Interfacial imbibing endocytosis microfluidic method for controllable preparation of monodisperse double emulsion

Abstract

The application provides an interface infiltration endocytosis microfluidic method for controllably preparing monodisperse double emulsion, which is prepared by using a microfluidic device, and steps are as follows: the outer phase fluid is filled in a collection container to make the liquid surface of the outer phase fluid be a horizontal surface, the outlet of an injection tube is arranged above the liquid surface of the outer phase fluid in the collection container, the inner phase fluid and the intermediate phase fluid are continuously injected into the inner tube and the outer tube of the injection tube by using injection pumps respectively, the inner phase fluid is sheared into droplets by the intermediate phase fluid at the outlet of the inner tube, and the monodisperse double emulsion is generated under the induction of the interfacial tension difference of the air phase, the intermediate phase fluid and the outer phase fluid when the intermediate phase fluid containing the inner phase fluid droplets contacts the liquid surface of the outer phase fluid; the interfacial tension of the intermediate phase fluid and the outer phase fluid at the outlet of the outer tube should satisfy γ AW >γ AO +γ WO The application can simplify the structure of the microfluidic device and the construction process thereof, and realize convenient, efficient and controllable preparation of the monodisperse double emulsion.

Description

Technical Field

[0001] The invention belongs to the field of emulsion preparation and relates to an interface infiltration endocytosis emulsification microfluidic method capable of controllably preparing monodisperse double emulsions. Background Art

[0002] Double emulsion refers to an emulsion with a droplet-encapsulated droplet structure, that is, the droplets dispersed in the continuous phase also contain droplets. The unique structure of double emulsion makes it have important uses in many fields such as active substance encapsulation, microcapsule preparation, micro-biochemical reaction, and controlled drug release. Usually, traditional double emulsions can be prepared by a two-step mechanical stirring process or a two-step membrane emulsification process. However, the size and structure of the droplets prepared by these methods are difficult to effectively control, and generally have size polydispersity. The microfluidic technology that has emerged in recent years has shown unique advantages in the controllable preparation of double emulsions due to its precise control of microscale fluid flow and dispersion. When preparing double emulsions, existing microfluidic technology usually requires the use of microfluidic devices with complex microchannel structures such as coaxial co-flow type, flow focusing type and cross-flow type, and the complex microchannel structure also involves precise control of the flow of three fluids: internal phase, intermediate phase and external phase. Therefore, although the existing microfluidic technology can produce double emulsions with controllable structure and uniform size, it still needs to rely on complex microfluidic devices and involves a tedious microfluidic device manufacturing process. It also requires operators to have professional microscale multiphase fluid manipulation skills. At the same time, the structure, size and size monodispersity of double droplets produced by traditional microfluidic technology are also easily affected by factors such as the geometric dimensions of the device microchannel, the flow conditions of the continuous phase and the physical parameters of the fluid (such as viscosity, interfacial tension, etc.), resulting in the droplet formation process being easily disturbed, thereby affecting the structure, size and monodispersity of the droplets. For example, when traditional microfluidic technology is used to prepare double emulsion droplets, the size of the external droplets of the double emulsion will increase with the increase of the microchannel size and decrease with the increase of the external phase flow rate, which is easily affected by changes in production process conditions. Furthermore, the preparation of double emulsions involves microscale flow manipulation and shear dispersion of three-phase fluids, typically requiring highly specialized fluid manipulation skills from specialized technicians to prevent phenomena such as dispersed phase adherence to the wall, continuous phase backflow, and mismatched flow rates between the liquid phases, which can lead to ineffective double emulsion droplet formation. Therefore, the development of novel microfluidic emulsification technologies with convenient operation, simple device structure, and robust emulsification processes is of great significance for the controllable preparation of monodisperse double emulsion droplets. Summary of the Invention

[0003] In response to the problems existing in existing microfluidic double emulsion preparation technology, such as complex device structure and cumbersome device construction process, high requirements for fluid manipulation, and many factors affecting droplet preparation, the present invention provides an interface infiltration endocytosis emulsification microfluidic method for the controllable preparation of monodisperse double emulsions, so as to simplify the structure and construction process of the microfluidic device and the double emulsion preparation operation process, make the double emulsion preparation process less susceptible to factors such as liquid phase flow conditions, liquid phase viscosity, and microchannel size, improve the robustness of its emulsification process, and realize the convenient, efficient and controllable preparation of monodisperse double emulsions.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0005] A microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis is disclosed. The method is prepared using a microfluidic device comprising a syringe pump, a nested syringe tube, and a collection container. The nested syringe tube comprises an inner tube and an outer tube, the inner tube being coaxially nested within the outer tube, and the inlets of the inner and outer tubes being respectively connected to different liquid outlets of the syringe pump. The steps are as follows:

