A method for preparing monodisperse microcapsules based on microfluidic platform

Abstract

The present invention belongs to the technical field of preparation of new microcapsule materials, and relates to a method for preparing monodisperse microcapsules based on a microfluidic platform. Microfluidics is used to make oil phase and water phase into water-in-oil type monodisperse droplets; then the monodisperse droplets are used as templates, and after initiation by an initiator in water, free radical polymerization is carried out at the oil-water interface to generate monodisperse microcapsules with a core-shell structure; wherein the oil phase includes methyl methacrylate, n-alkane phase change material and pentaerythritol tetraacrylate, and the water phase contains polyvinyl alcohol. Based on microfluidic technology, the present invention prepares monodisperse phase change material microcapsules with thick shell, uniform particle size, smooth surface and good morphology by an external water phase initiation method. In addition, the monodisperse microcapsules prepared by the present invention have obvious transmission switch effect.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of new microcapsule materials, and relates to a method for preparing monodisperse microcapsules based on a microfluidic platform. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] In recent years, microencapsulation technology has been widely used in the fields of biomedicine, pharmaceutical engineering, food engineering, composite materials, etc. Monodisperse microcapsules use droplets as templates, and then generate core-shell structures through polymerization reactions. The traditional method of preparing microcapsules by mechanical stirring has greatly limited the application of microcapsules due to uneven particle size, uncontrollable shell thickness, and severe deformation. Chinese patent CN202410251913.4 discloses a phase change microcapsule (MEPCM) and a preparation method thereof, which prepares a core material emulsified dispersion by sequentially adding an emulsifying dispersant and a phase change core material to a surfactant dispersion system, and using magnetic stirring to disperse the core material; then preparing a wall material suspension, and finally adding the wall material suspension dropwise to the core material emulsified dispersion system, polymerizing under magnetic stirring conditions to obtain a phase change microcapsule. Chinese patent CN202310655234.9 proposes an electroluminescent microcapsule shell material and a preparation method thereof. The raw materials of the microcapsule shell material include methyl methacrylate, styrene monomer, initiator, surfactant, reducing agent and compatibilizer, wherein the compatibilizer is a polymer prepared by polymerization of methyl methacrylate and styrene, and microcapsules can be obtained by emulsion polymerization. However, the polymerization rate of the above technology is difficult to control, and the prepared MEPCM has morphological defects such as particle shrinkage, depression, adhesion, and poor sphericity, and the emulsification method is mechanical dispersion, and the obtained microcapsule particle size is uneven and polydisperse. Summary of the invention

[0004] In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing monodisperse microcapsules based on a microfluidic platform. The present invention is based on microfluidic technology and prepares MEPCM with thick shell, uniform particle size, smooth surface and good morphology through an external water phase initiation method.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] In the first aspect, a method for preparing monodisperse microcapsules based on a microfluidic platform, wherein an oil phase and an aqueous phase are made into oil-in-water (O / W) monodisperse droplets using a microfluidic chip; then, the monodisperse droplets are used as templates, and after initiation by an initiator in water, free radical polymerization is carried out at the oil-water interface to generate monodisperse microcapsules with a core-shell structure; wherein the oil phase includes methyl methacrylate (MMA), a normal alkane phase change material (such as n-hexadecane) and pentaerythritol tetraacrylate (PETRA), and the aqueous phase includes polyvinyl alcohol (PVA).

[0007] The present invention adopts microfluidic technology to prepare monodisperse droplets, and can adjust the particle size and emulsion shell thickness of monodisperse droplets; at the same time, since the monodisperse droplets prepared by microfluidic technology are generated drop by drop, the number of the droplets gradually increases, so that the monomers in the early stage of free radical polymerization have more sufficient free radicals to participate in the reaction, and as time goes by, the initiator continuously decomposes the free radicals to ensure that the droplets in the later stage of the experiment also have sufficient free radicals to participate in the reaction. The process of generating monodisperse droplets through microfluidics and the coordination of free radical polymerization ensure that the surface of the prepared monodisperse microcapsules is smooth and has a good morphology.

