colloidal emulsion containing monodisperse nanospheres was prepared by the following method: Monodisperse nanospheres are diluted in a solvent and then ultrasonically dispersed to form a relatively stable colloidal emulsion containing monodisperse nanospheres; the monodisperse nanospheres are silicon dioxide or titanium dioxide; the diameter of the monodisperse nanospheres is 180~500nm.

9. The method for fabricating a photonic crystal film based on a microfluidic chip according to claim 8, characterized in that: The solvent is a mixture of ethanol and water; the volume ratio of ethanol to water is 1:1 to 1:

5.

10. The method for fabricating a photonic crystal film based on a microfluidic chip according to claim 6, characterized in that: The temperature of the oven is 40~80℃.

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