[0006] The outer phase fluid is placed in a collection container so that the liquid surface of the outer phase fluid is horizontal, the outlet of the injection tube is placed above the liquid surface of the outer phase fluid in the collection container, the inner phase fluid and the intermediate phase fluid are respectively continuously injected into the inner tube and the outer tube of the injection tube through the injection pump, the inner phase fluid is sheared into droplets by the intermediate phase fluid at the outlet of the inner tube, and when the intermediate phase fluid containing the droplets of the inner phase fluid contacts the liquid surface of the outer phase fluid, a monodisperse double emulsion is generated under the induction of the interfacial tension difference between the air phase, the intermediate phase fluid and the outer phase fluid;

[0007] The interfacial tension between the intermediate phase fluid and the external phase fluid at the outlet of the outer tube should satisfy γ AW >γ AO +γ WO , γ AW is the interfacial tension between the air phase and the intermediate phase fluid, γ AO is the interfacial tension between the air phase and the external phase fluid, γ WO is the interfacial tension between the intermediate phase fluid and the external phase fluid;

[0008] During the preparation process, the nested injection tube is controlled to be perpendicular to the liquid surface of the external phase fluid, the outlet of the nested injection tube is controlled to be above the liquid surface of the external phase fluid, and the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid is L±(1%~5%)*L, where L is a constant value ≥50μm.

[0009] In the technical solution of the interfacial infiltration endocytosis emulsification microfluidic method for controllably preparing monodisperse double emulsions, the adjacent two phases of the inner phase fluid, the middle phase fluid and the outer phase fluid are mutually immiscible or slightly soluble two phase fluids.

[0010] Further, in the above technical solution of the microfluidic method for preparing monodisperse double emulsion by interfacial imbibition endocytosis, the oil phase solution is used as the inner phase fluid, the aqueous phase solution is used as the intermediate phase fluid, and the oil phase solution is used as the outer phase fluid; or the two aqueous phase solutions that are not mutually soluble or are slightly soluble with each other are used as the inner phase fluid and the intermediate phase fluid respectively, and the oil phase solution is used as the outer phase fluid.

[0011] Further, in the above technical solution of the microfluidic method for preparing monodisperse double emulsion by interfacial imbibition endocytosis, the intermediate phase fluid or / and the outer phase fluid contains a reagent for stabilizing the interface. The reagent for stabilizing the interface includes a surfactant or / and nanoparticles for stabilizing the interface. The surfactant is dissolved in the intermediate phase fluid or / and the outer phase fluid, and the nanoparticles for stabilizing the interface are uniformly dispersed in the intermediate phase fluid or / and the outer phase fluid. A feasible method for preparing the intermediate phase fluid or the outer phase fluid is to dissolve or uniformly disperse the surfactant or / and the nanoparticles for stabilizing the interface in a solvent of the intermediate phase fluid or the outer phase fluid.

[0012] In the above technical solution of the microfluidic method for preparing monodisperse double emulsion by interfacial imbibition endocytosis, the aqueous phase solution or / and the oil phase solution contains at least one of a functional polymer, a monomer, a thickening agent, a salt, and a functional nanoparticle that can be dissolved in the aqueous phase solvent or the oil phase solvent. A feasible method for preparing the aqueous phase solution is to dissolve at least one of the functional polymer, the monomer, the thickening agent, the salt, and the functional nanoparticle that can be dissolved in the aqueous phase solvent in the aqueous phase solvent. A feasible method for preparing the oil phase solution is to dissolve at least one of the functional polymer, the monomer, the thickening agent, the salt, and the functional nanoparticle that can be dissolved in the oil phase solvent in the oil phase solvent.

[0013] When the inner phase fluid or / and the intermediate phase fluid contains a functional polymer or a monomer, the monodisperse double emulsion droplets prepared by the above technical solution can obtain monodisperse polymer microspheres or microcapsules after solidification; when the inner phase fluid or / and the intermediate phase fluid contains a functional polymer or a monomer and a functional nanoparticle, the monodisperse double emulsion droplets prepared by the above technical solution can obtain functionalized monodisperse polymer microspheres or microcapsules after solidification.

