Preparation method of core-shell structure microcapsule based on emulsion evaporation by combining microfluidics with ink-jet printing

Abstract

The invention relates to a core-shell structure microcapsule preparation method based on emulsion evaporation by combining microfluidics with ink-jet printing, and solves the technical problems of poor structure controllability, low preparation efficiency, narrow application range and difficulty in large-scale production of the existing core-shell structure microcapsule preparation method. The core-shell structure microcapsule is prepared according to the processes of oil phase preparation, water phase preparation, emulsion generation through a micro-fluidic chip, base material modification, deposition of emulsion droplets on a base material in an ink-jet printing mode and curing forming, the efficiency is high, and large-scale preparation is achieved.

Description

Technical Field

[0001] This invention relates to the field of functional particle technology, and more specifically, to a method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing. Background Technology

[0002] Due to their special functions in electricity, magnetism, optics, etc., functional particles are widely used in sensors, displays, photonic crystals, biomedical carriers and other fields.

[0003] One type of functional particle is the core-shell microcapsule, which has wide applications in drug delivery, adaptive materials, and flexible electronics, exhibiting excellent functionality and application potential. A core-shell microcapsule is a miniature capsule composed of a core and an outer shell. The core typically stores the active substance, while the outer shell provides protection and controlled release. Currently, the main methods for preparing core-shell microcapsules include the following: (1) Interfacial polycondensation method: Nanocapsules are prepared by spontaneous emulsification, but there is a problem that unreacted monomers remain in the oil core to form impurities, and it is only applicable to a limited number of specific soluble polymers, thus limiting its applicability.

[0004] (2) Template-based layer-by-layer assembly method: It is necessary to adsorb alternating polymer double layers on the surface of a solid template and then remove the sacrificial template by chemical etching. The steps are complicated, and the functional cargo needs to be encapsulated by polymer shell swelling and diffusion, resulting in low encapsulation efficiency.

[0005] (3) Dual emulsion evaporation method: The two-step emulsification process has the defects of uneven droplet size distribution and difficulty in controlling the final microcapsule morphology (particle size, shell thickness, porosity); even if a uniform emulsion is prepared by microfluidic technology, the product size is limited to tens of micrometers, which cannot meet the preparation requirements of nano / micron functional particles.

[0006] (4) Traditional emulsion internal phase separation method: Although it is a one-step process, the formation mechanism of core-shell structure is unclear, lacks effective mechanism characterization and guidance, and is difficult to stably control the uniformity and integrity of core-shell structure. In addition, it does not combine efficient molding technology to realize the direct preparation of functional layer.

[0007] The above methods all suffer from drawbacks such as poor structural controllability, low preparation efficiency, narrow applicability, or unclear mechanisms, and cannot meet the needs for large-scale, high-precision preparation of core-shell microcapsules and corresponding functional layers. Summary of the Invention

[0008] This application aims to address the technical problems of poor structural controllability, low preparation efficiency, narrow applicability, and difficulty in scaling up existing core-shell microcapsule preparation methods by providing a microfluidic-based method for preparing core-shell microcapsules using inkjet printing and emulsion evaporation.

[0009] The preparation method provided in this application is based on emulsion solvent evaporation technology, combined with an integrated approach of microfluidics and inkjet printing, to achieve efficient and precise preparation of core-shell structured functional particles and functional layers.

[0010] A first aspect of this application provides a method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing, comprising the following steps: Step 1, oil phase preparation: The shell-forming polymer and the solvent with poor core formation are dissolved in a good solvent to obtain the oil phase; Step 2, aqueous phase preparation: The dispersant was dissolved in deionized water to obtain an aqueous phase; Step 3, emulsion preparation: Water-in-oil emulsions are prepared using microfluidic chips. The aqueous phase is injected into the microfluidic chip, the oil phase is injected into the microfluidic chip, the flow rate ratio of the oil phase to the aqueous phase is adjusted, and the generated water-in-oil emulsion is collected. Step 4: Prepare the hydrophobic substrate: Step 5, curing and shaping: The water-in-oil emulsion obtained in the third step is placed in the liquid storage chamber of the printhead in the inkjet printer. The inkjet printer prints out emulsion droplets, which are deposited on the hydrophobic substrate. The emulsion droplets dry, thus forming core-shell structured microcapsules.