[0008] In a second aspect, a microfluidic device is provided for implementing the above-mentioned preparation method, comprising a microfluidic chip, wherein two water phase microchannels, one oil phase microchannel and a collection pool are arranged in the microfluidic chip, the two water phase microchannels are respectively located on both sides of the oil phase microchannel, and the outlets of the two water phase microchannels and the outlet of the oil phase microchannel are simultaneously connected to the inlet of the collection pool.

[0009] In a third aspect, a monodisperse microcapsule is obtained by the above preparation method.

[0010] A fourth aspect provides an application of the monodisperse microcapsules in a temperature-responsive transmission switch.

[0011] The beneficial effects of the present invention are:

[0012] 1. The present invention prepares monodisperse droplets based on microfluidic technology, which significantly improves the particle size adjustment accuracy and stability in the process of preparing microdroplets; by accurately controlling the two-phase flow rate in the microchannel, efficient and flexible adjustment of the particle size of the microdroplets is achieved, and the prepared emulsion has a consistent shell thickness and uniform particle size.

[0013] 2. The present invention uses an initiator in water to initiate the external water phase to ensure that the polymerization occurs at the oil-water interface, the polymer chain is generated from the outside to the inside, the polymerization is stable, and the obtained microcapsules have a thick shell, uniform particle size, smooth surface and no serious collapse.

[0014] 3. After research, it was found that the monodisperse microcapsules provided by the present invention have the optical property of temperature-variable transmission switch, and the difference in the average transmittance of ultraviolet-visible light in two phases can reach 21%, which has an obvious transmission switch effect.

[0015] 4. The present invention not only explores the energy storage performance of phase change material microcapsules, but also explores the transmission switch characteristics. The microcapsule layer can not only achieve efficient heat absorption and heat release before and after the phase change, but also change optical parameters such as transmittance, which provides the possibility of dynamic regulation of optical properties in different bands, and is of great significance to energy saving and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 Schematic diagram of the microfluidic device used in the embodiment of the present invention, wherein: 1. syringe pump; 2. syringe; 3. high-speed camera; 4. microfluidic chip; 5. magnetic stirrer; 6. beaker; 7. computer;

[0018] Figure 2 Schematic diagram of a dual-channel microfluidic chip used in an embodiment of the present invention, wherein 8 is a continuous phase inlet, 9 is a dispersed phase inlet, 10 is a cross intersection, 11 is a collection pool, and 12 is a droplet outlet;

[0019] Figure 3 for Figure 2 Schematic diagram of the structure of the middle cross intersection, where 13, continuous phase channel, 14, dispersed phase channel;

[0020] Figure 4 The droplets and phase-change microcapsules prepared in Example 1 of the present invention, a is the droplet, b is the phase-change microcapsule;

[0021] Figure 5 The SEM images of the phase change microcapsules prepared in Example 1 of the present invention, a is a low magnification, and b is a high magnification;

[0022] Figure 6 AFM images of the phase change microcapsules prepared in Example 1 of the present invention, a is a 2D image, and b is a 3D image;

[0023] Figure 7 The DSC curve of the phase change microcapsule prepared in Example 1 of the present invention;

[0024] Figure 8 The optical transmission characteristics of the phase change microcapsules prepared in Example 1 of the present invention, a is the melting of the core material, b is the crystallization of the core material;

[0025] Fig. 9 This is a UV-visible band test data diagram of the phase change microcapsule prepared in Example 3 of the present invention;

[0026] Fig.10It is a characterization diagram of the droplet particle size prepared in Example 1 of the present invention; the continuous phase flow rate of ad is 1200 μL / h, a is the droplet prepared when the dispersed phase flow rate is 160 μL / h, b is the droplet prepared when the dispersed phase flow rate is 240 μL / h, c is the droplet prepared when the dispersed phase flow rate is 320 μL / h, d is the droplet prepared when the dispersed phase flow rate is 400 μL / h, and e is the average particle size and coefficient of variation curve of the droplets prepared in Example 1;