[0014] In actual applications, the formulations of the inner phase fluid, the intermediate phase fluid, and the outer phase fluid are determined according to specific application requirements, and the formulations of the inner phase fluid, the intermediate phase fluid, and the outer phase fluid can be determined with reference to the prior art.

[0015] In the above-mentioned technical solution for the microfluidic method for controlled preparation of monodisperse double emulsions by interfacial infiltration and endocytosis, both the inner and outer tubes of the nested syringes are tubular components with conical outlets, and the outlet of the inner tube of the nested syringe is located within the outer tube of the nested syringe. The outer and inner tubes of the nested syringes can be made of metal, polymer, glass, or the like.

[0016] Furthermore, in the technical solution of the interfacial infiltration endocytosis emulsification microfluidic method for controllably preparing monodisperse double emulsions, the inner diameter of the outer tube outlet is 30 to 1000 μm, and the inner diameter of the inner tube outlet is 10 to 500 μm.

[0017] Furthermore, in the technical solution of the interfacial infiltration endocytosis emulsification microfluidic method for controllably preparing monodisperse double emulsions, the L is a constant value between 50 and 1000 μm.

[0018] In the above-described microfluidic method for controllable preparation of monodisperse double emulsions by interfacial infiltration and endocytosis, the number of cores in the double emulsion and the diameter of the double emulsion droplets can be adjusted by adjusting the distance between the outlet of the nested syringe and the liquid surface of the external phase fluid. Typically, the diameter of the monodisperse double emulsion droplets prepared by this technical solution ranges from 50 to 1000 μm.

[0019] In the above-mentioned technical solution of the interfacial infiltration endocytosis emulsification microfluidic method for controllable preparation of monodisperse double emulsions, the liquid level of the external phase fluid will rise as the preparation process of the monodisperse double emulsion proceeds. During the preparation process, the position of the nested syringe can be adjusted upward, or the position of the collection container can be adjusted downward, or the liquid level height in the collection container can be lowered (for example, by taking out part of the monodisperse double emulsion from the collection container) to ensure that the outlet of the nested syringe is above the liquid level of the continuous phase and the distance between the outlet of the nested syringe and the liquid level of the external phase fluid is maintained at L±(1%~5%)*L.

[0020] In practical applications, when the structure of the microfluidic device and the formulas of the inner phase fluid, intermediate phase fluid and outer phase fluid are determined, the flow rates of the appropriate inner phase fluid and intermediate phase fluid and the distance from the outlet of the nested syringe to the liquid surface of the outer phase fluid can be determined experimentally to ensure that the intermediate phase fluid containing the core can be sheared off from the outlet of the nested syringe to form double emulsion droplets.

[0021] The present invention is based on the interfacial tension difference (γ AW >γ AO +γ WO) is induced to allow the intermediate phase containing the inner phase fluid droplets to infiltrate the outer phase fluid to automatically generate a monodisperse double emulsion. The structure and construction process of the microfluidic device relied on by the method of the present invention are simple, and there is no need to rely on complex micro-manufacturing processes to construct complex microchannels. It is also less dependent on professional fluid operation skills.

[0022] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial technical effects:

[0023] 1. The present invention provides an interfacial infiltration endocytosis emulsification microfluidic method for the controllable preparation of monodisperse double emulsions. By selecting appropriate internal phase, intermediate phase, and external phase fluids, and controlling the outlet of the syringe to be above the liquid level of the continuous phase fluid and the distance between the outlet of the syringe and the liquid level of the continuous phase fluid to be at an appropriate value during the preparation process, monodisperse double emulsion droplets can be continuously prepared. The required microfluidic device only includes three structures: a collection container, a syringe pump, and a nested syringe. Its structure is simple and does not include complex microchannels. At the same time, its construction process is also very simple, and the construction of the microfluidic device does not require complex microfabrication processes.