[0011] Preferably, the mass ratio of the shell-forming polymer to the core-forming poor solvent is 1:4 to 4:1.

[0012] Preferably, the shell-forming polymer is PMMA, PS, or PVP; and the core-forming poor solvent is hexadecane or hexadecane bromide.

[0013] Preferably, the good solvent is DCM; the dispersant is PVA.

[0014] A second aspect of this application provides core-shell structured microcapsules prepared by the above-described microfluidic combined inkjet printing method based on emulsion evaporation.

[0015] A third aspect of this application provides a functional particle layer composed of core-shell structured microcapsules.

[0016] In a fourth aspect, this application provides a method for adjusting the core-shell structure of a core-shell microcapsule, wherein the alkyl mass ratio of the shell-forming polymer to the core-forming poor solvent is calculated based on a ternary phase diagram.

[0017] A fifth aspect of this application provides a method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing, comprising the following steps: Step 1, oil phase preparation: The shell-forming polymer and the solvent with poor core formation are dissolved in a good solvent to obtain the oil phase; Step 2, aqueous phase preparation: The dispersant was dissolved in deionized water to obtain an aqueous phase; Step 3, emulsion preparation: An emulsion was prepared by mixing the aqueous phase and the oil phase using a homogenizer. Step 4: Prepare the hydrophobic substrate: Step 5, curing and shaping: The emulsion obtained in the third step is loaded into the liquid storage chamber of the print head in the inkjet printer. The inkjet printer prints out emulsion droplets, which are deposited on the hydrophobic substrate. The emulsion droplets dry, thus forming core-shell structured microcapsules.

[0018] The beneficial effects of this invention are that it prepares core-shell structured microcapsules according to the process of oil phase preparation, aqueous phase preparation, emulsion generation (via microfluidic chip or homogenizer), substrate modification, emulsion droplet deposition on the substrate, and curing (drying), which is highly efficient and enables large-scale preparation. Inkjet printing can directly form functional layers.

[0019] The core-shell structured microcapsules exhibit good size uniformity with a coefficient of variation (CV) of <5%. The shell thickness can be controlled by adjusting the PMMA / poor solvent ratio (0.08-0.71 μm), and the core-shell interface is clear with no obvious pores.

[0020] The structural stability of core-shell microcapsules has also been improved.

[0021] The integrated process of emulsion preparation, molding and curing, and mechanism characterization, and mechanism verification (NMR / FIB, etc.), is key to guiding the phase separation process through ternary phase diagrams, enabling the design of core-shell structures (particle size, shell thickness, porosity).

[0022] Precise structural control is achieved by combining microfluidics / inkjet printing.

[0023] Further features and aspects of this application will be clearly described in the following detailed description with reference to the accompanying drawings. Attached Figure Description

[0024] Figure 1 In Example 1, the DCM / PMMA / hexadecane ternary phase diagram is shown, with the single-phase region, two-phase region, critical point, and junction line marked. Figure 2 This is a high-speed camera image of the microfluidic emulsion prepared in Example 1; Figure 3 This is a SEM image of the core-shell particles in Example 1, with a particle size of 1-2 μm; Figure 4 This is the FIB cross-sectional view in Example 1. A platinum protective layer is used during FIB milling to avoid sample damage. The milling current gradient is adjusted (50 nA for rough milling and 5 nA for polishing) to ensure a flat cross-section. Figure 5 This is the 1H-NMR spectrum from Example 1; Figure 6 This is the result of SEM detection of the functional layer in Example 1; Figure 7 This refers to the energy dispersive spectroscopy (EDS) analysis results in Example 2; Figure 8 This is a schematic diagram of the core-shell structure formation mechanism, showing the emulsion evaporation-phase separation-core-shell solidification process. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The specific embodiments described below are merely preferred embodiments of this application, and the scope of protection of this application is not limited thereto. Those skilled in the art can make modifications or variations based on the principles, concepts, and spirit of this application, and the resulting technical solutions should all be covered within the scope of protection of this application.

[0027] A microfluidics chip is a chip that enables various functions of routine physical, chemical, or biological experiments on a micrometer-scale chip, involving the manipulation of microfluidics. Microfluidics chips can be used to manipulate and generate microdroplets. The microchannel structure within a microfluidics chip is crucial. Based on different droplet generation methods, microchannel structures can be categorized into T-channels, flow-focusing microchannels, capillary coaxial microchannels, and stepped microchannels, among others. Flow-focusing microchannels are more stable than other structures, offering a wider controllable range for droplet size, which is beneficial for generating droplets with diameters much smaller than the chip channel size. Therefore, this embodiment uses a flow-focusing microfluidic chip as an optimized choice.