[0027] Fig.11 This is a characterization diagram of the droplet particle size prepared in Example 2 of the present invention; the dispersed phase flow rate (ad) is controlled to be 200 μL / h, a is the droplets prepared when the continuous phase flow rate is 500 μL / h, b is the droplets prepared when the continuous phase flow rate is 2000 μL / h, c is the droplets prepared when the continuous phase flow rate is 3500 μL / h, d is the droplets prepared when the continuous phase flow rate is 5000 μL / h, and e is the average particle size and coefficient of variation curve of the droplets prepared in Example 2. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] In view of the problems of uneven particle size and surface collapse in the existing preparation of phase change microcapsules, the present invention proposes a method for preparing monodisperse microcapsules based on a microfluidic platform.

[0031] A typical embodiment of the present invention provides a method for preparing monodisperse microcapsules based on a microfluidic platform, wherein an oil phase and an aqueous phase are made into water-in-oil type monodisperse droplets by microfluidics; then, the monodisperse droplets are used as templates, and after initiation by an initiator in water, free radical polymerization is carried out at the oil-water interface to generate monodisperse microcapsules with a core-shell structure; wherein the oil phase includes methyl methacrylate, a normal alkane phase change material (such as n-hexadecane) and pentaerythritol tetraacrylate, and the aqueous phase includes polyvinyl alcohol.

[0032] In some embodiments, the volume flow rate ratio of the oil phase to the water phase is 160-440:300-5000. Specifically, the flow rate of the oil phase is 160-440 μL / h.

[0033] In some embodiments, the mass ratio of methyl methacrylate, n-alkane phase change material and pentaerythritol tetraacrylate is 1:0.45-0.55:0.05-0.20, preferably 1:0.48-0.50:0.10-0.15.

[0034] In some embodiments, an initiator is added to water to prepare a collection liquid, and the collection liquid is heated to a free radical polymerization temperature; and then the monodisperse droplets are transported to the collection liquid for free radical polymerization. Specifically, the concentration of the initiator in the collection liquid is 0.6 to 0.9 mg / mL, preferably 0.625 to 0.875 mg / mL.

[0035] In some embodiments, the free radical polymerization reaction time is 5 to 7 hours.

[0036] In some embodiments, the initiator is a persulfate. The persulfate may be ammonium persulfate, sodium persulfate, potassium persulfate, etc., preferably ammonium persulfate. Specifically, the added mass of the initiator is 1.00-2.00% of the added mass of methyl methacrylate, preferably 1.25-1.75%.

[0037] In some embodiments, the concentration of polyvinyl alcohol in the aqueous phase is 0.005-0.015 g / mL.

[0038] In some embodiments, the free radical polymerization reaction temperature is 65-85°C, preferably 70-80°C.

[0039] Specifically, microfluidics is used to make the oil phase and the water phase into water-in-oil type monodisperse droplets; an initiator aqueous solution is used as a collecting liquid, and the collecting liquid is heated to a free radical polymerization reaction temperature; the collecting liquid then receives the monodisperse droplets, and a free radical polymerization reaction is carried out.

[0040] Another embodiment of the present invention provides a microfluidic device for implementing the above-mentioned preparation method, comprising a microfluidic chip, wherein two water phase microchannels, one oil phase microchannel and a collection pool are arranged in the microfluidic chip, the two water phase microchannels are respectively located on both sides of the oil phase microchannel, and the outlets of the two water phase microchannels and the outlet of the oil phase microchannel are simultaneously connected to the inlet of the collection pool.

[0041] In some embodiments, the material of the microfluidic chip is polydimethylsiloxane (PDMS). The PDMS microfluidic chip used has excellent light transmittance, which can realize the visualization of the droplet generation process.

[0042] In some embodiments, the outlets of the two water phase microchannels, the outlet of the oil phase microchannel and the inlet of the collection tank form a cross structure.