[0024] 2. The interfacial infiltration endocytosis emulsification microfluidic method for the controllable preparation of monodisperse double emulsions provided by the present invention achieves controllable double emulsion preparation by simply regulating the fluid flow rate and the distance between the outlet of the nested syringe and the liquid surface of the external phase fluid, making the controllable preparation of double emulsions more convenient and efficient. This significantly reduces the technical requirements for operators, making fluid manipulation more convenient and flexible, and thus has broad application prospects in the controllable preparation of monodisperse double emulsions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of a cannula microfluidic device for controllably preparing monodisperse double emulsions. In the figure, 1 is a nested syringe, 2 is a collection container, and 3 is a syringe pump.

[0026] Figure 2 Figures a) and b) are respectively the double emulsion prepared in Example 2 and the diameter distribution diagrams of the inner and outer droplets of the double emulsion. Figure 2 Figure c) shows the effect of changing the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid on the inner and outer droplet diameters of the double emulsion in Example 3 while keeping the inner and middle phase flow rates fixed. Figure 2 Figure d) shows the effect of changing the inner phase fluid flow rate on the inner and outer droplet diameters of the double emulsion by fixing the distance between the outlet of the nested injection tube and the liquid surface of the outer phase fluid and the flow rate of the intermediate phase fluid in Example 3.

[0027] Figure 3Figures a) to b) are high-speed camera images of the real-time formation process of the O / W / O double emulsion in Example 4, and the change in the number of cores in the O / W / O double emulsion with the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid.

[0028] Figure 4 Figures a) to b) are optical images of calcium alginate microcapsules after primary crosslinking and secondary crosslinking in Example 5, respectively. DETAILED DESCRIPTION

[0029] The following examples and accompanying drawings further illustrate the microfluidic method for the controllable preparation of monodisperse double emulsions through interfacial infiltration and endocytosis. It should be noted that the following examples are intended only to further illustrate the present invention and are not to be construed as limiting the scope of the present invention. Based on the above disclosure, non-essential improvements and adjustments made by those skilled in the art to the present invention remain within the scope of the present invention.

[0030] In the following examples, the water-soluble surfactant used is Pluronic F-127, which is a segmented polyether F127, an addition polymer of polypropylene glycol and ethylene oxide. Pluronic F-127 is its trade name; the oil-soluble surfactant is polyisobutylene succinimide (T154).

[0031] In the process of preparing the monodisperse double emulsion in the following embodiments, the liquid level of the external phase fluid will gradually rise as the preparation process of the monodisperse double emulsion proceeds. In the preparation process in the following embodiments, the position of the nested syringe can be adjusted upward, or the position of the collection container can be adjusted downward, or a portion of the monodisperse double emulsion can be taken out from the collection container to ensure that the outlet of the nested syringe is above the liquid level of the external phase fluid and the distance between the outlet of the nested syringe and the liquid level of the external phase fluid is maintained at L±5%*L.

[0032] Example 1

[0033] In this embodiment, a structure of a microfluidic device for preparing a monodisperse double emulsion is provided. The microfluidic device includes a nested injection tube 1, a collection container 2, and a syringe pump 3. The schematic diagram of the structure is shown in FIG. Figure 1 shown.

[0034] The nested syringe 2 consists of an inner tube and an outer tube, with the inner tube nested within the outer tube and coaxially arranged. The inner tube is made from a cylindrical glass capillary with an inner diameter of 500μm and an outer diameter of 960μm. The tail of the glass capillary is drawn using a needle puller to form a conical flat end with an inner diameter of approximately 50μm and an outer diameter of approximately 80μm. The outer tube is made from a square glass tube with a square through-hole in the center. The cross-sectional dimensions of the square through-hole are 1.0×1.0mm. The tail of the square glass tube is drawn using a needle puller to form a conical flat end with an inner diameter of 90μm and an outer diameter of 100μm. The distance between the tapered ends of the inner and outer tubes is 1500μm. The inlets of the inner and outer tubes of the nested syringe are connected to the liquid outlets of two syringe pumps through pipe fittings.

[0035] Example 2

[0036] In this example, the preparation of a monodisperse oil-in-water-in-oil (O / W / O) double emulsion is taken as an example to illustrate the microfluidic method for the controllable preparation of a monodisperse double emulsion by interfacial infiltration and endocytosis. The steps are as follows:

[0037] (1) Preparation of internal phase, intermediate phase and external phase fluids

[0038] Soybean oil was used as the internal phase fluid; Pluronic F-127 and sodium carboxymethyl cellulose were dissolved in deionized water to obtain an intermediate phase fluid, wherein the mass ratio of deionized water, Pluronic F-127, and sodium carboxymethyl cellulose in the intermediate phase fluid was 1:0.005:0.005; T154 was dissolved in tetradecane to obtain an external phase fluid, wherein the concentration of T154 in the external phase fluid was 0.04 g / mL.