[0028] For inkjet printing equipment, the MicroFab MJ-ABP-01 model from the United States can be selected. The invention patent application with publication number CN117939989A discloses a technical solution related to inkjet printing.

[0029] For the materials mentioned below, the shell-forming polymer can be polymethyl methacrylate (PMMA, Mw=35 kg / mol) or polystyrene (PS, Mw=35 kg / mol), manufactured by Acros Organics or Sigma-Aldrich. A good solvent can be dichloromethane (DCM, purity >99%), manufactured by Fisher Scientific UK. A poor core-forming solvent can be hexadecane (purity >98%) or hexadecane bromide, manufactured by TCI. A dispersant can be polyvinyl alcohol (PVA, Mw=31-50 kg / mol, degree of hydrolysis 87-89%), manufactured by Acros Organics. A substrate modifier can be hexamethyldisilazane (HMDS, purity 98%), manufactured by Sigma-Aldrich. A characterization aid can be deuterated chloroform (CDCl3), manufactured by Fisher Scientific UK.

[0030] The following is for reference. Figure 8 This paper introduces a method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing.

[0031] Example 1

[0032] Step 1, Oil phase preparation: Dissolve 1.0 wt% PMMA and 1.0 wt% hexadecane in DCM, and heat in a 40°C water bath for 1 hour to ensure complete dissolution of PMMA and formation of an oil phase.

[0033] Step 2, aqueous phase preparation: Dissolve 0.1 wt% PVA in deionized water and stir until completely dispersed to form an aqueous phase.

[0034] Step 3, emulsion preparation: The oil and aqueous phases were filtered through 0.2 μm PTFE membranes and then loaded into syringes. The syringe containing the oil phase was installed on the first syringe pump, and the syringe containing the aqueous phase was installed on the second syringe pump. Next, the oil phase was injected into the central channel of the flow-focusing microfluidic chip, while the aqueous phase was split into two channels injected into the chip side channels via a Y-type PEEK connector. This enabled the preparation of water-in-oil emulsions through the microfluidic chip (etched depth 5 μm, channel width 500 μm). The flow rate of the aqueous phase was 2 μL / min, the flow rate of the oil phase was 0.2 μL / min, and the flow rate ratio of the oil phase to the aqueous phase was Qo / Qw=0.1. Uniform oil droplets were generated at the focusing flow junction (width 8 μm), and the average droplet size was recorded using a high-speed camera (500 fps).

[0035] Microfluidic chips can precisely control the size of oil droplets, resulting in high uniformity and consistency in droplet size.

[0036] Step 4, Substrate modification: The glass cover glass was ultrasonically cleaned with an acetone-isopropanol mixture for 30 minutes, rinsed with deionized water, dried at 100°C for 2 hours, treated with air plasma for 30 minutes, and then prepared as a hydrophobic substrate by HMDS vapor deposition for 2 hours.

[0037] Step 5, curing and shaping: The water-in-oil emulsion obtained in the third step was dropped onto the surface of a hydrophobic substrate and allowed to dry freely at room temperature for 10 minutes. The DCM preferentially evaporated to initiate phase separation, and the evaporation process (evaporation time ~2 seconds) was recorded by a high-speed camera (250fps), ultimately forming core-shell structured microcapsules.

[0038] The specific method for adding emulsion droplets to a hydrophobic substrate can be as follows: An oil-in-water emulsion is loaded into the reservoir of the printhead in an inkjet printer. The nozzle diameter of the printhead is 80 μm. The controller is set to a bipolar drive waveform of 50-60V, with a printing frequency of 1Hz. The nozzle of the printhead outputs emulsion droplets onto the hydrophobic substrate, with a droplet volume of 150-250 pL. The size of the droplets output from the nozzle can be precisely controlled, exhibiting high uniformity and consistency. The particle size of the core-shell structured microcapsules can be controlled within 1-3 μm.

[0039] Numerous core-shell structured microcapsules are closely arranged to form a functional layer, the thickness of which can be controlled between 5-50 μm.