[0043] In some embodiments, the downstream of the cross intersection is a flow focusing structure; the flow focusing structure is a structure in which the channel width at the droplet formation location gradually expands according to the liquid flow direction. The flow focusing structure induces a hydraulic focusing effect, focusing the coaxial flow of the dispersed phase (oil phase) and the continuous phase (water phase) near the symmetry axis, and plays a role in promoting interface deformation and rupture, which is conducive to the formation of droplets.

[0044] In some embodiments, the inlets of two aqueous microchannels are connected.

[0045] In some embodiments, the collection pool is a diamond-shaped structure, and its outlet is a constricted structure, which delays the time from droplet generation to outflow.

[0046] In some embodiments, the outlet of the collection tank is connected to a reactor for performing free radical polymerization.

[0047] The third embodiment of the present invention provides a monodisperse microcapsule obtained by the above preparation method.

[0048] A fourth embodiment of the present invention provides a use of the above-mentioned monodisperse microcapsules in a temperature-responsive transmission switch.

[0049] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0050] In the following examples, the microfluidic device used is as follows Figure 1 As shown, according to the material flow direction, it includes a syringe pump 1, a syringe 2, a microfluidic chip 4, a magnetic stirrer 5, a beaker 6, and a computer 7. Among them, the microfluidic chip 4 is a dual-channel design, such as Figures 2-3 As shown, the dual-channel chip has two inlets and one outlet, namely the continuous phase (aqueous phase) inlet 8, the dispersed phase (oil phase) inlet 9 and the droplet outlet 12. The continuous phase inlet 8 and the dispersed phase inlet 9 converge at the cross intersection 10, and then communicate with the collection pool 11, and the collection pool 11 is connected to the droplet outlet 12. The diameters of the continuous phase inlet 8, the dispersed phase inlet 9 and the droplet outlet 12 are all 0.75 mm, the dispersed phase channel 14 and the continuous phase channel 13 are 40 μm wide, the channel width from the cross intersection 10 to the collection pool 11 is 60 μm, the width from the collection pool to the droplet outlet is 0.85 mm, and the overall height of the chip channel is 60 μm. The syringe 2 and the injection pump 1 and the droplet outlet 12 and the beaker 6 are connected with silicone hoses. The high-speed camera 3 is used to monitor the droplet generation state in the microfluidic chip 4 and transmit the video signal to the computer 7, thereby realizing the visualization of the droplet generation process.

[0051] Example 1

[0052] Prepare the oil phase: add 2 g MMA, 0.98 g hexadecane and 0.3 g PETRA into a beaker, transfer the prepared oil solution to an ultrasonic cleaner for 5 minutes, and use a 1 ml glass microinjector to draw the prepared oil phase for later use.

[0053] Prepare the aqueous phase: take 3 ml of 0.05 g / mL PVA solution in a measuring cylinder, add 7 ml of ultrapure water to dilute, stir with a glass rod to mix the aqueous solution evenly, and use a 2.5 ml disposable syringe to draw the aqueous phase for use.

[0054] Prepare the collection solution: take 40 mL of ultrapure water into a beaker, add 0.025 APS, stir with a glass rod until completely dissolved, place the beaker in a magnetic stirrer, set the temperature to 70 ° C, and the stirring speed to 160 rpm.

[0055] The water phase was injected into the continuous phase inlet of the microfluidic chip at a rate of 1200 μL / h, and the oil phase was injected into the dispersed phase inlet of the microfluidic chip at a rate of 300 μL / h. The chip intersections in the oil phase and water phase microfluidic chip formed O / W monodisperse droplets. The generated droplets were discharged from the outlet and dripped directly into the beaker below through the hose. After collecting for 2 hours, the water temperature of the collected liquid was raised to 80°C for reaction for 4 hours, and MEPCM was obtained by filtration and freeze-drying.