[0039] (2) Preparation of monodisperse O / W / O double emulsion

[0040] The microfluidic device described in Example 1 was used for preparation, and a culture dish was used as a collection container.

[0041] The external phase fluid is placed in a collection container, which is placed horizontally so that the liquid surface of the continuous phase fluid is horizontal. The outlet of the injection tube is placed above the liquid surface of the external phase fluid in the collection container. The internal phase fluid and the intermediate phase fluid are continuously injected into the inner tube and outer tube of the nested injection tubes through the injection pump at a flow rate of 0.7 mL / h and 4 mL / h, respectively. At the outlet of the inner tube, the internal phase fluid is sheared into droplets by the intermediate phase fluid. When the intermediate phase fluid containing the internal phase fluid droplets contacts the liquid surface of the external phase fluid, the interfacial tension difference γ between the air phase (A), the intermediate phase fluid (W) and the external phase fluid (O) is AW >γ AO +γ WO Under the induction of , a monodisperse O / W / O double emulsion containing a small droplet is generated;

[0042] In the preparation process, the nested injection tube is controlled to be perpendicular to the liquid surface of the outer phase fluid, the outlet of the nested injection tube is controlled to be above the liquid surface of the outer phase fluid, and the distance (H) between the outlet of the nested injection tube and the liquid surface of the outer phase fluid is kept in the range of 650±32.5 μm.

[0043] Figure 2 The a) to b) of FIG. are respectively optical microscope pictures of the O / W / O double emulsion prepared in the embodiment and diameter distribution diagrams of the inner and outer droplets in the double emulsion, and it can be seen from the diagrams that the O / W / O double emulsion droplets prepared in the embodiment encapsulate one small droplet, and the sizes of the inner and outer droplets are uniform.

[0044] Example 3

[0045] In the embodiment, the influence of the distance between the outlet of the nested injection tube and the liquid surface of the outer phase fluid, the flow rates of the inner phase and the outer phase fluid on the diameter of the O / W / O double emulsion droplet is investigated.

[0046] (1) The inner phase, intermediate phase and outer phase fluid are prepared according to the operation of step (1) of Example 2.

[0047] (2) Preparation of monodisperse O / W / O double emulsion

[0048] Referring to the operation of step (2) of Example 2, under the conditions that the flow rate of the inner phase fluid is 0.6 mL / h and the flow rate of the intermediate phase fluid is 4 mL / h, the distance (H) between the outlet of the nested injection tube and the liquid surface of the outer phase fluid is respectively controlled to be kept in the range of 650±32.5, 680±34, 710±35.5, 720±36 and 740±37 μm in the preparation process.

[0049] The diameters of the inner and outer droplets of the monodisperse O / W / O double emulsion thus prepared are shown in the c) of FIG. Figure 2 It can be seen from the diagram that, under the conditions that the flow rates of the inner phase fluid and the intermediate phase fluid are fixed, when the distance (H) between the outlet of the nested injection tube and the liquid surface of the continuous phase fluid is in the above distance, the monodisperse O / W / O double emulsion thus prepared has one inner core, and with the increase of the distance (H) between the outlet of the nested injection tube and the liquid surface of the continuous phase fluid, the diameter of the inner core of the O / W / O double emulsion is basically unchanged, and the diameter of the outer droplet gradually increases.

[0050] (2) Preparation of monodisperse O / W / O double emulsion

[0051] Referring to the operation of step (2) of Example 2, under the conditions that the flow rate of the intermediate phase fluid is 4 mL / h and the distance (H) between the outlet of the nested injection tube and the liquid surface of the external phase fluid is maintained at 650±32.5 μm, the flow rates of the internal phase fluid are controlled to 0.6, 0.7, 0.8, 0.9 and 1 mL / h respectively during the preparation process.

[0052] The diameters of the inner and outer droplets of the monodisperse O / W / O double emulsion thus prepared are as follows: Figure 2 As shown in Figure d), it can be seen from the figure that when the flow rate of the intermediate phase fluid and the distance (H) between the outlet of the nested injection tube and the liquid surface of the continuous phase fluid are fixed, the prepared monodisperse O / W / O double emulsions have a core. With the increase of the flow rate of the internal phase fluid, the diameter of the outer droplets of the O / W / O double emulsion remains basically unchanged, while the diameter of the core gradually increases.