[0040] Step 6, Mechanism Characterization: A ternary phase diagram of DCM / PMMA / hexadecane was constructed by 1H-NMR (Varian VNMRS-600, 599.42 MHz) to determine the phase separation critical point, with reference to... Figure 1 The 1H-NMR spectrum is as follows: Figure 5 As shown, the characteristic chemical shifts of DCM, PMMA, and hexadecane are marked. The phase separation process is guided by a ternary phase diagram, and the experimentally determined ternary phase diagram is shown below. Figure 1 The figure shows the phase behavior of the DCM / PMMA / HD mixture at ambient temperature and pressure. At each corresponding angle of the equilateral triangle, the concentration of each species is 100 wt% (pure phase), and 0 wt% on the opposite axis; the percentage of a particular species decreases linearly with increasing distance from its angle. For a given point within the ternary plot, the composition of DCM / PMMA / HD can be calculated using the following formula: In the formula, , , These are the vertical distances from the given point to the opposite sides of the DCM, PMMA, and HD angles, respectively.

[0041] A key feature of ternary phase diagrams is the bisection curve, which separates the single-phase and two-phase regions. The single-phase region lies near the DCM angle of the ternary phase diagram; any mixture within this region is a homogeneous DCM solution, with PMMA and HD completely dissolved. In the two-phase region, the ternary system will separate into two distinct liquid phases: a polymer-rich phase and an HD-rich phase. Connecting lines link the compositions of the equilibrium phases, as indicated by the red dots in the diagram. Specifically, any mixture with a monolithic composition along the connecting lines will split into two identical phase compositions.

[0042] After drying, the DCM gradually evaporates through diffusion in the aqueous phase, while PMMA and HD remain approximately constant within the emulsion droplet, resulting in a constant PMMA / HD ratio. This fixed PMMA / HD ratio leads to a straight line starting from a corner of the DCM, passing through the initial point of the droplet composition, and eventually reaching the PMMA / HD axis.

[0043] The dual-node system has a polymer-rich side and a HD-rich side, meeting at a critical point where the compositions of the two phases are identical. If we draw a line from the DCM angle through the critical point, it will end at approximately 80 wt% HD / 20 wt% PMMA on the PMMA / HD side. Any composition above this critical line will separate into a continuous PMMA phase surrounding the discrete HD phase. Otherwise, for any system below this line, small PMMA-rich droplets will separate from the bulky HD-rich continuous phase.

[0044] Furthermore, we noted that phase separation does not produce a pure binary mixture, i.e., a good solvent for the final drying of DCM / PMMA or DCM / HD. In fact, the two phases remain a ternary mixture of DCM / PMMA / HD. For example, with an initial composition of 67.3 wt% DCM, 9.9 wt% PMMA, and 22.8 wt% HD, phase separation yields a PMMA-rich phase containing 68 wt% DCM, 16.5 wt% PMMA, and 15.5 wt% HD, and an HD-rich phase containing 66.9 wt% DCM, 0.98 wt% PMMA, and 32.2 wt% HD. Note that the amount of HD in the PMMA-rich phase is almost the same as that in the PMMA, indicating that there is still sufficient HD in the PMMA-rich phase after phase separation. As the composition contacts the binode and moves further, the polymer-rich phase moves along the polymer-rich boundary towards the polymer corner until it reaches 100 wt% PMMA upon drying of the DCM. Similarly, the HD-rich phase moves along the HD-rich boundary, eventually yielding 100% HD.

[0045] We observed that when the droplet composition reached the phase boundary, Figure 2 The composition in Figure (i) is located on the polymer-rich side, and the composition in Figure (ii) is located on the HD-rich side. If the time from phase separation to the end of DCM evaporation is taken as t, the HD-rich droplets are more fluid at 0.1t, forming a single HD core at the center, while the PMMA-rich droplets are less fluid at 0.1t, and no obvious large droplets or films are observed at the O / W interface.

[0046] At the critical point, phase separation occurs when the DCM content in the composition reaches its maximum value. Depending on the droplet composition, i.e., the ratio of polymer to solvent-poor mixture in the initial mixture, either a polymer-rich phase or a high-density polymer (HD)-rich phase can be separated from the remaining mixture. If, during desolventizing, the component crosses the bisection curve of the ternary phase diagram on the polymer-rich side, the bulk phase is polymer-rich, and small droplets of the HD-rich phase appear and coalesce into liquid nuclei. On the other hand, if the component is on the HD-rich phase, PMMA-rich droplets will separate from the continuous HD-rich phase and migrate to the O / W interface. These small PMMA-rich droplets merge and engulf the surface, forming a polymer-rich wetting film. Further removal of low-boiling-point DCM promotes polymer precipitation and the formation of a solid polymer shell.