[0056] During the droplet formation process, the droplet size was precisely adjusted by changing the dispersed phase flow rate. The continuous phase flow rate was fixed at 1200 μL / h, and the dispersed phase flow rate was increased from 160 μL / h to 440 μL / h. The droplet sizes at different flow rates were statistically analyzed. The results are shown in Table 1:

[0057] Table 1 Effect of dispersed phase flow rate on particle size

[0058] sample Dispersed phase flow rate (μL / h) Droplet size (μm) CV(%) 1 160 32.5 1.3 2 200 34.4 1.5 3 240 34.6 2.5 4 280 35.7 1.3 5 320 36.0 1.5 6 360 36.6 1.7 7 400 37.3 1.4 8 440 39.1 2.0

[0059] It can be seen from Table 1 that the droplet size decreases with the increase of dispersed phase flow rate and is monodisperse.

[0060] Example 2

[0061] Prepare the oil phase: add 2 g MMA, 0.98 g hexadecane, and 0.2 g PETRA into a beaker, transfer the prepared oil solution to an ultrasonic cleaner for 5 minutes, and use a 1 ml glass microinjector to draw the prepared oil phase for later use.

[0062] Prepare the aqueous phase: take 2 ml of 0.05 g / mL PVA solution in a measuring cylinder, add 8 ml of ultrapure water to dilute, stir with a glass rod to mix the aqueous solution evenly, and use a 2.5 ml disposable syringe to draw the aqueous phase for later use.

[0063] Prepare the collection solution: take 40 mL of ultrapure water into a beaker, add 0.030 APS, stir with a glass rod until completely dissolved, place the beaker in a magnetic stirrer, set the temperature to 70 ° C, and the stirring speed to 180 rpm.

[0064] The water phase was injected into the continuous phase inlet of the microfluidic chip at a rate of 1600 μL / h, and the oil phase was injected into the dispersed phase inlet of the microfluidic chip at a rate of 200 μL / h. The chip intersections in the oil phase and water phase microfluidic chip formed O / W monodisperse droplets. The generated droplets were discharged from the outlet and dripped directly into the beaker below through a hose. After collecting for 2 hours, the water temperature of the collected liquid was raised to 80°C for reaction for 4 hours, and MEPCM was obtained by filtration and freeze-drying.

[0065] During the droplet formation process, the droplet size was precisely adjusted by changing the continuous phase flow rate. The continuous phase flow rate increased from 500 μL / h to 5000 μL / h. The droplet sizes at different flow rates were statistically analyzed. The results are shown in Table 2:

[0066] Table 2 Effect of continuous phase flow rate on particle size

[0067]

[0068] It can be seen from Table 2 that the droplet size decreases with the increase of the continuous phase flow rate and is monodisperse.

[0069] Example 3

[0070] Prepare the oil phase: add 2 g MMA, 0.98 g hexadecane and 0.3 g PETRA into a beaker, transfer the prepared oil solution to an ultrasonic cleaner for 5 minutes, and use a 1 ml glass microinjector to draw the prepared oil phase for later use.

[0071] Prepare the aqueous phase: take 1 ml of 0.05 g / mL PVA solution in a measuring cylinder, add 9 ml of ultrapure water to dilute, stir with a glass rod to mix the aqueous solution evenly, and use a 2.5 ml disposable syringe to draw the aqueous phase for use.

[0072] Prepare the collection solution: take 40 mL of ultrapure water into a beaker, add 0.035 APS, stir with a glass rod until completely dissolved, place the beaker in a magnetic stirrer, set the temperature to 70 ° C, and the stirring speed to 200 rpm.

[0073] The water phase was injected into the continuous phase inlet of the microfluidic chip at a rate of 1600 μL / h, and the oil phase was injected into the dispersed phase inlet of the microfluidic chip at a rate of 300 μL / h. The intersection of the oil phase and the water phase in the microfluidic chip formed O / W monodisperse droplets. The generated droplets were discharged from the outlet and dripped directly into the beaker below through the hose. After collecting for 2 hours, the water temperature of the collected liquid was raised to 80°C for reaction for 4 hours, and MEPCM was obtained by filtration and freeze-drying.