[0053] Example 4

[0054] In this embodiment, the number of cores contained in the O / W / O double emulsion is adjusted by regulating the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid during the preparation process.

[0055] (1) Prepare the inner phase, middle phase and outer phase fluids according to the operation of step (1) of Example 2.

[0056] (2) Preparation of monodisperse O / W / O double emulsion

[0057] Referring to the operation of step (2) of Example 2, under the conditions of an inner phase fluid flow rate of 0.6 mL / h and an intermediate phase fluid flow rate of 4 mL / h, during the preparation process, the distance (H) between the outlet of the nested injection tube and the liquid surface of the outer phase fluid was controlled to be maintained at 740±37, 950±47.5, 1020±51 and 1120±56 μm, respectively.

[0058] Figure 3 a) High-speed camera image during the preparation process of O / W / O double emulsion encapsulating a core. Figure 3 Figure b) shows the change in the number of cores in the prepared monodisperse O / W / O double emulsion as the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid changes. It can be seen from the figure that by adjusting the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid, the number of cores in the monodisperse O / W / O double emulsion can be controlled.

[0059] Example 5

[0060] In this example, the preparation of a monodisperse O / W / O double emulsion containing a controllable number of small droplets is used as an example to illustrate the method of the present invention for controllably preparing a monodisperse double emulsion based on the infiltration principle. Microcapsules are prepared using the prepared O / W / O double emulsion as a template. The steps are as follows:

[0061] (1) Preparation of internal phase, intermediate phase and external phase fluids

[0062] Soybean oil was used as the internal phase fluid; sodium alginate and calcium carbonate nanoparticles were dispersed in deionized water to create an intermediate phase fluid. The mass ratio of deionized water, sodium alginate, and calcium carbonate nanoparticles in the intermediate phase fluid was 1:0.015:0.001. T154 and acetic acid were dissolved in tetradecane to create the external phase fluid. The concentrations of T154 and acetic acid in the external phase fluid were 0.04 g / mL and 0.004 g / mL, respectively.

[0063] n-Octanol and soybean oil were fully mixed in a volume ratio of 1:4, and then calcium iodide was added and mixed thoroughly to obtain a collection solution, which was used to perform a secondary cross-linking reaction on the calcium alginate droplets. The concentration of calcium iodide in the collection solution was 0.8% (w / v).

[0064] (2) Preparation of monodisperse O / W / O double emulsion and calcium alginate microparticles

[0065] The microfluidic device described in Example 1 was used for preparation, and a culture dish was used as a collection container.

[0066] The external phase fluid is placed in a collection container, which is placed horizontally so that the liquid surface of the continuous phase fluid is horizontal. The outlet of the injection tube is placed above the liquid surface of the external phase fluid in the collection container. The internal phase fluid and the intermediate phase fluid are continuously injected into the inner tube and outer tube of the nested injection tubes through the injection pump at flow rates of 0.1 mL / h and 2 mL / h, respectively. At the outlet of the inner tube, the internal phase fluid is first sheared into droplets by the intermediate phase fluid. When the intermediate phase fluid containing the internal phase fluid droplets contacts the liquid surface of the external phase fluid, the interfacial tension difference γ between the air phase (A), the intermediate phase fluid (W) and the external phase fluid (O) is AW >γ AO +γ WO Under the induction of the acetic acid, a monodisperse O / W / O double emulsion containing a core is generated. At the same time, the acetic acid in the external phase diffuses into the middle phase and reacts with the calcium carbonate nanoparticles to generate Ca 2+ , so that the O / W / O double emulsion undergoes a single cross-linking to form calcium alginate microparticles encapsulating a core.

[0067] During the preparation process, the nested injection tube is controlled to be perpendicular to the liquid surface of the external phase fluid, the outlet of the nested injection tube is controlled to be above the liquid surface of the external phase fluid, and the distance (H) between the outlet of the nested injection tube and the liquid surface of the external phase fluid is maintained within the range of 740±37μm.

[0068] (3) Secondary crosslinking

[0069] The calcium alginate microparticles are collected with a collecting solution for secondary cross-linking, and after sufficient cross-linking, they are washed with isopropyl alcohol and water to obtain calcium alginate microcapsules.