[0047] The core-shell structure (shell thickness 0.25 μm, core diameter 0.98 μm) was verified by characterizing the particle cross-section using FIB / SEM (FEI Helios NanoLab 600). Figure 4 This is a FIB detection result image, showing a clear interface between the PMMA shell and the hexadecane core layer.

[0048] Figure 6 This is the SEM image of the formed functional layer.

[0049] Example 2 Step 1, Oil phase preparation: 0.5 wt% PMMA and 0.5 wt% hexadecane (functional carrier) were dissolved in DCM and stirred until homogeneous to form an oil phase.

[0050] Step 2, aqueous phase preparation: Dissolve 0.1 wt% PVA in deionized water and stir until completely dispersed to form an aqueous phase.

[0051] Step 3, emulsion preparation: Polydisperse emulsions (oil droplet size 10-20 μm) were prepared by mixing 2 mL of aqueous phase and 1 mL of oil phase using a homogenizer (German IKA T10 model) and shearing at 25.9 k rpm for 10 seconds.

[0052] Step 4, Substrate modification: The glass cover glass was ultrasonically cleaned with an acetone-isopropanol mixture for 30 minutes, rinsed with deionized water, dried at 100°C for 2 hours, and treated with air plasma for 30 minutes to obtain a hydrophilic substrate.

[0053] Step 5, Curing: The water-in-oil emulsion obtained in the third step was dropped onto the surface of the hydrophilic substrate and allowed to dry freely at room temperature for 10 minutes. The DCM preferentially evaporated to initiate phase separation, and the evaporation process (evaporation time ~2 seconds) was recorded by a high-speed camera (250fps), ultimately forming core-shell structured microcapsules.

[0054] The specific method for adding emulsion droplets to a hydrophilic substrate can be as follows: the water-in-oil emulsion is loaded into the liquid storage chamber of the printhead in the inkjet printer. The nozzle diameter of the printhead is 80μm. The controller is set to a bipolar drive waveform of 50-60V, the printing frequency is 1Hz, and the nozzle outputs emulsion droplets onto the hydrophilic substrate. The volume of the emulsion droplets is 150-250 pL.

[0055] Step 6, Characterization and Verification: Analysis of the bromine distribution using energy dispersive spectroscopy (EDS) confirmed that hexadecane bromide is located in the core layer. Figure 7 This is a bromine element distribution diagram. The surface uniformity of the functional layer was observed using a scanning electron microscope (SEM) (Hitachi SU70), showing that the core-shell particles are tightly packed to form the functional layer.

[0056] Example 3 Step 1, Oil phase preparation: PMMA and hexadecane were dissolved in DCM with a total solids content of 1.0 wt%. The solutions were prepared at PMMA to hexadecane mass ratios of 1:2, 1:4, and 2:1, respectively. The solutions were heated in a water bath at 40°C for 1 hour to ensure complete dissolution of PMMA and to form three oil phases.

[0057] Step 2, aqueous phase preparation: Dissolve 0.1 wt% PVA in deionized water and stir until completely dispersed to form an aqueous phase.

[0058] Step 3, emulsion preparation: The oil and aqueous phases were filtered through 0.2 μm PTFE membranes and then loaded into syringes. The syringe containing the oil phase was installed on the first syringe pump, and the syringe containing the aqueous phase was installed on the second syringe pump. Next, the oil phase was injected into the central channel of the flow-focusing microfluidic chip, while the aqueous phase was split into two channels injected into the chip side channels via a Y-type PEEK connector. This enabled the preparation of water-in-oil emulsions through the microfluidic chip (etched depth 5 μm, channel width 500 μm). The aqueous phase flow rate was 2 μL / min, the oil phase flow rate was 0.2 μL / min, and the flow rate ratio of the oil phase to the aqueous phase was Qo / Qw=0.1. Uniform oil droplets were generated at the focusing flow junction (width 8 μm), and the average droplet size was recorded using a high-speed camera (500 fps).