[0074] The droplets prepared in Example 1 are as follows Figure 4 As shown in a, the particle size is uniform, about 39.7 μm, and is monodisperse; the surface of the prepared phase change microcapsules is smooth without collapse, the particle size is uniform, about 39.1 μm, and has good sphericity. The particle size difference between the droplet and the microcapsule is only 0.6 μm, as shown in Figure 4 As shown in b.

[0075] The phase change microcapsules prepared in Example 1 have a smooth surface, a very high sphericity, no adhesion between particles, very few depressions, and no shrinkage on the surface of the microcapsules; the CV is 1.9%, the particle size is uniform, and it is monodisperse. Figure 5 The phase change microcapsules prepared in Examples 2 to 3 also have the same characteristics.

[0076] Figure 6 It can be seen that the surface of the microcapsule shows a relatively smooth morphology, and there are slight protrusions. The root mean square roughness (R q ) is 7.92nm, and the roughness parameter is below 8nm, indicating that the shell surface of the microcapsule is smooth and the surface roughness is small. The smooth surface produces sharper reflection, which will reduce light scattering and improve transmittance.

[0077] Figure 7 The results show that the microcapsules have two crystallization peaks of different sizes at 5.8℃ and 13.8℃; the melting peak is a single peak with a melting enthalpy of 207.2 J / g.

[0078] Figure 8Figure 2 is an optical transmission microscopic image of the microcapsules in the melting and crystallization states. It can be seen that when the microcapsule core material is melted, the microcapsules appear translucent in color, smooth in wall, with good sphericity and optical transparency. This is because the microcapsules have uniform particle size and less scattering effect on light, allowing light to pass through the microcapsule layer more smoothly, showing the transmission switch is "on"; when the microcapsule core material is crystallized, the microcapsule color turns black, and very serious depressions and shrinkage appear. This is because the density and volume of the PCM change greatly after crystallization, resulting in depressions in the shell, and the color becomes black because a large amount of non-uniform nucleation is generated during the solidification process of the PCM, and there are staggered and irregular grain boundaries between different PCM particles, presenting a quasi-multilayer structure. When the incident light passes through, Mie scattering will occur, which will cause the transmittance of ultraviolet-visible light to be significantly reduced, and the microcapsule appears to be in the "off" state of the transmission switch.

[0079] The microcapsules obtained in Example 3 were subjected to temperature-dependent transmission switch tests in the ultraviolet and visible bands. Fig. 9 As shown, when the microcapsule is in the "open" state, the transmittance gradually increases from the ultraviolet light to the visible band, with a peak at around 380nm, and then the transmittance shows a slow upward trend, but the growth rate is not large, and the average transmittance at 0.19-1.1μm is 22%; when the microcapsule is in the "closed" state, the transmittance in the 0.19-1.1μm band is generally lower than 1%, and the peak also appears at around 380nm, and the average transmittance is less than 1%, forming an obvious switching gap with the "open" state.

[0080] The droplet size prepared in Example 1 is as follows Fig.10 As shown in the figure, when the water phase flow rate is fixed at 1200μL / h and the oil phase flow rate increases from 160μL / h to 440μL / h, the droplet size is uniform, and the CV value fluctuates between 1.2% and 2.5%, all less than 5%, proving that the droplets have good monodispersity. The droplet size increases from 32.5μm to 39.1μm. The results show that the droplet size increases with the increase of the dispersed phase flow rate.