[0070] Under the same conditions as in steps (1) to (3) above, calcium alginate microcapsules containing two, three, or four cores can be prepared by increasing the distance (H) between the outlet of the nested injection tube and the liquid surface of the external phase fluid.

[0071] Figure 4 Figure a) is an optical picture of the monodisperse O / W / O double emulsion containing one, two, three and four small droplets prepared in this example after single crosslinking. Figure 4 Figure b) shows optical images of monodisperse O / W / O double emulsions containing one, two, three, and four small droplets, prepared in this example, after secondary crosslinking. As can be seen from the figure, the four calcium alginate microcapsules prepared in this example have uniform structure and size, and the number of cores within the microcapsules is precisely controllable.

Claims

1. A microfluidic method for the controlled preparation of monodisperse double emulsions by interfacial infiltration and endocytosis, characterized in that: The preparation is performed using a microfluidic device including a syringe pump, a nested syringe tube, and a collection container. The nested syringe tube includes an inner tube and an outer tube. The inner tube is coaxially nested in the outer tube. The inlets of the inner tube and the outer tube are respectively connected to different liquid outlets of the syringe pump. The inner tube and the outer tube of the nested syringe tube are both pipes with conical outlets. The outlet of the inner tube of the nested syringe tube is located in the outer tube of the nested syringe tube. The steps are as follows: The outer phase fluid is placed in a collection container so that the liquid surface of the outer phase fluid is horizontal, the outlet of the nested syringe is placed above the liquid surface of the outer phase fluid in the collection container, the inner phase fluid and the intermediate phase fluid are respectively continuously injected into the inner tube and the outer tube of the nested syringe via a syringe pump, the inner phase fluid is sheared into droplets by the intermediate phase fluid at the outlet of the inner tube, and when the intermediate phase fluid containing the droplets of the inner phase fluid contacts the liquid surface of the outer phase fluid, a monodisperse double emulsion is generated under the induction of the interfacial tension difference between the air phase, the intermediate phase fluid, and the outer phase fluid; The interfacial tension between the intermediate phase fluid and the external phase fluid at the outlet of the outer tube should satisfy γ AW > γ AO + γ WO , γ AW is the interfacial tension between the air phase and the intermediate phase fluid, γ AO is the interfacial tension between the air phase and the external phase fluid, γ WO is the interfacial tension between the intermediate phase fluid and the external phase fluid; During the preparation process, the nested injection tube is controlled to be perpendicular to the liquid surface of the external phase fluid, the outlet of the nested injection tube is controlled to be above the liquid surface of the external phase fluid, and the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid is L ±(1%~5%)* L , L It is a constant value between 50 and 1000 μm.

2. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to claim 1, characterized in that: The adjacent two-phase fluids in the inner phase fluid, the middle phase fluid and the outer phase fluid are two-phase fluids that are immiscible with each other or slightly soluble with each other.

3. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to claim 2, characterized in that: The oil phase solution is used as the inner phase fluid, the water phase solution is used as the middle phase fluid, and the oil phase solution is used as the outer phase fluid; Alternatively, two aqueous phase solutions that are immiscible or slightly soluble in each other are used as the inner phase fluid and the middle phase fluid respectively, and the oil phase solution is used as the outer phase fluid.

4. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to claim 3, characterized in that: The intermediate phase and / or the external phase fluid contains an agent for stabilizing the interface.

5. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to claim 4, characterized in that: The agent for stabilizing the interface includes a surfactant and / or nanoparticles for stabilizing the interface.

6. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to claim 3, characterized in that: The aqueous phase solution and / or the oil phase solution contains at least one of a functional polymer, a monomer, a thickener, a salt, and functional nanoparticles that can be dissolved in the aqueous phase solvent or the oil phase solvent.

7. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to claim 1, characterized in that: The inner diameter of the outer tube outlet is 30-1000 μm, and the inner diameter of the inner tube outlet is 10-500 μm.

8. The microfluidic method for controllably preparing monodisperse double emulsions by interfacial infiltration and endocytosis according to any one of claims 1 to 6, characterized in that: The number of cores in the double emulsion and the droplet diameter of the double emulsion are adjusted by adjusting the distance between the outlet of the nested injection tube and the liquid surface of the external phase fluid.

Images