[0059] Step 4, Substrate modification: The glass cover glass was ultrasonically cleaned with an acetone-isopropanol mixture for 30 minutes, rinsed with deionized water, dried at 100°C for 2 hours, treated with air plasma for 30 minutes, and then prepared as a hydrophobic substrate by HMDS vapor deposition for 2 hours.

[0060] Step 5, Curing: The water-in-oil emulsion obtained in the third step was dropped onto the surface of a hydrophobic substrate and allowed to dry freely at room temperature for 10 minutes. The preferential evaporation of DCM initiated phase separation, ultimately forming core-shell structured microcapsules.

[0061] Step 6, Mechanism Characterization: Morphology was observed using scanning electron microscopy (SEM), and shell thickness was measured using fibrillation-based microscopy (FIB). Results showed that in the first oil phase (PMMA / hexadecane = 1:2), the shell thickness was uniform (0.14 μm), and the core structure was intact. In the second oil phase (PMMA / hexadecane = 1:4), the shell was thinner (0.08 μm), with good particle sphericity. In the third oil phase (PMMA / hexadecane = 2:1), the shell thickness increased (~0.44 μm), with no obvious porosity. Therefore, shell thickness can be controlled by the PMMA / hexadecane ratio, resulting in a clear core-shell interface without significant porosity. Figure 4 As shown.

[0062] Therefore, the thickness of the shell can be controlled between 0.08 and 0.71 μm.

[0063] Therefore, the above preparation method can precisely control the size of core-shell structured microcapsules, resulting in high size uniformity and consistency, and high particle sphericity.

[0064] It should be noted that polyvinylpyrrolidone (PVP) can be used instead of PMMA.

Claims

1. A method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing, characterized in that, Includes the following steps: Step 1, Oil phase preparation: The shell-forming polymer and the core-forming poor solvent are dissolved in a good solvent to obtain the oil phase; Step 2, aqueous phase preparation: The dispersant was dissolved in deionized water to obtain an aqueous phase; Step 3, emulsion preparation: Water-in-oil emulsions are prepared using microfluidic chips. The aqueous phase is injected into the microfluidic chip, the oil phase is injected into the microfluidic chip, the flow rate ratio of the oil phase to the aqueous phase is adjusted, and the generated water-in-oil emulsion is collected. Step 4: Prepare the hydrophobic substrate: Step 5, curing and shaping: The water-in-oil emulsion obtained in the third step is placed in the liquid storage chamber of the printhead in the inkjet printer. The inkjet printer prints out emulsion droplets, which are deposited on the hydrophobic substrate. The emulsion droplets dry, thus forming core-shell structured microcapsules.

2. The method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing according to claim 1, characterized in that, The mass ratio of the shell-forming polymer to the core-forming poor solvent is 1:4 to 4:

1.

3. The method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing according to claim 1, characterized in that, The shell-forming polymer is PMMA, PS, or PVP; the core-forming poor solvent is hexadecane or hexadecane bromide.

4. The method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing according to claim 1, 2, or 3, characterized in that, The good solvent is DCM; the dispersant is PVA.

5. Core-shell structured microcapsules prepared by the microfluidic combined inkjet printing method based on emulsion evaporation for core-shell structured microcapsules as described in any one of claims 1-4.

6. A functional particle layer, characterized in that, It is composed of the core-shell structured microcapsules as described in claim 5.

7. A method for adjusting the core-shell structure of a core-shell microcapsule, characterized in that, The alkyl mass ratio of the shell-forming polymer to the core-forming poor solvent was calculated based on the ternary phase diagram.

8. A method for preparing core-shell structured microcapsules based on emulsion evaporation using microfluidics combined with inkjet printing, characterized in that, Includes the following steps: Step 1, Oil phase preparation: The shell-forming polymer and the core-forming poor solvent are dissolved in a good solvent to obtain the oil phase; Step 2, aqueous phase preparation: The dispersant was dissolved in deionized water to obtain an aqueous phase; Step 3, emulsion preparation: An emulsion was prepared by mixing the aqueous phase and the oil phase using a homogenizer. Step 4: Prepare the hydrophobic substrate: Step 5, curing and shaping: The emulsion obtained in the third step is loaded into the liquid storage chamber of the print head in the inkjet printer. The inkjet printer prints out emulsion droplets, which are deposited on the hydrophobic substrate. The emulsion droplets dry, thus forming core-shell structured microcapsules.

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