[0081] The droplet size prepared in Example 2 is as follows Fig.11 As shown in the figure, when the dispersed phase flow rate is fixed at 200 μL / h and the water phase flow rate is increased from 500 μL / h to 5000 μL / h, the droplet size shows an opposite trend, decreasing from 41.8 μm to 22.1 μm, which means that the droplet size decreases with the increase of the continuous phase flow rate. In addition, the CV value ranges from 1.5% to 2.9%, and the droplets still maintain good monodispersity.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing monodisperse microcapsules based on a microfluidic platform, characterized in that: The oil phase and the water phase are made into water-in-oil type monodisperse droplets by microfluidics; the monodisperse droplets are then used as templates, and free radical polymerization is carried out at the oil-water interface after initiation by an initiator in water to generate monodisperse microcapsules with a core-shell structure; wherein the oil phase includes methyl methacrylate, n-alkane phase change material and pentaerythritol tetraacrylate, and the water phase includes polyvinyl alcohol; The concentration of polyvinyl alcohol in the aqueous phase was 0.05 g / mL; The volume flow rate ratio of the oil phase and the water phase is 160~440 μL / h: 300~5000 μL / h; An initiator is added to water to prepare a collection liquid, and the collection liquid is heated to a free radical polymerization reaction temperature; and then the monodisperse droplets are transported to the collection liquid to perform a free radical polymerization reaction; The concentration of the initiator in the collected solution was 0.6-0.9 mg / mL; The prepared droplets have uniform particle sizes ranging from 22.1 to 41.8 μm, and the CV values ​​fluctuate between 1.2% and 2.9%; The mass ratio of methyl methacrylate, normal alkane phase change material and pentaerythritol tetraacrylate is 1:0.45~0.55:0.05~0.20; The initiator is persulfate, and the added mass of the initiator is 1.00-2.00% of the added mass of methyl methacrylate; The free radical polymerization temperature is 65~85℃; The free radical polymerization reaction time is 5~7 h.

2. The method for preparing monodisperse microcapsules based on a microfluidic platform according to claim 1, characterized in that: The mass ratio of methyl methacrylate, n-alkane phase change material and pentaerythritol tetraacrylate is 1:0.48~0.50:0.10~0.

15.

3. The method for preparing monodisperse microcapsules based on a microfluidic platform according to claim 1, characterized in that: The concentration of the initiator in the collected solution was 0.625~0.875 mg / mL.

4. The method for preparing monodisperse microcapsules based on a microfluidic platform according to claim 1, characterized in that: The initiator is ammonium persulfate; the added mass of the initiator is 1.25-1.75% of the added mass of methyl methacrylate.

5. The method for preparing monodisperse microcapsules based on a microfluidic platform according to claim 1, characterized in that: The free radical polymerization reaction temperature is 70~80 ℃.

6. The method for preparing monodisperse microcapsules based on a microfluidic platform according to any one of claims 1 to 5, characterized in that: The microfluidic device used includes a microfluidic chip, wherein two water phase microchannels, one oil phase microchannel and a collection pool are arranged in the microfluidic chip, the two water phase microchannels are respectively located on both sides of the oil phase microchannel, and the outlets of the two water phase microchannels and the outlet of the oil phase microchannel are simultaneously connected to the inlet of the collection pool; The material of the microfluidic chip is polydimethylsiloxane; The outlets of the two water phase microchannels, the outlet of the oil phase microchannel and the inlet of the collection pool form a cross structure.

7. The method for preparing monodisperse microcapsules based on a microfluidic platform according to any one of claim 6, characterized in that: The inlets of the two water phase microchannels are connected.

8. The method for preparing monodisperse microcapsules based on a microfluidic platform according to any one of claim 6, characterized in that: The downstream of the cross intersection is a flow focusing structure; the flow focusing structure is a structure in which the channel width at the droplet formation location gradually expands according to the liquid flow direction.

9. The method for preparing monodisperse microcapsules based on a microfluidic platform according to any one of claim 6, characterized in that: The outlet of the collecting tank is a necked structure.

10. The method for preparing monodisperse microcapsules based on a microfluidic platform according to any one of claim 6, characterized in that: The outlet of the collection tank is connected to a reactor for performing free radical polymerization.

11. A monodisperse microcapsule, characterized in that: Obtained by the preparation method according to any one of claims 1 to 5.

12. Use of the monodisperse microcapsules according to claim 11 in a temperature-responsive transmission switch.

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